2018 Vol. 33, No. 6

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Numerical simulation on influence of flow field of combustor inlet on a certain reversed-flow combustor performance
2018, 33(6): 1281-1289. doi: 10.13224/j.cnki.jasp.2018.06.001
Abstract PDF(1162KB) icon1021 icon807
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The asymmetrical flow field of combustor inlet was obtained by which the oriented vane was installed in the axial diffuser of a reverse-flow combustor test piece, and how the combustor performance was affected by the variety of the combustor inlet flow field was simulated based on experiments verification, and the scheme included no vane, vane deflexion angle of 25° and vane deflexion angle of 35°. The results indicate that the unevenness of the flow field of the combustor inlet is caused by the oriented vane with deflection angle. The flow of combustor inlet takes on a certain deflexion angle and tangential velocity. The airflow direction of the primary holes and dilution holes has a deflexion angle. When the deflexion angle of the oriented vane increases, the axial velocity of the primary holes and dilution holes increases to a certain extent, and the tangential velocity of the primary holes and dilution holes increases greatly. The total pressure recovery coefficient decreases when the deflexion angle of the oriented vane increases. With the increase of deflection angle of the oriented vane, the combustion efficiency is invariable basically. The outlet temperature distribution factor(OTDF) decreases greatly, and the temperature circumferential distribution unevenness decreases at the same radial height.
Comparison of combustion performance for different nozzles in gas turbine combustor
2018, 33(6): 1290-1297. doi: 10.13224/j.cnki.jasp.2018.06.002
Abstract PDF(912KB) icon1007 icon544
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The gas turbine combustor with -10# diesel was changed to one with burn natural gas, and based on the principle of least change of combustor, only the fuel nozzle design was changed. In order to understand the matching characteristics of the nozzle and combustor, three kinds of natural gas nozzles with different injector hole diameters were designed, nozzle could affect the injecting velocity of natural gas, natural gas concentration distribution, therefore, it could affect the combustion performance of combustor. So the combustion performance experiment for these three kinds of natural gas nozzles was carried out. The experimental results show that when the fuel is natural gas, the combustion efficiency increases, but the exit temperature distribution is poor, there is little effect on the wall temperature distribution. Based on the comparative analysis of the experimental results, the combustion performance of natural gas nozzle No.3 is the optimum.
Preliminary experiment on spontaneous ignition performances of cavity-based strut flameholder
2018, 33(6): 1298-1304. doi: 10.13224/j.cnki.jasp.2018.06.003
Abstract PDF(912KB) icon1106 icon552
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The spontaneous ignition performances of a cavity-based strut flameholder were preliminarily investigated with spray distances of 5－50mm at atmospheric pressure, the air temperature and oxygen volume fraction were within the range of 750－900℃ and 13.4%－15.8%, Mach number ranged from 0.20－0.28. Results showed that the flameholder could be autoignited when the inlet temperature was above 850℃. As the inlet temperature increased, the performances of spontaneous ignition improved. When the inlet Mach number became larger, the temperature range for successful spontaneous ignition became narrower. With the increase of fuel injection distance, the autoignition performances of the stabilizer were improved. The cavity structure of the stabilizer could stabilize the flame.
Effects of methane mole fraction and initial pressure on the combustion characteristics of methane/RP-3 kerosene mixture
2018, 33(6): 1305-1314. doi: 10.13224/j.cnki.jasp.2018.06.004
Abstract PDF(1189KB) icon935 icon504
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The combustion characteristics such as flame propagation characteristic, Markstein length and laminar burning velocity of methane/RP-3 mixture were obtained in a constant volume chamber at initial temperature of 450K, initial pressures of 0.1-0.3MPa, equivalence ratios of 0.7-1.5 and methane mole fraction of 0-0.8, and the effects of methane mole fraction and initial pressure on combustion stability and laminar burning velocity of methane/RP-3 mixture were analyzed. The results showed that at the equivalence ratio of 1.3, with the increase of methane mole fraction, the combustion of methane/RP-3 kerosene mixture became stable. The effect of initial pressure on combustion stability was greater. With the increase of initial pressure, the combustion stability of the mixture became worse. Markstein length of the mixture decreased with the increase of equivalence ratio. With the increase of methane mole fraction, the decrease tendency of Markstein length became slow, and with the increase of initial pressure, this decrease tendency became slow significantly. The laminar burning velocity of the mixture increased first and then decreased with the increase of equivalence ratio. At methane mole fraction of 0, 0.4 and 0.6, with the increase of methane mole fraction, the laminar burning velocity of the mixture increased gradually. At initial pressure of 0.1, 0.2, 0.3MPa, with the increase of initial pressure, the laminar burning velocity decreased evidently. With the increase of methane mole fraction and initial pressure, the peak value of laminar burning velocity of the mixture had the trend to move towards the fuel-rich zone.
Life cycle assessment of algae based aviation fuel on basis of engine type and related aircraft
2018, 33(6): 1315-1325. doi: 10.13224/j.cnki.jasp.2018.06.005
Abstract PDF(1092KB) icon861 icon524
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Consolidated discussion of life cycle assessment on algae based aviation fuel in combustion emissions on the basis of engine type and related aircraft was conducted by comparing with conventional jet fuel. Using the GREET （the greenhouse gases,regulated emissions,and energy use in transportation） model, passenger aircrafts were divided into six classes including single aisle, small twin aisle, large twin aisle, large quad, regional jet, and business jet. Each aircraft class was characterized by its average payload, potential flight range, and fuel consumption and emissions during landing, takeoff, taxiing, climbing referred to in the database of NASA-AAFEX, EASA, and CAAC. Also the emissions and energy input were discussed. The pump-to-wheel stage of algae based jet fuel in large twin aisle aircraft shows the least amount of greenhouse gases emission at 0.2351g/(kg·km) because larger aircraft has lower greenhouse gases emissions values than smaller aircraft due to higher engine efficiency and higher payload, however single aisle aircraft appears to be more sensitive to greenhouse gases emission in flight range than larger aircraft due to higher contribution of landing and takeoff.
Three-dimensional fiber random model to predict effective thermal conductivity of plain braided C/SiC composites
2018, 33(6): 1326-1335. doi: 10.13224/j.cnki.jasp.2018.06.006
Abstract PDF(1147KB) icon941 icon599
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A random microstructure cell model was developed to predict the effective thermal conductivity of plain braided C/SiC composites material, so as to describe the real distribution of fibers and the braiding-structure. Then, the influence mechanism of microstructures on macroscopic effective thermal conductivity was discussed. The random distribution of fibers was simulated by Monte Carlo method, and the effective thermal conductivity was calculated based on finite element method, and the results were presented in statistical forms. It was shown that, the Gaussian distribution function described the distribution of effective thermal conductivity accurately. For a random fiber distribution, fibers segregated in a microscopic level; Portions of the fibers came into contact and formed some local “heat flow obstacles”, which led to a smaller effective thermal conductivity than that of the general cell model.
Effects of spanwise distance and density ratio on the characteristic of double-jet film-cooling
2018, 33(6): 1336-1344. doi: 10.13224/j.cnki.jasp.2018.06.007
Abstract PDF(1117KB) icon850 icon534
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Double-jet film-cooling geometries on a flat plate were investigated using pressure sensitive paint (PSP) measurement technique. The spanwise distance between the double-jet film-cooling holes varied as 0, 0.5 and 1.0, while the streamwise distance was kept as 3.0. The density ratio was 1.0, 1.5 and 2.5, while the blowing ratio was 0.5, 1.0, 1.5 and 2.0. The effects of spanwise distance and density ratio on the effectiveness of double-jet film-cooling holes were studied. The results showed, at spanwise distance of 0, the lateral coverage of the film was suppressed. As the spanwise distance increased, the film covered more areas. However, while the spanwise distance was too large, the film coverage degraded. With the increase of density ratio, the lifting-off of the jets weakened, and the film-cooling effectiveness improved. At high density ratios, higher film-cooling effectiveness was achieved by the double-jet film-cooling holes with larger spanwise distance.
ptimization of combustion characteristics of aviation piston gasoline engine
2018, 33(6): 1345-1353. doi: 10.13224/j.cnki.jasp.2018.06.008
Abstract PDF(1100KB) icon1018 icon580
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In order to optimize the combustion characteristics of a two-stroke aviation piston gasoline engine, the influence of spark plug position, spark plug number and spark plug arrangement on combustion was studied. The simulation model of the gasoline engine combustion chamber was established by using Pro-E and AVL Fire software. The correctness of the model was verified by the in-cylinder pressure data. The different spark plug positions and different spark plug numbers were simulated and the results were analyzed. The results show that the double spark plug arrangement scheme is more beneficial to the rapid combustion of tissue than the single spark plug arrangement scheme,helping to promote combustion and heat release, shorten the duration of combustion; spark plug asymmetric arrangement scheme is more favorable than the symmetrical arrangement scheme for flame formation and diffusion.
Network model for calculation of labyrinth seal in compressor stator well with swirl flow and windage heating
2018, 33(6): 1354-1362. doi: 10.13224/j.cnki.jasp.2018.06.009
Abstract PDF(990KB) icon949 icon494
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The labyrinth seal in a compressor stator well was simplified to one-dimensional network model consisting of typical elements. Then the computational models for these elements were built. The present model for the leakage calculation of labyrinth seal didnt consider swirl flow and windage heating impacts. One-dimensional basic equations were used to describe the swirl flow in rotating disc cavity. And empirical correlations were used to calculate the rotor wall friction. Runge-Kutta method was employed to solve these equations about circumferential velocity and windage heating of the rotating flow. An area correction method with swirl flow was adopted, and windage heating made the change of airflow properties. The relative deviation of leakage flow rate result of one-dimensional network and CFD was less than 1.4% with swirl flow and windage heating. Without swirl flow and windage heating, the relative deviation was more than 9.9% and less than 20.1%. Compared with the experimental results, the one-dimensional network calculation results agreed well with each other, the relative deviation was no more than 7%. one-dimensional network calculation took the practical working tip clearance of the labyrinth seal. In rotating labyrinth seal experiment，the practical clearance was obtained by measuring the radial displacement of rotor caused by rotation and thermal deformation as well as the radial displacement of casing caused by thermal deformation.
Aerogel skeleton solid phase thermal conductivity by molecular dynamics simulation
2018, 33(6): 1363-1369. doi: 10.13224/j.cnki.jasp.2018.06.010
Abstract PDF(727KB) icon938 icon502
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A noncrystalline silica model and a primary particle model was built based on the theory of molecular dynamic and the algorithm of its simulation, and it explored how the solid phase thermal conductivity of aerogel was affected by the changes of external environmental conditions and aerogel internal structure. The results of silica aerogel solid phase thermal conductivity under four different enviromental temperatures, namely, 300,500,800K and 1200K were obtained. With the enviromental temperature rise the solid phase thermal conductivity increased slightly. The influence of the internal defect of primary particle on the solid phase thermal conductivity of skeleton was discussed. Within the range of porosity, the thermal conductivity of the solid phase decreased with the increase of the porosity. When the porosity increased gradually to 0.26, the model can well characterize the actual situation. The noncrystalline aerogel model and algorithm proposed will provide a reference for the microscale heat transfer analysis and structural design of this material.
Mechanism of internal flow instability in transonic axial flow compressor at different rotating speeds
2018, 33(6): 1370-1380. doi: 10.13224/j.cnki.jasp.2018.06.011
Abstract PDF(1794KB) icon974 icon602
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A transonic axial flow compressor rotor, the NASA Rotor 67, was chosen to investigate the triggering mechanism of internal flow instability in transonic axial flow compressor at the 100%, 80% and 60% rotating speeds with the help of numerical method. The comparative analysis of numerical results and experimental data showed that the trends of experimental performance curves were finely repeated by numerical results under three design rotating speeds. The fundamental flow mechanism was obtained by the detailed analysis of internal flow field in compressor. As the mass flow rate of compressor reduced at three rotating speeds, the starting position of tip leakage vortex (TLV) moved to the blade leading edge gradually, and tip leakage vortex also turned towards the pressure surface of adjacent blade. The deviated degrees between tip leakage vortex trajectory and compressor rotating shaft for near stall point were 3 degree, 6 degree and 9 degree than that for near peak efficiency point at the 100%, 80% and 60% rotating speeds, respectively. The blockage resulted from the interaction between tip leakage vortex and shock wave led to the internal flow instability in compressor at the 100% and 80% rotating speeds, and tip leakage vortex broken occurred at the 80% rotating speed. While at the 60% rotating speed, the leading edge spilled flow(LESF) of blade tip caused by tip leakage vortex near adjacent blade was the primary cause of internal flow instability in compressor, while a small scope boundary layer flow separation(BLFS) near the trailing edge of blade suction surface was not the primary cause.
Exploration of three-dimensional unsteady model for compressor post-stall under inlet distortion
2018, 33(6): 1393-1402. doi: 10.13224/j.cnki.jasp.2018.06.013
Abstract PDF(1250KB) icon984 icon543
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The improved three-dimensional model called compressor stability analysis code plus (CSAC+) was developed by adding an axisymmetric left characteristic. The steady aerodynamic performances and stall inception characteristics of NASA Rotor 37 under total pressure distortion inlet condition were modeled and analyzed by CSAC+. And compared with NUMECA simulation results, both of the modeling characteristics were fitted well. The relative error of total pressure ratio near stall point for both CSAC+ and NUMECA results was 1.05%. For near stall flow field analysis, it was found that as the flow rate decreased, a low speed or even reverse flow region appeared at the tip of rotor which was located behind the edge of the distortion zone. The region could be considered as the stall inception position under total pressure distortion. The stall inception and the post-stall flow characteristics of the compressor under inlet distortion were also analyzed with CSAC+. At the stall inception, the modal wave turned into part blade height stall after full development. The stall occupied 40% blade height, and the propagation frequency of the stall group was about 60% of the rotor rotation frequency. The stall group showed periodic exfoliation and fusion during propagation.
Cold model experiments and numerical study on crystallization two-phase flow in molten salt pump
2018, 33(6): 1403-1412. doi: 10.13224/j.cnki.jasp.2018.06.014
Abstract PDF(1261KB) icon725 icon560
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In order to reveal the regularity of the crystallization two-phase flow in the molten salt pump, Buckingham theorem was adopted to establish the similarity criterion for the solid-liquid two-phase flow in molten salt pump. According to the designed molten salt pump model test schemes, the internal flow was numerically simulated. At the same time, the high speed photography technology was employed to capture the flow. The differences between experimental and numerical simulation results were elaborated. The effects of particle diameter and density on external performance and internal flow of molten salt pump were researched. The obtained results were shown as follows: the error between the numerical simulation results and the test results was less than 10%. The absolute velocity of particles at the impeller outlet decreased from the blade pressure surface to the suction surface. The relationship of the velocity triangles between the solid and liquid phases in the impeller was obtained. When the particle density was greater than the liquid density, the circumferential component of the particle absolute velocity was less than that of liquid phase. Furthermore, the relationship of the velocity triangles at the impeller outlet was obtained for particles with the density of 2000, 2250, 2500, 2750, 3000kg/m3. The larger particle density meant the smaller circumferential component of the absolute velocity and the lower pump head.
Effects of blade chord exposure of recess vaned casing treatment on fan performance
2018, 33(6): 1413-1422. doi: 10.13224/j.cnki.jasp.2018.06.015
Abstract PDF(1328KB) icon848 icon517
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Numerical simulations were performed to investigate the effects of recess vaned casing treatment (RVCT) with four different blade chord exposures on a lift fan. According to the results, as the blade chord exposure extended, the stall margin of fan with RVCT increased by 1.27%, 8.01%, 12.3%, 32.4%, respectively, while the efficiency reduced by 0.82%, 1.38%, 2.2%, 4.1%, respectively, at design point. The introduction of RVCT resulted in the local circulation between recess cavity and main passage, the incidence and blade tip blockage decreased, the pressure difference between pressure and suction sides was balanced. With the increase of blade chord exposure, local circulation became much more intense and stall margin of the fan was enhanced. Also, the influence of RVCT on fan performance depended on the flow interaction between recess cavity and main flow, particularly, the bleeding and injection were primary parameters reflecting the capability of stabilizing the fan.
Application of EEMD and NRS in turboprop engine rotor fault diagnosis
2018, 33(6): 1423-1431. doi: 10.13224/j.cnki.jasp.2018.06.016
Abstract PDF(1274KB) icon800 icon474
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According to the nonstationary characteristics of vibration signals of turboprop engine rotor system, a rotor fault diagnosis method based on ensemble empirical mode decomposition (EEMD) and neighborhood rough set (NRS) was proposed. EEMD was used to decompose vibration signals. Then the time domain features and multiscale permutation entropies (MPE) of original vibration signals were calculated. Most of the fault information of rotor system was contained in the first several intrinsic mode functions (IMFs). Their time domain indicators, energy features and singular value decomposition (SVD) features were also separately calculated. NRS was applied to evaluate the attribute importance of different features, and sensitive features were selected. The sensitive feature set was fed into support vector machine (SVM) for recognizing different rotor fault states. Experimental results demonstrated that the fault diagnosis accuracy of the method reached 97.5%, and a large number of redundant features were eliminated, indicating that the method had stronger robustness.
Researches on metal rubber mechanics properties in retrospect and prospect
2018, 33(6): 1432-1445. doi: 10.13224/j.cnki.jasp.2018.06.017
Abstract PDF(1915KB) icon4268 icon725
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The literature related to the metal rubber mechanics properties in the past half century were summarized, providing a comprehensive overview on the state of the art of this research area. Then the researches related to metal rubber were reviewed systematically and thoroughly from several aspects, such as manufacture technology, macroscopic mechanics property and formulation mechanics, mechanics modeling, mechanics property and its influence parameters, novel metal rubber, and engineering application. Results showed that metal rubber preparation was still in the transition stage from the laboratory to the industrial production. Furthermore, the key problems related to the metal rubber study were solved to develop unified national standards of preparation process as well as performance testing methods and establish a database of metal rubber mechanics properties.
Section selecting for engine vibration measurement based on dynamic analysis
2018, 33(6): 1446-1455. doi: 10.13224/j.cnki.jasp.2018.06.018
Abstract PDF(1094KB) icon813 icon547
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Modeling method and optimization algorithm of vibration measurement sections selection of the engine was studied. The selection idea of vibration section was determined. The rotor-support-casing whole model was established .The rotordynamic characteristics were calculated under normal and fault conditions. And the section or bearing position of rotor in larger vibration was determined according to the number of sensors which the overall program requires. The initial layout of vibration sensor was completed. An optimization method for vibration measurement was proposed. The effective information of vibration data on each measuring point was determined by analyzing measured data and considering the signal-to-noise ratio and redundancy of measured signal. It was judged that whether the vibration measurement program was reasonable and the airborne measuring point was selected. A engine was taken as an example. The scheme of monitoring points was designed. The study showed that the airborne measuring point was the same as that of the real airborne sensor of the engine. It was verified that the establishment and optimization method and airborne sensor selection method were correct and reliable. The higher the elements sensitivity was, the more significantly the vibration of the rotor was reflected. The lower the vibration similarity was, the more completely the characteristics of engine vibration was reflected. The research result provides an important basis for the layout of vibration measurement of aero-engine.
Time-domain test method for nonlinear damping of fiber reinforced composite thin plate based on nonlinear squeezing transform
2018, 33(6): 1456-1463. doi: 10.13224/j.cnki.jasp.2018.06.019
Abstract PDF(828KB) icon750 icon507
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A time-domain test method for nonlinear damping of fiber reinforced composite thin plate based on nonlinear squeezing transform was proposed. The analytic signal was constructed based on the nonlinear squeezing transform, and the expression of nonlinear damping of the composite structure system was derived, so that the theoretical principles of acquiring the nonlinear damping parameters from the time-domain test view could be clarified. Then, the Matlab algorithm was written and numerical example was used to prove the correctness of the algorithm. The reasonable and standard test procedures were summarized and applied to real measurement of TC500 carbon fiber/resin composite thin plate. It was proved that the proposed method can effectively obtain its damping parameters in different decay time, thus it can be used to quantitatively evaluate nonlinear damping characteristic of composite structure under different excitation amplitudes and frequencies.
Calculation method of stress intensity factors of eccentric through cracks subjected to complex loading
2018, 33(6): 1464-1474. doi: 10.13224/j.cnki.jasp.2018.06.020
Abstract PDF(1253KB) icon980 icon515
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General weight functions only containning three coefficients for eccentric through cracks in a 3-D rectangular plate subjected to complex nonlinear loading were proposed. Three sets of reference stress intensity factors of 3-D rectangular cracked plate were obtained by the finite element method, and combining with binary Lagrange interpolation method, the three coefficients of each general weight function were also obtained. Self-consistency of general weight functions was verified and general weight functions were also validation when the crack surface was loaded by simple third-order, fifth-order, seventh-order, complex power law stress distributions and the residual stress distribution were conducted. Results showed that, the self-consistency error of general weight functions was smaller than 0.9%, when the crack surface was loaded by the complex power law stress distribution, error of the weight function method was smaller than 4.5%, when the crack surface was loaded by the residual stress distribution, error of the weight function method was smaller than 8.5%. This indicates that the proposed general weight functions has high computing accuracy, which could meet the challenge of calculating stress intensity factors of eccentric through cracks subjected to arbitrary complex nonlinear loading efficiently and correctly in engineering.
A test method for accelerating self-start of hypersonic inlets
2018, 33(6): 1475-1483. doi: 10.13224/j.cnki.jasp.2018.06.021
Abstract PDF(1070KB) icon1020 icon489
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To explore the feasibility of testing the accelerating self-start ability of hypersonic inlets in a blow-down wind tunnel, a self-starting test method based on continuous varying attack angle of a shielding plate fixed on the upstream hypersonic inlets was developed. In the test, the hypersonic inlet, together with a shielding plate, rotated from the limiting positive attack angle to the limiting negative attack angle. The shielding plate decelerated the freestream by shock wave, or accelerated the freestream by expansion waves. Hence, the continuous accelerating freestream downstream the shielding plate can be obtained for the inlet. The test method was verified with numerical simulations. Results show that: the deviation of the starting Mach number in the rotating process of the hypersonic inlet with a shielding plate at an angular velocity of 2(°)/s and the inlet self-starting Mach number is within 1%, indicating that the method based on the continuous varying attck angle of a hypersonic inlet with a shielding plate can be used to test the self-starting ability of hypersonic inlets in a blow-down wind tunnel.
Analysis on three-dimensional effects of rotor unsteady dynamic stall
2018, 33(6): 1484-1491. doi: 10.13224/j.cnki.jasp.2018.06.022
Abstract PDF(1194KB) icon754 icon486
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A CFD method with high precision was adopted to investigate the characteristics of three-dimensional (3D) effects of flow on rotor dynamic stall. The Helishape 7AD rotor was taken as example, and the influences of three-dimensional effects on rotor unsteady aerodynamic characteristics were researched. The effects of inflow Mach number on dynamic stall of rotor airfoil were investigated. On these bases, characteristics of unsteady vortex and induced flow on rotor dynamic separation were numerically analyzed, and the comparisons with the 2D states indicated that due to the effects of the rotation of blade and axial-induced velocity, the formation, convection and shedding of dynamic stall vortex on rotor blade section delayed compared with the 2D state of airfoil, and the intensity of vortex was weaker. As blade section was closer to root of rotor, differences for characteristics of dynamic stall between rotor blade section and the 2D state rotor airfoil were more obvious.
Conversion methods of turbofan-engine exhaust gas temperaturewith consideration of use factors
2018, 33(6): 1492-1499. doi: 10.13224/j.cnki.jasp.2018.06.023
Abstract PDF(680KB) icon879 icon487
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For the problem about qualified acceptance conversion exhaust gas temperature value of a type of turbofan-engine in the factory but occasionally unqualified exhaust gas temperature measurement value in the offsite ground test, the defect of exhaust gas temperature conversion method only considering single factor of air temperature was analyzed. A kind of exhaust gas temperature conversion method comprehensively considering use factors including the nonstandard atmosphere and the adjust law was put forward, the mathematics model was established, and the correcting coefficient of nonstandard atmosphere and the correcting coefficient of adjust law were obtained by calculation, which were verified by test on the bench. As a result, exhaust gas temperature conversion method considering use factors met the actual conditions of the engine, the relative error between the correcting coefficient obtained and the trial test data was less than 1.3%, effectively solving the problem about qualified conversion exhaust gas temperature value in the factory but unqualified exhaust gas temperature measurement value in the offsite ground test.
Effect of blade camber on aerodynamic performance of cycloidal propeller under hovering status
2018, 33(6): 1500-1509. doi: 10.13224/j.cnki.jasp.2018.06.024
Abstract PDF(1205KB) icon852 icon462
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A series of cycloidal propellers were studied numerically under hovering status. The effects of the blade relative camber X and the location of the maximum camber Y of the blade on the aerodynamic performance of cycloidal propeller were studied respectively. The results indicated that compared with the cycloidal rotors with the blades of symmetrical airfoils, the aerodynamic performance of cycloidal propeller was improved greatly under the moderate camber and appropriate location of the maximum camber of the blade chord. When the relative camber X was 4%C (C was chord length) and the location of the maximum camber Y was at 40%C-50%C from the leading edge, the lift and power of the cycloidal propeller were relatively lower, the hovering efficiency was higher than other conditions, and the overall aerodynamic performance was better.
Performance of air-dynamic lubrication thrust bearing and experiment
2018, 33(6): 1510-1518. doi: 10.13224/j.cnki.jasp.2018.06.025
Abstract PDF(1149KB) icon869 icon502
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To deal with the dynamic characteristics of the air-dynamic lubrication foil thrust bearing, a model of rigid-surface bearing was developed. Through numerical simulation, the effect of structural parameters and speed on performance of rigid surface air-dynamic lubrication thrust bearing were studied. Considering the manufacturing difficulties and the results of numerical simulation, a rigid-surface thrust bearing and a bump kind of aerodynamic compliant foil thrust bearing were developed. And a kind of foil metal was successfully used, the punching process and heat treatment were also accomplished. In order to measure the bearing capacity, lift-off speed, and drag torque in the on-off operation, a single-surface experiment rig was set up. It was found that different dynamic displacement responses occurred between the two kinds of bearings at the beginning of lift-off. Meanwhile, the lift-off speed of flexible surface bearing had a ratio of 1/2-2/3 advantage under the same axial load.
Dynamic output feedback robust H∞ fault tolerant control for aero-engine distributed control system
2018, 33(6): 1519-1527. doi: 10.13224/j.cnki.jasp.2018.06.026
Abstract PDF(790KB) icon973 icon462
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The output feedback fault tolerant control strategy was proposed for aero-engine distributed control system with network induced time delay and disturbance in occurrence of actuator partial fault. The areo-engine distributed control system model parameters were described quantitatively, and the closed-loop system was established based on dynamic output feedback controller. The stability analysis under the constraint of H∞ performance was given for the augmented closed-loop system, based on which the design approach of output feedback H∞ fault-tolerant controller was designed by means of linear matrix inequality. Simulation results showed that the system was asymptotically stable with the devised controller when actuator attenuation faults were 80% and 50%, respectively, and had a certain H∞ performance index 0.63. Similarly, then system had a good fault tolerant performance when actuator attenuation faults occurred.
Maintenance level decision for aero-engine based on deep belief network
2018, 33(6): 1528-1536. doi: 10.13224/j.cnki.jasp.2018.06.027
Abstract PDF(879KB) icon859 icon550
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The accurate maintenance level decision can avoid the excessive maintenance and shortage of maintenance and save maintenance cost on the premise of ensuring the safe operation of aero-engine. To achieve the classification and prediction for maintenance level, monitor information and characteristics of maintenance level, using algorithm of deep belief network（DBN）, were combined, excavating deep relationship between the condition monitoring and maintenance level decision making. The model can extract sample feature from DBN pretreatment and back propagation (BP) neural network reverse fine-tuning and improve the forecast accuracy of maintenance level. Taking the state parameters and maintenance level data of an airline CF6 engine as example, the analysis results showed that the model could excavate the deeper information of the sample through the construction of multi-layer network structure, which was superior to the traditional neural network in the classification ability and the accuracy of decision-making. So the model had strong ability of feature extraction and higher classification accuracy for the maintenance level. The model was able to get more accurate results maintenance level decision and avoided unnecessary losses due to misclassification of maintenance level.

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