2017 Vol. 32, No. 1

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Display Method:
Effect of air cooled radial stabilizator opening angle on performance of the mixer and diffuser.
2017, 32(1): 1-7. doi: 10.13224/j.cnki.jasp.2017.01.001
Abstract PDF(974KB) icon937 icon510
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For a new type of mixer and diffuser and aircooled stabilizator integration structure, a threedimensional numerical simulation model based on the N-S equation was created. Through numerical simulation, the flow field, flow resistance characteristics and mixing characteristics of different aircooled radial stabilizator opening angles in the mixer and diffuser were obtained. The results show that, the recovery coefficient declines as the aircooled radial stabilizator opening angle increases; the flow resistance cofficient and pressure loss coefficient of the mixer and diffuser increases with the growing aircooled radial stabilizator opening angle. Around the exit section of the mixer and diffuser, the total pressure recovery coefficient declines as the aircooled radial stabilizator opening angle increases, the difference between the maximum and the minimum values is 0.0032, and the thermal mixing efficiency increases with the whole range of 0.7268~0.8857.
Experiment on multitooth rim sealing.
2017, 32(1): 8-13. doi: 10.13224/j.cnki.jasp.2017.01.002
Abstract PDF(910KB) icon900 icon458
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The gas volume fraction method was used to achieve the distribution of the sealing effectiveness of multitooth rim sealing, and the sealing effectiveness varied with the nondimensional sealing flow rate，and finally the correlation of the minimum sealing flow rate was obtained（mainstream Reynold number from 1.42×105 to 3.20×105, rotating Reynold number from 5.27×105 to 1.36×106）. The measurement results of carbon dioxide volume fraction showed that the sealing effectiveness was low at high radius but high at low radius. The changes in the sealing effectiveness with the sealing flow rate agreed well with Owens sealing effectiveness equations, so the sealing characteristic could be predicted, and the experimental results expanded its application scope.
Experiment on pressure distribution and flow resistance characteristics of internal lamilloy.
2017, 32(1): 14-21. doi: 10.13224/j.cnki.jasp.2017.01.003
Abstract PDF(984KB) icon744 icon459
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Two kinds of lamilloy models with different percentages of film hole opening were experimentally studied at the Reynolds numbers of 1×104-6×104,target surface, impingement surface and pressure coefficients of pinfins surface,local and total loss coefficients of impingement jet, arounding flow,effusion were experimented to explore the mechanism of flow loss. Results showed that,the pressure distributions were characterized by the second maximum value because of the transition from an accelerating stagnation region flow to a decelerating wall jet. The low pressure coefficients on the target and impingement surfaces were caused by the sink of two jets and the backflow, respectively. The pressure coefficients distributions on two rows of pinfins relatively far away from the impingement hole were significantly affected by Reynolds numbers. At the Reynolds number less than or equal to 3×104, the pressure distributions were similar with flow across cylinder. At the Reynolds number greater than or equal to 4×104, it also had characteristics of backflow. The effusion loss coefficients were biggest, the impingement jet loss coefficients were smallest and the arounding flow loss coefficients were moderate. As the percentages of opening decreased one half, the effusion loss coefficients of film holes increased at least 4 times while the loss coefficients of impingement jet loss and arounding flow had slight changes.
Test and numerical prediction of ice accretions on civil aircraft wing.
2017, 32(1): 22-26. doi: 10.13224/j.cnki.jasp.2017.01.004
Abstract PDF(937KB) icon808 icon446
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The ice accretion test results on civil aircraft wing in Italy IWT (icing wind tunnel) were described. The numerical prediction of ice shapes was conducted based on the Lagrange method and Messinger model according to the icing wind tunnel test states. The icing shape test and numerical prediction results were compared and analyzed. A conclusion can be drawn that the numerical results and test data of the rime ice are consistent, while there is difference between those of the glaze ice. The possible reasons can be listed as follows: (1) the airflow variation during the glaze ice accretion strengthens the unsteady effect on icing prediction; (2) the icing thermal model adopted has some limitation for glaze ice prediction; (3) the icing wind tunnel work states and the test model roughness are sensitive to glaze ice accretion.
Experiment on supersonic reacting mixing layer of splitters with different geometric configurations
2017, 32(1): 27-34. doi: 10.13224/j.cnki.jasp.2017.01.005
Abstract PDF(1169KB) icon818 icon444
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To investigate the mixing, combustion characteristic and passive mixingenhancement methods of supersonic mixing layer, pressure matched supersonic mixing layer with different geometric configurations was explored using highspeed schlieren photographs, spontaneous emission imaging and planar laser induced fluorescence(PLIF) imaging．Results showed that, the influence of cavity on supersonic mixing layers was repressive under combustion condition. Splitters with sawtooth trail induced largescale streamwise vortexes and great influence of combustion enhancement in supersonic mixing layer.
Numerical analysis of heat transfer of moving EBW in micro propellant tank.
2017, 32(1): 35-41. doi: 10.13224/j.cnki.jasp.2017.01.006
Abstract PDF(866KB) icon761 icon466
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Numerical model of analyzing temperature field for propellant tank with moving resource electronbeam welding (EBW) was set up, with which the heat source of EBW was described by cone source and the latent heat of melting was determined by means of equivalent specific heat. Time evolutions of temperature distribution on tank, molten pool shape and size were obtained.Results showed that, the error ratio of temperature between calculation and measurement was less than 10%. During the later welding process, the pure cupper radiator plate installed on the outer surface of the tank could be used to reduce the temperature of the diaphragm of propellant tank from 503K to lower than 364K, avoiding the structure damage due to high temperature. The calculation method and heat radiation figuration can also be adopted to other products welding process.
Influence of coupled characteristics on the internallystaged combustor under lowpower operation
KANG Yao, LIN Yu-zhen
2017, 32(1): 42-52. doi: 10.13224/j.cnki.jasp.2017.01.007
Abstract PDF(1133KB) icon806 icon436
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An ultralow emissions combustor, namely low emission stirred swirl (LESS) combustor was studied, based on a scheme of internallystaged/lean premixed and prevaporized (LPP) combustion. The LESS combustor consists of central pilot stage and outer surrounded coaxially main stage, between which there exists a physical isolation, namely the step height. The existence of step height delayed the pilot and main jets mixing. Experimental and numerical studies were carried out to investigate the influence of the step height on the combustion performance. A single dome rectangular combustor was utilized to conduct the lean lightoff and blowout experiments, and pollutant emission experiments. The experimental results showed that with the increase of step height by 38%, the lean lightoff and blowout fuel air ratio decreased by 574% and 375%, the NOx emission increased by 35.1%, and the combustion efficiency increased by 1.78%; while the CO,unburned hydrocarbons (UHC) emissions decreased. Furthermore, the total pressure loss was kept nearly constant. Nonreacting and reacting flow fields were numerically investigated to analyze the coupled characteristics of pilot and main jets with different step heights. A comparison of flow characteristics, spray structure, and combustion component as well as temperature field with different step heights was conducted. The numerical results showed that the increase of the step height shifted the peak velocity outwards. The enlargement of the primary recirculation zone (PRZ) resulted in the increase of the combustion efficiency and NOx emission, while the CO, UHC emissions decreeased.
Experiment of wearing characteristics and its effect on leakage of finger seal
2017, 32(1): 53-59. doi: 10.13224/j.cnki.jasp.2017.01.008
Abstract PDF(829KB) icon922 icon464
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Wearing characteristics of rotor and its effect on leakage of finger seals under three different kinds of fit, namely clearance fit, transition fit and interference fit, were experimentally investigated. The wearing of the rotor, wearing length of seal and distribution of leakage coefficient were analyzed. The results show that the wearing is severer when the sliding distance between the seals and the rotor increases. For finger seal with clearance fit, the seal is partially worn and the wear and its effect on the leakage mainly occur at the beginning of the experiment. For finger seal with interference fit, the whole seal is worn and the wear occurs throughout the experiment. The effect of wearing on the leakage is notable at the beginning and then is gradually decreased. The effect of wearing on leakage is greater when the clearance is smaller or the interference is larger.
Performance of ultracompact interturbine burner with different inlet mass flow splits
2017, 32(1): 60-65. doi: 10.13224/j.cnki.jasp.2017.01.009
Abstract PDF(897KB) icon901 icon455
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An optimization analysis of inlet mass flow splits of ultracompact interturbine burner was introduced. The combustion performance in a smallscale interturbine burner was numerically analyzed using Chemkin software, and a detail kerosene RP3/air mechanism was used. Numerical results were qualitatively validated with the existing experimental data with respect to the combustion performance. Five split ratios of the core mass flow rate to cavity mass flow rate, 60/40, 65/35, 70/30, 75/25 and 80/20, were adopted to contrastively study the outlet temperature, combustion efficiency and pollutant emission using the simplified model. The results show that the combustion efficiency of the split ratio 65/35 decreasesd by 0249% compared with the highest efficiency among the five split ratios, but the NOx and CO emissions both decrease more than 50%. The conclusion based on this method can provide a basis for evaluating an optimum mass flow split at the design stage of ultracompact interturbine burner as well as for simplified performance analysis.
Probabilistic analysis of turbine disk fatigue life considering geometric uncertainties
2017, 32(1): 66-74. doi: 10.13224/j.cnki.jasp.2017.01.010
Abstract PDF(1042KB) icon878 icon533
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For the issues of a large number of geometric variables, hard to select geometric random variables and determine their probability distributions, rebuilding the finite element model in an automated fashion, and huge numerical computation comsuption when conducting the LCF (low cycle fatigue) life prediction considering geometric uncertainties of turbine disk. A geometric uncertainty probabilistic processing method was proposed. First, the design of experiments method was employed to determine key geometric parameters, which would be treated as random variables for LCF prediction. Second, the KS (KolmogorovSmirnov) method was adopted to determine the probability distributions of random variables. Third, a surrogate model was built to conduct Monte Carlo simulation. On this basis, turbine disk probabilistic analysis system was developed. The LCF life probabilistic analysis work of a GH720Li turbine engine disk was completed under the turbine disk probability analysis system, by which three key geometric parameters (inner diameter, outer diameter, rim thickness) and lifereliability curve of the turbine disk were obtained. Analysis results shows that the outer diameter of turbine disk has a strong impact on the LCF life.
Modeling for prior distributions reliability based on P value in Bayes inference of hit accuracy analysis
2017, 32(1): 75-81. doi: 10.13224/j.cnki.jasp.2017.01.011
Abstract PDF(763KB) icon793 icon440
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Based on the analysis of the concept and necessity of prior reliability for dispersion parameters prior distribution, the P value calculating model for given dispersion parameter (variance) was presented, the prior distributions reliability calculating model for onedimensional dispersion parameter was constructed, and the concepts of prior P value and prior reliability were presented. The variation of prior reliability was described, and the reject rule of prior distribution was given. To the analysis of prior reliability for twodimensional dispersion parameter, the independent solution model and integrated solution model for prior P value were carried out respectively. And with the interval divided by 005, 02 and 04, the principle and requirement of prior distribution selection was presented. From cases comparison result, it was easy to see that prior reliability can be easy to complete the difference comparison of prior distributions, and compared with traditional method only could describe prior reliability from qualitative view, the P value model not only calculated the numeric of prior reliability, but also could complete the correctness hypothesis test of prior distribution form probability view.
Maintenance decision method of a turbofan engine based on fault detection
2017, 32(1): 82-88. doi: 10.13224/j.cnki.jasp.2017.01.012
Abstract PDF(807KB) icon1055 icon523
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In the maintenance process traditional excessive maintenance of turbofan engines may result in performance deterioration, long maintenance cycle and high maintenance cost. In order to solve this problem effectively, based on turbofan engine overhaul manual and maintenance technology, the fault detection process and repair mode were studied in depth, and the fault diagnosis expert system and fault diagnosis model were established based on BP(back propagation) neural network, verifying the reliability of fault diagnosis model with several sets of real performance data, with the diagnostic accuracy rate up to 95%. Secondly, the two kinds of diagnostic information were combined to develop reliable maintenance program and optimize the maintenance process. Then a maintenance decision method was put forward. By a certain type of turbofan real validation, it shows that this method can effectively eliminate the fault of high exhaust temperature, helping to improve maintenance quality and reduce maintenance cost of the engine.
Effect of holeexpansion on hightemperature fatigue property of GH4169 superalloy hole structure
2017, 32(1): 89-95. doi: 10.13224/j.cnki.jasp.2017.01.013
Abstract PDF(836KB) icon916 icon473
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Fatigue specimen with central hole was designed based on the bolthole of a high pressure compressor disk. Of the asreceived (AR) specimens and after holeexpansion (HE), the surface profile and fatigue property in multiple alternating loads were characterized; moreover, failure analysis and the evolution of HE residual stress profile during fatigue cycle were investigated. Results showed that, after HE, the roughness of hole wall decreased, besides, the high temperature fatigue performances improved 1-3 times under multiple large load condition with the slight rise of fatigue data dispersion. The HE residual stress released to 60% during 20000 cycles at the maximum tensile stress of 663MPa,temperature of 600℃ and stress ratio of 01. Compared with the untreated specimens nucleating at machining marks, the HE crack initiated at metal accumulation by HE in the chamfer, presenting single source crack initiations.
Health status assessment based on uncertainty and importance degree improved DSmT
2017, 32(1): 96-104. doi: 10.13224/j.cnki.jasp.2017.01.014
Abstract PDF(801KB) icon741 icon409
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Considering the health status assessment problem of lower accuracy and objectivity, the index uncertainty and importance degree was introduced, and then a method of health status assessment based on uncertainty and importance degree improved DSmT （DezertSmarandache theory） was proposed. Firstly, the uncertainty and importance degree was employed to determine the reasonable weight of index. Then the method of fuzzy comprehensive evaluation was used to determine the basic belief assignment of each index by building triangle trapezoidal membership function, and then the basic belief assignment was combined to get the assessment results using the weight DSmT fusion rule based on the index weight. Finally, the method was used to evaluate a power supply system. The results indicate that the proposed method can assign reasonable weight to the index, and the health status assessment result is consistent with the actual state.
A method for determination of exponents in total strain life equation.
2017, 32(1): 105-113. doi: 10.13224/j.cnki.jasp.2017.01.015
Abstract PDF(878KB) icon776 icon448
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The fatigue strength coefficient and fatigue ductility coefficient in total strain life equation for a material can be determined by the monotonic tensile ultimate strength and percentage reduction of area of specimens. A method was investigated to determine the fatigue strength exponent and fatigue ductility exponent in total strain life equation by use of the monotonic tensile elongation and the fatigue test data under two different stress amplitudes. An analysis procedure was developed to determine all the four parameters in the total strain life equation according to a few fatigue test data and the monotonic tensile mechanical performance parameters. This method was verified by use of the fatigue test data of several titanium alloys and nickelbased alloys commonly used in aeroengine. The results indicate that the total strain life equation with its parameters obtained by use of the developed method can make a relatively accurate fatigue life prediction nearly within a scatter band of 3.
Quasistatic compression mechanical properties of EPDM material after pyrolysis.
2017, 32(1): 114-119. doi: 10.13224/j.cnki.jasp.2017.01.016
Abstract PDF(866KB) icon903 icon491
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In order to study the pyrolysis process of ethylene propylene diene monomer (EPDM) insulation material and its compression mechanical behavior under high strain rate, the thermal stability of EPDM was analyzed by thermogravimetric analysis (TGA). Based on the TGA curve and the thermal degradation temperature, the resistance furnace was set at different temperatures to complete the pyrolysis test. And then quasistatic compression tests were conducted by the universal testing machine. Results showed that, the mechanical properties of EPDM can be divided into three stages, the stressstrain curves first decreased, then rose and last reduced with the increase of pyrolysis temperature. Phased models were used to give a good description of mechanical properties of EPDM material under different degrees of pyrolysis. The second order Polynomial hyperelastic model including temperature related items was built to predict the mechanical response of EPDM material after different pyrolysis temperatures. Compared with the test results, the compression models can be used to effectively describe the mechanical behaviors of EPDM material with good accuracy.
Dressing method and dressing error analysis of aviationface gear grinding wheel
2017, 32(1): 120-129. doi: 10.13224/j.cnki.jasp.2017.01.017
Abstract PDF(1069KB) icon816 icon431
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According to the mechanical structure of a face gear grinding machine, an offset curve dressing method and a grinding wheel dresser were designed, and simulation and analysis of the dressing process were performed with VERICUT. The equation of facegear tooth profile with error caused by wheel dressing process was derived and the error cloud of facegear tooth profile was created with MATLAB, providing theory references for the research on error compensation of dressing process. The grinding and testing experiments were carried out at last. By comparing the result with the error cloud, the reason was analyzed and the error in the dressing process was compensated; the maximum tooth profile normal error was reduced by 3114%, and the precision of the tooth surface was improved.
Contact fatigue reliability assessment method of high speed fourpoint contact ball bearing of helicopter
2017, 32(1): 130-137. doi: 10.13224/j.cnki.jasp.2017.01.018
Abstract PDF(954KB) icon783 icon447
Abstract:
In order to efficiently and precisely analyze contact fatigue reliability of high speed fourpoint contact ball bearing, an effective reliability analysis method was proposed by combination with MCSFEM (stochastic finite element method based on Monte Carlo) and stressstrength interference theory. Under the complex working condition of high speed, high temperature and EHL (elastohydrodynamic lubrication), the finite element model based on the thermalstructure coupling analysis was established by using the FEM (finite element method). Considering the influence of the stochastic performance of material parameters, lubricant parameters and contact fatigue strength factors on the reliability, under the premise that the distribution type of contact stress of highspeed fourpoint contact ball bearing was determined by means of the MCSFEM and the KS (KolmogorovSmirnov) method, contact fatigue reliability assessment method of high speed fourpoint contact ball bearing was established based on stressstrength interference theory. Result showed that,compared with the traditional MCSFEM method, the consuming time of the proposed method only accounted for about 0243% of the traditional method, and the error between the above two methods was only 148%, validating the efficiency of the proposed method.
Calculation method of external meshed gear tooth root bending stress of high contact ratio gear.
2017, 32(1): 138-147. doi: 10.13224/j.cnki.jasp.2017.01.019
Abstract PDF(928KB) icon1006 icon498
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The tooth root bending stress calculation method of high contact ratio spur gear pair was studied. The gear tooth deformation and stiffness calculation of high contact ratio gear and load of single tooth were studied. The definition of load sharing ratio and the calculation method of high contact ratio gear tooth were given. The meshing point of high contact ratio gear pair with double teeth was taken as the point of computational load.The calculation method of tooth shape coefficient and stress concentration coefficient of double toothed meshing zone boundary of the dangerous section that located on position of high contact ratio gear tooth roots 30 degree transition curve were given. Calculation formulas of tooth root bending stress of the dangerous section was obtained. External gear pair with different contact ratios were designed, and the tooth root bending stress was tested by CL100 gear test machine. The test result show that, under high load, the tooth root bending stress theoretical calculation error of active gear is less than 785%, and the driven gear is less than 98%. Under low load, the tooth root bending stress theoretical calculation error of active gear is less than 241%, and the driven gear is less than 19%.
Fault diagnosis for rolling element bearings based on information exergy distance of acoustic emission signal
2017, 32(1): 148-154. doi: 10.13224/j.cnki.jasp.2017.01.020
Abstract PDF(1446KB) icon875 icon441
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Based on the information entropy theory, a fault diagnosis methodology for rolling element bearings was proposed. It is a fusion of wavelet energy spectrum exergy and Mahalanobis distance. Inner ring fault, outer ring fault, rolling element fault, inner ringrolling element fault and inner ringouter ring fault of rolling element bearing were simulated on a twin spool rotor test rig. The acoustic emission signals of each fault were collected. Single fault and coupling faults of rolling element bearings were successfully diagnosed using the information exergy distance method for acoustic emission signals. The diagnosis results show that the method has higher information utilization ratio than the information entropy method. It can diagnose early faults in rolling element bearing clearly and accurately, which is proved more effective than the information entropy distance method.
Rotational accuracy of the cylindrical roller bearing based on inner raceway profile
2017, 32(1): 155-161. doi: 10.13224/j.cnki.jasp.2017.01.021
Abstract PDF(839KB) icon751 icon441
Abstract:
Based on analysis of the geometric relation and motion relation of bearing, a mathematical model for radial runout of cylindrical roller bearing in consideration of inner raceway profile was developed to investigate the influence of inner raceway roundness error (ie., amplitude, order), the roller number and radial clearance on rotational accuracy. The model was validated to be reasonable by specific spot way. The results indicate that inner raceway roundness error has a significant influence on rotational accuracy of cylindrical roller bearings. The rotational accuracy of cylindrical roller bearings drops sharply with increasing the amplitude of inner raceway roundness error. The effect of loworder harmonic on the rotational accuracy is greater that highorder harmonic. When harmonic order is an integral multiple of the roller number, the rotation accuracy of cylindrical roller bearings significantly reduces. The rotational accuracy of cylindrical roller bearings could be improved by reducing the amplitude of inner raceway roundness error.
Analysis of torsional resonance of gear pairs based on contactfinite element method.
2017, 32(1): 162-167. doi: 10.13224/j.cnki.jasp.2017.01.022
Abstract PDF(833KB) icon834 icon472
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To simulate the continuous engagement of gear pair under resonance state, the contact finite element method was described and proved to be reasonable by comparing the meshing stiffness with national standard. The research object was a helical involute gear pair, the natural frequency of torsional vibration was got by spectral analysis method and frequency response analysis method. The occurrence, development and steady state of gear pairs torsional resonance were simulated numerically, and several dynamic parameters were analyzed quantitatively. The results showed that, the separation during the meshing process made the effect of meshing impact more significant. The maximum vonMises stress increased by 20% compared with the value when the meshing frequency was 3000Hz.
Integrated design and test of forebody/inlet for airbreathing hypersonic vehicle.
2017, 32(1): 168-176. doi: 10.13224/j.cnki.jasp.2017.01.023
Abstract PDF(922KB) icon865 icon467
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With constraint of all performance indexes, the integrated design of forebody/inlet and the wind tunnel test of hypersonic vehicle was developed, while the major performance of forebody/inlet was assessed. Results showed that:(1)the performances of forebody/inlet satisfied all the performance indexes at the design condition, and the wind tunnel test validated the numerical design method; (2)the numerical results agreed well with the wind tunnel test results, the max error of mass flow ratio was 4% and the max error of total pressure recovery coefficient was 42%, so the numerical method was efficient;(3)the additional drag of forebody/inlet increased with the increasing of inflow Mach number, the additional drag was up to 172% of the total drag at the angle of attack 0° when the Mach number was 4, which should be considered in the design;(4)the prearranged planning should be made to avoid failure of the wind tunnel test because the inlet may not be able to start, which should be considered during design of the wind tunnel test scheme.
Self-similarity characteristics of highly underexpanded sonic jet
2017, 32(1): 177-187. doi: 10.13224/j.cnki.jasp.2017.01.024
Abstract PDF(1120KB) icon827 icon448
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A three-dimensional large eddy simulation(LES) of a highly underexpanded jet with nozzle pressure ratio(NPR) of 5.60 and the magnitude of flow Reynolds number of 105 was carried out based on high-pressure gas jet injection model and high-resolution mesh. The near-field wave structures of the highly underexpanded jet were successfully captured by LES, and also agreed well with the available references data. The quantitative investigation of the radial distributions of streamwise velocity and nitrogen mass fraction was performed to reveal the self-similarity characteristics of the highly underexpanded jet.Result showed that,the self-similarity characteristics of radial profiles of streamwise velocity and nitrogen mass fraction previously observed for subsonic jets were also confirmed in the downstream jet core for the current highly underexpanded jet. The flow where the self-similarity started was still supersonic, showing a distinctive feature for the self-similarity characteristics of highly underexpanded jets. The proposed Gauss fitting formulas can well present the self-similarity characteristics of the regions close to or far away from the jet centerline. In addition, the development feature of the jet shear layer was studied, the jet growth rate obtained was compared with the previous experimental results, and the possible explanation for the difference was observed.
Effect of transport properties of high-temperature air on boundary layer stability and transition prediction
2017, 32(1): 188-195. doi: 10.13224/j.cnki.jasp.2017.01.025
Abstract PDF(981KB) icon804 icon496
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In order to study the effect of viscosity and thermal conductivity coefficient on the basic flow and flow stability in the boundary layer, the calculation model of the viscosity and thermal conductivity coefficient of high temperature gases was established by comparing Sutherland formula and Gupta fitting relation. Then Sutherland formula and the established model were applied to the 7species air model for chemical equilibrium flow respectively, and these models were compared in flatplate boundary layer of Mach number 10, 16 and 20 at the flight height of 30-5km. The calculation result shows that, within the high temperature range, the viscosity and thermal conductivity coefficient both affect basic flow, flow stability and transition prediction. The increase of viscosity can raise the disturbance growth rate, broaden the growth zone and advance the transition location, whereas the increase of thermal conductivity coefficient leads to opposite results.
Optimal design and truckmounted testing of aerodynamic performance for the propeller of high altitude airship
2017, 32(1): 196-202. doi: 10.13224/j.cnki.jasp.2017.01.026
Abstract PDF(961KB) icon832 icon423
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Considering the overall requirements of the propeller of a high altitude airship, the propeller was optimized and a truckmounted testing of aerodynamic performance was carried out. The blade element momentum theory was used to calculate the aerodynamic performance of propeller and verify it by wind tunnel test. By combining blade element momentum theory with genetic algorithm, the chord and twist angle of the original propeller can be optimized, making the propeller more efficient and lightweight,and the aerodynamic efficiency at design point of propeller increased by 23%. Then, a truckmounted testing system was proposed and applied into the acquired propeller test in different altitudes and atmosphere parameters, and the aerodynamic performance of optimized propeller at different conditions was acquired. The results obtained from the truckmounted testing for the propeller of high altitude airship show that the higher altitude means the smaller thrust and torque with the same rotational speed and free flow. The average relative error of the thrust and torque of the fullscale propeller are 28% and 92% at altitude of 36km. Thus, the test results are in good agreement with the numerical simulation, verifying the accuracy of the system.
Cold-side temperature control strategy in power measuring system of radioisotope heat source
2017, 32(1): 203-212. doi: 10.13224/j.cnki.jasp.2017.01.027
Abstract PDF(980KB) icon761 icon455
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System dynamic model was established based on the need of coldside temperature control in the power measuring system of radioisotope heat source. On the basis of the openloop simulation analysis, three control algorithms, namely, conventional proportion integration differentiation (PID) control, fuzzy control and support vector machine(SVM) intelligent predictive control, were designed respectively, with which the feasibility of temperature control of the measuring system could be verified. Results suggest that, the power measuring system presents high robustness and stability by combing the excellent nonlinear function approximation ability of SVM and the predictive control method to fit the nonlinear system model, and by correcting the data based on the feedback of the SVM predictions.
Cold start control strategy of a two-stroke direct injection spark-ignited kerosene engine
2017, 32(1): 213-220. doi: 10.13224/j.cnki.jasp.2017.01.028
Abstract PDF(809KB) icon781 icon450
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The cold start control strategy was designed for a twostroke sparkignited kerosene engine with airassisted direct injection. With the use of selfdeveloped electronic control unit, bench tests were carried out to verify the accuracy of the control strategy under 4℃ ambient temperature, and the effects of the key control parameters on cold start performance were researched under about 14℃ ambient temperature. The experimental results showed that, the ignition advance angle had effects on late stage of starting process; after the successful starting, ignition advance angle with 40° before top dead center was most beneficial to accelerate the warmup process. When applying the saturated ignition energy strategy, the cold start performance was the best, the average engine speed of warmup process raised to the maximum level, and the related engine speed fluctuation reached to the minimum value. The fuel enrichment factor bigger than 25 improved the dynamic performance of starting process, whose speed raising rate was increased, but the variations of cold start process were almost consistent when continuing to increase the fuel enrichment factor from 25 to 45. The air injection timing angle from 40° to 60° before top dead center was helpful to successful cold start; moderately advancing air injection timing angle at warmup condition can accelerate the warmup process. The fuel to air injection delay had direct influence on the fuel air mixture process, which may affect the motor dragging and starting process, and rapidly realize the best successful cold start when the fuel to air injection delay was about 6ms.
K-ELM method for sensor signal reconfiguration of aeroengine
2017, 32(1): 221-116. doi: 10.13224/j.cnki.jasp.2017.01.029
Abstract PDF(706KB) icon709 icon372
Abstract:
Northwestern Polytechnical University，Xian 710072，China)(1.Jiangsu Province Key Laboratory of Aerospace Power System,College of Energy and Power Engineering,Nanjing University of Aeronautics and Astronautics,Nanjing 210016,China;2.Collaborative Innovation Center for Advanced AeroEngine,Beijing 100191,China;3.AeroEngine Control System Institute,Aero Engine (Group) Corporation of China,Wuxi Jiangsu 214063,China)Abstract：A fast leaveoneout cross validation method was presented to provide a criterion for kernelbased extreme learning machine (K-ELM) used for sensor signal reconfiguration of aeroengine. The procedure can avoid N times explicit training (N is the number of training samples) so that the computation cost was reduced 1/N when compared with normal leaveoneout procedure. Simulation results show that this method can provide a fast and accurate criterion, allowing to select best kernel parameters for K-ELM.
Analysis on influence of dynamic characteristics of gas generator insolid propellant ducted rockets
2017, 32(1): 227-232. doi: 10.13224/j.cnki.jasp.2017.01.030
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Aerospace Science and Industry Corporation,Beijing 100074,China)Abstract：An integral model of gas generator/solid propellant ducted rocket/missile was established, and typical performance parameters in the typical trajectory were obtained by simulation. Results showed that, in the climbing and cruising phases, the relative error of the fuel mass flow rate and the thrust of the engine was less than 7%. But in the diving phase, due to the free volume effect, the relative error of the fuel mass flow rate was -30%, and the error of thrust was -50% correspondingly. However, the relative errors of flight velocity and flight range were less than 5% and 1% respectively. Therefore, for this typical climbcruisediving flight trajectory described, the dynamic characteristics of gas generator can be ignored in analysis of the missiles working process.
raSimulation study of working stability of a gas pressure regulator under external excitation vibration conditions.
2017, 32(1): 233-268. doi: 10.13224/j.cnki.jasp.2017.01.031
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Abstract：For the purpose of studying the working stability of pressure regulator working in launch vehicle gas pressurization system under external excitation vibration conditions, the vibration exciting source was introduced through the displacement coordinate of the regulator shell to modify the pressure regulator model and the dynamic working process of a gas pressurization system was simulated under external excitation conditions. As the pressure oscillation at a presssure regulator outlet was observed, contrast calculations considering different downstream pipe sizes and different parameters of a pressure regulator were carried out. The result shows that increasing the pipe sizes, decreasing the mass of the valve spool and the friction force between the valve spool and the shell can reduce the pressure oscillation intensity and benefit the regulators working stability under external excitation vibration conditions. The numerical study provides a reference for the design and optimization of pressure regulators and gas pressurization systems.
Aerodynamic optimization design of high bypass ratio fan blades
2017, 32(1): 239-247. doi: 10.13224/j.cnki.jasp.2017.01.032
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The automatic optimization method was applied to 3D aerodynamic design of a high bypass ratio fan blade. A genetic algorithm was used as numerical optimization method, and multiCPU parallel optimization was realized by using network communication protocol to greatly shorten the optimization time. The fan blade profiles, stack line, the flow passage in meridian plane, installation angle and chord length were set as design variables. The parameterization method based on modifications to these design variables was combined with the range limit of the design variables in the genetic algorithm, and it controlled and rationalized the individuals generated in optimization process.Dentons viscous volume force method was applied to flow field calculation of the fans,decreasing the calculation time and further reducing the optimization time. The optimization goal was set to improve the fan efficiency and keep total pressure ratio and mass flow rate unchanged at the design point, and the optimized fans performance at offdesign points was checked. The original fan was optimized in two steps, in which the design parameters were adjusted according to aerodynamic characteristics of the fan to be optimized. The final optimized fans efficiency increased from 09463 to 09560, and stability margin increased from 112% to 219%. Mach number of shock wave at blade tip section of the final optimized fan decreased slightly, and the shock wave leaned to the blade passages. Therefore, loss of the shock wave and its effect on boundary layer decreasd, and the stability margin increased.
Influence of diffuser on basic stage performance
2017, 32(1): 248-256. doi: 10.13224/j.cnki.jasp.2017.01.033
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The effects of vaneless diffusers and vaned diffusers with different entrance installation angles on a centrifugal compressor basic stage were studied with numerical calculations and tests. For compressor basic stage with vaneless diffuser, inner flowfield characteristics at nearsurge point, design point, and nearchoke point were analyzed, showing that vortex existed in the inlet and outlet of impeller blade and back of reflux blade at nearsurge point while flow state was good at designpoint and nearchoke point; as for nearchoke point, friction resistance loss increased with large flow speed, causing stage efficiency drop quickly. For compressor basic stage with single arc vaned diffuser, the effects on surge margin, choke margin and efficiency were analyzed with five different vaned diffuser entrance installation angles. The results show that when entrance installation angle of vaned diffuser decreases 3 degrees than the design value while outlet installation angle is fixed, the polytropic efficiency and polytropic energetic coefficient of stage achieve the best value.

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