2019 Vol. 34, No. 6

Display Method:
Functions and experiment on damping mechanism of spacer
2019, 34(6): 1185-1192. doi: 10.13224/j.cnki.jasp.2019.06.001
Abstract:
For the imperious internal demand of designing wide-chord blades of the high bypass ratio turbofan engines, the functions and design requirements of a spacer of the wide-chord blade were analyzed firstly, and the damping mechanism was revealed by the way of experimental study as well. Experimental results showed that the effect of vibration absorption of the spacer on the steady-state response of the blade under harmonic excitation was poor, while the effect under impact excitation was obvious, which reduced free vibration and cumulative fatigue damage effectively. The impact response time of the blade with a rubber spacer or a metal rubber spacer can be reduced by more than 50%. The preload of the spacer should be enough to locate the radial direction of blade steadily, decreasing the swing amplitude of blade and the mass loss by contact wear between dovetail and groove under windmilling condition. On the other hand, the flexibility of spacer should ensure that blade can swing an angle under high energy impact, so that the spacer absorbs impact energy by mean of deformation, in order to reduce the stress peak of the blade root.
Motion analysis and optimization of jointly adjusting mechanism of aero-engine stator vane
2019, 34(6): 1193-1200. doi: 10.13224/j.cnki.jasp.2019.06.002
Abstract:
Considering the problem of the complicated motion relationship and difficult optimization of jointly adjustment mechanism of aero-engine variable stator vane, a new method to design and optimize the jointly adjustment mechanism was proposed. The kinetic equation of the two-stage jointly adjusting mechanism was deduced using the graphic method and the homogeneous coordinate method and the MATLAB software. The key components of the two-stage jointly mechanism were optimized using the genetic algorithm. This developed method was applied to optimize a two-stage jointly adjusting mechanism. The optimization objects were the crank adjustable end length and the angle between the crank adjustable end and fixed end. The optimal result was obtained such that the first stage rocker arm rotation angle was twice the rotation angle of the zeroth stage rocker arm, and the first stage rocker arm rotation angular speed was also twice the zeroth stage rotation angular speed.
Stiffness characteristics of flange joint with a snap and its influence on structure vibration
2019, 34(6): 1201-1208. doi: 10.13224/j.cnki.jasp.2019.06.003
Abstract:
The stiffness characteristics of flange joint with a snap were studied by numerical simulation. The hysteresis characteristic of the flange joint with a snap was analyzed using ANSYS. Based on the analysis of the deformation and sliding of the snap contact surface, a Jenkins friction element was used in parallel with a spring element to simulate a section of the flange joint, and the simplified model of the bending stiffness of the whole flange structure was established according to different states of each section during the bending deformation of the flange. The simplified model can be utilized to simulate the stiffness characteristics of the flange joint with a snap accurately. The rotor model was built based on the stiffness simplified model and beam element, and the influence of the flange joint with a snap on the steady-state response of the rotor was analyzed. The results show that the hysteresis characteristic of the flange joint with a snap can affect the peak frequency and reduce the response peak significantly with the increase of snap interference, producing a good vibration suppression effect.
Influence of bearing arrangement on vibration characteristics of rotor shaft system
2019, 34(6): 1209-1216. doi: 10.13224/j.cnki.jasp.2019.06.004
Abstract:
Taking the three-span rotor shaft system as the research object, the orthogonal test method with interaction was used to analyze the influence of bearing position on the vibration characteristics of the rotor shaft system, and find out the optimal combination of bearing position and the primary and secondary orders of the influence on vibration. The simplified rotor shaft system model was introduced into ANSYS Workbench to simulate the vibration near the critical speed of the system at different bearing positions. The minimum vibration deformation in the first three order vortex states was the target parameter, and the relationship between the bearing position change and the target parameters was obtained. The results show that the interaction of bearing Ⅰ×Ⅱ has a great influence on the vibration characteristics of the shaft system, the position of the bearing Ⅰ has the greatest influence on the vibration characteristics of the shaft system, and the position of bearing Ⅲ has a relatively small influence.
Immersion ultrasonic testing of surface cracks on thermal barrier coatings
2019, 34(6): 1217-1224. doi: 10.13224/j.cnki.jasp.2019.06.005
Abstract:
In order to effectively detect the surface cracks on thermal barrier coatings (TBCs), the applicability of immersion ultrasonic testing method was studied. The TBCs samples were fabricated by the air plasma spray (APS), which was most commonly used in the TBCs process. The surface cracks with different depth, width and length were characterized by echo path difference and C scan image. Results indicated that the substrate materials had no obvious influence on the immersion ultrasonic testing results. By optimizing the detection parameters and selecting the instruments and probes properly, the surface crack with the depth of 0.1 mm and the length of 2 mm can be detected effectively by the immersion ultrasonic testing method. The length and depth of the surface cracks on TBCs can also be achieved by immersion ultrasonic testing method, make it an effective way to solve the TBCs surface cracks detection problem.
Active load reduction experiment of rotor system undersudden unbalance
2019, 34(6): 1225-1236. doi: 10.13224/j.cnki.jasp.2019.06.006
Abstract:
In order to finish the safety design of rotor system under sudden unbalance, the principle of load reduction by cone wall fused under sudden load was analyzed, the active load reduction experimental system with changing stiffness support was designed and experimental verification was finished. Research shows that the essence of cone wall fuse capable of reducing load is to reduce the stiffness of rotor support, accordingly, reduce the critical speed, the supporting load and amplitude in the deceleration process. The active load reduction structure change the support stiffness adaptively using changing stiffness, and can simulate the load reduction of cone wall fuse completely. Furthermore, it can verify the principle of load reduction by low-cost and highly repetitive experiment, and provide experimental conditions and data support for safety design of sudden unbalance.
Analysis on multiaxial high-cycle fatigue failure of 30CrMnSiA steel under proportional and non-proportional loading
2019, 34(6): 1237-1245. doi: 10.13224/j.cnki.jasp.2019.06.007
Abstract:
To analyze the failure law of high cycle multiaxial fatigue of 30CrMnSiA steel under proportional and non-proportional loading, multiaxial fatigue tests were carried out using 30CrMnSiA steel specimens under proportional and non-proportional (δ=90°) loading. The effects of stress amplitude ratio and phase angle on the fatigue life, fracture characteristics and crack initiation angle were analyzed. The results showed that the multiaxial fatigue life increased with the growing stress amplitude ratio for both proportional and non-proportional loadings. The fatigue source region, propagation region and final fracture region can be clearly observed. The transition of crack from stage Ⅰ to stage Ⅱ was observed when stress amplitude ratio was greater than 0.25 through analysis of crack initiation angles. And the stage Ⅰ propagation of the main crack was approximately along the maximum shear stress amplitude plane. Stage Ⅱ propagation of the main crack was approximately along the maximum normal stress plane. In addition, the crack aspect ratios of multiaxial fatigue test specimen were between 0.3 and 0.5, and the fatigue life corresponding to a 300 μm depth occupied more than 85% of the total fatigue life through analysis of fracture and surface crack path.
Mechanical wear condition monitoring method based on abrasive particle wear mechanism
2019, 34(6): 1246-1252. doi: 10.13224/j.cnki.jasp.2019.06.008
Abstract:
In order to solve the problem of low accuracy in monitoring the wear state of mechanical equipment, a mathematical model of monitoring the wear state based on the recognition of abrasive particle features was proposed based on different wear mechanisms with different shapes and textures. By identifying ball wear particles and cutting wear particles through shape feature, the shape and the texture features were combined to recognize fatigue wear particles and severe sliding wear particles. The feature vector of mechanical wear state monitoring was established based on the extracted feature parameters. Through the radical basis function neural network model by quantum particle swarm optimization (QPSO), the recognition and monitoring of mechanical wear state were realized. The experimental results show that the QPSO-RBF neural network model is simple in structure and 5% higher in recognition accuracy than the traditional PSO-RBF neural network model. It can be used for common mechanical wear condition monitoring
Code verification of physics evoked cloud method for compressible fluid dynamics
2019, 34(6): 1253-1272. doi: 10.13224/j.cnki.jasp.2019.06.009
Abstract:
In order to assess the credibility of the mesh free physics evoked cloud method (PECM) applied in simulation of compressible flows, the ideas and schemes of this method were analyzed a priori by combining the cognitions of physical laws, and based on the information of comparisons between numerical and referential solutions about nine one-dimensional models, code verification of PECM was implemented through a posteriori assessments, in which the referential solutions include numerical solutions of mesh free reproducing kernel particle method (RKPM) and exact solutions. The results of code verification indicate that strong discontinuities in various physical parameters or equations of state can lead to serious instabilities or infidelities of RKPM, whereas PECM still works robustly with excellent properties of accuracy and convergence even if very large density ratio exists.
Experiment on inlet total pressure distortion of middle-bypass ratio turbofan engine at high altitude
2019, 34(6): 1273-1251. doi: 10.13224/j.cnki.jasp.2019.06.010
Abstract:
Based on characterizations of the structure and aerodynamic stability, the experimental investigation on the inlet total pressure distortion of the middle-bypass ratio turbofan engine at high altitude was carried out. The detailed available distortion project designs, distortion installations selection, and data processing standard were introduced. The test results showed that within the range of flight height less than 14 km, the height affected the steady state comprehensive distortion index a little. When flight height was 11km, and flight Mach number was 0.8, under the comprehensive distortion index less greater than 12%, the middle-bypass ratio turbofan engine could work steadily at military cruising regime and military climbing regime with air bleeding, and power extractions was 136 kW, when the flight height was 14 km, and flight Mach number was 0.39.
Test and analysis on influences of low temperature on starting performance of turboshaft engine
2019, 34(6): 1282-1289. doi: 10.13224/j.cnki.jasp.2019.06.011
Abstract:
To investigate the influences of low temperature on turboshaft engine starting performance, application and tailoring of national military standard were discussed. Low temperature starting tests were conducted at -34 ℃ based on oil temperature in four-hour cold soak process. The influences of resistance torque, residual torque, ignition performance and warm-up effect on cold starting performance were investigated. Results showed that, initial resistance torque under -34 ℃ was 2.25 times of 25 ℃ and 1.53 times near the ignition. The Sauter mean diameter (SMD) was smaller for ignition boundary in the lower temperature. The influences of warm-up effect on low temperature starting was significant and the start-up time with warm-up was extended by about 25%. Heating up on the engine and cutting off oil lubricating can reduce initial resistance torque and improve the ignition performance, thus improving the low temperature starting performance. The conclusion provides a reference for the low temperature starting test, starting fuel supply control law optimization and research of similar engines.
Dynamic characteristics of terminal-sensitive submunition with a vortex-ring parachute at steady-state scanning stage
2019, 34(6): 1290-1296. doi: 10.13224/j.cnki.jasp.2019.06.012
Abstract:
The theoretical modeling, free-falling body and visual simulation methods were adopted to research the dynamic characteristics of the terminal-sensitive submunition with a vortex-ring parachute at steady-state scanning stage. According to the first Lagrange equation, the five-body dynamical model including the body, parachute, umbrella tray, friction disc and connecting rod was established. The ballistics calculation and visualization were implemented by combining ADAMS, MATALB and VR methods. The moving images, falling velocity and rotational speed were obtained by launching the test submunitions on a hot air balloon. A comparative study concluded that the vortex-ring parachute had the advantage of motion stability and could keep the terminal-sensitive submumition spinning at a constant speed in the process of free falling. The falling velocity in stability was 13.5 m/s, and the rotational speed was about 3 r/s. The steady-state scanning angle was close to the static hanging angle of the body. The simulation results were in good agreement with the flight test.
Intake and exhaust effect on aerodynamic characteristics of blended wing body civil aircraft with podded engines
2019, 34(6): 1297-1310. doi: 10.13224/j.cnki.jasp.2019.06.013
Abstract:
For the problem of the flow interaction between engine and airframe of blended wing body (BWB) civil aircraft with podded engines, taking a BWB civil aircraft designed by project team as the research object, the engine intake and exhaust effect on aerodynamic characteristics and its mechanism at low and high speed conditions were investigated by CFD method. The results indicate that the intake and exhaust mainly affect drag characteristics at high speed condition. As the engine intake mass flow decreases, the interaction between airframe/nacelle is intensified and the zero-lift drag of airframe is increased. The intake and exhaust effect on lift and pitching moment at low speed condition is mainly induced by the interference of engine suction effect on the airframe surface flow. The intake mass flow of engine has great effect on the aerodynamic characteristics of BWB transport. In the airframe/engine integration design of BWB transport, the interaction between airframe and engine should be considered and the effect of different intake and exhaust conditions on the local flow field of airframe and engine should be weighted.
Modeling and optimal design of power system for electric fixed-wing quadrotor hybrid unmanned aerial vehicle
2019, 34(6): 1311-1321. doi: 10.13224/j.cnki.jasp.2019.06.014
Abstract:
A modeling and optimal design method of power system was proposed to solve the problem of lack in theoretical method for power system design and selection of electric fixed-wing quadrotor hybrid unmanned aerial vehicle (eHAV). The need of power system was proposed by calculating the thrust-to-mass ratio. The models of propeller design and performance calculation were established using propeller and rotor theories. The brushless permanent magnet DC electric motor was modeled using statistic method and first order motor model. The relations of voltage and current between motor and battery were used to establish the battery selection method. A fully empirical model for battery discharge characteristics with voltage correction was used to calculate the endurance of eHAV. The optimal design flow of power system was established based on the matching method. The power system of an eHAV was optimized and selected. The results showed that the errors between the proposed rotor and propeller models and CFD method were less than 10%, and the fitting degree between the discharge model and the experimental data was greater than 0.97. The flight test showed that the error of endurance between the flight test result and the design value was less than 4%, verifying the correction and feasibility of the method of power system modeling and optimal design.
Aerodynamic performance influence of propeller slipstreamon engine intake
2019, 34(6): 1322-1333. doi: 10.13224/j.cnki.jasp.2019.06.015
Abstract:
For the integrated configuration of propeller/nacelle/intake,numerical simulation was carried out by using multiple reference frame (MRF) method and slip grid unsteady method, and the coupled flow field simulation of the internal and external flows of propeller/nacelle/intake integrated was realized. The aerodynamic performance influence of propeller slipstream on the intake under different working conditions was researched, and compared with the performance of the intake without the paddle configuration. Finally, the reason for the increase of the total pressure after the propeller paddle was explained by numerical analysis. The results show that the result of the multiple reference frame method is consistent with the time-average parameters result of the slip grid unsteady method, the multiple reference system method can be used to calculate the aerodynamic performance parameters of the propeller and the intake port. The work of the propeller increases the total pressure recovery coefficient of the intake port. The greater propeller speed means the greater increment of the total pressure recovery coefficient, and the propeller slipstream significantly increases the inlet port distortion index. The formula of the relationship between the total pressures before and after the paddle has been derived by numerical analysis, and compared with the simulated value, with the error within 3%.
Experimental and numerical study on pulsed-jet impingement heat transfer with an additional collection chamber
2019, 34(6): 1334-1343. doi: 10.13224/j.cnki.jasp.2019.06.016
Abstract:
An experimental and numerical study was performed to study the impingement heat transfer on the flat target surface produced by a pulsed-jet with an additional collection chamber. The current test was conducted under the following conditions, such as pulse frequency (f) ranged from 5 Hz to 40 Hz, jet Reynolds number (Re) ranged from 5 000 to 15 000, pulsation duty cycle (R) ranged from 0.2 to 0.8, jet-to-surface distance (H/d) ranged from 2 to 10. In the numerical simulations, the above parameter ranges were relatively extended, for example, 5 Hz≤f≤200 Hz, 5 000≤Re≤20 000 and 0.2≤R≤1.0. With respect to the pulsed-jet impingement without collection chamber, the pulsed-jet with an additional collection chamber was found to enhance the convective heat transfer, with a 8%-19% increase of the stagnation Nusselt number. Due to the additional collection chamber, the vena contracta effect near the jet orifice increased the approaching velocity towarded the target surface at the jet-on process. At the jet-off process the inertia role inside the additional collection chamber behaved. Among the current research conditions, the relatively optimal pulsation parameters such as f=80 Hz and R=0.8 were demonstrated. For the pulsed-jet impingement on a confined target, H/d=4 was a relatively optimal jet-to-surface distance.
Effect of temperature ratio on cooling characteristics of vane end-wall
2019, 34(6): 1344-1351. doi: 10.13224/j.cnki.jasp.2019.06.017
Abstract:
Experimental investigations of the cooling characteristics of a vane end-wall were carried out in a hot wind tunnel using infrared thermograph technique. Two mainstream-to-coolant temperature ratios of 1.53 and 2.29, and three coolant-to-mainstream mass flow ratios of 0.50%, 1.25% and 1.50% were chosen. Comparing the results obtained at high and low temperature ratio, the following three conclusions can be drawn. The experimental method of increasing the temperature ratio by increasing the mainstream temperature and keeping the coolant temperature constant led to a significant increase in the overall cooling effectiveness of the end-wall surface. The cooling characteristics of the end-wall surface changed as the temperature ratio increased. As the temperature ratio had different effect of cooling effectiveness at different positions of the end-wall, the areas with high and low cooling effectiveness changed. The scheme of hole-layout suitable for low temperature ratio may not be applicable to high temperature ratio. The effect of temperature ratio on the cooling characteristics was great at the leading edge, but not evident at the trailing edge.
Effect of rotation on the leading-edge region film cooling of a twisted turbine blade
2019, 34(6): 1352-1363. doi: 10.13224/j.cnki.jasp.2019.06.018
Abstract:
An experimental investigation was performed to investigate the effects of the rotation and blowing ratio on the film cooling effectiveness distributions of the leading-edge regions of a twist gas turbine blade using a thermochromic liquid crystal (TLC) technique. The experiments were carried out at three rotating speeds, including 400 r/min (positive incidence angle), 550 r/min (zero incidence angle), and 700 r/min (negative incidence angle). The averaged blowing ratio varied from 0.5 to 1.25. Nitrogen was used as the coolant to ensure that the coolant-to-mainstream density ratio kept at 1.04. The Reynolds number, based on the mainstream velocity of the turbine outlet and the rotor blade chord length, was 60 800. The results show that rotating speed is one of the most critical parameters in determining the film cooling effectiveness distributions on the leading edge. The position of the stagnation line moved from the pressure side (PS) to the suction side (SS) with the increase in rotating speed. Under the same blowing ratio, the area-averaged film cooling effectiveness increases monotonously with the increase in rotating speed. Under the same rotating speed, the area-averaged film cooling effectiveness increases with the increase in blowing ratio.
Numerical heat transfer of EPDM with variable thermal properties based on pyrolysis process
2019, 34(6): 1364-1372. doi: 10.13224/j.cnki.jasp.2019.06.019
Abstract:
In order to study the pyrolysis ablation process of ethylene propylene diene monomer (EPDM) insulator under thermal load, a variable thermal properties model, in which the thermal properties of aramid/EPDM insulator vary with temperature and time, was established based on pyrolysis kinetics, mass and heat transfer theory of porous media. The accuracy and reliability of the present model were verified by comparing with experimental results. Then numerical calculations for the ablation thermal response under thermal load were carried out. Results showed that at the initial stage of thermal loading, the surface of the material heated up rapidly. As the energy continued to transmit, the temperature advancement rate and the charring layer thickness reduced significantly, and the part of the material was still in their original state. The effect of temperature on the pyrolysis reaction rate presented an exponential trend. The closer to the surface reflected the faster reaction rate and vice versa. The variable thermal properties model has certain reference value for the ablation research of thermal insulation materials.
Application of adaptive treatment casing in multi-stage axial compressor
2019, 34(6): 1373-1379. doi: 10.13224/j.cnki.jasp.2019.06.020
Abstract:
An adaptive treatment casing with annular cavity guide vane was designed. The influence of different guide vanes on the flow field of subsonic multistage axial compressor was studied by means of steady numerical method. Results showed that when the guide vane perpendicular to the rotor chord wise weakened the leading edge overflow intensity of the blade tip, the treatment casing restrained the development of clearance leakage flow, improved the flow capacity of the rotor blade tip passage, and made the compressor basically unchanged while the speed characteristic was above 0.8 design speed, the stability margin of low speed was greatly improved, in which the total pressure ratio at the near-stall point increased by 10.2% at 0.7 design speed and the near-stall flow rate expanded by 8.5%, showing the strong adaptive stability-expanding ability.
Improved viscous inverse design method for three-dimensional turbomachinery blades
2019, 34(6): 1380-1388. doi: 10.13224/j.cnki.jasp.2019.06.021
Abstract:
An improved inverse design method for three-dimensional turbomachinery blades in viscous flow field was proposed. It was assumed that the camber line had a virtual moving speed. The virtual movement was calculated by the difference between the target load and the actual load, and was reasonably limited by the thickness of viscous sublayer. The camber line was smoothed by cubic B-spline interpolation, and the new blade profile was obtained by updated camber line and the given blade thickness. Verification results show that the method can modify the blade profile according to the design intention. It has strong robustness, fast convergence speed, and high degree of freedom of the blade, independent of the specific grid and solver, and also it has certain generality.
Study on reduction of waste grain rate for semi-spherical conic-column grain
2019, 34(6): 1389-1398. doi: 10.13224/j.cnki.jasp.2019.06.022
Abstract:
In order to reduce the waste grain of the semi-spherical conic-column grain, a model was built with the UG NX software and the calculations were programmed with the MATLAB software, the relations between the waste grain rate and the design parameters were obtained. The calculated results showed that the larger radius of circular groove meant the smaller waste grain rate and the decrease of waste grain rate. There was a negative correlation between the waste grain rate and the radius of the inner hole, the larger value meant the smaller waste grain rate. There was an approximate parabola relation between the waste grain rate and the radius of the circular center of the circular groove. When the value became big, the waste grain rate increased first and then decreased. The waste grain rate is approximately linear with the length of the cylinder, the larger value meant the higher residual rate. The maximum relative error between the calculated result and the actual data was 0.084%.
Fault feature extraction of rolling bearing using Birge-Massart threshold denoising with EEMD and spectral kurtosis
2019, 34(6): 1399-1408. doi: 10.13224/j.cnki.jasp.2019.06.023
Abstract:
For the difficulty of extracting fault feature by adopting the traditional resonance demodulation method due to noise interference, an effective fault feature extraction method of rolling bearing was proposed by integrating Birge-Massart-based threshold de-noising strategy with ensemble empirical mode decomposition (EEMD) and fast spectral kurtosis algorithm. EEMD was applied to decompose original fault signals and then extract intrinsic mode function (IMF) components containing fault information by kurtosis criterion. Birge-Massart strategy and fast spectral kurtosis were employed to filter and denoise fault signals. The fault features of the filtered signals were extracted by Hilbert envelope demodulation. Through the fault feature extraction of the simulated signals and experimental signals based on this developed method, the results demonstrate that the proposed method is effective to improve the signal-to-noise ratio of fault signals and to acquire the frequency feature of inner and outer ring faults. Using kurtosis factor criterion to select IMF components can effectively retain the impact features of the original fault signal and remove the influence of irrelevant IMF components.