2014 Vol. 29, No. 12

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Display Method:
Similarity solutions and approximation solutions of velocity and temperature in laminar boundary layer of subsonic and supersonic wedge flows
ZHAO Guo-chang, DU Xia, SONG Li-ping, KONG Jing-ru
2014, 29(12): 2785-2794. doi: 10.13224/j.cnki.jasp.2014.12.001
Abstract PDF(1166KB) icon1762 icon1450
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The variations in the dimensionless velocity due to changes in similarity variables of wedge flows with different wedge angles were obtained using the Runge-Kutta method by solving the third-order nonlinear ordinary differential equation of the dimensionless stream function that was obtained through similarity transformation, which described the wedge flow in the laminar boundary layer. The second-order linear homogeneous differential equation of dimensionless temperature based on the similarity variable in the laminar boundary layer of the subsonic wedge flow and the second-order linear non-homogeneous differential equation of dimensionless temperature on the similarity variable in the laminar boundary layer of the supersonic wedge flow were derived. The general temperature distribution solutions in the laminar boundary layers of subsonic and supersonic wedge flow, the similarity solutions and exponential form approximation solutions of dimensionless temperature in the laminar boundary layers under the condition of constant wall temperature for subsonic wedge flow and the condition of adiabatic wall for supersonic wedge flow were obtained by solving the above two differential equations. The effects of compressibility and viscosity of the supersonic gas in the laminar boundary layer on velocity and temperature were investigated using the wedge flow of wedge angle of 0 as a representative example. It is shown that the maximum absolute value of relative errors between the similarity solution obtained under the condition of incompressible and constant properties and the similarity solution obtained under the condition of compressible and variable properties is less than 9.8%. Results show that: the larger the Pr of the wedge flow, the more dramatic the change in dimensionless temperature in the area close to the wall; the viscous dissipation causes the temperature of the wedge flow from the wall to the main flow in the boundary layer to first increase and then decrease under supersonic flow conditions and with temperatures lower than the adiabatic wall temperature.
Low pollution combustor design and emission performance prediction based on stratified and staged combustion mechanism
LI Feng, GUO Rui-qing, GAO Xian-zhi, LÜ Fu-guo, WANG Yun-lei, SHANG Shou-tang
2014, 29(12): 2795-2800. doi: 10.13224/j.cnki.jasp.2014.12.002
Abstract PDF(834KB) icon2095 icon1329
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The dimension of diffuser, maximum diameter of outer casing and dimension of combustor exit were kept the same, and the combustor was designed as single annular combustor(SAC), dual annular combustor(DAC),twin annular premixing swirler(TAPS) combustor,center staged combustor(CSC)and triple-swirler combustor(TSC). The mathematical models(including the turbulence, spray, combustion, radiation and emission) were kept the same, and three-dimensional numerical simulation of five different combustors were developed to compare and study the pollution emission performance of five different combustors. The results show that, the CO emission value of the staged DAC in idle operation is the lowest, and the CO emission value of DAC is 62% lower than that of SAC. NOx emission value of the stratified TAPS combustor in design state is the lowest, and the NOx emission value of TAPS combustor is 43.5% lower than that of SAC.
One-dimensional unsteady simulation method of cavity in secondary air system
WU Hong, LI Peng, HUANG Dan-ping, TAO Zhi
2014, 29(12): 2801-2809. doi: 10.13224/j.cnki.jasp.2014.12.003
Abstract PDF(963KB) icon1554 icon1173
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The main purpose is to investigate one-dimensional calculation method of cavities. The general one-dimensional modeling rule was put forward for complex cavities with nonstandard structure and multi-connections. The method of characteristics was adopted, and the one-dimensional unsteady flow and heat transfer of cavity structure was simulated. One-dimensional compressible partial differential equations of cavities generally integrating variations of variable cross section, friction and heat transfer were transformed to ordinary differential equations, so characteristic numerical solutions of pressure, flow, temperature and other parameters along the flow direction in cavity were derived. Results were verified by commercial computational fluid dynamics software CFX. Result shows that, the method adopted for one-dimensional unsteady flow and heat transfer simulation of cavity is visual and accurate, so it's capable of simulating complex cavity with multi-connections. The results of the method are about 9.4% away from that of the CFX model. Thus, it can be a useful way of one-dimensional unsteady research on cavity in secondary air system.
Detailed chemical reaction mechanism of surrogate fuel for RP-3 kerosene
ZENG Wen, LI Hai-xia, MA Hong-an, CHEN Bao-dong, HU Er-jiang
2014, 29(12): 2810-2816. doi: 10.13224/j.cnki.jasp.2014.12.004
Abstract PDF(798KB) icon2051 icon1171
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The ignition characteristics of RP-3 kerosene were measured in a chemical shock tube and the ignition delay times of RP-3 kerosene at various conditions were gained. According to the chemical compositions and physical properties of RP-3 kerosene, a surrogate fuel including n-decane, toluene and propyl cyclohexane(volume fraction of 0.65,0.1,0.25) was provided, and the detailed chemical reaction mechanism for this surrogate fuel was developed. The ignition characteristics of this surrogate fuel in the chemical shock tube at various conditions were simulated using this detailed chemical reaction mechanism, and the simulation results were compared with the experimental data. The results show that the correlation for the logarithm of the ignition delay time of RP-3 kerosene and the reciprocal ignition temperature is linear under different pressures and equivalence ratios, and with the increase of ignition temperature and pressure and the derease of equivalence ratio, the ignition delay time is shortened. At the same time, the ignition delay times of this surrogate fuel computed by this detailed chemical reaction mechanism under different conditions agree well with the experimental data of RP-3 kerosene.
Experiment on heat exchange and cooling of pulse detonation engine detonation tube wall
HUANG Xi-qiao, LI Yang, XIONG Yue-fei, YUAN Yuan-yuan, ZHENG Long-xi
2014, 29(12): 2817-2823. doi: 10.13224/j.cnki.jasp.2014.12.005
Abstract PDF(924KB) icon1784 icon1125
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Experimental investigation for pulse detonation engine (PDE) tube wall temperature distribution along axial direction with or without cooling water using Pt100 thermal resistance was conducted. The results indicate that the outer detonation tube wall temperature increases as the engine's detonation frequency increases at the same axial location of detonation tube. At the same detonation frequency, the outer detonation tube wall temperature in the zone far away from the thrust wall is higher than that in the zone near the thrust wall. The outer detonation tube wall temperature and the temperature gradient reduces when the cooling water is filled into the detonation heat exchange system. The temperature of outer detonation tube wall could be decreased by 106.5℃ when the PDE works for 16s at the detonation frequency of 20Hz.
Measurement of transient velocity field at exit zone of valve pulse jet engine
CAI Wen-xiang, QI Bin, MA Hu, WU Xiao-song, SONG Xiao-dong
2014, 29(12): 2824-2829. doi: 10.13224/j.cnki.jasp.2014.12.006
Abstract PDF(1056KB) icon1475 icon1158
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Advanced TR-PIV (time-resolved-particle image velocimetry) system was used to measure transient velocity field at a Helmholtz-type valve pulse jet engine exit zone. Test results indicate the cyclical evolution process of velocity field and pressure at the exit zone of valve pulse jet engine, and the maximum time-averaged velocity of the engine is not at the nozzle's exit. The vorticity and duration in the exhaust stage was stronger than that in the inspiratory stage. Measured velocity field shows that transient high-temperature combustion gas does not fully expand at the exit plane, but continues to be expanded at the following exit zone, which is disadvantageous for improving the performance of pulse jet engine.
Heat transfer characteristics calculation for aero-engine shell-tube fuel-oil heat exchanger
LÜ Ya-guo, LIU Zhen-xia
2014, 29(12): 2830-2835. doi: 10.13224/j.cnki.jasp.2014.12.007
Abstract PDF(946KB) icon1742 icon1212
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A dimensionless relationship (Re~St·Pr2/3)was introduced for calculating the heat transfer coefficients in tube and shell sides of shell-tube fuel-oil heat exchanger, and a heat transfer characteristics calculation model of shell-tube fuel-oil heat exchanger was established based on efficiency-number unit method. Based on little experimental data of one shell-tube fuel-oil heat exchanger of aero-engine, the relationships of Re~St·Pr2/3 were fitted for tube and shell sides of this heat exchanger, and the relationships were applied to heat transfer characteristics calculation of a similar shell-tube fuel-oil heat exchanger. A case study shows that the relative errors of the outlet temperature in tube and shell sides are less than 6.5% and the relative error of total heat transfer is less than 7.4%, indicating that the calculation results are in good agreement with experimental data. The method presented can be applied to calculate the heat transfer characteristics of aero-engine shell-tube fuel-oil heat exchanger in design and validation stages.
Numerical investigation of influence of radial vane cavity on turbine inter-vane burner performance
LI Ming, TANG Hao, ZHENG Hai-fei, LI Yan
2014, 29(12): 2836-2844. doi: 10.13224/j.cnki.jasp.2014.12.008
Abstract PDF(1352KB) icon1434 icon1125
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Two turbine inter-vane burner (TIB) models with different radial vane cavities (RVC) were designed to investigate the influence of RVC on TIB. Computational fluid dynamic method was carried out to simulate the turbulent flow and combustion in the TIB. Comparisons show that the simulation results accord well with the experimental data. TIB performs well with 97.5% or higher combustion efficiency and 5.7% pressure loss. Airflow is detached from the convex surface of the vane with RVC in the same surface and the flow field is changed drastically. The RVC in the concave surface can alleviate the detachment and mitigate the radial profile of velocity distribution at the outlet. In the TIB with RVC in the concave surface of the vane, the combustion efficiency is relatively higher; the vane temperature is lower and the temperature distribution is more uniform in the passage and outlet. The emission of CO and unburned hydrocarbon is lower in the TIB with RVC in the concave surface. However, the emission of NO will increase.
Application of turbulent combustion models in spray combustion of an aero-engine
XU Rong, ZHAO Jian-xing, WANG Suo-fang, YAN Ying-wen
2014, 29(12): 2845-2853. doi: 10.13224/j.cnki.jasp.2014.12.009
Abstract PDF(1088KB) icon1944 icon1269
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A self-developed software was used to simulate for three-dimensional turbulent kerosene two-phase combustion processes in aero-engine annular combustor with swirl cup. Multi-dimensional empirical analysis method and multi-step reaction flamelet model mechanism were used to calculate pollutant emission levels of annular combustor with swirl cup. Prediction capability of four turbulent combustion models for spray combustion flow field and pollutant emission were analyzed and compared. Calculated results obtained by these models were in reasonable agreement with corresponding experimental data. It shows that these turbulent combustion models can be used to predict two-phase combustion flow fields and pollutant emission of annular combustor with swirl cup. But calculation accuracy of these models are different. Outlet temperature distributions and pollutants emission obtained by the multi-step reaction flamelet model are the closest to the experimental data. Simulation accuracy of the multi-step reaction flamelet model is higher than that of other models. Then it is clear that the calculation accuracy and reliability may be raised by adopting reasonable turbulent combustion model.
Study on thermoacoustic characteristic of lean premixed swirling flames
YANG Fu-jiang, GUO Zhi-hui, ZENG Yu-hui
2014, 29(12): 2854-2861. doi: 10.13224/j.cnki.jasp.2014.12.010
Abstract PDF(1089KB) icon1746 icon1275
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A lean premixed swirling combustor was constructed. The data of frequency of instable fluctuation, amplitude and distribution of pressure oscillation and the response of heat release from varying equivalent ratio were applied to obtain the nonlinear development of combustion instability from stability to limit cycle. A thermoacoustic network model with low orders was utilized to analyze the oscillating solutions for the experiments. The results from the experiments show that a typical nonlinear process can describe the root mean square of pressure oscillation and heat release response with the increasing equivalent ratio, and the flame has significantly different structures in different states. The results indicate that the frequency error between the calculation and experiment is less than 1% when the equivalent ratio is less than 0.7, while the frequency error is 13% when the equivalent ratio is greater than 0.7.
Combustion efficiency test method in scramjet engine
GUO Rui-qing, LI Feng, WANG Yun-lei, LÜ Fu-guo, SHANG Shou-tang, TANG Zheng-fu
2014, 29(12): 2862-2867. doi: 10.13224/j.cnki.jasp.2014.12.011
Abstract PDF(843KB) icon1249 icon989
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A scramjet engine combustion efficiency measure system was designed. The combustion efficiency was measured by chromatography method, and the results of chromatography method were compared with those of temperature method. The results indicate that the combustion efficiency measured by chromatography method was 80.7%, lower than the combustion efficiency of 84.5% measured by temperature method; the combustion efficiency could be measured more precisely by chromatogram method than by temperature method. The combustion efficiency measure system based on chromatogram method can work well, and thus can be used to measure the combustion efficiency of scramjet engine.
Experiment of combustion performance of a triple swirler combustor with no dilution holes
DING Guo-yu, HE Xiao-min, ZHAO Zi-qiang, JIN Yi, HONG Liang
2014, 29(12): 2868-2873. doi: 10.13224/j.cnki.jasp.2014.12.012
Abstract PDF(917KB) icon1581 icon1115
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Experiments were conducted to study the combustion performance of a triple swirler combustor with no dilution holes at different inlet airflow velocities and fuel-air ratios. The results show that the ignition fuel-air ratio increases from 0.0115 to 0.0174 with the growing inlet airflow velocity, while the lean blowout fuel-air ratio varies little and most of these values are below 0.005; at the same fuel-air ratio, the slower inlet airflow velocity means the higher combustion efficiency; the combustion efficiency is above 0.895 at all experimental conditions, and the outlet temperature distribution factor is about 0.1 at the state of high fuel-air ratio; in full consideration of all combustion performance, the experiment results have proved the feasibility of canceling dilution holes for high fuel-air ratio combustors and several technology innovations mentioned here in.
Sensitivity analysis of fault diagnosis of aero-engine rolling bearing based on vibration signal measured on casing
CHEN Guo, HAO Teng-fei, CHENG Xiao-yong, ZHAO Bin, WANG Hai-fei
2014, 29(12): 2874-2884. doi: 10.13224/j.cnki.jasp.2014.12.013
Abstract PDF(1819KB) icon2146 icon1095
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The sensitivity of fault diagnosis of aero-engine rolling bearing based on the vibration signal measured on the casing was studied. Firstly, the impulse response test was performed by two aero-engine rotor test rigs with casing. The response from both bearing housing and casing, which was caused by the impulse excitation from the location of rolling bearing, was measured and their differences were compared further. Secondly, the fault simulation test of rolling bearing was performed by these two aero-engine rotor test rigs. The time domain waveform, frequency spectrum and wavelet envelope spectrum of the signal measured on the casing were compared in detail with those of the signal measured on the bearing housing. The results show that when the coupling stiffness between rolling bearing and casing is small, there is a large attenuation of the vibration signal of faulty rolling bearing transmitted to the casing. However, by means of traditional envelope demodulation method based on wavelet transformation, the faults of outer and inner races still can be diagnosed well, but the diagnosis effect for rolling element is not as good as that for outer and inner races. The research results provide a test basis for actual fault diagnosis of aero-engine rolling bearing based on the vibration signal measured on the casing.
Coupling flutter of swept fan rotor blade with small aspect ratio
WU Chang-bo, ZHOU Bai-hao, CUI Hai-tao, GAO Yuan
2014, 29(12): 2885-2890. doi: 10.13224/j.cnki.jasp.2014.12.014
Abstract PDF(900KB) icon1492 icon1010
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Based on structural mechanics, blade coupling flutter characteristics of an engine blisk were analyzed.Analyses of resonance rotating speed, coupling flutter and stall flutter were accomplished by swept fan rotor blade with small aspect ratio. The unusual phenomena showing that the change of dynamic and static frequencies of second-order and third-order on the swept fan blade with small aspect ratio were found, and recognized as another problem relating to coupling flutter. By structure adjustment of swept fan rotor blade with small aspect ratio, it was found that swept-forward blade was an important factor to this unusual phenomenon. Reducing the swept degree of the blade appropriately can avoid the possibility of flutter by design.It is suggested the separation of order frequency degree for the blade should satisfy the design requirement of 10%.
Prediction method of elastic constants of 3-D braided ceramic matrix composites considering pores
SHI Duo-qi, NIU Hong-wei, JING Xin, ZHOU Xin-gui, YANG Xiao-guang
2014, 29(12): 2891-2897. doi: 10.13224/j.cnki.jasp.2014.12.015
Abstract PDF(822KB) icon1246 icon1008
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A method for predicting elastic constants of 3-D braided ceramic matrix composites was established by means of pore elements and taking into account its random distribution. The porosity was measured by industrial computed tomography (CT) scan systems. The Monte-Carlo technique was utilized to simulate the stochastic distribution of the pores in the 3-D braided ceramic matrix of the unit cell model. The effect laws of porosity on elastic constants of 3-D braided ceramic matrix composites were obtained through the finite element model of the unit cell. The results indicate that: (1) there exists obvious influence of porosity on the elastic constants of 3-D braided ceramic matrix composites; (2) for a certain porosity, the location distribution of pores has almost no effect on the elastic modulus along fiber bundle orientation; (3) the elastic modulus along fiber bundle orientation decreases with the increasing porosity. The tension test of SiC/SiC composites was also conducted at ambient temperature. The predicted value of elastic modulus matches with the measured data. The result has validated the proposed methodology for predicting the elastic constants of 3-D braided ceramic matrix composites with pores.
An efficient method for multidisciplinary design optimization of aircraft based on CFD/CSD coupling
ZUO Ying-tao, WANG Xiao-peng, CHEN Yun, CHEN Gang, GAO Zheng-hong
2014, 29(12): 2898-2904. doi: 10.13224/j.cnki.jasp.2014.12.016
Abstract PDF(894KB) icon1756 icon951
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A multidisciplinary design optimization method based on CFD/CSD (computational fluid dynamics/computational structure dynamics) coupling was built. The structural performance was predicted by the structural finite element equation, and the aerodynamic loads was predicted by solving N-S equations to get reliable optimization results. Surrogate model was adopted to alleviate the huge expense caused by high-fidelity models. RBF (radial basis function) was utilized to exchange data between fluid and structure, and energy conservation principle is guaranteed. Typical wing-body configuration was optimized by the proposed design optimization method to improve the aerodynamic and structural performance. After optimization, the drag and mass of the aircraft are reduced by 5.0% and 4.2%, respectively, and all the constraints are satisfied. All these indicate the effectiveness of the proposed method.
Buckling and post-buckling performance of aeronautic composite stiffened panel under compression
FENG Yu, HE Yu-ting, SHAO Qing, GAO Chao
2014, 29(12): 2905-2913. doi: 10.13224/j.cnki.jasp.2014.12.017
Abstract PDF(1204KB) icon1836 icon966
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Compression experiment on aeronautic composite stiffened panel was conducted to study the buckling load, failure load and failure modes. From the experimental results, the average failure load(968.25kN) was 1.65 times the average buckling load(587.5kN),indicating that the composite stiffened panel had a relatively high post-buckling bearing ability. Its primary failure modes are the debonding, crack of stiffeners and the splitting of panel. The failure section is usually located in the middle part of composite stiffened panel. The buckling load, failure load and post-buckling damage progress of stiffened panel were analyzed by using finite element software. Buckling load and failure load obtained were in well agreement with the experimental results. Compared with experimental results, the errors were -9.97% and 8.45% respectively, indicating the validity of the finite element model. Sequence of damage occurring in fiber and matrix was studied. The simulation results show that in post-buckling progress, the damage of fiber occurs earlier than that of the matrix, and especially the damage of fiber in middle part of stiffeners is most serious. There is little damage in matrix before the failure of composite stiffened panel.
Study on vibration localization of oblique impact of whole-circle bladed disk with tips system
DONG Ming-jing, DING Qian
2014, 29(12): 2914-2923. doi: 10.13224/j.cnki.jasp.2014.12.018
Abstract PDF(1383KB) icon1253 icon944
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Vibration localization of oblique impact of whole-circle bladed disk with tips was studied. Lumped parameter dynamical model of whole-circle bladed disk with tips was developed to calculate the natural frequencies under varying coupled stiffness. Vibration characteristics and rub-impact force of the blade at different orders were computed under mistuning tip clearance. Then, oblique impact/non-impact vibration localization factors with different coupling stiffnesses were analyzed under blade mistuning stiffness. Differences of vibration localization factors for two types of coupling stiffness were studied under random mistuning stiffness and tip clearance. The result shows that when the oblique impact or disk resonance occurs, even the tuning bladed disk system may have vibration localization phenomenon. On the other hand, vibration localization happens at every order of resonance for mistuning systems. Computations suggest that rub-impact force is directly associated with vibration localization. Blades turn more sensitive to mistuning due to the oblique impact effect. In addition, systems with weaker coupling stiffness often have relatively larger vibration localization factors. Also, mistuning stiffness has more influence on blade vibration localization sensitivity than the mistuning tip clearance.
Research and experiment on improved sectional combination control scheme for civil turbofan engine's startup process
KONG Xiang-xing, WANG Xi, ZHANG Shao-ji, YIN Chang-zhi, WANG Xiang-yu
2014, 29(12): 2924-2929. doi: 10.13224/j.cnki.jasp.2014.12.019
Abstract PDF(900KB) icon1571 icon1010
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A n-dot closed loop control algorithm was applied to the startup process for a civil turbofan engine. Therefore, an openned/closed loop sectional combination control scheme for turbofan engine's starup process was designed. The simulation result shows that the n-dot closed loop control algorithm could cause oscillation at the beginning of startup process of turbofan engine. To eliminate the parameters' oscillation at the beginning of startup process, the n-dot closed loop control algorithm was improved according to the rationale of surge recovery by using fuel air ratio unit as the control variable. The experiment results illustrate that the improved sectional combination control scheme could effectively restraine the parameters' oscillation, and furthermore the startup transition process had satisfying stability and repetitive. The numerical difference of high pressure rotor speed under different atmosphere conditions does not exceed 1.0% and the time delay does not exceed 0.9s; meanwhile the numerical difference of high pressure rotor speed under different flight conditions does not exceed 1.0% and the time delay does not exceed 1.2s.
Sensor fault diagnosis of aero-engine based on DE-RLSSVM algorithm
HOU Kuan-xin, DING Fa-jun, ZHANG Dao-xin, HUANG Xuan-hong, WEI Wu-guo
2014, 29(12): 2930-2935. doi: 10.13224/j.cnki.jasp.2014.12.020
Abstract PDF(892KB) icon2113 icon981
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In order to improve the generalization capability and sparsity of reduced least square support vector machine (RLSSVM), DE-RLSSVM was presented, whereby differential evolution (DE) algorithm was used to select the support vector of RLSSVM. Experiments on benchmark regression data sets show that the presented algorithm has good generalization and sparsity capabilities. Then, the presented algorithm was applied to sensor fault diagnosis of aero-engine. DE-RLSSVM algorithm was used to detected sensors faults, then to locate and isolate the faults. The simulations show that the sensor fault diagnosis system using the presented algorithm can detect and isolate hardware faults of sensor of aero-engine.
Design of open DEEC based on TTP/C bus and verification of PIL simulation
CHEN Jian, LIU Dong-dong, ZHANG Tian-hong
2014, 29(12): 2936-2941. doi: 10.13224/j.cnki.jasp.2014.12.021
Abstract PDF(863KB) icon1529 icon910
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With the self-development TTP/C (time trigger protocol/automotive class C) bus controller, a redundant architecture of open DEEC (digital electronic engine controller) was proposed, which was divided into three kinds of intelligent nodes: input, core calculation and output, and the task scheduling for each intelligent node was planned. Hardware platform of intelligent node was designed based on DSP (digital signal processor) and FPGA (field-programmable gate array), and the software was designed for each intelligent node. Finally, a PIL (process in the loop) simulation test platform for open DEEC was constructed.With an engine model as the controlled object, the state regulation experiments and bus fault injection experiments were conducted.The experiment results show that the open DEEC architecture is feasible and has a good reconstruction ability.
Timing control strategies of air-assisted direct injection engine
WANG Yong-wei, WEI Min-xiang, YANG Hai-qing, LIU Rui
2014, 29(12): 2942-2947. doi: 10.13224/j.cnki.jasp.2014.12.022
Abstract PDF(930KB) icon1483 icon981
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The electronic control unit and crankshaft position sensor for a air-assisted direct injection engine were designed and developed. On this basis, the timing control strategies of the air-assisted direct injection engine were presented, including software timing, air-assisted fuel injection timing and ignition timing. In order to achieve the precise control of the engine timing, a method of "count teeth delay" control was proposed. Simulation and bench test show that the timing control strategies based on the self-developed electronic control unit for air-assisted direct injection engine are accurate and feasible.
Numerical simulation on stall margin improvement of transonic compressor by a trapped vortex casing treatment
WANG Zhuo-qi, LU Li-peng, YUAN Wei, SONG Xi-zhen
2014, 29(12): 2948-2956. doi: 10.13224/j.cnki.jasp.2014.12.023
Abstract PDF(1156KB) icon1495 icon953
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A type of trapped vortex casing treatment (CT) was designed, using pressure difference between suction side at front and pressure side at rear of passage to drive fluid flowing back. Boundary flow was sucked into slot at rear of passage, then injected into main flow at front of passage. During this process, momentum of the fluid in the leakage was increased, and then the stall margin of the blade was enhanced. The loss of mixing is decreased by adjusting the direction of suction and injection to the direction of main flow. Also the size of CT in axial direction is inside the blade dimention, which means this CT could be used in each stage of multistage compressors, without overlapping with stators. Numerical simulation was used to evaluate the effectiveness of this CT. Result shows that this CT could increase the stall margin 17.39% of a transonic compressor rotor without compromise on efficiency.
Three-dimensional time-resolved measurements on rotor wake of low-speed axial compressor
WANG Si-chen, LI Ji-chao, LIN Feng, NIE Chao-qun
2014, 29(12): 2957-2964. doi: 10.13224/j.cnki.jasp.2014.12.024
Abstract PDF(1194KB) icon1416 icon1052
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Three-dimensional time-resolved measurements were conducted on the rotor wake of a low-speed axial compressor. Methods such as phase lock average, root mean square and power spectral density were used to analyze the steady and dynamic characteristics of the rotor wake of a low-speed axial compressor in throttle process. The results show that the rotor wake has high total pressure and high root mean square under absolute frame, and the wake intensity varies along spanwise direction. The averaged total pressure rise coefficient decreases sharply because of the interaction between the rotor wake and main flow. Power spectral density analysis shows that as the rotor running is close to stall, a frequency band around 0.5 blade passing frequency appears in the region over 90% span and its power increases as the mass flow decreases.
Optimization design of centrifugal/oblique flow compressor two-dimensional blade profiles in three-dimensional environment
TAO Sheng, ZHOU Zheng-gui, YAN Xin, YANG Li-ming, ZHANG Min
2014, 29(12): 2965-2972. doi: 10.13224/j.cnki.jasp.2014.12.025
Abstract PDF(1095KB) icon1585 icon1073
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As for strong three-dimensional flow in centrifugal/oblique flow compressor rotor blade passages, the two-dimensional blade profiles were optimally designed in three-dimensional environment. The efficiency of centrifugal/oblique flow compressor calculated by the Denton viscous volume force method was obviously higher, and the problem was solved by modifying the viscous dissipation in the energy equation. Then, optimization design software of two-dimensional blade profiles was built by combining the modified flow field calculation module with the parallel genetic algorithm. The software was used for designing tip profiles of centrifugal impeller and oblique flow impeller. The mass flow and pressure ratio of these two optimized impellers are very close to objective values, and the efficiency in whole working range is significantly improved. At the design point, the efficiency of centrifugal impeller is improved from 0.938 to 0.947, and the efficiency of oblique flow impeller is improved from 0.899 to 0.918.
Influence on aerodynamic performance of a highly loaded two-stage fan with variable inlet guide vane
WU Dong, JIN Dong-hai, CAO Zhi-peng, AN Li-ping, GUI Xing-min
2014, 29(12): 2973-2979. doi: 10.13224/j.cnki.jasp.2014.12.026
Abstract PDF(1067KB) icon1605 icon1019
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In order to improve the stall margin and decrease the rotor attack angle of a highly loaded two-stage fan at off-design speed, different forms of variable inlet guide vane(VIGV) and traditional adjustable inlet guide vane were simulated, and the aerodynamic performance and internal flow field of highly loaded two-stage fan were analyzed. The numerical simulation results show that: at the 80% design speed, the highly loaded two-stage fan's adiabatic efficiency increases obviously with the increase of the VIGV's positive prewhirl, and the adiabatic efficiency increases 3.5% with prewhirl angle of 30 degrees; although traditional adjustable inlet guide vane has a better effect on the expanding stability, the loss is biggest when it needs a large prewhirl angle; the slot form, the slot position and the solidity of VIGV have a considerable influence on aerodynamic performance, with the design depending on the particular working conditions of the highly loaded two-stage fan.
Life prediction of liquid rocket engine thrust chamber liner wall
SUN Bing, DING Zhao-bo, KANG Yu-dong
2014, 29(12): 2980-2986. doi: 10.13224/j.cnki.jasp.2014.12.027
Abstract PDF(1078KB) icon1545 icon964
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To understand the failure mechanism and predict the life of thrust chamber liner wall, fluid-thermo-structural coupled numerical simulation was carried out for the thrust chamber. The thermal and mechanical loading of thermo-structural coupled analysis were provided by fluid-thermal coupled analysis; for thermo-structural coupled model, a two-dimensional plane strain finite element analysis of the nonlinear deformation of the thrust chamber liner wall was performed. Through computation, the stress-strain distribution of thrust chamber liner wall at different stages of each cycle and the deformation process under cyclic loading were obtained, and a post processing method is applied to predict the life of the thrust chamber liner wall. The results show the fluid-structural coupled method can accurately carry out the loading data exchange from fluid-thermo coupled module to thermo-structureal coupled module and provide the accurate boundary conditions for structural analysis. The liner wall is under tensile stress during the pre-cooling, post-cooling and relaxtion phases, while under compression stress during the hot run phase. The residual stress and strain are increasing with the operate cycle increasing. The cyclic thermal and mechanical loading cause the liner wall to bulge and thin, and finally lead to the failure of the cooling channel. The analysis model is able to simulate the deformation of the thrust chamber liner wall under cyclic thermo and mechanical loading and predict the cycle life.
Effects of different injectors on spray characteristics of power-law non-Newtonian propellant
LI Long-fei, ZHANG Meng-zheng, YANG Wei-dong, WANG Yan-tao
2014, 29(12): 2987-2992. doi: 10.13224/j.cnki.jasp.2014.12.028
Abstract PDF(1443KB) icon1432 icon991
Abstract:
In order to seek the effective injector type of the power-law non-Newtonian propellant,a water-based simulants whose rheological behavior was in accord with actual propellant was used. The injectors, including plain orifice, impinging injector, shearing impinging pneumatic atomizer, effervescent atomizer and swirling injector were investigated by experiments, and the effects of different injectors and their structural parameters on the spray characteristics were compared. The results indicate that the impinging injector is effective and its impinging angle and injection velocity are the main influencing parameters to spray property. The effervescent atomizer is an effective injector type. Water-based simulants break up and produce drops when ratio of air/liquid mass flow rate is about 4%.
Characteristics of effective pivot point excursion for flexible joint
WANG Chao, REN Jun-xue, HAO Wen-qiang, LIU Yu, YANG Jing-xian
2014, 29(12): 2993-2999. doi: 10.13224/j.cnki.jasp.2014.12.029
Abstract PDF(966KB) icon1774 icon1012
Abstract:
A miniature flexible joint using silicone rubber elastomer and wrapped insulating boot was designed. The relation between effective and geometric pivot points was studied. The quadrinomial second order Mooney-Rivlin invariant model was used to describe the constitutive relationship of the elastomer. The excursions of effective and geometric pivot points of flexible joint at different vector angles under 0MPa and 9MPa vessel pressure were calculated respectively using ANSYS. Both effective and geometric pivot point cylinders were obtained. The simulation and experiment results of effective pivot point were compared. The accuracy of the geometric pivot point excursion was verified by the experiment of clearance crash. In addition, the reason of the effective pivot point excursion was also studied. Results show that the simulated effective pivot point cylinder has a good agreement with the experiment. The effective and geometric pivot points are of different concepts. The effective pivot point excursion is limited to a radius of 2.5mm, 1.4mm high cylindrical envelope while the geometric pivot point excursion is limited to a radius of 0.013mm, 0.6mm high cylindrical envelope. The effective pivot point excursion is caused by different strains of each reinforcement and elastemer.
Form grinding and experiment on segment topographic modification gear
WANG Hui-liang, DENG Xiao-zhong, YANG Jian-jun, XU Kai, SU Jian-xin, CHEN Qiang
2014, 29(12): 3000-3008. doi: 10.13224/j.cnki.jasp.2014.12.030
Abstract PDF(1420KB) icon1994 icon1000
Abstract:
Based on the form grinding method geometry theory and gear profile grinding machine kinematics principles gears, a segment topographic modification method of helical gear drives was proposed. Profile segment modification was achieved by changing length of involute occurrence line of invloute profile on the top and root of the tooth; longitudinal segment modification was achieved by attaching to a parabolic and linear radial feed motion when forming grinder is moving. The formula of topographic modification tooth flank was derived based on form grinding process, and the boundary of topographic modification tooth flank was divided and calculated to establish the equations of motion for every servo axis of form grinding machine. According to numerical simulation results of the tooth flank, machining on the five-axis computer numerical control (CNC) gear form grinding machine and on-machine topographic measurement can verify the feasibility of topological modification of tooth flank by the grinding method. Combined the given conditions of rotating speed and operating load gearbox loading experiment, the vibration energy level amplitude of gearbox is dropped 0.008dB and noise is reduced by about 2dB. The research results show that segment topographic modification is effective in reducing gear drives vibration and noise.

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