2012 Vol. 27, No. 10

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Heat transfer in direct transfer pre-swirl rotor-stator system
XU Guo-qiang, ZHAO Xi, LUO Xiang, CAI Xu, YU Hong-peng
2012, 27(10): 2161-2168.
Abstract PDF(1834KB) icon1896 icon784
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Heat transfer of direct transfer pre-swirl rotor-stator system was investigated by experiments.Contours of local Nusselt number on the rotating disk,distribution of circumferential-averaged Nusselt number along radial direction,and variation of average Nusselt number with rotating Reynolds number and mass flow rate coefficient were obtained.The results show that with the same mass flow rate and low rotational Reynolds number,peak zones of local Nusselt number arise at small radius.When rotational Reynolds number increases,peak zones of local Nusselt number move to larger radius and expand.With the same rotational Reynolds number,peak zones of local Nusselt number move to smaller radius and their ranges decreases.Average Nusselt number would increase when rotational Reynolds number or mass flow rate coefficient increases.
Frame plate and flame holder integration design and capability analysis
LI Feng, CHENG Ming, GUO Rui-qing, SHANG Shou-tang, TANG Zheng-fu, LI LONG-xian
2012, 27(10): 2169-2174.
Abstract PDF(1137KB) icon2142 icon703
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Based on the increasing demand for high thrust weight ratio and high stealthy aero-engine,the design method of integration design frame plate and flame holder afterburner was given and some model afterburner simulations and experiments were conducted.The results show that the length and can flow resistance could be reduced greatly,and the capability and thrust weight ratio of aero-engine can be increased apparently.This work would help to provide a new research direction and method for high thrust weight ratio and high stealthy aero-engine technology.
Experiment on performance of annular interstage turbine burner
SONG Shuang-wen, HU Hao-sheng, WANG Mei-juan, CHEN Jian, WANG Lu-feng
2012, 27(10): 2175-2179.
Abstract PDF(434KB) icon2008 icon610
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According to the interstage turbine burner(ITB)operation condition,an ITB annular combustor test rig, which used trap vertex combustor design, was designed and manufactured based on ITB being used in a certain turbo-shaft engine, and combustor performance experiment study was performed. The results show that: the lower flammable limit of the ITB is 10.2, and it is favorable to ignite when the pressure difference between the inner of the cavity and the outer of the cavity is reduced. As compared with the ordinary combustor, the combustion efficiency of the ITB is lower, and the combustion efficiency improves when the inlet temperature increases. The total pressure recovery coefficient of the ITB is lower, and the variation of inlet temperature has a less effect on the pressure recovery coefficient. The outlet temperature distribution factor(OTDF) is good, and the outlet temperature distribution factor decreases when the inlet temperature increases. When the inlet temperature increases, the wall temperature of the liner would be partially higher, and the cooling design of the liner should be optimized.
Rectangular tooth straight through labyrinth seal analytical model
WU Hong, LI Peng, TAO Zhi
2012, 27(10): 2180-2187.
Abstract PDF(1214KB) icon2089 icon594
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The main destination was to develop the analytical model of rectangular tooth straight through labyrinth seal based on fluid network method.Plenty of computational fluid dynamics simulation data was integrated,and the model was verified by commercial software Flowmaster GT version.The results show that the analytical model developed has high precision,and can be used under complicated conditions including super-sonic flow.Only geometric features and boundary conditions are required for modeling,convergence performs well,and straight through seals with different shapes can be modeled as well.Thus,it can be used as a standard model in secondary air system simulation widely.
Numerical simulation of flow and heat transfer performances in a direct transfer pre-swirl system
LUO Xiang, FENG Ye, XU Guo-qiang, ZHAO Xi, ZHAO Nan
2012, 27(10): 2188-2193.
Abstract PDF(987KB) icon1778 icon560
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In order to investigate the flow and heat transfer performances in a direct transfer pre-swirl system ,a numerical study was conducted by using CFD commercial software FLUENT with dimensional model and turbulence model respectively.Through the comparison,the following conclusions can be drawn:flow of the lower cavity is determined by the central inflow,and the two-dimensional computation does not reflect mixing of the central inflow and pre-swirl inflow in the higher cavity.Pressure distribution of the two- and three-dimensional computation is similar,and the measurements are within the two results;the heat transfer of the main disk is determined by the central inflow,the two- and three-dimensional computation is almost identical,and heat transfer results of Realizable k-ε turbulence model are mainly good with the measurements qualitatively and quantitatively.
Relationship of failure of fuel nozzle seal spring and engine smoking failure
XU Yong-gang, WANG Qiang
2012, 27(10): 2194-2199.
Abstract PDF(311KB) icon1698 icon571
Abstract:
The ultimate cause of the long-existing smoking failure of an engine type was explored by an explorative study of comparison analysis of flow tests, fuel nozzle structure analysis and spring failure mechanism analysis. The proof analyses of fuel nozzle and manifold flow tests on a smoking engine and a non-smoking engine show that the ultimate cause of engine smoking failure is the un-uniformity of manifold flow at the idle condition resulting from back pressure decrease on some fuel nozzles. The proof analysis of the structure of 14 nozzles of a smoking engine shows that the ultimate cause of the drifts of nozzle and manifold flow characteristics are the loss of the pressing mechanism of the seal spring, and the ultimate cause of that is the excessive un-evenness of the spring end leading to un-uniformity of pressure on the uneven end during nut screwing, which leads to abnormal fall-down and plastic deformation of the spring.
Full status two phase turbulent combustion model
WANG Fang, HUANG Yong
2012, 27(10): 2200-2204.
Abstract PDF(802KB) icon1498 icon711
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In Euler-Lagrange frame,the individual droplet burning behavior was added into the traditional point source two phase turbulent combustion model (TM),and then a full status two phase turbulent combustion model (FSM) was presented.The two kinds of two phase turbulent combustion models were tested by a set of methanol air two phase turbulent spray jet flame experimental data.The comparison results between the computational prediction results and the experimental data show that the FSM model can give two peaks in the averaged temperature profile,as well as more reasonable predictions.
Rotating long orifices with radiused inlets analytical model
LI Peng, WU Hong, TAO Zhi
2012, 27(10): 2205-2213.
Abstract PDF(1097KB) icon1676 icon558
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The main subjects are to introduce a new correlation for long orifices with radiused inlets by conducting computational fluid dynamics simulation under complex working conditions,and then,analytical model of long orifices with radiused inlets was developed based on fluid network method,and the model was verified by commercial CFD tool Simerics.It is shown that the model has high precision,it is applicable under complex conditions,and only geometric features are required for one-dimensional modeling.Thus it can be used as a standard model in secondary air system simulation widely.
Experiment on combustion characteristics of novel variable geometry flame-holder
LIU Yang, JIN Jie, WANG Hui-ru, YANG Mao-lin
2012, 27(10): 2214-2221.
Abstract PDF(1160KB) icon2029 icon569
Abstract:
A novel variable geometry flame-holder (“VGF” for short) based on v-gutter has been experimentally studied on a two-dimensionally combustion test-bed for its combustion characteristics .The effect of the change of gutter trailing edge width w on combustion efficiency and exit temperature distribution in different operating conditions was analyzed emphatically.Furthermore,the effect of the change of w on combustion status and flame structure was discussed by the combustion images in recirculation zone.Results show that: for the test conditions, (1) when w/h changes in 1.25~2.00, there is a certain range change in combustion efficiency.(2) w/h =1.25 shows specificity because the VGF combustion status and flame structure have changed at this point.(3) In the stable combustion condition,temperature of outlet cross-section center increases with the w decrease basically.Results and experimental data presented would enhance the phenomenological understanding of this novel VGF,and would contribute to the next experimental study and numerical simulation on it.
Experiment of flow characteristics of direct transfer pre-swirl system
CAI Xu, XU Guo-qiang, LUO Xiang, ZHAO Xi, LI Ye
2012, 27(10): 2222-2228.
Abstract PDF(1561KB) icon1778 icon564
Abstract:
Flow characteristics of a direct transfer pre-swirl rotor-stator system were investigated experimentally.Static pressure distribution on the stator,discharge coefficient of pre-swirl nozzles and mass flow rate distribution principle at the rim seal and receiver holes were obtained.The results show that the shapes of static pressure distribution on the stator are mainly affected by mass flow rate,and slightly affected by rotating speed of the disk;with equivalent mass flow rate of pre-swirl and disk cooling air,discharge coefficients of pre-swirl nozzles are mostly decided by mass flow rate coefficient at pre-swirl nozzles;for the physical model and operating conditions presented,the ratio of mass flow rate coefficient at the rim seal to total mass flow coefficient is above 0.7.
Effects of liner pressure loss on combustor ignition performances
XUE Xin, LIN Yu-zhen, ZHANG Chi, XU Quan-hong, DU Jiang-yi
2012, 27(10): 2229-2235.
Abstract PDF(1109KB) icon1764 icon615
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Based on a combustor of 3.0% liner pressure loss, two low pressure loss liners ( 2.5% and 2.0% ) were designed. The light lean ignition experiments and numerical simulation were conducted to study the effect of liner pressure loss on the combustor ignition performance. On the condition of pressure drop less than 3%, the ignition performances were almost the same. On the condition of pressure drop greater than 3%, the ignition performances of low liner pressure loss were better than that of the baseline liner, and 2.5% pressure loss liner was the best of the overall ignition performance. Combined with numerical simulation results, the flow structure of liner of 2.0% pressure loss was significantly different from that of the baseline liner, which had a negative effect on the performance of ignition. The flow structure of liner of 2.5% pressure loss was similar with that of the baseline liner, which had a positive effect on the performance of ignition.
Effect of serrated cut at trailing edge on performance of lobed mixer in forced mixing exhaust system
DING Yu-lin, LIU You-hong, XIE Yi, SHAO Wan-ren, WU Fei
2012, 27(10): 2236-2242.
Abstract PDF(1216KB) icon1782 icon679
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Based on a lobed mixer in the forced mixing exhaust system of a turbofan engine,geometric models of different serrated cuts at trailing edge were constructed.Through three-dimensional computational fluid dynamic simulations,the effect of serrated cut at trailing edge on the performance of a lobed mixer in a forced mixing exhaust system on the thermal mixing efficiency and total-pressure recovery coefficient were studied.The results show that the thermal mixing efficiency rises while the total-pressure recovery coefficient declines as the cut size of the serrated cut increases.The thermal mixing efficiency of one triangle (1-SJ) serrated modification model was 79.73%.The thermal mixing efficiency of two trapezoidal modifications (2-TX) was 77.50%,and the total-pressure recovery coefficient of 2-TX was 0.5 percentage higher than that of 1-SJ.
Design and simulation of electronic micro multiple fixed-volume fuel injection system
ZHANG Qi, YANG Kai, XU Guo-qiang, DU Fa-rong
2012, 27(10): 2243-2248.
Abstract PDF(669KB) icon1684 icon665
Abstract:
According to small-displacement gasoline engine's wide speed range and small fuel requirement, a new kind of Electronic Micro Multiple Fixed-Volume Fuel Injection System was proposed, and then the electronic-magnetic-mechanic-hydraulic coupled mathematical system model was built,after that the transient response characteristic from input voltage actuation to output fuel injection was analyzed, also the key parameters were deduced. Results show that injection system's high speed response frequency can reach 1000Hz which meets the highest engine speed requirements of small displacement engine, and this new injection system work principle is correct in theory.
Vaporization and spray characteristics of vaporizer
RUAN Chang-long, XU Quan-hong, SUN Dong-wen, ZHANG Chi, LIN Yu-zhen
2012, 27(10): 2249-2253.
Abstract PDF(469KB) icon1950 icon546
Abstract:
Experimental study on vaporization characteristics of a certain type of engine's “Γ” type vaporizer was presented.The experiments were conducted under the atmospheric air pressure,using hot gas to heat the vaporizer,just like what the engine did.The main factors of the vaporization rates and Sauter mean diameter (SMD) including the air/fuel ratio(AFR),vaporizer inlet air temperature and the temperature of the wall of the vaporizer were studied.From the test results,it can be concluded that all of these three factors have great effects on the vaporization rates and the SMD.The increases of these factors would cause an increase in the vaporization ratio and a decrease in the SMD,and among these factors the wall temperature plays the most significant role.
Application of similitude theory in modified design of a fan
JI Guo-feng, WANG Hua-qing, GUI Xing-min, DENG Shao-chun
2012, 27(10): 2254-2261.
Abstract PDF(1816KB) icon2687 icon577
Abstract:
A modified design of a fan was described, on the basis of enough performance and flow field analysis of original fan, in order to satisfy the more thrust requirement of a turbo-fan engine. The modified design method was: the design tool was “a general blading design system and its application for axial/centrifugal compressor”. According to the similitude theory, at the precondition of the equivalence of converse mass flow and converse revolution speed at the second stage inlet, the increase of the mass flow was growing with the pressure ratio. By CFD computation and analysis, all the performances met the requirement and the design result was perfect. The results show that as the speed of the fan increases 1.1 percent, the mass flow increases 7.1 percent, the pressure ratio increases 7.4 percent, the efficiency increases 2.9 percent, and the stall marge increases 0.8 percent. Analysis and valuation of the performance and matching characteristic indicate that this design can satisfy the more thrust requirement of the turbo-fan engine.
Method of measuring 3-D unsteady flow at exits of transonic compressor rotor passages using a two-hole tip-wedge pressure probe
LI Jing-yang, MA Hong-wei, HE Xiang
2012, 27(10): 2262-2268.
Abstract PDF(703KB) icon1935 icon580
Abstract:
A method of measuring 3-D(three-dimensional) dynamic flow field with a two-hole fast-response tip-wedged cylindrical pressure probe has been developed and applied in a transonic multistage axial compressor.The measuring method was based on the four-hole pneumatic probe and realized by rotating the probe at three angular positions.The least square fitting method was used to process the calibration data and the optimal fitting order was determined through optimizing the fitting error.In this way,the approximate functions of the flow parameters with higher accuracy were obtained.The probe is characterized by small size,high frequency,wide measurement range and high measurement precision compared with other similar probes.The unsteady flow field at the exit of the rotor was measured utilizing phase locked technique.The measurement results reflect the flow features of the compressor rotor,providing distributions of flow yaw angle,pitch angle,total pressure and Mach number at the rotor exit,which is the key to optimize the stage performance.Therefore,it verifies the engineering application of this fast-response pressure probe measuring technique which can provide a feasible measurement method for the flow diagnoses in transonic multistage compressors.
Analysis of blade vibration response induced by rotating stall in axial compressor
ZHANG Ming-ming, HOU An-ping, LI Jian-xiong, YAO Juan, CHEN Ying-xiu
2012, 27(10): 2269-2277.
Abstract PDF(1280KB) icon1505 icon1369
Abstract:
An experimental and numerical study was conducted to investigate the forced response of blade vibration induced by rotating stall in a low speed axial compressor. Measurements have been made of the transient stalling process in a low speed axial compressor stage. The CFD study was performed using solution of 3-dimensional Navier-Stokes equations, coupled with structure finite element models for the blades to identify modal shapes and structural deformations simultaneously. Interactions between fluid and structure were managed in a coupled manner, based on the interface information exchange until convergence in each time step. Based on the rotating stall measurement data obtained from a low speed axial compressor, the blade aeroelastic response induced by the rotating stall flow field was analyzed to study the vibration characteristics and the correlation between the phenomena. With this approach,good agreement between the numerical results and the experimental data was observed. The flow phenomena were well captured, and the results indicate that the rotating field stall plays a significant role in the blade vibration and stress affected by the flow excitation.
Analysis of matching characteristic of transonic tandem stator airfoil and its optimization
TAO Yuan, YU Xian-jun, LIU Bao-jie
2012, 27(10): 2278-2286.
Abstract PDF(1744KB) icon1826 icon524
Abstract:
Matching characteristic of tandem airfoil was researched by using numerical simulation.The forward and aft blade working characteristics were analyzed,and then,an attempt to optimize the blades with the controlled diffusion airfoil was made,by doing which a higher cascade performance was achieved.The result indicates that:the working status of forward blade changes obviously with the incidence,and the incidence range of whole stage almost depends on forward blade alone;aft blade incidence depends on the working status of forward blade deviation.Flow diffusion and turning in aft blade is weakened because of forward blade trailing edge's piling up,thus the working status of aft blade is improved on condition that the forward blade has large flow separations.Based on the analysis of tandem airfoil working characteristics,routine blade was replaced with controlled diffusion airfoil and a good result was achieved.
Influences of several parameters on aerodynamic performance of micro-radial turbine
BIAN Lei, YAN Ze-Xiang, ZOU Zheng-ping
2012, 27(10): 2287-2296.
Abstract PDF(2119KB) icon1740 icon497
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Based on the characteristics of the millimeter-scale radial turbine,the correlations between turbine performance and the aerodynamic parameters were studied by combined theoretical analysis and empirical correlation.The laws and the scope of the influences of the key parameters on micro-radial turbine performance during the aerodynamic design process were discussed.These criterions were proved to be reasonable through the design procedure of a millimeter-scale turbine and the related 3-D numerical analysis.Contraposing the unsuitability of the adiabatic wall condition of millimeter-scale turbine,the effect of heat transfer on turbine performance was discussed.The guidance was given to micro turbine aerodynamic design through those results.
Numerical investigation of effect of radial vane diffuser fillet on performance of centrifugal compressor
TANG Hui, NING Fang-fei
2012, 27(10): 2297-2306.
Abstract PDF(1884KB) icon2315 icon634
Abstract:
The effect of the radial vane diffuser fillet on single-stage centrifugal compressor performance was studied.It was shown that when the radii of fillets were relatively small,the effect of the fillet can be negligible.Then further increasing the radius of the fillet,the mass flow at choke decreased and the performance of the compressor started to deteriorate.Upon these results,the investigation of optimizing the compressor aerodynamic performance by modifying the structure of the fillets was performed.Therefore,the fillet structure with no fillet or small fillets on suction side which can prevent blockage and radius-changing fillets on pressure side which can reduce or remove the separation zone on pressure surface was proposed.As a result,the performance of the compressor was improved obviously by using this structure.Besides,separated effects of fillets in casing and hub on single stage performance were discussed.It was revealed that the fillets near the hub played the major role in performance optimization.
Effect of axial spacing on aerodynamic excitation of rotor blade
XIAO Da-qi, ZHENG Yun, YANG Hui
2012, 27(10): 2307-2313.
Abstract PDF(2740KB) icon1844 icon563
Abstract:
Mechanism of aerodynamic excitation due to wake,potential and shock wave interaction was studied by numerical simulation of unsteady flows in a high pressure turbine stage.The excitation source was identified by analyzing a space-time map and distortion tracing technique.The excitation source was identified as the upstream blade-passing frequency by analysis of unsteady pressure on the blade surface.The unsteady excitation strength was quantified by normalized unsteady disturbances.Several configurations with different axial spacings were calculated.The results indicate that with small changes in axial spacing while maintaining same time-average aerodynamic characteristics,the aerodynamic excitation increases while reducing axial gap and the aerodynamic excitation may excite the blade vibration in a torsion mode.
Strength considerations for concept design of turbine blade
YANG Xiao-guang, HU Xiao-an, SHI Duo-qi, WANG Jing-ke, HUANG-Jia
2012, 27(10): 2314-2320.
Abstract PDF(455KB) icon1897 icon506
Abstract:
Based on the importance of overall parameters for the subsequent detailed design,the potential problems of the strength in the concept design phase was investigated,then the effects of design parameters,such as AN2,wheel speed,solidity of blade and performance of the materials,on strength and life were studied.The results show that the values of AN2 for the advanced turbofan aero-engine are within 25m2·(r/min)2 ,the wheel speed is related to disc shape factor which must be designed with 2,the solidity must be designed to satisfy the strength of the fir-tree,and stress at the root of the blade must be defined within 250MPa to avoid failure from LCF(low cycle fatigue) and creep.These results would be useful for the turbine blade design of advanced aircraft engines and gas turbines.
Dynamic response of aero-engine rotor system with bearing misalignment
ZHANG Zhen-bo, MA Yan-hong, LI Jun, HONG Jie
2012, 27(10): 2321-2328.
Abstract PDF(987KB) icon1710 icon559
Abstract:
Based on the analysis of structural and dynamic characteristics,a dynamic model of flexible rotor systems under misalignment and unbalance excitations in aero-engines was developed by Lagrange equations.It described the mechanism and effect factors of nonlinear properties of response in misaligned rotors.The numerical results show that the rotor system and its coupling may behave in a complex and nonlinear way with the excitation of misalignment and unbalance.The response of the system presents nonlinear properties,including 1 and 2 harmonics,and the amplitude and spectrum signature closely relate to the amount of misalignment and the distribution of unbalance.
Internal structure of three-dimensional hollow blade with equal strength
LI Lin, XUE Zheng
2012, 27(10): 2329-2335.
Abstract PDF(615KB) icon1826 icon513
Abstract:
A research on the internal structure of the blade with equal strength was pressented.The research was based on bi-directional evolutionary structural optimization (BESO) method and ANSYS platform.In the topology optimization process of the internal structure of the blade,a method of stress reference on middle face was proposed to simplify the optimization model.Some special technical problems in the application of BESO were also solved.Finally,an optimized topological form of internal structure of the fan blade with equal strength was obtained.The results can provide a reference for the lightweight design of the aero-engine.
Structure optimization method of radial inflow impeller based on design of experiment and support vector machine
MI Dong, YIN Ze-yong, QIAN Zheng-ming, ZHANG Zhi-yi, FENG Li-yong
2012, 27(10): 2336-2341.
Abstract PDF(617KB) icon1573 icon594
Abstract:
The investigation of two critical techniques was conducted to shorten the structure optimization time of a radial inflow impeller. Firstly, in order to reduce optimization scale, the technique of design of experiment (DOE) was used to choose the critical ones from a large number of disk structure dimensions as the optimization design variables. Secondly, in order to lessen analysis time, the technique of support vector machine (SVM) was used to establish surrogate model for stress and vibration analysis of the radial inflow impeller. Based on the investigation above, a structure optimization method of radial inflow impeller was presented, which was low time-consuming. It was demonstrated by one example that the life of optimized impeller increased almost four times and optimization time was one twenty-seventh of that of traditional optimization method.
Life prediction method based on characteristic of cyclic stress
WEI Da-sheng, WANG Yan-rong, WANG Xiang-ping, WANG Hong-bin
2012, 27(10): 2342-2347.
Abstract PDF(1262KB) icon2006 icon544
Abstract:
Based on the characteristics of cyclic stress of two nickel-based superalloys, i.e .,the cyclic softening followed by hardening of powder metallurgy (PM) FGH95 and the cyclic softening of cast GH4169,a stress-weaken damage model (SWDM) was established to evaluate the effect of load histories on lives.The model can be used to predict the fatigue lives under different cyclic loading conditions,of which prediction the accuracy is not less than that of traditional methods,and its most significant advantage is to greatly reduce the number of samples for life modeling.
Analysis of elastoplastic response in FGH97 notched specimens based on viscoplastic constitutive model
YUAN Shan-hu, WEI Da-sheng, WANG Yan-rong
2012, 27(10): 2348-2355.
Abstract PDF(2298KB) icon1897 icon492
Abstract:
In order to solve the difficulties in measuring local stress and strain,the parameters of Chaboche viscoplastic constitutive equations for powder metallurgy super alloy FGH97 at 550℃,which were obtained based on the experiments of material mechanical properties,were used in the elastoplastic FEM (finite element method) analysis of notched specimens subjected to tensile and cyclic loading.The results show that:(1) plastic stress/strain state at notch root is obviously different from elastic one.With the increase of stress,location of maximum stress moves inside.(2) Under cyclic loading,with the increase of cyclic number,the stress and strain range along symmetric path at notch root changes little.Mean stress relaxation occured in the plastic zone at notch root gradually turns to be stable,and it also leads to different cyclic stress ratios compared with the applied load.(3) The plastic zone at notch root gradually increases,but the increasing range gradually decreases.The research result can provide support to further analysis of influencing factors which affect fatigue life of FGH97 notched specimens.
Computation of effect of different nozzle parameters on internal performance of convergent-divergent axisymmetric nozzle
SHAO Wan-ren
2012, 27(10): 2356-2363.
Abstract PDF(852KB) icon1639 icon524
Abstract:
The numerical simulation on convergent flap length, nozzle throat arc radius,divergent flap length and nozzle expansion ratio affecting the internal performance of an axisymmetric convergent-divergent nozzle was conducted by applying a three-dimensional(3-D) viscous flow program that the results of the simulation were compared with that of the scale model experiments.The investigation shows that:convergent flap length and nozzle throat arc radius have some effects on the flow coefficient under the condition of a big convergent half angle,and convergent flap length can be properly reduced on condition that convergent half angle is less than 45 degrees;divergent flap length and nozzle expansion ratio have big effect on the thrust coefficient,and selected divergent flap length and nozzle expansion ratio shall work hard for fully expanded nozzle flow on condition that divergent half angle is less than 16 degrees.
Transient response of startup process for fluidic control vector nozzle
WANG Meng-jie, Eriqitai, WANG Qiang
2012, 27(10): 2364-2370.
Abstract PDF(1183KB) icon1930 icon531
Abstract:
Three-dimensional unsteady numerical investigations of startup process of fluidic control vector nozzle were performed. The objective of this study was to gain the fluid field evolvement characteristic and response time of performance parameter. By analyzing fluid field and pressure distribution on up-wall at different time, the evolution of jet interaction wave systems and vortex, which were located at near field of injection exit, was presented. The flow structures were in accordance with pressure distribution. Through time response curves, mass and thrust coefficient showed drastically fluctuations while vector angle one varied almost monotonically. The response time of them was of milliseconds magnitude.
Application of new boundary method in Cartesian-mesh
HAN Yu-qi, JIANG Li-jun, ZHANG Chang-xian, GAO Ge
2012, 27(10): 2371-2377.
Abstract PDF(1501KB) icon1961 icon644
Abstract:
Adaptively-refined Cartesian-mesh approaches were employed for the computation of Euler equations,solid wall boundary was introduced by a discrete forcing immersed boundary approach,and shape of cut cell kept in accordance with that in the flow field,which efficiently relieved the time step restriction of small cut cell.To remedy the numerical suction peak,a novel method for reflection of ghost point along with interpolation scheme were devised which were applied for adaptively-refined Cartesian-mesh.Inviscid flows around RAE2822 airfoil,double NACA0012 airfoil and Suddhoo three-element airfoil were simulated and compared with published theoretical and single/multi domain structured mesh results.The results show that solid wall is efficiently resolved by the current discrete forcing immersed boundary approach and flows around complex geometries are adequately simulated by adaptively-refined Cartesian-mesh approaches.
Aerodynamic characteristics of sonic injection through diamond-shaped orifices in supersonic flow field
ZHANG Ding-wu, WANG Qiang, HU Hai-yang
2012, 27(10): 2378-2383.
Abstract PDF(633KB) icon1809 icon511
Abstract:
Three-dimensional supersonic flow field with sonic injector was numerically investigated,the characteristics of diamond-shaped orifice which were compared with that of the circular injector were analyzed,and at last the effect of the diamond-shaped orifice on the flow field with different injection angles was explored.It is found that the plume from diamond-shaped orifice can weaken the strength of the bow shock and reduce total pressure loss,and the fuel penetration height of diamond-shaped orifice is higher than that of the circular injector,however,the diffusivity is almost the same in spanwise direction regardless of the structure type of injector.With the increase of the injection angle,the penetration height of the fuel firstly increases and then decreases;the model with 60 degree injection angle has the best characteristics.The change of total pressure loss is not obvious when the injection angle changes within a certain range,whereas an injection angle which is too large would lead to a rapid increase in the total pressure loss.This investigation provides insight into the characteristics of flow field with diamond-shaped orifice,which is crucial for optimization of injector.
Numerical simulation of infrared radiation characteristic of exhaust system using Tam-Ganesan turbulence model
LI Xi-xi, Eriqitai
2012, 27(10): 2384-2389.
Abstract PDF(917KB) icon1940 icon535
Abstract:
The infrared signature in 3~5μm band of an axisymmetric nozzle was calculated by a three-dimensional code to investigate the improvement of Tam-Ganesan turbulence model in the infrared radiation (IR) of aircraft exhaust system.The flow fields of nozzle were simulated by the finite volume method (FVM),coupled with the standard k-ε turbulence model and Tam-Ganesan model respectively.The infrared signature of the exhaust system was calculated by FVM in non-gray absorbing-emitting media coupled with narrow band model (NBM).The final infrared signature has considered the atmosphere effect.A standard k-ε model was also investigated by being compared with the Tam-Ganesan turbulence model.The Tam-Ganesan turbulence model provided improved mean flow and infrared radiation predictions related to the standard model.It is shown the application of the optimal turbulence model is vital to the calculation of infrared radiation characteristics of exhaust system.
Simulation of three-dimensional magnetohydrodynamic enhanced scramjet
ZHENG Xiao-mei, YANG Xing-yu
2012, 27(10): 2390-2400.
Abstract PDF(1140KB) icon2143 icon625
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Simulation model of the three-dimensional magnetohydrodynamic (MHD) enhanced scramjet viscous inner flow field was established. Geometry of a scramjet applied both MHD controlled inlet and MHD energy bypass was designed at Ma=6. Numerical simulation was performed, and three-dimensional flow field structure, distribution pattern of the electric parameters, and characteristics of energy transformation were analyzed. The results show when flight Ma=8, MHD controlled inlet can be used to draw the compressive shock waves back to the cowl lip, the separation zone disappears, and the flow field of the inner inlet recovers to the design condition. The MHD energy bypass can decrease Ma of the flow before combustor efficiently, so as to improve engine performance. In the MHD generator, distributions of flow and electric parameters are comparatively ideal to make efficient effect, while the MHD accelerator needs large amount of energy input to make a significant acceleration. In the MHD accelerator, Joule heating dissipation is severe near the electrodes, which results in local high temperature, flow field complication and performance deterioration of the MHD accelerator.

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