2020 Vol. 35, No. 11

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Numerical simulation on cold expansion strenghthening ,technology process of GH4169,
HU Dianyin, LI Wenzhu, LIU Hui
2020, 35(11): 2241-2247. doi: 10.13224/j.cnki.jasp.2020.11.001
Abstract PDF(2957KB) icon487 icon313
Abstract:
On the basis of verifying the correctness of the three-dimensional finite element model for the cold expansion (CE) of central hole fatigue specimen of nickel-based superalloy GH4169, the influences of chamfering size, the order of chamfering-CE process and the reaming amount on circumferential residual stress distribution around the hole edge were studied through element deletion method. The results showed that the initial chamfer size less than the interference amount of the mandrel can reduce the residual compressive stress after CE. Lower residual compressive stress can be obtained at the hole edge by using the CE-chamfering process. The reaming process can lead to the increase of residual stress at the entrance of the hole edge and the minimum residual stress may be removed. Thus, reaming should be avoided as much as possible after cold expansion strengthening.
Topological optimization design of aero-engine support structure under multiple loading conditions
XING Guangpeng, SUN Zhigang, CUI Xiangmin
2020, 35(11): 2248-2262. doi: 10.13224/j.cnki.jasp.2020.11.002
Abstract PDF(6139KB) icon1166 icon482
Abstract:
The topological optimization technology based on the variable density method was introduced into the design of aero-engine external support structure (such as accessory support). Taking the total flexibility under multiple working conditions as the objective function and the volume as the constraint function, the structural design of an engine support based on the topological optimization was carried out. The initial model of the bracket was established according to the relative position relationship between the engine casing and the accessories, and the stress analysis of the external support structure of the engine was carried out. The design method of the external support structure of the engine was established based on the topology optimization under multi load conditions and the size optimization considering the influence of strength. The strength, vibration and profile of the final support structure were checked and evaluated. The results showed that the maximum stress of the final model appeared in condition 3, and the maximum principal stress was 345 MPa, which was lower than the fatigue limit of the material; the first natural frequency of the bracket was more than 125 times of the maximum speed frequency of the engine. This method was used to optimize the topology of the external support structure of an engine. On the premise of meeting the requirements of strength, vibration and contour, the final model weight was only 73% of the original model. The optimization results based on multi operating conditions are more in line with the actual working requirements of the engine, and the research of this method has a bright future in engineering application.
Dynamic characteristics of rotor and safety design of support structure with fan blade off
LI Chao, LIU Di, MA Yanhong
2020, 35(11): 2263-2274. doi: 10.13224/j.cnki.jasp.2020.11.003
Abstract PDF(4948KB) icon539 icon330
Abstract:
A pivot load response analysis method of comprehensively considering various mechanical processes, such as impact, inertia asymmetry, and deceleration over-critical for load control of aero engine under extreme load of blades off, was established. A safety design of buffer damping support structure for the thrust support was proposed, which can affect the dynamic characteristics of the rotor system by controlling the stiffness and damping parameters of the support structure, reducing the critical speed of the rotor. Quantitative evaluation of effectiveness for the buffer damping structure was carried out by the above pivot load response analysis method. The effects of pivot load during the impact-deceleration process was proved. Results showed that the impact effect and deceleration over the critical process caused by the blade off are the main factors that threaten the bearing capacity of the supporting structure. And the use of a buffer damping pivot structure can effectively reduce the pivot of the rotor system to 20% when fan blade off appeared, making it an effective design for the safety of the support structure.
Multiscale damage simulation of plain weave composites ,based on 3D general method of cells
ZHANG Long, CHENG Jun, QIU Rongkai
2020, 35(11): 2275-2283. doi: 10.13224/j.cnki.jasp.2020.11.004
Abstract PDF(3994KB) icon530 icon270
Abstract:
In order to solve the technical difficulty of operating multiscale simulation on the braided composites of highly complicated mesoscopic structure, a multiscale damage simulation method based on 3D general method of cells(GMC) model was developed. Based on the basic theory of the GMC method, the conversion formula of macroscopic and mesoscopic parameters was derived, and the iterative process of macroscopic and mesoscopic damage increment steps was developed. Taking the 2D plain weave ceramic matrix composite as an example, the mesoscopic damage simulation on the unit cell was examined and the multi-scale damage simulation on the flat test piece of the 2D plain weave composites was performed. The mesoscopic damage contours and macroscopic stress-strain curve were obtained. The research revealed that the unit cell mesoscopic damage process simulated by the method agreed with the damage mechanism described in the related literatures. The predicted stress-strain curve during the damage process of the flat test specimen was consistent with the test results, and the relative error of the predicted intensity value was less than 5%.
Numerical analysis on residual stress of foreign object damage on the leading edge of titanium alloy blade
ZHAO Zhenhua, ZHANG Junhe, WANG Lingfeng
2020, 35(11): 2284-2292. doi: 10.13224/j.cnki.jasp.2020.11.005
Abstract PDF(4666KB) icon579 icon259
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In order to study the distribution law of residual stress on foreign object damage (FOD) position in aero engine blades, the simulated blades were designed according to the characteristics of the aero engine blade leading edge. LS-DYNA software was used to simulate and analyze the impacting process of titanium alloy simulated blade at different angles based on Johnson-Cook constitutive and failure models. The damage morphology and macro size were compared between simulating results and FOD test results to verify the correction of the finite element model. The simulated residual stress distribution at the FOD position corresponding to different incident angles was extracted. The results showed that when the incident angle of steel ball was 0°, the contact force and deformation energy were significantly larger than other incident angles, indicating that the material failure and deformation at the skewed notch caused by a certain incident angle impact were less serious than the semi-circular notch formed by the 0° incident angle impact. There was a significant residual tensile stress area at the FOD notch root near the incident surface. As the incident angle increased, the range of the residual tensile stress area gradually expanded, and the maximum value of the residual tensile stress decreased.
Coupling vibration characteristics analysis and experiment,of shared support-rotors system
LEI Binglong, LI Chao, HE Kang
2020, 35(11): 2293-2305. doi: 10.13224/j.cnki.jasp.2020.11.006
Abstract PDF(9110KB) icon456 icon263
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In view of the structural system of high power to weight ratio turboshaft engine with shared load bearing frame between turbine stages, the dynamic equation of the shared support-rotor system was established to explore the coupling vibration conditions and vibration characteristics of the gas generator rotor, the dynamic turbine rotor and the Shared load bearing frame structure system. Based on the ANSYS finite element simulation platform, the coupling vibration characteristics of the common bearing-rotor system were simulated by transient dynamics analysis method. For the inter-turbine load bearing frame of turbosshaft engine, a simulation tester of shared supplate-rotor system was designed, and a vibrator was used to simulate the unbalanced excitation of the rotor. The theoretical calculation results showed that the rotor fulcrum and the supporting structure were connected by force balance and displacement coordination, and there was a coupling stiffness between them, which led to the coupling vibration of the shared bearing-rotor system. The simulation results of the vibration response of the system under unbalanced excitation showed that the shared support could affect the dynamic characteristics of the rotor, and the vibration of the corresponding rotor could be excited by different unbalanced excitation of the rotor. It was verified through experiments that when coupled vibration occurred, the vibration response spectrum of the rotor contained two rotor speed frequencies at the same time, and the coupling influence coefficient was defined. The coupling influence coefficients between the two rotors in the idle state on the ground were 33% and 6079%, respectively. The maximum continuous state were 1278% and 688%, and the maximum take-off state were 1356% and 581%, respectively. The coupling influence of the dynamic characteristics between the rotors was related to the frequency.
Analysis of load sharing mechanism and parameter matching of,gear split torque drive system
JIN Guanghu, XU Xintao, ZHU Rupeng
2020, 35(11): 2306-2315. doi: 10.13224/j.cnki.jasp.2020.11.007
Abstract PDF(3744KB) icon486 icon225
Abstract:
In order to improve the load sharing characteristics of the split torque drive system, the mechanism of affecting the load sharing performance was analyzed by constructing the analysis diagram of error and load. Considering the support stiffness, the torsional stiffness and time-varying meshing stiffness of the gear pairs, a dynamic model of the transmission system was established by using the lumped mass method. The dynamic model of the transmission system was solved by the Runge Kutta method, and the load sharing coefficient was calculated. The influence law and weight of backlash and center distance error on the load sharing characteristics were obtained by the orthogonal test method. The results showed that the backlash had correlation, and its value should meet certain rules; the center distance error had no correlation, and the center distance error of confluence stage had great influence on the load sharing and dynamic load coefficient. Therefore, in order to improve the load sharing characteristics of the split torque transmission, the design method of parameter matching should be adopted for the backlash and center distance errors.
Flow and temperature fields analysis of fan drive gearbox ,based on CFD
BAO Heyun, WANG Chunlei, LU Fengxia
2020, 35(11): 2316-2325. doi: 10.13224/j.cnki.jasp.2020.11.008
Abstract PDF(6589KB) icon545 icon266
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The GTF (geared turbofan) engine fan drive gearbox simulation model was established. The flow and temperature fields of fan drive gearbox were simulated by using the RNG(renormalization-group) k -ε turbulence model and the MRF (multiple reference frame) model. The results showed that local eddy currents appeared in the engaging-in and engaging-out region of the external gearing of the gearbox, due to the vertical direction of the two chamfer planes and fluid velocity in which the oil distribution plate nozzle was located. The highest temperature of the fan drive gearbox occurred in the planetary gear, followed by the sun gear, and the lowest one occurred in the inner ring. The temperature of planetary bearing roller was higher than the inner and outer rings of the bearing. The temperature of the inner ring of the planetary bearing was lower due to the way of inner-ring oil supplying, and the temperature of the outer ring of the planetary bearing was affected by the bulk temperature of the planetary gear, which was higher than the inner ring temperature. The temperature of the planetary gear had a peak value in the middle of the tooth width direction. In the direction of tooth height, there was a high temperature peak near the top of the tooth of the planetary gear, and a relatively low temperature peak near the root position.
maintaining reliability and uncertainty of rolling bearings
YE Liang, XIA Xintao, CHANG Zhen
2020, 35(11): 2326-2338. doi: 10.13224/j.cnki.jasp.2020.11.009
Abstract PDF(3578KB) icon433 icon233
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Three indicators, ie, the fluctuation range of instantaneous vibration value, fluctuation range of average vibration value and the average fluctuation range during the corresponding period of vibration sequence, were used to characterize the uncertainty of vibration performance of bearing in service comprehensively, so as to quantitatively analyze the internal specific relationship between the three uncertainty indexes and vibration performance maintaining reliability. The maximum entropy method and Poisson process theory were used to calculate the vibration performance maintaining reliability of bearings. The values of three uncertainty indexes were calculated in turn based on the grey bootstrap method, bootstrap method and maximum entropy method, and classical statistical method. A multivariate regression analysis model was established to analyze the expression of the relationship between the performance maintaining reliability and the three uncertainty indexes. Results showed that the linear correlation coefficients between performance maintenance reliability and the three uncertainties were -0843 7,-0779 8,-0759 7;-0835 4,-0843 9,-0808 2 for case 1 and case 2,respectively. Both cases show that the fluctuation range of instantaneous value and average fluctuation range have nonlinear influence on performance maintenance reliability.
Adaptive wavelet threshold function based on PSO-RWE ,for vibration signal denoising of rolling bearing
YANG Xu, QIU Ming, CHEN Lihai
2020, 35(11): 2339-2347. doi: 10.13224/j.cnki.jasp.2020.11.010
Abstract PDF(3616KB) icon701 icon204
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In view of the existing wavelet threshold denoising method that unknown parameters selection in existing functions depends on experience and brings about insufficient denoising or signal distortion after denoising, a particle swarm optimization (PSO) algorithm based on relative wavelet entropy (RWE) was proposed for adaptive optimization of unknown parameters in wavelet threshold function to achieve adaptive noise reduction of rolling bearing vibration signal. A wavelet threshold function with two unknown parameters was improved. The relative wavelet entropy was used as the fitness function to optimize the unknown parameters and the optimal wavelet threshold function was obtained. The vibration signal of rolling bearing acquired by simulation and experiment was analyzed. Results showed that the optimized wavelet denoising method can filter the noise from the denoised signal better, the signal waveform after denoising had better smoothness, the signal-to-noise ratio was 294% higher than the hard threshold, and retained more details of the original signal, presenting better denoising performance and practical value.
Effect of inaccurate source term loading on simulation ,precision for source term model
ZHU Jianqin, LI Lin, QIU Lu
2020, 35(11): 2348-2355. doi: 10.13224/j.cnki.jasp.2020.11.011
Abstract PDF(3213KB) icon333 icon226
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Numerical simulation of the real model and the source term model was carried out for a multi-perforated film cooling plate. On the basis of high-precision experimental comparison, the effect of inaccurate source term loading on the simulation results was explored, and the factors such as loading methods, discharge coefficient, and mesh parameters were analyzed. Results showed that the source term model could be used for numerical calculation of film cooling structure instead of establishing real holes with film hole. The source term loading method of accurate mesh positioning could achieve high precision under the coarse and fine meshes, while the point loading method was more sensitive to the grid. The mass flow rate calculation error caused by the inaccuracy of discharge coefficient empirical formulas would affect the calculation precision of the source term model, which was more pronounced at low blow ratios. The mesh density at the entrance and exit of the film hole should be not less than 4/mm2, and the height of first prism layer should be consistent with the turbulence model to ensure high simulation precision.
Energy distribution characteristics of gas at outlet of ,pulse detonation combustor
LI Xiaofeng, XIAO Junfeng, WANG Wei
2020, 35(11): 2356-2363. doi: 10.13224/j.cnki.jasp.2020.11.012
Abstract PDF(3799KB) icon368 icon211
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In order to improve the energy conversion efficiency of the gas at the outlet of the pulse detonation combustor, a numerical calculation method was used to study the energy distribution characteristics of the gas at the outlet of the pulse detonation combustor with a pneumatic valve and detonation reinforcement structure. Results showed that the expansion process of pulse detonation gas had three stages: primary expansion, secondary expansion and over expansion. The proportion of secondary expansion time and energy was largest in a single cycle; the distribution of gas pressure potential energy, kinetic energy, internal energy and energy flow density at the outlet of the combustion chamber was mainly affected by the gas pressure, and the change law was consistent with the gas pressure; the pressure potential energy, kinetic energy and internal energy of gas increased during the primary expansion stage accounted for 479%, 259% and 251%, respectively, in a single cycle; the pressure potential energy, kinetic energy and internal energy of gas increased during the secondary expansion stage accounted for 502%, 576% and 581%, respectively, in a single cycle.
Experiment on airfoil runback ice protection based on synthetic jet,
YANG Shengke, GUO Qiling, LUO Zhenbing
2020, 35(11): 2364-2370. doi: 10.13224/j.cnki.jasp.2020.11.013
Abstract PDF(2769KB) icon491 icon190
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A hybrid ice protection method combining thermoelectric systems and synthetic jet actuators was designed to solve the problem of runback ice. In this method, the thermoelectric system was arranged on the leading edge of the wing to prevent the supercooled water droplets from freezing. The synthetic jet slot was located downstream the thermoelectric system to change the trajectory of runback water. The effects of the liquid water content, the incoming flow and the velocity of synthetic jet on the anti-icing performance of the hybrid ice protection system were studied in the icing wind tunnel. The results showed that the hybrid ice protection method could keep both the leading-edge and downstream regions free from icing.
Flow and heat transfer characteristics of a two-diameter pulsating heat pipe
ZHANG Wang, LU Xiaojian, XU Guoliang
2020, 35(11): 2371-2377. doi: 10.13224/j.cnki.jasp.2020.11.014
Abstract PDF(2572KB) icon429 icon175
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In order to improve the heat transfer characteristics of pulsating heat pipes, a type of two-diameter pulsating heat pipe structure was proposed, and the applicable physical and mathematical model was developed based on the mass, momentum, and energy conservation equations. This two-diameter pulsating heat pipe adopted different pipe diameters between the evaporation section and the condensation section. The ratio of the two was defined as the diameter ratio. The above theoretical model was used to analyze the effect of the diameter ratio on the pulsating heat pipe motion and heat transfer characteristics. Results show that the two-diameter structure can effectively improve the self-excited oscillation mechanism of the pulsating heat pipe, especially when diameter ratio is less than 1. In terms of heat transfer characteristics, compared with the traditional equal-diameter pulsating heat pipe (diameter ratio equals to 1), using the structure of diameter ratio less than 1 can significantly reduce the thermal resistance of the pulsating heat pipe, but using the structure of diameter ratio more than 1 instead can decrease the heat transfer characteristics.
Experiment of rotor-stator interaction behaviors in ,a small multi-stage axial compressor
HE Xiang, MA Hongwei, YIN Yueqian
2020, 35(11): 2378-2384. doi: 10.13224/j.cnki.jasp.2020.11.015
Abstract PDF(3601KB) icon356 icon210
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The dynamic pressure signals were measured and analyzed by the Kulite transducers and the fast response pressure probes to investigate the rotor-stator interaction phenomenon in small multistage axial compressor. Results indicated that, at higher rotor speed, the 1st rotor tip flow-field agreed well with the typical supersonic-cascade flow features, and only the flow-field at the 1st rotor trailing-edge was disturbed by the rotor-stator interactions. However, at lower rotor speed, the rotor-stator interaction obviously increased in intensity and appeared at the 1st rotor leading-edge with the compressor throttling. Modal analysis was carried out for these frequency components of rotor-stator interactions, and then the propagation speed and modal number were obtained finally.
Study on opposed mixing flow in circumferential intake
LI Zhenpeng, FU Chao
2020, 35(11): 2385-2399. doi: 10.13224/j.cnki.jasp.2020.11.016
Abstract PDF(15194KB) icon255 icon173
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For studying the structures of opposed mixing flow at the outlet of radial centripetal turbine,large eddy simulation was used to simulate the convective mixing flow of the circumferential intake. Flow structures in different modes were extracted and analyzed by the proper orthogonal decomposition (POD) method. The results showed that there existed stagnation zone near the bottom center and a recirculation zone near both sides of the wall,and the flow was approximately symmetrical at the horizontal cross section. The instability of the vortex structure was strengthened due to the effect of the shear force along the streamwise direction. Furthermore,the upstream three-dimensional vortex ring structure was stretched and expanded,breaking into a complex vortex braid or hairpin vortex structure,which enhanced the mixing,and also the momentum and energy exchanged between the fluids. The POD results showed that the first mode had the highest energy weight,indicating that most of the energy in the pulsating field was concentrated in this mode,and the flow structure in this mode acted as the main flow structure.
Impact of incidence angle on tip leakage flow control ,by endwall suction in a compressor cascade
ZHANG Botao, LIU Bo, WANG Hejian
2020, 35(11): 2400-2412. doi: 10.13224/j.cnki.jasp.2020.11.017
Abstract PDF(7431KB) icon372 icon205
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In order to reduce the tip leakage loss and improve the tip passage blockage caused by the tip leakage vortex, numerical simulation was conducted to investigate the flow control effect of suction scheme with endwall slot in flow direction on the tip leakage flow in a diffuser cascade. The impact of incidence angle on flow control effect was analysed emphatically. Results showed that the leakage vortex intensity and the leakage loss were reduced by the endwall suction scheme by directly controlling the development of the tip leakage flow. The influence of endwall suction on the cascade flow field at the design and negative incidence angles was limited to the vicinity of the blade tip. However, at a large incidence angle, suction can advance the boundary layer separation in the low span region, and the position of the vortex shedding on the suction surface of blade raised to about 70% span. Therefore, the overall impact of the endwall suction scheme on the cascade at a large incidence angle was determined by both the reduction of leakage loss and the increase of separation loss. With the suction flow rate of 07%, the overall total pressure loss coefficient of aspirated cascade decreased by about 90%, 108% and 68%, respectively, at the incidence angles of -8°, 0°and +4°, and increased by about 57% at the incidence angles of +8°.
DMD analysis of compressor stall inception and rotor flow field ,under multiple conditions
LI Kangdi, DU Yunxiang, XU Zili
2020, 35(11): 2413-2420. doi: 10.13224/j.cnki.jasp.2020.11.018
Abstract PDF(3160KB) icon688 icon205
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The unsteady flow field of a transonic axial compressor Rotor 37 was numerically simulated, and the modal information of fluid pressure and velocity were obtained by the dynamic modal decomposition method(DMD). The stability of the compressor under different working conditions was determined, the main characteristic structures of the flow field were captured, and the stall aura of the compressor was found by the modal cloud diagram. The results showed that, the near stall point and the plugging point had unstable modal orders; the maximum error between DMD frequency and pressure spectrum was 063%; with the rise of backpressure, the fluid mass in the two adjacent blades gradually moved to the leading edge of the blade, and its range was expanded; at the near stall point, with the mixing of main flow and reflux, a semi-ellipsoidal vortex was generated in the middle of the blade suction surface and the flow channel was blocked, which was the initial manifestation of a spike stall.
Uncertainty analysis in scramjet performance parameters measurements
LIAO Wenhao, GUO Jinxin, LIU Xiaoyong
2020, 35(11): 2421-2428. doi: 10.13224/j.cnki.jasp.2020.11.019
Abstract PDF(1009KB) icon318 icon206
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Based on wind tunnel test uncertainty assessment of AIAA S-071A-1999 and the uncertainty study for the wind tunnel testing,aeroengine performance testing and rocket ground testing in the international space power community,an uncertainty analysis method for the scramjet performance testing was established,and corresponding analysis was given.Results showed that the uncertainty induced by the free-jet testing measurement was predominant in evaluating the overall scramjet performance,and the bias limit was over 90% in the uncertainty of scramjet performance parameters measurements.In conclusion,some valuable results and suggestions about the uncertainty of overall performance of scramjet were obtained,and these results can improve the accuracy in scramjet performance parameters measurements,showing prominent application prospect in scramjet development.
Lifting and propulsion devices for flight performance ,improvement of a compound helicopter
YANG Kelong, HAN Dong, SHI Qipeng
2020, 35(11): 2429-2439. doi: 10.13224/j.cnki.jasp.2020.11.020
Abstract PDF(6823KB) icon289 icon186
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To analyze the effects of lifting and propulsion devices for flight performance improvement of a compound helicopter, a model of performance prediction was developed. Based on the UH-60A helicopter equipped with a wing and a propeller, the influence mechanism of parameters of the wing and propeller, lift and propulsive force shares on the performance was analyzed. At low speeds, due to the low efficiency of the wing and propeller, equipping the wing and propeller decreased the lift-to-drag ratio of the helicopter. The higher rotor speed or blade twist of the propeller led to larger profile power of the propeller, and further reduced the lift-to-drag significantly. At high speeds, the efficiency of the wing and propeller was higher; the performance was significantly improved when the wing and propeller offloaded most of the lift and propulsive force with the decrease of the main rotor speed; the lift-to-drag ratio increased first and then decreased as increasing the lift and propulsive force shares. At a speed of 300 km/h, optimizing the lift and propulsive force share, at 100%, 95%, 85% and 80% of main rotor speed, increased the lift-drag ratio by 40%, 2133%, 270% and 306%, respectively.
Influence of computational domain size on large ,eddy simulation results,
KANG Kai, ZHANG Ziliang, WANG Weiqiang
2020, 35(11): 2440-2448. doi: 10.13224/j.cnki.jasp.2020.11.021
Abstract PDF(4395KB) icon508 icon192
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In order to save computing resources and improve computation efficiency, it is particularly important to ensure the accuracy of the calculation results and to select a computational domain as small as possible. The influence of computational domain size on large eddy simulations of turbulent channels with periodic boundary conditions was studied. Simulations were presented in channels with streamwise and spanwise sizes of 053πδ×2δ×0177πδ, πδ×2δ×05πδ, 2πδ×2δ×πδ and 3πδ×2δ×15πδ, wherein δ is the channel half-height. On the premise that the calculation conditions are the same and the settings meet large eddy simulation calculation requirements, the influence of calculation domain size on large eddy simulation numerical calculation results under friction Reynolds number of 540 and 930 was studied. It was found that the computational scale not less than 2πδ×2δ×πδ could well present the turbulence results. In addition, the accuracy of turbulence information in the same computational domain was improved at friction Reynolds number of 930.
Effects of thrust chamber conditions on its acoustic modes and their damping characteristics
QIN Jianxiu, ZHANG Huiqiang
2020, 35(11): 2449-2455. doi: 10.13224/j.cnki.jasp.2020.11.022
Abstract PDF(1471KB) icon319 icon187
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In order to determine whether acoustic characteristics obtained in cold case in engineering can represent those in actual cases, acoustic modes and their damping characteristics of thrust chamber were investigated under three conditions: cold case without flow, hot case with flow and turbulent two-phase reactive case. High-amplitude pressure oscillations featured with multi-mode acoustic characteristics were excited by imposing numerical constant-volume bomb into a limited region at the steady flow in a thrust chamber. The damping rate of pressure oscillation of each acoustic mode was evaluated by decay time and half-power bandwidth, thereby damping capacity of each acoustic mode was obtained. Results showed more acoustic modes were excited in cold case than those in two hot cases. The decay times in cold case were longer than those in two hot cases. Moreover, pressure oscillation of each mode in cold case decayed slower than that of the corresponding mode in two hot cases. For the cold case, the amplitude of the first tangential mode was the greatest for the most inspirable acoustic mode. The half-power bandwidth of the first longitudinal mode was the smallest for the most difficult mode to be attenuated. For the two hot cases, the first longitudinal mode was the most inspirable acoustic mode with greatest amplitude and the most difficult mode to be attenuated with smallest half-power bandwidth. Judging from main acoustic modes excited by numerical constant-volume bomb as well as relative damping characteristics, investigation on acoustic performance of thrust chamber in the cold case was reasonable to reveal the acoustic performance under the real condition.
Calculation method of aero-engine exhaust gas temperature margin ,and remaining life based on data
DU Fangzhou, SUN Youchao, GUO Yuanyuan
2020, 35(11): 2456-2464. doi: 10.13224/j.cnki.jasp.2020.11.023
Abstract PDF(3874KB) icon987 icon395
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To solve the difficulty of calculating and predicting important monitoring parameter exhaust gas temperature margin (EGTM), an EGTM calculation method and remaining life prediction model based on data were established according to the aviation industry standard implementation guidelines. The influencing factors of EGTM were split and the fan speed and exhaust temperature based on the revised similarity theory were corrected. The discrete test data of partial conversion/correction formula parameters were fitted to obtain the relationship curve. Support vector machines were used to learn the influencing factors of the engine bleed system, and the genetic algorithm was used to optimize the penalty factors and the kernel function parameter of the support vector machine to obtain EGTM parameter corrected by the engine bleed system; again, the wavelet transform was used to reduce the noise and feature extraction of the EGTM. The polynomial regression was used to fit the feature parameter to determine the single engine/average fleet EGTM performance decline rate, and the remaining life of EGTM was calculated. The model realized the whole process of calculation from data input to remaining life prediction. The EGTM calculation results had a goodness of fit up to 0994 compared with the results provided by original equipment manufacturer. Compared with the EGTM curve after wavelet transform, the fitting effect of the margin remaining life decay curve was 098. The results can be used as the theoretical support and reference basis for maintenance plan formulation and economic cost calculation.

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