2021 Vol. 36, No. 2

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Noise tests of pusher-propeller
ZHOU Jiajian, HAO Xuan, FU Zengliang, LIANG Bin, ZHOU Ping
2021, 36(2): 225-232. doi: 10.13224/j.cnki.jasp.2021.02.001
Abstract PDF(4854KB) icon602 icon147
Abstract:
The noise of a pusher-propeller was tested. The noise frequency spectrum characteristics of propeller at different revolution speeds with fixed pitch were obtained to research the noise level varying with revolution speed and pitch. The directivity characteristics at typical operating condition were also tested to get the directivity of tone noise, broadband noise and overall noise. The results showed that as the revolution speed and pitch increased, the contribution of broadband noise to overall noise increased. The broadband noise was comparable with the tone noise at large pitch and high revolution speed. The directivity of broadband noise agreed with the characteristics of blade self-noise. It is probable that the broadband noise is dominated by blade self-noise.
Experiment of intake fan noise and noise reduction of acoustic liner based on mode generator
ZHANG Tao, LIN Dakai, ZHANG Yingzhe, LEE Incheol
2021, 36(2): 240-248. doi: 10.13224/j.cnki.jasp.2021.02.003
Abstract PDF(3484KB) icon601 icon96
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In order to investigate the characteristics of engine intake fan noise and the noise reduction effect of acoustic liner, the intake fan noise was provided by a mode generator. The noise signal inside the intake was measured by using a fixed microphones array and a rotating microphones rake, and then the amplitude of acoustic mode inside the intake was determinated by using circumferential and radial mode decomposition method. The key factors affecting the results of mode decomposition were investigated. The circumferential mode was decomposed in time domain, and the time-resolved characteristics of amplitude and phase were obtained. Finally, the noise reduction effect of two acoustic liner samples was experimented. The results showed that: the main mode characteristics of fan noise could be obtained by the mode generator, including the mode amplitude and the rotating angular velocity; under the condition of satisfying the sampling theorem, the main mode produced by the mode generator was independent of the numbers of loudspeakers in the case of n=0; the influence of the numbers of sampling position of the rotating microphones rake on the results could be ignored if using the rotating microphones rake to measure the acoustic mode; and at the design frequencies, the acoustic liners had good noise reduction effect. It is concluded that: the intake fan noise source provided by the mode generator can be used for further experimental verification of acoustic liner design method.
Aerodynamic characteristics of quad tilt rotor aircraft in vertical flight
WANG Junjie, YU Zhiming, CHEN Renliang, WANG Zhijin, LU Jiaxin
2021, 36(2): 249-263. doi: 10.13224/j.cnki.jasp.2021.02.004
Abstract PDF(8822KB) icon820 icon119
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The computational fluid dynamics (CFD) method based on unstructured grid sliding grid technology and the experiment method of aerodynamic interference were used to simulate the flow field of the quad tilt rotor (QTR) aircraft in helicopter mode. The aerodynamic characteristics of the QTR aircraft in vertical flight and the effect of some parameters on the aerodynamic characteristics were studied. Results showed that the interference between the front and rear rotors of the QTR aircraft was not obvious, but the interference between the rotor and the wing was greater; the interference of the rotor rotation direction on the rotor and the wing was different, the aerodynamic force of the wing accounted for 15% of the rotor thrust in the right rotation, and 9% of the rotor thrust in the left rotation; during the vertical motion of the QTR aircraft, the rotor lift and torque change could cause changes in component force and low/head-up torque in the forward direction; during the vertical descent of the QTR aircraft, the rotor could enter into the vortex ring state. The presence of the wing effectively reduced the destructive effect of the vortex ring state, and the vortex ring reduced the impact of the airflow on the wing tip.
Numerical simulations of supersonic mixing layers with IPDG method
WANG Xian, LIU Wei, ZHAO Ming, LIU Zhengxian
2021, 36(2): 275-283. doi: 10.13224/j.cnki.jasp.2021.02.006
Abstract PDF(3555KB) icon454 icon51
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In order to satisfy the high-precision simulation of supersonic mixing layers, discontinuous Galerkin finite element numerical method based on internal penalty method (IPDG) was realized. The viscous flux was introduced as an auxiliary variable to reduce the Navier-Stokes equation order, the discontinuous Galerkin method was used for spatial discretization and the Newton-Krylov implicit method was used for time marching. Compared with the finite volume method, the numerical accuracy of the method was improved to the third-order. The numerical simulation of the supersonic mixing layers developed in two-dimensional planar space with a convective Mach number of 0.2 was carried out, and the reliability of the method was verified by comparison with the experimental data. The numerical results clearly indicated the development of flow transition and vortices in the mixing layer. Meanwhile, the adaptive mesh technology based on numerical solution error distribution was combined with IPDG method.The comparison showed that the number of adaptive grids was reduced by 9 times, and the calculation time was reduced by 8 times, thus significantly improving the calculation efficiency of the method.
Advances in rim seal aerodynamic technology for gas turbines
GAO Jie, HUANG Jingwei, DU Yufeng, HUO Dongchen, FU Weiliang
2021, 36(2): 284-299. doi: 10.13224/j.cnki.jasp.2021.02.007
Abstract PDF(2890KB) icon546 icon68
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In order to clarify the development status and trend of rim seal technology based on the research of relevant literatures, the development of the research about gas turbine rim seal aerodynamic technology was reviewed in five aspects: the prediction model of gas intrusion for rim seals, the unstable flow mechanism for rim seals, gas intrusion characteristics and flow mechanisms for turbine rim seals, the mutual interaction between the rim seal flow and the turbine mainstream, and turbine rim seal design and aerodynamic performance improvement. The common research methods and research results of rim seal flow were briefly summarized. The research result show that in the future, it is necessary to further improve the prediction model of gas intrusion theory of multiple seal structures under the influence of multi-parameter coupling, strengthen the turbine high parameter experiment and high-precision numerical calculation method. Besides, more in-depth and detailed research should be carried out on rotation-induced invasion under variable operating conditions, interference between rim seals, and unsteady interaction evolution mechanism between seal outflow and mainstream, and on this basis, it’s imperative to explore the design optimization technology of high-performance rim seal structure. In addition, strengthening the research on the influence of the purge flow under the air-heat environment on the cooling characteristics of the turbine, and the development of turbine low-dimensional aerodynamic design technology considering the purge flow effect is also an important direction for the development of rim seal technology.
Numerical investigation on induced mechanism of blow-down effect of brush seals with fluid-structure interaction
DU Chenyu, SUN Dan, LIU Yongquan, ZHAN Peng, XIN Qi
2021, 36(2): 310-319. doi: 10.13224/j.cnki.jasp.2021.02.009
Abstract PDF(5715KB) icon402 icon36
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The theoretical model of blow-down effect of brush seals was analyzed. The three-dimensional transient numerical model of blow-down effect of brush seals based on arbitrary Lagrange-Euler（ALE） fluid-structure interaction method was established. The axial, radial and sectional deflection characteristics of bristles were studied respectively. The radial blow-down displacements of bristles were analyzed quantitatively, and the induced mechanism of blow-down effect of brush seals was revealed. The results showed that the leakage can be calculated more accurately with consideration of blow-down effect, because the bristle radial clearance was reduced by blow-down effect. Blow-down effect of brush seals presented an unsteady deflection with bristle oscillation. Compared with bristle cross section in the radial middle and end position of backing plate, blow-down effect and bristle oscillation of bristle tip were stronger. Bristles had more radial blow-down displacements and stronger bristle oscillation with the increase of inlet-outlet pressure ratio. When the inlet-outlet pressure ratio was 2, 3 and 4, the maximum radial blow-down displacement of bristles in the middle of bristle pack was 0.004, 0.010 mm and 0.019 mm, respectively, under the studied condition. The initial condition for the bristles with a certain circumferential lay angle and the radial pressure gradient in bristle pack contributed to the induced blow-down effect, and blow-down effect was further influenced by the normal pressure and the tangential friction between bristles. Blow-down effect of brush seals can be weakened by increasing the circumferential lay angle.
Numerical analysis of tip leakage flow effect on compressor stability
WANG Hao, TU Baofeng
2021, 36(2): 320-328. doi: 10.13224/j.cnki.jasp.2021.02.010
Abstract PDF(3795KB) icon484 icon66
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To study the effect of tip leakage flow on the compressor stability, a tip leakage vortex model was developed, and implemented in the TUSIAC (three dimensional and unsteady stall inception analysis code) program. The program modeled rotors/stators as three dimensional actuator disks, where the viscous effect was reflected by the characteristic curve, and the three-dimensional unsteady Euler equations in the flow passages between them were solved, thus lower computational resources were required. The numerical simulation showed that the performance and stable margin of the compressor were degraded under the effect of tip clearance.The tip clearance did not change the type of the stall precursor, but shrinked the circumferential size of the stall cell, and made it rotate faster.The newly developed tip vortex model could predict the tip clearance effect on the compressor stability and the stall inception process, thus providing a practical approach to investigate the compressor stability and optimize the compressor design during the preliminary design phase.
Vibration fault analysis of aeroengine rotor disk cavity filled with oil
DING Xiaofei, CAO Hang, FENG Guoquan, JIANG Jianling
2021, 36(2): 341-351. doi: 10.13224/j.cnki.jasp.2021.02.012
Abstract PDF(4065KB) icon589 icon52
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In combination with the problems of rotor cavity filled with oil vibration encountered in the test of aero engine rotor in the project, the research was carried out from the theory of vibration, dynamic characteristics and vibration signal analysis, and the failure mechanism of rotor disk cavity filled with oil was analyzed. The characteristics and regularity of instability vibration were acquired, the process and criteria for disc cavity fluid accumulation fault identification as well as its vibration monitoring guidance were established. The result showed that the subharmonic vibration was produced when the rotor speed was above the critical speed of the rotor if the rotor cavity was filled with oil, which caused the self-excited vibration of the rotor; and the frequency of the self-excited vibration was close to the first order critical speed of the rotor; and the rotor frequency vibration was still dominant when the rotor speed was below the critical speed, and the oil deposit could cause the increasing peak value of the over critical speed; the above-mentioned fault identification process and criteria were applied to an rotor of an engine to accurately identify the characteristics of rotor cavity filled with oil. Oil was found in the fan's secondary disk cavity when the rotor was dismantled. After cleaning up the oil, the abnormal vibration disappeared, which verified the correctness of the conclusions.
Speed prediction for power turbine rotors of turboshaft engine on loss-of-load
GONG Lifeng, XIONG Qingyong, LUO Mingzhi, FU Qiuju
2021, 36(2): 352-357. doi: 10.13224/j.cnki.jasp.2021.02.013
Abstract PDF(945KB) icon550 icon63
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In order to meet the integrity of the rotor design requirements of the engine airworthiness regulation CCAR33.27 on turbine loses-of-load, the time-dependent law of the turbine speed on the moment of loss-of-load was studied. The multi-point steady-state method was used to study the relationship between the transient aerodynamic efficiency of the power turbine and the speed. On this basis, assuming that the power turbine inlet gas energy remains constant, the relationship between the torque and the speed of the power turbine was analyzed. Then, a combination of theoretical mechanics and engineering analysis was performed to establish a prediction model for the time-dependent change of rotor speed for the loss-of-load on a turbine, and the model was verified by engine test data, which proved the rationality and accuracy of the prediction model. The established prediction model can provide a theoretical basis for the design of power turbine strength and overspeed protection. The research results showed that the speed of the power turbine rotor can reach 160% in 200-300 ms after loss-of-load, which was close to the rupture speed of most disks. Special attention should be paid to the design of turboshaft-engine overspeed protection.
Failure mechanism and improvement of ball bearing in aliquid rocket engine turbopump
ZHANG Wenhu, LI Wenchao, DENG Sier, ZHANG Song, ZHENG Yanwei
2021, 36(2): 396-404. doi: 10.13224/j.cnki.jasp.2021.02.018
Abstract PDF(4296KB) icon748 icon83
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In view of the fault of ball bearing in a liquid rocket engine turbopump during the experiment, the failure mechanism of bearing was analyzed, the key structural parameters of bearing were optimized. The contact stress, contact angle, spin-to-roll ratio, slip ratio of cage and orbit trajectory of cage’s centroid were compared and analyzed by means of SARB (simulation and analysis of rolling bearings) software. Experiment was done to verify the improvement and the dynamic analysis results of ball bearing. Results showed that after the structural parameters of the bearing were improved, the contact angle between steel ball and inner ring was reduced, the cage slip rate declined from 10% to 4%, and the spin-to-roll ratio and slip speed were reduced, and the stability of steel ball and cage was improved.
Rolling bearing reliability evaluation method based on LTSA fusion dimensionality reduction method
LIU Lu, QIU Ming, LI Junxing, XU Yanlei, NIU Kaicen
2021, 36(2): 413-420. doi: 10.13224/j.cnki.jasp.2021.02.020
Abstract PDF(2052KB) icon401 icon41
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In order to ensure the safe and stable operation of rolling bearings under a given working condition, a reliability evaluation method of rolling bearings based on local tangent space alignment (LTSA) and Weibull proportional failure rate model （WPHM） was proposed. This method was used to extract the characteristic indexes in different analysis domains such as the time domain, frequency domain, time-frequency domain and statistics of the entire life cycle of the rolling bearing, select the characteristic indexes effectively and sensitively reflecting the running state of the rolling bearing, so as to construct high-dimensional multi-dimensional domain feature set; The local tangent space arrangement algorithm was used to fuse the high-dimensional multi-domain feature set to reduce the dimensionality, and a comprehensive feature index that can comprehensively reflect the degradation trend of rolling bearing performance was obtained as the response covariate of WPHM for reliability evaluation. Through the rolling bearing life test, the life of the test bearing was 491 min. It can be concluded that the bearing failed around 489 min, and the life error was less than 1%. Therefore, this method can effectively evaluate the operational reliability of rolling bearing.
Probabilistic damage tolerance assessment of surface features of aero engine life limited parts
DING Shuiting, ZHOU Huimin, LIU Junbo, ZHANG Gong, LI Guo
2021, 36(2): 421-430. doi: 10.13224/j.cnki.jasp.2021.02.021
Abstract PDF(2980KB) icon636 icon93
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In order to meet the safety requirements of airworthiness regulations (FAR/CCAR33.70) on life limited parts (LLPs), a probabilistic surface damage tolerance method was summarized based on the special material data, linear elastic fracture mechanics analysis and damage risk analysis. The damage tolerance assessment for hole features was analyzed and a new modified method for evaluating the probability of failure (POF) was proposed with higher efficiency. This method was verified referring to the test case provided by AC33.70-2. The assessment result showed that the POF of the disk with hole features was 2.677×10-4 times (20 000 cycles) without any in-service inspection and 1.514×10-4 times (20 000 cycles) with two inspections at 4 000 and 8 000 cycles based on the assumption that 90% of the parts are inspected at 4 000 cycles and an independent 90% of the parts are inspected at 8 000 cycles. Based on the modified method, the conservative POF was 3.406×10-4, demonstrating the preliminary compliance of airworthiness regulations. The surface analysis of damage tolerance assessment provides a support for evaluating the safety of hole features, which is instructive to other surface features.
Development history of civil turbine engine endurance test requirements
WANG Xiaoming
2021, 36(2): 431-439. doi: 10.13224/j.cnki.jasp.2021.02.022
Abstract PDF(2710KB) icon724 icon81
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The development history of 33.87 endurance test in aero-engine airworthiness standards CCAR-33R2 was comprehensively reviewed. Based on the interpretation of airworthiness regulation requirements, the current research of 33.87 endurance test in the world was deeply tracked. It showed the endurance test requirement remained essentially unchanged since 1 957 when the current 6 hour×25 cycles formats were implemented, but turbine engine designs had evolved significantly. The progress of engine design technology brought incompatibility with airworthiness regulations, so exploratory research and application on alternative test of 150 hour endurance test was carried out in the world. Despite of some existing issues for clarifications, the relevant research can provide reference for the accepted compliance method research and the airworthiness standard formulation and revision in China. It is of great significance for improving the compilation and revision ability about China's airworthiness technical regulations to track domestic and international airworthiness technology trends continuously and deeply, and then take positive response strategies timely and carry out targeted research on relevant provisions.
Simulation and optimization design of aviation nickel resistance temperature sensor
QI Lei, ZHANG Lei, PENG Yan, WANG Xi
2021, 36(2): 440-448. doi: 10.13224/j.cnki.jasp.2021.02.023
Abstract PDF(3170KB) icon500 icon67
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In order to meet the dynamic thermal response requirements of a aviation nickel resistance temperature sensor, the mathematical model was constructed, and the simulation analysis of six groups of design schemes was completed. The optimal design was determined through trial productions and verification tests. The sensor of a helical skeleton, which was composed of copper and filled with thermal conductive silicon grease, had the fastest dynamic thermal response. The simulation result of time constant was 17.3 s, and the test result was 16.58 s. This design of the sensor can meet the technical requirements.

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