Keywords: Alternative Fuels (Hydrogen, Ammonia, and Other Carbon Free Fuel)
Abstract: The interest in reduction of CO2 emission from aircraft has been increasing for the global green sky in the future carbon neutral society. ICAO Member States adopted a collective long-term global aspirational goal (LTAG) of net-zero carbon emissions by 2050. Japanese Ministry of Land, Infrastructure, Transport and Tourism has launched a public-private council for aiming of reduction of CO2 emissions from aviation sector. 　Hydrogen is one of the promising candidate for a fuel of the future net-zero carbon aircraft. Because hydrogen does not generate CO2, when it burned. However, there are many difficult challenges, when it uses in the aircraft. The innovative core-technologies that are necessary for the realization of hydrogen aircraft have been developing in Kawasaki Heavy Industries, Ltd. under the Green Innovation Fund of NEDO (New Energy and Industrial Technology Development Organization). Hydrogen engine, liquid hydrogen distribution system, liquid hydrogen tank and aircraft concept are the subject of this research, and each topic will be mentioned in the plenary session.

Keywords: Alternative Fuels (Hydrogen, Ammonia, and Other Carbon Free Fuel), Atomization, Evaporation
Abstract: The twin fluid atomizer was studied for liquid ammonia combustion in small gas turbine combustor. The pressure of the combustor was 0.25MPa. The low pressure of combustor tends to partially evaporate liquid ammonia in the mixer of the twin fluid atomizer. The increase of airflow rate of the twin fluid atomizer increases the combustor liner temperature so that promotes stable combustion. The correlations of unburnt NH3 and N2O emissions differ between the twin fluid atomizer and the pressure swirl atomizer.

Keywords: Atomization, Combustor Development, Small Gas Turbine Technology
Abstract: Recently, airblast fuel nozzles are widely implemented with more outstanding advantages such as low fuel supply pressure because the fuel is atomized by compressed air and high velocity from the compressor. The efficient and rapid airblast fuel nozzle design process is proposed and presented in this study for the combustion chamber of expandable gas turbine engine (GTE). The four key airbalst fuel nozzle performances are studied by implementing the existing empirical relations for the appropriate airbalst fuel nozzle of expandable engine. The quick verification of proposed empirical relations is performed before implementing to evaluate the airblast fuel nozzle configuration in the design stage. The rapid analysis results are obtained to finalize the first prototype of airblast fuel nozzle to manufacture to reduce the development time while the CFD analysis of combustion chamber is calculated to ensure the matching of the overall designed expandable engine. The testing results of first prototype are obtained and enhanced the analysis solvers of empirical relations for the next airblast model. The required pressure for the fuel pump is dramatically reduced from 30 bar of pressure nozzle to 8 bar of airblast fuel nozzle while maintaining the fuel flow rate, SMD, spray angle, velocity and spray structure.

Keywords: Alternative Fuels (Hydrogen, Ammonia, and Other Carbon Free Fuel), Combustion Phenomena, Propulsion/Aircraft Integration, Energy and Thermal Management
Abstract: In recent years, research and development of sustainable aviation fuel (SAF) has been conducted by many researchers and aviation industries. In this study, we focused on coconut SAF produced by the co-solvent method, which is achieving a minimum emission of waste and a low consumption of energy. The aim of this paper is to clarify the combustion performance of blends of coconut SAF and jet fuel. The combustion experiment was performed using a J-850 jet engine. The applied fuel composition rates were between 10 and 50% coconut SAF in the jet fuel blends. Fuel blends of coconut SAF show higher combustion efficiency than only jet fuel. However, engine performance becomes less effective in the case of increasing the coconut SAF. The reason was that the capric acid methyl and caproic acid methyl, which include the coconut SAF, carbon chain generally improves the ignition quality of the fuel because of the presence of oxygen elements; thus, the turbine inlet temperature increases.

Keywords: Combustor Development, Evaporation, Advanced Measurement Technique
Abstract: In gas turbine combustors, heated kerosene injection has the potential to obtain rapid mixing with air, accelerating or even skipping the atomization and vaporization, leading to more evenly distributed kerosene concentration and thus homogeneous temperature distribution. A triple-sector centrally-staged combustor with a novel impingement-cooling-backflow-intaking configuration was designed to explore the above effect. The combustor exit temperature was measured by gas analysis. A movable gas sampling rake enabled the acquirement of temperature distribution with a spatial resolution of 1.478/cm2. Independent combustion experiments were conducted under different kerosene phases with air condition of 0.5 MPa and 600 K. The results showed the capability of heated kerosene in forming uniform temperature distribution. Injecting gaseous kerosene (677K) resulted in a 36% decrement in the overall temperature distribution factor (OTDF) compared to liquid kerosene injection. Using heated kerosene remarkably inhibits the formation of high-temperature regions and achieves smoother averaged radial temperature distribution.

Keywords: Novel Cooling Technology, Heat Transfer Measurement, Others (Heat Transfer)
Abstract: Manifold microchannel heat exchanger could achieve high heat transfer performance with lower pressure drop. In this paper, a 3D printed manifold microchannel heat exchanger is tested. The micro channels have characteristic dimensions of 1 mm width and 3 mm depth. On a heating area of 45.2 mm×36.2 mm, the heat transfer coefficient is up to be 4571 W/m2K with a bottom temperature rise of 30 K. Meanwhile, the pressure drop is 48.5 kPa with the flow rate of 300mL/min (Re= 52). This proposed design is also potential for array arrangement, where the flow rate of each single heat exchanger could be adjustable which shows great potential in system integration.

Keywords: Novel Cooling Technology, Innovative Thermal Management Concepts, Heat Transfer Simulation
Abstract: This research paper presents a numerical and a comparative study of porous media in the thermal management of battery cells, namely prismatic and cylindrical battery cells, whose application is becoming more prolific in electric and hybrid-electric applications. The battery cells used in these applications can reach high temperatures during operation, and therefore necessitate the use of innovative and better cooling methods over the conventional air cooling. This paper addresses this issue by investigating the thermal behavior of different configurations of the porous media in battery packs and the subsequent effect on battery temperature. Numerical simulations of porous media integrated battery pack are carried out using ANSYS Fluent software by solving the governing fluid flow and heat transfer equations. This study provides insights into the design and optimization of battery cells for various applications. The current research includes a thorough comparative and numerical study of battery cells in a cylindrical 18650 Li-ion battery cell pack and a prismatic battery cell pack. The relationship between increasing the thickness of the porous media surrounding the battery cells and the corresponding temperature reduction and velocity flow distribution in the battery cells is also investigated for both cylindrical and prismatic cells. The focus of the current study is on relationship between temperature drop and the thickness of the enveloping porous media, and therefore, the inlet velocity, the porous media material and a few other parameters will be fixed in the main body. These investigations are achieved through numerical simulations in ANSYS Fluent, a commercial computational fluid dynamics (CFD) software.

Keywords: Thermal Management of Structures, Novel Cooling Technology, Heat Transfer Simulation
Abstract: The impingement cooling of hydrocarbon fuels represented by kerosene has broad application prospects in the field of hypersonic aircraft and engine thermal protection. However, compared with air and water, the thermal properties of kerosene are more complex and need to be further studied. Using the Reynolds average method and the SST k-ω turbulence model, the superalloy is used as the heat transfer material. By simplifying the model, the effects of different jet structures on the impingement cooling effect under the same inlet conditions are numerically simulated. The wall temperature distribution is used as the evaluation index of heat transfer performance, and the overall design of the stabilizer is based on this. The research shows that the wall temperature of the stabilizer shows a trendency of increasing annularly around the impact point. The increase of opening rate, hole pitch and distance of impingement will lead to the decrease of heat transfer effect.

Keywords: General Heat Transfer, Film Cooling, Internal Cooling, Turbines, New Aircraft Propulsion Concepts
Abstract: Pressure Gain Combustors (PGC) have demonstrated significant advantages over conventional combustors in gas turbine engines, contributing to a significant increase in thermal efficiency while releasing low NOx emission levels. PGC uses pressure waves to transfer energy and generate a rise in total pressure up to 30% during the combustion process. One of the main challenges in the practical implementation of PGC in gas turbines is the integration of the highly unsteady flow of the combustor with the downstream turbine. Additionally, as the exhaust of the PGC is extremely hot, cooling of the turbine blades would be essential. Due to the highly fluctuating unsteady flow of the pressure gain combustors, the three-dimensional CFD simulation of turbines becomes very expensive in terms of computational cost and time. In this work, an alternative approach of using one dimensional unsteady Euler model for the turbine is adopted that considers turbine cooling as well. The main parameters required for the turbine blade cooling are the bleed mass flow rate, bleed temperature, and bleed pressure. Due to the introduction of bleed flow, the blades are no longer adiabatic and the mass flow rate across the turbine is not constant. Comparing the unsteady 1D Euler results against a zero-dimensional calculation approach showed a very good match confirming the applicability of the 1D method.

Keywords: Heat Transfer Simulation, Monitoring Technologies, Development and Operation
Abstract: In response to the promotion of renewable energy, more precise adjustment of demand and supply for power is becoming indispensable. Demand for fast starting with gas turbines as well as extreme load changes during operation has been gathering attention to balance power supplies from renewable energy, which is susceptible to the weather condition. 　One of the major issues for fast start and load changes in gas turbines is the instant prediction of rotor temperature, which affects stress distribution in the rotor and clearance between the rotor and stator. 　In this study, a method for precise and instantaneous prediction of gas turbine rotor temperature is proposed using a reduced order model (ROM) constructed using the methods of proper orthogonal decomposition (POD) and response surface methodology (RSM). Prediction results are compared and appear to correspond well with finite element method (FEM) results.

Keywords: Heat Transfer Simulation, Computational Fluid Dynamics, Others (Aerodynamics and Design)
Abstract: The present work involves Computational Fluid Dynamic (CFD) modeling of fluid flow in a narrow gap between co-rotating cylinders subjected to an axial turbulent flow. Steady-state Reynolds-Averaged Navier-Stokes (RANS) simulations are performed using DLR code TRACE. The simulation results are validated with experimental data from the literature where a good agreement is observed for velocity and thermal profiles. The effects of rotation on the heat transfer rates are studied for various combinations of swirl parameters. It is found that the Nusselt number on the outer cylinder increases in the hydrodynamic entrance region with the increasing rotation. The turbulence is enhanced in this region due to shear stresses but is suppressed with flow development due to stabilizing effects of centrifugal forces.

Keywords: General Heat Transfer, Film Cooling, Internal Cooling
Abstract: This paper presents a comparative study to investigate the effect of different rib arrangements in conjuction with swirl cooling for turbine blade cooling. Multiple angled rib configurations are investigated for Reynolds numbers from 10000 to 50000. RANS and Detached Eddy Simulations (DES) are conducted to assess the differences in the results for both simulation methods. First results for an initial rib configuration at a relatively low Reynolds number of 10000 show a local improvement in Nusselt number around the ribs, which are primarily caused by the impingement of the swirling fluid on the protruding surface. Different rib configurations could enhance the Nusselt number further by ideally reducing the decay of swirl along the channel length.

Keywords: Heat Transfer Simulation, Computational Fluid Dynamics, Others (Aircraft Engines)
Abstract: Aeroengine icing is the key to flight safety, and rotating spinner ice accretion is a research hotpot in recent years. The Euler method was conducted to calculate supercooled water impingement process. The conduction balance model of phase interface was developed to simulate ice accretion. The momentum source terms of centrifugal force, Coriolis force, and shear force of rotating air were established to simulate the influence of rotating condition, and the results showed that momentum of shear force was far less than that of centrifugal force and Coriolis force. The maximum ice thickness accuracy is below 15%, which shows the precision of the ice accretion model. A heat transfer correlation of rotating spinner is developed based on surface temperature simulation and experiment data. The heat conduction process with different spinner structures and materials is corrected using thermal-fluid-structure coupling method.

Keywords: Computational Fluid Dynamics
Abstract: Simulations of Taylor-Green vortex flow were performed at Re = 1600 using the general one-equation and standard one- and two-equation turbulence models. General one-equation is an eddy viscosity model that has been derived from Wilcox's k − ω SST and supplemented with a decay of isotropic turbulence term. Spalart-Allmaras and k − ω SST were used as standard Reynolds-averaged models and their performance compared to the general one-equation model.

Temporal behavior of total kinetic energy and dissipation rate were compared to DNS data and iso-surfaces of Q-criterion were computed to visualize the onset of turbulence and breakdown of large structures into fine scales. The general one-equation model was able to accurately predict temporal behavior of dissipation rate compared to DNS along with resolution of small scales of turbulence. Standard one- and two-equation models were overly dissipative and failed to simulate turbulence development into fine scales.

Keywords: Computational Fluid Dynamics
Abstract: Future compressors require the use of novel technologies to improve their efficiency, off-design performance, and thermal management. A frequently discussed possibility to achieve these goals is the use of active cooling methods in compressors. Maintaining a low temperature during the compression process improves the overall performance of the compressor, e.g., its efficiency or mass flow capacities. It is thus essential to consider the effect of cooling during the early design stages. However, current preliminary design methods rely heavily on empirical data and experience and are therefore only partially applicable for the design of cooled compressors. In this work, we demonstrate how modern data-driven methods can be used to obtain a surrogate model for the fast and accurate prediction of cooled compressor performance parameters. To do so, we train a neural network to predict the total pressure and temperature ratio and the mass flow rate of a 4½-stage axial compressor test case with arbitrarily cooled stator blades. The performance predictions of our machine learning model extend over the full (numerical) operating range of the test case and deviate by only 0.25% from high-fidelity CFD simulations on the test data set. We further demonstrate the accuracy and capabilities of this approach by predicting extensive performance maps for cooled and adiabatic compressor configurations. The predicted performance maps show a high level of agreement with numerical results.

Keywords: Computational Fluid Dynamics, Turbines, Others
Abstract: Hybrid RANS-LES methods resolve the large scales of turbulence directly and are therefore a valuable tool for more precise predictions of separated and turbulent flows in turbomachinery at moderate computational costs. Intentionally, wall bounded and, therefore, small scale turbulence will be calculated using a RANS model, which is why the reliability of the prediction of blade and end wall boundary layer flows, depends on the quality of this model. The prediction of hybrid methods can be insufficient when the RANS model is used beyond its region of calibration. In order to overcome some limitation of RANS turbulence and transition models, the current paper discusses a way to force a seamless hybrid method to use LES in a wall boundary layer flow by means of grid refinement. A zonal hybrid method is imitated in a flow solver that provides seamless hybrid methods only. The MTU T161 low-pressure turbine cascade was used in this study at a Reynolds number of 90,000. The mesh was refined in the region challenging for RANS, which is the zone of separation on the suction side. In fact, a local mesh refinement can force the hybrid method into an LES-like behavior close to the wall. Compared to the reference IDDES simulation, where RANS is used in the wall boundary layer, the locally refined IDDES simulation accurately predicts the separation and reattachment of the suction side boundary layer. The computational costs of this approach compared to a uniformly fine grid of LES-resolution are reduced by up to 80%. A deeper analysis of the model functions in the boundary layer of the blade's suction side is performed. It reveals the regions in which grid refinements influence the model and in which local flow quantities are more decisive. Furthermore, the inspection of the shielding function alone is shown to be insufficient to classify a grid with respect to higher resolution LES or more dissipative RANS behavior.

Keywords: Computational Fluid Dynamics, Others (Aircraft Engines)
Abstract: Since the icing on an aircraft threatens navigation safety, ice accretion prediction is required during its design phase. When supercooled large droplets (SLD) with diameters over 40 µm impinge on an aircraft, splashing and rebounding occur, generating secondary droplets. Furthermore, liquid film on the wing surface, which generate under glaze ice conditions, significantly affects the impact behavior. In this study, we investigate the effect of impact velocity and angle on the characteristics of secondary droplets by simulating the impingement of a water droplet on a water film that occurred under glaze ice conditions. As a result, the tendency of the total mass of secondary droplets with impact angle is similar for different impact velocities. In addition, secondary droplets' ejection velocity, mass, and ejection angle are correlated with the secondary droplet formation time.

Keywords: Axial Compressors
Abstract: In this paper, a preconditioner-based data-driven polynomial chaos (DDPC) method is first proposed to study the influence of real leading-edge (LE) errors on aerodynamic performance of a two-dimensional compressor blade with scarce manufacturing error data. In case of scarce sampled data, the preconditioner is constructed to alleviate the ill-conditioned problem when using high-order statistical moments. Several test functions are used to validate the computational robustness, accuracy and advantage of the proposed method. By using preconditioner-based DDPC method, the uncertain impacts of real LE errors on aerodynamic performance are quantified. Results show that the overall performance of compressor blade is degraded and has a large performance dispersion at off-design incidence conditions. The actual performance values of compressor blade have a high probability of deviating from the nominal performance. The total pressure loss coefficient is more sensitive to LE errors than the static pressure ratio. Compared with uncertainty quantification (UQ) results obtained by the proposed method, fitted Gaussian and Beta probability distributions for scarce LE error data seriously underestimate the performance dispersion of compressor blade. The mechanism analysis illustrates that the large variations of the flow around the leading edge is the main reason for the overall performance degradation and the fluctuations of the entire flow field.

Keywords: Axial Compressors, Others (Aerodynamics and Design)
Abstract: To describe the variation of the non-uniform blade geometric profile caused by the manufacturing and service process of compressor blades, a two-dimensional multi-scale modeling method of blade non-uniform profile is proposed in this paper. This method divides the non-uniform geometric profile of the design shape into three scales: design profile, mean deviation profile, and irregular rough corrugated line. By combining the parameterization method, K-L expansion, non-intrusive polynomial chaotic (NIPC) for sparse girds, and one-dimensional random midpoint shift method, a two-dimensional non-uniform profile model of the compressor blade is constructed. The modeling results show that this multi-scale non-uniform profile modeling method can effectively characterize the non-uniform profile variations on the blade surface caused by machining errors, erosion, corrosion, and fouling, which is meaningful for investigating the effects of non-uniform profile variations on the blade surface on aerodynamic performance.

Keywords: Axial Compressors, Computational Fluid Dynamics, Others (Aerodynamics and Design)
Abstract: Different types of geometric variations often appear coupled in manufactured blades. It is desired to identify the ones that have the strongest impact on the performance. In this paper, the influence of multiple geometric variations on the compressor rotor blade at the design point is studied. Large quantities of deviated blades are constructed by adding tolerance data to the design-intent blade and assessed using CFD simulation. It is shown that the region near the lower and upper end of the blade is more sensitive to geometric variations. The Spearman correlation coefficient is used as the measurement of local sensitivity at 15%/50%/85% spans, and the stagger angle tolerance turns out to be an important influencing variation. Furthermore, experiments on linear cascades representing profiles at different spans are carried out to study the effect of stagger angle on flow characteristics. Results show that the stagger angle tolerance could lead to different changes in performance depending on the specific cascade profile.

Keywords: Axial Compressors, Aeroelasticity and Flutter, Structural Mechanics
Abstract: Shape-adaptive compressor blading is researched as an alternative to variable nozzle geometries and pitch variable fan blading. By integrating piezoceramic Macro Fiber Composite (MFC) actuators in the rotor blading, a simultaneous morphing of the blade twist and turning can be achieved. While operating under off-design flow conditions the piezoceramic actuation allows to reduce flow incidence and deviation of the respective shape-adaptive axial compressor component. With the overall goal to increase engine off-design efficiency, while maintaining a sufficient surge margin, this research aims to investigate the influence of the blade reference shape on its morphing behavior. An aerodynamic design methodology including a streamline curvature calculation is therefore coupled with structural morphing simulations. To consider the impact of reference design variations on the morphing capability a Design of Experiment is conducted, resulting in the investigation of axial compressor designs, ranging from high hub-to-tip ratio compressor rotors to scaled Ultra-High-Bypass-Ratio (UHBR) fan blading.

Keywords: Computational Fluid Dynamics, Aeroelasticity and Flutter, Axial Compressors
Abstract: Harmonic balanced large-eddy simulation(HB-LES) is proposed for the efficient high-fidelity simulation of the unsteady flows with low reduced frequency. Harmonic balance method for unsteady RANS simulation is originally introduced to large-eddy simulation, utilizing the difference in timescales between the period flow and the turbulent fluctuations. Periodic flow and turbulent fluctuation are computed without disregarding their nonlinear mutual interference by iterating short-time large-eddy simulation and harmonic balance method. Evaluation computations of HB-LES are performed for Stokes Boundary Layer at Reynolds number of 1790, and subsonic and transonic flow around pitching NACA64A010 airfoil. The accuracy and computational efficiency of the HB-LES are discussed by comparing with the conventional large-eddy simulation and experimental results.

Keywords: Computational Fluid Dynamics, Unsteady Flow and Flow Control in Turbine, Turbines
Abstract: This paper discusses Large-Eddy Simulation (LES) results of vortical flow structures over a low-pressure turbine cascade for aeroengine using lattice Boltzmann method (LBM). The LBM can perform large-scale parallel calculations with dense mesh systems thanks to its simple algorithm and fewer operation counts than the conventional Navier-Stokes simulation. The LBM-based LES uses a regular uniform mesh, and the result is expected to provide high accuracy in predicting turbulent flows. The LBM results are well validated by comparing with the experimental results. In the present study, we especially focus on the vortical flow structures of the transitional separated flow occurring on the suction surface of the turbine blade and the streamwise vortices shed from the recirculation region on the pressure side. The simulation is conducted at three Reynolds number conditions of 80k, 100k and 130k, and the results are closely examined in comparison with the experimental data as well as the Denton theory [1] to reveal the effect of Reynolds number on the flow structures and the aerodynamic loss of the cascade.

Keywords: Computational Fluid Dynamics, Others (Structure and Dynamics), Others (Aerodynamics and Design)
Abstract: Considering modern aerial vehicle design, wing icing, with its consequent aerodynamic performance degradation, has become an inevitable topic due to the increasing number of accidents. Ice accretion occurs when supercooled water droplets come into contact with the surface of cold aerofoil and freeze. Unmanned Aerial Vehicles (UAVs), often have low-altitude and low-cruise-speed characteristics, are more critical to any exposure to ice accretion during the flight, resulting in an increase in the aircraft-gross weight and change in aerodynamics profile. The present study numerically simulated the ice shape to assess the impact of ice on the aerodynamic properties of the RG-15 aerofoil. The numerical results were compared with published experimental ice shapes and were in good agreement with the experimental data. The propellent aerodynamic performance was additionally evaluated by estimating the pressure, drag, lift and moment coefficient of the UAV under different cloud conditions driven by temperatures. At -10℃, it is shown from the numerical results that the effective chord length would increase up to 1.9% due to the ice accretion along the leading edge compared with the clean one and the center of mass would move forward by 0.85%, respectively. The study provides important insights into the effect of icing at a relatively low Reynolds Number at 1500m altitude, which can be used to optimum flight performance under certain icing conditions and demonstrate a general scope of fixed-wing icing for small UAVs.

Keywords: Turbines, Others (Aerodynamics and Design)
Abstract: The main objective of this research is to investigate a low loss airfoil of low pressure turbine (LPT) by aerodynamic rigs with test conditions aerodynamically equivalent to that of aero engines. Linear cascade rig tests were conducted to validate the airfoil performance. The measured total pressure loss of front-loaded airfoil is lower than that of aft-loaded airfoil. It was indicated that the lower velocity diffusion rate of the suction side contributes to reduce the profile loss generation. Rotating rig tests were conducted to validate the efficiency of the multiple stage LPT which has front-loaded airfoils in a rear stage. The measured efficiency agreed well with the CFD prediction. It was confirmed that front-loaded airfoils performed as intended in rotating, multiple stage condition. Finally, the engine test was conducted to demonstrate the performance of the LPT. The test data showed the LPT efficiency agreed with the prediction.

Keywords: Acoustic Issues, Axial Compressors, New Testing Technology
Abstract: Experimental study was conducted to clarify the mechanism of sound generation and to find the reduction method of the cascade aeroacoustic noise, a component of the aeroengine noise. The sound characteristics were examined using a linear compressor cascade in subsonic flow in which the Mach number was ranged from 0.3 and 0.5. From the measurement results of the far-field noise, the tonal and the broadband noises were detected. The low-frequency broadband noise increased in proportion to the sixth power of the mainstream velocity regardless of the incidence. On the other hand, the high-frequency broadband noise increased in proportion to the eighth power at low incidences and to the fifth power at high incidences. The tonal noise was revealed to have strong relationship with the velocity fluctuation around the blade trailing edge. The effect of blade surface riblet on the aeroacoustic noise was examined, and the possibility of noise reduction was found.

Keywords: Turbines, Acoustic Issues, Others (Aerodynamics and Design)
Abstract: Existing scaling approaches have been extended to include a rotor blade row and resulting similarity parameters have been derived. The scaling approach has been applied to a 1.5-stage axial turbine configuration and investigated numerically. The results of the steady-state simulations performed have shown that aerodynamic similarity can be achieved. The upscaled configuration with a multiplication factor 2 exhibits a similar aerodynamic performance compared to the reference geometry when conserving the derived similarity parameters and maintaining the total temperature level. The investigation on aeroacoustic similarity when scaling was evaluated with a focus on rotor-stator interactions and proven for the test case at hand using the unsteady simulation results. A linear behaviour of the sound pressure amplitude and sound power level with the shroud radius for the geometric scaling was found. The consistent results numerically validate the scaling approach that has so far only been investigated for an axial compressor vane row and can be used for future sub-scale tests with a focus on aeroacoustics.

Keywords: Acoustic Issues, New Testing Technology
Abstract: Acoustically lined panels are known to well absorb high-intensity sound propagating through duct such as nacelle of aircraft. The larger the bypass ratio of the future turbofan engine is, the shorter the nacelle length is to attain the better fuel consumption. The shorter nacelle in return requires more sound attenuation due to the distortion to fan blades and the reduced area of lined wall. Thus, the shorter nacelle requires the acoustic liners attenuate more sound under high-speed grazing flow inside nacelle. As one solution to technical challenge, the authors proposed a new concept of acoustic liner taking advantage of a fine perforated film (FPF). A resonance type acoustic liner combined with FPF showed better sound attenuation under grazing flow conditions. The research and development on the new concept of acoustic liner, including computational design, flow duct rig test, and small turbofan engine test, is overviewed.

Keywords: Axial Compressors, Acoustic Issues
Abstract: Modern civil turbofan aero-engines are faced with the challenge of noise control in a shorter nacelle and a larger bypass ratio fan design, and the concept of soft vanes, in which fan outlet guide vanes (OGV) are implemented with permeable surfaces, is proposed to further reduce the rotor-stator interaction noise in future aero-engines. A three-dimensional cascade model is used to study the noise reduction of perforations on OGVs under practical situations. The effects of spanwise coupling of the unsteady loading are studied and comparisons are made between a fully coupled case and a decoupled situation. The noise reduction effects of a perforated-plate based soft vane design under practical background mean flow at different operating conditions are then estimated using an in-house impedance model that accounts for the tangential mean flow and other practical factors.

Keywords: Others
Abstract: The Sustainable Flight National Partnership (SFNP) was launched in the President’s 2022 budget and is intended to accelerate the maturation of the most promising yet high risk aircraft and engine technologies in the 2020s to enable 2030s in-service impact with significant reduction in fuel consumption and emissions up to 30% lower than the highest performing aircraft in service as of December 2021 and contribute to meeting the goal of net-zero greenhouse gas (GHG) emissions by 2050 as articulated in the 2021 U.S. Aviation Climate Action Plan. The Advanced Air Transport Technology Project (AATT) is part of the NASA research portfolio that supports SFNP goals. AATT conducts research to identify and mature promising technologies that will enable cleaner, quieter subsonic transport airplanes to meet national and international sustainable aviation goals including lower environmental impact, increased efficiency, and reduced noise around community airports. The primary AATT research themes that support SFNP are Electrified Aircraft Propulsion (EAP), Transonic Truss-Braced Wing (TTBW) and Advanced Propulsors. An overview of progress towards the SFNP goals will be presented.

Keywords: System and Control, Optimal and Intelligent Technology, Others (Control and Diagnostics)
Abstract: This paper proposes a novel approach for robust control synthesis for uncertain singular nonlinear systems. Admissible uncertainties of various nature are considered through a generic description via polynomial differential equations and polynomial inequalities. Feedback controllers are considered in such a generic description via a vector of design parameters. It is explained how a controller that makes the system robustly globally asymptotically stable can be obtained by solving three convex optimization problems.

Keywords: Others (Control and Diagnostics)
Abstract: In turbofan engines, the increase in fuel temperature due to fuel pump recirculation makes the cooling of lubrication system difficult. Increasing air-cooling capacity as a countermeasure for this problem has resulted in higher fuel consumption rates and increased weight of auxiliary equipment. Various variable displacement pumps, such as electrified fuel systems, have been investigated as a way to reduce fuel pump recirculation. This study was conducted on a double gear pump (DGP) with a variable displacement mechanism that can switch and halve the discharge flow rate. This system has the advantage that the variable displacement mechanism can be realized with a relatively simple mechanism. However, because the discharge flow rate of the pump is changed significantly in a short period of time, there is a risk of fuel pulsation. This study reports the results of an Amesim simulation to investigate the reduction of pulsation during mode switching.

Keywords: Optimal and Intelligent Technology, Others (Control and Diagnostics), System and Control
Abstract: A software development process capable of supporting DO-178C software level A was constructed for the purpose of improving the reliability of aircraft engine control software. By adopting a model-based development method and modern tools, an efficient development process was achieved while minimizing the increase in development man-hours required for obtaining certification.

Keywords: System and Control, Others (Control and Diagnostics)
Abstract: Reheat turbofan engines require concurrent control of engine operating line and speed. To control them, the control system that takes into consideration the effects of both duel and exhaust nozzle is needed. Multivariable control is needed for this purpose. In this paper, we create system that be able to with H control method. Control system design that can be controlled from IDLE to MIL with main fuel flow and exhaust nozzle area.

Keywords: General Heat Transfer, Film Cooling, Internal Cooling, Novel Cooling Technology, Heat Transfer Measurement
Abstract: Additive Manufacturing (AM) is set to be a game-changer in the design of internally-cooled hot gas components for gas turbines. AM allows for the much more intricate designs required for highefficiency, hydrogen-burning turbines. Therefore, the impact of AM on pressure losses and heat transfer in internal cooling channels is of acute importance to thermal engineers. In this paper, a new test rig for the measurement of the two above-mentioned parameters will be presented along with the measurement data for a selected number of tested geometries. These consist of test specimens with different hydraulic diameters (4 and 10 mm) and printing directions of 0°, 45° and 90° to the build plate. In addition, the numerical simulations of these geometries will be discussed. The focus is on the comparison with the experiments and matching with different roughness levels.

Keywords: Novel Cooling Technology, Gas Turbines for Electric Power Generation, General Heat Transfer, Film Cooling, Internal Cooling
Abstract: The paper proposes and evaluates an internal tetrahedral lattice structure for additively manufacturing impingement/effusion cooling for gas turbine hot parts. Polymer additive manufacturing was used to fabricate specimens to match the Biot number of an actual gas turbine. Three types of specimens were fabricated, including a baseline case, a pin-fin structure case, and a tetrahedral lattice structure case. Numerical simulations were conducted to analyze the flow pattern on the internal side and examine the effect of the tetrahedral lattice structure on impingement/effusion cooling. Infrared thermography was used to measure the overall cooling effectiveness on the specimen surface. The results showed that the tetrahedral lattice structure improved cooling effectiveness by 3.59%, 6.46%, and 2.69% at M=0.4, M=0.6, and M=0.8, respectively, compared to the baseline case.

Keywords: General Heat Transfer, Film Cooling, Internal Cooling, Thermal Management of Structures, Novel Cooling Technology
Abstract: Gas turbine blade cooling was crucial for enhancing turbine efficiency and durability. In particular, wedge-shaped channels were commonly used for trailing edge internal cooling. However, conventional cooling channel structures such as pin fins had limitations in achieving uniform heat transfer. To address this issue, a new approach using bionic cooling structures generated through self-organized equation had been proposed. This study investigated the performance of self-organized structures in comparison to pin-fin structures. Results showed that self-organized structures provided better heat transfer performance with lower pressure drop, and more uniform temperature distribution. Specifically, under the same level of pressure loss, the selected self-organized structure decreased the pressure drop by 47%, reduced the temperature variance by 51%. These findings highlighted the potential of self-organized structures as a promising alternative to conventional cooling channel structures for gas turbine blade cooling.

Keywords: General Heat Transfer, Film Cooling, Internal Cooling, Novel Cooling Technology, Heat Transfer Simulation
Abstract: This study inserts a diamond model, a type of lattice structure based on triply periodic minimal surfaces (TPMS) that exhibits outstanding thermomechanical characteristics, in a wedge-shaped channel of a gas turbine blade trailing edge to improve flow uniformity and enhance heat transfer. The flow and heat transfer are revealed by numerical simulations for stationary and rotating conditions. The results are compared with the conventional pin fin structure at the Reynolds number of 10,000 with rotation numbers of 0.0-0.28. It is found that the diamond model reduces recirculation flow at the inner wall, improving heat transfer near the tip and outlet. The flow fluctuations due to the rotational effects are minor in the diamond model, considerably reducing the heat transfer differences between the leading and trailing walls. Although the diamond model causes high-pressure losses, the diamond model provides much higher total heat transfer than the pin fin structure by about 155-179%.

Keywords: Conjugate Heat Transfer, General Heat Transfer, Film Cooling, Internal Cooling, Heat Transfer Simulation
Abstract: In the cooling design process of double-wall turbine blade, it is necessary to accurately calculate the temperature of the outer surface. Existing researches mainly rely on fluid-solid coupled simulation. However, it costs high computational resource for double-wall blade. Therefore, an equivalent heat transfer model is proposed in present study to describe the overall heat transfer capacity inside the double-wall structure, and a random forest model is established to predict the equivalent heat transfer coefficients. As a result, the established random forest models can accurately predict the heat transfer coefficients of the three characteristic regions on the inner side of the outer wall, with the mean relative errors of all samples in the test dataset only 3.13%, 3.77%, and 2.95%, respectively. And the relative error is only 1.02% comparing the calculated temperature distribution by the heat conduction calculation using predicted heat transfer coefficients to the complete fluid-solid coupled simulation.

Keywords: Heat Transfer Simulation, General Heat Transfer, Film Cooling, Internal Cooling, Conjugate Heat Transfer
Abstract: Transpiration cooling is one of the most promising cooling methods for aero-engine thermal protection due to its excellent cooling performance and temperature uniformity. The real blade and combustor in aero engine are composed of walls with different curvatures, which will have great influence on the application of the cooling structure. However, simplified flat structures of transpiration cooling are generally employed in the current numerical studies and experimental models. Hence, the cooling mechanism of transpiration cooling in the curved surface model is not clear, which is not conducive to its practical application. Herein, the effects of wall curvature, porosity and mainstream pressure gradient on the cooling efficiency and cooling uniformity of transpiration cooling structures are discussed in detail through experiments and numerical simulation methods. Besides, the cooling efficiency and cooling uniformity of structure on suction side and pressure side under different blowing ratios are analyzed, providing guiding suggestions for the design of transpiration cooling structure on curved surfaces.

Keywords: General Heat Transfer, Film Cooling, Internal Cooling, Conjugate Heat Transfer, Heat Transfer Simulation
Abstract: The laminate structure has been widely used in aero-engine turbine blades. In this paper, a univariate sensitivity analysis of nine geometric variables of the 161-laminate structure was conducted. The linear correlation coefficient between the mass flow rate of cooling air per unit area and the porosity of film holes was found to be 0.99. The main parameters that affect the average temperature of the outer surface of the laminate structure are the diameter of the impingement hole and the incident angle of the film hole under a certain mass flow rate of cooling air. A two-step optimization strategy was proposed based on the results of the sensitivity analysis. Results obtained from the strategy indicated that the average temperature of the outer surface of the optimized structure was reduced by 40.6K while the mass flow rate of cooling air was reduced by 5.4%.

Keywords: Turbines
Abstract: The characteristics map is the main illustration of the performance of a turbomachinery. However, the data regularities hidden in the characteristics map are seldom investigated over different turbines. To explore the laws in characteristics maps and to build a mathematics model to describe the maps, 18 axial turbine maps were collected. The pretreatment is performed on the maps to interpolate and correct performance lines, firstly. Then, the peak efficiency points and chocked mass flow distributions of each speed line are analyzed with the methods of parameter shift and generalized linear regression. Finally, a data-driven reduced order model is built to describe characteristics maps. The results shows that there are several generalized linear correlations between performance parameters and the speed. Only several coefficients are enough to describe the characteristic map using the reduced ordered model.

Keywords: Turbines, General Heat Transfer, Film Cooling, Internal Cooling, Gas Turbine Performance
Abstract: Accurately estimating turbine cooling requirements at a preliminary design stage is crucial for modeling the overall propulsion system. The operating conditions of both compressor and combustor are significantly influenced by these requirements. Empirical cooling models have thus far provided reliable initial estimations. However, for next-generation aero-engines, this empirical data becomes outdated. An alternative semi-empirical approach based on an established cooling model is built into a collaborative turbine preliminary tool chain to address this challenge. This cooling model is calibrated for the two cooled high-pressure turbines developed by P&W and GE within the NASA Energy Efficient Engine (E3) program. The resulting data is discussed to provide a better understanding on design decisions affecting cooling requirements. This work concludes with a discussion on the most relevant approaches for reducing cooling requirements.

Keywords: Turbines, Others (Aerodynamics and Design), General Heat Transfer, Film Cooling, Internal Cooling
Abstract: This paper presents an efficient multifidelity process for the design and analysis of cooled axial flow turbine components. The process is initiated with data from a 0D performance model. First, a 1D meanline method is used to define the general turbine layout and the cooling requirements. Then, the blade profile geometry and the boundary conditions for a cooling design method are generated using 2D through-flow and passage flow simulations. Finally, the 3D blade and internal cooling geometry are analyzed using 3D computational fluid dynamics (CFD) simulations. The process is applied to a nozzle guide vane of a next-generation turbofan engine, and the resulting data is compared and evaluated. This approach provides an efficient and effective means of validating novel engine concepts by refining and assessing turbine components in a timely manner.

Keywords: Centrifugal and Mixed-Flow Compressors, New Aircraft Propulsion Concepts, Aircraft Electrified Propulsion
Abstract: A variety of architectures are available for the sustainable transformation of aircraft propulsion, ranging from pure electric, based on batteries and electric motors, to hybrid electric. These hybrid electric engines are an extension of the electric architecture with a gas turbine burning sustainable fuels. Most of these architectures still require a compressor, either as part of the gas turbine or to supply air to the fuel cell. The different system integration specify new demands on the compressor compared to the compressor in a conventional turbofan. When fuel cell systems are used, further requirements for the compressor arise due to the necessary matching between the fuel cell stack and the air supply system, which are summarized. These new requirements must be considered during the design phase. The compressor design is based on the requirements from the modeling of the propulsion architecture. Subsequently, the main dimensions can be determined followed by the meridional shape and the blade modeling before the design is recalculated using computational fluid dynamics. Finally, the design is adjusted until the required boundary conditions are achieved. This paper reviews new aircraft propulsion architectures and fundamentals of compressor design to outline the compressor requirements in future aircraft propulsion architectures.

Keywords: Axial Compressors, Computational Fluid Dynamics
Abstract: Corner stall, which often occurs at the junction of blades and endwalls, decreases the aerodynamic performance of compressors. To suppress this corner stall, much research has been conducted on optimization of tip clearance flow and slot jet flow1,2). In this study, a means was devised to further suppression of the corner stall by utilizing an ejector effect of the slot jet flow to suction separated flow at the corner stall region. A detailed 3D flow analysis was conducted using Detached-eddy simulation (DES). As a result, the effectiveness of this means to suppress the corner stall was confirmed.

Keywords: Axial Compressors, Unsteady Flow and Stability Enhancement in Compressor Flow Control
Abstract: Modern aero-engines are facing the predicament of inlet swirl which can be generated by S-ducts, boundary layer ingesting design, and so on. First, experiments were conducted on a low-speed fan to explain whether circumferential uniform and non-uniform bulk swirl with the same intensity have the same impact on the performance. Then, the availability of the foam-metal type impedance boundary-controlled (IBC) casing treatment (CT) on the performance recovery of the fan was evaluated. The results showed that the uniform bulk swirl which generates the same pressure characteristic as the offset bulk swirl has a higher swirl intensity and a lower efficiency loss on the performance of the fan. The IBCCT extended the stall margin for over 7.7% for clean inlet and over 11% for the paired swirl inlet.

Keywords: Unsteady Flow and Flow Control in Turbine, Axial Compressors
Abstract: Axial compressors tend to experience significantly increased losses during off-design operation and are prone to flow separation under high aerodynamic loads. Active flow control (AFC) presents a way to counteract this by means of local injection or aspiration, in order to obtain more favourable momentum distributions. It is a strength of active injection methods that the injection rates may be adapted during compressor operation, in order to maximise the benefit at different operating points. This paper investigates the potential of varying the mass-flow rate of a suction-side stator injection, in order to improve the off-design performance.

Keywords: Turbines, Computational Fluid Dynamics, New Concept
Abstract: The VANT is one of the variable geometry components of the variable cycle gas turbine engine to meet the power requirement at part load conditions by controlling the mass flow rate through the engine turbine section. However, the provision of the part clearances near the hub and casing endwall allows the leakage flow to occur which further increases the loss at the exit of the turbine nozzle vane. The provision of the pivot to hold the vane in endwalls creates a blockage to the leakage flow and changes the flow field of the turbine nozzle passage. As the operating Reynolds number of the LPT is of the order of 105, flow experiences a transition between laminar and turbulent flow regime. Hence, in the present study, two different turbulent models i.e. widely used SST k-ω and SST γ-Reθ were selected to analyse the part clearance flow field. The flow field is analysed using nondimensional vorticity superimposed by streamlines at different streamwise planes. The SST k-ω model predicts higher vorticity extent in the region near endwalls and vane tip whereas SST γ-Reθ model predicts higher vorticity extent in the region near vane and pivot surface. SST γ - Reθ model predicts 3 to 5% lower mass flow averaged total pressure loss coefficient at the exit of the nozzle vane.

Keywords: Turbines, Others (Aerodynamics and Design), Computational Fluid Dynamics
Abstract: Although it is well known that the tip gap affects the performance and the efficiency of a gas turbine, this negative influence cannot be avoided. Many methods have been developed to minimize the resulting aerodynamic losses. However, all these methods lead to extensive additional manufacturing effort and cost. This paper explores whether it is possible to decrease the tip gap losses through a simple and inexpensive inclined grinding of the blade tip of the high-pressure turbine rotor blades. A numerical study is carried out, comparing different tip gap geometries with a reference configuration. Next, a squealer cavity geometry is added to the tip of the blade and its influence on the polytropic efficiency of the high-pressure turbine is investigated. The study shows that both, divergent and convergent inclination of the blade tip reduce the efficiency of a gas-turbine based aeroengine by up to 0.52 percentage points. The squealer cavity geometry increases the polytropic efficiency by up to 0.132 percentage points in comparison to the flat tip case.

Keywords: Turbines, Computational Fluid Dynamics, Others (Aerodynamics and Design)
Abstract: This paper presents the aerodynamic performance of a two-stage low-pressure shrouded turbine using CFD. Two types of seals (stepped and straight seal) were applied to the blade tip for each stage. Parametric studies were performed for various clearance sizes, and the variation in leakage fraction and isentropic efficiency of each stage (including the whole stage) was analyzed. As the tip clearance increased, the leakage fraction increased and the stage efficiency generally decreased. Also, the discharge coefficients obtained from 3D shrouded turbine simulation and the labyrinth seal-only simulation were compared. The discharge coefficient of the 3D shrouded blade seal was predicted to be about 30% lower than that of the labyrinth seal-only cases.

Keywords: Turbines, Computational Fluid Dynamics
Abstract: Improving the off-design performance and turndown capability of power cycles for concentrated solar power (CSP) applications is critical considering possible heat source and cooling fluctuations. In this paper, the effect of different geometrical blade parameters on the aerodynamic performance of large-scale axial turbines operating with supercritical carbon dioxide (sCO2) mixtures at both design and off-design conditions is evaluated. 3D steady state multi-stage Reynolds-Averaged Navier Stokes equations Computational Fluid Dynamics (CFD) simulations are performed where the k-ω SST turbulence model is used. The leading-edge thickness, inlet wedge angle, stagger angle, stator/rotor axial gap, and number of stages are varied within specific ranges defined based on practical considerations to improve the turbine operational flexibility through extending the off-design operation range. The results revealed that the stagger angle has the largest influence on the operational flexibility. A change of 17.1% in the minimum allowable part-load mass flow rate relative to the design value was observed corresponding to a change in the stagger angle between -5° and +5° from the reference design angle. This increase in the stagger angle resulted in an increase in the design point total-to-total efficiency of 2.3 percentage points. The leading-edge thickness had the least influence with a maximum change in the minimum part load mass flow ratio of 0.63% for the investigated range and a negligible change in the design point efficiency.

Keywords: Aeroelasticity and Flutter, Computational Fluid Dynamics, Structural Mechanics
Abstract: Axial compressors of aero engines should achieve both high efficiency and low weight. Recently, blade-integrated disks (blisks) have been adopted to meet these requirements. Because of this trend, problems of high-cycle fatigue (HCF) associated with forced response vibrations are occurring more frequently these days. Rotor blade fatigue can be caused by not only wakes and potential effects of adjacent stator vanes but also the asymmetric geometries inside compressors. Even the measurement probes can be the cause of severe blade failure. Although, there have been many previous studies on developing simulation approaches for the accurate prediction of blade vibration induced by adjacent stator vanes, studies of vibration induced by the measurement probes have been scarce. Thus, in this study, the vibration induced by measurement probes is studied using fluid structure interaction (FSI) simulation approach and an experimental test rig. The ways to predict and reduce blade vibration are established and validated.

Keywords: Aeroelasticity and Flutter, Computational Fluid Dynamics, Structural Vibration and Damping
Abstract: Even though flutter could cause a catastrophic damage especially for a rotational machine, it still is a difficult task to predict an onset of a flutter accurately. Thus, this study aims to construct and demonstrate a two-way coupled fluid-structure interaction (FSI) methodology for a flutter prediction and conduct a validation against a series of a thin hydrofoil experiment. A two-way coupled FSI methodology is developed on ANSYS workbench. Two different turbulent models, k-omega SST and SAS SST, are evaluated, and it is clearly seen that the k-omega SST does not result unsteady motion whereas the SAS SST model resolves detailed unsteady vortex topology. Also, by performing two-way coupled FSI simulation, SAS demonstrated its capability to reproduce flutter motion. Then, the methodology is applied over different inlet conditions, and an onset of the flutter is successfully captured. The final manuscript will further discuss analysis of blade motions during flutter.

Keywords: Computational Fluid Dynamics, Others (Aerodynamics and Design)
Abstract: Numerical analyses are performed to clarify the thickness and scale factors of a fluidic oscillator on the flow field and frequency performance. Specifically, 10 m/s ideal air is injected into fluid oscillators with different thickness and scale factors, and the oscillation frequency performance is evaluated. The results show that the tangential velocity of the monitoring point grows as the thickness of the oscillator increases, but the amplitude of the increase gradually decreases. The influence of the boundary layer may essentially be ignored after the thickness reaches 3.375 mm and above, and the oscillation frequency remains largely unaltered. The numerical results additionally demonstrated that the tangential velocity grows as the scale increases when the oscillator's scale is less than three times and then tends to remain consistent. With the increase of scale factors, the oscillator frequency gradually decreases, but the rate of reduction slows.

Keywords: Axial Compressors, Aeroelasticity and Flutter, Unsteady Flow and Stability Enhancement in Compressor Flow Control
Abstract: High bypass civil engines or military engines fan encounter strong inlet distortion. During crossing inlet distortion, first harmonic vibration power damages blade severely. The worst scenario is not to increase the fan speed. In this study, both blade vibration strength and fan performance are evaluated through response analysis and unsteady RANS CFD simulations. As the blade passes through the distortion in one revolution, the shock wave of the tip vibrates, which causes the second blade natural frequency and strong resonance in the first mode. To reduce blade vibration, we designed a blade with a thicker root chord length and wider chord and reduced blade number, pushing the 2nd mode to a higher frequency and 3rd mode. Comparing flow field with base and redesign blade, adiabatic efficiency decrease is slightly 0.3% and stator exit flow field still does not change. It was confirmed that this method is effective for the vibration control of distortion fans.

Keywords: New Diagnostics Technique, Axial Compressors, Small Gas Turbine Technology
Abstract: In this study, an assessment of the performance of an industrial gas turbine during compressor fouling conditions is undertaken. The assessment is carried out through a performance diagnostic method previously reported in literature. The diagnostic method identifies and isolates faults in the components of the gas turbine, and considers health parameters of the compressor (efficiency and flow capacity) estimated by a digital-twin. The digital-twin is integrated within a gas turbine system operating in the field. Data processing of the compressor efficiency and compressor flow capacity was required to obtain a meaningful trend of the compressor health indices. Results demonstrate that the previously reported diagnostic method applied to the problem of compressor health parameters estimated by the digital-twin can be a powerful tool to initiate maintenance actions on axial compressors before gas turbine performance deteriorates.

Keywords: New Diagnostics Technique
Abstract: This work proposes a novel method for measuring the three-dimensional (3D) temperature distribution of premixed flames. Cesium chloride was added to the flame as fluorescence particles, and two high-speed cameras equipped with different narrow bandpass filters were utilized to capture the fluorescence of cesium atoms in two wavelength bands. By using a fiber endoscope bundle, a total number of nine projections at each band were recorded, and the temperature field was reconstructed by a tomographic algorithm. In order to validate the effectiveness of this method, a series of experiments have been conducted on a laboratory-scale methane/air-premixed flame. The reconstructed temperature was compared with the thermocouple measurements, and the results obtained demonstrate the capability of the system to determine the premixed flame temperature on a 3-D basis.

Keywords: New Diagnostics Technique
Abstract: This paper reports a 3D schlieren technique called fiber based schlieren tomography (FBST) which combines a fiber-based schlieren system and computed tomography to measure the 3D density fields of flows with improved temporal resolution and compactness. The FBST was able to measure the volumetric density distribution with a field-of-view of 38 mm × 38 mm × 38 mm at a frame rate of 5 kHz. The FBST method was demonstrated on a supersonic CO2 jet to measure the high-speed 3D density fields.

Keywords: General Heat Transfer, Film Cooling, Internal Cooling, Heat Transfer Simulation
Abstract: The effect of coolant crossflow on film cooling effectiveness on the surface of a model turbine blade is investigated numerically. One or two rows of laid-back fan-shaped holes are arranged on the pressure and suction surfaces, respectively. The numerical results show that the film cooling effectiveness can be strongly affected by the internal crossflow effect. On the pressure surface, the internal crossflow causes an obvious flow bias, which increases the momentum of the coolant and deteriorates the wall attachment effect of the coolant. The film cooling effectiveness under crossflow conditions is lower than that of the plenum conditions. On the suction surface, the internal crossflow has little influence on the film cooling effectiveness, and the effectiveness under crossflow conditions is consistent with that of the plenum conditions. Additionally, the film cooling effectiveness of single and double rows of film holes at different crossflow velocities is also discussed.

Keywords: Turbines, Others (Aerodynamics and Design), General Heat Transfer, Film Cooling, Internal Cooling
Abstract: In order to improve the thermal efficiency of gas turbines, efficient cooling concepts for turbine vanes are becoming increasingly important. However, evaluating the performance of a cooling design is computationally intensive and usually requires a coupled CFD-FEM simulation. This approach is not practical in the early design phase when the cooling design is frequently changed. To overcome this limitation, a simplified yet physical approach is required to develop an initial cooling design.

This study presents a comprehensive approach for turbine vane cooling design that is integrated into an optimization tool chain. The model uses a vane geometry model, aerodynamic flow field, and coolant conditions from an internal turbine design tool chain. The cooling geometry is modeled in multiple radial sections using variable geometric parameters to account for variations in airfoil geometry and flow field. Both internal cooling, such as impingement or convective cooling, and external cooling, such as film cooling, are considered. This approach enables significant improvements in cooling design by reducing cooling air requirements as well as optimizing temperature distribution and thus minimizing thermal stresses during the early design phase. Consequently, a detailed 3D model of the vane is created with substantially reduced effort.

Keywords: General Heat Transfer, Film Cooling, Internal Cooling, Conjugate Heat Transfer, Others (Heat Transfer)
Abstract: This study investigates the effect of pin-fin diameter on the cooling performance of impingement/effusion cooling, a widely used method for cooling hot components of gas turbines. The cooling performance was evaluated using numerical methods and analyzing the overall cooling effectiveness, accounting for all heat transfer mechanisms, including convective and conductive heat transfer inside the structure. The study examined three fin diameters (1d, 2d, 3d) for both double-layer and triple-layer impingement/effusion cooling shapes, resulting in a total of six variables. The coolant mass flow rate was set to achieve a blowing ratio of 1.0. The results demonstrated that increasing the fin diameter improved cooling performance by enhancing the effect of conductive heat transfer. Furthermore, the results supported our inferences that as the volume of the internal structure increased, the cooling performance also increased.

Keywords: Computational Fluid Dynamics, Turbines, Conjugate Heat Transfer
Abstract: The effect of impinging distance and jet Reynolds number on conjugate heat transfer of an impingement/film cooled turbine blade leading edge model is investigated numerically. Three typical jet Reynolds numbers, 6000, 12000, and 18000 are studied. Impinging distance P of 3djet, 4djet and 5djet are employed, where djet is the impingement hole diameter. The numerical results show that the flow filed for impinging distance of 3djet and 4djet is similar where two symmetrical vortices are generated beside each impinging jet. However, only one vortex is generated by each impinging jet on the suction side for impinging distance of 5djet. The coolant attaches more tightly on the pressure side for 𝑃𝑑𝑗𝑒𝑡⁄=5 , resulting in higher uusselt number. The uusselt number is highest for 𝑃𝑑𝑗𝑒𝑡⁄=3 and lowest for 𝑃𝑑𝑗𝑒𝑡⁄=4 at each jet Reynolds number. The overall cooling effectiveness is slightly influenced by impinging distance. The heat transfer performance becomes better with the increase of jet Reynolds number. The temperature uniformity becomes better with the increase of impinging distance. In the confined space of blade leading edge cavity, a suitably larger impinging distance can achieve better heat transfer performance and more uniform temperature distribution.

Keywords: Conjugate Heat Transfer, Heat Transfer Simulation
Abstract: The swirled cooling air supplied by pre-swirl system is crucial for limiting turbine thermal fatigue. By considering wall temperature distribution variation of the rotor disc, this will provide a more realistic thermal boundary condition. This study investigates thermal conjugate effect on heat transfer characteristics of rotor-stator pre-swirl system for pre-swirl inflow jet Reynolds numbers Rew of 1.3 × 105 ~ 6.8 × 105 and rotational Reynolds number ReΦ of 3.2 × 105 ~ 6.4 × 105. The results demonstrate under-prediction and over-prediction of Nusselt number Nu distributions arising from conjugate analysis, at low and high radial regions respectively. Significant under-prediction of jet-impingement heat transfer greatly distort overall heat transfer characteristics at higher pre-swirl inflow conditions due to current assumption-based Nusselt evaluation method, posing regional overheating risks under current understanding of cavity heat transfer characteristics. Temperature profiles within cavity serving as reference temperature in Nusselt evaluation can better ensure comparability regardless of conjugation.

Keywords: Axial Compressors, Computational Fluid Dynamics, Others (Aircraft Engines)
Abstract: Boundary Layer Ingestion (BLI) may be one of methods to increase the total performance of the next generation airplanes to achieve the electrification and further weight reduction [1, 2]. However, due to the non-uniform inlet flow, the engine performance has not yet been resolved. Additionally, although atmospheric air includes amount of water vapor (occasionally liquid), the effect of moist air on the BLI engine has never been studied. In this study, unsteady moist-air flow simulation of full-annulus axial flow compressor blade rows assuming a BLI condition is conducted. Under the BLI condition, a large flow separation on the stator blade was locally observed as the comparison to those of the uniform flow condition. In the moist-air condition, evaporation occurs in the rotor flow passages, and the effect of evaporation on the flow under the BLI condition was distinguished.

Keywords: Axial Compressors
Abstract: A review of the tandem compressor aerodynamics is given. The aerodynamic effects of the tandem configuration are explained, and the sweet spots are identified. Data of existing tandem designs is collected and presented in appropriate diagrams, in order to identify the trends and reasonable parameter selections. Both the midspan and endwall flow is addressed and a critical assessment of the tandem design is given. Promising directions for further research are identified.