2015 Vol. 30, No. 9

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Aero-derivative industrial gas turbine dual fuel lean premixed low emission combustion technology
WEI Shu-ming, SUO Jian-qin
2015, 30(9): 2049-2057. doi: 10.13224/j.cnki.jasp.2015.09.001
Abstract PDF(891KB) icon1193 icon808
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Development of aero-derivative gas turbine dual fuel low emission combustion technology was studied, and major technical approaches to the success of the development were summarized. Range of fuel-air ratio of dual fuel combustor, effect of fuel-air ratio on CO and NOx emission, and design of transition operation were discussed; considerations in designing dual fuel low emission combustion were summarized comprehensively. By study of a variety of dual fuel lean premixed fuel-air modules, as well as long-term and lasting research and development on combustion test, the result shows that, the designed dual fuel combustion can meet the requirements of low pollution in the range of 50%-100% operation, and such low emission combustion technology and design of transient operation are practicable and can be directly used into the typical product of aero-engine.
Heat transfer characteristics of rotor-stator cavity with small mass flow rate
LIN Li, WU Kang, TAN Qin-xue, REN Jing, JIANG Hong-de
2015, 30(9): 2058-2065. doi: 10.13224/j.cnki.jasp.2015.09.002
Abstract PDF(1058KB) icon1259 icon715
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Thermochromic liquid crystal (TLC) was used in the transient heat transfer experiments of rotor-stator cavity with central inlet and small mass flow rate. The effects of mass flow rate and rotation speed on rotary disk were studied. Results showed that, under the conditions concerned, changes of mass flow rate had a great impact on heat transfer in mid-radius and lower-radius region, and had a less impact on higher-radius region; increase of rotation speed intensified the heat transfer over the rotary disk; Nusselt number over the mid-radius and higher-radius region increased with radius when turbulent flow parameter was low; the experimental results were correlated by turbulent flow parameter and compared with results from Reynolds analogy, and the difference was less than 15%, verifying the applicability of Reynolds analogy on rotor-stator cavity to a certain extent.
Experiment on effect of initial pressure and narrow gap height on detonation initiation distance in narrow gap
ZHANG Peng-gang, PAN Zhen-hua, ZHU Yue-jin, WANG Qian
2015, 30(9): 2066-2072. doi: 10.13224/j.cnki.jasp.2015.09.003
Abstract PDF(908KB) icon1081 icon701
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Single detonation in stoichiometric ethylene/oxygen mixtures was experimentally studied at initial pressure (5-45kPa) to achieve change rule of detonation initiation distance (DID) of detonation wave in narrow gap. The narrow gap detonation tube was formed by the cross-section with width of 10mm, height of 1.0,2.2,2.9,4.0mm, and length of 1220mm. Detonation initiation position was decided by soot records and high-speed digital imaging. Effect law of initial pressure and narrow gap height on detonation initiation distance was achieved. The results indicate that: (1) detonation initiation distance is reduced with the increase of narrow gap height at initial pressure of 10-20kPa; (2) detonation initiation distance initially decreases with increase of narrow gap height and then increases at initial pressure of 25-40kPa, and increases at initial pressure of 45kPa with the increase of narrow gap height; (3) compositing the influence of initial pressure and the narrow gap height, non-dimensional empirical formula for detonation initiation distance varying with initial pressure and narrow gap height is achieved.
Simulation analysis of air conditioning system of civil aircraft
WU Cheng-yun, WANG Guang-wen, LI Ge-ping, XIN Xu-dong
2015, 30(9): 2073-2079. doi: 10.13224/j.cnki.jasp.2015.09.004
Abstract PDF(989KB) icon1270 icon845
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The mathematic models of civil aircraft air conditioning system (ACS ) main components were built, and corresponding simulation modules, together with cabin/cockpit heat load module etc were developed on the Matlab/Simulink platform. By applying the built component modules, the ACS simulation model was established. The flight test instrumentation was installed on domestic civil commercial aircraft ACS and the test was conducted. By comparison with the test data, it is found that the error of the simulation results is within 2%. This shows that high accuracy of the simulation module and valid simulation methods have been achieved. It is of great value in civil aircraft ACS design, optimization and airworthiness compliance/verification.
Numerical analysis on infrared radiation characteristics of two-dimensional S-nozzle with small offset
YU Ming-fei, JI Hong-hu, LI Ning, WANG Hao, SI Ren, LIU Jian
2015, 30(9): 2080-2087. doi: 10.13224/j.cnki.jasp.2015.09.005
Abstract PDF(1168KB) icon1323 icon716
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In order to reduce the infrared radiation of aircraft, and make the exhaust system match the aircraft afterbody, a kind of unconventional two-dimensional(2-D)S-nozzle was designed to suppress the infrared radiation characteristics. There was a small offset given that the nozzle's center line and the engine's axis were not collinear. Based on the distribution of temperature, pressure and species mass fraction of the two-dimensional S-nozzle obtained from CFD results, the infrared radiation characteristics of two-dimensional S-nozzle was calculated with reverse Monte-Carlo method, then analyzed and compared with axisymmetric nozzle. The results show that, the two-dimensional S-nozzle is capable of shielding the high temperature elements inside the exhaust system effectively, and the infrared radiation characteristics of the exhaust system can be further suppressed by 33%.
Application of pipeline network algorithm in turbine inner cooling blade heat transfer calculation
SHI Liang, XIE Ming, HAN Wan-jin, YAN Pei-gang
2015, 30(9): 2088-2099. doi: 10.13224/j.cnki.jasp.2015.09.006
Abstract PDF(1371KB) icon1034 icon728
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Based on the concept of pipeline network algorithm, the calculation procedure applicable to inner cooling channel heat exchange has been developed. Coupled with external flow field solver HIT3D, the Mark II blades condition 5411 test results were used to verify the validity of pipeline network procedure, showing that heat transfer coefficient and temperature had good agreement with the test values. On this basis, for the complex inner cooling channel flow paths of a certain type of high-pressure turbine rotor blade, a fluid network computing model was established. An exhaust film hole was added to the suction side of blade tip, and the two groups of adjacent passages of the front and rear serpentine channels were connected with three through tubes separately to balance the pressure. Retrofit design and prototype employed pipeline network procedure to calculate flow and heat transfer parameters. Results show that, under the same inlet boundary conditions of cooling air, the maximum temperature and the average temperature have decreased more than 10K as compared with prototype, and adverse conditions such as concentration of local high temperature on suction side have been improved. The improvement effect has been confirmed through full three-dimensional CFX simulation.
Mathematical modeling analysis of hollow fiber membrane onboard inert gas generation system
CAI Yan, LIN Gui-ping, ZENG Yu, PENG Long, SHEN Xiao-bin, SUN Bing
2015, 30(9): 2100-2107. doi: 10.13224/j.cnki.jasp.2015.09.007
Abstract PDF(986KB) icon1076 icon769
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Differential equations mathematical model was built up, and solved by orthogonal collocation method to study the onboard inert gas generation system (OBIGGS), some of the results were verified by experiments. Results show that, the nitrogen-enriched air (NEA) oxygen mass fraction decreases with increasing of feed air temperature, then increases when the NEA oxygen mass fraction to a minimum value; in condition of differential pressure between the feed air and exhaust gas is constant,the NEA mass flow rate of hollow fiber membrane increases gradually with decreasing of exhaust gas pressure; pressure drop of retentate gas and the NEA mass flow rate both increase with increasing of hollow fiber membrane length,mass flow rate of feed air and the NEA oxygen mass fraction are influenced by the NEA mass flow rate obtained from hollow fiber membrane air separation,when the NEA mass flow rate is larger, the mass flow rate of feed air and the NEA oxygen mass fraction of the both increase.
Theoretical model and experiment of convective heat transfer in microchannel heat sinks
ZHAI Yu-ling, XIA Guo-dong, JIANG Jing, LI Yun-fei
2015, 30(9): 2108-2114. doi: 10.13224/j.cnki.jasp.2015.09.008
Abstract PDF(1007KB) icon1104 icon713
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The characteristic of fluid flow and heat transfer in microchannel heat sinks was investigated theoretically and experimentally. Firstly, the theoretical model of convective heat transfer in the microchannel heat sink was presented. Secondly, the values of pressure drop and Nusselt number were measured and calculated based on the experiments. Furthermore, the experimental results were compared with those obtained from theoretical model, average error about 10%. Lastly, the conductive thermal resistance, convective thermal resistance and capacitive thermal resistance were also analyzed under different Reynolds numbers and aspect ratios of channel. Results indicate that,the convective thermal resistance plays an important role in the heat transfer performance of microchannel heat sinks, with the proportion about 90% when Reynolds number and aspect ratio of channel are 985 and 1, respectively; while the conductive thermal resistance can be neglected (less than 10%) under small Reynolds number, and the capacitive thermal resistance to total thermal resistance decreases with the increasing Reynolds number and aspect ratio of channel.
Experiment on performance of a hyper-combustor utilized in turbine based combined cycle engine
ZHU Zhi-xin, HE Xiao-min, XUE Chong, HONG Liang, QIN Wei-lin
2015, 30(9): 2115-2121. doi: 10.13224/j.cnki.jasp.2015.09.009
Abstract PDF(937KB) icon1667 icon733
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Experiments were conducted on a hyper-combustor of the turbine based combined cycle engine. First a model hyper-combustor rig and experimental system were designed, and then experiments were conducted to study the combustion performance including ignition characteristic, lean blowout characteristic and combustion efficiency under different inlet velocity coefficient, inlet temperature and fuel/air ratio(FAR). The test results show that the ignition equivalence ratio firstly decreases and then increases,lean blowout equivalence ratio and combustion efficiency increase with the turbo duct inlet velocity coefficient increasing from 0.10 to 0.25.The ignition and lean blowout equivalence ratio decrease and combustion dfficiency increases when the turbo duct inlet temperature increasing from 573K to 873K. Similarly the combustion efficiency increases when the bypass duct inlet velocity coefficient or temperature increases. The minimum ignition and lean blowout equivalence ratio obtained from the experiment is 0.984 and 0.6 respectively.
Thermo-physical properties for surrogate models of aviation kerosene
PEI Xin-yan, HOU Ling-yun, MO Chong-kang, DONG Ning
2015, 30(9): 2122-2128. doi: 10.13224/j.cnki.jasp.2015.09.010
Abstract PDF(908KB) icon1944 icon835
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Based on the liquid-phase product analysis of aviation kerosene RP-3, three kinds of surrogate models, including single-specie, three-species and 13-species surrogate were proposed. The investigations covered the temperatures ranged from 300 to 1000K under the pressures from 1 to 15MPa. The distributions of the four thermo-physical properties were calculated under supercritical pressure conditions with temperature rise and decrease in density, viscosity and thermal conductivity, as well as specific heat increase. Drastic changes of thermo-physical properties occurred near the pseudo-critical temperature, especially for the specific heat under the pressure of 3MPa. The variation in pressure will change critical temperature location and has a certain influence on distributions of density and thermal conductivity, as well as the peak value of specific heat. The heat sink of RP-3 calculated from the three-species surrogate is in good agreement with the experiments.
Experiment on combustion characteristics of n-heptane droplets in micro-tube
YAO Rong, LI Jun-wei, QIU Zuo-zhen, HUANG Jing-huai, WANG Ning-fei
2015, 30(9): 2129-2139. doi: 10.13224/j.cnki.jasp.2015.09.011
Abstract PDF(1501KB) icon1122 icon670
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To understand the effect of micro-tube on the droplet formation and combustion stability, the following researches were performed by using the n-heptane as fuel in 4mm internal diameter quartz tube. Firstly, without heating, the stability of the flame and quartz tube drips was studied. The results showed that without heating, quartz tube was easy to form droplets, and when the n-heptane volume flow rate was lower than 40μL /min, the flame stability was influenced by dripping easily, the evaporation rate of the droplets was mainly affected by the flame position under the influence of the effect of air volume flow rate; when the fuel volume flow rate was larger than 40μL/min, the flame stability was not affected easily by the dripping of droplet due to the formation of liquid film. Secondly, the influences of heating on the droplet formation and the combustion characteristic were studied. It was found difficult to form droplets when the n-heptane volume flow rate was lower than 60μL/min, and when the n-heptane volume flow rate was greater than 60μL/min, the droplet could drip, and film didn't appear when the wall temperature was 180℃. Droplet evaporation was greatly influenced by air velocity; under the influence of air velocity and the droplet dripping, the temperature of micro burner had a greater impact on evaporation rate of droplet. The flame was more easily formed under fuel-rich condition than fuel-lean condition. Hence, air velocity has strong impact on the tube wall temperature, the lower air velocity means the higher wall temperature, the higher evaporating rate of fuel droplet and lower droplets dripping frequency.
Applications of anisotropic unstructured mesh adaption insupersonic combustion simulations
ZOU Jian-feng, SHENG Dong, FANG Lei, ZHENG Yao
2015, 30(9): 2140-2150. doi: 10.13224/j.cnki.jasp.2015.09.012
Abstract PDF(2855KB) icon1233 icon666
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Anisotropic unstructured mesh adaption has been introduced and used in 2-D simulations of supersonic combustion in the DLR (Deutsches Zentrum für Luft-und Raumfahrt) scramjet combustion chamber. Three cases of non-reaction flow simulation with slip wall conditions, non-reaction flow simulation with non-slip wall conditions and reaction flow simulation (with nonslip wall conditions) were carried out. In the calculations, large gradient areas with anisotropic characteristics, such as shockwaves, jet-flows, boundary layers, and flames, were detected and well refined with anisotropic meshes. As a result, compared with the initial simulation using an isotropic mesh, element numbers were reduced by 36.2%, 36.4% and 36.8%, respectively, in case of slip conditions, nonslip conditions and reactions, meanwhile the accuracy and resolution in large gradient areas was even better. The results show high efficiency and high accuracy of anisotropic mesh approach compared with the isotropic mesh, for the problems with significant anisotropic characteristics such as supersonic combustion. It has been demonstrated that Hessian metrics based on Mach numbers can be used to generate anisotropic meshes for the supersonic combustion simulation.
Research on limiters of unstructured grid
LI Fang, SUN Wei-zhe, LIU Xin, XU Jin-xiu
2015, 30(9): 2151-2159. doi: 10.13224/j.cnki.jasp.2015.09.013
Abstract PDF(1248KB) icon1551 icon635
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Six limiters and methods of their parameters were researched, of which the adaptive VenkatakrishnanM limiter was able to balance the compression and dissipation of limiter by changing parameters adaptively. Numerical computations show that, limiters of unstructured grid are susceptible to neighbor set methods, and the common-face method has about 15% higher precision than the common-node one; under conditions of high Mach number, the compressive limiters have about 10%-40% higher precision than the dissipative ones; flow fields computed with the direction gradient method are more smooth than the augment method; the adaptive VenkatakrishnanM limiter is able to simulate complex supersonic flows.
Geometry regulating law of variable cycle engine during mode transition
ZHOU Hong, WANG Zhan-xue, ZHANG Xiao-bo, ZHANG Ming-yang
2015, 30(9): 2160-2166. doi: 10.13224/j.cnki.jasp.2015.09.014
Abstract PDF(1002KB) icon1251 icon608
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The inertial rotor dynamics and volume dynamics of variable cycle engine were considered. The influences of mode selector valve area, core driven fan stage inlet guide vane, low pressure turbine area, nozzle throat area and their different combined adjustments on variable cycle engine mode transition performance were analyzed and compared with the test data. The results indicate that the simulation model established can calculate the characteristic of variable cycle engine mode transition correctly. It is suggested that the core driven fan stage inlet guide vane should been closed/opened when the mode selector valve area is opened/closed during mode transition. The parameters can change more smoothly by adding reasonable regulation of low pressure turbine area and nozzle throat area.
Partially averaged Navier-Stokes method for simulation of supersonic flow over a ramped-cavity
LUO Da-hai, YAN Chao, WANG Xiao-yong
2015, 30(9): 2167-2173. doi: 10.13224/j.cnki.jasp.2015.09.015
Abstract PDF(1037KB) icon1156 icon547
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Partially averaged Navier-Stokes (PANS) model was adopted to numerically investigate the supersonic ramped-cavity flow. The objective of current study is to assess the capability of PANS method in the prediction of unsteady supersonic turbulent flow. Comparison of PANS, Reynolds averaged Navier-Stokes (RANS) and detached eddy simulation (DES) results with the available experimental data shows that: (1) velocity profiles, wall-pressure and skin-friction coefficient distributions predicted by PANS model with variable unresolved-to-total ratio of kinetic energy are consistent with DES results; and (2) both of PANS results with variable unresolved-to-total ratio of kinetic energy and DES results are in good agreement with the experimental data and superior to those predicted by RANS; and (3) unsteady Raynolds averaged Navier-Stokes (URANS) model predicts two dimensional steady geometries of free shear layer, while DES and PANS resolve more abundant flow structures; and (4) PANS model with constant unresolved-to-total ratio of kinetic energy cannot return to RANS model in the near-wall region despite it can resolve more scales of motion compared with RANS; and the predicted velocity profiles of upstream turbulent boundary layer mismatch the log law, thus downstream flow simulation deviates a lot from the experiment.
Initial flow of 2-D planer nozzle
ZHANG Huan-hao, CHEN Zhi-hua, JIANG Xiao-hai
2015, 30(9): 2174-2180. doi: 10.13224/j.cnki.jasp.2015.09.016
Abstract PDF(1429KB) icon1051 icon614
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Based on the compressible Navier-Stokes equation, the initial flow structures of a supersonic planar jet at Ma=1.4 were investigated numerically with use of large eddy simulation (LES) and combination of the high-order hybrid WENO/TCD schemes. The numerical results illustrate clearly the initial flow characteristics of a supersonic planar jet, such as the generation and evolution of the main vortex ring and shock structures. Since the vortex-induced shock pair appears in the main vortex ring, the interaction of shock with vortex can accelerate the instability of jet shear layer, making the first roll up location differ from the subsonic case of just downstream the vortex-induced shock pair. After the vortexlets formation, the subsequent interactions with the vortex-induced shock pair would lead to a significant shape deformation of shock and accelerate the instability of main vortex ring.
Mixing characteristics of supersonic mixing layer induced by forced vibration
ZHANG Dong-dong, TAN Jian-guo, LÜ Liang, WANG Qian-cheng
2015, 30(9): 2181-2188. doi: 10.13224/j.cnki.jasp.2015.09.017
Abstract PDF(1101KB) icon1382 icon541
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Through combining an experimental study with numerical simulation, an analysis of mixing characteristics of a supersonic mixing layer was carried out, which was influenced by forced vibration under the condition of convective Mach number 0.22. The indexes of momentum mixing, Reynolds stress and scalar mixing were adopted to assess the mixing efficiency of supersonic mixing layer. The results show that forced vibration has an important effect on the mixing efficiency. Compared with no vibration, forced vibration advances the instability position of mixing layer and enlarges the scales of rolled-up spanwise vortices, which can promote the mixing of upper and lower streams. Meanwhile, with forced vibration, both momentum and scalar are more fully mixed. The peak value of Reynolds stress increases by about 48% when the vibration frequency is 4500Hz and the momentum thickness increases by 120% at 160mm position downstream the trailing edge of thin metal plate.
Comparison and analysis of WENO schemes base on supersonic boundary layer transition
LIU Chao-yang, WANG Zhen-guo, SUN Ming-bo, WANG Hong-bo
2015, 30(9): 2189-2195. doi: 10.13224/j.cnki.jasp.2015.09.018
Abstract PDF(983KB) icon1236 icon586
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Large eddy simulations of the transition process in a supersonic flat-plate boundary layer at free-stream Mach number of 4.5 and Reynolds number of 10000 were carried out using high precision weighted essentially non-oscillation (WENO) schemes. The inviscid flux was discretized by fifth-order, seventh-order, ninth-order WENO schemes separately and the viscous flux was discretized by fourth-order center difference scheme. The temporal discretization was made by means of third-order Runge-Kutta with total variation diminishing(TVD). By imposing a pair of the most unstable oblique first-mode disturbances on the inflow boundary, the transition progress of the flow from laminar, transition process to full turbulence was compared using three WENO schemes. Results indicate that the fifth-order WENO scheme is more dissipative than the seventh-order and ninth-order schemes, so it's difficult to capture eddy and pulse in the flow field. The dissipation of ninth-order WENO scheme is small, enabling to capture smaller eddy and high frequency. To study a problem with high frequency fluctuation or capture fine eddy, it's advisable to use the scheme higher than seventh-order.
Influence on macroscopic stiffness of rotor mesostructure based on finite element method
CHENG Li, GAO Jun-yu, QU Ke, LI Shuai-ying
2015, 30(9): 2196-2202. doi: 10.13224/j.cnki.jasp.2015.09.019
Abstract PDF(977KB) icon1231 icon620
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A research thought of establishing the mapping function based on the rules of dynamics parameters of macroscopic system due to the non-linear behavior of mesostructure for rotor system was put forward which based on finite element method, and then the dimensions of rotor systems were reduced legitimately. By simplifying the rotor model of contact structure of rod bolt in a type of engine disk appropriately, the effects of inhomogeneous rod bolt preload on the rotor macroscopic stiffness under different eccentric states of disks were analysed with ANSYS, nonlinear characteristics of stiffness were obtained.Results show that, when the bolts are evenly preloaded, along with the change of preload forces,the variation trend of nonlinear characteristics is related to the eccentric angle alteration; when half of the bolts are loose, the eccentric angle is larger while the loose preload forces are smaller, and the nonlinear characteristics are more obvious.
Contact characteristics response analysis of blade-disc dovetail structure under rubbing condition
MA Hui, WANG Di, TAI Xing-yu, NAI Hai-qiang, WEN Bang-chun
2015, 30(9): 2203-2211. doi: 10.13224/j.cnki.jasp.2015.09.020
Abstract PDF(1495KB) icon1096 icon558
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Targeting a compressor dovetail structure, the finite element model of blade-disc based on software ANSYS was established. The pulse force was used to simulate the rubbing force under local rubbing condition and the effects of two rubbing conditions on contact characteristics of dovetail structure were analyzed. The first condition involved the influence of different rotating speeds on contact characteristics of dovetail structure when the intrusion was constant. The other condition involved the influence of different intrusions on contact characteristics of dovetail structure when the rotating speed was constant. The results show that the maximum contact pressure and the maximum sliding distance of dovetail structure increase with the rotating speed, the variation law of the maximum contact pressure becomes more complicated, but the variation law of the maximum contact sliding distance becomes gradually steady and the change of amplitude between the maximum contact sliding distance decreases. The maximum contact pressure and the maximum sliding distance of dovetail structure increases with the intrusions, but excessive intrusions will lead to the mutation of the maximum contact sliding distance. By analyzing the spectrums of contact pressure and contact sliding distance under different working conditions, it can be seen that the amplitude of multiple frequencies increase when these multiple frequencies are close to natural frequencies of the blade.
Finite element analysis of hard-coating composite structure considering strain-dependent characteristic
SUN Wei, LIU Ying, LI Hui
2015, 30(9): 2212-2218. doi: 10.13224/j.cnki.jasp.2015.09.021
Abstract PDF(981KB) icon1012 icon635
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On the basis of introducing the strain-dependent characteristic of hard-coating material, the dynamic characteristic solution theory of iterative finite element method was derived. Moreover, the processes of calculating natural frequency and vibration response were presented, which can be summarized as: the hard coating material parameters were corrected by the vibration response, and then the dynamic parameters were solved by the iterative solution program. At last, a cantilever beam coated with MgO+Al2O3 hard coating was chosen to display the effectiveness of the proposed method. Considering the strain-dependent characteristic of MgO+Al2O3 hard coating, the natural frequency and vibration response were obtained under different exciting levels and also compared with the relative values obtained by linear calculation. Results show that the hard-coating composite structure cantilever beam displays the soft nonlinear phenomenon, and the resonance responses reduce by 29%-48% compared with linear calculation correspondingly to different exciting levels. This shows that the strain-dependent characteristic of hard-coating material can promote the effect of vibration reduction.
Principle of exhaust valve ablation at an aero piston engine
ZHANG Hong-tao, MENG Xian-zhao, FENG Yan-peng
2015, 30(9): 2219-2225. doi: 10.13224/j.cnki.jasp.2015.09.022
Abstract PDF(902KB) icon1206 icon624
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Serious exhaust valve ablation occurred at an aero piston engine during operating process due to the domestic high lead content fuel. Through micro metallographic analysis about the new, served and ablated exhaust valves from these engines, and based on the engine structural design and actual operating environment, a conclusion was drawn. Too high operating temperature making damage to the anti-corrosion protection layer on the exhaust valve's sealing area is the primary cause of the exhaust valve ablation, and the lead from the high lead content fuel deposited on the sealing area making the exhaust valves in poor-cooling condition is the predominant cause of hotter exhaust valves. The corresponding solution could improve the exhaust valve's cooling condition and decrease their operating temperature by running these engines with low lead content fuel to reduce the lead deposition. The practice shows that the anti-corrosion layer has been well protected and the fault of exhaust valve ablation is fixed in these engines.
Effect of foreign object damage at different impact angles onhigh cycle fatigue strength of TC4 titanium alloys
BAO Zhen-qiang, HU Xu-teng, SONG Ying-dong
2015, 30(9): 2226-2233. doi: 10.13224/j.cnki.jasp.2015.09.023
Abstract PDF(876KB) icon1574 icon570
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Based on the air-gun impact test device, the foreign object damage (FOD) simulation test of TC4 titanium alloy plate specimens was conducted at different impact angles. The high cycle fatigue (HCF) strength of smooth and impact damage samples was obtained with the step-test method. The relationship among the impact angles, impact positions, macroscopic geometry of impact damage and HCF strength of the damaged samples was studied. Results show that, the effect of impact damages on the HCF strength at different impact angles is not the same. When the impact damage appears at the edge of sample, the maximum decrease of HCF strength occurs in the impaction of 30°; while the impact damages appear at the middle of sample, the maximum decrease of HCF strength occurs in the impaction of 60°. In most cases, impact notches at the samples' edge compared to impact pits at the sample's intermediate surface have a more seriously effect on the HCF strength. However, at the impaction of 60°, the impact pit damage has a more serious effect. The geometry of the impact damage to a certain extent can characterize the changes of the HCF strength severity of damaged sample.
Research on problem of deterministic stress coupling in transonic compressor
ZHAO Jun, LIU Bao-jie
2015, 30(9): 2234-2240. doi: 10.13224/j.cnki.jasp.2015.09.024
Abstract PDF(1033KB) icon955 icon541
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Two-dimensional steady/unsteady, and three-dimensional unsteady calculation programs were developed based on three-dimensional steady Denton program. Researches on deterministic stress coupling were conducted on two cases:two-dimensional transonic compressor cascade and three-dimensional single-stages transonic compressor near stall point. It is found that, there are some deviations from time-averaged value of solution and unsteady solution of time-averaged equations when deterministic stresses are applied to coupling processing. The deviation of the coupling error originated from three sources: spatial difference discrete,viscosity correlation terms,mixing-plane processing. In multi-row coupling cases,the influences of mixing-plane are vital. It has a vital effect on the coupling calculation results. The simple mixing-plane processing can't get an ideal effect.
Three-dimensional body-force model for effect on compressor performance of inlet distortion
YIN Chao, HU Jun, GUO Jin, YAN Wei, ZHANG Chen-kai
2015, 30(9): 2241-2250. doi: 10.13224/j.cnki.jasp.2015.09.025
Abstract PDF(1391KB) icon1023 icon591
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A three-dimensional model called compressor stability analysis code (CSAC) was preliminarily developed to assess the effect of inlet distortion on aerodynamic performance of compressor.By solving the three-dimensional compressible Euler equations with the source item, the annular flow field of compressor interior could be simulated.The blade force and power source item were calculated with the aerodynamic parameters extracted from the three-dimensional steady-state Navier-Stokes (N-S) solutions.The way for correlating the source item with inlet aerodynamic parameters was also given. The aerodynamic performances of NASA Rotor 37 under clean inlet condition were calculated and analyzed with this model,the result under clean inlet was also compared with three-dimensional steady-state N-S solutions under the same inlet conditions. The accuracy of this model was verified.Finally,the performance of Rotor 37 under steady circumferential total pressure distortion was simulated.Results show that,total pressure distortion not only reduces the performance and the stability, but also induces total temperature distortion at the exit of compressor rotor.The research shows this model can correctly reflect the effect of distortion on compressor with much less compute resources, proving that this model is a suitable tool for compressor distortion analysis in current period.
Influence of the U-shape inlet pipe on a centrifugal compressor performance
WANG Lei-lei, LAO Da-zhong, ZHAO Ben, LIU Heng, YANG Ce
2015, 30(9): 2251-2260. doi: 10.13224/j.cnki.jasp.2015.09.026
Abstract PDF(1567KB) icon983 icon522
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The effects of the U-shape pipe on a centrifugal compressor were investigated with experimental and numerical simulation methods. Compared with straight pipe inlet, the bend pipe resulted in a significant performance degradation of the compressor at the high mass flow rate. The pressure ratio and efficiency dropped by 10% and 18%, respectively. The numerical results show that the distortions of the static pressure and the total pressure were generated at the outlet of U-shape pipe. The pressure distortions were induced by the circumferential nonuniform geometry of downstream compressor volute. When transported to the upstream blade channels, the outlet pressure distortions encountered with the inlet pressure distortions. These coupled distortions changed the flow structure and inlet conditions in the impeller inlet, and also the mass flow rates distribution in the blade channels. The entropy increase existed at the distortion regions of the impeller. Meanwhile, the mean load of whole main blades increased about 8% due to the variations of the static pressure distribution at main blade surfaces.
Effects of rotating disturbance on aerodynamics stability of axial-flow compressor
MAO Zhi-ming, HU Jun, ZHANG Huan, YAN Wei
2015, 30(9): 2261-2270. doi: 10.13224/j.cnki.jasp.2015.09.027
Abstract PDF(1701KB) icon1101 icon566
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Experiments were carried out on a two-stage low-speed axial-flow compressor with a newly designed rotating disturbance generator, so as to study the influences of rotating frequency, disturbed sector and the number of disturbed cells on the compressor aerodynamics stability. The experiments show that the compressor experienced significant degradation in its stall margin when the disturbance rotated at the “dangerous frequency”, which didn't change at different disturbed sectors and cells. A two-dimensional incompressible model considering rotating disturbance was developed based on M-G model. This model can calculate the influence of rotating disturbance with different disturbed sectors and cells on the aerodynamic stability and stall process of the compression system. When analyzing by building a mathematical model for the experiment compressor and employing the two-dimensional incompressible model, it was found that the rotating disturbance will induce the modal wave and affect the compression system stall margin more severely if the rotating frequency was close to the rotating stall propagate frequency.
Analysis on thermal control method of satellite in orbit based on self-driven thermostatic valve with sensitive wax
GONG Meng-meng, WANG Jin, LI Yun-ze, WANG Jun
2015, 30(9): 2271-2277. doi: 10.13224/j.cnki.jasp.2015.09.028
Abstract PDF(916KB) icon1064 icon533
Abstract:
To improve the thermal control adaptability of spacecraft, a satellite single-phase fluid loop thermal control technology based on self-driven thermostatic valve with sensitive wax was presented. Then, two kinds of improved control strategies were proposed. One was the self-driven thermostatic valve with sensitive wax as the controlling object, the other was the combination control with mechanical pump and self-driven thermostatic valve with sensitive wax as the controlling objects. The mathematical model of self-driven thermostatic valve with sensitive wax, heat load, radiator and other components was built by lumped parameter method, temperature dynamic performance of this thermal control system was calculated by numerical simulation method under periodic disturbance of outer heat flux and step disturbance of heat consumption of electrical equipment when a satellite in the orbit. Result shows that,the thermal control strategy with combination of mechanical pump and self-driven thermostatic valve with sensitive wax can realize the precise thermal control of loop, which not only take the advantages of self-driven thermostatic valve to achieve the reliability requirements of the system and reduce energy consumption, but also overcome the disadvantage of self-driven thermostatic valve with sensitive wax, such as temperature limit and steady-state error.
Design of distributed control system and investigation on bus communication performance of a turbofan engine
TIAN Fei-long, GUO Ying-qing, LI Rui-chao, JIANG Cai-hong
2015, 30(9): 2278-2285. doi: 10.13224/j.cnki.jasp.2015.09.029
Abstract PDF(989KB) icon1657 icon623
Abstract:
A partially distributed engine control system was designed based on the centralized FADEC (full authority digital engine control) of domestic turbofan engine by geographical distribution principle. A reasonable classification of various signals in the control system was presented. According to communication requirement assessment for distributed turbine engine control, Time-triggered CAN (controller area network) bus was determined as the engine area network and the communication strategy was designed. TrueTime was exploited to develop a distributed control system simulation. Impact of network delay and data dropout on the engine performance was studied. The results show that bus utilization is 50% at 250kbit/s and 12.34% at 1Mbit/s, which meets the communication requirement. The network-induced delay of the time-triggered system is 12ms. It prolongs the rise time of high pressure rotor speed for 0.02s. However, the engine response is significantly slower under the random packet dropout, which should be taken into account at the design phase.
Simulation research on compartmental tank propellant management based on AMESim
SU Li-chao, LIU Jian-yong, ZHANG Cheng-liang, SHI Jing-cheng
2015, 30(9): 2286-2290. doi: 10.13224/j.cnki.jasp.2015.09.030
Abstract PDF(915KB) icon1344 icon517
Abstract:
According to the research on the method of multi-subjects dynamic modeling, an AMESim mechanical, hydraulic and control dynamic complicated model of propellant feed system based on the compartmental tank was established, and then numerical simulation was made on the dynamic characteristics of the propellant feed system under different working conditions. The results of dynamic change of the propellant, the comsumption rate and the centroid displacement of the propellant were obtained. The simulation results show that the dynamic change of the compartmental tank propellant is influenced by the compartments general layout, initial compartments volume, structure design, flight trajectory and etc, so the simulation model can provide guidance to improve compartmental tank overall and structure design.
ICT local inspection of solid rocket motor's defects
CHEN Qing-gui, LU Hong-yi, ZHOU Yuan, LI Shen, LI Peng, YU Guang-hui
2015, 30(9): 2291-2297. doi: 10.13224/j.cnki.jasp.2015.09.031
Abstract PDF(1063KB) icon1059 icon532
Abstract:
To inspect solid rocket motor's defects locally, local inspection scheme of solid rocket motor's defects was proposed for narrow fan-beam industrial computed tomography(ICT). Translation/rotation scan mode and rotation only scan mode were used to inspect solid rocket motor's defects locally. To demonstrate the effectiveness of local inspection scheme, narrow fan-beam ICT was used to inspect one solid rocket motor locally. Convolution backprojection algorithm and wavelet transform algorithm were applied to reconstruct ICT images locally. Results show that translation/rotation scan mode is effective for narrow fan-beam ICT to inspect solid rocket motor's defects locally, rotation only scan mode is not effective. For using projections outside the local defect area, the reconstructed image quality of convolution backprojection algorithm is better than that of wavelet transform algorithm. It is of great significance for improving the inspection efficiency of solid rocket motor's defects and for reducing the inspection cost.
Vibration mode and dynamical characteristics of helical planetary gear train
LIN He, WANG San-min, DONG Jin-cheng
2015, 30(9): 2298-2304. doi: 10.13224/j.cnki.jasp.2015.09.032
Abstract PDF(1218KB) icon1315 icon665
Abstract:
Helical planetary gear transmission was applied more extensively in high-speed and heavy load situations, as the vibration mode and dynamic characteristic had significant influence on vibration and noise reduction. Targeting the helical planetary gear transmission system, co-moving coordinate system was conducted, the multi-degree of freedom nonlinear dynamical equations including gyroscopic effect and backlash was derived, and the natural characteristic of the system was solved. The results show that helical planetary gear train has three typical vibration modes: axial translational-rotational coupled vibration mode (multiplicity r=1), translational vibration mode (multiplicity r=2) and planet vibration mode(multiplicity r=N－3,N>3); in consideration of mesh stiffness, backlash, general errors and external load, influence laws of mesh phase difference and excitation ways to dynamical coefficient have been studied, showing that mesh phase difference makes the dynamical coefficient increase; when stiffness fluctuation coefficient ζ=1.723, the system is bifurcated into 2-period sub-harmonic response, with the changes of excitation parameters, internal engagement turning into the chaotic state is earlier than external engagement.

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