In response to the performance requirements of high-efficiency cooling, high-reliability and long-life of turbine blades, the influences of the film hole inclination angle and the film plate thickness of a typical double-wall structure on the overall cooling efficiency, the maximum thermal stress and the maximum thermo-mechanical stress of the structure were analyzed based on the numerical method of fluid-thermal-solid coupling. The inner surface of the film plate generated large thermal stresses, especially at the edge of the film holes and pin-fins. As the film hole inclination angle decreased from 90° to 30°, the overall cooling efficiency increased significantly, but the thermo-mechanical stress under centrifugal force also increased sharply. When the film plate thickness was small, the overall cooling efficiency was affected by the impingement cooling and unevenly distributed. With the increase of the film plate thickness, the thermo-mechanical stress of the film holes and pin-fins under centrifugal force was significantly reduced.

Due to the complex operating environment in aero-engine combustors, the laws governing the effects of multi-parameter coupling on the atomization characteristics of a kerosene jet in a swirling crossflow remain unclear. Utilizing a laser particle sizer and planar laser imaging techniques, data on droplet size and spray cone angle under the cross-effect of multiple parameters, including air pressure, air temperature, swirler pressure drop ratio, fuel temperature, and fuel-air ratio, were obtained. Semi-empirical models incorporating dimensionless parameters such as the Weber number, Reynolds number, Ohnesorge number, and swirl number were developed. The test results indicated that the correlation coefficient between the droplet size and the gas Weber number was as high as 0.964. The Weber number was mainly affected by the inlet pressure and the pressure drop ratio of the swirler, while the swirl intensity had a relatively minor impact on the droplet size. The correlation coefficient between the spray cone angle and the swirl intensity was 0.866, indicating that the fuel distribution was significantly affected by the swirl intensity, and this effect was notably stronger than that of the momentum ratio. The spray characteristic data and semi-empirical models established under swirling conditions could provide valuable support for optimizing aero-engine combustor performance and designing cross-flow atomizing nozzles.

To address the challenge of oxygen volume fraction analysis in the inerting process of multi-compartment fuel tanks for civil aircraft, an oxygen volume fraction analysis model based on flow pattern recognition with the incorporation of a gas blending correction term was proposed. By incorporating the gas blending effect between adjacent compartments into the modeling process, the model became more adaptable to real-world engineering scenarios. Through engineering applications on a certain regional airliner platform, the blending coefficient correction and model simulation accuracy verification were completed based on 16 development test flights and 4 compliance test flights. The results demonstrated that the model’s simulation error remained within a lower limit of −0.26%, meeting engineering requirements. It revealed that during the post-flight ground phase, adjacent compartments can achieve oxygen volume fraction convergence within 15 min due to mixing effects, verifying the promoting role of blending in inerting uniformity. Neglecting blending effects could lead to significant deviations between simulation data and flight test data during the descent phase, with oxygen volume fraction errors reaching 1.5% in the forward compartment during the post-flight ground phase. The research outcomes could provide a reliable technical support for inerting system design and airworthiness compliance verification, helping to gain recognition from multiple national airworthiness authorities.

To verify the feasibility of the jet impinging-regenerative channel composite cooling technology, the steady-state liquid crystal technology was used to measure the Nusselt number of ambient air under the initial crossflow cooling, jet impinging cooling, and jet impinging-initial crossflow composite cooling, respectively. The experimental results showed that the heat transfer effects of jet-impinging cooling and jet-impinging-initial crossflow composite cooling were improved by 207.55%—370.24% and 428.35%—545.35%, respectively, compared with the situation of initial crossflow cooling, and the heat transfer performance of jet impinging-initial crossflow composite cooling was better than that of jet impinging cooling under all flow conditions. The optimal relationship among the number of jet holes, jet flow rate, and initial crossflow rate can maximize the heat transfer performance: Jet impinging can greatly improve the heat transfer performance of the target surface, but the improvement amplitude decreased with the increase of flow rate, and the increase of jet holes can improve the uniformity of temperature distribution on the target surface. When the jet touched the target surface and the momentum was suitable, the initial crossflow can further increase the Nusselt number effectively. When the flow rate was too small and the jet cannot reach the target surface, the combined disturbance of the initial crossflow and jet impinging can also improve the heat transfer performance.

In order to improve the high-altitude performance of aviation piston engines, detailed design and research work were carried out from four aspects: one-dimensional theoretical verification calculation of heat exchanger, performance experiment, simulation of heat exchanger with air duct and UAV flight experiment. The one-dimensional theoretical calculation was carried out using the ε-NTU method. The concept of cold side mixing coefficient (η) was proposed, which represented the degree of air side mixing caused by the opening of fins. And the selection and verification of heat exchanger were completed; an engine ground performance experiment bench was built and the impact of the upwind temperature of the heat exchanger on the engine cylinder head temperature was analyzed. Besides, a joint simulation model of heat exchanger with air duct was used to predict the high-altitude effluent temperature of the engine, and flight experiment validation was completed. The results indicated that the temperature of the windward surface of the heat exchanger affected the engine cylinder head temperature directly, and the increase of cylinder head temperature was basically consistent with the increase of windward temperature. Validated by flight tests, the coupled simulation model for the air duct and heat exchanger exhibits a prediction error of less than 3.1% in terms of the engine cylinder head temperature, which is sufficient to meet the accuracy requirements for engineering calculations. If the joint design results of the heat exchanger with air duct can meet the heat dissipation requirements of engine at the highest altitude take off state, the engine water cooling system design can meet the full climbing usage requirements of UAV.

In an attempt to clarify the effect of thermophysical property settings of the mainstream working fluid on the turbine vane cooling effectiveness assessment and their definition principles in the conjugate heat transfer numerical simulation, three-dimensional conjugate heat transfer analysis of the preliminary cooling design of a gas turbine vane was conducted in this study, wherein both the vane surface temperature distribution and the average cooling effectiveness discrepancies with distinct defining methods of the mainstream specific heat capacity, dynamic viscosity and thermal conductivity were carefully examined. Moreover, the influencing mechanism and selection principle of the mainstream thermophysical properties were also analyzed and proposed. Results showed that the mainstream flow and heat transfer characteristics around the vane were dissimilar, resulting from the unequal turbine inlet Reynolds number, passage Mach number and Peclet number of different thermophysical properties, among which the Peclet number was found to play a key role in deriving more accurate temperature profile for the turbine vane. Meanwhile, compared with the specific heat capacity and dynamic viscosity, keeping the thermal conductivity of mainstream consistent with the hot gas could guarantee a more reliable evaluation of the cooling performance for turbine vane.

To solve the problem that the cold blade profile strength reserve and other performance deviate from the design index caused by the traditional gravity center tilting and hot-to-cold transformation methods, an optimization method combining gravity center tilting and hot-to-cold transformation was proposed. The core ideas of gravity center tilting and hot-to-cold transformation included the center of gravity correction based on the blade deformation law and the coordinate conversion based on the deformation of key data points, respectively. Combined with UG automatic modeling, ANSYS secondary development and iSIGHT integrated platform, the optimization process of gravity center tilting and hot-to-cold transformation was realized. The optimization example of a first-stage rotor blade showed that the maximum stress of the cold blade was respectively reduced 47% by the proposed method when the hot blade profile coincided with the target blade profile.

With the advantages of good flame stability and high total pressure recovery coefficient, the small slot wide evaporative fuel supply/flame stabilization integrated flameholder has a good application prospect in the afterburner of wide-range aspirated engine in the future. To investigate the influences of structural parameters on the performances of the flameholder lean ignition and lean blowout, the lean ignition and lean blowout test and cold state numerical simulation of the flameholder with different slot width and hole ratio were carried out in rectangular test section under the condition of air velocity of 40—115 m/s and air temperature of 573 K. The results showed that: (1) with the increase of the hole ratio, the number of vortices in the local recirculation increased, the fuel atomization and evaporation were enhanced, and the ignition and lean blowout fuel/air ratio of the combustion chamber decreased; (2) with the increase of incoming flow speed, the ignition and lean blowout fuel/air ratio of large hole ratio flameholder decreased first and then increased, and the ignition and lean blowout fuel/air ratio of small hole ratio flameholder decreased continuously; (3) with the increase of slot width, the size of vortex system in the local recirculation zone increased, the fuel atomization and evaporation were enhanced, and the ignition and lean blowout fuel/air ratio of the combustion chamber decreased.

To explore the high-altitude combustion performance of the combined ramjet engine combustor, the effects of inlet pressure, temperature, and Mach number on the combustion performance of the duty-cycle evaporator flame stabilizer were experimentally studied under conditions of an inlet pressure of 0.03—0.08 MPa, a temperature of 500—800 K, and a Mach number of 0.1—0.2. The research revealed that rising temperatures contributed to improved combustion efficiency at low equivalence ratios, but the efficiency gain gradually decreased as the equivalence ratio increased. At an inlet temperature of 700 K, as the equivalence ratio increased from 0.38 to 0.48, the rate of increase in combustion efficiency dropped from 10.9% to 2.0%. As the inlet pressure increased from 0.04 MPa to 0.08 MPa, the combustion efficiency at an equivalence ratio of 0.4 increased rapidly from 36.15% to 73.41%. Additionally, within the range of 0.1—0.2 for the inlet Mach number, the combustion efficiency increased and then decreased, with the maximum efficiency occurring at a Mach number of 0.15. Moreover, as the equivalence ratio increased, the optical image distribution of the flame downstream the flame stabilizer gradually expanded, with an uneven flame distribution and a brighter region closer to the lower sidewall; accordingly, the outlet temperature displayed an overall “hook” pattern.

In response to the future development needs for efficient, advanced, zero-emission gas turbines, a system for generating superheated water vapor (200 ℃) was established and an axial-tangential micro-mixing swirl nozzle was designed to conduct experiments on pure oxygen combustion under conditions of water vapor dilution in this study. The results showed that as the flow rate of water vapor (H₂O(g)) dilution increased, the concentration of oxygen decreased, leading to four distinct flame structure processes: attached to the inside of the nozzle, attached to the outlet of the nozzle, flame lifting, and blowout occurrence. Moreover, an increase in flame resistance against blowout with higher equivalent ratios was observed. Subsequently, flame stability with H₂O(g)CO₂/N₂ dilution at different equivalent ratios was investigated, finding that H₂O(g) dilution exhibited better stability compared with CO₂ dilution. Furthermore, flame temperatures under three diluted gases were measured, finding that water vapor (H₂O(g)) dilution yielded the highest temperature. Finally, through PIV analysis of the cold flow field within a glass tube, a prominent reflow area on its exterior was identified, and the distribution of axial velocity demonstrated a minimum point 20 mm above the nozzle exit, which enhanced flame stability and improved resistance against blow-out.

The flow condensation heat transfer characteristics of refrigerant R134a in three types of serrated mini channels were studied using air jet impingement cooling method on the channel wall. The equivalent diameters of the channels were 1.13, 1.18 mm, and 1.44 mm, respectively. The experimental conditions included: vapor quality from 0 to 1, mass flux from 56 to 430 kg/(m²·s), heat flux in ranges of 8.4—44.2 kW/m², and the saturation temperature of refrigerant between 50 ℃ and 70 ℃. The local condensation heat transfer coefficient of the channel was obtained, and the effects of serrated fin geometry, vapor quality, saturation pressure, mass flux and heat flux on the condensation heat transfer were analyzed. The results indicated that the increase in vapor quality and mass flux led to an increase in fluid turbulence, a decrease in condensate film thickness, and enhanced condensation heat transfer. The increase in saturation temperature was accompanied by a decrease in the liquid phase thermal conductivity, liquid vapor density ratio, and viscosity ratio of the refrigerant. This increased the thermal resistance of the liquid film while reducing the shear force at the gas-liquid interface, thereby weakening the condensation heat transfer. The higher heat flux indicated the greater heat transfer coefficient. However, as the vapor quality decreased and the liquid film thickness increased, the effect of heat flux gradually decreased and tended to disappear. For serrated mini channels with the same fin height, reducing the fin spacing can increase the condensation heat transfer coefficient. For serrated channels with the same fin spacing, the effect of fin height variation on condensation heat transfer coefficient was not significant. Based on experimental data, a correlation was proposed to calculate the condensation heat transfer coefficient of different serrated mini channels.

To validate the cooling characteristics of supercritical pressure aviation kerosene on metal test sections under high thermal loads, numerical simulations were employed to obtain relevant experimental conditions. The influence of cooling water flow rate on the heat transfer within the test section walls was discussed. The experiments verified the impact of cooling fuel flow rate on the cooling effectiveness and the temperature distribution on the gas-side wall of the test section. Simulations were conducted to model the effect of gas inlet temperature distribution on the wall cooling performance. The following conclusions were drawn: for each cooling fuel flow rate, there existed a corresponding cooling water flow rate that minimized the impact of the water cooling channel on fuel cooling. As the cooling fuel flow rate increased, both the average and maximum temperatures on the gas side gradually decreased. Experimental data showed that under an average mainstream gas temperature of 904 K in the test section, when the cooling fuel flow rate reached its maximum value of 0.09 kg/s, the highest wall temperature on the gas side can be reduced to 539 K. The experimental values were slightly higher than the corresponding simulation values, with a simulation error within 12%, and the relationship between the maximum temperature of the gas side wall surface and the required cooling fuel flow per unit area of the gas-side wall surface was fitted into an empirical formula. Under the influence of 2200 K gas at the test section inlet, the gas-side wall temperature first decreased sharply and then slightly increased. Supercritical pressure fuel can control the metal wall temperature below 920 K.

The microstructure and elastic modulus evolution of electron beam-physical vapor deposition (EB-PVD) thermal barrier coating were studied. The sintering test of EB-PVD thermal barrier coating at 1150 ℃ was carried out, and the microstructure of the test piece after sintering was observed by scanning electron microscope (SEM), and the evolution of columnar crystal gap in ceramic layer was obtained. The elastic modulus of ceramic layer was measured by nanoindenter. The results showed that the elastic modulus of ceramic layer increased rapidly at the initial stage of sintering and then became stable. In order to relate the elastic modulus of ceramic layer with the micro-structure evolution, a simplified cylindrical crystal model of ceramic layer was established based on the prepared microstructure, and the evolution law of the elastic modulus was obtained by using the sintering model based on the microstructure evolution. The results showed that the microstructure evolution induced by sintering led to the change of elastic modulus of ceramic layer. The sintering model based on the microstructure evolution can accurately predict the evolution law of elastic modulus with sintering time, and the error between the measured value and the calculated value was less than ±20%.

To address the issue of seal life degradation in SR20 aircraft landing gear shock absorbers caused by the replacement of original X-rings with domestic O-rings, a comparative study on the sealing performance differences between O-ring and X-ring rubber seals was conducted through finite element analysis. By establishing a Mooney-Rivlin hyperelastic material model, the sealing behavior under 5 MPa pressure and dynamic reciprocating motion conditions was simulated, with a focus on comparative analysis of key indicators including stress state, contact area, and leakage volume for both seal types. Additionally, based on parametric optimization design, the sealing performance of O-rings and X-rings with different cross-sectional dimensions was compared, ultimately determining the optimal cross-sectional size parameters for sealing performance. The results indicated that the single-seal structure of the O-ring exhibited poorer sealing stability under dynamic conditions compared with the multi-lip structure of the X-shaped rubber sealing ring.

Considering the problem of difficult characterization of degraded features in time-varying operating conditions of aero-engine multi-source sensor data, a prediction model fusing an improved convolutional autoencoder and temporal fusion transformer (TFT) decoder was proposed to enhance the accuracy of single-point prediction of remaining life and the quantification of time-varying uncertainty through multi-scale temporal and spatial feature fusion. The improved convolutional autoencoder utilized its multi-scale convolution unit (MSCU) to extract feature information at different scales from multi-dimensional sensor time-series data, and flexibly captured local dependencies among information in the sequence while avoiding the information loss problem. The TFT decoder efficiently captured the global dependencies in the data and revealed the importance of the features through these mechanisms, thus providing an explanation for the degree of influence of the data features. Test validation using publicly available datasets and comparative analysis with state-of-the-art prediction models showed that the MS1DCAE_TFT model improved the root mean squared error and score index by at least 0.2% and 65.5% on the FD001 and FD003 datasets, while quantile regression predicted the uncertainty quantification of its life intervals, which can provide a reliable engine remaining life prediction solution.

To investigate the impact of blade platform damping devices on the dynamic response of vibration in a certain type of aero-engine gas turbine blades, a friction model was established based on the global-local unified slip model theory. By integrating the finite element analysis software ANSYS and harmonic response calculation procedures, simulation analysis was conducted on grouped three-tooth turbine blades. When the ratio of the normal pressure between the damper and the blade platform to the excitation force acting on the blade fell within an appropriate range, the simulated resonance amplitude of the second-order mode of the blade can be reduced to below 25% of the undamped state. Based on the simulation results, structural designs for two types of turbine blade platform dampers were completed. For high-frequency vibration modes of a certain turbine blade, a high-frequency vibration reduction test plan was designed, and a corresponding test system was constructed. High-order modal vibration reduction tests were carried out on grouped turbine blades, and the first-order resonance amplitude was reduced to 70.72% of the undamped state. By combining simulation results with experimental data, key parameters influencing the vibration reduction characteristics of turbine blades were identified, leading to the development of a comprehensive methodology for the structural design and experimental validation of turbine blade platform dampers under critical modal conditions.

A numerical model of an aero-engine gear transmission system dynamics under “mechanical-inertial-thermal” loading was constructed by considering the speed and power of each axis of the transmission system, the eccentricity of the shaft end due to the deformation of the casing, the material properties of the gears and the friction of the gear surface. The modal characteristics of the system under the real meshing state, including the bevel gear transmission, were described. The form of transmission of vibration in a high-speed gear chain was supplemented. Various forms of coupling such as pitch-pitch, pitch-vortex, pitch-torsion between gear pairs, pitch-vortex, pitch-pitch and other forms of coupling between duplex or triple shafts and their gears were included. The transfer of the above forms throughout the transmission chain was also included. A study of structural vibration avoidance methods for thin-spoke plate gear drive systems was carried out. It was found that by improving the thickness of the spoke plate of the gears in the transmission system of the aircraft development, the inner diameter of the shaft and other structural parameters, it was possible to achieve a reduction of the maximum value of the vibration stress in the gears of the transmission system by 15% to 59% under the prerequisite that the mass of the transmission system can be increased by only 11%.

TC4ELI titanium alloy has a wide application prospect in hydrogen fuel engines, but there is a risk of hydrogen damage. TC4ELI with different hydrogen contents was obtained by high-temperature gaseous hydrogen charging. Combined with scanning electron microscope, X-ray diffraction and other microscopic characterization methods, mechanical tests such as nano-indentation and uniaxial tensile tests were carried out to deeply investigate the influence of hydrogen on the microstructure and mechanical properties. The results showed that hydrogen atoms preferentially dissolved in the β phase, and then diffused from the hydrogen-rich β phase to the hydrogen-poor α phase. When the hydrogen mass fraction reached 0.28% and 0.52%, δ hydride precipitated in α phase and β phase successively. With the increase of hydrogen mass fraction, the elastic modulus and fracture strain of TC4ELI decreased significantly, and the fracture mode gradually changed from transgranular dimple fracture to intergranular brittle fracture due to the influence of hydride. Moreover, the hydrogen damage sensitivity increased with the decrease of strain rate. The low-cycle fatigue life of hydrogen-charged TC4ELI was significantly reduced due to stress-induced hydride cracking at low stress level, while the hydrogen-charged TC4ELI showed better anti-fatigue performance due to hydrogen-induced local plasticity at high stress level.

In order to accurately predict the fatigue life of the hole edge structure of the installation seat with a 2D stress gradient, an improved TCD-SWT (theory of critical distance-Smith-Watson-Topper) fatigue life prediction model was proposed. For the hole edge structure of the installation seat with relatively large thickness, the 2D stress gradient characteristics of the hole edge were considered, and the TCD method was improved. The gradient descent method was used to develop a computational program that extracted the actual stress gradient line at the stress concentration region of the hole edge. By combining the SWT parameters along the gradient line, the critical distance was determined, and a fatigue life prediction model was established. Based on the principle of damage equivalence, a feature simulation design method for the hole edge structure of the installation seat was developed, ensuring that the stress gradient and the distribution of damage parameters along the gradient line at the dangerous section of the simulated specimen closely resembled those of the actual structure. High-temperature fatigue tests on the simulated specimens were carried out to verify the prediction accuracy of the improved TCD-SWT model. The results showed that the improved model significantly enhanced the prediction accuracy compared with the traditional model, with prediction results consistently falling within a ±1.4 dispersion band.

A study on the dynamic testing, analysis and model updating of 2.5D woven resin-based composite plates in the hygrothermal environment was carried out. Firstly, modal tests for the free-free composite plates in the hygrothermal environment were conducted. Secondly, a modal analysis method of composite structures in the hygrothermal environment was specifically developed by taking advantage of a predictive model of the degrading mechanical properties of the fiber/resin matrix materials. Finally, the dynamic model of the composite plate in the hygrothermal environment was updated by exploiting the modal test data. The test results clearly revealed the impact of the temperature and humidity on the natural vibration characteristics of the free composite plates. The proposed modal vibration analysis method was proved to be able to effectively predict the evolving trend of the free composite plate’s frequencies in the hygrothermal environment. After key elastic parameters were updated, the consistency between the tested/predicted natural frequencies of the first 6 modes of the free composite plates was significantly improved. The maximum frequency error decreased from 12.21% to 2.4%. Meanwhile, the equivalent elastic parameters of the composite material in the hygrothermal environment, including the shear modulus, were experimentally derived.

In response to the phenomenon that composite laminates are prone to delamination under fatigue load, which often starts from the edge, analytical methods were used to solve the interlayer stress of composite laminates and obtain the distribution of interlayer stress at each interface under tensile and bending loads. The concept of local average stress was proposed to process the interlayer stress near the free boundary. The improved Hashin delamination failure criterion was used as the delamination criterion to select the local average stress between dangerous layers, which was introduced into the composite Stress-Fatigue life N (Abbreviated as S-N) curve model. The composite material life data under tensile and three-point bending fatigue loads were used for fitting, and the fitted model was used for life prediction. The results showed that the fitting accuracy was high, and the predicted life was within ±2 times the error band. The model was compared with three commonly used S-N curve models, finding that the overall prediction results of this model were the best, with the smallest prediction error for tensile and bending fatigue life.

The complete control law of quad-tiltrotor dynamic flight in the tilting transition corridor was designed by combining the sliding mode theory and interference observer. The tilt angle curve of quad-tiltrotor in the transition flight state was optimized by using genetic algorithm. In the time domain simulation environment, the tilt angle was used as the weight factor of the rotor controller and the fixed wing controller for control assignment. The time-domain response of the control system was analyzed, and the attitude responses before and after the tilt angle curve optimization were compared. The simulation results showed that the designed controller had good dynamic performance (fast response speed) and strong robustness. The effects of horizontal and lateral maneuvering coupling during transition flight were further reduced; the conversion efficiency of transition mode was improved and the attitude fluctuation of quad-tiltrotor was reduced. Thus, the time to reach the extreme values of roll and pitch angles during tilting state significantly decreased, the change amplitude of yaw angle throughout the tilt process was reduced by 25%, and the amplitude of flight altitude change was only 0.75 m.

In order to solve the problems of synergism that have not been considered in the control process of aero-engine binary vector nozzle and some safety performance indexes that cannot be met, a scheme for the cooperative control of aero-engine binary vector nozzle was proposed based on forward and inverse models. Meanwhile, a dynamic command planning algorithm and a fuzzy event-triggered cooperative control algorithm were developed. The dynamic control performance of the binary vector nozzle under various conditions was verified. Simulation results showed that the cooperative scheme eliminated the anti-regulation issue of the nozzle exit area, and the dynamic tracking accuracy of the ratio of the exit area to the throat area was controlled within 5%, presenting great significance for the safe control of the aero-engine.

The interference mechanisms between the rotor passage vortex and tip leakage vortex were analyzed numerically to control the secondary flow losses in a highly loaded rotor with a low aspect ratio and large camber angle. The impact of end-wall fillets on these losses was also investigated. The results revealed that, at the leading edge up to 50% axial chord length, after the horseshoe vortex was evolved and formed into the hub passage vortex, it quickly moved to the upper part of the blade, limiting the development of the shroud passage vortex and reducing the vorticity of the tip leakage vortex. After 50% axial chord length, the high-speed shear effects between the leakage flow and the mainstream were intensified, rapidly strengthening the tip leakage vortex. The shroud passage vortex was pushed away from the suction surface by the combined action of the hub passage vortex and tip leakage vortex, which prevented it from sucking low-energy fluid onto the suction surface and restricted its growth. Due to the entrainment effect of the passage vortex system, low-energy fluid was accumulated at the blade tip, increasing the flow losses and deviation angles there. As a result, the main cause of losses was attributed to the secondary flow caused by the end-wall. The effect of end-wall fillet on the highly loaded rotor with a low aspect ratio and large camber angle was significantly different from the traditional turbines. When the fillet radius was smaller than the boundary layer thickness at the leading edge of the hub, the fillet could weaken the strength of the horseshoe vortex and the hub passage vortex, but it could increase their influential region. This intensified the entrainment effect of the vortex system, reduced the accumulation of low-energy fluid within the 30%—50% axial chord length range on the suction surface, and increased the radial pressure gradient. Therefore, as the radial migration of the hub passage vortex decreased, its entrainment of low-energy fluid on the suction surface was reduced, resulting in reduced vorticity. When the fillet radius was larger than the boundary layer thickness at the leading edge of the hub, the fillet could weaken the effect region of the horseshoe vortex and the hub passage vortex, increasing the accumulation of low-energy fluid on the suction surface close to the blade root and decreasing the radial pressure gradient. Then the radial migration position and vorticity of the hub passage vortex increased, and low-energy fluid was accumulated on the suction surface. Consequently, turbine efficiency decreased as the fillet radius increased.

In view of the high power density integrated electric fuel pump of more-electric engine, which is difficult to meet the demand of fuel quantity supply and regulation of the afterburn state, an afterburn fuel pump along with its regulating system based on intermediate-stage air-driven engine pressurizer was proposed, the mathematical models of the engine component level and the air turbine driving machine were established, and the whole-system numerical simulation combined with the model of the fuel/oil system was carried out. Accordingly, the fuel system and engine performance of the scheme were analyzed under the typical afterburn stage, and compared with the conventional drive mode. The results showed that the fuel system based on the pressurized intermediate-stage bleed air-driven afterburn pump can effectively avoid the energy loss of the conventional fuel system with large regulation ratio fuel supply throttling or bypass return, and reduce the fuel temperature rise under the premise of ensuring the effect of oil cooling. When the engine was under afterburn stage, the bleed air-driven afterburn fuel pump system reduced the extracted power by 46.1% and the main fuel temperature by 27.9% compared with the conventional solution, showing almost no impact on the engine performance.

In order to investigate the effects of different tip winglet structures and cascade transition surfaces on the aerodynamic performance of the compressor cascade, a variable transition surface study was carried out for the suction surface tip winglet under Mach number of 0.5 condition, and the optimal transition surface scheme was selected for the study of the flow field under the variable incidence angle condition. The results showed that the tip winglet structures with different transition surface shapes can improve the flow state of the flow field and reduce the flow loss, and the tip winglet structure with a 15° angle between the transition surface of the tip winglet and the top of the cascade can reduce the total pressure loss of the cascade by 7.69% under the designed incidence angle. Under different incidence angles, the tip winglet scheme had the effect of improving the flow field, reducing the sensitivity of the flow field to the change of incidence angle, and making the flow field of the cascade more stable, and at 6° incidence angle, the scheme reduced the total pressure loss of the cascade by a maximum of 9.89%.

The prohibitive computational cost of the model construction of CoKriging for hundreds or thousands of variables prevents the practical application of CoKriging. Therefore, the surrogate-based optimization design of multi-stage axial flow compressor with hundreds or thousands of variables cannot be conducted. To break the curse of dimensionality of the CoKriging model, a correlation function based on infinite-width Bayesian neural network (IBNN) along with CoKriging modeling method utilizing the IBNN correlation function was established. The theoretical analysis demonstrated that the IBNN correlation function was not dependent on the spatial distance to measure the similarity of any two points. Furthermore, the number of hyperparameters of the IBNN function was fixed as 3, being independent of the number of modeling variables like the existing correlation functions. Therefore, the modeling efficiency can be decreased significantly. To verify the effectiveness and efficiency of the proposed method, aerodynamic problems of axial flow compressor with 5, 31, 144 and 1512 variables were solved. Performance of the proposed method was compared with multi-fidelity deep neural network, and Hierarchical Kriging, etc. The proposed method can build the surrogate models efficiently with adequate accuracy. The surrogate models for the aero-dynamic performance prediction with 144 and 1512 variables can be tuned within 0.1 and 7 seconds.

To address the limitations of existing specific time-frequency transformation methods in extracting complex dynamic features from vibration signals, as well as the feature selection bias in the channel attention mechanism and the improper pooling strategy design in the traditional MobileNetV3 network leading to information loss, a planetary gearbox fault diagnosis method based on MobileNetV3-AHFF and MS-HNNE (Mahalanobis distance hierarchical nearest neighbor graph embedding for efficient dimensionality reduction) with fused time-frequency transformations was proposed. By integrating short-time Fourier transform, continuous wavelet transform, and chirplet transform image coding techniques, the vibration signals of the planetary gearbox were transformed into multidimensional time-frequency images, which were then fused to construct a comprehensive feature image representing the signal characteristics. An adaptive hierarchical feature fusion (AHFF) module was designed to enhance the representational ability of the deep learning network. The supervised MS-HNNE algorithm was used to replace the pooling layer before the fully connected layer of MobileNetV3. During the process of dimensionality reduction, the internal structure and key information of the data were retained. The Softmax function was used to complete the classification task for the low-dimensional data. Compared with the existing fault diagnosis models, experimental results from the DDS (drivetrain diagnostics simulator) and Southeast University planetary gearbox fault diagnosis showed that this method not only significantly improved the diagnostic accuracy, but also enhanced the model generalization ability. Its highest diagnostic accuracy reached 99.9% with certain application prospects.

To improve the lubrication efficiency and application range of bearing jet lubrication, the causes and influencing factors of the air curtain effect within high-speed angular contact ball bearings were investigated. Based on computational fluid dynamics (CFD), a finite element analysis model was constructed for the single-phase flow field characteristics within the bearing chamber. The flow field characteristics of the bearing under different guide/pocket clearances and rotational speeds were analyzed. Based on the Q criterion in the second generation vortex recognition technology, the evaluation method and evaluation standard for the air curtain effect were put forward; and the formation mechanism of air curtain within the bearing chamber was analyzed. The effects of different rotational speeds, guide clearances, and pocket clearances on the air curtain effect were compared. The main influencing factors of the air curtain effect were analyzed using an orthogonal experimental method. The results showed that the air curtain effect within the bearing chamber intensified as the bearing speed increased. Increasing the guide and pocket clearances can reduce the air curtain effect. The impact of rotational speed on the air curtain effect was much greater than the impact of cage clearance changes. The pocket clearance had a more significant influence on the bearing’s air curtain effect compared with the guide clearance.

The nozzle critical area control plan is an important safeguard for the operational safety and performance of aero-engines. However, it is susceptible to multiple uncertainties such as sensor drift and guide vane drift, which may lead to a reduction in the engine’s surge margin and thrust. To quantitatively analyze the impact of sensor and vane drift on the engine, a nozzle critical area control plan design method based on fan surge margin constraints was proposed. A component-level engine model was used to develop the control plans for engine pressure ratio, pressure drop ratio, and difference of rotational speed. The equivalence of the three nozzle control plans was verified, and the robustness of these strategies was analyzed under conditions where speed, temperature, pressure sensors, and high-pressure vanes experienced drift at typical operating points. The results showed that, in case of pressure sensor drift, the pressure ratio control plan exhibited better robustness than the pressure drop ratio control plan. In the case of guide vane drift, the pressure ratio control plan demonstrated the best robustness, followed by the pressure drop ratio control plan, while the slip ratio control plan showed the least robustness.