2019 Vol. 34, No. 3

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Effects of fuel distribution on propagation of rotating detonation wave
2019, 34(3): 513-520. doi: 10.13224/j.cnki.jasp.2019.03.001
Abstract PDF(995KB) icon976 icon517
Abstract:
To study the effects of fuel distribution on the propagation of rotating detonation wave, two injection schemes of H2/air were investigated by simulations and experiments. The mixing of H2 and air was simulated in rotating detonation chamber, and homogeneity degree was proposed to quantitatively evaluate the mixing. The relationship of homogeneity degree and axial distance was revealed for the two injection schemes. Rotating detonation wave was studied by experiments, and its propagation velocity, stability and equivalent ratio limit were analyzed for the two injection schemes. The results indicated that the homogeneity degree increased significantly in the front portion of chamber when fuel injection holes moved forward. With the increase of the homogeneity degree, the propagation velocity and stability of rotating detonation wave were dramatically increased, and the lower limit of equivalent ratio expanded from 1.08 to 0.57. These results can provide references for the design of injection schemes of rotating detonation engine.
Temperature measurement and calculation analysis in a kerosene-fueled scramjet combustor
2019, 34(3): 521-528. doi: 10.13224/j.cnki.jasp.2019.03.002
Abstract PDF(883KB) icon922 icon547
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In order to obtain temperature distribution of the scramjet combustor and analyze working characteristics of the engine, temperature measurement was conducted via tunable coherent anti-Stokes Raman scattering (CARS) technique in a direct-connect combustor at the inflow Mach number 2.0, stagnation temperature 1100K and stagnation pressure 1.0MPa. Three-dimensional parallel numerical simulation on the experimental condition was carried out to compare the difference between the experimental and numerical results. Results showed that the temperatures of the incoming flow in the isolator obtained in experiment and numerical simulation had a maximum relative error of 0.8%. In the core flow of the combustor, at equivalence ratios of 0.6 and 0.8, the measured temperatures were 40K and 150K below the simulated values, respectively and the relative errors were 4.2% and 13%, respectively. In the recirculation flow of the cavity, the measured temperature was 140K below the simulated value at equivalence ratio of 0.6, with a relative error of 11.7% and 170K below at equivalence of 0.8, with a relative error of 7.5%. Both the numerical simulation and the experiment show that temperature and pressure distributions in the combustor are significantly influenced when the fuel of equivalence ratio of 0.2 is injected at the main fuel injector, but thrust performance of the expansion section and downstream region will not make much difference.
Experiment on variable-frequency-energy ignition performance ofinternally-staged combustor
2019, 34(3): 529-538. doi: 10.13224/j.cnki.jasp.2019.03.003
Abstract PDF(990KB) icon906 icon558
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At ambient temperature and pressure, the ignition performance of the internally-staged combustor under different ignition energy and ignition frequency combinations was experimentally investigated. The ignition energy values ranged from 1J to 15J, the ignition frequency values ranged from 1Hz to 15Hz, and air pressure drop remained at 1.5%. The experimental results indicated that, as the ignition energy increased, the excess air coefficient of lean ignition increased rapidly at first and then increased slowly, while the ignition delay time was shortened sharply and then slowly. As the ignition frequency increased, the excess air coefficient of lean ignition increased slowly, and the ignition delay time was shortened rapidly and then slowly, this regularity was more pronounced at lower ignition energy. When the ignition power was greater than 35 W, increasing the ignition power had little significance to improve the ignition performance, and the ignition energy had more significant effect on ignition performance than ignition frequency; under the same ignition power, it was better to raise the ignition energy to improve the ignition performance. A model of ignition based on Lefebvres and WANG Yanshengs ignition models was obtained by combustor reference velocity, Sauter mean diameter, ignition energy and ignition frequency, and the prediction error of the model was controlled within ±10%.
Test on effect of wake on film cooling for turbine blade withdust-pan shaped holes
2019, 34(3): 539-547. doi: 10.13224/j.cnki.jasp.2019.03.004
Abstract PDF(1090KB) icon781 icon462
Abstract:
The effect of unsteady wake on the film cooling effectiveness of the turbine blade was studied using the pressure sensitive paint (PSP) measurement technique. The test blade had two rows of dust-pan shaped film holes on the suction surface and the pressure surface, respectively. The blowing ratio varied from 0.25 to 1.5 and the wake Strouhal number of 0, 0.12, 0.36. Results showed that as the wake Strouhal number increased, the span-wise averaged film cooling effectiveness of the suction surface decreased by up to 0.07 and the span-wise averaged film cooling effectiveness of the pressure surface decreased by up to 0.024. For the wake cases, an increase in the blowing ratio caused a decrease in film cooling effectiveness on the suction surface. The film cooling effectiveness increased first and then decreased on the pressure surface as the blowing ratio increased.
Cooperating work characteristics of pulse detonation turbine engine
2019, 34(3): 548-555. doi: 10.13224/j.cnki.jasp.2019.03.005
Abstract PDF(854KB) icon857 icon494
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The cooperating work analysis model of pulsed detonation turbine engine (PDTE) was established in order to analyze the cooperating work characteristics of PDTE and its overall performance.On the one hand, using the model to evaluate the performance of PDTE prototype and compare it with the experimental results, the calculation results showed that: the model calculation error was no more than 11.2%. With the increase of operating frequency, the thrust of PDTE prototype can be further improved, but the cooperating work line gradually moved to the compressor surge boundary.On the other hand, the engine performance after replacing the main combustion chamber with a pulse detonation combustor (PDC) was studied by using a turbojet engine as a prototype.The calculation results showed that the windward area and the turbine inlet temperature of the PDTE were the same with the original turbojet engine. The optimal compression ratio of compressor of the PDTE was reduced from 5.5 of the original engine to 2.25. The flow rate was the same with that of the original turbojet engine when the PDTE operating frequency reached 41.5Hz, meanwhile, the thrust increased by 20.2% compared with the original turbojet engine, and the specific fuel consumption reduced by 14.0%.
Experiment on turbulent flow in rotating smooth channel with 1D hot wire
2019, 34(3): 556-566. doi: 10.13224/j.cnki.jasp.2019.03.006
Abstract PDF(1359KB) icon713 icon442
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In order to obtain the velocity models of turbulent boundary layer and mainstream in rotating smooth straight channels at different Reynolds numbers and higher rotation numbers，a correction formula for the logarithmic law of rotation channels with a wider range of rotation numbers was constructed，the hot wire was used to measures the average velocity and wall friction velocity at four different flow locations in a rotating smooth straight channel. The Reynolds number and rotation number respectively ranged from 15000－25000 and 0－0.444，the wall of the channel was at room temperature and there was no heat exchange between the fluid and the wall. Results showed that rotation had a great influence on the velocity of channel section. The rotation led to the overall deflection of the velocity model to trailing side，but the highest speed occurred in the area near the leading side；the dimensionless averaged velocity model near the trailing side was strictly arranged in the order of rotation number，and logarithmic law was distributed in the logarithmic law area. At the same time，wall shear stress monotonously decreased with the increase of the number of rotations at the leading side，and the trend of the change at the trailing side was contrary to this. The slope of the logarithmic law formula modified by rotation decreased monotonously with the increase of rotation number and decreased gradually at the trailing side. The rotation correction formula of the logarithmic law area was put forward，and the error of the formula was controlled within 15%.
Phase change heat transfer characteristic of ice crystal ingested into turbofan engine
2019, 34(3): 567-575. doi: 10.13224/j.cnki.jasp.2019.03.007
Abstract PDF(913KB) icon804 icon482
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Through analysis of airflow parameters in low pressure compressor flow passage, and by discretization of the motion equation and phase change heat and mass transfer equation of ice crystal, the ice crystal radii, ice crystal temperature, ice crystal velocity, liquid water mass fraction of ice-water mixture, heat transfer coefficient and mass transfer coefficient between ice crystal surface and airflow in low pressure compressor along axial position of compressor were calculated. The trajectory of ice crystal in low pressure compressor and collision characteristics between ice crystal and blades were obtained. The result shows that the liquid water mass fraction of 20μm ice crystal at adhesion position is 10.22% while liquid water mass fraction of 100μm ice crystal at the compressor outlet is just 2.1% and there will be no ice accretion inside the compressor.
Combustion characteristics of randomly distributed mesoscale droplets
2019, 34(3): 576-583. doi: 10.13224/j.cnki.jasp.2019.03.008
Abstract PDF(837KB) icon732 icon496
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The evaporation/combustion characteristics of randomly distributed droplets in spray combustion were studied numerically, the randomness of the droplet size, coordinate distribution and number density was considered in detail. The large eddy simulation was carried out by the one step general package reaction mechanism, while the resistance characteristics and evaporation rate of droplets with different number density at different inflow rates and ambient temperatures were analyzed, and the interaction between droplets was analyzed in combination with the combustion modes. The results show that the combustion modes of the droplets include three flame modes (fully-enveloped flame, partially-enveloped flame and wake flame) of a single droplet at the same time. The concentration of ethanol vapor on the surface of each droplet presents asymmetrical distribution, and the core region of the reaction deflects at an angle. In the strongly convective environment, the variation of average surface evaporation rate and resistance coefficient of evaporation/combustion droplets is similar to that of a single evaporation/combustion droplet, the strong interaction between droplets could accelerates the heat and mass transfer of evaporation/combustion of droplets.
Effective dielectric constant of composite medium containing ellipsoid nanoparticles
2019, 34(3): 584-591. doi: 10.13224/j.cnki.jasp.2019.03.009
Abstract PDF(945KB) icon767 icon439
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The S-parameter retrieval and MG (Maxwell-Garnett) effective medium theory were employed to calculate the effective dielectric constant of composite medium containing ellipsoid nanoparticles. Two influential factors, including volume fraction and aspect ratio of ellipsoid, were considered to analyze the applicability of the two effective models. Results showed that S-parameter retrieval had better adaptability to changes in shape and volume fraction of doped nanoparticles. In the considered volume fractions and aspect ratios, the S-parameter retrieval was well applicable. However, the MG effective medium theory was easily affected by the volume fraction and aspect ratio. When the aspect ratio of ellipsoid was 2, 3 or 4, the maximum volume fraction under applicable MG effective medium theory was 8%, 4% or 2%. Therefore, as the ellipsoid becomes flattened, the applicable range of MG effective medium theory will continue to decrease.
Experiment on the thermal management performance of phase change material under vibration environment
2019, 34(3): 592-599. doi: 10.13224/j.cnki.jasp.2019.03.010
Abstract PDF(944KB) icon721 icon461
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In order to study the thermal management performance of phase change material based heat sinks under vibration environment, two heat sinks based on pure stearic acid and stearic acid/foam copper phase change materials were prepared and experimentalized under static and vibrational environments. The experimental results showed that the presence of copper foam can effectively enhance the thermal performance of phase change material based heat sinks. When the heat flux was 5000W/m2, the equilibrium temperature decreased by 19℃ after adding copper foam, and the effective thermal control time was extended by 19.4%. Under the vibration environment, the equilibrium temperature of pure stearic acid test specimen was reduced by 9.5℃, the effective thermal control time was extended by 13.2%, and the effective thermal control time of the stearic acid/foam copper test specimen was extended by 10.5%. Hence forced convection caused by vibration can enhance the thermal performance of phase change material based heat sinks. With respect to the vibration frequency, the amplitude variation had less influence on the result, and in a vibration frequency range, the influence of vibration became larger with the increase of frequency. This study can provide a reference for the application of phase change materials thermal control technology for airborne electronic equipment.
Robust design method for critical speeds of multi-supported and flexible rotor system
2019, 34(3): 600-607. doi: 10.13224/j.cnki.jasp.2019.03.011
Abstract PDF(753KB) icon856 icon455
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A method for robust design using response surface method and tolerance model to consider the variation of the influencing factors of the rotor system was proposed. According to this method, response surface methodology was used to obtain the functional relationship between multi-parameters and multi-objectives, while the multi-order critical speed distribution was taken as the constraint condition, and the sensitivity of the critical speed to minimize the variation of the support stiffness was formulated for the design goal. This proposed method was applied to the critical speed distribution design of low-pressure rotor system of a small bypass ratio turbofan engine. In consideration of the variation of each support stiffness, the critical speed distribution of the flexible rotor system meets the given standards. Meanwhile, the sensitivity of the critical speed to the variation of the support stiffness is lowest, proving that this method is feasible and effective.
A 3D general method of cells model for plain weave composites
2019, 34(3): 608-615. doi: 10.13224/j.cnki.jasp.2019.03.012
Abstract PDF(1019KB) icon1283 icon475
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In order to solve the technical difficulty of applying the general method of cells (GMC) to develop braided composites multiscale simulation, a 3D GMC model used to multiscale simulation for 2D plain weave composites were developed. The basic theory and solution flow of the 3D GMC were outlined. Then, on the basis of the study on the meso-structural characteristics of 2D plain weave composites, its 3D GMC model was established. The correctness of the model was verified by comparison with the caculated macro- and meso-mechanical responses of the traditional finite element unit cell model. The GMC-based finite element multiscale simulation was performed on the modal analysis of 2D plain weave composites flat specimen. The test data revealed that the accuracy of the most of the first five natural frequencies predicted by the GMC model was significantly improved compared with the traditional finite element method. The advantage of this study is that multiscale simulation can be performed on the basis of the proposed 3D GMC model, helping to reveal the interaction between macro- and meso- mechanical response.
Monte Carlo-based competitive failure delivery simulation model of engine
2019, 34(3): 616-626. doi: 10.13224/j.cnki.jasp.2019.03.013
Abstract PDF(1022KB) icon698 icon433
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To solve the problem of the complicated modeling process and the slving difficulty when using conventional analytical methods to predict the engine delivery time,a method based on Monte Carlo simulation to predict the first delivery time of the engine was proposed. By analyzing the historical data of the engine fleet, the exhaust gas temperature margin (EGTM) decline rule and the lifetime distribution of performance degradation excess were studied. The time distribution of the first hardware damage occurred of each major hardware was counted, the probability of occurrence of accidental damage was calculated, and the time distribution of accidental damage was determined. Performance degradation, hardware damage and accidental damage were subjected to competitive analysis, and a Monte Carlo simulation model was established to predict the law of time when the engine is first delivered. Combined with the actual data provided by the engine fleet, the Kolmogorov-Smirnov test was used to determine the distribution type of first delivery time. After analysis, the reliability error of the simulation results was very small, between -1% and 2%, and the rationality and feasibility of the method was verified.
Stress rupture properties and fracture behavior of thin wall specimens of DD6 single crystal superalloy with ［001］ direction
2019, 34(3): 627-634. doi: 10.13224/j.cnki.jasp.2019.03.014
Abstract PDF(984KB) icon853 icon446
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The stress rupture properties and the fracture character of thin wall specimens of DD6 single crystal superalloy with ［001］ direction were investigated at 980℃ and 250MPa. Result showed that stress rupture life of the thin wall specimens was less than that of the standard sample, which exhibited thin wall effect obviously. There was a function relationship between thickness and stress rupture life. The edge zone of the fracture surface of thin wall specimens was oxidized seriously, while the inside zone was affected by microvoid coalescence fracture. The fracture of thin wall specimen was indicated by coalescence of the “surface oxidation-crack initiating-crack growth” and “inside creep damage”. The extent of surface oxidation was more serious, while the stress rupture life was shorter.
Numerical modelling of elastic ring squeeze film damper based on thick plate and force coefficient identification
2019, 34(3): 635-642. doi: 10.13224/j.cnki.jasp.2019.03.015
Abstract PDF(947KB) icon829 icon427
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The two way couple model of elastic ring squeeze film damper(ERSFD) was established through numerical approach. The governing equation of the fluid block was obtained by Reynolds equation and the equation of motion of the elastic ring was solved by finite element method with thick plate. The coupled equations were solved through block iteration method. The transient pressure profile of inner film and outer film were obtained and the force coefficients of ERSFD were identified. The results show that the height of the boss has significant influence on the damping of the ERSFD. The increase of the height of the boss from 0.15mm to 0.30mm results in a drop of damping from 5790(N·s)/m to 718(N·s)/m. The stiffness coefficients of ERSFD have close relations with the thickness of the ring as well as the number of boss. The increase of thickness of elastic ring from 0.8mm to 1.0mm leads to the increase of the stiffness coefficients from 1.44×106N/m to 2.51×106N/m.
Analysis and experiment of coupled bending and torsional vibration of a rub-impact dual-rotor system
2019, 34(3): 643-655. doi: 10.13224/j.cnki.jasp.2019.03.016
Abstract PDF(1339KB) icon1005 icon525
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For a dual-rotor system of aero-engine, the coupled bending and torsional dynamic equations with rub-impact force were first established using the Lagrange equation. The Runge-Kutta method was used for numerical calculation. Combined with waterfall map, spectrum diagram, bifurcation diagram, Poincaré map and amplitude-frequency curve, the spectral characteristics and bifurcation characteristics of the bending vibration and torsional vibration were analyzed. The torsional vibration of the rotor experimental platform was measured by incremental encoders to verify the spectral characteristics obtained from the simulation analysis. The research results show that the torsional vibration exhibits characteristic frequencies similar to bending vibration, including multiple frequency, fractional frequency, and the combined frequency of working frequency and multiple/fractional frequency, but these are more obvious in the torsional vibrations; bending and torsional vibrations have similar bifurcation process and same bifurcation point, and there are jump phenomena of amplitude at each bifurcation point.
High-temperature fretting fatigue life prediction model based on continuum damage mechanics
2019, 34(3): 656-663. doi: 10.13224/j.cnki.jasp.2019.03.017
Abstract PDF(804KB) icon996 icon481
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A high-temperature fretting fatigue life prediction model based on continuum damage mechanics (CDM) was developed to predict the fretting fatigue life of the aero engine dovetail joint structure at different temperatures. Considering the complex influence of temperature on the fretting fatigue, the temperature dependent damage rate factor was introduced in the fretting fatigue life prediction model based on non-linear continuous damage (NLCD) model. The model was used to predict the fretting fatigue life of titanium alloy TC11 dovetail joint structure of an engine simulated samples at different temperatures. Compared with the test results, the life predictions were within 2 times of the error range, proving the validity of the life prediction model.
Inverse identification of support stiffness and damping of hoop based on measured FRF
2019, 34(3): 664-670. doi: 10.13224/j.cnki.jasp.2019.03.018
Abstract PDF(626KB) icon847 icon481
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To create the dynamic model of the aeroengine pipeline system effectively, it is necessary to obtain mechanical characteristic parameters of the hoop such as the support stiffness and damping under dynamic load. An inversed method for identifying the support stiffness and damping was proposed based on the measured frequency response function (FRF). The inverse identification procedure was determined for the single pipeline supported by double hoops. The dynamic model of the pipeline system were created by the developed finite element method, and the formulas of solving the FRF of pipeline system was also given. The inverse identification algorithm based on sensitivity analysis was proposed to identify the stiffness and damping of the pipeline hoop. A typical pipe hoop was chosen as an example to obtain the support stiffness and damping. The identified mechanical characteristic parameters of the hoop were inputted into the created finite element (FE) model. It was found the relative errors between calculated and measured natural frequency and corresponding FRF were less than 9%. Then, the rationality of the developed identification method was validated. In addition, the identification results indicate that the support stiffness and damping of the hoop are frequency dependent, and the horizontal and vertical values of these parameters are different.
Modal characteristics analysis for pipelines considering influence of fluid medium
2019, 34(3): 671-677. doi: 10.13224/j.cnki.jasp.2019.03.019
Abstract PDF(743KB) icon870 icon493
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According to the requirement for the dynamic design of the external pipelines of aero-engine, and for solving the wet modal characteristics of complex pipelines, the Timoshenko beam theory and the energy method were used to derive the equation of the vibration of pipeline, in consideration of the effects of mass, pressure and velocity of fluid. Based on the existing pipe element in the ANSYS, an equivalent method to consider the pressure and velocity of fluid was established by using the stiffness and damping element, and it can be used in wet modal calculation of pipelines in ANSYS. Results showed that, the lateral force difference caused by the pressure of fluid could reduce the bending stiffness of the pipeline, and the axial tension caused by pressure could increase the bending stiffness; the effect of the pressure was related to the degree of axial constraint of the supports, and the Poissons ratio. The effect of the fluid velocity on the wet modal of the pipeline was related to the boundary conditions, the modes of vibration and the axial elongation of the pipeline. At high velocity, the modal frequency was zero, that was, the buckling instability occurring.
Duct sound propagation prediction based on grazing flow duct test
2019, 34(3): 678-684. doi: 10.13224/j.cnki.jasp.2019.03.020
Abstract PDF(750KB) icon930 icon443
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Acoustic complex pressure distribution on the duct wall opposite to the acoustic liner sample was obtained from grazing flow duct test with and without flow. Based on the test model and data, sound prediction study was carried out to validate the 2D and 3D duct sound propagation models. Result showed that 2D and 3D prediction results were very consistent, especially in the absence of flow. Duct sound propagation predictions were well matched to the corresponding grazing flow test results with and without flow at different frequencies, which verified the sound propagation model accuracy. Considering the influence of flow and frequency, the error between prediction and test results with flow was bigger than the situation without flow, and error at low frequency was bigger than that at high frequency.
Analysis on trim and stability of helicopter casting objects
2019, 34(3): 685-691. doi: 10.13224/j.cnki.jasp.2019.03.021
Abstract PDF(666KB) icon844 icon424
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A six freedoms flight dynamics model for a helicopter with pylons was built based on the theory of component-level. Trim calculation was conducted, and the result compared with the existing conclusion. Stability was analyzed for the helicopter casting objects with different patterns at different flight velocities. The result indicated that there was great effect on rolling angle and lateral control-stick when the helicopter cast objects by one-side due to the asymmetry of the recoil force. With the increase of the forward-flight velocity, casting objects had a greater effect on Dutch mode. Dutch mode evolved into two divergent aperiodic modes as the helicopter cast objects at a velocity higher than 50m/s, flight stability became worse obviously. The helicopter should cast objects at a lower velocity.
Design and analysis of three-dimensional bio-inspired flapping wing mechanism based on spatial RURS linkage
2019, 34(3): 692-700. doi: 10.13224/j.cnki.jasp.2019.03.022
Abstract PDF(952KB) icon934 icon442
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To mimic the spatial figure-of-eight trajectory of insect wing tips, a flapping wing mechanism based on spatial revolute-universal-revolute-spherical (RURS) four-bar linkage was designed to enable output of the three-dimensional spatial figure-of-eight trajectory with one input. Denavit-Hartenberg parameters method was used to establish the kinematic model of the spatial four-bar mechanism. Based on the genetic algorithm, the optimal parameters of linkages facilitating the flapping wing flight were acquired. A micro air vehicle virtual prototype was designed based on the optimal spatial four-bar linkage, meanwhile, the result of kinematic model was verified by ADAMS prototype simulation. The flapping amplitude of the flapping wing mechanism was 149.8°, and the twist angle was 29.9°, meanwhile the designed figure-of-eight flapping pattern was similar to insects in nature. The maximum size of the flapping wing mechanism was no more than 5.8cm, and the time asymmetric flapping pattern found from the simulation results can improve the aerodynamic performance to a certain extent, providing valuable insight weight to design light weight and efficient micro-air-vehicles.
Flight test of a fluidic thrust vectoring flying wing without rudder
2019, 34(3): 701-707. doi: 10.13224/j.cnki.jasp.2019.03.023
Abstract PDF(771KB) icon849 icon481
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In order to control the flying wing pitching and rolling without rudder, the layout named“single engine-inverted Ⅴ-double nozzle” was proposed based on the basic bypass dual throat fluidic thrust vectoring nozzle. Then the nozzle of the layout was tested for the first time. Finally the aircraft installed with the layout nozzle had a successful test flight and the flight data were collected and analyzed. The results show that the vector angle varies linearly with the nozzle valve opening and the nozzle does not present hysteresis. The aircraft equipped with the layout nozzle can be controlled by the bypass dual throat thrust vectoring nozzle without the rudder. In the aspect of rolling maneuverability for the aircraft, the vector control is similar to the rudder. But for pitch maneuverability, the effect of vector control is weak. The angle between the two nozzles should be increased, making it more suitable for the control of flying wing aircraft.
Fault diagnosis of civil aero-engine driven by unbalanced samples based on DBN
2019, 34(3): 708-716. doi: 10.13224/j.cnki.jasp.2019.03.024
Abstract PDF(887KB) icon935 icon435
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Through combination of deep belief network (DBN), sampling and integration technology, a fault diagnosis model of civil aero-engine based on unbalanced sample driving was proposed. By analyzing the historical flight data of civil aero-engines, the model used DBN to extract the internal features of the performance parameters, then used the sampling technology to equalize the unbalanced samples, and finally adopted integrated technology for fault classification. The model was applied to historical flight data of CFM56-7B series engines. Compared with common fault diagnosis methods, the experimental results showed that the model had higher accuracy of 0.996 and AUC value of 0.948, and can effectively deal with high-dimensional and unbalanced problems of civil aero-engine samples.
Load distribution and stiffness calculation of integral shaft bearings considering mandrel deformation
2019, 34(3): 717-727. doi: 10.13224/j.cnki.jasp.2019.03.025
Abstract PDF(1202KB) icon908 icon388
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Due to the high load-bearing and long-life performance requirements of the integral shaft bearings, a three-row rolling element hybrid structure was proposed to improve the overall carrying capacity by line contact at the both sides of bearing. In order to evaluate the bearing performance of the new bearing, a mechanical analysis model considering the influence of the shaft deflection of the bearing was established based on the rolling bearing design method and the flexible beam theory. Then, the influences of external force, external force position and clearance on the loading distribution and stiffness of bearing were studied in detail. The load analysis shows that with the radial force increase, the additional torque generated by the shaft and the maximum contact load of each rolling row increase; with the force acting distance decrease, the additional torque generated by the shaft and the bearing load of each rolling row significantly reduce; when the radial clearance of the roller row increases, the maximum contact load of each rolling row increases, the bearing area decreases, and the load distribution uniformity decreases. The stiffness analysis shows that with the radial force increase, the main stiffness of each rolling row increases significantly; however, the decrease of the load acting distance and the increase of the radial clearance of the roller row will cause the main stiffness to decline to a certain extent.
Load adaptability of vortex generators in blade passage
2019, 34(3): 728-736. doi: 10.13224/j.cnki.jasp.2019.03.026
Abstract PDF(1330KB) icon718 icon403
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Secondary cross flow limits the aerodynamic loading level of turbomachinery. Vortex generators have the potential to attenuate secondary cross flow when they are implemented at the endwall of the blade passage. An efficient method for designing the optimal vortex generator layout was presented based on a mathematical model (BAYC model) and an optimization procedure with response surface methods. In order to illustrate the proposed method, three layouts of vortex generators were optimized in an NACA 65 straight cascades. The flow mechanism of the vortex generators to control the endwall secondary cross flow were analyzed under design and off-design conditions. The results demonstrate that a higher vortex generator and a larger number of vortex generators can be more efficient to weaken the secondary cross flow when the incidence angle of the cascade is large. The application of the vortex generators can improve the load adaptability of the compressor cascade.

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