2015 Vol. 30, No. 7

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Velocity and temperature similarity solutions of wedge flow laminar boundary layer with wall injection
ZHAO Guo-chang, DU Xia, SONG Li-ping, SHAN Long, KONG Jing-ru, PENG Da-wei
2015, 30(7): 1537-1545. doi: 10.13224/j.cnki.jasp.2015.07.001
Abstract PDF(1199KB) icon1188 icon834
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The mathematical model of the wedge flow laminar boundary layer with wall injection boundary was established. Based on this model, the similarity solutions of dimensionless velocity and temperature distribution in the laminar boundary layer were obtained by solving the ordinary differential equations of the dimensionless stream function and dimensionless temperature. The ordinary differential equations were derived through similarity transformation from the partial differential equations describing the flow and heat transfer of wedge flow laminar boundary layer with wall injection. The curve fitting of dimensionless stream function derived takes into account the wall injection effect of cooling gas. The Runge-Kutta method was used to solve the ordinary differential equations of dimensionless stream function and dimensionless temperature in order to analyze the variations in the dimensionless velocity and temperature distributions in the wedge flow laminar boundary layer with wall injection with changes in wedge angle, blowing parameter, and cooling medium temperature. The results of the dimensionless velocity and temperature similarity solutions in the laminar boundary layer of wedge flows with wedge angles of 0°, 18° and 36° show that both the velocity boundary layer thickness and temperature boundary layer thickness of the laminar wedge flows with wall injection enlarge with the increase of blowing parameter and reduce with the increase of wedge angle; the boundary layer temperature gradient near the wall is larger with lower cooling media temperatures, smaller blowing parameters, and larger wedge angles.
Characteristics of low swirl flow and combustion in a limited space
DENG Yang-bo, SONG De-yan, XU Zhen, JIANG Xi
2015, 30(7): 1546-1553. doi: 10.13224/j.cnki.jasp.2015.07.002
Abstract PDF(1555KB) icon1502 icon765
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To further understand the characteristics of low swirl flow and its effect on the propagation and stability of flame, the characteristics of low swirl flow and combustion in a limited space were studied, through combining experiment method with numerical simulation method. Results show that,changing the diameter of the hole in the plate of center hole can form the swirl injectors with different swirl numbers;in cold state, with increasing of swirl number, gradually formed the “W” shape the velocity vector distribution on spanwise section. there are higher velocity in the annulus zone, lower velocity in central zone and lower velocity outside zone on vertical section. The absorption and heat expansion of gas, vorticity induced and temperature baroclinic effect induce a transition from high swirl flow with recirculation in cold state to low swirl flow without recirculation in combustion state; In a limited space, the low swirl combustion cannot form detached flame, but form a flame similar to the diffusion combustion flame; the temperature distribution boundary and chemical reaction boundary gradually get shorter along spanwise section, and gradually get wider along vertical section.
Influences of pressure ratio and Reynolds number on flow characteristics of labyrinth seal in compressor stator well
LIU Gao-wen, CHEN Kai, GANG Tie, ZHENG Hai-liang
2015, 30(7): 1554-1560. doi: 10.13224/j.cnki.jasp.2015.07.003
Abstract PDF(927KB) icon1156 icon764
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To study the flow characteristics of a labyrinth seal in a compressor stator well, numerical simulations on the performances of a labyrinth seal with inlet and outlet rotating disc cavities of an aero-engine compressor was carried out. Sealing characteristics, swirl characteristics and windage heating characteristics were studied in depth at pressure ratio range 1.05-1.30 and Reynolds number range 100-50000. The differences of the flow characteristics of straight-through labyrinth with/without inlet and outlet rotating disc cavities were compared. The computational results show that inlet and outlet rotating disc cavities have obvious influence on the flow of the labyrinth. With the increase of pressure ratio, the discharge coefficient increases, and the sealing effect grows worse, while the outlet swirl ratio and windage heating decreases. With the increase of Reynolds number, the discharge coefficient increases significantly, the outlet swirl ratio and windage heating decreases. At high Reynolds number, the discharge coefficient, outlet swirl ratio and windage heating changes slightly.
Effects of inlet flow parameters oscillation on combustion instability of gas turbine combustor
XIE Fa, ZHANG Shan-shan, JIANG Hong-de
2015, 30(7): 1561-1565. doi: 10.13224/j.cnki.jasp.2015.07.004
Abstract PDF(827KB) icon1873 icon896
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The effects of inlet flow parameters oscillation on combustion instabilities of a gas turbine combustor were studied by introducing perfectly stirred reactor (PSR) model. The simulation results demonstrate that, for lean premixed combustor (combustor operating at low inlet equivalence ratio), when the relative oscillation amplitudes of inlet temperature, inlet mixture mass flow rate and inlet equivalence ratio are the same, the oscillation of inlet equivalence ratio has the largest effect on combustion instability phenomenon, then followed by inlet mixture mass flow rate, and the inlet temperature yields the lowest effect.
Unsteady swirling flow in low emissions stirred swirls combustor
QIN Hao, DING Zhi-lei, LI Hai-tao, LIN Yu-zhen, LI Ji-bao
2015, 30(7): 1566-1575. doi: 10.13224/j.cnki.jasp.2015.07.005
Abstract PDF(1330KB) icon1142 icon835
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The unsteady flow characteristics of low emissions stirred swirls (LESS) combustor swirlers outlet were studied, in combination with experiments and CFD calculation. One-dimensional hotwire tests results show periodic velocity oscillations of 2249Hz existed in the flow field of pilot stage outlet, but didn't appear at main stage outlet. Transient large eddy simulation (LES) calculation had been adopted to verify that velocity at swirlers outlet tested by one-dimensional hotwire has a difference of 8% to real three-dimensional flow. And the simulation results show periodic velocity oscillations of 2331Hz with a difference of 3.6% to experiments. The periodic velocity oscillation phenomenon is dominated by processing vortex core movement in pilot through spectrum analysis and correlation analysis.
Three-dimensional numerical simulation of the parametric properties of continuously rotating detonation engine
WU Dan, LIU Yan, WANG Jian-ping
2015, 30(7): 1576-1582. doi: 10.13224/j.cnki.jasp.2015.07.006
Abstract PDF(935KB) icon1546 icon806
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Based on Euler equations with one-step chemical reaction model in generalized coordinates, three-dimensional numerical simulation of the continuously rotating detonation engine (CRDE) were performed to investigate the effect of inlet total pressure on its parametric properties. It is found that the peak value of the detonation wave increases with the inlet total pressure; however, the choking ratio of the injection Laval nozzle along the head end is not influenced by it. Across the whole head end of CRDE, combustible gas is injected into the combustion chamber subsonically for different inlet total pressures. With the increase of inlet total pressure, the average pressure inside the chamber increases obviously, but the average axial velocity changes little. The mass flux, force and specific impulse of CRDE increase with the inlet total pressure. However, the ratio of the mass flux of CRDE to the maximum mass flux of the injection Laval nozzle remains the same under different inlet total pressures, almost equal to the choking ratio of the injection Laval nozzle. As the maximum mass flux of the injection Laval nozzle has a linear growth with the inlet total pressure, the above analysis provides a theory explanation about why the mass flux of CRDE increases linearly with the inlet total pressure.
Numerical study of flow characteristics in rotating S-shaped passage with ribs
WANG Shun-bin, ZHANG Li, ZHAO Shu, ZHU Hui-ren, SUN Rui-jia
2015, 30(7): 1583-1591. doi: 10.13224/j.cnki.jasp.2015.07.007
Abstract PDF(1291KB) icon1350 icon753
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For better understanding of the flow characteristics of turbine blade internal cooling passage, a numerical study was conducted to investigate the influences of rib, turn and rotation on the flow characteristics in full S-shaped passage with ribs. The Reynolds number was 17000, three outlet discharge ratios were 27%,49%,24%, rotation numbers were 0,0.03,0.06,0.09. The results reveal that the fluid has stronger turbulence and lower velocity with higher blockage ratio near the leading edge of passage 1. Turn causes the flow separation and shift of mainstream downstream the turn. There is a big range of low velocity area near the bulkhead in the passage 3. Coriolis force makes the fluid shift towards the wall to which the Coriolis force points, the mainstream shifts towards suction surface and pressure surface in passage 2 and passage 3 respectively. Rotation affects the distribution of the secondary flow in passage and promotes the flow of low velocity circumfluence area downstream the turn.
Scrubbing inerting engineering calculations in multi-bay fuel tank of an aircraft
LIU Yu-lin, WANG Xue-de, MU Xiao-hong, YANG Guo-liang
2015, 30(7): 1592-1598. doi: 10.13224/j.cnki.jasp.2015.07.008
Abstract PDF(994KB) icon1207 icon814
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In order to research the scrubbing inerting process in multi-bay fuel tank of an aircraft, scrubbing gas was transformed into two sections, fuel mass transfer section and no-mass transfer section. By theoretical calculation, fuel was in mass transfer with scrubbing gas and the amount of oxygen escaped to the gas phase space was obtained. The no-mass transfer section could be used to access the gas space directly considered as fuel washing process. The other section could be combined to build the model for engineering calculations by working out the amount of oxygen spilling from fuel. In this way,the whole scrubbing inerting process was transformed into washing process with escaping gas. The results show that the model for the conversion of scrubbing inerting to washing with overflow is really credible. The results of the model are consistent with experiment results. As time increases, the gas phase oxygen volume fraction will increase and then decrease again, converging to a final gas phase oxygen volume fraction equal to the value of the scrubbed gas. The result of multi-bay fuel scrubbing shows the time required for stabilizing is related to the distance from the inlet and the volume of each bay.
Aeroacoustic characteristic of siren incentive system
DING Zhi-lei, LIN Yu-zhen, QIN Hao, TANG Guan-qiong
2015, 30(7): 1599-1604. doi: 10.13224/j.cnki.jasp.2015.07.009
Abstract PDF(861KB) icon1292 icon775
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Based on siren incentive system, the energy transform relationship between unsteady flow fluctuation velocity brought by siren actuator and acoustic particle velocity got by the two-microphone technique was derived. And the effect of incentive intensity, frequency, Mach number and the sensor spacing on the acoustic particle velocity was studied through the aeroacoustic characteristic experiment, verifying the theoretical model. The results are as follows: acoustic particle velocity can't be fully converted by unsteady flow fluctuation velocity, the transform relationship between velocities mentioned above is related to Mach number. Under incompressible condition, Mach number less than 0.3, the energy transform factor is proportional to the square of Mach number, and the larger Mach number means, the larger energy transform factor, and the higher conversion efficiency of unsteady flow to acoustic energy.
Influence of spray orientation parameters on spray lubrication process of aero spur gears
WANG Yan-zhong, NIU Wen-tao, TANG Wen, GUO Mei, LI Guo-quan
2015, 30(7): 1605-1610. doi: 10.13224/j.cnki.jasp.2015.07.010
Abstract PDF(1025KB) icon1404 icon834
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Spray orientation parameters influencing lubrication initial conditions of gear meshing point were systematic definied through the analysis of spray lubrication process of aero spur gears, then the computational fluid dynamics(CFD) method of spray lubrication process was established. Three kinds of spray parameter including spray angle, spray point position and spray distance were calculated, jet states were obtained with different meshing instantaneous of gears. The varying rules of the oil/air ratio and oil/air total pressure at the entrance of contact point were compared in the meshing process under different spray parameters.Result show that, nozzle should offset a small angle to driving wheel when spray lubrication using engaging-in side in order to get better lubricating effect,and spray point position should offset engaging-in side, spray distance should take into account the structure, working condition, not general idea that the closer the better.
Design method and revising strategy of inherent characteristics for dynamical similarity test model of blade
LUO Zhong, GUO Jian, ZHU Yun-peng, WANG De-you
2015, 30(7): 1611-1617. doi: 10.13224/j.cnki.jasp.2015.07.011
Abstract PDF(1038KB) icon1385 icon788
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In allusion to the problem of designing the similarity test model of using straight blade to predict the inherent characteristics of the real torsion blade, a dynamical similarity model designing method of the straight test model blade and a revising strategy were put forward under the condition to have the same inherent characteristics. Research shows that, the torsion blade when the torsion angle in the similar intervals (natural frequency error is less than 5%), can predict the inherent characteristics directly using the geometry similar straight blade. When the torsion angle not in the similar intervals, need to modify the inherent characteristics with correction coefficient, and the modified values can predict the inherent characteristics of the prototype blade accurately.
Finite element analysis for the effect of notched radius on fatigue life
JIN Dan, TIAN Da-jiang, LI Jiang-hua, LIN Wei, CHEN Xu
2015, 30(7): 1618-1623. doi: 10.13224/j.cnki.jasp.2015.07.012
Abstract PDF(930KB) icon1313 icon768
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A series of tests for low cycle fatigue were conducted for the notched specimens of Mod.9Cr-1Mo ferrite steel under nonproportional loading. The crack initiation life was measured by the direct-current(DC) potential difference method. The effects of the notched radius and strain path on crack initiation life were discussed. The test results show that the ratio of the crack initiation life to the fatigue life is related to the strain path and notched radius. ANSYS software was used for simulation, while the von Mises yield criterion, multlinear kinematic hardening rule, and uniaxial cyclic stress-strain curve were employed to indicate the material elastic-plastic behavior. The simulation results show that the stress concentration at the notched root occurs significantly for any strain paths. It is obvious that the maximum equivalent stress lies in the notched root. But the stress decreases with the increase of distance. For different notched radiuses, the changing trend of the stress gradient with the distance to the notched root differs with the strain paths. Smith-Watson-Topper (SWT) model was used to predict the fatigue life based on the simulation results. The better prediction results are gained for the larger notched radius and most results are in a factor-2 scatter band. But for smaller notched radius, the predictions are conservative.
Influence of contact characteristics on thermal induced vibration of non-continuous rotor
XU Ning, LIU Zhan-sheng, DONG Yan-yang, WANG Zhen-lin, WANG Qing-chao
2015, 30(7): 1624-1631. doi: 10.13224/j.cnki.jasp.2015.07.013
Abstract PDF(1040KB) icon1215 icon629
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According to the contact characteristics of the non-continuous structure in gas turbine rotor and the asperity theory, the contact stiffness and contact thermal resistance equivalent model were introduced. Dynamic model for a non-continuous rotor of gas turbine was established. The influence of contact parameters on steady and transient state dynamic characteristic of rotor was analyzed.The thermal deformation of rotor caused by bolt looseness was studied, and the vibration characteristics of rotor based on fast start-up process were analyzed. Result shows that, the pre-tightening force, surface roughness of contact surface and bolt number have a certain influence on critical speeds of rotor, the maximum transient thermal deformation of rotor caused by bolt looseness in start-up process is up to 7μm, and the maximum response amplitude caused by rotor across the first critical speed is increased about 30μm. The influence of contact parameters, contact stiffness and contact thermal resistance of non-continuous rotor on thermally induced vibration characteristics analyze should not be ignored.
Comparison of two reliability models for performance degradation analysis
WANG Zhi-hua, ZANG Guang-kui, ZHANG Yong-bo, FU Hui-min
2015, 30(7): 1632-1637. doi: 10.13224/j.cnki.jasp.2015.07.014
Abstract PDF(897KB) icon1087 icon578
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In order to investigate the general reliability assessment methods based on performance degradation data, two commonly used stochastic process approaches, bilinear process method and random-effect model were studied. Analyzing procedure and effectiveness of these two methodologies were studied and compared. Meanwhile, the two approaches were illustrated through practical applications. The residual plots and the 10th percentile curves of the two methods were presented to demonstrate the comparative results. The random-effect model yielded more volatile residuals and a lower and unsafe 10th percentile curve. Consequently the bilinear process model can be concluded to derive more reasonable results due to its one-stage estimation property.
Pultrusion and properties of the twisted carbon fiber/phenolic resin Z-pin
ZHANG Xiang-yang, LI Yong, CHU Qi-yi, LI Wen
2015, 30(7): 1638-1644. doi: 10.13224/j.cnki.jasp.2015.07.015
Abstract PDF(889KB) icon1170 icon660
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The main goal is to solve the pore defect of the pultruded carbon fiber/phenolic resin Z-pin and obtain the three-dimensional reinforcement of ablation resistant composite. On basis of the analysis of the pore formation and phenolic resin curing process, the twisted yarn was utilized to elevate the resin's inner pressure to eliminate the pore defects in Z-pin. The results showed that, along with the increase of the twist number within the specific range, the size and amount of pores declined obviously, and also the phenolic resin mass fraction and maximum insertion depth decreased, while the compressive property arose firstly and declined afterwards. When the twist number was 80twist/m, Z-pin of good quality was obtained with approximately 32% phenolic resin mass fraction, which can be used for ultrasonic insertion, with the maximum insertion depth up to 10mm in room temperature.
Experiment of jet noise reduction technology using lobed mixer
SHAO Wan-ren, HE Jing-yu, WU Fei, LI Xiao-dong
2015, 30(7): 1645-1650. doi: 10.13224/j.cnki.jasp.2015.07.016
Abstract PDF(937KB) icon1482 icon663
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On the basis of the baseline nozzle with annular mixer, the far field noise spectra performance and the noise reduction of the nozzle with lobed mixer were investigated under cold jet condition through scaled model experiments of high bybass ratio turbofan engine mixing exhaust system. The experiments were carried out on the jet noise experiment rig in the anechoic chamber. The experimental results show that, compared with the baseline nozzle with annular mixer, the nozzle with lobed mixer has better jet noise reduction at low frequencies, but the sound pressure level increases at high frequencies, while overall sound pressure level reduces at downstream(θ=150°)but increases at middlestream and upstream. With increased velocity differences between core exit flow and fan exit flow of lobed mixer, the nozzle with lobed mixer has better noise reduction at low frequencies, but the sound pressure level increases at high frequencies, while overall sound pressure level reduces at downstream(θ=150°)but increases at middlestream and upstream.
Comparison on aerodynamic and stealthy performanceof flying wing unmanned aerial vehicle withthree conformal intake inlets
ZHANG Le, ZHOU Zhou, XU Xiao-ping, WANG Hong-bo
2015, 30(7): 1651-1660. doi: 10.13224/j.cnki.jasp.2015.07.017
Abstract PDF(1444KB) icon1489 icon758
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Based on stealth and structural loading requirements of flying wing unmanned aerial vehicle (UVA), three dorsal S-shaped inlets with three conformal intakes were designed. According to the ratio of the upper and bottom of the sectional projection shape of the intake, three inlets, i.e.: triangular, trapezoidal and rectangular inlets, were named. The coupled numerical simulation was carried out on the inflow/outflow integrated for flying wing UAV, and the simulation method based on shooting and bouncing ray (SBR) was also performed to study the electromagnetic scattering of inlet. Then the aerodynamic and stealthy performance of flying wing UAV with three conformal inlets was obtained. Results indicate: (1) The lift/drag and the longitudinal moment characteristic of the model with rectangular inlet are the best.(2) As the three inlet models are arranged in previous order, the total pressure recovery coefficient increases gradually, and the distortion coefficient decreases; moreover, the airflow along the inlet becomes smooth gradually, and then, of course, the internal flow characteristic of the model with rectangular inlet shows the best.(3) At the attack angle 0° the mean value of the three inlet models radar cross-section (RCS) increases first and then decreases basically.The stealthy performance of the model with rectangular inlet is the best with the terminator open, but the model with triangular inlet shows better when the terminator is short-circuited.
Flow field of cylindrical membrane inflation under the fluid-structure interaction
WANG Cong-lei, SUN Jian-hong, XU Chang-yue, HOU Bin
2015, 30(7): 1661-1669. doi: 10.13224/j.cnki.jasp.2015.07.018
Abstract PDF(1302KB) icon962 icon595
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Numerical research on the flow field characteristics of the cylindrical membrane inflation was performed by the Euler-Lagrangian method. The results show that bumps are formed at two ends of the cylindrical membrane, swinging vertically during the inflation within inlet velocity range (50-90m/s) and inlet pressure range (1.0-1.4MPa). With the analysis on the flow structure, vorticity transportation and the mechanism of vortex/shock interaction in the flow field inside the cylindrical membrane, it is found that there is a cured shock adjacent to the inlet tube, making flow deflection. Vortexes formed by the deflected flow interact with shock, resulting in local supersonic zones. Based on the discussion about cylindrical membrane stress distribution, the local stress concentrations at the top and two ends of the cylindrical membrane are considered as important factors influencing the safety and stability. Comparing the results of different inlet pressures and velocities, it is found that the influence on safety caused by the inlet velocity is less than the inlet pressure, and the influence on stability caused by the inlet velocity is greater than the inlet pressure.
Transition prediction based on amplification factorand Spalart-Allmaras turbulence model
SHI Ya-yun, BAI Jun-qiang, HUA Jun, YANG Ti-hao
2015, 30(7): 1670-1677. doi: 10.13224/j.cnki.jasp.2015.07.019
Abstract PDF(1119KB) icon1186 icon628
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To verify the simulation accuracy of current model coupling amplification factor transport equation with Spalart-Allmaras (S-A) turbulence model, Schubauer and Klebanoff flat plate (S-K), S809 low speed airfoil, 30p30n multi-element airfoil and complicated 3-D HiLiftPW-1 configure were selected for free transition calculation, and then, simulation results were compared with experimental results. Separately, current coupling model was compared with Langtry-Menter (L-M)transition model for S809 test cases. Test examples indicate that current coupling transition model can basically capture transition location and transition process, meanwhile, current coupling model performs better than L-M transition model in separated flow transition, and simulation accuracy increases by 10%; the maximum error of multi-element airfoil's transition position simulated is 6.5% compared with experiment data. For three dimensional high-lift configuration, comparison between full turbulence and free transition shows that considering boundary layer transition can simulate aerodynamic force coefficient more accurately and accuracy is promoted by 1%.
Study of variable geometry supersonic inlet aerodynamic performance in a wide Mach number range
ZHAO Hao, XIE Lü-rong, GUO Rong-wei, WANG Jian-yong, ZHANG Jun
2015, 30(7): 1678-1684. doi: 10.13224/j.cnki.jasp.2015.07.020
Abstract PDF(1012KB) icon1666 icon645
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In order to improve the off-design aerodynamic performance of supersonic inlet, a two-dimensional variable geometry inlet with the free stream Mach number from 2.0-4.5 was designed. Numerical simulation was applied to investigate the inlet aerodynamic performance, and a superior scheme of variable geometry was acquired. The aerodynamic performance was compared between variable geometry inlets and fixed ones. The results indicate that the variable geometry technique could improve the inlet aerodynamic performance at the starting Mach number; Mach number at the throat of variable geometry inlet decreases with the increase of the inlet ramp angle and contraction ratio when the free stream Mach number ascends. The variable geometry inlet has better aerodynamic performance during a wide range of Mach number, its mass flow rate and total pressure recovery coefficient are 19.4% and 55.8% respectively higher than the fixed ones in some states.
Scramjet nozzle with adjustable cowl scheme
PANG Li-na, XU Jing-lei, GE Jian-hui
2015, 30(7): 1685-1690. doi: 10.13224/j.cnki.jasp.2015.07.021
Abstract PDF(855KB) icon1073 icon609
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The difference of cold/hot pitch moment will result in difficulty of vehicle attitude control when the hypersonic vehicle works at the relay point and cruising end point under the influence of cold and hot expansion conditions. To solve this problem, an adjustable cowl scheme was adopted and investigated, and also proven in effectively decreasing the difference of cold/hot pitch moment. The flow-field with different cowl angles was numerically simulated to obtain the performance parameters of nozzle. The results showed that, when the cowl angle was adjusted to 6°, the difference of cold/hot pitch moment was reduced by 29.57% and the thrust coefficient decreased only 0.42% in design Mach number 4.5. Finally, a wind tunnel experiment was carried out, and numerical simulation was performed based on the conditions of the wind tunnel experiment. The results of the simulation were in good agreement with experiment data, validating the effectiveness and correctness of the adjustment scheme and the results of numerical simulation.
New approach to improve the endwall flow of compressor—leading edge strake blade technique
YI Wei-lin, TANG Fang-ming, CHEN Zhi-min, JI Lu-cheng
2015, 30(7): 1691-1698. doi: 10.13224/j.cnki.jasp.2015.07.022
Abstract PDF(1387KB) icon1156 icon645
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Targeting the high flow incidence angle induced by inlet endwall boundary layer skew in compressor, the LESB(leading edge strake blade) concept was elucidated with reference to the strake wing theory from aircraft. The modeling method was developed by adding leading edge strake to main blade, and the LESB technique was formed. In order to validate the effect of technique, the LESB modeling was applied to the NACA65 diffuser cascade with turning angle 60° after the numerical method was verified by cascade test data. The performance improvement was compared between original blade and LESB at 0° and 5° incidence angles with endwall boundary layer skew through the flow field structure, performance parameters and action mechanism. The results show that LESB technique can organize effectively the flow field near endwall and improve the compressor performance. The LESB modeling with 15% span can improve the performances of 30% and 40% span at 0° and 5° incidence angles separately.
Aerodynamic optimization for twisted S1 stream surface of multi-stage turbine considering cooling air
WANG Long-fei, WANG Song-tao, LUO Lei, LU Shao-peng, WEN Feng-bo
2015, 30(7): 1699-1710. doi: 10.13224/j.cnki.jasp.2015.07.023
Abstract PDF(1263KB) icon1678 icon834
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To shorten the turbine aerodynamic design cycle and further explore the potential improvement of turbine blades, an aerodynamic optimization platform of twisted S1 stream surface for multi-stage turbine with advantages of fast speed and short design period was presented. The platform could conduct multilayer parallel optimization for multi-column blades under the premise of cooling air, avoid disadvantage of poor matching between blade columns in single column optimization, and overcome the defect of aerodynamic efficiency shift for multilayer S1 stream surface. A two stage high pressure turbine has been optimized; the results showed that, aerodynamic efficiency considering cooling air of three S1 stream surfaces of 10%, 50%, 90% blade spanwise height was increased by 0.569%, 0.490% and 0.405%, the first stage and second stage aerodynamic efficiency considering cooling was improved by 0.18% and 0.05%, and aerodynamic efficiency considering cooling air of the turbine was increased by 0.15%, showing the significant effect of optimization. The analysis indicated that, the optimization reduced the channel transverse secondary flow loss of first stage stator blades and the shock loss of first stage rotor blades effectively, and the original blade design of turbine second stage was more reasonable. Coolant injection of flow channel hub was the important reason to reduce the effectiveness of S1 stream surface optimization.
Prediction method of vehicle alternator cooling fan rotation noise
WANG Yuan-wen, DONG Da-wei, YAN Bing
2015, 30(7): 1711-1720. doi: 10.13224/j.cnki.jasp.2015.07.024
Abstract PDF(1146KB) icon1089 icon642
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A set of accurate and time-saving methods were proposed to predict the rotation noise of vehicle alternator cooling fan. First, to predict the overall noise and main order noise magnitudes of the original fan, an acoustic analogy method combined with large eddy simulation (LES) and Ffows-Williams and Hawkings (FW-H) equations was applied. Second, to predict the change of rotation noise caused by blade angle modification, a vector composition method was proposed in case only the blade distribution angle was changed. The main order noise magnitudes of the modified fan were eventually calculated. Calculations and experimental results indicate that the maximum prediction error of the overall noise of the original fan is 4.3dB, and the prediction errors of main rotation noise magnitudes in orders 12 and 18 are 1.24dB and 4.26dB, respectively. The rotation noises of the modified fan in orders 12 and 18 are decreased by 9.3dB and 10.5dB, while the prediction errors of their sound pressure level (SPL) variations are 0.36dB and 0.43dB, respectively. The results show that this set of methods can effectively predict the rotation noise of fan, providing a significant guide to the design of blade distribution angles.
Stabilizing analysis of trapezoidal circumferential grooves on an axial rotor
DENG Jing-liang, CHU Wu-li, ZHANG Hao-guang
2015, 30(7): 1721-1730. doi: 10.13224/j.cnki.jasp.2015.07.025
Abstract PDF(1161KB) icon1188 icon584
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In order to investigate the stabilizing effect of circumferential grooves in different meridional shapes, two trapezoidal grooves structures and an equal-width grooves structure were designed for the transonic rotor— Rotor 67.The numerical simulations showed that the composite stability margin of circumferential grooves in design speed was increased from 5.9% to more than 20%, and the normal trapezoidal grooves had best effect in the mall flow margin. The blade load distribution was improved, and the average work of the blade was increased too. Comparison of these various grooves shows that the upstream three grooves dominate the biggest contribution, and the normal trapezoidal one's relative contribution to stabilizing effect is the best.
Pumping speed of cryopump for xenon
LING Gui-long, WEI Li-jun, CAI Guo-biao
2015, 30(7): 1731-1736. doi: 10.13224/j.cnki.jasp.2015.07.026
Abstract PDF(775KB) icon1142 icon580
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The xenon pumping speed testing system of the large-diameter external cryopump was designed to meet the plume test requirements for prototype electric propulsion. The flowmeter method was utilized to measure the xenon pumping speed. The test results show that the averaged effective pumping speed of double-cryopumps is 52200L/s, and that of single-cryopump is 27100L/s. The pumping speed ratio of two configurations is 1.93. It can be concluded that the pumping speed has in linear relationship with the number of cryopump, and the coefficient is irrelevant with the gas type. The averaged effective pumping speed of xenon is less than its nominal pumping speed, and the averaged pumping efficiency is 0.83. Under the identical inflow conditions, the averaged effective pumping speed ratio of nitrogen is 0.53, slightly less than the theoretical pumping speed ratio of 0.55. Consequently, it can be concluded that results assessment of large-diameter external cryopump design index can guide the engineering application, showing certain reference significance.
Abnormal phenomenon of thrust reduction of range rocket nozzle under high altitude condition
ZHANG Fu, WANG Peng-xin, RUAN Wen-jun, WANG Hao, ZHU Chen-guang
2015, 30(7): 1737-1744. doi: 10.13224/j.cnki.jasp.2015.07.027
Abstract PDF(1057KB) icon966 icon591
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To research abnormal phenomenon of thrust reduction of a range rocket nozzle was chosen to study, nozzle with the same inlet pressure and different environment pressures were simulated numerically by applying the AUSM+ (advection upstream splitting method)scheme,SST(shear-stress transport) turbulence model and LU-SGS(lower-upper symmetric Gauss-Seidel)implicit algorithm were used to solve 2-D axial symmetry RANS(Reynolds-averaged Navier-Stokes) equations. The differences in thrust characteristics were obtained when the environment pressure varied from 50.67kPa to 101.32kPa, and the cause of these differences was analyzed. Results indicate that static thrust of the outer nozzle exit boundary rises toward the negative direction when the environment pressure gradually decreases, absolute value increases firstly and then decreases. Dynamic thrust and total thrust of the outer nozzle exit boundary slightly changes at the environment pressure ranging from 60.80kPa to 101.32kPa, but dynamic thrust and total thrust of the outer nozzle declines sharply when the environment pressure is less than 60.80kPa.
Numerical study on the plumes of solid rocket motor under various flight conditions
NIU Qing-lin, FU De-bin, LI Xia
2015, 30(7): 1745-1751. doi: 10.13224/j.cnki.jasp.2015.07.028
Abstract PDF(1063KB) icon1322 icon665
Abstract:
To analyze the behaviors of solid rocket motor plumes under different flight conditions, the finite volume method based on the MUSCL (monotonic upstream-centered scheme for conversation laws) Roe format was employed after establishment of governing equations including Navier-Stokes (N-S) equation and chemical reaction terms. Combined with the results from thermal calculations, chemical reaction flow and single species flow were numerically simulated for a solid rocket motor under various flight conditions. Results show that both the initial angle of the jet and the length of the first Mach shock cell rise with the increase of altitudes and the decrease of the incoming Mach numbers. The effect of the length of the first Mach shock cell is more significant than initial angle of the jet in chemical reaction flow than that of single species flow. Centerline temperature with various flight conditions is much different. The initial angle of the jet and the length of the first Mach shock cell are determined by incoming total pressure and the centerline temperature determined by the structure of shock, afterburning effect, and incoming conditions.
Experiment on breakup mechanism of impinging jet of power-law liquid
LI Jian-jun, XIA Zhen-yan, TIAN Yan
2015, 30(7): 1752-1758. doi: 10.13224/j.cnki.jasp.2015.07.029
Abstract PDF(1418KB) icon1102 icon591
Abstract:
High-speed photography technology was used to investigate four kinds of shear-thinning Carbopol gel non-Newtonian power-law fluids with different Carbopol mass fractions by self-developed impinging jet system,the breakup pattern, spray cone angle and breakup length of liquid sheet of impinging jet were experimented and analyzed under different jet conditions. Results show that power-law fluids with different rheological properties have different breakup pattern,the higher viscosity means the more complex breakup pattern, when Weber number is about 8000, four kinds of Carbopol gel achieve to fully developed pattern,and show the similar breakup pattern;as Weber number increases, the spray cone angle increases gradually and tends to be a stable value less than the impinging angle. with increasing of the Carbopol mass fraction, the biggest spray cone angle decreases, eventually converging to 60°,the breakup length slightly increases first and then decreases of four kinds of Carbopol gel, but the theoretical results agree well with the experimental results in trend.
Aero-engine condition monitoring method based on cluster features weighting
ZHOU Yuan, ZUO Hong-fu, WANG Li-na
2015, 30(7): 1759-1765. doi: 10.13224/j.cnki.jasp.2015.07.030
Abstract PDF(1123KB) icon1268 icon549
Abstract:
A model for aeroengine condition monitoring based on fuzzy C-means clustering algorithm with cluster features weighting(FWFCM) was proposed. This model is composed of two parts: one is offline-learning module, in which the module parameters are iteratively computed, and the other is online-monitoring module, in which the realtime data can be classified according to the parameters. Then the realtime data are inputed into the offline-module and the module parameters are updated. Result shows that, compared with the data weighted fuzzy clustering algorithm(DWFCM) and the classic fuzzy C-means clustering algorithm (FCM), the average condition recognition accuracy of the proposed method in offline module and in online module is 5.233% and 8.358% higher than the other two algorithms, respectively. It can be shown that the FWFCM works well for aeroengine condition monitoring with good rebustness and generalization, and has practical application value for uncertained aeroengine condition monitoring.
Limit management of aircraft engine based on nonlinear model predictive control method
DU Xian, GUO Ying-qing, CHEN Xiao-lei
2015, 30(7): 1766-1771. doi: 10.13224/j.cnki.jasp.2015.07.031
Abstract PDF(892KB) icon2198 icon706
Abstract:
In order to solve conservatism problem resulted from Min-Max selection structure currently implemented in aircraft engine control,a nonlinear model predictive controller was designed, by incorporating penalty functions into the nonlinear sequential quadratic programming (SQP) algorithm. Simulation results show that nonlinear predictive controller, whether outputs hit their limits or not, achieved faster response than Min-Max logic, particularly apparent when outputs reached their limits. In this case, the setting time is reduced from 1.16s to 0.82s, and almost no overshoot occurred.
Design and experiment of hydraulic amplified direct drive valve based on giant magnetostrictive material
YANG Zhao-shu, HE Zhong-bo, YU Jun-tao, LI Dong-wei
2015, 30(7): 1772-1783. doi: 10.13224/j.cnki.jasp.2015.07.032
Abstract PDF(1462KB) icon1129 icon650
Abstract:
A novel direct drive electro-hydraulic servo valve was proposed based on magnetostrictive material and hydraulic amplification mechanism. The frequency response of the servo valve was greatly enhanced with a considerable volume flow rate maintained. A series of structure design and analysis were conducted via finite element method and fluid mechanics theory, meanwhile, a prototype of the magnetostrictive direct drive valve was fabricated. A magneto-mechanical-hydro coupled model was established within AMESim environment, both the numerical simulation and experimental result indicated that the proposed magnetostrictive direct drive valve approached a bandwidth higher than 100Hz; the load volume flow rate reached 30L/min under a system pressure of 21MPa.
Engine reverser thrust system safety design
ZHANG Yan-hui, QIN Hao, WANG Dai-jun
2015, 30(7): 1784-1792. doi: 10.13224/j.cnki.jasp.2015.07.033
Abstract PDF(1038KB) icon1638 icon610
Abstract:
The overall safety requirements of reverser thrust system were attained by studying airworthiness regulation 25.933, relative airworthiness advisory circulars and background information of reverser thrust system, combining reverser thrust system accident of civil aircraft. These offer useful instructions for improving the safety of reverser thrust systems. A aircraft's reverser thrust system preliminary scheme was assessed by using of system safety assessment method. Results indicate that system architecture don't meet safety requirements,there is a single failure in the system architecture which can lead to thrust reverser device accidentally opened. To eliminate the single failure, the scheme of sync lock control would be isolated from the engine accessory unit (EAU) was proposed,which not only evidently improve the safety of the reverser thrust system of a type aircraft, but also provide important instructions for designing the reverser thrust system on other type aircrafts.

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