2009 Vol. 24, No. 9

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Effect of cut angles at trailing edge on the performance of a lobed mixer
LIU You-hong, GUO Nan, LI Jiang-ning, CAI Juan, XU Xing-ping
2009, 24(9): 1917-1922.
Abstract PDF(949KB) icon1767 icon486
Abstract:
The principle of effect of different cut angles at trailing edge of a practical lobed mixer on the thermal efficiency and the total-pressure recovery coefficient was studied by 3D-CFD(computational fluid dynamics)numerical simulation.The results show that,when the angles cut at trailing edge of the lobed mixer vary from 2.5° to 15°,the thermal efficiency augments and the total-pressure recovery coefficient decline as the angle increases,and when the cut angles vary from 15° to 60°,the thermal efficiency declines and the total-pressure recovery coefficient augments as the angle increases.
Numerical study of low emissions for twin annular premixing swirler combustor
YAN Ying-wen, LI Hong-hong, ZHAO Jian-xing, ZHANG Jing-zhou, LIU Yong, DANG Xin-xian
2009, 24(9): 1923-1929.
Abstract PDF(1960KB) icon2103 icon457
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The influences of different combustor configuration and spray mode on two phase spray combustion flows and combustion performances of twin annular premixing swirler(TAPS) combustors were studied by using Fluent software.Standard k-ε model was applied to simulate the turbulent viscosity.The fuel droplet trajectories were modeled in Lagrangian frame of reference by using discrete phase model(DPM).Non-premixed combustion model was used to model turbulence-chemistry interaction.The results reveal that exit averaged temperature can be improved and exit pollutant emissions decrease greatly with the change of combustor configuration and spray mode,and the combustion performance of TAPS combustor exceeds conventional model combustor.
Experimental research on ignition and lean blowout for micro gas turbine ethanol combustor
ZHANG Chi, WANG Jian-chen, QIN Qing-qin, DU Peng, YAO Xiang, LIN Yu-zhen, XU Quan-hong
2009, 24(9): 1930-1936.
Abstract PDF(815KB) icon1870 icon493
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An experimental investigation was conducted on the combustor of micro gas turbine burning ethanol as a renewable biomass fuel,including 4 kinds of fuel supply modes.The ignition and lean blowout performance characteristics of this combustor under atmospheric pressure and temperature inlet condition were obtained.The research results indicate that,at atmospheric pressure and temperature,the equivalence ratios of lean ignition and lean blowout for the ethanol combustor with swirl-cup decrease with the increasing airflow rate,and the swirl-cup combustor has better ignition and lean blowout performance than the premixed prevaporized combustor.
Comparative numerical simulation of combustion flows in a dual-fuel-combustor
MU Yong, ZHENG Hong-tao, LI Zhi-ming, YANG Jia-long
2009, 24(9): 1937-1944.
Abstract PDF(2194KB) icon1604 icon497
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Combustion flows with different fuels as heptane and pyrolysis gas in a dual-fuel-combustor of gas turbine were simulated by a CFD(computational fluid dynamics) method.The RNG(renormalization group) k-ε turbulence model,single chemistry reaction system,infinite-rate reaction velocity,discrete phase modeling for liquid fuel,upwind discretization scheme and the SIMPLE algorithm were applied.Some performances of combustor such as: combustion efficiency,temperature uniformity at outlet,temperature distribution of walls,distribution of air mass flow and the first air excess coefficient,were also analyzed.Some results show that: 1) the distribution of mass flow rate is consistent with different fuels,2) there is a 1% higher combustion efficiency and lower temperature uniformity at outlet with pyrolysis gas than that of oil fuel,3) the average temperature at outlet with pyrolysis gas is 20～40K lower than that of oil fuel with the same chemical enthalpy injected in the combustor,and 4) the first air excess coefficient α of pyrolysis gas is higher than that of oil fuel.
Analysis of uncertainties in two-parameter transient heat transfer measurements with liquid crystal
BAI Jiang-tao, ZHU Hui-ren, LIU Cun-liang
2009, 24(9): 1945-1951.
Abstract PDF(1168KB) icon1590 icon451
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This paper introduced a method of measuring heat transfer coefficient and dimensionless heat transfer temperature in transient film cooling measurements with liquid crystal,and through the uncertainties of heat transfer coefficient and dimensionless heat transfer temperature,analyzed the impact of dimensionless main flow temperature and dimensionless secondary flow temperature on two-parameters' uncertainties amplification parameters.The results indicate that,increasing the main flow temperature or increasing the difference between two measurements' secondary flow temperatures will decrease the uncertainties of heat transfer coefficient and dimensionless heat transfer temperature.
Experimental study on heat load of detonation tube
GONG Ji-shuang, FAN Yu-xin, WANG Jia-hua, LIU Hong, ZHANG Jing-zhou
2009, 24(9): 1952-1958.
Abstract PDF(1672KB) icon1617 icon444
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A pulse detonation engine(PDE) with diameter and length of 61mm and 1140mm respectively,was used to get the heat loads of detonation tubes which were designed into two types.The first one is that its heat transfer was controlled by natural convection and thermal radiation,and the other one was mainly influenced by forced convection.The same relations between heat load and working frequency were acquired in two conditions,namely,the heat load increased along with the increase of working frequency.However,with the doubling of the frequency from 20Hz to 40Hz(or from 25Hz to 50Hz) of the detonation tube,the heat load increased more than 100%.In addition,the vaporizing rate of kerosene was got at different frequencies,providing a reference for the design of PDE evaporator.
Experimental research on film cooling characteristics of cylindrical hole with transient liquid crystal measurement technique
LIU Cun-liang, ZHU Hui-ren, BAI Jiang-tao, XU Du-chun
2009, 24(9): 1959-1965.
Abstract PDF(1108KB) icon2134 icon520
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Film cooling characteristics of cylindrical hole were measured using a transient liquid crystal measurement technique which can process nonuniform initial temperature.The influence of momentum flux ratio was tested.The results show that jets of large momentum ratio lift off from the wall after ejecting out and the cooling effectiveness in the upstream is very low.However,the area covered by jet and the effectiveness increase streamwise because the jets reattach the wall after lifting off,and moreover the cooling effectiveness in the region between adjacent holes is higher than that in the downstream hole centerline region.The cooling effectiveness distribution of small momentum ratio is just opposite to that of large momentum ratio.The normalized heat transfer coefficient distributions are similar for all momentum ratios in the downstream region.Heat transfer in the region between jets is stronger than the heat transfer in the hole centerline region because of the couple vortices.In the upstream region,a large and strong vortex is induced by the lifting off jet.And,a local region with high normalized heat transfer coefficient is formed due to this vortex.
Investigation of heat transfer characteristics of aircraft icing under runback water
DU Yan-xia, GUI Ye-wei, XIAO Chun-hua, YI Xian
2009, 24(9): 1966-1971.
Abstract PDF(1844KB) icon1820 icon435
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The heat transfer characteristics of aircraft icing process were investigated based on the theories of liquid-solid phase change and film flowing.The heat transfer model which coupled runback water flowing with liquid-solid phase change was established and the influence of airflow parameters on the characteristics of icing growth was analyzed.The results indicate that the runback water on the icing surface will accelerate the liquid-solid phase change and speed up the icing process.The shear stress caused by the airflow is the key factor to the runback water flowing.The higher the airflow speed,the greater the shear stress and stronger the runback water flowing becomes,and vice versa.Under the condition of runback water flowing,the speed and temperature of the airflow are the main causes affecting the icing accretion.The higher the airflow speed or the lower the temperature,the greater the icing rate will be.The liquid water content and the collection efficiency have weak effect on the icing rate comparatively.
Experimental study of influence of inlet temperature on aviation kerosene coking characteristics
WANG Ying-jie, XU Guo-qiang, DENG Hong-wu, LUO Xiang, WANG Qin
2009, 24(9): 1972-1976.
Abstract PDF(961KB) icon1680 icon451
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Experiments were performed to study the influence of the inlet temperature on RP-3 coke deposition characteristics.The flowing RP-3 was stressed to 5MPa,and heated up to 427℃ in a stainless steel tube(inner diametr 1.8mm,outer diametr 2.2mm,1Cr18Ni9Ti) with constant heat flux.The inlet temperature was investigated at 80,100,127℃ and 150℃.The amount of surface coke deposition was measured by weighing method.And the results show that,as RP-3 inlet temperature increases,coke deposition peaks shifts upstream and grows up slightly;the total amounts of coke deposition increase firstly and then maintains at a certain value when inlet temperature reaches 127℃.
Experimental study of pollution emissions of a dry low-NOx combustor
LIU Kai, CAI Jiu-ju, ZHANG Bao-cheng, MA Hong-an
2009, 24(9): 1977-1980.
Abstract PDF(837KB) icon2216 icon509
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Experimental study of combustor of heavy-duty gas turbine(E) was conducted on high-pressure test system.The content of CO and UHC was very low,the combustion was stable and efficient,with the combustion efficiency over 99% and pollution emissions(NOx) up to 204mg/N·m3(15%O2) under rated condition.But,this couldn't meet the design requirements.The results indicate that: the radio of on-watch-fuel is large,which makes the content of NOx larger;uneven premixed fuel is another important reason that makes the content of NOx larger.The conclusion has provided a reliable basis for gas turbine's design and development.
Numerical studies about the discharge coefficient of film cooling hole at narrow space
HU Bo, MAO Jun-kui, LIU Zhen-xiong, HUANG Ju
2009, 24(9): 1981-1988.
Abstract PDF(1516KB) icon1882 icon444
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Numerical simulations about the discharge coefficient Cd of film cooling at narrow space were carried out in this paper,and the characteristics of the flow around film hole in small cooling channel were also investigated.Blowing rate M(0.5～2.0),film cooling hole Reynolds number Re(5000～10000) and the ration of film cooling height to the film cooling diameter H/D(0.33～1.0) were changed to study the average discharge coefficient of a row of film holes.A finite volume method together with SIMPLE algorithm,second order upwind discrete format,was used to solve the three dimensional incompressible Navier-Stokes equations.The Realizable k-ε turbulence model was applied and non-equilibrium wall function was used for near wall treatment.The results show that the discharge coefficient Cd increases with the blowing rate M,especially when the M＜1;under the same blowing rate conditions,the discharge coefficient decreases with the Re rising faintly.In the same Re cases,the Cd becomes smaller when the H/D decreases.And the numerical results indicate that the decrease of Cd is very notable especially when H/D＜0.75.
Research on application of micro channel in the blade cooling structure
MA Shi-yan, XU Guo-qiang, DENG Hong-wu, TAO Zhi, DING Shui-ting
2009, 24(9): 1989-1993.
Abstract PDF(1447KB) icon1407 icon456
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Numerical method was used to analyze the characteristics of heat transfer and flow resistance in micro channels in the middle of turbine blades;and the effect of aspect ratio and the rib aspect ratio in the micro channels was also studied.The result shows: in the case of the inlet Re=11000,if the rib aspect ratio is invariable,and the aspect ratio of micro channel increases,the integrated effect of heat transfer will increase firstly and then decrease;if the aspect ratio is invariable,and the rib aspect ratio increases,the integrated effect of heat transfer also will increase firstly and then decrease.
Creep research of Ni-based single crystal superalloy: experiment,mechanism and material model
YANG Xiao-guang, BAI Lu, SHI Duo-qi, YU Hui-chen
2009, 24(9): 1994-2000.
Abstract PDF(2489KB) icon1716 icon424
Abstract:
A new creep model of Ni-based single crystal superalloy was presented.Differential constitutive equations were based on transmission electron microscope(TEM) observation from creep experiment of single superalloy DD6 and mechanisms of single crystal superalloys generation 1 and 2.The non-linear equation was developed under the framework of crystal plasticity and derived from Orowan equation and evolution of dislocation density developed during the creep deformation process with effect of resolving stress level on slip system and temperature.Typical curve shape obtained by the present approach was calculated with a wide range of temperatures and loads in different orientations to demonstrate the validity of the proposed model.
Crystal-plasticity-based creep modelins for Ni-based single crystal superalloy
BAI Lu, YANG Xiao-guang, SHI Duo-qi, YU Hui-chen
2009, 24(9): 2001-2006.
Abstract PDF(1506KB) icon1824 icon437
Abstract:
The second part of modeling creep behavior for single crystal superalloy was presented in this paper.and a dislocation-based creep model was devoted to creep predictions.The constitutive equations described the relation between macroscopic strain rate and shear strain rate on slip systems derived from the slip theory,and the activity of various slip systems has been modeled based on the research of microscopic mechanisms.Results obtained by the present approach were compared with creep data with various temperatures and loads in different orientations,including single crystal superalloys DD3 and CMSX-4,to demonstrate the validity and applicability of the proposed model.
Influence of cell strut shape on the mechanical properties of Voronoi open-cell foams
LU Zi-xing, WANG Jian-yue
2009, 24(9): 2007-2011.
Abstract PDF(669KB) icon1507 icon457
Abstract:
The new equation was proposed to control the cell strut shape of three dimensional foams.Based on the Voronoi random foam models,the influences of cell strut shape on isotropic elastic properties,nonlinear compressive behavior and tensile behavior were investigated.In addition,effects of the interaction between the cell strut shape and the model irregularity were discussed on a comparative basis.The results show that the elastic modulus and the dimensionless stresses under compression and tension decrease evidently as struts turn into a concave shape.Effects of cell strut shape are larger than those of model irregularity,and become more significant as the models are more irregular.
Fatigue crack growth probability model based on stress ratio
WANG Kun-qian, XU Ren-ping, LIN Jie-hui
2009, 24(9): 2012-2018.
Abstract PDF(2036KB) icon1803 icon503
Abstract:
Based on Paris formula,a fatigue crack growth probability model was established in consideration of the influence of stress ratio on fatigue crack growth rate and the dispersion of fatigue crack growth.The parameters of this probability model were estimated by using the principle of no-linear function linearization.Through this probability model and surfaces,the regulations of the effect of stress ratio on fatigue crack growth can be mastered and the probability fatigue crack growth rate curves at any stress ratios can be obtained.Availability and feasibility are indicated by an analysis of the 30CrMnSiNi2A steel test data.
Numerical study of generalized method of cell with weak interfacial bonding
GAO Xi-guang, SUN Zhi-gang, LIAN Ying-qi, SONG Ying-dong, ZHU Ru-peng
2009, 24(9): 2019-2025.
Abstract PDF(1485KB) icon1617 icon449
Abstract:
In order to validate the ability of the generalized method of cell(GMC) with weak interface in modeling the interface debonding within continuum fiber reinforced composite,three kinds of week interface were considered in this paper to study the effect of the interface on global mechanics behavior of composite.The numerical results indicate that the method developed in this paper expands the GMC in analysis of composites with complicated behavior.
Research on multi-axial fatigue test loading spectrum formation based on damage equivalent principle
ZHAO Yong-ming, SONG Ying-dong
2009, 24(9): 2026-2032.
Abstract PDF(775KB) icon1820 icon475
Abstract:
A new method based on damage equivalent principle was developed for multi-axial fatigue test loading spectrum formation.It could be applied to uniaxial stress destroying mode with several dangerous positions under multi-axial loading.Firstly,the stain histories of the initial crack position were decomposed into a series of simple individual cycles by the rain-flow counting algorithm.And these cycles were divided into several groups by the stain amplitude,then all the combinations of multi-axial loading cycles were searched according to the damage equivalent principle,and several constant multi-axial loading cycles were found.After these constant cycles were linked,the fatigue test loading spectrum was presented,with the damage equivalent to the origin loading spectrum.According to the test of simple structure,the method can assure the equivalent damage of the test spectrum and the origin spectrum,and the operation is simple and feasible.
Crack analysis of the first stage blade on a gas turbine
ZHAO Ping, HE Qing-hua, LI Wei
2009, 24(9): 2033-2039.
Abstract PDF(2191KB) icon1735 icon510
Abstract:
To clarify the physical cause of premature blade cracking during the accelerated mission test(AMT) in a test cell environment,initial fracture graphic investigation and analysis of the cracked blades was carried out and an in-depth analysis of the blade was undertaken using ansis system XactLIFETM of Life Prediction Technologies inc(LPTi's XactLIFETMM) system.Results show that the blades have suffered excessive airfoil creep damage,leading to excessive blade lengthening and airfoil untwisting particularly in the trailing edge region.It's believed that this uneven rubbing action might have contributed to the fatigue crack nucleation and growth process just below the platform in the shank region of the blade under AMT fatigue cycling conditions.Excessive creep deformation is therefore believed to be the significant contributor to the overall crack nucleation process.
Probability characteristics for vibratory mode of detuned bladed disk assemblies
YU Chang-bo, WANG Jian-jun, LI Qi-han
2009, 24(9): 2040-2045.
Abstract PDF(940KB) icon1519 icon446
Abstract:
A modeling method was given to introduce detuning into finite element(FE) model based on a typical bladed disk assembly,in which random machining errors were considered as well.A modal localization factor was defined based on the blade strain energy,which assessed quantitatively the behavior of mode localization.ANSYS program and Monte Carlo simulations were performed with regard to the subjects of statistical characteristics of natural frequencies and mode shape.Results indicates that the detuning in blade design can increase the modal localization of bladed disk assemblies significantly,which requires consideration of the both aspects of vibration localization and aeroelastic stability for detuning design of bladed disk assemblies.
Dynamic model of elastic impact of helicopter rotor blades
WANG Yi-feng, WANG Hao-wen, GAO Zheng
2009, 24(9): 2046-2050.
Abstract PDF(1781KB) icon1800 icon462
Abstract:
A dynamic model was developed to investigate the elastic impact of helicopter rotor blades.General kinematical relations for a beam theory were established to treat the finite rotation.Hertz' theory of elasticity was presented to treat local elastic deformation.The compatibility equation of displacement was adopted to calculate the impact loads.Dynamic equations of elastic impact of rotor blades were derived by Hamilton principle.In comparison with Timoshenko's example,the validity of the results has been demonstrated.The impact response of helicopter blades under the impact of a lumped mass was also discussed.
Reliability-based multidisciplinary design optimization for turbine blade using double loop approach
NI Jun, YU Kua-hai, YUE Zhu-feng
2009, 24(9): 2051-2056.
Abstract PDF(2036KB) icon2025 icon465
Abstract:
A reliability-based multidisciplinary design optimization(RBMDO) framework for turbine blade was presented.Double loop approach was used to integrate the reliability analysis and the optimization method.Multidisciplinary feasible method was used to decouple the multidisciplinary analysis.Kriging model was employed to establish the approximation of the multidisciplinary analysis.The Hasofer-Lind Rackwitz-Fiessler(HL-RF) algorithm for reliability analysis was recommended systematically.Based on the approximation,the RBMDO framework was finished.The case study shows that,this framework could make the design reach the best performance with a good reliability.It indicates that the reliability-based multidisciplinary design optimization method is available and feasible for the engineering application.
Test-based syntonic analysis of the aero-engine inserted-board inlet dynamic distortion pressure
JIANG Yong, ZHANG Bai-ling, CHEN Shi-guo, CHEN Ge, MEI Fei
2009, 24(9): 2057-2062.
Abstract PDF(927KB) icon1740 icon424
Abstract:
Some observations from measuring the inserted-board airflow inlet distortion dynamic pressure field were presented in this paper.When the inserted-board rose above 35%,the inlet airflow disturbance occurred at about 32Hz.The pressure wave equation calculation shows that the Phase1 syntonic frequency is 34Hz.This syntony lies between the engine and inserted-board.Its frequency is steady at different rotor speeds and fluxes.The follow-on analysis indicates that the low frequency pulse pressure of component below 150Hz is powerful,steady and seasonal.The high frequency component is mainly stochastic pressure pulsation with minimum power.The changes of its rate and acceleration are great.When the engine is about to surge,the power of the syntonic frequency increases greatly while the power of other low frequency components and high frequency components decreases rapidly,so a typical syntonic pressure oscillation is formed.
Design of a two-dimensional mixed-compression supersonic inlet with boundary layer consideration
LUO Guang-qi, ZHENG Jiu-zhou, SONG Di-yuan
2009, 24(9): 2063-2068.
Abstract PDF(975KB) icon1749 icon478
Abstract:
Based on constant shock intensity method,a two-dimensional mixed-compression supersonic inlet was designed for flight at Mach number of 3.0.The correction was made for the effects of boundary layer.Quasi-one-dimensional analysis shows that the designed inlet has a good performance.By two-dimensional viscous simulation of inlet flows with terminal shocks,flow status of complicated flow field was presented in two-dimensional mixed-compression supersonic inlet.The reflections and intersections of various shock waves inside the inlet and the separation flows induced by shock wave/boundary layer interaction were displayed reasonably.Boundary layer bleed was considered to minimize separation and provide uniform flow at the engine-face station.Starting characteristic was obtained through numerical simulation under various outflow back pressure.Calculations with bleed indicate that boundary layer bleed can be used to stabilize the terminal shock location and prevent choking of the inlet,which is beneficial to resist outflow back pressure.The presented method is applicable to preliminary inlet design and numerical simulation.
Computational aeroelasticity with an unstructured grid method
ZHENG Yun
2009, 24(9): 2069-2077.
Abstract PDF(3161KB) icon2032 icon477
Abstract:
A computational aeroelasticity method based on unstructured grids was developed to study fluid/structure interaction problems.The aerodynamic model was used for solving the compressible Reynolds average Navier-Stokes equation on moving grids.A nodal-centered finite volume method with mixing unstructured grids was adopted to handle the complex fluid/structure problems.The structure vibration was modeled by a linear model.The structure deformation due to the aerodynamic loading was approximated by solving the structure dynamic equation and projected to the aerodynamic domain by grid deformation method.This method was validated by solving a harmonic pitching airfoil and used for numerically simulating the flutter boundary of the AGARD 445.6 wing.
Computational analysis on internal performance of a convergent-divergent nozzle with throat fluidic injection
ZOU Xin-hua, WANG Qiang
2009, 24(9): 2078-2084.
Abstract PDF(1453KB) icon1611 icon445
Abstract:
The results of a computational study were presented to investigate the impact of throat fluidic injection on the flow field in an axisymmetric nozzle.With the increase of secondary pressure ratio(SPR),both the nozzle thrust ratio and mass flow ratio were reduced under the same nozzle pressure ratio(NPR).In addition,the effect of throat fluidic injection on the nozzle thrust ratio was less than 2%,but the effect on the nozzle mass flow ratio more than 15%.With the impact of the divergence ratio and adjustment sheet of the nozzle on the throat control effect presented,a better nozzle model was obtained within the scope of the investigation.
Experimental investigation of pneumatic characteristics for S-shaped inlet in missiles
JING Jian-peng, GUO Rong-wei
2009, 24(9): 2085-2090.
Abstract PDF(2141KB) icon1685 icon401
Abstract:
Experimental investigation of an S-shaped inlet was made in this paper.The results show that: 1) When the yaw angle is constant and the attack angle changes from negative to positive,the total pressure recovery increases at first and then keeps almost constant,while the distortion coefficient drops at first and then rises a little.2) When the attack angle is constant and the yaw angle increases,the total pressure recovery and distortion coefficient increase at first and then decline.3) Under the combination of high incidence and yaw,the total pressure recovery is low and the distortion is high,but the performance will be better if the yaw angle increases farther.4) At the matching point of the inlet and engine,the power spectrum of the flow at the exit is like white noise and not sensitive to the variation of attitude angle and free stream Mach number.5) When the engine is running under small mass flow,the inlet model surge occurs,the frequency of surge is 150Hz.
Research on aero gas turbine performance in the condition of fault based on thrust work potential
HE Xing, SUN Feng-rui, ZHANG Ren-xing
2009, 24(9): 2091-2095.
Abstract PDF(314KB) icon1795 icon465
Abstract:
The mathematical model of the gas turbine performance in the condition of fault was established by using the thrust work potential transfer function,which is a figure of merit of the work potential based on the second law of thermodynamics.The performance matrix of fault model was derived by using the small deviation method.The thrust work potential transfer function was compared with the efficiency,which was the traditional function.The thrust work potential transfer function among the components was compared.The thrust work potential transfer function of the gas turbine system was analyzed.The results show that the thrust work potential transfer function can express the gas turbine performance wonderfully in the point of view of transferring the work potential contained in fuel into useful thrust work.This lays a foundation for the future study of the capability of the gas turbine under the conditions of all kinds of faults.
Computation and analysis of aeroheating of scramjet inlet cowl lip
PAN Sha, TIAN Zheng-yu, FENG Ding-hua, DING Guo-hao, LI Hua
2009, 24(9): 2096-2100.
Abstract PDF(1784KB) icon2066 icon436
Abstract:
Aeroheating of scramjet inlet cowl lip was investigated using numerical simulation method.Three cases were investigated depending on cowl lip position relative to forebody shock,and computational fluid dynamics(CFD) method was used to calculate blunt bow shock flow and simulate shock/shock interaction flow field.The results were validated with experiments in reference,showing that the inlet leading edge always bears more serious aerothermal challenge than forebody nose.Computation shows that it is shock/shock interaction and compressing supersonic flow post forebody shock that increase cowl lip heat transfer for hypersonic vehicle with airbreathing scramjet.This must be fully considered in the thermal protection and structure design.
Numerical simulation of conductive pipe's inner flow
HUANG Li-keng, GAO Zheng-hong
2009, 24(9): 2101-2106.
Abstract PDF(1597KB) icon1196 icon420
Abstract:
To implement the jet driving rotor which jets at the rotor-tip,the flows inside the conductive pipe were numerically simulated,and the effect of the flows inside the conductive pipe by outlet shape was analyzed.The influences of different inlet pressures and different outlet shapes were compared,the mass flow rate and outlet velocity of the conductive pipe were analyzed,and then the effect of the turning moment was gained through integrative analysis.Thus,the validity of the jet driving rotor was confirmed,and an applicable optimized design method was found out to minimize the total loss of the conductive pipe.
Numerical analysis on tip leakage flow of circumferential skewed blades according to flow rates
JIN Guang-yuan, OUYANG Hua, DU Zhao-hui
2009, 24(9): 2107-2114.
Abstract PDF(2020KB) icon1674 icon480
Abstract:
Tip leakage flow in lower pressure axial flow fans with circumferential forward-skewed,backward-skewed and radical blade,were investigated numerically at the off-designation conditions and validated experimentally.The circumferential skewed effects on origination and development of tip leakage vortex were discussed according to flow rates.The results show that as flow rates decrease,tip leakage vortex origination move towards the leading edge,and circumferential skewing strengthen the mixing between tip leakage vortex and main flow;tip leakage vortex of forward-skewed blade is located most far from leading edge,vortex strength is weakest,and movement is slowest.The circumferential forward blades stabilize tip leakage flow,decrease end-wall losses at off-designation conditions and improve stable operation rang.
Numerical simulation against unsteady flow from cavity leakage of turbomachinery stage
LEI Yun-tao, YUAN Xin
2009, 24(9): 2115-2121.
Abstract PDF(1330KB) icon1684 icon476
Abstract:
An unsteady numerical simulation was performed for the effect of the unsteady flow from the cavity leakage on the turbine stage.LU-SGS-GE(lower upper symmetric Gauss Seidel Gaussian elimination method)implicit scheme and high precision high resolution MUSCL TVD(monotone upstream-centred scheme for conservation laws,total-variation-diminishing) scheme were used to solve 3-D Navier-Stokes equations.The dual-time step implicit scheme was used for unsteady calculation.The results show that the patch of the cavity leakage through the rotor passage is moved close to the suction surface owing to the effect of the secondary flow.As the path is convected downstream,it migrates radially towards midspan.With the leakage flow entering into the rotor,there is more unsteadiness on the root of the rotor than that of the mid-span,and the unsteadiness becomes weak as the leakage flow migrates downstream.
Optimized design of a small type high speed centrifugal compressor
ZHOU Jian-hui, FAN Wei-jun, TIAN Xiao-pei, FANG Xiang-jun
2009, 24(9): 2122-2127.
Abstract PDF(1510KB) icon1406 icon425
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A small high speed centrifugal impellor had been modified by rearranging the blade thickness and meridian line type;then the improved impellor was simulated with Fine/Turbo software.The result shows that: the adiabatic efficiency of the improved impellor increases by 2.4% and it also has wilder surge margin.Besides,changing radial flow impellor to inclined flow impellor will comparatively decrease the separation of blades with sacrifice of the pressure ratio.
Composing and adding effect of rotor blade unsteady aerodynamic force
DU Hong-jun, LI Gang, HU Jun
2009, 24(9): 2128-2132.
Abstract PDF(1142KB) icon1597 icon469
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The rotor blade unsteady aerodynamic force in a single-stage low speed compressor with inlet guide vane(IGV) was simulated numerically in this paper.By analyzing the unsteady blade force located on leading edge and trailing edge of the rotor tip and hub,the adding effect of the upstream wakes and downstream potential effect was illustrated.The upstream wakes affect the whole blade chord range while the downstream potential effect influences only part of the trailing edge.By shifting the clocking position of IGV and stator blade,the amplitude of whole rotor pulsant pressure force can be reduced by 19.4%,while on leading edge of the rotor tip,it can only be reduced by 9.4%.
Monitoring of stage-pressurization characteristics for multistage axial flow compressors and its applications
LI Ying-hong, ZHANG Bai-ling, ZHANG Pu
2009, 24(9): 2133-2138.
Abstract PDF(465KB) icon1774 icon457
Abstract:
A method for monitoring of stage-pressurization characteristics of multistage axial flow compressors was developed to locate the specific compressor stages,where flow field was poorly matched at a given operating condition.The newly developed method was used to analyze rig-test data of a turbojet engine.The results show that,ill-matched compressor stages during engine speed transient could be located accurately.Then the method was successfully used to control on-off switching of the bleed valve of the test engine.It demonstrates that the method is promising in surge boundary detection,engine transient process control,and stage-level compressor flow control.
Design of microturbo engine integrated measurement and control system
SU San-mai, YANG Heng-hui, TU Qiu-ye, CAI Yuan-hu
2009, 24(9): 2139-2144.
Abstract PDF(940KB) icon1678 icon507
Abstract:
To meet the requirement of microturbo engine measurement and control,a set of integrated measurement and control system was designed.The system can implement engine ground test,control system's semi-physical simulation and electric fuel pump test.Signal processing outputs of all sensors were connected to measurement computer and engine Electronic control unit(ECU).ECU receives commands from measurement computer by RS232,and also samples p2 to complete speed control indirectly.Engine speed test and signal processing method,as well as electric fuel pump pulse width modulation(PWM) drive circuit were introduced in detail.Based on engine characteristics analysis,control law was designed.By adopting multithreading programming method,measurement computer software was developed in LabWindows/CVI platform.The application shows that the system test is more efficient and the design scheme is not only simple,but also practical.It can be applied to same kind of engine test and research.
Research on the sensitivity between the machine adjustment parameter errors and the spiral bevel gears surface errors
TANG Jin-yuan, CAO Kang, ZHOU Chao, LI Guo-shun
2009, 24(9): 2145-2151.
Abstract PDF(2145KB) icon1640 icon452
Abstract:
The effect law between the machine adjustment parameter errors and surface errors of the hypoid gears by SFT(spiral format tilt) was researched.Based on the gear meshing theory,the equations of theoretical tooth bearing and error tooth were established,the analytical expression of tooth surface processing errors caused by the machine adjustment parameter errors was derived,and the concept of error influence coefficient was proposed.The impact of surface errors caused by machine adjustment parameter errors can be obtained according to the error influence coefficient.By comparing the theoretical tooth bearing with error tooth,the effect law of the whole tooth surface law errors caused by the machine adjustment parameter errors was determined.The major impacts of the machine adjustment parameter errors were determined by the analytical and numerical method.The content and methods of this research provide a theoretical basis and practical guidance to compensate the machine adjustment errors for the spiral bevel gears surface errors.
Finite element analysis on preheating process of N2O monopropellant thruster
SUN Wei, FANG Jie, ZHANG Jia, LI Le, CAI Guo-biao
2009, 24(9): 2152-2156.
Abstract PDF(747KB) icon1728 icon478
Abstract:
Numerical simulation on preheating process of N2O monopropellant micro-thruster was conducted as per orthogonal experimental design theory in order to study the influence of four factors-preheating power,surface emissivity,thickness of the combustor chamber and the adiabatic stuff-on the preheating process.Results of the simulation indicate that influence of the preheating power is most remarkable among the selected four factors,which is followed by the surface emissivity.Influence of the remaining two factors is not apparent.Preliminary results of preheating experiment under ground circumstance have testified the validity of the simulation model,providing a basis for further structural and experimental design.

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