2013 Vol. 28, No. 3

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Assessment of optimum confidence interval of reliability with three-parameter Weibull distribution using bootstrap weighted-norm method
XIA Xin-tao, XU Yong-zhi, JIN Yin-ping, SHANG Yan-tao, CHEN Long
2013, 28(3): 481-488.
Abstract PDF(515KB) icon1955 icon1382
Abstract:
The bootstrap weighted-norm method was proposed to evaluate the optimum confidence interval of reliability with three-parameter Weibull distribution.Based on the difference between the empirical values and the theoretical values of reliability,an information vector of the optimum parameters of the Weibull distribution was structured in the light of six criterions of the minimum weighted-norm.By bootstrap resampling the information vector of the optimum parameters,a generated information vector was obtained to simulate the probability density function of the parameters.The estimated truth-value and its confidence interval of the parameters were solved and the estimated truth-value function and its optimum confidence interval function of the reliability could accordingly be established under the given confidence level.The case studies of the rolling bearing performance life,the helicopter component failure and the specimen fatigue life indicate that the estimated truth-value function is in accord with empirical values of reliability by using bootstrap weighted-norm method, and the optimum confidence interval function is able to describe true state of the test results.
Fretting fatigue life prediction based on critical plane approach for dovetail joint
XU You-liang, CUI Hai-tao, CHEN Wei
2013, 28(3): 489-493.
Abstract PDF(566KB) icon1941 icon1347
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The contact stress and strain of the dovetail joint of aeroengine were analyzed. According to the critical plane approach of multiaxial fatigue theory, the multiaxial fatigue damage parameters: CCB (Chu-Conle-Bonnen), FS (Fatemi-Socie), MSSR (modified shear stress rang), and SWT (Smith-Watson-Topper), were introduced to predict the fretting fatigue life of the dovetail joint. By comparing the predicted fatigue life with the experimental life, the results show that: the maximum prediction error of fretting fatigue life was 23%, helping to predict satisfactorily low-cycle fretting fatigue life. And, the minimum prediction error was 1.23% based on SWT parameter. The predicted crack tip initiated at the end of contact area in agreement with the experiment test. In general, the critical plane approach can be used to predict the fretting fatigue effectively. The models based on FS, MSSR and SWT can predict the fretting fatigue crack position, while the models based on MSSR and SWT can predict the fretting fatigue life more correctly.
Bayes sequential test technique for binomial product based on posterior probability
LIU Qi, WANG Nan, TANG Min
2013, 28(3): 494-500.
Abstract PDF(392KB) icon1816 icon1197
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Defects of Bayes hypothesis test method based on posterior loss and sequential posterior odd test (SPOT) method based on risks were analyzed. According to the requirement of binomial product's Bayes sequential test in equipment test and evaluation, considering the constraints of producer's risk and consumer's risk, posterior probability based sequential test model (PBSTM) was constructed, the PBSTM solving algorithm and formulas of actual posterior risks were presented. At last, with an example in equipment reliability analysis, the superiority and effectiveness of PBSTM was proved by data.The result shows :PBSTM guaranteed in theory that the results of sequential test can satisfy the small probability event principle and risks requirement simultaneously, and avoid the defects of existing methods.
Analysis of power metallurgy superalloy turbine disc's burst speed
FENG Yin-li, WU Chang-bo, GAO Peng, CHEN Wei
2013, 28(3): 501-506.
Abstract PDF(608KB) icon1951 icon1332
Abstract:
The average stress method,modified average radial stress method,residual deformation method,and local plastic strain method which were used for burst speed forecast were introduced.power metallurgy(P/M) superalloy turbine disc's burst speed was analyzed with these methods.By comparing the forecast results with test results,it can be found that the forecast results agreed well with the test results using the modified average radial stress method,residual deformation method and local plastic strain method.However,the forecast burst speed by the average stress method based on radial stress distributing equably are not in agreement with test results.
Experiment of effect of shot peening strengthening on TC11 alloy simulation blade's HCF life
WANG Mei, LU Shan, GU Yuan-xing, LIU Liang, ZHANG Huan
2013, 28(3): 507-512.
Abstract PDF(628KB) icon2013 icon1236
Abstract:
The vibration characteristic measurement and high cycle fatigue(HCF) comparison test were applied out to unstrengthened,steel grit strengthened and double strengthened blades.Through experimental results and fracture analysis,the three kinds of blades' natural frequency,damping ratio crack origin and HCF limit were studied and compared.The study indicates that the first order damping ratio is improved about 40%—50%,and HCF limit is improved more than 40%,and HCF life is improved accordingly.The article also give the reason of HCF limit improvement was also analyzed from strengthening mechanism.The experimental data accumulated and the study result can offer references to engineering design.
Excitation coil manufacturing technology for high temperature active magnetic bearing
JIN Chao-wu, LU Xu-dong, ZHU Yi-li, XU Long-xiang
2013, 28(3): 513-519.
Abstract PDF(1288KB) icon1686 icon1207
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In view of many defects and deficiencies of high temperature excitation coil at home and abroad,a new type of maze like excitation coil structure was proposed.Firstly,the monolayer maze like coil was manufactured by electric discharge machining (EDM) wire cutting,and the high temperature resistant insulating material was put into the gap of coils sufficiently and uniformly.Secondly,the vacuum soldering process was utilized to connect each layer.Finally,the packaged coils were used in a single degree-of-freedom (DOF) high temperature active magnetic bearings (HTAMB) test,and the HTAMB can achieve stable levitation for 20 hours at 550℃.The results show that the welding line resistance value is small,the shear strength of the selected solder and welding line shaped by copper parent metal are credible and coil insulation performance between turns and layers is fine in high temperature environment.Therefore,the high temperature excitation coil is feasible in theory and technology.The oxidized and impaired excitation coil internal structure caused by high temperature levitation test shows that the high temperature resistant insulating material used in encapsulated coil has certain flaws,and they need further research.
Method for reliability analysis on constant-stress zero-failure accelerated life test
ZHANG Yong-bo, FU Hui-min, WANG Zhi-hua
2013, 28(3): 520-524.
Abstract PDF(292KB) icon2245 icon1802
Abstract:
Given that there is not yet an effective method for dealing with the zero-failure data in the accelerated life tests among engineering projects,a method for reliability analysis on the constant-stress zero-failure accelerated life test was proposed.This method can equivalently covert the zero failure data in the accelerated stress level to the normal stress level. Then, reliability assessment and life prediction on the product under zero-failure accelerated life test condition could be achieved in the normal stress by dealing with the converted data. Based on this method, analysis was conducted on the zero-failure accelerated life test data of one kind of satellite earth sensor pintle. The result shows that this method has well solved the problem of reliability assessment and life prediction when the product is subject to zero-failure accelerated life test by fully utilizing the information.
Buckling of lattice truss cores sandwich structures with carbon fiber reinforced
ZHANG Lei, QIU Zhi-ping
2013, 28(3): 525-530.
Abstract PDF(746KB) icon1580 icon1481
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Considering the geometrical configuration of the structure and the deformation mode of the lattice truss,a new displacement field assumption was proposed based on the equivalent continuum theory,and finite element method program was prepared for buckling analysis of lattice truss-core composites.By comparing with the compression test of a group of samples,the buckling behavior of sandwich structures with carbon fiber reinforced lattice truss cores was studied,and the validity was affirmed.Furthermore,the relationship between the buckling load of lattice truss-core composites and lattice parameters (including length,radius and angle of lattice truss) was discussed.The results demonstrate that the little difference exists in bulking load between pyramidal and tetrahedral lattice truss sandwich structures when the volume fraction of the cores are the same, the latter is a little higher.The conclusions are meaningful for the design of lattice truss-core composites.
Analysis and application of baseline model of aero-engine exhaust gas electrostatic monitoring signals
SUN Jian-zhong, ZUO Hong-fu, LIU Peng-peng, YU You-feng, CHEN Zhi-xiong
2013, 28(3): 531-540.
Abstract PDF(766KB) icon1849 icon1422
Abstract:
A study on the application of the aero-engine exhaust gas electrostatic monitoring technology for gas path component condition monitoring was conducted.The exhaust gas electrostatic monitoring signal (EGEMS) was taken as a new gas path parameter and its deviation from the baseline in EGEMS root mean square (RMS) value was monitored for real-time gas path component anomaly detection. Firstly, the exhaust gas soot emission characteristics were studied from the electrostatic monitoring point of view, and then the baseline composition of the EGEMS, the main influencing factors as well as the EGEMS features of the typical faults were studied. Furthermore,two baseline model mining methods were proposed respectively for a single parameter (fuel flow rate) based baseline model (parametric model) and a multi-parameter based baseline model (nonparametric model) which was obtained using multi-state estimation technique. The case study on a real EGEMS data set from a turbo-shaft engine shows that the established baseline model can characterize the EGEMS under various operating conditions of the test engine, and can effectively detect the anomaly of the gas path components.
Shear properties of X-cor sandwich
SHAN Hang-ying, XIAO Jun, SHANG Wei, LI Ning, ZHANG Xiang-yang
2013, 28(3): 541-549.
Abstract PDF(692KB) icon1859 icon1181
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A series of experiments were carried out for comparison under shear loading,including X-cor sandwich,foam sandwich and Z-pin sandwich,so as to investigate Z-pin enhancement effect on foam sandwich.By studying on the difference between test and formual data the modifed formula of shear modulus and strength was achieved.The result shows that shear properties are related to modulus stiffness discount M and time facotr T,indicating the beginning of Z-pin pull from face skin: M and T were affirmed by craft level.
Simulation on working process of 10N attitude-control thruster combustion chamber at lower-pressure condition
MAO Xiao-fang, TANG Zhen-yu, CAI Guo-biao
2013, 28(3): 550-555.
Abstract PDF(769KB) icon1813 icon1111
Abstract:
A simulation model for the working process of rocket engine combustion chamber was described. Simulation was implemented by using this model for a 10N thruster working at different lower supply pressures. Comparisons were made to find some characteristics of chamber pressure and thrust of the thruster when it worked in long-pulse and short-pulse modes at regular and lower supply pressures. According to the theoretical thrust obtained by simulation and the experimental thrust in long-pulse mode, it can be concluded that the thrust efficiencies are 94%, 91% and 90%, respectively, while supply pressures equal to 1.48, 1.0, 0.6MPa, separately. Meanwhile, simulation results of short-pulse mode cases show that, when the supply pressure decreases to 0.4MPa, the thruster cannot be ignited in short-pulse mode.
Simulation and experiment for preheating process of N2O monopropellant thruster with inner-heater
WU Jing, SUN Wei, CAI Guo-biao
2013, 28(3): 556-560.
Abstract PDF(935KB) icon1917 icon1219
Abstract:
In order to promote the preheating effect of N2O monopropellant thruster, the structure of the thruster was improved and inner-heating mode was set up. The preheating experiment of the thruster with inner-heater was conducted in a vacuum chamber, and the catalyst was heated to 260℃(533K) with 10W after 5800s, confirming the feasibility and advantage of the inner-heating mode. 3-D model of the thruster was built and finite element software was utilized to analyze the preheating process. Time-dependent temperature filed of the structure was obtained. Numerical result agrees well with the experimental data, which demonstrates the accuracy of the simulation model. Then a simplified system model of the thruster with inner-heater was designed and 10,5,3W power were utilized to simulate the preheating process in space environment. The result shows that the catalyst will be heated to 250℃ with 10W and 5W power in 3600s, which can provide some references for the practical application of N2O monopropellant thruster.
Numerical simulation of priming process of propellant pipelines
CHEN Hong-yu, LIU Hong-jun, LIU Shang
2013, 28(3): 561-566.
Abstract PDF(570KB) icon1936 icon1072
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A mathematical model of the priming process of propellant pipelines was presented based on one-dimensional fluid theory using the method of characteristics (MOC) and finite deference.Coordinate transformation technique was employed to change fluid motion in time-dependent domains to ones in time-independent domains.The details of the method were presented with an illustration of the priming process of a simple piping system (system consisted of a tank,a pipe and a isolation valve).The results exhibited greater consistency with conventional method of characteristic calculations.The influence factors to the surge pressure of priming process have been studied future.The results show that the surge pressure can be effectively reduced by increasing the initial gas pressure, decreasing the tank pressure and increasing the polytrophic exponenting.
Experiment of primary rocket-piloting combustion under ramjet-mode condition in RBCC
XU Chao-qi, HE Guo-qiang, LIU Pei-jin, QIN Fei, PAN Ke-wei
2013, 28(3): 567-572.
Abstract PDF(691KB) icon1856 icon1098
Abstract:
The experimental studies were performed to investigate primary rocket piloting liquid kerosene (JP-10) combustion in rocket-based combined cycle (RBCC) combustor under typical ramjet-mode condition.Due to the low total temperature of incoming airflow in ramjet mode,the primary rocket with relative low mass flowrate was employed as a piloting flame to achieve reliable ignition and stabilized combustion of liquid kerosene (JP-10) in RBCC combustor.The secondary fuel (JP-10) has been injected into airflow by two strut injectors located behind the primary rocket and an upstream cavity flush-wall injector.The effects of cavity and the location position of strut and wall injection have been investigated..The strut injectors make the fuel easily be distributed into main airflow,and the results indicate that the injected fuel can accomplish steady and efficient combustion due to the interaction with the rocket plume.The comparisons of the pressure distributions in the combustor under different injection conditions show that the strut injection plays an important role in the combustion of wall injection fuel,and additional wall injection associated with cavity would improve the performance of RBCC combustor.Moreover,the wall injection location and the distance between the wall injection and cavity need to be further considered to obtain optimal engine performance.
Performance investigation of hypersonic rectangular MHD generator
HUANG Hao, HUANG HU-lin, ZHANG Yi-ning, LIU Zhen-de
2013, 28(3): 573-582.
Abstract PDF(2556KB) icon1737 icon1540
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Three dimensional magnetohydrodynamics (MHD) five-equation model associated with low magnetic Reynolds assumption was used to simulate the flow phenomenon for a rectangular Faraday type MHD generator with segmented electrode,and the effects of load factors,intensity of magnetic field and the width of the electrodes on the performance of the generator were investigated.The results show that,the electrical power density reached its maximum value when the loading factor is 0.50,and with the increase of the load factor,the slowing capacity of the generator is reduced.At the magnetic field strength of 8T,the 500mm long generator can reduce the Mach number from 6 to 3 below,the temperature could be kept below 800K,and power generation can reach the amount of megawatt-scale of per cubic meter of the duct.
Calculation of internal flow in pump of liquid rocket engine based on theory of relative stream surface
MA Dong-ying, LEI Zong-qi, LIANG Guo-zhu
2013, 28(3): 583-590.
Abstract PDF(2237KB) icon1731 icon1137
Abstract:
The theory of relative stream surface was applied to calculate and analyze the internal flow in a centrifugal pump of a liquid rocket engine.Streamline curvature method was used for calculation.Modularized calculation programs were developed to simulate the flow process in different parts of the pump,which allowed the calculation of every part to be conducted independently.The interaction between different parts was dealt with by the idea of mixing plane to convert the unsteady problem to steady problem.The effect of viscosity was corrected by several loss coefficients.The result shows that the inducer and the centrifugal impellers increase the pressure while the guide vane remains only changes the direction of the velocity, which consist with theoretical analysis.
Hyper-radial visualization and its application in launch vehicle design
SUN Xing-liang, FANG Jie, CAI Guo-biao
2013, 28(3): 591-596.
Abstract PDF(767KB) icon1658 icon952
Abstract:
Considering the deficiency of traditional visualization methods when dealing with high-dimensional multi-objective design optimization, the hyper-radial visualization (HRV) method was studied. HRV provided a lossless visualization way to represent the hyperspace Pareto frontier, enabled designers to realize the complex Pareto set intuitively, and identified a better trade-off design quickly as well. Besides, with the purpose of assisting designers to choose a more specific optimal design solution, the designers' preference was incorporated by the weights and color marks with range-based preferences. A multi-objective optimization design of a sub-orbit launch vehicle was accomplished by HRV, which indicates the HRV method is feasible and efficient for high-dimensional multi-objective design optimization.
Effect of meshed pitch deviation on transmission error in hypoid gears
DENG Xiao-zhong, XU Ai-jun, ZHANG Jing, LI Ju-bo, YANG Jian-jun
2013, 28(3): 597-602.
Abstract PDF(886KB) icon1791 icon1691
Abstract:
One measurement approach of tooth-tooth transmission error(TE) containing the meshed pitch deviation(MPD) was derived from the concept of the total transmission error in gear driving,and the TE offset formula of the effect of the MPD was proposed with the geometric relationship of the gear surface and the MPD.Then,the TE result of hypoid gears was obtained through the measurment experiments built on the platform of Y9550 type rolling tester.Finally,the TE curve was simulated by the MPD data gained by the JD45+gear measurement center,and the meshing state of gear teeth was analyzed.The effect of MPD on TE was verified by the contrast of the theory and practical TE curve.Experimental results show that the actual tooth-tooth TE curve can be replaced by the theoretical curve which includes the meshed pitch deviation at light loads,so as to lay the foundation for further study of the movement accuracy and stability of the gear transmission under actual working condition.
Design of 3-DOF hybrid magnetic bearing based on leakage coefficient and magnetoresistance coefficient iterative method
LIU Cheng-zi, DENG Zhi-quan, MEI Lei, HUA Chun
2013, 28(3): 603-612.
Abstract PDF(1868KB) icon1707 icon939
Abstract:
An iterative parameter design method based on leakage coefficient and magnetoresistance coefficient were presented.For each component of the hybrid magnetic bearing,structural parameters were ultimately obtained based on its leakage and magnetoresistance coefficients calculated using an iterative loop algorithm.The calculations were constrained to the degree of magnetic flux density unsaturation for the design goal of achieving a minimum volume while maintaining the maximum required levitation force.Finite element analysis (FEA) software was used to execute simulation analysis and modeling of the three-dimensional magnetic,demonstrating the rationality and validity of the parameterization method and its result.The displacements of rotor and control current curves of the magnetic bearing under floating,static suspension,static shock and at 30 000 r/min were presented.The experimental results testify that the hybrid magnetic bearing designed by the method has a good levitation performance.
Dynamic analysis of tooth profile modification to herringbone gears based on analytical solutions
GUO Jia-shun, WANG San-min, WANG Ying
2013, 28(3): 613-620.
Abstract PDF(1325KB) icon1508 icon1003
Abstract:
Based on the structure of a single-stage herringbone gear transmission,a nonlinear lateral-torsional-axial coupling dynamic model and corresponding dynamic equations considering the time-varying mesh stiffness,tooth profile modification and tooth backlash were proposed,for which the tooth profile modification was considered as a time-varying tooth backlash.The numerical solutions were analyzed and the results show that the total tooth separation can be suppressed with rational tooth profile modification.Then,according to the method of multiple scales,perturbation analysis of the dynamic equations finds that appropriate analytical frequency response solutions for the case cause no total tooth separation at primary resonance.Compared to the numerical method,the analytical method is more efficient.At last,the influence of the modification parameters on the amplitude of the dynamic load factor was analyzed on the basis of the analytical solutions.The analysis results present that the magnitude of tip relief decreases as the helical angle increases to reduce the dynamic load factor,while the length of modification increases in this case.In addition,the optimal solution domain of the minimum dynamic load factor is a meniscoid zone,it increases firstly as the support stiffness of the driving gear increases to a value,after that value,it decreases when the support stiffness of the driving gear continues to increase;the optimal solution domain decreases as the support stiffness of the driven gear continuously increases.
Effects of grinding parameters on surface integrity of GH4169 nickel-based superalloy
HUANG Xin-chun, ZHANG Ding-hua, YAO Chang-feng, REN Jing-xin
2013, 28(3): 621-628.
Abstract PDF(760KB) icon2078 icon1058
Abstract:
The influence rules of grinding parameters on the surface topographic characters, including surface roughness, surface topography, surface microhardness and surface residual stresses of the surface integrity, were studied to optimize the grinding parameters when grinding the GH4169 nickel-based superalloy by using single crystal corundum grinding wheel. The wheel speed was selected as 15, 20, 25m/s, the grinding depth selected as 50, 100, 150μm, and the workpiece speed selected as 5, 10, 15m/min. The results show that, the surface roughness is most sensitive to the workpiece speed, the surface microhardness and the surface residual stresses are most sensitive to the wheel speed. And the influence rules of grinding parameters on the surface morphology, the gradient of microhardness, microstructure and the gradient of residual stress were studied, revealing the formation rules of metamorphic layer of the surface integrity. The plastic deformation layer is in range of 5～10μm, the depth of the microhardness change is 80～100μm, the residual stress affected layer thickness is 80～200μm,thus providing relevant experimental data base for research of the surface integrity control in grinding nickel-based superalloy.
Experimental verification of numerical simulation of oil-air two-phase flow in bearing chamber
WANG You-yong, WANG Suo-fang, AI Jun-feng, LI Bin
2013, 28(3): 629-635.
Abstract PDF(1018KB) icon1980 icon973
Abstract:
In order to search a reasonable numerical model to simulate the flowing characteristic of the oil-air two-phase flow in a bearing chamber, a simplified test rig was set up. Various rules of air flow proportion at the vent and oil temperature rise at the scavenger under different operating conditions were obtained through this experimental investigation. Based on Mixture multiphase model and Eulerian multiphase model with standard k-ε turbulence model and RNG (renormalization group) k-ε turbulence model respectively, the universal computational fluid dynamics software Fluent was used to simulate the two-phase flow in a bearing chamber under some given operating conditions. The comparison shows that the relative error of oil temperature rise between the test result and the computational result under Mixture multiphase model with RNG k-ε turbulence model is only 2.72 percent when rotate speed is 2200r/min. Therefore, this computational model is accurate at high speed, based on which the distribution characteristics of oil-air two-phase flow velocity field, pressure field and temperature field are acquired.
Influence of flow parameters on flow separation control of cascade with synthetic jet
XIE Yong-hui, QU Huan-cheng, HE Hai-yu
2013, 28(3): 636-645.
Abstract PDF(1824KB) icon1896 icon1052
Abstract:
With the application of large eddy simulation (LES) and structural hexahedral mesh, the unsteady numerical model of the low-pressure high-lift turbine Pak B cascade was established. The mechanism and influence of the flow separation control using synthetic jet were discussed in detail. The separation zone of flow becomes larger when Reynolds number decreases and angle of attack increases without synthetic jet. The separated flow has not reattached on the cascade when the angle of attack is 5°. After using synthetic jet control method, the flow separation under different flow parameters is controlled effectively. Meanwhile, the effects of synthetic jet control with different jet pitch angles were compared, and there exists an optimal jet pitch angle 30° which leads to the best flow control effect. The location of separation on the boundary layer of the cascade is delayed with synthetic jet, but the reattachment location moves forward and the size of separation bubble decreases. The adverse pressure gradient zone decreases evidently. The shear layer at the suction side moving downstream is not uplifted fully and it adheres to the wall of blade quickly, which avoids the formation of large scale vorticity and controls the flow separation.
Computations of unsteady transonic flow over airfoil at low Reynolds number
ZHU Hai-tao, SHAN Peng
2013, 28(3): 646-658.
Abstract PDF(2965KB) icon1363 icon1004
Abstract:
Transonic flow over a thin airfoil at low Reynolds number was studied numerically by directly solving two-dimensional full Navier-Stokes equations through 5th order weighted essentially non-oscillatory(WENO) scheme without using any turbulence model.A series of distinguished unsteady phenomena for a thin 2-D transonic airfoil flow were presented.Due to continuous adverse pressure gradient in the subsonic flow downstream of the sonic line, the unsteady separated boundary layer with main vortex and secondary vortex was developed at the rear of the airfoil.At the trailing edge,the vortex-shedding was characterized by periodical connection of the main vortex and secondary vortex on the other side of the airfoil.The unsteady separation and vortex-shedding occurred with the same period.On the airfoil surface,the average pulse pressure related to the unsteady supersonic region was obviously smaller than that related to the vortex-shedding at the trailing edge.With the attack angle increasing from 0° to 2°, the frequency of vortex-shedding decreases about 4.2%.At last, the turbulence intensity and many second-order statistics in the wake region were investigated.
Conanda effect on aerodynamic performance and flow field of turbine cascade
FENG Yan-yan, SONG Yan-ping, CHEN Huan-long, CHEN Fu
2013, 28(3): 659-665.
Abstract PDF(1480KB) icon1664 icon963
Abstract:
Based on a real turbine inlet guide vane, the two-dimensional flow field of a turbine cascade was simulated by using the circulation control blade profile with different Coanda surfaces. At the cascade exit being high subsonic and supersonic conditions, the aerodynamic performance and the detailed flow fields of different blade profiles were explored. The mechanism of Coanda effect on turbine cascade was discussed. When Mach number at the cascade exit was 0.60, the jet entrained the mainstream well and the loss reduced. When Mach number at the cascade exit increased to 0.85, the ability of the jet carrying the mainstream was still fine. When the cascade exit was at supersonic flow condition, on the Coanda surface with a small curvature in front, the jet turmed to the center of the flow channel and detached the wall in advance on account of the shock wave. On the Coanda surface with a large curvature in front, the jet adhered to the blade quite well. However, it did not mix with the mainstream for good due to the fillet between the jet exit and the suction surface.
Identification of component characteristic parameter for whole turbofan engine
WANG Jun, SUI Yan-feng
2013, 28(3): 666-672.
Abstract PDF(541KB) icon1848 icon1062
Abstract:
In order to solve the difficulty to directly obtain all characteristic parameters of the components in the whole turbofan engine, it was determined ultimately that the number of corrected parameters by using the condition number of the correlations between parameters, on the basis of sensitivity calculation of the characteristic parameters of engine components to engine performance. Thus, the identification problem could be solved in engineering by the least square method. The simulation results show the efficiency of high compressor was 0.982 consistent with initial value of 0.98 , indicating that the method is theoretically feasible. From the identification results of concrete example, the efficiency value of components were in accord with the actual results with the compressor temperature test; in contrast, the efficiency value compared with the design state was higher than 12.7% , which did not match the actual engine operating conditions. Clearly, the identification problem was ill-posed, so parameters can be amend should not exceed 6.
Performance comparison and analysis of high temperature rise combustor engine and two-combustor engine
MAO Yan-hui, YANG Jin-hu, LIU Cun-xi, MU Yong, LIU Fu-qiang, XU Gang
2013, 28(3): 673-680.
Abstract PDF(1269KB) icon1723 icon1079
Abstract:
One-dimensional steady method was used to calculate the high temperature rise combustor engine and two-combustor engine's overall performance in consideration of the component efficiency. The overall performance was compared at total pressure ratio 32 and turbine inlet temperature 1900K for two-combustor engine and turbine inlet temperature 2400K for high temperature rise combustor engine. The way of temperature rise distribution between combustors of two-combustor engine was also analyzed. Results show that the specific thrust of high temperature rise combustor engine is 2.7 percent higher than that of two-combustor engine, while the specific thrust fuel consumption is 3.8 percent lower. The two-combustor engine is helpful to decrease the total pressure loss under supersonic condition, and its specific thrust increase ratio is higher than high temperature rise combustor engine when Mach number is more than 1.5.
Lattice-Boltzmann method for simulation of flow characteristic in constant area isolator of scramjet
FENG Yong-chang, LI Hui-xiong, HE Hong
2013, 28(3): 681-687.
Abstract PDF(1029KB) icon1645 icon1378
Abstract:
In order to seek a new method to study the complex flow field of isolator,the influence of flow parameters upon the internal flow field of isolator under different conditions was studied by numerical simulation with coupled double distribution function lattice-Boltzmann method(LBM),and the parameters included the back pressure,entrance Mach number,and boundary layer thickness.The results show that with the increase of the back pressure and boundary layer thickness or with the decrease of entrance Mach number,shock train would move upwards along the isolator.From this study,it can be concluded that the coupled double distribution function LBM is an efficient approach for simulating the complex flow field of scramjet.
Flow resistance characteristics of supercritical aviation kerosene in helix tube
FU Yan-chen, DENG Hong-wu, LV Pin, XU Guo-qiang, RAN Zhen-hua
2013, 28(3): 688-694.
Abstract PDF(979KB) icon1783 icon1089
Abstract:
Based on the experimental results,the effects of pressure,mass flow rate and style of helix tubes on the flow resistance characteristics were analyzed,and the flowing characteristics of aviation kerosene at supercritical pressure flowing through a helix tube were investigated .The results show that:the variation curve of local resistance coefficient was divided into 3 parts by critical Reynolds number and pseudo-critical temperature.Below the pseudo-critical temperature and Reynolds number,the local resistance coefficient was related to Regnolds number and D/din;below the pseudo-critical temperature and above the critical Reynolds number,it was just related to D/din;above the pseudo-critical temperature,it was not only related to Regnolds number and D/din,but also to huge variation of density and viscosity.Furthermore,a relational formula was proposed to predict the coefficient of local resistance with pressure,temperature and ratio of screw diameter versus inlet diameter when hydrocarbon fuel flowed through the helix tube at supercritical pressure.
Simulation of droplets impacting on solid surface at low velocity
XU Shuang, ZHAO Ning, WANG Chun-wu, WU Jie
2013, 28(3): 695-700.
Abstract PDF(512KB) icon1600 icon1044
Abstract:
In the background of icing problem caused by the droplets which impacted on the surface of aircraft,the level set interface tracking method was used, the surface tension in the incompressible N-S equations was denoted by the level set function and the second-order projection method for variable-density flows was used to solve 2-D incompressible Navier-Stokes equations;the water and gas multiphase problems at low velocity were simulated. In order to simulate the water and gas multiphase problems of the density ratio up to 1000, the numerical oscillations caused by the large density ratio between the interface can be eliminated by smoothing the density at the interface within a few grids. So the topological changes and movements of large droplets,which are different in surface tension when impacting on the solid interface,can be successfully simulated. The numerical results show that the method can be used to model the incompressible multi-phase flow with large density and viscosity density.Considering the surface tension, the movements of the surface at different surface tensions can be simulated.
Experiment on heat transfer characteristics with inclined impingement
SHAN Wen-juan, MAO Jun-kui, LI Yi, SHEN Yi
2013, 28(3): 701-708.
Abstract PDF(946KB) icon1576 icon948
Abstract:
Experiments were conducted to investigate the heat transfer characteristics of a typical cooling structure of blade tip clearance active control system with 45 degree inclined impingement.In experiments,jet Reynolds number Re(33297～83242) and the ratio of jet impingement distance to the diameter of the jet hole H/d(2～6) were changed.Heated foil and infrared thermal imaging technology were used to investigate the local Nu(Nusselt number) and Nu(average Nusselt number) by varying those parameters.It was found that there existed two peaks of heat transfer coefficient along the jet line,located at the main and secondary stagnation points respectively.The two peaks were more evident in larger Re and smaller H/d cases.The experimental results show that the flow characteristics are significantly strengthened with the increase of Re increasing,which results in much larger Nu and Nu.With H/d decrease,the local heat transfer at the main stagnation point increases faintly,meanwhile,the local heat transfer at the secondary stagnation point is enhanced greatly.
Turbofan engine transient modeling based on inter-component volume method
TANG Shi-jian, TONG Wan-jun
2013, 28(3): 709-713.
Abstract PDF(486KB) icon2193 icon1100
Abstract:
The effect of mass and energy storage in a volume was considered. A modeling approach for real time turbofan engine model was presented by employed inter-component volume (ICV) method. The pressure and temperature differential equations were established. The pressure and temperature were calculated through numerical integral without iterative. A turbofan engine transient model was coded by means of employing the solver equations and C++ programming language. By comparison, the calculation results have quite remarkable consistency with those results calculated by Gasturb 10 which is famous commercial software in aero-engine. The simulation results show that the maximum relative errors of high pressure compressor,turbine inlet temperature and the surge margin of compressor are within 1% and ICV method avoids iterative so the computer's running time is evidently reduced.
Motor power selection and economic analysis of more electric environmental control system
CHEN Wei-wei, SU Xiang-hui
2013, 28(3): 714-720.
Abstract PDF(816KB) icon1629 icon1262
Abstract:
A computation model of parameters matching for more electric aircraft environmental control system was proposed to determine the value of motor power under different flight conditions.The influential factors to the selection of motor power and the economy of system were analyzed.The results show that the motor power increases with the flight altitude,and decreases with the Mach number at the same altitude,in terms of a definite air supply pressure.For a given flight condition,a higher air supply pressure will lead to a higher motor power.The performance penalty of more electric environment control system will be smaller than that of traditional environment control system and a longer flight time will bring a better economic benefits,under the same air supply pressure and flight condition.

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