2015 Vol. 30, No. 10

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Structural design and optimization for the deformation approaching to hot pofile of a swept fan blade with smaller hub-to-tip ratio
WANG Yan-rong, HUANG Zhong-shan, FU Zhi-zhong, SHI Liang
2015, 30(10): 2305-2311. doi: 10.13224/j.cnki.jasp.2015.10.001
Abstract PDF(916KB) icon1339 icon854
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An iterative method was proposed for determining the cold blade profile from a hot blade profile based on the aerodynamic design. The method was applied to the design optimization of the gravity center tilting of a rotor blade. The optimization was based on the hot profile and the stress calculation on the cold profile. In that way, it could reduce the influence on the aerodynamic performance. A multi-objective optimization procedure of the gravity center tilting based on the commercial package iSIGHT was established by proposing a method of automatically updating the finite element mesh in the determination of cold blade profile. The effect of the disk on the optimization of gravity center tilting of a blade was investigated by referencing a swept fan blade with smaller hub-to-tip ratio. The results show that the maximum values of stress and deformation of a rotor blade are respectively decreased by 10.6% and 46% by the proposed method for a given hot profile from the aerodynamic design.
Approach to construction of fatigue design curve
YANG Xiao-guang, HUANG Fei, MIAO Guo-lei, SHI Duo-qi
2015, 30(10): 2312-2317. doi: 10.13224/j.cnki.jasp.2015.10.002
Abstract PDF(904KB) icon1074 icon801
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Tolerance limit concept was used to construct design curves against the deficiencies of the existing methods. Comparative analysis was implemented to evaluate the safety of the design curve. Experimental result shows that fatigue scatter varies with stress levels. Based on approximate Owen tolerance limit, an improved design curve has been developed to comply with the feature of fatigue scatter that becomes small in high stress levels and large in low stress levels. According to the fatigue test results of Ti-6246, the fatigue life derived from the new method increased by 146% at 925MPa and decreased by 60.2% at 820MPa compared with other methods. Reliability and economy can be improved with the new fatigue design curve.
Nonlinear and non-Guassian rank filter method
FU Hui-min, XIAO Qiang, LOU Tai-shan, XIAO Meng-li
2015, 30(10): 2318-2322. doi: 10.13224/j.cnki.jasp.2015.10.003
Abstract PDF(935KB) icon1282 icon764
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A nonlinear and non-Guassian rank filter (RF) method based on the principle of rank filter was presented. Furthermore, its filter recursive process was also given. Unscented Kalman filter(UKF) only for Gaussian distribution and particle filter (PF) for non-Gaussian distribution were the two common nonlinear filter methods, but PF had the problems of particle degeneracy, particle impoverishment caused by resampling and complicated calculation. Compared with the two methods, the proposed RF is suitable for not only Gaussian distribution but also non-Gaussian distributions such as multivariate t distributions and extreme value distributions, and RF is simple to calculate and easy to apply in engineering. Moreover, it has low amount of calculation. From the simulation comparisons of RF, UKF and PF in the example, the filtering accuracy of RF increased at least 500%.
Experiment of surface finishing on aero-engine blisk by magnetic abrasive finishing
CHEN Yan, ZHOU Kun, NIU Feng-li, LI Chang
2015, 30(10): 2323-2330. doi: 10.13224/j.cnki.jasp.2015.10.004
Abstract PDF(1345KB) icon1238 icon790
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When finishing the blisk with the process of magnetic abrasive finishing, the interference between the workpiece and the magnetic pole is serious. Machining with radial magnetic pole instead of axial magnetic pole can effectively avoid interference, but the finishing pressure and the finishing efficiency are low. By analyzing the mechanism of radial magnetic abrasive finishing and the microscopic forces carried by the single magnetic abrasive particle, it derived that increasing the variance ratio of magnetic field intensity could significantly increase the magnetic abrasive finishing efficiency. With finite element simulation and analysis, it showed that slotting rectangular grooves along the axis direction on the surface of magnetic pole could improve the variance ratio of the magnetic field intensity. Through the magnetic abrasive finishing experiment to nickel-based superalloy blisk and analyzing the experimental data, it was concluded that the magnetic abrasive finishing with radial magnetic pole as the tool can realize finishing the blisk without interference, the magnetic abrasive finishing efficiency can be increased by 31% after the slotting rectangular grooves on the magnetic pole. The surface roughness value of the blisk was reduced from 1.2μm to 0.18μm. It verified the feasibility that the magnetic abrasive finishing can realize finishing the blisk surface with high efficiency and quality.
Influence of different impact energies on damage and residual strength of laminates
CUI Hai-po, WEN Wei-dong, ZHANG A-long
2015, 30(10): 2331-2337. doi: 10.13224/j.cnki.jasp.2015.10.005
Abstract PDF(910KB) icon1366 icon684
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The damage processes of composite laminates under impact loading and static loading after impact were analyzed based on the three-dimensional (3-D) progressive damage theory and whole-process analysis method. The influence rules of impact energy on the damage and residual strength of T300/BMP-316 composite laminates with different layer parameters and dimensions were researched. Results show that there is a threshold of impact energy for the composite laminates. The residual strength of composite laminates will decrease rapidly if impact energy exceeds the threshold value. The threshold value of impact energy for T300/BMP-316 composite laminates is between 5.0J and 5.5J. During the impact process, the dropping velocity of impactor is fluctuating, and layer parameters can influence the dent depth of the surface of composite laminates.
Probabilistic failure risk assessment method of turbine engine life limited parts for airworthiness requirements
ZHANG Gong, ZHOU Yan-pei, DING Shui-ting
2015, 30(10): 2338-2345. doi: 10.13224/j.cnki.jasp.2015.10.006
Abstract PDF(862KB) icon1443 icon780
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In order to meet the requirement of airworthiness regulations on engine life limited parts (ELLPs), a theoretical model integrating stress-strength interference model, linear elastic fracture mechanics and zone based probabilistic analysis was established to assess the failure risk of ELLPs. The numerical algorithm and the computer program were also developed. The method was calibrated by the test case provided in the advisory circular. The assessment results are 1.45×10-9 times/cycle without any non-destructive inspection and 1.0×10-9 times/cycle with an inspection at 10000 cycles, respectively. The results measure up to the calibration test case very well, indicating the method to meet the terms of the regulation, thus is applicable to the current civil engine type certification.
Contact pressure analysis by using singular integral equation method
LIU Chuang, CUI Hai-tao
2015, 30(10): 2346-2351. doi: 10.13224/j.cnki.jasp.2015.10.007
Abstract PDF(933KB) icon1172 icon743
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The numerical solution of singular integral equation (SIE) was summarized, the 2nd type of SIE was solved by piece-wise continuous linear function procedurefor two elastic bodies contact, the SIE was deduced by correlating the slip function and gap function between the two bodies. The contact bodies include the cylinder contact with half space body, parabola shape indentor contact with half space body and tenon contact with mortise cases. These equations were solved by using the piece-wise continuous function method, then contact pressure on the contact surface was acquired. The results of SIE analysis were compared with those obtained from contact theory and finite element method (FEM) analysis. For cylinder contact with half space body, the maximum contact pressure of SIE method is compared with contact theory and FEM, the relative tolerance is 0.3% and 0.5% respectivelyfor tenon contact with mortise, the relative tolerance of maximum contact pressure between SIE method and FEM is 1.8%, proving the effectiveness and applicability of SIE method.
Reliability evaluation method of ion thruster withvery few failure data
LI Jun-xing, ZHANG Yong-bo, FU Hui-min, WANG Zhi-hua
2015, 30(10): 2352-2356. doi: 10.13224/j.cnki.jasp.2015.10.008
Abstract PDF(840KB) icon1231 icon758
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A reliability evaluation method of ion thruster was established under the situation that only two ion thrusters were tested and the results were represented by very few failure data. Meanwhile, the significant test information from the last failure data test to non-occurrence of failure was fully developed by introducing the concept of interval statistic. Best linear unbiased point estimator of the life distribution parameters was calculated by using Gauss-Markov theorem. And then the one-side lower confidence limits of reliability and life were given. At last, while evaluating the reliability of NASA's XIPS-13 ion thrusters, the one-side lower confidence limits of the reliability with the demanding lifetime 10000h was 0.87 and the one-side lower confidence limits of the lifetime with a given reliability 0.9 was 9024.6h. It demonstrates that this method has high accuracy and can be easily applied in engineering.
General weight functions for corner quarter-elliptical crack in three-dimensional rectangular plate
JIA Xu, HU Xu-teng, SONG Ying-dong
2015, 30(10): 2357-2367. doi: 10.13224/j.cnki.jasp.2015.10.009
Abstract PDF(1183KB) icon1286 icon943
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General weight functions of the corner quarter-elliptical crack in three-dimensional rectangular plate were studied. Uniform, higher-precision and relatively wider-application-range approximate expressions of reference stress intensity factors were obtained, by using the reference finite element data of the stress intensity factor when the crack surface was subjected to in-plane uniform, linear and secondary power law distribution loading along the plate width. On this basis, the general weight functions of the corner quarter-elliptical crack in three-dimensional rectangular plate were obtained, the accuracy of the general weight functions was validated by finite element method finally when the crack surface was subjected to in-plane 3,5,7 times power law distribution loading. The results show that the accuracy of established general weight functions is raised from 4%(point A) and 6%(point B) to 1.06%(point A) and 1.6%(point B) compared with the existing general weight functions. The accuracy of complementary validation of stress intensity factors calculated by general weight function method under seven times power law distribution loading reaches 3.67%(point A) and 7.45%(point B).
Combustion characteristics for direct injection piston aviation engine
HU Chun-ming, GU Jun, ZHOU Hao
2015, 30(10): 2368-2375. doi: 10.13224/j.cnki.jasp.2015.10.010
Abstract PDF(1132KB) icon1510 icon758
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Based on the structure characteristics of the ROTAX914 carburetor piston aviation engine, a single-cylinder low pressure air-assisted direct injection aviation testing engine was developed. The influences of different controlling parameters, including injection timing, injection duration, injection pressure, ignition advance angles, on the combustion characteristics of the engine were investigated. The results show that: the engine combustion efficiency gets higher and the combustion cyclic variations get lower at the optimal start injection. With the increase of engine speed and load, the optimal start of injection is advanced accordingly. With the decrease of the direct injection duration and the injection pressure, the peak cylinder pressure and the rate of pressure rise are reduced, the rapid combustion period is extended and the combustion cyclic variations get higher. With the advancing of the ignition time, the peak cylinder pressure and the rate of pressure rise are increased, the combustion phase gets earlier and the combustion cyclic variations are reduced.
Heat transfer enhancement mechanism of transverse direction type serrated fin in turbulent flow based on field synergy principle
LI Juan, LING Xiang, PENG Hao
2015, 30(10): 2376-2383. doi: 10.13224/j.cnki.jasp.2015.10.011
Abstract PDF(1091KB) icon1426 icon661
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The heat transfer and flow characteristics of TD (transverse direction) type serrated fin in plate-fin heat exchanger were studied numerically. To explore the heat transfer enhancement mechanism of TD type serrated fin, three dimensional numerical model was established to examine the temperature gradient field, velocity field and fields synergy in turbulence flow. Furthermore the effect of fin height, fin space and fin width on the heat transfer and flow characteristics were analyzed respectively. The integrated heat transfer performance factor were calculated. Results show that: the temperature field and velocity distribution was uniformperiodic longitudinal vortex was formed because of the fin strong disturbancethe synergy of velocity field and temperature gradient was improved owing to vortex enhancing the heat transfer efficiency and improving integrated heat transfer performance factor.
Response characteristics of accumulator pressure in pumped phase-change cooling system
YUAN Jun-fei, TANG Da-wei, CAO Hong-zhang
2015, 30(10): 2384-2390. doi: 10.13224/j.cnki.jasp.2015.10.012
Abstract PDF(948KB) icon1172 icon677
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The accumulator works as a key component of the mechanically pumped two phase cooling system, and its response characteristics will directly affect the system performance. An experiment and theoretical analysis for the influence of the accumulator pressure on pump startup process, heat startup process and stable operation process were made. The results show that the lower accumulator pressure means the more stable mechanical pump starts owing to the characteristics of working fluid R134a and operating characteristics of the gear pump. Pressure change of the accumulator has low impact on the heat startup process, and the startup apparent stability. In the steady operation stage, the lower accumulator pressure indicates the greater fluctuations of the evaporator outlet temperature.
Heat transfer characteristics in two-pass rib-roughened channel at high rotation number with different channel angles
WANG Hui, TIAN Shu-qing, DENG Hong-wu
2015, 30(10): 2391-2400. doi: 10.13224/j.cnki.jasp.2015.10.013
Abstract PDF(1492KB) icon1023 icon636
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To match the real engine operating condition, Reynolds number and rotation number range of current experiment were expanded from 10000 to 70000 and 0 to 2.08 by increasing the air pressure. Experiment was conducted to investigate the heat transfer characteristics in a square two-pass channel with inclined 45 degree ribs, and three different channel angles (0 degree, 22.5 degree, 45 degree) were selected to study the effect of channel angle on heat transfer characteristics. Results indicate that in the first channel, channel angle has a larger effect on trailing wall than leading wall, especially near the inlet of the channelin the second channel, channel angle has a smaller effect on both trailing wall and leading wall. To the region average heat transfer distribution, the 45 degree channel is higher than other channels (0 degree, 22.5 degree), and 0 degree channel is the lowest.
Experiment on impact of initial diameter on breakup characteristic of single droplet
JIN Ren-han, LIU Yong, ZHU Dong-qing, FENG Zhi-peng, WANG Suo-fang
2015, 30(10): 2401-2409. doi: 10.13224/j.cnki.jasp.2015.10.014
Abstract PDF(1298KB) icon1263 icon681
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The high-speed camera was applied to measure droplet deformation and breakup in the continuous and uniform air jet flow. Impacts of the initial diameter on breakup mode, deformation time, deformation and breakup total time and non-dimensional Sauter mean diameter were obtained. Result shows that,critical Weber number increases with the increasing initial diameter. The breakup model is changed into hybrid breakup model constituted by many single breakup models with the increasing initial diameter. Under the same Weber numbers, the deformation time and deformation and breakup total time in the region of larger diameter are both larger than the region of the smaller diameteras the Weber number increased, the deformation time showes the linear variation of first decreasing and then keeping the same, and the deformation and breakup total time showes the linear variation of first decreasing then increasing and decreasing again. The impact of the initial diameter is stronger than the impact of initial relative velocity of gas-liquid on non-dimensional Sauter mean diameter.
Performance test of slinger combustor of turbojet engine running in engine test
LIU Deng-huan, JIN Jie, WANG Fang, PAN Ning-min, JING Wen-ming
2015, 30(10): 2410-2415. doi: 10.13224/j.cnki.jasp.2015.10.015
Abstract PDF(925KB) icon1678 icon642
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An engine test was performed to measure the outlet temperature of a turbojet-engine combustor from low to high engine rotating speed. Results show that this slinger combustor has a poor performance at low engine speed, and the performance parameters of the combustor rise with the increasing of engine speed. The indicators of the slinger combustor meet basically the design requirements when the engine reaches the design-point state. Under the design-point state, the measured outlet temperature distribution factor of the slinger combustor is less than 0.31, and combustion efficiency can reach 98.1%.
Experiment of flow field characteristics in a lean premixed prevaporized low emission combustor
DENG Yuan-hao, YAN Ying-wen, DANG Long-fei, DAI Chao, XU Hua-sheng
2015, 30(10): 2416-2424. doi: 10.13224/j.cnki.jasp.2015.10.016
Abstract PDF(1271KB) icon1227 icon657
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Particle image velocimetry (PIV) was applied to measure flow field characteristics in lean premixed prevaporized (LPP) low emission combustor with twin annular swirling multi-point direct injection (TAMI) dome. Influences on non-combustion and combustion of the mean parameters, such as vorticity, turbulent intensity and shear strain rate, were studied separately. And the influences of different inlet conditions on the combustion flow field were also investigated. The experimental results show that the recirculation zone dimension of combustion flow field is far less than that of non-combustion one, and the mean parameters change significantly. The recirculation zone is shorter and wider with the increase of inlet fuel-air ratio, but longer and narrower with the increase of inlet air mass. These experimental results contribute to the design of LPP low emission combustor.
Numerical research of the ram-rotor test system at off-design conditions
HAN Ji-ang, GUAN Jian, ZHONG Jing-jun, YUAN Chen-guang
2015, 30(10): 2425-2439. doi: 10.13224/j.cnki.jasp.2015.10.017
Abstract PDF(1486KB) icon1011 icon641
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Numerical simulation on the flow passage of the ram-rotor test system was carried out under different back pressure and rotational speeds by using FLUENT software. Results show that characteristic curves of the ram-rotor are steep. Steady operation range of the ram-rotor is narrow, and relative mass flow rate range of the ram-rotor is from 26.57% to 1.96%. At high back pressure or low rotational speed, the flow in the vane passage is not sensitive to the low pressure zone located at the leading edge of the ram-rotor. Back pressure and rotational speed have little impact on flow loss of the vane segment. With back pressure rising, flow in the ram-rotor segment experiences such four compression processes as oblique shock, λ-shape shock/shock train, λ-shape shock/normal shock and λ-shape shock. With the increasing of rotational speed, the shock wave incident location on the shroud approaches downstream passage gradually, which causes high total pressure ratio and large loss. The support segment experiences minimum loss condition when back pressure rises. As rotational speed increases, total pressure recovery coefficient in the support segment changes from 0.944 to 0.875, which means high flow loss.
Deterministic stress modelling in transonic compressor based on nonlinear harmonic method
ZHAO Jun, LIU Bao-jie
2015, 30(10): 2440-2449. doi: 10.13224/j.cnki.jasp.2015.10.018
Abstract PDF(1253KB) icon979 icon705
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Three-dimensional unsteady, nonlinear harmonic method calculation procedures were developed based on three-dimensional Denton steady solver. The high-modeling-precision advantage of nonlinear harmonic method was validated by contrast the deterministic stresses(DS) field solved with unsteady and nonlinear harmonic method for two three-dimensional single-stage and multi-stage transonic compressor simulation cases,and the five sources of modeling error were analyzed. Results show that with the increase of harmonic orders, the value of deterministic stress constantly goes to a limit, presenting the characteristic of “harmonic convergence”. Only first two harmonic components taken into account was the best choice in the simulation cases because of its high benefit-cost ratio.
Numerical simulation of transition flows based on S-A turbulence model and intermittency transport equation
DU Lei, NING Fang-fei
2015, 30(10): 2450-2461. doi: 10.13224/j.cnki.jasp.2015.10.019
Abstract PDF(1570KB) icon1929 icon687
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Considering the intermittency transport equation in γ-Reθt model independent of a specified turbulence model, a numerical simulation method for transitional flow by coupling the S-A turbulence model with intermittency transport equation was proposed. To control the generation and development of turbulence, two coupled functions related to the intermittency were applied on the production and destruction terms of S-A model respectively. As the model equations are local type, they can be easily implemented into an existent CFD code and 3-D transitional flows can also be solved directly. Four typical test cases indicate that the presented model has the equal accuracy as γ-Reθt model. And due to pruning of two equations, the current model can decrease 15% time cost.
Quick calculation method of internal/external conjugation for steady/unsteady flow field in cooled turbine
TIAN Yong, JI Lu-cheng, SHAO Wei-wei, XIAO Yun-han
2015, 30(10): 2462-2471. doi: 10.13224/j.cnki.jasp.2015.10.020
Abstract PDF(1380KB) icon1101 icon623
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A source transfer method, which is used to couple the flow network calculation of blade internal flow and source simulation of blade external cooling, was embedded into a 3D aero code, which is usually used to calculate blade external flow, then a quick simulation of a whole cooled blade was carried out. A computer program called CTUCP was developed based on this method. CTUCP was first used to calculate the steady cooling of the turbine vane cascade C3X, and the result was compared with the result of CFX, proving that CTUCP can calculate stably, faster by one order of magnitude, and give close prediction of the blade wall temperature distribution trend except at the leading edge. Next, CTUCP is used to calculate pulsed cooling of C3X, obtaining the characteristic of the coolant and wall temperature under two different pulse amplitudes.
Vortex structure of secondary flow in transonic axial compressor with low Reynolds number
HU Jia-guo, WANG Ru-gen, LI Kun, GUO Fei-fei
2015, 30(10): 2472-2480. doi: 10.13224/j.cnki.jasp.2015.10.021
Abstract PDF(1204KB) icon1503 icon664
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To explore the flow pattern under conditions of high altitude low Reynolds number in transonic compressor, simulation for NASA Rotor37 was conducted to probe for its vortex structure in secondary flow at high altitude condition. The study finds that the pressure side branch of horseshoe vortex induces a small-scale vortex located on the pressure side corner area near hub, corner vortex form a two-stage vortex with downstream and upstream directions, shedding vortex is developed from blade root and shed from the trailing edge, and leakage vortex near stall point only partially rupture, not as the main reason for the instability. Channel shock waves induce two radial vortexes near suction side and pressure side, the pressure side radial vortex forms a closed bubble separation, suction side radial vortex crash in blade tip passage and induce separation vortex, triggering compressor's instability under low Reynolds number. Vortex structure is consisted of horseshoe vortex, corner vortex, radial vortex, leakage vortex, separation vortex, shedding vortex and other small-scale vortexes.
Finite volume compact algorithm suited to computation of supersonic flow field
ZHU Zhi-bin, YUAN Xiang-jiang, CHEN Lin
2015, 30(10): 2481-2487. doi: 10.13224/j.cnki.jasp.2015.10.022
Abstract PDF(1047KB) icon1125 icon628
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In order to combine the advantages, a compact scheme based on finite volume method was developed. A characteristic limiter was used to prevent non-physical oscillations across discontinuity, so the scheme was suited to simulate supersonic flows in aerospace flight. The performance of the scheme was assessed by computing several typical problems. Numerical results reveal that the present scheme can capture discontinuities with few oscillations and simulate various waves sharplybesides, the scheme is able to distinguish small-scale flow structures clearly, and the results solved by the scheme are highly consistent with exact solutions.
Improvement and verification of γ-Reθt transition model
QIAO Lei, BAI Jun-qiang, HUA Jun, XU Jing-lei, ZHANG Yang
2015, 30(10): 2488-2497. doi: 10.13224/j.cnki.jasp.2015.10.023
Abstract PDF(1388KB) icon1430 icon712
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A defect of γ-Reθt transition model in outflow transition simulation, i.e., secondary wall friction coefficient up-jump in turbulent zone was investigated and the solution was proposed. The reason of secondary friction coefficient up-jump phenomena was discussed and proved to be the inappropriate solution of transitional momentum thickness Reynolds number that resulted in the failure of boundary layer indicator in the transition model. This problem was addressed by a boundary layer indicator defined by the ratio of shear stress magnitude over vorticity magnitude. When the secondary friction coefficient up-jump was suppressed, friction coefficient value in turbulent zone was lower than expectation. To solve this problem, a viscos sublayer indicator was introduced by Langtry in early time. However, that indicator may be active outside the boundary layer, leading to an incorrect solution of intermittency. To address this problem, a limiter based on viscosity ratio, intermittency and boundary layer indicator was defined upon the viscos sublayer indicator. Finally, the case was validated by flat plate Aerospatiale A-foil and a Reynolds number of 2.1×107 NACA 642A015 finite wing. Results show that the modification introduced improves the capture of γ-Reθt transition model to boundary layer and viscos sublayer,and friction coefficient distribution is better predicted.
Blowing control in S-shaped inlet with significant boundary layer ingestion
LIU Lei, CHEN Fu, SONG Yan-ping, CHEN Huan-long
2015, 30(10): 2498-2507. doi: 10.13224/j.cnki.jasp.2015.10.024
Abstract PDF(1884KB) icon1190 icon639
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Numerical simulation of blowing active flow control on a half flush-mounted S-shaped inlet was performed for improving its aerodynamic performance. The blowing control mechanism and influence of parameters (i.e. blowing location, blowing mass flow, blowing angle) variation on effect of blowing flow control were analyzed in detail. Results show that location selected for blowing has significant influence on effect of blowing, the 1st bend just before the separation point is the best blowing location. The total pressure recovery coefficient has a little rise about 0.56% and circumferential total pressure distortion coefficient and swirl distortion coefficient at exit reduce about 43.14% and 83.60% respectively in comparison with the prototype when blowing at 1st bend with blowing angle of 20° and ratio of blowing mass flow to air intake design mass flow about 1.75%. In addition, bigger angle doesn't mean better, on the contrary, little blowing angle should be selected for avoiding the high-energy air from pipes mixing with mainstream in the air intake. Moreover, blowing mass flow rise has different effects on total pressure recovery, circumferential total pressure distortion and swirl distortion. The improvement of first two becomes more obvious with the increase of blowing mass flow, while the third declines rapidly firstly, then falls slowly and even presents an increasing trend at last.
Error analysis of lateral jet interaction flow field of supersonic vehicle with traditional numerical method
YANG Lei, YE Zheng-yin
2015, 30(10): 2508-2515. doi: 10.13224/j.cnki.jasp.2015.10.025
Abstract PDF(1143KB) icon1061 icon558
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With CFD method, the lateral jet interaction flow fields in supersonic cross-flows were simulated under real nozzle boundary condition and simplified nozzle boundary condition respectively. Three-dimensional N-S equations closed with k-ε turbulence model were solved and the unstructured grids were used to process spatial discretization for the flow field. By comparison, the calculated values were in good agreement with the experimental results, validating the numerical method. Further study showed that the boundary conditions had an effect on the lateral jet interaction flow field. Compared with the simplified nozzle boundary condition, due to the nonuniformity of the jet flow field at the nozzle exit, the separation vortex and the shock waves under real nozzle boundary condition moved forwards, thus causing the change of the interaction force and moment. Because of the influence of the frictions, the static thrust of the nozzle under the real nozzle boundary condition had a loss. When the pressure ratio was 500, the errors of the total normal force and total pitching moment between these two boundary conditions were 8.21% and 22.4% respectively, the errors were large. The real nozzle boundary should be considered when simulating the lateral jet interaction flow field accurately.
Research on elastic deformable geometry of hypersonic inlet with multiple forces
YANG Shun-kai, ZHANG Kun-yuan, WANG Lei, LI Yong-zhou
2015, 30(10): 2516-2522. doi: 10.13224/j.cnki.jasp.2015.10.026
Abstract PDF(902KB) icon1056 icon602
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Since 2-D hypersonic inlet should work with Mach numer ranging from 4.5 to 6.0, an elastically deformable scheme of inlet's compression surface with multiple forces was explored in this work. With numerical computation, the optimal number of forces was firstly studied. The results showed that three forces were more effective in elastic deformation. Then the inlet deformation with the three forces was analyzed by the method of fluid-structure interaction (FSI). The results indicated that the distribution of static pressure on the deformable compression surface was almost consistent with that on the ideal surface. The results of performance analysis demonstrated that the flow coefficient of the 2-D inlet designed at Mach numer is 6.0 could reach 0.98 at Mach numer is 4.5 and 1.00 at Mach numer is 5.0 after deformation. Furthermore, the total pressure at exit section just remained unchanged compared with fixed geometry inlet. These indicate that the elastically deformable scheme of 2-D inlet with multiple forces is feasible, and also helpful to improve the inlet's characteristics at off-design points.
Identification of unmanned coaxial helicopter model based on UKF
ZHANG Xing-wen, CHEN Ming, MA Yi-min, WANG Bao-bing
2015, 30(10): 2523-2530. doi: 10.13224/j.cnki.jasp.2015.10.027
Abstract PDF(1222KB) icon1107 icon579
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Nonlinear model of the unmanned coaxial helicopter system was built, and on account of considering its strong nonlinear character, as well as the aerodynamic parameters were variable under different flight modes, the unscented Kalman filter (UKF) was introduced to solve the nonlinear model identification problem of coaxial helicopter. It did not only avoid the limitations that linear model was only appropriate to hover modes of helicopter model, but also provided the basis for the online adaptive control of helicopter system, in which autonomous unmanned coaxial helicopter's full envelope flight could be possible. Identification of the FH-1 unmanned coaxial helicopter developed by Beijing University of Aeronautics and Astronautics was simulated by the approach and the predictive error method(PEM). Simulation experiment results show that the online identification of coaxial helicopter nonlinear system based on UKF does not depend on the selection of initial parameters, parameters can converge within the validity period of 10s, and the accuracy of identification reached 80%,which is higher than the classical PEM, so it has a certain practicality.
Research of short take off and vertical landing engine modeling techniques
REN Bing-tao, LI Qiu-hong, KANG Lan, WANG Yuan
2015, 30(10): 2531-2538. doi: 10.13224/j.cnki.jasp.2015.10.028
Abstract PDF(935KB) icon1215 icon631
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The component-level model of variable cycle engine for short take off and vertical landing (STOVL) was built based on modeling method of two-spool-turbofan engine. On the basis of characteristics extrapolation method, the shaft-driven lift fan mathematical model was built. Models of the bypass duct were built using neural network for mapping the bypass total pressure loss. According to the structure and specialty of short takeoff and vertical landing, the static and dynamic co-working equations were set up. With reference to foreign researches' simulation data, the design point was calculated. According to Bevilaqua's method, transient simulation of switching between conventional turbofan and hover turboshaft cycle was carried out. The results of numerical simulation indicate that the error of the mathematical model and foreign research data is less than 1.5%, and the thrust meets hover state requirements. Both models can offer high levels of thrust by increasing the fuel flow a little. The performance variation in simulation is consistent with the specialty of STOVL, so the modeling method of STOVL proposed is feasible.
Research of object-oriented general aero-engine modeling techniques
HU Wei-bo, CHENG Bang-qin, CHEN Zhi-min, ZHAO Hang
2015, 30(10): 2539-2545. doi: 10.13224/j.cnki.jasp.2015.10.029
Abstract PDF(916KB) icon1048 icon634
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To carry out calculation of specified engine performance quickly, general aeroengine performance simulation system was built based on object-oriented technique. At the same time, a variable component method of gas thermodynamic properties for calculation was adopted to overcome the defects in the current calculation model. In the performance simulation of engine, coupling, bleeding, cooling and power extraction were considered. Moreover, debug can be achieved easily and correctly because some exception handling facilities were added into it. Thus, reliability of system was improved. A simulation of two-spool mixed turbofan engine was performed, and the results were compared with experimental data. The results show that the variable component method has good accuracy. The error of thrust is usually less than 3%, and that of specific fuel consumption is less than 2.5%. Besides the precision has improved especially at high altitude and low Mach number.
Force and heat effect of shock wave in nozzle interior on nozzle for celestial body outside earth taking off
HE Wei-dong, DANG Hai-yan
2015, 30(10): 2546-2552. doi: 10.13224/j.cnki.jasp.2015.10.030
Abstract PDF(1021KB) icon906 icon589
Abstract:
In order to study the force and heat effects of the shock wave on nozzle, numerical simulation was carried out. The effects of force and heat on the nozzle, and the distribute pattern of the shock wave inside the nozzle were mostly analyzed when the probe rose in different flow deflectors and rising angles. The condition for the shock wave to leave from the interior of nozzle was achieved. When the shock wave entered the interior of nozzle but did not cling to the wall of nozzle, the extra force and heat was not generated. But when the shock wave in the interior of nozzle clung to the wall of nozzle, the extra force and heat was generated in the wall-clinging area. The conclusion makes contribution to the structural layout design of the probe.
Research on the pressure oscillation characteristics ofdouble pulse solid rocket motor
LIU Wei-kai, HE Guo-qiang, WANG Chun-guang
2015, 30(10): 2553-2560. doi: 10.13224/j.cnki.jasp.2015.10.031
Abstract PDF(1017KB) icon1402 icon646
Abstract:
In order to reveal the relationship between the melting of pulse separation device (PSD) and the pressure oscillation, several melting moments were selected for research. Large eddy simulation (LES) was carried out for the numerical simulation of II pulse flow field, and the pressure-time curve and fast Fourier transformation (FFT) results were obtained successfully.The analysis results show that the additional disturbance in the flow field generated by opening PSD when the Ⅱ pulse is working, and the acceleration of interstage narrow channel, are the main factors to obstacle vortex shedding caused by boundary layer separation. In the early ignition, the double pulse motor (DPM)is prone to slight pressure oscillation. With the PSD melting, the whole flow field becomes more and more stabilized.

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