2015 Vol. 30, No. 3

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Numerical simulation of compressible flows based on hybrid Cartesian grid method
SHEN Zhi-wei, ZHAO Ning, HU Ou
2015, 30(3): 513-525. doi: 10.13224/j.cnki.jasp.2015.03.001
Abstract PDF(11708KB) icon1469 icon1071
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An adaptive hybrid Cartesian grid (AHCG) method with a finite volume type Reynolds average Navier-Stokes (RANS) flow solver was developed for simulation of compressible viscous flows. While the near body region was provided with body-fitted structured grids to resolve the boundary layers, the remaining computational domain was tessellated with generated Cartesian grid, and feature-based grid adaptations were carried out for simulating the flowfield more accurately. By using the ADT (alternating digital tree) algorithm, the costed turnaround time of chimera type hole-cutting and identification of donor cells could be decreased very efficiently, and 0.062s was costed, up to only 1/1847 of the normal traversal approach when the grid number reached 500000. Through simulations of flow past 2-D cylinder and 2-element airfoil, it is concluded that steady AHCG method can predict surface pressure distribution, lift and drag coefficients successfully and has the ability of solving complex configurations. The simulation of unsteady flow past 2-D cylinder and the capture of 3-D wing tip vortex past a NACA0015 rectangular wing demonstrates that unsteady AHCG method with dynamic adaptive mesh refinement is especially suited for vortex-dominated flows.
Numerical simulaton of nozzle pressure ratio effect on vector performance and separation control for shock vector control nozzle
WANG Meng-jie, Eriqitai, WANG Qiang, WU Meng
2015, 30(3): 526-536. doi: 10.13224/j.cnki.jasp.2015.03.002
Abstract PDF(8783KB) icon1601 icon888
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The phenomenon that vector angle of shock vector control nozzle decreases with increasing nozzle pressure ratio (NPR) has been verified by numerous researches. The study was involved with the mechanism of vector angle variation with NPR and multi-slot cavity and multi-slot assistant injection for separation control. A way for improvement of vector performance at large NPR conditions was studied. Results indicate that, the mechanism of vector angle variation with NPR is mainly due to the transition of separation region structure (from open to closed), which is located downstream the secondary injection. This leads to the reduction of thrust vector force caused by wall pressure difference. With the help of multi-slot assistant injection, the separation can be kept open at large NPR conditions. Vector performance can be improved by atmosphere pressure injection without need of bleeding air from engine.
Numerical simulation of nanosecond pulse plasma aerodynamic actuation
LI Fan-yu, LI Jun, WU Yun, LIU Dong-jian
2015, 30(3): 537-545. doi: 10.13224/j.cnki.jasp.2015.03.003
Abstract PDF(3189KB) icon1738 icon912
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A nanosecond pulse plasma aerodynamic actuation kinetic model was presented based on its effect on flow field mechanism. The effect of nanosecond pulse plasma aerodynamic actuation on flow field was represented by fast heating of thermal source. Simulative investigation of one nanosecond pulse was performed under static flow field conditions. The simulation results show that the temperature and pressure rise abruptly in the narrow space in static flow field by nanosecond pulse plasma aerodynamic actuation. One zone is high (716K, 225.95kPa) and the other one is relatively low (380K, 131.7kPa). They induce a strong compressional wave and a weak compressional wave following strong and weak rarefaction waves respectively. The compressional wave and rarefaction wave propagate to the far field at a high speed (above 400m/s) and then the speed reduces soon(357m/s). Local speed is induced when the compressional wave passes by. The maximum induced local speeds in the normal and tangential directions of actuator are above 60m/s at beginning and soon reduce to about 10m/s with the reduction of compressional wave.
A universal moving-embedded grid method for CFD simulation of unsteady aerodynamic characteristics of rotor
ZHAO Guo-qing, ZHAO Qi-jun, WU Qi
2015, 30(3): 546-554. doi: 10.13224/j.cnki.jasp.2015.03.004
Abstract PDF(4781KB) icon1589 icon914
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Targeting the problem on grid generation for the CFD simulation of the unsteady aerodynamic characteristics of helicopter rotor, a highly-efficient and universal moving-embedded grid generation method was proposed. Firstly, the orthogonal and body-fitted grid around rotor blade were generated by using Poisson equations and folding approach. Then, considering the twist distribution and the complex pitching, flagging motion of rotor blade, a method for the identification of hole cells named disturbance diffraction method was established. In order to ensure the closeness of hole envelope surface, the grid refinement strategy in the hole-cutting procedure was improved. Meanwhile, based upon the determination of the hole boundary, an modified minimum distance scheme of donor element method with high efficiency and robustness was developed for searching the donor cells. On these basis, the CFD simulation method for unsteady flowfield of rotor was conducted by solving the RANS (Reynolds-averaged Navier-Stokes) equations. Finally, the aerodynamic characteristics and location of the blade tip vortex for C-T(Caradonna-Tung) and 7A (Helishape 7A) rotors were simulated by the presented method in hovering and forward flight respectively. The errors of numerical results are less than 5% according to the experiment data, and the effectiveness of CFD simulation on the unsteady aerodynamic characteristics of different rotors is demonstrated.
Influences of geometry of hull tail on aerodynamic drag of stratospheric airships
ZHANG Hai-jun, GUO Xue-yan, YANG Fan, DAI Ren
2015, 30(3): 555-562. doi: 10.13224/j.cnki.jasp.2015.03.005
Abstract PDF(5424KB) icon1756 icon850
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LES (large-eddy simulation) method was used to simulate the external flow field around hulls of the LOTTE and M-LOTTE airships at zero incidence angle in order to analyze the momentum boundary thickness and trailing vortex structure of stractospheric airship. Q distribution together with vorticity was used to visualize the trailing vortex structures of revolutional body. The Q distribution shows that compared with the LOTTE airship, the separation region in the tail of M-LOTTE airship is much smaller. Influence of axial symmetry momentum boundary layer thickness of revolutional bodies on aerodynamic drag of airship was analyzed. It has been found that the momentum boundary layer thickness increases obviously toward to the tail end for both of the two airship hulls and apparently thinner momentum boundary layer thickness exists for the M-LOTTE airship. The distribution of momentum boundary layer thickness explains the fact that the total drag coefficient of the M-LOTTE airship hull was 17.2% smaller than that of the LOTTE airship. It can be concluded that hull tail geometry of the airship can significantly determine the total aerodynamic drag.
Design for inward turning basic flowfield with controlled center body and two incident curved shock waves
LI Yong-zhou, ZHANG Kun-yuan, ZHU Wei, YANG Shun-kai
2015, 30(3): 563-570. doi: 10.13224/j.cnki.jasp.2015.03.006
Abstract PDF(2381KB) icon1632 icon912
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A basic flowfield with controlled center body and two incident curved shock waves was designed by rotational method of characteristics. The two incident shock waves were intersected at the initial point of the center body. Both incident shock waves and reflected shock waves were inversely designed by the given radial total pressure recovery coefficient distribution,and the wall was inversely designed by the given axial Mach number distribution. The basic flowfield with high compression efficiency was divided into three shock waves and four regions. On the basis of the basic flowfield,the inward turning inlet with circle shape intake was designed and corrected by viscosity. The computational results indicate that the flowfield characteristics and the shock waves of the core of inward turning inlet are consistent with those of the basic flowfield at design point. The inlet has good compression efficiency and mass capture ratio with incoming Mach number varying from 4.0 to 7.0. At design point, the pressure ratio of the throat is 17.7 and the total pressure recovery coefficient is 0.729. The internal total drag coefficient decreases from 0.23 to 0.22 with incoming Mach number varying from 5.0 to 7.0.
Numerical investigation on trailing edge jet and boundary layer ingestion in distributed propulsion system
DUAN Jing-yao, YUAN Wei, LI Qiu-shi
2015, 30(3): 571-579. doi: 10.13224/j.cnki.jasp.2015.03.007
Abstract PDF(3466KB) icon1453 icon896
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In order to study the influence of boundary layer ingestion on airframe aerodynamic performance and propulsion efficiency of the distributed propulsion system with trailing edge jet, a two-dimensional airfoil with trailing edge jet and boundary layer ingestion, modeling the airframe, was studied numerically to discuss the influence of incoming angle of attack, jet angle and boundary layer ingestion on aerodynamic performance and propulsion efficiency. Some suggestions on design and application of the distributed propulsion system were carried out. Results show that trailing edge jet and boundary layer ingestion are able to improve the lift-drag ratio at medium/small incoming angle of attack (2° and 0.6°). Propulsion efficiency is able to reach the level over 80%. However, drag of airfoil rises significantly at high incoming angle of attack (4°) with jet angle increasing, resulting in adverse impact on both aerodynamic performance and propulsion efficiency.
Effects of downstream throat on aerodynamic performance of dual throat nozzle
FAN Zhi-peng, XU Jing-lei, WANG Yang-sheng
2015, 30(3): 580-587. doi: 10.13224/j.cnki.jasp.2015.03.008
Abstract PDF(3673KB) icon1352 icon894
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Numerical simulation studies on 2-D dual throat nozzle (DTN) were performed on the downstream throat height H. The contents include: effects of H on the nozzle's maximum vector angle and the flow development in the nozzle's thrust cavity. The results show that: H has a significant influence on the nozzle's thrust vector angle; especially in two cases of H greater than 1 and H less than 1, the flow development in the nozzle's thrust cavity has a large difference. In all cases, it appears that the maximum vector angle could be achieved when the flow in the nozzle's thrust cavity has changed to the supersonic flow, meanwhile the sonic line at the downstream throat of the nozzle has vanished. The nozzle can achieve the maximum vector angle with a low ratio of secondary injection in the case of H greater than 1. The nozzle could be achieved maximum vector angle at larger ratio of secondary injection in the case of H less than 1, while the maximum vector angle is greater than that in the case of H greater than 1.
Movement research and three-dimensional numerical analysis on cicada's wing
DONG Qiang, ZHANG Xi-jin, ZHAO Ning, HUANG Qiang-qiang
2015, 30(3): 588-594. doi: 10.13224/j.cnki.jasp.2015.03.009
Abstract PDF(2293KB) icon1290 icon1027
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A cicada was regarded as a research object. Firstly, its wing movement equations were gotten by analyzing the cicada's movement images from high-speed camera. Then, a three-dimensional model of the cicada's wing was established, and the numerical simulation method of flow field around the cicada's wing was studied based on Fluent software. Finally, the average lift and drag coefficients of the three-dimensional cicada's wing model were analyzed under the situation of different movement parameters (flapping frequency, flapping amplitude and maximum torsional angle). The research result shows that the maximum torsional angle greatly impacts the aerodynamics of cicada's wing, so the torsional movement must be considered in the design and manipulation of the flapping-wing maro air vehicles mimicking cicada.
Numerical simulation and experiment on shot peening of Al-Li alloy
WANG Yong-jun, SUN Bao-long, ZHANG-Wei, GAO Guo-qiang, QIAO Ming-jie
2015, 30(3): 595-602. doi: 10.13224/j.cnki.jasp.2015.03.010
Abstract PDF(2785KB) icon1384 icon836
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According to the characteristics of shot peening process, a three-dimensional finite element model was established by using ABAQUS finite element software to simulate the residual stress field. Based on this model, the effects of shot parameters such as velocity, diameter and shot number on residual stress field of Al-Li alloy were studied respectively. Then the distributions of the residual stress field of single shot model, uniform array shots model and random shot model were compared. Furthermore, the residual stress distribution in Al-Li alloy specimen thickness direction was measured by using X-ray residual stress analyzer and electrolytic polishing method. The depth of residual stress layer is 0.24mm. The maximum residual stress occurs at the depth of 0.08mm. It verifies the validity of the finite element model.
Methods of airworthiness verification for approved life of aero-engine limited-life parts
WANG Da-wei, SUN Dan, WANG Wei, ZOU Tian-chun
2015, 30(3): 603-610. doi: 10.13224/j.cnki.jasp.2015.03.011
Abstract PDF(1137KB) icon2010 icon1008
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Based on the traditional safe life method, studies on verification process and certification factors of airworthiness of approved life for aero-engine life-limited parts were conducted. Airworthiness requirements and compliance of advisory circular for life-limited parts were taken as a guide, and management methods of life-limited parts life determination in the general specification for aero-engine were used as a reference. The process and methods of the airworthiness compliance verification were given by calculation analysis and experimental verification. The criterion of life-limited parts was studied using typical civil aero-engines. The key technologies of the calculation and analysis verification for approved life of life-limited parts were given from the criterion, the processing of load spectrum and stress analysis of their structural dangerous points. The key technologies of the experimental verification were given by obtaining the experimental conditions, scheme of experimental temperature, experimental overstress factor and scatter factor. A method of guidance is provided for the airworthiness certification of approved life for aero-engine life-limited parts. The proposed methods provide an important reference for Civil Aviation Administration of China to draw up airworthiness advisory circular of aero-engine life-limited parts.
Failure modes of space shuttle main engine high-pressure fuel turbopump
LIU Shi-jie, LIANG Guo-zhu
2015, 30(3): 611-626. doi: 10.13224/j.cnki.jasp.2015.03.012
Abstract PDF(3657KB) icon1701 icon1329
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A summary analysis for space shuttle main engine (SSME) high-pressure fuel turbopump(HPFTP) failure modes was given, while the failure problems and corresponding solutions of HPFTP critical components were comprehensively analyzed. The study shows that:(1)there exists significant differences in the failure modes among the SSME HPFTP, the expendable liquid rocket engine hydrogen turbopump and aero gas turbine; (2) the important failure modes affecting HPFTP life are turbine blade fracture and the thermal mechanical fatigue of thermal shield system; the turbine blade fractures are induced by the high temperature creep deformation and high-speed centrifugal force; the HPFTP start and shutdown transient effects seriously affect the turbine blades as well, which should be considered in the turbine blade life prediction; (3) sub-synchronous vibration which is mainly caused by the bearings and the pump interstage seal, is a critical failure mode encountered during the preliminary design phase of SSME HPFTP; (4) the failure of lift-off seal, a proprietary seal failure mode of SSME HPFTP, is also an important part of HPFTP failures.
Modeling for whole missile turbofan engine vibration with support looseness fault and characteristics of casing response
WANG Hai-fei, CHEN Guo, LIAO Zhong-kun, ZHANG Zhang, SHAO Fu-yong
2015, 30(3): 627-638. doi: 10.13224/j.cnki.jasp.2015.03.013
Abstract PDF(7680KB) icon1465 icon845
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For the structural characteristics of a certain type of missile turbofan engine, a rotor-support-casing whole model established. The rotor and casing were modeled by means of the finite element beam model; the support was modeled by lumped-mass model; support looseness fault model was also introduced. The coupled system response was obtained by the numerical integral method. Impact characteristics of symmetrical stiffness and asymmetric stiffness models were analyzed based on casing acceleration signal. It is found that looseness fault could lead to acceleration time-domain waveform of casing with up-down asymmetrical impact characteristics and multiple frequency characteristics in frequency spectrum. Time-domain waveform and frequency spectrum characteristics of the simulation results and the actual missile turbofan engine test data are very consistent. Asymmetric stiffness looseness model is verified more suitable for missile turbofan engine looseness fault modeling.
Study on three-dimensional through-thickness crack growth based on energy model
GAO Chao, WU Li-ming, HE Yu-ting, ZHANG Teng, HOU Bo
2015, 30(3): 639-648. doi: 10.13224/j.cnki.jasp.2015.03.014
Abstract PDF(6806KB) icon1270 icon719
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The effective energy release rate at crack tip was given by using the relation between energy release rate and stress strength factor. The effective energy release rate was equal to crack growth resistance at the crack growth, and the calculation method of three-dimensional through-thickness crack growth profile based on energy model was presented according to the equality relation of effective energy release rate for the crack tip front edge; the three-dimensional through-thickness crack growth profile of different thickness specimens could be calculated by using this method, and the finite element simulation and tests for single edge crack plates of different thickness were conducted to validate the calculation method. The simulation and test results show that the method of three-dimensional through-thickness crack growth profile based on energy model can be used to calculate crack growth profile of three-dimensional structures. The "crack tunneling" of crack tip disappeares when the thicknesses of single edge crack plates increase, and the crack growth profile turns into "saddle shape". The crack growth rate at specimen surface is smaller than crack growth rate at specimen middle face.
A forming method for improving surface integrity of film cooling holes
ZHAO Hua-long, ZHOU Ren-kui, ZHAO Hong-yan, ZHAO Wei, ZHU Wen-yu, YANG Xiao-jun, LI Ming, DENG Yue
2015, 30(3): 649-655. doi: 10.13224/j.cnki.jasp.2015.03.015
Abstract PDF(1432KB) icon1563 icon760
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In order to solve the problems of forming process of turbine blade of aero-engine film cooling holes, such as severe heat effect, a helix drilling and spiral drilling processing method for microholes by ultrafast laser was proposed, and a double power laser system was designed for machining of film cooling holes efficiently and without heat effect; the reason of heat effects was analyzed from two aspects of action mechanism and actual machining process; the main influential factors were pointed out and the optimization of process parameters and experimental verification targeting at these factors were processed using DD6 material. The experimental results show that the composite processing method using 500fs laser and microseconds laser can increase fine drilling efficiency about 10 times, and can also process the film cooling holes on turbine blades without recast layer and micro-cracks; the process parameters include beam scanning speed of 2400r/min, overlap rate of 12%, feeding amount of 5μm, repetition frequency of 20kHz and coaxial blow with the air pressure of 0.6Pa. They also show that ultrafast laser with reasonable process parameters and processing methods can process film cooling holes without heat effects, so it is an effective technological method to improve the surface integrity of film cooling holes.
Static strength of 2.5 dimensional woven complex structures
LIU Hao-long, CUI Hai-tao, WEN Wei-dong
2015, 30(3): 656-664. doi: 10.13224/j.cnki.jasp.2015.03.016
Abstract PDF(3119KB) icon1135 icon787
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From the perspective of macro and micro combinations, a series of failure criterions and corresponding stiffness reduction methods for multi-failure models of warps and wefts were developed based on modified Hashin criterion. Systematic static strength analytical method for 2.5 dimensional woven complex structures was presented based on gradually damage concept. Also, the tension stress-strain curves along the warp and weft were simulated, and the fitting curves were in good agreement with the experimental results with the errors of calculated stress less than 6.5% for given strains; and for 2.5 dimensional woven connection structure simulation of compressor, gradually damage process was simulated. The result shows that main damage of the structure occurs around the chamfer of the root; specifically, matrix compress failure on the root of suction surface can cause great deformation as a major cause of the destruction of the structure.
High precision and multiple view point cloud data fusion in blade three-dimensional profile measurement
LAI Wen-jing, BAO Hong, BAI Yu-lei, SHEN Zuo-chun, ZHOU Yan-zhou
2015, 30(3): 665-671. doi: 10.13224/j.cnki.jasp.2015.03.017
Abstract PDF(1824KB) icon1224 icon928
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High precision and multiple view point cloud data fusion is one of the bottlenecks in the blade measurement. A mechanical device of the multiple view point cloud data fusion using phase-measuring-profilometry was presented. A reference plane data rotating algorithm was designed, and the accuracy of three-dimensional blade data high precision fusion is (0.06±0.01)mm. The structure and method of the device are simple and practical with high efficiency and accuracy. Many blades can be measured simultaneously. It can thus replace coordinate measuring method.
Inclusion shape's effects on effective optical constants of mixed particles
WANG Xi-ying
2015, 30(3): 672-676. doi: 10.13224/j.cnki.jasp.2015.03.018
Abstract PDF(1173KB) icon1088 icon734
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Based on the concept of electromagnetic field average, the effective optical constants of mixed particles containing ellipsoidal inclusions were studied with Maxwell-Garnett effective medium theory. The effects of shape scale factors and volume fractions of inclusions on the effective optical constants of mixed particles were analyzed. The results show that: a critical value has been found in the shape scale factors of inclusion. When the shape scale factor is smaller than the critical value, the differences in the effective optical constants of mixed particles containing ellipsoidal and spherical inclusions increase with the growing shape scale factor. Otherwise, little effects are shown in the effects of shape scale factors on the effective optical constants of mixed particles. The value of effective optical constants for mixed particles varies between that for the background and inclusions. With the increase of volume fraction of inclusions, the effective optical constants of mixed particles will approach to those of inclusions.
Computational methodology of water film flow in three-dimensional ice accretion on upwind surface
CAO Guang-zhou, JI Hong-hu, SI Ren
2015, 30(3): 677-685. doi: 10.13224/j.cnki.jasp.2015.03.019
Abstract PDF(2851KB) icon1471 icon799
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The thin water film flow on the ice layer affecting the three-dimensional (3-D) ice accretion on the upwind surface was analyzed. A mathematic model for simulating the flow was developed. A very thin precursor water film beyond the contact line was introduced to deal with the film flow on the dry surface. To treat with the phenomenon that some water film was blew off the surface behind the ice horn, a computational methodology was introduced that the top part of the water film which exceeding the critical height was blew away. The ice shape contrast and water film flow analysis on the airfoil-plane indicates the rationality of the mathematic model and the feasibility of the computational methodology. The research indicates: icing model involving the water film flow can simulate 3-D glaze ice well and provide the ice layer boundary closer to the experimental result than Messinger model. The water film height on the ice layer is about 10-5m and its velocity is about 10-2m/s.
Experiment on effect of triple axial swirler on combustor performance
DING Guo-yu, HE Xiao-min, ZHAO Zi-qiang, ZHU Zhi-xin, GE Jia-wei
2015, 30(3): 686-693. doi: 10.13224/j.cnki.jasp.2015.03.020
Abstract PDF(2388KB) icon1493 icon795
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Experiments were conducted to study four different triple axial swirlers combustor about flow drag performance and combustion performance of a triple axial swirler combustor at different inlet airflow velocities, inlet airflow temperatures and fuel-air ratios with fixed atmospheric pressure. The test results show that: the total pressure loss coefficient of triple axial swirler combustor increases with inlet airflow velocity increasing (from 40m/s to 70m/s), and inlet airflow temperature rise is helpful to ignition and lean blowout; by comparing the combustion performance of the triple axial swirler combustor of "clockwise—counterclockwise—clockwise"rotational direction combinations with the combustor of "counterclockwise—counterclockwise—clockwise" rotational direction combination, the total pressure loss coefficient is a little higher and the lean blowout performance is better, while the combustion efficiency is a little lower; decreasing the inner swirler airflow rate would lead to increase of total pressure loss coefficient, and decline of lean blowout fuel-air ratio and combustion efficiency.
Numerical simulation for ion catalytic effect in ignition process of pulse detonation engine
MU Yun-tao, WANG Yu-qing, LI Li-han, ZHENG Dian-feng, ZHANG Hui-qiang
2015, 30(3): 694-700. doi: 10.13224/j.cnki.jasp.2015.03.021
Abstract PDF(1688KB) icon1490 icon841
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The gas composition was devived using the theory of gas ionization after hydrogen-air mixed gas ionization. The catalysis effect of active group on combustion rate and intensity was found out with the theoretical analysis, and the influences on deflagration to detonation transition (DDT) process in different ignition energies and different concentrations of active group were analyzed. Fully considering the hydrogen-air combustion reaction 23-step kinetics mechanism, the the numerical simulation method was used to study DDT process in different cases by FLUENT, and the theoretical analysis was verified. Results show that when the ignition temperature is in the range of 2000-2500K, the reactive group in the process of ignition can increase the combustion rate; DDT time can be shortened by 9.91%-21.08%, and DDT distance can be shortened by 3.32%-8.08%. With increase of the ignition temperature, DDT time and DDT distance increase. Gas ionization effect should be considered if ignition energy is high.
Comparison of autoignition characteristics of n-heptane, methylcyclohexane and toluene
LI Bin, LI Ping, RAO Fan, ZHANG Chang-hua, LI Xiang-yuan
2015, 30(3): 701-706. doi: 10.13224/j.cnki.jasp.2015.03.022
Abstract PDF(1668KB) icon1250 icon764
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The autoignition characteristics of three C7 hydrocarbon fuels, n-heptane, methylcyclohexane and toluene, were comparatively investigated. Ignitions were performed behind the reflected shock waves in a shock tube. The ignition delay times of these fuels were measured at the same igintion conditions with constant fuel mole fraction of 1.0%, equivalence ratio of 1.0, ignition pressure of 1.0×105Pa (one more 2.0×105Pa for n-heptane) and temperatures of 1166-1662K. The correlation formula of ignition delay dependence of three fuels on igintion conditions was deduced separately. Results show that the ignition delay time of n-heptane is the shortest while that of toluene is the longest at the same ignition conditions. The ignition delay time of methylcyclohexane is most sensitive to the temperature while that of n-heptane is the least. The comparison of current ignition delay times with the predictions of available chemical kinetic reaction mechanisms has been presented to validate the reliability of mechanisms. The important chemical reactions during the ignition process have been obtained from the sensitivity analysis.
Optimal design of profiled endwall for turbine cascade
TANG Hui-min, LIU Shuai-qiang, LUO Hua-ling
2015, 30(3): 707-713. doi: 10.13224/j.cnki.jasp.2015.03.023
Abstract PDF(3543KB) icon1533 icon844
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A method based on non-uniform rational B-spline (NURBS) surface technique coupled with mesh deforming technique was developed to design the profiled endwall for turbines cascade. This method has the advantages of flexible geometry representation and automatic rapid remeshing. An optimal design procedure of profiled endwall has been developed by integrating the commercial CFX solver and the optimization driver Isight. This procedure was applied to optimal design the profiled endwalls of Pack B turbine cascade. The total pressure loss coefficient of turbine cascade was reduced by 12.96% after optimization. The results show that the static pressure field on the endwall of turbine cascade is changed, so the horseshoe vortex and the passage vortex in turbine cascade passage are weakened. Therefore, the aerodynamic performance of the turbine cascade is improved.
Effect of contoured casing design on tip-leakage loss in a turbine
WEI Zuo-jun, QIAO Wei-yang, SHI Pei-jie, ZHAO Lei
2015, 30(3): 714-725. doi: 10.13224/j.cnki.jasp.2015.03.024
Abstract PDF(5896KB) icon1771 icon764
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Based on Menter's SST (shear stress transport) turbulence model coupled with Langtry-Menter transition model, the effects of fully contoured casing and partial contoured casing on the tip-leakage loss was numerically investigated in the highly-loaded low-pressure turbine cascade T106 with tip clearance. The results show that: the contoured casing design changes the vortex structures and loss components in tip region, and such effect is obviously impacted by the height of contoured casing arc. The increase of the spanwise size of the pressure side/tip junction separation bubble leads to stronger blocking effect, thus reducing the kinetic energy of the tip-leakage flow. Partial contoured casing could reduce the additional cross flow near the endwall caused by the local divergence of blade passage, and lead to larger spanwise loss reduction area at outlet. Therefore the cascade outlet loss is reduced essentially, and the maximum is up to 6.1% compared with original casing. The tip-gap size sensitivity analysis shows that both kinds of contoured casings can effectively reduce the tip-leakage loss in a certain. Moreover, the partial contoured casing achieves broader effective tip-gap size and lower loss.
Aerodynamic optimization design of an aspirated compressor rotor blade
ZHAO Zhen-guo, ZHOU Zheng-gui, TAO Sheng
2015, 30(3): 726-735. doi: 10.13224/j.cnki.jasp.2015.03.025
Abstract PDF(3868KB) icon1397 icon763
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The aerodynamic design method of aspirated compressor rotor blade was investigated. An iterated design method was adopted by using the results of three-dimensional (3-D) flow field calculations to provide loss calculation model of S2 flow surface, thus improving S2 flow surface calculation precision. The optimization design software in which the suction parameters and profile parameters were related to the design of two-dimensional random rotating surface profiles and 3-D blades was developed, by combining the optimization method and numerical simulation method. An aspirated compressor rotor was designed by this software, and the numerical simulation results show that its total pressure ratio is 1.631 and isentropic efficiency is 0.965 at design point under the condition of 0.86 tip blades loading, and high aerodynamic performance is achieved.
Dynamic responses for a fluid-structure coupling system with variable mass in a tank of spacecraft
MA Chi-cheng, ZHANG Xi-nong, LUO Ya-jun, ZHANG Shuai
2015, 30(3): 736-745. doi: 10.13224/j.cnki.jasp.2015.03.026
Abstract PDF(2922KB) icon1936 icon725
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Dynamic characteristics of a fluid-structure coupling system with variable mass in a tank of spacecraft were mainly investigated. Dynamic model of system was established by using boundary element method and finite element method based on virtual mass method (VMM). The effect of variable mass on the dynamic response of the system was mainly considered. The vibration responses of the system with variable mass tank were calculated by using Newmark direct integration method. Results show that the decrease of the mass of system induces the increase of the vibration frequencies of the system, and generates an additional negative damping. The frequency range can be determined by the range of the mass of the system. It is derived that the additional negative damping induced by variable mass is proportional to rate of change of the mass. For lateral vibration of the system, the additional negative damping effects the vibration stably in the whole process, while for longitudinal vibration of the system, the influence of additional negative damping increases with time prolonged.
Optimizated control scheme for turbofan engine under inlet distortion conditions
WU Bin, HUANG Jin-quan, YE Wei, WANG Ke-hong
2015, 30(3): 746-753. doi: 10.13224/j.cnki.jasp.2015.03.027
Abstract PDF(2640KB) icon1582 icon689
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A control scheme of satisfying different inlet distortions was proposed for turbofan engine. The turbofan-engine performance was improved by increasing the pressure ratio under low inlet distortion conditions, and the pressure ratio was reduced with addition of guide vane adjustment to provide additional stall protection at high inlet distortion. By using the differential evolution algorithm with border buffer zone(DEBZ), the control scheme of the turbofan engine pressure ratio and variable guide vanes in envelope was optimized and obtained according to the requirements of stall margin with different inlet distortions. The simulation over full envelope was accomplished with the model, control algorithm and control scheme. Using the proposed control scheme, the simulation results show that thrust performance of turbofan engine can be improved more than 8% when the distortion index is 2, and the stall margin requirements can be satisfied when the distortion index is 8 with more than 1% thrust performance improvement.
Quantitative analysis on constant pressure valve stability
WANG Hua-wei, WANG Xi, LI Zhi-peng, DANG Wei, LI Hong-sheng
2015, 30(3): 754-761. doi: 10.13224/j.cnki.jasp.2015.03.028
Abstract PDF(2746KB) icon1760 icon806
Abstract:
A quantitative methodology on constant pressure valve (CPV) stability analysis was presented. Firstly, the main parameters affecting static property of CPV were got by static analysis. The root-locus plots of CPV were achieved through small deviation dynamic analysis. By defining the concept of critical inlet pressure, the quantitative results of five main structural parameters' effect on the CPV stability margin was got: the spring stiffness has a little effect on stability margin; the increase of spool diameter, damping coefficient, load, and decrease of constant pressure chamber volume could enlarge the stability margin. The analytical result has an excellent consistence with AMESim simulation result and engineering experience. Finally, two conclusions were presented for enhancing the stability margin of CPV: (1) for improving problem of CPV, the most effective method is to change the outlet area; (2) for CPV design problem, based on the inlet pressure requirement and the minimum load, the critical inlet pressure need be determined firstly, and then the spool area and constant pressure chamber volume are taken as main design parameters by dynamic analysis.
Evaluation for stability of manufacturing process based on grey relation
XIA Xin-tao, QIN Yuan-yuan, QIU Ming
2015, 30(3): 762-768. doi: 10.13224/j.cnki.jasp.2015.03.029
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Abstract:
Based on the grey system theory, the stability evaluation of manufacturing system could be put into effect via grey relation analysis of the two data series in the manufacturing process. According to these two data sequences obtained in the manufacturing process with certain property, the data series could be sorted, so the sorting data figure was achieved. The grey relation between two data series was established by means of the distribution features of sorting data figure. And the stability evaluation of manufacturing process can be realized through calculation and analysis of the grey confidence level. Computer simulation experiment and actual case indicate that through analyzing the grey relation of two data series, if the grey confidence level is not less than 90%, the manufacturing system is stable; otherwise, the manufacturing system is not stable. The method proposed is very good at testing the stability of the manufacturing system, with accuracy up to 100%.

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