2016 Vol. 31, No. 6

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Development trend and characteristics of liquefied natural gas as the aviation fuel
LIU Ai-guo, CHEN Xin, CHEN Bao-dong, ZENG Wen, WANG Cheng-jun
2016, 31(6): 1281-1288. doi: 10.13224/j.cnki.jasp.2016.06.001
Abstract PDF(737KB) icon1515 icon1049
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The characteristics, development trend and existing problems of liquefied natural gas(LNG)as aviation fuel were analyzed. The differences among LNG, new and traditional aviation fuels were compared and analyzed by using the method of horizontal comparison in order to study the feasibility of LNG as the aviation fuel. The results showed that LNG had the advantages of wide source, good economy and strong adaptability compared with the new aviation substitute fuels. Compared with the traditional aviation fuel, LNG had large reserves which can be used for more than 100 years; it also had the advantages of wide flammability limit, low emissions of NOx only accounting for 1/4 of aviation kerosene; LNG had high energy density and lower cost, as the fuel cost is only half of the aviation gasoline and 1/3 of aviation kerosene. As a highly potential aviation fuel, LNG also can be used for cooling high temperature components of engine with cold energy. It was also pointed out that many work had to be done on matching power system with the aircraft structure, effectively transforming the fuel phase and researching the reaction characteristics of different fuels in the combustion chamber if LNG was used as an aviation fuel.
Pressure effect on the heat transfer characteristics of hydrocarbon fuel in the horizontal circular tube at supercritical pressures
ZHU Kun, XU Guo-qiang, JIA Zhou-xia, ZHANG Qi-jun
2016, 31(6): 1289-1296. doi: 10.13224/j.cnki.jasp.2016.06.002
Abstract PDF(963KB) icon1180 icon826
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Experiments were performed to investigate the pressure effect on the heat transfer characteristic of hydrocarbon fuel RP-3 in the horizontal circular tube at supercritical pressures. The mechanisms of heat transfer variation due to the radial thermal property, buoyancy and acceleration effects were discussed as well. The results showed that the heat transfer coefficient increased with the rising fuel bulk temperature. Under different pressures, the fuel thermal property variation's gradient led to the discrepancies of heat transfer and Nux peak points at the same dimensionless bulk temperature. The main reason of the heat transfer distribution was attributable to the radial thermal property gradient due to the temperature discrepancy between the tube inner wall and bulk fuel. However, the buoyancy and acceleration effect were limited in the experiment region. It showed that the dimensionless parameter Grq/Grth precisely reflected the heat transfer characteristic variation of the supercritical hydrocarbon in the horizontal circular tube.
Experiment on geometrical limits of gaseous detonation of ethylene/oxygen mixtures in narrow gaps
PAN Zhen-hua, ZHANG Peng-gang, ZHU Yue-jin, PAN Jian-feng
2016, 31(6): 1297-1302. doi: 10.13224/j.cnki.jasp.2016.06.003
Abstract PDF(869KB) icon1213 icon757
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To study the detonation limits of detonation, the gaseous detonation of stoichiometric ethylene/oxygen mixtures through narrow gaps with height of 1.0-4.0mm was experimentally studied by varying initial pressure of 0.004-0.04MPa. The soot film was utilized to record the cellular structure of detonation, and the high-speed cinematography was used to capture the flame. Results show that the smaller narrow gap height means the higher critical initial pressure for limits of detonation propagation. For unsteady detonation propagation modes near the detonation limits, including "stuttering" detonation and galloping detonation, the corresponding range of initial pressure becomes wider as the height of gap decreases. By considering both initial and boundary conditions, the ratio of hydraulic diameter to cellular width is found to be an appropriate sensitivity parameter to characterize the mixture. The range of this ratio for defining detonation limits in different narrow gap sizes is 0.326-0.403.
Analysis of leakage flow through finger seal based on porous medium
BAI Hua-lei, WANG wei, ZHANG Zhen-sheng, HU Guang-yang
2016, 31(6): 1303-1308. doi: 10.13224/j.cnki.jasp.2016.06.004
Abstract PDF(925KB) icon1211 icon744
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The finger seal was treated as porous medium. The pressure gradient was regarded as the source term of momentum equation. The coefficient in source term was confirmed by experimental results. A porous medium model for the leakage through finger seal was put forward by combining with the finer seal configuration. The computational results showed a good agreement with the experimental results, the model was proved to be practicable for simulating the leakage of finger seal. Flow field computational results show that the influence of the porosity of finger contact pad on leakage is great, and the pressure grads in the finger seal are mainly distributed below the inner diameter of aft cover plate.
Heat release model related to flame variation mechanism and modal analysis
WANG Kun, FANG Ai-bing, XING Shuang-xi, CUI Yu-feng, NIE Chao-qun
2016, 31(6): 1309-1317. doi: 10.13224/j.cnki.jasp.2016.06.005
Abstract PDF(1106KB) icon1319 icon767
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Coupling relationship between flame variation and acoustic velocity variation was established by G-equation method for combustor with the central body,the mathematical function of combustion heat release model was obtained. In early work, the heat release model was usually derived with the premise of ignoring the combustion expansion effect and the influence of equivalence ratio or temperature on thermo-acoustic instability was studied discretely, This model was developed invoking the combustion expansion effect, which is very different from early work. Result showed that it was the turbulent flame velocity but not the combustion expansion effect the response of heat release strongly. When turbulent flame velocity was fixed, the density expansion rate had very weak influence on the magnitude of the transfer between the heat release rate and acoustic perturbation, and no influence on the phase at all; but when the turbulent flame velocity was changed, both of the magnitude and phase of the transfer function were strongly influenced. Then acoustic modal analysis with the heat release model was carried out to determine the natural frequencies and their corresponding growth rate. At last the influence of the equivalence ratio and inlet air temperature on combustion instability was discussed successively. The cloud chart of stable zones and instable zones were developed,which is very useful to understand and control thermo-acoustic instability.
Numerical simulation of two-phase flow and heat transfer in complex rotating multi-cavity system
LUO Lei, JI Hong-hu, SHI Xiao-juan
2016, 31(6): 1318-1326. doi: 10.13224/j.cnki.jasp.2016.06.006
Abstract PDF(1330KB) icon1133 icon723
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The numerical simulation of oil-gas two-phase flow and heat transfer of complex rotating multi-cavity system in aeroengine air system and lubrication oil system were studied, and the flow and heat transfer characteristics were analyzed. Mixture model and Eulerian model were used to calculate the velocity, pressure and temperature of a multi-inlet and multi-outlet rotating multi-cavity system of the typical small turbofan engine, which consists of cavities behind and in front of the fan disc, the front bearing chamber, and the cavity in front of the axial-flow disc. Result shows that under same calculation condition, the velocities of two models are similar; the pressures are slightly different only in cavity in front of the axial-flow disc, where the pressure of Eulerian model is 93% of the Mixture model; the temperature of Mixture model is higher, and the front and back bearing temperature of Eulerian model is 93% and 94% of Mixture model, respectively; Mixture model costs 63% of the time of Eulerian model in one iteration.
Flow and heat transfer characteristics for inter-layer liquid cooling of 3D-IC with staggered micro-pin fins
MA Dan-dan, XIA Guo-dong, ZHAI Yu-ling, LI Yun-fei, JIANG Jing
2016, 31(6): 1327-1334. doi: 10.13224/j.cnki.jasp.2016.06.007
Abstract PDF(963KB) icon1203 icon688
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The laminar flow and heat transfer characteristics of fluid were numerically investigated through uniform and double-side heat flux 3D-IC ( three-dimensional integration circuit) with interlayer heat-removal structure for heat transfer areas of 1cm2 and volume flow ringing from 36mL/min to 290mL/min. 3D-IC with rectangle micro-channels and staggered micro-pin fins for pitches of 200μm and structure heights of 200μm was analyzed. Results show that inter-layer liquid cooling of 3D-IC with staggered micro-pin fins has better heat exchange effect than that with rectangle micro-channels. For the heat flux density of 1.25MW/m2,the average temperature and maximum temperature of the heating surface are only 318.31,323.16K, decreased 12.31,20.14K than that with rectangle micro-channels at the volume flow of 290mL/min, corresponding to about total power of 250W and volume heat source of 8.3kW/cm3.
Numerical simulation on film cooling characteristics of heart shaped hole
XIAO Yang, JIN Tao, HE Li-ming, DING Wei, LV Zhi-hui, DAI Sheng-ji
2016, 31(6): 1335-1342. doi: 10.13224/j.cnki.jasp.2016.06.008
Abstract PDF(1202KB) icon1194 icon782
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A heart shaped film cooling hole was firstly presented to improve the cooling effectiveness of modern gas turbine. The flow field performance and cooling performance were analyzed through numerical simulation. The result of heart shaped film cooling hole was compared with that of cylindrical film cooling hole. The comparisons show that the heart shaped film cooling hole can reduce the strength of counter rotating vortex pair, thus the coolant-surface attachment is improved. For heart shaped film cooling hole, the expansion structure on the hole exit allows the coolant to flow along spanwise direction, resulting in a better spanwise averaged film cooling effectiveness than that of cylindrical hole. By comparing with cylindrical hole, the heart shaped hole increases the film cooling performance. The heart shaped film cooling hole shows enhancements of approximately 70.93%, 246.94%, 598.9% and 879.07% at blowing ratio of 0.5-2.0, respectively. In terms of heat-flux ratio, the hearted shaped hole shows the lowest heat-flux ratio at blowing ratio of 1.5, indicating that the hearted shaped hole provides the best film cooling performance at blowing ratio of 1.5.
Influence of low temperature plasma discharge zone length on ignition initiating
GUO Xiao-jing, ZHENG Dian-feng, YU Yong, ZHANG Hui-qiang
2016, 31(6): 1343-1350. doi: 10.13224/j.cnki.jasp.2016.06.009
Abstract PDF(1173KB) icon1178 icon732
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For the fixed length of low temperature plasma discharge zone with the same discharge zone gap, the volume size's influences on pulse detonation engine ignition initiating were studied. Propane was taken as fuel, air and pure oxygen as oxidant. The chemical reaction kinetics mechanism was fully considered in detail, and the low temperature plasma discharge zones were equivalent to high temperature and high pressure fire nucleus. Numerical simulations of the ignition initiating process were carried out by Fluent software. The lengths of the discharge zone of 20, 40, 60mm was comparatively analyzed. Results show that the low temperature plasma discharge zone equivalent to high temperature and high pressure fire nucleus is feasible, and complete ignition initiating process can be got; different lengths of discharge zone have strong influences on the initial flame form, the flame propagation speed and deflagration to detonation transition (DDT) time, but little influence on the detonation wave peak pressure.
Effects of incoming boundary layer on injection characteristics of a scramjet combustor
ZHOU Xun-huang, CHEN Rong-qian, YOU Yan-cheng, ZHU Cheng-xiang, HUANG Yue
2016, 31(6): 1351-1358. doi: 10.13224/j.cnki.jasp.2016.06.010
Abstract PDF(1161KB) icon1358 icon782
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Effects of incoming boundary layer on flow field characteristics and mixing performance of transverse jet in a scramjet combustor were numerically investigated by using Reynolds-averaged Navier-Stokes. Results indicate that there is a critical dynamic pressure ratio for every specific flow status. Only when the injection dynamic pressure ratio is less than that value, increasing incoming boundary layer thickness could effectively improve the jet penetration depth and mixing efficiency. Otherwise, variation of incoming boundary layer rarely affects the jet penetration depth and mixing efficiency. For the cases studied, the critical dynamic pressure ratio was around 0.900. At the same dynamic pressure ratio condition, the thick incoming boundary layer cases were only 0.93 times the total pressure recovery coefficient of the thin cases. The friction loss of imcoming boundary layer is the dominant factor affecting the total pressure recovery of the scramjet combustor, and variation of incoming boundary layer thickness makes little influence on total pressure recovery induced by the jet and its downstream flow field features.
High temperature fatigue life model for single crystal nickel superalloy based on principal component analysis
WANG Rong-qiao, JIANG Kang-he, HU Dian-yin, JING Fu-lei, SHEN Xiu-li
2016, 31(6): 1359-1367. doi: 10.13224/j.cnki.jasp.2016.06.011
Abstract PDF(1039KB) icon1132 icon678
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Fatigue damage in single crystal nickel superalloys is closely related to crystallographic slip along definite crystallographic planes. Thus, it is physically motivated to consider these crystallographic planes as critical planes. The mesoscopic parameters on the critical plane are all connected to the viscoplastic constitutive model, leading to inevitable multicollinearity among them. To address this issue, principal component analysis was performed to eliminate the effect of multicollinearity and determine dominant damage factors. Furthermore, a life model was formulated based on the determined orthogonal dominant damage factors. Compared with the life model which is directly formulated by the original mesoscopic parameters, result shows that this model is much simpler with reliable and stable material constants. The life model is then validated with isothermal fatigue testing results of DD6 at 760℃ and 980℃. Most of the predicted lives are within the triple factor of the measured lives.
Excitation characteristics of rotor/stator-interaction flow field and resonant design of bladed disk
LI Lin, MA Hao-ran, WANG Pei-yi
2016, 31(6): 1368-1376. doi: 10.13224/j.cnki.jasp.2016.06.012
Abstract PDF(1239KB) icon1257 icon688
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Based on the computation and analysis of three-dimensional unsteady flow induced by rotor/stator-interaction, the characteristics of flow excitation to bladed disk were studied, including frequency-components and circumferential wave-components in the wake of stator. By combining the resonant condition of bladed disk, a design principle was given for determining the stator-structural period from the view of avoiding resonance, namely, the stator-structural period should ensure that in the wake excitation there was neither modal frequency-component of bladed disk nor circumferential wave-component corresponding to the nodal diameter of the bladed disk. The formula was given to predict frequency-components and circumferential wave-components in wake of stator, making it easier to determinate stator-structural period in design phase. It is shown by numerical analysis that this method can determinate the rationality (inducing the resonance or not) of stator-structural period without need of performing numerical simulation of three-dimensional unsteady flow induced by rotor/stator-interaction.
Analysis on torsional feature of continuous fiber reinforced metal matrix composite turbine shaft
SHA Yun-dong, JIA Que-yue, LUO Li, ZHAO Feng-tong, LUAN Xiao-chi
2016, 31(6): 1377-1384. doi: 10.13224/j.cnki.jasp.2016.06.013
Abstract PDF(988KB) icon1084 icon650
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To realized design and analysis of composite parts structural integrity, the low pressure turbine shaft was taken as the object of research. Firstly, four kinds of micromechanical methods were utilized to calculate the mechanical parameter of continuous filament reinforced metal matrix composite. Secondly,the calculated parameters of RVE (representative volume element) finite element model were taken as input and the mechanics analysis model of fiber reinforced metal matrix composite shaft was built. The optimal solution could be got by calculating the deformation and bearing capacity of continuous filament reinforced metal matrix composite shaft with torsion load and by comparing with the deformation and bearing capacity of shaft with different laminate schemes; in case of certain fiber volume fraction, the deformation of scheme 4 is the smallest, and the critical buckling torque of scheme 2 is the greatest.
Reliability analysis of hierarchical systems based on Bayesian network
LIU Yu, HAN Feng, YAN Kai, LU Xi-cheng
2016, 31(6): 1385-1392. doi: 10.13224/j.cnki.jasp.2016.06.014
Abstract PDF(1034KB) icon1211 icon655
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Reliability modeling of hierarchical systems is significantly difficult because of the complex system structures and imbalanced reliability information at different system levels. A Bayesian network reliability analysis methodology was proposed to model the reliability of binary-state hierarchical systems considering the combination of Bayesian network and Bayesian information aggregation approach to represent the failure relationship among system elements. An example illustrated that, the proposed methodology can significantly improve the accuracy of system-level reliability modeling and reduce the variances of the posterior failure distribution of system by considering the cascading failure dependency and utilizing all available reliability information throughout the system.
Investigation on disk containment of aero-engine turbine casing
TANG Jin, TANG Guang, XUAN Hai-jun, JIANG You-wei
2016, 31(6): 1393-1399. doi: 10.13224/j.cnki.jasp.2016.06.015
Abstract PDF(1003KB) icon1441 icon764
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To investigate an aero-engine auxiliary power unit turbine disk burst at the predict speed impact on the turbine casing containment, the casing containment test was conducted on a high speed spin tester. The prefabricating cracks were cut at three positions separated on the disk circumferential to make the disk burst at the predicted speed, the impacting process was recorded on the film by a hi-speed camera. The test results show that, the casing was penetrated and the disk fragments were successfully contained within the containment ring and sever plastic deformation was found in the containment ring. The numerical simulations were carried out using LS-DYNA to study the turbine casing containment, the simulation results show a good agreement with the test results. The results can be used as a reference for the engine disk containment design.
Predominant factor related to stress intensity factor range on creep-fatigue crack growth of nickel-superalloy FGH97
LIU Hao, BAO Rui, YUE Chen-yang, FEI Bin-jun
2016, 31(6): 1400-1407. doi: 10.13224/j.cnki.jasp.2016.06.016
Abstract PDF(1309KB) icon1108 icon588
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The scanning electron microscopy was adopted to identify the fracture features of specimen in FGH97, which had been tested under the conditions of stress-ratio of 0.05, 750℃ and various dwell times. It was found that, for dwell time of 90s, the fatigue striation feature gradually disappeared with the increment of the stress intensity factor range values, and the turning point of neglecting fatigue loads located at the medium stress intensity factor range evel. But the corresponding stress intensity factor range values located at the lower levels for 450s and 1500s dwell time. Based on the trinomial model including fatigue item, creep item and creep-fatigue interaction item, the time-dependent and cycle-dependent components were employed to describe the test data of creep-fatigue crack growth in FGH97. The proportions of contribution to crack growth rate (CGR) of the two components are significantly influenced by stress intensity factor range values at different dwell times. The model for describing the time-dependent crack growth rate is proposed according to the analysis results. Furthermore, the stress intensity factor range values, which could affect the predominant factor of time-dependent component or time-dependent and cycle-dependent component on CGR, are obtained at various dwell times.
A parallel magnetic low stiffness vibration isolator
DONG Guang-xu, ZHANG Xi-nong, LUO Ya-jun, YAN Bo
2016, 31(6): 1408-1416. doi: 10.13224/j.cnki.jasp.2016.06.017
Abstract PDF(1248KB) icon1249 icon634
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In order to suppress the low frequency micro-vibration, a parallel magnetic low stiffness isolator consisting of the carrier beam with ends clamped and a magnetic spring was proposed.The magnetic spring was constructed by four permanent magnet pairs,furthermore, those magnets of each magnet pair were assigned in attractive interaction and symmetrically distributed on the surface of the beam. The equivalent current method was employed to establish the model of permanent magnet, and then the magnetic force calculation between two permanent magnets was developed according to Ampere's force law. Finally, the approximate expression of the magnetic force was obtained by curve fitting. The calculation method of equivalent stiffness of the proposed isolation system was acquired based on the analysis of the equivalent stiffness of beam. By ignoring the nonlinear effects of the isolator, the isolation characteristic of the isolator was analyzed by numerical simulation. Results demonstrate that,compared with the traditional vibration isolator, the isolator discussed can effectively isolate the low frequency vibration of the structure. The natural frequency of the system can be reduced. It not only broadens the bandwidth of the isolator, but also improves the damping characteristics of the system; moreover, the peak of resonance is attenuated greatly.
Calculation method of stress intensity factor based on the three-dimensional stress field at the crack tip
JIA Xu, HU Xu-teng, SONG Ying-dong
2016, 31(6): 1417-1426. doi: 10.13224/j.cnki.jasp.2016.06.018
Abstract PDF(1212KB) icon1270 icon706
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An approach for calculating stress intensity factors was proposed based on the first several items of the theoretical polynomial solution of the elastic crack tip stress field in infinite body, and the stress intensity factors were calculated by fitting the finite element solution of elastic crack tip stress field in actual crack bodies. This method did not need assuming the stress and strain state at crack tip in calculated of stress intensity factors, and the calculated results were more in line with the actual stress and strain state in the three-dimensional crack bodies. First, the availability of this method was validated based on the theoretical solution of center-through-crack stress field in a two-dimensional infinite plate, and the fitting item of the polynomial function to determine the stress intensity factors was explored. Then by calculating the stress intensity factors of center through crack in two-dimensional infinite plate, embedded circle crack in three-dimensional infinite body and center through crack in three-dimensional finite thickness plate, the validity and rationality of the proposed method had been verified by comparative analysis with theoretical solutions of the infinite plate and infinite body, and also with the finite element solutions based on displacement extrapolation method and 1/4 point opening displacement method. Studies show that this method can reasonably reflect the actual stress and strain state of crack tip in three dimensional crack bodies, and the calculated stress intensity factors are more reasonable.
Effect of axial spacing between rotor-stator on vibration stress of blade
WANG Xiang-peng, WANG Yan-rong, TIAN Ai-mei
2016, 31(6): 1427-1434. doi: 10.13224/j.cnki.jasp.2016.06.019
Abstract PDF(1214KB) icon1114 icon697
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The effects of stator-rotor axial spacing on the vibration stress of rotor blade were investigated by numerical simulation method. With use of the CFD program, the unsteady flow of compressor rotor blade row under the action of the wake of the front stator vanes was simulated, then structural dynamic response analysis under loading with the dynamic pressure of finite element model, which was got by interpolation procedures, was presented. Results indicate that under the examined range of axial spacing, the rotor blade vibration stress decreases with the increase of axial spacing because the wake intensity is weakening along the direction of flow, which has a great contribution to the fluctuations of pressure of blade surface.
Aero-engine distributed control system topology optimization method
SONG Jun-qiang, TANG Li-li, PAN Mu-xuan, HUANG Jin-quan
2016, 31(6): 1435-1440. doi: 10.13224/j.cnki.jasp.2016.06.020
Abstract PDF(872KB) icon1439 icon631
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Improved NSGA (non-dominated sorting genetic algorthm) -Ⅱ was used to optimize the network topology of aero-engine distributed control system while setting the reliability and weight of the control system as subjects. Taking the former reliability evaluation method's shortcoming into consideration, a method was proposed. Results show that reliability and weight of the control system increase with the increasing of nodes added into the circle topology or the increase of fundamental cycle's number. But when the number of fundamental cycle is larger than two, weight increases quickly without obvious increase of control system reliability. So, the number of fundamental cycles in aero-engine distributed control system topology shouldn't be larger than two in order to keep a balance between the topology's weight and the reliability.
Performance optimization of aeroengine based on Fibonacci search method
YANG Dan-dan
2016, 31(6): 1441-1449. doi: 10.13224/j.cnki.jasp.2016.06.021
Abstract PDF(1226KB) icon1149 icon605
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The principle of Fibonacci search method for performance optimization of aeroengine was introduced. The total performance model of turbojet containing two ejectors with variable area and Mach number was established. This aeroengine was optimized in maximum thrust mode, minimum fuel consumption mode and minimum turbine inlet temperature mode in the area of optimization parameters by using Fibonacci search method. The process of applying Fibonacci search method into the optimization was illustrated. The optimization results on different height and Mach number were given. Results show that, the constrained boundaries satisfied by the optimized performance are closely related with the flight height and Mach number. Different flight heights and Mach numbers correspond to different optimal control strategies. In spite of the flight mission, the targeted steady state performance from the control based on this optimization method is the best. This optimization method is not only applicable to the turbojet engine, but also lays a certain foundation for optimal control of other types of aeroengine.
Real-time monitor and diagnosis of combustion system based on kernel principal component analysis
ZHU Fei-xiang, LI Ben-wei, ZHAO Yong, SONG Han-qiang
2016, 31(6): 1450-1459. doi: 10.13224/j.cnki.jasp.2016.06.022
Abstract PDF(1302KB) icon1170 icon635
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According to the shortage of gas turbine engine combustor condition monitoring method, fault location and incipient fault detection, the low-turbine exhaust circumferential temperature field data were utilized to study the deflection law of gas in turbine through flow region, and the normalized temperature field data were analyzed by taking advantage of kernel principal component analysis (KPCA) method. Based on two engines' fault data, the fault detection and identification for the combustor fault and thermocouple sensor were developed respectively. The method of combining exhaust temperature field deflection law with kernel principal component analysis method to study combustor camber fault and thermocouple sensor fault was proved to be effective. Results show that, this method improves the fault orientation level from combustion level to camber level for gas turbine engine combustor with loop tube camber.
Self-scheduled control method for aero-engine based on sum of squares programming of polynomial
WU Bin, HUANG Jin-quan
2016, 31(6): 1460-1468. doi: 10.13224/j.cnki.jasp.2016.06.023
Abstract PDF(1222KB) icon1203 icon656
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Given that existing LPV(linear parameter varying) controller design methods is for affine system but not for polynomial LPV system, a self-scheduled control method based on SOS(sum of squares)programming was put forward for the high pressure rotor speed and pressure ratio controller design.The state-space models were obtained under different rotor speeds by non-linear model, and then these state-space models were used to get engine LPV model by polynomial fitting method. A self-scheduled control structure was proposed to ensure no static error. Combining bounded real theory with SOS theory, the robust stability conditions of the closed-loop system were obtained as SOS constraints, leading to the SOS programming to get gain scheduled controller. LPV model and engine nonlinear model were both used to examine the controller. Results show that the settling time of the high-pressure rotor speed/engine pressure ratio control system is less than 2s, and the steady state error is less than 0.1 percent.
Flow field characteristics of the U-shaped throttling constant differential pressure valve
LI Jia, LI Hua-cong, FU Jiang-feng, WANG Shu-hong
2016, 31(6): 1469-1476. doi: 10.13224/j.cnki.jasp.2016.06.024
Abstract PDF(981KB) icon1031 icon570
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As the research object of a U-shaped throttling constant differential pressure valve, numerical simulation study was carried out based on three-dimensional modeling technology, the preliminary model of pressure valve was designed, then structured grid was divided by using periodic mesh. Finally the inner-flow performance was simulated and the flow field of the pressure valve was analysed, and then the performances between different pressure valve's output opening were compared. The inner flow state indicates: under different flux and opening, the pressure gradient is large because of area change, pressure drop is mainly concentrated around the break zone, and some low-speed ranges and secondary vortex flows move around. The predicted performance of the external characteristics shows that: for both different flow rate and different opening degrees at the same flow conditions, pressure difference is maintained at around 0.9MPa, meeting the design requirements. And pressure change has a similar trend at different degrees of opening, the greater opening means the larger pressure, and low flow is accordingly faster.
Effect on parafoil aerodynamic performance of leading edge
NIE Shuai, CAO Yi-hua, TIAN Si-ying
2016, 31(6): 1477-1485. doi: 10.13224/j.cnki.jasp.2016.06.025
Abstract PDF(1241KB) icon1017 icon596
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Two-dimensional and three-dimensional steady flow field of parafoils with profile based on Clark-Y and with different leading edges and arc-anhedral angles were numerically simulated without considering the impact of flexibility, so as to study the effect of leading edge and arc-anhedral angle on parafoil aerodynamic performance. Results show that while enhancing the glide performance, the leading edge cut leads to the decrease of lift coefficient and increase of drag coefficient, and the reduction of lift coefficient gets more severe with the increase of cut size; the lip located in leading edge cut can effectively reduces the profile drag of parafoil; the lift reduction of parafoil increases as the value of arc-anhedral angle gets larger; in addition, this modified LLT (lift line theory) model exhibits high accuracy within the range of small and median angles of attack.
Synthetical optimization design of rotor airfoil by genetic algorithm
WANG Qing, ZHAO Qi-jun
2016, 31(6): 1486-1495. doi: 10.13224/j.cnki.jasp.2016.06.026
Abstract PDF(1326KB) icon1478 icon606
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According to the flight characteristics of helicopter and working environments of rotor, a group of airfoil design states, objective functions and constraint conditions suitable to the medium utility helicopter were proposed. The airfoil optimization was accomplished at multi-objective, multi-state and multi-constrain based on the classical rotor airfoil SC1095 used in "black hawk" helicopter (UH-60A) by genetic algorithm. The optimized rotor airfoil had larger camber and maximum thickness compared with the SC1095 airfoil. Results demonstrate that the pitching moment coefficient decreases by 57.2%, maximum lift coefficient increases by 3.7% and drag coefficient decreases by 7.5%. Meanwhile, there are some improvements of optimized airfoil aerodynamic characteristics under unsteady conditions compared with SC1095 airfoil. The areas of drag divergence and moment divergence of optimized airfoil decrease. After that, a rotor blade is constructed by using the optimized airfoil,results indicate that the FM (figure of merit) is increased and blade pitching moment coefficient is decreased compared with the baseline blade composed by SC1095 airfoil.
Vibratory loads prediction of rotor with trailing edge flaps
LIU Shi-ming, YANG Wei-dong, YU Zhi-hao, WU Jie
2016, 31(6): 1496-1503. doi: 10.13224/j.cnki.jasp.2016.06.027
Abstract PDF(1101KB) icon1195 icon618
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A rotor aeroelastic model with elastic blade and rigid trailing edge flap and its load calculation method were developed. The inertial forces and aerodynamic forces of flap were described as generalized mass and generalized forces. The aerodynamic forces of the common airfoil were calculated with the unsteady/dynamic stall model, and those of the flapped airfoil were got from a coupled aerodynamic model corrected with experimental data. The nonlinear elastic deformation was considered by a large deformation blade model. The force integration method was used to predict the vibratory structural loads. The predicted results and the test results were compared to verify the aeroelastic model and the load calculation method. The results show the accuracy of the blade structure model is quite high. Vibratory loads of rotor can be calculated well with the aeroelastic model, the average error of flapwise moment is 9.1%. Prediction in the vibratory loads of blade with flap motion is implemented with corrected flapped airfoil aerodynamic model.
Flow field simulation and fuel regression rate analysis of HTPB solid fuel ramjet
LI Xin-tian, LU Xin, LI Yan-cheng, LIU Jun-yi, GAO Jing-jing
2016, 31(6): 1504-1510. doi: 10.13224/j.cnki.jasp.2016.06.028
Abstract PDF(1036KB) icon1144 icon612
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A fuel regression rate simulation model of solid fuel ramjet was constructed based on the conservation laws. With two-dimensional axisymmetric model and two-equation chemical reaction model, numerical simulations of HTPB (hydroxyl terminated polybutadiene) solid fuel ramjet flow field were performed and the influences of inlet air conditions on flow field distributions and fuel regression rate characteristics were analyzed. Results show that combustion flame layer is developed between the central oxygen region and solid fuel wall. The thickness of the combustion layer decreases and shifts toward the fuel wall with the increase of inlet air mass flow rate and total temperature. With the increasing axial location, the fuel regression rate increases sharply first and then increases slowly. At last, the fuel regression rate decreases quickly near the aft-mixing chamber. This trend matchs well with the experimental results of the reference. The average fuel regression rate increases with the increase of inlet air total temperature and air mass flux. An average fuel regression rate formula is fitted with the simulation results.
Design and numerical simulation of oxygen-hydrogen axisymmetric heater with multi-injector
LI Xuan, XU Xu
2016, 31(6): 1511-1520. doi: 10.13224/j.cnki.jasp.2016.06.029
Abstract PDF(1256KB) icon962 icon600
Abstract:
In order to meet the working requirement and achieve the uniform parameters of hydrogen-oxygen heater outlet in free jet test stand, the heater was designed into axisymmetric structure, seven injectors with coaxial shear type for injection were adopted. The three-dimensional flow field was calculated by using the CFD simulation software with the hydrogen-oxygen single step reaction model and the parameters under design conditions were obtained. The results demonstrate that: with the increasing ratio of the center nozzle and the periphery nozzle distance L to the injection panel radius R(L/R), the combustion efficiency first increases and then decreases; the injection panel temperature decreases with the growth of L/R, ultimately reache around 600K; the uniformity of oxygen substance concentration and total temperature in heater outlet remains unchanged with L/R approximately; the Mach number in the outlet mainstream is around 6, which can satisfy the working requirement. The good comprehensive performance can be achieved when the influence area of each injector is approximately equal. The velocity ratio of hydrogen to oxygen gets higher, the area completing combustion will be shorter, and the injection panel temperature increases. Compared with the single-injector heater and nineteen-injectors heater, seven-injectors heater is reasonable.
Static characteristics analysis of foil thrust bearing considering the rarefield gas effect
YAN Jia-jia, LIU Zhan-sheng, ZHANG Guang-hui, WEI Ji-qin
2016, 31(6): 1521-1529. doi: 10.13224/j.cnki.jasp.2016.06.030
Abstract PDF(1125KB) icon1117 icon595
Abstract:
A modified Reynolds equation considering the rarefield gas coefficient for the bump type gas foil thrust bearing was established based on the first-order slip velocity boundary condition. The coupled modified Reynolds and lubricating film thickness equations were solved using Newton-Raphson iterative method and finite deference method. The static characteristics including axial load capacity and lift-off speed were obtained. The effects of rarefied gas and bearing structural parameters on the static characteristics were analyzed and discussed. The results indicate that with the influence of rarefield gas, the axial load capacity decreases, and the lift-off speed increases. And the rarefield gas has a slighter effect under a higher operating speed and a larger foil compliance coefficient. When the assembled clearance is smaller than 10 μm, the lift-off speed increases rapidly with increasing of the assembled clearance of the foil thrust bearing. Therefore, the axial clearance should be controlled carefully in assembling the foil thrust bearing.
A viscous inverse problem method for turbomachinery three-dimensional blade profile
NING Fang-fei, JIA Xin-liang, JU Peng-fei
2016, 31(6): 1530-1536. doi: 10.13224/j.cnki.jasp.2016.06.031
Abstract PDF(1053KB) icon1111 icon558
Abstract:
A viscous inverse problem method used in turbomachinery blade aerodynamic design was presented. The proposed method could be used to directly solve the blade geometry according to the given objective surface pressure distribution or pressure difference distribution from pressure side to suction side. In the proposed method, the blade surface was considered as movable wall, and the movement of the blade wall was evaluated on the basis of the solution of the momentum equation along the normal direction of blade wall. Result shows that,the proposed method is quite robust and needs less computational resources because it is based on the steady RANS(Reynolds-averaged Navier-stokes) simulation, and it does not need viscous correction since the simulation itself is in the real viscous flow environment. Examples using the developed inverse problem method were presented. Verification results show that the proposed method can achieve the desired target in both single blade row and multi-blade row environment, and computational process has good stability and convergence.

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