2015 Vol. 30, No. 2

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Numerical study of flapping wing/tail aerodynamic interaction for flapping wing micro air vehicle
WANG Yan-gang, CHEN Wei-xiong, DENG Shuang-hou, ZHAO Xu-min
2015, 30(2): 257-264. doi: 10.13224/j.cnki.jasp.2015.02.001
Abstract PDF(985KB) icon2165 icon1265
Abstract:
Taking the two-dimensional rigid flapping wing micro air vehicles model as research object, the aerodynamic characteristics of both single wing and tandem wing configurations were numerically evaluated. The numerical analysis methodology was transient and based on the dynamic grid technology. Simulation was conducted on the influence of reduced frequency of tandem wing, flapping wing to tail dimensionless horizontal distance and angle of attack on the aerodynamic performance. Results show that: (1) The tail of tandem wing is beneficial to the overall aerodynamic performance. Compared with the single wing configuration, the thrust coefficient and propulsive efficiency of tandem wing configuration are increased by 28.7% and 5.7% when the flapping wing to tail dimensionless horizontal distance is half of the wing length, respectively. (2) Reduced frequency is the key parameter that significantly influences the thrust. The higher reduced frequency strengthens the vortex-shedding and then results in an increase in thrust coefficient. The propulsive efficiency of single and tandem wings approaches maximal value when reduced frequency is about 1.0. (3) For the tandem wing configuration, the propulsive efficiency is optimized when the wing to tail flapping dimensionless horizontal distance is 1.1. (4) As the angle of attack increases from 0 degree to 20 degree, the lift coefficient increases and the thrust coefficient decreases. The flapping wing of the two configuration is predominated by drag at the moment angle of attack being 9 degree.
Image distortion calibration method of round nozzle based on ZEMAX software
YUE Mao-xiong, XIE Feng, BAI Han-chen, ZHANG Long, YUAN Qiang
2015, 30(2): 265-270. doi: 10.13224/j.cnki.jasp.2015.02.002
Abstract PDF(902KB) icon1773 icon1016
Abstract:
It is significant that the flow field has been visualized accurately for understanding and controlling it within a round nozzle, and the accurate visualization can validate the results of numerical calculation. Therefore, firstly, reduction of effective view field from image distortion because of the thickness of round nozzle was revised. Cylindrical lens were added outside round nozzle for calibrating distortion. Design of the cylindrical lens was introduced to calculate the foci of thickness lens and optimize it by ZEMAX software. Static state experiments indicate that the effective view field is increased from less than 30% to more than 80%. Secondly, it was supposed the refractive index as 1 and the spreading ray as parallel ray within round nozzle during calibrating design. Analysis indicates the effect of these supposes is small for some flow fields of high-temperature and high-pressure. Thirdly, the feasible methods for flow field visualization were analyzed, and the dynamic results were given. At last, feasibility of the calibration method and the limitation to quantitative interferometry were pointed out. The research is of reference signification to flow field of combustion in round nozzle.
Parameter design method of double juxtaposition 3-D asymmetric several-S-shaped nozzles
WEI Yong-bin, AI Jun-qiang
2015, 30(2): 271-280. doi: 10.13224/j.cnki.jasp.2015.02.003
Abstract PDF(1115KB) icon1345 icon1060
Abstract:
A suit of parameter design methods of double juxtaposition 3-D asymmetrical several-S-shaped nozzles based on CFD numerical simulation technology was estabished, and the exactitude and feasibility of the parameter design methods were approved primarily. The several-S-shaped centerline on the condition of Z direction eccentricity angle of 0: Y direction eccentricity angle and location parameter L of the first S curve are smallest,and the two parameters of the second S curve are biggest. The two parameters of the third S curve are between the biggest and the smallest of the pre two S curves. Every S curve uses the law which turns slowly at inlet, but quickly at outlet to favor controlling the airflow separation and turbulence of the leeward. The section uses the law which shrinkages quickly and turns slowly at inlet, but shrinkages slowly and turns quickly at outlet,and the aspect ratio and the side obliquity varies at the same rate at inlet and outlet. The side obliquity only distributes on the first S curve to favor stabilizing fluid flow and increasing stealth performance. Confluence implement uses wedge fundus/highness aspect ratio restriction, and it should not exceed 0.26.
Numerical investigation of hypersonic curved shock sidewall compression inlet
ZHANG Lin, ZHANG Kun-yuan, WANG Lei, WANG Yuan
2015, 30(2): 281-288. doi: 10.13224/j.cnki.jasp.2015.02.004
Abstract PDF(1053KB) icon1584 icon1058
Abstract:
Curved surface compression system with wall Mach number linear distribution was used to improve the topwall of the reference sidewall compression inlet, then curved shock sidewall compression inlet was obtained and Compared with the reference sidewall compression inlet. The numerical result shows that: the wall Mach number distribution of topwall with curved surface is consistent with the given Mach number distribution at the design and inviscid condition, and its wall pressure distribution is basically the same as that of two-dimensional curved surface at viscous condition. Compared with the reference sidewall compression inlet, when the topwall used curved surface compression, its wall pressure distribution was improved to a certain extent, and the pressure gradient at the end of surface changed smoothly. And the performance of off-design condition is improved effectively; especially the mass flow capture ratio increases 6% and reached 0.799 at inflow Mach number of 4, and the total pressure recovery of throat section increases 1.9%. At inflow Mach number of 5, its mass flow capture ratio increases 5.2% and reached 0.909, and the total pressure recovery of throat section increases 3.2%. With the increase of the angle of attack, the inlet's ability of capturing mass flow improved and the flow field distortion of isolator exit section decreased. But the total pressure recovery of throat section decreased sharply.
Research on inlet distortion under crosswind for civil aircraft
LIU Kai-li, SUN Yi-feng, ZHONG Yuan, ZHANG Kun-yuan, ZHANG Hui-liu
2015, 30(2): 289-296. doi: 10.13224/j.cnki.jasp.2015.02.005
Abstract PDF(1057KB) icon2253 icon1533
Abstract:
The inlet aerodynamic performance of distortion under crosswind for a high bypass ratio turbofan engine was numerically simulated to meet the need of civil aircraft engine/airframe integration. The flow characteristics and their underlying flow physics were investigated. The investigation suggests that: typical flow phenomena of separations, reattachments and ground vortex are found to be the root causes for the inlet distortion under crosswind; there is a sudden intensification in the distortion index as the onset of the inlet internal flow is separated with the increasing speed of crosswind; the civil aircraft inlet tolerance of crosswind would be reduced as the nacelles are affected by the ground vortex phenomenon; the distortion characteristics of civil aircraft inlet are also affected by the engine massflow, whilst the hysteresis loop of the distortion index is captured for the flow separation and reattachments are not exactly repeatable as the engine corrected mass flow rates vary.
Influence of key design parameters on aerodynamics performance of cycloidal propeller
TANG Ji-wei, HU Yu, SONG Bi-feng
2015, 30(2): 297-305. doi: 10.13224/j.cnki.jasp.2015.02.006
Abstract PDF(1300KB) icon1462 icon1101
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The two-dimensional cycloidal propeller model was simplified from a cycloidal propeller aircraft developed by Northwestern Polytechnical University. The dynamic mesh method of spring-based smoothing and local remeshing was adopted to achieve blades' rotating and pitching movement in the unsteady numerical simulation. The influence of the key design parameters on aerodynamics performance of cycloidal propeller was researched. The result shows that, the aerodynamics efficiency of hovering status is found higher with the increase of blade number; when the airfoil thickness increases, the thrust level is higher while the aerodynamics power is lower; the aerodynamics efficiency of hovering status and power loading reach highest when the pitching axis is located at middle chord length of blade; when the maxium pitching angle is higher, the aerodynamics power becomes larger and aerodynamics efficiency of hovering status is lower; and when the sum of maxium pitching angle at top position and maxium pitching angle at bottom position is constant, the thrust, aerodynamics power and aerodynamics efficiency of hovering status are higher if the maxium pitching angle at top position is small.
Effect of slot orientation on synthetic jet-based separationcontrol in a serpentine inlet
HE Peng, DONG Jin-zhong
2015, 30(2): 306-314. doi: 10.13224/j.cnki.jasp.2015.02.007
Abstract PDF(1142KB) icon1607 icon1081
Abstract:
A numerical study was conducted to investigate synthetic jet-based boundary layer separation control in a serpentine inlet. Rectangular slots were chosen in this study, spanwise and streamwise orientations of these slots were discussed in detail. The results illustrate streamwise oriented synthetic jet has a higher resistance to the adverse pressure gradient. It penetrates deeper and exhibites stronger persistence than spanwise case as well. When jet momentum coefficient is equal to 1.62×10-3, and the characteristic frequency is 1, separation length is reduced by 38.39% relative to uncontrolled flow field. The performance of serpentime inlet using streamwise oriented synthetic jet are also superior to spanwise case. Outlet pressure coefficient is increased by 158.91%; total pressure recovery coefficient is increased by 0.71%, and total pressure distortion coefficient is reduced by 56.75%.
Flux splitting DSMC-IP method in near space hypersonic flow field
XU Xiao, WANG Xue-de, TAN Jun-jie
2015, 30(2): 315-323. doi: 10.13224/j.cnki.jasp.2015.02.008
Abstract PDF(1168KB) icon2114 icon1004
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According to the characteristics of the hypersonic flow field in near space, the computational format of the mass equation of direct simulation Monte Carlo-information preserve (DSMC-IP) method was improved by the Van Leer scheme. The local Mach number was set as the standard of the flux splitting, and the transport fluxes on both sides of the cell interfaces were reconstructed. So the computational format has the characteristic of the flux splitting, and the application problems of the DSMC-IP method in hypersonic flow field were solved. The two-dimensional hypersonic flow field in near space was simulated by the improved flux splitting DSMC-IP method with unstructured grid. The solution of computation by the flux splitting DSMC-IP method has good agreement with the results of experiment and reference value, and the statistics dissipation of direct simulation Monte Carlo (DSMC) method was reduced significantly. When the flow becomes more rarefied, the non-equilibrium effect becomes more obvious. In this situation the results of flux splitting DSMC-IP method differs within 10% from the reference values, so the characteristic of the flow field is well reflected in non-equilibrium situation. The results prove the feasibility and validity of the flux splitting DSMC-IP method.
Experiment of noise reduction in separate flow system using chevron nozzles
HE Jing-yu, SHAO Wan-ren, XU Ying-bo, LI Xiao-dong
2015, 30(2): 324-330. doi: 10.13224/j.cnki.jasp.2015.02.009
Abstract PDF(985KB) icon1426 icon1152
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The noise reduction characteristics of chevron nozzles was investigated in separate flow system. All the experiments were carried out on the jet noise rig in the anechoic chamber. The effect of the structural parameters and distribution of chevron nozzles on cold jet noise reduction was explored in which shear velocity ratio was 0.92. The results show that chevron nozzles reduce jet noise at low frequencies, but increase jet noise at high frequencies. Besides, chevron nozzles has a best low-frequency noise reduction at downstream with lowest high-frequency noise penalty. The noise is decreased at the low frequencies and the peak noise reduction is 5dB when penetration angles of chevron nozzles are increased. The chevron nozzle only on fan has a good low frequency noise reduction and an ability of noise suppression at high frequencies. Although slight differences are observed with varying number of chevron, it seems that the effect is less significant than that of the penetration angles. The sound pressure level downstream is reduced significantly by chevron nozzles.
Comparison of trapped vortex cavity with/without injection in annular central bluff-body trapped vortex combustor
HAN Ji-ang, LI Xiao-dong, ZHONG Jing-jun
2015, 30(2): 331-340. doi: 10.13224/j.cnki.jasp.2015.02.010
Abstract PDF(1591KB) icon1793 icon1037
Abstract:
The three dimensional Reynolds-averaged Navier-Stokes (N-S) equations, renormalization group (RNG) k-ε turbulent model and standard wall functions were adopted to numerically simulate the cold flow field of annular central bluff-body trapped vortex combustor under trapped vortex cavity with/without injection. The effects of trapped vortex cavity with/without injection on the vortex structure, flow parameters in the trapped vortex cavity and the overall performance of the annular central bluff-body trapped vortex combustor were analyzed. Results show that a relatively stable double vortex structure can be formed in the trapped vortex cavity with trapped vortex cavity injection compared to trapped vortex cavity without injection. With the existence of trapped vortex cavity injection, the total pressure loss coefficient of the annular central bluff-body trapped vortex combustor is reduced about 9.2% at the exit section and the average flow parameters of the trapped vortex cavity also increase. The trapped vortex cavity injection has little influence on changing trend of flow parameters along flow-path height direction at the exit section of the annular central bluff-body trapped vortex combustor.
Correlation analysis of energy and stress distributions on variable thickness turbine disk
DING Shui-ting, WANG Zi-yao, LI Guo
2015, 30(2): 341-348. doi: 10.13224/j.cnki.jasp.2015.02.011
Abstract PDF(993KB) icon1239 icon1007
Abstract:
A segmented theoretical method was proposed to derive the temperature and stress distributions of a variable thickness turbine disk under given heating energy on the inner and outer rims, and the correlation between the energy distributions presented by the energy transfer coefficient, and the temperature/stress distributions of the turbine disk was established. By applying the correlation to an aero-engine low pressure turbine disk and comparing the temperature and stress distributions with those obtained from numerical simulation, the results from these two methods show a good agreement; the relative deviations of the temperature and stress distributions are no more than 2% and 13%, respectively; under constant boundary heat flow condition, the temperature of the inner rim increases while that of the outer rim decreases; both the overall equivalent stress level and the maximum equivalent stress of the turbine disk decline with the increase of the energy transfer coefficient. The above results validate that the correlation between the energy and stress distributions obtained from the segmented theoretical method proposed is feasible and correct.
Heat conduction loss correction of thin-skin calorimeter on back surface for state-variable measurement
YANG Qing-tao, BAI Han-chen, LIU Ji-chun
2015, 30(2): 349-355. doi: 10.13224/j.cnki.jasp.2015.02.012
Abstract PDF(990KB) icon1353 icon965
Abstract:
A heat conduction loss correction method of thin-skin calorimeter under state-variable conditions based on energy balance principle was presented to meet the requirements for scramjet pulse combustion tests. Then thin-skin calorimeter was numerically simulated and verified in a test, and the measurement results with/without correction were compared and analyzed. Finite element analysis showes that the method can compensate the heat conduction loss on the back surface, and the measurement errors of the heat flux with correction are not greater than 4%, while those without correction are not less than 20% for the numerial examples. Thin-skin calorimeter and coaxial thermocouple were used in scramjet pulse combustion test to measure the surface heat fluxes at the same axial positions of the axsymmetric model. In cold-state test, the relative deviation between the heat flux results is -11.2% without correction using thin-skin calorimeter and using coaxial thermocouple, and is 3.3% with correction. Hot-state test results indicate that oscillation combustion occurs during the test, and the thin-skin calorimeter used in the test can not reflect change of the combustion states because the response time of the thin-skin calorimeter is about 0.02s, which is close to the oscillation period (about 0.03s).
Experiment on lean blowout performance of triple axial swirler combustor
DING Guo-yu, AN Bo-kun, HE Xiao-min, ZHAO Zi-qiang, JIN Yi, XUE Chong
2015, 30(2): 356-361. doi: 10.13224/j.cnki.jasp.2015.02.013
Abstract PDF(864KB) icon1915 icon838
Abstract:
Experiments were conducted to study the lean blowout (LBO) performance of triple axial swirler combustor at different inlet airflow velocities, inlet airflow temperatures, triple axial swirler rotational direction combinations and airflow mass flow rate distributions. The results show that: the lean blowout fuel-air ratio (LBO FAR) of triple axial swirler combustor decreases with increasing inlet airflow velocity and inlet airflow temperature, and inlet airflow temperature has great effect on LBO performance; the LBO performance of scheme with rotational direction combination of counterclockwise-counterclockwise-clockwise is improved by about 50% compared with that of clockwise-counterclockwise-clockwise at the same inlet airflow velocity; the LBO FAR decreases to a little extent when the inner swirler airflow mass flow rate decreases.
Aerodynamic characteristics analysis of eccentric drum basedon three-dimensional model
CHEN Lu-miao, WANG Hong-yu, QIN Zhao-ye, CHU Fu-lei
2015, 30(2): 362-367. doi: 10.13224/j.cnki.jasp.2015.02.014
Abstract PDF(1055KB) icon1297 icon852
Abstract:
In order to obtain the pressure distribution inside the cavity of drum with labyrinth seal, and understand its aerodynamic characteristics, a three-dimensional model of the flow field channel of drum with labyrinth seal was developed, and the static pressure on the surface of drum with and without eccentricity between the drum and the stator was calculated. Then, the mechanics characteristics of drum under aerodynamic loads was analyzed. The simulation results show that different eccentricities complicate the surface static pressure, and change the circumferential static pressure amplitudes obviously. The amplitude of static pressure with the largest eccentricity increases 3 times compared with that without eccentricity. The maximum fluctuation of drum stress amplitude caused by circumferential static pressure considering eccentricity is about 3%.
Numerical simulation of runback film breakup on two-dimensional anti-icing airfoil surface
BU Xue-qin, MA Wen-tao, LIN Gui-ping
2015, 30(2): 368-375. doi: 10.13224/j.cnki.jasp.2015.02.015
Abstract PDF(990KB) icon1156 icon842
Abstract:
In order to accurately estimate the heat-load of the anti-icing system of airfoil, the numerical simulation of runback flow state on the two-dimensional anti-icing airfoil surface was presented. Based on shear-driven model, the velocity distributions before and after film breakup were derived respectively. By introducing the minimum energy criteria, the rivulet model was established, and the critical thickness of film breakup was solved by numerical method. By using the user defined function method in Fluent software to program and load the calculation procedures, the flow characteristics of runback flow were obtained based on film model and rivulet model respectively. The results indicate that, under a certain icing condition, the ranges of the runback flow increase by 33% and 17% in two different examples respectively due to the rivulet model, thus largely affecting the distribution of the heat-load of the anti-icing system.
Visualization experiment on film distribution characteristics of shaped film holes based on thermochromic liquid crystal
WU A-sai, ZHU Hui-ren, LIU Cun-liang, HE Yi-hong, LU Cong-ming, ZHANG Cong-xiao
2015, 30(2): 376-383. doi: 10.13224/j.cnki.jasp.2015.02.016
Abstract PDF(1254KB) icon1262 icon864
Abstract:
Black nylon net coated with thermochromic liquid crystal was set at different locations downstream the film holes. The film distribution of cylindrical hole, water-drop hole and fan-shaped hole were visualized according to the colorful dimensionless temperature images on the nylon net under three blowing ratios of 0.5, 1 and 2. Results show that the stream-wise expansion of film hole weakens the exit mean momentum and intensity of kidney eddies slightly, so the coverage area and thickness of film are increased. The lateral expansion greatly improves the film coverage area and attachment performance by decreasing the intensity of the kidney eddies, exit mean momentum and film thickness and increasing the velocity in the spanwise direction. High blowing ratios make the film lift off the wall and decrease the film coverage aera. In addition, the interaction of jets issued from adjacent holes of film holes row has the effects of pressing the film towards the surface, making the cooling and coverage performance of film holes row better than that of an individual film hole.
Control method of inlet turbulent intensity in rotating channel and validation
WU Xue-wang, SUN Ji-ning, ZHANG Chuan-jie, JIN Zhao
2015, 30(2): 384-391. doi: 10.13224/j.cnki.jasp.2015.02.017
Abstract PDF(940KB) icon1205 icon835
Abstract:
In the experiments of rotating channels, in order to acquire an ideal inlet turbulent intensity in rotating channel and better simulate the flow and heat transfer in a inner-cooling channel of turbine, a control method of inlet turbulent intensity was proposed and implemented by experiment in current work. In a square channel of 40mm×40mm, a hot wire anemometry is used to measure the turbulent characteristics downstream of a grid which has a diameter of 3mm and mesh size of 12mm. The grid Reynolds numbers range from 2200 to 3900. It is shown that the turbulent intensity of flow after the grid increases significantly and then decreases along downstream direction. Its value on the same position increases as the grid Reynolds number increases. In a short length, the flow after the grid reaches a turbulent intensity of 5% which is equal to the value in a real turbine inner-cooling channel. Besides, it is revealed that the flow will be more likely to become homogeneous and isotropic at a lower grid Reynolds number. A classic formula was used to fit the data of turbulent intensity in central channel after grid along downstream direction. The experiment data fit well with the curves.
Life scatter factor of Birnbaum-Saunders distribution
MA Xiao-bing, CHEN Qin-feng, ZHANG Yuan-xin
2015, 30(2): 392-396. doi: 10.13224/j.cnki.jasp.2015.02.018
Abstract PDF(751KB) icon1492 icon930
Abstract:
A method for reliable fatigue life analysis and assessment based on Birnbaum-Saunders(B-S) distribution was studied, and life scatter factor formulas of B-S distribution based on median value and mean value was derived respectively. Then, for some special cases of test data, life scatter factor formulas of B-S distribution based on the maximum and minimum order statistics was established. Formulas show that, the median and mean life scatter factors are decreased with the increasing of the scale parameter of B-S distribution, and the maximum and the minimum life scatter factors are constant. Case calculation results show that life scatter factors of B-S distribution are usually less than that of the lognormal distribution's.
Rotordynamic prediction of mode order transition when rotor has an overhang
Konstantin Shaposhnikov, HONG Jie, ZHANG Da-yi, MA Yan-hong
2015, 30(2): 397-409. doi: 10.13224/j.cnki.jasp.2015.02.019
Abstract PDF(1199KB) icon1545 icon811
Abstract:
Nowadays rotating machinery grows and develops extremely fast due to its multi-branch application. Although the fields of rotordynamics and rotor balancing had a strong background based on previous experience in order to perform efficient and safe operation for the rotating machines, still there are problems which are hard to be dealt with in some special cases. One of them is balancing of the rotor with huge overhang. Rotor with overhang is inherent to have console modes, which previously often were observed separately from the other modes in rotordynamic literature. In such a way console modes, their behavior, order of appearance and interaction with other modes were described in current paper in more details. Obtained results confirmed that console modes obey the principle of orthogonality in the same way as all other modes and hence could be efficiently balanced using modal balancing method. Simulation results revealed likelihood of such phenomena as modes order transition, when the rotor has an overhang. As a consequence perfectly balanced console rotor could not be so due to modes order transition effect when the bearing stiffness in situ differs from bearing stiffness of balancing equipment. Described results will be useful for engineers who are involved in area of rotating machinery vibration tuning for the rotor with huge overhang and benefit them to recognize these modes efficiently and to perform balancing successfully.
Multiple faults diagnosis method of engine bleed system based on improved signed directed graph
LIU Jun-qiang, WANG Xiao-lei, ZHANG Ma-lan, XIE Ji-wei, ZUO Hong-fu
2015, 30(2): 410-421. doi: 10.13224/j.cnki.jasp.2015.02.020
Abstract PDF(1151KB) icon1133 icon896
Abstract:
To diagnose multiple faults in signed directed graph (SDG) model, an improved signed directed graph (ISDG) multiple fault diagnosis model was proposed. The proposed ISDG model can meet the requirements of multiple faults combinations diagnosis in incomplete information conditions. The diagnosis process in incomplete information conditions can be established by interactive method. The optimum test sequence was determined by the maximal gain-cost ratio. This model improved the efficiency and reduced the cost in the multiple fault diagnosis process. Finally, the multiple faults of an civil engine bleed system were diagnosed with the interactive algorithm. The multiple faults can be diagnosed by ISDG model, so the diagnostic efficiency was improved by diagnosing multiple faults. After using combinational logic, the minimum cost is reduced by 7.25 than the maximum cost, and gain-cost ratio increases by 32.2%. These results explain that the cost can be reduced by 32.2% by using combinational logic.
Dynamic characteristics of a open crack in hollow shaft rotor system
LU Zhen-yong, CHEN Yu-shu, HOU Lei, LI Zhong-gang
2015, 30(2): 422-430. doi: 10.13224/j.cnki.jasp.2015.02.021
Abstract PDF(1266KB) icon1359 icon886
Abstract:
Dynamic characteristics of a open crack in hollow shaft rotor system was investigated. By using the finite element method, the equations of motion were formulated, where the weight and the unbalanced excitation were considered and the stiffness matrix was derived with the consideration of the time-varying of the neutral axis in the crack element cross-section. By using the harmonic balance method, the equations were solved approximately and analyzed numerically. The three-dimensional amplitude-frequency curves of different crack depth were obtained to indicate that the vertical response peaks were presented at critical rotating speeds and the subcritical rotating speeds. The varying of the critical rotating speed versus different depths and different locations of the crack was analyzed to obtain that the deeper crack which located near the disc with a larger inertia parameter made a greater impact on the system, and the critical rotating speed decrease quick. The nonlinear responses of the system at the subcirtical rotating speeds were investigated respectively, where the super-harmonic resonances were shown correspondingly. The proposed modeling method of the hollow shaft crack provides a theoretical guidance for nonlinear dynamic studying the aero-engine rotor systems with crack faults.
Remaining useful life estimation method of helicopter's main retarder based on EM-KF algorithm
SUN Lei, JIA Yun-xian, CAI Li-ying, WANG Wei-guo, LIN Guo-yu
2015, 30(2): 431-437. doi: 10.13224/j.cnki.jasp.2015.02.022
Abstract PDF(990KB) icon1252 icon799
Abstract:
A remaining useful life prediction method was proposed based on Kalman filter and expectation-maximization algorithm to solve the estimation problem of remaining useful life of helicopter's main retarder with introduction of indirect condition information. The proposed method can estimate the model parameters rapidly and effectively by updating characteristic value of vibration signal, and then remaining useful life distribution of main retarder was estimated at different working times. Finally, the case analysis was conducted through the test data of main retarder. The results demonstrate that the proposed method can effectively estimate the remaining useful life distribution of main retarder. Through comparison of real remaining useful life and estimated remaining useful life of main retarder, it is found that the estimated remaining useful life is mainly contained within 95% confidence interval, showing the proposed method has well accuracy, which can avoid the occurrence of the fault.
Response model of giant magnetostrictive actuator based on elastic damping pedestal
XUE Guang-ming, HE Zhong-bo, LI Dong-wei, LI Yu-long, YANG Zhao-shu
2015, 30(2): 438-445. doi: 10.13224/j.cnki.jasp.2015.02.023
Abstract PDF(1175KB) icon1093 icon786
Abstract:
Giant magnetostrictive actuator was placed on elastic damping pedestal to compensate the uncontrollable deformation of giant magnetostrictive material caused by environment, and steady-state responses of the output and base were calculated. Vibration differential equations were established when the system was simplified into a linear system with two degrees of freedom. Natural angular frequencies of the system were calculated, and amplitude-frequency characteristic was analyzed by harmonic excitation input. The experimental data of the output and base displacements were achieved by input of harmonic current with different amplitudes and frequencies. Relative errors and absolute errors between the model and experimental results were calculated and compared. The calculation shows that relative errors between the model and experimental results are not more than 9%, and the absolute errors are not more than 0.01mm, verifying the accuracy of the model.
Influence on flow field and performance of supersonicexpander with different strake wall section shapes
ZHONG Jing-jun, HUANG Zhen-yu, YANG Ling, HAN Ji-ang
2015, 30(2): 446-454. doi: 10.13224/j.cnki.jasp.2015.02.024
Abstract PDF(1332KB) icon1122 icon857
Abstract:
The three dimensional Reynolds-averaged N-S equations and the standard k-ε turbulent model were adopted to simulate numerically the flow field of the three-dimensional flow-path of the supersonic expander under three kinds of strake wall section shapes at the design point. It's found that the suction surface of supersonic expander with rectangle strake wall section shape has high air velocity, low flow losses after the shock waves, and thus higher adiabatic isentropic efficiency can be obtained; the supersonic expander with positive trapezoid strake wall section shape has high outlet averaged Mach number, static pressure ratio and expansion ratio, its comprehensive performance is relatively optimal; the main sources of flow losses at outlet include low-speed air caused by corner boundary layer separation and backflow as well as pressurization process of high-speed air after oblique shock waves. The comprehensive performance of supersonic expander could be further enhanced by optimizing the structure of strake wall in radial direction.
Numerical calculation and analysis of fan turbulence broadband noise's characteristics
TONG Fan, QIAO Wei-yang, WANG Liang-feng, JI Liang, WANG Xun-nian
2015, 30(2): 455-462. doi: 10.13224/j.cnki.jasp.2015.02.025
Abstract PDF(1155KB) icon1675 icon898
Abstract:
Based on the fan self-noise empirical prediction model developed by Gliebe and the turbulence -blade interaction noise analytical prediction model developed by Mugridge-Morfey and using GE R4 Fan for study, a detailed analysis of fan self-noise and rotor wake turbulence-OGV (outlet guide vane) interaction broadband noise (turbulence interaction noise) characteristics is performed. Different fan design parameters and different turbulence parameters' effects on the fan self-noise and turbulence interaction noise is investigated. Calculation results show that turbulence interaction noise dominates the fan broadband noise. Turbulence interaction noise is about 6-10dB higher than rotor self-noise and about 20dB higher than outlet guide vane self-noise. In addition, the incoming flow velocity of OGV plays the most important role in turbulence interaction noise and 15% increase of the velocity can lead to an increased sound power of about 4dB. The turbulence intensity has relatively important effects on the turbulence interaction noise and 30% increase of turbulence intensity can result in about 1.5dB higher sound power.
Experiment on noise reduction physical mechanism of serrated trailing edge structure
XU Kun-bo, QIAO Wei-yang, JI Liang, CHEN Wei-jie
2015, 30(2): 463-472. doi: 10.13224/j.cnki.jasp.2015.02.026
Abstract PDF(1341KB) icon1588 icon851
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Basic characteristics of wake turbulence flow field of airfoils with serrated trailing edge and straight trailing edge were comparatively analyzed, and noise of two trailing edge structure was measured through line array method. The results show that the turbulence intensity of wake turbulence flow field and turbulence intensity in three directions of airfoil with serrated trailing edge are significantly reduced compared with airfoil with straight trailing edge. The noise field results show that trailing edge noise has a huge decrease on airfoil with serrated trailing edge, while the leading edge noise is nearly the same. Serrated structure widens the wake region and accelerates the breakdown of large vortex, resulting in additional horseshoe vortex. Turbulence decay rate along the flow direction becomes larger.
Numerical investigation of endwall losses control in turbine by leading edge fillet based on teardrop curves
WEI Zuo-jun, QIAO Wei-yang, ZHAO Lei, SHI Pei-jie
2015, 30(2): 473-482. doi: 10.13224/j.cnki.jasp.2015.02.027
Abstract PDF(1408KB) icon1171 icon876
Abstract:
To investigate the endwall losses control in turbine by leading edge fillet based on teardrop curves, and to study the control mechanism of sencondary flow losses in turbine by leading edge fillet based on teardrop curve, the investigation was carried out with the well-known T106 cascade which was developed for highly loaded low pressure turbines. The effect of design parameters of different leading edge fillet of turbine endwall on endwall losses control in burbine was compared and analyzed. The results show that total pressure loss coefficient is obviously affected by extension length of leading edge fillet, extension location of on suction side and pressure side. The best configuration shows a reduction of total pressure loss coefficient of T106 cascade by about 5.1%. Moreover, compared with the leading edge fillet by cosine curves, the modification based on teardrop curves do not show much more reduction to endwall losses, but the latter obtain smooth connection with the original profile which causes no blades surface pressure fluctuation locally.
Numerical study on three-dimensional optimization of low-speed axial compressor rotor blade
ZHANG Chen-kai, HU Jun, WANG Zhi-qiang, YIN Chao, YAN Wei
2015, 30(2): 483-490. doi: 10.13224/j.cnki.jasp.2015.02.028
Abstract PDF(1276KB) icon1501 icon823
Abstract:
To deepen the knowledge of endwall flow in the large-scale low-speed axial compressor, reduce accordingly its flow loss and improve its aerodynamic performance, numerical simulation and optimization were presented. With numerical tool, three-dimensional stacking principle was optimized to improve the design operation point aerodynamic performance for the prototype rotor of a large-scale low-speed axial compressor in low speed simulation. Results show that, near-hub region of the optimized rotor cannot undertake large blade loading; compared with the prototype rotor, the main region of performance improvement of optimized rotor locates near the hub region, and a certain degree of positive bend in this region effectively helps to reduce its flow loss. It shows the effect of “loaded leading edge”, which suppresses flow separation near the trailing edge; consequently nearly 19.4% of total pressure loss is reduced.
Judgement method and test verification for tooth surface curvature interference of spiral bevel gears
CAO Xue-mei, DEND Xiao-zhong, GENG Long-long
2015, 30(2): 491-497. doi: 10.13224/j.cnki.jasp.2015.02.029
Abstract PDF(907KB) icon1561 icon814
Abstract:
A tooth surface curvature interference judgment method was presented based on the tooth surface topology structure, and the criterion for tooth surface curvature interference was given by constructing topology deviation of the two tooth surfaces. This method could intuitively identify if there is the tooth surface curvature interference, and could reflect the actual contact field of meshing. Tooth surface curvature interference of a pair of spiral bevel gears was calculated. The analysis results show that the toe, the heel and the tip of the pinion on working flank will be subject to curvature interference, and the contact pattern will be at the regions of the toe and the heel; the tip of the pinion on non-working flank will be subject to curvature interference. The spiral bevel gear pair was processed by computer numerical control gear milling machine and the contact pattern was tested. The contact patterns are located at the toe and the heel of the pinion on working flank; on non-working flank, meshing occurs on the tip of the pinion. The test results are consistent with the predicted results by the proposed method.
Bifurcation characteristic and modeling of transverse-torsional spur gear vibration considering friction and multiple clearances
SHENG Dong-ping, ZHU Ru-peng, JIN Guang-hu, LU Feng-xia, BAO He-yun
2015, 30(2): 498-506. doi: 10.13224/j.cnki.jasp.2015.02.030
Abstract PDF(1208KB) icon1404 icon873
Abstract:
Using the mass centralized method, a six degree of freedom transverse-torsional coupled nonlinear gear-rotor-bearing vibration model with multiple clearances and tooth surface friction was established, while time-varying meshing stiffness, gear backlashes, bearing clearances were considered in the model as well. By studying Poincare maps and global bifurcation diagrams under above parameters, the bifurcation characteristics of the system were obtained. Under a certain gear backlash, meshing damp and low tooth surface meshing friction, the system enters into a chaos state by the way of quasi-periodic motion with the increase of the rotation rate. While the tooth surface meshing friction coefficient increases, namely system is changed from well lubricated state to dry lubrication, the window of the chaos motion is split into two pieces at a critical point, and the system motion enters into a chaos state again by the way of crisis; Under a certain rotation speed, meshing damp and tooth surface friction coefficient, the system enters into a chaos state by way of crisis with the increase of the gear backlash, and the bifurcation and chaos motion happens when dimensionless gear backlash is less than 3 or bigger than 7, and the system motion is locked into a period motion by channel of reverse bifurcation; Under a certain rotation rate, meshing damp and gear backlash, the system enters into a chaos state by the way of crisis with the increase of the tooth surface friction coefficient. Meanwhile, it could be observed that, with the increase of the meshing damp, the window of the chaotic motion is split into 2, 3 and 4 sub-windows subsequently. But at last, system always is locked into a period motion by channel of quasi-periodic motion.
Measurement method of defect maximum diameter vector feature of solid rocket motor in volume space
ZHU Min, LI Peng, LU Hong-yi, YU Guang-hui
2015, 30(2): 507-512. doi: 10.13224/j.cnki.jasp.2015.02.031
Abstract PDF(858KB) icon1221 icon742
Abstract:
Based on the three-dimensional scanning data of solid rocket motor by industrial computed tomography, and considering the computation time and measurement accuracy, the traditional space maximum distance measuring method, named as challenge method, was improved by combining the defect features of the solid rocket motor volume space data field. The defect maximum diameter vector feature measurement method in volume space based on classified seed point method was proposed. The solid rocket motor with presetted defects was designed. Experiments show that the proposed method can improve the measurement accuracy and shorten the computation time compared with traditional challenge method, and the maximum errors of maximum diameter and axial acute angle are less than 10%, which is the foundation for solid rocket motors three-dimensional visualization fault diagnosis.

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