2018 Vol. 33, No. 10

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Design method of metallic W-ring in aero-engine
2018, 33(10): 2305-2314. doi: 10.13224/j.cnki.jasp.2018.10.001
Abstract PDF(1142KB) icon1232 icon704
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Targetting the sealing property and strength,a research on the compression ratio of metallic W-ring was carried out. Based on the determined compression rate, the axial clearance of the casing was optimized, the influence of key structural parameters of the metallic W-ring on the strength was studied. After the sensitivity analysis, the structural parameters of the metallic W-ring were further optimized. The relationship between the buckling and the axial stiffness of the metallic W-ring was researched, and stiffness experiment was used to verify the simulation results, and support the evaluation of the critical buckling loads. The results showed that under the typical operating condition, the reasonable compression ratio range of the metallic W-ring was 3.2%-6.08%. The thickness had the greatest effect on the maximum equivalent stress. The final optimization results were as follows: the thickness increased by 5.0%, the radius of wave peak and wave trough increased by 9.0%, the contact radius increased by 7.7%, the outer diameter of the ring reduced by 5.8%, the maximum equivalent stress reduced by 5.7%; buckling load was linearly related to axial stiffness.
Experiment on sealing characteristics of bolted flanged connections for aero-engines
2018, 33(10): 2315-2323. doi: 10.13224/j.cnki.jasp.2018.10.002
Abstract PDF(974KB) icon1084 icon731
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The leakage factors of the bolted flanged connections were analyzed systematically and studied experimentally. The experimental system of sealing characteristics of bolted flanged connections was designed and constructed to study the influences of bolt loading method, preload and number of bolts on the sealing characteristics of flange connection. The results show that the loading method of JIS B 2251 can obtain more uniform preload, the gas leakage lasts longer than other methods up to 600s, and the workload is smaller; increasing the preload can increase the duration of the pressure drop, from 400s of 6.0kN to 540s of 7.5kN and 650s of 9.0kN. The increase in the number of bolts makes the leakage rate of the t=0 moment drop from 2.6cm3/s to 1.7cm3/s, thereby improving the sealing performance of the experimental piece. This study can provide a reference for the sealing characteristic analysis and structural design of bolted flanged connections.
Prediction and test verification of mechanical properties of fiber reinforced composites
2018, 33(10): 2324-2332. doi: 10.13224/j.cnki.jasp.2018.10.003
Abstract PDF(937KB) icon1153 icon823
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For the problem of predicting mechanical properties of unidirectional fiber reinforced composite with uniform arranged fiber, based on the composite micro-mechanical finite element method, the representative volume element (RVE) model with periodic boundary conditions was researched and established, the basic mechanical properties were realized. By comparing simulation results of B/Al fiber reinforced composites which obtained by applying the RVE model with test results and analytical solutions, it showed that prediction of the mesoscopic mechanical model with periodic boundary conditions kept a preferable consistency with test results and analytical solutions, and the efficiency of the RVE model was proved. Based on the mechanical properties test of unidirectional fiber reinforced SiC/TC4 composite sheets, the longitudinal/transverse elastic modulus and Poissons ratio of different layup structures were obtained, and the error between the calculated longitudinal/transverse elastic modulus and the mean value of the respective test values was less than 5%, the comparison of structural mechanics properties predicted results showed that the parameters of elastic mechanics agree well and the calculation model was reasonable.
Molecular dynamics simulations of dry friction dampers with coating
2018, 33(10): 2333-2342. doi: 10.13224/j.cnki.jasp.2018.10.004
Abstract PDF(1092KB) icon1095 icon660
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To study and simulate its mechanical characteristics of dry friction process, the shear movement of nanoscale asperities was studied. A molecular dynamics model was created. This model predicted shear movement of two hemispherical deformable asperities by adopting a suitable potential. Shear and normal forces during shear movement of two single-crystal copper asperities were analyzed. The residual deformation energy after the movement was also studied. A dry friction model based on nanoscale asperities was developed through multi-scale analysis and statistical methods. And its results were compared with experimental results. The following conclusions were summarized. In case of dry friction of single-crystal copper in vacuum, the normal contact stiffness on joint surfaces and normal load were in direct proportion, while sliding coefficient of friction was only relevant with surface roughness. The results of simulation were coincident with the results from pure copper friction experiments. This method was proved to be able to analyze dry frictional characteristic of dry friction damper working surfaces covered by wear-resistant coating accurately. For surfaces with known micro parameters, this method can predict the sliding coefficient of friction accurately.
Test method for the combined high and low cycle fatigues of turbine blade based on the whole engine operation
2018, 33(10): 2343-2350. doi: 10.13224/j.cnki.jasp.2018.10.005
Abstract PDF(947KB) icon990 icon1156
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The turbine blade is subjected to both high cycle and low cycle loads synchronously during aero-engine operation. Therefore, using a low thrust turbojet engine as research platform, a test scheme based on the electrical leads on how to assess the blade dynamic stress was put forward in particular for the blades used in harsh conditions i.e. high rotation speed, small size and high temperature. The dynamic stress of 30mm height turbine blades operated at the rotation speed of 40000r/min and in 950℃ was obtained by use of a combined value simulation and experiment measurement method. Moreover test methods of the combined high cycle and low cycle fatigues based on the whole engine operation, including the methods on how to obtain the resonance vibratory stress and to compose the load spectrum, were developed. The engine test was carried out and the combined high cycle and low cycle fatigues of high pressure turbine blade were investigated. The results show that blade dynamical stress reaches 112.7MPa at the rotation speed of 34920r/min, which may lead to the high cycle fatigue failure of the turbine blade and the high cycle load is the major reason for the initialization of the crack, and the low cycle load is the major reason to result in the crack propagation, and both of them will affect the life of the turbine blade synthetically.
Design of low cycle fatigue simulating specimen for bolt holes of a turbofan engine high pressure turbine disc
2018, 33(10): 2351-2358. doi: 10.13224/j.cnki.jasp.2018.10.006
Abstract PDF(988KB) icon1348 icon710
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Basic criterion of low cycle fatigue simulating specimen design was proposed based on the theory of tensile strain energy life prediction model. Simulating specimen for bolt holes of a turbofan engine high pressure turbine disc was optimized in design while comprehensively considering the ability of the test machine, thread connection strength and required number of bank disc. The optimizing objectives were as follows: the distribution of the first principal stress and strain within 0.8mm on the virtuak crack of the simulating specimen was consistent with the real bolt holes, and the ratio of the second principal stress to the first principal stress at the maximum stress point of the simulating specimen was consistent with the real bolt holes. Elastic plastic analysis was conducted to check the stress/strain consistency. The difference between safe life obtained by simulating specimen test and real turbine disc test was 4.48%.
Parameter optimization method of rotor dynamic vibration absorber
2018, 33(10): 2359-2366. doi: 10.13224/j.cnki.jasp.2018.10.007
Abstract PDF(848KB) icon1004 icon654
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The parameters of the dynamic vibration absorber used to suppress the excessive vibration of the rotor system were designed to optimize the vibration suppression. The dynamic equation of the dynamic vibration absorber-rotor coupling system was established by using the finite element method, and the response expression of the half-numerical half-resolution of the coupled system was obtained. The design optimization strategy was used to find the best design variable of the dynamic vibration absorber by combining the coordinate solution of the response solution and the bounded boundary. The sensitivity of the dynamic vibration absorber to the optimal deviation of different parameters was analyzed by comparing with the existing optimal design method of dynamic vibration absorber. The results show that the optimized the dynamic vibration absorber can reduce the amplitude of first order resonance by 45.4%, which shows the effectiveness of the method; this method is 11.2% and 9% higher than that of two effective conventional optimization methods, which can optimize the optimization effect of the dynamic vibration absorber; compared with the damped optimal deviation, the vibration suppression performance of the dynamic optimized vibration absorber has a higher sensitivity the optimal deviation of stiffness.
Correction method of SHPB experiment considering adiabatic deformation and interfacial friction effects
2018, 33(10): 2367-2375. doi: 10.13224/j.cnki.jasp.2018.10.008
Abstract PDF(903KB) icon877 icon644
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GH4169 super alloy was tested using high temperature split Hopkinson pressure bar (SHPB) technique. The temperature sensitivity of the material under high strain rates was obtained and the parameters of Johnson-Cook constitutive model were fitted. A semi-empirical model was established to describe the distribution of stress, strain and temperature inside the specimen during compression based on the numerical calculation method. Then a new method for correcting the constitutive parameters was put forward to decouple the interfacial friction effect and adiabatic deformation from the result of SHPB experiment. The experimental results showed that the yield strength and flow stress of GH4169 super alloy decreased with the increase of temperature. And it was confirmed that adiabatic deformation and interfacial friction effect obviously affected the accuracy of SHPB experiment, thus the results can not reflect the work hardening properties of the material. After multiplying the hardening term by the correction factor of 1.2, the modified constitutive parameters accurately reflected the stress-strain characteristics of the material under high strain rates.
Rolling bearing collaborative fault diagnosis technology for casing vibration signal
2018, 33(10): 2376-2384. doi: 10.13224/j.cnki.jasp.2018.10.009
Abstract PDF(1209KB) icon1038 icon673
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A cooperative diagnosis technique for rolling bearing faults was proposed for aero-engine rolling bearing fault diagnosis based on casing measuring point signal. Firstly, the minimum entropy deconvolution was used to eliminate the influence of the signal transmission path and enhance the impulsive component in the signal.Then,the resonance band was extracted by applying wavelet transform. Finally,the non-periodic signal components in the resonance band were suppressed by using autocorrelation analysis while the signal-to-noise ratio was further improved. Two bearing tests were carried out respectively on the artificial fault bearing and the real fault bearing on the rotor tester with casing. Test results showed that compared with other typical methods, the spectrum peaks corresponding to the fault characteristic frequencies in the envelope spectrum obtained by the proposed cooperative diagnosis method were more clear and obvious.
Analysis of impact factor of ignition characteristics and activation energies about liquid propulsion fuel
2018, 33(10): 2385-2391. doi: 10.13224/j.cnki.jasp.2018.10.010
Abstract PDF(662KB) icon873 icon689
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The combustion efficiency and pollution emission of real fuel were improved by studying the ignition delay time of fuel. The ignition characteristics of RP-3 were accomplished by applying reflected shock wave in the shock tube and the apparent activation energies were analyzed. The endpoints of ignition were judged by means of retrodicting the maximum OH- spectrum curves to the basic values. The normalizations of auto ignition characteristics about different volume fractions were conducted. Result showed that, the normalizing data appeared good concentration in the chart. The apparent activation energies of RP-3 varied little about 154-171kJ/mol in different operating conditions. There was a positive correlation between the ignition delay time and the equivalence ratio or fuel volume fraction in the mixture, but there was a negative correlation between it and the pressure of mixture. The index impact factors about fuel volume fraction and pressure between RP-3 and JP-10 were roughly equal.
Applicability of reaction mechanisms to multi-field coupling simulation of air/H2 combustion system
2018, 33(10): 2392-2403. doi: 10.13224/j.cnki.jasp.2018.10.011
Abstract PDF(1506KB) icon1046 icon658
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For an air-hydrogen combustion system, a dynamic finite volume numerical model considering the multi-field coupling of flow, heat transfer and combustion was established, a general library of reaction mechanisms and physical property parameters was constructed. The thermodynamic calculation method and three sets of hydrogen-oxygen reaction mechanism methods were used for simulation calculation, and the latter can also describe the process of ignition and flameout, and reveal the impact of various elementary reactions and species changes on the combustion and flow transient process. The Williams mechanism fitted best with the results of the thermodynamic calculation, which was validated by experiments, followed by the Conaire mechanism, and the Evans mechanism was relatively poor. Compared with the Conaire mechanism, Williams reaction mechanism lowered the quenching temperature from 1200K to 1155.3K, reduced the calculation error from 4.7% to 2.74% under the low temperature condition of 1222.3K, and made the application of multi-coupling numerical system more extensive and the calculation result better. Under low temperature, H2O2 and related reactions had a great influence on the description accuracy of the hydrogen-oxygen mechanism.
Nonlinear dynamic responses of a self-excited thermoacoustic system subjected to acoustic forcing
2018, 33(10): 2404-2413. doi: 10.13224/j.cnki.jasp.2018.10.012
Abstract PDF(1188KB) icon1121 icon659
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On the combustion experimental platform of high temperature and pressure, the thermoacoustic system with a concentric stratified swirl-stabilized partially premixed-prevaporized flame with self-excited response was excited by external-excited signal with frequency ff of 78-716Hz and amplitude A of 0.026-0.629, and its nonlinear dynamic responses were studied. It was found that the system self-excited frequency fn was 366.85Hz; when the ratio of external-excited frequency to self-excited frequency was 1.022 and amplitude A was 0.629; the flame was dominated by the harmonic frequency and its state trajectory was dense in a very narrow closed zone. When the ratio of external-excited frequency to self-excited frequency and A was in other ranges, the flame responded not only at ff and fn, but also at the harmonic, combining and divided frequencies. It showed that when amplitude A was large enough and external-excited frequency was close to the self-excited frequency, the flame was phase-locked. When the flame was not phase-locked, the nonlinear responses of the harmonic, combining and divided frequencies appeared, and the flame oscillated quasi-periodically. Forced van Der Pol oscillator model can predict phase-locked, odd harmonic frequencies and combining frequencies 2fn±ff.
Calculation of nozzle remote infrared imaging based on multi-scale multi-group wideband model and integrated differential hybrid algorithm
2018, 33(10): 2414-2423. doi: 10.13224/j.cnki.jasp.2018.10.013
Abstract PDF(1125KB) icon717 icon455
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To solve the problem that existing k distribution model is not suitable for high temperature flow 3-5μm wave band emission radiation transmission attenuation characteristic in atmospheric long distance calculation,multi-scale multi-group technology used in full-spectrum model before was applied in wideband model, and the grouping state points on the spectral absorption coefficient were adjusted.The calculation results of one-dimensional/quasi one-dimensional numerical example of infinite width multilayer gas radiation characteristics show that multi-scale multi-group technology can improve the calculation precision of original full spectrum and wideband model while keeping compatibility with rational of gray wall. On this basis, the coupling heat transfer characteristics and the remote infrared characteristics of V nozzle trailing edge contraction with cooling device were studied. The results show that the gas radiation effect on the solid wall temperature distribution in the nozzle can not be ignored. The prediction error of the remote infrared images for transonic exhaust system at 70km with use of the multi-scale multi-group wideband model is about 7%.
Effect of pilot strutures on smoke emissions in the TeLESS Ⅱ combustor
2018, 33(10): 2424-2433. doi: 10.13224/j.cnki.jasp.2018.10.014
Abstract PDF(1042KB) icon963 icon515
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The effects of different pilot structures on smoke emissions of TeLESSⅡ combustor were investigated. Smoke emissions of prefilming airblast atomizer and airblast simplex atomizer were tested through gas analysis method under pilot fueled mode and pilot-main fueled mode. The results indicated that the pilot structures had a great influence on the smoke emissions under pilot fueled mode, but less influence under pilot-main fueled mode. Numerical simulation was adopted to analyze different smoke emission performances with two pilot structures under pilot fueled mode. The simulation results show that the different pilot structures change the distribution of fuel in the main combustion zone, leading to significant differences in the mass fraction and distribution position of smoke precursor acetylene and different smoke emissions of combustor outlet.
Inlet temperatures effect on combustion instabilitycharacteristics of stratified swirl flame
2018, 33(10): 2434-2441. doi: 10.13224/j.cnki.jasp.2018.10.015
Abstract PDF(910KB) icon868 icon529
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In order to investigate the effects of inlet temperature on the combustion instability in stratified swirl combustor, the dynamic pressure under various inlet temperatures was tested using a single doom combustor, and the effects of inlet temperature on pressure oscillation were analyzed using a theory. The experimental results showed that the mode of combustion instability in this combustor was Helmholtz mode. With the increase of inlet temperature from 530K to 650K, the amplitude of pressure oscillation decreased. Analysis showed that the increase of inlet temperature can enhance fuel atomization and evaporation and then strengthen its mixing with air, making equivalence-ratio oscillation less impossible. Therefore combustion instability was less prone to occur and the dynamic pressure amplitude was smaller.
Numerical simulation and a hybrid method of supersonic turbulent base heating
YUAN Junya, CAI Guobiao, ZHAO Lu
2018, 33(10): 2442-2450. doi: 10.13224/j.cnki.jasp.2018.10.016
Abstract PDF(392KB) icon782 icon510
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Detached eddy simulation (DES) model was used to better capture large vortex structure and unsteady flow feature near cone base. Good base heating results were achieved using proper grid and numerical method. The influence of inflow conditions (like Mach number, Reynolds number) and configuration (bluntness ratio of the cone) on base heating was discussed based on numerical computational results. Compared with base heat flux, base pressure can be predicted more accurately by numerical simulation and the time consuming was shorter. A hybrid method combining numerical simulation with experimental correlation was proposed to predict supersonic turbulent base heating. A review of base heating experiment and correlations for slender cone was presented, and a revised correlation was proposed based on the above simulation results. Compared with the experiment data, the maximum error was 24%, a good result for base heating prediction. This proves that the hybrid method using the revised correlation performs well in predicting supersonic turbulent base heating of slender sphere cone and can meet needs of engineering design.
Application of center-line probe in transonic wind tunnel
2018, 33(10): 2451-2457. doi: 10.13224/j.cnki.jasp.2018.10.017
Abstract PDF(968KB) icon771 icon520
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In the 0.6m×0.6m continuous transonic wind tunnel of CARDC, experiments for center-line probes with different arrangements of orifices, different length and different installation sites were conducted. Results indicated that, the Mach number fluctuation tested with the center-line probe of symmetry orifices was weaker than that of staggered orifices. And when the experiment Mach number was below 1.0, the experiment result of short center-line probe agreed well with the long probe. But when the experiment Mach number was higher than 1.0, the Mach number fluctuated severely due to the nose cone of the short probe. And when the experiment Mach number was below 1.0, the machining quality of orifices along the center-line probe had a great influence on the test results.
A shear layer phase shift correction method based on simplified ray model
2018, 33(10): 2458-2464. doi: 10.13224/j.cnki.jasp.2018.10.018
Abstract PDF(788KB) icon719 icon504
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A shear layer phase shift correction method for three-dimensional finite thickness wind tunnel based on simplified ray model was presented. And its physical basis was explained with the help of numerical simulation. A comparison of the simplified ray model with Amiets method and average Mach number method was given. The presented simplified shear layer correction method was validated experimentally using a microphone array to localize an inflow source. Lastly, the curved shear layer phase shift correction method using the simplified ray method was given. It was found that if inflow Mach number was less than and equal to 0.3 and measurement angle ranged from 40° to 140°, when the source and mircophones were on the same plane, the difference between the three correction methods was less than 1%.
Turboshaft engine overall design method based onbalance of componentsdifficulty coefficients
2018, 33(10): 2465-2475. doi: 10.13224/j.cnki.jasp.2018.10.019
Abstract PDF(1047KB) icon1054 icon507
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In order to complete the design of the fifth-generation turboshaft engine from the conceptual design stage to the preliminary design stage, the integrated design method based on the overall performance and size and mass of the turboshaft engine was studied. Through statistical evaluation of typical models of turboshaft engines at home and abroad, a database of technical parameters such as overall performance, overall structure, and the components aerodynamic/structure/strength/material properties of turboshaft engines was established; the concept of difficulty coefficient was proposed, and the technical parameters of the turboshaft engine were selected in the conceptual design stage using difficulty coefficient. An integrated design calculation model and program for the overall performance and size and mass of the turboshaft engine were developed, the overall performance of the tuboshaft engine was achieved under the constraints of the design criteria. Design of overall performance and other components performance, such as the aerodynamic/structural/strength/size/mass of the rotor components, was completed under the constraints of the design criteria. Results show that this design method can complete the overall design scheme of the turboshaft engine, and in this way, the fifth-generation turboshaft engine with 1500 kW shaft power was designed with specific fuel consumption (SFC) of 0.248kg/(kW·h) and P/W of 10.26kW/kg.
Numerical investigation of effect of vortex generators on Bump inlet performance
2018, 33(10): 2476-2482. doi: 10.13224/j.cnki.jasp.2018.10.020
Abstract PDF(912KB) icon878 icon523
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To control the flow separation and effectively reduce outlet total pressure distortion of a S-shaped duct Bump inlet, vortex generators (VGs) were designed and installed at the entry of the S duct.The commercial CFD software was used to simulate the internal and external flow fields at the design point (Ma=2.0) and off design points (Ma=1.8,0.8), and predict the effectiveness of VGs with different parameters.The simulation results indicate that,VGs installation can suppress flow separation and remarkably reduce the total pressure distortion at exit of Bump inlet at design point.At some off design points,it can increase the total pressure distortion at exit of Bump inlet.It can slightly increase the total pressure loss.And VGs with different vane distance make a similar influence on the total pressure loss.
Experiment on coaxial shear injector of GO2/GCH4 based on PLIF
2018, 33(10): 2483-2491. doi: 10.13224/j.cnki.jasp.2018.10.021
Abstract PDF(1226KB) icon908 icon532
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Based on the results of numerical simulation, experimental research on the GO2/GCH4 coaxial shear injector was carried out using non-intrusive optical diagnostic techniques, including PLIF（planar laser induced fluorescence）, high-speed camera and so on. The OH distribution of combustion chamber, the development of combustion flow field and the flame structure were obtained by measuring the combustion flow field at different operating conditions. The results showed that there were obvious shear combustion layers in the combustion flame of GO2/GCH4. As the axial distance increased, the flame gradually lost its stability. With the increase of the velocity ratio, the vortex of the flow field was obviously strengthened, the flame root stabilization section became shorter and the flame structure had more curl and wrinkles. The simulation of OH distributions is consistent with the measurement of OH distribution, indicating the simulation model can simulate the combustion flow field of GO2/GH4.
Creation and control of hydraulic vibration signal withwide frequency range and high amplitude
2018, 33(10): 2492-2499. doi: 10.13224/j.cnki.jasp.2018.10.022
Abstract PDF(937KB) icon809 icon473
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A hydraulic vibration system with wide frequency range was designed by using the pulsation generator, in order to study the dynamical characteristics of the full scale propellant feed system after the pump in the liquid rocket engine, and the cold fluid tests and data analysis were conducted. Within the range of 0-1200Hz, the hydraulic vibration system can create pressure fluctuation signal with amplitude more than 1.5MPa and high signal-to-noise ratio. The target of wide frequency range and high amplitude was reached. By controlling the electric motor revolving speed, the controlled excitation frequency can be realized to satisfy different frequency actuating methods. Increasing the system inlet steady pressure can improve the hydraulic vibration signal amplitude. By appropriately distributing local resistors, the hydraulic vibration signal amplitude and signal-to-noise ratio can be improved within widefrequency range.
Bond stress monitoring of SRM interface based on fiber optic sensor
2018, 33(10): 2500-2507. doi: 10.13224/j.cnki.jasp.2018.10.023
Abstract PDF(930KB) icon842 icon452
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Bond stress is an important aspect of structural integrity of SRM (solid rocket motor) and also the critical parameter in health monitoring. In order to realize the bond stress real-time online monitoring. A polymer packaged FBG (fiber Bragg grating) sensor was designed and embedded into HTPB(hydroxyl-terminated polybutadiene) propellant/liner bond specimen. The response of FBG sensor was studied when the specimen was subjected to tensile stress by simulation of FBG sensor reflection spectra and stress testing. Results showed that the center wavelength of the FBG sensor decreased with the increasing tensile stress of the specimen, and the sensor had a good linearity and stability. The FBG sensor was intact and the strength of the bonded specimen met the technical specifications in specimen bonding performance test, verifying the feasibility of the designed sensor and embedding method.
Numerical analysis for underwater ignition two-phase flow field of solid rocket motor
2018, 33(10): 2508-2514. doi: 10.13224/j.cnki.jasp.2018.10.024
Abstract PDF(849KB) icon1145 icon560
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Two-phase gas-liquid flow field in the underwater ignition process of solid rocket motor was numerically solved by using FLUENT software, turbulence model and VOF (volume of fluid) model. The flow process of gas and the development process of gas bubble at the beginning of ignition were analyzed.The distribution of gas density, pressure and temperature in the wake flow field was numerically simulated. The study showed that:at the beginning of ignition,a complete shock wave was established in the nozzle, after which the mechanism of shock wave was destroyed.No continuous expansion-compression waves were formed because of the gas was affected by pressure disturbances;the gas bubbles head was kept at a large diameter, and the middle gas channel had a periodic expansion-contraction;the parameters had different degrees of shock phenomenon:the wake flow field of the gas density greatly changed at the exit of nozzle with the reason for compression of the water and the increasing quality of gas; the total pressure of the outlet of the nozzle was drastically compressed by the water environment, forming a high pressure zone at the exit of the nozzle; the gas temperature reduced to 1750K or less gradually after three cycles of change.
Study on casing treatment stability extension and stator matching on multistage high-loading fan
2018, 33(10): 2515-2524. doi: 10.13224/j.cnki.jasp.2018.10.025
Abstract PDF(1278KB) icon755 icon440
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A two-stage high-loading fan with three-dimensional numerical simulations was studied. The simulation results were used to propose a scheme that enlarged the stall margin of multistage high-loading fans without sacrifice of the flow capacity when operating with a large mass flow rate. Furthermore, a circumferential groove casing treatment was used and adjustments were made to the upstream stator angle to match the casing treatment. The stall margin was thus increased to 16.3%, without reduction in the maximum mass flow rate or the design thrust performance.
Fast and accurate locating method forsculptured surfaces measured with coordinatemeasuring machines based on iterative algorithm
2018, 33(10): 2525-2532. doi: 10.13224/j.cnki.jasp.2018.10.026
Abstract PDF(872KB) icon790 icon420
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The blade is a typical part with sculptured surfaces, the locating of these parts for measurement with coordinate measuring machines (CMM) is a difficult and time-consuming task because there are no locating datum planes. To solve this problem, a multistage location algorithm including pre-location and fine-location, considering radius comprehension, was proposed based on iterative closest point algorithm. By establishing the relationship of locating errors and geometric errors of locating points, a near-optimal locating point sequence was generated using the greedy algorithm and six-point principle. Combining multi-stage location algorithm and locating point sequence, an iterative locating process for the part with sculptured surfaces measurement with CMM was researched and programmed. In the simulation and experiment of localizing a turbine blade with sculptured surfaces, only 12-18 points were need to maintain the location errors with in 0.1mm.The efficiency and accuracy of this method are desirable.
Experiment on circumferential mode characteristics ofaxial compressor tip flow
2018, 33(10): 2533-2541. doi: 10.13224/j.cnki.jasp.2018.10.027
Abstract PDF(1211KB) icon831 icon446
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Experiments measuring circumferential mode characteristics of compressors were made for the high demand for the number of sensors, and the aliasing of circumferential wave number when insufficient sensors were provided. A calibration and prediction of higher circumferential mode numbers was proposed using two sets of measuring points, unsteady pressure fluctuations near the tip region in an axial compressor were studied experimentally using this method and the upper limit of identifiable mode numbers was five times of the original method. Circumferential mode characteristics were captured both on blade passing frequency (BPF) and rotational instability frequency (RIF) under several flow conditions. The characteristic spectrum of rotating instability with broadband hump existed within a large range of flow conditions. Both frequency range and dominant circumferential wave number decreased with the flow rate, while at the same time circumferential angular velocity of rotating instability increased; strength of the pressure fluctuations varied significantly in time domain.
Design method for global properties of point-contact tooth surfacebased on envelope-approximation theory
2018, 33(10): 2542-2553. doi: 10.13224/j.cnki.jasp.2018.10.028
Abstract PDF(1077KB) icon672 icon425
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A method (envelope-approximation theory) based on the surface moving frame was presented to design the global properties of point-contact tooth surface. The presented method proposed a universal approach to reconstruct the second tooth surface with motion invariants of the first tooth surface. The proposal reconstruction approach was formulated for approximating the conjugate surface of the first tooth surface to the first tooth surface under the movement transformation described with motion invariants of the first tooth surface. The basis function of the previously mentioned approximation was taken as the characteristic curve on the first tooth surface, the interpolation condition was designated as the local structure of the second tooth surface along the contact curve. Based on the experiment data of tooth contact, a variational inequality model for the global optimal design of tooth surfaces was established to determine the loaded meshing characteristics of the second tooth surface according to the position, orientation and dimension of the contact area on the first tooth surface under load-deformation condition. Different from the previous studies about tooth contact analysis, the presented method, freeing the tooth surface optimization design from unnecessary restrictions of the specific machine tool processing parameters, can satisfy the predesigned loaded meshing characteristics and ensure that the tooth surface can be generated by multi-axis flank milling with a conical cutter. A numerical example was given to validate that above-mentioned design method can construct unbroken spiral bevel gear tooth surface with excellent loaded meshing characteristics, for exanple, the loaded contact ratio was increased to 2.122 and the loaded transmission errors amplitude was lowered to 0.063°.
Rolling bearing fault diagnosis based on IITD and FCM clustering
2018, 33(10): 2553-2560. doi: 10.13224/j.cnki.jasp.2018.10.029
Abstract PDF(1066KB) icon1152 icon409
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An improved intrinsic time-scale decomposition (IITD) method was proposed based on Akima interpolation and linear transformation of intrinsic time-scale decomposition (ITD). Furthermore, based on approximate entropy (AE) and fuzzy C-means clustering (FCM), a new analysis method of using IITD for fault vibration signal of rolling bearing was proposed as well. The vibration signal was decomposed with IITD to obtain a certain number of proper rotation (PR) and a trend. By using mutual information analysis, three PR components were sifted out and the AE was calculated as the eigenvectors. The constructed eigenvectors were put into FCM classifier to recognize different fault types. These results were compared with the methods based on empirical mode decomposition (EMD) and ITD approximate entropy and FCM respectively. The classification coefficient with use of this method was calculated more closer to 1 and average fuzzy entropy was calculated more closer to 0. Accurate fault identification was presented for roller bearings normal, inner faults, outer faults, rolling body fault signals and different damage degree signals of rolling body faults.

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