2014 Vol. 29, No. 5

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Research progress on pulse detonation turbine engine
ZHENG Long-xi, LU Jie, YAN Chuan-jun, QIU Hua, WANG Zhi-wu, HUANG Xi-qiao, LI Xiao-feng
2014, (5): 993-1000.
Abstract PDF(966KB) icon2477 icon1283
Abstract:
Basic concept,main structures and primary characteristics were reviewed of pulse detonation turbine engine.A detail trend at home and abroad of its development was presented;the results of our recent experimental researches were summarized;the key technology and research areas of pulse detonation turbine engine were discussed.Performance calculations show that the specific fuel consumption of pulse detonation turbine engine could have a reduction about 5% to 15% compared with that of traditional turbine jet engine. The specific power of the turbine driven by pulse detonation combustor is higher than that driven by constant pressure combustor under the same inlet conditions of the combustors.A self-aspirated model was successfully achieved by driving the turbine with pulse detonation combustor whose oxidant was supplied by the turbine driven compressor.The results verify the feasibility of substituting the traditional constant pressure combustor with pulse detonation combustor.
Capability prediction of high temperature rise center-staged combustor
SHANG Shou-tang, GAO Xian-zhi, GUO Rui-qing, GUO Da-peng, GAO Wei-wei, LI Feng
2014, (5): 1001-1007.
Abstract PDF(939KB) icon1603 icon1276
Abstract:
Based on the increasing demand for high temperature rise combustor of high thrust-mass-ratio aeroengine, a design method of center-staged combustor was given and three-dimensional numerical simulation was conducted on the design model using the same diffuser, outer case and exit dimensions of single annular combustor. The capability of center-staged combustor was compared and analyzed with the numerical simulation results and experimental results obtained from single annular combustor. The results show that, by using the center-staged combustor, the total pressure recovery coefficient can be improved compared with the single annular combustor, and the outlet temperature distribution factor (OTDF) of the combustor is lower than that of single annular combustor in addition to higher temperature rise, but the CO and NO emissions are higher than that of single annular combustor in slow train state. At the designed 0.045 fuel/air ratio state, the temperature rise can reach 1360K, and the total pressure recovery coefficient is no less than 0.96; OTDF can be no more than 0.14; the radial temperature distribution factor (RTDF) at outlet can be no more than 0.10, with the combustion efficiency no less than 0.987.
Experiments of flow and heat transfer performances for air-cooling laminated turbine vane
WU Xiang-yu, TAO Zhi, DU Zhi-neng, ZHANG Shu-lin, YOU Hong-de
2014, (5): 1008-1013.
Abstract PDF(951KB) icon1473 icon986
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Flow resistance and heat transfer coefficients of typical double wall laminated film cooling configuration within a turbine vane were experimentally studied. The specimen was in large scale, and made of transparent organic glass. Laminated configuration consisted of double wall laminates, pin-fins, staggered arrays of impingement and film holes. The number ratio of impingement holes, pin-fins and film holes was 2:1:1. Five experiment vanes were installed in static cascade, and experiments were carried out under constant heat flux. Re of internal cooling air in the experiment was from 104 to 2×105, and Re of external fluid was from 105 to 3×105. The experiment results show that flow resistances of front channel and back channel of the vane are in the same level, and both of them decrease as Re of cooling air increases. Nu of front channel is slightly higher than that of back channel. Both of them increase as Re of cooling air increases. And experiment results were obtained from experiment vanes were compared with that obtained from laminated flat plates, and the tendency of the results agrees well.
Influence of measure-density on combustor characteristics
YANG Zhi-min
2014, (5): 1014-1019.
Abstract PDF(856KB) icon1118 icon975
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The apparatus of scan measurement was used to gather the temperature pattern at the combustor outlet, where the average working temperature of gas was about 1700K and the maximum temperature was about 1950K. Consequently, the measurement part was cooled by water or air. Usually, for intermittent measurement devices, the interval of circle angel could be changed to get a high-density temperature distribution. A continuous measurement manner was adopted to get point in circle. The angle between two measure-points was 1.286°.The annular combustor outlet was about 40 to 50mm in height, where 5 or 6 measure points were usually arranged. In this device, 10 measure points were arranged in a range of 45.5mm. Four thermocouples were arranged in circle to obtain 2800 measure-points of the temperature field in a single experiment. Data were drawn from the whole datasheet at intervals. Each group of data whose number decreased in turn, included temperature points of 2800, 1400, 700, and 350, respectively. Several groups of temperature distributions with different densities were established. Subsequently, data processing was conducted to calculate the main combustor characteristics, including arithmetic or integral average temperature, OTDF (overall temperature distribution factor) and RTDF(radial temperature distribution factor). It is found that the data from different groups with different measuring densities result in significant difference on the combustor characteristics. The veracity of temperature characteristics increases with the growing measure-density.
CFD numerical simulation of Hyshot scramjet
WANG Pei-yong, CHEN Ming, XING Fei, LI Qiong
2014, (5): 1020-1028.
Abstract PDF(1141KB) icon2001 icon1045
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CFD numerical simulation was carried out for cold flow and combustion flow of the Hyshot scramjet to test the accuracy of turbulence flow model and turbulent combustion model. For cold flow, the predicted wall pressure profile was in accurate agreement with experimental data and the simulation result was insensitive to turbulence flow model choice. However, the predicted field of turbulence variables (turbulence kinetic energy and its dissipation rate) in cold flow is strongly influenced by turbulence flow model choice; these turbulence variables affect the mixing of hydrogen fuel and air and the subsequent combustion. Indeed, the simulation of combustion flow showed strong dependence on turbulence flow model and turbulent combustion model choice. The best combustion simulation result with SST k-ω turbulence flow model and EDM turbulence combustion model has good agreement with experimental wall pressure data, but the pressure peak location is slightly deviated. The effect of fuel injection angle was also simulated. Eight injection angles of hydrogen fuel were tested and it was shown that the scramjet has best fuel/air mixing and combustion efficiency with injection angles of 99° and 114°.
Experiment of cooling effectiveness with double-outlet film hole
LI Guang-chao, LING Xu, KOU Zhi-hai, WU Chao-lin, ZHANG Wei
2014, (5): 1029-1035.
Abstract PDF(1093KB) icon1318 icon1013
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In order to understand the cooling characteristics of the double-outlet film holes further,the platform for testing film cooling effectiveness was established.The cooling effectiveness of the cycle holes and four kinds of double-outlet holes with various orientation angles was studied at the blowing ratios from 0.3 to 2.0 by infrared measurement.The results show that:compared with the cycle hole,the surface averaged cooling effectiveness of the double-outlet holes is improved by 18%-37% with 30,45 and 60 degrees of orientation angles.At the low blowing ratios,the cooling effectiveness of the double-outlet holes with 30 degree of orientation angles is most significantly improved.At the high blowing ratios,the cooling effectiveness of double-outlet holes with 60 degree of orientation angles is most significantly improved.The double-outlet holes with 45 degree orientation angles can significantly improve the cooling effectiveness at both high and low blowing ratios.The cooling effectiveness of the double-outlet holes with 75 degree of orientation angles is lower than that of the cylindrical holes.
Analysis of cooling air flow field in front power compartment of tracked vehicle
WANG Rui, WANG Yi-chun, FENG Chao-qing
2014, (5): 1036-1041.
Abstract PDF(937KB) icon1332 icon890
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Cooling air flow fields of front power compartment in tracked vehicle were researched,while both physical and mathematical models were built.Cooling air flow fields around inner and exterior of a power compartment equipping with several radiators with different entry boundary conditions were simulated.These studies were compared with the experimental results.The influence of vehicle speeds on change regular of cooling air mass flow of radiators was analyzed.The research shows that,under the same rotating speed of the fan,mass flows of two fans and two radiators change about 10% from 0 to 70km/h of vehicle speeds,and the total mass flow of two radiators is nearly stable.For the radiators and fans,the change rate of cooling air mass flow between the simulation and experiments are less than 5% when vehicle speeds change from 0 to 70km/h.
Civilian turbofan engine emission prediction based on combustor multi-reactor model
CAO Ming-dong, WANG Zhan-xue, CAI Yuan-hu, LIU Zeng-wen, GONG Hao
2014, (5): 1042-1052.
Abstract PDF(1506KB) icon1520 icon1035
Abstract:

JetA was chosen as an aviation fuel,while simplified flame front model,combustion chemical equilibrium model,combustion kinetic model,fuel atomization model,fuel evaporation model and emissions generation model were developed.The turbofan engine emissions (NOx,unburned hydrocarbons (UHC),CO) under different operation conditions were calculated based on combustor multi-reactor model.The results show that,the higher combustion chamber flame temperature means the greater NOx emission levels;the fuel droplets atomization diameter is large when engine works under low rotate speed conditions,leading to increase of UHC and CO emissions levels;the combustor multi-reactor model has a better compatibility and fast computation speed,so it is considered as a promising method for integrating with engine performance program to predict the emission when the engine operates under different work conditions in design period of engine.
Overall performance and combustion organization based on turbine inter-vane burning technology
ZHENG Hai-fei, TANG Hao, LI Ming, MO Da
2014, (5): 1053-1061.
Abstract PDF(1177KB) icon1619 icon983
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The turbine inter-vane burning technology was applied to achieve the purpose of high thrust-weight ratio, low specific fuel consumption, low pollution and expanded stable working range of aero-engine. For this purpose, the burner placed between the turbine vanes was reheated to increase the gas temperature in the turbine, and then improve the overall performance of aero-engine. This works elaborated the potential advantage of the turbine inter-vane burning technology of enhancing the aero-engine overall performance based on overall thermodynamic cycle performance analysis, helping to research key technology, parameters and mechanism problem about combustion in this technology. And it is observed that: (1) for the jet-swirl scheme, radial vane cavity plays a decisive role in temperature distribution at the exit of combustor, and combustion efficiency can be improved by reducing the equivalence ratio in combustion ring cavity while leading to lower pollutant emissions quantity of CO, UHC (unburned hydrocarbon), NOx; (2) the jet-vortex scheme has better combustion performance when the secondary jet-flow angle is 60 degrees.
Effect of different step heights on ignition and blowout performance of internally-staged combustor
FU Zhen-bo, LIN Yu-zhen, FU Qi-hui, ZHANG Chi
2014, (5): 1062-1070.
Abstract PDF(996KB) icon1593 icon1047
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A lean-burn internally-staged combustor was designed.Using a single module rectangular test article,the effects of three different step heights on ignition and blowout performance were studied herein.Only the pilot stage nozzle was fueled in the tests.The lean ignition test was operated with normal and negative inlet pressures under normal inlet temperatures condition,and the lean blowout test was operated with the normal and raised inlet temperature under the normal inlet pressure condition.The experimental results indicate that the lean ignition and blowout boundaries are simultaneously widened with the increasing the step height;the inlet temperature rise is good for lean blowout performance with narrowing the lean blowout fuel air ratio differences in these three cases,and the maximum differences decrease from 40% to 13% under the test condition of the inlet temperature of 320-570K;the ignition performance under the negative inlet pressure and normal inlet temperature condition is rather good for all three cases with little difference of the lean ignition fuel air ratio,and the maximum differences don't exceed 10% under the test condition of the liner total pressure drop of 0.5%-1.5%.
Coupled heat transfer numerical simulation of wall temperature of can-annular combustor flame tube
DONG Hong, WEN Xue-you, LI Ming-jia, HE Xing
2014, (5): 1071-1078.
Abstract PDF(1358KB) icon1411 icon1071
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The wall temperature distribution of a can-annular reversed combustor flame tube was obtained and analyzed to ameliorate the flame tube design, since the flame tube was often ablated partly and cracked when a gas turbine running. The distributions of flow field, temperature field and wall temperature were obtained by the method of three-dimensional numerical simulation of coupled heat transfer, while heat conduction and radiation of solid, heat convection between gas and solid, radiation of flame and flue gas were took into account. The simulation result was checked by experiments, so the temperature distribution of flame tube can be predicted with the method of three-dimensional numerical simulation of coupled heat transfer. According to the simulation result, the wall temperature of combustor flame tube doesn't exceed the design value 1223K, but the temperature and temperature gradient are relatively high at several primary holes and the joint of the flame crossover tube and flame tube, and the cooling design of these parts needs to be improved.
Investigation on combustion instability in model premixed combustor
FU Xiao, GUO Zhi-hui
2014, (5): 1079-1085.
Abstract PDF(1037KB) icon1448 icon1011
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Experiments and numerical simulations were conducted on combustion instability in model premixed combustor with bluff body flame holder.Pressure transducers were used to measure frequency and amplitude of the combustor dynamic pressure at different equivalence ratios. Results show that instability frequency increases from 251Hz to 258Hz with the growing equivalence ratio.The ratio between instability amplitude and atmospheric pressure increases from 2.7% to 6.1%.The periodic vortex shedding frequency of 260Hz was calculated by steady and unsteady numerical simulation. The first five combustor nature acoustic mode frequencies were obtained by acoustic mode analysis.The third longitudinal acoustic mode frequency is near the experiment value.The mechanism is the coupling between symmetric vortex shedding periodicity behind bluff body flame holder and the third longitudinal acoustic mode of the combustor.
Influence of oxygen addition in multi-swirl pilot zone on atmospheric pressure ignition characteristics
WANG Bo-sen, ZHANG Chi, LIN Yu-zhen, JIANG Wen-bin
2014, (5): 1086-1090.
Abstract PDF(937KB) icon1632 icon927
Abstract:
The ignition experiments were conducted on atmospheric pressure and normal temperature. The experimental research object was a model combustor with multi-swirl air atomizing nozzle. The systematic parameters for study consist of atmospheric pressure, normal temperature, pressure drop of chamber of 1%-6%, ignition energy of 20J and 12J, mass flow ratios of oxygen and air in pilot zone of 0-0.04. The change rule of ignition fuel-air ratio of multi-swirl air atomizing nozzle. The results indicate that when ignition fuel-air ratio is small enough, maximum ignition air flow velocity at combustor inlet increases with the rising oxygen addition mass flow in pilot zone. On the condition of the same ignition energy and pressure drop of chamber, while the mass flow ratio of oxygen and air in pilot zone increases, the ignition fuel-air ratio reduces. When the mass flow ratio of oxygen and air in pilot zone increases to a threshold value (20J-0.01, 12J-0.015), the trend of ignition fuel-air ratio of curve changes. When it continues rising to another threshold value (20J-0.025, 12J-0.03), the ignition fuel-air ratio will not change.
Experimental investigation on shedding vortex and lift mechanism of flapping wing model with single degree of freedom
BAO Feng, YANG Qi, HE Yi
2014, (5): 1091-1098.
Abstract PDF(1272KB) icon1474 icon845
Abstract:
Based on flow visualization experiment and particle image velocimetry (PIV) measurement, the shedding vortex of flapping wing model with single degree of freedom was studied experimentally and several conclusions were obtained as follow. (1) A horn-shape shedding vortex with a wingspan-direction movement is generated around the leading edge as well as the trailing edge during flapping. (2) The shedding vortex leads to alternative pressure differences with unequal scalar on both sides of the flapping wing. (3) Both attack angle and inflow speed are not zero, which are essential factors to the lift generation of study object. (4) The maximum circulation of the shedding vortex appears at about 3/5 of the upward flapping journey, as well as the downward flapping journey. (5) The circulation of the shedding vortex is proportional to the flapping speed. (6) The flapping wing generates more work during the downward flapping journey, as compared with the upward flapping journey, resulting in the generation of lift within a whole flapping cycle.
Effect of rearview mirror edge structure on flow field and aerodynamic noise
CHEN Xin, WANG Huai-yu, GAO Chang-feng, ZHANG Wu, XIE Chen
2014, (5): 1099-1104.
Abstract PDF(1027KB) icon1436 icon832
Abstract:
Numerical simulation of exterior flow field and aerodynamic noise caused by different rearview mirror edge structures was conducted by the large eddy simulation(LES). The results show that various mirror cover edge structures have an effect on the airflow velocity and direction, affecting greatly the rear flow field of rearview mirror and sound pressure level at monitoring point. Compared with the original model, the vortex flow behind model 1 is farther away from the body surface, helping to reduce aerodynamic noise. Sound pressure level drops by almost 10dB in 1/3 octave center frequency at a monitoring point. The vortex flow behind model 2 is separated and located nearer to the body surface, leading to rise of aerodynamic noise. The mirror cover edge structure of model 1 improves the flow field and aerodynamic noise around the rearview mirror and A-pillar.
Numerical simulation on morphing winglets for its drag reduction mechanisms
ZHANG Qing-feng, XIONG Ke, LI Wei, CHEN Shuang
2014, (5): 1105-1111.
Abstract PDF(1013KB) icon1608 icon983
Abstract:
The most critical geometric parameters of winglets in drag reduction efficiency were summarized. Then the numerical simulation method was utilized to reveal the optimal range of these parameters, which is the theoretical basis of morphing winglet design. The advantages and disadvantages of morphing winglets in aerodynamic performance, aerodynamic load distribution and wingtip vortices were discussed compared with traditional winglets. The results show that morphing winglets can increase the drag reduction efficiency by 2.2% compared with traditional winglets and weaken the wingtip vortices by 15% in the takeoff phase of flight. It is beneficial to enhance the fuel efficiency of aircraft and the airport spatial security. However, morphing winglets increase the bending moment at the wing root. For this reason, aircraft designers have to strik a balance between the aerodynamic benefits and the structural disadvantages in morphing winglet designs.
Finite element analysis of dynamic stability of bearingless rotor
WEI Li-jun, LI Shu, LI Xue-chang
2014, (5): 1112-1121.
Abstract PDF(1504KB) icon1262 icon812
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Dynamic stability equations of bearingless rotor blades were investigated using a simplified model.The aerodynamic loads of blades were evaluated using two-dimensional airfoil theory.Perturbation equations were obtained by linearization of the perturbation.A normal-mode approach was used to transform the equations expressed by nodal degrees of freedom into equations expressed by modal degrees of freedom,which can reduce the dimension of the equations.The stability results of rotor blades were presented using eigenvalue analysis.The shape function matrix was obtained using spline interpolation,which simplified the analysis and made assembly of the inertial matrix,damping matrix,and stiffness matrix a simple mathematical summation.The results indicate that the method is efficient and greatly simplifies the analysis.
Aerodynamic interaction of fuselage,horizontal stabilator and vertical stabilator of helicopter
LÜ Shao-jie, CAO Yi-hua, XIAO Yang
2014, (5): 1122-1127.
Abstract PDF(992KB) icon1636 icon886
Abstract:
The panel method was used to simulate the helicopter fuselage flowfield.For the isolated fuselage of rotor body interaction (ROBIN) model,the pressure coefficient distribution along the top centerline was calculated in forward flight.The computational results were compared with the referenced data and computational fluid dynamics(CFD) results,validating accuracy of the methodology.Discrete vortices system was used to simulate the lifting surfaces,including horizontal stabilator,vertical stabilator and short wing.Aerodynamic interaction of fuselage,horizontal stabilator and vertical stabilator of UH-60 helicopter with short wing was computed and analyzed when the lifting surface parameters were adjusted.The results indicate that,change of the installation angle will have significant influence on the airflow around the lifting surface as the greatest influential parameter.Horizontal stabilator parameters,in particular the installation angle,can yield evident impact on the pressure coefficient of vertical stabilator and short wing,while decrease of the vertical stabilator span and increase of short wing installation angle can respectively increase their own pressure coefficient.
Application of multiscale turbulent model in cylinder flow
XU Huan, LI Zhi-qiang, DONG He, TANG Yang-yang, DI Ya-chao
2014, (5): 1128-1134.
Abstract PDF(1200KB) icon1496 icon888
Abstract:
The unsteady flow around a smooth cylinder under the supper-transition flow region Reynolds number was simulated using the multiscale turbulent model based on the variable interval time average method.The computational results show that the multiscale turbulent model can successfully simulate the lift and drag coefficients,however, standard k-ε model and SST k-ω model can only accurately simulate one of them.This model can also accurately predict vortex shedding characteristics, and its error is smaller than 5.8% of SST k-ω model and 37.6% of standard k-ε model.Also,for the prediction of surface mean pressure coefficient distribution,the error of multiscale turbulent model is only 3.6%,however,the predicted errors using SST k-ω model and standard k-ε model increase to 13% and 53.7%.For the prediction of surface friction factor distribution and the separation angle,the error of separation angle of multiscale turbulent model is only 0.78%.Correspondingly,the predicted errors of standard k-ε model and SST k-ω model are 1.04% and 1.83%.Compared with the experimental results,the results of the multiscale turbulent model are better than those of standard k-ε model and SST k-ω model.So,the study verifies further that this model can be used in simulation of complex turbulence.
An aerodynamic design method and verification for counter-rotating compressor
HU Ying-jiao, WANG Song-tao
2014, (5): 1135-1144.
Abstract PDF(1149KB) icon1559 icon891
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An aerodynamic design method combined with boundary layer suction was proposed for counter-rotating compressor. For high-loaded compressor, because of the problems (such as strength problem) caused by boundary layer suction used in the rotating parts, the boundary layer suction was used only in the stator, while the rotor was designed by the low reaction design principle to ensure its efficiency based on the increasing rotor exit axial velocity. A counter-rotating compressor was designed to demonstrate the method above. The three dimensional viscous numerical simulation results show that, two-stage counter-rotating compressor with total pressure ratio of 5.85 and efficiency of 88% is attained at tip tangential speed 370m/s of the first rotor and 350m/s of the second rotor.
Numerical investigation on rotating instability phenomenon in tip flow field of transonic compressor rotor
FU Lei, YUAN Wei, SONG Xi-zhen, ZHOU Sheng, LU Li-peng
2014, (5): 1145-1153.
Abstract PDF(1272KB) icon1597 icon941
Abstract:
Numerical simulations were performed on tip unsteady flow field of a transonic compressor rotor with different work mass flows. The results show that no oscillation occurs in tip flow field of rotor under high mass flow condition, which can be regarded as steady flow field for analysis, and the oscillation of tip leakage vortex is intensive under low mass flow conditions. Furthermore, periodical interference within the tip leakage flow between adjacent blade passages emerges. As a result, a phenomenon called "rotating instability" caused by the oscillation of tip leakage vortices and its circumferential propagation, is found in stationary frame. The dominating cell number of "rotating instability" flow field is nearly 40% of the blade passage number, and the cell size in circumferential direction is 2-3 pitches.
Accelerated CFD computing of turbomachinery on GPU platform
JU Peng-fei, NING Fang-fei
2014, (5): 1154-1162.
Abstract PDF(1094KB) icon1592 icon846
Abstract:
The well-developed turbomachinery computational fluid dynamics code multi-block aerodynamic prediction (MAP) was solved by data-parallelized computing and implemented on a graphic processing unit(GPU) platform with the help of compute unified device architecture (CUDA) technology.The second-order upwind spatial scheme and the implicit temporal scheme in the original program were retained,while the linear system was solved by implicit iterations.During the test of two turbomachinery examples on a single GPU,a speed-up appeares to be 8.89 times comparing with one central processing unit (CPU) process and 2.39 times comparing with four CPU processes,with no extra deviation induced into the result.
Observation and analysis of flow features in blade tip region of compressor rotor
LIU Dong-jian, LI Jun, JIANG Ai-wu, LI Cheng-long, LI Fan-yu
2014, (5): 1163-1169.
Abstract PDF(1107KB) icon1422 icon837
Abstract:
In order to investigate the evolutionary tendency of the compressor rotor's real rotating environment and explain its associated flow mechanism, the filament traces method was used for flow field visualization in a low-speed axial compressor rotor. And the unsteady multiblade-passage numerical simulations were also carried out to study the flow field characteristic of the blade tip region and its formation mechanism. Based on experimental results, the evolution processes of the complex flow inside the rotor passages were seen clearly as the compressor was throttled towards the stability limit. The results show that as the rotor's mass flow is reduced, the trajectory of blade tip leakage flow moves upstream towards the leading edge of the blade tip. When the compressor is operating near stall condition, the interface between the main flow and the tip leakage flow is nearly parallel to the rotor leading edge plane at the blade tip. Meanwhile the large backflow region appears on the suction side of the blade tip, and the backflow is found to be collected at the leading edge near the blade tip. And the further research shows that the axial momentum ratio of the tip leakage flow to the main flow in the clearance region increases as the flow coefficient decreases, serving as a mechanism for the forward movement of the tip leakage flow and the growth of the backflow region.
Numerical investigation of effect of outlet hub geometry on performance of large scale axial fan
YIN Chao, HU Jun, TU Bao-feng, YAN Wei, ZHANG Chen-kai
2014, (5): 1170-1176.
Abstract PDF(1137KB) icon1312 icon853
Abstract:
Four different outlet hub geometries of a large scale axial fan were designed and investigated. CFD methods were used to compare the fan characteristics and analyze the flow field structures in the blade tip and blade root. The results show that variation of outlet hub geometry has little effect on the fan's tip flow structure; there is a large separated flow in the blade root region which occupies 20% of blade height when the fan isn't provided with outlet hub, causing serious loss and decrease of efficiency; with the same blade tip clearance, the fan's efficiency increases when the outlet hub diffuser angle decreases; a matching straight or convergent hub could make the blade root separated vortex move backwards, reduce the separated area to 5% of blade height and increase at least 2 percentage points of the fan efficiency.
Investigation of thermal fatigue failure characteristics on typical cooling laminated configurations
WU Xiang-yu, LI Xu, SHI Yan, ZHANG Cui-hua, DU Zhi-neng
2014, (5): 1177-1183.
Abstract PDF(1448KB) icon1483 icon817
Abstract:
Superalloy test pieces for three different typical forms of cooling laminated configurations were designed and processed. High working temperature of cooled turbine blades in real engine was simulated; the thermal fatigue life of each type of cooling laminated configuration by thermal cycling loading was studied experimently; the reasons for its destruction and damage locations were analyzed, and the data were compared with the numerical results. The results show that thermal fatigue cracks in each configuration occur near the film holes of exhaust plate and extend along longitudinal direction of film hole. The cracks extention at inner surface is greater than that at outer surface. 211-type has the shortest thermal fatigue life among three cooling laminated configurations, and the thermal fatigue lifes of 161-and 141-type cooling laminated configurations are on the same level.
Improved algorithm of flight conversion ratio for aero-engine based on probability
LI Hong-wei, YE Bin, CAI Na
2014, (5): 1184-1190.
Abstract PDF(1063KB) icon1412 icon891
Abstract:
For SPEY MK202 engine, the stress standard evaluation methods fail to contain various random factors. In order to explain the differences in the actual working life of engine component, as well as the dispersion of the fatigue characteristic parameters of component and the randomness of the whole engine load spectrum, statistical analysis of measured data, finite element analysis of stress and Monte Carlo simulations of component were combined to put forward the improved algorithm of flight conversion ratio for aero-engine based on probability. Actual example shows: the flight conversion ratio of ascertainable method for life assessment is the average value of the improved algorithm; for a single flight conversion rate, the average conversion rate of improved algorithm is 2% smaller than that of ascertainable method; for comprehensive flight conversion rate, the average conversion rate of improved algorithm is 1% smaller than that of ascertainable method; and the single fight conversion rate and comprehensive flight conversion ratio of improved algorithin are in normal distribution.
Turbine shroud multidisciplinary design optimization with double-loop strategy
JIA Zhi-gang, WANG Rong-qiao, HU Dian-yin
2014, (5): 1191-1196.
Abstract PDF(984KB) icon1523 icon810
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Because of the low efficiency on the classical multidiscipline design feasible(MDF), the strategy of the MDF improved by variable complex method was studied. Considering comprehensively the optimization accuracy and efficiency for the turbine shroud, the response surface method representing the high precise analysis simplified the calculation difficulty and then improved the optimization efficiency; by reasonaby introducing variable complex method, the double-loop optimization strategy periodically employed the high precision analysis and updated response surface equation to ensure precision. The turbine shroud multidisciplinary design optimization (MDO) with double-loop shows that this optimization object reduces by 1.4% obviously than that of classical MDF(0.97%), and it totally costs 2h39min equivalently to 1/3 of that of classical MDF.
Creep behavior of thin-walled plate with cooling holes of nickel-based single crystal superalloy DD6 under high temperature
AI Xing, GAO Hang-shan, WEN Zhi-xun, LIU Da-shun, YUE Zhu-feng
2014, (5): 1197-1204.
Abstract PDF(1154KB) icon1698 icon910
Abstract:
Thin-walled plate specimens with cooling holes were used to model the air-cooled turbine blades. Specimens without holes were employed for comparison. The effect of cooling holes on the creep life of nickel-based single crystal cooling blades was studied. Experimental results show that at 950℃, the creep lives of specimens without cooling holes are nearly twice the specimens with cooling holes when the stress is kept as 377MPa. The scanning electron microscopy(SEM) analysis on the fractured surface reveals that the creep damage stems from the local region around the holes and the ruptures initially occurs at holes edges. Based on the crystal plasticity theory, a creep model for the creep experimental data of single crystal material was developed, and implemented into the Abaqus user subroutine(UMAT) to simulate the plate specimens with and without holes. The results show that stress concentration and redistribution occur around the cooling holes, and the form of the fracture surface is consistent well with numerical analysis. For engineering application, the relationship between the creep life and the maximum resolved shear stress amplitude of dodecahedron slip system is expressed by an exponential function. The creep test result shows that the formula has good accuracy under 950℃,377MPa.
Modeling and calculation of impact of mesh-out at corner contact in gear drive
ZHOU Chang-jiang, ZHANG Cheng, TANG Jin-yuan
2014, (5): 1205-1210.
Abstract PDF(1137KB) icon1464 icon811
Abstract:
Based on the mechanism analysis of impact of mesh-out at corner contact in gear transmission,a calculation model including system equivalent error and teeth synthetic deformation was established on the line of meshing.The synthetic deformation of the point in mesh-out beyond the normal path was reversed,on basis of meshing theory and the curve of gear deformation and load-history.By combining the system equivalent error with the teeth synthetic deformation,the point of mesh-out at corner contact and the impacting point were determined.Given uniform normal velocity at meshing points,the minimum rotation speed of the driven gear in mesh-out at corner contact and the impact velocity were solved.And then the impact force of mesh-out at corner contact was confirmed.The example calculation shows that,the impact force of mesh-out at corner contact is 70% to 80% of that of mesh-in at corner contact; namely,the impact of mesh-out is smaller than that of mesh-in.It verifies that impact in mesh-out and mesh-in has a different effect on "mesh synthetic base pitch error".
Boundary element method of hydrodynamic characteristics of lubricant in three-leaf dislocated floating-ring bearing
HUANG Ming-han, ZHANG Wen-zhong, TONG De-sheng, PENG Hong-mei, YANG De-quan
2014, (5): 1211-1215.
Abstract PDF(1065KB) icon1123 icon819
Abstract:
The problem of hydrodynamics of the three-leaf dislocated floating-ring bearing was studied by means of boundary element method. The law including the distribution of pressure on boundary surface (axial, bearing and floating-ring) and its friction loss in different eccentricities was obtained. The results show that the inner friction of three-leaf dislocated bearing increases from 390.875 to 1091.65, and the inner friction of three-leaf dislocated floating-ring bearing increases from 94.2523 to 114.5069 with eccentricity varying from 0 to 0.075 in nondimensional. So changing the pressure and flow field of bearing by adding floating-ring is more stability and less wasted work of friction than three-leaf dislocated bearing.
Active design of face gear drive for modifying ease-off topology flank
PENG Xian-long, HU Xi-wen, FANG Zong-de
2014, (5): 1216-1222.
Abstract PDF(1327KB) icon1735 icon899
Abstract:
A method to redesign ease-off topology surfaces of pinion and face gear with given meshing performance was proposed to improve the meshing performances of face gear drives with small number of machining parameters.The face gear could be manufactured through shaping,and the pre-designed transmission errors could determine the relationship between the rotation angle of the shaper and the rotation angle of the face gear, thereby forming ease-off topology flank of the face gear.And then the ease-off topology flank of the pinion was calculated according to the location and direction of the pre-designed contact path and the pre-designed size of contact ellipse;finally,a grinding method of conjugation of point contact was used to obtain the ease-off topology flank of the pinion,while the linear equations between machining parameters and calculated ease-off topology flank of the pinion were deduced.The results show that,the transmission error and contact path simulated by tooth contact analysis (TCA) were the same as the pre-designed transmission error and contact path,with the difference between the length of contact ellipse simulated by TCA and the length of pre-designed contact ellipse from 0.1752mm to 1.16mm.
Improved uncertainty propagation method of dynamic model for Mars entry spacecraft
FU Hui-min, XIAO Qiang, WU Yun-zhang
2014, (5): 1223-1233.
Abstract PDF(1649KB) icon1072 icon801
Abstract:
In order to research the uncertainty propagation laws of Mars entry dynamic equations for the Mars entry phase, an improved method was presented for analyzing the effect of the initial state uncertainties and uncertainty factor on the system state in the state trajectories. When applying the method to the entry phase of one of the NASA Mars exploration missions, the simulation results agreed well with the Monte Carlo method, especially the flight path angle simulation at least reaching 92%. It is found that the improved method can not only predict the uncertainty propagation laws with high accuracy of at least 92% in flight path angle simulation and large application scope from -0.1 degree to 0.1 degree, compared with local linearization method, but also save several hours relative to Monte Carlo method.
Real time control algorithm of aviation piston engine air-fuel ratio
LI Yi-hua, HU Dong-ning, HU Chun-ming, LIU Na
2014, (5): 1234-1241.
Abstract PDF(1155KB) icon1411 icon886
Abstract:
Adopting the proportion-integration-differentiation neural network (PIDNN) control algorithm, the advantages of both the tradition PID and neural network were combined. It was used to control the engine air-fuel ratio under different operating conditions, and when the condition changed, it could control the air-fuel ratio to the target value. An engine model was built in software AMESim. The PIDNN control algorithm was built in software MATLAB. Through the model-in-the-loop, the simulation results show that: at different altitudes, the PIDNN could control the air-fuel ratio to the targets accurately. When the engine operating condition changes, the PIDNN could control the air-fuel ratio to the target within 0.5s and ensure the overshoot under 0.2, which results in the improvements of the engine dynamic property, fuel economy and rapid responsibility.
Investigation on adhesive interface specimen deformation and failure process under tension using digital speckle correlation method
JIANG Ai-min, LI Gao-chun, GUO Yu, QIU Xin, WANG Yu-feng
2014, (5): 1242-1248.
Abstract PDF(1501KB) icon1396 icon879
Abstract:
The deformation and failure process of adhesive interface specimen under tension was observed. By digital speckle correlation method (DSCM) to deal with images, displacement and strain field of speciman surface varying with load and their evolution process were achieved. The results show that during the tensile process the adhesive interface specimen with stress-release flap could be vulnerable crack at the tip of stress-release flap because of strain concentration. DSCM is an effective experimental method for studying characteristic of deformation and failure of adhesive interface specimen. The quantificational measurement results of adhesive interface deformation field are consistent with the data obtained from the experiment.

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