Keywords: Others (Aircraft Engines)
Abstract: Towards the global environmental goal of carbon neutrality by 2050, the research and development activities are vigorously carried out all over the world. In Japan, the heavy industries have been executing cutting-edge technology development of hydrogen gas turbines, ammonium gas turbines, and related technologies for realizing green gas turbine systems. The development of fast start-up and flexible gas turbine technologies have also been performed as a government project for introducing huge amount of renewable energy in the near future. In the field of aircraft propulsion, the industries, universities and JAXA are actively progressing cooperative research of aero-propulsion electrification. The hydrogen propulsion and the hybrid propulsion are also current enthusiastic targets of research activity. The fundamental knowledge of academia is thought critically essential for the topics concerning hydrogen utility. Recently, the Japanese government started powerful support for green technology activities in the frameworks of Green Innovation Program and Green Transformation Initiative. In the lecture, the current R&D activities in Japan toward green energy era are introduced from the academic point of view. The historically significant developments of domestic gas turbines are briefly reviewed as well. It is hoped to establish a global cooperation which is extremely important for all these activities.

Keywords: Alternative Fuels (Hydrogen, Ammonia, and Other Carbon Free Fuel), Combustion Phenomena, Emissions (NOx, SOx, Soot)
Abstract: The authors have focused on the use of lifted flame as a method to achieve low NOx emission in hydrogen gas turbine combustors. The objective of this study is to investigate the combustion conditions of a lifted flame formed on an injector hole smaller than 1 mm. Four types of hydrogen injectors have been used: 0.2, 0.4, 0.6, and 0.8 mm. The formation condition of the lifted flame and the flame stability, flame base height and length, and NOx emission in this burner were investigated. The experimental results showed that the flame stability and flame length depended on the hydrogen injection hole diameter. The NOx emission decreased with the decrease of the injection hole diameter. As the air flow velocity increased, the effect of the residence time of the burned gas became more significant. As a result, the difference in NOx emissions for each injection hole diameter became smaller.

Keywords: Combustor Development, Alternative Fuels (Hydrogen, Ammonia, and Other Carbon Free Fuel), Combustion Instability
Abstract: Ammonia is well recognized as one of the most advanced hydrogen carriers. However, the challenge on flame stabilization still needs to be addressed when applying NH3 as a fuel, which is caused by its low reactivity and low flame speed. In the present study, flame stabilization mechanism of swirl NH3/air flame with a secondary non-premixed H2 injection were analyzed and compared with the fully premixed NH3/H2/air flames. Simultaneous PIV and NO-PLIF techniques were performed to reveal flame stable enhancement mechanism. Results show that the flame stabilization mechanism largely depends on the way in which hydrogen is introduced. Larger extension on flame stable region can be obtained when applying the secondary hydrogen injection at flame root, comparing with the fully premixed NH3/H2/air flames. In comparison, large NO was observed at flame root for non-premixed mode, which provides heat release and intermediate species to prevent the flame blow-off. The secondary H2 injection at flame root contributes to the flame stabilization by providing the hot gas and more intermediates to ignite the flame, and increasing the flame resistance to the strain. In comparison, however, the flame stabilization for fully premixed NH3/H2/air flame near the blow-off is solely contributed by the flame resistance to the strain.

Keywords: Alternative Fuels (Hydrogen, Ammonia, and Other Carbon Free Fuel), Gas Turbines for Electric Power Generation, Combustion Phenomena
Abstract: The effects of air temperature, equivalence ratio and combustion conditions on the stability of ammonia / air flames were investigated experimental. At first step, the flame stability range was investigated between non-premixed flame and premixed flame. As a result, comparing the results of non-premixed and premixed combustion, the flame stability range of non-premixed combustion is significantly narrow. The results suggest that, to keep the ammonia / air flame, it is necessary to supply the suitable fuel / air mixing condition before flame. Also, in premixed flame, the flame stability range of burner method becomes wider than that of the upward propagation method. It is suggested that it is important to circulate radical species containing NH2 together with sufficient heat.

Keywords: Heat Transfer Measurement, New Testing Technology, Turbines
Abstract: Effective endwall cooling can be achieved by utilizing design related gaps between turbine components for coolant injection. For dimensioning purposes, it is essential to understand the influence of slot geometry and coolant related parameters on both film cooling effectiveness and heat transfer. To account for the influence of the radial pressure gradient on secondary flow and thus on film cooling performance, an annular sector cascade has been developed and integrated into the high-speed turbine test rig at the Institute of Fluid Machinery and Fluid Dynamics (SAM) of the University of Kaiserslautern-Landau, Germany. The cascade is equipped with four state-of-the-art nozzle guide vanes with axisymmetrically contoured endwalls. An exchangeable insert in the central passage endwall allows different upstream slot geometries to be investigated. It incorporates various measurement techniques such as five-hole probes, pressure sensitive paint and infrared thermography to investigate both thermal and aerodynamic aspects of film cooling.

Keywords: General Heat Transfer, Film Cooling, Internal Cooling, Heat Transfer Simulation, Others (Heat Transfer)
Abstract: Film cooling with compound angle holes has a wide application in gas turbines. However, it is difficult to evaluate film cooling effectiveness rapidly. The purpose of this paper is to construct a prediction model based on conditional WGAN that is able to predict effectiveness of compound angle holes on a flat plane. For film cooling injection that has a velocity component opposite to the main flow direction, four parameters are selected as labels of training data: compound angle, inclination angle, blowing ratio and density ratio. Change these four parameters, get 162 groups of real data through CFD method and use this data to train the conditional WGAN model. The prediction model performs well in this situation, results show that conditional WGAN can map relationships between four labels and their corresponding film cooling effectiveness distribution.

Keywords: General Heat Transfer, Film Cooling, Internal Cooling, Heat Transfer Simulation
Abstract: The adiabatic film cooling effectiveness was measured using pressure sensitive paint (PSP) on a flat plate for a 7-7-7 fan-shaped film cooling hole as the baseline and baseline with compound expansion at the leading edge of the hole (C.E.). The C.E. cooling hole showed a different pattern of film cooling effectiveness compared to the baseline cooling hole, and demonstrated better cooling performance at the high blowing ratio condition. Numerical simulations were conducted to simulate the behavior of the coolant fluid for the baseline cooling hole and the C.E. cooling hole. The C.E. cooling hole shows a high momentum flow that is laterally distributed through the expanded flow path. In addition, the C.E. cooling hole shows a different vortex pair structure compared to the baseline cooling hole, resulting in a different distribution of film cooling effectiveness.

Keywords: Structural Vibration and Damping, Rotordynamics, Structural Mechanics
Abstract: In this study, a practical optimization method of mistuned bladed disks that optimizes the resonant stress, the stability for the blade flutter and the amount of unbalance by rearranging blades on a disk is proposed. The reduced-order model FMM (Fundamental Mistuning Model) is used to reduce the computation time. To verify the proposed optimization method, first, the original mistuned bladed disk, which has the maximum amplification factor and the minimum stability, is generated by MCS (Monte Carlo simulations). Next, the optimal bladed disk with the minimum amplification factor, the minimum amount of unbalance and the maximum stability is searched by using MCS and DDE (Discrete Differential Evolution) which is an optimization technique based on the genetic algorithm. From the analysis results, the validity of the proposed optimization method is verified.

Keywords: Structural Vibration and Damping, Structural Mechanics, Others (Structure and Dynamics)
Abstract: The structural mechanical properties of blades in turbomachinery depend on the operating speed. In addition to effects such as stress stiffening and spin softening, the rotational speed influences the nonlinear contact properties in shroud-coupled turbine blades. A change in operating point consequently leads to changes in natural frequencies, vibration modes and effective damping. For the design of new turbine blades, the correct modeling of all combined speed-variable properties is necessary to safeguard the blades against high cycle fatigue at any operating point. A nonlinear computational model with a variable-speed formulation of the structural properties is developed and the dynamics of a medium-pressure turbine blade with shroud coupling is analyzed at several operating points. In a rotational test rig, the disk and blade assembly is excited with higher-harmonic excitation force components at different speeds. The comparison of the amplitude responses shows the rotational speed influence on the damping and resonance frequency and successfully validates the developed computational model.

Keywords: Structural Vibration and Damping, Axial Compressors, Aeroelasticity and Flutter
Abstract: The demand for lighter axial compressor rotors can be met by employing blisks, denoting an integral part of disk and rotor blades. Due to lower structural damping, blisks may face aeromechanical challenges. Although numerical simulations of aeromechanical phenomena have advanced, there is a lack of validation data. This demand is met with the presented set of data for structural and aerodynamic damping of higher modes. Therefore, the critical damping ratio of an isolated axial compressor blisk is quantified in a closed-loop axial compressor test facility at the Institute of Thermal Turbomachinery and Machinery Laboratory (ITSM), University of Stuttgart, Germany. Two modes are investigated at an engine order (EO) 23 and in different flow conditions using a novel excitation system. Total damping values are derived from blade vibration test data by means of a laser-based Blade Tip Timing (BTT) measurement system and are compared to Ansys CFX-based damping calculations.

Keywords: Turbocharger Technology, Turbines, Others (Structure and Dynamics)
Abstract: In vehicle turbochargers, boost pressure is required to generate high torque at low engine speeds, where the gas volume is low and the flow to the turbine is intermittent, and a variable capacity turbine with a variable geometry system or a multi-entry turbine is applied to make effective use of engine pulsation. In the European and U.S. markets, the double-scroll turbine, in which the scroll flow path is divided in the circumferential direction, is being applied as one of the options of the multi-entry turbine. This paper describes the technological development of the double-scroll turbine that achieves all of the aerodynamic performance, structural strength, and manufacturability.

Keywords: Turbocharger Technology, Centrifugal and Mixed-Flow Compressors, Advanced Measurement Techniques
Abstract: This paper deals with the component level breakdown of performance characteristics of a centrifugal compressor using detailed measurements. The compressor stage used for Heavy-Duty applications consisting of impeller, vaneless diffuser and the volute has been experimentally tested in a gas stand. Several static pressure measurements combined with total pressure and temperature measurements on the compressor stage have been carried out. Based on the detailed measurements, the component level aerothermal performance parameters are calculated on the entire compressor map that includes tip speeds from subsonic to supersonic speeds. The effect of individual component performance characteristics and their impact on the design of the entire stage is discussed both at design and off design conditions. Better understanding of the component level performance aids to design of a compressor stage for increased efficiency, range and larger surge margin. In addition to the detailed measurements, a 1D model for the entire compressor stage is created using well established models found in the literature. The measured experimental data is then correlated with the predictions from the 1D model and the differences are discussed in details, along with model calibration.

Keywords: Turbocharger Technology, Performance of Turbocharger and Small Gas Turbine, Others (Aerodynamics and Design)
Abstract: The transition towards a more flexible operation in energy generation occurring in thermal power plants and propulsion technologiy, is one of the main drivers in the design of robust and flexible turbomachinery components. To address this, an axial-radial diffuser test rig has been designed at the Institute of Thermal Turbomachinery and Machinery Laboratory (ITSM) at the University of Stuttgart, in collaboration with MAN Energy Solutions SE. The parameters considered for the design of the components of this test rig are described, which allow to experimentally investigate scaled diffuser geometries of industrial turbocharger turbines at generic and well-controlled inlet conditions. Furthermore, a numerical study has been carried out using the commercial software Omnis 5.2 by Cadence. The results contain the comparison of experimental and CFD data, regarding the inlet conditions and pressure distribution along the diffuser, as well as the pressure recovery and loss coefficients for two different operating points.

Keywords: Axial Compressors, Unsteady Flow and Stability Enhancement in Compressor Flow Control, Computational Fluid Dynamics
Abstract: The concept of "morphing cascade" has been proposed to address the problem of deterioration in compressor performance at off-design points caused by mismatch between geometry and incoming flow conditions. To evaluate the improvement of blade performance at off-design points due to blade morphing driven by smart materials, a two-dimensional transonic cascade with shock-induced boundary layer separation at the off-design point is investigated by means of finite element method and computational fluid dynamics. Results show that cascade morphing driven by piezoelectric materials can suppress the shock-induced boundary layer separation by changing the curvature at the rear section of the cascade. In addition, the cascade morphing can also change the shock structure in the cascade passage and thus reduce the shock loss. Specifically, numerical experiments show that a 4.2% chord length deformation of cascade trailing edge can reduce the total loss at the off-design point by 37.5%.

Keywords: Others (Aerodynamics and Design)
Abstract: To reduce the fuel consumption of turbofan engines, high pressure compressors are required to have smaller core size due to engine’s higher bypass ratio and higher overall pressure ratio. The relative increase in tip clearance relative to the blade height in the rear stage results in performance degradation issues. Three-dimensional designs such as sweep and dihedral are expected to desensitize the aerodynamic performance and stability of compressor blades against tip clearance change. A series of experiments are conducted to investigate the characteristics of both a baseline rotor and a modified rotor in a low-speed 1.5-stage compressor rig under design and large tip clearance configurations. The modified rotor features tip dihedral and increased meridional velocity towards the outer radius region compared to the baseline. Tip clearance sensitivity is shown by the experiments to be lessened for the modified rotor. At large tip clearance, the kink point that occurs in the blade total pressure rise characteristic moved to the lower flow rate for the modified rotor compared to the baseline. The mechanism of this improvement is investigated through experiments and unsteady CFD.

Keywords: Axial Compressors, New Concept
Abstract: In order to obtain the stator dihedral scheme which can simultaneously take into account the two modes, the flow topology in the corner region of the core driven fan stage (CDFS) stator suction surface is analyzed, and the appropriate stator dihedral scheme is selected according to the separation spiral node position of the suction surface under different modes. According to the improvement of CDFS peak efficiency and stability margin by different dihedral schemes, the optimal dihedral scheme is selected. The internal flow field and aerodynamic performance of CDFS baseline stator and optimal dihedral stator under different modes are compared and analyzed. The results show that the root positive dihedral design can increase the axial velocity of the stator root and reduce the load in the front section of the stator root under two modes, which are beneficial for suppressing the flow separations and reducing aerodynamic loss.

Keywords: Long Blade Technology, Advanced Measurement Techniques, Aeroelasticity and Flutter
Abstract: The modern energy market requires a more flexible operation of conventional steam turbines. The frequent load changes increase the risk of self-excited and forced blade vibrations especially for the last stage blades. Verified numerical methods are necessary in order to predict these phenomena reliably. For this purpose, unsteady pressure transducers are applied to the rotating blades of the last stage of a LP steam turbine to measure the unsteady pressure response during experiments under steam conditions. To qualify these transducers for the measurements, the effects of centrifugal acceleration of up to 85000 g as well as blade vibration and deformation are quantified in two experiments: a spin test with the pressure transducers is performed to quantify the effect of centrifugal acceleration and a blade vibration excitation experiment under vacuum conditions is carried out to investigate the influence of blade vibration and deformation. The results show that the acceleration leads to a pressure offset and a change in sensitivity. Furthermore, blade vibration and deformation result in an additional amplitude. With these investigations, unsteady pressure transducers are qualified for experiments in a model steam turbine.

Keywords: Long Blade Technology, Efficiency Enhancement
Abstract: The exhaust efficiency of the low-pressure turbine plays an important role in the efficiency of the steam turbine. By improving the exhaust performance, the kinetic energy of the last stage rotating blades can be converted into potential energy, and it becomes possible to improve the turbine efficiency. However, the flow field in the diffuser is closely related to the flow pattern of the last stage rotating blade, and the flow field in the downstream exhaust chamber has a complicated three-dimensional flow field. The exhaust performance of the low-pressure turbine, turbine efficiency, and flow pattern around the low-pressure end blades were verified using our demonstration power generation facility (T-Point 2). The results showed good agreement between the CFD predictions and the measured values.

Keywords: Long Blade Technology, Structural Vibration and Damping
Abstract: With the increase in renewable energy, steam turbines are also required to have a wide operating range from low to high loads and more flexible operation. Steam turbine LP-End blades are the components that are greatly affected by these factors. Especiallyat high-load operation, risks for flutter vibration are increased and it leads to serious damage when it occurs. Therefore, highly reliable design and its validation are required. This paper describes the design evaluation method and verification test results for steam turbine long blades flutter vibration at high-load operation. In the design phase, the unsteady flutter analysis is performed assuming the flutter vibration mode to calculate the aerodynamic damping. Subsequently, the damping caused by friction at the contact points of the tip shroud and the intermediate connections of the blades is analytically calculated and the relationship between mechanical damping and the vibratory stress is obtained. From aerodynamic damping and mechanical damping, the stability evaluation is carried out. If the aerodynamic damping is negative, vibration stress levels are evaluated. The validity of the analytical value of the mechanical damping is confirmed by the electromagnetic excitation test of the full-scale blade. The rotating blades are forced to excite in flutter vibration mode and the actual mechanical damping is measured. Finally, vibration measurements of the last stage blade were performed in an actual power plant by using BVM (Blade Vibration Monitoring). These measurements were monitored remotely for three years.

Keywords: Innovative Thermal Management Concepts, Electric/Hybrid Propulsion, Component Damage, Failure, and Life Assessment
Abstract: The emphasis on environment-friendly propulsion systems has accelerated the development of (hybrid)-electric aircrafts. Managing the waste heat of individual components is critical for improving the system level performance in any propulsion system. Electrical components, in (hybrid)-electric aircraft propulsion systems, though characterized by higher efficiencies can still result in higher heat fluxes because of high-power density requirements. Effectively dissipating this heat is a challenge in aerospace applications. Heat exchangers play an important role in waste heat dissipation. New heat exchanger concepts are being explored to meet the constraints and challenges without compromising the performance. This paper addresses two important aspects associated with Thermal Management System design. Firstly, a simulation tool to model the Thermal Management System and to understand the design trade-offs. Secondly, comparative investigations of the thermal performance and mechanical integrity of compact heat exchanger concepts when integrated into the overall TMS and over the engine/heat exchanger life cycle.In summary, this work addresses two main areas in the context of a hybrid electric propulsion system (a) developing a TMS tool for efficient design of the TMS and (b) comparing the results from von-mises stress analysis of two compact heat exchanger concepts integrated into the hybrid electric TMS.

Keywords: Operational Flexibility
Abstract: The increasing share of electricity produced from renewable energy sources (RES), with the consequent strong penetration in the current energy network, is causing a growing need of balancing power to compensate power supply from such fluctuating sources. For these reasons, nowadays the power plants are running more often at part-load providing ancillary services and sustaining the grid operability. Therefore, an increase in efficiency during part-load operation impacts positively the year-round efficiency. A possible solution for flexibility enhancement, is based on the intake conditioning. Such concept, after a general introduction, is here applied to increase the temperature of the intake of power oriented combined cycle (PO-CCGT), mitigating the Gas Turbine off-design and resulting in an enhanced efficiency. In this work, a statistical analysis of actual PO-CCGT production profiles and climatic data is performed considering the Italian context, to assess the potential of this practice under the economic and environmental point of view.

Keywords: New Concept
Abstract: The measurement of unsteady dynamic pressure is essential in a compressor stage as it provides important information about the aerodynamic performance of the compressor blades. Unsteady dynamic pressure measurement also allows us to understand the behavior of the airflow as it passes through the compressor stage, including possible instabilities or fluctuations such as surge. This information is key to optimizing the design and operation of the compressor, as well as ensuring its overall reliability and longevity. In addition, unsteady pressure measurements can provide valuable data for improving the overall efficiency and performance of the engine or system in which the compressor is used. This paper presents insights from the unsteady dynamic measurements in the two fan stages of the CRISR rig (Counter Rotating Integrated Shrouded Propfan). The experiments took place as part of the CRISPmulti measurement campaign at DLR's M2VP test facility in Cologne between Oct 2021 and Jun 2022. On the one hand, these measurements serve to better understanding of the aerodynamic behavior of the CRISP fan stages in order to ultimately optimize the aerodynamic design. On the other hand, they are used to validate and improve the numerical simulations. Another important aspect is a comparison of the results of an undisturbed fan with a disturbed fan with an inlet distortion. For this purpose, a grid is placed in the flow channel to simulate the effects of Boundary Layer Ingestion (BLI).

Keywords: Alternative Fuels (Hydrogen, Ammonia, and Other Carbon Free Fuel)

Keywords: Others (Aerodynamics and Design)
Abstract: The field of aeromechanics includes phenomena that may lead to vibrations of turbomachinery components, foremost turbomachinery blades. Whereas low-amplitude vibrations can be tolerated, vibrations occurring at high amplitude may lead to failure due to material overload or fatigue, making them intolerable. When designing turbomachinery components, optimization is commonly performed to meet various objectives such as performance, operating margin, fuel flexibility or costs, to name a few. Aeromechanical phenomena usually necessitate complex simulations and/or testing, making it challenging to include in an optimization process. This keynote lecture will first provide a brief introduction into turbomachinery aeromechanics, showcasing highlights from recent numerical and experimental research. Thereafter, light is shed onto the potential that an optimization of turbomachinery components may give when specifically including aeromechanics as an additional optimization objective.

Keywords: Combustion Phenomena, Emissions (NOx, SOx, Soot), Combustor Development
Abstract: In order to secure a stable low-carbon energy supply for preserving the global environment, hydrogen attracts attention as gas turbine fuel for power generation. Kawasaki Heavy Industries (KHI) has developed proprietary combustion technologies for 100% hydrogen with advanced hydrogen dry low NOx micro-mix combustor, and also adapted a DLE combustor for hydrogen / natural gas mixtures. In this study, the effect of hydrogen admixing to natural gas on the flame stability and Nitrogen oxides (NOx) emissions was investigated for a dry premixed can type combustor with supplemental burner at atmospheric conditions. Therefore, the reaction zone and flame behavior behind of main burner have been visualized by OH radical chemiluminescence imaging and high-speed imaging respectively. As a result, it was found that the flame length of the premixed main burner becomes shorter with increasing share in hydrogen and the flame approaches the trailing edge of the main burner. The present combustor was capable to be operated at fuel mixtures up to 30 vol% hydrogen share with only marginal increase in NOx emissions.

Keywords: Emissions (NOx, SOx, Soot), Alternative Fuels (Hydrogen, Ammonia, and Other Carbon Free Fuel), Combustor Development
Abstract: NOx emission characteristics of micro-mix (MMX) burner for hydrogen aircraft under high pressure and temperature were investigated experimentally and numerically. The three types of experiment to investigate the effect of Inlet temperature, Inlet pressure, NOx emission and Air Fuel ratio (AFR) on NOx emission under high pressure and temperature were conducted. And steady RANS simulation with detailed chemistry and CHT analysis was performed and compared with the experimental data. As a result, we confirmed linear relationship between inlet temperature and Emission Index of NOx (EINOx). And EINOx increases in proportional to 0.7 powers of inlet pressure of which index is higher than the generally known index of 0.5. The numerical simulation results suggested that the combustion process of MMX was composed of regimes starting with premixed combustion and ending with non-premixed jet combustion.

Keywords: Computational Fluid Dynamics, Ignition, Combustion Simulation
Abstract: The reentrant step, based on a typical step structure, was proposed in this study as an improvement of the center cone-based backward-facing step for achieving pilot ignition in the augmented/ramjet combustor. The reentrant step offers increased flame stability and better performance when meeting more critical challenges. Numerical simulations were conducted to investigate the flow characteristics of the step structure in the augmented/ramjet combustor, including the flow field, reflux ratio, mass exchange rate, and residence time. The results indicated that the reentrant step was more effective at igniting the augmented/ramjet combustor than the typical backward-facing step. The Da3/4h-Dr3/4h reentrant step structure demonstrated the best performance, establishing a recirculation zone that was beneficial for flame stability and propagation. Overall, the reentrant step with its simple structural form, low pressure loss, and improved flame stability is a reliable alternative for achieving pilot ignition in the augmented/ramjet combustor.

Keywords: Novel Cooling Technology, General Heat Transfer, Film Cooling, Internal Cooling, Computational Fluid Dynamics
Abstract: Narrow channel double-wall cooling has demonstrated significant potential in enhancing cooling efficiency and extending the lifespan of turbine blades. In this study, the film cooling performance of narrow channel double-wall cooling were investigated numerically. The results indicate that the cross-flow within the impingement channel of double-wall cooling was weakened due to the flow extraction effects of film holes. The stronger the cross-flow in the channel, the easier it is for the cold air to escape from film holes when the cooling air is inadequate. While the coolant is sufficient, film cooling effectiveness was gradually decreased due to the developed impingement cross-flow. Besides, the hole geometries effects on film cooing were also discussed both in cross-flow and no cross-flow cases.

Keywords: General Heat Transfer, Film Cooling, Internal Cooling, Heat Transfer Measurement
Abstract: In modern gas turbines, the endwall of the first-stage vane is cooled by the combined effect of film cooling and purge flow. In order to examine the complex interaction between the mainstream and those cooling flows, we conducted wind tunnel tests using a three-vane linear cascade. The effect of mainstream turbulence on the film cooling performance was investigated with a fast-response PSP (Pressure Sensitive Paint) at the average blowing ratios (BRs) of 0.5, 1.0, 1.5 and 2.0 for a fixed purge flow rate. The cooling effectiveness by the combined cooling of film cooling and purge flow shows a maximum value at BR = 1.0, and as BR increases to BR = 1.50 and 2.00, the cooling effectiveness begins to decrease because the film coolant jet begins to penetrate the mainstream. The high mainstream turbulence enhances the lateral mixing of film coolant and results in better cooling performance.

Keywords: General Heat Transfer, Film Cooling, Internal Cooling, Heat Transfer Simulation, Novel Cooling Technology
Abstract: The present study employs single-row impingement jets as the research model to investigate the effect of internal-crossflow on the flow structure and impingement cooling. Numerical results demonstrate that the presence of internal-crossflow induces a significant change in the flow structure of impingement jets. Specifically, the flow within the impingement hole is partitioned into low-speed and high-speed zones by the internal-crossflow, and this partition becomes more distinct with increasing strength of internal-crossflow. Furthermore, the internal-crossflow causes an increase in coolant loss through the impingement hole, which results in a reduction of the discharge coefficient of the impingement hole at the same Reynolds number and geometric size. Regarding the impact of internal-crossflow on impingement cooling, the results show that the jet in the high-speed zone exhibits a higher heat transfer capacity in the stagnation zone. Consequently, the highest heat transfer coefficient shifts towards the direction of internal-crossflow as the strength of internal-crossflow increases under the same external-crossflow strength.

Keywords: Turbines, General Heat Transfer, Film Cooling, Internal Cooling, Heat Transfer Simulation
Abstract: Under the realistic running conditions of gas turbines, the temperature at mainstream inlet is always non-uniform due to the effects of combustion process, and different types of hot streak (HS) could be found at the inlet. The existence of HS may result in some potential negative impacts on the cooling performances of vane leading edge (LE). Nowadays, the two configurations, i.e., traditional showerhead film cooling (SFC) and novel double wall cooling (DWC), have been proposed in LE designs of turbine vanes, but until now there is no comprehensive study to evaluate the two models considering HS effects. In this work, using the two cooling structures, four different temperature profiles are considered at the mainstream inlet of the cascade. The results reveal that: in both models, HS could cause a local high-temperature region on LE, and the thermal characteristics of this area are dependent on HS pattern. Compared to SFC, DWC shows a better cooling ability and a lower thermal stress on the vane surface. The cooling characteristics in DWC model are less sensitive to the HS pattern. However, the problem of the extremely high thermal stress within the pin-fins of DWC should be carefully considered.

Keywords: Rotordynamics
Abstract: In the present energy scenario, heat-pumps are assuming an important role to improve building energy efficiency and electrification of thermal users, thus contributing to the penetration of renewable power sources at a wide scale. In this paper, an innovative heat pump prototype manufactured by Carrier Corporation using a high-speed radial compressor is characterized at University of Genoa laboratories during both steady-state operation and surge. Compressor surge in a heat pump closed loop is seldom studied in the open literature: similarly, to conventional open circuit applications, an adequate system identification is needed to define surge precursors and thus prevent such unstable operation. To this goal, system dynamic behavior is investigated both in sub-synchronous frequency range and in blade pass frequency one to identify the dominant spectral contents in vibro-acoustic response. Electrical current signal is analyzed to identify coupling phenomena between vibro-acoustic and electric behavior due to compressor electric motor control system.

Keywords: Rotordynamics, Structural Vibration and Damping, Turbines
Abstract: A full 3D rotor/stator FE model with CMS-based superelement modal reduction is developed. The method enables a high fidelity and efficient rotordynamic analysis for a newly designed power turbine (PT) with a slim spoke frame stator. In parallel, the stator support structure dynamic stiffness is quickly assessed using the FE simulated frequency response functions (FRF) data on the requirement of API standard. The results of the dynamic stiffness of the stator shows far lower than the API standard recommended. The derived support dynamic stiffness is directly applied to the unbalance response analysis of the PT rotor incorporating the bearing characteristics. The comparison of the unbalance response shows that the rotor with FRF representation of stator structure and the full FE model with superelement are very well cross validated. Finally, the rotordynamic analysis of full FE model shows that with the slim spoke frame, the PT still meets all the API requirements.

Keywords: Structural Vibration and Damping
Abstract: The design of low-pressure turbine (LPT) for aero engine requires accurate evaluation of blade forced response analysis with consideration of vibration response variation, as this is a critical factor for ensuring blade reliability. LPT blades have friction damping structures such as tip shrouds and under-platform dampers, and mistuning effect due to variation in material properties and friction damping structures causes variation in forced response. Accurate understanding of this variation is necessary to improve blade reliability and expand design space. To obtain the variation in vibration response under actual operating conditions, vibration measurements were conducted in actual aero engine test. In addition to strain gauges on blade surface, non-contact blade vibration measurement using non-intrusive stress measurement system (NSMS) was applied. As a result of the engine test, it was confirmed that the measured data of the strain gauge and NSMS measurements showed good agreement, and the variations in vibration response and damping characteristics of all blades were obtained.

Keywords: Turbocharger Technology, Alternative Fuels (Hydrogen, Ammonia, and Other Carbon Free Fuel), Combustion Simulation
Abstract: Hydrogen combustion engines suffer from low engine performance despite the vast body of research, with reported values of power density not exceeding 30kW/L. This is attributed to poor engine-turbocharger matching, since a large air flow rate is required to support the very lean operation, necessitated by constraints of low nitrogen oxide emissions and stable deflagration combustion. Thus, the present study performs a model-based investigation (1D engine simulation) on a 1.6L SI engine platform, to determine the boost demand and boosting system layout (multi-stage or VGT) for two different fuel injection strategies (PFI and DI), in order to achieve high power density (60kW/L), within safe combustion performance boundaries. The operating conditions considered at wide open throttle between engine speed of 1000 and 4000 RPM. Additionally, an analysis is performed to determine whether conventional turbo-matching methodology is sufficient to unlock the potential of hydrogen engine performance.

Keywords: Small Gas Turbine Technology, Others (Small Gas Turbine and Turbocharger)
Abstract: A study to modify and develop a turbofan engine using a micro turboprop engine has been conducted. The turbofan engine has been designed by adding a fan blade module as well as other required accessories to the existing turboprop engine. CFD and FEM methods were used for numerical analyses of the additional fan module to assess its aerodynamic performance and structural stability. Components of the fan module were fabricated with consideration for manufacture and assembly, and a test rig was also designed and built to measure the turbofan engine performance. The performances of turbofan engine were measured and compared to an existing micro-turbojet engine. The performance tests were conducted in two phases. In the first phase, the robustness of the designed turbofan and test rig were investigated and in the second phase, the maximum power test has been conducted to measure performance variables such as engine thrust, engine exhaust temperature (EGT) and fuel flow rate according to the engine RPM. The test results indicated that the turbofan engine SFC was reduced by 30~40% of the existing turbojet engine, demonstrating the successful implementation of turbofan characteristics.

Keywords: Turbocharger Technology, General Heat Transfer, Film Cooling, Internal Cooling, Others (Testing Technologies)
Abstract: Turbochargers are subject to highly transient inlet conditions during load changes. In order to conduct experimental investigations of such conditions a test rig is presented, which is capable of rapidly switching between turbine inlet conditions to simulate a sudden load change. The construction of this new test rig was motivated by the current lack of such facilities for the large size required for a new project. This paper details the design of the test rig and the experimental setup with results of the first project, which focuses on the heat transfer through the backside of the turbine wheel into the bearing housing.

Keywords: Small Gas Turbine Technology, Centrifugal and Mixed-Flow Compressors, Turbines
Abstract: This paper presents the results of simulations of a supercritical CO2 system integrated with a 180-kW nominal power piston engine. The supercritical CO2 system is based on a micro gas turbine and operates in a Brayton system (without a condenser). The results of the calculations were referred to the nominal point of the system and are given as maps of parameter changes normalized to the nominal point. The supercritical CO2 system itself is not controlled (only the speed of the turbomachinery is kept constant), while the power of this system depends on the current state of the reciprocating engine and directly influences the amount and temperature of the exhaust gases fed to the heater.

Keywords: Multi-Physics in Gas Turbines, Reliability and Maintenance, Computational Fluid Dynamics
Abstract: In this study, the modeling of rough surfaces by eddy viscosity-based roughness models is investigated. The surface is representative for deterioration in aero engines. The test case is T106C at a Reynolds number of 50,000. The profile has been widely used in the past for the evaluation and validation of roughness models as there is a detailed description of the experiments. Using scale-resolving simulations, a high-fidelity test rig is established that allows to compare local flow effects in addition to the provided experiments. That way, the shortcomings of the current models are identified and improved accordingly. The results show that the wake loss of the model-based simulation approach is already over-predicted for the smooth surface. Furthermore, the modeled wake loss for the rough surface is significantly lower than that of the experiment. Suggestions are made to improve the roughness models. Nevertheless, they do not allow to reproduce the experimental results. In order to highlight die interdisciplinary challenges in maintenance, repair, and overhaul (MRO) of aero engines we will quantify the influence of roughness.

Keywords: Axial Compressors, Computational Fluid Dynamics
Abstract: In the compressor, low-Reynolds-number effect is an important problem. The performance of compressors and other main components decreases obviously at high altitude. To improve the flow condition and reduce flow loss under the condition of high altitude and low Reynolds number (Re), the flow loss mechanism of compressor at low Re is studied in this paper. The effect of surface roughness on compressor performance at low Re was also investigated based on understanding the difference of flow structure at different Re. The results show that the open separation at low Re is the decisive factor affecting the compressor mass flow and efficiency. In addition, the roughness arrangement from leading edge to transition point and not too large roughness can effectively improve compressor performance at low Re.

Keywords: Axial Compressors, Reliability and Maintenance
Abstract: Engines and, thus, the compressor suffer operational, particle-based wear during operation depending on ambient conditions and particle size. Fouling describes the deposition of small particles on the blade surfaces leading to an increased blade thickness and surface roughness.

In experiments, the effect of fouling in the compressor is evaluated. Rough stator vanes are distributed equally spaced around the circumference or clustered within a stator row. The worn vanes are coated with a randomly distributed surface structure of spherical representing fouled blades. The roughness parameters are based on measurements from a CFM-56 engine.

The results show a better integral flow field for a non-uniform distribution. Losses in adjacent passages of the rough vanes are visible in wake flow measurements. Therefore, one-third of coated vanes, equally spaced around the circumference, behave like an almost entire rough stator row. However, clustering the rough stators results in circumferential asymmetric inflow for the trailing rotor.

Keywords: Axial Compressors, Unsteady Flow and Stability Enhancement in Compressor Flow Control, Computational Fluid Dynamics
Abstract: The present study aims to investigate the aerodynamic characteristics of a high load booster stage blade profile at a low Reynolds number (Re). Specifically, the blade profile at a cross section of the orthogonal blade root in the downflow passage was selected as the research object. High-precision parameterization methods were used to modify and design the original blade profile. Large eddy simulation method was employed to study the response characteristics of the laminar flow separation and transition to leading edge pressure spikes at low Re. The regulatory mechanism of the leading edge pressure spikes on the aerodynamic characteristics of typical booster stage blade profiles was also clarified. The results revealed that the introduction of a leading edge pressure spike coupled with a front loading pressure gradient distribution can effectively suppress the development of separation bubbles on the blade surface at low Re, weaken the reflux intensity in the near wall region, and reduce the trailing edge flow blockage. Furthermore, it weakens the aerodynamic strength of the blade surface vortex dynamics and improves the aerodynamic performance of the supercharged stage blade profile at low Re numbers. The outcomes of this research provide essential information for the aerodynamic design and flow regulation of the booster stage blade profile at low Re.

Keywords: Long Blade Technology, Others (Steam Turbines), Atomization
Abstract: We experimentally and theoretically investigate the structural effects of trailing edge thickness on the fragmentation process of liquid film into droplets sheared by a developed turbulent gas. To control the boundary-layer thickness of the turbulent gas flow, which is an essential length scale for instabilities, we employ an annular pipe flow. The liquid film slowly propagates along the inner wall and the gas flows at speeds of up to 100 m/s in the center. At the trailing edge of the pipe with the thickness of 0.5, 1.0, and 2.0 mm, the sheet stagnates, and then, ligaments elongate in the axial direction due to the Rayleigh-Taylor instability, which eventually disintegrate into droplets. We quantitatively clarify the ligament elongation mechanism and the size of the scattered droplets. The measurement results show that the circumferential wavelength of the ligament shortens as the trailing edge thickness decreases. We construct a theoretical model describing the properties of the ligaments, including the trailing edge thickness, and showed that the droplet size dispersed downstream can be predicted from the diameter of the ligament.

Keywords: Others (Steam Turbines), Unsteady Flow and Flow Control in Turbine, Computational Fluid Dynamics
Abstract: The unsteady numerical study of 360-degree whole circumferential flow in the first admission stage was carried out to clarify the flow and loss characteristics. The fundamental flow features and losses of the partial arc stage were evaluated and discussed in two load conditions and the case of two full-opened and one half-opened nozzle sectors.

Keywords: Gas Turbine Performance, New Diagnostics Technique, Monitoring Technologies
Abstract: This paper introduces a system to analyze the performance and thermodynamic characteristics of a jet engine in real time, including graphs and parameters such as combustion efficiency, compressor efficiency, turbine efficiency, thermal cycle, compressor map, turbine map, isentropic and polytropic efficiency, etc. Parameters and graphs are calculated and drawn instantaneously when the engine is running. The system is capable of running online while the engine is running and offline to analyze past engine results. The system can export a summary report of the transient and steady state performance after the end of the test. The results of the system help analyze the performance of each engine component at different operating points to detect abnormalities, or help research to improve engine efficiencies

Keywords: Gas Turbine Performance, Turbines, General Heat Transfer, Film Cooling, Internal Cooling
Abstract: Under the NASA Energy Efficient Engine (E3) program, two high pressure turbines (HPTs) were separately developed and tested by General Electric (GE) and Pratt & Whitney (P&W). Despite the corresponding NASA E3 design reports and several subsequent publications related to these HPTs, there is still no uniform and consistent data base, leading to the absence of some essential parameters. Therefore, 0D performance models of the NASA E3 HPTs were generated based on the available literature. The performance results agree well with the literature data and will be presented. Moreover, a well-known turbine cooling modeling approach is calibrated using the 0D performance models and further 1D turbine models, which were created in a collaborative process documented in this work and an accompanying paper. This is crucial since the predicted coolant mass flows significantly affect the gas turbine efficiency. Based on the obtained calibration results, a simplified turbine cooling model is also derived and calibrated in this paper, being applicable for performance studies in the early phase of preliminary design. In order to quantify the error due to simplification, both the original and the simplified turbine cooling model are applied in two parametric studies.

Keywords: Combustor Development, Gas Turbine Performance
Abstract: In this study, the thermal efficiency of a small gas turbine with a pressure ratio of 14 and a turbine inlet temperature of 1200 K was analyzed by cycle analysis when constant volume combustion was applied. At the same equivalent ratio, the combustion pressure of constant volume combustion was higher than that of constant pressure combustion, but the cycle-averaged turbine inlet pressure was lower than that of constant pressure combustion. The thermal efficiency of constant-volume combustion was equivalent to that of constant-pressure combustion, even when the pressure ratio was reduced by two. For the same pressure ratio, constant-volume combustion provided a 1-point improvement in thermal efficiency. On the other hand, the adiabatic efficiencies of the compressor and turbine are important to obtain such an improvement in thermal efficiency, and experimentally these efficiencies were lower when the gas turbine was operated with pulse combustion than with constant-pressure combustion.

Keywords: Gas Turbine Performance, Others (Aircraft Engines)
Abstract: Adaptive cycle engine has the ability to meet the multiple mission requirements of the next-generation aviation propulsion system. Adaptive fan is one of the crucial components of ACE, and therefore it is indispensable to precisely describe the adaptive fan characteristics to improve the accuracy of ACE performance prediction. This paper presents a high-fidelity simulation approach to ACE. Integration is performed by coupling the artificial neural networks (ANN) model obtained from the three-dimensional (3D) adaptive fan simulation with the zero-dimensional (0D) ACE model. The results from the high-fidelity model are compared with those of the original 0D model. At off-design conditions, the deviations of thrust, specific fuel consumption, turbine inlet temperature, and bypass ratio are up to 4.7%, 1.6%, 29K, and 2.1%, respectively, due to the consideration of the effects of the aerodynamic interaction inside the adaptive fan, variable geometry and split ratio on the component and engine performance.

Keywords: Alternative Fuels (Hydrogen, Ammonia, and Other Carbon Free Fuel), Combustor Development
Abstract: In response to global warming, the movement to reduce greenhouse gas emissions is accelerating. At the 2021 Climate Change Summit and COP26, the leaders of major emitters announced ambitious targets for the reduction of greenhouse gas emissions by 2030. In addition, a target of virtually zero emissions by 2050 to 2060 was announced. The International Energy Agency reports that 50% of the world's final energy consumption is thermal energy. Hydrogen fuel is indispensable for the decarbonization of heat. Each country has made progress in various areas such as the use of hydrogen in industrial fields, the introduction of hydrogen power generation, and the investigation of CO2-free hydrogen chain for the import of hydrogen. On the other hand, Japan leads other countries in the movement toward the use of hydrogen energy with its 2014 "Strategic Roadmap for Hydrogen and Fuel Cells," 2017 "Basic Hydrogen Strategy," and 2020 "Green Growth Strategy. Kawasaki announced the "CO2-free Hydrogen Supply Chain (CO2-free Hydrogen Chain)" in its 2010 Mid-term Business Plan and since then has been not only developing technologies and products to realize the concept, but also working on technology verification and building a consortium for collaboration with the aim of commercializing the concept. This paper introduces the current development status of hydrogen utilization, mainly with regard to combustors, using our small and medium-sized gas turbine power generation systems as examples.

Keywords: Combustor Development, Alternative Fuels (Hydrogen, Ammonia, and Other Carbon Free Fuel), Emissions (NOx, SOx, Soot)
Abstract: Kawasaki Heavy Industries, Ltd. (KHI) recently demonstrated a pure hydrogen gas turbine combustor based on the micromix combustion technology in an M1A engine test. The objective of this paper is to present the recent improvements of the combustor regarding to the reduction of NOx emissions and enhancement of fuel flexibility. The improvements have been demonstrated in a combined heat and power plant in Kobe, Japan. NOx could be reduced down to less than 35 ppmv (O2-16%) by reducing the flame size and the introduction of an additional supplemental burner system based on KHI DLE combustor for natural gas. Moreover, the fuel flexibility could be enhanced and the operation was confirmed between 20 and 100 cal.% H2 over the entire load range.

Keywords: Alternative Fuels (Hydrogen, Ammonia, and Other Carbon Free Fuel), Centrifugal and Mixed-Flow Compressors, Gas Turbine Performance
Abstract: Global goals to mitigate emission in societies necessitates the diminish the use of fossil fuels. Therefore, the alternative fuels and technologies are investigated in many applications e.g. aeroplanes, ships, power generation and storage. Hydrogen has been recognized to be one of very attractive fuel to be used for fossil free power generation. Hydrogen can be produced using renewable energy and electrolysers. Low emission hydrogen can also be produced using bio or fossil methane and carbon capture. Gas turbines are very efficient and versatile power generation devices, and they are also suitable for using hydrogen as a fuel. Since many applications require relatively small-scale facilities (few magawatts) and the production of green hydrogen is not done in very large scale, the small-scale power system using recuperated gas turbine with the waste heat recovery is studied. Hydrogen is used as fuel and technical feasibility and performance such system is studied.

Keywords: General Heat Transfer, Film Cooling, Internal Cooling, Heat Transfer Measurement, Others (Heat Transfer)
Abstract: Pulsating film cooling flow over cutback surface with teardrop-shaped dimples was experimentally investigated. Heat transfer measurements were performed by a transient technique with compensation of three-dimensional heat conduction. Three types of cutback surfaces were examined: smooth surface, surface with teardrop-shaped dimples of 0deg staggered arrangement, and that of 30deg in-line arrangement. The pulsation conditions were varied with respect to the Strouhal number and the velocity amplitude. The results showed that for 0deg staggered arrangement, the surface-averaged film cooling effectiveness and net heat flux reduction (NHFR) were decreased by 7.0% and 12%, respectively, from steady flow case when the pulsation Strouhal number was equal to the vortex-shedding Strouhal number behind the lip. This indicated that the cooling-flow pulsation at the same frequency as the unsteady vortex shedding caused the enhancement of the mixing between the cooling and main flows and resulted in deterioration of the cooling film.

Keywords: General Heat Transfer, Film Cooling, Internal Cooling, Structural Mechanics
Abstract: Effusion cooling is a common technique for turbine vanes in high heat load areas, requiring a denser arrangement of film holes. Moreover, the high-stress region around the holes due to stress concentration will interfere with the reduction of the hole spacing. This paper investigates the stress interference phenomenon of effusion cooling plates under thermal expansion conditions. The effects of hole spacing and inclination angle on stress interference and concentration are discussed. The results show that the stress interference phenomenon is more apparent when the spacing ratio is less than 4, and the stress interference will significantly increase the stress concentration coefficient. The smaller the inclination angle of the air film hole, the more significant the increase of the stress concentration coefficient due to stress interference.

Keywords: General Heat Transfer, Film Cooling, Internal Cooling, Heat Transfer Simulation
Abstract: The aerodynamics and cooling performance of the GE-E3 turbine casing and blade squealer tip, supplied with coolant from both the tip and casing, was numerically studied using three-dimensional steady Reynolds-Averaged Navier-Stokes (RANS) equation and standard k-ω turbulence model. A slot and double rows of film holes were arranged on the casing surface. The outlet total pressure loss and film cooling effectiveness of the blade tip and casing were compared under four blowing ratios (0, 0.5, 1.0, 1.5) and three swirl ratios (0.6, 0.8, 1.0). Results show that the casing purge flow enters the tip clearance from the suction side, generating the cavity leading vortex. This obstructs the tip leakage flow on the pressure side. The casing film cooling injection redirects the mainstream away from the blade tip. The total pressure loss coefficient reaches a minimum value at a blowing ratio of 1.0, dropping 3.1% compared to the case without casing cooling. An over-low blowing ratio inhibits cooling on the tip pressure side. The casing film cooling effectiveness proximal to the front of the tip pressure side is relatively poor. As the blowing ratio increases, the cooling performance of both the blade tip and turbine casing improves markedly. Reducing the swirl ratio of the casing purge flow augments the cavity leading vortex, which reduces the tip leakage loss. However, the averaged total pressure loss slightly increases due to the intensification of the upper passage vortex. Reduction in the swirl ratio greatly enhances the tip cooling efficiency at the leading edge. The region casing with unsatisfactory cooling effect adjacent to the tip pressure side also gradually vanishes. Nonetheless, the casing coolant gathers downstream of the slot. This related work provides a reference for establishing an efficient cooling layout on the turbine casing

Keywords: Rotordynamics, Structural Vibration and Damping, Structural Mechanics
Abstract: Throughout the entirety of the procedure for designing aeronautical gas turbine engines (GTE), the rotordynamic problem has been important consideration at every stage. The dynamic response of the rotor depends on not only the characteristics of the rotor but also the stiffness of its housing structures. In the majority of rotordynamic simulation studies, the bearing stiffness is taken with static stiffness of the engine housing structure. Nevertheless, the structural stiffness of the engine casing is always affected by the operating frequency, damping and inertia effects. This variation in stiffness is referred to as the structure's dynamic stiffness. In this paper, the casing structure dynamic stiffness of a small GTE is investigated using a Frequency Response Functions (FRF) test on a Siemens Testlab instrument. According to experiment results, in a non-damped supporting system, the dynamic stiffness decreases with frequency and is smaller than the calculated static stiffness. This phenomenon could decrease the critical speed of rotor, which may lead to serious engine damage. Additionally, the dynamic stiffness is also calculated through finite element method (FEM) using Harmonic Response Analysis (HRA). The results show a good agreement between experiment and simulation. These results highlight the significance of considering the dynamic stiffness of the engine casing in rotordynamic simulation studies, especially for non-damped supporting systems.

Keywords: Rotordynamics, Others (Structure and Dynamics)
Abstract: This paper presents numerical studies of rotor-stator interactions for a subsonic compressor. Focus put on an effect of the Tyler-Sofrin mode (TSM) on the unsteady pressure on the blade surface. Blade Count Ratio (BCR) and the rotational speed of the rotor are selected as calculation parameters. Numerical results show that the unsteady pressure changes with the BCR and the rotational speed. In particular, the strong pressure fluctuation is generated at specific condition of the BCR and the rotational speed. This phenomenon is a resonance of the TSM and the acoustic propagation of disturbances. The resonance condition depends on the ratio of the rotational speed of the TSM and the circumferential acoustic propagation speed.

Keywords: Others (Structure and Dynamics), System and Control, Others (Control and Diagnostics)
Abstract: Is it possible to remotely operate a tiny matter of a less-than-one-centimeter machine to perform a medical task in life? Especially, in the present technology, neither mechanism nor battery are small enough to set up into the structure of such that tiny machine. Yet, magnetic field as one of the potential power-sources can be drive promisingly (e.g. magnetic levitation to drive a vehicle, etc.). Here, Electromagnetic Actuation System (EMA) is proposed as an electromechanical energy conversion device, capable of converting electrical energy to electromagnetic field and to mechanical energy, respectively. Since magnetic field of the system is controllable in both direction and magnitude, the system can magnetically manipulate a small matter to move to any position and direction within three-dimensional space effectively as if having a tiny machine. The experimental result reports a feasibility of the system to control 6-DOF locomotion of the small matter perfectly.

Keywords: Performance of Turbocharger and Small Gas Turbine
Abstract: When diesel engines are used on marines, underwater exhaust presents a challenge, which results in a lower pressure ratio and pressure ratio fluctuations of the turbine. In such a case, a significant portion of the turbine energy loss occurs as residual velocity loss in the form of swirling flow at the outlet pipe. This study employs a 3-dimensional numerical simulation (CFD) method to investigate the mechanism of residual velocity loss caused by low pressure ratios and large pressure ratio fluctuations of turbines due to wave motion. The results indicate that the fluctuating back pressure environment not only causes a change in the direction of the turbine outlet swirling flow, but also leads to the swirl number exceeding the critical swirl ratio under high speed ratio operating conditions, resulting in the formation of a central recirculation zone (CRZ) at the outlet of the pipe. Moreover, the larger the speed ratio, the larger the CRZ. Based on these results, a brief model is derived to explain the change in intensity and direction of the outlet swirling flow, illustrating that the intensity of the swirling flow is linearly related to the speed ratio under the same pressure ratio condition. Finally, the study investigates the effect of pipe outlet vortex breakdown on turbine swallowing capacity, which indicates that vortex breakdown causes a "blockage" effect on the turbine. Collectively, these findings provide a theoretical basis for fluid dynamic control and turbine design strategies with low pressure ratio.

Keywords: Performance of Turbocharger and Small Gas Turbine, Computational Fluid Dynamics
Abstract: Low-fidelity modelling approaches remain attractive due to an unrivalled ability to predict full turbine performance maps quickly compared to high-fidelity approaches such as CFD, especially in the preliminary design process. As improvements in performance on a component level approach a point of diminishing returns, the ability to efficiently optimise the complete charging system for a given duty is a topic that is attracting significant research interest. A hybrid meanline model with the integration of Artificial Neural Networks (ANN) to act as surrogate models for loss and blockage prediction has been proven to display great potential in wide-range radial turbine performance prediction, demonstrating enhanced accuracy in comparison to traditional approaches. In contrast to the conventional application of a surrogate model in optimization problems, the choice of surrogate model for hybrid meanline modelling has not been studied thoroughly considering the wide range of geometrical variables and the dimensionality of the problem. Therefore, this paper presents a further investigation into the structure of the hybrid meanline model, specifically regarding the choice of the surrogate model algorithm and the corresponding impact of the training database size. By optimizing the surrogate model hyperparameters via Bayesian Optimization (BO), the effect of the hyperparameters on the performance of the surrogate models has been isolated. As an advanced automated machine learning method, BO can effectively reduce the cost of surrogate model training while also enhancing model performance. Various hybrid meanline models with different surrogate loss and blockage models were tested on unseen radial turbine geometries and a comparison of the predicted efficiency has been presented.

Keywords: Performance of Turbocharger and Small Gas Turbine, Computational Fluid Dynamics, Turbines
Abstract: The objective is to evaluate the performance of a radial-inflow gas turbine for automotive application using three-dimensional modelling and numerical simulation techniques in Computational Fluid Dynamics (CFD), mainly employing steady-state RANS and SST turbulence modelling.

The evaluation sensitivity in function of modelling parameters is determined and discussed, and once that a compromise on the adopted numerical configuration is achieved, simulation campaigns are presented, and the results are compared with available experimental data.

A discussion on the methodology limitations is held to examine if they cause inaccuracies and to determine if additional modelling elements should be employed to enhance the prediction capabilities.

Other important points studied are the flow characteristics in regions subjected to geometrical simplifications, and their impact on the turbine performance, such as the gap between the rotor and the shaft protection cover, the fillet radius between the rotor hub and the blades, and the rotor tip gaps.

Keywords: Axial Compressors, Unsteady Flow and Stability Enhancement in Compressor Flow Control, Computational Fluid Dynamics
Abstract: The effect of the axial position of axial slot casing treatment (ASCT) on the compressor performance and flow stability is investigated numerically in a two-stage counter-rotating axial flow compressor. The results show that the compressor stall margin can be improved by the axial slot casing treatment at different axial positions. When the ASCT covers the blade leading edge, the occurrence of spillage at the blade leading edge can be effectively suppressed, which contributes to the improvement of the stall margin. The tip flow field in the rear rotor is improved by the ASCT to a different extent. The ASCT changes the flow structure of the leakage flow and reduces the intensity of the tip leakage flow.

Keywords: Axial Compressors
Abstract: Tip clearance exists in turbomachinery widely. It is the gap reserved by the relative rotation between the blades and the shroud， which is in order to avoid mutual wear in the compressor during abnormal operation caused by the thermal expansion and deformation of the blade or other components. This paper considers the compressor blade tip clearance increased and performance declined from the phenomenon of rotor blade cropped and casing abradable coating worn under abnormal operating condition. The developed meridian surface model is modified by ignoring the blade body force in the blade tip gap. The results show that the modified prediction model can catch the stall inception point when the tip clearance increases. The disturbance mode and flow field reveal that the worsening of tip flow field by the enhanced intensity of tip clearance flow is the main reason of the stall in the compressor. Blade unloading is the dominating reason for the fact that abradable liner worn (ALW) cases has larger stability operation range than the rotor blade cropped (RBC) cases.

Keywords: Unsteady Flow and Stability Enhancement in Compressor Flow Control, Centrifugal and Mixed-Flow Compressors, Performance of Turbocharger and Small Gas Turbine
Abstract: The lower side of the operation range of compressors is limited by surge, which is known as the most dangerous flow instability in the system including compressors. Therefore, the prediction of surge phenomenon is essential for more stable operation. The purpose of this study is to investigate the unsteady internal flow field over the surge cycle. Deeper understanding of surge behaviors will be helpful in finding precursors to surge. Regarding a transonic centrifugal compressor with a vaneless diffuser used for vehicle turbocharger, a large scale of detached eddy simulation (DES) with 908 million computational grids was conducted by using supercomputer Fugaku. A mild and deep surge cycle was successfully reproduced by imposing a throttle valve model at the pipe outlet to control the mass flow rate. Finally, flow phenomena at consecutive stages during one deep surge cycle were investigated.

Keywords: Centrifugal and Mixed-Flow Compressors, Computational Fluid Dynamics
Abstract: With the continuous improvement of centrifugal compressor pressure ratio, vaned diffuser gradually becomes one of the key factors restricting the stability of centrifugal compressor with high-pressure ratio. A novel vaned diffuser casing treatment has been created to increase the stable operating range at low mass flow rates. This paper investigates the tube diameter of recirculation technology by parameterization to study the effect of different recirculating mass flow rates on the stability improvement. Results show that the greater the recirculating flow rate, the lower the mass flow rate operating conditions can be operated. However, the flow loss in the diffuser will increase accordingly. The increasing of comprehensive margin presents the omnibus change of mass flow rate and total pressure ratio, thus it is used as a standard to measure the improvement of operating range. When the diameter of recirculating tube is 1.5mm, the maximum increase of comprehensive margin is 3.21%.

Keywords: Centrifugal and Mixed-Flow Compressors, Unsteady Flow and Stability Enhancement in Compressor Flow Control, Computational Fluid Dynamics
Abstract: This paper presents the mechanism of impeller stall inside a high-pressure ratio centrifugal compressor with bleed slots, used in aviation gas turbines. Impeller stall was studied using an experimental test and numerical analysis. In the test, the location of stall inception was investigated by high frequency pressure transducers. For numerical analysis, Detached Eddy Simulation (DES) was conducted to obtain detailed flow fields inside the compressor. Both the experimental result and numerical analysis showed that a pressure disturbance occurred first near the leading edge of the splitter blade prior to the main blade. Numerical analysis also revealed that a vortex generated at the leading edge of the main blade developed toward the passage of the splitter blade pressure side and became a blockage, forming a leading-edge separation vortex on the suction surface of the splitter blade and inducing impeller stall.

Keywords: Gas Turbine Performance, Turbines, Computational Fluid Dynamics
Abstract: This paper presents a new 2D method for the analysis of gas turbines with massive cooling by air from compressor bleeds. The method is built on a stream function-based technique and utilizes a finite element solution process. Various cooling air injection techniques, including film cooling, trailing edge injection, and disc/endwall coolant flow, are incorporated into the analysis. Two key effects of air cooling are observed: (i) increased mass flow downstream of the injection surface and (ii) reduction in total gas temperature, leading to total pressure losses. To account for both these effects, suitable 2D models are developed and applied. The proposed method is used to develop a new industrial gas turbine. Some numerical results are presented in the paper. The comparison of the predicted results with measured test data shows a good agreement.

Keywords: New Concept, Gas Turbine Performance, Others (Cycle Innovation)
Abstract: Recently, there has been ongoing research to explore the use of hydrogen and ammonia as fuels for gas turbines. In this study, a system that applies the ammonia cracking process to a gas turbine combined cycle is proposed. The ammonia is used to cool the gas turbine combustor, and the heat absorbed from the combustor is used to supply energy required for the cracking process. The hydrogen or hydrogen and nitrogen mixture generated from the cracking process is co-fired with natural gas to improve the performance of the system. If only the hydrogen is co-fired with natural gas, the output increases, but the efficiency decreases. If the hydrogen and nitrogen mixture is co-fired with natural gas, the output increases by a maximum of 2.56%, and the efficiency increases by 0.1%. In addition, no extra fuel supply is required for ammonia cracking. Hence, the proposed method contributes to the reduction of CO2 emissions.