2009 Vol. 24, No. 2

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Numerical simulation of vortex and discharge pulse in positive discharge blowers with countercurrent cooling
LIU Zheng-xian, XU Lian-huan
2009, 24(2): 241-246.
Abstract PDF(1608KB) icon1520 icon470
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The vortex and discharge flow with fluctuation of involute type three-lobe positive discharge blowers with countercurrent cooling was numerically investigated by means of computational fluid dynamics(CFD).The dynamic mesh techniques were used to approach the rotating displacement of cell cubage and the alterability of computational area.The non-uniform mesh was applied to the rotor-stator coupled area.The characteristic of inner air flow was discussed.Based on the analysis of instantaneous characteristics of vortex and pulse flow,it's founded that countercurrent cooling could avoid the backflow eddy at the discharge outlet.At the same time,the pulse amplitude in countercurrent cooling is about 20%～25% of that in air cooling in a working cycle.This pulse flow greatly weakened could play an important role in reducing aerodynamic noise in positive discharge blower.
Design of three dimensional afterbody/nozzle configuration of airbreathing hypersonic vehicle
XU Da-jun, CHEN Bing, CAI Guo-biao, XU Xu
2009, 24(2): 247-254.
Abstract PDF(1194KB) icon1688 icon394
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Three dimensional configuration design of afterbody/nozzle was studied in this paper.Flow filed numerical simulations were conducted on NASA single expansion ramp nozzle experiment model.Numerical simulation results of two-dimensional and three-dimensional flow field without/with side fence were compared with experiment data and structure of three-dimensional flow filed.From the viewpoint of hypersonic vehicle airframe/propulsion integrated design,three-dimensional configuration of afterbody/nozzle was constructed with side fences.Parameters of cowl length and side fence inclination angle were investigated to analyze their effects on thrust,lift and pitch moment acted on overall vehicle.The results show three dimensional effect of afterbody/nozzle flow field could not be neglected.
Modeling study on tilt-rotor's aeroelastic stability in cruise flight
XUE Li-peng, ZHANG Cheng-lin
2009, 24(2): 255-261.
Abstract PDF(2424KB) icon2020 icon445
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It's assumed that the rotor blade and nacelle were of a rigid body and the wing was represented by an elastic beam,the blade pitch/flap/lag structural coupling and pitch/gimbal coupling were considered,and then,tilt-rotor/wing dynamic equations were founded on the inertial coordinate frame according to Newton's Second law and finite element method.These two dynamic equations were coupled through the common degrees of freedom between the rotor hub and the nacelle/wing system,and then the tilt-rotor/nacelle/wing coupled system aeroelastic stability model of a full-hinged tilt-rotor during cruise flight was acquired.The rotor aerodynamic model was based on the improved element-momentum theory,with consideration of the velocity's unsteady aerodynamic influence of perturbation parts.The calculation shows that the model is correct.
New ant colony algorithm and its application on optimization design of flight vehicle
CHE Jing, TANG Shuo, WANG Wen-zheng, HE Kai-feng
2009, 24(2): 262-268.
Abstract PDF(781KB) icon1553 icon464
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Ant colony algorithm(ACA) is a new bionic optimization algorithm developed in recent years.With global and efficient characteristics,it has been applied in discontinuous space successfully.To introduce it to aircraft design field,a high dimensional,multi-objective and multi-restrained ACA for continuous space was built.In an example,it was applied to the multi-objective optimization design of aerodynamic configuration for hypersonic cruise vehicle(HCV).Through comparison with Pareto genetic algorithms(GA),ACA shows its advantage.Finally,from our research work,ACA has great reference values for complex,multidimensional and large-scale optimization problems in aircraft design field.
Thermodynamic cycle analysis of solid propellant air-turbo-rocket
CHEN Xiang, CHEN Yu-chun, TU Qiu-ye, ZHANG Hong, CAI Yuan-hu
2009, 24(2): 269-276.
Abstract PDF(946KB) icon1849 icon451
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Solid propellant air-turbo-rocket(SPATR) is an air-breathing propulsion system.A numerical model of performance and characteristics analysis for SPATR was presented and the corresponding computer program was written according to the operation characteristics of SPATR.The influence on the SPATR performance at design point caused by the gas generator exit parameters and compressor pressure ratio had been computed and analyzed in detail.The off-design performance of SPATR at sea level and high altitude had also been computed.The performance of thrust and specific impulse for SPATR with different solid propellant had been compared at off-design points,and the off-design performance comparison had been made between fuel-rich and oxygen-rich.The computation results indicated that SPATR operates within wide range of Mach number(0～3) and altitude(0～12 km),and SPATR possesses high specific thrust(1 200 N/(kg/s)and high specific impulse(7 000 N/(kg/s) when fuel-air ratio of combustor equals fuel-air ratio.
Multiple objectives optimization of hingeless rotor tapered box-beam blades based on aeroelastic stability
WANG Hong-zhou, LIU Yong, ZHANG Cheng-lin
2009, 24(2): 277-286.
Abstract PDF(1914KB) icon1689 icon434
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The analysis model of tapered box-beam blade with the stability of flapping and lagging was built based on the finite element method(FEM).The sensitivity analysis method was provided under the condition of multiple constraints and objectives.The optimization was realized by using the non-dominated sorting genetic algorithm(NSGA-Ⅱ).Finally,the optimization result was compared with the designed model.The results show that the optimum solution results in a 1.147 times increase of the autorotational inertia,a 5.74%～8.6% reduction of the total rotor blade mass and a reduction in the peak-to-peak blade stress of 29.6%～30.1%,under the constrained conditions of blade rotating frequencies,autorotational inertia and aeroelastic stability.
Influence of velocity on aerodynamic characteristics of cars in overtaking process
KANG Ning, ZHENG Hao, LAN Tian
2009, 24(2): 287-291.
Abstract PDF(747KB) icon1596 icon475
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The unsteady flow fields around overtaking and overtaken cars in overtaking process at two different speeds were numerically simulated with moving mesh technology.The side forces,rolling moments and yawing moments of the cars during the overtaking process were calculated and analyzed.The influences of the flow field on the aerodynamic forces were analyzed according to the distribution of velocity and pressure fields.The results show that the maximum side force,rolling moment and yawing moment of the overtaken vehicle become bigger,the maximum side force and rolling moment of the overtaking vehicle will become bigger,the yawing moment will become smaller with the increase of the overtaking speed.
Effect of modeling and ground clearance on aerodynamic characteristics of cars
XU Xiao-ming, ZHAO You-qun
2009, 24(2): 292-295.
Abstract PDF(1407KB) icon1636 icon460
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Analyzed the aerodynamic characteristics through simulation of different treatment methods of car modeling,placement of engine,ground clearance and the removal mode of the cooling air in engine cabin with FLUENT software.The results show that: adding the wheels has the greatest impact on the aerodynamic characteristics,there is a best place for engine,and different ground clearances have great impact on the result of simulation.So,selecting the removal mode of the cooling air in engine cabin has to consider both the drag coefficient and lift coefficient.
Dynamic investigation on hypersonic sidewall compression inlets with cowl valve during the process of transition
WU Jun-qi, ZHANG Kun-yuan
2009, 24(2): 296-301.
Abstract PDF(1454KB) icon1628 icon443
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This paper aims at studying the transition of boosting to taking-over of scramjet.According to the working requirement of the sidewall compression inlets from completely close to completely open state,a new variable geometry inlet scheme for sidewall compression inlet——variable cowl valve scheme was presented.With the numerical simulation and experiment,the influence of variable cowl on performance of inlets was researched during the process of transition.Based on the numerical simulation,a variable cowl inlet model adjusted by remote control system have been designed,and this scheme has been firstly tested in Mach 3.85 wind tunnel.It proves that,at mach 3.85,the inlet can be opened and closed normally,thus further validating the feasibility of this scheme.
Performance and boundary layer of flow in axisymmetric mixed-compression supersonic inlet with cavity
MO Zhan, WANG Xin-yue, WEI Jun-guang
2009, 24(2): 302-306.
Abstract PDF(925KB) icon2196 icon516
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In order to improve the performance of axisymmetric mixed-compression supersonic inlet with fix-geometry,the performance of a supersonic inlet with cavities at the cone surface or the cone's corners was investigated by the numerical simulation.The effects of the cavities position on the cone on the performance of the inlet and the boundary-layer were presented.On the one hand,the shocks on the cones and the inlet's entrance Mach number were changed.On the other hand,the thickness of the boundary layer behind the cavities was increased and the velocity distribution in the boundary layer was also changed.When the cavities were at the cone's surface,the boundary layer thickness behind the cavities at the second and the third cone surface increased 33.3% and 52.4%,respectively.When the cavities were at the cone's corners,the boundary layer thickness behind the cavities increased 16.7% and 9.1%,respectively.The inlet's pressure recovery and the pressing ratio with cavities were higher than no cavities at high Mach number(3.7 to 4.5).Under design condition,the inlet's pressure recovery at the cavities of the cone's corners increased about 1.8%,and the pressure recovery at the cavities at the cone surface increased about 4.3% than no cavity.Besides,the mass capture ratio and starting Mach number were not influenced by the cavity at the cone's corners.
Experimental investigations of interaction of a pulse detonation combustor with a turbine
DENG Jun-xiang, ZHENG Long-xi, YAN Chuan-jun, JIANG Lian-you, LI Na, XIONG Cha
2009, 24(2): 307-312.
Abstract PDF(1296KB) icon1878 icon474
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Experimental investigations of a principle model of interaction of pulse detonation combustor(PDC) with turbine were made by using gasoline and air as fuel and oxidizer.The experimental results show that pulse detonation combustor can run stably.During PDC detonating,the air mass flow at the compressor outlet is about 100 kg/h more than that of PDC required for detonation.The full pulse detonation is achieved before the PDC outlet.The peak pressure and wave speed of pressure wave are significantly reduced after expansion through the turbine.Larger fill fraction can lead to a stronger detonation wave and a strong shock wave can be less affected by an obstacle like a turbine than a weak one.The turbocharger does not exhibit any signs of damage after over 40 minutes of detonation testing.
Effects of fuel-supply position on detonation waves and working frequency in an aero-valve pulse detonation engine
ZHENG Dian-feng, ZHANG Hui-qiang, WANG Jia-hua
2009, 24(2): 313-317.
Abstract PDF(1004KB) icon2241 icon448
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Based on the coordinately working of aero-valve gasoline-air pulse detonation engine(PDE),the effects of fuel-supply position(before or after aero valves) on the pressure peaks of detonation wave and PDE's working frequency were investigated.Experimental results show that PDE can achieve higher pressure peak for fuel supplied before aero valves than that after aero valve.A time-series analysis model was established for aero-valve PDE,the predicted filling velocity under given working frequency agrees well with the experiment.The further results based on this model show that there are small influences on the working frequency for different fuel-supply positions under the same filling velocity,while the realizable working frequency can be two times larger when deflagration to detonation transition(DDT) time reduces from 3.8 ms to 2 ms.These results are helpful for PDE's design and optimization.
Experimental research of the performance of the trapped-vortex combustor
HE Xiao-min, XU Jin-sheng, SU Jun-qing
2009, 24(2): 318-323.
Abstract PDF(1180KB) icon2038 icon405
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Trapped-vortex combustor(TVC) is a novel and compact gas turbine combustor with two pilot zones and a main zone.The pilot zone utilizes cavities to establish the recirculation zone needed for stable combustion,and the main zone is for power.In the research,inlet air pressure was fixed;with different inlet temperatures and inlet air flowrates,experiments were conducted to study TVC performance including pressure loss,ignition limit,lean blowout limit(LBO) and combustion efficiency.Experimental result shows total pressure loss increases from 3%～6% vary with increasing the inlet Mach number of the main zone,the flow drag coefficient is 24～25 which changes little with the inlet air flowrate.Ignition limit and LBO is independent on the inlet air flowrate,and improves with increasing inlet temperature from 300 to 500 K.The fuel/air ratio of ignition limit and LBO is 0.011 and 0.004 5 respectively.When cavity is fueled only,the combustion efficiency of TVC is 90%～95%.When the cavity and main zone are fueled together,the efficiency increases(84%～99.5%) with decreasing the fuel/air ratio.
Diffusion cooling optimization of two layers porous plate using genetic algorithm
SHI Jun-xiang, WANG Jian-hua
2009, 24(2): 324-330.
Abstract PDF(482KB) icon1670 icon442
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An optimization method of diffusion cooling with two layers porous matrix was presented in this paper.Coolant was injected into the solid matrix under certain differential pressures and characteristic sizes of the porous matrix.With the variation of the porous material,porosity and thickness ratio,the minimum temperature of the hot surface is ultimately subject to cooling optimization when the global constraint conditions of mass and cost,etc,are satisfied.In this paper,the genetic algorithm was used to find the feasible optimization design with the analytical solution of one-dimensional LNTE model.The results show that the porosity of the porous plate close to the coolant reservoir should be as large as possible,but this phenomenon is not correct on the porosity of the porous plate close to the hot surface,its value depends on the balance of effects on the effective thermal conductivity,heat convective coefficient and coolant mass flow rate.
Numerical simulation and design improvement of leading-edge film cooling in an inlet guide vane
LIU Jie, AN Bai-tao, JIANG Hong-de, LIU Jian-jun
2009, 24(2): 331-339.
Abstract PDF(2685KB) icon1463 icon445
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The numerical investigations on the leading-edge film cooling of an inlet guide vane were performed and described in this paper.The program CFX was employed to obtain the numerical solution.The original design was simulated to obtain flow and heat transfer characteristics of the leading edge film cooling.The film cooling characteristics and interactions between jets and mainstream around the leading edge,especially near the stagnation line,were analyzed in detail.To provide better coolant coverage around the leading edge,the cooling configuration was modified based upon the analysis and understanding of the 3-D prediction for the original design.The modified designs were compared with the original design,providing better coolant coverage around the leading edge.
Research on heat transfer characteristic of lamilloy internal surfaces using transient liquid crystal technique
KONG Man-zhao, ZHU Hui-ren, YUAN He-peng
2009, 24(2): 340-346.
Abstract PDF(1037KB) icon1752 icon427
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Experiment was carried out to describe the hear transfer coefficient distribution of inner surfaces(target plate,impingement plate and pins) of large scale lamilloy configuration model by utilizing the narrow-band transient iiquid crystal technique(TLC).The mechanism of heat transfer intensification was also interpreted.The result shows that: heat transfer coefficient distribution of inner surfaces of lamilloy can be obtained by using the TLC technique and more detail information are also available;heat transfer coefficient of inner surface is linearly increased with growing Reynolds number and gradually reduced with the higher channel.
Effects of flow split among swirlers and primary holes on the lean blowoff limits of a combustor with swirl cup
XU Hao-peng, WANG Fang, HUANG Yong, ZHANG Yu-fang
2009, 24(2): 347-352.
Abstract PDF(1067KB) icon1791 icon438
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An experimental research was conducted for the effect of flow split among swirlers and primary holes on the lean blowoff(LBO) limits of a single dome rectangular model combustor with dual-radial swirl cups.It's found that the decrease of air into the swirlers will improve the lean blowoff limits about 18%,and the air flowrate of the inner swirler has the greatest impact on the blow-out limits.Besides,the decrease of air into primary holes will increase the combustor lean blowoff limits about 13.1%.If the air flux into both the swirl cups and primary holes was cut down,the blowout fuel-air ratio would be reduced further,helping to widen the stability limits of combustors.
Experimental investigation of kerosene supersonic combustion test using aerated-liquid injectors
WANG Liao, ZHANG Cheng-liang, WEI Bao-xi, XU Xu
2009, 24(2): 353-359.
Abstract PDF(1519KB) icon1883 icon478
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Experimental investigation of kerosene supersonic combustion was performed on direct-connect supersonic combustion test facility by using aerated-liquid injectors.In the test,kerosene equivalence ratio was 0.97 and 0.33,and hydrogen,air and nitrogen were used as effervescent gas respectively.The experimental results show that,cavity flameholders can achieve kerosene self-ignition and flame-holding effect by producing an eddy with low speed and high temperature,kerosene can prolong the resident time in combustor and achieve sufficient heating by the effect of this eddy.The hydrogen can self-ignite and release energy while injecting into the supersonic combustor,therefore adding hydrogen by aerated-liquid injector can improve the combustion performance of kerosene,and even achieve stable combustion without cavity flameholder.
Influence of structural damping on stability of the rotor system
CHENG Li, FAN Jia-dong, CHEN Xue-feng
2009, 24(2): 360-364.
Abstract PDF(1740KB) icon1786 icon459
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According to the characteristics of the rotor system of a turbo-fan engine,a simplified rotor dynamic model with structural damping and squeezed film damping was constructed.Stability of the rotor system was analyzed by the Routh-Hurwitz criterion and the tracing method of the steady-state.The results show that the structural damping may cause the rotor system to be out of stability within a range of speed over the system's critical speed and may reduce the threshold speed for dynamic instability caused by the squeezed film damping.
Research on nonlinear fluid-solid interaction dynamic lubrication in floating ring bearings
YANG Jin-fu, CHEN Ce, YUAN Ping, WU Wen-feng, DONG Chun-Wei
2009, 24(2): 365-370.
Abstract PDF(2000KB) icon1807 icon513
Abstract:
An experiment of floating ring bearings and flexible rotor in a micro turbo-engine was presented.Some nonlinear behaviors of fluid-solid interaction in floating bearings were studied.And nonlinear frequency characteristics of five typical vibrations in floating ring bearings were presented.Furthermore,the difference and correlation between power frequency characteristic in critical speed range and whirl frequency harmonic response characteristic were illustrated.At the same time,the method to control vibration and to eliminate whirl was described.Based on the analytical expressions of load capacity and whirl frequency in single oil film lubrication bearings,the stability of floating ring bearings was analyzed.The experiment shows that the whirl ratios of outer and inner oil film in floating ring bearings approach 0.5 and 0.3,respectively,in squeezing vibration,which matches the theoretical analysis considerably.This research provides experimental and theoretical evidence for future floating ring bearings design and performance research.
General dynamic model of aeroengine's rotor system during maneuvering flight
ZHU Chang-sheng, CHEN Yong-jun
2009, 24(2): 371-377.
Abstract PDF(2075KB) icon2005 icon546
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A general motion model of a linear or nonlinear flexible aeroengine's rotor with unbalance multi-rigid-disk,multi-lumped-mass and multi-bearing was presented by using Lagrange's equation during any maneuvering flight and for any position of aeroengine installed in airplane.The influences of different maneuvering flights on the dynamic characteristics of an aeroengine's rotor system were discussed.It is shown that an additional damping effect,an additional stiffness effect and an additional un-periodic external exciting force acted on the aeroengine's rotor system may be introduced due to the maneuvering flight,which will great affect the dynamic characteristics of an aeroengine's rotor system,especially increasing the vibration amplitude of the aeroengine's rotor system and significantly shifting the center of motion orbit of the aeroengine's rotor system to the uncentralized position may result in the particle impact between the rotor and the stator.The influence of the maneuvering flight on the dynamic characteristics of the aeroengine's rotor system must be considered in studying the dynamic characteristics of the aeroengine's rotor system.
Dynamic characteristics of active magnetic bearing system with metal rubber annuluses
XIE Zhen-yu, WANG Tong, ZHANG Jing-ting, GAO Hua, HUANG Pei-zhen
2009, 24(2): 378-384.
Abstract PDF(2499KB) icon1880 icon445
Abstract:
To reduce the vibration of flexible rotor supported by active magnetic bearings,metal rubber annuluses were introduced and set around the active magnetic bearings,which are called as complex bearings.Dynamic characteristics of the system supported by the complex bearings were studied in this paper by theoretical analysis,experimental modal analysis and actual operation of the system.The results show that the metal rubber annulus can increase the first bending modal damping of the system obviously,and help the system to get across the first bending critical speed safely.
Aeroengine reliability allocation based on fuzzy prorating method and fuzzy synthetic assessment
DU Li, LIU Yu, HUANG Hong-zhong, PENG Wei
2009, 24(2): 385-389.
Abstract PDF(1583KB) icon1759 icon432
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In this paper,an approach based on fuzzy prorating method and fuzzy synthetic assessment was proposed to allocate the reliability indices,by utilizing the existing reliability information from the similar version of aeroengine in the early design phase.The proposed approach not only considers the reliability information and data from the old version products,but also combines the information from fuzzy synthetic assessment as a complement.This method efficiently utilizes the certain and uncertain information simultaneously to further optimize the reliability allocation results.
Investigation of non-synchronous response of adaptive squeeze film damper with metal rubber oil film ring
MA Yan-hong, WANG Hong, HONG Jie
2009, 24(2): 390-395.
Abstract PDF(1110KB) icon1766 icon437
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Adaptive squeeze film damper with metal rubber oil film ring(ASFD/MR) was designed to improve characteristics of the squeeze film force of the squeeze film damper(SFD).Comparative study on suppressing the non-synchronous response between ASFD/MR and SFD In this paper,was presented.It is shown that ASFD/MR has a well capability to suppress non-synchronous response and a better effect on reducing vibration.
Weak nonlinear free vibration study of electromechanical integrating toroidal drive
HAO Xiu-hong, XU Li-zhong, REN Zhi-xia
2009, 24(2): 396-402.
Abstract PDF(2771KB) icon1493 icon394
Abstract:
As for a new-style generalized composite transmission-electromechanical integrated toroidal drive,the nonlinear changes of the electromagnetic mesh stiffness between worm and planets were analyzed.Firstly,weak nonlinear motion differential equation of toroidal drive in the form of perturbation was presented.Then,approximative analytic solution of frequency and displacement response were obtained by Linstedt-Poincare(L-P) perturbation method.Lastly,influences of the changes of the electromagnetic mesh stiffness on frequencies and amplitudes of system vibration were discussed,a number of useful results were given.Amplitudes of every direction vibration are not affected almost by increasing order of the small parameter ε,while free vibration frequencies change obviously..
Experiment and numerical simulation of rotating-speed difference effects on a dual-stage counter-rotating compressor flow field and performance
LIU Bo, HOU Wei-min, CHEN Yun-yong, ZHAO Xu-min
2009, 24(2): 403-408.
Abstract PDF(1379KB) icon1924 icon424
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Preliminary researches on the rotating-speed difference in the counter-rotating compressor were presented.Some different rotating-speed differences were introduced and tested on a dual-stage axial counter-rotating compressor.The result of comparing computational simulation with experimental measurement indicates a good agreement between them.Consequently,it is verified that the rotating-speed difference is one of important influential factors to the performance of the compressor.
Numerical investigation of low-Mach number flowfield inside of vaned diffuser based on the pseudo compressibility method
GAO Li-min, LEI Jiang, WANG Huan
2009, 24(2): 409-413.
Abstract PDF(671KB) icon1619 icon461
Abstract:
Owing to the type of the flow governing equation system,and the low efficiency of standard time-marching algorithm in solving the low Math number flows,a time marching code was explored to solve the incompressible internal flow field of turbomachinery based on the pseudo compressibility method.In the full paper,we explained our exploration in some detail;in this Abstract,we just added some pertinent remarks listing three topics of explanation.In the first topic,a universal N-S equation system was derived,which can govern both high subsonic and low Mach number flow by a pseudo compressibility factor developed by Chorin.In the second topic,four step Runge-Kutta time-marching method with the central difference scheme was employed to resolve the N-S equations.Also in the second topic,we pointed out how the optimal pseudo compressibility factor was determined.In the last topic,some numerical results and the analysis for a vane diffuser of a tested centrifugal compressor were presented.The analysis of these results shows preliminarily that:(1) for the low Mach number flowfield,both efficiency and accuracy of the time marching algorithm based on the pseudo compressibility method is higher than that of the traditional time-marching algorithm;(2) the pseudo compressibility method is a compensator for the time-marching algorithm,and the application of the time-marching algorithm is extended by introducing the pseudo compressibility method.
Research on flow instability mechanism of transonic compressor at low Reynolds number
WANG Ru-gen, ZHOU Min, ZHAO Ying-wu, XIA Qin-bing, ZENG Ling-jun
2009, 24(2): 414-419.
Abstract PDF(1492KB) icon2144 icon477
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The effect of low Reynolds number on the flow instability mechanism of transonic compressor was studied numerically.The result shows that the radial vortex exists in the compressor inner flow field,which is formed from separation flow in the boundary layer transition zone.Under centrifugal force,radial vortex flows from blade hub to blade tip and converges at the blade tip flow field.As Reynolds number decreases,the effect range of radial vortex is extended,a bigger boundary layer separation zone is formed at the blade tip,which is decisive to the flow instability of transonic axial compressor before blockage zone due to shock and tip leakage flow is fully developed.
Experimental investigation on the span loading in compound lean compressor cascades with slots air injection
CHEN Huan-long, CHEN Fu, SONG Yan-ping
2009, 24(2): 420-426.
Abstract PDF(2503KB) icon1652 icon459
Abstract:
An experimental investigation was conducted for the influence on the loading of span by 60° turning angle plane compound lean compressor cascade,which was designed with tangent air injection slots in different inflow incidences.The experimental results show that not only the diffusion factor of cascades is increased and the turning of airflow is improved effectively,but also the static pressure of outlet in negative lean cascades presents a "C" distribution from hub to shroud by tangent air injection.The integration of slots injection and compound lean blade technologies will be an investigation direction in the future.
Research on aeroengine performance parameters forecast based on multiple linear regression forecasting method
SONG Yun-xue, ZHANG Ke-xing, SHI Yong-sheng
2009, 24(2): 427-431.
Abstract PDF(956KB) icon1972 icon515
Abstract:
Based on the research of aeroengine performance parameters relativity,an aeroengine performance parameters forecasting method was proposed using multiple linear regression model,in which the effect of multiple factors on dependent was considered.Some aeroengine performance parameters,such as p4.95,N2,T3,N1,pB,were analyzed before forecasting of EGT series.At last,the proposed model was verified through some types of aircraft aeroengine performance parameters data obtained from flight experiment,and then compared with adding-weight one-rank local-region method.The result shows that the proposed model has a better forecast accuracy.It can be used as a supporting model in the decision-making of this aeroengine fault forecast.
Analysis of the flow in return vanes of a two-stage centrifugal compressor
GAO Xing, LIU Bao-jie
2009, 24(2): 432-438.
Abstract PDF(2482KB) icon1909 icon587
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To examine the influences of some typical design parameters(the inlet flow condition,blade number,and vane loading distribution) on the performances of the return vanes in a two-stage centrifugal compressor,a series of return vanes were designed and analyzed numerically by 3-D viscous code.It was found that the secondary flows in the return vane were usually very strong;however,improving the inlet flow uniformity,increasing the blade number and optimizing the vane loading distribution could weaken the secondary flows.Among these approaches,the effect of changing the vane loading distribution was most significant.Generally,the forward loading return vane could achieve higher total pressure recovery coefficient and much more uniform discharge flow than the backward loading return vane.
Two dimensional numerical simulation of small turbojet engine
CAO Zhi-peng, LIU Da-xiang, GUI Xing-min, ZOU Zheng-ping, YUE Ming
2009, 24(2): 439-444.
Abstract PDF(1208KB) icon1618 icon471
Abstract:
two-dimensional Euler equation,combustion model and loss calculation methods were used to establish the numerical simulation model of engine.A body fitted coordinate system is used to adapt the complex geometry boundary.Unsteady Euler equation was solved by implicit high order Godunov scheme,which had the characteristic of shock capturing and good numerical stability.The data comparisons of calculation and design showed: the components simulation precision was higher than that of whole engine,the turbine simulation precision was higher than that of compressor;the analysis of meridional plane calculation results showed: Flow separation at the exit of centrifugal compressors and simplifications of combustion chamber holes had big influence on total performance parameter calculation results.
Numerical simulation of deposition for aluminum/magnesium-loaded fuel-rich propellant ducted rockets
WANG De-quan, XIA Zhi-xun, HU Jian-xin, GUO Jian
2009, 24(2): 445-449.
Abstract PDF(642KB) icon1632 icon399
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Based on stochastic trajectory model and Mundo deposition model,the 3-D two-phase flow field in solid rocket ramjet was numerically simulated.The influences of the inlet angle,the burner exit configuration,particle size distribution at particle boundary and condensing fraction of Al2O3 on the deposition were discussed.The results indicate that the change of inlet angle has a little effect on the depositing position,and with the increase of inlet angle,the deposition around inlet will be distributed irregularly.We can also find that increasing the gas generator nozzle numbers is adverse to reduction of deposition.The change of condensing fraction has a little effect on the depositing position,and with the increase of particle diameter,the total deposition mass has a maximum value if deposition from big particle is neglected.
Study on the characteristics of bipropellant-fueled pulse rocket engine with high combustion chamber pressure
LIANG Shu-qiang, LIU Yü, QIN Li-zi, WANG Hai-xing
2009, 24(2): 450-457.
Abstract PDF(2476KB) icon2109 icon503
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By using a moving injector,the combustion chamber pressure of pulse rocket engine is much higher than feed system supply pressure.In order to analyze the characteristics of bipropellant-fueled pulse rocket engine,a mathematics model was presented.The zero-dimensional models were used for combustion chamber and extrusion rooms,and the one-dimensional,quasi-steady model was used for nozzle flow.Using N2O4 and MMH as propellant,the equation sets were calculated with fourth-degree Runge-Kutta method.According to calculated results,the maximal pressure and average pressure of combustion chamber are much higher than supply pressure,on account of the nonequivalent mass flow rate in combustion chamber.The performance difference between pulse rocket engine and conventional constant-pressure liquid rocket engine(LRE) was compared.Results show that,under the same supply pressure,the same mean thrust and area ratio,the vacuum specific impulse of pulse rocket engine has increased by 7.5%,but the throat area is only 10.2% of LRE.
Application of PSO-based rough set theory and neural network to aeroengine fault diagnosis
YANG Hai-long, SUN Jian-guo
2009, 24(2): 458-464.
Abstract PDF(1072KB) icon2066 icon389
Abstract:
A new method based on neighborhood rough set model and neural networks(NN)integrated with particle swarm optimization(PSO) algorithm was presented in this paper for fault diagnosis of aeroengine.Firstly,using the algorithm of attribute reducing based on neighborhood rough set model,we deleted the unnecessary attributes from the decision table.Secondly,the PSO was used to train the weights and the thresholds of NN instead of BP algorithm.Therefore,The NN trained by PSO was applied to aeroengine fault diagnosis.The simulation results indicate that the method has shortened the training time and increased the diagnosis accuracy.
Dynamic acceleration process identification for turbofan engine using Volterra-Laguerre expansion model
WANG Hai-tao, XIE Shou-sheng, HU Jin-hai, PENG Jing-bo
2009, 24(2): 465-469.
Abstract PDF(487KB) icon1753 icon430
Abstract:
The problem of modeling the nonlinear dynamic respondence of aeroengine was studied based on the volterra-laguerre expansion.The structure of Volterra-Laguerre expansion was described and the identification arithmetic of the volterra-laguerre progression model of aeroengine was proposed using the theory of laguerre progression.The comparison between the result of volterra model,the volterra-laguerre expansion and the true shows that the volterra-laguerre expansion can better describe the dynamic process from low to high rotating speed of aeroengine with less parameters that should be identified,and the dynamic simulation error of high and low rotors is less than 1% and the error of temperature exit of high-pressure turbine is less than 3 ℃.The model is suitable for aeroengine and control system simulation.
Parameterized analysis of bending stress of involute teeth
LI Jie, WANG Le-qin, SUN Qing-jun
2009, 24(2): 470-476.
Abstract PDF(956KB) icon1573 icon436
Abstract:
The parameterized teeth model was established based on the involute and tooth root transitional curve equations with the defined interval of independent variables,and the force was loaded at the highest point of single pair meshing teeth according to the handbook.A two dimensional finite element parameterized analysis method about the tooth bending stress was presented.Through examples,the results of finite element method are in good agreement with those of the actual designing method,proving the accuracy of the model modified factor of the latter.But the stress from the former method is appreciably bigger when the tip rounding radius of generating rack is smaller or the pressure angle of tooth is bigger.The actual designing method only focuses on the tensile stress which is proved smaller than the compressive bending stress.The maximum tensile bending stress decreases with the increase of the tip rounding of the generating rack,the modification coefficient and the pressure angle.The effect of the pressure angle and the tip rounding is more prominent,while the teeth number has only slight effect on the bending stress.

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