2011 Vol. 26, No. 6

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Design and performance investigation of sidewall compression scramjet inlets operating from Mach 4 to Mach 7
JIN Zhi-guang, ZHANG Kun-yuan, LIU Yuan
2011, 26(6): 1201-1208.
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Three-dimensional sidewall compression scramjet inlets with fore body compression operating in a large Mach number range from 4 to 7 were designed.The selection principles of the inlet primary design parameters were discussed and a high performance inlet scheme with curved surface compression was given.The complex flow field structure and the global performance of the scramjet inlet were investigated by means of numerical simulations.Results indicate at Mach 4 starting point,the sidewall compression scramjet inlet has a mass capture ratio of 0.753 ,and can work at above 6 degrees attack angle.At Mach 6,the inlet has a mass capture ratio of 0.945 and a total pressure recovery coefficient of 0.504 at the isolator exit,and 0.388 at Mach 7 cruising point.Numerical simulations also show that with the increasing attack angle,the captured mass flow increases nearly linearly,but the total pressure recovery coefficient decreases dramatically.As the yaw angle increased,the inlet total pressure recovery coefficient also decreases dramatically,but the mass capture ratio only drops slightly.It is also found that a pair of vortex occurre at the bottom of the isolator because of the pressure difference between the upper and lower walls of the isolator entrance,which increase the flow field distortion,and decrease the total pressure along the isolator.
Numerical simulation of swirling flow with different turbulent models
FENG Xi-ping, ZHAO Sheng-hai, LI Jin-xian, CAO Qi
2011, 26(6): 1209-1214.
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To certain type swirl setting,the swirling flow field of swirl setting interior was simulated based on Navier-Stokes equations by using computational fluid dynamics (CFD) method with renormalization group (RNG) k-ε and Reynolds stress model (RSM) turbulence model,respectively.By analyzing the simulation results and comparing them with the experiment results,the turbulence model's applicability research in swirling flow numerical simulation was performed.Research shows that:the results of swirling flow simulation differ a lot from the experiment results,because RNG k-ε turbulence model is based on the Boussinesq eddy-viscosity hypothesis,which couldn't consider the anisotropy of eddy-viscosity nor describe the transport process of turbulence energy transformation to average movement energy.Thus,RSM turbulence model could conquer the problems and consist with the experiment results,and the simulation results reflect the characteristics of swirling flow.RSM turbulence model is applicable to swirling flow numerical simulation.
Application of recycling/rescaling method in hybrid LES/RANS simulation method
CHEN Ti, LIU Wei-dong, FAN Xiao-qiang, SUN Ming-bo
2011, 26(6): 1215-1222.
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A hybrid large eddy simulation/Reynolds-averaged Navier-Stokes (LES/RANS) simulation method together with the third-order weighted essentially non-oscillatory (WENO) scheme were used to compute the flow field of a Mach number is 2.88 compression ramp flow.A recycling/rescaling method was used to generate turbulent fluctuating inflow boundary conditions.When fixed inflow boundary conditions were applied,the incoming turbulent boundary layer could not resist the adverse pressure gradient due to lack of reasonable turbulent energy.So the separation zone was overpredicted heavily.When recycling/rescaling method was used,large scale turbulent structures were stimulated in a length ten times the inflow boundary layer thickness.Thus,the results demonstrate the unsteady features of shock/turbulent boundary layer interactions.Time-and spanwise-averaged wall pressure is in good agreement with experimental values.
Experimental and computational investigation of single-expansion-ramp-nozzle
TAN Jie, JIN Jie, DU Gang, XU Jing-lei
2011, 26(6): 1223-1230.
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An experimental study was conducted for two high-speed two-dimensional(2-D) single-expansion-ramp-nozzles with different ramp contours at nozzle pressure ratios Rnp between 4 and 60 under wind off condition.The wall static pressure distributions and schlieren flow visualization were obtained.A computational investigation was also conducted to determine the performance of the nozzle and enrich the details of flowfield.Results from this study indicate that under highly overexpanded conditions of cowl trailing edge,the inner nozzle flow is dominated by shock-induced boundary-layer separation and accompanied by four to five oblique shocks.Moreover,the free shock and restricted shock separation are identified respectively in SERN 1 and SERN 2,which exert large influence on the wall pressure distributions and overall performance of nozzles.The performance of two models has little difference in the vicinity of design point,the axial thrust coefficient reaches 0.96 and thrust vector angle is about 9 degrees at the design point.Through the low Rnp regime,the performance of nozzles show large variation and the difference is obvious between SERN 1 and SERN 2.In general,the performance of SERN 2 is superior to SERN 1.
Acoustic properties of a slit resonator attached to a pipe with flow
DAI Xi-wen, JING Xiao-dong, SUN Xiao-feng
2011, 26(6): 1231-1236.
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To investigate the acoustic properties of a slit resonator attached to a pipe with flow,a theoretical model based on the discrete vortex method was set up.The discontinuity conditions at the joint between the pipe and the resonator were formulated using the mass and momentum conservations,then combined with a discrete vortex model the acoustic impedance and the absorption coefficient of the resonator were computed.The numerical simulation indicates that the flow field around the slit is dominated by the rolling-up and flapping motion of the shed vortex sheet,which agrees with the previous flow visualization results and validates the "lip" assumption of the shear layer at the slit in the semi-empirical models.The present results reveal that the acoustic resistance of the resonator is mainly determined by the sound pressure levels and the grazing flow speed,while the acoustic reactance is dominated by the depth of the cavity,the thickness of the plate and end correction.
Natural vibration analysis of bearingless rotor blades
LI Xue-chang, LI Shu
2011, 26(6): 1237-1243.
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Natural vibration characteristics of bearingless rotor blades design were investigated by transfer matrix method,and the natural frequencies of blade vibration were calculated with a fixed or spring restrained torque tube end.Coupling of pitch/lead-lag was also considered.Parametric studies were performed to examine the effects of several model parameters on vibration natural frequencies.Some flapwise and chordwise bending mode shapes were revealed.The results indicate that pitch/lead-lag coupling of the torque tube end has little influence on natural frequencies,the pitch angle of blade has complex influence on natural frequencies,and the distance of mass center from elastic axis has slight influence on high natural frequencies.
Impact of geometry parameters on the thrust and infrared radiation characteristics of two-dimensional ejector nozzle
LIU Fu-cheng, JI Hong-hu, LIN Lan-zhi, HUANG Wei, LIU Chang-chun, SI Ren
2011, 26(6): 1244-1250.
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The thrust and infrared radiation(IR) characteristics in the waveband of 3~5 μm of two-dimensional(2-D) ejector nozzle were studied numerically.The flow field of the exhaust jet was calculated with commercial software.The infrared radiation characteristics were calculated with an IR analysis software (NUAA-IR) developed by our research group.The results show that spacing ratio and area ratio have different impacts on the thrust ratio and mass-flow ratio of the 2-D ejector nozzle.Spacing ratio and area ratio have greater impact on wide detected plane within a small azimuth angles.In relation to a 2-D nozzle,the integral IR intensity of a 2-D ejector nozzle can be reduced about 50%.
Integral inference method for da／dN-ΔK and P-da／dN-ΔK curves
FU Hui-min, WU Qiong
2011, 26(6): 1251-1256.
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The integral inference method for fatigue crack growth (FCG) curve was established based on the two-variance regression theory. The estimates of da／dN-ΔK curve and P-da／dN-ΔK curve with high confidence level and high survival probability were also given. FCG data scatter with stress intensity factor ranges in reality, which limits the group test method's application. The presented method analyzes FCG curve as an integration, thus it can exploit the lengthwise information among the FCG rates corresponding to different stress intensity factor ranges. Therefore, compared with group test method, the presented method can not only save specimens, but also have higher precision in the evaluations of da／dN-ΔK and P-da／dN-ΔK curves.
Low cycle fatigue life experiment of sheet metal with coldworking hole
YANG Xing-yu, WANG Yu-ya, DONG Li-wei, MENG Xiang-ming, TUO Wei
2011, 26(6): 1257-1265.
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In order to enhance the fatigue strength of the pressure equalizing hole on labyrinth seal disc for a compressor,three kinds of coldworking techniques with different processes were designed,namely,one-sided multiple extrusion process,cylindrical extrusion process and T shape extrusion process.Simulations on sheet metal with hole specimen for low cycle fatigue experimentation were designed using two kinds of materials(stainless steel 1Cr11Ni2W2MoV and high temperature nickel-alloy ЗП742).Sheet metal with hole specimen was strengthened using two kinds of coldworking techniques,namely,single-side and repetitious extrusion method and T head extrusion method.And contrastive low cycle fatigue experimentation was done under two kinds of experiment temperatures,i.e.normal temperature and high temperature.The experimentation and analysis was made for different fatigue loads on how to influence the strength effect.The experiment results show that the effect of T head coldworking techniques is better for sheet metal filleted hole to improve low-cycle fatigue intension of the sheet metal with hole simulation specimen effectively.Under the same strength technique conditions,the size of low cycle fatigue load will influence the strength effect,and the smaller load means more obvious effect.
Experimental verification on bidirectional sequential method to solve dynamical response caused by aerodynamic loads
ZHANG Da-yi, MA Yan-hong, HONG Jie, CHEN Lu-lu
2011, 26(6): 1266-1273.
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An experimental system was erected to verify the precision of bidirectional sequential method of solving dynamical responses of blades caused by aerodynamic loads.The following results were obtained by comparison of calculation and experiment.Bidirectional sequential method is suitable for solving dynamical response of blades both in resonance state and in nonresonant state.The calculation results are correct in illuminating the vibration response both in time domain and in frequency domain.Bidirectional sequential method has a good calculation precision on solving vibration displacement and vibration stress whose relative errors are less than 40%.The method could satisfy the demands of most engineering problems.
Support vector machine complex method for multi-dimensional sensor calibration
MA Ying-kun, ZHANG Xi-nong
2011, 26(6): 1274-1281.
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A support vector machine(SVM) complex calibration approach was proposed to solve the parameters uncertainty and coupling nonlinearity.The simulation of the calibration of a multi-dimensional sensor was conducted by the SVM complex calibration method,which was then utilized to calibrate a six-dimensional force sensor system.It can be seen from the results that,as compared with other traditional calibration methods,the SVM complex calibration method can improve the calibration accuracy significantly,without increasing data samples;additionally,the complex calibration method also has better generalization performance in comparison with the SVM black box modeling,indicating that it can provide a basis for the design of sensors.
Numerical simulation of the dynamic process of aero-engine blade-to-case rub-impact
LIU Shu-guo, HONG Jie, CHEN Meng
2011, 26(6): 1282-1288.
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Numerical simulation of the dynamic process of aero-engine blade-to-case rub-impact was conducted by explicit-implicit integration scheme.This took full account of low-frequency liner steady-state response and high-frequency nonliner time-transient response due to the rub-impact.By taking the structure of a certain high-pressure turbine as example,the process of blade-to-case rub-impact was simulated,and the dynamic response characteristic of the blade during the process was analyzed.The results show that,the stress wave,which affects the stress distribution of blade,will be generated and propagated on the body of blade during the process of rub-impact;after the process of rub-impact,the dynamic response of blade is a decaying harmonic motion at the damped low-order natural frequency.
Study on the correlative property of excitation on compressor rotor blades
FANG Li-cheng, LI Shun-ming, DU Jian-jian, CHEN Mo-li
2011, 26(6): 1289-1294.
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The correlation of the three excitation forms (up-stream blade rows wakes, inlet distortion and rotating stall)was studied to analyze complex flow field of the blade role. The experimental samples were obtained by a single-stage low speed axial compressor test rig.Research focused on analysis of these three types of periodical excitation,employed autocorrelation and cross-correlation approach.Experimental results show that there is high correlation between excitation signals,and the correlation degree rely heavily on even signal. In addition,there is lower amplitude of cross-correlation frequency than amplitude of autocorrelation signal;There is low magnitude correlation among three excitations,correlation mainly exist in the first two of the even degree signal.
Structure design and shape optimization in arc dovetail
LV Hui-ting, HAO Yan-hua, HUANG Zhi-jian, WU Fu-xian
2011, 26(6): 1295-1300.
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In order to design the structure of arc dovetail,and analyze arc dovetail and triangle transition structure in the joint of blade and dovetail,a new type of blade profile was designed.Based on aforementioned work,size constraint relations between the blade profile and dovetail's top face were built,the blade and dovetail's parameter model was created using ANSYS software,and the blade profile and dovetail's structure were optimized.The results indicate that the optimized back stress of the new structure is 827.11 MPa,down by 6.51% than the original structure;the quality of new structure of the blade/dovetail is 0.869 42 kg,down by 1.85% than the original structure;the distribution of stress is more uniform and stress gradient is smaller among dorsal throat,leaves basin throat and leaves body.On the whole,the blade profile of optimal blade and dovetail structure is better as compared with that of initial blade and dovetail structure.
Data processing of blade's transient heat transfer experiment in short duration wind tunnel
ZHU Hui-ren, CHENG Wen-juan, LI Hong-cai
2011, 26(6): 1301-1309.
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Four data processing methods of blade's transient heat transfer experiment in short duration wind tunnel were studied in this paper,and the applicability of the methods were determined,showing guiding significance for the future experiments.If the time period of establishing steady flow in test section is negligible compared to the experimental time,the heat transfer coefficient can be treated as a constant,otherwise varying heat transfer coefficient curve versus time should be considered.The impulse response method based on one-dimensional and semi-infinite assumption is effective.The method of two-dimensional transient thermal analysis with least restrictive conditions can be used to handle all cases of heat transfer experimental data and verify the accuracy of other methods.
Effects of temperature distribution and level on heat transfer on a rotating free disk
ZHAO Xi, XU Guo-qiang, LUO Xiang
2011, 26(6): 1310-1320.
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In gas turbine engines, with the existence of the intense forced convection and significant buoyancy effects, temperature distribution and level on turbine or compressor disks affect the heat transfer characteristics strongly. In this paper, numerical simulations were performed to analyze these influences for a free disk, with the laminar and turbulent flow respectively. The influences of temperature distribution on the heat transfer were observed by using incompressible cooling air, and temperature profiles of nth order monomial and polynomial were assumed on the disk. The analysis revealed that the heat transfer for two flow states on the free disk is determined by the exponent n of the monomial profile when specifying the rotating Reynolds number; for an arbitrary polynomial profile, the local Nusselt number can be deduced from results of monomial profiles. To study the effects of temperature level on heat transfer singly, monomial profiles were used and the local Nusselt number of compressible and incompressible cooling air were compared.And both for two flow states, the following conclusions could be drawn: the relative difference of local Nusselt number is mainly controlled by nondimensional local temperature difference, and almost independent of the monomial's coefficient C, exponent n and the rotating Reynolds number. Subsequently, a correction method for heat transfer of the free disk is presented and verified computationally, with which the local Nusselt number, obtained with a uniform and low temperature profile, can be revised by arbitrary distribution and high temperature magnitude.
Heat transfer characteristics in an internal coolant passage with crossflow-induced swirl, impingement and film cooling holes
ZHANG Zong-wei, ZHU Hui-ren, ZHAO Shu, GUO Tao
2011, 26(6): 1321-1327.
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The effects of Reynolds number and bleeding ratio on heat transfer of impingement target surface,bleeding-hole surface and impingement channel side surface were investigated in large-scaled test models for the cooling passages in gas turbine blade.A transient liquid crystal technique was used to measure the local heat transfer coefficients of inner surfaces of impingement channel.The results show that,on impingement channel inner surfaces,the main causation of high heat transfer coefficient is caused by the first,second and third impingement,respectively.The average heat transfer coefficient of impingement target surface is the highest on the same Reynolds number by the direct impingement.The average heat transfer coefficient of bleeding-hole surface is higher than channel side surface.The impingement and swirl play a primary role on the Nusselt number of the researched surfaces.The heat transfer was augmented distinctly with increase of Reynolds number.The bleeding ratio also affects the value and distributions of heat transfer coefficients of all inner surfaces.
Experimental study on lean-blow-out of double/fuel-lean trapped vortex combustor
ZHANG Tao, SONG Shuang-wen, FAN Wei-jun, ZHANG Rong-chun
2011, 26(6): 1328-1333.
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To investigate lean-blow-out (LBO) performance of trapped vortex combustor (TVC) in high inlet flow,experiments were employed by changing Ma and temperature of main air and height to length (H/L) of the cavity.The results of experiments show that:(1) Mach number of main air has great effect on LBO.When Mach number of inlet main air becomes bigger,LBO decreases.As Mach number of inlet conditions varies,the change of LBO is great.(2) Temperature rise of main air is conducive to LBO,but after 600K,the effect is less.(3) LBO decreases when after body of cavity gas amount becomes bigger.(4) When the H/L is 0.88,the best LBO is achieved.
Experimental study of flow friction characteristics for a rotor-stator system with centre inflow of cooling air
LI Fu-qing, LUO Xiang, XU Guo-qiang
2011, 26(6): 1334-1340.
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The friction characteristics of a rotor-stator system with centre inflow of cooling air for two sealing geometry were experimentally studied.The experimental results show that:the friction coefficient will decline with the increasing ratio of sealing clearance and mass flow coefficient,and increase with the rotating Reynolds number.For the stationary case,the ratio of sealing clearance affects the friction coefficient much obviously than the mass flow coefficient;for the rotating case,the ratio of sealing clearance affects the friction coefficient less obviously than the mass flow coefficient and the rotating Reynolds number.
Effects of flow orientations on the coking characteristic of jet fuel RP-3
WU Han, DENG Hong-wu, XU Guo-qiang, JU Yin-chao, SUN Ji-ning
2011, 26(6): 1341-1345.
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In order to investigate the effects of flow orientations on surface coke deposition of oxygen-saturation RP-3 fuel flowing through a single-channel heated stainless-steel tubes.The system pressure was 5 MPa and the mass flow rate was 780 kg/ (m2·s).Experiments were conducted for different tube orientations,namely:horizontal,vertical with flow from bottom to top and vice versa.High outlet temperature and high pressure were utilized to simulate actual working conditions.The amount of surface coke deposition was obtained by weighting method.The results show that,the deposition initially increases and then decreases with fuel temperature under different flow orientations,and the location of coking peak value moves by gravity along the experimental segment,but the shapes of surface coke deposition distribution curve are similar,and total deposition is the same.
Two-dimensional numerical simulation of a turbofan engine with air bleeding in compressor
JIN Dong-hai, GUI Xing-min
2011, 26(6): 1346-1351.
Abstract PDF(1126KB) icon2329 icon21
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To assess the fan,compressor and whole engine performance of a turbofan engine on 0 km and 21 km operating conditions,considering air bleeding in compressor,an aero-engine S2 stream-surface flow simulation software (AES-S2) was used.AES-S2 numerical simulation model consists of two-dimensional Euler equation,combustion model and loss model.A body fitted coordinate system was used to adapt the complex geometric boundaries.The implicit higher-order Godunov scheme has the characteristic of shock capturing and good numerical stability.Simulation results show that:AES-S2 runs with favorable stability and convergence speed;the simulation precision of fan and compressor is higher than that of engine;two-dimensional simulation of engine can provide a reliable matching performance with acceptable engineering precision.
Numerical evaluation of tandem rotor for highly loaded transonic fan
ZHAO Bin, LIU Bao-jie
2011, 26(6): 1352-1361.
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Transonic tandem rotor was designed for highly loaded fan at a corrected tip speed of 381m/s and another conventional rotor was designed as a baseline to evaluate the loading superiority of tandem rotor with three-dimensional (3-D) numerical simulation. The aft blade solidity and its impact on total loading level were studied in depth. The result indicates that tandem rotor has potential to achieve higher loading level and attain favorable aerodynamic performance in a wide range of loading coefficient 0.55~0.68, comparing with the conventional rotor which produced a total pressure ratio of 2.0 and loading coefficient of 0.42.
Secondary flow analysis for non-axisymmetric endwall on the high-load compressor cascade
WU Ji-chang, LU Xin-gen, ZHU Jun-qiang
2011, 26(6): 1362-1369.
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The effectiveness of a non-axisymmetric endwall on a high-load compressor cascade was discussed.First of all,the trigonometric function was used to complete non-axisymmetric endwall profiling.Then the method of calculating the mixed-out secondary loss for the compressor cascade was established.Finally,the detailed numerical simulations were conducted on the cascade flow field with non-axisymmetric hub endwall.Numerical results show that with the non-axisymmetric hub endwall,the loading distribution near the endwall would be changed and the secondary loss would be reduced in both the design and off-design condition.It has been indicated that the mass average total pressure loss can decrease by 9.4% in the design and by 7.7% and 11.8% in the off-design condition(±3°),respectively.When the non-axisymmetric contour height equals to be 4% of blade span,the secondary flow loss should be the lowest.
Optimization and design of an impeller assist heart pump device
YANG Xiao-chen, ZHANG Yan, GUI Xing-min
2011, 26(6): 1370-1376.
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Design ideas and techniques applied in aeronautical turbomachinery were used to develop the impeller blood pump LAP-Ⅰ,which was designed for clinical use for Asian patients.By combining aeronautical turbomachinery technique with medical need,an integrated rotor and a cantilever stator were applied in the structure design,a further improvement was made in the tandem cascades stator and the impeller blood pump LAP-Ⅱ was obtained.The simulation results of computational fluid dynamics show that,the pressure rise characteristic of blood pump LAP-Ⅱ meets the medical requirement,and the flow status in the pump is fluent.The maximal comparative shear stress (S) value is reduced evidently;and the streamlines show that the longest time required for blood to travel through the pump is decreased,thus the property of anti-hemolytic application is improved.
Geared turbofan engine transient modeling research based on CMF method
TONG Wan-jun, TANG Shi-jian
2011, 26(6): 1377-1383.
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On the basis of thermodynamics,gas dynamics and gas turbine principles,a detailed research on how to model the transient performance of a geared turbofan engine was performed,and the relevant solver equations were deduced simultaneously by employing constant mass flow (CMF) method in the paper.A geared turbofan engine transient model was successfully coded by means of employing the solver equations and C++ programming language.On the comparable basis,the calculation results have quite remarkable consistency with those results calculated by Gasturb 10,a famous commercial software in aero-engine performance simulation,with maximum errors within 1.5%.Hence,these consequences show the correctness and applicability of the solver equations.
Speed control design and test for piston EFI engine of unmanned helicopter
ZENG Guo-gui, LIAO Zhi-lin, KAN Zhao-cheng
2011, 26(6): 1384-1388.
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The engine speed in warm condition was controlled by feed-forward and proportional feedback according to the characteristics of electronic fuel injection (EFI) engine and the requirements of engine speed at different phases in unmanned helicopter.The smooth transition from low to normal speed condition was achieved by speed feed-forward,load feed-forward,speed parameter model and feedback PID(proportion,integration,differential).The normal speed was controlled by using the complex scheme of feed-forward,load-forward,auto-trim,difference of rotational speed feed-forward and PID feedback.It proves that the complex control scheme is effective to constant engine speed control by use of the engine ground test at drive simulation platform.
Switching control system design for aero-engine based on mixed sensitivity
LIU Xiao-feng
2011, 26(6): 1389-1395.
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A systematic framework of switching controllers design for aero engines according to the safe boundaries was presented.Firstly,an approach to design the switching strategy and stability conditions were proposed.Secondly,based on mixed sensitivity robust control and switching control theory,by constructing linear matrix inequalities,a sufficient condition was proposed in terms of matrix inequalities.The simulation based on calculated controllers' parameters shows that using the using switching strategy can eliminate the delay effect caused by integrator wind-up,and can improve the dynamic performance of the engine control system,and guarantee the stability in some peculiar occasions.
UIO-based sensor fault diagnosis for aero-engine control systems
TAN Dao-liang, HE Ai, KONG Xiang-xing, WANG Xi
2011, 26(6): 1396-1404.
Abstract PDF(1377KB) icon1982 icon22
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The problem of sensor fault detection and isolation for aero-engine control systems was studied and an approach to overcome the impact of various disturbances on the performance in diagnosis of the control systems was proposed in this paper.This approach applied unknown input observer (UIO) theory to decouple the disturbance in the aero-engine dynamic model.Then,a bank of UIOs for the sensors in the control system were designed,and a series of residual features for the control system's sensors were extracted.By analyzing the characteristics of magnitudes in the queue of residuals,this paper accomplished the sensor-fault detection and isolation.Numerical simulation results with the disturbances of Gaussian white noise,a moderate change in the operating point of the engine,and non-Gaussian noise show that,the UIO-based method can effectively detect and isolate sensor faults irrespective of the class of the system disturbance,and outperform the Kalman filter-based algorithm in term of diagnosis robustness.
Progress of investigation on combustion instability of solid rocket motors
WANG Ning-fei, ZHANG Qiao, LI Jun-wei, SU Wan-xing
2011, 26(6): 1405-1414.
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The present situation and progress of investigation on combustion instability of solid rocket motors were introduced both at home and abroad in details.This paper attempts to organize these theories and lessons by detail physical concepts,prediction models,experimental methods and numerical simulations.The following viewpoints are proposed:(1) theoretical studies on energy transport mechanism between flow field and acoustic field,as well as the complex effect of aluminum,shall be emphasized;(2) experimental faculties for distributed combustion and pulsing triggering instability shall be established;(3) stability prediction program shall be developed.The analysis could provide a reference for research on combustion instability of solid rocket motors.
Research on combustion efficiency of cavity-type ramjet
TAN Jian-guo, HUANG Guo-qing, PAN Yu, WANG Zhen-guo
2011, 26(6): 1415-1419.
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Direct-connected experiments were conducted to reveal combustion performance of cavity-type ramjet under different incoming flow and excess air coefficients.Results show that the combustion efficiency decreases with excess air coefficient,but depends little on the temperature of the incoming flow.Generally speaking,90% combustion efficiency of cavity-type combustor is sufficient enough to satisfy the requirement of ramjet.
Numerical simulation and hot test investigation of plug nozzle in solid rocket motor
REN Jun-xue, LIU Yu, LIAO Yun-fei, XIE Kan
2011, 26(6): 1420-1425.
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A clustered type of plug nozzle,with 16 unit nozzles and an area ratio of 25,and a compared bell nozzle were designed to gain the performance characteristics of plug nozzle.The thrust performances of the nozzles were evaluated with numerical simulation method.A ground hot test was done to measure the thrust performance the clustered plug nozzle.The result shows that the numerical simulation results of the flow phenomenon and thrust performance accord with the experimental results.The thrust efficient of the plug nozzle in ground reaches 92.6% and is 9.1% higher than the bell nozzle with the same area ratio and length,reflecting the altitude compensation effects of plug nozzle.However,its thrust efficient in high attitude is 5.8% lower than the compared bell nozzle.
Design and experiment for a GH2/GO2 fuel-rich preburner
LI Mao, GAO Yu-shan, CHEN Ze, JIN Ping, CAI Guo-biao
2011, 26(6): 1426-1430.
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Scheme design,numerical simulation and experimental study were used to investigate a fuel-rich preburner of full flow staged combustion cycle engine in order to validate the ignition reliability and products’ temperature uniformity.Gaseous hydrogen and gaseous oxygen were selected as the propellants.Three types of structure schemes,namely,shear tricoaxial injector,multi-injector,division combustion,were analyzed contrastively.The numerical results show that,the product temperature can reach a nicer uniformity in a short preburner length by using the scheme of shear tricoaxial injector.And,the credible ignition reliability and good product temperature uniformity were validated in the experimental test.The temperature uniformity can maintain well in a large range of mass flow.
Fatigue evaluation of helicopter transmission system
KANG Li-xia, CAO Yi-hua, NING Xiang-rong
2011, 26(6): 1431-1435.
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By studying various work items of helicopter transmission key parts fatigue design,the methodology of fatigue design of key parts was discussed.And a fatigue assessing process of transmission system gear was advanced.By investigating the time between overhaul (TBO) and flight life on the outfield of transmission system,a fatigue evaluation technology which can be used to the whole life of helicopter transmission was proposed.Besides,basic contents and process of the fatigue evaluation were both listed.The methodology described in this paper can give some theoretical guidance and engineering practical significance on the helicopter transmission research,use,maintenance,and fatigue evaluation.
Study on meshing characteristics of helipoid gears with surface modification
SU Jin-zhan, FANG Zong-de, WANG Zu-bing
2011, 26(6): 1436-1440.
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The modification of tooth surface of pinion was applied to improve the meshing characteristics of helicoid gears.The modified shaper tooth surface could be generated by an imaginary rack cutter with the parabola profile,and the derivation of the mathematical of helicoid gears was developed by simulating the meshing kinematics between the shaper and the generated gear.By considering the assemble errors,the tooth contact analysis model was established on the conditions of continuous tangency of two contact surfaces.The results of computerized simulation of meshing and contact show that,the convex type transmission error can be produced by the modification of rack cutter profile,the amplitude and symmetry of transmission error can be changed by modulating the modification parameters;and the crossing angle has a great effect on the contact ratio,the contact ellipses and the sensitivity of assembly errors of the helicoid gears.

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