2020 Vol. 35, No. 10

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Deformation and fracture patterns of sub-millimeter droplets under supersonic conditions
SHI Honghui, SHI Shun, LIU Chen
2020, 35(10): 2017-2027. doi: 10.13224/j.cnki.jasp.2020.10.001
Abstract PDF(3017KB) icon544 icon477
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Based on the deformation behavior and mechanism of droplet deformation under supersonic conditions, the deformation and fracture process of sub-millimeter water droplets(0.44-1.09 mm) under shock was observed in a horizontal shock tube. The shock Mach number range was 1.07-2.11. Using the schlieren method, in combination with the high-resolution high-speed camera to record the deformation and fracture characteristics of droplets under different crush modes, the droplet streak images of the bag-shaped crushing, multi-modal crushing, shearing and explosive crushing modes were obtained. The droplet pattern image was analyzed on the temporal and spatial relationship of the motion parameters of the droplet. The development law of the droplet deformation stage with different diameters, the dimensionless lateral deformation width of the droplet and the dimensionless windward surface displacement of the droplet with the dimensionless time were obtained. And the maximum dimensionless lateral deformation was obtained with different droplet breaking modes when the initial diameter of the droplet was the same. As for the width changes, the dimensionless transverse maximum deformation widths variation range of the bag-shaped, multi-modal and shear crushing modes was 1.15-1.61, and the dimensionless maximum transverse deformation widths variation range of the explosive crushing mode was 0.21-0.68.
Comparative analysis on methods for contact testing total enthalpy of high temperature and high speed flow
LONG Yongsheng, ZHU Xinxin, YUAN Jie
2020, 35(10): 2028-2035. doi: 10.13224/j.cnki.jasp.2020.10.002
Abstract PDF(2434KB) icon456 icon480
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There exist large errors in measurement of the total enthalpy of high temperature and high speed flow, such as engine tail flame, combustion heating and arc heater. The total enthalpy of high-temperature and high-speed flow was measured by using the enthalpy probe and the heat flux-pressure probe, respectively. The enthalpy probe was the mass suction water-cooled probe with optimized structure, and the heat flux-pressure probe was based on the Fay-Riddell formula. Results indicated that when the enthalpy ranged from 2.5 MJ/kg to 5 MJ/kg, the enthalpy error tested by the enthalpy probe was about 3.38% and the error tested by the heat flux-pressure probe was about 3%. The average enthalpy deviation tested by the enthalpy probe and the heat flux-pressure probe was about 4.65%. These two methods of testing enthalpy can be used to ensure the accuracy in the ground simulation test, which can reduce the error of the tested enthalpy and improve the simulation accuracy.
Experiment on laminar combustion characteristics of n-tetradecane
LIU Yu, WANG Jinduo, GU Wu
2020, 35(10): 2036-2045. doi: 10.13224/j.cnki.jasp.2020.10.003
Abstract PDF(4139KB) icon476 icon372
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The laminar burning velocity and Markstein length of n-tetradecane/air mixture were obtained under initial pressure of 0.1 MPa, initial temperatures of 420, 450 K and 480 K within a wide equivalence ratio range from 0.8 to 1.4 in a constant volume chamber, and the effects of initial temperature and equivalence ratio were analyzed. The results showed that the increase of initial temperature and equivalence ratio had little effect on the stability of the flame propagation images. Under the initial temperature of 480 K and equivalence ratio of 1.3, there was no crack or cellular structure in the flame. The effect that the increase of initial temperature can increase the flame propagation speed and promote the formation of flame front was observed, which was more significant in the lean mixture. With the increase of equivalence ratio, the Markstein length of n-tetradecane/air mixture decreased and the flame stability became worse. With the increase of temperature, the Markstein length decreased, and the unstretched flame speed and laminar burning velocity increased. In addition, compared with the laminar burning velocity of RP-3 kerosene, the laminar burning velocity of n-tetradecane was higher under most conditions.
Instantaneous and simultaneous PIV and OH-PLIF measurement for lean premixed swirl flame
ZHANG Jun, TU Xiaobo, CHEN Shuang
2020, 35(10): 2046-2055. doi: 10.13224/j.cnki.jasp.2020.10.004
Abstract PDF(10061KB) icon669 icon450
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To better study the flame flowfield and structure in lean and premixed swirling flames,a premixed swirling burner with strong confined combustor was designed,and the experimental instantaneous and simultaneous system of PIV (particle image velocimetry) and OH-PLIF (planar laser-induced fluorescence) was built. With this system,the measurement research was carried out in swirling flame under typical operating condition,meanwhile time-averaged and instantaneous simultaneous flame velocity flowfield and OH distribution structures in multiple sections were obtained. Results showed that multiple flame reaction zones existed in the bottom corners of combustor under condition of unsteady combustion at low equivalence ratio,accompanied by flash back in corner vortices. Due to shear effect of swirling flow,lots of wrinkles appeared along the edge of OH distribution structure,and many isolated OH blocks were observed. The root of swirling flame lied at inner side of shear layer of the jet flow. As equivalence ratio increased,the swirling flame velocity flowfied and OH distribution structures were similar to low equivalence ratio. But the combustion was more stable,and the flame height increased somehow. It was found that the typical two vortices were split into multiple vortices sometime. There were phenomena with vortex moving and breaking down.
Numerical simulation of performance of engine lip electro-thermal anti-icing system
WU Peipei, YAN Tao, MA Saiqiang
2020, 35(10): 2056-2063. doi: 10.13224/j.cnki.jasp.2020.10.005
Abstract PDF(2656KB) icon351 icon441
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A three-dimensional coupled numerical simulation method was applied to simulate the performance of an engine lip electro-thermal anti-icing system at different conditions. The balance temperature of engine lip surface and the dynamic response time of surface temperature rise were obtained to estimate the performance of the anti-icing system. The simulated results were compared with experimental results in icing tunnel. And based on the comparison,simulated results were corrected. The study showed that the balance temperature of engine lip heating surface was above 273.15 K and the dynamic response time was less than 60 s,indicating that this anti-icing system could meet the requirement,and the severe anti-icing conditions were mainly those with higher flight speed and lower ambient temperature. And after correction the simulation coincided with experiment. The results can effectively guide the engineering development and provide a reference to improve the accuracy of anti-icing simulation.
Heat transfer performance of pre-cooler under unsteady inflow pressure condition using dynamic mode decomposition method
YAO Lichao, FU Chao, ZHANG Junqiang
2020, 35(10): 2064-2077. doi: 10.13224/j.cnki.jasp.2020.10.006
Abstract PDF(8395KB) icon429 icon339
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The heat transfer performance of a staggered-tube-bundle pre-cooler under unsteady inflow pressure condition was numerically studied with large eddy simulation method, and the dominating flow structures were identified using the dynamic mode decomposition method. The influences of the inflow pressure frequency on the internal flow, heat transfer performance and entropy generation within the pre-cooler were analyzed. Results suggested that the inflow pressure frequency had little impact on both the time-averaged heat transfer performance and the transient heat transfer performance. When the inflow pressure frequency reached the natural frequency of 950 Hz, the flow resonance occurred and the heat transfer fluctuated dramatically. The shear layer and shedding vortexes were the dominating flow structures, and their spatiotemporal evolution determined the transient heat transfer performance. When flow resonance occurred, the evolvement of the shear layer was closely related to the inflow velocity fluctuation. For the upstream cylinders, the period of the shedding vortexes was the same with that of the inflow pressure and velocity, while the period of the shear layer development was twice of the inflow pressure and velocity. Moreover, the entropy generation relied on the dominating flow structures, and its spatiotemporal evolution was in accordance with that of the dominating flow structures.
Effects of fully shielded guiding strut on infrared signatures of exhaust system
WANG Hao, JI Honghu, SANG Xueyi
2020, 35(10): 2078-2088. doi: 10.13224/j.cnki.jasp.2020.10.007
Abstract PDF(5046KB) icon448 icon350
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In order to suppress the contribution of the last-stage turbine rotor to the infrared (IR) radiation in backward of the exhaust system, the fully shielded guiding strut (FSGS) was designed. IR signatures of the baseline axisymmetric exhaust system and the exhaust system with FSGS under different cooling conditions were obtained by experiments. The results indicated that the wall temperature of the FSGS was lower than that of the last-stage turbine rotor. However, the wall temperatures of the heat shield and nozzle of the exhaust system with the FSGS increased. FSGS had an outstanding effect on suppressing the IR radiation of the exhaust system within the directions of 0° ~ 10°, and its IR radiation intensity was 13.9% lower than that of the baseline axisymmetric exhaust system at 0° detection angle. The application of film cooling on the FSGS can further reduce the IR radiation of the exhaust system in those directions mentioned above. Under the blowing ratios (BR) of 0.5, 0.7 and 0.9, the IR radiation intensity of the exhaust system at 0° detection angle was weakened by 18.1%, 25.8% and 34.5%, respectively. Therefore, the FSGS with film cooling is a very effective way to suppress the IR contribution of the last-stage turbine to the exhaust system.
Simulation and application of aircraft fuel temperature
ZHANG Ruihua, LIU Weihua
2020, 35(10): 2089-2096. doi: 10.13224/j.cnki.jasp.2020.10.008
Abstract PDF(2266KB) icon703 icon445
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In order to study the fuel temperature change rule during flight, a thermal network method was adopted to establish a thermal model of the fuel tank, and the boundary conditions corresponding to the flight experiment were input into Matlab/Simulink software platform to verify the credibility of the model. Based on that, the change rule of fuel temperature in each tank compartment throughout the voyage was analyzed. Results showed that the calculation method and simulation model had high credibility; when the error between the experimental value and the calculated value exceeded 1.67 K, the simulated temperature was higher than the experimental temperature. The fuel temperature in the fuselage tank was high in most sections, representing the flammability exposure time level of the entire fuel tank system as the focus of attention for airworthiness compliance certification. Taking the cruise end stage as an example, the fuel temperature of the fuselage tank was 25 K higher than the wing tank fuel temperature on the standard long-range flight, the average temperature was 7 K higher on the fuselage tank fuel temperature than the wing tank, the hot day was shorter during the voyage, and the fuel temperature of the fuselage tank was 12 K higher than that of the wing tank. The fuel temperature of the wing fuel tank rebounded greatly during the descent phase of the aircraft, and its flammability exposure time was mainly concentrated at the end of the voyage.
Influence of ring material on thermodynamic performance of self-lubricating spherical plain bearing
QIU Ming, ZHANG Yatao, LU Tuanliang
2020, 35(10): 2097-2103. doi: 10.13224/j.cnki.jasp.2020.10.009
Abstract PDF(3382KB) icon420 icon331
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In order to study the influence of ring material on the performance of self-lubricated spherical plain bearings,a thermo-mechanical coupling model based on ABAQUS software was established. The performance difference of spherical plain bearing of 2024 aluminum alloy and GCr15 was analyzed under certain working conditions,including the magnitude of equivalent stress,heat conduction process of friction pair,distribution of contact stress and temperature. Results showed that the equivalent stress of the ring of the aluminum alloy bearing was less than the minimum yield stress,which can meet the use requirements,meanwhile,the equivalent stress of the liner was reduced by 35.4%,and the liner of the aluminum alloy bearing reached the stable thermal state faster than the GCr15 bearing. In addition,the frictional contact stress of the aluminum alloy bearing was reduced by 15.4%, the temperature of ring was reduced by 2 ℃ the temperature of liner was reduced by 15.7 ℃,and the stress and temperature distributions of inner ring and liner were more uniform. In summary,the 2024 aluminum alloy spherical plain bearings had longer wear life and better performance than GCr15 bearings in some cases. The temperature rise process and temperature distribution of the GCr15 bearing were verified by experiments,which were in good agreement with the results of finite element analysis.
Static load sharing characteristic of twice load splitgear transmission configuration
JIN Guanghu, GAO Peng, ZHOU Zhenyu
2020, 35(10): 2104-2114. doi: 10.13224/j.cnki.jasp.2020.10.010
Abstract PDF(6815KB) icon565 icon362
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According to the deformation coordination condition and the moment balance equation of the configuration, a static model was developed to enhance the load sharing characteristics of the face gear and cylindrical gear twice load split transmission configuration, taking into consideration the center deviation of gears, bearing deformation of shaft and bearing, etc. The influence of the torsional stiffness and supporting stiffness of the shaft on the load sharing characteristics was studied. The results showed that the input shaft torsional stiffness had little influence on the load sharing characteristics. When the ratio of the torsional stiffness of the split torque shaft was appropriate, the face gear split torque drive could obtain better load sharing characteristics, but the load sharing performance of the cylindrical gear split torque drive remained almost unchanged. Reducing the torsional stiffness or increasing the supporting stiffness of the compound gear shafts could improve the load sharing characteristics of the whole configuration. Therefore, in order to improve the load sharing characteristics of the transmission structure, the torsional stiffness and supporting stiffness of the shaft need to adopt the method of parameter matching design.
Analysis of roller bearing cage broken under high DN value
LIU Lu, HUO Shuai, ZHENG Kai
2020, 35(10): 2115-2122. doi: 10.13224/j.cnki.jasp.2020.10.011
Abstract PDF(2591KB) icon556 icon400
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The failure mechanism of high DN value (bearing inner diameter multiply speed) bearing cage was analyzed. The results of roller bearing cage broken under the theory of ultra-high cycle fatigue showed that the method of designing of cage based on high cycle fatigue didn’t apply to high DN value cage. The stress causing fracture within over-long design life was far below fatigue limit of the material. The centrifugal stress caused by high speed contributed a lot to high DN value bearing cage fracture, and the main reason causing cage fracture was attributable to stress concentration because of the small pocket fillet. Therefore increasing pocket fillet and clean-up machining would help avoid cage fracture, and increase reliability of bearings.
Numerical investigation of gas journal foil bearing performance with thick top foil
WANG Rui, HOU Anping, LI Zhong
2020, 35(10): 2123-2135. doi: 10.13224/j.cnki.jasp.2020.10.012
Abstract PDF(5069KB) icon455 icon395
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A type of gas journal foil bearing with thick top foil (TTF-GJFB) was presented, and its modeling and analysis were carried out. The Newton-Raphson iterative method was used to solve the Reynolds equation and the force equilibrium equation to predict this novel bearing static performance. The dynamic stiffness and damping coefficients of this bearing were derived and solved by using reduced coefficient method and small perturbation method. Based on those methods, the comparative study of TTF-GJFB and traditional foil bearing was carried out, and the effects of bearing initial clearance, bump foil width and top foil mass on the bearing performance of novel foil bearing were studied. Results showed that TTF-GJFB had higher bearing load capacity and deflection angle than traditional foil bearing. The capacity increase was at least 23%. The dynamic characteristics of TTF-GJFB differed from those of traditional foil bearing. The initial clearance of TTF-GJFB affected the attitude angle and bearing load capacity. The width of the bump foil had great effect on the dynamic characteristics. Within the range of medium and low excitation ratio, the dynamic coefficients decreased with the declining width of the bump foil. The mass of top foil of TTF-GJFB affected the dynamic characteristics of bearing at high excitation ratio, dynamic stiffness coefficient increased and dynamic damping coefficient decreased.
Tooth width design of non-orthogonal arc tooth face gear
CHEN Yong, FENG Zhanrong, WANG Lixia
2020, 35(10): 2136-2143. doi: 10.13224/j.cnki.jasp.2020.10.013
Abstract PDF(2959KB) icon402 icon221
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Taking the arc tooth cylindrical gear as a hypothetical tool, a non-orthogonal arc tooth surface gear was proposed based on the gear meshing principle, and the single tooth full tooth surface of this type of gear was mathematically modeled to calculate the effective tooth width. The Catia secondary development verified the calculated tooth width value, and discussed the change rule of the tooth width of this kind of face gear by changing the size of the shaft intersection angle and the pressure angle. Results showed that: when the shaft intersection angle continued to increase, the inner and outer diameters gradually increased, and the increase of the change curve of the outer diameter was more obvious than the inner diameter, so the effective tooth width continued to increase. As the pressure angle continued to increase, the inner and outer diameters gradually decreased, and the inner diameter change curve decreased more than the outer diameter, so the effective tooth width gradually increased.
Aero-heating characteristics of flight body with high spinning speed
ZHANG Jun, XU Zhe, JIA Guangchen
2020, 35(10): 2144-2151. doi: 10.13224/j.cnki.jasp.2020.10.014
Abstract PDF(4789KB) icon408 icon263
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As a typical projectile with high spinning speed was taken as an example, the flight data of the projectile at supersonic, transonic and subsonic states were separately defined as the inflow conditions, and the fluid-thermal analysis was simulated by a combination of sliding mesh and multi-coordinate approaches. The coupling implicit algorithms based on density, Roe-FDS （flux difference splitting） flux scheme and SST (shear stress transfer) k -ω turbulence were also applied in simulations. The pressure, temperature, density,heat flux and turbulent kinetic energy on the surface of the flight body with high spinning speed were studied, and compared with the flow field disregarding the spinning speed. Results demonstrated that the streamlines interfered with each other, and disturbance of the airflow on the surface of the was more intense under the spinning conditions. Moreover, airflow accumulations at the tail of the were obvious, and the development and evolution of turbulence were more complicated. The velocity, pressure, temperature, and heat flux on the surface of the flight body were higher than those disregarding the spinning speed, especially at supersonic regimes.
Development path and future trend of carrier-based advanced trainer engine
PENG Yunlong, WU Xiong, DING Ting
2020, 35(10): 2152-2158. doi: 10.13224/j.cnki.jasp.2020.10.015
Abstract PDF(1080KB) icon376 icon301
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To explore the development path and future development trend of carrier-based advanced trainer engine, three development stages of advanced trainer engine were summarized, the technical performance requirements of carrier-based advanced trainer engine and the current situation of carrier-based advanced trainer engine abroad were emphatically analyzed. It was found that the carrier-based advanced trainer engine should be developed based on mature turbofan engines for long life, wide flight envelope, low fuel consumption, strong performance retention, easy maintenance and “sea adaptation”, or a mature carrier-based fighter power with lower status was chosen, according to the aircraft platform power demand. In the future it would be further developed in the aspects of higher weight ratio, lower fuel consumption, greater extraction power, longer service life and aircraft-engine integration design.
Effect of different environmental factors on dynamic characteristics of pressure transmission pipe
LI Bo, ZHANG Heyu, YANG Jun
2020, 35(10): 2159-2165. doi: 10.13224/j.cnki.jasp.2020.10.016
Abstract PDF(2000KB) icon464 icon238
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In order to explore the effect of different factors on the dynamic characteristics of the pressure transmission pipe in the dynamic calibration and operation,the pressure transmission model and the relationship between vibration frequency were deduced. The parameters affecting the dynamic characteristics of the transmission pipe,including static pressure,temperature,gas medium,were established. The experimental verification of different environmental factors was carried out by using special experimental device of the transmission pipe. Results showed that the static pressure only affected the output of the transmission pipe at the resonant frequency,but increased nonlinearly with the increase of the static pressure,and had no significant effect on the dynamic characteristics; with the increase of temperature,the resonant frequency increased but the output amplitude decreased; different gas media would change the dynamic characteristics of the transmission pipe mainly depending on the sound velocity of the medium. This study provides a reference for the data evaluation and correction of the transmission pipe in the use environment.
Simulation of flow field and calculation of safe operating envelope of shipborne helicopter based on chimera grid
TAN Wenyuan, CAO Yihua
2020, 35(10): 2166-2175. doi: 10.13224/j.cnki.jasp.2020.10.017
Abstract PDF(3830KB) icon341 icon241
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In order to ensure the shipboard helicopter safety, based on the chimera grid method, the flow field of CG-47 Ticonderoga class cruiser with UH-60 Black Hawk helicopter was simulated. The flow field of this combination under different wind direction angles and speed conditions was studied. The flight dynamics model was used to calculate manipulated variable and attitude angle. Finally, according to the safe landing criterion, the theoretical safe operating envelope of this combination was drawn. The results showed that the roll angle and periodic pitch control increased with the incoming velocity, while the pitching angle was affected by the incoming flow and the ship structure. The smaller wind direction angle meant the greater maximum landing speed. Generally, the left side speed was larger than the right side speed.
Drag reduction performance of hemispherical body with porous opposing jets
FAN Weijie, ZHOU Jin, LI Shibin
2020, 35(10): 2176-2185. doi: 10.13224/j.cnki.jasp.2020.10.018
Abstract PDF(5216KB) icon381 icon214
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Drag reduction performance of a hemispherical body with equal area porous opposing jets was numerically studied using the two-equation shear stress transfer (SST) k -ω turbulence model. Based on the presupposition of equal total jet area, the porous opposing jets were applied around the stationary point of the hemispherical body. By changing the total pressure ratio and number of the jets, the effects of each parameter on the drag reduction were analyzed and the interactions of the porous opposing jets were also discussed. The numerical results showed that opposing jet could reduce the drag of the hemispherical body effectively. With the increase of the total pressure ratio of the jets, the recirculation zone was enlarged and thus the drag reduction performance was improved. Moreover, the drag reduction performance was first improved and then dropped as the number of jets increased. In this study, two opposing jets obtained the best drag reduction performance with the highest percentage of the drag coefficient reduction as 29% due to the interaction of two opposing jets. The porous opposing jets demonstrated the possibility of achieving good drag reduction performance.
Modal analysis and dynamic stress test verification of shrouded pretwist turbine blade,
YUAN Wei, CHEN Guozhi, ZHANG Hongxiao
2020, 35(10): 2186-2194. doi: 10.13224/j.cnki.jasp.2020.10.019
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The non-linear contact prestress modal analysis mechanism of aero-engine shrouded pretwist turbine blade was introduced. The modal analysis of a turboshaft engine power turbine blade was carried out on the platform of ANSYS software. The results showed that the first order frequencies of 9-13 nodal diameter of blade blisk obtained by non-linear contact prestress modal analysis method were consistent with dynamic stress test frequencies, and the difference was basically stable at about 12%-13%. The results indicate that the calculation accuracy is improved obviously compared with the traditional method.
Calculation of design allowable values for TC11 titanium bar and forging at room temperature
ZHONG BIN, MA Shaojun, ZHANG Shichao
2020, 35(10): 2195-2204. doi: 10.13224/j.cnki.jasp.2020.10.020
Abstract PDF(2016KB) icon442 icon323
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In view of the basic problems and principles of statistics, the elements of direct calculation for design allowable value of metallic material tensile strength at room temperature were briefly analyzed. The design allowable values for TC11 titanium bar and forging were calculated and analyzed. Result showed that the lower limit of series allowable values for TC11 bar with different sizes calculated by regression method was closer to the actual product strength compared with specified S-basis values. The calculated ultimate strengths were 31-85 MPa higher than specified lower limit. The allowable value calculated by non-regression method for TC11 forging ultimate strength was 11 MPa lower than specified S-basis value. Calculated values were higher than A-basis values of TC11 alloy in domestic material data handbooks, ie 15%-72% higher for bars, 39% and 52% higher for forging ultimate strength and yield strength.
Model validation of three-dimensional curved asymmetric structure by radial axial Tchebichef moments
ZHANG Hao, ZANG Chaoping
2020, 35(10): 2205-2215. doi: 10.13224/j.cnki.jasp.2020.10.021
Abstract PDF(5384KB) icon337 icon239
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Using the idea of integral, the curved case was considered to be accumulated by a number of cylindrical cases. The mode shape data were interpolated into a three-dimensional pixel space of circle×points×layer, which can realize the identification of the mode shape of curved case by radial axial Tchebichef moment (RAT moment). The feature moment set was extracted from the mode shape data by using the RAT moment function to achieve compression of the mode shape data. Correlation analysis based on RAT moment can well describe the double modes phenomenon, which can make up for the defects of traditional modal assurance critertiom （MAC）values for double modes description. The eigenvalue of the moment was used as the objective function instead of the mode data, which was applied to model verification. The data amount of the moment eigenvalue was much smaller than the mode shape data, which can improve the calculation efficiency and avoid the non-convergence of the updating result. Considering that most engineering components were not completely axisymmetric, an aero-engine casing with an asymmetric boss was taken as an example. Based on RAT moments for mode calculation, correlation analysis and model updating, it was found that both frequency and RAT moments were used for model verification. Correlation was significantly improved, for example, the correlation of the ninth-order mode was increased from 35.35% to 67.21%. The frequency difference of each mode pair was also significantly reduced, and the maximum frequency difference was reduced from 14.56% to 9.09%. It was proved that the RAT moment function can be used in the model confirmation of asymmetrical three-dimensional surface.
Adaptation coefficient of keV energy Xe particles to copper surface in Maxwell model
SHANG Shengfei, JIANG Lixiang, XIANG Shuhong
2020, 35(10): 2216-2222. doi: 10.13224/j.cnki.jasp.2020.10.022
Abstract PDF(2459KB) icon330 icon203
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Experimental study was carried out on the ion thruster plume thermal effect within the scope of thruster exit radius of 500, 700 mm and 900 mm, the angle of 0°-15° (assuming the thruster exit plane as the center of the circle, thruster exit axis as 0°) with the help of the heat flux sensor. PIC-DSMC (particle in cell direct simulation of Monte Carlo) algorithm was used to simulate the experimental conditions under different adaptation coefficients. The results showed that the adaptation coefficient of keV energy Xe particles to the surface (copper) of the heat flow sensor was close to 1.
Prediction model of leakage rate of liquid sheet in pintle injector
WANG Kai, LEI Fanpei, YANG Anlong
2020, 35(10): 2223-2234. doi: 10.13224/j.cnki.jasp.2020.10.023
Abstract PDF(4239KB) icon350 icon276
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In order to predict accurately the leakage rate of liquid sheet in pintle injector,the relative deformation models of a liquid sheet and a liquid jet were established,based on the analysis of a spray field structure of a pintle injector element,and by combining with three methods of theoretical derivation,numerical simulation and experimental research. Taking the deformation of liquid sheet and liquid jet into consideration,the models of actual blocking rate and actual leakage rate were established for the first time by introducing coefficient of interaction to characterize the interaction between multi-injector units. Through multi-parameter verification of the numerical simulation and experimental data,the results showed that the predicted values of theoretical model were consistent with the numerical simulation and experimental data. Under the interaction of liquid sheet and liquid jet,the main causes of the deformation of liquid sheet and liquid jet were respectively a flow of liquid sheet around liquid jet and a transverse broadening of the root section caused by an asynchronous movement of the position of the front and rear edges at the root of liquid jet. Besides,the larger effective momentum ratio meant the greater relative deformation of liquid sheet and the smaller relative deformation of liquid jet. For the geometry structure with a certain blocking rate,the results showed that the leakage rate increased with the increase of the effective momentum ratio,and the increasing trend was fast first and then slow. The actual leakage rate was less than the geometric leakage rate,because the actual blocking rate was larger than the geometric blocking rate due to the deformation of liquid sheet and liquid jet. In addition,it was found that the leakage rate was only related to the dimensionless parameters characterizing the flow field structure (effective momentum ratio) and the geometry structure (ratio of sheet thickness to jet diameter and blocking rate),independent of the absolute value of injection velocity. The constant coefficients in the model were given for the engineering design prediction,providing an important guiding significance for considering the thermal protection of pintle tip in the early stage of design.
Algorithm of “turning square into circle” for valve hole
SU Zhishan, LI Huacong
2020, 35(10): 2235-2240. doi: 10.13224/j.cnki.jasp.2020.10.024
Abstract PDF(1547KB) icon326 icon245
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By studying the method of flow coefficient stability control of valve hole in aero-engine control system, a set of algorithms for transforming the square hole into small circular holes with regular arrangement were proposed. The correctness of the algorithm was verified by an example, and the conversion error was less than 0.7%, which basically realized the constant flow coefficient in engineering sense. The algorithm converted the square holes with poor machining process and low measurement accuracy into small round holes with regular arrangement and combination. So the influence of changes in flow coefficient caused by square holes was eliminated, the processing method of the valve hole was changed, the hazards to people and the environment were reduced, the measurement precision of the valve hole was improved, and the hydraulic power of the valve was reduced, presenting great engineering application value. The algorithm can transform the square, trapezoid (including triangle) and its combined holes, showing universal applicability in engineering.

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