2014 Vol. 29, No. 9

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Helicopter performance improvement by rotor morphing technologies
HAN Dong, LIN Chang-liang, LI Jian-bo
2014, 29(9): 2017-2023. doi: 10.13224/j.cnki.jasp.2014.09.001
Abstract PDF(1311KB) icon2190 icon961
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To investigate the effect of rotor morphing technologies on helicopter performance improvement, a rotor model was derived. A fuselage model was coupled with this rotor model to establish the computational model of helicopter power. Several rotor morphing technologies, including varying rotor diameter, varying rotor speed, varying blade chord length and varying blade twist angle, were compared to investigate the influence on the helicopter power at different flight states. At the forward speed of 130km/h, 10% reduction of the rotor speed, 10% reduction of the rotor diameter, 10% reduction of the blade chord length and the blade twist angle variation from -12 degree to -6 degree, the power can reduce by 15.7%, 14.6%, 5.8% and 3.1%, respectively. At the forward speed of 250km/h, 10% reduction of the rotor speed and 10% reduction of the rotor diameter, can reduce the power by 14.5% and 23.9%, respectively. The results indicate varying rotor speed can achieve better performance improvement than varying blade chord length or varying blade twist angle. In high forward speed, varying rotor diameter can achieve better rotor power saving than varying rotor speed.
Aerodynamic structural characteristic of box six-component strain-gauge balance in heat state test
LUO Hua-yun, HOU Min-jie, WANG Yue-gui, GU Yang
2014, 29(9): 2024-2030. doi: 10.13224/j.cnki.jasp.2014.09.002
Abstract PDF(1514KB) icon1804 icon898
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In order to explore the abnormal phenomena of output signals of three dimensional force sensor in heat state test of box six-component strain-gauge balance,the balance frame,aerodynamic layout and heat state test were analysed for the four-component mechanical single desktop balance and box six-component strain-gauge balance, while the heat stress in stability segment of box six-component strain-gauge balance produced by high temperature flow by restriction of framework and installation was not eliminated or compensated at all. The fuel heater was moved to the exit of stability segment by symmetrical arrangement frame in order to preserve the best special function of heat state test in nozzle model test facility.The heat state test validates that thrust measure value of balance is resumed normally from abnormal negative value, and the problem of abnormal balance output signals is solved by reducing balance mechanical joint, increasing equilibrium of balance and predigesting installation and test of fuel heater, showing that it satisfies the balance heat state test performance requirement.
Numerical simulation of two-dimensional curved compression surface with isentropic surface coordinate transformation
ZHANG Lin, ZHANG Kun-yuan, WANG Lei, LI Yong-zhou
2014, 29(9): 2031-2039. doi: 10.13224/j.cnki.jasp.2014.09.003
Abstract PDF(2414KB) icon1532 icon930
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Different coordinate transformation matrixes were used to scale the coordinate of isentropic surface, and a series of two-dimensional curved compression surfaces with different curvature were obtained. The curved compression surfaces were studied using numerical simulation, and then compared with the curved compression surfaces with wall Mach number linear distribution and controllable law of pressure rise. The result shows that: the surface length can be shortened obviously due to coordinate transformation of isentropic surface, and the curved compression surface length scaled using x axis scaling factor of 0.7 can be reduced by 30% at the same total turning angle. The curved compression surfaces with different x axis scaling factors produce dispersed compression waves that will not be converged to one point, and the isentropic compression flow characteristics can be kept. Wall pressure distribution is improved to a certain extent and wall Mach number distribution tends to be linear with decreasing x axis scaling factor. The curved compression surfaces with x axis scaling factor of 0.5 and wall Mach number linear distribution have similarity in the flowfield structure, wall pressure, wall Mach number distribution, exit total pressure recovery coefficient and exit Mach number distribution.
Aerodynamic characteristics of design Mach number of 5 two-dimensional inlet with mixed-compression under typical condition
WENG Xiao-chai, GUO Rong-wei, ZHU Dan-dan
2014, 29(9): 2040-2046. doi: 10.13224/j.cnki.jasp.2014.09.004
Abstract PDF(1792KB) icon1699 icon1008
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The aerodynamic characteristics of a design Mach number of 5 two-dimensional inlet with mixed-compression during reentry under typical condition were investigated experimentally using wind tunnel and simulation. The results show that: when the free stream Mach number is higher than the design Mach number of 5, the external ramp oblique shocks of inlet intersect in advance and impinge on the cow inner surface, causing shock-shock interaction in combination with the cow oblique shock. Though the flow separations occur, the turbulence intensities upstream the inlet exit are less than 3.337 and 3.256 respectively when the free stream Mach numbers are 7 and 6, and the power spetrum density of the dynamic pressure signals in the duct generally presents the characteristics of white noise, causing little damage to the structure of the engine. Accordingly, in order to improve the mass flow of the inlet working over a wide rang of free stream Mach number, the design Mach number of inlet can be reduced properly.
Application of eN method in three-dimensional hypersonic boundary layers
YU Gao-tong, LUO Ji-sheng
2014, 29(9): 2047-2054. doi: 10.13224/j.cnki.jasp.2014.09.005
Abstract PDF(1890KB) icon1355 icon972
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A simple algorithm of saddle-point method (SPM) in eN method was presented by using internal wave theory, and distribution of N was computed on a model made up of plate, cone and cylinder at the cases of 30-45 km altitudes, Mach number of 10, attack angles of 0° and 10°. The results and conclusions show that: as the altitude increases, the transition position moves downstream, and the transition area becomes smaller and even disappears. On the plate part (windward side), the transition possibility in 10° attack angle cases is bigger than that in 0° attack angle cases, and the transition area is larger too. But on the cone part (leeward side), the transition possibility in 10° attack angle cases is less, and the transition area is smaller, even inexistence. And the transition positions of these two series of cases are different.
Investigation of basic flowfield with center body consisting of four spline curves diffusing reflected shock wave
LI Yong-zhou, ZHANG Kun-yuan, ZHONG Qi-tao
2014, 29(9): 2055-2062. doi: 10.13224/j.cnki.jasp.2014.09.006
Abstract PDF(1872KB) icon1709 icon1037
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A basic flowfield with center body consisting of four spline curves diffusing reflected shock wave was designed to meet the operation requirement of the hypersonic inward turning inlet in a wide Mach number range. The compression efficiency increased obviously when the incoming flow Mach number was higher than that of the design point(6.0), and the exit total pressure recovery coefficient increased by 2.3% compared with the basic flowfield with concave arc center body at cruise point(incoming flow Mach number of 7.0). Besides, the inward turning inlets with circular shape intake were designed based on these two categories of basic flowfield. The numerical simulation results from the incoming flow Mach number of 5.0-8.0 indicate that the four spline curves inlet has higher compression efficiency when the incoming flow Mach number is higher than that of the design point. The pressure ratio is approximately equal while the throat exit total pressure recovery coefficient of four spline curves inlet increases by 1.1% when the incoming flow Mach number of 8.0 under viscous condition.
Analysis of aerodynamic characteristics of flexible wing of dragonfly based on CFD/CSD method
MENG Ling-bing, ANG Hai-song, XIAO Tian-hang
2014, 29(9): 2063-2069. doi: 10.13224/j.cnki.jasp.2014.09.007
Abstract PDF(1355KB) icon2617 icon999
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A methodology of fluid-structure bi-directional interaction based on computational fluid dynamics/computational structure dynamics (CFD/CSD) was presented. The donor-receptor relationship between two sets of grid system was identified by alternating digital tree (ADT). The local interpolation methods were used for data exchange between these two sets of grids. Flow with moving boundaries was dealt with by Delaunay graph mapping method. The code for nonlinear structural finite element and information transfer was developed and used to connect with the code of flow solver 3D2MUFS developed in the Micro Air Vehicle Center of Nanjing University of Aeronautics and Astronautics (NUAA). It was applied to the aerodynamic computation of dragonfly flapping flight with flexible wing. Results show that the time-averaged vertical force coefficient of the dragonfly wing increases from 0.31 to 0.53, and the time-averaged thrust coefficient increases from 0.07 to 0.13 by flexible deformation. This confirms that the flexible deformation can improve the aerodynamic performance of flapping wing.
Preliminary analysis of jaws inlet performance under design conditions
GU Tian-lai, FU Lei, ZHANG Shuai, ZHENG Yao
2014, 29(9): 2070-2078. doi: 10.13224/j.cnki.jasp.2014.09.008
Abstract PDF(2079KB) icon1611 icon890
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The design method of the three-dimensional inward turning hypersonic jaws inlet was introduced. Corresponding design codes were developed. Thereafter, a CFD technology was used to verify this method and the design codes with the generated jaws inlet model under the height of 30km, design Mach number of 5 and attack angle of 0°, respectively. Finally, geometry and aerodynamic performances of jaws inlet under design conditions affected by the design parameters, such as the streamline tracing outlet profile, the compression angle set of base field and the design Mach number, were compared and analyzed. Result shows that compared with a low aspect ratio, the geometry performance will be better if the aspect ratio of rectangle-outlet approaches 2 with shorter total length and smaller surface area. Moreover, the compression angles should be set between 8° and 12° in preliminary design for relatively better performances, with the latter compression angle smaller than the former.
Flow field and aerodynamic characteristic of deflectable nose projectile at different angles of attack
GUO Yu-jie, CHEN Zhi-hua, HAN Jun-li
2014, 29(9): 2079-2084. doi: 10.13224/j.cnki.jasp.2014.09.009
Abstract PDF(1378KB) icon1618 icon1151
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Based on DES (detached eddy simulation) method and AUSM (advection upstream splitting method) scheme, the supersonic flow field and aerodynamic characteristic of deflectable nose projectile were simulated numerically at non-zero angle of attack and different deflectable angles. The results show that, at non-zero angle of attack, the shock wave on the windward of the projectile head with deflectable nose was much stronger than that of the normal one. When the effective angles of incidence of both projectiles were equal, the structures of flow field of head were all the same, and the flow field of tail fins were not affected by the deflectable angles even different angles of attack of projectiles. From the time history of aerodynamic force coefficients versus angle of attacks, it's found that the projectile with deflectable nose has good longitudinal static stability. Besides, the raising gradient of lift coefficient is much larger than that of drag coefficient, showing the lift-to-drag ratio is higher than normal projectile. Therefore, increasing the angle of attack properly can improve the aerodynamic characteristic of deflectable nose projectiles.
A dynamic ensemble extreme learning machine model for aircraft engine health condition prediction
ZHONG Shi-sheng, LEI Da
2014, 29(9): 2085-2090. doi: 10.13224/j.cnki.jasp.2014.09.010
Abstract PDF(1017KB) icon1587 icon984
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A dynamic ensemble extreme learning machine (ELM) model was proposed for aircraft engine health condition prediction. The AdaBoost.RT algorithm was used to integrate ELM to construct the ensemble model. During the training process, the neighboring samples of every training sample were employed to evaluate the local performance of ELM. In the prediction process, the neighboring samples of new samples in the training sample set were selected firstly, then the combined weights of ELM were determined by the performance on the neighboring samples, implementing the dynamic ensemble of the weak learning machine. Fuel flow was utilized as a health index for aircraft engine health condition prediction. For short term prediction, the mean absolute percentage error (MAPE) of the dynamic ensemble ELM model was 3.688%, less than the MAPE of the single ELM model and the static ensemble ELM model, which were 3.830% and 3.719%, respectively. And for long term prediction, the MAPE of the dynamic ensemble ELM model was 3.075%, also less than that of the single ELM model of 4.355% and the static ensemble ELM model of 3.884%. Thus, the dynamic ensemble ELM model is better for the aircraft engine health condition prediction.
Active control of flexible structure vibration based on fuzzy fractional order PIPIλDμ
SHENG Xian-jun, ZHONG Sheng, JIANG Tao
2014, 29(9): 2091-2096. doi: 10.13224/j.cnki.jasp.2014.09.011
Abstract PDF(1343KB) icon1475 icon923
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In order to prevent wings vibration due to external interference, for the control object of flexible cantilever beam a scheme of fractional order proportion integration differentiation controller based on parameters self-correction was proposed. After the parameters were optimized by genetic algorithm firstly, they were set online by fuzzy rule for the second time in order to achieve real-time optimum control. Numerical simulation was carried out by Simulink software, and result shows that the proposed fractional order proportion integration differentiation controller has a memory ability and a strong dynamic characterization ability. Compared with the conventional proportion integration differentiation controller, the steady state time of system response decreases by 0.9s under impulse stimulation; the reduced amplitude of system response increases from 88% to 96% under harmonic stimulation; the system tends to be more stable and the response jitter reduces under random stimulation.
Mass optimization of turbine disk based on sequential sampling algorithm
XU Sheng-li, LIU Hai-tao, WANG Xiao-fang, SONG Yang
2014, 29(9): 2097-2103. doi: 10.13224/j.cnki.jasp.2014.09.012
Abstract PDF(1069KB) icon1663 icon859
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A sequential sampling algorithm based on Monte Carlo-based space reduction and local boundary search was introduced. This algorithm utilized the information of the current samples to reduce the design space in order to generate new samples with better space-filling and projective properties. The comparative results with existing sequential sampling algorithm demonstrate that this algorithm can efficiently generate better samples. This sequential sampling algorithm combined with Kriging model and genetic algorithm was used in the mass optimization of turbine disk, obtaining mass reduction of 10%. The results show that this sequential sampling algorithm provides a flexible and efficient approach for the engineering structure optimization.
Experimental test method for high-frequency modal damping of turbomachinery blades
GUO Xue-lian, FAN Yu, LI Lin
2014, 29(9): 2104-2112. doi: 10.13224/j.cnki.jasp.2014.09.013
Abstract PDF(1591KB) icon2269 icon966
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High-frequency modal damping ratio experimental identification of turbomachinery blade was studied using NASA Rotor37 blade. The blade was tested by random acoustic excitation in order to obtain evident high frequency response. It is shown, both numerically and experimentally, that the obtained frequency-response curve at high-frequency also showed the information of the excited modes from the supporting structure. Therefore the vibration of the supporting structure was also monitored by several sensors. Then a data processing approach was proposed to distinguish the blade dominant peaks by comparing the energy transfer ratio of the blade with that of the supporting structure. After wavelet threshold denoising, the blade's modal damping ratios less than 10kHz were obtained by fitting the blade dominant peaks. Additionally, the results show that the magnitude of blade's high-frequency modal damping is less than 1% when it is produced by general metal materials, and the magnitude has a downward trend along with the frequency.
Fatigue life prediction method of 2.5 dimensional woven composites
QIU Rui, WEN Wei-dong, CUI Hai-tao
2014, 29(9): 2113-2120. doi: 10.13224/j.cnki.jasp.2014.09.014
Abstract PDF(1549KB) icon1682 icon823
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A fatigue life prediction method was developed to predict fatigue life of 2.5 dimensional woven composites subjected to fatigue loading. This method consisted of unit-cell model, fatigue damage criterion and material property degradation technique. Stress analysis was performed by three dimensional finite element technology based on the unit-cell model. Modified three dimensional Hashin fatigue damage criterion and Mises criterion were adopted to identify fatigue damage separately for the yarns and matrix. The stiffness property sudden degradation rules were applied to establish the fatigue damaged material properties; the residual stiffness and strength models considering fiber volume fraction were used to establish the undamaged material properties. The coincidence of predicted fatigue life and experimental data was studied, and the comparison results validated the fatigue life prediction method. The results indicate that the tensile-tensile fatigue life in warp direction increases with the warp fiber volume fraction increasing, while weft fiber volume fraction has little effect on tensile-tensile fatigue life in weft direction.
Parameters design of smart spring vibration suppression system based on common point of amplitude frequency characteristic curve cluster
NI De, ZHU Ru-peng, BAO He-yun, LU Feng-xia, FU Qiu-ju
2014, 29(9): 2121-2128. doi: 10.13224/j.cnki.jasp.2014.09.015
Abstract PDF(1379KB) icon1752 icon901
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A design method of system parameters for undamped smart spring vibration suppression system was studied. The dry friction damping of the system was transformed equivalently to viscous damping by equivalent linearization technique, as a result, the mathematical model of the system was established. The dimensionless differential equations of vibration were derived and the analytic solution of frequency response characteristics was obtained. The amplitude frequency characteristics of the system were numerically analyzed. The study results reveal that the amplitude frequency characteristic curve cluster of the system has a common point that will be shifted to the left as the mass ratio increases and to the right as the stiffness ratio increases. There is an optimum value, for the control parameters of system, which could make the peak value of amplitude frequency characteristic curve of the system be minimum. The optimum control parameter will reduce with the increase of the mass ratio, but it is not affected by the stiffness ratio. The formulas of frequency ratio, optimum control parameter and minimum amplitude corresponding to the common point of amplitude frequency characteristic curve cluster were derived. The selection principle and range of system parameters were proposed. The design method and procedures of system parameters of smart spring vibration suppression system were presented.
Analysis of parameter-nonparametric fusion on space bearing friction moment
XU Yong-zhi, XIA Xin-tao
2014, 29(9): 2129-2135. doi: 10.13224/j.cnki.jasp.2014.09.016
Abstract PDF(994KB) icon1563 icon900
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Parameter-nonparametric fusion method was put forward to analyze the characteristic of space bearing friction moment, by using statistical method to judge the basic characteristic of space bearing friction moment; symbol judgment method was used to determine the time sequence characteristic of space bearing friction moment; while rank sum judgment method was used to determine the state characteristic of space bearing friction moment; these three methods were fused to analyze the overall characteristic of space bearing friction moment, in order to evaluate the friction characteristic of space bearing. The method can avoid the effect of the plus or minus and some mini-max values and time sequence on overall characteristic of space bearing. The basic characteristic, the time sequence characteristic and the state characteristic of space bearing were discovered to reflect the overall characteristic on space bearing; the results show that the better space bearing are determined according to working performance and stabilization of the space bearing, at the same time, on the basis of the time sequence and state characteristic of the space bearing, the optimal overall space bearing was chosen, with the credibility up to 99%, in line with the current selection of space bearings; there were more information of the space bearing with use of the fusion method, showing that the fusion method could choose the space bearing of the optimal overall characteristic from a handful of space bearings.
An oil flow management valve for solving oil leakage at low rotating speed
GU Zhi-ying, LI Guo-quan, YU Li, MA Fang
2014, 29(9): 2136-2141. doi: 10.13224/j.cnki.jasp.2014.09.017
Abstract PDF(1560KB) icon1477 icon842
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Targeting the oil leakage of bearing chamber of aero-engine at low rotating speed, the reasons of the oil leakage of bearing chamber of aero-engine at low rotating speed were analyzed. A efficient method solving the problem was proposed, including the design of oil flow management valve applied to the oil supply pipeline of rear bearing chamber. The opening pressure and flow resistance characteristics tests of oil flow management valve were carried out, and the result shows that the opening pressure and flow resistance characteristics of the oil flow management valve can satisfy the requirements of supplying a little oil to the bearing chamber for lubricating bearing, and also preventing oil leakage with oil overabundance of bearing chamber of aero-engine at low rotating speed. The research can be a reference for solving the problem of oil leakage for the bearing chamber of aero-engine at low rotating speed.
Influence physics of mainstream pressure gradient on film hole discharge coefficient
ZHU Hui-ren, LUO Jian-xia, HUANG Xiao-yang, LIU Zhi-gang
2014, 29(9): 2142-2149. doi: 10.13224/j.cnki.jasp.2014.09.018
Abstract PDF(1488KB) icon1650 icon871
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Film hole discharge coefficients at different mainstream pressure gradients (zero pressure gradient, positive pressure gradient and negative pressure gradient) were tested, and influence physics of mainstream pressure gradient on film hole discharge coefficient was analyzed. Result shows that the maximum amplitude of effect on film hole discharge coefficient of mainstream positive and negative pressure gradients are 22% and 26% respectively. At different mainstream pressure gradients, bending effect and crushing effect of mainstream on jet are different, together with the changed interaction of jet with mainstream, and therefore the film hole discharge coefficient will be different. Crushing effect makes jet narrower and enhances the jet flow loss. Bending effect can change jet flow track; the positive pressure gradient makes jet flow close to the wall but far away from the free ejection direction, resulting in more flow loss; to the contrary, the negative pressure gradient may decrease the flow loss. The mixing effect enhances the momentum dissipation of jet, while at positive pressure gradient, the mixing effect is restrained and then momentum dissipation of jet decreases, however, the rule is opposite at negative pressure gradient.
Investigations on ablation failure of high power pistons
QIN Zhao-ju, ZHANG Wei-zheng, SONG Li-ye, YUAN Yan-peng
2014, 29(9): 2150-2156. doi: 10.13224/j.cnki.jasp.2014.09.019
Abstract PDF(1513KB) icon1715 icon836
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Numerical simulation of combustion characteristics at wall burning condition in a diesel engine was conducted using software AVL FIRE, and the thermal boundary conditions of finite element calculation for piston at wall burning condition were obtained. Moreover, the finite element analysis of piston during ablation process was carried out using software ANSYS, and the rules of influence of wall burning on piston ablation were achieved. Meanwhile, a corresponding experiment of piston ablation was made on the diesel engine, and the calculated results accorded with the experimental results. The results show that the resolving method established can be used to simulate the ablation process of piston. The abrasion of injection nozzle, which leads to bigger gas temperature and wall heat transfer coefficient of gas on piston throat in a wide crank angle range, may cause ablation failure of piston. Meanwhile, the ablation amount firstly increases and then decreases with the increase of diameter of injection nozzle, and peaks when the diameter increases by 15%. The ablation amount increases with the ablation time, but the speed of ablation reduces slowly.
Numerical simulation of ice accretion on rotor airfoil of helicopter considering effects of centrifugal force
CHEN Xi, ZHAO Qi-jun, ZHAO Guo-qing
2014, 29(9): 2157-2165. doi: 10.13224/j.cnki.jasp.2014.09.020
Abstract PDF(1992KB) icon1850 icon909
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Considering the effects of centrifugal force, a method of numerical simulation for ice accretion on rotor airfoil of helicopter was established. Firstly, the body-fitted and body-orthogonal grids around an airfoil were generated and the viscosity flowfield around rotor airfoil was solved by Navier-Stokes (N-S) equations. Based on the solution of flowfield and Lagrange method, the equations of water droplets motion were established. Then, in order to improve the computational efficiency in searching the position of the water droplet, the method combined with the displacement vector was presented. Finally, in combination with the characteristics of blade motion, a three-dimensional ice accretion model considering the effects of the centrifugal force was presented. The comparison between the calculated results and experimental data indicates that the current approach can effectively simulate the ice accretion on airfoil of blade. Compared with the results of conventional ice accretion model, the amount of ice accretion was reduced by 22.3%. Considering the blade flapping motion, the amount of ice accretion was reduced more. As a result, the importance of the centrifugal force and blade motion in blade numerical simulation of ice accretion was pointed out. Comparing the ice shape and amount of the different sections of blade, the ice accretion characteristics of blade were discussed and analyzed. The results show that the effects of the centrifugal force increase with the increasing radial displacement, and the amount of ice accretion on the rotor lower surface decreases with the increase of the flapping angle.
Numerical investigation on particle deposition characteristics in vicinity of film cooling holes
ZHOU Jun-hui, ZHANG Jing-zhou
2014, 29(9): 2166-2173. doi: 10.13224/j.cnki.jasp.2014.09.021
Abstract PDF(1730KB) icon2810 icon876
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Numerical study on the particles movement and deposition in the vicinity of film cooling holes was performed, focusing on the effects of particle diameter and film outflow blowing ratio on the particle movement and deposition characteristics. Based on the EI-Batsh deposition model including particle sticking/rebounding and particle detachment, user definition functions were linked with FLUENT to predict the particle deposition, and verify the calculation data with relevant experimental data. The research results show that the deposition rates of 1,2μm diameter particles increase with the growing blowing ratio, but the deposition rates of 3,4μm diameter particles decrease with the growing blowing ratio.1 μm diameter particles are prone to deposit in the local region between adjacent film cooling holes under the suction of kidney vortices, and the particle deposition rate of the blowing ratio of 2 is about 5 times higher than that of the blowing ratio of 0. The trajectories of 5μm diameter particles are less affected by the film outflow. The total deposition rate decreases with the increase of blowing ratio, and the total deposition rate at blowing ratio of 2 decreases by 1.7% compared with that at blowing ratio of 0.
Pumping performance for double-stage lobe mixer/ejector
PAN Cheng-xiong, ZHANG Jing-zhou, SHAN Yong
2014, 29(9): 2174-2180. doi: 10.13224/j.cnki.jasp.2014.09.022
Abstract PDF(1828KB) icon1769 icon902
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The pumping performances of double-stage lobe mixer/ejector were experimentally and numerically investigated. The aerodynamic characteristics difference of mixer/ejector between two inlet modes of mixing duct was illustrated and the effects of mixing duct area ratio and length-diameter ratio on the pumping performance of double-stage lobe mixer/ejector were preliminarily analyzed. The results show that the inlet mode of mixing duct has strong influence on pumping capacity. Under the present configuration parameters, the pumping capacity of single-stage lobe mixer/ejector is 10% superior to that of double-stage lobe mixer/ejector in the case of confined inlet. While in the case of open inlet, the pumping capacity is 35% superior to that of confined inlet at most. The pumping capacity of double-stage lobe mixer/ejector is stronger than that of single-stage lobe mixer/ejector. Especially for the mixing duct with bigger area ratio or less length-diameter ratio, the pumping performances of double-stage lobe mixer/ejector in the case of open inlet is superior to that of confined inlet.
Effect of angle between lamilloy and rotation axis on heat transfer capability of limited lamilloy
BAI Guo-qiang, CHANG Hai-ping
2014, 29(9): 2181-2187. doi: 10.13224/j.cnki.jasp.2014.09.023
Abstract PDF(1672KB) icon1401 icon774
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Heat transfer characteristics in condition of different angles between lamilloy and rotation axis in limited lamilloy under rotating state was researched by numerical simulation. The relation between lamilloy heat transfer capacity and angle between lamilloy and rotation axis was acquired. Results show that surface heat transfer coefficients present similar characteristic with different angles between lamilloy and rotation axis. The surface heat transfer coefficient is highest and the effect of buoyancy force is smallest when the angles between lamilloy and rotation axis are 90°and 270°. The surface heat transfer coefficient is lowest and the effect of buoyancy force is biggest when the angles between lamilloy and rotation axis are 0°and 180°. The effects of Coriolis force and buoyancy force are researched separately. The effect of Coriolis force in parallel to the lamilloy on flow is more remarkable than that perpendicular to the lamilloy.
Experiment on lean blow-out performance of pilot stage in internally-staged combustor
LI Hai-tao, XU Quan-hong, FU Zhen-bo, LIN Yu-zhen
2014, 29(9): 2188-2194. doi: 10.13224/j.cnki.jasp.2014.09.024
Abstract PDF(1247KB) icon1671 icon871
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An experimental research was conducted on the lean LBO (blow-out) performance at constant pressure status of internally-staged single annular layout LESS (low emissions stirred swirl) combustor. Using single head speeimen, this experiment mainly focused on the effect of three parameters on the combustor lean blow-out performance, i.e. mass flow number of the pilot stage centrifugal nozzle, inlet temperature and the fuel type, respectively. The experimental result shows that: the pilot stage centrifugal nozzle with small mass flow number can reduce LBO equivalence ratio. When the inlet temperature is below 150℃,increasing the inlet temperature can reduce LBO equivalence ratio rapidly; but there is little effect when the inlet temperature exceeds 150℃. LBO equivalence ratio variational trends of gaseous fuel is different from those of liquid fuel with the flame tube pressure drop, but they tend to be the same value, and when the flame tube pressure drop is in the range of 5%, LBO equivalence ratio of gaseous fuel is less than that of liquid fuel.
A tip clearance control technology for turbine
YANG Jia-li, TU Meng-pi, ZHANG Yi-li, ZHANG Li-zhang, YANG Cheng-wu
2014, 29(9): 2195-2201. doi: 10.13224/j.cnki.jasp.2014.09.025
Abstract PDF(1326KB) icon1757 icon829
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Based on the theory of turbine tip clearance change, a structure was developed to adjust the choke acreage of the cooling air flow throttle automatically without other drivers, and the cooling air of turbine casing was controlled to regulate the turbine casing diameter. So the turbine tip clearance was limited in a certain range and its trend was controlled effectively. Three cases were simulated for a general turbine with or without turbine tip clearance control structure. The results show that the turbine tip clearance control structure can adjust the cooling air for turbine casing and the change rate of turbine tip clearance is 6.5%, however, the change rate of the turbine tip clearance without the structure is 20%. So the structure is beneficial to control the change of turbine tip clearance.
Optimization of fan rotor blade in high bypass ratio turbofan engine
WANG Zhi-qiang, SHEN Xi-gang, HU Jun, LIU Zhi-jie, ZHENG Ning
2014, 29(9): 2202-2209. doi: 10.13224/j.cnki.jasp.2014.09.026
Abstract PDF(2311KB) icon1895 icon843
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By using sweep design technique, the fan rotor blade of a high bypass ratio turbofan engine was optimized in three-dimensional configuration. The influence of the sweep design parameters at blade tip and hub on the performance of the fan rotor were studied by solving three-dimensional steady Navier-Stokes (N-S) equations. The results show that both forward sweep at blade tip and backward sweep at blade hub can enhance the performance of the fan rotor, increase its chock point mass flow and enlarge its stable working range. The blade was optimized by the combined choice of forward sweep at blade tip and backward sweep at blade hub. The calculation result of the single rotor shows that the total pressure ratio and isoentropic efficiency at design mass flow point are increased 5% and 2%, respectively, and the chock point mass flow is increased about 2%. The core and bypass of fan/compressor combined calculation results show that the stable working range of the bypass is enlarged at different rotating speeds of take off, cruise and climbing state after optimization. The mass flow is increased about 2.3% at the chock point, and decreased about 5.2% at stall point at rotating speed of cruise. The total pressure ratio and isoentropic efficiency of the bypass are increased about 2% and 0.8% at design mass flow point, while the performance of the core does not change significantly after optimization.
Research on S1 stream surface for cooling air mixing and variable thickness flow slice in multi-stage
LUO Lei, LU Shao-peng, WANG Song-tao, WANG Long-fei, CUI Tao
2014, 29(9): 2210-2220. doi: 10.13224/j.cnki.jasp.2014.09.027
Abstract PDF(2830KB) icon1561 icon972
Abstract:
To reduce the difficulty of aerodynamic design in air-cooled turbine, a set of calculation ideas based on multi-stage air-cooled turbine were presented in consideration of the cooling air mixing, warped S1 stream surface and variable thickness along with flow passage; the parameterization method program and automatic mesh generation program of warped S1 stream surface slice with cooling condition were prepared, and the traditional plane slice was modified. Comparative analysis of the difference among the modified plane slice, warped S1 stream surface slice and three-dimensional calculation was made, and aerodynamic design of a high-pressure turbine with warped S1 stream surface slice was optimized. The results show that: in comparison with three-dimensional calculation, the maximum gap of mass flow in modified plane slice is up to 22.68%, and 3.58% in warped S1 stream surface slice; the warped S1 stream surface slice is closer to three-dimensional calculation on one-dimensional data; blade pressure and Mach number contour distribution of warped S1 stream surface slice are closer to three-dimensional calculation than that of modified plane slice. After aerodynamic optimization in warped S1 stream surface slice, compared with original model, the stage efficiency has been increased by 0.41%, while mass flow has only been increased by 0.21%.
Model of tip clearance leakage flow blockage in micro-scale centrifugal impellers
SUN Qian-wei, SONG Xi-zhen, LI Qiu-shi
2014, 29(9): 2221-2228. doi: 10.13224/j.cnki.jasp.2014.09.028
Abstract PDF(1580KB) icon1993 icon819
Abstract:
The model of tip clearance leakage flow blockage in micro-scale centrifugal impellers was studied through theoretical analysis in combination with numerical simulations. Based on both low Reynolds number and high Mach number working condition of micro-scale rotating machinery, a model of tip clearance leakage flow blockage was established considering the compressibility and viscous loss. The features of micro-scale tip clearance leakage flow were analyzed and the viscous effect was explained with the help of numerical simulations. It is concluded that viscous effect is important in driving the tip clearance leakage flow, in agreement with differential pressure meanwhile resulting the increase of initial blockage of tip clearance flow. The verification of tip clearance leakage flow blockage model was carried out on a micro-scale centrifugal impeller. Tip clearance leakage flow blockage result extracted from numerical result was compared with model prediction results, and the result of improved tip clearance leakage flow blockage model shows more accurate evaluation and more suitable in micro-scale condition.
Scheme on aerodynamic design of core driven fan stage
LAI An-qing, HU Jun, TU Bao-feng
2014, 29(9): 2229-2238. doi: 10.13224/j.cnki.jasp.2014.09.029
Abstract PDF(2608KB) icon1869 icon780
Abstract:
To achieve the core driven fan stage(CDFS)design indexes, the effect of different types of inlet guide vanes(IGV)on performance of CDFS was analyzed with CFD numerical simulation. The results show that the configuration using variable IGV and fixed stator can meet the CDFS design indexes; different types of IGV conversions have remarkable effects on performance of CDFS; the proper variable camber location and the closed angle in variable camber IGV are important to achieve the design goal; stator oriented in negative attack angle is favorable in single bypass mode in mode conversion; the CDFS loss is mainly influenced by rotor passage shock in single bypass mode and by the separation flow in IGV suction surface in double bypass mode.
Radial vortex phenomenon and instability mechanism of transonic axial-flow compressor
HU Jia-guo, WANG Ru-gen, LI Shao-wei, GAN Tian
2014, 29(9): 2239-2246. doi: 10.13224/j.cnki.jasp.2014.09.030
Abstract PDF(2517KB) icon1626 icon865
Abstract:
Numerical investigation was made on NASA Rotor 37 and the result was compared with an experiment. Working conditions from blocking point to stall point were calculated to study the rules of boundary layer separation and the instability mechanism of transonic axial-flow compressor. The research discovers a radial vortex behind passage shock wave in suction side boundary layer, which facilitates boundary layer separation and converges part of airflow near suction side to blade tip. With working conditions go to stall point, blade tip passage is jammed by two pieces of blocking zone; one located in the front of blade pressure side is caused by the interference of clearance leakage vortex and passage shock, while the other located on suction side after 50% chord is caused by the interference of radial vortex and leakage flow. The two blocking zones' expansion arouses instability of the compressor.
Load sharing and lightweight optimization design of torque-split transmission system based on FA-NSGA
FU Chen-xi, ZHAO Ning, ZHAO Yong-zhi, FU Bi-bo
2014, 29(9): 2247-2255. doi: 10.13224/j.cnki.jasp.2014.09.031
Abstract PDF(1505KB) icon1518 icon834
Abstract:
The load sharing characteristics and lightweight were considered as the objectives, so a multi-objective optimization design of torque-split transmission system was conducted. First of all, a non-linear dynamics model of torque-split transmission system was established. Load sharing coefficients under different powers and speeds were calculated to measure load sharing characteristics of torque-split transmission system. Afterwards, a multi-objective optimization model including minimum load sharing coefficient and mass was developed with the torque-split transmission system parameters selected as design variables, and the effects of different working conditions were taken into consideration. In order to improve the solution efficiency, a modified fitness approximation mechanism non-dominated sorting genetic algorithm (FA-NSGA) was promoted. Three benchmark functions were used to test the convergence and effectiveness of FA-NSGA. The test results show that satisfactory optimal solutions in all three test functions are achieved by using FA-NSGA, and more than 60% of the computation times of real fitness can be reduced at the same time. Finally, a given instance was solved by using FA-NSGA, and the satisfactory design variables were selected from the Pareto optimal solution. Compared with the reference design, the selected one reduces the load sharing coefficient by 0.05, and the mass by 3.57kg at the same time.
A fault monitoring technique for wear of aero-engine rolling bearing
WANG Hong-wei, CHEN Guo, CHEN Li-bo, SONG Ke, LI Ai
2014, 29(9): 2256-2263. doi: 10.13224/j.cnki.jasp.2014.09.032
Abstract PDF(1598KB) icon1791 icon797
Abstract:
Multiple intelligent debris classifying system (MIDCS) to detect sensitive wear particles whose size are 10μm or more in long axis on the aero-engine rolling bearing for wear fault monitoring was developed. The MIDCS overcomed the shortcomings, such as the insensitivity to large wear particles in the traditional spectral analysis, and cumbersome detection steps in the ferrographic analysis. The MIDCS could be used to directly detect wear particles whose size are 10μm or more in long axis in the flowing oil. Seven digital characteristic parameters and their identification were proposed for the moving wear particles in the flowing oil, implemented the auto-identification for the wear particles. The basic identification accuracy of the MIDCS is above 99%. Through the experiments on the real oil samples from aero-engines, result shows that the MIDCS is superior to the spectral analysis in terms of the ability and timeliness on detecting the wear abrasion fault of the aero-engine rolling bearing.
Impact of torsional stiffness on dynamic load sharing coefficient oftwo-input cylindrical gear split-torque transmission system
GUI Yong-fang, ZHU Ru-peng, FU Bi-bo, LI Hai-feng, WANG Qi-bo, JIN Guang-hu, LI Zhi-jun
2014, 29(9): 2264-2272. doi: 10.13224/j.cnki.jasp.2014.09.033
Abstract PDF(2192KB) icon1714 icon848
Abstract:
A dynamic model with bend-torsion coupling was established for two-input cylindrical gears split-torque transmission system, in which the time-varying mesh stiffness, backlashes, mesh errors and mesh damping of gear pairs were considered. With use of the characteristics of closed loop structure, differential equations could be obtained without rigid displacement, using the relationship between relative meshing displacement and the transmission shaft torsional displacement. Through solving the dynamic equation of system by the fourth-order Runge-Kutta method, the load sharing coefficients of system were acquired. The results show that load sharing coefficient of system is little influenced by torsional stiffness of input shaft. The load sharing coefficient of split and synthesized torque stages is sensitive to torsional stiffness of duplicate gear shaft, and reduction of the torsional stiffness of duplicate gear shaft contributes to the improvement of load sharing performance of system. When torsional stiffness of duplicate gear shaft is less than 1.1×105(N·m)/rad, the load sharing coefficient of system is less than 1.06. Torsional stiffness of output shaft has no significant effect on the load sharing coefficient of split and synthesized torque stages.

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