2021 Vol. 36, No. 3

Cover
  Previous Issue | Next Issue 
Display Method:
Vibration responses analysis for double disks rotor system with uncertainties
LIU Yanxu, LIU Baoguo, FENG Wei
2021, 36(3): 488-497. doi: 10.13224/j.cnki.jasp.2021.03.005
Abstract PDF(5406KB) icon470 icon209
Abstract:
The nonparametric method based on the maximum entropy method of random matrix was used to model the dynamics of uncertain rotor system. The effects of model uncertainties and parametric uncertainties on the fluctuation of natural frequencies of an uncertain double disk rotor system were studied with nonparametric method. The sensitivity of vibration responses of this system to model uncertainties and parametric uncertainties in different speed ranges was studied. Thus, the modeling errors that cannot be considered by parametric methods were taken into account. The results showed that: the effects of model and parametric uncertainties on system natural frequency fluctuation were different. For variation coefficient 0.04 of elastic modulus of rotating shaft, the first-order natural frequency had 1.19% and 3.58% fluctuation, and the second-order natural frequency fluctuated by 1.82% and 3.64%; for variation coefficient 0.04 of support stiffness, the first-order natural frequency had 0.01% and 6.17% fluctuations, and the second-order natural frequency fluctuated by 0.68% and 6.18%, respectively. The sensitivity of vibration responses of the rotor system to the two kinds of uncertainties was related to speed ranges: within the range of lower than 120 rad/s and upper than 430 rad/s, the system responses were not sensitive to the two kinds of uncertainties; within the range of 120-200 rad/s and 270-430 rad/s, the effects of model uncertainties on the response fluctuation were greater than those of parametric uncertainties. The research results can provide a theoretical reference for the prediction of random responses of complex rotor systems.
Prediction of composite fan blade high cycle fatigue weak-link point location
TANG Xu, ZHANG Yukun, CHEN Yong
2021, 36(3): 498-508. doi: 10.13224/j.cnki.jasp.2021.03.006
Abstract PDF(6184KB) icon698 icon189
Abstract:
A method for predicting the high cycle fatigue weak-link point location of composite fan blade was proposed. Using the layup information file, a full-scale fan blade finite element model was established by normal extruding shell elements in ACP (ANSYS composite pre-post). Based on ANSYS-Workbench and Tecplot application program interface, the developed post-processing program completed the layup blade finite element data extracts and database creation. According to the composite material CLD (constant life diagram) model, the weak-link point index was applied to predict the location of blade high cycle fatigue failure. Case results showed that the blade failure location height did not exceed 40% of the entire blade height. First failure stress of 1st bending mode，1st torsion mode and 2nd torsion mode was layer normal stress, while 2nd bending mode, 3rd bending mode and stripe mode failures first occurred in layer shear stress. The layer normal stress weak-link point of blade bending mode was located in chord middle; the torsional mode vibration stress amplitude points were all structural plys, and S3 weak-link point was near the trailing edge. Compressive average stress could cause high cycle fatigue blade failure, and the area with a smaller static stress value could become a weak-link point.
Acoustic test and numerical analysis of tilt rotor in hover
YUAN Mingchuan, LI Shangbin, JIANG Lusheng
2021, 36(3): 520-529. doi: 10.13224/j.cnki.jasp.2021.03.008
Abstract PDF(5646KB) icon527 icon230
Abstract:
The aeroacoustic characteristics of tilt rotor in hover were investigated based on acoustic test and numerical computation. The test was conducted with isolate model tilt rotor, and the acoustic data of different collective pitch angles and blade tip Mach number were measured. The numerical computation was made based on CFD (computational fluid dynamic) and FW-H(Ffowcs Williams-Hawkings) equation, and the calculation accuracy was validated by test data. The acoustic results of different observation positions were compared, the effects of thrust coefficients and blade tip Mach number on tilt rotor noise were analyzed, and the acoustic characteristics of isolate rotor and dual rotors were calculated. Results showed that, the overall sound pressure level of tilt rotor increased with thrust coefficients and blade tip Mach number, the decrease of tilt rotor blade tip Mach number can reduce overall sound pressure level although the thrust coefficient was increased to maintain rotor lift; the acoustic directivity of dual tilt rotors was longitudinally symmetrical, the local maximum overall sound pressure level occurred at several azimuths, due to the superposition in noise radiation and aerodynamic interaction of the two rotors.
Numerical investigation on throttle characteristics of precooled engine inlets
WANG Hai, SUN Bo, ZHUO Changfei
2021, 36(3): 553-563. doi: 10.13224/j.cnki.jasp.2021.03.011
Abstract PDF(6008KB) icon328 icon214
Abstract:
In order to study the throttle characteristics of the precooled engine inlet before and after precooling, the two-dimensional axisymmetric inlet was used as the object, and the porous medium coupled source term method was used to conduct numerical simulation research. Under different working conditions, the precooling effect and the aerodynamic performance before and after precooling were compared. Studies indicated that when the mass-flow-ratio of turbine channel increased, the cone surface pressure of the subsonic diffuser section decreased, the area of the low-velocity zone decreased, the coefficients of total pressure recovery of both outlets showed a downward trend, and the precooling effect of the turbine channel was better. The total temperature of the outlet of the ramjet channel was also reduced by the influence of the precooler, and the degree of decline at high-velocity conditions was larger, but the degree of decline was not affected by the mass-flow-ratio of the turbine channel. In the high-velocity working condition of the same mass-flow-ratio of turbine channel, the turbine channel flow capacity was enhanced after precooling.
Design of improving volumetric efficiency of hypersonic waverider and rapid prediction of flow field
HOU Qiang, SU Weiyi, SUN Fei
2021, 36(3): 564-574. doi: 10.13224/j.cnki.jasp.2021.03.012
Abstract PDF(4417KB) icon584 icon177
Abstract:
In order to develop an aerodynamic design and prediction method that combines the high lift-to-drag ratio of waverider and the high volumetric efficiency of lifting vehicle, research was carried out in three aspects. Based on fusion design concept of lifting vehicle and waverider, a hypersonic waverider design method with large volumetric efficiency and high lift-drag ratio was proposed. Numerical simulation was carried out to obtain the influence of typical design parameters on the aerodynamic performance, such as the volumetric efficiency and lift-drag ratio. Based on the proper orthogonal decomposition method and radial basis function, a rapid prediction model of hypersonic waverider flow field and aerodynamic performance was established and the rapid prediction of flow field was studied. The research showed that compared with ordinary waverider, when the height was 5 and 10 mm, the volume increased by 8.00% and 15.00%; the rapid prediction method based on the proper orthogonal decomposition method can accurately and quickly obtain the flow field of waverider with different design parameters and the prediction error was not higher than 2.00%.
Design and performance analysis of variable damping paradrogue for an aerial refueling
XU Yang, LIU Xueqiang, JI Kang
2021, 36(3): 575-583. doi: 10.13224/j.cnki.jasp.2021.03.013
Abstract PDF(3882KB) icon325 icon177
Abstract:
To break through the restrictions imposed by traditional paradrogue on the speed and altitude of the tanker aircraft, a variable damping paradrogue with aero-elastic structs was designed. The flaky spring deformation and canopy configurations were obtained by fluid-structure interaction (FSI) analysis, and the trend of paradrogue drag was investigated by computational fluid dynamics (CFD). The hose configuration and the paradrogue draught position were simulated. Results demonstrated that the magnitude of the drag and draught position variation of this design was reduced to 70% and 60% of the traditional type respectively. This design can generate self-adaptive drag, and limit the paradrogue movement, so it is applicable at a broader range of speed and altitude.
Multi-objective optimization design method for propeller structure of a high-altitude airship
CHENG Junjie, WANG Haifeng, SHANG Lingling
2021, 36(3): 584-591. doi: 10.13224/j.cnki.jasp.2021.03.014
Abstract PDF(3034KB) icon363 icon209
Abstract:
To avoid the resonance of blade caused by rotating exciting force, it is necessary to increase the bending frequency of blade, but this will inevitably increase mass. In order to solve contradiction between low mass and high frequency, a two-objective optimization method of propeller was proposed. The minimum mass and maximum bending frequency were taken as two optimization objectives. The laying angle, thickness and region of the composite were taken as design variables. The maximum strain, maximum tip displacement and torsion angle at the 50%, 75% and 85% section of the blade were taken as constraints. The non-dominated sorting genetic algorthm Ⅱ (NSGA-Ⅱ) algorithm was used to optimize the propeller, and the Pareto solution of mass and frequency was obtained. The rotation frequency of the two blades at 520 r/min was 8.76 Hz and the crossing frequency was 17.33 Hz. The scheme far away from these two points was selected on the Pareto solution set according to the frequency. Through manufacturing and testing, the frequency of the real blade was 12.29 Hz, which was far away from the two resonance points, but can effectively avoid the blade resonance.
Mechanism of internal/external flow coupling effects on the performance of distributed ducted fan
GONG Tianyu, YUAN Wei
2021, 36(3): 592-605. doi: 10.13224/j.cnki.jasp.2021.03.015
Abstract PDF(6301KB) icon611 icon271
Abstract:
The coupling effects of internal/external flow has a significant impact on the aerodynamic performance of the distributed ducted fan.In order to further reveal the aerodynamic performance and mechanism of the internal/external flow coupling effect during the climbing and cruising of the distributed ducted fan, this problem was discussed in detail through three-dimensional RANS (Reynolds-averaged Navier-Stokes) numerical simulation and experimental methods. Results showed that the rotor blades and lip affected the thrust significantly in different flight conditions. With the increase of dimensionless mass flow rate, the rotor inlet flow direction changed from negative angle of attack to positive angle of attack, and the thrust coefficient increased. There was an optimal air angle of attack, resulting in highest aerodynamic efficiency in the climbing condition. At cruising condition state, the lip friction resistance was the least and the propulsion efficiency was the highest. Either larger or smaller dimensionless mass flow rate could increase the frictional resistance and differential pressure resistance of the lip wall, thereby reducing the propulsive efficiency.
Flow and thermal analysis of oil air two-phase medium in bearing chamber
LI Yanjun, YANG Fu, LIU Zhenxia
2021, 36(3): 606-615. doi: 10.13224/j.cnki.jasp.2021.03.016
Abstract PDF(5640KB) icon447 icon195
Abstract:
To obtain the flow and thermal analysis methods of oil air two-phase medium in bearing chamber，and find out the rule of flow and heat transfer in oil air two-phase medium, the flow velocity, temperature distribution, volume fraction and heat transfer coefficient distribution of two-phase medium in the engine bearing chamber were analyzed by CFD methods. Based on the local temperature in different positions of the bearing chamber, the heat transfer coefficient was obtained by calculating the heat flow under the temperature gradient method. The results showed that: the flow velocity of two-phase medum increased first then decreased with the increase of radial height, its maximum appeared when the dimensionless radial height was 0.6. The temperature of two-phase medium in the area between the rotor and the wall in the bearing chamber decreased first and then increased during the increase of radial coordinates. The oil in the bearing chamber was mainly distributed on the oil scavenger structure and the outer wall of the bearing chamber. The oil film in the area of the same shear component and gravity direction nearby the oil scavenger structure was thinner, the local heat transfer coefficient was smaller; the oil film in the area at opposite direction was thicker, and the local heat transfer coefficient was larger.
Research status and development trend of aircraft fuel tank on-board inerting technology
FENG Shiyu, LIU Guannan, JIANG Rongjie
2021, 36(3): 616-625. doi: 10.13224/j.cnki.jasp.2021.03.017
Abstract PDF(1720KB) icon680 icon370
Abstract:
In order to effectively reduce the risk of fuel tank explosion, the method of fuel flammability and oxygen concentration index focusing on the technology of the on-board inerting was introduced. According to the fuel explosion limit, the safe oxygen concentration of civil aircraft can be set as 12%, and that of military aircraft set as 9% by directly striking the fuel tank with the fire bomb to determine the maximum pressure. It analyzed the difference between equilibrium and non-equilibrium dissolution of gas in fuel oil and introduced the characteristics of separation membrane, the distribution of inerting gas and the simulation method. The development trend of on-board inerting technology in the future was analyzed. The results showed that: domestic inerting technology has become the mainstream inerting technology, but there is a lack of research on the flammability of domestic fuel, which can be further studied in the future. In addition, research on cooling inerting, green inerting, adsorption inerting and other technologies can be intensified, and it’s expected to have our own intellectual property rights.
Cooling characteristics of pin-fin arrays with non-uniform diameters
BAI Wandong, LIANG Dong, CHEN Wei
2021, 36(3): 626-633. doi: 10.13224/j.cnki.jasp.2021.03.018
Abstract PDF(3255KB) icon559 icon176
Abstract:
Three pin-fin array with non-uniform diameters were considered for the purpose of cooling　characteristics optimization.　Combined method of transient liquid crystal technique test　and numerical simulation was employed to investigate　their heat transfer and pressure drop characteristics. The results showed that low pressure drop can be achieved when downsizing several rows of pin-fin diameters with a small cost of heat transfer loss. Within the Reynolds number from 10 000 to 50 000, the pin-fin array with 1.4-folds diameters ratio between odd and even rows caused just 6% decrease on average heat transfer factor, however, its friction factor declined as large as 21%.
Experiment on effect of main swirl number on the flow and combustion characteristics of three-stage swirl combustor
TANG Chaowei, LI Jianzhong, JIN Wu
2021, 36(3): 634-645. doi: 10.13224/j.cnki.jasp.2021.03.019
Abstract PDF(8171KB) icon580 icon220
Abstract:
To study the effect of main swirl number on the flow and combustion characteristics of three-stage swirl combustor, two different main swirl number swirlers were designed. The flow field and flame structure were obtained with particle image velocimetry (PIV) and flame spontaneous emission. Results showed that the change of main swirl number had a great influence on the outlet flow, the lean ignition fuel air ratio and the lean blowout fuel-air ratio. With the increase of the main swirl number, the position of the vortex core was close to the center and upstream location. The height of the center toroidal recirculation zone was increased, while the vorticity of the outflow was decreased. The recirculation velocity and turbulence intensity inside the center toroidal recirculation zone were increased, and the flame structure was symmetrical. The successful ignition time was reduced. Compared with primary stage swirl number 0.7, the lean ignition fuel-air ratio of primary stage swirl number 0.8 was increased by 48%, 41%, 26%, and 24% at volume flow rate of 200, 250, 300，350 m3/h, respectively. Besides, the lean blowout fuel air ratio was increased by more than 30% in each operating condition. During the combustion process, the flame burned outward at a certain “V” opening angle. During the ignition process, the flame developed to the inner side along the boundary of the center toroidal recirculation zone.
Influence of pulsating frequencies on characteristic of radial turbine rotor inlet flow
WANG Zhihui, MA Chaochen, ZHU Fei
2021, 36(3): 646-654. doi: 10.13224/j.cnki.jasp.2021.03.020
Abstract PDF(4140KB) icon356 icon144
Abstract:
Detailed understanding of the flow interaction within the complex geometry of turbine stage coupled with the imposed unsteady pressure waves was presented. A fully validated numerical model was established based on ANSYS CFX code. For this purpose, four unsteady simulations of 20, 40, 60 and 80 Hz together with the steady state simulations were conducted. The flow angle distribution in a pulsating cycle and at the circumferential and spanwise positions was analyzed in different pulsating frequency conditions. The results showed that the pulsating frequency mainly affected the inlet incidence angle of rotor at the high pressure side, moreover, the lower the pulse frequency, the greater the negative incident angle of the low pressure side. It was also found that the absolute flow angle distribution at circumferential potion was similar and the relative flow angle fluctuations during the pressure decrements instances was significantly lower as compared with that during pressure increment instances.
Asymmetric leading edge design of diffusion cascade based on NURBS
YANG Guanhua, GAO Limin, WANG Haohao
2021, 36(3): 655-663. doi: 10.13224/j.cnki.jasp.2021.03.021
Abstract PDF(2851KB) icon420 icon195
Abstract:
Leading edge has an important influence on aerodynamic performance of diffusion cascade. No distinct designs were performed for two sides of symmetric circular and elliptical leading edge. In order to further improve the diffusion cascade aerodynamic performance, an asymmetric leading edge design method based on the 3rd-order non-uniform rational B-splines (NURBS) curve was developed, which realized the asymmetric leading edge shape while ensuring the continuous curvature. The design method was applied to two particular blades with circular leading edge. Numerical results showed that the total pressure loss coefficient could be reduced by 26.3% and 23.5%, respectively, compared with original blade profiles，and the overall aerodynamic performance was developed. At the inflow angle of 51.83°, compared with the symmetric curvature continuous leading edge blade, the leading edge suction peak intensity was reduced by 13.4%, and the leading edge transition onset was delayed by 4.6% chord length. The diffusion cascade overall aerodynamic performance was better with big inflow angle.

Copyright © 《Journal of Aerospace Power》 All Rights Reserved.

Supported by: Beijing Renhe Information Technology Co., Ltd.