2014 Vol. 29, No. 4

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Numerical simulation of flow and heat transfer performance in turntable
YANG Zhi-min, JIA Zhen, ZHAO Yu, ZHANG Shu-hua, GE Xin
2014, 29(4): 737-747. doi: 10.13224/j.cnki.jasp.2014.04.001
Abstract PDF(1715KB) icon1623 icon945
Abstract:
For coolant water path of turntable scoured by hot gas at combustor exit, two-dimensional and three-dimensional physical models of were established to simulate the flow and heat transfer process in internal path. The effect of inlet pressure and mass flow of coolant water on flow resistant and heat transfer performance was investigated. The results show that: (1) increasing inlet pressure of coolant water has little influence on wall temperature of turntable, and the wall temperature of structure 1 increases by 5K and the wall temperature of structure 2 increases by 7K when the inlet pressure of coolant water of turntable increases from 2.3×105Pa to 8.3×105Pa; (2) the wall temperature of structure 1 decreases about 120K and the wall temperature of structure 2 decreases about 100K when the inlet velocity of coolant water increases from 0.5m/s to 5.3m/s; the cooling effect is obvious; (3) shortening passage area of structure 2 will gain better heat transfer effect with the smaller mass flow of coolant water.
Combustor design and performance prediction based on parametric model
LI Feng, SHANG Shou-tang, GUO Rui-qing, CHENG Ming, TANG Zheng-fu, SONG Bo
2014, 29(4): 748-754. doi: 10.13224/j.cnki.jasp.2014.04.002
Abstract PDF(776KB) icon1616 icon934
Abstract:
By combining the three-dimensional model software and grid generation software, the combustor parametric model and high quality and high speed gridding in the full flow field has been realized. Based on the research of the parametric modeling, an optimizing design, CFD analysis and performance prediction of the combustor have been accomplished, and the rule of the combustor performance variation with structural parameters was presented. The results show that the combustor capability has no significant change with the radial swirler parameters and the primary holes area. The combustor capability has significant change with position and profile of the primary holes and dilution holes, and the combustor outlet temperature profile and emission change greatly when the total hole area of the burnerinnerliner changes. The parametric model method is helpful to provide a fast design method for the aero-engine combustor design.
Numerical simulation of friction torque of rotating disc for rotor-stator system with central inflow
ZHANG Da, HAN Jian-qiao, LUO Xiang, XU Guo-qiang
2014, 29(4): 755-762. doi: 10.13224/j.cnki.jasp.2014.04.003
Abstract PDF(1132KB) icon2262 icon1067
Abstract:
In order to investigate the friction torque performance of rotating disc for rotor-stator system with central inflow, numerical simulation was conducted by using computational fluid dynamic (CFD) commercial software CFX in consideration of flow parameters and geometric structure respectively. A test rig for the friction torque of rotating disc was developed to test the friction torque of free disc. The numerical simulation results were compared with the previous empirical associated correlation for the friction torque of rotating disc for rotor-stator system with central inflow. The results show that compared with the previous empirical associated correlation, the difference of dimensionless the moment coefficient is within 10%. It is convenient to use turbulent parameter which represents the rotating speed and superimposed flow to analyze the friction torque of the rotating disc. For a given value of the turbulence parameter, the magnitudes of the rotating speed and superimposed flow have effect on the friction torque. Compared with the flow parameters, geometric parameters have smaller influence on friction torque.
Three-dimensional combustion numerical simulation of scramjet internal and external flow fields
NIU Dong-sheng, HOU Ling-yun, PAN Peng-fei, MA Xue-song, LU Jin-li
2014, 29(4): 763-769. doi: 10.13224/j.cnki.jasp.2014.04.004
Abstract PDF(902KB) icon1891 icon987
Abstract:
The coupling flow fields between internal combustion and external flow of a kerosene-fueled scramjet model were simulated by three-dimensional numerical methods. Good agreements between computation and experiments results are obtained for wall static pressure distributions of the combustor, of which the average relative error is 4.9%, validating that the numerical scheme employed is reliable. Results show that the combustion process of internal flow field is affected by air mass flow captured in the external flow field, and it in return influences the external shock wave structure. The pressure relief holes play a significant role in keeping mass flow matching between different components of the scramjet. In addition, flow filed near the first set of injectors was found asymmetric, due to the interaction between shock wave and boundary layer in the inlet as well as the oblique shock wave induced by the pressure relief holes there.
Experiment of heat transfer in internal cooling channel with tip and trailing edge outflows
LIANG Wei-ying, ZHU Hui-ren, ZHANG Li, XU Du-chun
2014, 29(4): 770-776. doi: 10.13224/j.cnki.jasp.2014.04.005
Abstract PDF(984KB) icon1747 icon939
Abstract:
Detailed local heat transfer distribution and average heat transfer trend at different inlet Reynold numbers with four discharge ratios were acquired by utilizing transient liquid crystal measurement.The purpose of this experimental study is to understand the effect on the heat transfer characteristic of a high pressure turbine blade internal cooling channel with different tip and trailing edge discharge ratios. The results show that: local heat transfer distributions are similar under different inlet Reynold numbers and the same discharge ratio; the discharge ratio has critical impact on local heat transfer distribution, especially in the second and third channels, where local and average heat transfer of these two channels have been weakened by outflow of the first tip hole. Different discharge ratios between the second tip holes and trailing edge have no obvious impact on local and average heat transfer of the first and second channels, but have critical impact on the third channel, while local and average heat transfer of this channel will be enhanced tremendously when the discharge ratio of trailing edge is raised.
Formation mechanism of microbubble emission boiling
TANG Ji-guo, SUN Li-cheng, ZHU Guang-yu
2014, 29(4): 777-782. doi: 10.13224/j.cnki.jasp.2014.04.006
Abstract PDF(1006KB) icon1644 icon1059
Abstract:
In order to explore the mechanism of microbubble emission boiling with high heat transfer performance, numerical simulations were conducted for the velocity field around a single film on the heating surface with the software of FLUENT, and then compared with experimental results. Experimental results indicate that there exists the collapse of film on the heating surface as for water when microbubble emission boiling occurs, and the increase of subcooling and wall superheat would enhance the collapse of film. However, as for ethanol, microbubble emission boiling hardly occurs. Simulation results indicate that there exists marangoni convection around the film under subcooled condition. Moreover, increase of subcooling and surface superheat could enhance marangoni convection around film of water. However, marangoni convection is rather weak near the film of ethanol. Therefore, the disturbance caused by strong marangoni convection near the film at the interface of air and liquid may lead to the collapse of film. This may be one of the reasons triggering microbubble emission boiling.
Analysis on supercooled large droplet impingement characteristics and ice shape of two-dimensional airfoils
DU Chen-hui, YU Jia, LIN Gui-ping, SHEN Xiao-bin, BU Xue-qin
2014, 29(4): 783-791. doi: 10.13224/j.cnki.jasp.2014.04.007
Abstract PDF(996KB) icon1829 icon1012
Abstract:
Based on existing supercooled large droplet (SLD) dynamic characteristics, the effects of droplet deformation on drag were analyzed, and the effects of drag change, rebounding and splashing of SLD on droplet impingement characteristics were analyzed by several typical rebounding/splashing models. The splashing model from software of FENSAP-ICE and rebounding model from software of LEWICE 2.0 were used to study the influence of rebounding and splashing to ice shape. The results show that the droplet diameter distribution is influenced greatly by the breaking up before droplet impingement, which should be considered in calculation of impingement characteristics and ice shape; breaking up, splashing and rebounding of SLD results in the decrease of local water collection coefficient and droplet impingement region; the splashing occurs mainly near the leading edge of airfoils and rebounding occur near the edge of the impingement region; with the droplet size increasing, splashing becomes weak, while rebounding is still obvious; the effect of drag change induced by SLD deformation on ice shape and ice accretion region is negligible; compared with the ice shape without considering splashing and rebounding, the ice shape considering splashing and rebounding is approximately the same at the leading edge, while the whole ice accretion region is smaller.
Numerical investigation of two-phase spray combustion performance for LPP low-emission combustor
ZHU Jia-wei, YAN Ying-wen, LI Shi, DENG Yuan-hao
2014, 29(4): 792-800. doi: 10.13224/j.cnki.jasp.2014.04.008
Abstract PDF(1215KB) icon1799 icon1069
Abstract:
Two-phase spray combustion flow field, temperature field and pollution emission performance of lean premixed prevaporized (LPP) low-emission combustor were calculated by software of Fluent. When the structure of pilot swirler and the inlet condition of LPP low-emission combustor were kept unchanged, influences of different primary swirler angles on combustion flow field, temperature field and pollution emission were investigated. Standard k-ε model was applied to simulate turbulent viscosity; fuel droplet trajectories were modeled by discrete phase model; non-premixed chemical equilibrium model was used to simulate the chemical reaction rates. Numerical results are as follow: (1) There are obvious primary recirculation zone, corner recirculation zone and lip recirculation zone in LPP low-emission combustor head. (2) The shape of primary recirculation zone is olive, and the length of primary recirculation zone is very long. With the increase of primary swirler angle, the primary recirculation zone becomes fatter and shorter, and the area of corner recirculation zone becomes smaller. (3) With the increase of primary swirler angle, the pressure loss will increase. (4) The production rate of thermal NOx is directly related with the area of temperature over 1950K and the highest temperature of gas. Near the flame front of pilot swirler and primary swirler, because of the high temperature, it is the main production area of thermal NOx. (5) With the increase of primary swirler angle, outlet temperature distribution factor increases firstly and then decreases. When the primary swirler angle is 45 degrees (just C project), outlet temperature distribution factor is the least, which means that the outlet temperature distribution is most uniform. (6) Under the same case, the combustion performance of C project is best.
Experiment of blow-out performance of premixed flame on porous media surface
ZHANG Long, XU Quan-hong, ZHANG Chi, LIN Pei-hua, LIN Yu-zhen
2014, 29(4): 801-806. doi: 10.13224/j.cnki.jasp.2014.04.009
Abstract PDF(873KB) icon1482 icon917
Abstract:
Experimental investigation was conducted on the premixed flame on porous media surface used for micro combustor, and the flow field characteristics and blow-out performance of porous media under different pore sizes and porosities were obtained. The research results indicate that the boundary layers of the flow field at the exit of porous media become thinner compared with pipe flow; the width of mainstream region is increased by about 50%, and the maximum speed fluctuation amplitude in this region reaches 2.2 times of the former. When the porosity of porous media decreases with the constant pore size, or the pore size of porous media decreases with the constant porosity, the speed fluctuation amplitude of mainstream region decreases. This becomes more obvious under small pore size condition with the maximum speed fluctuation amplitude decreasing from 2.435m/s to 1.099m/s. The flow field at the exit and flame shape have great influence on the blow-out performance of premixed flame on porous media surface. With the decrease of pore size and porosity, the blow-out velocity increases under the same equivalence ratio. The influences of porous media parameters can nearly double the blow-out velocity.
Response of hypersonic flow field on disturbance wave in free-stream and boundary-layer disturbance wave evolution
WANG Zhen-qing, TANG Xiao-jun, MENG Xiang-nan, LV Hong-qing
2014, 29(4): 807-816. doi: 10.13224/j.cnki.jasp.2014.04.010
Abstract PDF(1315KB) icon1953 icon1049
Abstract:
To investigate the interaction between hypersonic flow field and disturbance wave in free-stream, a high-order accuracy finite difference method was used to conduct directly numerical simulation of hypersonic transient flow field over a blunt cone under the action of slow acoustic wave. And Fourier frequency spectral analysis was used to study the temporal and spatial evolution of disturbance wave modes in boundary-layer. Results show that consecutive ∽-deformation appeares in bow shock and initial disturbance is enlarged greatly. The disturbance modes outside and inside the boundary-layer differ a lot. For spatial evolution (along the flow direction), the low frequency perturbation modes are dominated within a nose radius; with the disturbance development from upstream to downstream, the high frequency components increase quickly and low frequency components are almost restrained from growth. The ratio between low frequency and high frequency components transforms quickly. In the downstream of the flow field, most of the low-frequency disturbance component are attenuated, or no longer increase; there only exists a special frequency range of unstable wave rapid growth in the boundary-layer. Viewed from the temporal evolution, the dependence of dominant mode on the excitation of upstream is bigger than that of the other mode. Mode competition exists in both the temporal and spatial evolution of disturbance wave modes in boundary-layer.
Experiment on aero-engine altitude simulated pressure distortion
TIAN Jin-hu, QIAO Wei-yang, PENG Sheng-hong
2014, 29(4): 817-823. doi: 10.13224/j.cnki.jasp.2014.04.011
Abstract PDF(1107KB) icon1765 icon979
Abstract:
Because of the importance of experiment on aero-engine altitude simulated pressure distortion, the experimental project was discussed in detail. The experiment on aero-engine altitude simulated pressure distortion was launched by moving flashboard. The aerodynamic stability characteristic of aero-engine based on turbulent condition of moving flashboard was obtained, and the magnitude relations of key destabilizing factors such as pressure distortion, altitude low Reynolds number, air bleeding and power extraction to engine stability were obtained preliminarily. The effects of pressure distortion, altitude low Reynolds number, air bleeding and power extraction on critical complex total-pressure distortion descriptor are a fall of 11.11% of complex total-pressure distortion descriptor from altitude 1km to 18km and a fall of 14.69% from altitude 1km to 20km. It provides a testified platform and experimental database for aero-engine altitude aerodynamic stability.
Analysis and evaluation on RCS characteristics of helicopter considering modulated effect of rotor
JIANG Xiang-wen, ZHAO Qi-jun
2014, 29(4): 824-834. doi: 10.13224/j.cnki.jasp.2014.04.012
Abstract PDF(1936KB) icon1532 icon972
Abstract:
Considering the modulated effect of rotor, a panel-edge method suitable for solving radar cross section (RCS) characteristics of the whole helicopter was developed. In order to improve grid generating quality of large shape changes, the high density grids were generated considering the accuracy and efficiency. Simultaneously, the density and scale of electromagnetic grids need to meet the radar wave length ratio. The blade pitching and flapping motions were included by inclination of disk, and the RCS characteristics of the whole helicopter effected by rotor were simulated by the quasi-static method. Then calculations and simulations on RCS of an helicopter about the polarization, attitude and frequency responses were carried out. According to the relationship between RCS of helicopter and detecting distance of radar, four-stage warning mechanism and angle domains were presented. The results show that the RCS dynamic responses of the whole helicopter is continuous and symmetric considering the rotating rotor, and the oscillation scattering is strong, with the amplitude of RCS between -5 to 12dB ·m2. Compared with even blades, the RCS of odd blades is reduced from 2 to 5dB ·m2, and the RCS envelope and time domain responses of scattering peak are controlled. Finally, the radar stealth performance can be improved.
Characteristic analysis of unsteady aerodynamic interactions of contra rotating open rotor
XIA Zhen-feng, YANG Yong
2014, 29(4): 835-843. doi: 10.13224/j.cnki.jasp.2014.04.013
Abstract PDF(1141KB) icon1728 icon883
Abstract:
Unsteady aerodynamics of contra rotating open rotor (CROR) was simulated by solving unsteady Reynolds averaged Navier-Stokes equations based on dynamic patched technology. To analyze the aerodynamic interactions and slipstream flows interactions between the front-rotor and aft-rotor, a 10×10 CROR configuration was adopted and compared with the 10-bladed single rotor. Result shows that,compared with the single rotor, the thrust coefficients and power coefficients of the front-rotor decrease while those of the aft-rotor increase, with 20 periodical oscillations during one rotation period. The spectral analysis of front-rotor and aft-rotor thrust coefficients show that the fluctuations occur at even multiple numbers of blade passing frequency of single rotor, and the amplitude of aft-rotor thrust at twice the blade passing frequency is prominent. Due to the periodical passing of blade tip vortices of front-rotor, the thrust distributions on aft-rotor blade are changed and fluctuate unsteadily. Compared with the single rotor, the axial velocity increases while the cirumferential velocity decreases in the slipstream behind front-rotor. The aft-rotor accelerates the slipstream while recovers swirls.
Multiple parameters dynamic modeling and analysis of helicopter rotor multi-layer elastomeric damper
LI Rui-rui, YANG Wei-dong, YU Zhi-hao
2014, 29(4): 844-851. doi: 10.13224/j.cnki.jasp.2014.04.014
Abstract PDF(1012KB) icon2763 icon901
Abstract:
According to the requirement from the helicopter rotor system dynamic modeling method based on the flexible multibody system dynamics method,a time-domain embedded multi-layer elastomeric damper model based on internal variable theory was developed in consideration of the structural characteristics of the embedded multi-layer elastomeric damper. By using the multi-layer internal variable field, the model is more capable to calculate the dynamic characteristic of the damper over a wide strain amplitude and excitation frequency range and under dual frequency excitation condition. The influence of the metal shims of embedded multi-layer elastomeric damper was considered in modeling process, and the influence of the temperature rise during the damper operation on elastomeric material was considered by temperature shift function, improving the accuracy of damper. The calculational results and the experimental data were compared to verify the effectiveness of damper model under different strain amplitudes, excitation frequencies and dual frequency excitation conditions. This work provides an embedded multi-layer elastomeric damper model for calculating and analysis of helicopter rotor system aeroelastic stability.
Mechanism of mass flow matching in scramjet
HUANG Xing, CHEN Yu-chun, WANG Xiao-dong, LI Jie, CAI Yuan-hu
2014, 29(4): 852-857. doi: 10.13224/j.cnki.jasp.2014.04.015
Abstract PDF(966KB) icon1621 icon816
Abstract:
Combustor performance computing model based on lumped parameter equations was used to simulate the 1-D flow field in the isolator and combustor along with the critical area method. The simulation of mass flow matching between isolator and combustor at every mode in dual-mode scramjet was achieved, and the mechanism of mass flow matching was analyzed. The results show that at the non-separation supersonic mode and the separation supersonic mode, the mass flow matching between isolator and combustor is achieved by lowering the Mach number at the throat when the fuel mass flow increases in combustor, while at the transonic mode and the subsonic mode, it is achieved by increasing the total pressure at the throat when the fuel mass flow increases in combustor.
Integrated flow field characteristics of helicopter/particle separator: Part 1 influence of advance ratio
ZENG Ping-jun, SUN Shu, HUANG He-xia, DU Mo-chen, CHEN Wei, TAN Hui-jun, LI Guang-sheng
2014, 29(4): 858-866. doi: 10.13224/j.cnki.jasp.2014.04.016
Abstract PDF(1039KB) icon1717 icon871
Abstract:
Integrated flow field characteristics of helicopter/particle separator of typical layout were studied by simulation method.Firstly,the validity of the numerical method used was verified by experimental data.Then,the integral particle separator was installed onto helicopter like “Apache”,then a typical layout scheme of helicopter/particle separator was formed,and the integrated flow field characteristics in different advance ratios were analyzed.The study results show that under the condition of higher advance ratio,a complex three-dimensional flow separation appears in the gear box upstream the entrance of the integral particle separator.That is to say,the particle separator operates under the condition of nonuniform freestream.Moreover,compared with the independent particle separator,the total pressure loss of the particle separator under integrated condition at the mainstream exit and the scavenge exit both increased by 1% and 8%, respectively.
Integrated flow field characteristics of helicopter/particle separator: Part 2 influence of rotor disk load
HUANG He-xia, ZENG Ping-jun, TAN Hui-jun, DU Mo-chen, SUN Shu, CHEN Wei, LI Guang-sheng
2014, 29(4): 867-874. doi: 10.13224/j.cnki.jasp.2014.04.017
Abstract PDF(1094KB) icon1526 icon847
Abstract:
Integrated flow field characteristics of helicopter/particle separator under the interference of rotor downwash flow were studied by combination of the actuator disk model combining three dimensional viscosity simulations.Firstly,the ROBIN (rotor body interaction) experiment model was used to check the validity of the numerical methods,then an Apache-like helicopter with different rotor disk loads under different advance ratios were investigated.Finally some comparisons between the integrated flow and the independent flow of particle separator were made.The results show that rotor downwash flow has much more influence on separated flow characteristics of particle separator at lower advance ratio and the total pressure loss of scavenge exit is reduced under the downwash flow environment.At higher advance ratio,compared to no disk load state, the separation section upstream the gear box moves to the sides and becomes bigger while the performance of particle separator changes little when the separator operated in the downwash environment.
Structural optimization design method of twin-web turbine disk with tenon
LU Shan, ZHAO Lei
2014, 29(4): 875-880. doi: 10.13224/j.cnki.jasp.2014.04.018
Abstract PDF(870KB) icon1701 icon890
Abstract:
A 3-D structural optimization design method for twin-web turbine disk with tenon was presented, covering strategies of partial speedy optimization/totality-subtle optimization for disk and tenon structure with total mass of disk with tenon as the objective function and the partial management of design parameters. The structural optimization design platform for twin-web turbine disk with tenon was established based on software of ANSYS. Two models of twin-web turbine disk with tenon were designed for a high-pressure turbine rotor. And the influence of basic parameters, such as radius of disk outside edge neck, thickness of disk outside edge, on the stresses of several critical points of disk with tenon was studied. According to the optimization results, the method presented is proved feasible, as the distribution of stress in twin-web turbine disks is more uniform than that in single-web turbine disk; the masses of two models of twin-web turbine disk are 19.90% and 17.35% lighter than that of the single-web turbine disk model under the condition of meeting structure strength criterions, while the calculational time for optimizing the twin-web turbine disk with tenon model by the method presented is just 1/3 of that by the conventional 3-D optimization method. It is demonstrated that the method presented is reasonable and highly efficient.
A method for determination of parameters in total strain life equation
WANG Yan-rong, LI Hong-xin, YUAN Shan-hu, WEI Da-sheng, SHI Liang
2014, 29(4): 881-886. doi: 10.13224/j.cnki.jasp.2014.04.019
Abstract PDF(795KB) icon1530 icon898
Abstract:
In order to improve the prediction precision of total strain life equation in a wide range of fatigue life with the equation parameters having definite physical significance, the relationship among parameters of total strain life equation, monotonic ultimate tensile stress and percentage reduction of area was established based on the physical significance of the fatigue strength coefficient and the fatigue ductility coefficient of total strain life equation. Parameters in the total strain life equation for TC4, GH4169 and GH901 alloy were fitted and fatigue life predictions were carried out combining with monotonic tensile and fatigue test data. The results show that fatigue life predictions using the total strain life equation with the parameters fitted by the developed approach give better estimation within a scatter band of about two for TC4, GH4169 and GH901 alloy.
Signal transmission model with gradient temperature based on finite difference time domain
MEN Xiu-hua, LI Shun-ming, SONG Fang-zhen, XU Jia
2014, 29(4): 887-893. doi: 10.13224/j.cnki.jasp.2014.04.020
Abstract PDF(908KB) icon1525 icon866
Abstract:
A signal transmission model with gradient temperature was established on the basis of finite difference time domain(FDTD) method. And then, an iterative solution was applied to realize the signal transmission with different temperatures at different times. It shows that the time domain average voltage amplitude of output signal gradually attenuates with temperature rise, and at 573K the voltage amplitude is only about 90% of that of 303K, with the attenuation rate nearly 10%. The corresponding vibration test with gradient temperature was conducted. The power spectrum peak and time domain average voltage amplitude of output signal gradually reduce with temperature rise, which is consistent with the results of proposed model. The results of study will help to improve the accuracy of vibration test.
Rotating substructure method for 3-D finite element rotor model reduction
ZUO Yan-fei, WANG Jian-jun, MA Wei-meng
2014, 29(4): 894-900. doi: 10.13224/j.cnki.jasp.2014.04.021
Abstract PDF(862KB) icon1685 icon986
Abstract:
For reducing 3-D finite element rotor model, rotating substructure method, a reduction method easy to operate which was derived from the basic principle of Guyan reduction method and analysis theory of rotor dynamics was presented, and it could be practically used by ANSYS program. 21% degrees of freedom of a turbofan engine rotor model was reduced by this method. The maximum percent error of the first 20 order natural frequencies of reduced model is 0.43% and all the modal assurance criterion are 1 except that of the 17th mode of vibration of 0.98. The maximum critical rotating speed error is 0.46%. All the results show that the proposed method is valid.
In-situ experiment on early growth of small fatigue crack of nickel-based superalloy GH4169
ZHANG Li, HUANG Xin-yue, WU Xue-ren, YU Hui-chen, ZHANG Min, LI Hong-liang
2014, 29(4): 901-906. doi: 10.13224/j.cnki.jasp.2014.04.022
Abstract PDF(1047KB) icon1853 icon1182
Abstract:
Small fatigue crack initiation and propagation behaviors at room temperature of a directly aged nickel-based superalloy GH4169 were studied by in-situ scanning electron microscope (SEM) fatigue test. The results showed that under tension-tension fatigue loading with R=0.1, small fatigue the crack initiation period was only about 20% of the total fatigue life. Small fatigue cracks initiated at surface inclusions and grew as semi-elliptical surface cracks. The surface crack broke through one side of the specimen and subsequently became a corner crack with fast growth rates, leading to the final fracture. The early growth of small fatigue cracks was strongly affected by the local microstructure of materials, and the scattering of small fatigue crack growth rate was large.
Numerical study guide vane coolant on performance of turbine stage
ZHONG Yi-cheng, ZHANG Cun-yuan, XU Wei-zu, PAN Shang-neng
2014, 29(4): 907-916. doi: 10.13224/j.cnki.jasp.2014.04.023
Abstract PDF(1362KB) icon1485 icon860
Abstract:
Numerical simulation on a three-dimensional twisty high-pressure gas turbine guide vane with the whole body coolant injection was conducted. Detailed analysis of different coolant injection rate affect the blade aerodynamic performance, cooling efficiency and cascade channel loss was performed at the condition of design speed. Comparative analysis was made to learn the influence of changed rotational speed on the performance of turbine stage at the same coolant injection rate. The results show: different coolant injection rate affect static pressure near holes area more obviously, while the impact on the downstream of rotor surface static pressure is very little. Guide vane coolant injection has less influence on the mainstream flow angle in the cascade channel. Coolant injection rate increased from 2.50% of main flow rate to 6.25%, the adiabatic temperature of the blade surface dropped by 11.19%, total pressure loss and energy loss of guide vanes cascade channel increased 12.95% and 12.01% respectively, while the turbine stages power and efficiency dropped by 2.39% and 1.51% respectively.
In-duct circumferential acoustic mode measurement of axial fan/compressor
WANG Liang-feng, QIAO Wei-yang, JI Liang, YU Suo-yuan
2014, 29(4): 917-926. doi: 10.13224/j.cnki.jasp.2014.04.024
Abstract PDF(1146KB) icon1226 icon937
Abstract:
In-duct circumferential acoustic mode of a single stage fan was measured using equidistant microphone array with high back ground noise and high rigid wall reflection. Primary circumferential acoustic mode amplitude was obtained by utilizing the cross-correlated(CC) reference channel mode detection technique and the conventional root mean square-averaging (RMS) mode detection technique. The results were compared with Tyler and Sofrins duct mode theory, finding that both CC mode detection technique and RMS mode detection technique can obtain the ideal mode detection results with high back ground noise and high rigid wall reflection, and the mode amplitude of the former was lower than that of the latter. This is because CC mode detection technique decreases the impact of random noise on the mode amplitude. It is also found that the error of mode amplitude from CC mode detection technique is lower than 1dB when the number of microphone in the circular microphone array is more than four times of the circumferential acoustic mode order.
Numerical investigation of axial seal flow in turbine cavity
ZHANG Jing-hui, MA Hong-wei
2014, 29(4): 927-934. doi: 10.13224/j.cnki.jasp.2014.04.025
Abstract PDF(1686KB) icon1575 icon824
Abstract:
Hot gas ingestion and seal flow in axial seal configuration was investigated numerically. The results show that the unmatched mesh strategy on sealing surface affects the numerical transfer because of bigger gradient of parameters which lead to higher sealing effectiveness. The steady simulation underestimates the circumference pressure unevenness downstream the vane and ignores the interaction of stator and rotor; as a result the sealing effectiveness is much bigger than unsteady simulation. The unsteady results agree with the experimental date very well. Three vortexes appear in the cavity meridian plane, and guide the flow near static disc to rotor disc for supplement the flow required by disc entrainment. Rotating hot gas ingestion and egress structures appear in seal clearance, and the ingestion flow has bigger tangential velocity. The seal clearance vortexes in seal clearance have positive effects on sealing efficiency.The transient radial velocity is 3 times bigger than time-averaged value on sealing surface. The hot gas ingestion is affected by the circumferential distribution of static pressure downstream of vane and rotor rotation.
Numerical investigation on subsonic axial-flow compressor rotor with implementation of axisymmetric casing contouring optimization
GAO Xiang, CHU Wu-li
2014, 29(4): 935-943. doi: 10.13224/j.cnki.jasp.2014.04.026
Abstract PDF(1056KB) icon1537 icon777
Abstract:
For the study object of a subsonic axial-flow compressor rotor of Northwestern Polytechnical University, a reliable numerical simulation method was presented, and then axisymmetric contouring optimization for the casing under the condition of peak efficiency was conducted with the module DESIGN/3D in software package NUMECA, and the optimal rotor was obtained finally. The optimal rotor pushed the tip clearance leakage vortex away from the suction side at the leading edge of the blade. Although this led to an increase of the magnitude of leakage vortex and flow loss at the first 30% axial chord, the magnitude of leakage vortex and flow loss were greatly reduced at the last 70% axial chord of the blade, thus reducing the total loss, and increasing the peak efficiency and absolute total pressure at the outlet. The efficiency of the optimal rotor increases about 0.36% under the peak efficiency condition, which increases more under large mass flow rate condition, but under the near stall condition, the optimal rotor forms low velocity zone earlier at the blade tip area, leading to an earlier stall and making the stability margin of the optimal rotor smaller.
Parametric research on improved Qiu slip factor modelfor centrifugal compressor impellers
MENG Fei, TIAN Xiao-pei, SHAN Peng
2014, 29(4): 944-952. doi: 10.13224/j.cnki.jasp.2014.04.027
Abstract PDF(1142KB) icon2002 icon870
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To adapt the slip factor model proposed by Qiu to the through-flow design of micro-centrifugal impellers, three empirical parameters were introduced to reduce the system error. Firstly, the solving method of these empirical parameters and the impact on the design accuracy were researched. It is seen that empirical parameter cr influences the design accuracy greatly. Secondly, with employment of the improved Qiu slip factor model, a micro-centrifugal impeller was designed. The predicted slip factors impacted by cr in the model were compared with the impeller-outlet-averaged slip factors resulted from the CFD flow field simulation. The most suitable values of cr were found at different prescribed design overall parameters. It is found that cr nearby 0.7 has a best estimation, though the overall parameters of micro- or large-centrifugal compressor impeller vary widely.
Aero-engine fault-tolerant control based on mode switch
YANG Zheng-shan, QIU Xiao-jie, ZHUANG Xi-ming, HUANG Jin-quan
2014, 29(4): 953-964. doi: 10.13224/j.cnki.jasp.2014.04.028
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Abstract:
By combining aero-engine control and fault diagnoses methods, the aero-engine fault-tolerant control system based on control mode switch was designed, including task-level mode and engine-level mode. In case of failure of the engine components, the task-level mode could change the control strategies and modes to recover or reduce the aero-engine performance. In case of failure of a control loop, the control strategies were switched to other fault-tolerant control loops according to fault conditions, so as to ensure that the aero-engine continues to work normally. Numerical simulation result shows, the designed fault-tolerant control system can recover the aero-engine performance in 100% in case of failure of the components in the process of steady state or accelerated. And the designed fault-tolerant control system can switch to the fan speed control loop smoothly in 3 seconds in case of failure of the compressor speed control loop.
Robust fault diagnosis for aero-engine compressor sensor based on LMI and discrete model
HE Chen, ZHANG Xiao-dong, Patton R J
2014, 29(4): 965-972. doi: 10.13224/j.cnki.jasp.2014.04.029
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Abstract:
A robust fault diagnosis approach for aero-engine compressor sensor based on the linear matrix inequality(LMI) and the H∞ optimization theory was presented for aero-engine compressor health monitoring. The aero-engine compressor discrete model was obtained by using the linear fitting approach based on the neural network in consideration of both the uncertainties of model and noise. The design parameters of unknown input observer (UIO) were obtained by solving LMI and H∞ optimization for fault diagnosis of sensor with strong robustness. The main advantage of this approach lies in that it can handle both uncertainties of model and noise simultaneously compared with fault diagnosis approach of UIO existing. The numerical simulation was conducted by using the gas turbine compressor model provided by ALSTOM Company. The result shows that less than 2% sensor fault can be detected under white noise modeling uncertainty and sinusoidal external disturbance.
Active fault tolerant controller designo of aero-engine main fuel metering valve
FU Qiang, FAN Ding, PENG Kai
2014, 29(4): 973-979. doi: 10.13224/j.cnki.jasp.2014.04.030
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Abstract:
In case of failure of aero-engine main fuel metering valve actuator, the output of system will have the jumping problem, and will not track the system to the desired output. The model reference adaptive design method of active fault tolerant controller will solve this problem. Firstly,the actuator faults have been described mathematically. Secondly, the system nominal model was selected as the reference model, and the output error minimization selected as optimization objective; then lyapunov stability theory was used to search for a suitable adaptive law, and an adaptive fault tolerant controller was designed. Finally, the numerical simulation of different fault diagnosis of engine operating points was conducted. The simulation results show that, in case of jumping fault and blocking of the main fuel metering valve, adaptive fault tolerant controller can automatically adjust the parameters, making the system output track the model output, and the final tracking error is nearly zero.
Influential factors analysis to additional ejection force in concentric canister launcher
YU Yong, MU Yun-tao
2014, 29(4): 980-986. doi: 10.13224/j.cnki.jasp.2014.04.031
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Abstract:
When the missile is launched by concentric canister launcher, the bottom will be affected by additional ejection force depending on the exhaust slit width, reinforcing device configuration, diversion cone configuration and some other factors. An additional ejection force theory formula was developed using the integral form momentum equation. Qualitative analysis and explanation of various factors on additional ejection force were also conducted. Numerical simulation technology was used to verify the theoretical analysis. The study results show that there is a positive correlation between the force on tube bottom and the additional ejection force. The additional ejection force can be enhanced by decreasing the gap between two concentric canisters. The force on tube bottom will be decreased when diversion cone is installed. Smoother generatrix of diversion cone means smaller force on the tube bottom. The same amount time is needed for exhausts to reach steady state whether there is a diversion cone.
Failure mode of reusable rocket engine based on fuzzy fault tree and factor analysis
HOU Jin-li, JIN Ping, CAI Guo-biao
2014, 29(4): 987-992. doi: 10.13224/j.cnki.jasp.2014.04.032
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Abstract:
To confirm weak parts of engine and guide the reusable rocket engine reliability design, the key failure mode analysis of major components for space shuttle main engine (SSME) was conducted based on fuzzy fault tree analysis and factor analysis. The result show that the elementary event of highest critical importance is the bearing failure of high-pressure oxidizer turbine pump caused by flaking, pits, wear and corrosion, which is obtained by fuzzy fault tree analysis. The typical failure mode of highest comprehensive factor in engine system is turbine blade failure evaluated by considering risk time, and probability in factor analysis.

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