2014 Vol. 29, No. 10

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Combined variable geometry regulation schemes for variable cycle engine
LUO Guang-qi, LI You, LIU Kun, WU Tao, HU Shen-dao
2014, (10): 2273-2278. doi: 10.13224/j.cnki.jasp.2014.10.001
Abstract PDF(774KB) icon1759 icon1253
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Based on object-oriented design thought, a caculation model of double bypass variable cycle engine (VCE) was built, and the typical engine work points were selected to study optimized method of combined variable geometry regulation. The results show that suitable adjustment of fan guide vane angle can adequately develop double bypass VCE performance advantage at subsonic cruise and supersonic cruise points of double bypass VCE. The scheme 4 at the subsonic and supersonic cruise points are all better than adjustment schemes at the design point.
Integrated control for supersonic inlet/engine
SUN Feng-yong, ZHANG Hai-bo, YE Zhi-feng
2014, (10): 2279-2287. doi: 10.13224/j.cnki.jasp.2014.10.002
Abstract PDF(1052KB) icon2113 icon971
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A component-level mathematical model of supersonic inlet with bleeding adjustment was developed to study of integrated performance for supersonic inlet/engine. Meanwhile, a coupling mathematical model of supersonic inlet and turbofan engine was built via a biaxial turbofan engine component-level models and inlet component-level models to describe their collaborate relationship. The properties of outside and inside flux of the intake were calculated base on this integrated component-level model for inlet/engine. Inlet bleeding properties in supersonic working mode were also analyzed. At last, the engine installed thrust was verified to be effectively enhanced 3% by the bleeding adjustment of inlet when the aircraft worked at supersonic flight in the middle and afterburner states.
Aerodynamic design of the ejector of 2m×2m supersonic wind tunnel
REN Ze-bin, LIAO Da-xiong, ZHANG Guo-biao
2014, (10): 2288-2293. doi: 10.13224/j.cnki.jasp.2014.10.003
Abstract PDF(815KB) icon1822 icon1011
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The performance parameters of the ejector were analyzed and computed based on one-dimensional gas dynamic equations under different conditions. The ejector was characterized by multi-nozzles and constant-area mixing. The design compression ratio was 2.1 to 2.7, and the ejection coefficient was 0.392 to 0.651. Twenty four nozzles were installed on two layers, with the area ratio of 0.235. The computational results have good accordance with the 1:13 scale pilot ejector test results. The five experimental compression ratios were a little higher than the design values. Although the operating parameters of the ejector were partly deviated from the design values according to the overall adjustment, the compression ratios and ejection coefficients were still consistent with the computed values. The debugging results of the 2m×2m supersonic wind tunnel show that the performance of the ejector meets the requirements of testing.
Integrated aerodynamic optimization design of convergent-divergent nozzle and vehicle afterbody
REN Chao-qi, WANG Qiang, HU Hai-yang
2014, (10): 2294-2302. doi: 10.13224/j.cnki.jasp.2014.10.004
Abstract PDF(1006KB) icon1696 icon1003
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The aerodynamic characteristics of axisymmetric convergent-divergent nozzle and vehicle afterbody were studied. Based on the response surface method of orthogonal polynomials by combining with the self-programming, the three-dimensional flow field was numerically simulated. Flux coefficient and thrust coefficient were selected as the optimization indicators, while half convergence angle, throat radius, half expansion angle, bottom area and tail contraction angle were selected as the research objects to analyse under two conditions. By constructing and solving the function of response surface, the results show that half convergence angle and half expansion angle affect about 90% of aerodynamic characteristics; half convergence angle, throat radius and bottom area affect about 85% when discussing flux coefficient only; half expansion angle affect about 85% when discussing thrust coefficient only; half convergence angle, half expansion angle and throat radius affect more than 90% when discussing condition H=0km, Ma=0 only; half convergence angle and half expansion angle affect more than 85% when discussing condition H=20km, Ma=2 only.
Numerical simulation of two-dimensional convergent-divergent nozzle with pneumatic throat control
GUO Fei-fei, WANG Ru-gen, WU Pei-gen
2014, (10): 2303-2310. doi: 10.13224/j.cnki.jasp.2014.10.005
Abstract PDF(1082KB) icon1796 icon985
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The two-dimensional convergent-divergent nozzle with a circle-to-square convergent part was designed. The project of the throat area control with pneumatic injection was numerical simulated. The influences of nozzle exit width-to-height ratio, pressure drop ratio and injection angle on the throat area and nozzle performance were analyzed. The results show that the static pressure near the wide side in the rectangular nozzle throat section is lower than that near the narrow side. The static pressure near the wide side decreases and that near the narrow side increases with the increase of exit width-to-height ratio. At the same pressure drop ratio, the range of throat area control(RTAC) and the efficiency of throat area control(ETAC) increase while the nozzle coefficient of total pressure recovery decreases with the increase of exit width-to-height ratio. At a fixed exit width-to-height ratio, RTAC and ETAC decrease firstly and then keep at the same level while the nozzle coefficient of total pressure recovery increases with the increase of pressure drop ratio. ETAC increases with the increase of injection angle.
Natural laminar flow nacelle optimization design based on EFFD method
HE Xiao-long, BAI Jun-qiang, XIA Lu, CHEN Song, QIAO Lei
2014, (10): 2311-2320. doi: 10.13224/j.cnki.jasp.2014.10.006
Abstract PDF(1388KB) icon2044 icon982
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Aerodynamic shape optimization of natural laminar flow (NLF) nacelle was studied using extended free-form deformation (EFFD) technique. An parameterization method for nacelle section based on EFFD using Bernstein base functions was implemented. γ-θ transition model coupling with k-ε shear stress transport (SST) turbulent model was used for transition prediction. An optimization system for NLF nacelle design was established in combination with EFFD, a hybrid grid deformation method, Kriging surrogate model and an improved particle swarm optimization. Both flow-through nacelle and powered nacelle were optimized using the optimization system. Optimized flow-through nacelle maintained a laminar flow about 48% and its drag coefficient was 0.0003 less than initial flow-through nacelle. Powered nacelle maintained a 41% laminar flow after optimization. These results indicate that the optimization system is applicable in NLF nacelle design.
Application on MLP high order reconstruction scheme
FU Lin, GAO Zheng-hong, ZUO Ying-tao
2014, (10): 2321-2330. doi: 10.13224/j.cnki.jasp.2014.10.007
Abstract PDF(1698KB) icon2490 icon996
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Under the frame of finite volume methodology, MLP (multi-dimensional limiting process) scheme was further modified by introducing a shock-detect function to decrease the numerical dissipation in smooth regions, then supersonic flow over facing step, unsteady flow over an airfoil with ice accretion, hypersonic flow over double wedge configuration flow and subsonic flow over DLR F6-WB complex configuration were investigated by utilizing MLP high order reconstruction scheme and HLL-HLLC (Harten-Lax-van Leer with contact) approximate Riemann solver to validate the performances of proposed schemes in sophisticated compressible flow simulations. The research illustrates that: MLP can keep strict monotone flow characteristics even in the complex high-dimension fluid simulations consisting of strong oblique shock waves not aligned with grids; it has the similar computational efficiency compared with traditional MUSCL (monotone upstream-centered schemes for conservation laws) scheme and can achieve fifth or even higher order reconstruction; it features low numerical dissipation so that more accurate shock position can be captured, therefore MLP scheme is promising for aerospace engineering applications.
Experiment on low-speed delta wing using nanosecond pulse plasma actuation
HUA Wei-zhuo, LI Ying-hong, NIU Zhong-guo, ZHAO Guang-yin, LIANG Hua, HAN Meng-hu
2014, (10): 2331-2339. doi: 10.13224/j.cnki.jasp.2014.10.008
Abstract PDF(1130KB) icon1649 icon981
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Force measurement experiment was conducted to improve the aerodynamic characteristics of 47 degree sweep blunt leading edge delta wing using nanosecond pulse dielectric barrier discharge plasma aerodynamic actuation at the freestream flow velocity of 30m/s. In order to investigate the optimized actuation position, flow control effects at five different actuation positions were studied experimentally.The results show that the actuation position determines flow control effect.Plasma aerodynamic actuation at leading edge of delta wing can significantly improve the aerodynamic characteristics of delta wing and delay stall, while plasma aerodynamic actuations at different spanwise positions on the upper surface have little effect on the flow control.It is also found that flow control effect depends on actuation frequency.When the peak-peak actuation voltage is 13kV and actuation frequency is 200Hz, the flow control effect is best, which increases lift coefficient from 1.31 to 1.44 by 9.6% at attack angle of 30 degree, with lift-drag ratio by 3.3%.
Numerical investigation on space aero-thermodynamic characteristics of nose cone of supersonic flight
LIN Jia, WANG Jian-hua
2014, (10): 2340-2347. doi: 10.13224/j.cnki.jasp.2014.10.009
Abstract PDF(1089KB) icon1748 icon927
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A numerical investigation of the space (0-46km) aero-thermodynamic characteristics of a nose cone model under a state of supersonic flight was performed using commercial software STAR-CCM+ with validated turbulence model and numerical strategy. Then the environment distinctions of the ground high enthalpy wind tunnel and space flight were discussed as follow: (1) To achieve a certain stagnation temperature, the ground high enthalpy wind tunnel environment relies on a coupling effect of supersonic aero-thermodynamics and arc-heating. (2) At the same stagnation temperature condition, a high-temperature flow covers the whole nose cone specimen in the ground high enthalpy wind tunnel case, while in the space flight aero-thermodynamic, a high-temperature area appears just near the stagnation region. (3) At the same stagnation temperature, the stagnation pressure of the space flight is far lower than that in the ground high enthalpy wind tunnel experiment. Numerical simulation results indicate that at the same free-stream Mach number, the stagnation temperature goes down at first and then goes up with the increase of flight altitude, while the stagnation pressure drops all the time; at the same altitude, the stagnation temperature and pressure have an exponential increase with the increasing free-stream Mach number, meanwhile the shock wave moves gradually to the solid wall, and the stagnation region becomes thinner with the increasing free-stream Mach number, but this trend will be not significant when the Mach number is larger than 4.
Numerical simulation on combustion characteristics of biofuels with different calorific values
ZHOU Li, XIA Jiao-hui
2014, (10): 2348-2354. doi: 10.13224/j.cnki.jasp.2014.10.010
Abstract PDF(930KB) icon1360 icon1078
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Combustion characteristics of the two-dimensional simplified combustor were simulated numerically for methane, marsh gas and biomass gas, with introduction of standard k-ε turbulence model, eddy-dispassion turbulence combustion model and P-1 radiation heat transfer model. The temperature distribution, NOx mass fraction distribution, flow field structure in the combustor were analyzed to obtain the combustion characteristics of fuels with different calorific values by comparing the combustion situations of different cross sections. Results show that, under the condition of same mass flow of inlet air and fuel, the combustion temperature decreases with the decline of calorific value of fuels, the temperature distribution is more uniform, the NOx emissions are diminished, and the flow velocity is reduced; the proper regulation of excess air coefficient can improve the effect of combustion burning, and the temperature distribution still meets the law that combustion temperature of fuels with high calorific value is higher than that of fuels with low calorific value; the mixing of combustible components with different calorific values in biofuels syngas will change the calorific value of syngas, and the appropriate mixing ratio can play a better role for biofuels.
Effect of swirl cup design parameters on combustion performance
CHENG Ming, LIN Hong-jun, LI Feng
2014, (10): 2355-2361. doi: 10.13224/j.cnki.jasp.2014.10.011
Abstract PDF(935KB) icon1424 icon1072
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Based on the three-dimensional numerical simulation and rig test,the effect of swirl cup's design parameters of head of flame tube, such as the relative flow rate and the swirl number of secondary swirler, on combustion performance of an aero-engine main combustor was researched. The researched performance includes the outlet temperature field distribution and nitrogen oxides (NOx) emissions.It is shown that the result of numerical simulation and rig test is consistent: with the increase of the secondary swirler's relative flow rate,the outlet temperature field of the main combustor deteriorates, and the nitrogen oxides emission slightly reduces;with the deviation of swirl number of the secondary swirler from the benchmark design value, the outlet temperature field deteriorates, while nitrogen oxides emission increases with the increase of swirl number.
Numerical investigation of effect of truncated cone with different cooling structures on infrared suppressing characteristics of nozzle cavities
ZHANG Bo, JI Hong-hu, ZHANG Zong-bin, LUO Ming-dong
2014, (10): 2362-2368. doi: 10.13224/j.cnki.jasp.2014.10.012
Abstract PDF(935KB) icon1701 icon1096
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The characteristics of infrared suppressing on 3-5μm band of truncated cone, which was one of the high temperature components of engine nozzle were numerically investigated. Different arrangements of film cooling gap and film cooling hole structures were disposed on the truncated cone which showing strong infrared characteristics, and cold gas flowed into truncated cone through blades from by-pass channel, causing wall temperature drop of truncated cone and blades, furthermore, the infrared radiation intensity was depressed. By comparison of the two cooling structures, it is found that the method of film cooling gaps downwards can make wall temperature and infrared radiation intensity decrease more than that of film cooling holes, while lower thrust efficiency can be gotten.
Large eddy simulation of non-reacting flow fields in stratified swirl combustor
ZHANG Ji-min, ZHANG Hong-da, HAN Chao, YE Tao-hong
2014, (10): 2369-2376. doi: 10.13224/j.cnki.jasp.2014.10.013
Abstract PDF(1286KB) icon2279 icon826
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The non-reacting flow fields of the stratified swirl combustor with a central bluff-body were studied through large eddy simulation (LES) under three swirl numbers 0.25, 0.45 and 0.79. Smagorinsky eddy viscosity model with dynamic procedure was selected as the sub-grid scale turbulence model. Influence of swirl intensity on the bluff-body recirculation zone, vortex breakdown and precessing motion was investigated. The LES results showed overall good agreement with experimental data. The axial lengths of bluff-body recirculation zone approximately 20mm showed no obvious variation under three swirl numbers. Q-criterion was used to visualize vortices structures, the spiral vortices were formed as the result of the Kelvin-Helmholtz instability of swirl shear layers; the vortex breakdown occurred upstream with the increase of swirl intensity. Power spectrum density (PSD) indicates the existence of precession motion, which decays along the flow direction. And precession motion appears at the terminal of bluff-body recirculation zone under higher swirl numbers 0.45 and 0.79. The precession frequencies are approximately 78Hz under three swirl numbers.
Adverse effect of non-condensable gas on the operating performance of loop heat pipe
HE Jiang, LIN Gui-ping, BAI Li-zhan, MIAO Jian-yin, ZHANG Hong-xing
2014, (10): 2377-2384. doi: 10.13224/j.cnki.jasp.2014.10.014
Abstract PDF(923KB) icon1968 icon922
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Nitrogen was injected into the loop heat pipe(LHP) as non-condensable gas(NCG), and the operating performance of the LHP with NCG was studied for different NCG inventories, while heat loads were applied to the evaporator and heat sink temperatures. Under the adverse effects of NCG: the operating temperature of the evaporator was elevated by 2-10℃ depending on the heat load and heat sink temperature; such effect was notable for a smaller heat load(less than 60W) or at lower heat sink temperature(-5℃); the temperature controlling performance varied, leading to a corresponding failure range for the heat load; the startup temperature and super tup overshooting increased, and the startup time was prolonged; the temperature oscillation phenomenon and operating failure could be triggered. According to the temperature variations of the characteristic points along the loop, the physical mechanism of the effect of NCG on the operating performance was analyzed and discussed.
Adaptive mesh refinement-based numerical simulation of initiation in supersonic combustible mixtures using hot jet with detailed reaction model
CAI Xiao-dong, LIANG Jian-han, LIN Zhi-yong, QIN Hui
2014, (10): 2385-2392. doi: 10.13224/j.cnki.jasp.2014.10.015
Abstract PDF(1472KB) icon1634 icon860
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Open-code program AMROC of block-structured adaptive mesh refinement was adopted to conduct high-resolution numerical simulation of two-dimensional detonation initiation in supersonic combustible mixtures using hot jet. Detailed chemistry mechanism of hydrogen, oxygen, argon was considered in the simulation. Detonation initiation in supersonic combustible mixtures and the formed elaborate detonation cell were investigated. Results show that the hot jet is similar with a pneumatic ramp in supersonic combustible mixtures, so as to realize shock-induced combustion. The continuous ejection of hot jet in supersonic combustible mixtures could result in forming of overdriven detonation and irregular detonation cell. The disturbance and compression function of hot jet plays an important role in the forming of overdriven detonation and its irregular detonation cell. Disturbance and compression function of hot jet propagates at local sonic velocity, yielding an impact on the forward detonation front after getting across the subsonic zone behind the detonation front. In this way overdriven detonation could be maintained to form the irregular detonation cell.
Numerical investigation of gas-liquid two-phase cold-flow around bluff-body stabilized burners
XU Huan, LI Zhi-qiang, DONG He, YANG Qing, SHAO Xing-chen
2014, (10): 2393-2401. doi: 10.13224/j.cnki.jasp.2014.10.016
Abstract PDF(1148KB) icon1566 icon851
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Based on the variable time interval average method, a multi-scale two-phase turbulent model was put forward and established. Compared with the experiment results, the rationality of the multi-scale gas-liquid two-phase mathematic model, the modeling parameters and interactive mechanism of gas-liquid two-phase flows was proved. Its relative error of drag coefficient was 1.45%, and the fluctuating lift coefficient was 0.323%. This model could also accurately predict vortex shedding characteristics with its relative error of St was 2.17%. However, its relative error of size of the recirculation zone was 2.33%. And the computational results were better than those of the standard k-ε and RNG (renormalization group) k-ε models. Using the multi-scale two-phase turbulent model, the two-phase flow around six different bluff-body stabilized burners was predicted. The computational results show that the ship-shaped and cone-shaped structures have good overall performance in these six different bluff-body stabilized burners. The recirculation zone of ship-shaped structure is larger than cone-shaped by 10.53%. The time-averaged drag coefficient of ship-shaped structure is larger than cone-shaped by 4.776%. The root-mean-square value of fluctuating lift coefficient of ship-shaped structure is smaller than cone-shaped by 44.73%. And by comprehensive comparison, the ship-shaped structure has the best performance.
Numerical investigation of windage heating within shrouded rotor-stator cavity system with central inflow
WANG Qian-shun, ZHANG Da, LUO Xiang, XU Guo-qiang
2014, (10): 2402-2409. doi: 10.13224/j.cnki.jasp.2014.10.017
Abstract PDF(1029KB) icon1600 icon764
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The rotating disk surface temperature rise due to windage heating effect by numerically modeling the turbulent flow within a rotor-stator cavity which is available with a peripheral shroud and imposed through airflow was dealt with. The windage heating may be defined as viscous friction heating caused by relative velocity differences across the boundary layers between the fluid and the rotating disk surface. The kinetic energy dissipation process could transform the rotating shaft power into thermal heating. Commercial finite volume based solver, ANSYS/CFX was employed to numerically simulate this physical process by using the shear stress transport (SST) turbulence model. CFD results include the rotating disk surface temperature axial distribution and tangential velocity distribution of the fluid domain. The velocity difference between the result obtained by particle image velocimetry (PIV) experiments and CFD simulation are within 5%. The adiabatic disk temperature rise can be calculated by the tangential velocity of disk and fluid in large gap ratio and turbulent parameter. CFD temperature distribution results and those estimated via velocity differences are within 10%.
Influencing factors of flow resistance in oil-air separator
XU Rang-shu, HU Hui, SHAO Chang-hao, NIU Ling
2014, (10): 2410-2416. doi: 10.13224/j.cnki.jasp.2014.10.018
Abstract PDF(1049KB) icon1329 icon820
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In order to analyze the influencing factors of flow resistance in the oil-air separator of the aero-engine, flow field in the oil-air separator was caculated numerically using computational fluid dynamics (CFD) and Reynolds stress model (RSM). The flow resistance of calculation and experiment under the same operating conditions were compared to ensure the applicability of the model. Enough number of flow resistance values of different operating conditions and structures had been calculated for the binary quadratic space trend surface regression. The results show that the increasing of flow rate and rotational speed will bring greater flow resistance. The design of the breather hole eccentricity and the reducing the plate tip radius can reduce the flow resistance, the breather hole eccentricity design has the best eccentricity about 7.5mm.
Influence of blade tip clearance at near-stall condition on transonic axial-flow compressor
XIE Fang, CHU Wu-li, LI Xiang-jun, LIU Chuan-le
2014, (10): 2417-2423. doi: 10.13224/j.cnki.jasp.2014.10.019
Abstract PDF(1228KB) icon1677 icon798
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Numerical simulation with high density grid was carried out to study blade tip clearance of a transonic axial-flow compressor rotor 37 at near-stall condition. The blade tip clearance included design clearance, half design clearance, quarter design clearance,2 times design clearance and zero clearance. The results show that stall margin is improved 4%, and adiabatic efficiency and pressure ratio don't decline obviously, when the blade tip clearance reduced from design clearance to half design clearance. Details of the flow field were analyzed based on different stall forms and vortex dynamics. The change of clearance may improve stability margin greatly and clearance plays an important role in leakage vortex and separation of boundary layer, or even induces different stall forms. This has provided necessary basic research for design of the compressor are provided, and discussed the application condition of clearance control technology in aerodynamics.
Phase space reconstruction and fractal characteristic of rotating stall in impeller of centrifugal compressor
WANG Le, ZHANG Jia-zhong, ZHOU Cheng-wu, TIAN Mei
2014, (10): 2424-2433. doi: 10.13224/j.cnki.jasp.2014.10.020
Abstract PDF(1189KB) icon1560 icon795
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Based on phase space reconstruction and fractal theory in nonlinear dynamics, a method was proposed to analyze the dynamics characteristic of rotating stall in the impeller of centrifugal compressor. The rotating stall of impeller in low speed centrifugal compressor (LSCC) was numerically simulated, and the time series of pressure at rotating stall was obtained at various locations at impeller outlet. The technique of phase space reconstruction was applied to these pressure time series, and a low-dimensional dynamical system, which the dynamic properties were included in, was reconstructed. In order to determine the time delay and the embedding dimension in the reconstructed phase space, C-C method was introduced to deal with the pressure time series. The fractal characteristics of the reconstructed dynamic system phase diagrams were analyzed, and the corresponding fractal dimensions were given. The results show that the pressure signal of the impeller after rotating stall is in chaotic state, and some fractal structures are found in the reconstructed phase space. These fractal structures reveal the intrinsic dynamics of rotating stall flow. When the data collection points in the same radius, they have the similar fractal dimension, nearly 3.39. The fractal dimension decreases with the radius of collection points increasing.
Optimization design of a two-stage counter-rotating compressor under overall working conditions
ZHANG Peng, LIU Bo, CAO Zhi-yuan, SHI Lei
2014, (10): 2434-2442. doi: 10.13224/j.cnki.jasp.2014.10.021
Abstract PDF(1239KB) icon1503 icon806
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In order to improve aerodynamic performance of the counter-rotating compressor in an all-round way, overall working conditions optimization design was carried out on the Rotor 2 of a two-stage counter-rotating compressor in multistage environment based on artificial neural network and genetic algorithm. The changes of geometry, overall performance and flow field were compared and analyzed. Results show that: after the optimization, the overall isentropic efficiency and pressure ratio of the counter-rotating compressor are both improved, meanwhile the range of mass flow is widened. The isentropic efficiency of the counter-rotating compressor increases by 0.3% on the design point, increases by 1.5% near the stall point, and the surge margin increases by 6.37%. After the optimization, the overall isentropic efficiency and pressure ratio of the Rotor 1 are almost unchanged, but those of Rotor 2 are raised much. The isentropic efficiency of Rotor 2 improves by 1% on the design point, and the isentropic efficiency is improved by 2.5% near the stall point. Also, the flow fields of Rotor 1, Rotor 2 and outlet guide vane (OGV) at the tip are improved remarkably near the stall point.
Effect experiment of rotating distortion on the development of modal wave
YAN Wei, HU Jun, YANG Fan, WANG Zhi-qiang, YIN Chao
2014, (10): 2443-2449. doi: 10.13224/j.cnki.jasp.2014.10.022
Abstract PDF(1033KB) icon1491 icon751
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In order to explorer the mechanism of the "dangerous frequency", a rotating distortion generator was designed to investigate the effects of rotating distortion on the stall inception of a two-stage low speed axial flow compressor. Experiment results show that the rotating distortion generator can output a rectangle-like total pressure distribution at different rotating speeds. The compressor exhibited significant loss in total-static pressure rise and stability margin arising from rotating distortion, especially when it rotated at a particular speed. Detailed measurements and analysis suggest that the modal wave appears firstly in the distorted area and is restrained when it spreads into un-distorted zone. When transmit frequency of modal wave is equal to the distortion rotating frequency, the modal wave needs least time to develop into rotating stall, the loss in stability margin is the maximum. The time-frequency analysis of the stall inception signal suggests that the "dangerous frequency" is equal to the transmit frequency of the modal wave.
Numerical simulation of unsteady flow field on abnormal stagger angle of cascade
ZHANG Guo-chen, LIU Bo, YANG Xiao-dong, CAO Zhi-yuan
2014, (10): 2450-2456. doi: 10.13224/j.cnki.jasp.2014.10.023
Abstract PDF(943KB) icon1781 icon913
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Tow-dimensional steady and unsteady numerical simulation was predicted by commercial softwave NUMECA when the stagger angle of cascade was abnormal. The main aim is to investigate cascade passage block resulting from abnormal stagger angle affecting the flow field and unsteady aerodynamic force of the blade and the adjacent cascade passage. The results show that it has an effect on the cascade field passage along the suction side when abnormal stagger angle is positive. With the increase of abnormal stagger angle, the flow is more deteriorated and the large scale of boundary layer separation is generated. The main frequency of vortex shedding decreases with the increase of abnormal stagger angle; but the secondary frequency of vortex shedding increases with the increase of abnormal stagger angle. And relative fluctuation quantity of unsteady aerodynamic force increases rapidly arising from the changing angle; accounting for the blade fatigue breakdown.
Method of dynamic pressure measurement based on semi-infinite pressure tube effect
YANG Lin, WANG Si-chen, LIN Feng, LI Ji-chao, NIE Chao-qun
2014, (10): 2457-2463. doi: 10.13224/j.cnki.jasp.2014.10.024
Abstract PDF(899KB) icon1700 icon1088
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The amplitude-frequency characteristic of dynamic pressure signal through the semi-infinite and finite pressure tube was investigated, also its relationship with the shape of the inner diameter of the tube. With a semi-infinite pressure tube, a time-resolved total pressure probe with a Kiel structure was designed, and used to measure large angle inflow total pressure and calibrate its dynamic transfer function. The measurement results of the axial compressor rotor wake fields show that the semi-infinite pressure dynamic probe could get large gradient total pressure field, such as rotor wake and blade end flow. For design of the dynamic probe with pressure tube, both pressure tube diameter change and bending could attenuate signal energy, while semi-infinite pressure tube can availably keep dynamic pressure signal energy and decrease resonance effect.
SVM diagnosis method of rotor vibration faults based on integration of information exergy
AI Yan-ting, CHEN Chao-long, TIAN Jing, WANG Zhi
2014, (10): 2464-2470. doi: 10.13224/j.cnki.jasp.2014.10.025
Abstract PDF(824KB) icon1592 icon882
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Through extracting the information exergy characteristics, the support vector machine (SVM) diagnosis method of rotor vibration faults based on integration of information exergy was put forward. First of all, the rotor unbalance fault, shafts misalignment fault, rotor crack fault and rubbing fault were simulated respectively on the rotor test bench, and vibration acceleration signals of these four typical kinds of faults under multi-point was gathered; secondly, the information exergy characteristics of the rotor vibration fault process change law based on time-domain singular spectrum entropy and frequency-domain power spectrum entropy was extracted; finally, using the extracted information exergy characteristic was used as a fault vector, the SVM fault diagnosis model was established, and the rotor vibration fault was diagnosed. The diagnostic results of examples indicate that the use of information exergy characteristic combined with SVM in rotor vibration fault diagnosis make the diagnosis accuracy rate reach 97% improving the accuracy of diagnosis effectively.
Estimation method of blade high cycle fatigue life based on ultra-high cycle fatigue test of specimen
LI Quan-tong, TONG Xu-dong, GAO Xing-wei, CHEN Wei, CHENG Li
2014, (10): 2471-2475. doi: 10.13224/j.cnki.jasp.2014.10.026
Abstract PDF(840KB) icon1985 icon967
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According to girder vibration theory of beam, "af"value, which is the product of blade tip vibration amplitude "a" and frequency "f", was deduced to express vibration stress of blade. Based on the ultra-high cycle fatigue test result of a type of aero-engine compressor blade material specimen and "af" value theory, the blade high cycle fatigue life was deduced. The results of blade first order bending high cycle fatigue validated the deduction. It shows that when "af" value is 1700, 1800, 1900mm/s, the fatigue lives of ultra-high cycle fatigue test specimen and actual blade are in the vicinity of 1×107, 0.7×107 and 0.5×107 cycle, indicating the fatigue life of ultra-high cycle fatigue test specimen is consistent with the actual blade.
Design methodology for particle dampers applied to a wheel structure
LIU Bin, WANG Yan-rong, TIAN Ai-mei, TANG Wei, FENG Huan-huan
2014, (10): 2476-2485. doi: 10.13224/j.cnki.jasp.2014.10.027
Abstract PDF(1025KB) icon1605 icon796
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By use of a discrete element method (DEM), the design methodology for cavity size and filling schemes of particle dampers applied to a wheel structure was investigated through a series of orthogonal simulation tests. A two-dimensional equivalent vibration model of a typical wheel was established, in which the configuration was evaluated based on the specific parameters when it vibrated in the umbrella-shaped mode. On the basis of experimental tests and analytical study, conclusions can be drawn as follow: (1) with the capability of describing the umbrella-shaped vibration of the wheel structure, the two-dimensional equivalent model is effective to reflect the influences on the cavity caused by interior particles' motion; (2) a dramatic increase in the attenuation due to the presence of particles is clearly evident while it differs in particle types; (3) the damping performance is significantly affected by the cavity size and particle mass ratio, moreover, the latter should be guaranteed first; (4) enough clearance between particles and wall of cavity is also required, so there is an optimal filling rate for an immutable enclosure, fixed particle size and type. Given the fact that the design scheme agrees well with the optimal case given by experimental tests, the design methodology can be used to acquire the optimal cavity size and filling scheme at the design stage of a wheel structure.
Illusive component identification method in noisy signal EMD processing
LI Ji-yong, LI Shun-ming, CHEN Xiao-hong, JIANG Xing-xing
2014, (10): 2486-2492. doi: 10.13224/j.cnki.jasp.2014.10.028
Abstract PDF(910KB) icon1445 icon907
Abstract:
According to the fact that there exists illusive components when noisy signal is under Hilbert-Huang transform, an improved singular value decomposition (SVD) was firstly proposed for two improvements: one was that the reconstructed phase space was employed instead of traditional matrix such as Hankle matrix in order to remove redundancy, the other was that a singular value energy entropy component difference method was proposed, making it easier to determine order of reconstruction singular value. Secondly, a spectrum ratio method was raised to identify illusive components, making it easier to identify illusive components. Intrisinc mode function (IMF) was obtained by empirical mode decomposition (EMD) and trend term was detrended, then the signal was reconstructed for subsequent SVD operation; the denoised signal was obtained and illusive component was eliminated, lastly the signal time-frequency distribution was calculated. The SNR raised 5.5% when the jointly proposed method employed in simulation signal, the illusive component identity ratio raised to 100%, two-span rotor fault vibration signal analysis results show that the jointly proposed method is effective in time-frequency distribution calculation and identification of noisy signal illusive components.
Fault diagnosis of aero-engine gas path based on SVM and SNN
WANG Xiu-yan, LI Cui-fang, GAO Ming-yang, LI Zong-shuai
2014, (10): 2493-2498. doi: 10.13224/j.cnki.jasp.2014.10.029
Abstract PDF(903KB) icon1902 icon804
Abstract:
In order to distinguish similar faults of aero-engine gas path fault diagnosis and improve the diagnostic accuracy, a fault diagnosis method based on support vector machine(SVM) and synergetic neural network(SNN) was put forward. Firstly, the SVM after being optimized was used to diagnose and classify the faults preliminarily form measured data, and the diagnosis results were analyzed to obtain indistinguishable similar faults, then the SNN was introduced to distinguish similar faults and further determine corresponding fault model, finally this fault model was simulated based on actual data. The experimental results show that the preliminary fault diagnosis accuracy based on SVM is 96%, and after further distinguishing similar faults through SNN, the accuracy is increased to 100%.
Onboard real time modeling of aircraft engines with Hammerstein-Wiener representation
WANG Ji-qiang, YE Zhi-feng, HU Zhong-zhi
2014, (10): 2499-2506. doi: 10.13224/j.cnki.jasp.2014.10.030
Abstract PDF(719KB) icon1296 icon842
Abstract:
An identification-based approach for aircraft engine modeling using the nonlinear Hammerstein-Wiener representation was proposed. Hammerstein-Wiener modeling for both limited flight envelope and extended flight envelope was investigated. Simulation shows that the resulting model can be valid over 10% variation of rotational speed of the engine, compared with those linear models that are only valid over 3%—5% change of rotational speed. It is further demonstrated that the proposed method can be utilized over large envelope up to 20% variation of rotational speed of the engine. The fundamental idea is to use nonlinear models to extend the feasible/valid region rather than those linear models. This may consequently simplify the switching logic in the onboard digital control units. This is often overlooked in aircraft engine control community, but has been emphasized in the research.
Fuzzy intelligent selection of gas turbine gas path measurement parameters
JIANG Rong-jun, GAO Jian-hua, LIU Yong-bao, HUANG Shu-hong
2014, (10): 2507-2514. doi: 10.13224/j.cnki.jasp.2014.10.031
Abstract PDF(845KB) icon1367 icon785
Abstract:
According to the needs of gas turbine gas path performance monitoring and diagnosis, based on the influence coefficient matrix by gas path small deviation analysis, the measurement parameters were classified into target clustering with required number by fuzzy clustering analysis method starting from the correlation requirements of parameters selection. Furthermore, from the sensitivity requirements of parameters selection, the representative measurement parameters of each multi-element clustering were picked out by fuzzy comprehensive evaluation method. Thereby the fuzzy intelligent selection of gas turbine gas path measurement parameters was realized. The case study shows that fuzzy clustering analysis method can carry out the parameter correlation selection directly, so it is reliable and convenient to select the reasonable measurement parameter group for a target request; it's also more efficient and reliable for the measurement parameter sensitivity selection with fuzzy comprehensive evaluation method.
Active controllability and separation mechanics of non-contact hydrostatic mechanical seal
ZHANG Guo-yuan, ZHAO Wei-gang, CHEN Yao, WEI Jun-chao
2014, (10): 2515-2522. doi: 10.13224/j.cnki.jasp.2014.10.032
Abstract PDF(985KB) icon1320 icon864
Abstract:
To explain the separation phenomena and meet the requirement of the leakage of the non-contact hydrostatic mechanical seal, an active controllable method for mechanical seals based on the change of the closing force was proposed. The principle of the method was developed, including: control strategy, control components and control flow. Taking the shaft mechanical seals in the high-speed turbopump as the object, the design for the controllable seal was carried out, and the influence of the controllability and the control elements on the performance of the seals were obtained by the theoretical and experimental methods. The existing separation speed theory was developed, and with the experiment results, the mechanism of the separation speed for the controllable seal was validated. The results show that the strategy of regulating the closing force could satisfy the leakage of the seal; and the range of the control sensitivity coefficient is[1, 3.19]. The developed separation speed theory can reasonably explain the transformation process from the contact state to non-contact state between the mechanical seal faces in the takeoff stage. The results are helpful to design, monitor and control the special mechanical seal under special working conditions.
Computer numerical control face milling spiral bevel gears by application of disc cutter with concave end
LI Geng-geng, WEI Bing-yang, DENG Xiao-zhong
2014, (10): 2523-2528. doi: 10.13224/j.cnki.jasp.2014.10.033
Abstract PDF(1022KB) icon1724 icon871
Abstract:
In order to solve the poor machining efficiency and cutting chatter problem during computer numerical control(CNC) machining of spiral bevel gears by universal cutter, a machining method of face milling spiral bevel gears by a disc cutter with concave end was presented. Based on the research of spiral bevel gears geometry structure, a bigger diameter disc cutter with concave end was selected, and the setting order of cutter orientation angles was changed actively, then the functions of cutter tilt and yaw angle were separated, so the tooth surfaces machined with big cutting strip width and without bottom land gouge could be realized. Through the cutter yaw angle determined by cutting contact point positions in tooth surface machined, the bottom land gouge interference can be avoided effectively. Then through the tilt angles of both side tooth surfaces determined by the theory of sculptured surfaces machined by flat end cutter respectively, big cutting strip width and high machining efficiency can be ensured. The results show that with a spiral bevel gear as an example, the cutting times of two tooth flanks with a disc cutter with concave end are 7 and 6, and the maximum machining errors are 0.0394mm and 0.0418mm, respectively. This method has advantages such as longer cutter life and bigger cutting strip width, fewer cutting times and higher processing precision for machining spiral bevel gears.

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