2015 Vol. 30, No. 1

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Coupling solutions of flow and heat transfer in the Blasius laminar boundary layer flow over a vertical flat plate
ZHAO Guo-chang, SHAN Long, SONG Li-ping, DU Xia, KONG Jing-ru, ZHAO Heng
2015, 30(1): 1-9. doi: 10.13224/j.cnki.jasp.2015.01.001
Abstract PDF(1148KB) icon3314 icon1188
Abstract:
The combined effects of thermal radiation, temperature dependent viscosity, slip and no-slip boundary conditions over a permeable vertical flat plate on the dimensionless velocity and temperature fields of Blasius laminar boundary layer flow were deeply investigated. By taking similarity variables, the coupled partial differential equations describing the velocity and temperature fields were transformed into nonlinear ordinary differential equations, and then solved numerically using the Runge-Kutta method. The effects of dimensionless parameters on the velocity and temperature fields were investigated with a focus on the analysis of velocity and temperature profiles, with the dimensionless parameters varying under the slip boundary condition. The results indicate that the existence of suction will make the boundary layer thinner, and the boundary layer will be thicker in the case of injection. In contrast with no-slip boundary conditions, the boundary layers of velocity and temperature are all thinner at wall slip boundary conditions. Increasing either the variable viscosity parameter a or the injection and suction parameter will increase the local skin friction coefficient and the local Nusselt number Nu while reducing the velocity and temperature boundary layers thickness. Furthermore, the temperature boundary layer thickness will decrease as the Biot number Bi, Brinkmann number Br decrease or as the Prandtl number Pr and thermal radiation parameter R increase.
Performance comparison between high temperature rise triple-swirler combustor and double-swirler combustor
LI Feng, GUO Rui-qing, SHANG Shou-tang, CHENG Ming, TANG Zheng-fu, SONG Bo, GAO Xian-zhi
2015, 30(1): 10-15. doi: 10.13224/j.cnki.jasp.2015.01.002
Abstract PDF(791KB) icon2578 icon1101
Abstract:
With use of the parametric modeling method, when the size of diffuser, the maximum dimension of outer case and exit size of combustor were kept the same as single annular combustor (SAC), the combustor head swirler was redesigned from the double-swirler structure into triple-swirler structure; the three-dimensional flow and combustion processes of double-swirler combustor (TSC) and triple-swirler combustor (TSC) were numerically simulated, and the performance of two high temperature rise combustors were compared. The results indicate that, the traditional DSC cannot meet performance requirement such as combustion efficiency of high temperature rise combustion with fuel air ratio of 0.037; by using the TSC, the total pressure recovery coefficient, combustion efficiency and temperature rise can be improved compared with the DSC; the outlet temperature distribution factor (OTDF) and radial outlet temperature distribution factor (RTDF) of TSC is lower than that of DSC. With fuel air ratio of 0.037, the total pressure drop of designed high temperature rise TSC is less than 5%, OTDF reaching 0.162, RTDF reaching 0.106, and combustion efficiency is more than 99%.
Experiment on combustion performance of ramjet engine withtrapped-vortex combustor
HE Xiao-min, QIN Wei-lin, ZHU Zhi-xin, NIU Zhi-gang, FEI Li-qun, PENG Li, YANG Cheng-yu
2015, 30(1): 16-21. doi: 10.13224/j.cnki.jasp.2015.01.003
Abstract PDF(798KB) icon3009 icon1133
Abstract:
Experiments were conducted to study the combustion performance of ramjet engine model with trapped-vortex combustor under different inlet temperatures and velocity coefficients. The results show: with the increase of inlet velocity coefficient increases (0.20-0.35), the ignition and lean blowout fuel air ratios rise, and the combustion efficiency changes little. As the inlet temperature increases(573-773K), the ignition fuel air ratio and lean blowout fuel air ratio decreases, and the combustion efficiency increases varying with increase of the excess air coefficient(1.1-2.1). The minimum ignition fuel air ratio and the lean blowout fuel air ratio is 0.0035 and 0.0028 respectively, the maximum combustion efficiency obtained from experiment is 93%.The results prove the feasibility of applying the cavity to the ramjet combustor.
Numerical simulation and analysis of steady-state performances for face and cylinder gas film seal system
MA Gang, LUO Xian-hai, SHEN Xin-min
2015, 30(1): 22-28. doi: 10.13224/j.cnki.jasp.2015.01.004
Abstract PDF(953KB) icon2494 icon1135
Abstract:
The steady-state performances analysis model of face and cylinder gas film seal system was established; the solving method and process based on the finite element numerical method for the pressure distribution of gas film were given; the face area was solved coupling with the cylinder area, and the method of numerical simulation calculation for the steady-state performances of face and cylinder gas film seal system was presented. The numerical simulation method was verified by comparing with the Fluent software results. The influence of film thickness and rotating speed of axle on the steady-state performances of the gas film seal system, such as face opening force, cylinder opening force, leakage, friction torque, was studied. Calculation and analysis show that with the increase of film thickness, the leakage increases and friction torque decreases; with the increase of face film thickness, the face opening force decreases slowly, and extreme value of cylinder opening force appears; with the increase of cylinder film thickness, both face opening force and cylinder opening force decrease; the influence of cylinder film thickness on the steady-state performances is more obvious than that of face film thickness. The coupling of seal pressure of gas film in the face and cylinder structure has a distinct effect on seal performance, and the steady-state performances numerical calculation method provides the foundation for the dynamic characteristics analysis.
Effect of inlet temperature and equivalence ratio on working process of pulse detonation engine
JIANG Tao, WENG Chun-sheng
2015, 30(1): 29-37. doi: 10.13224/j.cnki.jasp.2015.01.005
Abstract PDF(1178KB) icon2500 icon1144
Abstract:
To investigate the effect of inlet temperature and equivalence ratio on the working process of pulse detonation engine, the Euler-Lagrange model considering chemical reaction mechanism for gas-droplets two-phase detonation was built, while the gas-droplets two-phase detonation equations were calculated respectively by the two-dimensional space-time conservation element and solution element(CE/SE) method and variable-step fourth-order Runge-Kutta method. Numerical results show that increasing the inlet temperature can accelerate the droplets atomization and evaporation, shorten the deflagration to detonation transition distance and time, and reduce the peak pressure of detonation wave; when equivalence ratio is less than 1.1, increasing the equivalence ratio can shorten the deflagration to detonation transition distance and time and also increase the peak pressure and speed of detonation wave; when equivalence ratio is greater than or equal to 1.1, increasing the equivalence ratio can slightly shorten the deflagration to detonation transition distance and time and also increase the speed of detonation wave, but has a very small effect on the peak pressure of detonation wave.
Numerical study on effect of hot jet ignition on flame acceleration and detonation initiation in detonation tube
ZHAO Wei, HAN Qi-xiang, WANG Jia-hua, ZHANG Gui-hua
2015, 30(1): 38-45. doi: 10.13224/j.cnki.jasp.2015.01.006
Abstract PDF(1023KB) icon2354 icon1215
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To study the effect of hot jet ignition on flame acceleration and detonation initiation in detonation tube, 2-D numerical simulations with propane mechanism including 34 reaction steps among 26 chemical species were performed, and the flame propagation law in detonation tube and deflagration to detonation transition (DDT) time and distance were obtained with 5 different configurations of hot jet sub-chamber. The results show that turbulence plays a key role during flame acceleration process in detonation tube, and the shock/flame interaction dominates the detonation initiation. According to the definition of DDT process, the DDT time is between 1.4-2.0ms, and the minimum value is obtained in the hot jet sub-chamber with 150mm length and 8mm in orifice diameter. The hot jet sub-chamber length and orifice diameter exert a minor effect on the DDT distance.
Experiment of combustion performance of internally-staged combustor pilot stage
FU Zhen-bo, LIN Yu-zhen, ZHANG Chi, XU Quan-hong
2015, 30(1): 46-52. doi: 10.13224/j.cnki.jasp.2015.01.007
Abstract PDF(849KB) icon2648 icon1176
Abstract:
A internally-staged combustor was studied. The combustion performance experiments using a single module rectangular combustor were performed under the idle condition of a large thrust aero-engine. The effects of flare angles of pilot swirl cup, step heights and pilot airflow rates on pollution emissions, combustion efficiency and lean blowout fuel/air ratio (LBO FAR) were investigated experimentally. The experimental results indicate that under the idle condition, NOx emission can decrease by 42% with CO, unborn hydrocarbon (UHC) emissions increasing by 2.5 times, combustion efficiency decreasing by 1.75% and LBO FAR increasing from 0.0038 to 0.0067 when the flare angle of pilot swirl cup increases from 60 degree to 100 degree; NOx emission can decrease by 37% with CO, UHC emissions increasing by 1.5 and 1.2 times, respectively, combustion efficiency decreasing by 1.32% and LBO FAR increasing from 0.0042 to 0.0061 when the step height decreases by 24%; NOx emission can increase by 13.5% with CO, UHC emissions decreasing by 55.6% and 38.9%, respectively, combustion efficiency increasing by 1.46% and LBO FAR decreasing from 0.0061 to 0.0051 when the pilot airflow rate decreases by 20%.
Effect of fuel-air ratio and inlet parameters on performance of triple swirler combustor
DING Guo-yu, HE Xiao-min, ZHAO Zi-qiang, JIN Yi, WU Ze-jun
2015, 30(1): 53-58. doi: 10.13224/j.cnki.jasp.2015.01.008
Abstract PDF(965KB) icon2655 icon1095
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Experiments were conducted on a triple swirler combustor at fixed atmospheric pressure. Firstly the triple swirler combustor model and experimental system were designed, and then experiments were conducted to study the effect of inlet airflow velocity, inlet temperature and fuel-air ratio on the combustion performance, including flow drag performance, ignition performance, lean blowout performance and combustion efficiency performance. Results show that: the triple swirler combustor can be ignited successfully and operated stably at all experimental cases, and inlet airflow velocity has little effect on the ignition performance; the total pressure loss coefficient increases with inlet airflow velocity increasing while the flow drag coefficient decreases non-linearly with the increasing of inlet airflow velocity,and the inlet airflow has not been at the full development state; as inlet airflow temperature increases, the ignition performance and lean blowout performance become better and the combustion efficiency improves.
Effect of main flow orientation angle on cooling characteristics of single row of cylindrical film cooling holes
NIE Jian-hao, ZHU Hui-ren
2015, 30(1): 59-66. doi: 10.13224/j.cnki.jasp.2015.01.009
Abstract PDF(1170KB) icon2418 icon1187
Abstract:
The effect of main flow orientation angle on the film cooling characteristics of single row of cylindrical film cooling holes was numerically studied. With the same distance between the centers of film cooling holes when the blowing ratio was 1.0,results were compared with two other reference flow configurations of single row of cooling holes. Main flow orientation angle was 0 degree and the hole compound angle was 0 degree in one reference configuration, while main flow orientation angle was 0 degree and the hole compound angle was 45 degree in the other reference configuration. The results show that compared with the reference configuration with 0 degree main flow orientation angle and 0 degree hole compound angle, the film cooling effectiveness of the configuration with 45 degree orientation angle is more uniform and its average cooling effectiveness is higher; compared with the reference configuration with 45 degree compound angle, the average cooling effectiveness of the configuration with 45 degree orientation angle is lower in the region near the holes but higher in the region far away from the holes. Numerical simulations were also conducted when blowing ratios were 0.5 and 1.5. It is found that the distributions of film cooling effectiveness in the three flow configurations are obviously different from each other. So it is necessary to further investigate numerically and experimentally the effect of main flow orientation angle on the film cooling.
Dynamic characteristics of blades-disk-shaft rotor system with mistuned features
LI Chao-feng, ZHOU Shi-hua, REN Xiang, WEN Bang-chun
2015, 30(1): 67-75. doi: 10.13224/j.cnki.jasp.2015.01.010
Abstract PDF(1149KB) icon2447 icon1071
Abstract:
The finite element method was adopted to establish the dynamics model of blade and blades-disk as well as blades-disk-shaft. Based on the analysis of tuned/mistuned structure and the dynamic characteristics of model in different levels, the graphs of different modes and frequency distribution were presented. It was found that the characteristics of the blades considering disk and shaft rotor had a very big difference. Some severe separate and coupled effects mode appeared in some models. In addition, as the mistune may cause the blades-disk and blades-disk-shaft modal coupling in different vibration of blade types, the vibration frequency separation and concentration appeared, even leading to the loss of the system modal and localized vibration. The mistuned structure led to more continuous modal frequency. It thus brings some difficulties for design of the the blade rotor system.
A calculation method of contact stiffness between interfaces based on modal experiment
HU Dian-yin, SI Wu-lin, WEI Jia-ming, WANG Rong-qiao
2015, 30(1): 76-81. doi: 10.13224/j.cnki.jasp.2015.01.011
Abstract PDF(894KB) icon2263 icon1051
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A calculation method was proposed to calculate contact stiffness between interfaces in a view of modal experiment on the basis of Hertz contact and Greenwood-Williamson (G-W) model. Formula with coefficient for calculating contact stiffness was deduced; afterwards the first order natural frequency curves with various contact stiffness coefficients were drawn by using numerical simulation. The contact stiffness coefficient was chosen via experiment data of the first order natural frequency, and then the formula for calculating contact stiffness was obtained. The first order natural frequencies under different centrifugal forces and different geometry models together with vibration response under exciting force were calculated using corrected formula, and comparisons were made with experiment data. The maximum calculation error of the first order natural frequency is 1.73% and that of vibration response is 9.5%, which agree well with experiment data and testify the validity of method. Analysis of damping effect caused by dry friction on system vibration attenuation was also conducted and evident vibration attenuation is found near the first order natural frequency.
Nonlinear vibration of rotor systems caused by assembly processof a bearing outer ring of an aero-engine
WANG Si-ji, LIAO Ming-fu, LIU Yong-quan, WANG De-you, JIANG Yun-fan, LIAO Jun, LI Hao
2015, 30(1): 82-89. doi: 10.13224/j.cnki.jasp.2015.01.012
Abstract PDF(1533KB) icon2609 icon1186
Abstract:
According to the assembly process parameters features of turbine supports of an aero-engine, the vibration characteristics in a rotor system with different assembly process parameters between an outer ring of the bearing and a casing were carried out experimentally. The parameters of assembly process of a bearing outer ring were interference fit, clearance fit and transition fit. The influence on the fit of bearing outer ring and vibration of the rotor caused by casing temperature field and outer ring tinghtening torque were also carried out. The results show that: when assembly process of a bearing outer ring is clearance fit, subharmonic, super-subharmonic frequencys, nonlinear resonances occur and outer ring tightening torque in increases is one of the main factors that suppress rotor vibration. Assembly relationship of bearing out ring from the transition to the clearence occurs which is caused by temperature field of the casing.
Detail-structure optimization of single crystal turbine blade underthe condition of geometric and dynamic constraints
LI Shi-feng, WEI Gang, SUN Fei-yan, LIU Qiang-jun, HE Ai-jie, CHEN Yong-xi
2015, 30(1): 90-95. doi: 10.13224/j.cnki.jasp.2015.01.013
Abstract PDF(917KB) icon2546 icon975
Abstract:
Take the air inlet window of blade tenon as detail-structure optimization object, the relationship model between maximum cast residual stress and structure parameters and temperature were established by the simulation of cast residual stress field of single crystal turbine blade based on the recrystallization critical stress of DD6 single crystal superalloy. The detail-structure optimization of air inlet window of blade tenon was studied under the conditions of geometric and dynamic constraints. Finally, through the analysis and comparison with the actual air window of blade tenon, this method was effectively verified. The results show that the maximum cast residual stress of optimized air inlet window of blade tenon is completely reduced by over 20%, and the recrystallization is effectively eliminated.
Vibration analysis of aero-engine casing under radial harmonic excitation
WEN Deng-zhe, CHEN Yu-shu
2015, 30(1): 96-105. doi: 10.13224/j.cnki.jasp.2015.01.014
Abstract PDF(1457KB) icon2388 icon996
Abstract:
The casing was simplified using a simply supported end and a fixed supported end cylindrical shell based on geometric characteristics of thin-walled structures of aero-engine casing. The dynamic equations were established and solved by multi-scale method, and the stability of zero solution and non-zero solution of casing dynamic equations under the radial harmonic excitation was studied. Then the transient process of system mode from single-mode motion to composite mode motion and the transfer of energy between the modes were studied; in addition, the vibration characteristic of casing under radial harmonic excitation was also numerically simulated. Results show that periodic motion, periodic doubling motion and chaotic motion appear alternately with the increase of radial harmonic excitation.
Mesoscopic modeling of three-dimensional four-directional braided composites using energy method
GONG Long-dong, SHEN Xiu-li
2015, 30(1): 106-113. doi: 10.13224/j.cnki.jasp.2015.01.015
Abstract PDF(962KB) icon2339 icon1113
Abstract:
Based on the motion rules of three-dimensional four-directional braiding yarn carriers and the interior fiber bundle's force analysis, a mesoscopic modeling approach using energy method was established, which divided the modeling process as follows: adjusting the control point after jamming of fiber bundle, changing the position of fiber bundle due to extrusion and interwinding to each other and establishing the fiber bundle trajectory according to the minimum strain energy. By analyzing the geometric dimension of unit cell model, the relationship between unit cell model and braided parameters was provided. The fiber bundle model established by this approach was not interfered but compacted, and the fiber bundle trajectory, composed of a space curve and two tangent lines, was almost a straight line. Compared with the experiment result, the fiber bundle trajectory and cross section of model are consistent with the electron microscope scan images, and braided structure size calculated is in agreement with the measured data. The maximum relative calculation error of pitch length is about 5%, especially when braided angle is 21 degree or so, the relative calculation error is below 2%.
Structure research and photoelastic test verification of twin-web turbine disk with high thrust-weight ratio
DONG Shao-jing, SHEN Xiu-li, KANG Bin-peng, FAN Jiang, LI Shou-qiu, LUAN Yong-xian, HUO Cheng-min
2015, 30(1): 114-120. doi: 10.13224/j.cnki.jasp.2015.01.016
Abstract PDF(962KB) icon2602 icon1031
Abstract:
To meet the design requirements of high thrust-weight ratio engine, the topology optimization was carried out with the evolutionary structural optimization algorithm based on the conventional turbine disk, and the shape of twin-web turbine disk was determined. A work of the twin-web turbine disk including finite element analysis and size optimization was provided according to the results of topology optimization. And the mass of the twin-web turbine disk reduces by 23.6% compared with the conventional turbine disk at the same stress level. A rotating three-dimensional photoelastic test was carried out, verifying the rationality of the design and the accuracy of the calculation results.
Fatigue test of electron beam welding for TA19 in civil aircraft engine
SONG Li, YANG Jun-jie, CHEN Tie-feng
2015, 30(1): 121-128. doi: 10.13224/j.cnki.jasp.2015.01.017
Abstract PDF(1292KB) icon2018 icon950
Abstract:
Fatigue test for welding specimen of electron beam welding and base metal specimen of TA19, which was made of titanium-based alloy often used in the blisk of civil aircraft engine, was performed at temperature 20, 300, 450℃. Fracture mechanism of welded joint was discussed by comparing the fracture face microstructures of welded metal with that of base metal. Then the stress-fatigue life (S-N) curves of both base metal and welded metal were created based on Basquin model in the fatigue life range of 104 to 106 cycles, showing that few test data of fatigue life can go beyond the two times error margin in the corresponding models, which indicates that the S-N curve obtained by test is reasonable. Through comparison of the S-N curves of welding specimen and base metal specimen, it can be seen that fatigue performance of welding specimen is higher than that of base metal specimen at temperature 20℃, while the differences of the fatigue performance between welding specimen and base metal specimen vary with the stress amplitude at temperature 300℃ and 450℃. Also, in above fatigue life range, the differences of calculated life prediction for welding specimen and base metal specimen are within the two times error margin. Thereby, the conclusion can be drawn that the fatigue performances of both are closer.
Optimization design of reverse deformation based on measuring results for investment cavity of turbine blade
XIE Xiao-na, WANG Wen-hu, ZHANG Yan, WANG Yuan-bin
2015, 30(1): 129-135. doi: 10.13224/j.cnki.jasp.2015.01.018
Abstract PDF(884KB) icon2035 icon971
Abstract:
As the trial and error method and the numerical simulation method have difficulty in accurately reflecting the deformation of the hollow turbine blade in the process of investment casting, a comprehensive compensation method of the reverse deformation based on the measuring result was prompted. Firstly, through inspection by three coordinates measuring machine (CMM) and statistical analysis of the investment blade sample, three kinds of deformation including shrinkage, torsion and bending of the blade body section were calculated, then a comprehensive compensation algorithm for the design of blade mold cavity based on the reverse deformation was established, in order to achieve optimization design of the investment cavity. Taking the tip section of the investment blade sample for example, the profile error of the blade body,the maximum error of leading edge,the maximum error of trailing edge decreased by 50%,68%,31%, compared with the uncompensated method. Finally the experiment results show that the method can effectively improve the forming precision, and precisely controll the shape of the hollow turbine blade.
A design method for high efficiency propeller
XIANG Song, WANG Ji, ZHANG Li-guo, TONG Sheng-xi, WU Jiang, LIU Yuan-qiang
2015, 30(1): 136-141. doi: 10.13224/j.cnki.jasp.2015.01.019
Abstract PDF(955KB) icon3120 icon1811
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A design method for high efficiency propeller was presented. This method could calculate the geometric characteristics of maximum efficiency propeller, including the chord distribution, pitch-angle distribution, efficiency, thrust coefficients, torque coefficients and power coefficients based on the given flight velocity, rotating speed of propeller, thrust, diameter, blade number and airfoil. The propeller of an aircraft was designed using the parameters under climbing and cruise conditions, respectively. The chord distribution and pitch-angle distribution were obtained. Wind tunnel test of scaled model of propeller (diameter 0.84m) was carried out. The test results show that cruising efficiency of propeller is 83.02%, and climbing efficiency is 79.13%.
Rolling characteristics of vehicle with twist fin
ZHAO Bo-bo, LIU Rong-zhong, GUO Rui, ZHANG Jun, LIU Gao, CHEN Liang
2015, 30(1): 142-148. doi: 10.13224/j.cnki.jasp.2015.01.020
Abstract PDF(883KB) icon1939 icon915
Abstract:
A twist fin improved from oblique plate tail was proposed to meet the requirements of vehicle speed and rotating speed matching. According to the characteristics of twist fin providing rolling moment for vehicle, the twist rate and average attack angle were introduced to represent geometric features of twist fin based on the model of oblique plate tail. Based on correction-type blade element theory, four degrees of freedom rigid body equations were established to describe the motion law of aircraft, and the results were compared with the balancing rotating speed obtained by numerical simulation method. The results show that increasing the average attack angle and the twist rate, and reducing the span length of twist fin can improve the vehicle rotating speed, while increasing the root shoot ratio of twist fin has little effect on improving the vehicle balancing rotating speed. When the average attack angle of twist fin stays unchanged, the vehicle balancing rotating speed and twist rate show a linear relationship.
Unsteady aerodynamic characteristics of dual rotor micro air vehicle
CAI Hong-ming, WU Zhi-lin, ANG Hai-song, XIAO Tian-hang
2015, 30(1): 149-154. doi: 10.13224/j.cnki.jasp.2015.01.021
Abstract PDF(1080KB) icon2429 icon980
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A method based on computational fluid dynamics (CFD) was developed to predict the unsteady aerodynamic characteristics. The computational method includes numerous techniques such as momentum source model, preconditioning method, unstructured overset grids and Spalart-Allmaras (S-A) turbulence model. The effectiveness of the computational method in simulating dynamic flow field of dual rotor micro air vehicle was validated by calculating hovering Caradonna-Tung rotor and pitching NACA0012 airfoil. The dynamic flow field of dual rotor micro air vehicle was numerically simulated; the hysteresis curve of unsteady aerodynamic coefficient was calculated and the effects of reduced frequency, forward speed and propeller speed on unsteady aerodynamic characteristics were analyzed. The computational results show that the hysteresis effect of moment coefficient increases as induced frequency, forward speed and propeller speed increase, and the hysteresis effect of lift coefficient increases as induced frequency and forward speed increase, however, the hysteresis effect of lift coefficient changes slightly as the propeller speed changes.
Unsteady aerodynamic force of tilt ducted fan during transition period
YANG Lei, YE Zheng-yin
2015, 30(1): 155-163. doi: 10.13224/j.cnki.jasp.2015.01.022
Abstract PDF(1537KB) icon2465 icon934
Abstract:
In order to study the unsteady aerodynamic force of the tilt ducted fan powerplant during transition period, a unsteady numerical simulation method based on sliding meshes was used. A disk model based on inner flow field information and blade element theory was utilized to simulate the fan propeller, and the Navier-Stokes (N-S) equations were solved to simulate the process of ducted fan during pulling up. The results demonstrate that the hysteresis properties of unsteady aerodynamic force of the ducted fan are obvious at transition period. The increase of pitch rate of the tilt ducted fan delayes the flow field separation, and increase lift and drag of ducted fan. The aerodynamic performance of the ducted fan is excellent in transition period at low speed. Higher speed and larger angles of attack worsen the aerodynamic performance of ducted fan, and the curve of the pitch moment is in a mess against the transition flight.
Numerical study of gas-steam ejection gas-liquid two-phase flow field under water
HU Xiao-lei, LE Gui-gao, MA Da-wei, LI Ren-feng
2015, 30(1): 164-172. doi: 10.13224/j.cnki.jasp.2015.01.023
Abstract PDF(1111KB) icon2201 icon926
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Based on computational fluid dynamic method and homogeneous multiphase theory,vaporization model was adopted to simulate vaporization between gas and cooling water, and missile's motion was simulated by dynamic zone mesh motion method. Three-dimensional unsteady gas-steam ejection gas-liquid two-phase flow field was studied. Compared with the experiment of solid rocket flow field injection with water, this proved that the numerical method was reliable. The flow field structure, secondary flow, load characteristic and internal trajectory in variable depth ejection during ejection were studied. The results show that the evaporation occurs on the wall of the pipe. The gas-steam high temperature region migrates with the increase of tube volume during ejection. Isolation region and secondary flow exist at cross section of the tube and pipe, and form different eddy structures. The maximum impact force occurs on the wall of the pipe between 30° and 60° bend angle at 0.16s. With the ejection depth increasing 10 m, the pressure of monitor is added by 0.25MPa and time of missile motion is delayed 0.01s.
Effect of local hump on stability of compressible boundary layer on flat plate
LI Hui, HUANG Zhang-feng
2015, 30(1): 173-181. doi: 10.13224/j.cnki.jasp.2015.01.024
Abstract PDF(1131KB) icon2042 icon911
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Direct numerical simulation (DNS) method was performed on compressible boundary layer on flat plate with a local hump, and linear stability theory (LST) was applied to conduct the stability analysis based on the mean flow with Mach number of 4.5. The interactions between the disturbances with different frequencies and the local hump with various heights were simulated by solving the perturbation equations, and the effect of local hump on the stability was characterized by a transmission coefficient. The results show that, the local hump affectes the mean flow locally when the height of the local hump is smaller than 0.2 times of the boundary layer thickness. Local hump destabilizes the disturbances with frequency smaller than the most unstable disturbance frequency, and stabilizes the disturbances with frequency larger than the most unstable disturbance frequency, wherein the most unstable disturbance frequency is the frequency of the most unstable second modal disturbance of the boundary layer on flat plate at the center position of the local hump. Transmission coefficient quantitatively describes the effect of local hump on the instability. The local hump with height 0.2 times of the boundary layer thickness enables the correction of the N of e-N method 0.8, about 10% of N at the transition location, which can not be neglected in the transition prediction process.
Gray dynamic prediction of large gear tooth profile error measurement under multi-impact factors coupling
LI Qiang, WANG Zhong-yu, YAN Hu, WANG Qian
2015, 30(1): 182-194. doi: 10.13224/j.cnki.jasp.2015.01.025
Abstract PDF(1225KB) icon2080 icon913
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A large side-mounted model of gear measurement mechanism was proposed, and the main error sources and features of measurement precision were analyzed. A grey dynamic prediction method was presented to deal with multi-impact factors coupling. Firstly, the error sources influenced tooth profile measurement precision were analyzed and demarcated according to the characteristics of measurement mechanism, and then the sensitivity coefficients of various error sources were calculated. Secondly, the limited error source data were separately resampled, and a grey generation operation was given; the measurement results affected by each error source were calculated in the resampling process; then the error coupling results could be obtained in the error synthesis process. Finally, the measurement precision of large gear tooth profile could be improved greatly by removing the coupling effect existing in measurement result. Compared with the measurement results obtained by the three-coordinate 0.5μm precision measurement machine, the experiment results show that the measurement system presented can meet the measurement requirement of tooth profile for large gear of three-level precision above.
Ease-off flank topography design for aviation spiral bevel gears with higher-order transmission errors by modification of conjugate flank
CAO Xue-mei, DEND Xiao-zhong, NIE Shao-wu
2015, 30(1): 195-200. doi: 10.13224/j.cnki.jasp.2015.01.026
Abstract PDF(870KB) icon2511 icon984
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A lean flank design methodology for spiral bevel gears by modification of conjugate flank was proposed for the predesigned higher-order transmission errors and contact pattern. The conjugate flank of gear was used as reference flank to construct the pinion flank. The reference flank was modified according to the predesigned higher-order transmission errors, and then it was modified secondly according to the predesigned contact pattern, so the topology of the pinion flank also could be controlled precisely to meet the need of the precise control of higher-order transmission errors and contact pattern. The developed approach was illustrated with numerical example and the result showed that the transmission error was 6-order function with the magnitude 3.1", and contact path orientation was nearly 25° from root cone. The digital rolling test was employed for tooth contact analysis, and the results showed that the shape and magnitude of transmission errors, contact path orientation and contact ellipse could be precisely controlled. This proposed flank methodology basing on modification of conjugate flank can also serve as a basis for developing a general technique of flank design for other gear types.
Analysis of behavior mechanism and influential factors of load sharing in an epicyclic gear system
LIAO Ying-hua, QIN Da-tong, LIU Chang-zhao
2015, 30(1): 201-208. doi: 10.13224/j.cnki.jasp.2015.01.027
Abstract PDF(1014KB) icon2132 icon969
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The elastic deformations of bearings of the coaxial members and a sun-planet-ring path were respectively considered on the carrier's and planet's bearing center, and then an equivalent model of an epicyclic gear system was established. The load sharing behavior of an epicyclic gear system was simulated by the motions of the carrier rigid body, and a model to calculate load sharing in an epicyclic gear system was presented. And then the quantitative relations among load sharing, the equivalent stiffness of bearing and errors were obtained by the proposed approach, and the influences of all kinds of factors on load sharing were analyzed. The results show that when the difference between the equivalent stiffness of carrier bearing and the equivalent stiffness of planet bearing is more than two orders of magnitude, load sharing is only related to the equivalent stiffness of planet bearing and tangential position error of the planet, so the load can be evenly distributed by reducing tangential position error of planet and the equivalent stiffness of planet bearing. Cyclical excitations will be caused by the eccentricity errors of planet or sun, and the dynamic load coefficient can be increased, so the dynamic loads will be evenly distributed by reducing the eccentricity errors of the planet and sun.
Spirac machine-tool setting calculation method by predetermined contact pattern length factor
XUAN Jia-min, WEI Wen-jun, LIU Ping-yi, DONG Xue-zhu, LI Hai-tao
2015, 30(1): 209-218. doi: 10.13224/j.cnki.jasp.2015.01.028
Abstract PDF(1166KB) icon2266 icon917
Abstract:
Based on the method that the length of the instantaneous contact ellipse at the reference point almost decides the length of the contact pattern, a machine-tool setting calculation method was obtained. According to the Spirac cutting theory, a mathematical model of the epicycloids hypoid gear was built and the parameters of the instantaneous contact ellipse at the reference point of the gear tooth surface were obtained. By adding the cutter tilt angles to the machine setting iteration variables and taking the contact pattern length factors equaling to the predetermined values as the iteration conditions based on the required position of the reference point, the required pressure angle and the required spiral angle of the tooth surfaces at the point, the machine-tool setting parameters were solved. Finally, with a pair of epicycloids hypoid gear as an example, the result obtained from this method was compared with that from the Spirac to verify its accuracy, and the tooth contact analysis under different predetermined contact pattern length factors was accomplished. The results show that with this method, the problem of repeated adjustment of the cutter tilt is solved, and through precise control of different predetermined contact pattern length factors of the gear tooth surfaces equal to the design values, the pre-control of the contact pattern lengths of the gear tooth surfaces is achieved.
Dynamic characteristics under various excitations for a helicopter transmission system
LIN He, WANG San-min, DONG Jin-cheng
2015, 30(1): 219-227. doi: 10.13224/j.cnki.jasp.2015.01.029
Abstract PDF(1196KB) icon1958 icon899
Abstract:
For a helicopter transmission system which consists of spiral bevel gears and planetary gear train, the purely torsional vibration model was established, and the non-linear dynamical equations containing backlash was built using the lumped-parameter method. Through the finite element method, the time-varying mesh stiffness was obtained, and the dynamical equations were solved by the 4-5 order Runge-Kutta algorithm with variable time step; by means of dynamic load coefficient, phase plane plots, Poincaré maps and fast Fourier transform spectra, the dynamic characteristics of transmission system were studied under various excitations of the time-varying mesh stiffness, backlash, general transmission errors and external load. The results show that mesh stiffness has the greatest effect on the transmission system, with the maximum dynamic load coefficient of 1.5; backlash has a limited effect on the response characteristics; to some extent, mesh errors can suppress the vibration of the gear system; external load fluctuation has various effects on different speed stages, and the maximum dynamic load coefficient is stemmed from the combined drive gears.
Mechanism of improvement on axial-flow compressor stability with assembled casing treatment
ZHANG Hao-guang, WANG Yun-peng, WU Jun, CHU Wu-li, WU Yan-hui
2015, 30(1): 228-236. doi: 10.13224/j.cnki.jasp.2015.01.030
Abstract PDF(1638KB) icon2209 icon879
Abstract:
Influences of the stability of subsonic axial-flow compressor were investigated by full-annulus unsteady numerical method with axial skewed slot casing treatment(CT),self recirculation casing treatment and assembled casing treatment respectively. Assembled casing treatment was composed of axial skewed slot and self recirculation casing treatment. The numerical results show that the ability of assembled casing treatment to improve the rotor steady operating range is the best, followed by self recirculation casing treatment. Compressor could gain 12.86%,16.47% and 22.72% stall margin improvements with three kinds of casing treatment. The fundamental flow mechanism was obtained by detailed analysis of the flow-filed in rotor passage. The analytic results indicate that the bad effect made by flow separation is weakened with assembled casing treatment, and high velocity flow discharged from injecting part can restrain the tip clearance leakage flow spillage from adjacent tip passage at leading edge. The leakage flow is also sucked into axial skewed, preventing the occurrence of leading edge spilling flow.
Low-speed modeling design for tip flow field of compressor rotor blade
LI Yan-kai, HUANG Tian-hao, MENG De-jun, MIAO Yu-lu, YU Wen-sheng, TENG Jin-fang
2015, 30(1): 237-247. doi: 10.13224/j.cnki.jasp.2015.01.031
Abstract PDF(1359KB) icon2373 icon903
Abstract:
A low-speed compressor is designed for tip flow field of first stage rotor in the high-speed compressor with an inlet guide vane. It was prepared for subsequent experiments of the low-speed compressor stall and blade tip flow loss. The design used blade design and numerical simulation methods to ensure similar distribution of blade surface pressure coefficient and blade inlet and outlet main aerodynamic parameters of high- and low-speed compressors. High-speed prototype compressor was taken as research object to design a low-speed compressor. It included adjustment of flow-path geometry, iterative design of blade profiles and breakthrough the limitation of the geometric similar principle for inlet guide vane and first-stage rotor blade design. Finally, the comparative analyzed of geometry, aerodynamic parameters and flow-field structure of high- and low-speed compressor proved that the low-speed modeling design is useful. This design guarantees the similarity of processing capacity factor and rotor diffuser factor is 98.16%, 94.95%, respectively, which is under the same flow coefficient.
Large eddy simulation of unsteady flow field in a two-dimensional moving compressor cascade
ZHAO Long, GENG Shao-juan, ZHANG Hong-wu
2015, 30(1): 248-256. doi: 10.13224/j.cnki.jasp.2015.01.032
Abstract PDF(1421KB) icon2118 icon961
Abstract:
Using single-passage and multi-passage caculation models, large eddy simulations were conducted to study the unsteady oscillating features of internal flow field in a two-dimensional moving compressor cascade during the throttling process. The changes of vortex structure and oscillating frequency were analyzed. The resutls show that at working conditions with larger mass flow rates, two unsteady oscillations resulted from flow around leading edge and separation on blade suction surface coexist. Both frequencies almost keep constant. Flow structures of separation on suction surface are of small scale. At working conditions near stall limit, large scale separations occur on suction surface. The oscillating frequency decreases dramatically, lower than blade passing frequency.

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