2010 Vol. 25, No. 7

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Numerical simulation on a film-cooled rotating model with 30° injection holes
YANG Bin
2010, 25(7): 1443-1453.
Abstract PDF(1954KB) icon1172 icon390
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The flow and heat transfer characteristics were numerically investigated on a film cooling model under different rotating operating conditions.The computational model was originated from the mid-span section of a typical turbine rotor with two rows of 14 staggered injection holes angled 30° both on the suction surface and pressure surface,and the flow through the coolant plenum and all the hole-pipes were resolved as a part of the computational domain by specifying the coolant mass flux in the plenum.The computations primarily focus on under-standing the rotational effect on film cooling performance in mechanism research approach.In the present study,the Reynolds number(Re) based on mainstream velocity and injection hole diameter varied from 1835.5 to 5507.4,and the averaged blowing ratio(M) ranges of 0.5 to 1.5.Results show that the coolant will move on to the high-radius locations near the suction and pressure surfaces due to the strong centrifugal effect,which leads to the decrease in adiabatic effectiveness accordingly.The discharge coefficients(Cd),on the pressure surface,are much higher than that on the suction surface under a given operating condition.In addition,the critical values of angular speed which represent the equilibrium of centrifugal force and Coriolis force near the pressure surface are also presented.
Measured overall effusion cooling effectiveness over a wide blowing ratio range using infrared imaging
ZHANG Chi
2010, 25(7): 1454-1463.
Abstract PDF(1597KB) icon1306 icon465
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Experimental investigations were performed on the overall cooling effectiveness η of a flat effusion wall over a wide range of blowing ratio(M=0.47～5.27).The effusion wall had a staggered multi-hole pattern typical of gas turbine combustor application,with a ratio of hole pitch to row spacing P/S=1∶2,a porosity PS/d2=72,and an inclination angle α=30°.The current paper documented distribution of the overall cooling effectiveness on the wall surface,based on infrared imaging of the 2-D surface tem...
Experimental research on film cooling characteristics of cylindrical hole and expanding hole on the leading edge
ZHU Hui-ren, ZHANG Xia, LIU Cun-liang
2010, 25(7): 1464-1470.
Abstract PDF(8883KB) icon2057 icon400
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Film cooling characteristics of expanding hole and cylindrical hole on the leading edge were measured using a transient liquid crystal measurement technique considering the influence of curvature.Local distribution characteristics and quantitative relationships of different holes' film cooling effectiveness were analyzed under different average blowing ratios.The results show that:(1) As compared with the cylindrical hole,the expanding hole jet has a larger coverage,the offset angle of the main coverage area is smaller.(2) In different test regions,the average cooling effectiveness of cylindrical hole rises firstly and then decreases with increasing average blowing ratio.In the region between the first and second row of holes,the average cooling effectiveness of expanding hole monotonously increases with average blowing ratio.In the downstream region after the second-row holes,the average cooling effectiveness of expanding hole is basically the same under all average blowing ratios.(3) Within the experimental range,the laterally averaged effectiveness of expanding hole is much larger than that of cylindrical hole.
Design and experimental study on whirl aero-valve for pulse detonation engine
ZHENG Dian-feng, YANG Yi-yong, WANG Jia-hua
2010, 25(7): 1471-1477.
Abstract PDF(791KB) icon2005 icon447
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In order to study the air-breathing pulse denotation engine(PDE),whirl aero-valves of different configurations were designed.The "closed" plane of aero-valve thrust wall was constituted by the curved blade.The drag coefficients of different aero-valves were obtained by experimental study and calculation using specific structural parameters,and the distinction of these drag coefficients was widely remarkable,showing consistency with theoretical calculations.The detonation combustion experiments show that the aero-valve with a larger drag coefficient can produce detonation waves,and the pulse detonation engine can achieve coordinated action if the aero-valve drag coefficient is bigger than 10,and blockage ratio more than 60 percent.The design principles and the theoretical calculation method about aero-valve were obtained.These results are very useful for optimal design of aero-valve.
Numerical prediction of lean blowout in aero-engine combustor
CAI Wen-xiang, ZHAO Jian-xing, HU Hao-sheng, DANG Xin-xian, WU Xiao-song
2010, 25(7): 1478-1484.
Abstract PDF(2680KB) icon1953 icon454
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In the arbitrary curvilinear coordinates,three-dimensional two-phase reaction flow fields in the rectangular combustor with double axial swirler and the reverse-flow annular combustor with swirl cup were numerically investigated.Renormalization group(RNG) k-ε,second order moment-eddy break up model(SOM-EBU) and six-flux model were used to consider the influences of turbulence viscosity,reaction rate and radiative heat transfer,respectively.Semi-implicit method for pressure linked equation(SIMPLE) algorithm was used to solve the flow field,and particle source in cell method was adopted to consider the coupling between gas-phase and liquid-phase.The fuel steady stepwise method was proposed to predict the lean blowouts of combustors.Predictions are in agreement with corresponding experimental data,showing that this method for predicting lean blowout is reliable and can be used for engineering applications.
Numerical research of ice accretion on two-dimensional airfoils
SUN Zhi-guo, ZHU Cheng-xiang, FU Bin, ZHU Chun-ling
2010, 25(7): 1485-1490.
Abstract PDF(939KB) icon1984 icon438
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The computational procedure for ice accretion is an iterative process.The overall calculation of ice simulation at each time-step involves five main parts: generating grid using Poisson equations,calculating flowfield by solving Navier-Stokes equation,calculating particle trajectory,thermodynamic analysis and ice accretion calculation,reconstruction of the ice boundary.The code is modular and contains six separate program elements including plot results.At last,the results calculated using the present software were compared to numerical and experimental data presented in American Institute of Aeronatutics and Astronautics(AIAA) papers,with ice shapes containing rime-ice,glaze-ice and mixed-ice.
Coupled heat transfer calculation on an airfoil electrothermal anti-icing surface
BU Xue-qin, LIN Gui-ping, YU Jia
2010, 25(7): 1491-1496.
Abstract PDF(2032KB) icon1684 icon479
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The phenomenon of heat and mass transfer on an anti-icing surface was analyzed,and the calculation of internal-external coupled heat transfer was studied in this paper.The evaporation mass flux was evaluated according to the heat and mass transfer analogy.The skin surface was discrete,and the finite difference equations of the energy and mass conservation were developed,enabling to couple the external heat loads,thermal conduction within the skin and the internal heat flux.The energy finite difference equations were solved by Gauss-Seidel iteration method.The coupled heat transfer calculation was an iteration process triggered with an initial surface temperature and maintained by under-relaxation factors.The surface equilibrium temperature,runback water and runback icing were obtained after convergence.The numerical results in this paper were compared with the icing tunnel experimental data and numerical results from reliable literatures,showing good agreement with them.
Reduction of detailed reaction mechanism using methods based on simulations of perfectly stirred reactor
WANG Hui-ru, JIN Jie
2010, 25(7): 1497-1505.
Abstract PDF(795KB) icon1817 icon478
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A method based on simulations of perfectly stirred reactor(PSR) and improved application mode of connectivity method and principal component analysis of the rate sensitivity matrix was adopted to reduce the detailed reaction mechanism of aviation fuel(surrogate fuel).The detailed mechanism containing 1020 irreversible reactions of 131 species was assembled using the combustion mechanism of surrogate fuel(80% decane and 20% 1,2,4-trimethylbenzene by weight) and the NOX formation mechanism.The aim was to accurately reproduce the temperature and concentrations of important species(CO,CO2,and NO) with less than 5% error at the condition of inlet temperature 800K,pressure 101325Pa,residence time 3ms,without heat loss and constant reactor volume in an adiabatic PSR.The results showed that the reduced mechanism met the desired target over a wide range of equivalence ratio(0.5～2.0).
Small scale mixing enhancement of fuel/air using multi-source vortex technology
ZHANG Yu-fang, HUANG Yong, WANG Fang, WU Yao-zeng, XIAO Ying
2010, 25(7): 1506-1511.
Abstract PDF(606KB) icon1614 icon443
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With the multi-source vortex(MSV) structure fixed on the exit plane of axial swirler,the flow field of combustor was simulated and the effect of MSV on the mixing enhancement of fuel/air was studied.The total temperature of the air inlet was 294.28K and the fuel was ethane(C2H6).The results indicate that,a small scale streamwise vortex is produced downstream each tab,helping enhance the local mixing of fuel and air.The mixing non-uniformity is 13.0% for combustor without MSV,while it declines to smaller than 7.4% with MSV.The mixing non-uniformity decreases when the total blockage of tabs increases,indicating a mixing enhancement of fuel/air.
Study of wall temperature on the interstage turbine single vortex combustor
ZHANG Rong-chun, FAN Wei-jun, XING Fei
2010, 25(7): 1512-1517.
Abstract PDF(1106KB) icon2052 icon447
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Because the distance between combustion zone and wall is very short,the overhigh wall temperature is a longstanding problem of trapped vortex combustor(TVC),which limits the actual application of TVC.The experimental study of wall temperature distribution on the TVC was reported in the paper,and the influences of fuel supply quantity and inlet parameters of main stream on the wall temperature distribution were investigated.Meanwhile,the rationality of cooling structure and air jet entrance structure was analyzed.The test results show that the hot spot temperature of combustor appears in the after-wall.The distribution of wall temperature is greatly influenced by the fuel supply quantity and the mach number of main stream,but little influenced by the temperature of main stream.
Numerical research on flow dynamics and infrared radiation characteristics for scaled chevron convergent nozzle
PAN Cheng-xiong, ZHANG Jing-zhou, SHAO Wan-ren, SHAN Yong
2010, 25(7): 1518-1523.
Abstract PDF(615KB) icon1910 icon423
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Computational fluid dynamics/intercooled recuperated(CFD/IR) was numerically simulated to investigate the effects of the chevron structure on flow dynamics and infrared radiation characteristics of scaled turbofan engine convergent nozzle.The results based on the present parameters show that:(1) The total pressure loss and thrust coefficient loss are bigger in the chevron convergent nozzle than in the baseline case,these losses are weak with little tab inclined angles.(2) The chevron convergent nozzle could pump more secondary flow,and hence the core of plume for chevron convergent nozzle attenuates faster than the baseline nozzle.(3) The plume 3～5μm infrared radiation for the chevron nozzle along lateral direction is about 15% less than the baseline nozzle,the tab inclined angle makes no difference in the plume infrared radiation suppression.(4) The infrared shelter from the inner hot components appears when the chevron tabs incline inside,the 3～5μm infrared radiation for the chevron nozzle is reduced relatively by 10%～20% in comparison with the baseline nozzle along trailing direction.
Effect of the holes array arrangement on the full coverage film cooling characteristics
YANG Cheng-feng, ZHANG Jing-zhou, YANG Wei-hua
2010, 25(7): 1524-1529.
Abstract PDF(940KB) icon1710 icon472
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The characteristic of flow field,adiabatic wall film cooling effectiveness and total film cooling effectiveness of full coverage film discrete holes wall were numerically investigated using the standard k-ε two-equation turbulent model,in order to understand the effects of blowing ratio and holes array arrangement.The results show that holes array arrangement with long hole to hole downstream distance and short hole to hole lateral distance is the optimal arrangement.Under this arrangement,the penetration of film outflow is weaker and film coverage region is larger,while the adiabatic wall film cooling effectiveness is better.The total film cooling effectiveness is consistent with the adiabatic wall film cooling effectiveness,showing that the holes array arrangement with long hole to hole downstream distance and short hole to hole lateral distance is the optimal arrangement.
Theoretical analysis of steady-state operating characteristics of a cryogenic loop heat pipe
BAI Li-zhan, LIN Gui-ping
2010, 25(7): 1530-1535.
Abstract PDF(674KB) icon1944 icon457
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Based on energy balance,pressure balance and mass conservation,a steady-state mathematical model of a cryogenic loop heat pipe(CLHP) with nitrogen as the working fluid was established in this paper,and the modeling results showed good agreement with the experimental data.Theoretical investigation of the steady-state operating characteristics of the CLHP was conducted based on the mathematical model,where the effects of the parasitic heat load and power applied to the secondary evaporator on the performance of the CLHP was studied.The conclusions below were drawn: the heat transport capability of the CLHP is obviously reduced as compared with ambient loop heat pipe;when the heat load applied to the primary evaporator is small,the steady-state operating temperature is high due to the existence of the parasitic heat load and adverse elevation.However,the performance of CLHP at small heat loads can be notably improved by applying heat load to the secondary evaporator.The maximum operating temperature/pressure drops as the volume of the gas reservoir increases,and the maximum heat transport capability of CLHP will be limited accordingly.
Investigation of cold flow field of a multi-injection combustor with different geometries
WU Yao-zeng, HUANG Yong, WANG Fang, ZHANG Yu-fang
2010, 25(7): 1536-1544.
Abstract PDF(1243KB) icon1975 icon459
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A numerical investigation was conducted to study some key parameters of multi-injection combustor,including swirl numbers,space between venturis,distance between the dome and the diffuser.The influence law of these parameters on the multi-injection combustor's recirculation zone was concluded.This shows that,with increase of the swirl number,the reverse velocity of the recirculation zone will rise.When the swirl number increases from 0.82 to 1.24,the maximal reverse velocity is 52% greater and the recirculation zone is 34% longer.When the space between venturis changes from 0 to 0.4 times the exit diameter of venture,the radii of recirculation zone is 33% bigger and the length is 43% larger.With the increasing area of inlet of the diffuser and the growing distance between the dome and the diffuser,the distribution of the flow is more uniform.
Numerical simulation on flow and heat transfer of elliptical pin-fins in cooling channel
DENG Ding-yuan, GAO Hang-shan, YU Kua-hai, YUE Zhu-feng
2010, 25(7): 1545-1552.
Abstract PDF(1331KB) icon1660 icon460
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Numerical simulation was conducted to investigate the flow and heat transfer performance of elliptical pin-fin arrays in turbine blade cooling channel.Then,the impacts of array spacing,angle of attack,ratio of long axis and short axis on flow and heat transfer in pin-fins channel were obtained.The result indicates that,when the angle of attack is 0°,the pressure loss coefficient and average Nusselt number of elliptical pin-fins channel is about 51.7% and 83.75%,respectively,of the same fin section-area and arrays circular pin-fins channel;when the ratio of long axis and short axis is 5/1.8,the pressure loss coefficient is only 28.1%～35.5% of circular pin-fins channel(ratio of long axis and short axis is 3/3),and average Nusselt number is 71.1%～75.06% of circular pin-fins channel.
Investigation of a variable geometry scramjet inlet with a rotating cowl operating in a large Mach number range
JIN Zhi-guang, ZHANG Kun-yuan
2010, 25(7): 1553-1560.
Abstract PDF(1103KB) icon1741 icon438
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A simple variable geometry scramjet inlet with a rotating cowl operating in a large Mach number range from 4 to 7 was designed.During the inlet design,one-dimensional flow theory was used to distribute the internal and external compressions.The inlet self-starting characteristics at Ma=4 and the global performance at different incoming Mach numbers were studied by means of numerical simulations.Results indicate:(1) Inlet's self-start can be realized successfully at Ma=4 under the help of the boundary layer diverter placed at the entrance of the cowl section.(2) Variable geometry inlet achieves a mass capture ratio of 70 percent at the starting Mach number,which is very favorable to the acceleration of the hypersonic vehicles.(3) Global performance parameters of the variable geometry inlet are greatly increased in the whole operating range compared with the fixed geometry inlet.(4) Position of the cowl rotation axis has a great effect on the inlet self-starting characteristic.
Research on wing structure deformation for aerodynamic force and inertial force of flapping-wing
ZHANG Ya-feng, SONG Wen-ping, SONG Bi-feng, ZHANG Wei
2010, 25(7): 1561-1566.
Abstract PDF(2279KB) icon1789 icon494
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This paper explored the effects of aerodynamic force and inertial force on the structure deformation of wing by finite element model.The study indicates that the aerodynamic force and inertial force are at the same level.The inertial force of wing has crucial influence on the structure deformation of wing.The maximum deformation was produced by aerodynamic force or resultant force when wing was located horizontally.The study of the structure deformation provides a technical guide for design and optimization of flapping-wing.
Cavity flow oscillations and aeroacoustic characteristics at supersonic speeds
YANG Dang-guo, FAN Zhao-lin, LI Jian-qiang, JIANG Wei-min, TIAN Jun
2010, 25(7): 1567-1572.
Abstract PDF(722KB) icon1758 icon476
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Cavity flow oscillations and aeroacoustic characteristics at supersonic speeds were investigated based on flow-fields of three types of cavity flow.The data presented herein was obtained over Mach number of 1.5 at a Reynolds number of 2.26×107 per meter with a boundary-layer thickness of approximately 0.024m.The length-to-depth ratios of the cavities were 15,12 and 6,respectively.The results indicate that the intense noise resulted from impingement of shear-layer and the cavity rear-face occurs in the cavities.Sound pressure level(SPL) in the region upstream of the cavity rear-face is more than that in the region downstream of the cavity front-face and in the middle of the cavity.The compressible or shock waves induced by impingement of shear-layer and the cavity floor disturb the sound feedback mechanism from the cavity rear-face to the front-face at supersonic speeds,causing self-sustained flow oscillations and peak frequencies of the cavity tone inside cavities for transitional and closed cavities with large length-depth ratios.However,the shear-layer bridges the open cavity,which has no influence on the mechanism.The self-sustained flow oscillations and some peak frequencies occur inside the open cavity.
Effect of spillage slot on the performance of two-dimensional hypersonic inlet
ZHAO Liang, YUAN Hua-cheng, LI Bo
2010, 25(7): 1573-1580.
Abstract PDF(1420KB) icon1905 icon473
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The inlet model of HyShot program was simulated.The flow fields of the HyShot inlet under the design and non-undersign conditions,as well as the inlet's performance with the variation of Mach numbers were obtained.The design for slotting at two-dimensional hypersonic inlet was brought forward hereby and a two-dimensional hypersonic inlet working at Mach number 4.0～6.0 was designed.Furthermore,two new inlet models were designed by raising or lowering the height of the original slot.By comparing the simulation results of these three inlet models and the inlet without slot under different Mach numbers,it shows that the spillage slot improves the performance of inlet effectively and expands the inlet's operating region.It can also be found that different slot heights would fairly affect the performance of inlet.
Effects of degree of sidewall shade on performance of two-dimentional supersonic inlet with non-sideslip
ZHANG Long-dong, ZHANG Kun-yuan, NAN Xiang-jun
2010, 25(7): 1581-1587.
Abstract PDF(1178KB) icon1640 icon436
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This paper investigated the effects of the degree of sidewall shade on the performance of a two-dimentional mixed-compression rectangular cross-section inlet designed for Mad =2.4 working in Ma∞=2.51 and 2.27 of non-sideslip flight condition.The relationships between inlet performance parameters at throat and sidewall shade were obtained,and the reasons of these changes were analyzed.The results indicate that,the performance parameters will change obviously when the bottom of the sidewall is located after the flat compression surface.For the two-dimentional mixed-compression inlet of this paper,when the back positioned sidewall is adopted,the starting performance will be improved while significantly increasing the drag and reducing the flow coefficient.
Quantitative research on performance degradation of single-stage compressor
LI Ben-wei, LI Dong, LI Jiang-hua, WANG Yong-hua, YANG Xin-yi
2010, 25(7): 1588-1594.
Abstract PDF(1374KB) icon1618 icon469
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The change of the blade shape will result in the performance degradation of compressor.Traditionally,the calculation of the compressor performance degradation is accomplished by assuming that the blade surface varies evenly,or the loss coefficient is introduced into the model,which often produces error.The paper simulated the change of the blade shape caused by fouling using the method of adding random size in the fouling position.Meanwhile,the effect of the ingredients of the blade foul and tip clearance increase on the compressor performance was analyzed.The quantitative performance degradation at different work conditions,and the change of the air float field and the total temperature around the blade surface were gained.The results offer theoretical and applicative value for the research of the engine performance degradation and fault analysis.
Unsteady numerical investigation of the influence of axial gap on the turbine loss
ZHOU Li, ZHANG Xin, CAI Yuan-hu
2010, 25(7): 1595-1601.
Abstract PDF(1215KB) icon1619 icon414
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The unsteady flowfield of the turbine stage was investigated numerically under different axial gaps,and the influences of the axial gap on the aerodynamic loss and the flow unsteadiness were discussed.Results show that the flow unsteadiness in the turbine stage becomes stronger with the reduction of the axial gap,and the corresponding flow becomes non-uniform.The total pressure loss coefficient of the turbine with the larger axial gap is bigger than that with the design axial gap.The reason is that the mixing distance between the wake and the main flow becomes much larger.Due to the much stronger flow unsteadiness under the smaller axial gap,the corresponding aerodynamic loss of the turbine stage is larger.There exists an optimum axial gap to minimize the aerodynamic loss.
Investigation on root blade profile of a large meridional expansion turbine
TANG Hong-fei, HUANG Hong-yan, WANG Zhen-feng, HAN Wan-jin
2010, 25(7): 1602-1608.
Abstract PDF(1672KB) icon1668 icon502
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The investigation focused on the design characteristic of root blade profile in the large meridional expansion turbines.And,the effect of root blade profile optimized design on the flow separation at vane inlet and radial pressure distribution at vane outlet was also studied.With the commercial numerical simulation solver,NUMECA,optimized design of root blade profile was applied into a large meridional expansion turbine.Then full three-dimensional numerical simulations on the original and optimized profiles were carried out.The numerical results show that,wider profile and convergent-divergent root profile would adjust radial distribution of massflow at inlet,weaken or even eliminate incoming flow separation at the upper endwall,hence controlling the flow loss in shroud;meanwhile,such profiles could improve mach number distribution and radial distribution of pressure at outlet,weaken or even eliminate radial flow of S1 section separation in the suction side at exit,thereby reducing flow loss in hub.
Numerical investigation about the effect of a partial circumference casing treatment on a compressor
LIU Jian-yong, YUAN Wei, LU Ya-jun
2010, 25(7): 1609-1614.
Abstract PDF(868KB) icon1459 icon424
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In order to analyze the effect of nonsymmetrical slots on a compressor,unsteady numerical investigation on a partial circumference casing treatment and a whole circumference casing treatment with a single stage transonic axial compressor was carried out.The numerical results show that the partial one could obtain better compressor performance than the whole one,both of which contain the same number of slots.Due to the symmetry of slots,the partial casing treatment brought about large-size symmetry in the circumferential tip region,which could cause a special low-frequency unsteady effect.Moreover,it was found that the partial circumference casing treatment,which supplied both high-frequency and low-frequency unsteady effects,could improve both the tip leakage vortex and trail-edge separated vortex.
Influence of shock/tip leakage vortex interaction on flow stability in a single-stage transonic axial compressor
ZHANG Zhuo-xun, WU Yan-hui, CHU Wu-li, ZHANG Hao-guang
2010, 25(7): 1615-1621.
Abstract PDF(1083KB) icon2031 icon505
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Three-dimensional numerical simulations were conducted to analyze the flow field in a single-stage transonic compressor Stage 35.Firstly,three kinds of gridding were modeled to investigate their prediction accuracy on overall performance and blade-element curves.The criterion for choosing the optimum gridding is that the prediction matches best the experimental data.Then,the internal flow filed of the optimum gridding was analyzed to find out the most probable influential factor of the flow stability;and it is found that low-energy fluid near pressure surface at rotor tip most likely induces the flow instability.As the mass fow rate reduces,the intensity and swirl ratio of the tip leakage vortex(TLV) increase with the blade loading.The breakdown of the TLV occurs due to the interaction of shock/TLV at the near-stall condition,thus most possibly leading to low-energy fluid accumulated near the pressure side of rotor tip passage.
Research on environmental factor based on degradation data
FENG Jing, ZHOU Jing-lun
2010, 25(7): 1622-1627.
Abstract PDF(498KB) icon1604 icon462
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In consideration of the characteristics of degradation failure for highly reliable,long-life-products,it's difficult to gather enough failure data in limited test period.Research on environment factor based on life failure data is not applicable.The definition and mathematical models of environment factor were proposed based on performance degradation data.The environment factor model for compound Poisson process degradation path was given.For the environment factor,a point estimation method based on quadrature and an interval estimation method based on binomial distribution were proposed,respectively.A numerical example was given to illustrate the efficiency and validity of the methods.
Investigation of rolling bearing fault diagnosis based on scale-based concurrent matrix
QIN Hai-qin, XU Ke-jun, SUI Yu-song, JIA Ming-ming
2010, 25(7): 1628-1633.
Abstract PDF(2354KB) icon1521 icon504
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Based on the fact that rolling bearing vibration signal's three-dimensional(3-D) graphics and two-dimensional(2-D) graphics contain different fault information,the texture feature vectors were extracted from different scale-based concurrent matrixes which were received from 2-D wavelet translation.The gray degree association was employed to express these texture feature space geometry similarity.The method was used to analyze different bearing defects' real test vibration data.The result shows that this means can get high pattern classification accuracy,but it will decrease with growing malfunction size because of influences of rolling bearing elements.It's also found that the normalization of texture feature vector is not reasonable to some diagnosis ways.
Robust performance analysis of mistuned bladed disks
YAO Jian-yao, WANG Jian-jun, LI Qi-han
2010, 25(7): 1634-1639.
Abstract PDF(1329KB) icon2021 icon459
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The transfer matrix model of the mistuned bladed disk was constituted in the state space.The effects of mistuning parameters on robust performance of mistuned bladed were evaluated using the structured singular value(SSV) of the mistuned transfer matrix.The robust performance of a simplified bladed disk model with two-degree-of-freedom per sector was analyzed.The influences of excitation order,damping,mistuning strength and intentional mistuning on the robust performance of the system were also considered.The numerical results indicate that,the robust performance of the mistuned bladed disk could be effectively enhanced by increasing the system damping,keeping the mistuning strength beyond the threshold value,and by introducing some appropriate intentional mistuning to the system.
Optimal calibration interval of test system based on reliability index
HAN Xu, ZU Xian-feng, CAI Ying-bo
2010, 25(7): 1640-1645.
Abstract PDF(443KB) icon1573 icon469
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Based on analysis and improvement of simple response method(SRM) and Weibull reliability method for calibration intervals of test system,and by taking into account fault decisions on the calibration process,the decision risks on verification of test system were resolved.In this paper,related national measurement standards on reliability index of test system were firstly introduced,then some usual calibration interval determination methods were also discussed,and furthermore the reliability probability functions for observational value of test reliability were given.By synthesizing different parameters with principal component analysis(PCA) method,the estimation values of the optimal calibration interval were corrected.Lastly,the results of verification on digital multimeter(DMM) measurement channel in automatic test system(ATS) show that the calibration intervals optimization methods are feasible.
Test system design for small H2/O2 rocket engine
LIU Wan-long, DIAO Peng, WANG Chong, LIANG Guo-zhu, ZHANG Xue-jun
2010, 25(7): 1646-1652.
Abstract PDF(802KB) icon1872 icon465
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The H2/O2 rocket engine test system has been designed based on general test requirements of small 1000N H2/O2 rocket engine.The design of gas feed system was introduced.The choice of the mass velocity and pipe diameter was discussed particularly.The comparison type thrust-measuring device and the computer measurement & control system have been designed.The scaling and confirmatory tests have been carried out.The test system can be used for cold flow tests and firing tests of small H2/O2 rocket engine under different work conditions,and can also be supervised and controlled remotely by computer with high accuracy.
Analysis on acoustic longitudinal oscillation frequency in combustion chamber with sudden change sections
ZHANG Qiao, LI Jun-wei, WANG Ning-fei
2010, 25(7): 1653-1658.
Abstract PDF(732KB) icon1819 icon434
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Combustion chamber with case bonded propellant,often used in solid rocket motors,can be simplified into an "H" type sudden change section configuration with tube grain in the middle and cavities connected at both head end and aft end.In the paper,a physical model of "H" acoustic cavities was established;then the longitudinal frequency was calculated by theoretic and finite element model(FEM) methods.Symmetrical and unsymmetrical "H" acoustic cavities were used separately to investigate the influences of geometrical parameters on the oscillation frequency.The results indicate that the ratio of the length of grain to combustion chamber,the ratio of inner-outer grain radius and grain position have cooperative effects on the frequency.Considering the reasonable volumetric loading fraction of the grain,it is concluded that oscillation frequency,which is smaller than that in cylindrical cavity at beginning,increases continuously with burning surface regression.
Study on virtual test technology of liquid propellant engine
DUAN Na, ZHANG Li-hui, XU Shan-shan, ZHU Zi-huan, YU Hai-lei
2010, 25(7): 1659-1663.
Abstract PDF(851KB) icon1658 icon446
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The framework of the virtual test bed was designed.Objective/relationship mapping storage structure database system was developed,and the implementation flow of test management was analyzed.The development process of modeling and simulation module and virtual environment module was mainly explained.Then,the unique collaborative computing environment was developed via various interfaces,and the examples were given.At last,the advantages of applying virtual test in liquid rocket engine were concluded.
Mesh stiffness function and stability analysis for parametric vibration of spiral bevel gears
WANG Yan-zhong, ZHOU Yuan-zi, LI Guo-quan, GUO Mei
2010, 25(7): 1664-1669.
Abstract PDF(463KB) icon2062 icon454
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Theoretical study of the time-varying mesh stiffness is critical to geared system dynamics.For spiral bevel gears at high speed and heavy load in aero-engines,a numerical solution was applied to investigate the compliance and stiffness for each instantaneous contact,based on the static deflections and directional forces obtained by TCA(tooth contact analysis) and LTCA(loaded tooth contact analysis).Analytical form for state transition matrix of parametrical excited system including periodically varying stiffness was derived from the assumption that the time-varying mesh stiffness is piece-wise linearity.By adjusting the pinion machine tool settings,different contact patterns,transmission error,contact ratio and mesh stiffness under the same load condition for a pair of spiral bevel gears were treated.The Floquet theorem was applied,therefore,a program to calculate the magnitudes of the characteristic multipliers was used to investigate the instability among the working rotation speed interval,based on a two-degree-of-freedom dynamic system.The influence of time-varying mesh stiffness on parametric vibration stability of the spiral bevel geared system was investigated.
Algorithm for determination of the initial point in error tooth contact analysis
TANG Jin-yuan, LEI Guo-wei
2010, 25(7): 1670-1675.
Abstract PDF(5823KB) icon1895 icon468
Abstract:
The initial selection and determination in error tooth contact analysis(ETCA) of spiral bevel gear were investigated.Based on the geometric equivalent relationship,the point P' which is closer to the initial mesh-point P was calculated.The process of calculating P' wasn't involved with the rotating operation of two tooth surface equations in the installation coordinate system;as compared to the equation of directly solving point P,the new algorithm was simple,then iterative method was used to calculate the initial mesh-point P.The calculation examples show that the new algorithm can reduce the sensitivity of the initial value,and improve the stability and efficiency of ETCA,thus making the algorithm of ETCA more suitable and the selection of initial value more simpler.
Aero-engine high stability control scheme design based on angle of attack predictive model
CHEN Ting-hao, ZHANG Hai-bo, SUN Jian-guo
2010, 25(7): 1676-1682.
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Abstract:
A study of engine stability control for super-maneuvering flight was carried out.High level of engine-face distortion often occurs during super-maneuvering flight of the combat aircraft.In this case,engine stall will be caused if conventional controller is still used.For this issue,an advanced predictive control system,in which an angle of attack(AOA) predictive model was used,for aero-engine was designed.Firstly,an angle of attack predictive model was established to estimate the engine-face distortion in real time.Then,a high stability predictive controller was designed using augmented linear quadratic regulator(ALQR) method based on the former estimator.Finally,digital simulation was carried out on the engine/three-degree-of-freedom aircraft nonlinear integrated model.The results show that the stability control concept proposed in this paper is effective and feasible.

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