2014 Vol. 29, No. 11

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Mechanism of suction surface boundary layer suction in three-dimensional high loaded diffuser cascades
GUO Shuang, LU Hua-wei, SONG Yan-ping, WU Chui-jie
2014, 29(11): 2529-2536. doi: 10.13224/j.cnki.jasp.2014.11.001
Abstract PDF(970KB) icon1913 icon1099
Abstract:
The highly loaded diffuser compressor cascade with a full-span suction slot was numerically simulated under five different chordwise suction positions in the first step. The influences of aerodynamic parameters such as suction position on the suction flow distribution were studied in detail. Then experiments on the effects of partly-span suction flow on the performance of a three-dimensional cascade were carried out. The simulation region includs the inner cavity of the suctior blade, and the boundary conditions in simulations are set according to the experimental conditions. The suction flow is C-type distributed along the spanwise direction in full-span suction schemes. Both of the partly-span suction schemes mainly improve the flow field around the midspan, while the suction flow around the blade roots also suppress the back flow in the corner region. Both the three-dimensional flow field of the cascade passage and inner cavity of the aspirate blade influenced the spanwise distribution of the suction flow. Therefore it is necessary to design tailored suction slots/orifices according to the characteristics of the three-dimensional high loading diffuser compressor cascades.
Numerical simulation on an aero-engine vane pump
ZHANG Qun-feng, YAN Pan-pan, SHAN Jian-ping, HE Wan-fa
2014, 29(11): 2537-2542. doi: 10.13224/j.cnki.jasp.2014.11.002
Abstract PDF(967KB) icon1960 icon1081
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The internal flow field of an aero-engine vane pump was simulated with the function of the secondary development of computational fluid dynamics software Star-cd. The impacts of incorporating/neglecting the cavitation model on simulation results, the gap size between the tip of vane and stator of vane pump were analysized. The sizes and positions of cavitation in vane pump were predicated under different working conditions. The simulation results demonstrate that cavitation is generated, developed and collapsed during the rotation of rotor, which leads to accumulation and release of the mass of oil, correspondingly to a reduced and increased area of cavitation respectively, and the transient volume flow rate of inlet is stable while that of outlet fluctuates significantly. The simulation results show the difference between cycle averaged valume flow rate at inlet/outlet and total averaged volume flow rate is less than 1.5%, and the difference between total averaged volume flow rate and averaged volume flow rate obtained from the experiment of the vane pump is less than 3%. The simulation results also demonstrate that expanding the gap between the tip of vane and the stator results in a decrease of the average volume flow rate of the vane pump and an increase in the leakage, which can be seen from that the averaged volume flow rate of the gap size equaling 0.07mm is reduced 3.1% relative to that of the gap size equaling 0.02mm. It is estimated that if the inlet duct is designed to face the suction port, the flow resistance and the area of cavitation can be reduced.
Numerical investigation of stator cavity leakage influence to a compressor performance
CHEN Mei-ning, XIE Wei-liang, WANG Hong-tao
2014, 29(11): 2543-2549. doi: 10.13224/j.cnki.jasp.2014.11.003
Abstract PDF(1088KB) icon1627 icon995
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Three-dimensional numerical simulations were carried out for a compressor to investigate the stator cavities' influence to the performance and flow field. Detailed analyses of the performance and flow field came to some conclusions: the cavity leakage flow led to decreases in the efficiency, pressure ratio and stall margin of the compressor. The compressor stall margin declines by 5.19% due to the cavity leakage flow. The cavity leakage flow mainly influences the root flow of the stator and rear blades, and changes the compressor stall mechanism. The cavity leakage flow causes flow separation near the hub of the first stator, as a result the second rotor incidence angle increase sharply; consequently the flow separates at the suction side of the second rotor, causing the compressor stall earlier than that without the cavity.
Application of design method of low reaction and aspiration axial compressor in multistage axial compressor
HU Ying-jiao, WANG Song-tao
2014, 29(11): 2550-2560. doi: 10.13224/j.cnki.jasp.2014.11.004
Abstract PDF(960KB) icon1296 icon990
Abstract:
With further understanding of the internal flow details in the low reaction and aspiration axial compressor stages, the design method of low reaction and aspiration axial compressor used in the three stages was further improved. A verification aerodynamic design of a low reaction and aspiration axial compressor with three stages was carried out. From these three-dimensional viscous numerical results, a compressor was attained with total pressure ratio 6.1 and efficiency 88.1%, without consideration of the influence of the bleed flow at inlet tip tangential speed 370m/s. Boundary layer suction was used only in the first and third stator. The total bleed flow was around 11.3% of the inlet.
Inducer tip endwall bleeding effects on centrifugal compressor stability enhancement
KANG Jian-xiong, HUANG Guo-ping, ZHU Jun-qiang, WEN Dian-zhong
2014, 29(11): 2561-2569. doi: 10.13224/j.cnki.jasp.2014.11.005
Abstract PDF(1080KB) icon1768 icon1016
Abstract:
Numerical simulation was carried out to explore the benefit of inducer tip endwall bleeding effects on centrifugal compressor stability enhancement. Based on the experimental results of the centrifugal compressor with a self-recirculating casing treatment on top of inducer, three tip bleeding configurations (A, B and C) with different bleed rates were simulated. The result shows that bleed position and bleed range have grate influence on stability enhancement effect. Configurations C is the best location because it has the largest bleeding area covers the whole tip backflow zone. Additionally, with the variation of suction flow rate, there are two different mechanisms of stability extension.When the flow rate is low, bleeding can suppress the tip leakage flow and remove low momentum fluid, so the channel blocking will be reduced to delay endwall stall. Otherwise, larger rate of suction flow will occupy the channel and the main flow will be pushed towards hub side to improve the rim power of the rotor. Considering the compression efficiency, lower bleeding rate has advantages. For configuration C, 5% is the optimum bleed rate with the margin increase by 19.6%.
Optimization design for counter-rotating compressor with non-axisymmetric endwall contouring
ZHANG Peng, LIU Bo, CAO Zhi-yuan, NA Zhen-zhe, SHI Lei
2014, 29(11): 2570-2578. doi: 10.13224/j.cnki.jasp.2014.11.006
Abstract PDF(1317KB) icon1978 icon1062
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In order to explore the effects of non-axisymmetric endwall on counter-rotating compressor, taking the rotors of a counter-rotating compressor as research object, based on artificial neural network and genetic algorithm, the optimization of non-axisymmetric endwall contouring was carried out successively on rotor 1(R1) and rotor 2(R2) in multistage environment. The changes of flow field and performance before and after optimization were compared and analyzed. The purpose was to further improve the performance of the counter-rotating compressor with implementation of non-axisymmetric endwall contouring. The results show that on the optimization condition point, the non-axisymmetric endwall changes the static pressure distribution near rotors' hub endwall, decreases the circumferential static pressure gradient, and reduces the intensity of secondary flow;meanwhile it also changes the flow capacity along the radial span of rotors,and improves the efficiency of upper area;finally the efficiency of the counter-rotating compressor is increased by 0.78%.
A prediction model for tip clearance of multi-stage axial compressor in different operating conditions
YANG Dong, LI Shao-bin, LI Qiu-shi
2014, 29(11): 2579-2586. doi: 10.13224/j.cnki.jasp.2014.11.007
Abstract PDF(844KB) icon1650 icon1122
Abstract:
A prediction model for tip clearance of multi-stage axial compressors in different operating conditions was proposed, considering the effect of thermal and mechanical loading. The radial and axial temperature distribution across every stage of the multi-stage axial compressors was considered by the proposed model to ensure the accuracy. The model was validated by General Electric Company (GE) E3 engine test results. The comparison shows that the proposed model has high accuracy to uncover the varying rule of tip clearance in different operating conditions, and the relative errors are 0.8%, 5.6%, 3.7% in the calculation of tip clearance for stage 3, 5, and 10, respectively. The estimated trend in the variation of disk cavity cold airflow with tip clearance is consistent with the experimental data, and the relative errors are 9.7% and 6.7% in the estimated tip clearance of stage 3 and 10, respectively. The maximum change of tip clearance obtained with the active control technology in the tests is 0.2032mm at the stage 10, which is estimated as 0.14mm using the model. The magnitude of tip clearance and the tip clearance active control technology effects are estimated quite well, and the proposed model is verified.
Investigation and control of centrifugal compressor inlet flow field
WANG Chen-fang, ZHANG Yang-jun, ZHENG Xin-qian, WANG Zeng-quan, XING Wei-dong
2014, 29(11): 2587-2592. doi: 10.13224/j.cnki.jasp.2014.11.008
Abstract PDF(958KB) icon1675 icon1060
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Three-dimensional numerical simulation was conducted on a turbocharger centrifugal compressor to study the inlet flow field of the design point and the points near surge at different rotating speeds; inlet guide vanes on the shroud of centrifugal compressor were presented as a flow control method based on the inlet flow field study and verified by experiment. Investigation shows that the pressure difference of the pressure side and suction side of the blade near surge leads to tangential velocity near shroud in the inlet flow field opposite to the impeller rotating direction, and the tangential velocity increases with the growing impeller speed; at the design point, there are two opposite tangential velocity areas before each blade pressure side and suction side and the area of tangential velocity opposite to the impeller rotating direction is not limited to the area near shroud. Inlet guide vanes on the shroud can decrease the tangential velocity opposite to the impeller rotating direction near surge effectively, and experimental result shows that the centrifugal compressor pressure ratio is improved by 3.4% and the efficiency by 3.0% at 90000r/min near surge. The overall performance is improved.
Layout optimization and influence law of cascade plasma flow control
ZHANG Hai-deng, WU Yun, LI Ying-hong, ZHAO Qin, ZHAO Xiao-hu
2014, 29(11): 2593-2605. doi: 10.13224/j.cnki.jasp.2014.11.009
Abstract PDF(1723KB) icon1449 icon1081
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In order to improve the plasma flow separation control abilities on highly loaded compressor cascade, optimizations of plasma aerodynamic actuation layouts were researched based on characteristics of the highly loaded compressor cascade flow field and plasma aerodynamic actuation. With typical actuation layout, influence factors on plasma compressor cascade flow control was studied experimentally. Results show that among the layouts of plasma aerodynamic actuations on suction surface, the actuation effect of streamwise direction near blade leading edge is better than that of pitchwise direction or that near trailing edge, and the multigroup electrodes of streamwise direction are most effective in flow control; the control effect of pitchwise plasma aerodynamic actuation on endwall is better than that of streamwise direction; the control effect of streamwise plasma aerodynamic actuations on suction surface combined with pitchwise ones on endwall is the best among all plasma aerodynamic actuation layouts. As the actuation voltage increases, the control effect of plasma aerodynamic actuation on flow separation becomes better, while with the increase of the incidence angle, the control effect is enhanced firstly and then decreases; by coupling the flow field instability, the unsteady plasma aerodynamic actuation leads to a better flow control effect than the steady plasma aerodynamic actuation method.
Blade-twist aerodynamic characteristics of coaxial rotors in hover
SHAO Wei-ping, HE Min-tao, HAO Yong-ping
2014, 29(11): 2606-2612. doi: 10.13224/j.cnki.jasp.2014.11.010
Abstract PDF(904KB) icon1639 icon1036
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To meet the improvement of blade aerodynamic performance, blade-twist of coaxial rotors in hover design method was proposed.In this method, geometric installation angle was set for single rotor blade-twist, and the simulation results show reasonable blade-twist design can improve the rotor performance by 7.0%.In order to achieve hover coaxial rotor blade-twist design, the installation angle of upper and lower blade tips and rotors must be corrected, according to the blade tip vortex's impact, as well as coaxial rotor aerodynamic characteristics. Finally, the simulation results of coaxial rotors method show wing-twist lift is increased by 10.3% than that without twist of rectangular wing.
Application of ray-tracing method in calculating RCS for spherical convergent flap nozzle
CUI Jin-hui, SHANG Shou-tang, YANG Qing-zhen, LI Zhao-hong, CHEN Li-hai
2014, 29(11): 2613-2620. doi: 10.13224/j.cnki.jasp.2014.11.011
Abstract PDF(1078KB) icon1551 icon1005
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Numerical simulation of spherical convergent flap nozzles with different trailing edges shaping measures was finished using the self-developed electromagnetic scattering characteristic program based on the ray-tracing method. Radar cross section (RCS) of inner cavity scattering field and edge diffraction field was obtained for above several different SCFN. Meanwhile, induced electric current of inner cavity wall at different azimuth angles was calculated. With the method of analyzing the induced electric current, the change law of RCS was explained essentially. The analysis results show that the shaping measures for the trailing edge of the nozzle have a significant and obvious effect on decreasing the RCS of edge diffraction field and improving the electromagnetic stealth performance. Compared with ordinary occultation algorithm, the ray-tracing method shortens computational cycle by 21%, and improves the computing efficiency obviously. The analysis method using induced electric current can explain the change law of RCS clearly and intuitively with a high reliability.
Components level mathematical model of two-stage turbocharging reciprocating engine propeller propulsion system and analysis of its flying characteristic
ZHOU Yi-cheng, SHAN Peng, ZHU De-xuan
2014, 29(11): 2621-2632. doi: 10.13224/j.cnki.jasp.2014.11.012
Abstract PDF(1433KB) icon2585 icon1099
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A flying characteristic simulation method was studied for two-stage turbocharging reciprocating engine propeller propulsion system suitable for medium/high altitude low-speed long-endurance multi-role aerial vehicle systems at 10-20 kilometers height. With introduction of the simulation method for gas turbine engine with component models, and based upon component maps or algebraic equations, this method solved joint-working equations of the propulsion system by Newton iteration method to obtain co-operation points of the system. A full-power holding requirement and turbocharger-engine collaboration condition were stated. The regulating rules in both full-power holding mode and power lapse mode were analyzed. The influences of regulating rules on turbocharger operating lines were discussed. Finally, the altitude-velocity characteristics of the propulsion system and components were investigated. The research shows three results. This method enables rapid convergence and usually needs only 5-6 iterations to obtain one operating point. The regulation scheme of two gas-bypass valves can not only meet the design objectives, but also allow effective adjustment to the operating points of the turbochargers. This method can be extended conveniently to the simulations of more complex multi-stage turbocharging systems.
Calculations of unsteady aerodynamic interaction between main-rotor and tail-rotor of helicopters based on CFD method
FAN Feng, XU Guo-hua, SHI Yong-jie
2014, 29(11): 2633-2642. doi: 10.13224/j.cnki.jasp.2014.11.013
Abstract PDF(1265KB) icon1568 icon872
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Numerical calculation research was performed for helicopter main-rotor/tail-rotor interaction by using the CFD method. A computational method was established for aerodynamic interactions of main-rotor/tail-rotor configuration, wherein the three-dimensional unsteady Reynolds-averaged Navier-Stokes (RANS) equations were used as the control equations, and overset grid technique was employed to simulate the relative motion between the main-rotor and tail-rotor. Based on the developed method, the aerodynamic characteristics of main-rotor/tail rotor interaction in hover, low-speed forward flight and cruising state were calculated, and the influence of the tail-rotor rotation direction on the interaction characteristics was analyzed. The results indicate that the interference influence of main-rotor on tail-rotor is obvious in all calculation states, but not always negative, depending on the flight condition. The interference influence of tail-rotor on main-rotor is relatively obvious in hover, but negligible in forward flight condition. In addition, the tail-rotor rotation direction has a significant effect on the aerodynamic force of tail-rotor, so reasonable selection of the tail-rotor rotation direction can improve the aerodynamics of tail-rotor.
Research and validation of variable cycle engine modeling method
WANG Yuan, ZHANG Ping-ping, LI Qiu-hong, HUANG Xiang-hua
2014, 29(11): 2643-2651. doi: 10.13224/j.cnki.jasp.2014.11.014
Abstract PDF(1058KB) icon1915 icon975
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The key components modeling techniques of variable cycle engine(VCE) were studied. Two fans of VCE were divided into tip and hup sections during modeling process to suit the characteristic of VCE. The relationship between the valve opening, the bypass inlet total pressure, the dynamic pressure and total pressure recovery coefficient of bypass was got based on flow field analysis, and modeled by intelligent network. The co-working equations between components of VCE were set up. Then the component-level model of VCE was got. The bypass model was improved. The design point calculations were completed based on the European Space and Propulsion System Simulation Database, and simulations were carried out. The results of simulations indicate that the mathematical model exhibits the same performance as the actual engine experiment. At low Mach number, the double bypass mode achieves higher thrust and lower specific fuel consumption, and at high Mach number, the single bypass mode shows higher thrust and lower specific fuel consumption. So the modeling method of VCE proposed is feasible.
Post-processing methods for wall heat-flux in aeroheating numerical simulation
ZHANG Sheng-tao, CHEN Fang, LIU Hong
2014, 29(11): 2652-2658. doi: 10.13224/j.cnki.jasp.2014.11.015
Abstract PDF(1033KB) icon1490 icon922
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A systematic study of post-processing methods for wall heat-flux in aeroheating numerical simulation was conducted and a post-processing method differing from conventional differential or integral methods was proposed. The comparisons among different post-processing methods were done by three cases. The results indicate that, even if the flow parameters remain the same, significant differences and grid-dependence in wall heat-flux prediction are observed using different post-processing methods. The differential method depends strongly on the grid used in calculations. Enhancement of the order of finite difference cannot always weaken its grid-dependence and improve its accuracy in wall heat-flux prediction, which is also related closely to the grid distribution near the wall. The integral method derived directly from the integral energy balance equation can significantly achieve a lower grid-dependence and thus a high accuracy. The proposed method can be compared with the integral method in the aspect of grid-dependence and accuracy. Especially, in the stagnation region, it has even weaker gird-dependence. Moreover, it is simpler and easier to be implemented numerically, thus further improving the computation efficiency.
Numerical simulation of dynamic derivatives based on rigid moving mesh technique
MI Bai-gang, ZHAN Hao, WANG Ban
2014, 29(11): 2659-2664. doi: 10.13224/j.cnki.jasp.2014.11.016
Abstract PDF(975KB) icon1652 icon1016
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Based on rigid moving mesh technique, a unsteady method of simulating each pitching dynamic derivative was developed. Firstly, the pitching combined dynamic derivative was calculated by using the method of small amplitude pitching forced oscillation; then the lag of wash derivative could also be obtained by using the small amplitude plunging forced oscillation method; finally the pitching damping derivative was calculated by the difference between the combined dynamic derivative and the lag of wash derivative. The international dynamic derivative standard model Finner missile was taken as an example to testify the methods, the calculation error of pitching combined dynamic derivative is 2.76%, and the lag of wash derivative calculated is 11.5% of pitching damping derivative, in agreenment well with the references. The research shows that the methods of separating dynamic derivatives have been proved reliable and useful in engineering, and these methods can also be used in lateral and directional dynamic derivative analysis.
Application of digital speckle correlation method to disk surface thermal deformation measurement
DING Shui-ting, WANG Zi-yao, LI Ye
2014, 29(11): 2665-2671. doi: 10.13224/j.cnki.jasp.2014.11.017
Abstract PDF(928KB) icon1410 icon836
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To overcome the limitations of thermal deformation measurement conducted by strain gages, the DSCM (digital speckle correlation method) was used to determine the real-time surface thermal deformation of a static hollow disk subjected to thermal load on the outer rim. In the experiment system, electromagnetic induction heating method was applied to simulate the heat boundary of the disk and the real-time temperature distribution of the disk was obtained by infrared thermometer. Meanwhile, for the purpose of improving accuracy of DSCM, measures were taken by considering the range of field of CCD (change coupled device) camera view, the usage of medium focal length micro lens and the arrangement of illumination to lessen the effects of error factors like off-plane displacement and speckle image quality. The comparison between the experimental and theoretical results of thermal deformations shows that a good agreement is achieved, although some deviations still exist, and the maximum absolute deviations and relative deviations are 6μm and 31%, respectively; the absolute deviations of the outer rim are larger while the relative deviations are smaller,and this case is contrary to the inner rim. The results validate that the feasibility of DSCM for disk surface thermal deformation measurement, thus providing an effective experimental tool on turbine thermal deformation investigations.
Heat transfer experiment on film cooling of turbine blade leading edge
TAN Xiao-ming, ZHU Xing-dan, GUO Wen, ZHANG Jing-zhou, WANG Yong-ming, PANG Bing-hua, SU Yun-liang, LIU Song
2014, 29(11): 2672-2678. doi: 10.13224/j.cnki.jasp.2014.11.018
Abstract PDF(1089KB) icon1975 icon941
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Detailed experimental study on film cooling effect of one enlarged model of turbine blade leading edge cooling structure was carried out. The surface temperature distribution of blade was captured by the infrared radiation camera. The influence of adiabatic cooling efficiency and pressure loss were analyzed by different film angles of leading edge, blow ratios, main flow Reynolds numbers. In the experiment, the range of three-row film angle on leading edge was 35 degree to 90 degree; the range of main flow Reynolds number was 76112-142624, and the range of blow ratio was 0.44-2.64. The results show that: the film cooling on the stagnation region of leading edge is getting better with the decrease of film angle; the pressure loss coefficient is lowest with film angle of 45 degree and highest with film angle of 75 degree; with increase of main flow Reynolds number, the adiabatic cooling efficiency decreases, and the pressure loss coefficient increases; the adiabatic cooling efficiency reaches to the maximum when blow ratio increases to 1.32 and then decreases when blow ratio keeps increasing.
Method of infrared thermography measurement for temperature field of turbine vane in hot wind tunnel
HUANG Ming-hai, ZANG Shu-sheng, GE Bing, WENG Shi-lie
2014, 29(11): 2679-2683. doi: 10.13224/j.cnki.jasp.2014.11.019
Abstract PDF(930KB) icon1544 icon918
Abstract:
A method of obtaining the temperature field of the surface of turbine vane in hot wind tunnel utilizing infrared thermography measurement was presented. After the acquirement of infrared thermograms, overall corrections were implemented pertaining to the specific disturbance of hot wind tunnel caused by variations in the transmission rate of quartz glass window with the vane surface temperature, as well as by thermal radiation of gas components such as carbon dioxide and water vapor. A geometrical transformation could help reproducing the temperature field of the vane surface, by taking into consideration the curvature of the vane surface. The results show that corrections as large as 110-140K exists for infrared thermography measurement of this testing in hot wind tunnel. Under hot gas circumstances, temperature correction based on gas conditions is indispensable.
Effects of geometry on characteristics of central toroidal recirculation zone generated by an axial swirler
ZHU Yu, ZHANG Qun, XU Hua-sheng, ZHONG Shi-lin
2014, 29(11): 2684-2693. doi: 10.13224/j.cnki.jasp.2014.11.020
Abstract PDF(1153KB) icon1605 icon945
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The non-reaction flow field generated by a single axial swirler was simulated by using FLUENT software. The variation laws of dimensions and strength of central toroidal recirculation zone (CTRZ) with the change of swirler structures were analyzed, and an empirical formula for the length of CTRZ was obtained. The computed results were compared with experiment measurements, and the comparisons of the results indicate that the empirical formula can calculate the length of CTRZ correctly with an error lower than 5%; the length of CTRZ decreases with the increase of swirl number and expansion ratio; the width of CTRZ increases with the increase of expansion ratio; the swirler has a complex impact on backflow ratio of the center plane of vorticity; there is a critical angle of 43° for Venturi; at both sides of the critical angle the CTRZs are quite different.
Numerical simulation of aircraft hot air anti-icing system and ice ridge prediction
WANG Kun, BAI Jun-qiang, XIA Lu, LI Xin, MA Xian-wei
2014, 29(11): 2694-2703. doi: 10.13224/j.cnki.jasp.2014.11.021
Abstract PDF(1121KB) icon1733 icon962
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A numerical simulation method was built based on the conception of fluid-solid coupled heat transfer, and ice prediction under hot air anti-icing system was carried out in associated with ice accretion thermodynamics model. Both the internal and external flow fields were got by solving N-S equation using cell-centered finite volume method. The droplet impingement result was calculated by Euler method based on the external flow field. Three-dimensional heat transfer partial differential equation was solved to get the heat transfer characteristic of the thin-gauge skin. Heat transfer from internal flow to external flow field was accomplished by using interface interpolation method. Three-dimensional ice accretion thermodynamics model was built with which ice ridge was predicted. The result shows that the heated wing surface temperature can get as high as 308 K, and ice ridge is accreted on both the upper and lower surfaces just after the heated zone when the hot air anti-icing system is on. Then, by analyzing the result, it proves that the method is rational and effective.
Flow field and spray of a high shear air-blast nozzle
LI Zhen-xiang, GUO Zhi-hui, CHE Jun-long, FU Yu
2014, 29(11): 2704-2709. doi: 10.13224/j.cnki.jasp.2014.11.022
Abstract PDF(943KB) icon1472 icon906
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The flow field and spray characteristics of a high shear air-blast nozzle were investigated numerically and experimentally. Particle dynamics analyzer (PDA) was employed to experimentally study on the velocity field and spray field of the high shear air-blast nozzle under different air-liquid ratios. And through numerical calculation of the flow field of the nozzle, the calculated results agreed with the experimental data. The results show that the design of high shear air-blast nozzle is reasonable. Two swirl air flows could finish strong momentum exchange inside the nozzle, and fuel is highly sheared. The high shear air-blast nozzle can achieve good atomization under wide regulation ratios. When the air-liquid ratio is of 10 times, the Sauter mean diameter distribution of spray is between 20-60μm. With the increase of air-liquid ratio, line averaging Sauter mean diameter decreases. The calculation model of Sauter mean diameter is derived for the nozzle. The results can provide references for high shear air-blast nozzle design.
Self-calibration extended Kalman filter method
FU Hui-min, LOU Tai-shan, XIAO Qiang, WU Yun-zhang
2014, 29(11): 2710-2715. doi: 10.13224/j.cnki.jasp.2014.11.023
Abstract PDF(1088KB) icon1315 icon904
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A self-calibration extended Kalman filter(SEKF)method was presented. Recursive algorithms of the SEKF were established for three nonlinear dynamic models with unknown inputs, such as unknown systematic error, gust and fault. In many nonlinear engineering cases, such as navigation, signal process, fault diagnosis, the conventional extended Kalman filter (EKF) cannot eliminate the effect of the unknown inputs, and maybe always lead to greater filtering errors or even diverge. The proposed SEKF is applied to compensate and correct the unknown inputs, and improve filtering accuracy. Numerical simulation shows that mean and standard deviation of state estimate errors of SEKF decrease to 1/12 and 1/4 respected to the conventional EKF, respectively, and the filtering accuracy is effectively improved. The SEKF method is simple to calculate and easy to apply in engineering.
Optimization design of tenon connection structure based on coordinate correlation method
HAO Yan-hua, HUANG Zhi-jian
2014, 29(11): 2716-2721. doi: 10.13224/j.cnki.jasp.2014.11.024
Abstract PDF(854KB) icon1446 icon862
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To solve the problem about the design optimization process interruption due to geometric dimensional interference in the process of structure optimization design, a method(coordinate correlation method) was established, making suitable for optimization design of structure modeling. This method was applied to aeroengine tenon connection structure optimization design; the process was smooth, and structural modeling of 790 times was completed without any problems due to geometric changes. The optimization design results show that the maximum stress on the groove throat area drops by 19.1% though the changes before and after optimization of tenon connection structure shape are not big. The stress levels are significantly lower, and the structure model meets the engineering requirements.
Distribution characteristic of durability load accumulation based on changeable task frequency mixing
ZHAO Fu-xing, QIU Dong, YANG Xing-yu, ZHENG Xiao-mei
2014, 29(11): 2722-2728. doi: 10.13224/j.cnki.jasp.2014.11.025
Abstract PDF(984KB) icon1403 icon828
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Based on results of distribution characteristic of durability load accumulation of fixed task frequency mixing, distribution characteristic of durability load accumulation based on changeable task frequency mixing was deduced. Results show that distribution function of durability load accumalation of changeable task frequency mixing tends to be normal as well. The process of durability load accumulation with changeable task frequency mixing in real flying operation was demonstrated by numerical simulation, and the numerical results coincide with the theoretical results, which further demonstrates the analyzed results. Results can be used in life reliability forecasting based on changeable task frequency mixing.
Analysis and correction of computational methods on disk radial burst speed
FENG Yin-li, HE Yun, CHEN Wei, LIU Hong-bin
2014, 29(11): 2729-2734. doi: 10.13224/j.cnki.jasp.2014.11.026
Abstract PDF(827KB) icon2070 icon1004
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The meanings and characteristics of theoretical computation method and average radial stress computation method for disk radial burst speed were analyzed. According to the meanings of theoretical computation method, the correction method for disk radial burst speed was put forward on the basd of finite element computational results. By application example, relative to theoretical method's computation result indicates that the correction method has higher calculation precision than the average radial stress method.The calculation precision is improved from 6.6% to less 0.5%. The correction method is more convenient and applicable than theoretical method.
An experimental scheme of investigating fatigue life of turbine casing slot
LIU Chun-feng, ZHANG Yun-hua, ZHANG Xiao-yong, YAN Xiao-jun, NIE Jing-xu
2014, 29(11): 2735-2742. doi: 10.13224/j.cnki.jasp.2014.11.027
Abstract PDF(874KB) icon1555 icon835
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An experimental scheme of studying the fatigue life of the turbine casing slot was presented. With the scheme, the stress field of the critical section was obtained by numerical analysis, and mechanical loading was applied to simulate the total stress field of the critical section at room temperature. Under the load, the fatigue life of the turbine casing slot can be obtained. Using the proposed scheme, structural improvement measure of new turbine casing, modification measure of old turbine casing and the effect of corrosion were evaluated experimently. The results show that: (1) rounding the new turbine casing slot corner with a 0.8mm-radius can increase the safe life by 69% and 198% with confidence of 50% and 95%, respectively; (2) a fatigue life similar to the new turbine casing slot can be obtained through cutting a 1.5mm-radius corner on the old turbine casing slot; (3) corrosion can affect the fatigue life of the turbine casing slot significantly.
Envelope residuals research of face gear based on disc grinding wheel tooth grinding
GUO Hui, ZHAO Ning, ZHANG Shu-yan
2014, 29(11): 2743-2750. doi: 10.13224/j.cnki.jasp.2014.11.028
Abstract PDF(1205KB) icon1945 icon911
Abstract:
The principles and processes for grinding face gears with disc grinding wheel were described. The envelope residual mechanism was studied for two machining methods of profile envelope and longitudinal envelope. The envelope residual computing models for two kinds of cutting mode were established, and the generating characters of envelope residual were investigated. The influences of cutting parameters, such as circumferential feeding angle, longitudinal feeding and grinding disk diameter on surface envelope residuals were analyzed. Computing results indicates that longitudinal envelope has much higher efficiency than profile envelope. A grinding experiment of face gear by profile envelope was performed. When the tool circumferential feeding angles were taken as 2 degree, 1 degree, 0.5 degree and 0.2 degree, respectively, the tooth surface roughness was improved significantly, and the number and direction of the grinding traces were consistent with the envelope simulation results. The appropriate feeding parameters adopted according to the envelope residual computing results can ensure surface roughness level of face gear teeth by grinding.
Numerical study and validation for two-phase flow of oil and gas in aero-engine bearing cavity
LÜ Ya-guo, ZHANG Mei-hua, LIU Zhen-xia, HU Jian-ping
2014, 29(11): 2751-2757. doi: 10.13224/j.cnki.jasp.2014.11.029
Abstract PDF(1036KB) icon1658 icon827
Abstract:
In order to test whether the traditional one-way coupling model was suitable for flowfield calculation of two-phase flow of oil and gas in bearing cavity, two-way coupling model was established. The distributions of air velocity and turbulence kinetic energy in two model cavity after injecting oil with different rotation speeds, were comparative investigated. The data calculated by two-way coupling model were compared with the experiment data in the reference. Some important conclusions were found: in the two-way coupling model, the change law of air velocity distribution after injecting oil is similar with the one-way air flow. However, air velocity reduces markedly at every point and the difference of average air velocity is the maximum in the case of the rotation speed of 8000r/min between these two models; the influence of droplet motion and evaporation on air velocity and turbulence kinetic energy is significant, especially the air velocity which will drop 10%-15% due to the coupling effect of the droplets in mainstream chamber, indicating influence of droplets on the air field cannot be ignored.
Experimental of foil friction effects on dynamics characteristicof rotor-foil bearing system
XU Fang-cheng, LIU Zhan-sheng, ZHANG Wen, MA Rui-xian, WANG Yu
2014, 29(11): 2758-2766. doi: 10.13224/j.cnki.jasp.2014.11.030
Abstract PDF(1435KB) icon1538 icon931
Abstract:
In order to study the effects of foil friction between bump foil and bearing housing on dynamics characterict of rotor-foil bearing system, a test rig was developed for bump-type gas foil bearing. By experiment comparing between two sets of bearing supporting a 0.458kg rotor which have different surface roughness of bearing housing cylindrical hole with speed from 0-80000r/min, the effects of friction between bump foil and bearing housing on rotor dynamics charecteristic are studied. The results indicate that bump-type gas foil journal bearing with 19.98mm diameter can support the rotor's stable running at a quite high speed, and the vibration amplitude at bearing support is around 20μm. Reducing the surface roughness (friction coefficient) of bearing housing cylindrical hole enables relatively easy slippage of bump foil between the top foil and bearing housing, helping to absorb and eliminate high frequency vibration of rotor, and improve the stability of rotor system.
Theory and experiment on air flow field in bearing chamber
WANG Tao, CHEN Guo-ding, CHEN Bo
2014, 29(11): 2767-2773. doi: 10.13224/j.cnki.jasp.2014.11.031
Abstract PDF(965KB) icon1601 icon826
Abstract:
Investigations into the pressure and velocity fields for the air in an aero-engine bearing chamber were conducted using the finite element numerical method and experimental study. The influence of the operating parameters, such as the rotor speeds and the sealing air mass flow rates, on the pressure and velocity distributions of air in bearing chamber was discussed. The research results show preliminarily that the air pressure in bearing chamber mounts up with the increasing rotor speeds, nondimensional radial coordinate and sealing air mass flow rates. In contrast, the nondimensional tangential velocity of air in bearing chamber increases with the enhanced rotor speeds, and decreases with the increasing sealing air mass flow rates. The experiment results show that as the rotor speeds or the sealing air mass flow rates increase, the experimental data of air pressures agree more with the computational results. The operating parameters from computational and experiment can contribute to further complete the research on aspects of the air in bearing chamber.
A wide-range-input AC/DC converter for FADEC system application
JIANG Wen-liang, ZHU Yin-yu, JIN Zhao-sheng, HUANG Jin-quan
2014, 29(11): 2774-2779. doi: 10.13224/j.cnki.jasp.2014.11.032
Abstract PDF(883KB) icon1388 icon843
Abstract:
According to the output characteristics of the special generator for full authority digital electronic control (FADEC) system of aero-engine, a constant current variable frequency control AC/DC (alternating current/direct current) transform technique based on current feedback was proposed with purpose of accommodating to the wide-range-output of the special generator, so as to meet the power supply requirements of FADEC system. The control strategy, topological structure and operation principles were embodied along with the overvoltage test and protection design. Experiments results prove the reliability of the converter in full temperature range from -55℃ to 125℃, and compliance with the stipulations of national military standard GJB181A covering aircraft electric power characteristics. Research findings has been successfully applied in certain aero-engine numerical control system and validated in both bench test and flight platform experiment.
Fault tolerance analysis of high-bypass-ratio turbofan engine turbine monitoring temperature
ZHAO Lin, WANG Xi, SONG Zhi-ping
2014, 29(11): 2780-2784. doi: 10.13224/j.cnki.jasp.2014.11.033
Abstract PDF(835KB) icon1437 icon897
Abstract:
A turbine monitoring temperature analytic method was proposed for fault tolerance of high-bypass-ratio engine, so as to prevent engine control from degrading caused by turbine monitoring temperature sensor failure or overtemperature caused by undetected sensor failure. The analytic method includes two parts: one analytic method is based on turbine total exhaust temperature which is a main analytic unit; the other is based on air flow model as a redundant unit, which is used when the main analytic temperature differs a lot from the measurement temperature. An experiment on engine trial data was carried out. The results show that the main analytic unit's steady state error is less than 0.33%. The redundant unit's steady state error is less than 0.8%. Experiment results show these two analytic units are both valid and suitable for engine fault tolerant control.

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