2019 Vol. 34, No. 12

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Analysis of effect of synthetic jet on fluid-solid coupling characteristics around cylinder
DING Lin, YANG Lin, WANG Haibo
2019, 34(12): 2529-2538. doi: 10.13224/j.cnki.jasp.2019.12.001
Abstract PDF(954KB) icon622 icon335
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The active control of the characteristics of flow around a bluff body and flow-induced vibration was numerically investigated by using the synthetic jet. Results showed that the vortex-induced vibration of the cylinder was well suppressed with the increase of the momentum coefficient of synthetic jet. As the jet position moved from the rear stagnation point to the front stagnation point, the vortex shedding mode of the cylinder wake showed the evolution of the steady state-transition state-antisymmetric 2S vortex shedding mode attached to the backflow surface of the cylinder. The two-degree-of-freedom vibration trajectory of the cylinder was in the shape of “8”, “one” in the case of complete suppression, and “crescent” in the case of partial suppression. The introduction of synthetic jet can effectively reduce the lift force on the cylinder. When the synthetic jet was located at the edge of 1/4 arc on the leeward side of the cylinder, the in-flow oscillation and cross-flow oscillation of the cylinder can be suppressed with the best suppression effect.
Active modulation to streamwise vortex drag reduction of turbulent boundary layer by asynchronous vibration with double piezoelectric vibrator
BAI Jianxia, JIANG Nan, TANG Zhanqi
2019, 34(12): 2539-2548. doi: 10.13224/j.cnki.jasp.2019.12.002
Abstract PDF(982KB) icon654 icon288
Abstract:
A closed-loop control circuit comprising of hot wire sensitive filament sensor, microprogrammed control unit (MCU) controller and double piezoelectric vibrators was designed to realize the coherent structure’s drag reduction in turbulent boundary layer under closed-loop active control. Asynchronous vibration of the spanwise piezoelectric vibrators on the wall was adopted. By inputting three different vibration frequencies to the piezoelectric vibrator, the maximum drag reduction efficiency of 16.03% at 160 Hz was acquired. The vibration of the piezoelectric oscillator made the turbulent kinetic energy concentrate around the maximal energy and modulated the coherent structure, which changed the structure of the turbulent boundary layer near the wall. When the vibration frequency of piezoelectric vibrator was close to the characteristic frequencies of coherent structures, the disturbance of piezoelectric vibrator exerted the most significant burst influence on coherent structures, and the drag reduction efficiency reached the maximum. Closed-loop control saved about 75% energy input and achieved a comparable control effect as open-loop control. Under the controlled condition with added condition detection, the time period of the conditional phase average waveform became shorter. The disturbance of piezoelectric oscillator was used to modulate streamwise vortex, thus the wall friction resistance was reduced, and the drag reduction effect was obtained.
Numerical simulations of jet mixing enhancement of novel actuator
HONG Liang, Eriqitai, GONG Jian
2019, 34(12): 2549-2558. doi: 10.13224/j.cnki.jasp.2019.12.003
Abstract PDF(1008KB) icon620 icon310
Abstract:
High-momentum novel and conventional actuators jets were used to enhance the mixing of a high speed large-scale round jet. The comparation of the blowing jet on streamwise vortices, flapping and interaction area between the novel and conventional actuators was studied. The jet mixing enhancement flow hysteresis was analyzed. Results show that the novel actuator is superior to the conventional actuator in terms of the blowing period, blowing momentum, peak jet momentum ratio. The jet mixing enhancement hysteresis consists of the actuator hysteresis and flow field hysteresis. Both the conventional actuator and novel actuator peak jet momentum lags behind the piston peak movement speed by 19.5%, and the actuator peak momentum lags behind the flow field about 5%. Compared with the conventional actuator, the interaction area of the novel actuator fluid tab is larger, leading to a better jet mixing enhancement effect.
Calibration of dynamic characteristics of pressure tube cavity by different calibration devices
LI Bo, YANG Jun, SHI Yusong
2019, 34(12): 2559-2568. doi: 10.13224/j.cnki.jasp.2019.12.004
Abstract PDF(811KB) icon684 icon322
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In order to explore the consistency and data accuracy of each calibration method in the dynamic pressure calibration of the pressure tube cavity, a simple straight-tube type of pressure tube cavity was established to carry out the dynamic characteristic calibration research. The theoretical and simulation methods were used to analyze and establish the model of the pressure tube cavity. The consistency between the theoretical model and the simulation results was very high. Three kinds of sinusoidal pressure calibration devices were used to carry out dynamic calibration for the same pressure tube cavity. Results showed that the dynamic characteristics obtained by the three calibration methods were consistent with the trend of theoretical analysis. For the calibration of the fundamental frequency of the pressure tube cavity, the deviation between the tests was less than 0.55%. However, the maximum deviation from the theoretical value of the fundamental frequency was -3.17%, and there was a large deviation from the other resonance frequencies. This study provides a reference for structural design of pressure tube cavity and compensation correction of dynamic characteristics in the future.
A computation model for auxiliary power unit air bleeding performance based on flat rating
LIU Wei, XIA Shangzhou, HUANG Xing
2019, 34(12): 2569-2576. doi: 10.13224/j.cnki.jasp.2019.12.005
Abstract PDF(810KB) icon699 icon305
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To overcome the disadvantages of the computation model for auxiliary power unit (APU) air bleeding performance in engineering, the structure characteristics and working principle of APU with load compressor were researched. A model based on the matching principle between APU and air start turbine and an interpolation model of variable geometry characteristics of load compressor were presented. On this basis, the regulation law based on APU flat rating was researched, and the relationship among the shaft power load, the APU turbine inlet temperature, the exhaust gas temperature and the inlet guide vane angle of load compressor was determined, consequently the APU bleeding performance was computed at various states in flight envelope. The model was validated with GTCP131-9A’s test data. Results showed that, the deviation of air bleeding mass flow was within 3%, while the deviation of air bleeding pressure was within 4%; in addition, the turbine inlet temperature limit at different altitudes was only related to the shaft power load, but not to the inlet temperature. The model provides a good reference for performance simulation and regulating law design of APU with load compressor.
Development trends of aero turboshaft engines
ZOU Wangzhi, ZHENG Xinqian
2019, 34(12): 2577-2588. doi: 10.13224/j.cnki.jasp.2019.12.006
Abstract PDF(938KB) icon1742 icon488
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Based on the history of the internationally famous turboshaft engines, the development trends of turboshaft engine industry were summarized, showing distinctive features of serialization, dual-use and international cooperation. Basides, the national-level development programs have played a leading role in the progress of turboshaft engines. Based on the statistical analysis method, the future trends of turboshaft engine structural layout and performance were predicted. In terms of structural layout, turboshaft engines would be developed towards the direction of compact layout, and the stage numbers of compressor and turbine show a decreasing trend. More specifically, single-stage/two-stage centrifugal compressors and single-stage turbines would be more extensively used in turboshaft engines with power output less than 1 500 kW, while axial-centrifugal compressors and two-stage turbines would be more commonly used in engines with power output greater than 1 500 kW. In addition, forward facing output with concentric shaft would become the main power output layout. In terms of engine performance, for the advanced turboshaft engines in the future, the pressure ratio and turbine inlet temperature would be up to 30 and 1 900 K, respectively, the specific fuel consumption would be as low as 0.20 kg/(kW·h), the specific power and power to mass ratio would reach 400 kW/(kg/s) and 14 kW/kg, respectively.
Numerical simulation for flow field of helicopters based on WENO-piecewise linear scheme
ZHANG Juhui, CHEN Renliang, KONG Weihong
2019, 34(12): 2589-2598. doi: 10.13224/j.cnki.jasp.2019.12.007
Abstract PDF(979KB) icon769 icon321
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A high-precision CFD method based on WENO(weighted essentially non-oscillatory)-piecewise linear scheme was established for numerical simulation on the rotor/fuselage aerodynamics interaction flow field. And it was suitable for the CFD solver of cell-centered scheme. The pressure coefficient on the surface of the fuselage of different rotor/fuselage model examples in forward flight was calculated by the method, and the calculation results were in good agreement with the experimental results, verifying the effectiveness of the calculation method. Then, the method was extended to simulate the flow field of X3 compound high-speed helicopter rotor/wing/propeller model in hover, and the flow field was compared with flow field of single rotor and rotor/wing model in hover. The results showed that the wing acted as a retarder on the downwash of rotor, causing the irregular flow under the wing. Furthermore, the slipstream of propeller and the downwash of rotor interfered with each other to produce a certain deflection, and the speed of downwash was faster than the speed of slipstream, the downward deflection of propeller slipstream was significant.
Three-dimensional effect of unsteady dynamic stall of cycloidal propeller
ZENG Jianan, ZHU Qinhua, SHEN Suiyuan
2019, 34(12): 2599-2607. doi: 10.13224/j.cnki.jasp.2019.12.008
Abstract PDF(1061KB) icon622 icon312
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The reliability and applicability of two overset mesh methods were verified. Then numerical analysis of the unsteady vortex flow and induced separation characteristics of cycloidal propeller in the two-/three-dimensional cases was carried out, laying the foundation for studying the distribution of spanwise aerodynamics with azimuth and the induced velocity distribution of the global flow field, meanwhile the wake capture accuracy and vorticity dissipation characteristics were also analyzed. Results showed that, under the influence of three-dimensional effects such as tangential velocity and spanwise induced velocity of cycloidal propeller, the difference of transient aerodynamic extremum between the two calculation results reached 44%. The generation, shedding and reattachment of three-dimensional dynamic stall vortices were obviously weaker than two-dimensional airfoil, yielding a great impact on the unsteady aerodynamic characteristics of cycloidal propeller.
Numerical simulation of flow field around hypersonic vehicle at different reentry heights
OUYANG Wenchong, LIU Yanming, DENG Weifeng
2019, 34(12): 2608-2615. doi: 10.13224/j.cnki.jasp.2019.12.009
Abstract PDF(1368KB) icon752 icon392
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Based on the axisymmetric N-S equation and the 7-component 18 chemical reaction, the flow fields around the RAMC-Ⅱ vehicle at the reentry height between 20 km to 90 km were numerically simulated and the algorithm was verified. Not only was the electron number density distribution calculated, but also the collision frequency, average temperature and total pressure distribution at different reentry heights were given. The analysis showed that the electron number density inecreased first and then decreased with the increasing reentry height. When the reentry height was constant, the electron number density decreased with the axial direction, and the Gaussian distribution was consistent along the direction perpendicular to the surface of the vehicle. The maximum value of collision frequency decreased with the increase of the reentry height. When the reentry height was constant, the collision frequency decreased in the axial direction. The maximum average temperature at the same reentry height gradually decreased with the axial distance. The maximum total pressure decreased with the increase of reentry height, and the maximum total pressure decreased with the axial distance at the same reentry height.
Ice fracture criterion coupled thermal/mechanical effect based on stress analysis
XIAO Chunhua, GUI Yewei, YANG Shengke
2019, 34(12): 2616-2626. doi: 10.13224/j.cnki.jasp.2019.12.010
Abstract PDF(939KB) icon593 icon309
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Considering the effect of the external aerodynamic force and skin heating, the computational model of stress inside ice on the leading edge of NACA 0012 airfoil was established according to the thermal de-icing physical process. The finite element method and triangular element were employed to solve the governing equations. The effects of external aerodynamic force and skin heating on the ice adhesion interface stress were obtained. The study showed that, without skin heating, the variation of airflow speed changed the intensity of interfacial stress of ice adhesion interface and the variation of angle of attack changed the distribution of interfacial stress of ice adhesion interface. An approximate linear increasing trend for maximum interfacial shear stress existed along with the increasing airflow speed. But external aerodynamic force contributed little to ice fracture. For skin heating, the coupled stress of ice adhesion interface and principal stress inside ice increased along with the increase of heat flow rate, which can be easily larger than the shear strength of adhesion interface and key factor for ice fracture. The preliminary ice fracture judgement criterion was founded based on the relationship between interfacial stress and adhesion strength related with interfacial temperature. Ice fracture appears when the sum of the interfacial stress generated by the external aerodynamic force and the interfacial thermal stress generated by the skin heating are greater than the shear strength related to the skin surface temperature. The fracture location is the area where the coupled stress exceeds the shear strength.
Preliminary study on influence of icing cloud parameters on ice shear strength on solid wall
XIAO Chunhua, LIN We, YANG Shengke
2019, 34(12): 2627-2634. doi: 10.13224/j.cnki.jasp.2019.12.011
Abstract PDF(798KB) icon896 icon280
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The ice shear strength test equipment was established in the test section of icing wind tunnel, and used to measure the shear strength between ice and solid wall of airplane. The reasonable range of ice shear strength was obtained. The ice shear strength measurement was implemented in test section of 0.3 m×0.2 m icing wind tunnel. The influences of icing cloud parameters on the ice shear strength between ice and solid wall were obtained. Research showed that the maximum value of ice shear strength appeared when the icing environmental temperature was between -15 ℃ and -10 ℃. The higher airflow speed indicated the larger impact force of droplets on solid wall. The gap among droplets was easier to be filled in. Thus, the ice shear strength was increased. The minimum value of ice shear strength happened when the mean volume diameter (MVD) of droplets was near 35 μm. The ice became compact and the gap among droplets was smaller along with the decrease of MVD. And the droplets easily spread out and were difficult to be frozen immediately. The ice shear strength increased due to the filling of gap among droplets.
Effect of ignition on detonation combustion of kerosene engine based on time-frequency analysis
HU Chunming, ZHAO Yingbo, LIU Na
2019, 34(12): 2635-2641. doi: 10.13224/j.cnki.jasp.2019.12.012
Abstract PDF(805KB) icon522 icon278
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Based on the instantaneous heat release rate, the time-frequency analysis of knock combustion was carried out on a self-developed piston-type aviation kerosene engine. The influence of the dual-spark ignition strategy on knock combustion was investigated. The result showed that the excessive heat release rate of the engine in 8.2-14.8 kHz frequency band led to knock combustion. Delaying synchronous phase ignition advance angle reduced the heat release rate in the major frequency band and inhibited knock. With the increase of the asynchronous ignition phase difference of the dual-spark ignition, the knock factor (KF) and the heat release rate in the major frequency band decreased gradually. Increasing ignition energy led to a slight increase in the knock tendency, but it can improve the power performance of the engine to some extent.
Thermometry method for high speed flying particle at low temperature based on laser induced fluorescence technique
ZHOU Jiangning, YIN Yimin, GUO Qiuting
2019, 34(12): 2642-2647. doi: 10.13224/j.cnki.jasp.2019.12.013
Abstract PDF(716KB) icon504 icon284
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A thermometry method was presented for high speed flying particles in low temperature applications with difficulty in measurement. Rhodamine B was doped in cellulose acetate particles to visually show spacial temperature distribution of these particles. The ratio of 600 nm photo luminescence fluorescence signal from these dye doped particles and 532 nm laser signal for excitation was applied to further eliminate interference from laser intensity fluctuation. Spectrum of dye particles at different temperature ranging from 20 ℃ to 80 ℃ was analyzed. Photo luminescence intensity, temperature sensitivity (-0.012 5 ℃-1 temperature coefficient at 80 ℃ and -0.037 9 ℃-1 temperature coefficient at 20 ℃) and measuring accuracy were significantly enhanced with temperature decline, further proving the potential of this technology at low temperature applications. Temperature behavior of high speed dye particle hitting target was present by this technique.
Experiment on film cooling characteristics for longitudinal corrugated heat-shield
WANG Minmin, ZHAO Xi, LIN Li
2019, 34(12): 2648-2655. doi: 10.13224/j.cnki.jasp.2019.12.014
Abstract PDF(927KB) icon637 icon295
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Detailed experimental study on film cooling effect of one afterburner longitudinal corrugated heat-shield was carried out. The surface temperature distribution of the heat-shield was captured by an infrared thermal imaging camera. The influence of adiabatic cooling efficiency was analyzed by different plate types, blow ratios and perforated percentages. In the experiment, flat panel and longitudinal corrugated heat-shield were adopted; the range of blow ratio was 0.5-3.0; the perforated percentage was 1.4%-3.7%. Results showed that, the film cooling efficiency of longitudinal corrugated heat-shield fluctuated with the fluctuation of corrugated plate structure and became larger than that of flat panel, while the film cooling efficiency of flat panel increased gradually along the way; with the increase of blow ratio, the film cooling efficiency increased gradually and reached to the maximum when the blow ratio increased to 3.0; the film cooling efficiency on the valley of the longitudinal corrugated surface was relatively higher than that on the wavy peak; the smaller the blow ratio, the more obvious the change of the film cooling efficiency with the fluctuation of corrugated plate; the film cooling efficiency changed and increased slowly along the high blow ratio (blow ratio of 2.0-3.0). As a whole, the film cooling efficiency increased gradually with the increase of the perforated percentage, and the film cooling efficiency at small perforated percentage (perforated percentage of 1.4%, 2.7%) was not much different, but on the leeward side of secondary flow, the film cooling with large perforated percentage was high.
Experiment on effects of airflow ratio on spray characteristics of dual-axial swirl cup
WANG Zhikai, CHEN Sheng, LIU Ran
2019, 34(12): 2656-2662. doi: 10.13224/j.cnki.jasp.2019.12.015
Abstract PDF(739KB) icon1525 icon299
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In order to explore a way to improve the spray performance under low injection pressure differential, from the perspective of regulating airflow split, effects of airflow ratio of primary swirler to secondary swirler on the spray characteristics of dual-axial swirl cup were studied by experimental system. The influences of airflow ratio on mean drop diameter, drop size distribution parameter and spray angle were obtained. The experimental results indicated that increasing the airflow ratio, the mean drop diameter decreased, and the swirl cup had good spray property over a wide range of injection pressure differential, which could achieve the improvement of the spray performance under low injection pressure differential. The spray angle increased with the airflow ratio, and firstly increased but then remained constant with the injection pressure differential. For a given total airflow of swirl cup, the optimal comprehensive spray performance was obtained when the airflow ratio was about 1.
Experimental on the thermal effects of pulsed dielectric barrier discharge plasma
TIAN Yongqiang, CAI Jinsheng, YANG Leilei
2019, 34(12): 2663-2676. doi: 10.13224/j.cnki.jasp.2019.12.016
Abstract PDF(1083KB) icon658 icon302
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A dielectric barrier discharge plasma actuator (DBDPA) was installed at the test section of a small calorimetric wind tunnel to study the thermal effects of dielectric barrier discharge plasma where the actuator was actuated by a pulsed dielectric barrier discharge plasma power source. The discharge power and the thermal power of the actuations were calculated by Lissajous figure method and the calorimetric principle, respectively, while their characteristics were studied. The following conclusions could be drawn: (1) the discharge power, thermal power and thermal efficiency of the dielectric barrier discharge plasma increased with the peak-peak discharge voltage and the discharge frequency; (2) both the power and thermal power of the actuator were power functions of the peak-peak discharge voltage and the discharge frequency, namely, the discharge power was proportional to the peak-peak discharge voltage to the power 1.75, and to the discharge frequency to the power 1, while the thermal power is proportional to the peak-peak discharge voltage to the power 5.0 and to the discharge frequency to the power 1.5; (3) to increase the thermal efficiency and the proportion of gas heating power in the total thermal power, it is better to give priority to increase the peak-peak discharge voltage instead of the discharge frequency.
Experiment on combustion characteristics of surrogate fuel for RP-3 aviation kerosene
LIU Jing, HU Erjiang, HUANG Zuohua
2019, 34(12): 2677-2685. doi: 10.13224/j.cnki.jasp.2019.12.017
Abstract PDF(938KB) icon769 icon291
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The laminar combustion characteristics of surrogate fuel for RP-3 aviation kerosene were investigated experimentally in a constant volume bomb. The experiments were performed at initial pressures of 0.1, 0.3 MPa, initial temperatures of 390, 400, 420 K, and over the equivalence ratio range of 0.8-1.5. Furthermore, the laminar combustion velocities of the surrogate fuel and RP-3 aviation kerosene were contrastively analyzed. Results showed that decreasing the initial pressure or equivalence ratio increased the stability of the flame front, which was established by increased Markstein length. The effect of the initial temperature on the Markstein length was not clear. Increasing the initial temperature or decreasing the initial pressure led to an increase in the laminar combustion velocity of the surrogate fuel. With the increase of equivalence ratio, the laminar combustion velocity illustrated an increase initially and then decreased gradually, and the highest value was measured at the equivalence ratio was 1.2. Furthermore, the laminar combustion velocity of the surrogate fuel agreed well with that of RP-3 aviation kerosene under the same conditions.
Numerical study on influence of local regular coating on temperature measurement of film-cooled vane
YANG Guang, AI Yanting, XU Yi
2019, 34(12): 2686-2694. doi: 10.13224/j.cnki.jasp.2019.12.018
Abstract PDF(1011KB) icon526 icon271
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In order to study the influence mechanism of temperature measurement coating on measuring accuracy of fine thermocouple, a three-dimensional model for film-cooled vane was established based on conjugated heat transfer(CHT) method. SST(shear stress transport) γ -θ turbulence model was carried out on the film-cooled vane sprayed with alumina coating on the front edge of suction, front edge of pressure and trailing edge of pressure surface. The error between the numerical results and the experimental results was controlled below 5%, verifying the effectiveness of the numerical method. The results showed that, the coating had a significant effect on the flow characteristics of gas near the wall. However, the numerical results of three coating conditions showed that the temperature difference amplitude at the front edge of pressure was smaller than that at the front edge of suction, and the temperature measurement error was 35.5% lower than that at the trailing edge of pressure. In addition, on the pressure surface and the front edge of suction, the best temperature measurement area was between the middle and the lower end of the coating, while on the trailing edge of the pressure surface, the best temperature measurement area was close to the upper end of the coating.
Effects of inlet misalignment and axisymmetric contouring on endwall heat transfer characteristics in transonic turbine cascade
LI Zhigang, BAI Bo, LIU Luxuan
2019, 34(12): 2695-2705. doi: 10.13224/j.cnki.jasp.2019.12.019
Abstract PDF(1586KB) icon497 icon300
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To evaluate the effects of endwall misalignment and axisymmetric endwall contouring on the endwall heat transfer characteristics in the realistic transonic gas turbine cascade, the guide cascade in the first stage of an industry gas turbine was taken as the research object. The commercial CFD software ANSYS Fluent 15.0 was adopted to numerically investigate the endwall flow and heat transfer characteristics for three types of endwall configurations, including: the simplified flat endwall, the realistic cascade outer endwall (vane shroud) and inner endwall (vane hub) with axisymmetric convergent endwall contouring in axial direction, at the gas turbine design condition (inlet turbulence intensity of 16%, exit Mach number of 0.85). The endwall thermal load distribution, secondary flow field near endwall and backward step vortices development were illustrated and compared for three endwall configurations with two combustor-turbine platform misalignment structures (inlet endwall step height of 0, 6.78 mm). Results showed that compared with the flat endwall configuration, the axisymmetric convergent endwall contouring and upstream endwall misalignment can result in dramatical changes in the endwall secondary flow pattern and thermal load distribution. In general, the axisymmetric convergent endwall contouring can result in a relative reduction in the endwall thermal load, especially for regions of endwall juction around the vane leading edge and downstream the vane throat, where thermal corrosions were more likely caused due to the poor cooling film coverage. In real gas turbine engines, the combustor-turbine endwall misalignment can dramatically enlarge the high thermal load region (upstream the cascade leading edge) which was migrating to the downstream cascade passage, and result in a significant increase (up to 140%) in the heat transfer level. Therefore, the important influences of the endwall contouring and endwall misalignment should be carefully taken into account for the endwall cooling scheme design of the first stage guide cascade in the real gas turbine engines.
Impact of Reynolds number on unsteady flow in axial flow compressor rotor
CHEN Zhiyang, WU Yanhui, AN Jinhuaiyuan
2019, 34(12): 2706-2718. doi: 10.13224/j.cnki.jasp.2019.12.020
Abstract PDF(1076KB) icon662 icon331
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Experimental measurements were conducted for an axial high-speed subsonic compressor rotor on the ground. Numerical investigations were carried out at two altitudes to explore the mechanism of circumferential propagation characteristic at different Reynolds number (Re). Results showed that, on the ground, rotating instability (RI) was measured near stall condition, which was characterized by a hump frequency band in the spectrum. Characteristic frequencies of numerical pressure signals were limited in the frequency band of RI on the ground. The spectrums of the neighboring passages indicated that the flow unsteadiness rotated in the compressor. The circumferential disturbance was result of the periodic interaction between the blade tip leakage flow and the blade tip load. At the altitude of 20 km, there were several circumferential disturbances with different characteristic frequencies in the compressor near stall condition. The radial flow from the hub to tip induced by the suction surface flow separation was dominant in the tip region. The blade tip load was influenced both by the radial flow and tip leakage flow, as a result of the circumferential disturbance at low Re.
Three-dimensional optimization correction of Moses stall model
ZHANG Xingfa, LI Jun, SONG Guoxing
2019, 34(12): 2719-2728. doi: 10.13224/j.cnki.jasp.2019.12.021
Abstract PDF(771KB) icon480 icon286
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Through the low-speed axial flow compressor stall experiment, and in combination with the compressor stall simulation cloud map and the measured blade radial pressure pulsation diagram in the experiment, partial leaf high stall other than full leaf high stall was found after the stall. Based on the stall prediction Moses model, by comparing the total pressure loss calculated from different radial sections, it was found that variation of the installation angle of the radial blade section had an influence on the calculation result of the model. The parameter k in the model was optimized by introducing the parameter B. The predicted results of the optimized model can predict the situation after the compressor stalls more accurately than the original model. The optimized model can provide good reference design data for the compressor design. The high subsonic axial compressor was optimized, and the high-speed compressible factor was taken into account in the model derivation, and the model was improved. The improved model was compared with the original model in predicting and calculating the high subsonic axial compressor pressure ratio. Feature accuracy increased by 30%.
Convolutional neural network diagnosis method of rolling bearing fault based on casing signal
ZHANG Xiangyang, CHEN Guo, HAO Tengfei
2019, 34(12): 2729-2737. doi: 10.13224/j.cnki.jasp.2019.12.022
Abstract PDF(914KB) icon891 icon308
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A fault diagnosis method based on convolutional neural network (CNN) was proposed for the weak fault of the engine casing under the rolling bearing fault excitation. The one-dimensional original signal was converted into image signal by using three preprocessing methods: matrix graph method, kurtosis graph method and wavelet scale spectrum. Then the convolutional neural network was used to identify the fault. Through comparative analysis, the fault identification rate of rolling bearing was 95.82%, which was higher than other vibration signal pretreatment methods. At the same time, the fault recognition rate of convolutional neural network was about 7% higher than that of traditional support vector machine (SVM) because it can use deep network structure to extract the fault characteristics of rolling bearing adaptively. The results show that the proposed method is feasible and effective, and has a good generalization ability and robustness.
Continuous dynamic numerical analysis of residual stress field under multi-point laser shock peening
GOU Lei, MA Yu’e, DU Yong
2019, 34(12): 2738-2744. doi: 10.13224/j.cnki.jasp.2019.12.023
Abstract PDF(665KB) icon658 icon314
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In order to improve the efficiency and accuracy of numerical simulation of laser shock peening(LSP), a continuous explicit-dynamic impact simulation strategy was proposed based on the traditional simulation strategy. The explicit-dynamic analysis was used directly to simulate the multiple shot peening. And then the implicit-static analysis was used to obtain the stable residual stress field after being balanced. The three-dimensional finite element model of a plate was established by ABAQUS. Based on this strategy, the distribution of residual stress field after repeated impacts was studied. After Python post-processing, the simulated values were in good agreement with the experimental measurements. It was shown that the maximum residual stress was -212.5 MPa; the mean value was -216.7 MPa, and the error was 1.9% when the laser power density was 1 GW/cm2. With the increase of laser power density from 1 GW/cm2 to 4 GW/cm2, the depth of residual stress layer increased from 0.7 mm to 1 mm. The simulation accuracy was effectively improved on the basis of greatly improving the simulation efficiency, providing a simulation idea for large area LSP numerical simulation of large-scale structures.
Calculation of gear meshing stiffness and loaded tooth contact analysis based on ease-off surface topology
WEI Bingyang, YANG Jianjun, NIE Shaowu
2019, 34(12): 2745-2752. doi: 10.13224/j.cnki.jasp.2019.12.024
Abstract PDF(731KB) icon709 icon292
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Based on the theory of rack-gear equal-tangential conjugate generating, the construction of numerical model of tooth surface and ease-off surface of gears was presented. Through analysis on the tooth surface meshing information of ease-off surface implication, the contact path, transmission errors and falls of contact line were obtained. Combining the ease-off simulation of tooth surface and the non-linear element coupling gear stiffness analysis, the computational method on time-varying meshing stiffness, loaded transmission errors for the modified tooth surface was presented. The computation was done by traversing the sequence contact lines according to the contact path, then the tooth meshing stiffness, loaded transmission errors and load distribution map were obtained. Two examples on topological tooth surface for symmetrical and bias modification of the 2-order paraboloid were acquired, and a series of results for the tooth meshing stiffness, loaded transmission errors and load distribution map under varied loads were gained. Results showed that the varied effects of tooth meshing stiffness weakened obviously with the increasing loads, and the fluctuation of loaded transmission errors was closely related to meshing stiffness and modification gradient of tooth surface. The bias modification was better than the symmetrical one in the performance of meshing stiffness, loaded transmission errors and load distribution.

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