2007 Vol. 22, No. 6

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Operating characteristics of a high radius pre-swirl cooling system
P. New, P. R. N. Childs
2007, 22(6): 849-858.
Abstract PDF(462KB) icon1403 icon394
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An experimental investigation into pre-swirl effectiveness and receiver hole discharge coefficient characteristics for a high radius injection pre-swirl cooling systems was carried out on a physically representative experimental rig with a 450 mm diameter rotor.The receiver holes and pre-swirl nozzle were located at a radius of 181 mm and 180 mm respectively.The experimental work was mainly conducted at 5 000～12 000 r/min,4 bar absolute pressure and 1.132 kg/s air supply.The maximum air supply temperature was 190 ℃.Pressure and temperature distributions in the pre-swirl system were examined with an emphasis on the velocity effectiveness of the pre-swirl system as a whole and on the discharge coefficients of the rotating 'receiver holes' in the rotor.The results showed that the velocity effectiveness increased with increasing swirl ratio resulting in reduced blade cooling flow temperature.Different seal flow configurations caused very different effectiveness at different speeds,but outflow through the inner and outer seals always gave the highest effectiveness compared other configurations.Increasing the seal flow rate reduced the effectiveness.For the coefficient of discharge,except for the low speed range,it increased with increase in swirl ratio for most speeds.
Numerical study of streamwise vortex formation in micro-lobed burners
LIU You-hong
2007, 22(6): 859-863.
Abstract PDF(1007KB) icon1627 icon403
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Numerical study was conducted for streamwise vortex formation of micro-lobed burner and micro-lobed mixer in the dimension of millimeter to investigate the possibility of burning intensification made by streamwise vortices.It was found that though the beginning,developing and disappearing of streamwise vortex are evident in the 4-lobed burner and the 8-lobed burner,the intensity and affecting range of the streamwise vortex are much less than that in the corresponding micro-lobed mixers.The streamwise vortices are not visible in the 12-lobed burner;by contraries the beginning,developing and disappearing of streamwise vortex can be seen evidently in the same 12-lobed mixer.The reason for streamwise vortex development difference in both micro-lobed burners and micro-lobed mixers is that the burning makes the gas products expand rapidly and the initial streamwise circulation decay quickly.
Study on influence of configuration parameter of open-end swirl injector on its dynamics
YANG Li-jun, FU Qing-fei, ZHANG Xiang-yang, WANG Yong-tao
2007, 22(6): 864-868.
Abstract PDF(341KB) icon1852 icon494
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In order to study the influence of configuration and operating parameters of open-end swirl injector on its dynamics,a group of swirl injector models were designed based on the physical dimension of RD120 pre-burner kerosene injector.The calculation result shows that,the amplitude of flow rate of open-end swirl injector declines with the increase of fluctuation frequency,and the delay phase increases with fluctuation frequency.The bigger pressure-drop means wider amplitude of flow and lower delay phase.The open-end swirl injector with larger geometrical characteristic A and length/diameter ratio can dampen more flow rate fluctuations.Since the delay phase increase linearly with the length of vortex chamber,the axial spacing of tangential inlet could be adjusted to filter the fluctuation of a certain frequency.
Experimental investigation on pulse detonation engine nozzles
FAN Wei, YAN Chuan-jun, LI Qiang, HU Cheng-qi, YE Bin
2007, 22(6): 869-872.
Abstract PDF(300KB) icon2002 icon536
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10 nozzles from 3 typical types are chosen under experimental tests.The results show that all nozzles can augment the thrust of baseline pulse detonation engine(PDE)and there is an optimal nozzle area ratio where thrust augmentation is maximized.Amongst all tested nozzles,the maximal augmentation of 24% is attained by a convergent-divergent nozzle.Moreover,it is validated that fill-fraction has little effect on thrust augmentation.
Experimental study of flow distribution characteristics for a rotor-stator system
LUO Xiang, XU Guo-qiang, CAI Yi, TAO Zhi, DING Shui-ting
2007, 22(6): 873-876.
Abstract PDF(291KB) icon1438 icon473
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The flow characteristics of rotor-stator cavity system with blade-cooling flow and disk-cooling flow was experimentally studied.And,the cooling flow rate of the clearance between stator and rotor as well as the hole of rotor flange was obtained.The experimental results show that:the blade-cooling flow rate will increase with the total flow rate and rotating speed;the ratio of the blade-cooling flow rate to the total flow rate will increase with decline of the total flow rate,and increases with the rotating speed.The blade air flow is almost half of original flow when the numbers of holes become half of original holes.
Entropy generation analysis of portable vapor compression refrigeration system
ZHONG Xiao-hui, ZHANG Xing-zhou, WU Yu-ting, DU Chun-xun, MA Chong-fang
2007, 22(6): 877-880.
Abstract PDF(1059KB) icon1397 icon521
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This paper introduceds a portable refrigeration system based on development of micro electro-mechanical systems(MEMS) technologies,and describes how the entropy generation changes at each component in a vapor compression refrigeration system as the system scale is decreased.Although the quantitative evaluation of the entropy generation is not made here,it is clear that the micro compressor is the most difficult component to be miniaturized in a portable refrigeration system.If a portable vapor compression refrigeration system is expected to be successfully operated,a great deal of efforts must be made to develop a workable micro compressor and to minimize the refrigerating output loss of the evaporator.
Investigation on a centrically slit flame holder for afterburner
ZHANG Xiao-chun, LI Jiang-ning, XU Xing-ping, LIU Tao, QIAN Ren-zhang, DU Yi-qing
2007, 22(6): 881-887.
Abstract PDF(1036KB) icon1636 icon578
Abstract:
A new centrically slit flame holder(CSFH) for afterburner is presented,and the experimental research work shows that it has simpler structure,lighter weight, higher combustion efficiency,and better stability.The PIV technology was applied to study flow fields of the flame holder wake,which reveals that the good combustion characteristics depend on the recirculation zone structure of slit flame holder and the particular vortex shedding patterns.
Vortexes evolvement and development in the model of trapped vortex combustor
FAN Wei-jun, KONG Zhao-jian, XING Fei, GAN Zhi-wen, YANG Mao-lin
2007, 22(6): 888-892.
Abstract PDF(1109KB) icon1998 icon440
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The large-eddy simulation(LES) has been used to described the computational simulation of the dual vortexes.The results indicate that in the case of primary airflow, fore-cavity and back-cavity flow injection,the vortexes could create in the cavity for some geometry conditions.The progress of trapped vortex development in the cavity is also investigated,the new result that influences the evolvement of vortexes in the cavity is obtained.
Critical heat flux of nano-fluids boiling in vertical small tubes with closed bottom
Lü Lun-chun, LIU Zhen-hua
2007, 22(6): 893-897.
Abstract PDF(784KB) icon1808 icon577
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An experimental investigation has been performed to study the nucleate boiling characteristics and the critical heat flux(CHF) of water and water based CuO nanoparticle suspensions(nanofluids) in vertical small tubes with closed bottom.The experimental results indicated that the CHF and the particle concentration of the nanofluid in the tubes had hdlany change with the heating times in the boiling process.The boiling heat transfer of the nanofluids is somewhat poor compared with that of the base fluids,since the decrease of the active nucleate cavities results in the decrease of the solid-liquid contact angle on the heated surface with a very thin nanoparticle sorption layer.The boiling critical heat fluxes for the nanofluids increase significantly than that of the base fluids.An empirical correlation is proposed for predicting the CHF of nanofluids boiling in the vertical tubes with closed bottom.
A GPA diagnostic system foraeroengine applications
Yi-Guang Li
2007, 22(6): 898-908.
Abstract PDF(971KB) icon1741 icon459
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In this research,a GPA(Gas Path Analysis) diagnostic system enhanced with GPA Index is described for gas path sensor and component fault diagnosis.A method of measurement correction is used in order that the measurement data obtained at un-standard ambient and operating conditions can be used for diagnostic analysis.The developed diagnostic system has been implemented into a Cranfield University gas turbine performance and diagnostic analysis software PYTHIA for gas turbine performance degradation analysis.The developed method and software have been applied to a model aero gas turbine engine to test the effectiveness of the system.The analysis shows that the developed diagnostic system can diagnose degraded sensor and components effectively using performance deviation measured at un-standard ambient and operational conditions.Theoretically,the idea of the diagnostic approach can be applied to different gas turbine engines.
Stability analysis and improvement of ZP/LTR method of aeroengine
YANG Gang, YAO Hua
2007, 22(6): 909-914.
Abstract PDF(1511KB) icon1616 icon455
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Zero placement/loop transfer recovery(ZP/LTR) method was analyzed theoretically to find and demonstrate the conditions of stability.However,these strict conditions have placed constraint on the application of ZP/LTR method.Kalman filter was thus introduced for the purpose of improvement of ZP/LTR method.With some special parameters selected,Kalman filter loop could approximate and replace original target feedback loop(TFL).While the performance of ZP/LTR method is maintained,the stability of final closed-loop system could be guaranteed along with the stability of Kalman filter loop.The stability conditions of improved ZP/LTR method was presented and demonstrated,showing that the stability conditions of improved ZP/LTR method were less strict,thus expanding the scope of applications for original ZP/LTR method.
Robust adaptive fuzzy trajectory linearization control of an aerospace vehicle
ZHANG Chun-yu, JIANG Chang-sheng
2007, 22(6): 915-922.
Abstract PDF(473KB) icon1863 icon507
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This paper presents a robust adaptive fuzzy trajectory linearization control(RAFTLC) method and its application to an aero-space vehicle(ASV) flight control system.Based on the system's prior knowledge,the nominal fuzzy system is designed to estimate the unknown disturbances and uncertainties.A robust adaptive item is used to overcome the approximate error and weights error of the nominal fuzzy system.The bounds of the approximate error and weights error are adjusted on line.Uniform ultimate boundedness of all the signals of the composite closed-loop system is proved using Lyapunov theory.Finally,the flight control system of an ASV is designed based on the proposed method.Simulation results demonstrate the effectiveness and robustness of the control scheme.
A new method to control fuel flow of aircraft engine's starting process based on PSO Algorithm
ZHANG Dong-fang, LI Ying-hong, CHEN Dong-lin
2007, 22(6): 923-927.
Abstract PDF(1016KB) icon1906 icon488
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In order to solve the real time application demand of the fuel flow control in aircraft engine's starting process,a new nonlinear predictive control method based on particle swarm optimization(PSO) algorithm is presented.The method established a predictive model with last suares support vector machines(LS-SVM),and then carried out the receding horizon optimization with PSO algorithm.The example validated that the new control method can reduce the rotors' rotating speed fluctuation and the steady state can be attained 5～6 seconds earlier than that without optimization.The result of the emulation shows that the method is suitable for the fuel flow control,and it can achieve the best control pattern of fuel flow when the restriction is provided accurately.
Control strategy for piston ECU engine of small-size unmanned helicopter in overrunning stage
WANG Xiao-qing, HUANG Yi-min, YANG Yi-dong
2007, 22(6): 928-932.
Abstract PDF(598KB) icon1995 icon492
Abstract:
Dogleg control strategy was proposed for piston electronic control unit(ECU) engine of a small-size unmanned helicopter in overrunning stage,and then compared with traditional method of increasing rotational speed in fixed slope.Through analysis of engine ground test data,it's learnt that dogleg method can resolve efficiently the rich oil and overrunning problem,and achieve rotational speed control with strong robustness.
The role of AVDR in linear cascade testing
Bo Song, Wing F. Ng
2007, 22(6): 933-944.
Abstract PDF(1067KB) icon7788 icon2273
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Linear cascade testing plays an important role in the research and development of turbomachinery and is widely used over the world.The ideal cascade model of a turbomachinery blade row is two-dimensional.In actual linear cascade testing,the flow through the test section converges due to the development of the boundary layer and secondary flow along the sidewall surfaces of the test section.Axial velocity density ratio(AVDR) is adopted to account for the deviation of the tested cascade flow from the ideal 2D model.Among numerous published cascade works,the influence of AVDR on cascade performance is seen to be complicated with many affecting factors,such as those related to cascade/blade geometry and flow conditions.Also,controlling AVDR is limited by the facility capability.Furthermore,real blade-to-blade flow in turbomachines is usually associated with AVDR greater than unity due to limited span of blades between the hub and shroud such that cascade testing without reducing AVDR could be favored sometimes.All these facets add complexity and diversification to the matter.The current paper reviews previous studies and results on AVDR.Consolidated understanding on the role of AVDR and recommendations on how to deal with it in linear cascade testing are provided.
Development and prospect of aspirated fan/compressor
LIU Bo, NAN Xiang-yi, WANG Yan-gang, JIANG Jian, JIN Jun
2007, 22(6): 945-954.
Abstract PDF(1177KB) icon1799 icon635
Abstract:
Aspirated fan/compressor(ASFC) is an integral part of high pressure ratio compression system.So,the background,necessity,technical features and research trend of ASFC were reviewed and analyzed.With ASFC technology,it shall be possible to increase efficiently fan/compressor pressure ratio,but also reduce the axial length and weight of the engine as well as the noise of fans.Meanwhile,it increases the flexibility and payload of the flight vehicle,thus reducing the fuel consumption.However,this new structure also leads to some problems in strength and aeroelasticity,so some analytical results and suggestions are presented.
A two-dimension numerical method for multi-stage axial compressor performance in engineering applications
CHENG Rong-hui, LEI Pi-ni, LIU Bo, ZHOU Bai-hao, ZHOU Sheng
2007, 22(6): 955-960.
Abstract PDF(1460KB) icon1912 icon460
Abstract:
The multi-stage axial compressor performance was measured using a streamline curvature method based on two-dimension(axisymmetric) mathematical model.The influence of various factors on the deviation angle and loss was represented by components.After being verified through a number of experiment data,this method offers an extremely high accuracy.By comparing the calculated results and test data for a multi-stage axial compressor,this method demonstrates that it could assist in predicting the characteristics of multi-stage axial compressor and spanwise parameter distribution under off-design working conditions.
Mechanism of stall margin improvement associated with the blowing circumferential grooved casing treatment
ZHANG Hao-guang, CHU Wu-li, WU Yan-hui, DENG Wen-jian, ZHANG Xia
2007, 22(6): 961-966.
Abstract PDF(816KB) icon1521 icon453
Abstract:
Tangent blowing in the circumferential grooves has the effect of achieving broader stall margin in the previous experiments.Three-dimentional numerical simulation has been performed for a subsonic axial-flow compressor rotor both with the blowing circumferential grooved casing treatment and archetypal casing treatment.The calculated overall performance lines showed good agreement with the experiments.The mechanism was that the blowing circumferential grooved casing treatment can achieve broader safety margin and improve the efficiency compared with archetypal casing treatment.This conclusion was obtained by detailed analyzing the flow-field at the blade tip of two kinds of casing treatment.
A study on the full flowpath and the aerodynamic characteristic of an axisymmetric hypersonic vehicle
SUN Shu, ZhANG Hong-ying, WANG Cheng-peng, L Ying-wei, CHENG Ke-ming, WU Yizhao
2007, 22(6): 967-973.
Abstract PDF(614KB) icon1806 icon424
Abstract:
Using the combined experiments and computational fluid dynamics(CFD),a study was carried out to investigate the aerodynamic characteristics and the full flowpath of an axisymmetric hypersonic vehicle.Results indicate:(1) Over the tested range the Reynold number brings no obvious influence on the flow pattern and the aerodynamics characteristic of the hypersonic vehicle.(2) Despite the fact that the drag coefficient is not sensitive to the change of the angle of attack,the lift coefficient and the flow structure of the full flowpath is highly affected.(3) With the increase of the free stream Mach number,the drag coefficient fluctuates slightly though changes can be found in the full flowpath.(4) Over the tested flight conditions the friction drag of the axisymmetric hypersonic vehicle occupies a significant proportion of the total aerodynamic drag and at the design condition the proportion reaches 62%.(5) The experimental results prove the reliabilities of the CFD.
Multidisciplinary design optimization for aerodynamics/structural dynamics of tilt rotor blade
PENG Ming-hua, CAI Jie, ZHANG Cheng-lin
2007, 22(6): 974-979.
Abstract PDF(540KB) icon1978 icon515
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With multidisciplinary design optimization method,an aerodynamic model of tilt rotor blade was set up based upon vortex theory.The structural dynamic characters were analyzed by using software such as CATIA,ANSYS and ADAMS.The aerodynamic model and structural dynamic model were integrated via the help of iSIGHT multidisciplinary design optimization software,thus establishing a multidisciplinary design optimization(MDO) system for aerodynamic/structural dynamics of tilt rotor blade.Take XV-15 tilt rotor blade,for example,this approach to multidisciplinary design optimization of aerodynamic/structural dynamics of tilt rotor blade was feasible and efficient.
Experimental investigation of effects of temperature boundary layer on multi-scale coherent structures in wall turbulence
TAIN Yan, JIANG Nan
2007, 22(6): 980-985.
Abstract PDF(382KB) icon1717 icon561
Abstract:
The velocity time sequence at different vertical locations of turbulent boundary layer in wind tunnel was finely measured using a hot-wire anemometer,at a resolution higher than the corresponding minimum turbulence time scale.As compared with normal temperature,the heat convection could accelerate the exchanges of momentum,mass and energy in wall turbulence,and also facilitate the development process of turbulent boundary layer.Wavelet analysis method was employed to study the effects of temperature boundary layer on phase-averaged waveforms of multi-scale coherent structures during ejection and sweep process in wall turbulence.The research reveals that heat convection enhances dramatically the strength of coherent structures,contributing much to the exchange of momentum,mass and energy in wall turbulence.
Analysis on aerodynamic performance of complex iced airfoils
CHEN Ke, CAO Yi-hua, AUNG Ko-wynn, LI Dong
2007, 22(6): 986-990.
Abstract PDF(681KB) icon1472 icon442
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To classify smoothly the complex structured grid,the aerodynamic performance of complex iced airfoil with hybrid multi-block grid was analyzed and calculated.An unstructured grid was applied to the zone near the iced airfoil,whereas a structured grid was applied to save the storage and computational time.The flux restructuring was simplified through point-to-point connection between different grids.The Reynolds-averaged N-S equations are solved using SST turbulence models the entire flow area.The results of numerical simulation show that structured/unstructured hybrid multi-block grid is feasible for calculating the aerodynamic performance of complex ice accretion,given the fact that ice accretion has serious influence upon aerodynamic performance of airfoil.
Methods for stress based life and its reliability analyses of discs with medium-long and long life
YANG Jian-qiu, LU Shan
2007, 22(6): 991-995.
Abstract PDF(1346KB) icon1700 icon537
Abstract:
Considering the difficulty in calculating the stress concentration factor of mortise of a disk and the error of life is big by using the traditional stress-life method,an improved stress-life method is proposed to compute the life of disks.It includes the concept of stress correction coefficient,a new method to determine the stress concentration factor of mortise of a disk and a new method for correcting the stress ratio.When once the stress correction coefficient of the bars was computed,the improved Stress-Life method can be used to calculate disk's life with the experimental data of bars without notch,at the same time,the influence of the stress concentration is also considered.Then a new stress-life probabilistic model is built for the purpose of life reliability analysis.Finally,the fatigue life reliability of a fan disk is analyzed by the method given,and the computational results fit well with experimental ones.
Nonlinear responses of two-span rotor-bearing system with coupling faults of crack and pedestal looseness
LUO Yue-gang, WEN Bang-chun
2007, 22(6): 996-1001.
Abstract PDF(1660KB) icon1757 icon447
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A dynamic model was set up for the two-span rotor-bearing system with coupling faults of crack and pedestal looseness supported on three plain journal bearings.The nonlinear dynamics behaviors that induced by crack,pedestal looseness and coupling faults are numerically studied.In the case of crack faults,quasi-periodic motion appears within the range of sub-and super-critical speed range.When the pedestal looseness fault occurs,the quasi-periodic motion appears in the sub-critical speed range,but chaotic motion takes place within the super-critical speed range.The pedestal looseness fault is the main influence on the coupling fault system,and there is period-3 motion appearing in the system.The influence of crack fault increases along with the depth of crack.The results may provide theoretical references for fault diagnosis,dynamic design,and safe operation of rotor-bearing system.
Design and application of the damp shroud featuring equal strength and small loss
HUANG Zhi-jian, HAO Yan-hua, ZHANG Jun-Feng, ZHAO Pu-yang
2007, 22(6): 1002-1006.
Abstract PDF(733KB) icon1607 icon439
Abstract:
In accordance with the working characteristics of damping shroud for aeroengine blade,a kind of design method for blade shroud featuring streamline airfoil and equal strength has been established,and successfully applied to the structure design of the high-rotating shrouded fan blade.The result demonstrated the practicability of this method,with which the shroud structure designed has the features of light weight,smooth flow path,small loss of airflow,and high reliability etc.
Study of nonlinear response of cracked Jeffcott rotor in hovering state
YANG Yong-feng, REN Xing-min, QIN Wei-yang
2007, 22(6): 1007-1012.
Abstract PDF(490KB) icon1871 icon441
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The nonlinear response of crack Jeffcott rotor in leveling and hovering state was studied,while a mathematical model of crack Jeffcott rotor in hovering state was set up,and the corresponding motion equation was derived.The results show that,there are three ways leading to chaos,which are quasi-periodic bifurcation,intermittence bifurcation and instability period-3 motion to chaos.Generally speaking,the hover can depress the nonlinear response of system,but increase considerably the amplitude of system response,thus creating a bigger possibility of axis crack and rotor collision.And,the hover will also lead to nonlinear response near the fraction frequency of swing critical speed.
Regression analysis method for interval censored data
AO Liang, FU Hui-min
2007, 22(6): 1013-1017.
Abstract PDF(1569KB) icon1955 icon409
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A new method of regression analysis for interval censored data is presented,the regression equation for interval censored data is established,and the best unbiased integral estimators of the regression coefficients and their covariance matrix are given.The regression analysis methods for interval censored data from extreme distribution,Weibull distribution and normal distribution are discussed in detail.As the cross information among test data in different states is fully exploited,this method can reach higher precision than traditional method.
FEM simulation of cracked gear body under elastic supporting condition
SHAO Ren-ping, ZHANG Yan-chao, HUANG Xin-na, ZENG Zejun
2007, 22(6): 1018-1024.
Abstract PDF(1714KB) icon2150 icon473
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The dynamic characteristics of the fault gear were simulated using ANSYS numerical analytical software,if the gear and shaft are considered to have an elastic support relationship.The changes of dynamic characteristics of rear gear in the case of crack faults were studied in order to analyze the influences of different kinds of faults upon the dynamic characteristics.The results show that,the dynamic characteristics are influenced by the position and the size of cracks,and the position has a bigger influence than the size of crack,namely, the crack in the middle of gear body is more influential than the outer crack.Moreover,the setting method of elastic supporting boundary condition was studied during simulation process,and also compared with the fixed supporting and free supporting boundary conditions.The analytical results and findings provide an approach to study the fault causes and diagnosis of gear.

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