2013 Vol. 28, No. 7

  Previous Issue | Next Issue 
Display Method:
Application on numerical simulation of atomization of liquid jet in crossflow using two atomization models
LIU Jing, XU Xu
2013, 28(7): 1441-1448.
Abstract PDF(1532KB) icon1674 icon1219
Abstract:
The liquid jet atomization in crossflow was numerically simulated using TAB model and Reitz wave instability model, both of which were often used in atomization simulation. The influence of different experience parameters of these two models were analyzed for reference. Both of these two models could give correct penetration, but TAB model could also provide better liquid distribution, SMD and liquid droplets velocity than Reitz wave model; proper experience parameter values were presented. The other cases with different inject velocities were calculated using TAB model with the same experience parameter, and good results were also attained. This method can be used in later prediction calculation.
Effect of fueling scheme on scramjet combustion performance
DENG Wei-xin, LE Jia-ling, YANG Shun-hua, TIAN Ye, ZHANG Wan-zhou, XU Ming-heng
2013, 28(7): 1449-1457.
Abstract PDF(1851KB) icon1780 icon1101
Abstract:
Effect of fueling scheme on scramjet combustion performance was investigated based on pulse wind-tunnel direct connected experiment platform. Both pressure measurement and high speed videos were employed.The time evolution of flame with ethylene injected at different single injectors was demonstrated by high speed videos.Under the limits of producing effective thrust and avoiding inlet un-start,the first and second injectors' least and largest fuel equivalence ratios(ER) for combustion were obtained from injecting characteristics experiments.The coupling of the first and second injectors with others was studied.With these initiatory results gained above,different fueling schemes for best combustion performance were investigated under three indexes:isolator undisturbed length,combustor inner thrust and fuel specific impulse.The optimum values for these three indexes were 149.6mm,1622.3N and 1354.0s separately.
Characteristic scales and influential factors in supersonic combustion
LI Xiao-peng, ZHANG Tai-chang, QI Li, FAN Xue-jun
2013, 28(7): 1458-1466.
Abstract PDF(2132KB) icon2055 icon1083
Abstract:
Using the hydrogen,ethylene and kerosene (chemically surrogated by a mixture of n-decane 0.8 and 1,2,4-trimethylbenzene 0.2 by mass fraction) as fuels,the characteristic scales in supersonic combustion and the related influence factors were analyzed,and the operating range of scramjet under the typical flight conditions was calculated.At last,the applicability of flamelet model for the numerical simulation of supersonic combustion was explored.The results show that the operating range of scramjet for these fuels decreases successively and Damkohler number(Da) varies boardly in the order of magnitude,and flamelet in eddies regime is usually the main part,where Taylor micro-scale plays an important role.At the same time,it is found that the flamelet model needs to be considered carefully in numerical simulation of supersonic combustion compared with subsonic combustion.
Experiment on cylinder icing in injection driven icing wind tunnel
MENG Fan-xin, CHEN Wei-jian, LIANG Qing-sen, ZHANG Da-lin
2013, 28(7): 1467-1474.
Abstract PDF(1817KB) icon1757 icon1270
Abstract:
Small injection driven icing wind tunnel was designed and built for icing research.Icing atmospheric conditions were calibrated and the uniformity range of icing cloud was given.Tests were conducted to validate the repeatability of ice accretions.Ice shapes on 25.4mm and 50.8mm cylinders were measured experimentally under rime and glaze icing conditions in present icing wind tunnel.Results show that the thickness of rime ice and glaze ice is linearly increased with time under the test conditions and within the icing time range.Good ice shape similarity is achieved by applying scaling equations and the maximum deviation of dimensionless thickness is about 10%.
Design and numerical simulation of two-dimensional oxygen-hydrogen heater with multiply jet
TIAN Liang, CHEN Chao-qun, XU Xu, SONG Gang-lin, ZHANG Yan
2013, 28(7): 1475-1481.
Abstract PDF(1646KB) icon1540 icon1051
Abstract:
For generating uniform air flow at Laval nozzle outlet,the influences of the form,velocity ratio and pressure drop of the injection was studied.An air heater with two forms of injection and a Laval nozzle were designed,then FLUENT was used to simulate the combustion and flow filed.The result show that:there is little influence from the form of the injection,which mainly influences the temperature of the injector;the lower velocity rate and oxygen drop of the jet means the more uniform of nozzle outlet and approximative contraction ratio in two directions is better for the outlet.
Numerical simulation on infrared radiation characteristics of serpentine 2-D nozzle
LIU Chang-chun, JI Hong-hu, HUANG Wei, YANG Fang-fang
2013, 28(7): 1482-1488.
Abstract PDF(1703KB) icon2126 icon1191
Abstract:
A kind of unconventional serpentine two-dimensional(2-D) nozzle was designed to suppress the infrared radiation characteristics of an axisymmetric exhaust system.Based on the distribution of temperature,pressure and species mass fraction of the exhaust system obtained from CFD results,the infrared radiation characteristics of the axis nozzle and serpentine 2-D nozzle were calculated with reverse Monte-Carlo method,then analyzed and compared with the 2-D nozzle.The results show that,serpentine 2-D nozzle are capable of shielding the high temperature elements inside the exhaust system effectively,and the infrared radiation characteristics of the exhaust system is further suppressed much more,as the core passage flow and bypass flow mixing is enhanced by the help of its three-dimensional flow effect compared with the 2-D nozzle. Meanwhile,the infrared suppression goes better as the offset increases.Compared with the axis nozzle,the infrared radiation characteristics of the exhaust system reduces by more than 70% on average,while the thrust loss is less than 3%.
Numerical simulation of turbulent heat transfer using GAO-YONG turbulence model
WANG Yong, GAO Ge, LI Zhi-qiang, JIANG Li-jun, CUI Shu-xin
2013, 28(7): 1489-1494.
Abstract PDF(1216KB) icon1880 icon1146
Abstract:
GAO-YONG turbulence model was applied to calculation of turbulent heat transfer. Both plate turbulent shear flow and 2-D plane impinging jet flow were calculated. The calculation result of plate turbulent shear flow indicates that, GAO-YONG model can well describe flows from near-wall region to outer area without any special near-wall treatments (such as wall-function and low Reynolds number modification). This is different from widely used turbulence models. As for impinging slot jet, the results of Nusselt number are also consistent with the experimental data and reflect different characteristics under both impingement heights, validating the ability of GAO-YONG turbulence model to calculate complex turbulent heat transfer problems.
Numerical study on air throttling influence of ignition transient on the scramjet combustor
TIAN Ye, LE Jia-ling, YANG Shun-hua, ZHANG Wan-zhou, DENG Wei-xin
2013, 28(7): 1495-1502.
Abstract PDF(1833KB) icon1828 icon1209
Abstract:
A proper shock train generated by air throttling could facilitate ignition.The effects of air throttling on ignition transient were studied by solving unsteady Navier-Stokes equations, and the mechanism of air throttling for ignition was also analyzed during the ignition transient (0— 1.0ms ).Computational fluid dynamics results show that:under the inflow air conditions of Mach number 2.0,static temperature 548.8K,static pressure 101555.9Pa and the equivalence ratio 0.5,the pilot H2 is used for ignition,the location of air throttling is 845mm from the combustor entrance,and the flux of air throttling is 30% mass flux of inflow air. Ignition is achieved by air throttling, and flame goes out without air throttling at last.
Flow and heat transfer characteristics in latticework cooling structure with dimple vortex generators
ZHANG Xiang, RAO Yu
2013, 28(7): 1503-1509.
Abstract PDF(2188KB) icon1732 icon1121
Abstract:
The flow and heat transfer characteristics in the latticework cooling structure with U shaped sub-channels combined with dimple vortex generators were studied experimentally and numerically,the numerical computation model could reasonably predict the heat transfer and pressure loss in the latticework cooling channels.Based on the satisfactory validation of numerical computation,a comparative numerical investigation was made on the flow and heat transfer in the latticework cooling structures with three sub-channel configurations:U shaped sub-channels with dimples,U shaped sub-channels and rectangular sub-channels.The computational results show that,as compared to the case of rectangular sub-channel,U shaped sub-channels could improve the flow capability in the bottom of the sub-channels,helping to reduce the flow resistance while decreasing the heat transfer slightly.The Dimples arranged in the U sub-channels distinctively increased the turbulent mixing in the bottom flow,thereby significantly enhancing the convective heat transfer while increasing the flow resistance in the cooling channels.
Effect of clearance height on tip leakage reduced by spontaneous tip injection
HU Jian-jun, KONG Xiang-dong, XU Jin-liang
2013, 28(7): 1510-1516.
Abstract PDF(1508KB) icon1846 icon1143
Abstract:
The steady cascade flow field with different tip clearance height was obtained by numerically solving three-dimensional Reynolds-averaged N-S equations(RANS)and energy equations under the condition of single-hole spontaneous tip injection.The influences of clearance height on the interaction characteristics of the spontaneous injection with the tip leakage flow,the mass flow rate of leakage flow and the blade load were analyzed.The results show that the spontaneous jet has significant blocking effect on the leakage flow, the leakage ratio decreases by 0.06% with 1mm(t/H=0.5%) tip clearance,and meanwhile the blade load increases by 1.39%.The blocking effect decays with the increasing clearance height and can be ignored when the clearance height rises to 4 mm (t/H=2%);decreasing clearance height can effectively improve the controlling effect of spontaneous jet on leakage flow and reduce the flow losses caused by flow separation;the presence of spontaneous tip injection significantly changes the flow field of tip gap and the distribution of static pressure coefficient near the suction.The calculation results show that a vortex similar to the Karman vortex street appears downstream the jet flow when the leakage flow moves around the spontaneous jet.
Experiential method for realizing correlation of experimental characteristics of axial flow compressors
XIANG Hong-hui, HOU Min-jie, LIU Zhi-gang
2013, 28(7): 1517-1525.
Abstract PDF(2056KB) icon1488 icon991
Abstract:
Steady state performance experimental data of more than ten axial flow compressors were arranged and analyzed based on systematic idea. The inherent correlative law of the discrete experimental data in existing aerodynamic and structural design systems was explored statistically. Based on selection of the correlation reference point, estimation of the stability boundary, generalized fitting of the characteristics, solution of the correlation reference point and other aspects, an experiential analysis method for correlating the experimental characteristics of multistage axial flow compressors were built successfully. The results show that the experiential method has good prediction ability for large flow low-speed compressor off-design characteristics, with its general relative error less than ±10%. This analysis method can be applied to experiential reconstruction and advanced evaluation of the off-design characteristics of same type newly designed compressor, providing a technical support for discrete experimental data mining of axial flow compressors.
Two 3-D multi-cascade co-design inverse methods based on streamline curvature approach and Clebsch formulation for single-stage centrifugal compressors
TIAN Xiao-pei, SHAN Peng
2013, 28(7): 1526-1538.
Abstract PDF(2927KB) icon2918 icon987
Abstract:
Two strategies extended the single-cascade methods from a compressible three-dimensional inverse method for radial and mixed flow turbomachines to two three-dimensional multi-cascade co-design methods for single-stage centrifugal compressors.These two three-dimensional methods and a typical quasi-three-dimensional streamline curvature through-flow inverse method were employed to design the same subsonic high-speed single-stage centrifugal compressors.The compressor performances were simulated by a commercial Reynolds averaged Navier-Stokes (RANS) equations solver.The studies show that two three-dimensional co-design methods are reasonable and feasible.It was found that:firstly the blade camber angle designed by the three-dimensional methods was larger than that designed by the quasi-three-dimensional method;and secondly with regard to two three-dimensional methods with different boundary conditions,the co-design result differences between the diffusers were small,but those between the deswirlers were relatively large.
Numerical simulation of aerodynamic performance of scaled fan of a civil high-bypass-ratio turbofan engine
ZHU Fang, CHEN Yun-yong, WEI Fei-fei, JIN Dong-hai, WANG Yan-rong, GUI Xing-min
2013, 28(7): 1539-1548.
Abstract PDF(2018KB) icon2025 icon1199
Abstract:
According to the testing demand for the half-scaled fan of a civil high-bypass-ratio turbofan engine,the aerodynamic performance of scaled fan was simulated using three-dimensional CFD software.The effects of geometry scale,elastic recovery angle and bypass-ratio on the performance of the fan were also analyzed.The numerical simulation results show that the design objectives for the scaled fan can be met basically under all kinds of corrected rotating speed.When the geometry of the fan was scaled down to the half,the adiabatic efficiency of the bypass and core passages decrease by 1.26% and 0.77%,respectively.Under 80% corrected rotating speed,0.36 degree reduction of the elastic recovery angle at fan tip could expand the stall margin by 4.04%,while the total pressure ratio and the adiabatic efficiency decreased at near design point.The total pressure ratio-mass flow characteristic and adiabatic efficiency-mass flow characteristic of the bypass and core passages for turbojet engine were represented a band of curves within a certain scope,under the bypass-ratio effect.
Numerical calculation model of axial compressor stability enhancement bywith discrete tip injection
SHI Pei-jie, QIAO Wei-yang, WEI Zuo-jun, XU Kun-bo
2013, 28(7): 1549-1556.
Abstract PDF(1528KB) icon1589 icon1015
Abstract:
A numerical calculation model for axial compressor stability enhancement by tip injection was developed.The model solved Navier-Stokes equation with source terms for annulus duct without blades.The effect of blades,including the force and energy applied to the flow by the blades,was modeled by the source terms.The current source terms of every iteration step varied according to the inlet parameters.Variation of manual disturbance was introduced to the model to predict the compressor's stall margin.The performance and stall margin of a transonic single stage compressor were calculated by the model with/without tip jet.The performance and stall margin predicted by the model without tip jet agree well with the experiment result,and the difference between the massflow of the stall margin predicted by the model and that got by the experiment is less than 0.7%.The effect of stability enhancement by tip injection is obvious from the results of the model compared with the results in open literature,helping to verify the model.
Post stall transient model for axial compressor with closed-coupled valve under non-constant speed condition
HUANG Wei, HUANG Xiang-hua
2013, 28(7): 1557-1563.
Abstract PDF(1164KB) icon1738 icon998
Abstract:
To provide a verification platform for various active surge controllers,a new rotating stall and surge model for axial compressor was proposed.Based on Moore-Greitzer post stall transient model,influences of spool dynamics and higher harmonics of rotating stall waves were considered in the proposed new model.In addition,a closed-coupled valve was included in the model as an actuator.Several conclusions can be made from simulation results.Firstly,with the increasing of rotor speed,the instability behavior of compressor transforms from rotating stall to surge.Secondly,as an internal disturbance,the spool dynamic may lead to instability even under large throttle opening conditions.Finally,even the initial disturbance only includes the first harmonics,the higher harmonics may become strong and have a significant effect on the behavior of rotating stall.
One-dimensional characteristic optimization design for ten-stage high pressure compressor in commercial engine
SHI Lei, LIU Bo, ZHANG Peng, LI Jun, WANG Lei
2013, 28(7): 1564-1569.
Abstract PDF(1299KB) icon1801 icon1243
Abstract:
HARIKA algorithm was applied to simulate the characteristic of a ten-stage high pressure compressor. With introduction of genetic algorithm (GA), one-dimensional design parameters were selected as optimum variables, and functions containing peak efficiency and margin were used as optimization objectives. Compared with initial characteristic, peak efficiency of characteristic after optimization at designed speed increased by 12.3%, and its margin increased from 11.7% to 25.13%. Then HARIKA algorithm was used to simulate variable geometry compressor characteristics. Setting angles of inlet guide vane and first three stage stators after optimization at different engine corrected speeds were presented. The performance characteristics of compressor including peak efficiency, peak pressure and flow margin were improved to great extent. Calculation results of compressor characteristics in one-dimensional and three-dimensional were compared at engine corrected speed of 1.0, 0.9. The maximum deviation of their margin was not more than 6.25%.
Aerodynamic layout of spanwise truncated curved waverider compression inlet
WU Ying-chuan, HE Yuan-yuan, YU An-yuan, LE Jia-ling
2013, 28(7): 1570-1575.
Abstract PDF(1210KB) icon2009 icon1424
Abstract:
A new osculating curved cone (OCC)method for streamlining tracing axisymmetric flow fields of isentropic compressing waves was used to design the waverider lower surface and inlet lip inner surface.The waverider surface was spanwisely truncated according to the constraint of the vehicle's and engine's width.The numerical and experimental analyses show that OCC waverider inlet has some advantages compared with the same compression ratio four-stage ramp inlet. At Mach number is 4.5,the new inlet's capture mass flow rate increases by 12% and total pressure recovery coefficient increases by 39%.At Mach number is 6,the new inlet's capture mass flow rate increases by 4% and total pressure recovery coefficient increase by 50%.The supersonic combustion ramjet engine's performance is efficiently increased too.
Flow characteristic experiment on vector-enhanced dual-throat thrust-vectoring nozzle
ZHOU Hui-hua, TAN Hui-jun, ZHOU Hui-chen, CAI Jian-gang
2013, 28(7): 1576-1581.
Abstract PDF(1450KB) icon1652 icon992
Abstract:
Model tests of a vector-enhanced dual-throat thrust-vectoring nozzle were performed to obtain the internal flow characteristics,including the internal flow pattern and the static pressure distributions at different secondary flow pressure ratios.The test results indicate that after adding divergent part to the tail of traditional dual-throat vector-nozzle,the jet flow is deflected upwards beyond 20 degrees at a secondary flow ratio of 2.8%.Therefore the design concept of the vector-enhanced nozzle is feasible.In the concave cavity of the nozzle,the static pressure distribution of the vector-enhanced nozzle is basically the same as that of a traditional dual-throat nozzle.At the additional divergent part,the surface pressure of the bottom wall is obviously higher than that of the top wall,accounting for the vector angle augment.In addition,the vector angle increases monotonously with the pressure ratio of the secondary flow,but the vector enhancing effect of the divergent part remains basically unchanged.
Effect of transition on optimization of stratospheric airship hulls
ZHANG Hai-jun, GUO Xue-yan, DAI Ren
2013, 28(7): 1582-1590.
Abstract PDF(2703KB) icon1624 icon1002
Abstract:
Shape optimization of a stractospheric airship was conducted with a gradient algorithm to reduce the aerodynamic drag. The total drag coefficient as the objective function was evaluated by solving the Navier-Stokes equations. The shear stress transport(SST)κ-ω turbulent model with transition criterion and the Realizable κ-ε full turbulent model were applied when solving the flow field in the optimization steps. The aerodynamic performance of the flow structure around these two optimized airships was thoroughly analyzed based on the flow field obtained through large-eddy simulation. The influences of the transition model and the full turbulent model on the optimized objective function and the hull shape itself were compared. It is found that aerodynamic performance of the optimized hull taking laminar-turbulent transition into account is obviously better than the other. The existence of the laminar region enables to change the shape of rear part of the hull and determine a better shape with smaller separation zone.
Analysis of aeroheating-temperature field coupling characteristics for thermal protection panel of quasi-wavrider
CHENG Xing-hua, YANG Tao, FENG Zhi-wei
2013, 28(7): 1591-1597.
Abstract PDF(1483KB) icon1624 icon1140
Abstract:
For thermal protection panel of quasi-waverider, the loose coupling algorithm was applied to drive the iteration of the aeroheating and heat transfer analysis. Then, the coupling characteristics of aeroheating-temperature field were studied. The results show that, before radiative equilibrium, the errors of cold wall and radiative equilibrium aeroheating are +55.1% and -15.4% over actual aeroheating respectively, so coupling analysis for aeroheating-temperature field was required. As the local adiabatic wall temperature is not changed with time, the surface heat-transfer coefficient is a key parameter for coupling effect. Only two aeroheating calculations are needed during calculation of coupling aeroheating-temperature field with average heat convection coefficient, and the error of predicted wall temperature is less than 2.5%, thus highly improving the analysis efficiency of coupled aeroheating-temperature field.
Assessment parameters and calculation methods of structural efficiency on rotor system in aero engine
MA Yan-hong, CHEN Lu-lu, ZHANG Da-yi, HONG Jie
2013, 28(7): 1598-1606.
Abstract PDF(1119KB) icon1732 icon1089
Abstract:
Based on the structural features and mechanical characteristics of aero engine rotor system,a calculation method and assessment parameters of structural efficiency were proposed.The method includes the bearing capacity,resistance to deformation and dynamic environment adaptability.A structural efficiency assessment on the rotor system of a typical turbofan engine was conducted.The study shows the assessment parameters include the average stress coefficient,the ratio of equivalent stiffness,maximum deformation at ultimate inertia loads,dimensionless M-H factor and the bending strain energy coefficient.Which can reflect the effect of structural style and material property to the stress level,deformation distribution and the power sensitivity under various loads effectively.The features of the structure of the engine rotor system were presented and further optimization was concluded.
Vibration characteristics of accessory gearbox structure system of engine
GUO Mei, CHEN Cong-hui, WANG Jian-jun, LIANG Zuo-bin, LI Jin-hua
2013, 28(7): 1607-1612.
Abstract PDF(1456KB) icon1876 icon1257
Abstract:
Based on finite element method(FEM) and software of Masta, the vibration response characteristics of accessory gearbox under the inner meshing excitation were calculated and analyzed. Firstly the static meshing error (displacement) excitations of gear pairs in each stage were obtained. Then the vibration response of case shell of accessory gearbox under the inner meshing excitation was researched. Finally the basic vibration characteristics of the accessory gearbox under the inner meshing excitation were discussed. The maximum vibration amplitudes obtained at key positions of the case shell are 80g lower than the limited value of 150g. The results indicate that the method and technique presented can be used effectively to predict and evalute the vibration characteristics of the accessory gearbox in design process.
Experiment on DZ125 notch fatigue behavior at high temperature
HU Xiao-an, WANG Jing-ke, YANG Xiao-guang, SHI Duo-qi, HUANG Jia
2013, 28(7): 1613-1617.
Abstract PDF(1162KB) icon1588 icon1044
Abstract:
Notched fatigue behavior of directional solidified superalloy DZ125 at 850℃ was investigated.Different U type notched specimens with three stress concentration factors including 1.91,3.01,and 4.35 were tested.Crack initiation and propagation were observed in situ.The fatigue life and crack initiation and propagation were analyzed.The results indicate that stress concentration factor is an important parameter infect the life to fatigne failures,while converse results obtained at low stress range.With the increase of norminal stress,the notch fatigue life became more sensitive to stress concentration factor.Through in situ observation,it's found that the locations of the crack initiation and propagation were not at the root of the notch,but at the location with maximum principal stress.
Investigation on stiffness of circumferential distributed tie-rod rotor with curvic couplings of trochal disk
LI Pu, YUAN Qi, GAO Jin, TAN Lu-yi, LI Yi-feng, LIU Hua-feng
2013, 28(7): 1618-1623.
Abstract PDF(1232KB) icon2792 icon1974
Abstract:
Based on the circumferential distributed tie-rod rotor model with curvic couplings, the stiffness of every part of the rotor was acquired with analytical method. Three-dimensional finite element nonlinear contact method was adopted to analyse the flexural stiffness and torsional stiffness of the curvic couplings after preloading by using the commercial finite element software ANSYS. The stiffness correction coefficient and stiffness nondimensional coefficient were obtained. Coefficient of tie-rod stiffness ratio was adopted to describe the relation between the stiffness of tie-rods and disks. Results show that stiffness correction coefficient keeps steady when the stiffness nondimensional coefficient is less than 1, while it drops abruptly and the coefficient of tie-rod bend stiffness ratio increases when stiffness nondimensional coefficient exceeds 1. This means the preload is not enough and slip between curvic couplings happens. Stiffness nondimensional coefficient reflects some certain stress status of the curvic couplings, providing a basic guide for design and fault diagnosis of gas turbine rotor with curvic couplings.
Multibody contact dynamics research on ball bearing
YAO Ting-qiang, WANG Li-hua, ChI Yi-lin, HUANG Ya-yu
2013, 28(7): 1624-1636.
Abstract PDF(3943KB) icon1446 icon1351
Abstract:
Considering the dynamic contact relationship between balls,rings and cage,a new method was brought out for multibody dynamics analysis of ball bearings in mechanical systems.The searching algorithm for prediction of dynamic contact force was carried out based on the triangle mesh models of ring races.The three dimensional multibody contact dynamics model of angular contact ball bearing was constructed with lubrication and Hertz contact and calculated by generalized-α algorithms under axial preload and rotated radial load.The results of dynamic contact force,trajectory of motion,phase diagram and frequencies were achieved and verified by the Gupta classical model.The angular acceleration and ratio of revolution to rolling of a ball were periodic varying with amplitude 184.5 rad/s-2 and 0.01 respectively under light load and middle speed.The harmonic frequencies of angular acceleration and dynamic contact force were similar such as 56.1Hz and 112.2Hz.The vibration of cage center was quasi-periodic with two frequencies 83.3Hz and 200Hz under middle load and high speed.
Optimal design of modified helical gear tooth surfaces based on minimum amplitude of loaded transmission error
JIANG Jin-ke, FANG Zong-de, SU Jin-zhan
2013, 28(7): 1637-1643.
Abstract PDF(1573KB) icon1954 icon1168
Abstract:
An approach based on the minimum amplitude of loaded transmission error of drive gears was proposed to reduce vibration and noise.The modified tooth surfaces were represented by a sum of two vector functions that determine the theoretical tooth surface and deviation surface fitted by triple B splines based on tooth surface mesh data from the curves created by double parabolas and a straight line,including: profiled,longitudinal and both profiled and longitudinal curves;and normal vector of the deviation surface was deduced.Besides,LTCA was applied to the modification technology,and genetic algorithm was used to optimize the parameter of curve,and draw up a set of calculation procedures simulating TCA and LTCA of the modified helical gears.The results show that the loaded transmission error represents a linear increase in amplitude with the increasing load on theoretical tooth gears,however,its amplitude come into fluctuations and finally tends to be stable due to increasing contact ratio with the increasing load on modified gears,thus providing a new method for optimal design of modified helical gear tooth surfaces.
Effect of axial piecewise parabolic modification on fretting wear parameters of involute spline couplings
HU Zheng-gen, ZHU Ru-peng, JIN Guang-hu, NI De
2013, 28(7): 1644-1649.
Abstract PDF(1446KB) icon1954 icon1130
Abstract:
A piecewise parabolic function of involute spline couplings axial modification was presented,and the modified geometric model of involute spline couplings was built.Based on the finite element method,the fretting frictional contact property of typical involute spline couplings was analyzed,and the contact stress and relative slip distributions of modified and unmodified involute spline couplings were obtained,as well as the effects of modified position and modified quantity on contact characteristics of modified involute spline couplings were considered.The following conclusions can be drawn from the analysis results.The piecewise parabolic function meets the axial modification requirement of involute spline couplings,and the modification curve is smooth.Axial modification can effectively reduce phenomena of concentrated contact stress and relative slip for involute spline.Modified positions should be the ends and latter half of external spline in the typical model.Modification quantity of the ends should be a reasonable choice for the model,and modification quantity of the back is generally larger than that of the front.
Semi-physical simulation on integrated helicopter/engine control system
ZHANG Hai-bo, YE Fei, LI Yong-jin, CHEN Guo-qiang
2013, 28(7): 1650-1658.
Abstract PDF(1865KB) icon1570 icon1553
Abstract:
Based on the simulation platform of integrated helicopter/engine system control,semi-physical simulations were carried out for integrated helicopter/engine model and integrated control algorithm.The core part of anti-disturbance control of the integrated system adopted a novel algorithm of cascade proportional integration differential(PID)+torque feed forward+collective compensation,and the optimization control was multi-mode real-time optimization based on the simplified engine adaptive system model.The simulation tests show that the established integrated helicopter/engine model can simulate the engine's total process from start to idling,then to helicopter flying,and the droop and overshoot of the power turbine is within 4% in the whole process.The engine's dynamic and static quality meets the requirements of helicopter flight control in different flight conditions.The semi-physical simulation results of the integrated system multi-mode optimization were validated.The established semi-physical simulation platform of integrated helicopter/engine control system is valuable for engineering applications.
Node adaptive refinement for trajectory optimization based on second-generation wavelets
FENG Zhi-wei, ZHANG Qing-bin, TANG Qian-gang, ZHANG Yong-he
2013, 28(7): 1659-1665.
Abstract PDF(1335KB) icon1541 icon978
Abstract:
A mesh adaptive refinement method for solving trajectory optimization problem by using direct method based on second-generation wavelets was proposed to deal with the conflict between accuracy and efficiency. The original trajectory optimization problem was transformed into a nonlinear programming problem that was solved by standard nonlinear programming codes. Then the wavelet transformation of control or state function was performed, and the wavelet coefficients were obtained. A new node could be determined based on the magnitude of coefficients and the relationship between wavelet coefficients and dyadic nodes. The results demonstrate that the proposed method can balance accuracy of the solution and speed of computations by setting appropriate threshold of wavelet coefficients. Compared with the Gauss pseudospectral method software package, the number of nodes are reduced by 10% approximately, and the optimality accuracy is increased by an order of magnitude by using the method.
Systematic model for operating boundary analysis of aero-engine life limited parts
DING Shui-ting, QIU Tian
2013, 28(7): 1666-1674.
Abstract PDF(1575KB) icon1614 icon1035
Abstract:
In order to meet the urgent needs for enhancing system safety level of aero-engine,the required attributes and technology foundations of systematic model for engine life limited parts operating boundary analysis (SMELLIPOBA) was analyzed.The development of relevant technology foundations in recent years was discussed based on substantive aero-engines characteristics and some exploratory research results.The development situation of SMELLIPOBA was introduced.The research directions in the future of this field were predicted.The conclusion can be drawn is that:SMELLIPOBA which meets the airworthiness requirements should includethe following five characteristics namely:coupling, dynamicity, uncertainty,multidiscipline and multiscale,and development of SMELLIPOBA in future will mainly depends on the development in these characteristics as well.
Direct-connect experiment and numerical simulation on dual-combustor ramjet
TAN Jian-guo, WU Ji-ping, WANG Zhen-guo
2013, 28(7): 1675-1680.
Abstract PDF(1250KB) icon1784 icon998
Abstract:
The flow field structure and performance of dual-combustor ramjet (DCR) were investigated through direct-connected experiment and numerical simulations.Semi-global kinetic mechanism was adopted in the simulations.The simulated pressure distributions agreed with the experimental data.Results show that:rapid reaction occurs in the mixing-layer between central high-temperature fuel-rich gas and peripheral air,the thermal choked throat appears at the position of 0.9m,and the combustion efficiency reaches a relatively high level.A method of assessing performance according to experiment and numerical simulation was brought forward.Results show that:the performance of the DCR presented is good under the condition of Mach number is 4.0,altitude is 17km.When the equivalence ratio is 0.9,the internal thrust is 8.3kN and specific impulse is 12.29kN ·s/kg.However,increasing equivalence ratio leads to unstart of inlet.

Copyright © 《Journal of Aerospace Power》 All Rights Reserved.

Supported by: Beijing Renhe Information Technology Co., Ltd.