2016 Vol. 31, No. 7

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Current investigation progress of plasma-assisted ignition and combustion
HE Li-ming, LIU Xing-jian, ZHAO Bing-bing, JIN Tao, YU Jin-lu, ZENG Hao
2016, 31(7): 1537-1551. doi: 10.13224/j.cnki.jasp.2016.07.001
Abstract PDF(1374KB) icon1512 icon640
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The basic principle of plasma-assisted ignition and combustion was introduced, and three pathways of plasma-assisted combustion, i.e.: heating enhancement, kinetic enhancement and transport enhancement, were summarized. The latest research achievements in application verification, action mechanism and numerical simulation of plasma-assisted combustion in the world, especially in domestic fields, were reviewed. Four research directions of plasma-assisted combustion were put forward, including: plasma-assisted ignition and combustion mechanism, coupled multi-field simulation, test and diagnosis investigation, and other scientific and technical issues concerning plasma-assisted ignition and combustion application in aviation engine, respectively. In the meantime, some suggestions on these research works were presented below: to quantitatively study the three effects of plasma-assisted ignition and combustion, and established the relationship between each effect and ignition and assisted-combustion characteristics; to build detailed kinetic mechanism model of plasma-assisted ignition and combustion; to develop new testing techniques of plasma-assisted ignition and combustion using advanced test and diagnostic facilities; to consider the adaptation issue when plasma-assisted ignition and combustion were applied into various types of combustion chambers of engines, especially the problem of light weight and miniaturization of plasma power supply.
Analysis on detonation pressurized combustion characteristic of reformed gas
WU Sen, LIU Qian, ZHENG Hong-tao
2016, 31(7): 1552-1561. doi: 10.13224/j.cnki.jasp.2016.07.002
Abstract PDF(1140KB) icon848 icon541
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In order to improve the thermal efficiency of gas turbine, an idea of effective combination of chemically recuperation (CR) with continuously rotating detonation pressurized combustion (CRDPC) was put forward. The effects of different forms of methane steam reforming on the heat recovery, the characteristics of pressurized combustion flow field and combustion performance of reformed gas were separately investigated through experimental and numerical researches. Results show that synergistic catalytic reforming has the best performance, with methane conversion rate of 46.51% and total enthalpy increase rate of 25.28%; the difference of reformed gas components has little effect on the detonation wave flow structure, but the increase of H2 mass fraction can improve the detonation wave propagation speed, and will intensify the precombustion in the contact discontinuity between fresh mixed gas and detonation products from the previous wave; under the premise of the same total pressure and stoichiometric ratio, when H2 mass fraction increases by about 1.1%, the inlet mass flow rate of premixed gasdecreases by about 4.5%, but the pressurized ratio of CRDPC decreases by about 6.0%, mainly due to the precombustion at the contact discontinuity.
Influence of biodiesel fuels on double swirler combustor performance and emissions
ZHANG Shan-jun, MA Hong-yu, JIA Chun-yan, JIN Ge
2016, 31(7): 1562-1568. doi: 10.13224/j.cnki.jasp.2016.07.003
Abstract PDF(962KB) icon1314 icon568
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An experimental study was conducted by using different mixing ratios of biodiesel fuels and diesel oil on an angle 90° double swirler combustor under simulative pressure condition to investigate the influence of biodiesel fuels on the combustor performance and emissions of gas turbine. The experimental results show that with the increment of fuel-air ratio, the combustion efficiency and NOx emissions increase, and the outlet temperature distribution factor(OTDF), radial temperature distribution factor(RTDF) and CO emission decrease; with the increment of biodiesel fuels-diesel oil ratio, the combustion efficiency and outlet temperature rise gradually drop, and the outlet temperature distribution factor and NOx emissions decreases first and then increases, and the radial temperature distribution factor and CO emission increase. With the increment of fuel-air ratio, the influence of biodiesel fuels changes and wears off. Different best biodiesel fuels-diesel oil ratios exist under different conditions of fuel-air ratio.
Effect of triple swirler with an outer ring on combustion performance
MO Da, CHENG Ming, ZHANG Cheng-kai, LIN Hong-jun, WAN Bin
2016, 31(7): 1569-1574. doi: 10.13224/j.cnki.jasp.2016.07.004
Abstract PDF(1026KB) icon967 icon550
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Triple swirler combustor with two different dome structures was investigated. The reference type was case 1, and the dome for the installation of outer ring was case 2. Numerical simulation was conducted for the flow field and combustion field of the two combustors. The combustion efficiency, smoke emission and exit temperature distribution of the two designs were measured by gas analysis and thermocouple under the same experimental conditions. The results showed that the combustion efficiency of the triple swirler was more than 99.7%. The flow field and temperature field distributions of the combustor with an outer ring were improved compared with the reference type; besides, the recirculation zone was plumper, and the effects of fuel mixing with air and fuel atomization were increased, and the outlet temperature distribution factor (OTDF) and smoke emission decreased by 36% and 25% respectively.
Experiment on influence of rotational speeds on labyrinth seal in compressor stator well
KONG Xiao-zhi, LIU Gao-wen, LEI Zhao, CHANG Ran, LIU Yang
2016, 31(7): 1575-1582. doi: 10.13224/j.cnki.jasp.2016.07.005
Abstract PDF(997KB) icon1226 icon591
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A rotating experiment rig with high rotational speeds was designed for the experiment of labyrinth seal in a compressor stator well. The influences of rotational speed (1500-8100r/min) on the working tip clearance, leakage characteristic, windage heating and swirl characteristics at different pressure ratios (1.05-1.30) were studied. Results show that the working tip clearance decreases and the mass flow rate declines with the increasing of the rotational speed. For low pressure ratios, increasing the rotational speed results in falling discharge coefficient, while the variation of discharge coefficient is relatively small for high pressure ratios. The windage heating of system increases as the rotational speed increases. Higher rotational speed gives much larger temperature rise. In addition, it is obvious that increasing the rotational speed leads to an increase of the swirl ratio at a specific radial location. However, the swirl ratio shows a decrease with increasing radius in the outlet cavity.
Computation on oil/gas separation performance of axialbreather with honeycomb structure
ZHAO Jing-yu, LIU Zhen-xia, LÜ Ya-guo, HU Jian-ping, REN Guo-zhe
2016, 31(7): 1583-1590. doi: 10.13224/j.cnki.jasp.2016.07.006
Abstract PDF(978KB) icon1084 icon602
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To study the oil/gas separation efficiency of axial breather with honeycomb structure in aero-engine, the oil/gas two-way coupled flow mathematical model and oil droplet impaction model with the wall were established. On the basis of verifying the rationality of flow resistance and oil/gas separation efficiency, the effects of the oil/gas separation performance of axial breather with honeycomb structure under different rotational speeds, mass flow rates and enviromental temperatures were calculated and analyzed. Results show that the increase of rotational speed will improve the oil/gas separation efficiency, while the increase of mass flow rate and enviromental temperature will lead to the decrease of the oil/gas separation efficiency. The honeycomb hole structure has little effect on flow resistance, but plays a major role in the oil separation of axial breather, where the contribution rate to the oil separation accounts for 80% or more.
Experiment on active clearance control system of high pressure turbine case with thermal deformation control
XU Yi-jun, MAO Jun-kui, WANG Peng-fei, ZENG Jun, WANG Dai-jun, GUO Wen
2016, 31(7): 1591-1601. doi: 10.13224/j.cnki.jasp.2016.07.007
Abstract PDF(1083KB) icon1391 icon670
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An experimental rig was established to get the performance of high pressure turbine case with thermal deformation control, serving as one of the most important parts of active clearance control (ACC) system. The distribution of temperature and radial deformation was measured to show how the turbine case responded to the temperature variation. In experiments, the coolant mass flow rate of inlet was changed, then the information of temperature and radial deformation was recorded. The rules of those parameters varying in axial and circumferential directions were also studied. It was found in experiments that the temperature of case could be controlled with impingements formed by the staggered jet holes in cooling pipes, which were placed outside the case. Therefore the thermal deformations were also controlled due to those jet impingements. With the increase of coolant mass flow, the response time of thermal deformation decreased significantly at first and then tended to be a certain value. The experimental results showed that the radial thermal deformation of case was substantially uniform. But uneven circumferential distribution of coolant jetting from the pipes can still lead to some non-uniformity of radial thermal deformation in circumferential direction. The maximum relative deviation was about 8.75%. At the same time, the case's temperature in axial direction was also affected by the coolant flow and structural parameters. The maximum relative difference of radial deformation in axial direction as 6.99% was observed in experiments.
Density experimental measurement and prediction method oforganic working fluid at high temperature and high pressure
ZHU Xiao-xun, XU Guo-qiang, QUAN Yong-kai, GAO Wei, SONG Gu, ZHAO Li-ping
2016, 31(7): 1602-1609. doi: 10.13224/j.cnki.jasp.2016.07.008
Abstract PDF(885KB) icon1072 icon597
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In order to solve the problem of the density measurement at high temperature and high pressure (HTHP), particularly in a supercritical state, a density measurement method at HTHP was designed and a density prediction method based on least square support vector machine (LSSVM) was proposed. This experimental method was used to measure the density at different (T, p) points firstly. Then, by learning from the experimental data, the density prediction model based on LSSVM (DP-LSSVM) could be established, and the continuous density values in T-p plane could be predicted by DP-LSSVM, especially in supercritical region where the density was difficult to measure by experimental means. Hexamethyldisiloxane was taken for example. By using the proposed method, the density function on T (600-850K) and p (1.3-2.25MPa) was obtained, and density in this area could be calculated. By comparing the calculation results with the published data, it is found that the relative error is only 2.4%, the effectiveness of the method is proved.
Effect of vapor injection rate on direct contact condensation of vapor
TANG Ji-guo, YAN Chang-qi, SUN Li-cheng, MO Zheng-yu
2016, 31(7): 1610-1616. doi: 10.13224/j.cnki.jasp.2016.07.009
Abstract PDF(1063KB) icon1121 icon600
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In order to investigate the effect of vapor injection rate on the direct contact condensation and evolution of vapor bubble surface, a high-speed video camera was employed to record the process of vapor condensation in the cold bulk at a certain liquid subcooling and different vapor injection rates. Experimental results showed that the bubble surface was relatively smooth throughout the whole slow process of bubble condensation when the vapor injection rate was less than 0.36m3/h. As the vapor injection rate increased to 0.74m3/h, surface wave appeared on the bubble surface and the bubble was split up into some tiny bubbles finally. When the vapor injection rate was larger than 1.13m3/h, surface wave on the bubble was very violent. The bubble instability was enhanced and the bubble would collapse into many microbubbles. Furthermore, with the increase of the vapor injection rate, the diameter of these microbubbles decreased and the average velocity increased. When the vapor injection rate exceeded 1.13m3/h, the bubble relative radius decreased and the change rate of bubble radius increased rapidly. The strong surface wave on the bubble could increase the bubble effective area of heat transfer significantly, resulting in a substantial enhancement of heat and mass transfer between vapor and cold bulk.
Shock control parameters with 3-D bump serials on sweep wing
TAO Yang, DENG Feng, LIU Guang-yuan, LIU Zhi-yong, ZHOU Ling
2016, 31(7): 1617-1622. doi: 10.13224/j.cnki.jasp.2016.07.010
Abstract PDF(1081KB) icon1004 icon535
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For sweep wing at transonic speed, 3-D bump serials as an effective way of drag reduction have simple structure, high efficiency and good robustness. Using global optimization algorithm to explore the design parameter space, the bump length,3-D bump spanwise design parameters for the influence of design parameters on the bump drag reduction effect were studied, finding that bump peak position and height of drag coefficient were the most sensitive, 3-D bump spanwise design parameters were not sensitive to the drag coefficient, and the bigger bump length and bump relatively spanwise length were more conducive to drag reduction. Based on this, optimization research into the sweep natural laminar wing with three different types bump serials were carried out. Through the optimization results, it shows that the drag divergence Mach number of sweep natural laminar wing can be increased by 3-D bumps serials, the larger average bump length and control area means the better effect; 3-D bump serials have good local control features, so that they can be used for partial inhibition of strong shock wave. 3-D bump serials have good effect on wave drag of conventional sweep wings wave drag, and can restrain the trailing edge flow separation induced by shock wave.
Pattern recognition with uncertainty for engine gas path diagnosis
BAI Lei, HU Jun, HUANG Shun-zhou, YANG Lei, HE Long
2016, 31(7): 1623-1629. doi: 10.13224/j.cnki.jasp.2016.07.011
Abstract PDF(876KB) icon1050 icon557
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For the ill-posed problem in aero-engine gas path diagnosis that the amount of measuring parameters is less than the amount of parameters to be measured, considering the uncertainty of both the measuring parameters and the theoretic model component characteristics, a fault diagnostic algorithm called variational weighed least squares was built using engine counterbalance technology and non-linear mathematical model. The algorithm was applied to an engine fault diagnosis. The results show that the difference between the measurements and calculation results can be obtained with the algorithm. At the same time, through modifying the original mathematical model by employing fault parameter corrections, the thrust maximum deviation between the calculation and measurement decreases from 8.25% to 1.66%, and the maximum deviation of fuel consumption rate from 6.25% to 1.50%.
Effect of bleeding on vortex region and starting performance of hypersonic inward turning inlet
LI Yong-zhou, ZHANG Kun-yuan, ZHANG Liu-huan
2016, 31(7): 1630-1637. doi: 10.13224/j.cnki.jasp.2016.07.012
Abstract PDF(1225KB) icon1201 icon583
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The effect of bleeding positions and bleeding slot forms on the vortex region and starting performance of hypersonic inward turning inlet was researched. The numerical results indicate that bleeding slot in the downwash region of inward turning inlet can obviously reduce the vortex region on the exit plane,and the bleeding slot in the separation region can efficiently promote inlet starting performance with less mass flow losses. Combined T slot has the best comprehensive bleeding efficiency. Compared with the original inlet, when the relative bleeding mass flow rate is 1.01%, the total pressure recovery coefficient of exit plane increases 12.8%, distortion index decreases 37% on the design point Mach number 6.0. The starting Mach number decreases from 5.2 to 4.1, and self-starting Mach number decreases from 6.2 to 4.8.
Numerical investigation for influence of powered effect on aerodynamic characteristics of civil aircraft take-off configuration
GUO Shao-jie, ZHOU Pei-pei, WANG Bin, SHI Xiao-tian
2016, 31(7): 1638-1648. doi: 10.13224/j.cnki.jasp.2016.07.013
Abstract PDF(1419KB) icon1072 icon552
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To investigate the influence of engine powered effect on aerodynamics characteristics of civil aircraft at takeoff condition, the method was employed to solve the 3-D compressible Reynolds-averaged N-S(Navier-Stokes) equations on a multi-block structured grid. Firstly, the turbine powered simulator model and a high-lift standard model were computed to validate the reliability of method; the excellent agreements between computational and experimental data demonstrated that the method was feasible to predict the engine power effect and flow field around a civil aircraft high lift configuration. Secondly, the engine power effect on aerodynamic characteristics of a typical civil aircraft were researched with flow-through and powered nacelles. Results show that aerodynamic characteristics based on powered nacelles differ obviously from flow-through ones. It's recommended that the engine power effect should be considered with powered nacelle in numerical simulation to gain more credible aerodynamic characteristics.
Linear instability analysis of the confluent shear layer and boundary layer flows
WANG Yi-fan, LIU Feng-jun, PIAO Ying
2016, 31(7): 1649-1657. doi: 10.13224/j.cnki.jasp.2016.07.014
Abstract PDF(1031KB) icon1367 icon619
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The linear stability theory (LST) was used to study the confluent shear layer/boundary layer flows. The mean velocity profile exhibited a superposition of the Blasius boundary layer and a shear layer expressed as hyperbolic tangent function. A global method with high order difference schemes was used to solve the Orr-Sommerfeld equation. The numerical procedure was validated by comparing the present results for boundary layer and shear layer with the published articles. The unstable wave modes associated with both shear layer and boundary layer were identified. On this basis, the interactions between the boundary layer mode and the shear layer were examined. Due to the presence of the shear layer, the neutral curve of the boundary layer mode moved to the upper left, resulting in decrease of critical Reynolds number. When the shear layer was brought close to the wall, the boundary layer unstable mode may be destabilized or stabilized, depending upon the disturbance frequency. In the confluent flow, the wall boundary layer has a stabilized effect on the shear layer mode, which occurs in the low frequency range.
Hydrodynamic stability and transition prediction with the chemical equilibrium gas model
FAN Yu, WAN Bing-bing, HAN Yu-feng, LUO Ji-sheng
2016, 31(7): 1658-1668. doi: 10.13224/j.cnki.jasp.2016.07.015
Abstract PDF(1392KB) icon1120 icon573
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For the real gas effects on the hypersonic boundary-layer flow stability of a flat plate, calculation was performed using the 7 species chemical equilibrium model, where viscosity and thermal conductivity were calculated using a mixing rule. The energy transport due to the species' diffusion was also taken into account. The flat plat base flow was computed under the conditions of Mach number of 10-20, wall temperature of 500-3500K, and flight altitude of 20-30.5km. The flow stability was analyzed, and the N number of relative growth rate of disturbance was given. The result shows that the second and third modes of instability waves are merged under high Mach numbers, taking their tolls on transition together. With the change of Mach number, the wall temperature, flight altitude, and variation trends of real gas instability model are almost the same as the perfect gas. Compared with the perfect gas model, real gas model's envelope line of N is lower, therefore affecting the transition prediction.
Oscillation characteristics of shock train in deflected center-line isolator
XIONG Bing, FAN Xiao-qiang, WANG Zhen-guo
2016, 31(7): 1669-1675. doi: 10.13224/j.cnki.jasp.2016.07.016
Abstract PDF(1045KB) icon970 icon546
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An investigation was conducted on the oscillation characteristics of shock train in deflected center-line isolator by using unsteady numerical simulation methods. The effects of back-pressure of isolator exit and expanded ratio of isolator on the oscillation characteristics of shock train were analyzed. The results show that the peak exit total pressure corresponds to the smallest displacement of the shock train leading edge and the valley exit total pressure corresponds to the largest displacement. The further research indicates that the self-excited oscillation of shock train in isolator only occurs under several back-pressure conditions and the shock train keeps steady under high back-pressure finally. Compared with the straight isolator, the shock train self-excited oscillation is prone to occur in deflected center-line isolator under the same incoming flow Mach number of 2.0. In addition, under the same back-pressure condition, the larger expanded ratio(eg.37%) means the lower oscillation frequency, amplitude and time-mean exit total pressure the flow field can be got when the self-excited oscillation phenomena occurs.
Suction control of boundary layer in S-shaped air intake and its influence on fan-stage performance
LIU Lei, CHEN Fu, SONG Yan-ping, CHEN Huan-long, LI Long-ting, QIN Yong
2016, 31(7): 1676-1685. doi: 10.13224/j.cnki.jasp.2016.07.017
Abstract PDF(1978KB) icon1011 icon554
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To investigate the evolution process of an S-shaped air intake exit distortion as well as its influence on the downstream fan-stage performance, a series of suction control for the single air intake were carried out at first. And then the best suction solution was selected and applied to the whole structure numerical simulation. Results show that the choked mass flow and the maximum efficiency of the fan-stage increase about 0.63% and 0.57% respectively after suction. In addition, the low energy fluid gathering at cross section bottom decreases ceaselessly as it gets to the tip station of the rotor hub. Since it attaches the tip of the rotor hub, the circumferential location of this low energy fluid migrates gradually along the opposite rotation direction and finally covers about 3 flow passages at the rotor blade front edge. Under effect of the air intake flow angle increase caused by the non-uniform air admission and the adverse pressure gradient in the rear part of the flow passage, serious flow separation occurs at the stator blade suction side but mainly exists at 50% span and below and weakens after suction.
Effect of freestream turbulence intensity on boundary layer flow control strategy of ultra-high-lift low pressure turbine
SUN Shuang, LI Wei, LEI Zhi-jun, LU Xin-gen, FU Yu, ZHU Jun-qiang
2016, 31(7): 1686-1694. doi: 10.13224/j.cnki.jasp.2016.07.018
Abstract PDF(1078KB) icon1298 icon531
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The flow control strategy combined upstream wakes and surface roughness on boundary layer development were investigated experimentally, and the effect of freestream turbulence intensity(FSTI) on the separations and transitions characteristic of the boundary layer in the flow control process was also studied.Result shows that the roughness strip with the ratio of roughness height and chord of 1.05×10-4 deposits between the velocity peak and separation onset can reduce the profile loss at freestream turbulence intensity of 0.4% and 2.2% in the low Reynolds number. At Reynolds number of 85000, the boundary layer momentum thickness in wakes passing region, wakes-induced transition region and natural transition region is affected by the FSTI, thus, resulting in a difference of the profile loss at the two operating conditions. However, there is no variation of the calmed region at different FSTI.
Frequency spectrum of unsteady pressure on rotor blade with rotor-stator interaction
ZHANG Xiao-bo, WANG Yan-rong, HUANG Zhong-shan, WANG Xiang-peng
2016, 31(7): 1695-1703. doi: 10.13224/j.cnki.jasp.2016.07.019
Abstract PDF(1373KB) icon1219 icon554
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The unsteady pressure on compressor rotor blade surface due to rotor-stator interaction was simulated by use of multi-channel model and phase lagged method based on single-channel model. The unsteady pressure on rotor blade surface in both time domain and frequency domain was analysed, and its higher order dominant frequencies were studied. The results show that the results of phase lagged method agree well with those of multi-channel method, the unsteady pressure peak frequencies of rotor blade are the BPF(blade passing frequency) and its harmonics, and the unsteady pressure amplitude of 2BPF is approximately 2 times of 1BPF above the middle position of blade height, this can be attributed to the wake transportation and shock oscillation. The results can provide a reference for investigating thoroughly the causes of high cycle fatigue failure of blade due to its vibration.
Coupling optimization design of aspirated airfoil with low Reynolds number in high altitude based on CST method
LI Jun, LIU Bo, YANG Xiao-dong, ZHANG Peng
2016, 31(7): 1704-1711. doi: 10.13224/j.cnki.jasp.2016.07.020
Abstract PDF(985KB) icon995 icon545
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A optimization design method was studied which coupled airfoil with aspirated scheme in the condition of low Reynolds number based on class shape transformation(CST) method. Research results show that:the coupling optimized design can make the total pressure loss reduce by 65%, the static pressure ratio increase by 0.02, and aerodynamic performance gets an obvious enhancement the in the condition of high altitude of 20km and low Reynolds number. Due to the penalty functions introduced, optimized airfoil aerodynamic performance was also improved in the condition of ground. To aspirate airfoil in the condition of low Reynolds number in high altitude, the design of increasing the load in the front of the aspiration location appropriately, and controlling the boundary layer by aspiration was optimum. And the optimal aspiration location was located in the region of the laminar bubble. Aspiration in the region of the laminar bubble can completely eliminate the laminar separation bubble. And the growth of the displacement thickness and momentum thickness can be inhibited effectively, and the momentum loss within boundary layer can be reduced significantly.
Influence of tip cascade structure on clearance flow in a compressor
CHEN Yi, WANG Jian-ming, MA Chi, CHEN Chao, SHEN Zhen-hua
2016, 31(7): 1712-1718. doi: 10.13224/j.cnki.jasp.2016.07.021
Abstract PDF(1258KB) icon1088 icon550
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A new tip cascade structure, consisting of some small blades on top of the conventional blades, was proposed to reduce the tip clearance flow loss in compressor. The numerical simulation was carried out to investigate influence of the tip clearance on the three-dimensional flow field in compressor cascades with moving end-wall. The simulation results show that the structure can improve the tip clearance flow condition. The leakage flow from pressure side to suction side on top of the blade is suppressed in terms of pressure relief and diversion. The strength of the leakage vortices is weakened effectively, and the diffusion loss of leakage vortices is reduced, so the aerodynamic performance of compressor will be improved, and the total pressure loss coefficient decreases by 1.158% compared with conventional blade in cascade exit.
Experiments of plasma flow control in a transonic axial compressor
ZHANG Wen-qiang, LI Ji-chao, LI Gang, NIE Chao-qun
2016, 31(7): 1719-1724. doi: 10.13224/j.cnki.jasp.2016.07.022
Abstract PDF(846KB) icon1116 icon512
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In order to improve the stall margin, experiments were conducted in a transonic axial compressor with dielectric barrier discharge (DBD) plasma actuators. Power supplies of sinusoidal alternating current (AC) and nanosecond (NS) pulse were chosen to provide excitation. Improvement of the stall margin and efficiency of the compressor at 40% and 65% of its design speed were compared and analyzed. At 40% of design speed, AC and NS can extend the flow range of the compressor, and AC excitation got a stall margin improvement (SMI) of 15.33%. Effects of both actuations were significantly weakened at 65% of the design speed and the effects of NS excitation were better than AC excitation. In terms of efficiency, NS excitation had a smaller impact and even slightly improved the efficiency at 40% of the design speed. Experimental results show that appropriate choice of power supply can help to improve the effects of stall margin improvement and provide reference for the design of DBD plasma actuator in a real compressor.
Dynamics analysis on ball bearing-mechanism with clearance and impact of cage
YAO Ting-qiang, WANG Li-hua, LIU Xiao-bao, HUANG Ya-yu
2016, 31(7): 1725-1735. doi: 10.13224/j.cnki.jasp.2016.07.023
Abstract PDF(1530KB) icon1180 icon512
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The three-dimensional contact dynamics models were established between balls and rings based on the geometric structural equations of ring races torus. Considering the three-dimensional dynamic models between balls and cage with clearance and impact, the multibody contact dynamics model of ball bearing-crank slider mechanism was constructed. The dynamic responses of ball bearing-mechanism, such as dynamic errors, relative motion trajectories of ring center and cage center, dynamic forces, were obtained. The motion accuracy and dynamics characteristics of ball bearing-mechanism were calculated by generalized-α algorithms under different rotating speeds, radial clearances of ball bearing and pocket guide clearances of cage. The calculated results show that the constraint force, dynamic errors, relative motion trajectories of ring center, cage and ring center, force of ball bearing, impact force between balls and cage all increase with the increasing of rotating speed and radial clearance. The relative motion trajectory between cage and ring, impact force between balls and cage, skidding of balls increase with the increasing of pocket guide clearance of cage.
Effect of foreign object damage on fatigue strength of stainless steel
ZHAO Zhen-hua, CHEN Wei, GUAN Yu-pu, GE Ning, LI Yong-jian
2016, 31(7): 1736-1743. doi: 10.13224/j.cnki.jasp.2016.07.024
Abstract PDF(1540KB) icon1162 icon545
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Based on air gun method, the foreign object damage (FOD) simulation test of stainless steel plate specimen was carried out. The macroscopic characteristics of damage were observed by three-dimensional numerical microscope,whilst the microscopic characteristics of damage were observed by scanning electron microscope. It was found that, the macro damage characteristics include compressional deformation, material shear loss, plastic deformation, etc., and the micro damage characteristics of damaged specimens involve micro cracks, plastic deformation,micro notches and lamellar structure,etc. By step loading test method, the high cycle fatigue test was made on FOD specimen. The test results show that the fatigue strength of FOD specimen deceases over 14% compared with non-damaged specimen. Fatigue strength decreases with the increasing damage size. The origin of the fatigue cracks lies in micro cracks or micro notches, indicating that FOD provides favorable conditions for fatigue crack initiation and growth.
Evaluation parameters and calculation methods of structural efficiency for whole aero-engine
YU Ping-chao, MA Yan-hong, WANG Cun, CAO Chong, HONG Jie
2016, 31(7): 1744-1753. doi: 10.13224/j.cnki.jasp.2016.07.025
Abstract PDF(964KB) icon1510 icon568
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Based on the functions and design requirements of aero-engine, the intensions of whole structure efficiency were elaborated in detail. Considering the load feature of whole structure, the evaluation parameters of whole structure efficiency were put forward from both the deformation resistance and dynamic environment adaptability. By establishing the normalization method of evaluation parameters such as rotor-to-stator clearance variation, strain energy distribution coefficient and sensitivity coefficient and the operation rule of structure efficiency coefficient, the analysis process of structure efficiency was defined. A structural efficiency assessment on low bypass ratio turbofan engine was conducted, by which the calculation process of the structure efficiency evaluation was given in detail. A structure scheme 2 was introduced based on the original structure scheme of the low bypass ratio turbofan engine, and then was compared with the original structure scheme based on the structure efficiency evaluation method. Result shows that the original structure is superior to the structure 2 both in the deformation resistance and the dynamic environment adaptability, and its structure efficiency coefficient is 0.11, which is higher than the structure 2, validating the practicability of the proposed structural efficiency evaluation method.
Natural frequency calculation and validation of fiber reinforced composite thin plate under cantilever boundary
XUE Peng-cheng, LI Hui, CHANG Yong-le, WEN Bang-chun
2016, 31(7): 1754-1760. doi: 10.13224/j.cnki.jasp.2016.07.026
Abstract PDF(1098KB) icon1021 icon547
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The natural frequencies of fiber reinforced composite thin plate (FRCP) under cantilever boundary condition were calculated and verified based on the way of combination of theory with experiment. Firstly, according to the structural features of FRCP, its theoretical model was established by considering the influence of fiber orientation. Then, the modal shape functions were expressed by orthogonal polynomial method and consequently natural frequencies of FRCP were theoretically calculated by Ritz method. Finally, TC500 fiber/epoxy composite thin plate was taken as a study object, and its frequency results were measured based on the established natural characteristic experiment system of FRCP. It was found by comparison that the natural frequencies calculated based on the orthogonal polynomial method had a good agreement with the experimental results, and the relative errors were within the range of 2.2%-9.7%, thus the effectiveness of above method had been verified.
High-precision measurement for the three-dimensional profile of gas turbine blade's leading edge
XIANG Zhi-cong, HU Zhong, BAI Yu-lei, BAO Hong, SHEN Zuo-chun, ZHOU Yan-zhou
2016, 31(7): 1761-1765. doi: 10.13224/j.cnki.jasp.2016.07.027
Abstract PDF(1060KB) icon1108 icon499
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In order to solve the bottleneck problem of high-precision measurement for the gas turbine blade's leading edge, a high-precision measuring device using phase measurement profilometry was designed for the three-dimensional measurement for the metal gas turbine blade's leading edge, based on the calibration accuracy improved by a kind of examining ball array. By the means of designing a multiple view data fusion algorithm and a recursive algorithm of nonlinear least squares, the three-dimensional profile of the blade's leading edge was measured with high precision, and the radii and centers of blade's leading edge from sixteen sections of blade's leading edge were fitted finally. The result shows that the comprehensive error of the blade's leading edge measuring system, methods and algorithms is ±0.03mm. The experimental device and methods are of high efficiency and accuracy, contributing to the progress for blades measurement and modeling techniques.
Analysis on penetration mechanism of oil jet lubrication for high speed rolling bearing
LIU Hong-bin, WANG Hai-yang, ZHANG Lei, SHI Yong-sheng, LIU Gong-ping
2016, 31(7): 1766-1776. doi: 10.13224/j.cnki.jasp.2016.07.028
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Abstract:
Based on aerodynamics, the airflow characteristics between bearing rings of high-speed bearings were researched. And the movement process of the lubrication oil between bearing rings was analyzed by establishing the mathematical model of gas phase flow and gas-liquid two-phase flow, so as to explore the penetration mechanism of the lubrication oil at a high DN value. The original data of the gas-liquid two-phase flow between bearing rings were obtained. And then, the VOF (volume of fluid) model was applied to numerical analysis on the gas-liquid two-phase flow of lubrication oil interacting with the airflow between the bearing rings, so as to catch the interface of the oil and airflow for studying the movement process, the distribution characteristics of lubrication oil and the effects of different parameters on oil volume fraction between bearing rings. The characteristics of the gas phase flow between rings of high-speed rolling bearing, the motion of lubrication oil in different speeds, the pressure and velocity characteristics of the gas-liquid two-phase flow and the effects of the initial airflow on the entrance of the lubrication oil were obtained. Results show that the effect and the interference of turbulence on the lubricating oil can be avoided by jetting oil onto the small end face of bearing near bearing inner race, which is conducive to the oil flow into the ring. The radial force of the air flow between bearing rings is beneficial to the movement of the lubricating oil, and with the increase of the speed, the force increases linearly. The initial state of the air flow affects the movement of the oil between bearing rings, and the oil has little effect on the movement of the air flow. At low speed, the pressure around the bearing change is small. When the speed is high, the periodic fluctuation pressure can not be ignored. At low speed, increasing oil volume flow can effectively raise the oil volume fraction between bearing rings , but at high speed, the oil volume fraction increase is not obvious by increasing oil volume flow.
Effects of supply pressure and temperature of oil on jet characteristics of lubricating nozzles for an aviation gears
ZHANG Rui-qiang, LIU Shao-jun, HU Xiao-zhou
2016, 31(7): 1777-1784. doi: 10.13224/j.cnki.jasp.2016.07.029
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Abstract:
In order to study the effects of supply pressure and temperature of oil on the diffusion angle and volume flow of jet oil sprayed by nozzles, both the two phase flow model and single phase flow model of the jet flow field of three dimensional nozzles were simulated by employing the large eddy simulation based on the FLUENT software. The rationality of the simulation results was demonstrated by the diffusion angle and volume flow of jet oil measured by the method of high speed visualization and weighting jet oil, respectively. The diffusion angle of jet was approximately zero within the scope of 100 millimeters along the axis apart from exit of nozzle and the volume flow of jet oil sprayed by nozzle increased nonlinearly when the supply pressure and temperature of oil varied between 0.1MPa and 1.0MPa, 50℃and 100℃, respectively.Results indicate that the diffusion angle of jet varies very little when the supply pressure and temperature of oil are varying under actual working conditions. The interaction between supply pressure and temperature has a significant effect on the volume flow of jet. There is a combination of the supply pressure and temperature of oil in contour line of volume flow of jet causing the least effect on volume flow of jet when the supply pressure and temperature of oil fluctuate in a small rage.
Experiment on acoustic characteristic of combustion chamber with acoustic resonators
YAN Yu, WANG Yan-tao, LI Jia-ming, LI Long-fei
2016, 31(7): 1785-1792. doi: 10.13224/j.cnki.jasp.2016.07.030
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Abstract:
In order to obtain influence of acoustic resonators on the acoustic characteristic of combustors, a model combustor with axial resonators was investigated experimentally in cold flow tests. The length, area ratio (section area of acoustic resonators divided by section area of combustor) and number of acoustic resonators were changeable in the experiments. It was found that the eigen frequencies of combustor decreased as the length of acoustic resonators increased. The results show that there exists an optimal acoustic resonator length for restraining 1T mode, which is independent from area ratio of acoustic resonators and a little smaller than quarter wave length of 1T mode. For restraining 1T mode, there also exists an optimal area ratio, which is 0.17 in present study. This also indicates that the distribution of acoustic resonators can dramatically affect the acoustic characteristic of a combustor, with acoustic wave decaying faster for more resonators at the same area ratio.

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