2012 Vol. 27, No. 9

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Experiment of in-cylinder mixture formation process low-pressure GDI engine
HU Chun-ming, LI Ji-qi, BAI Hong-lin, REN Li-hong, DONG Liang-liang
2012, 27(9): 1921-1927.
Abstract PDF(1101KB) icon1785 icon579
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A low pressure direct injection transparent optical engine bench was developed,and the in-cylinder mixture formation process was filmed.Different mixture formation patterns were analyzed in conditions of different combustion chamber geometries,fuel injection timings and engine speeds.The research results show that:guidance of the combustion chamber with decentralized cavity piston is better than that of the proto-engine's combustion chamber;fuel injection timing plays a key role in the mixture formation,and a good mixture formation can be obtained if choosing an injection timing when intake flow is not that strong and the piston moves in the middle position of the cylinder,when the intake flow is strong,an increased engine speed can accelerate the evaporation of the fuel droplets,but the guidance of the combustion chamber is weaked,which results in a bad mixture formation.On the contrary,when the intake flow is weak,higher engine speed can promote the effect of combustion chamber's guidance to the fuel plume.
Effect of internal combustion wave rotor technology on performance of gas turbine engine
LI Jian-zhong, GONG Er-lei, WEN Quan, WANG Jia-hua
2012, 27(9): 1928-1934.
Abstract PDF(975KB) icon1765 icon601
Abstract:
To investigate internal combustion wave rotor technology which improved performance of gas turbine engine,the thermodynamic cycle analysis model of an internal combustion wave rotor gas turbine engine was established.When the parameters of exit Mach number of the internal combustion wave rotor channel and compressor pressure ratio were changed,their influence on the performance of the internal combustion wave rotor gas turbine engine was investigated,and the variable disciplinarian of thermodynamic cycle parameter of the internal combustion wave rotor was discussed.When the compressor pressure ratio equals 3.6,the specific cycle thrust and thermal efficiency increases by up to 23.709%,and the specific fuel consumption decreases by up to 19.165%.When the exit Mach number of the internal combustion wave rotor channel equals 0.6,the specific cycle thrust and thermal efficiency increase by up to 23.736%,the corresponding compressor pressure ratio equals 4.4 at the same time,the thermal efficiency improves 32.216%,specific fuel consumption decreases by 24.366% and entropy generation decreases by 7.864%.It is validated that the technology of the internal combustion wave rotor can enhance the performance of gas turbine engine.The results can provide theory and practice for lucubrating the key technology of the internal combustion wave rotor gas turbine engine.
Experiment on multi-tube air-breathing two phase pulse detonation engine
ZHANG Qun, FAN Wei
2012, 27(9): 1935-1938.
Abstract PDF(412KB) icon1762 icon550
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A six-tube air-breathing two phase pulse detonation engine (PDE) model has been developed with diameter of 200mm and a total length of 1500mm.Under nearly atmospheric pressure,a proof-of-principle experiment on the engine model was successfully performed by using liquid gasoline/air mixture.Each tube in the PDE model can operate at a repetition frequency up to 35Hz with all the tubes running at the same time experimentally.Therefore a frequency up to 210Hz was reached in the PDE model.Several ignition control strategies were developed for the multi-tube air-breathing PDE model. Some rules of how different ignition control strategies affect the engine operation have been explored.The results in the investigation supplied a technology preparation to bring PDE to production.
Large-eddy simulation of two-phase reacting flows and combustion performance in model combustor
HE Yue-long, DENG Yuan-hao, YAN Ying-wen, LI Jiang-hua, ZHAO Jian-xing
2012, 27(9): 1939-1947.
Abstract PDF(1369KB) icon1992 icon560
Abstract:
Instantaneous gas-liquid two-phase turbulent combustion flows in model combustor were computed by using an Eulerian-Lagrangian two phase large-eddy simulation (LES) approach in three-dimensional arbitrary curvilinear coordinates,and combustion performance was estimated by an empirical-analytical design methodology.The k-equation subgrid scale model was used to calculate the subgrid eddy viscosity,and the EBU (eddy-break-up) subgrid scale combustion model was applied to predict the chemical reaction rate.The gas phase governing equations were solved by SIMPLE (semi-implicit method for pressure-linked equations) algorithm in non-staggered grid system,and a stochastic separated flow formulation was employed to track the droplet trajectory velocities,sizes and temperature history by Lagrangian equations of motion and thermal balance.Numerical simulation results were in reasonable agreement with the instantaneous velocity by particle image velocimetry (PIV) system and temperature measurements at the exit plane.It shows that in an arbitrary curvilinear coordinates,the Eulerian-Lagrangian two phase LES formulation can be used to investigate turbulent two-phase reacting flows and combustion process in model combustor,and combustion performance results are in reasonable agreement with the measurement results.It shows that the empirical-analytical design methodology can be applied to predict the combustion performance in gas turbine combustors,especially for pollution emissions,and it provides a useful tool for designing advanced gas turbine combustor of low emissions of pollutant and high performance.
Effects of equivalence ratio and gap size on the propagation behavior of detonations
ZHANG Chao, TANG Hao, LI Ming, Sudip Bhattrai
2012, 27(9): 1948-1957.
Abstract PDF(1542KB) icon2237 icon496
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To explore the feasibility of micro-scale pulse detonation engine propulsion system,detonation limits in narrow channels have been investigated.By observing and measuring the propagation behavior of premixed hydrogen-oxygen detonation flames in narrow gaps,effects of gap size and equivalence ratio on detonation wave pressure and velocity were experimentally analyzed.Outside the detonation limit,the detonation wave coming from the guide section can reach a steady state in the gap by self-adjustment of the pressure and velocity.The distance required by the adjustment process was growing when the gap size decreased.According to the definition of velocity deficit,the characteristics of the velocities of shock and flame front along the micro-channel were summarized,and four propagation models-steady detonation,sub-steady detonation,low-speed detonation and non-detonation were observed.
Evaluation methods of the fuel mixing efficiency for Scramjet
ZHANG Wan-zhou, LE Jia-ling, TIAN Ye, YANG Shun-hua, DENG Wei-xin, CHENG Wen-ming
2012, 27(9): 1958-1966.
Abstract PDF(1091KB) icon1909 icon663
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Three commonly-used evaluation methods for scramjet were summarized and analyzed,to improve the precision and objectivity for mixing evaluation,three new methods were imposed:the flow-field mixing efficiency,the flammable mixing efficiency and the flammable region percentage.The flow-field mixing efficiency can estimate the mixing performance of the flow structure and the effect of the mixing enhancement measurements.The flammable mixing efficiency and the flammable region percentage that took the flow-field blowout limits into consideration can connect with the ignition and combustion directly,objectively estimate the mixing efficiency for different lean and rich regions,and predict the region that combustion may occur.Then the three methods are verified and compared with the existed methods by two-dimension computational cases.
Theoretical solution on heat transfer in oscillatory pipe flow and analysis of enhanced heat transfer
LI Ming-zhen, DONG Jin-zhong
2012, 27(9): 1967-1973.
Abstract PDF(535KB) icon1766 icon550
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By solving the momentum and energy equations of the oscillatory flow driven by a sinusoidally varying pressure gradient,the general analytical solutions of the velocity profile,the temperature profile and the enhanced thermal diffusivity were obtained.Based upon the analytical solutions,it is found that three parameters influenced the enhanced heat transfer for the problem are the dimensionless oscillatory frequency,the dimensionless amplitude and the Prandtl number of the fluid.The velocity profile is directly determined by the dimensionless oscillatory frequency,and the enhanced thermal diffusivity increases with the increase of dimensionless oscillatory frequency,dimensionless amplitude and Prandtl number.
Experiments of plasma assisted combustion's effect on combustion products
ZHAO Bing-bing, ZHANG Peng, HE Li-ming, DU Hong-liang
2012, 27(9): 1974-1978.
Abstract PDF(699KB) icon1870 icon650
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Experiments of plasma assisted combustion (PAC) in propane-air mixtures were conducted.The plasma was produced by dielectric barrier discharges (DBD), and the emission spectrums of air and propane-air mixture were tested respectively.The variation of O2 and CO volume fractions with time was measured using the gas analyzer.The effect of discharge voltage,air flow and propane flow on combustion products were analyzed and discussed.The results show that in PAC,the variation rates of O2 and CO volume fractions increase compared to that in normal combustion,and the combustion efficiency enhances in stable combustion due to the decrease of O2 and CO volume fractions;increasing air flow and propane flowand decreasing discharge voltage can weaken the effects of PAC.
Breakup characteristics and surface wave phenomenon of round liquid jets in crossflows
WANG Xiong-hui, HUANG Yong, WANG Fang, WANG Shao-lin, LIU Zhi-lin
2012, 27(9): 1979-1987.
Abstract PDF(921KB) icon2138 icon603
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An experiment was conducted to investigate column breakup process of round liquid jets in crossflow.High-speed camera was employed to observe surface wave phenomenon and the formation of droplets.The injectors used in the experiment were plain orifice nozzle and their diameters were 0.3mm and 0.5mm.The test liquid was tap water.Test Weber number covered the range of 1.7~7,and liquid-to-air momentum flux ratio varied from 3.4 to 83.Present results indicate that the surface wavelength,is in negative proportion to the logarithm of Weber number.With the increase of the logarithm of Weber number,the diameters of droplets increase linearly.Droplets' velocities,both streamwise direction and cross stream direction,are independent on their diameters.In the range of the experiment,droplets' cross stream velocity equals to about 0.94 vj,and droplets' streamwise velocity is about 0.085 ua.The results of surface wavelength and droplet's diameter and velocity can significantly improve the accuracy of primary breakup model.
Further detailed analysis about shock wave reflection outside Laval nozzle in different working states
YU Yong, XU Xin-wen
2012, 27(9): 1988-1996.
Abstract PDF(1045KB) icon1893 icon549
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When ratio of environmental pressure to total pressure increases from design state to third limit condition (normal shock at the outlet of nozzle), there are different shock wave phenomena outside the Laval nozzle. According to extant theory about shock wave reflection, the working range between design condition and the third limit condition was subdivided into several sections: strong oblique shock wave condition, Mach reflection condition, regular reflection and dual solution domain. Three critical ratios of environmental pressure to total pressure were proposed and determined to replace flow-deviation angle for estimating different Laval nozzle working statuses. Varying tendency of these critical ratios of Laval nozzle in various aspect ratios were also given with a figure. The pressure ratios corresponding regular reflection, Mach reflection and strong oblique wave in a planar Laval nozzle with aspect ratio 5 were 0.0841, 0.0959 and 0.2005 respectively, and then the accuracy of these values were verified with numerical simulation.
Research on local DQ-Lagrange method for solving flow field in step flow
SUN Dan, YANG Jian-gang, ZHAO Huan, LI Guang-chao
2012, 27(9): 1997-2003.
Abstract PDF(835KB) icon1579 icon523
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An upwind local differential quadrature-Lagrange interpolation method to solve the Navier-Stokes equations for the flow field in the complex step flow was set up.The method to impose the essential boundary condition and the natural boundary condition was improved.The effect of support domain size,boundary condition treatment method and the upwind scheme on the accuracy of the calculation were analyzed.Calculation simulation shows that the high order Lagrange interpolation may cause numerical oscillation.The local differential quadrature method was recommended.The upwind support domain can improve the accuracy of the solution.Solution accuracy may be better in case of that the velocity support domain is lager than the pressure support domain.
Design of streamline-traced hypersonic inlets based on two-dimensional curved surface basic flowfield
LI Yong-zhou, ZHANG Kun-yuan, WANG Lei, NAN Xiang-jun, ZHANG Lin
2012, 27(9): 2004-2012.
Abstract PDF(1266KB) icon2394 icon577
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The rectangular and circular shape intake hypersonic inlets and rectangular to elliptical shape transition hypersonic inlet have been designed with the technologies of streamline tracing and varying section using an optimized two-dimensional(2-D) curved surface basic flowfield with controlled pressure gradient.It proved that hypersonic inlets with various entrance and exit shapes can be designed based on 2-D curved surface basic flowfield.Utilizing this design method,three hypersonic inlets with different entrance and exit shapes have been generated and compared with typical 2-D inlets under the same constraints.The numerical simulation shows that Mach number distributions and general performance for unconventional inlets approximate the basic flowfield at design point under the inviscid condition,which has the characteristics of 2-D basic flowfield that shock structure is simple and exit distortion is low.This kind of inlet has the roughly equivalent general performance.Comparison with typical 2-D inlet indicates that they significantly reduce the length of external compression portion,have greater flow ability to capture and demonstrate better performance at off design points.In conclusion,this design method is feasible and is worth being investigated further.
Research on aerodynamic characteristics of autorotating coaxial twin-rotor
JI Le-qiang, ZHU Qing-hua, Cui Zhao, LI Jian-bo
2012, 27(9): 2013-2020.
Abstract PDF(1200KB) icon2140 icon714
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In order to investigate the aerodynamic characteristics of autorotating coaxial twin-rotor,the wind-tunnel test of an autorotating coaxial twin-rotor was performed with the theorical investigation.The blade element theory is adopted to calculate aerodynamic force and moment.The aerodynamic interaction model and the dynamic inflow model were used to investigate the inflow of the autorotating coaxial twin-rotor.The comparison between experiment and calculation shows that the error is less than 5% when the rotor speed is greater than 300r/min.Thus,the model of the aerodynamic characteristics of autorotating coaxial twin-rotor was verified.The relationship of speed and lift of the twin-rotor and the design parameters which included pitch angle,shaft angle,the distance between the upper rotor and the lower rotor,and wind speed of the wind tunnel was obtained.The aerodynamic interaction between the rotors was analyzed.The method of calculation for the thrust ratio of the upper rotor and the lower rotor was derived.
Well-posedness of the multi-freedom time domain impedance boundary condition for broadband sound propagation numerical simulation
LI Xiao-yan, LI Xiao-dong
2012, 27(9): 2021-2027.
Abstract PDF(833KB) icon1660 icon613
Abstract:
The main objective is to validate the feasibility and accuracy of a multi-freedom time domain impedance boundary condition for broadband sound propagation problems.The NASA(National Aeronautics and Space Administration) grazing incidence tube experiment data was selected for numerical validation.The linearized Euler equation was solved by a high order computational aeroacoustics approach.The obtained numerical results are in good agreement with both the experimental data and results from single frequency simulation.It is demonstrated that the multi-freedom broadband impedance boundary condition is viable and accurate for the description of broadband sound propagation over impedance surfaces.
Research of water hammer and its suppression methods for spacecraft propulsion system
YAN Zheng, PENG Xiao-hui, CHENG Yu-qiang, WU Jian-jun
2012, 27(9): 2028-2034.
Abstract PDF(1083KB) icon2020 icon637
Abstract:
In order to investigate the water hammer dynamics of spacecraft propulsion system during the priming and shutdown processes,dynamic simulation of a certain unified propulsion system (UPS) was conducted firstly based on UPS simulator modeled previously.Then the water hammer suppression effect of orifice and bent pipe on the propellant supply pipeline was analyzed thoroughly.Results show that water hammer phenomena occur obviously in almost the whole propulsion system during the priming and shutdown processes.However,the frequency and the peak pressure of water hammer during the priming process are both lower than that of the shutdown process,especially the peak pressure.The results also show that both the orifice and the bent pipe can suppress the oscillation of pressure and flow rate significantly during the priming processes,but only orifice with small diameter can suppress the water hammer effectively during the shutdown process.Moreover,in contrast to their weak suppression of water hammer during the shutdown process,bent pipe can suppress the oscillation of flow rate especially effective in the priming process.
Mathematical model of isentropic expansion process based on Φ function
ZHENG Hai-fei, TANG Hao
2012, 27(9): 2035-2040.
Abstract PDF(405KB) icon1661 icon594
Abstract:
Recently,the calculation of ideal value was involved in the main mathematical model of isentropic expansion process,so compared with the actual value,the results had a certain error.Deriveing the mathematical model of isentropic expansion process based on Φ function by using the definition type of process efficiency.Compared with the results from the mathematical model of isentropic expansion process based on entropy and the mathematical model of isentropic expansion process based on ideal value,concluded that:(1) accuracy can be improved when applying the mathematical model of isentropic expansion process based on Φ function;(2) application of the mathematical model of isentropic expansion process based on Φ function is simple,and can greatly improve the programming efficiency and computational efficiency.
PIV experimental study and numerical simulation of single expansion ramp nozzle supersonic flow field
YU Kai-kai, XU Jing-lei, MA Jing
2012, 27(9): 2041-2047.
Abstract PDF(799KB) icon1806 icon493
Abstract:
The experiment choose TiO2 which had good following performance as well as scattering property.The flowfield of the single expansion ramp nozzle (SERN) under different pressure ratios was researched by particle image velocimetry (PIV) and numerical method.In the experiment,the structure of the flowfield,the pressure on the upper expansion wall,the velocity vector,and so on have been successfully obtained.From the processed images,the shock and expansion wave can be observed clearly,and the velocity at the outlet has been further analysized.The experimental data agreed very well with the data from the computational fluid dynamics (CFD).Therefore,the accuracy and reliability of the PIV experiment and the CFD result were both validated.
Modified reduced model for rapid analysis of tip clearance of high pressure turbine
YANG Xiao-guang, HUANG Jia
2012, 27(9): 2048-2055.
Abstract PDF(987KB) icon2232 icon507
Abstract:
Considering the effects of temperature,rotating speed and pressure difference in engine operating conditions for predicting changes in turbine tip clearance,a modified reduced model was presented.In the process of designing structures for high pressure turbine in an aircraft engine,tip clearance was predicted using this modified model,and results show that the modified model can predict tip clearance changes into engine operating conditions more accurately.By simply inputting geometric,heat transfer,material and population parameters in this model,the variation of tip clearances can be obtaine quickly,and the conditions when the maximum and minimum tip clearance happened can be determined.Therefore,this method can be a way to evaluate tip clearance efficiently during the preliminary design of an aircraft engine.
Simulating and validating the stress-strain curve of the matrix cracking of ceramic matrix composite
SUN Zhi-gang, MIAO Yan, SONG Ying-dong
2012, 27(9): 2056-2062.
Abstract PDF(848KB) icon1740 icon509
Abstract:
The matrix random cracking of ceramic matrix composite was simulated by Montel Carlo model.The shear-lag model was used to analyze the micro-stress field of the damaged composites,and the formula of the stress-strain behavior was derived.The uniaxial tensile experiment of unidirectional-C/SiC composites at ambient temperature has been performed,and the simulated stress-strain curve was compared to the experimental data.The tensile stress-strain curves of SiC/CAS and SiC/Si3N4 composites were simulated,which agreed well with the related experimental results.Besides,infuence of the model parameters on stress-strain curve was analyzed.Research shows that the higher the Weibull modulus,the more evident the non-linear phenomenon;the higher the thermal residual stress,the earlier the non-linear phenomenon appears;the effect of the minimum cracking stress on the stress-strain is similar to the effect of the Weibull modulus;the Monte Carlo model can simulate the stress-strain curve of ceramic matrix composites efficiently.
Flutter analysis of a two-dimensional wing with aerodynamic and structural nonlinearity
WANG Yi-feng, SHAO Song, ZHU Qing-hua, ZHANG Cheng-lin
2012, 27(9): 2063-2074.
Abstract PDF(1660KB) icon1954 icon592
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The unsteady and dynamic stall aerodynamic behavior of airfoil at low Mach number was investigated,and the modified Leishman-Beddoes (L-B) model was modeled from the viewpoint of the convection of the flow on the airfoil surface.Based on the modified L-B model,the flutter analysis model of a two-dimensional wing with aerodynamic and structural nonlinearity at low Mach number was presented.The modification to L-B is effective by comparing with experimental airfoil airload results,and the wing flutter experimental results also verify the analysis model of the two-dimensional wing aeroelastic system.Results demonstrates that the stall flutter of airfoil aeroelastic system is closely related to the initial pitch angle and the inflow velocity,and the quasi-periodical oscillation motion of the two-dimensional wing aeroelastic system mainly caused by the coupled cubic nonlinear stiffness in pitch and plunge.
Evaluation of multi-process plans based on fuzzy comprehensive evaluation and grey relational analysis
WANG Pei, ZHANG Ding-hua, CHEN Bing, LI Shan, MA Guan-ghui
2012, 27(9): 2075-2085.
Abstract PDF(684KB) icon1920 icon553
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To provide evidence for enterprises to choose the best process plan,the method of multi-process plan evaluation based on fuzzy comprehensive evaluation and grey relational analysis was proposed.In this method,the fuzzy comprehensive evaluation and grey relational analysis were integrated to build a multi-process plan evaluation method.Hierarchical analysis was made in the structure figure of process plan selection process by various factors which affected the quality of process plans,and the hierarchical model of these factors was built.While standardizing data,membership degree was adopted to finish it.While caculating weight,the fuzzy comprehensive evaluation and the variation coefficient method were combined to calculate weight instead of the average weight method in the grey relational analysis.Then,sorting process plans were achieved by correlation coefficients and combined weight.Finally,an aircraft engine blade was developed to illustrate the feasibility and validity of the proposed evaluation method.
Location method of acoustic emission source in non-uniform temperature field
CHEN Ya-nong, HE Tian, XIAO Deng-hong, LIU Xian-dong
2012, 27(9): 2086-2092.
Abstract PDF(527KB) icon1674 icon474
Abstract:
In view of the location accuracy decrease of time division of arriving (TDOA) method in non-uniform temperature field,the location performance of acoustic emission beam-forming was studied.Firstly,the propagation characteristics of acoustic emission signals were obtained by using plate wave theory,and the main factors affecting the accuracy like dispersion phenomenon are analyzed on the basis of the results.Then,the location performance of acoustic emission beam-forming based on uniform linear array wss explored by numerical simulation,and show that the positioning accuracy on sensors array direction is stable in certain speed range.The artificial acoustic emission sources which were created by breaking a mechanical pencil lead on the plate surface before and after heating were implemented to verify the simulation.The results were analyzed and show that the acoustic emission beam-forming method has high location accuracy in non-uniform temperature field and good prospect of application for positioning stator-rotor rub of aero-engine in which stator has uneven temperature.
Life scatter factor method based on any two pieces of experimental information
YAO Gang, LU Shan
2012, 27(9): 2093-2098.
Abstract PDF(271KB) icon1668 icon578
Abstract:
Life scatter factor method based on any two pieces of experimental information was proposed in order to avoid the situation that the technology life was lower and wasted,which was caused by the worst result made for accidental factors.The calculation formulas of the life scatter factors based on any two pieces of experimental information of small sample logarithm normal distribution were deduced,and the life scatter factors were calculated with the given confidence level.The numerical example shows:the technology life based on the method and the life scatter factor is close to the technology life based on the traditional median life,and the new method is logical.The application of the method was given in the end.
Numerical simulation of an aero-engine fan with inlet distortion
LIU Yong-quan, LIU Huo-xing, ZHENG Ning
2012, 27(9): 2099-2105.
Abstract PDF(825KB) icon2347 icon649
Abstract:
The method of replacing the blade row forces with distributed bulk body force source terms was developed to simulate fan flow field with inlet distortion.The fan with clean inlet and inlet steady total pressure distortion in an aeroengine were simulated respectively.It demonstrates that the results of fan with clean inlet agree well with the solutions of RANS(Reynolds-averaged Navier-Stokes).In the case with inlet distortion,this code can obtain the propagation of inlet distortion correctly.The unsteady simulation shows that large-scale strong reaction and three-dimentional transportation were main property of flow field with inlet distortion. The attraction of the distributed bulk body force model is obvious in that it can be relatively independent of the empiricism while at the same time demands much less computer resources.
Stall improvement mechanism of vaneless diffuser flow path control in a centrifugal compressor
WANG Yong-sheng, TONG Zhi-ting, LIN Feng, NIE Chao-qun
2012, 27(9): 2106-2112.
Abstract PDF(681KB) icon1966 icon455
Abstract:
To investigate the stall improvement mechanism of vaneless diffuser flow path control,a centrifugal compressor was simulated and compared with existing experimental data.According to characteristics of flow field and stall mechanism,a convergent-divergent type of impeller-diffuser casing designed was analyzed.The result shows that the stable flow range of centrifugal compressor increases by 2.8%,however,no obvious positive effects are found on the adiabatic efficiency which is slightly lower than that of the prototype.
Design research of small flow rate multi-stage high-loaded axial compressor
XIE Ya-dong, SHAN Peng
2012, 27(9): 2113-2121.
Abstract PDF(1350KB) icon1566 icon442
Abstract:
The pressure ratio of a five stage foreign compressor with small flow rate is 6.On condition that not exceeding its pre three stage axial length,a three stage compressor was designed and its maximum pressurizing ability was researched.By using positive pre-whirl,end-bend stator and the measure that properly boosted the shroud of the second and third stages,the design result of this three stage compressor was that the mass flow rate was 5.80kg/s,pressure ratio was 5.445,efficiency was 0.8272,surge margin was 11.8%,and average stage pressure ratio was 1.759.On condition that not exceeding the limit of a certain axial length,the small flow three stages got the pressure level of 5.5.The flow characteristic curve has been cliffy.
Thermo-structure integrative computation for nozzle in SRM
ZHENG Xiao-ya, WANG Wei-xiang, CAI Fei-chao, CHEN Feng-ming
2012, 27(9): 2122-2127.
Abstract PDF(706KB) icon1986 icon456
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The thermo-structure computation procedure of nozzle in SRM(solid rocket motor) was embedded in software FLUENT based on user-defined function (UDF). It realized coupled heat transfer data picked using UDF macro commands.Contact boundary identify procedure was complied and direct constraint method was applied to solve boundary nonlinear problem.Then it achieved thermo-structure integrative computation for nozzle in SRM.
System simulation and optimal design of hybrid rocket motor with pump feed system
ZHU Hao, KONG De-shuai, CAI Guo-biao
2012, 27(9): 2128-2133.
Abstract PDF(668KB) icon1711 icon454
Abstract:
System simulation and optimal design of hybrid rocket motor with pump feed system were proposed.The high concentration hydrogen peroxide was selected as the oxidizer.Based on the fact that the high concentration hydrogen peroxide can be easily catalyzed,a pump feed system was used and a system simulation procedure was programmed.The genetic arithmetic was used in the hybrid rocket motor optimal design process.The optimal design results show that hybrid motor with a pump feed system shows more engineering application potential compared with hybrid motor with a gas pressure feed system,because its performances are better.
Investigation of priming process of propellant lines using Fourier spectral method
CHEN Hong-yu, LIU Hong-jun, CHEN Jian-hua, LIU Shang
2012, 27(9): 2134-2139.
Abstract PDF(536KB) icon1802 icon468
Abstract:
A mathematical model was presented for the priming process of propellant lines with moving boundary conditions based on one-dimensional fluid transient theory.The nonlinear hyperbolic partial differential equations governing the unsteady motion of fluid were solved by the Fourier spectral method.A coordinate transformation technique was employed to reduce fluid motion in time-dependent domains to ones in time-independent domains.The results obtained from the Fourier spectral method exhibit greater consistency with method of characteristics.In addition,spectral method requires less computer calculation time with less numerical error,which shows that the method is more suitable to solve fluids motions in such a complex system.The analysis shows that initial gas pressure,tank pressure and ploytropic exponent all have vital effects on surge pressure.
Disturbance rejection control method for turboshaft engines based on LQ/H∞
LIAO Guang-huang, LI Qiu-Hong, LU Chen-hao, HUANG Jin-quan
2012, 27(9): 2140-2146.
Abstract PDF(651KB) icon1662 icon446
Abstract:
The linear quadratic (LQ)/H∞ control method was proposed for turboshaft engines to reject disturbance.The collective pitch was treated as disturbance during modeling.The state feedback law was obtained based on linear matrix inequality (LMI), and it satisfied both LQ index and H∞ disturbance rejection index.The disturbance rejection method based on reference adjustment was proposed.The adjustment of power turbine rotor speed reference was achieved by proportional derivative (PD) control according to collective pitch variation,and the overshoot or droop of the real speed was suppressed during maneuver.Simulation results show that the methods proposed can suppress the disturbance effectively and run in realtime.
Mission reliability allocation of spaceflight TT&C system based on adaptive particle swarm optimization
ZHANG Xin-gui, WU Xiao-yue
2012, 27(9): 2147-2154.
Abstract PDF(576KB) icon1669 icon482
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The mission sequential logic relations were described by sequential diagram,mission reliability model of each phase and the reliability allocation model were built,and the constraint conditions and the allocation objective were discussed.The adaptive particle swarm optimization (APSO) was designed,which adaptively adjusted the convergence speed by altering the value of weighted coefficient ω during population iterating.With this method,the global results can be searched quickly in the initial stages,and the local results can be obtained effectively in the later stages.By simulation,it shows that the APSO can reach more optimal results and convergence in solving the mission reliability allocation of spaceflight TT&C(tracking telemetry and command) system.
Calculation of start-up pressure of two-wheel bootstrap air cycle machine with foil air bearing
ZHAO Yun-feng, HU Wen-chao, ZHU Gang, NING Jia-qiang
2012, 27(9): 2155-2160.
Abstract PDF(583KB) icon1869 icon499
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Through an analysis of the start-up principle of two-wheel bootstrap air cycle machine (ACM) with foil air bearing,the method to calculate the start-up pressure has been established has been established.According to this method,a program has been composed to calculate the start-up pressure of one ACM under different conditions.The calculation results matched the actual test data well,which demonstrates that this calculation method is of high accuracy.Calculation and analysis show that the turbine outlet pressure and the bearing preload have great effects on the bearing start-up pressure.The lower the turbine outlet pressure,the lower the start-up pressure is.Meanwhile,the greater the preload,the higher the start-up pressure is.

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