Oil film cavitation can’t be avoided during normal operation of squeeze film damper (SFD). In order to study the change of rotor fundamental frequency vibration during long-term operation of SFD and the erosion of SFD oil film cavitation effect on the metal surface of inner and outer rings of SFD, experimental study of SFD cavitation effect under low oil supply pressure (0.02—0.05 Mpa) was carried out based on a full-scale aeroengine high-pressure rotor test rig to investigate the change of rotor fundamental frequency vibration during long-term operation of SFD at critical speed, and the effect of oil film cavitation on the internal and external surface morphology of SFD after long-time operation. The experiment results showed that the SFD oil film cavitation could erode the surface of the inner ring of SFD after long-time operation, forming water drop, oval and irregular pit groups, proving that assessing the SFD cavitation effect near the critical speed is a necessary experiment content for the operation safety of SFD under low oil supply pressure.

The performance degradation of the piston pump is mainly caused by the increasing leakage of some key friction pairs. The leakage flow of the key friction pairs was analyzed theoretically, and the total leakage flow of the piston pump was established by introducing the degradation rate parameters of the equivalent clearance and the working condition factors. In the case of considering the measurement error, the HP (Hodrick-Prescott) filtering method was used to filter out the random noise. The degradation model of the piston pump was developed using Wiener process by calculating the total leakage flow of the piston pump after filtering noise. Based on the developed model, the remaining useful life was established. The degradation model analysis results showed the failure probability of the piston pump using HP filter was less than 1%, whereas it was 28% using raw data when the piston pump ran 900 h. Therefore, the degradation model using HP filter is more suitable for the piston pump.

In order to establish the high-temperature fatigue life prediction model of GH4169 electron beam welded joints, fatigue tests at different temperatures were carried out to obtain the stress-life (S-N) curves respectively. The influence of temperature on the fatigue performance of joints was analyzed. The fatigue damage mechanism was studied by metallographic analysis and scanning electron microscope (SEM) test. The results showed that the effect of temperature on the fatigue performance of the joint was related to the load level. Under the load above 980 MPa, the fatigue performance showed an obviously downward trend with the increase of temperature. In addition, the fracture mechanism of joints presented transgranular brittle fracture at room temperature and cleavage fracture at high-temperature. On the basis of the above analysis, considering the changes of yield strength and grain size with temperature, the parameters in Basquin model were modified in combination with fatigue test data, and the high-temperature fatigue life prediction model of welded joints was established. The results showed that the prediction accuracy of the modified model was high when the yield strength and grain size were considered comprehensively, while the accuracy of the model was within 2 times of the dispersion band.

The reusable liquid rocket engine can greatly reduce the cost of space transportation. One of the key factors for the reusable performances is cyclic life of inner wall structures of thrust chamber. The constitutive equations of wall materials of the thrust chamber were established based on Chaboche kinematic hardening model and Norton creep model. The temperature fields and stress-strain distributions of the thrust chamber under various working conditions were obtained by employing the analysis of transient thermo-mechanical coupling; the damages and cyclic life of the inner wall structure were investigated by Lagneborg cumulative damage model by considering the coupling effects of creep and fatigue. The investigation showed that the key patterns of damage in wall structures of thrust chamber were low-cyclic fatigue and creep-fatigue interaction damage with low-cycle fatigue damage ratio 65.8%, and creep-fatigue interaction damage ratio 29.8%. Therefore, in order to accurately predict the cycle life of thrust inner wall structures, the influencing factors of structures under the action of creep-fatigue interaction damage should be considered.

A rolling bearing fault diagnosis method based on joint locally linear embedding and sparse self-representation (JLLESSR) and parameter-optimized support vector machine is proposed for rolling bearing vibration signals with strong nonlinearity and containing more redundant and irrelevant features, which leads to difficulties in extracting essential features and fault identification. The method constructs a unified feature extraction framework, relying on local linear embedding (LLE) to mine the local geometric structure of high dimensional data, and self-representation to mine the global geometric structure of high dimensional data in low dimensional space, to obtain the embedding features characterizing the operating state of rolling bearings. Then, the obtained features are fed into a cross-validation support vector machine (CV-SVM) for fault identification. Finally, the proposed method is tested on a rolling bearing fault data set, and the experimental results show that the proposed method can effectively identify different types of rolling bearing faults, and the fault diagnosis accuracy can reach 98.5%.

In order to deeply investigate the mechanism of “critical following speed”, a cantilever rotor dynamic model was established. The dynamic characteristics of the rotor system under “critical following speed” were analyzed. The cantilever rotor experimental system was designed and established, and experimental verification was finished on the overspeed test bench. The analysis results showed that from a certain rotational speed, when the diameter rotational inertia was equal to polar rotational inertia, the vibration pendulum angle response of the disk increased with the increasing rotational speed. The characteristics of the mode shape under “critical following speed” lied in that the disk (diameter rotational inertia was equal to polar rotational inertia) was located at the node of mode shape. The vibration displacement of the disk center was 0, but the pendulum angle of the disk was not 0 and increased with the increasing rotational speed, and the phase angle was kept constant. If the rotor was not a single-disk structure, the diameter rotational inertia and polar rotational inertia of the component should be calculated to determine whether the “critical following speed” phenomenon occurred. Considering the mass of the rotating shaft, when the disk satisfied the condition which diameter rotational inertia was equal to polar rotational inertia, the phenomenon of “critical following speed” did not occur, and the natural frequency line could be close to the speed line within a wide range, which would widen the “resonance vibration” region. “critical following speed” made vibration extremely sensitive to unbalanced load, which should be avoided in rotor dynamics design.

In order to effectively improve the assembly accuracy of the short precision bolted connection structures, the influencing factors of the centroid and centroid eccentricity after combination of the two-stage disks were analyzed, the translational rotation behavior and centering principle during the matching process of the two-stage disks were expounded, and a two-stage rotor was established. Centroid deviation prediction model and initial imbalance prediction model were established. A process optimization model was proposed, the installation phase of the rotor disk connected by short precision bolts was taken as the variable, and the centroid eccentricity and the mini-mum initial unbalance amount were taken as the optimization objective, which were verified by the physical test. The results showed that the maximum relative error of the module length of the centroid deviation was 13.28%, the maximum accuracy of the calculation result of the combined unbalance increased by 37.3%, and the process optimization results were consistent with the test results, which had important reference significance for the optimization of the assembly process of short precision bolted connection structures.

The influences of adding or not adding the shunt injection with different preswirl ratios on the pressure, the circumferential flow velocity, the growth rate of the circumferential swirling flow and rotordynamic characteristics coefficients in each seal cavity were compared and analyzed. The effec-tiveness of the shunt injection was quantitatively analyzed and evaluated. Studies showed that the shunt injection device had a strong inhibitory effect on the circumferential flow of the seal, and also a different influence on the pressure in each cavity, with a more obvious influence on the pressure in C3—C6. The growth rate of the circumferential swirling flow was introduced to measure the effect of the shunt injection. With the addition of shunt injection, the circumferential swirling flow growth rate for labyrinth seal was reduced along the direction of leakage to C8, and slightly rebounded at C9. The labyrinth seal without shunt injection remained largely unchanged. The shunt injection increased the direct damping of C3—C6, decreased the cross-coupled stiffness of each cavity, thus improving the effect damping of each cavity, and enhancing the system stability. The preswirl ratio influenced the direct damping of C1—C2. The shunt injection made the cross-coupled stiffness of each cavity decrease more at the high preswirl ratio. The effect damping was less affected by the preswirl ratio, thus the shunt injection had a better suppression effect on inlet the positive preswirl ratio.

A compact vibration absorber with multiple frictional dynamic absorber was presented to dissipate the excessive vibration of rotor passing through the critical speed. The ring-like absorber integrated multiple cantilevered oscillators and the frictional damping suitable for high temperature and complex environment. In order to gain effective models for the design and performance analysis, the finite element method, combined with the Lagrange equation approach, was employed for modeling of the vibration absorber-rotor system. The harmonic balance method was applied to effectively solve the governing equation of the system. On this basis, the effects of the mass ratio, frequency ratio, the number of oscillators and the normal force on the friction surfaces on the vibration mitigation performance of the absorber were investigated. The sensitivity of its effectiveness to the random deviation of some parameters was also addressed. Numerical results showed that the presented absorber can obviously reduce the maximum response amplitude of the rotor, with the maximum relative ratio reaching above 70%. Besides, the performance of the absorber was very robust.

The flow-induced vibration response of the exhaust tower was analyzed by theoretical and numerical simulation methods to investigate the structural safety of the exhaust tower under the combined action of natural wind load and internal flow. The exhaust tower’s co-current response and mean response under the action of wild wind load were achieved. Then, using the computational fluid dynamics approach, shear stress transport (SST) k-ω turbulence model and dynamic mesh numerical technology, the exhaust tower’s two-way fluid-structure interaction numerical simulation was realized. The exhaust tower’s velocity, pressure, and vorticity distribution under the action of internal and external flow mixing were also obtained. The vortex shedding frequency of the exhaust tower under a specific wind load was close to the first-order modal frequency of the structure. The gained stress was within the allowable stress range of stainless steel.

In order to study the effects of windward angle on aerodynamic characteristic of drogue, a 1∶1 full-scale drogue with variable windward angle was designed to simulate the real structure of invariable drag characteristic drogue and adaptive variable drag characteristic drogue, and a kind of aerodynamic characteristic measurement test method was developed in FL-14 wind tunnel. The variation tendencies of unfolding process, deformation results and drag for drogue at different windward angles were achieved in the test. The results indicated that: the wind speed for complete unfolding showed a rising trend with the increase of windward angle. Drag value of drogue increased with windward angle. Invariable drag characteristic drogue’s windward angle kept unchanged when bearing the load of wind while adaptive variable drag characteristic drogues’ decreased. The drogue with 1 mm springs achieved excellent performance of adaptive drag characteristic adjustment at the windward angle of 46° and within the speed range of 55 m/s and 75 m/s, and its drag value kept stable.

In order to explore the influence of the design parameters of the turbo-electric distributed propulsion (TeDP) system on mission fuel consumption, a performance model of the propulsion system and an integrated aircraft-engine evaluation model were established. The influences of the design parameters of the propulsion system on the weight and fuel consumption of the aircraft were studied based on a 150-seats civil aircraft concept. In addition, various operating strategies of battery were analyzed. The results showed that: there existed optimal values of turbine inlet temperature and relative power of electric system to achieve a minimum fuel consumption in mission profile; the energy use of battery should be prioritized to provide power supplementation when the load can't working at full power, which can achieve the reduction of fuel consumption using a battery with energy density higher than 400 W∙h/kg. The integrated design method established can provide supports for the optimization design of the TeDP.

The Reynolds number index (RNI) and Reynolds number ratio (RNR) are commonly used as important dimensionless numbers for Reynolds number related problems in the development of aero-engine. However, the former is mostly used in the engineering development stage and the latter mostly used in the early stage of research, and the two have long been in a fragmented state at the application level. In order to clarify the relationship between RNI and RNR, RNI was firstly derived from two perspectives: $ \varPi $ theorem and algebraic derivation of dimensionless numbers, whose physical meaning was RNR considering Mach number correction, which represented the Reynolds number strong similarity principle. Secondly, the relationship between RNI and RNR was compared, in which the relative difference between these two was only a function of temperature; and when the difference between RNI and RNR was within the working temperature ratio range of 0.94—1.06, these two were considered interchangeable; given the temperature ratio gap between working conditions was too large, this was one of the reasons why the current Reynolds number correction formula with RNR as the independent variable had too much errors in practice. Finally, the operation point at cold and hot states based on RNI of 1.0 was given as one of the applications of RNI, which guaranteed the strong Reynolds number similarity; and the results of two sets of cold and hot state conversions were given, and the $ \varPi $ functions of cold and hot state conditions were calculated to be consistent, and the cold and hot state modelling was considered to satisfy the similarity principle. The relationship between RNI and RNR explained and analyzed herein can be used as a basis for selection of dimensionless parameters for Reynolds number related problems in all stages of aero-engine development.

In order to investigate the influence of three-dimensional sawtooth configuration on the flow field structure of incident shock-wave/boundary-layer interaction, the flow field of wedge with sawtooth leading edge/plate was numerically simulated and analyzed, and the influence laws of different sawtooth depths on the flow field were summarized. The results showed that, compared with the wedge with straight leading edge, the sawtooth wedge was affected by overflow. Meanwhile, the incident shock wave presented a curved three-wave structure, the shock wave intensity was weakened, the wave angle was reduced, and the flow field structure moved backward; the separation zone on plate presented a “concave” spatial structure. The spreading direction of the separation zone was low in the middle but high on both sides, and the flow direction was short in the middle but long on both sides. With the increase of sawtooth depth, the flow field structure moved backward, and the three-dimensional characteristics of the separation zone became more obvious. In the overflow model, due to the side overflow, the separation at the symmetrical plane was the largest, and the separation zone presented a three-dimensional “semi concave” spatial structure. Compared with the original overflow model, the sawtooth overflow reduced the intensity of the incident wave system and the side overflow.

In view of the problems of complex structure, large number of parts, low assembly efficiency and high assembly cost of aero-engine, an assembly sequence optimization method based on improved flower pollination algorithm (IFPA) was proposed. The optimization target evaluation system was constructed with the influence factors of assembly priority, assembly stability, assembly aggregation, assembly redirection and basic component position. Different representation schemes, initial population generation against independent learning, and dynamically adjusted transition probability were adopted, uniform and elite variation was introduced in global and local pollination rules, and genetic mutation was added. The effectiveness of IFPA was verified by applying it to the assembly planning of aero-engine low-pressure compressor, and the parameter influence of IFPA was discussed. And compared with particle swarm algorithm, genetic algorithm, ant colony algorithm and flower pollination algorithm, the probability of finding the optimal sequence increased by 41%, 42%, 41% and 20%, respectively, which verified that IFPA can solve the assembly sequence planning superiority in question.

Based on the method of wavelet domain denoising, the noise signals from in-cylinder pressure were extracted, at crank angle of 0°—45°, fast Fourier transform was used for simultaneous analysis of the noise signal in the time and frequency domains, then the feature map was outputted. The map was inputted into convolutional neural network (CNN) for identifying different features in order to distinguish non-knock and knock. The knock test was conducted on a direct injection engine fueled with aviation kerosene. The result revealed that: the time-frequency map was significantly different between knock and non-knock, because slight knocking and severe knocking both produced large-amplitude noise signals within crank angle of 10°—30°. Wavelet denoising was better than bandpass filtering in knocking feature extraction, while CNN was better than Support Vector Machine (SVM) in knocking feature recognition; under four different operating conditions, the knock recognition accuracy was all over 91% by wavelet domain denoising combining with CNN method; the precision and recall of the knock were 83.16% and 98.79%, respectively.

The effects of Weber number and air-liquid momentum ratio on the atomization characteristics of prefilm nozzle were experimentally studied. The fluctuation shape of oil film is obtained by front photographing with high-speed camera, and the fluctuation frequency of oil film is analyzed by proper orthogonal decomposition method. The oil film thickness is obtained by using the idea of liquid discontinuity, the atomized droplets SMD is measured with PDPA. The results show: The air-liquid momentum ratio has a great effects on the oil film thickness, and the Weber number has a great effects on the oil film fluctuation frequency. The air-liquid momentum ratio increased from 0.75 to 30.39, the minimum oil film thickness decreased from 0.38 mm to 0.15 mm, and the SMD increased from 38.8 μm reduced to 33.5 μm; The Weber number increased from 11.91 to 61.51, the oil film fluctuation frequency increased from 2.9 Hz to 207.0 Hz, the initial atomization distance decreased significantly, and the SMD reduced from 37.1 μm to 24.9 μm.

In order to explore the applications of outlet temperature field measurement for a small annular combustor by gas analysis, the design of multipoint non-mixed water -cooled gas sampling probe was introduced for adaptation of a small annular combustor, two five-point non-mixed water -cooled gas sampling probes and double platinum rhodium thermocouple were fixed respectively on a displacement mechanism at the combustor outlet; swinging 180° with displacement mechanism, bidirectional data measurements were achieved; the gas temperature was calculated by measuring carbon dioxide (CO₂), carbon monoxide (CO) and unburned hydrocarbons (UHC). Test results showed that the combustor outlet temperature fields measured by gas analysis method and thermocouple method were consistent basically, the relative deviation of them was within 2%; at the same time, gas analysis method was proven to be dominant in measuring high gas temperature from aeroengine combustor with high upper limit of temperature measurement and high precision.

To investigate the influence of MIPCC technology on the temperature field in the pre-compressor section, a three-dimensional mathematical model was proposed to study the droplet atomization and evaporation process using the Eulerian-Lagrangian method. The mass transfer and momentum exchange between gas-liquid phase were realized by two-way coupling method. Compared with existing experimental results, the accuracy of the temperature in the mathematical model was verified. The effects of W-A ratio, velocity, particle size, and cone angle on the temperature of inlet air were analyzed by response surface methodology in the aero-engine, and a four-factor and three-level response surface methodology was established. The results showed that the temperature drop ratio of engine intake air temperature was 3.67%−26.02%. The visualized nonlinear multivariable design optimization equation based on multiple regression method and the effects of W-A ratio, velocity, particle size and cone angle on inlet cooling effect were obtained. When the W-A ratio was 0.08, the particle size was 10.47 μm, the velocity was 39.52 m/s and the cone angle was 24.79°, the minimum inlet temperature of aero-engine was 449.60 K.

In order to study the systematic influence of cruise altitude on the generation of water contaminant in the fuel tank, a water contaminant generation model was established based on the heat and mass transfer equation, and the generation characteristics of dissolved water, suspended water, condensed water and free water in the fuel tank at different cruise altitudes were calculated. The results showed that: a majority of suspended water generated during the climbing phase, and the higher cruise altitude indicated the more suspended water, the amount of suspended water produced at 11 km of cruise altitude was 5.5% greater than at 7 km of cruise altitude; a majority of condensed water was produced during the cruise phase, and the total amount of condensed water decreased as cruise altitude rose, at 11 km of cruise altitude, the amount of condensed water produced was 34.4% less than at 7 km of cruise altitude; the total amount of free water generated increased as cruise altitude rose, but the rate gradually slowed down, at 9 km of cruise altitude, free water generation was 1.88% higher than at 7 km, and at 11 km of cruise altitude, it was 0.92% higher than at 9 km.

The model of variable geometry performance for compressor variable stator vane (VSV) was established based on the principle of backbone map. The advantages and applicability of the compressor backbone map were introduced. Based on the compressor backbone map, the VSV model correction method was developed. By adjusting the proportional correction coefficients of the flow coefficient, work coefficient and loss coefficient, the high-precision modeling of compressor performance varying with VSV angle deviation was realized. An automatic optimization method was established, which improved execution efficiency and reduced manual intervention. As a result, compared with the experimental results, the relative error of the model reached a level of less than 0.2%, which verified the correctness and accuracy of the correction method. The correction method by scaling the specific backbone map parameters could be used to the correction of other secondary effects on compressor maps (e.g. Reynolds number effects).

An integrated optimization design platform of blade and casing treatments in a low-speed axial compressor was constructed. A practical partitioning approach for free-form deformation (FFD) parameterization combined with engineer parameters was applied to achieve multi-objective optimization. Taking both efficiency and stall margin into consideration, the optimal design improves the stall margin by 7.21% with negligible peak efficiency variation. After the analysis and calculation of blockage and loss distribution, the influence mechanism on stall margin and efficiency is further studied. Results show that with the combined effected of deformed blade and casing treatment, the location of peak blockage moves downstream from 24.7% rotor tip chord to 33.6% rotor tip chord and the location of peak efficiency moves downstream from 21.4% rotor tip chord to 30.6% rotor tip chord. The main reason for stall margin improvement is the suppression of tip leakage and the elimination of low energy blockage flow at tip region.

To improve the flow quality of linear cascade tests with high-loading blade sections and ensure the reliability and accuracy of test data, the evaluation parameters of flow quality of linear cascade were established, and two passive control schemes of intermediate streamlined upper end-wall and its coupling with outlet adjustable tailboards were proposed. The control strategies of the above two schemes on the flow quality of high-loading linear cascade were studied by numerical simulation method verified by experiments. The results showed that both schemes can effectively suppress the deterioration of flow field near the upper end-wall area, thus improving the inflow accuracy, flow periodicity and two-dimensionality of cascade. When the set angle and gap of the upper end-wall and the tailboard angle matched the ideal intermediate streamline of cascade, the two schemes presented the best improvement on the flow quality. The scheme of intermediate streamlined end-wall combined outlet tailboards was superior to the intermediate streamlined end-wall scheme, such that the inlet Mach number deviation of the central three blade passages was less than ±0.005, and the incidence angle was less than ±0.3°. And the periodicity deviation of inlet and outlet Mach numbers shall not exceed 0.005, and the periodicity deviation of inlet and outlet flow angles shall not exceed 0.3°. The axial velocity density ratio (AVDR) of cascade was 1.1 at the incidence angle of 0°. The two control schemes showed good applicability to the flow quality adjustment of cascade at high incidence angle.

Based on the appearance of waves in the compressor blade processing, cascades with four kinds of waves were processed, and the plane cascade experiment was carried out, then the influences of aerodynamic performance and pressure distribution were obtained and the mechanism was analyzed. Results showed that the loss of those profiles with waves was overall larger than that of original profile. Under negative attack of angle, the influence of wave spread to the downstream and pressure side and changed the pressure distribution of profile. Moreover, the flow experienced repeated acceleration-deceleration changes on suction side of the blade where waves appeared. The width of the wave directly determined the frequency of acceleration-deceleration changes, and different initial phases of waves affected the acceleration circumstances of leading edge. The wave on suction side could change the “spike” close to the leading edge, the action mechanism for waves changing transition position was related to the characteristics of the airfoil itself; when waves occurred before the location of transition, the variation of “spike” could change the location of transition.

Accurate measurement of blade tip displacement is the basis for the application of blade tip timing (BTT) technology to the vibrational mode reconstruction and real-time condition monitoring of rotating blades. A high-precision BTT calibration device based on a laser displacement sensor was designed. The time-domain calibration data of the blade tip displacement were directly obtained in the experiment, verifying that the speed fluctuation was one of the main sources of the measurement error of the blade tip displacement. On this basis, a local fifth-order fitting rotation speed fluctuation correction method was proposed to improve the BTT measurement accuracy, and the experimental verification was completed on the calibration device. The experimental results showed that the local fifth-order fitting method can effectively improve the BTT measurement accuracy under different working conditions. The measurement error can be reduced by up to 90% under the condition of non-linear increase in rotational speed, and the measurement error can be reduced by 38% to 63% under the condition of constant speed. The algorithm was applied to the experimental data of a single-stage axial flow compressor, and the corrected error was as high as 0.4 mm, which effectively reduced the uncertainty of the real-time measurement of blade tip displacement by BTT technology.

In order to study the influence of blockage rate on the spray characteristics of pintle injector, based on the design idea of a plane pintle injector element, the test parts of the plane pintle multi-injector elements with replaceable components were designed. At the same time, PLIC VOF (piecewise linear interface calculation volume of fluid) multiphase flow simulation method with each phase individually identified and the high-speed photography test method were used to study the influence of blockage rate on the spray angle, spray diffusion angle and spatial distribution of liquid spray in the liquid-liquid pintle multi-injector elements. For the multi-pintle injector element with radial circular orifices, the blockage rate was changed by changing the diameter and the number of radial orifices. For the multi-pintle injector element with radial rectangular orifices, the blockage rate was also changed by changing the rectangular aspect ratio of radial orifices. It was found that the blockage rate had important effect on the spray concentration spatial distribution of spray field. When the total momentum ratio remained unchanged, the effect of blockage rate on the spray field was directly produced by the spatial distance between the adjacent spray fans, and also indirectly produced by the effective momentum ratio on the other hand. The influence of radial orifice shape on the spray field was also essentially transformed into the influence of the blockage rate and effective momentum ratio. The influence of the blockage rate change on the spray angle was only indirectly realized by the effective momentum ratio, which was caused by the change of radial orifice diameter and shape. The spray angle theoretical model of pintle injector element was also applicable to multi-pinlte injector element. Meanwhile, the influence of the blockage rate on the spray diffusion angle and the spray concentration spatial distribution was achieved through two action ways. In addition, the spray radial distribution range increased under the condition of high total momentum ratio, and the liquid spray mass rate increased in the central and outer regions of the spray fan due to the interaction between adjacent injector elements.

The influences of different factors on the flow characteristics of the internal flow field, the motor performance parameters and the force on the pintle were studied, and the control performance of the pintle motor was explored. Based on the method of numerical simulation, the flow field in nozzle under different pintle profiles and pintle tail groove designs was calculated and studied. The results showed that the thrust adjustment range of pintle variable thrust solid rocket motor was large, and the force variation of pintle was also large. The change of pintle profile had no significant effect on pintle load, and the maximum load decreased 28%. The design of the tail groove of the pintle can balance the pintle load to a large extent, and the maximum load was reduced by 56%. The design of the guide groove of the valve body of the pintle had a significant effect on reducing the force on the pintle, and the maximum load decreased 91%, which greatly enhanced the control performance of the pintle variable thrust solid rocket motor.

Large Eddy Simulation (LES) was used to compute the three-dimensional unsteady plume flow field. Low-frequency and high-energy large-scale coherent structures in the flow field were extracted by using low-pass filters. Spatial reduction was achieved by Fourier transform and Proper Orthogonal Decomposition (POD) in the azimuthal direction of the plume, while temporal reduction was achieved by extracting the Fourier mode from the leading temporal POD mode. Consequently, a spatiotemporal reduced-order model (ROM) for supersonic plume reaction turbulence was established. The results demonstrated that low-pass filters and POD truncation can successfully filter high-frequency and low-energy small-scale structures in the supersonic plume. The azimuthal modes m=0 and m=1 accounted for 80.9% of the energy in the plume. In the m=0 azimuthal mode, the pressure POD spatial mode showed sharp peaks in the core region of the jet due to the interaction between compression wave and shock wave. Furthermore, POD spatial modes of the component and temperature exhibited sharp disturbances downstream because of afterburning. An alternating wave packet structure with a steady wavelength was displayed in the POD spatial mode under the m=1 azimuthal mode. The POD spatial mode of both components and temperature showed a similar wave packet structure. In addition to reducing numerical instability, temporal reduction based on Fourier mode energy selection guaranteed excellent reconstruction accuracy. This research can support target intelligent feature engineering applications by offering theoretical techniques for evolution laws and feature extraction on supersonic rocket exhaust plumes.

Thrust management is one of the important functions of civil aircraft flight management system. In different flight phases and flight states of the whole route, the flight management system needs to calculate the aircraft thrust requirements for engine, and then use the required thrust as the target thrust to generate the command of engine throttle control. Of which, thrust target value calculation is the core of thrust management. According to different flight characteristics of each phase, the calculation method of aircraft thrust target value was studied by using flight dynamics. The calculation process of climb, cruise, descent phases at different flight modes were analyzed in detail. Taking Boeing 737-800 flight record data as an example, the thrust target value calculation method was simulated and verified. The results showed that the calculated thrust value was consistent with the flight performance theory, and the relative error between the calculated thrust and the actual flight record data in typical flight phases was less than 3%. The thrust target value calculation method can provide a reference for civil aircraft thrust management system design.