2014 Vol. 29, No. 8

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Experiment of flow field in lobed mixer
ZHANG Zhe-heng, WANG Dong-ming, ZHANG Bao-hua, HU Wen-cheng, YU Ting-ting
2014, (8): 1761-1768. doi: 10.13224/j.cnki.jasp.2014.08.001
Abstract PDF(1307KB) icon1710 icon1123
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In order to obtain the three-dimensional flow field of afterburner lobed mixer, a five-hole probe with thermocouple was applied to measure the flow field of the lobed mixer. The velocity and temperature fields in different sections at the lobed mixers outlet were obtained in the experiments, and the change rules of the thermal mixing efficiency and the total pressure recovery coefficient in the flow direction were measured. The experimental results indicate that a pair of inverse direction streamwise vortexes are generated in the trailing edge of lobed mixer, which strengthens the degree of the mixed convection between inner bypass and external bypass. The closer to the trailing edge of the lobed mixer, the greater the mixing degree of the flow between inner bypass and external bypass, the quicker the thermal mixing efficiency increasing, the faster the total pressure recovery coefficient declining.
NOx emissions of kerosene combustion at elevated pressure jet stirred combustion reactor
ZHANG Chi, TIAN Ye, XUE Xin, LIN Yu-zhen, XU Quan-hong
2014, (8): 1769-1774. doi: 10.13224/j.cnki.jasp.2014.08.002
Abstract PDF(901KB) icon1905 icon978
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In order to study the combustion product NOx emissions of hydrocarbon fuel, a jet stirred combustion reactor (JSCR) experimental system was built and validated preliminarily. Then, kerosene RP-3 combustion NOx emission was tested using the experimental system under the conditions of pressures in jet stirred combustion reactor of 2×105Pa and 3×105Pa, inlet temperature of 650K, and equivalence ratios of 0.5 to 1.2. The study results show that when equivalence ratio of 0.5 to 1.2, the amount of kerosene combustion NOx emission firstly increases with the growing equivalence ratio and reaches the maximum value in the vicinity of the equivalent ratio of 0.95, and decreases subsequently; the amount of kerosene combustion NOx emission increases with the pressure rise. The jet stirred combustion reactor can be used as a verification test rig for combustion products of hydrocarbon fuels.
Effects of swirler structure on the performance of lean-direct-injection combustor
ZENG Qing-hua, KONG Wen-jun, AI Yu-hua, WANG Bao-rui, SUI Chun-jie
2014, (8): 1775-1781. doi: 10.13224/j.cnki.jasp.2014.08.003
Abstract PDF(899KB) icon2020 icon934
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In consideration of swirler design of single element lean-direct-injection (LDI) injector, the effects of the swirler structures, including swirler stage number, swirl direction of dual-stage swirler and shrinking angle of mixing section, on the combustor performance (total pressure loss, combustion efficiency and pollutant emissions) were studied experimentally. The results show that, the swirler structures have great effect on the performance of combustor. The total pressure loss of dual-stage co-swirl combustor is greater than that of the single-stage swirl combustor with the same swirl number as the dual-stage co-swirl combustor. The total pressure loss of dual-stage counter-swirl combustor is slightly lower than that of the dual-stage co-swirl combustor. Combustor's total pressure loss increases with the inerease of shrinking angle. Under different lean fuel-air ratios, compared to the single-stage swirl combustor and dual-stage co-swirl combustor, the dual-stage counter-swirl combustor has higher combustion efficiency and lower pollutant emissions. In addition, combustion efficiency and pollutant emissions are affected by the shrinking angle. The optimal shrinking angle selection should strike a blance among the total pressure loss, the combustion efficiency, and the level of pollutant emissions.
Experiment on effect of Knudsen number on micro-scale similarity flow characteristics
ZHENG Jie, ZHU Hui-ren, GUO Tao, MENG Tong, WU A-sai, LU Hong-kang
2014, (8): 1782-1788. doi: 10.13224/j.cnki.jasp.2014.08.004
Abstract PDF(1011KB) icon1760 icon1061
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In order to investigate the effect of Knudsen number (Kn) on the micro-scale similarity flow characteristics, a micro-scale hole and another similar scaling-up hole with same length-to-diameter ratio were chosen, with their theroetical hole' diameters of 0.3574mm and 3.6mm, respectively. At the constant Reynolds number (Re), different Kn were chosen to analyze the discharge coefficients of these two holes. Results shows that at the same Re, the discharge coefficients of the two holes are in good agreement with each other while the Kn of these two holes, however, the discharge coefficients don't maintain the same when the Kn are different. As a conclusion, it is necessary to ensure the Kn of the similar scaling-up coupon is the same with the micro-scale coupon when similar scaling-up model is used to investigate micro-scale flow characteristics.
Effect of spirality flow on heat transfer in rotating limited lamilloy
BAI Guo-qiang, CHANG Hai-ping
2014, (8): 1789-1795. doi: 10.13224/j.cnki.jasp.2014.08.005
Abstract PDF(1281KB) icon1503 icon970
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The effect of spirality flow on heat transfer in limited lamilloy was researched by numerical simulation in rotation state. It is found that because of the side wall, the symmetric spirality flow was encased in the rotating limited lamilloy, which can restrain secondary flow produced by Coriolis force, contributing to the heat transfer in rotating limited lamilloy. The centrifugal force and Coriolis force have a significant impact on spirality flow. The impact field of spirality flow decreases with the increasing rotation speed. The heat transfer of rotating limited lamilloy can be increased by designing the length of rotating limited lamilloy reasonably.
Deflagration to detonation transition characteristic in U-bend square tube
WANG Wei, QIU Hua, FAN Wei, XIONG Cha
2014, (8): 1796-1801. doi: 10.13224/j.cnki.jasp.2014.08.006
Abstract PDF(834KB) icon2239 icon868
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To shorten the axial length of detonation tube, a practicable way was used by replacing straight detonation tube with a curve one. A series of two-dimensional numerical simulations were performed in U-bend square tubes, and the effect laws of ignition position, ignition energy, inner radius of bend-section on formation and diffusion of detonation wave were studied. The simulation results show that the deflagration to detonation transition (DDT) time reduces with the increase of inner radius of bend-section; when the inner radius of bend-section is the maximum, the DDT distance is the shortest; the increasing ignition energy means the increasing shock wave strength in detonation tube and the decreasing DDT time; when the ignition position is set at 300mm after the inlet of the detonation tube, the peak pressure of detonation wave is the highest, and the DDT time is the shortest.
Numerical simulation on gas-liquid two-phase detonation combustion induced by shock wave focusing
YANG Qing, LI Zhi-qiang, DI Ya-chao, XU Huan
2014, (8): 1802-1809. doi: 10.13224/j.cnki.jasp.2014.08.007
Abstract PDF(1191KB) icon1602 icon968
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Numerical simulation on gas-liquid two-phase detonation combustion of kerosene-air was conducted induced by shock wave focusing and setting obstacles. The numerical model of gas-liquid two-phase flow was established for the fuel injection, atomization and mixing of pulse detonation engine (PDE) by an Eulerian-Lagrangian formulation. Computational results show that the reflection and focusing of the ring shock wave can ignite the combustible mixture inside the capacity of detonation tube. Re-reflection and focusing of the reflecting shock wave could form higher temperature and pressure points (2700K, 25MPa) near the obstacles, which can lead to local explosion, further generate stable pulse detonation combustion (velocity of 1900m/s, temperature of 2950K) and shorten the length of deflagration to detonation transition (DDT) to 0.45m effectively.
Numerical simulation on infrared radiation characteristics of round to rectangular nozzles with different chevrons considering engine components
LI Wei, ZHANG Bo, WANG Fei, JI Hong-hu, HUA Jia, ZHANG Zong-bin, LUO Ming-dong
2014, (8): 1810-1816. doi: 10.13224/j.cnki.jasp.2014.08.008
Abstract PDF(1067KB) icon1971 icon984
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Considering the impacts of the center cone, lobe mixer, flame holder and afteburner cavity, the round to rectangular nozzle transition from axial symmetry convergent-divergent nozzle was designed, different chevrons were devised and assembled to the nozzle exit. Numerical simulations were carried on the flow, heat transfer and infrared radiation characteristics. The results indicate that the precision of the infrared radiation intensity distributions were more in line with the actual rules by taking the hot components into account. Compared to the basic round to rectangular nozzle, the length of high-temperature regions decrease with multiple small chevrons and further decreasesd with simple large one, individually. Furthermore, the infrared radiation intensity decreases obviously detected from 0 degree. The plume mixing with ambient flow and infrared suppressing characteristics are enhanced in rectangular nozzle with chevrons from axis one. At the same time, it will cause a little thrust lost.
Experimental technique and its validation for heat transfer in cooling channels at high rotation numbers
CHENG Jun-hua, NI Bin, DENG Hong-wu, TIAN Shu-qing, CHEN Hao
2014, (8): 1817-1823. doi: 10.13224/j.cnki.jasp.2014.08.009
Abstract PDF(1191KB) icon1548 icon910
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Based on analysis of cooling channel heat transfer theory and test system optimization, an experimental technology at high rotation numbers with gas pressure in cooling channel higher than 500kPa was developed and implemented. The rotation number and Reynolds number ranged from 0 to 2.08 and 104 to 7×104, respectively, which covered the work parameters of real engine turbine blade. It is found that the effects of Reynolds number and rotation number on heat transfers in cooling channel are able to be separated. Under the condition of the same rotation number, the ratio of cooling channel heat loss and total heat and test error can be reduced to 18% and ±10% respectively in this scenario.
Deviation angle models suitable for wider range of blade profile camber in axial-flow compressor
LIU Bo, MA Nai-xing, YANG Xiao-dong, CAO Zhi-yuan
2014, (8): 1824-1831. doi: 10.13224/j.cnki.jasp.2014.08.010
Abstract PDF(1161KB) icon1703 icon990
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A set of models were selected after studying a series of deviation angle models, and the design deviation angle model was revised. On this basis, a deviation angle model for axial-flow compressor was developed by combining the calculation of S1 flow field. In addition, an off-design deviation angle model was used. The results show that the program for calculating S1 flow field is accurate in a certain incidence angle range. Through verification of a series of cascades, the prediction accuracy of the design deviation angle models is improved, and the error is reduced to 1° no matter the blade profile camber is big or small. The prediction model of axial-flow compressor's design deviation angle is applied to a series of axial-flow compressors, and the error is reduced to 2°. This means that the model is effective.
Algorithm for constructing the line-shape feature point clouds of aero-engine ruled blades
ZHOU Yu, WANG Hao-chen, DU Fa-rong
2014, (8): 1832-1837. doi: 10.13224/j.cnki.jasp.2014.08.011
Abstract PDF(1147KB) icon2181 icon1061
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By means of the surfaces' geometry features, an algorithm for constructing the line-shape feature point cloud was proposed for reverse design of ruled blade surface requiring high accuracy and complex shape in aviation field. On the basis of the quick recognition for boundary of blades' scattered point clouds, the ruled generatrix vector was extracted with the aid of reverse projection method. The annealing algorithm was applied to match boundary point clouds non-rigidly by means of solving multi-objective optimization problem of boundary point clouds. The equal diversion points were constructed to get inerratic-orderly line-shape feature point clouds which were beneficial to generate high quality blade surfaces quickly. The proposed algorithm has great effect in dealing with point clouds of ruled blades and has a certain theoretical significance and application value on surface reconstruction of point cloud of ruled blades surface. The feasibility of proposed algorithm is verified by experiments.
Prediction method of stall margin in axial-flow transonic compressor
ZHONG Yong-jian, TENG Jin-fang, XU Xi, QIANG Xiao-qing, WU Ya-dong, OUYANG Hua
2014, (8): 1838-1845. doi: 10.13224/j.cnki.jasp.2014.08.012
Abstract PDF(1245KB) icon2138 icon955
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Performance of single stage axial-flow transonic compressor Stage 35 of design pressure ratio 1.82 and Stage 37 of design pressure ratio 2.05 at different rotation speeds was presented. Based on the HARIKA program, three models for respectively predicting cascade efficiency, deviation angle and head rise were improved. Two methods for predicting stall margin of axial-flow compressors were used. The first one was separation mass flow prediction method in HARIKA program. The second one was stalling static pressure rise coefficient prediction method proposed by Koch. Good agreement was achieved between the computation results and experiment data. The efficiency error of Stage 35 at design point decreases from 3.9% to 1.5%. The efficiency error of Stage 37 decreases from 3.1% to 1.9%. The minimum error of mass flow of stall margin predicted by two methods is 1.3% and 1.6% respectively. The result indicates that two methods used to predict stall margin are feasible.
Flutter analysis of turbomachinery based on phase lagged boundary condition
YANG Xiao-dong, HOU An-ping, LI Man-lu, WANG Rui, ZHOU Sheng
2014, (8): 1846-1854. doi: 10.13224/j.cnki.jasp.2014.08.013
Abstract PDF(1339KB) icon1834 icon890
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Based on phased lagged boundary conditions, an efficient aerodynamic damping computational model of a transonic compressor rotor with double passage was established. Numerical results of rotor aerodynamic performance, flutter boundary and blade modal analysis were consistent closely with experimental results respectively. The aerodynamic damping results of rotor with different interblade phase angles (IBPA) and first bending mode were calculated using double passage method and conventional multiple passage energy method. The numerical results indicated that the aerodynamic damping attained by double passage method and conventional multiple passage energy method agreed with each other. The efficiency was improved by almost 7.7 times than conventional multiple passage energy method and the memory requirement was about 0.45 times to the conventional method. The aerodynamic damping results for different vibration amplitudes demonstrates that the nonlinear fluid dynamics effects are significant at such a small geometric displacement. Compared with the damping at design point, aerodynamic damping of rotor is reduced at near flutter operation condition, while the minimum aerodynamic damping is gotten at the same interblade phase angle (-42.4 degree).The results show that IBPA has significant influence on the flutter of rotor blades.
Optimization of aspirated airfoil based on artificial bee colony algorithm and NURBS
YANG Xiao-dong, LIU Bo, ZHANG Guo-chen, NA Zhen-zhe
2014, (8): 1855-1862. doi: 10.13224/j.cnki.jasp.2014.08.014
Abstract PDF(1154KB) icon1601 icon1110
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To improve the optimization design quality of aspirated airfoil of axial compressor, an automatic optimization system was developed based on artificial bee colony (ABC) algorithm and non-uniform rational B-splines (NURBS). The mechanism of ABC algorithm was researched and the performance was compared with genetic algorithm (GA) commonly used at present. The comparison indicated that ABC algorithm can obtain better global optimum and the convergence speed was 50% higher than GA. NURBS was applied to parameterize the airfoil and distortion problems in the process were studied. The optimization system was validated by optimizing an aspirated cascade, both parameters of the profile and the suction settings were treated as optimization variables. Results show that the best suction location which could bring the most performance improvement is at about 58.44% axial chord length. 64.8% decrease of the flow loss is obtained if compared with the initial cascade and the separation of the flow is restrained.
Numerical study on effects of blade tip air jet on the flow field of wind turbine blade tip
GAO Xiang, HU Jun, WANG Zhi-qiang
2014, (8): 1863-1870. doi: 10.13224/j.cnki.jasp.2014.08.015
Abstract PDF(1149KB) icon1471 icon854
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In order to design a more suitable wind turbine for the non-grid-connected wind power system, the method of arranging air jet on the blade tip was adopted to change the flow field of blade tip. Orifices were arranged on the top of the blade tip at three chordwise positions. Using the CFD numerical simulation method, the aerodynamic performances and flow field distribution of a wind turbine based model and models with orifices were obtained under different rotating speeds. When the rotating speed was below 1200r/min, all the power growth rates of wind turbine with orifices were almost zero, indicating air jet had no effect on the aerodynamic performance of wind turbines at this range of rotating speed. When rotating speed was higher than 1200r/min, with the increase of rotating speed, the power growth rates of the wind turbine with air jet at middle of the chord raised fast. The air jet affected the pressure distribution on the blade surface of 75% blade height, and the low pressure area on the suction side was larger at high rotating speed. The vorticity of blade tip vortex of the blade with air jet at middle position was lower than the other model. Meanwhile, the dissipation of the blade tip vortex was faster than that of the other model, improving the downstream flow field and the efficiency of the wind turbine. There was no obvious change when the orifice was set at the trailing edge. But for the model with orifice at leading edge, the output power declined, and the wrticity of blade tip vortex is slightly larger than the based model. This conclusion provides the foundation for designing wind turbine applicable for non-grid-connected wind power system.
Optimization design for aspirated compressor airfoil and aspiration plan
LI Jun, LIU Bo, YANG Xiao-dong, SHI Lei
2014, (8): 1871-1877. doi: 10.13224/j.cnki.jasp.2014.08.016
Abstract PDF(1077KB) icon1585 icon823
Abstract:
A method was developed by combining intelligent optimization algorithm and quasi-three dimensional cascade calculation programme, and an aspirated compressor airfoil was optimized using this method. And there was a detailed analysis of changes in the original and optimized flow fields. Optimized airfoil can make the total pressure loss reduce by 40% and the static pressure ratio increase by 0.6%.The best suction position locates in upstream the start position of the separation region, and the optimized airfoil has more uniform load distribution. In addition, the performance of optimized airfoil has a great improvement within the whole incidence angle range. The results show that more uniform load distribution can improve the airfoil performance, decrease the separation region and reduce the energy output on suction. For the airfoil with a small separation region in trailing edge, the best suction location is located upstream the start position of the separation region.
Overview of several ice accretion effects on aircraft flight dynamics
SU Yuan, XU Zhong-da, WU Zhen-long
2014, (8): 1878-1893. doi: 10.13224/j.cnki.jasp.2014.08.017
Abstract PDF(1436KB) icon1858 icon902
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An overview of the studies about several ice accretion effects on aircraft flight dynamics was presented here. Special attention was paid to the following areas: the way to obtain the aerodynamic data of iced aircraft, the flight dynamic modeling and simulation of iced aircraft, the effect of ice accretion on the stability and handling quality characteristics as well as the flight performance. Based on the progress of existing research in these areas, some key issues deserving more attention of the researchers for resolution are addressed, including: obtaining the aerodynamic data of iced aircraft through numerical simulation method, consummating the calculation model of effects of ice accretion on aircraft aerodynamic derivatives and enhancing the investigation on stall problems of tailplane. The simulated ice wind tunnel, numerical simulation method, stall of tailplane should be further studied and more test data should be obtained in the future.
Strongly coupled RANS algorithm for simulating hovering rotor flow
JI Chang-rui, YANG Xiao-quan, YANG Ai-ming, SI Jiang-tao, LIU Pei-qing
2014, (8): 1894-1903. doi: 10.13224/j.cnki.jasp.2014.08.018
Abstract PDF(1499KB) icon2122 icon892
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In the rotating coordinate system, Reynolds-averaged Navier-Stokes (RANS) equations and Spalart-Allmaras (S-A) equation model were coupled as a new strongly coupled RANS equation, then a strongly coupled RANS algorithm based on overlap grids was proposed and applied to simulate helicopter rotors viscous flow in hover. In order to improve efficiency, a new implementation method of multigrid algorithm based on overset grids was proposed for solving the difficulty of implementation in chimera grids system. The effectiveness of strongly coupled RANS method and the proposal of multigrid algorithm based on chimera grids was verified using Caradonna-Tung (C-T) and ONERA 7A hover test cases. The results show that the proposal of multigrid algorithm based on overlap grids has much higher efficiency, and the speed up ratio of three-level multigrid is about 7.7; the accuracy of strongly coupled RANS algorithm is super higher than loosely coupled RANS algorithm, especially in the prediction of performance parameters relevant to drag force.
Applicability investigation about several common schemes and turbulence models in high speed flow
SHI Lei, YAN Ming, YANG Yun-jun, ZHOU Wei-jiang
2014, (8): 1904-1910. doi: 10.13224/j.cnki.jasp.2014.08.019
Abstract PDF(1263KB) icon1404 icon961
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Several common spatial dispersion schemes and turbulence models in current computational fluid dynamics were compared and analyzed to investigate complex flow phenomenons such as strong shock waves, shock waves/boundary layer interaction, flow separation and turbulent flow in hypersonic flight. The results demonstrate that the resolutions of strong shock waves are the same by different schemes. Roe and LDE (low diffusion E-CUSP (convective upwind split pressure)) schemes show better agreement in friction coefficient and heat transfer coefficient with experimental data than other schemes. The friction coefficient predicted by S-A (Spalart-Allmaras) turbulence model is greater than that by k-ω SST (shear stress transport) turbulence model about 10%. The separation zone of the latter is twice the size of the former and the separation point is located in front.
Radar cross section characteristics of rotor based on computational electromagnetics method
JIANG Xiang-wen, ZHAO Qi-jun
2014, (8): 1911-1921. doi: 10.13224/j.cnki.jasp.2014.08.020
Abstract PDF(1726KB) icon1202 icon897
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By taking Maxwell's equations as the governing equations, and employing four-stage Runge-Kutta method for the temporal discretization and Steger-Warming flux splitting scheme for the spatial discretization, the MUSCL(monotonic upstream-centered scheme for conversation laws) scheme was used to calculate the flux, and a numerical methodology for simulating the RCS(radar cross section) of rotor based on finite volume time domain method was developed. The O-type body fitted and orthogonal grid around rotor was generated using algebraic method. It has been demonstrated that the method is effective to simulate the RCS of the rotor. Firstly, calculations on RCS of rotor and airfoils about the polarization, angle of incidence and size have been conducted emphatically. Secondly, the influences of RCS on geometries of rotor airfoil have been investigated. Finally, the stealth of rotor airfoil has been obtained through linear weighted sum method. The results show that the RCS envelop of the rotor is represented by a continuous and oscillating area of strong scattering. The maximum radar detection range of the three blades rotor is 82.2% of the two blades rotor, helpful to control the maximum scattering peak. In four important scattering angle domains, the maximum radar detection ranges of HH02 rotor airfoil are 105.1%, 99.4%, 86.6% and 83.5% of NACA0012 airfoil, respectively, and the radar stealth performance of HH02 rotor airfoil is the best.
Effect of active blade pitch control on helicopter rotor performance
WANG Chao, LU Yang, CHEN Ren-liang
2014, (8): 1922-1929. doi: 10.13224/j.cnki.jasp.2014.08.021
Abstract PDF(1382KB) icon1541 icon889
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In order to find out the influence rule and the essence of the effect of active blade pitch control on helicopter rotor performance, a rotor aerodynamic model was built firstly in consideration of the impact of second order harmonic blade pitch control, and then corresponding helicopter flight dynamic model was established. Rotor power was taken as the evaluation basis to investigate the effect of second order harmonic blade pitch control on rotor performance in trimming conditions. For the sample helicopter, the rotor power obtained with any second order harmonic blade pitch control increases when advance ratio is 0.2; 5% rotor power reduction can be achieved by second order harmonic blade pitch control with amplitude of 1.5° and initial phase of 90°when advance ratio is 0.35. By analyzing the distribution of angle of attack and drag coefficient on rotor disc of sample helicopter, the essence of using second order harmonic blade pitch control to improve rotor performance was summarized: in the high speed and high load status, an appropriate second order harmonic blade pitch control can improve the distribution of angle of attack on rotor disc, and delay the occurrence of retreating blade stall, thus decreasing the rotor power eventually and improving the rotor performance effectively.
Adaptive artificial viscosity entropy stable scheme for hyperbolic conservation laws
REN Jiong, FENG Jian-hu, LIANG Nan, LIU You-qiong
2014, (8): 1930-1939. doi: 10.13224/j.cnki.jasp.2014.08.022
Abstract PDF(1535KB) icon1521 icon886
Abstract:
The entropy stable conditions may not be met if entropy conservation schemes are used to solve the equations of hyperbolic conservation laws. To achieve entropy stability, the total entropy of a numerical scheme must be dissipative. The frequently-used method is to add a viscosity mechanism to an entropy conservative scheme. By considering the change characteristics of the size of adaptive artificial viscosity in different parts of the computational domain, a new simple entropy stable scheme was proposed by combining the flux of entropy conservation with the corrected flux of adaptive artificial viscosity. According to the adaptivity of adaptive artificial viscosity, this scheme can achieve the overall high resolution without using any limiters but adjusting the viscosity proportional coefficients C. So the computed solution was stable at its discontinuous parts with enough numerical dissipation while maintaining the high order accuracy at smooth parts with very small viscosity. At the end, several numerical examples were performed to analyze the characteristics of the proposed scheme with reference to the numerical results of entropy stable ERoe scheme and high resolution entropy stable EYee scheme.
Dynamic analysis of rotor-ball bearings system based on elasto-hydrodynamic lubrication with rubbing-misalignment coupling fault
ZHANG Jun-hong, MA Liang, MA Wen-peng, WANG Jun, BA Lin, LI Shu-ming
2014, (8): 1940-1952. doi: 10.13224/j.cnki.jasp.2014.08.023
Abstract PDF(1730KB) icon2104 icon1061
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Dynamic responses of rotor-ball bearing system with elasto-hydrodynamic lubrication (EHL) under rubbing-misalignment coupling faults were studied. Nonlinear dynamic differential equations of rotor-ball bearing system with rubbing-misalignment coupling faults based on EHL and Hertz theory were established. The system equations are numerically integrated to obtain the vibration responses by Runge-Kutta method. Compared with the dynamic characteristics of the rotor system of aero-engine, these were verified through the experimental data. The results show that: (1)Consideration of EHL theory has greatly affected the single rubbing fault system. The onset rotating speed of quasi-periodic to 2-periodic of system with consideration of EHL theory increases more obviously than that without EHL theory, and the rotating speed range of 2-periodic is wider than that without EHL theory. (2) Consideration of EHL theory has greatly affected the rubbing-misalignment coupling fault system. The onset rotating speed of 2-periodic to quasi-periodic increases more obviously than that without EHL theory. (3)By comparing the calculation results with experiment results, it's found that the vibration response at the half and double fundamental frequency of the coupling fault system are weaker than that without EHL theory. The model considering the EHL theory is more accurately to reflect the vibration characteristics of the coupling faults rotor system.
Vibration reduction optimization design for parameterized composite blade
CHEN Kun, LIU Yong, ZHANG Cheng-lin, NI Xian-ping
2014, (8): 1953-1960. doi: 10.13224/j.cnki.jasp.2014.08.024
Abstract PDF(1036KB) icon1681 icon940
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For blade dynamics optimization design, a parametrization model of composite multi-cell C-type blade section was estabished for engineering design. The parameterized design of aerodynamic shape of the blade section, the internal structure of components and composite material layer was implemented, and a parameterized method capable of maintaining a constant C-type beam fiber area was presented. Then in combination with the composite blade parameterization model and aero-elastic analysis model, the optimal parameters of blade sections could be obtained to reduce the hub vibration via the optimal process based on multi-population genetic algorithm(MPGA). The "Dolphin" helicopter's blade profile modeling and performance calculation contrasts were given, with total error less than 3%. With use of the blade parameterization model of blade for rotor dynamic optimization, the results show that the rotor's weighted optimizaton vibration load coefficient decreases by 4.15%, and the balance weight of blade is more smooth after optimization, helping to ease the blade internal stress/strain mutation; some balance weight assigned to the blade tip can increase the rotation inertia of the rotor, and improve the safety for autorotative glide.
Dynamics and reliability for rubbing rotor considering the characteristic of parameter’s random distribution
YANG Le-chang, ZHANG Jian-guo, SUN Jing, HAN Jian-chao
2014, (8): 1961-1967. doi: 10.13224/j.cnki.jasp.2014.08.025
Abstract PDF(1302KB) icon1445 icon912
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A kind of modified Jeffcott rotor/stator system was studied, both stability characteristic and reliability characteristic were analyzed while considering the influence of parameter's random distribution. A reliability formula was deduced as well as the reliability index of 0.95 is calculated by using the FORM (first order reliability method) and CMC (Crude-Monte-Carlo) method respectively. In addition, the boundary of rubbing problem is determined due to the reliability requirement. Furthermore, the effects of various parameters on the rotor steady-state response and security domain were discussed as well as the sensitivity of parameters also been considered. Finally, the solution of general rotor/stator rubbing problem is derived in the space of three parameters(coefficient of friction, speed and clearance) corresponding to the specific requirement in practice.
Method of confirming prior parameters value during complexity equipment system testability evaluation with small sample
ZHANG Xi-shan, HUANG Kao-li, YAN Peng-cheng, LIAN Guang-yao, WANG Shao-guang
2014, (8): 1968-1973. doi: 10.13224/j.cnki.jasp.2014.08.026
Abstract PDF(1087KB) icon1440 icon917
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In order to overcome non-standard prior information processing and poor result credibility during the testability evaluation under small sample test, the method of confirming system testability prior parameters value from expert experience information, subsystem testability information and virtual simulation information was investigated. The testability parameters' prior value was estimated by the weighted fuzzy uncertainty method, subsystem data conversion and Dempster-Shafer (D-S) evidence fusion method based on the similarity measure respectively, according to different kinds of testability prior information. The example analysis shows that the prior parameters value during testability evaluation by the proposed method are lower than that of methods from literatures about 0.8%.
Fault processing policy based on dual-redundant control law for aero-engine control sensors
JIANG Cai-hong
2014, (8): 1974-1980. doi: 10.13224/j.cnki.jasp.2014.08.027
Abstract PDF(863KB) icon1261 icon804
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A fault processing policy was proposed for the circumstance under which all the dual-redundant closed-loop feedback control sensors went wrong. This policy was based on dual-redundant control law and may maintain the performance of turbofan engines. When pair of controlling sensors went wrong and the primary control law was unable to implement, control system performs the backup control law instead of the primary one so that the fault sensors were isolated from the closed control loop. This fault processing policy may not only avoid increasing engine weight and cost with the additional sensors hardware, but also avoid the error of analytical sensor signal. It can improve the engine mission reliability and control quality.
Multi-objective optimization design of slipper film in aero-engine fuel piston pump
XU Pei-pei, YE Zhi-feng, WANG Bin
2014, (8): 1981-1986. doi: 10.13224/j.cnki.jasp.2014.08.028
Abstract PDF(1069KB) icon1829 icon861
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Spherical swash plate axial piston pump with conical cylinder was taken as research object, the friction power loss, leakage power loss and volumetric efficiency with the change of slipper mechanical structure parameters in slipper film design was analyzed, then the genetic algorithm was used for the multi-variable multi-objective optimization problem. Weighting coefficient optimization results show that after optimization the friction power loss and leakage power loss of the fuel piston pump in design point reduce by about 7%, the volumetric efficiency improves slightly.And the optimized parameters of mechanical structure also show a performance advantage in the cases of different rotor tilt angles and plungers. Thus this proves the multi-objective genetic algorithm is an effective method for the design of hydrostatic pressure lubrication film in aero-engine fuel piston pump.
Modeling method of bearing chamber oil/air two-phase flow under multi-geometrical conditions
SUN Heng-chao, CHEN Guo-ding, CHEN Bo
2014, (8): 1987-1995. doi: 10.13224/j.cnki.jasp.2014.08.029
Abstract PDF(1518KB) icon1743 icon829
Abstract:
The similarity of oil/air two-phase flow in aero-engine bearing chambers was derived according to the basic theorems of thermodynamic and fluid dynamic firstly, the similarity criterion numbers such as Froude number, Euler number, Reynolds number, Prandtl number and Eckert number were obtained, then the model of aero-engine bearing chamber oil/air two-phase flow was built under multi-geometrical and operating conditions following the principle of system similarity. The oil/air two-phase flow fields of prototype and modeling bearing chambers were solved by numerical simulation, and the better consistency of flow fields dimensionless physical characteristic parameters, such as dimensionless tangential velocity, temperature and pressure between prototype and modeling bearing chambers, illustrates that the similarity criterion numbers and modeling method of aero-engine bearing chamber oil/air two-phase flow proposed are reliable. The proposal modeling method has certain reference value for guiding experiment design of bearing chamber oil/air two-phase flow as well as promoting the shift of theory investigation to engineering application of aeroengine lubrication system design.
Denoising method for electrostatic monitoring signal of roller bearing based on spectrum interpolation and difference spectrum of singular value
ZHANG Ying, ZUO Hong-fu, TONG Pei-sheng, CHEN Zhi-xiong, BAI Fang
2014, (8): 1996-2002. doi: 10.13224/j.cnki.jasp.2014.08.030
Abstract PDF(1155KB) icon1690 icon845
Abstract:
Electrostatic sensor was implemented in roller bearing experiment investigation to monitor defects. In consideration of various strong noises involved in the electrostatic monitoring of roller bearings and the difficulty to obtain defect characteristics, a united denoising method was put forward based on spectrum interpolation and difference spectrum of singular value. Firstly, the spectrum interpolation was used to eliminate the power line interference; then the resultant signal was used to construct Hankel matrix; the number of useful components was automatically selected based on the difference spectrum of singular value, and finally the signal was reconstructed. Simulation and practical experiments show that the useful components of the signals involving high power line interference cannot be extracted by performing difference spectrum of singular value method or the wavelet denoising method; the presented denoising method can highlight the defect characteristic frequency in early stage more effectively than the spectrum interpolation and wavelet denosing method.
Classification of corner vortex shedding in solid rocket motor
ZHANG Xiang-yu, HE Guo-qiang, LIU Pei-jin
2014, (8): 2003-2011. doi: 10.13224/j.cnki.jasp.2014.08.031
Abstract PDF(1341KB) icon1778 icon858
Abstract:
A test motor named C1x was numerically simulated by the three-dimensional large eddy simulation (LES) method to study the acoustic-vortex coupling caused by corner vortex shedding. The results show that three-dimensional LES method obtains more accurate result on corner vortex shedding motion and lock-on characteristic than the two-dimensional LES and the axisymmetric LES. Two types of the corner vortex shedding are determined according to whether an acoustic feedback cycle is formed in the chamber. One type of the corner vortex shedding causes the acoustic-vortex formation feedback cycle (named 1st vortex shedding), and the other is dissipated during convecting downstream (named 2nd vortex shedding). Step expansion ratio and aspect ratio upstream and downstream the step of combustion are the important parameters for summarizing the corner vertex shedding type.
Notch strength and notch sensitivity of double base propellant
HU Shao-qing, JU Yu-tao, WEI Zhen, ZHOU Chang-sheng
2014, (8): 2012-2016. doi: 10.13224/j.cnki.jasp.2014.08.032
Abstract PDF(829KB) icon1332 icon871
Abstract:
To obtain the notch strength and notch sensitivity of double base propellant, uniaxial tensile tests on the double-edge U-notched thin plate specimens and standard specimens were carried out under the strain rate of 10-4s-1 at (20±1)℃.Results show that the stress concentration factor of notched specimens has a significant effect on the notch strength within certain limits. When the stresscon centration factor is less than the notch sensitivity factor (1.99~2.22), the notch strength of double-edge U-notched thin plate specimans is approximately equal to its fracture strength and independent of the stress concentration factor. This indicates that the double base propellant is insensitive to notch in this case. The uniaxial tensile test results of standard specimens is used to predict the value of the notch strength and notch sensitivity factor of double base propellant, and the predictions are consistent with the test results of the notched specimens proving the validity of this prediction method.

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