2021 Vol. 36, No. 5

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Thermo-mechanical fatigue behavior and life modelling in nickel based single crystal superalloy
CHEN Jingyang, JING Fulei, YANG Junjie
2021, 36(5): 897-906. doi: 10.13224/j.cnki.jasp.2021.05.001
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Mechanical strain-controlled thermal mechanical fatigue (TMF) tests were performed on thin-walled tubular specimens made of nickel based single crystal superalloy DD6, and the effects of thermal cycles, phase shift and load-controlled mode on stress-strain behavior and fatigue lifetime were studied. The experimental results indicated that the lifetime of TMF was shorter than that of isothermal fatigue (IF) at the peak temperature due to the asymmetry of stress and additional damage induced by thermal cycles. In addition, the lifetime under out-of-phase (OP) cycles was less than that under in-phase (IP) cycles in mechanical strain-controlled mode, which was in contrast with that in stress-controlled mode. According to the results of viscoplastic analysis based on slip systems with Walker constitutive model, the correlation between the damage generated in single crystal superalloy under different TMF loadings and the microscopic parameters on slip systems was identified. Moreover, the max Schmid stress, max slip shear strain rate, cyclic Schmid stress ratio and slip shear strain range were selected as the damage parameters, and then a new life model based on microscopic parameters was proposed for the TMF life prediction. The predicted TMF life of DD6 under different phase shift and different load-controlled mode was within a factor 2 of the experimental life.
Hot-modal test technology of turbine blades based on 3D laser scanning
DAI Jiangbo, LUO Xianqiang, FU Shunguo, WANG Qi, FENG Haibo
2021, 36(5): 907-915. doi: 10.13224/j.cnki.jasp.2021.05.002
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The high temperature modal test technology of engine turbine blades based on 3D laser scanning technology was presented, which realized the modal test of turbine blades at high temperature of up to 900 ℃. A set of high temperature environment simulation device was designed to realize the simulation of different temperature environments. Based on the basic excitation technology of the shaking table and 3D laser scanning technology, the 3D test models of turbine blades under different temperature environments were established, the accurate modal shape, modal frequency and other parameters were obtained, by which the feasibility of the method was verified. The analysis results showed that the natural frequency of turbine blades decreased due to the increase of temperature, and the first-order frequency decreased by 6% compared with the ambient temperature at 900 ℃, The modal shape of blade tip was slightly distorted due to thermal stress.
Failure simulation and test verification of cone under impact load
YU Lei, GENG Jingyan, LI Baiyang, WANG Weiguo, CAO Jiajian, WU Hailong, ZHOU Qing
2021, 36(5): 916-922. doi: 10.13224/j.cnki.jasp.2021.05.003
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According to the load characteristics of aeroengine supporting cone structure, the failure mechanism of cone under the impact load of fan blade out was studied.By using the explicit dynamic finite element simulation method, transient analysis on the dynamic failure process of the cone structure under the impact load was carried out. The drop impact test of the cone was carried out, and the test results were compared with the analysis results. It was discovered that the failure of the cone thinning position under impact load was shear failure. The explicit dynamic finite element simulation method provided a feasible method for accurately simulating the failure of the cone failure under impact load, the error between the peak acceleration obtained by analysis and the test result was less than 5%. The GISSMO (generalized incremental stress state dependent damage model) can be used to accurately predict the fracture time and position at the cone thinning position.The analysis method and failure model verified by the test can be used to determine the failure design parameters of the cone under the impact load of fan blade out, so as to improve the accuracy of the load reducion design of the cone structure.
Identification of fan surge precursors based on acoustic array signals
LI Zepeng, QIAO Baijie, WEN Bi, CHEN Xuefeng
2021, 36(5): 923-934. doi: 10.13224/j.cnki.jasp.2021.05.004
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An approach for identification of the aero-engine surge precursors was proposed utilizing microphone array measurement, thereby the additional disturbance of classical intrusive measurement was avoided. A transient test on a multi-stage fan experiment was carried out from designed operating condition to surge margin, and the surge inception was realized by signal processing approaches including short-time Fourier transform, spectral analysis and acoustic mode analysis. The results demonstrated the occurrence of asynchronous frequency when the fan operated near the surge margin, and the frequency was about 70% of the blade passing frequency. The cause of such phenomenon was the resonance of azimuthal modes inside the rotor-stator row. The surge-warning was realized by characterizing the feature frequency and mode spectrum.
Influence of position error of bolt hole on assembly mechanical characteristics of short precision bolted connection structure
JIAO Junjie, MO Rong, XU Guangqing, FU Xuan, SUN Huibin, CHANG Zhiyong
2021, 36(5): 935-947. doi: 10.13224/j.cnki.jasp.2021.05.005
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In order to study the influence of position error of bolt hole on assembly mechanical characteristics, the error model and finite element model considering the position error were built, and the influences of position error on the connection stiffness and stress of bolt hole edge of single short precision bolted connection structure were studied. Computing model and finite model of position error of short precision bolt group were established, and the effects of assembly phases of two parts and assembly position of the 1st bolt on connection stiffness of short precision bolt group were analyzed. It was concluded that position error had a small influence on axial stiffness, and a significant effect on tangential stiffness. The projection of position error in the direction of tangential load was a major influencing factor to the tangential stiffness, and the stress of bolt hole edge reached the maximum at the position of 180°. By computing and comparing standard deviation of the projection and length of position error, three better assembly plans of bolts were obtained.
Numerical simulation on laser shock peening of TC4 titanium alloy
WANG Bohan, CHENG Li, DING Junliang, CUI Wenbin, WANG Changkai, LI Dongchun
2021, 36(5): 959-968. doi: 10.13224/j.cnki.jasp.2021.05.007
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The continuous explicit dynamic impact strategy was used to carry out the numerical simulation study on laser shock peening of TC4 titanium alloy for aviation. According to the shock wave energy change curve, the solution time 3 000 ns of a single shock was determined, and the stress wave propagation process was analyzed. On this basis, a multi-point impact simulation was carried out, and the effects of power density, impact times and spot overlap rate on residual stress and strain field were analyzed. It was concluded that increasing the power density had a better effect on increasing the residual compressive stress on the surface; increasing the number of impacts had a better effect on increasing the depth of the residual compressive stress; the 50% spot overlap rate effectively avoided uneven impact and overlap gaps phenomenon. The change trend of the residual compressive stress on the surface of the specimen obtained by the experiment and the simulation was the same, and the numerical value was basically consistent. When the impact was 1 and 3 times, the errors of these two were 4.1% and 2.6%, respectively, indicating that the simulation results have certain reference significance.
Pre-cooling characteristics of high temperature inlet air for turbine power combined with ramjet
LIN Aqiang, ZHENG Qun, XIA Quanzhong, ZHANG Hai, LIU Gaowen
2021, 36(5): 987-996. doi: 10.13224/j.cnki.jasp.2021.05.010
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To solve the negative effect of high temperature inlet air on the turbo engine performance in the turbine-based ramjet combined cycle engine, numerical analysis on the pre-cooling section of a real high-altitude simulation experiment was carried out. Based on the Eulerian-Lagrangian multiphase flow method, the heat and mass transfer process of gas-liquid two-phase was analyzed. And then, the temperature and pressure fields in the pre-cooling section were explored at different high altitudes and high Mach number inlet air conditions. Results showed that mass injection had an obvious improvement on temperature drop. The flow loss in the pre-cooling section with injection device was mainly caused by the dissipative entropy production due to the viscous dissipation, while the heating entropy production caused by the temperature gradient change of the flow field due to the gas-liquid heat transfer temperature difference was not significant. By comparing the cooling effect of 4%-7% water/air ratio at the high-altitude simulation inlet air conditions, it can be discovered that the airflow temperature drop in the pre-cooling section was within the range of 32.30-90.08 K, and the total pressure drop coefficient was reduced from 1.42%-1.86% to 0.95%-1.46% before and after mass injection cooling. Therefore, mass injection cooling can improve inlet air flow field characteristics of turbine engine at high altitude and high Mach number.
Prediction of Helmholtz dampers on limit cycle of thermoacoustic instabilities
YU Zhijian, YANG Yang
2021, 36(5): 997-1006. doi: 10.13224/j.cnki.jasp.2021.05.011
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Whether Helmholtz method can be used to predict the effects of Helmholtz damper on thermoacoustic limit cycle was investigated. Corresponding experimental validations were performed in a Rijke tube. The limit cycle properties of the Rijke tube equipped with a damper were calculated by the Helmholtz equation coupled with nonlinear heat release model, impedance model and damping rate. The impedance model of the damper was validated in an impedance tube. Results showed that the reflection coefficients of dampers could be calculated by the modified impedance model. The impedance increased with the purge mass flow. Without dampers, the relative errors of predicted limit cycle eigen-frequency and velocity amplitude were 3.4% and 7.2% at the heating voltage of 85 V, respectively. With dampers, the calculated maximum relative errors of those were 3.7% and 6.2%, respectively, under low mass flow. This passive control can be enhanced by increasing purge mass flow due to the vortex shedding. It is advisable to install the damper close to the pressure antinodes.
Multi-material topology optimization for heat transfer structure based on ordered-EAMP model
YAN Hao, WU Xiaoming
2021, 36(5): 1007-1021. doi: 10.13224/j.cnki.jasp.2021.05.012
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A density-based ordered-EAMP (exponential approximation of material properties) interpolation model was presented to solve topology optimization problems of multi-material heat transfer structure.Compared with the classical SIMP/RAMP, the numerical examples showed that the proposed interpolation had the characteristics of stable calculation, fast convergence and less gray units of optimized structure. A density filtering scheme for multi-material was constructed in the iterative formula for solving the optimization model based on the optimization criterion (OC) method. The example showed that the scheme can effectively reduce the gray units and the value of optimal objective function. The MATLAB-ANSYS combined calculation was used to achieve the topology optimization of multi-material heat transfer structure in complex thermal environment under three kinds of thermal boundary conditions. The results showed that compared with the structure of single material with large coefficient of conductivity, the multi-material heat transfer topology optimization structure corresponded to the optimal distribution of various heat conduction coefficient materials, which was characterized by smaller dissipation of heat, the dissipation was reduced by 20.3% in numerical example 4, and the heat transfer efficiency was higher.
Particle deposition characteristics and film cooling performance of flat plate with trench
YOU Xuelei, YUE Guoqiang, WANG Shaoliang, ZHANG Luyang, JIANG Yuting
2021, 36(5): 1022-1032. doi: 10.13224/j.cnki.jasp.2021.05.013
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The effects of different trench depths on the particle deposition distribution and film cooling performance of the flat plate were explored by embedding the cooling holes into the trench. The result showed that the existence of the trench structure improved the particle deposition and film cooling performance on the flat plate, and effectively blocked certain particles inside the trench. Under the same blowing ratio, the increase of the trench depth made the overall particle impact efficiency increase. When the blowing ration was relatively small, the three trench depth structures all reduced the particles deposition and capture on the flat plate, and improved the downstream film cooling efficiency of the cooling holes. However, under the large blowing ratio, different trench depths had different performances on particle deposition distribution and film cooling efficiency. Comparing the performance of different trench depth structures under various working conditions, the structure with a trench depth of 0.8 times film cooling hole diameter improved the particle deposition distribution and can also promote the downstream film cooling efficiency of the cooling holes.
Modal decomposition and rapid prediction of shock train oscillation for inlet
SUN Fei, SU Weiyi, HOU Qiang, WANG Mouyuan
2021, 36(5): 1040-1051. doi: 10.13224/j.cnki.jasp.2021.05.015
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To study the self-excited oscillation in the isolator, the unsteady characteristics of the two dimensional planar inlet were numerically simulated using the finite volume method program with time and space terms of the two-order implicit and upwind discrete schemes, unstructured grid, and shear stress transport (SST) k -ω turbulence model when the high backpressure was applied, and the self-excited oscillation of the shock train was successfully captured. On this basis, proper orthogonal decomposition (POD) and dynamic modal decomposition (DMD) methods were utilized to analyze the oscillation. The results showed that the self-excited oscillation is a complex oscillation phenomenon dominated by a low frequency and coupled with multiple frequencies. Both the predictive models based on the POD and DMD methods can accurately and quickly predict the evolutions of flow field with the prediction error less than 0.2%. The time consuming of the former and the latter was 0.22 s and 0.05 s, respectively.
Unsteady flow simulation of contra-rotating propfans using immersed body-fitted grids boundary method
WANG Jingyuan, SHAN Peng, ZHOU Yicheng
2021, 36(5): 1060-1071. doi: 10.13224/j.cnki.jasp.2021.05.017
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An unsteady numerical simulation of the transonic flow of a full-circumferential blades of contra-rotating propfans was carried out by using the immersed body-fitted grids boundary method and the developed CFD program. The flow chart of this program, grid generation strategy and flow solver principle were introduced.The influence of unsteady interaction of tip and wake vortexes on the front and rear rotors was analyzed.The unsteady fluctuations of the thrust, power and propulsion efficiency of the contra-rotating propfans were calculated and compared with the corresponding results of NUMECA simulation. The difference between thrust and efficiency of the rear rotor simulated by those programs was more than 10%. Compared with NUMECA’s single channel steady simulation of contra-rotating propfans, the proposed method and program had more accurate simulation results and extremely convenient grid construction when using the the same order of total grids number.
Laws and prediction of axial compressor performance map based on data-driven
LIU Tantao, GAO Limin, FENG Xudong
2021, 36(5): 1072-1082. doi: 10.13224/j.cnki.jasp.2021.05.018
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To explore the inherent laws of axial compressors’ performance maps, more than 50 axial compressors’ characteristic data were studied based on data analysis and thermodynamic principle. By introducing a variety of thermodynamic parameters into the performance curves and novel performance parameters, the research of laws between physics quantities of compressors was performed from three aspects which were peak efficiency lines, near-surge zones and near-stall zones. The relationship between compressor characteristic parameters and design indicators was found and the prediction algorithm was developed to predict the performance of compressors based on design indicators and performance parameters. It showed that there was a linear relationship between thermodynamics parameters within working speed range. The performance parameters of compressors were obviously correlated with design total pressure ratio and little correlated with design efficiency. The prediction algorithm can predict the performance map of compressors (total pressure ratio less than 8) well just relying on the design indicators and performance parameters without blades geometry information.
Regression analysis and parameters optimization of output characteristics for aviation pressure reducing regulator
ZHANG Changshuai, WANG Hui, ZHAO Guochao, FU Peng
2021, 36(5): 1094-1102. doi: 10.13224/j.cnki.jasp.2021.05.020
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To study the impact of design parameters and interdependencies on an aviation dual-stage gas pressure reducing regulator’s output characteristics, the AMESim model was established and verified by comparing results with the test. A quadratic regression model of the output characteristics and design parameters was obtained by the response surface method to analyze design parameters’ influence. The quadratic regression model was optimized by using the non-dominated sorting genetic algorithm-Ⅱ (NSGA-Ⅱ) to obtain the optimal design parameters. The response surface results showed that the feedback hole area was the primary factor affecting overshoot, whose interaction with the spool seal’s dynamic leakage area had a significant impact on overshoot. The spool mass was the primary factor affecting output pressure pulsation intensity, whose interaction with the spring stiffness and diaphragm stiffness had a significant influence on pulsation intensity. The optimization indicated that the output characteristics would be optimal when the spool mass, feedback hole area, mainspring stiffness, auxiliary spring stiffness, spool seal’s dynamic leakage area and diaphragm stiffness in Ⅱ-stage structure were 52.26 g, 9.06 mm2, 67.27 N/mm, 10.68 N/mm, 0.64 mm2 and 89.49 N/mm, respectively. The output pressure overshoot was reduced by 28.72%, and the pulsation intensity reduced by 40.63%.

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