2018 Vol. 33, No. 5

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Display Method:
Online washing injection parameters selection and experimentsfor a certain type of turbofan engine
2018, 33(5): 1025-1032. doi: 10.13224/j.cnki.jasp.2018.05.001
Abstract PDF(1131KB) icon1586 icon1458
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In order to resolve the problem of determining the injection parameters when spraying to wash a certain type of turbofan engine from the inlet lip for the long distance of inlet and the irregular flow passage, the droplet size and motion trajectory were taken as the optimization goal, and the droplet on the airflow inlet face of the engine and the penetrating ability were taken as the effect target to carry out numerical simulation by using linearized instability sheet atomization（LISA）and Spalart-Allmaras（S-A）models.The nozzle design parameters were determined by optimized selection so that the commissioning workload and trial cost were reduced. Trial run of aircraft inlet combined with engine flow passage online washing was conducted to further measure and evaluate performance of the injection parameters predetermined nozzles. The trial run validation results showed that engine was washed in cold operation state and the injection parameters were determined as spray cone angle of 18°, installation upward offset angel of the nozzle on the spray frame of 7°30′and the washing vehicles feed liquid pressure of 1MPa. The optimal injection parameters, including nozzle type, injection pressure, spray angle and installation angle,for engines cold start or idle condition, were effective, making the washing droplet not only cover the entire engine entrance section and penetrate the whole blade cascade, but also not cause accessional blade erosion.
Performance analysis and test of multi-rotor aircraft withvariable rotor collective pitch and rotation speed
2018, 33(5): 1033-1040. doi: 10.13224/j.cnki.jasp.2018.05.002
Abstract PDF(838KB) icon1630 icon1332
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The critical influential factors limiting the flight performance of conventional multi-axis aircraft were analyzed. The method to improve the flight performance of multi-rotor aircraft was studied by means of variation of rotor collective pitch and rotational speed. Based on dynamic stall, unsteady flap and dynamic inflow model, a comprehensive aerodynamic theoretical model was developed to analyze the flight performance. A demonstrator multi-axis rotor aircraft was developed for flight test. The flight experimental results and theoretical results showed that the aircraft required power increases obviously with the increase of takeoff weight. Under different payloads and rotor rotational speed conditions, experimental and theoretical required very good agreement of the power results up to 97% at light load reach and 95% at heavy load respectively. By means of comparison and analysis, the theoretical performance analysis method was validated. And furthermore the simulation demonstrated that variation of the rotor collective pitch and rotational speed evidently improved maximal take-off weight and flight duration of multi-axis aircraft.
Numerical simulation of ideal MHD equations using HLLC scheme
2018, 33(5): 1041-1049. doi: 10.13224/j.cnki.jasp.2018.05.003
Abstract PDF(998KB) icon1690 icon1216
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A new flux calculating method based on the original HLLC (Harten-Lax-Vanleer contact wave) approximate riemann solver for ideal magnetohydrodynamics (MHD) equations was developed. The governing equations were discretized by finite volume method, and the time integration employed the implicit LU-SGS (lower-upper symmetric Gauss-Seidel) scheme. A hyperbolic divergence cleaning technique was introduced to suppress divergence of magnetic field. The numerical results of 1-D MHD shock-tube problem showed that HLLC-MHD scheme could accurately capture the magnetohydrodynamics waves, and the maximum numerical error was not more than 10%. The results of 2-D Rotor problem showed that HLLC-MHD scheme could be used to simulate the multi-dimension ideal MHD problem and accurately capture the Alfven wave of magnetic field. By comparing the results with and without divergence cleaning technique, the hyperbolic divergence cleaning technique could drop the peak value of magnetic field divergence from 50 to 2, and restrain the magnetic field divergence accumulation in the high divergence region, but also propagate the error to the low divergence region and cause the accumulation of the divergence at the boundary. It will influence the stability of the calculation.
Starting technical scheme of a micro gas turbine adapting to plateau
2018, 33(5): 1050-1056. doi: 10.13224/j.cnki.jasp.2018.05.004
Abstract PDF(862KB) icon1746 icon1201
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In order to ensure the micro gas turbine can be reliably and safely operated on the plain and plateau area not less than 4500 m, this technical solution was designed by reducing flow number of single centrifugal fuel atomized nozzle, considering the parameter matching of oil supply control system. When the ignition and fuel supply quantity at starting process was reduced, and the coupling of nozzle and oil control system was changed, the problem of starting over temperature on the plateau was solved. The test on plain and plateau showed that the success rate of ignition start-up was 100%, the highest exhaust temperature was 720℃ through plateau starting process, which was consistent with the state of the original design working environment on the plain, and the starting time was less than 40s. This can guarantee the safety of ignition and starting process and reliability on plain and plateau, helping to satisfy gas turbine property on the condition of plain and plateau.
Experimental of the pylon installation effect on hot jet noise
2018, 33(5): 1057-1064. doi: 10.13224/j.cnki.jasp.2018.05.005
Abstract PDF(876KB) icon1443 icon1135
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This experiment was made to study the installation effect on the radiated noise from separate flow nozzles with a bypass ratio of 5.5 at take-off condition, as well as the jet noise reduction of pylon-based chevron nozzles. All the experiments were conducted on the hot jet noise rig located in the anechoic chamber. The results indicated that the pylon made an azimuthal dependence on the far field radiated jet noise frequency spectrum. The pylon was effective at low-frequency with reducing noise but produced an increase of noise at high-frequency. The most significant low-frequency noise reduction was observed in position located above the pylon where the peak noise reduction was 3.7dB on frequency spectrum. There was little effect of chevron nozzles on the jet noise radiated from the top of the pylon. The low-frequency noise reduction on the pylon was observed below and laterally while the position below the pylon had the best low-frequency noise reduction whose peak noise reduction was about 1.3dB on frequency spectrum. The largest impact of pylon on high-frequency noise was only on the side. The installation had little effect on the far field overall sound pressure level directivities.
Aero-structural multi-disciplinary optimization method for three-dimensional wing
2018, 33(5): 1065-1075. doi: 10.13224/j.cnki.jasp.2018.05.006
Abstract PDF(1108KB) icon1492 icon1418
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An aero-structural multi-disciplinary optimization method for 3D wing was developed using Euler equations, continuous adjoint method, FFD(free-form deformation) strategy and a linear quadrilateral shell model. The objective function is the weighted sum of drag coefficient and the structural weight of the wing box. The design variables include the control points of FFD volume and the thicknesses of ten skin segments. The gradients of lift coefficient and drag coefficient with respect to design variables were adopted by continuous adjoint method, the gradients of wing box weight were acquired directly, and the gradients of the stress were obtained with finite difference method. The aero-structural multi-disciplinary optimization method was applied to a high aspect ratio wing in transonic regime, and a comparison between the results from aero-structural analysis of single-disciplinary optimization and aero-structural optimization was presented. It showed that the drag coefficient and the weight can decrease simultaneously through aero-structural optimization while the constraints were satisfied to keep the results reasonable.
Numerical investigation on the effects of boundary layer ingestion on aerodynamic performance of distributed propulsion system
2018, 33(5): 1076-1083. doi: 10.13224/j.cnki.jasp.2018.05.007
Abstract PDF(899KB) icon1979 icon1319
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To explore the effect of boundary layer ingestion (BLI) on the aerodynamic performance of aircraft, the aircraft/engine integrated simulation method based on the streamwise-body-force model was used to calculate a distributed propulsion system. Results show that BLI mainly affect the flow field of center body parts and cowling of engines, but yield small impact on lift and drag of the blending field and outer wing of BWB. Under the same flying conditions and constant angle of attack, the lift coefficient and drag coefficient increase with the increase of the non-dimensional mass flow rate of the engines. Therefore, a best non-dimensional mass flow rate of the engines corresponding to maximum lift-to-drag ra-tio exists. Engine installation location directly influences the localized supersonic flow of fuselage surface and the shock wave distribution of cowling. Layout of engines at the trailing edge could get better lift-to-drag ratio, where the non-dimensional mass flow rate of the engines corresponding to maximum lift-to-drag ratio is 0.65.
Optimal design of shaving cutter based on gear shaving mesh transmission characteristic
2018, 33(5): 1084-1092. doi: 10.13224/j.cnki.jasp.2018.05.008
Abstract PDF(1274KB) icon1272 icon1131
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For the tooth profile “concave” errors in shaving, a gear shaving mesh analysis model was established to study the gear shaving mesh transmission characteristic with different contact ratios. An optimal design of shaving cutter was proposed. The impact of gear shaving mesh transmission characteristic with different contact ratios on “concave” error was obtained by shaving experiment. And the correctness of the optimal design was verified. Results showed that: increasing the contact ratio can decrease the curve amplitude of transmission error and instantaneous ratio, but excessive increase led to local oscillation of curve and unstable drive. Thus the “concave” error was formed significantly. The contact deformation caused by gear shaving mesh status with different contact-ratios was the main factor affecting the gear shaving mesh characteristic. The better gear shaving mesh transmission characteristic meant the smaller shape and total deviation of gear gets. The optimal design of shaving cutter based on gear shaving mesh transmission characteristic can reduce the “concave” error effectively.
Optimization and test of parameters of the cryogenic hydrodynamic mechanical seal
2018, 33(5): 1093-1102. doi: 10.13224/j.cnki.jasp.2018.05.009
Abstract PDF(1371KB) icon1454 icon1397
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Based on analyzing the extreme working conditions, such as high-speed, cryogenic, high-pressure and low viscosity lubricants, a thermo-elastic-hydrodynamic-mechanical multi-field coupling model for the non-contact hydrodynamic mechanical seal in the high-speed turbopump was presented, and the model couple the multi-parts in the seal system, such as seal stator, rotor, sealed fluid and the static supporting elements. The performances of the seal are obtained by solving numerically the coupling model and the main parameters of the seal are optimized. The optimization targets are the maximum of the open force of the seal W and the leakage Q and the minimum of the seal-film generated power (or temperature rise). The seal sample with the optimization parameters is used in the experimental test with the liquid nitrogen as the sealed fluid, and the rapid start-up and friction characteristics of the seal under the cryogenic conditions are obtained. The results show the optimization parameters of the seal with the internal spiral-shaped and external herringbone grooves combination structure are that the groove number is 30 and the groove-depth is 3μm. The friction coefficient of the seal under the cryogenic conditions is 0.14.
Numerical simulation of two-phase air/oil flow in high speed angular contact ball bearing chamber
2018, 33(5): 1103-1111. doi: 10.13224/j.cnki.jasp.2018.05.010
Abstract PDF(1070KB) icon1765 icon1207
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Based on the model of gas liquid two-phase flow of lubrication oil in bearing chamber, the flow characteristics of the lubricating oil in the simplified model of the high-speed angular contact ball bearing chamber were calculated by volume of fluid (VOF) method and moving reference frame (MRF) model, the velocity, pressure and distribution of lubricant oil were obtained. Then the influence of the rotational speed of the bearing and lubricating oil inlet flow parameters such as the impact on the oil volume fraction were analyzed. The flow path of the lubricating oil in the bearing chamber,and the influence mechanism of the lubricating oil into the cavity were discussed. The results showed that at the bearing high-speed rotating stage, with the agitation of the lubricant and the cage was formed in the chamber. The two phase flow field in the bearing chamber between the bearing rings pressure had the periodic characteristics, spray lubricating oil was difficult to enter the cavity through the pressure between rings. The volume fraction of the oil in the chamber nonliear decreased with the increase of the bearing speed, and increased with oil supply. Injection angles had a great influence on the bearing chamber and bearing raceway of the oil volume fraction, and choosing the appropriate angle can get better lubricating effect. The results of this study provide some reference for the design of high speed bearing oil spray lubrication system.
Coupled modulated vibration signal component separation andfault diagnosis of planetary gearbox
2018, 33(5): 1112-1120. doi: 10.13224/j.cnki.jasp.2018.05.011
Abstract PDF(1178KB) icon1819 icon1201
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Aiming at the status that planetary gearbox vibration signal is usually appeared as coupling problem of steady state modulation component and shock modulation component under fault condition, different solution models have been established and a new method for the separation of coupled modulated vibration signals has been proposed. Shock modulated component separation was realized by the application of sparse total variation model, using an improved asymmetric penalty function, according to a strategy of coefficient of kurtosis and selection of regularization parameters based on mean square index, using majorization-minimization (MM) to solve the model. Steady state component separation was achieved by using base tracking. Simulation and experimental results verify the effectiveness of the proposed method for the separation and separation of vibration signals of planetary gearbox in a strong noise environment. The results of experimental show that this method can quickly isolate the weak shock modulation components under the noise D of 0.15. The algorithm has fewer iteration times and better convergence effect.
Influence of gas-solid thermal coupling on micro-vibration of aerostatic bearing at micron scale
2018, 33(5): 1121-1129. doi: 10.13224/j.cnki.jasp.2018.05.012
Abstract PDF(1156KB) icon1474 icon1052
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Based on gas lubrication theory and rarefied gas dynamics, and in combination with boundary slip and gas-solid thermal coupling analysis technology, the influence of local deformation of gas film on the gas-vortex and micro-vibration caused by temperature effect was studied. The research results show that: the maximum deformation variable of the gas film increases linearly with the temperature rise, considering that the gas-vortex movement velocity of thermal coupling is significantly smaller than the traditional numerical analysis method, under the coupling conditions, different operating temperatures have varied impact on the micro-vibration of the aerostatic bearing. With the increase of temperature, the micro-vibration intensity decreases, but the temperature increase does not change its natural frequency, and different gas environment influences the movement velocity and micro-vibration intensity of the gas-vortex, of which the molecular number plays a major role. The effect of environmental factors should be taken into account in the actual work process to reduce the micro-vibration.
Very high cycle fatigue test of TC17 alloy under asymmetric loading
2018, 33(5): 1130-1135. doi: 10.13224/j.cnki.jasp.2018.05.013
Abstract PDF(767KB) icon1018 icon566
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The fatigue failure of TC17 alloy was investigated under asymmetric loading with the help of piezoelectric fatigue tester (20kHz) and electromagnetic resonance fatigue tester (110Hz), and could be divided into surface induced failure mode and interior induced failure mode. Micro cracks near the center cross section of the specimen surface caused by slip trace under cyclic loading and the machine defects were the main reasons that caused the surface induced fatigue failure. The interior induced failure was mainly caused by the cleavage fracture of primary α phase. The frequency effect on the fatigue strength and fatigue failure mechanism was not obvious. And the variation of the failure mode resulted in a bilinear stree-fatigue life (S-N) curve of TC17 alloy. The formation of interior fracture could be divided into three stages: cleavage fracture of primary α phase, short crack propagation and long crack propagation. The critical stress intensity range of long crack propagation can be determined as 3.3MPa·m1/2 under the stress ratio of 0.1 at room temperature.
Dynamic hysteresis characteristics model of rubber damping ringbased on bristle friction theory
2018, 33(5): 1136-1143. doi: 10.13224/j.cnki.jasp.2018.05.014
Abstract PDF(852KB) icon1039 icon536
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The dynamic characteristics of rubber damping ring were theoretically developed. The high elastic properties, frequency-related dynamic properties and friction-related dynamic properties were comprehensively considered, and the effect of shape factors was taken into account as well; a model of rubber damping ring with dynamic hysteresis characteristics was presented based on the bristle friction theory. Compared with the former model based on Coulomb friction theory, this model could describe the dependence of friction velocity and calculate the nonlinear characteristics of friction stress nearby the point of zero velocity, producing a lot of tiny wave features to the dynamic hysteresis loops. Experimental research on the measurement of radial dynamic hysteresis characteristics was conducted. Experimental results show that the actual dynamic hysteresis loops of rubber damping ring are approximate elliptic curves with many tiny waves instead of smooth ones. And the wave characteristics of the hysteresis loops are relatively obvious at higher exciting frequencies. The experimental research proves that the rules and trends of theoretical model based on the bristle friction theory and actual situation are consistent, and their characteristics are similar.
Numerical analysis for aeroelastic stability of labyrinth seals
2018, 33(5): 1144-1150. doi: 10.13224/j.cnki.jasp.2018.05.015
Abstract PDF(876KB) icon1163 icon614
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Labyrinth seal in aero engines may be prone to aeroelastic instabilities. Based on the energy method of the aeroelastic stability analysis from the rotor blades, the flutter characteristic of two different models of labyrinth seal was calculated to compare the unsteady aerodynamic force and modal aerodynamic damping ratio under different vibration nodal diameters. Analysis showed that the energy method can be used to predict aeroelastic stability of labyrinth seal model and provide a reference for aero engine seal disk structure design. The aerodynamic work and modal aerodynamic damping ratio of low order vibration mode of labyrinth seal model before and after improvement were given by numerical calculation; the model at 2 nodal diameter vibration mode no longer fluttered after improvement, showing that the aerodynamic stability of model after improvement was better than that before improvement.
Numerical simulation of small crack closure characteristic of the notched FGH97 powder metallurgy superalloy specimen
2018, 33(5): 1151-1157. doi: 10.13224/j.cnki.jasp.2018.05.016
Abstract PDF(938KB) icon928 icon569
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Plasticity-induced crack closure (PICC) effect of small crack of notched FGH97 powder metallurgy superalloy specimen was investigated by finite element method (FEM). The influences of five principle factors, namely mesh element size, notch profile, load level, stress ratio and the constitutive model, on crack closure were analyzed. Crack propagation rate was predicted via Walker formula and compared with the test results to confirm the accuracy of FEM. The results show that crack closure level tends to converge if the size of forward plastic zone is ten times bigger than the element size around the crack tip; notch profiles affect crack closure in the closure transient zone, the load determines the crack closure stabilization level; crack closure level decreases with the increase of stress ratio till disappearance; compared with perfectly elastic-plastic constitutive model, the multi-linear elastic-plastic constitutive model shows much less dependency on mesh element size. The predicted crack propagation rate in consideration of crack closure fits well with test results.
Automatic optimization method for multi-disk rotor structure of aero-engine based on UG and Workbench platform
2018, 33(5): 1158-1164. doi: 10.13224/j.cnki.jasp.2018.05.017
Abstract PDF(710KB) icon1081 icon582
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At present, the optimization design of an aero-engine rotor is limited to single disk optimization, and the optimization needs to be performed by manual adjustment. In view of the convenience of aero-engine rotor data exchange between the optimization and model building software platforms and the reduction of manual adjustment, an automatic optimization method of multi-disk rotor structure of aero-engine based on UG and Workbench platform was proposed. Firstly, based on the UG platform, parametric geometrical modeling of multi-disk rotor structure can be made, and a standardized template was generated, in order to optimize the similar disk optimization problem. Then based on the Workbench platform, with APDL and Python redevelopment code, extraction of multi-disk rotor structures state variables and automatic optimization of process control were completed. The results of a numerical example showed that under the condition of satisfying geometrical and strength requirements, the mass of rotor was reduced by 33%, and the stress distribution was more uniform. And the method was proved to be of good stability and precision.
Experiment on the effect of protrusion amount on sealing efficiency of different rim seals
2018, 33(5): 1165-1172. doi: 10.13224/j.cnki.jasp.2018.05.018
Abstract PDF(933KB) icon1075 icon588
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The effect of different protrusion amounts on various parameters (static pressure, total pressure, sealing efficiency) was experimentally studied by measuring carbon dioxide volume fraction, so as to obtain the change rule of the sealing efficiency and the minimum flow rate of sealing air of different sealing structures. In the experiment, the experimental parameters of different dimensionless sealing flow rates were measured under the condition that the annulus Reynolds number and the rotating Reynolds number changed within a certain range. The results show that the change of the protrusions amount has little effect on the static pressure in the cavity, and the static pressure change near the sealing ring is almost negligible. The total pressure and sealing efficiency will increase with the increasing protrusion amount. However, the degree of change in the different sealing structures is different. As a whole, the efficiency of radial rim seal is most obvious, and the improvement of the axial rim seal and double teeth rim seal is less. For each additional protrusion, the minimum sealing flow rate required for each of the three structures can be reduced by 0.96%, 0.30%, 0.28%, respectively. In addition, the rotating Reynolds number will have a more significant effect on the sealing efficiency after the protrusions are installed.
Influence of aspect ratio and roughness on flow behavior in rectangle microchannels
2018, 33(5): 1173-1177. doi: 10.13224/j.cnki.jasp.2018.05.019
Abstract PDF(575KB) icon1059 icon544
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The influence of aspect ratio on the flow behavior in metallic rectangle microchannels was experimentally investigated. The results of flow behavior in silicon microchannels were compared to investigate the influence of roughness. The width of metallic microchannels was 0.4 mm and the aspect ratios were 0.50, 0.67, 1.00, respectively; and the relative roughness of the metallic microchannels ranged from 0.1609% to 0.2145%. The widths and heights of the silicon microchannels were both 0.4mm, and the relative roughness was 0.00325%. All experiments were performed with air. The experiments were completed with Reynolds number within the range of 250-3000. Results of experiments showed that the onset of transition from laminar flow to turbulent flow occurred earlier in unsmooth microchannels. And the critical Reynolds number decreased with the increase of aspect ratio. In laminar region, the friction factors for all the rectangle microchannels decreased roughly with the increase of Reynolds numbers. In transition region, the friction factors increased then decreased. At very low roughness, the transition enhancement was not found.
Heat transfer characteristics of a rotating cavity with axial throughflow of cooling air
2018, 33(5): 1178-1185. doi: 10.13224/j.cnki.jasp.2018.05.020
Abstract PDF(1028KB) icon979 icon595
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Targeting the flow structure and heat transfer of the aero-engine compressor rotating cavity,an isothermal rotating cavity with axial throughflow was investigated experimentally. By comparing the changes of the local Nusselt number and average Nusselt number in different working conditions, the effects of various forces in a rotating system on the flow structure and heat transfer were analyzed, and correlations of the Nusselt number and non-dimensional parameters were obtained.The results showed that the flow structure and heat transfer were mainly affected by the inertia force, centrifugal force and Coriolis force. The rotating cavity can be divided into two zones: the inertial convection zone located in the low radius cavity where the inertia force occupies the leading position and the rotational convection zone located in the high radius cavity where the Coriolis force occupies the leading position.The inertia force rises with the mainstream rate and the Coriolis force rises with the angular speed.Heat transfer is enhanced with increase of the inertia force and coriolis force respectively.These two forces effects on heat transfer suppress each other.With the coaction of these two forces,heat transfer changes with various working conditions and radius. The changes of average Nusselt number and local Nusselt number are consistent with the variation of variables.
Experiment on flow and heat transfer of aviation kerosene with time variation of inlet mass flow rate
2018, 33(5): 1186-1192. doi: 10.13224/j.cnki.jasp.2018.05.021
Abstract PDF(684KB) icon1071 icon626
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Characteristics of turbulent flow and heat transfer of compressed liquid kerosene were studied experimentally with sudden changes of the inlet mass flow rate. Flow and heat transfer experiments were conducted at a fuel temperature range of 300-650K, a Reynolds number range of 3000-60000 and a supercritical pressure of 3MPa. The fuel temperature, pressure and mass flow rate, and tube outside wall temperature were measured. Fuel skin friction coefficient and Nusselt number were calculated through unsteady control volume analysis based on momentum and energy conservations. The present results show that the time change of mass flow rate has very little effect on the skin friction coefficient and Nusselt number for compressed liquid kerosene tube flow when the temperature of kerosene doesnt exceed critical value 650K.
Effects of percent pitch on performance of high load tandem cascade
2018, 33(5): 1193-1203. doi: 10.13224/j.cnki.jasp.2018.05.022
Abstract PDF(1294KB) icon1183 icon598
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In order to investigate the mechanism of the forward and aft cascades performance changes at different percent pitches, a series of tandem cascades were designed according to Lieblein factor. The tandem cascades were simulated at six different percent pitches. On this basis, the forward and aft blade stacking lines of a tandem cascade were curved to analyze the influence of the spanwise non-uniform percent pitch on the performance of tandem cascade. The results showed that the expansion of cascade passage and pressure distribution changed with the variation of the percent pitches. The load of forward blade increased while the load of aft blade decreased with the rising percent pitch. Compared with original cascades, the total pressure loss coefficient decreased both at forward and aft blades, the total pressure loss coefficient of T5 blade decreased 51.3% at 80% percent pitch. The incidence angle range of tandem was influenced by forward cascades; the positive incidence angle range increased with rising percent pitch. Corner separation of aft cascades decreased while the percent pitch increased. The total pressure lose coefficient decreased 14.5% when the tandem cascades were positively curved. The total pressure loss coefficient decreased 15.6% and 55.2% when the forward blade was negatively curved or the aft blade was positively curved while the other blade kept straight.
Influence of part-span and full-span synthetic jets on theflow structures within a high-speed compressor stator
2018, 33(5): 1204-1214. doi: 10.13224/j.cnki.jasp.2018.05.023
Abstract PDF(1849KB) icon1078 icon619
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A simulation study on the use of synthetic jets for corner separation control on a high-speed compressor stator cascade was conducted. The effect of two jet configurations on flow structures and aerodynamic performance were compared. Results indicated that by periodically blowing and suction, synthetic jets could delay the corner flow separation and reduceing the total pressure loss coefficient significantly. Due to different control effects at different control phases, the loss coefficient at cascade outlet presented a feature of periodic fluctuation. The key for the effectiveness of synthetic jets lied in its control on passage vortex and corner secondary flow. At the incidence angle of 2°, the maximum loss reductions obtained by part-span and full-span configurations were 22.2% and 23.8%, respectively. The part-span configuration could not control the midspan flow, hence the wake loss was higher in this scheme and the control effect was weaker than the full-span one. Both jet configurations showed good adaptation characteristic at off-design conditions, while the full-span configuration could take advantage at relatively large incidence angles. At the incidence angle of 4°, the observed magnitude of total pressure loss coefficient of the full-span configuration was 2.8% higher than that of the part-span one.
Effects of the rim seal coolant gas on aerodynamic performance of mainstream flow in high-pressure turbine
2018, 33(5): 1215-1225. doi: 10.13224/j.cnki.jasp.2018.05.024
Abstract PDF(1437KB) icon961 icon539
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In order to research the effects of the rim seal on the mainstream flow in a high-pressure turbine,the mainstream flow features of the original no-coolant gas ingestion and the four kinds of seal types for a turbine stage were compared.The analysis of computational grid independence and reliability validation for the numerical method was performed to guarantee the accuracy of the numerical calculation. The study shows that seal structure will reduce the efficiency of rotor and the stage power. The sealing flow injected through the rim seal interacts with the boundary layer of the mainstream flow,changing the flow of the partial areas. The mainstream flow separated at the outlet of the seal will increase the energy loss of stator and affects the development of passage vortex in the turbine stage.It plays a significant role in the formation of secondary flows as the major contributor to the aerodynamic losses in turbine passages. The rounded shape inside the compound seal has a reduced influence on aerodynamic performance of the mainstream.
Shock loss control methods for transonic turbine cascades
2018, 33(5): 1226-1235. doi: 10.13224/j.cnki.jasp.2018.05.025
Abstract PDF(1284KB) icon1021 icon537
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Two shock control methods were presented in order to reduce the shock loss in highly-loaded transonic high pressure turbines. For the suction side shock, the controlled expansion designed concept, combined with a curvature based blade design method, was brought forward to control the flow expansion by adjusting the curvature distribution on the suction surface. The suction side shock strength and the pressure non-uniformity at the cascade outlet were effectively reduced with the decreased pre-shock Mach number at the trailing edge. The reduced shock method based on a bump designed on the suction surface was developed to control the pressure side shock effects. The shock/boundary-layer interaction and the reflected shock were obviously weakened with the pre-compression effect and the weakening effect as a result of the bump induced compression waves and expansion waves. In addition, analysis of controlled expansion and reduced shock methods indicated that their controlling effects on two shocks were independent, and thus could be used separately. With the combined shock control methods, numerical results showed a 29.66% reduction in the suction side shock strength, a 29.28% reduction in the pressure non-uniformity at the cascade outlet and a 12.11% reduction in the total pressure loss coefficient for the improved profile.
Simulation research on transient air-fuel ratio control of aero piston engine
2018, 33(5): 1236-1244. doi: 10.13224/j.cnki.jasp.2018.05.026
Abstract PDF(995KB) icon993 icon485
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In order to solve the problems like the large dynamic overshoot in the control of transient air-fuel ratio of aero piston engine, the model predictive control strategy based on improved particle swarm optimization algorithm and Elman(VPSO-Elman) neural network was proposed. The engine model used in the simulation was established based on a real engine in AMESim. The model predictive control system was established in MATLAB/Simulink. Coupling simulation was carried out to test the effect of the model prediction control. The simulation result shows that, compared with proportional integral derivative (PID) control, using VPSO-Elman network model prediction control the air-fuel overshoot can be reduced by 20%, callback time could be reduced by about 75%; for different throttle opening rate, VPSO-Elman controller also has a good control effect.
Multidisciplinary modeling and integrated optimization of axial piston pump
2018, 33(5): 1245-1255. doi: 10.13224/j.cnki.jasp.2018.05.027
Abstract PDF(1307KB) icon999 icon524
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In order to realize the precise modeling and optimization design of axial piston pump under the condition of mechanical hydraulic coupling, a method for multidisciplinary coupling modeling and integrated optimization for axial piston pump was put forward. Taking domestic I3V2-10S type axial piston pump as the study object, the mechanical model and the hydraulic model were respectively built in ADAMS and AMESIM. The interface communication between ADAMS and AMESIM was successfully implemented and the simulation of the mechanical and hydraulic coupling models was completed. Besides, in order to achieve the minimum outlet ripple ratio of this pump, the coupling model was integrated by iSIGHT software. The structures in valve plate pair such as oil suction and discharge orifice maximum equivalent diameters, oil suction and discharge dead angles, piston wrap angle, oil suction and discharge pre-opening degree, were optimized in iSIGHT. The results showed that the outlet flow ripple ratio of this pump was reduced by 14.59%,18.57%,21.50%,23.44%,24.03% and 25.49%, respectively, after optimization when the load was 10,14,18,22,26,30MPa, respectively. Finally, the correctness of simulation and integration optimization data was verified by experiments.
Ignition process of a 3-D dual-burning rate solid rocket motor with erosive burning
2018, 33(5): 1256-1262. doi: 10.13224/j.cnki.jasp.2018.05.028
Abstract PDF(786KB) icon947 icon469
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Targeting 3-D dual-burning rate solid rocket motor(SRM), the erosive burning rate, burning surface temperature, mass source, momentum source, energy source and igniter inlet boundary condition were investigated to aid in the ignition transient flow field simulation with erosive burning, using the user defined function module of commercial CFD code. The focus was put on the analysis of simulation results and comparison between simulation and test results indicate that: in the initial stage of ignition, the flow structure is highly complicated and the pressure varies drastically in the head-ending region; the open of nozzle closure leads to a negative pressure gradient and the shake of pressure gradient; the calculated results are consistent with the experiments showing, it is appropriate to compute the 3-D burning surface temperature using 1-D unsteady heat transfer equation for the solid phase, and the calculated approach is accurate and valid.
Control method of pressurization and venting flow ratein cryogenic tank
2018, 33(5): 1263-1269. doi: 10.13224/j.cnki.jasp.2018.05.029
Abstract PDF(831KB) icon935 icon492
Abstract:
The model of pressurization rate in cryogenic tank with liquid nitrogen as the working medium was deduced from thermal analysis of the tank, two working conditions in experiment were set up to verify the model. Then experiment was mainly carried out contrastively in direct venting mode, venting mode and parallel mode to measure ullage pressure and venting rate of vapor in the storage tank, the masses of venting vapor of three models were compared, the TVS(thermodynamic venting system) efficiency of different models within pressure control range during single cycle was analyzed. Results of experiment showed that the vapor parallel model had obvious advantages on mass of venting vapor and depressurization rate of ullage than other models, and the venting mass of vapor in parallel model could reduce 97% than that in venting.
Material defects data model of probabilistic risk assessment on life limited part
2018, 33(5): 1270-1280. doi: 10.13224/j.cnki.jasp.2018.05.030
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Abstract:
In order to meet the airworthiness requirements, a method for obtaining material defect (hard α inclusions) distribution data of typical titanium alloy was explored. According to the theoretical model of titanium alloy disk manufacturing process, the defect distribution baseline was acquired, using the detected defect distribution and the probability of detection(POD) of nondestructive test in the manufacturing process. The programs of POD test and microsection test, which meet the airworthiness requirements, were proposed. The key test technologies were determined to obtain POD curve and detected defects data, including specimen specifications, nitrogen mass fraction and distribution of hard alpha inclusions, ultrasonic test standard, steps of microsection, etc. Then, the exceedance curve of defect distribution was acquired by the use of theoretical deduction and logarithm linear fitting. The characteristics of material defects and airworthiness requirment were determines, then a method of obtaining POD curve and defect distribution curve was put forword.The method provides inputs for probabilistic risk assessment on aero-engine disk, supporting the airworthiness forensics of aero-engine disk.

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