2012 Vol. 27, No. 12

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Numerical simulation and analysis of nitrogen-enriched air flow in a center wing tank
WANG Xue-de, WANG Zhi-wei, LIU Wei-hua, ZHANG Sheng-qi, WANG Xiao-ping
2012, 27(12): 2641-2647.
Abstract PDF(990KB) icon2155 icon1614
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Under the different nitrogen-enriched air(NEA) parameters, the inerting process was studied by numerical simulation of a civil airplane center wing tank(CWT). The study show the inerting rule of the CWT under different flow rates and different oxygen concentration. The results show that, when the NEA containing volume fraction of about 95% of the nitrogen and the volume flow rate of the NEA are 0.021, 0.028m3/s and 0.042m3/s, the average oxygen volume fraction distribution versus volumetric tank exchange (VTE) are almost the same; when the volume flow rate of the NEA is 0.042 m3/s and the volume fraction of the nitrogen are 92%, 94% and 98%, the inerting ratio versus time are the same. It is conclusion that the inerting time of the CWT has nothing to do with the flow rate under the same oxygen concentration, and the flow rate of the NEA determines the inerting ratio of each bay. Based on comparative analysis of the numerical result, it proves that the shrink analogy method can be used to simulate the inerting process of the CWT. The research provides reference for optimizing the design of a transport airplane inerting system.
Large eddy simulation of anti-vortex film cooling
WU Hong, YANG Qing
2012, 27(12): 2648-2654.
Abstract PDF(971KB) icon1827 icon1603
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Large eddy simulation was used to investigate the fluid flow and heat transfer mechanism of anti-vortex film cooling. The interaction between the main hole and the side holes was obtained, and the mechanism that turbulence structures affected film cooling effectiveness was analyzed by comparing with standard round hole case for the same blowing rate. It is found that the presence of side hole jets decrease the size and strength of the counter-rotating vortex pair of the main hole jet, and supply coolant for its entrainment. The temperature of the main hole jet does not rise sharply at the exit of the main hole because the side hole jets supply to the low-pressure area behind the exit of the main hole. Due to the side hole jets' effect, the main hole jet does not form whole hairpin structures but near-wall streaks, decreasing its mixing with the main hot stream and enabling the coolant to cover and cool down the wall better.
Experiment on shock wave focus in resonator
ZENG Hao, HE Li-ming, RONG Kang, ZHANG Qiang
2012, 27(12): 2655-2659.
Abstract PDF(432KB) icon2369 icon2084
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In order to investigate three-dimensional shock wave focus of two-stage pulse detmation engine(PDE), three-dimensional shock wave focus initiation principle device was independently designed, and a complete set of experimental system was established.Experiments on non-reaction three-dimensional shock wave focus were conducted.It is found that resonant frequency increases with the increase of the incidence angle of resonator.As airflow exit area decreases, resonant frequency of resonator increases and the dynamic pressure amplitude of resonator bottom increases.As nozzle diverging angle increases, the highest alpha-frequency increases and the quantity of beta-frequency increases.When the nozzle diverging angle is 30°, the dynamic pressure amplitude of resonator bottom is maximal.As ‘L’ increases, resonant frequency decreases and the dynamic pressure amplitude of resonator bottom decreases.
Measurement and analysis of atomization characteristics of oxygenated bio-fuel
ZHANG Chi, FU Qi-hui, RONG Long, LIN Yu-zhen, XU Quan-hong
2012, 27(12): 2660-2665.
Abstract PDF(625KB) icon1907 icon1421
Abstract:
A pressure-swirl atomizer was adopted to measure the atomization characteristics of oxygenated bio-fuel and its different blends with conventional kerosene RP-3.The study was conducted to analyze the effect of the chemical composition and physical-chemical properties on the atomization characteristics of the oxygenated bio-fuel.For the blends with 50% or less oxygenated bio-fuel, a Sauter mean diameter (SMD) prediction model was developed.The experimental results show that decrease the oxygenated bio-fuel in the blends, the atomization would be improved.In addition, increase the supply pressure drop, the difference of atomization among the fuel blends would be reduced.When the supply pressure drop is larger than 1.0 MPa, SMD of the fuel blends can achieve less than 40μm.By analysis, currently the oxygenated bio-fuel can not be directly used for aero-engine, and the fuel-hydroprocessing or aircraft modification is necessary for meeting the demands of the long-term future aviation.
Effect of cavity physical dimension on forward-facing cavity and opposing jet thermal protection system cooling efficiency
LU Hai-bo, LIU Wei-qiang
2012, 27(12): 2666-2673.
Abstract PDF(1585KB) icon1917 icon1256
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Design of the thermal protection system (TPS) with the forward-facing cavity and opposing jet combined configuration was investigated numerically for the hypersonic vehicle.The numerical method was validated with the related experiments.The flow field parameters and surface heat flux distribution were obtained by solving the Navier-Stokes (N-S) equations.The validity of the combined TPS was testified and the effect of the cavity physical dimension on cooling efficiency of the combined TPS was discussed.The results show that the TPS with smaller diameter cavity has smaller aerodynamic heating and the TPS with larger length cavity has higher heat flux reduction.The recirculation region plays a pivotal role for the reduction of heat flux.The aerodynamic heating is more sensitive to the changing of the cavity diameter than the cavity length.
Initiation mechanism investigation of saltation and smoothness oblique detonation waves
HAN Xu, ZHOU Jin, LIN Zhi-yong, LIU Shi-jie
2012, 27(12): 2674-2680.
Abstract PDF(1178KB) icon1960 icon1500
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Euler equations with chemical reaction were used to study the difference in the initiation mechanism and characteristics of saltation and smoothness oblique detonation waves (ODW).The result shows that the criterion which determines the oblique detonation wave configuration is whether a subsonic zone exists behind the oblique shock wave(OSW).If the OSW raised by the flame behind it can lead to the formation of a subsonic zone, the transverse shock wave and triple point would appear and saltation ODW would form.The smoothness ODW would form if all zones are supersonic behind the OSW so the flame can not touch the upriver OSW.The OSW critical angle which leads to the formation of transverse shock wave is calculated from the equations of OSW.When the OSW angle is bigger than this critical angle, saltation ODW would form.otherwise, smoothness ODW would form.
Flow and heat transfer characteristics of drop-shaped micro pin-fin heat sinks with cross flow
ZHOU Ming-zheng, XIA Guo-dong, CHAI Lei, ZHOU Li-jun, GAO Ning
2012, 27(12): 2681-2686.
Abstract PDF(519KB) icon1789 icon1463
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Three drop-shaped micro pin-fin heat sinks with different tail angles were designed based on the optimization of traditional round micro pin-fin heat sink.The flow resistance and heat transfer characteristics of the heat sinks were experimentally investigated using deionized water as working fluid.The results show that the micro pin-fin with tail angle of 60° has the lowest flow resistance among the heat sinks.The streamlined structure of drop-shaped micro pin-fins improves the distribution of flow and delays the conversion from laminar to turbulent flow.The smaller the angle, the more obvious the effect.The optimal angle of drop-shaped micro pin-fin is different under different flow rates.The heat sink with tail angle of 60° has the strongest heat transfer coefficient at the corresponding Reynolds number in this experiment (Reynolds number is equal to 200-1000).When the tail angle decreases to 30°, the heat transfer is also enhanced in the tail section of micro pin-fin.However, the flow is affected by the micro pin-fin behind, so the heat resistance is higher than other heat sinks under the same pump power.
Effects of liner pressure loss on combustor lean blow-out and combustion efficienly performances
XUE Xin, LIN Yu-zhen, ZHANG Chi, XU Quan-hong, DU Jiang-yi
2012, 27(12): 2687-2691.
Abstract PDF(936KB) icon2042 icon1593
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Based on a liner with 3.0% pressure loss liner, two low pressure loss liners (2.5% and 2.0%) were designed.The light lean ignition experiments were conducted to study the effect of liner pressure loss on the combustor lean blow-out and combustion efficiency.Under the idle conditions, the lean blow-out fuel air ratios of low pressure loss liner were lower than that of the baseline liner, and 2.5% pressure loss liner had the lowest.Under the high pressure and high temperature connditions, the low pressure loss had no effect on the combustion efficiency.Compared with the results of ignition, it was acceptable to reduce the liner pressure to 2.5% without negative effect on the combustion characteristic of combustor.
Experiment on forced convection-condensation heat transfer characteristics based on finned plate configuration
GU Li-hao, LING Xiang, PENG Hao
2012, 27(12): 2692-2698.
Abstract PDF(1060KB) icon1709 icon1418
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Experimental investigation of forced convection-condensation heat transfer and flow characteristics based on finned plate heat exchanger for condensing heat recovery was studied.With the experimental data, the effect of outlet flue gas temperature and velocity on condensation performance was studied, and the performance curves of Reynolds number-Nusselt number and Reynolds number-friction factor have been obtained.Meanwhile, the comparison of experimental results between wind tunnel test (using air as working fluid) and condensation test (using flue gas as working fluid) was also presented.From these results it can be seen that, due to the extensive non-condensable gas (about 92%), enhancement of overall heat transfer performance is not obvious, and the forced convection-condensation heat transfer coefficient is 10%-20% times more than that of the forced convection without condensation.A heat transfer criterion-based relational expression under the operating condition was also obtained.These results provide insight into improved designs of finned plate heat exchangers for condensing heat recovery.
Cooling characteristics of ramjet engine combustor with inclined multihole heat shield
DING Ji-ping, JI Hong-hu, SI Ren
2012, 27(12): 2699-2705.
Abstract PDF(903KB) icon1847 icon1516
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Based on numerical investigation, the characteristics and design method of ramjet engine combustor with inclined multihole heat shield was researched.First, the temperature distribution of ramjet engine combustor with no-hole heat shield was calculated, and then, according to the temperature distribution, the array of inclined holes in the heat shield (plan A) was designed, after that, the temperature distribution of inclined multihole heat shield was calculated.Using similar methods after two more distribution improvements (plan B and plan C), the non-uniform distributed solutions of inclined multihole which met the demand for the cooling was obtained.The results show that using the design approach in cooling flow reduced from 17.45% of plan A to 14.99 % of the plan C, the lowest cooling efficiency of inclined multihole heat shield improves from 70% of plan A to 85% of plan C.
Experiment on blade pitch control of electrically controlled rotor based on adaptive filter control algorithm
LU Yang, DONG Wei-sheng, HONG Liang, FENG Jian-bo
2012, 27(12): 2706-2713.
Abstract PDF(1302KB) icon1712 icon1392
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A new control algorithm based on the adaptive filter in time domain was brought forward.Based on this, the control system of electrically controlled rotor (ECR) blade pitch with double closed-loop was developed.Then, utilizing the test rig of model ECR, the pitch control experiments were performed in hover state.The experiments show that the developed control system of ECR blade pitch can work reliably through the tests.The control law based on the adaptive filter is successful in ECR collective pitch control, cyclic pitch control and collective pitch mixing with cyclic pitch control.The amplitude of the blade pitch was fitted well with the expected value, and the phase lag was about 10°～15°.The phase lag between the servo flap deflection and the response of blade pitch was about 20°～30°.Because of the structural and aerodynamic differences among different blades and servo flaps, the effect of blade pitch control will be reduced to some extent.
Study of variable geometry bleed cavity of TBCC inlet
ZHANG Hua-jun, GUO Rong-wei, XIE Lü-rong
2012, 27(12): 2714-2723.
Abstract PDF(2418KB) icon2035 icon1449
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Scheme of variable geometry bleed cavity which was used in over/under type of turbine-based combined cycle(TBCC) inlet in full Mach number range and its design method were presented.The characteristic of inlet flow field and the inlet aerodynamic performance affected by bleed cavity and the configuration of cavity geometry parameters were investigated, based on which the law of inlet aerodynamic performance affected by cavity geometry parameters was abtained.Three-dimensional numerical simulation of over/under type TBCC inlet with bleed cavity was performed. The paper presents the influence of free stream Mach number on variable geometry design parameters, and aerodynamic characteristics of the inlet in full Mach range. Once the bleed cavity is opened, the width of the cavity entrance and the height of the throat keep decreasing. The decreasing rate is very high at the beginning, but becomes relatively low later. When the free stream Mach number is lower than 2.0, or higher than 2.5, the leading angle at the entrance of the bleed cavity is decreasing as the increase of Mach number. When the free stream Mach number is less than 2.5, the total pressure recovery of the inlet is beyond 0.8.When the free stream Mach number is from 2.5 to 4.5, the total pressure recovery of the inlet is beyond 0.3. The aerodynamic characteristics of the inlet meet the demands of the scheme. At ramjet mode, the exit Mach number of the ramjet diffuser is all below 0.4 and the exit pressure of the ramjet diffuser is all beyond 0.5 standard atmosphere pressure(50.6625kPa). The ramjet diffuser can fulfill the combustion condition of the ramjet combustion chamber.The feasibility of the variable geometry bleed cavity scheme was confirmed by the numerical and wind tunnel test results.
Control integrated design for hypersonic vehicle
ZHANG Yong, LU Yu-ping, LIU Yan-bin, NAN Ying, XU Zhi-hui
2012, 27(12): 2724-2732.
Abstract PDF(1077KB) icon2095 icon1806
Abstract:
Since hypersonic vehicles involve characteristics of strong coupling of aerodynamics/propulsion/control and nonlinearity, a suit of control-oriented integrated design tool was developed.In the conceptual design phase, considering the aircraft control performance as the optimization goal, the vehicle was designed based on integrated and optimized parameters of aerodynamic, propulsion, structures and control.Considering the fidelity requirement and computational efficiency of the model generation, a parameterized mathematical model was established and an linear quadratic regulator(LQR) reference command tracking control system was designed.The design parameters were adjusted constantly, and then the trade-off study of the control-relevant static and dynamic properties and the comparison of control effects were accomplished.Finally, a new shape of vehicle was chosen according to the control requirement, and the corresponding validation of simulation was accomplished.Simulation results show that the method of control integrated design applied in the early stage of the conceptual design phase, can expand flight envelope, increase the stall margin effectively, reduce fuel consumption, improve the control surface efficiency, and reduce the engine choking restriction. Thus the method of control integrated design plays a guiding role in improving design efficiency and the performance of control for hypersonic vehicles.
Unsteady characteristics of hypersonic inlet below self-starting Mach number
WANG Wei-xing, GUO Rong-wei
2012, 27(12): 2733-2741.
Abstract PDF(1535KB) icon1957 icon1392
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The unsteady characteristics of a hypersonic mixed-compression inlet below the self-starting Mach number were numerically studied.The results show that the inlet works at un-starting mode, and oscillation phenomenon of the flow in the inlet appears with a frequency of about 250Hz.The flow oscillation occurs primarily in front of the throat and attenuates downstream the throat.The disturbance propagates downstream from the throat with the speed of the flow.The ratio of the length to height of the isolator has no effect on the flow oscillation, but the Mach number of the freestream offects the flow oscillation greatly.With the freestream Mach number approaching to the self-starting Mach number, the flow oscillation becomes more and more intense, but the flowfield retains steady when the freestream Mach number is too low.The pressure drag of the inlet also fluctuates periodically with the frequency of about 250Hz.
Contour design of super/hypersonic dual-inflection nozzle
GUO Shan-guang, WANG Zhen-guo, ZHAO Yu-xin, LIU Jun
2012, 27(12): 2742-2748.
Abstract PDF(740KB) icon2155 icon1373
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In order to achieve multi-Mach number run for the direct-connected test bench and high temperature wind tunnel, a straightforward technique has been developed to quickly determine a design of the super/hypersonic dual-inflection nozzle.The nozzle was divided into two sections to be designed, and the first was shared for different test Mach number.B-Spline functions were used to describe the Mach number distribution along the axial line of the nozzle.The preliminary nozzle contour was generated by a new computer program that solved the axisymmetric Euler equations using the method of characteristics.The final nozzle design was obtained by adding the boundary-layer thickness which was solved with the reference temperature method.An example of a dual-inflection supersonic nozzle design was employed to illustrate the technique with a computational fluid dynamics calculation.The simulation results indicate that desired Mach numbers are obtained at the nozzle exit, and the good flow quality is attained for different nozzles within Mach number error less than 1.2% in the test rhombus region.The present technique improves the design precision of the converging-diverging nozzle, cancels waves completely, and achieves the nozzles with different exiting Mach numbers which shares subsonic section and a portion of supersonic section.
Residual useful life prediction for aircraft engine based on information fusion
WANG Hua-wei, WU Hai-qiao
2012, 27(12): 2749-2755.
Abstract PDF(508KB) icon1749 icon1844
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The monitoring information has been utilized and fused for performance degradation evaluation.In consideration of random and error information, Bayesian linear model has been used for performance degradation evaluation of aircraft engine.The result of the performance degradation evaluation has been seen as input variable, and the reliability evaluation model has been built based on gamma random process which was used for forecasting residual life under predetermined reliability index.For example, the effect of different monitoring parameters on residual useful life prediction was analyzed.The method can integrate performance monitoring with reliability analysis into one framework, which utilizes monitoring information adequately. As a result of above, the goal of an accurate prediction of residual useful life has been achieved, which accords with the demand of maintenance risk control for aircraft engines.
Sensitivity analysis and dynamic optimization design of supports' positions for engine pipelines
LIU Wei, CAO Gang, ZHAI Hong-bo, LIU Yong-shou
2012, 27(12): 2756-2762.
Abstract PDF(619KB) icon1917 icon1433
Abstract:
Considering empirical feature and casualness in the design for engine pipelines, the support was simplified as translation-constrained elastic spring element, the lengths between every two supports were defined as supports' positions, and the finite element method (FEM) and the discrete sampling method were applied to the dynamic sensitivity analysis of engine pipeline structure.Compared with other structure parameters, the numerical results demonstrate that some supports' positions play more important roles for complex piping.The effect of supports' amount and stiffness on the fundamental frequency and random vibration responses was discussed.The position optimizations of complex pipelines' supports were implemented to maximize difference between fundamental frequency and external excitation frequency, and minimize the random vibration standard deviation by penalty function method.
Progress in titanium fire resistant technology for aero-engine
LUO Qiu-sheng, LI Shi-feng, PEI Hui-ping
2012, 27(12): 2763-2768.
Abstract PDF(542KB) icon1958 icon1724
Abstract:
According to the titanium fire resistant technology for aero-engine, the research condition of titanium fire resistant technology was generalized and analyzed from several aspects, which include the analysis of mechanisms of titanium fire and burn resistant, the research conditions of burn resistant alloy system and burn resistant coat, and the structural design of burn resistance related to the abroad research situation.The research results of titanium fire resistant technology were mainly introduced.Meanwhile, when the ralationship is established between titanium alloy Kai-burning and environments, the risk problems of burn resistant titanium alloy in the construction are fundamentally solved.
Reliability model of TT&C and communication task based on task arc
YAN Hua, WU Xiao-yue
2012, 27(12): 2769-2777.
Abstract PDF(914KB) icon1642 icon1382
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Reliability model of tracking, telemetry and command (TT&C) and communication task was constructed based on task arc division.According to time sequence of TT&C and communication resources, and the resources taking part in task and task success criterion, the TT&C and communication task can be divided into several successive task arcs.General task arc and idle task arc were defined, and their reliability modeling methods were proposed by using Markov approach.Moreover, the modeling methods considering the preparation time after resource opening and the resource close time were proposed.In these cases, task arcs were re-divided, and each of them was modeled according to the corresponding methods discussed.The task reliability can be obtained by solving these task arc models one by one.Finally, examples with numerical results under several cases show efficiency of the modeling methods.
Fatigue-crack-initiation numerical modelling of a Ni-base powder metallurgy alloy
MU Yuan-wei, LU Shan, ZHANG Hong
2012, 27(12): 2778-2785.
Abstract PDF(1316KB) icon1420 icon1017
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A simplified three-dimensional numerical model was presented to simulate the micro-crack nucleation and growth to some predefined dimension (approximately 0.38mm) on the throat surface of a Ni-base powder metallurgy (PM) specimen.The numerical simulation of micro-crack initiation was based on the Tanaka-Mura micro-crack initiation models, where individual grains of the mesoscopic model were simulated using the Voronoi tessellation.Four improvements were made in the model.(1) Considering crack initiation along with 12 principal slip systems on octahedral slip planes of face centered cubic (FCC) crystal in three-dimensional (3-D) models.(2) Considering the effect of secondary phase precipitate due to impinging slip and dislocation pileup.(3) The Tanaka-Mura theory of fatigue-crack-initiation from notches was applied to simulate the crack initiation from another crack tip.(4) The coalescence of random initiated micro-cracks was simulated once they intersected with each other and a macro-crack was finally formed.The calculated results were in good agreement with the experimental data which verified the rationality of the simulation model.The applicability of the proposed model for treating fatigue-crack-initiation life in engineering structures was preliminarily achieved.
Application of wide angle diffused meridian passage with three-dimensional design concept
WANG Lei
2012, 27(12): 2786-2791.
Abstract PDF(467KB) icon1798 icon1421
Abstract:
Based on the three-dimensional design concept, a design method of low pressure turbine nozzle blade in wide angle diffused meridian passage was presented. The result indicates that smaller inner wall angle of divergence and bigger outer wall angle of divergence should be used to keep the flow stability near inner wall when design meridian passage, meanwhile make the vane lean to pressure side to increase the reaction near inner wall and keep the lean direction near outer wall to decrease the trend of passage vortex moving to mean radius for decreasing or eliminating the possibility of flow separation and increasing flow stability near the outer wall, and so decreasing the loss. This method has been applied and verified on a real aero-engine low pressure turbine.
Effect of hub rotation on conner flow field of an annular cascade
YU Chun-hua, JIANG Hong-de, YUAN Wei, LI Shao-bin
2012, 27(12): 2792-2798.
Abstract PDF(1693KB) icon2034 icon1252
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The effect of rotating speed on corner flow separation and its mechanism has been investigated by numerical simulation on an experimental annular cascades.The results show that the positive rotation of hub wall would reduce blockage in cascades.The mass flow rate of cascades is improved when the rotation speed increase.The 3-D hub corner separation can be removed by the rotation speed increasing.The detail analysis results show that the increasing of the leakage mass flow rate is the key reason for the corner separation removed.
Numerical simulation on separation control by filleting casing tongue of after-burning fuel pump
XUE Mei-xin, PIAO Ying
2012, 27(12): 2799-2804.
Abstract PDF(1366KB) icon1554 icon1168
Abstract:
Unsteady flow field inside an after-burning fuel pump was investigated by large eddy simulation method with the dynamic subgrid-scale stress model.The cavitation erosion mechanism of the original casing tongue was discussed, and then, the characteristics of transient flow around the casing tongue and pump performance were investigated under different filleting radius conditions.The results show that the flow separation at the original tongue under small flow-rate condition brings strong shearing vortex which induces cavitation.The separation attachment location formed by the vortex shedding agrees well with the real cavitation damage core region.Under small flow-rate condition, tongue filleting results in diversion vortex in the diffuser tube, which suppresses the flow separation around the tongue face as well as the attached shearing vortex, while the 4mm filleting radius case can avoid tongue cavitation.Within the design flow-rate, tongue filleting raises the pump head, and the smaller the flow-rate, the larger the head increase amplitude, which reaches 3% under small flow-rate condition.
Ultra-high-lift low-pressure turbine blade boundary layer passive control in different flow conditions
ZHANG Bo, LI Wei, LU Xin-gen, ZHU Jun-qiang
2012, 27(12): 2805-2813.
Abstract PDF(1570KB) icon1635 icon1201
Abstract:
Effects of Reynolds numbers, free stream turbulence intensities (FSTI) and angle of attack on the steady boundary layer development of an ultra-high-lift low-pressure turbine blade were investigated.The three different types of passive separation control devices, which were dimple, cylindrical wire and rectangular trip, were investigated to further improve the blade performance.Numerical simulation results show that:as the Reynolds increases the profile loss decreases;as the FSTI increases, the profile loss decreases, and then increases;as the attack angle increases in the negative direction, the profile loss decreases, and then increases; as the attack angle increase in the positive direction, the profile loss increases rapidly;when the Reynolds number and the FSTI changes, it is found that the dimple can suppress the separation bubble better and when the attack angle changes, it is found that the wire and strip can suppress the separation bubble better.It is also found that the three passive control methods hasten the transition process so the separation is suppressed, but it increases the turbulent wetted area.
Analysis of stress process for face gear with arcuate tooth pinion
FANG Zong-de, LI Jian-hua, PENG Xian-long, CAI Xiang-wei, ZHANG Zuo-pin
2012, 27(12): 2814-2819.
Abstract PDF(1339KB) icon1677 icon1292
Abstract:
In order to provide theoretical justification for tooth surface contact strength and tooth root bending strength design of face gear with arcuate tooth pinion, the rules that the tooth surface contact stress and tooth root bending stress of the face gear with arcuate tooth pinion vary with load and errors of alignment were studied.Theory of elasticity and stress influencing matrix of finite element method were applied respectively in the contact stress and bending stress calculation based on tooth contact analysis (TCA) and load tooth contact analysis (LTCA).The calculation was illustrated by a numerical instance.The results show that the contact strength and bending strength under heavy load are determined by the strength in the single tooth meshing area, the misalignment error of axial displacement and shafts angle increase the contact stress and bending stress respectively, and the misalignment errors of shafts angle and distance between axes have little effect on the contact stress, but the misalignment errors of axial displacement and distance between axes are able to reduce the bending stress, and compared to face gear with spur pinion, the contact stress and bending stress of face gear with arcuate tooth pinion are significantly smaller.
Solution of dynamic characteristics of journal bearing based on two phase flow theory
SUN Dan, ZHANG Chu, GUO Rui, YANG Jian-gang
2012, 27(12): 2821-2827.
Abstract PDF(680KB) icon2019 icon1482
Abstract:
The computational fluid dynamics(CFD) two phase flow and dynamic mesh technologies were applied to the numerical calculation of dynamic characteristics of journal bearing.A new journal bearing dynamic characteristic solving model using the two phase flow theory of CFD model was established.The two phase flow theory of computational fluid dynamics for the journal bearing dynamic characteristics did not need to define the oil film rupture boundary condition, and it can generate more complementary and more accurate flow information.The pressure distribution characteristics of the sliding bearing were compared, and the cavitation characteristics and the effects of the journal bearing were calculated.Finally, the effect of the two phase flow theory of CFD model on dynamic characteristics of journal bearing was analyzed.Calculation results show that the cavitation ratio increases significantly with the increase of rotating speed, eccentricity, and vaporization pressure, and decreases slowly with the increase of inlet pressure.Using two phase flow, calculation results also show that the direct stiffness increases, the cross stiffness decreases and the direct and cross dampings decrease.The deviation between the single phase flow and the two phase flow increases with the increase of eccentricity.
Leakage flow of pocket damper seal at high rotational speed
LI Zhi-gang, LI Jun, FENG Zhen-ping
2012, 27(12): 2828-2835.
Abstract PDF(1386KB) icon1811 icon1261
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The leakage flow characteristics of the pocket damper seal(PDS) was numerical investigated with consideration of the rotor growth effect at the high rotational speed using finite element analysis/computational fluid dynamics(FEA/CFD).The leakage flow rate of the experimental pocket damper seal with 0.13mm clearance at three different pressure ratios and three different rotational speeds was conducted.The accuracy of the present numerical approach was demonstrated by comparison of the experimental data and numerical results without consideration of rotor growth.Six pressure ratios and six rotational speeds were utilized to analyze the leakage flow characteristics of the pocket damper seal.The influence of the higher pressure and higher rotational speed on the leakage flow characteristics of the pocket damper seal was analyzed.The obtained results show that for pressure ratio down to 0.26, the leakage flow rate of the pocket damper seal increases with the decreasing pressure ratio.The leakage flow rate of the pocket damper seal obtains the maximum value when the pressure ratio equals to 0.26.The Mach number of the leakage flow obtains 1 at the last fin clearance when the pressure ratio is 0.26.At the higher rotational speed, the leakage flow rate of the pocket damper seal decreases with the increasing rotational speed with and without consideration of the rotor growth effects.The rotor growth effect should be taken into account to predict the leakage flow rate of the pocket damper seal when Mach number exceeds 0.35.
Experimental investigation of miniature flexible joint thrust vector characteristics
ZHANG Xiao-guang, LIU Yu, REN Jun-xue, YANG Jing-xian, YANG Wei
2012, 27(12): 2836-2841.
Abstract PDF(714KB) icon1684 icon1267
Abstract:
Two miniature flexible joints which have the same structure but different elastomer materials (natural rubber and silicone rubber, respectively) were designed.Axial deflection variation due to vessel pressure was tested.Spring torque at various temperatures (-50～70℃) and vessel pressures were also studied.In addition, the reinforcement hoop compressive stress at the inner radius was measured to examine the applicability of existing empirical formulas for miniature flexible joints.Results show that the axial compressive stiffness increases slightly nonlinearly with the vessel pressure, while the spring rate keeps almost constant over the vector angle range from 0°to 6°.Spring rates of different flexible joints experience different variations as the vessel pressure increases.The temperature shows a pronounced effect on the spring rate.For the natural rubber elastomer flexible joint, the spring rate increases significantly at low temperatures.However in the silicone rubber elastomer case, the spring rate remains stable throughout the temperature range from -50℃ to 70℃.The stress empirical formula which would cause give much higher stress due to pressure is not applicable to the miniature flexible joint.
Fault diagnosis method for liquid-propellant rocket engines based on the dynamic cloud-BP neural network
LIU Yin-jie, HUANG Qiang, CHENG Yu-qiang, WU Jian-jun
2012, 27(12): 2842-2849.
Abstract PDF(1070KB) icon1802 icon1240
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A fault diagnosis method for liquid-propellant rocket engines was proposed based on the dynamic cloud-BP(back propagation) neural network in the way of the integration of cloud model and BP neural network. The Cloud transform method was used to identify the network configuration and to extract the cloud features. And a unit time-delay was also introduced into the input layer to describe the dynamic characteristics of the engine. Results with test data show that the method can isolate the existed 3 fault modes precisely. A 0 expectation, 0.2 standard deviation noise was used to simulate the entironmental noise and stochastic noise, and the method can still detect and classify the fault accurately acount to lasting-rule. The method can run in real-time with the single processing time being 1.124×10-4s.
Research on aircraft engine component-level models based on GasTurb/MATLAB
ZHANG Shu-gang, GUO Ying-qing, LU Jun
2012, 27(12): 2850-2856.
Abstract PDF(991KB) icon5846 icon2046
Abstract:
Aircraft engine component-level models were developed in MATLAB using the dynamic link library technology based on GasTurb which is an aircraft engine performance analysis software.An aircraft engine component-level model library consisted of 22 models including turbojet, turbofan, turboshaft, and turboprop engine types was built in Simulink.Then the seamless transition was achieved from GasTurb to MATLAB.The application example and simulation results verified the validity and high customizability of the models.The interaction barrier between performance analysis and control system development was eliminated and a flexible simulation platform was provided for the future research on engine control and fault diagnosis.

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