2017 Vol. 32, No. 5

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Study on bleed air anti-icing system of aircraft
2017, 32(5): 1025-1034. doi: 10.13224/j.cnki.jasp.2017.05.001
Abstract PDF(1233KB) icon1780 icon711
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The basic structure and application background of the bleed air anti-icing system of aircraft was introduced, and its development history and present development situation at home and abroad were reviewed. The main research contents were analyzed from four key points, including the calculation of anti-icing surface droplet impingement property, the modeling of external icing/runback water of skin, the study of the internal structure parameters of bleed air anti-ice system, and multiphase coupling simulation of anti-icing system. Finally, the development trend of bleed air anti-icing system was shown via the analysis of the accurate prediction of three-dimensional accreting process of runback ice, optimization method of internal structure parameters of bleed air anti-icing system, the determination of the anti-icing systems safety boundary and margin, the parameters scaled model icing-wind tunnel experiment of anti-icing system.Key words: bleed air anti-icing; icing/runback
Combustion characteristics of direct injection piston aviation kerosene engine
2017, 32(5): 1035-1042. doi: 10.13224/j.cnki.jasp.2017.05.002
Abstract PDF(1144KB) icon1576 icon551
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Based on the experiment implemented on a low pressure air-assistant direct injection piston aviation engine, the influence of different start of injection timings, advance ignition angles, excess air ratios on the combustion characteristics was analyzed, and the difference between aviation kerosene and gasoline in the aspect of mixture formation, ignition delay period, flame propagation velocity and anti-detonating quality was compared. The result shows that：the fuel atomization will get higher and the cyclic variation coefficient get lower at the optimal start of injection timing, the cold start for aviation kerosene is harder than gasoline. Aviation kerosenes optimal advance ignition angle is bigger than gasolines under same conditions since its flame propagation velocity is lower than gasoline, and the impact of thermal efficiency on aviation kerosene is more obvious than on gasoline when the optimal advance ignition angle is deviated from the minimum advance for the best torque. Compared with gasoline, aviation kerosene is more suitable for burning in the enviroment with biger fuel mole fraction, when the excess air ratio is with in the range of 0.80 to 0.85, the ignition delay period of aviation kerosene will be the shortest and the cyclic variation coefficient will be the lowest. Under the low speed and high load condition, the knock intensity gets higher significantly. The anti-detonating quality of aviation kerosene is worse than gasoline.
High temperature heat pipe enhanced thermal protection structure for scramjet combustion chamber
2017, 32(5): 1043-1050. doi: 10.13224/j.cnki.jasp.2017.05.003
Abstract PDF(1039KB) icon1640 icon533
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Based on advanced thermal management method, a novel thermal protection structure was proposed for scramjet combustion chamber. High temperature heat pipe panels were used to decrease the local high temperature by achieving isotherm. Simultaneously, fuel pipes were embedded to achieve active cooling. The performance was analyzed by numerical simulation, and the influences of the design parameters were evaluated. A sample panel was prepared and evaluated by quartz lamp heating test. In typical circumstance, its unit area mass was 35.4% and 38.2% of oxygen-free copper panel and high temperature super alloy panel, respectively. The maximum temperature difference was less than 80K when the maximum temperature was 1123K in the local heating test. As a proposed thermal protection method, the structure can improve the scramjet thermal protection performance compared with the traditional fuel cooling method.
Gas turbine primary combustor error analysis of combustion efficiency and exhaust emission using gas analysis method
2017, 32(5): 1051-1057. doi: 10.13224/j.cnki.jasp.2017.05.004
Abstract PDF(831KB) icon1360 icon544
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The gas analysis system for measurement of combustion efficiency and exhaust emissions for aero gas turbine main combustor was introduced. The measurement error on combustion efficiency and exhaust emissions were analyzed in consideration of four aspects: sampling probe error, traversing mechanism movement, sampling probe temperature control and instrument error. Results e showed that by using mixed sampling probe and traversing mechanism, the measurement error for combustion efficiency was less than 0.21%, the error for air-fuel ratio and emissions was less than 1.11% and 2.24%, respectively. Combustion efficiency and emission volume fraction distribution under different combustor operational conditions were statistically analyzed. It is clear that under high power and high fuel air ratio conditions, these distributions are relatively uniform, thus it is appropriate to reduce a certain number of sampling points. Generally speaking, a large amount of sampling points is necessary to ensure the measurement accuracy of gas analysis method.
Modeling and analysis of non-isothermal of droplet flash evaporation in vacuum environment
2017, 32(5): 1058-1065. doi: 10.13224/j.cnki.jasp.2017.05.005
Abstract PDF(1064KB) icon1087 icon497
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To reveal the mechanism of droplet flash evaporation in vacuum in depth, a complete non-isothermal model for heat and mass transfer was established. The variation of temperature field and droplet radius was solved exactly, and the accurate position of solid-liquid interface in freezing stage was tracked in real time. Based on the experimental study, the change of droplet shape before and after phase change was observed, and the numerical model was validated to accurately predict the basic features of the process. The effects of initial radius, initial temperature, vacuum pressure and subcooling degree on flash evaporation were studied. Results showed that the vacuum pressure was the major factor in the whole process which would affect the final equilibrium temperature. The initial radius mainly affected the precooling and freezing time, while the initial temperature and subcooling degree only affected the precooling time.
Theoretical analysis and experiment of power loss in giant magnetostrictive actuator
2017, 32(5): 1066-1073. doi: 10.13224/j.cnki.jasp.2017.05.006
Abstract PDF(965KB) icon1158 icon563
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The performance of giant magnetostrictive actuator (GMA) is seriously affected by temperature rising under high frequency large current. In order to reduce GMAs temperature, pipe cooling was presented and its working principle was introduced. According to Ohms law, coil loss was obtained under the action of alternating current (AC) and direct current (DC). Based on Maxwell equation and imaginary part of complex permeability, the eddy current loss and hysteresis loss of GMM were deduced, respectively. Then, it was found that GMM power loss accounted for 5% of GMA power loss when the drive frequency reached 50 Hz. Finally, the experiment platform of GMA thermal characteristic was built and the result indicated that the calculation of GMA power loss was in good agreement with that of theory. And the pipe cooling had good cooling effect on GMA temperature. GMM rod temperature could be controlled within 50℃. The maximum error of the experiment and simulation was within 3℃. The research result further indicates the calculation of GMA power loss is valid and has a significant guidance for the design and application of GMA.
Atomization characteristics of cross-flow injector in the fluidic nozzle throat
2017, 32(5): 1074-1081. doi: 10.13224/j.cnki.jasp.2017.05.007
Abstract PDF(1384KB) icon1560 icon516
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In order to study atomization effects of the cross-flow injector and the influence on engine thrust，a series of cold-flow tests were performed using impinging injector,reverse injector and horizontal injector. The Sauter mean diameter of droplet in spray field at the exit of engine nozzle and thrust characteristics of engine were studied at different test cases. The test results indicate that with the increase of pressure ratio, the droplet diameter decreases;the injection case of the minimal droplet diameter is the throat and expanding section injection when the pressure ratio is given, and the injector of the best atomization quality is the impinging injector; meanwhile, the ability to control the throat and thrust ratio for three kinds of injectors increases with the increasing mass flow ratio under the throat and expanding section injection.
Study on key factors of mistuned vibration for blade-disk system of some-stage compressor
2017, 32(5): 1082-1090. doi: 10.13224/j.cnki.jasp.2017.05.008
Abstract PDF(1360KB) icon1251 icon591
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Based on the blade disk basic sector of certain stage compressor, blade disk finite element model considering non-linear tenon contact was established, free-interface substructure-fixed interface prestressed modal synthesis super element approximate analysis method was proposed, meanwhile, mistuned parameters recognition method of linear expression was fitted based on the blade static-frequency test and dichotomy combined with finite element analysis, exploring the effects of mistuning key factors on blade disk vibration. Results show that the non-linear tenon contact cannot be neglected, and the accuracy of super element method is 3.07%, so the proposed method meets the requirement. In addition, blades mean frequency, disk stiffness ratio and frequency veering have an effect on mistuned bladed disks vibration amplitude, resonance frequency and strain energy and other parameters.
Experiment on axial clearance on high-speed dual-turbine rotor stability
2017, 32(5): 1091-1098. doi: 10.13224/j.cnki.jasp.2017.05.009
Abstract PDF(1262KB) icon1176 icon486
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The axial clearance under different bearing gas supply pressures can be measured through rotor static test. The effects of the axial clearance on the stability of high-speed dual-turbine rotor of generator can be analyzed by vibration test and analysis methods, including three-dimensional spectrum, axis center tracks and frequency spectrum characteristics. Results showed that the gas film half-speed whirl and gas film whip appeared during run-up when the left and right sides of the axial clearance were not equal. When the axial clearance of the left and right ends of the rotor was equal, the gas film half-speed whirl and gas film whip disappeared, which could enhance the stability of gas bearing rotor system.
Prediction of model Ⅰ interlaminar fracture performance for Z-pins reinforced ceramic matrix composites
2017, 32(5): 1099-1104. doi: 10.13224/j.cnki.jasp.2017.05.010
Abstract PDF(834KB) icon991 icon10
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Based on the experimental results and toughening mechanism of model Ⅰ interlaminar fracture toughness for Z-pins reinforced ceramic matrix composites, a simple pullout model of Z-pins was proposed. The inconsistency of pullout displacement in the scale of Z-pins diameter was considered carefully, prediction model of model Ⅰ interlaminar fracture performance for Z-pins reinforced ceramic matrix composites was obtained by means of the simple double cantilever beam (DCB) theory, and the predicted results were in good agreement with the experiments. Using this analysis as a foundation, the effect on crack tips energy release rate with different Z-pins diameters and crack lengths was studied, and then compared with the method of spring element. Results show that with the increase of diameters, the differences of energy release rate at crack tip gradually increase by two methods, but the difference is relatively small when crack tip is close to Z-pins; however, with the increase of crack lengths, there is a big difference in the two methods energy release rate at crack tip, the inconsistency of pullout displacement in the scale of Z-pins diameter cant be ignored.
Hard object impact damage characteristics of aero engine fan blade
2017, 32(5): 1105-1111. doi: 10.13224/j.cnki.jasp.2017.05.011
Abstract PDF(828KB) icon1537 icon48
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Based on the foreign objects damage data of civil aviation engine fan blades in recent 20 years, the most typical features of hard object impact damage were filtered, and the fan blade damage characteristics were classified according to the engine maintenance manual. Then the relevance and differences between the damage types and engine types, the damage position features, and damage size features were analyzed. The results indicate that the damage type of engine fan blades hard object impact has diversified characteristics, in which the occurrence probability of two damage types (notch and dent) is larger, and there are some differences in specific engine type of different damage types. The analysis of the damage position and size features shows that there is a certain cluster statistical law of the fan blades damage position, and the damage size characteristic presents a certain statistical distribution. The results are able to provide technical reference for the actual maintenance of aero engine fan blades.
Detailed deduction and analysis of the general analytical model of coupling vibration in a rotor system
2017, 32(5): 1112-1119. doi: 10.13224/j.cnki.jasp.2017.05.012
Abstract PDF(863KB) icon1132 icon14
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Based on the mechanism of linear and nonlinear forces on the rotor system, the linear scale factor, nonlinear scale factor and coupling ratio was introduced as characteristic parameters, the general expressions of damping and stiffness forces were established, so a general form of linear and nolinear coupling vibration model was formulated. Considering a single-disc rotor system excited only by mass unbalance force, the steady-state and transient-state solutions were derived through multi-scale method. The analysis on the analytical solutions showed the vibration mechanism of linear and nonlinear coupling effects and responses. The influence of transient time scale factor on responses was analyzed through numerical calculation. When transient time scale factor was larger, the transient-state solution decayed faster, approaching the steady-state solution closer. The amplitude-frequency characteristics were also analyzed by the short time Fourier transform of the steady-state solution. It can be seen that the first harmonic generation has nonlinear characteristics and the third harmonic generation has double-peak characteristics, further elaborating the influences of nonlinear scale factor on the coupling vibration of the rotor system.
Aeroengine rotor system vibration characteristics under action of rotating stall transverse load
2017, 32(5): 1120-1130. doi: 10.13224/j.cnki.jasp.2017.05.013
Abstract PDF(1776KB) icon1202 icon24
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To analyze the transverse vibration in rotor system caused by rotating-stall, a dynamical rotor system model with the transverse load by the fluctuation of pressure and flow coefficient was proposed by Mansoux model coupling with unbalance and rubbing load. Numerical calculation technology was used to investigate the vibration characteristics of rotor system under the conditions with/without the action of transverse load respectively. Furthermore, the influence of transverse load on the stability of rotor system was analyzed by axes contrails, spectrogram, Poincare figures and Bode figures at the same time. It indicates that the vibration of compressor caused by stall is nonlinear and mainly dominated by low frequency. This provides a certain theoretical basis and methods for reference for the aircraft engine design and vibration monitoring.
Design method of axisymmetric basic flowfield with controlled expansion law
2017, 32(5): 1131-1137. doi: 10.13224/j.cnki.jasp.2017.05.014
Abstract PDF(937KB) icon1012 icon18
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In order to make the design methodology of streamline traced nozzle more flexible, an innovative axis symmetrical basic flow field design methodology with controlled expansion law on wall was explored while a centre body was placed in the flowfield. In the design process, Method of characteristics (MOC) was used to inversely solve the wall with given expansion law. The main design parameters, such as expansion law, centre body and oblique angle, were parametrically investigated. Then the variation of structure and performance of basic flowfield with these parameters were obtained. Using this basic flowfield, a rectangular streamline traced nozzle was designed and analyzed. Results show that, inverse design can be achieved by MOC; when the inlet and exit flow parameters are stable, there is a suitable expansion law corresponding to the maximum thrust performance. The radius of centre body and length ratio of basic flowfield, with less effect on thrust, can be used as the parameters to optimize the moment characteristics of derivative nozzle. When the oblique angle increases, the length and thrust of basic flowfield decrease rapidly, so the choice of oblique angle should be considered carefully.
Application of large-scale CFD flowfield visualization analysis system
2017, 32(5): 1138-1147. doi: 10.13224/j.cnki.jasp.2017.05.015
Abstract PDF(1232KB) icon1061 icon23
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A new visualization system for large scale computational fluid dynamics（CFD）flowfield data, called flow field visualization analysis system or FVAS for short, was presented. FVAS has several complete and practical functions such as three dimensional steady and unsteady flow field data preprocessing and feature extraction, volume rendering, glyph (streamline, isosurface, etc) rendering, texture rendering and so on. Many different data analysis methods and favorable interactions were also supported in the system. FVAS could show the inner-outer flow structure characteristics and complicated physical phenomena with eight ways of demonstration, three kinds of display modes and five types of views. FVAS also implemented animation display function for time-varying data and multi-core parallel rendering. Such cases verify that our system is simple, useful, and strongly universal. A variety of mixed rendering technologies can effectively show the internal responses in flow field data such as combustor dataset, air inlet dataset. Interactions including section and subdivision can show local features and details in multiple views, and analysis tools like chart and graph can statistically analyze the information of special grid cell. 300 test cases were completed in our system test. Compared with the traditional CFD software, our system can promote more than 70% rendering efficiency. The system fault rate is 0.6%, transaction success rate is 100%, and it can effectively accelerate the analysis and statistical process of flow field data.
Influence of internal contraction section configurations on self-starting ability of hypersonic inlets
2017, 32(5): 1148-1159. doi: 10.13224/j.cnki.jasp.2017.05.016
Abstract PDF(1257KB) icon1077 icon23
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To explore the influence of different internal contraction section configurations on self-starting ability of hypersonic inlets, the self-starting processes of two-dimensional hypersonic inlets with angulated and curved internal contraction sections were investigated using quasi-steady numerical simulations. The self-starting ability and the variation of separation zone in the self-starting process of two inlet configurations with different initial cowl compression angles were compared. And influences of compression strength distributions along internal contraction section on self-starting ability were also analyzed. Results show: (1) for the same internal contraction ratio, different internal contraction section configurations and initial cowl compression angles influence the self-starting ability of hypersonic inlets greatly. And the self-starting ability of the curved internal contraction section configuration is much better than that of the angulated one. (2) Both the total compression strength of the internal contraction section and the compression strength distributions along internal contraction section have major influences on the self-starting ability of hypersonic inlets. Also, the compression strength distribution determines the position of the massive separation zone under the critical condition.
Flow characteristics of a rectangular supersonic inlet under over-speed state
2017, 32(5): 1160-1167. doi: 10.13224/j.cnki.jasp.2017.05.017
Abstract PDF(1318KB) icon1076 icon10
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To aid in understanding the flow mechanism in supersonic inlet under the over-speed state, a numerical simulation was performed to obtain the flow structure of a rectangular inlet whose design Mach number was 2.0, operating under different inflow Mach numbers and backpressures. Results indicate: for the design case of Mach number 2.0, the core flow of shock train was deflected from the cowl-side surface to the ramp-side surface associated with the backpressure increase. While the inlet operated under the over-speed state, the core flow of shock train was deflected to the ramp-side surface firstly and then to the cowl-side surface due to the effects of the cowl-lip separation bubbles and the cowl shock in turn. For the case of inflow Mach number 2.5, a Mach-stem appeared at the joint point between forebody oblique shock and cowl shock once the backpressure increaseed to a certain value. However, this flow structure didnt appear in the case of inflow Mach number 3.0. Under the above two over-speed states, with the increase of backpressures, the transmit shock of forebody oblique shock was transformed into normal shock, and the transmit shock of cowl shock also changed its shape.
Busemann pressure rise distribution based design of inward turning basic flowfield with controlled and cancelled shock waves
2017, 32(5): 1168-1175. doi: 10.13224/j.cnki.jasp.2017.05.018
Abstract PDF(1359KB) icon1088 icon25
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An inward turning basic flowfield with controlled and cancelled shock waves was proposed based on Busemann pressure rise distribution by combining the method of Busemann design and method of characteristics. By this method, the aerodynamic truncation of the basic Busemann flowfield was realized. Then the inward turning basic flowfield with controlled and cancelled shock waves and a streamline traced sugar-scoop inlet were numerically simulated by inviscid CFD. The results show that the flowfield results solved by method of characteristics agree well with CFD，indicating that the inward turning basic flowfield with controlled and cancelled shock waves is reasonable and feasible. It inherits the high compression efficiency of Busemann design and keeps the reflected shock waves under control，and the shock cancellation is almost achieved，so it performs better than the classical truncated Busemann inlet. At the design point of Mach number 7，the flow parameters of throat section are uniform，with a pressure ratio of 18.32，a total pressure recovery coefficient of 0.878 and a compression efficiency of 0.936. There is almost no reduction of total pressure in isolator. The outflow is straight and uniform and the flow angle deviation is all within ±0.4 degree. The traced sugar-scoop inlet has a more circle-like outlet and inherits the characterisitics of inward turning basic flowfield with controlled and cancelled shock waves.
Steady- and transient-state numerical simulation of turboprop engine of propeller-free-turbine types
2017, 32(5): 1176-1182. doi: 10.13224/j.cnki.jasp.2017.05.019
Abstract PDF(1061KB) icon1326 icon26
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In order to simulate the performance of an integral turboprop propulsion system by a mathematics model, the propeller was taken as one of the internal flow components of the turboprop engine greatly influenced by external flow under the flight conditions. With introduction of propeller map and an imaginary mass method, this component-level turboprop engine mathematics model balanced two mass flow rates and powers of the propeller-free-turbine rotor and gas generator. The corresponding code was developed, and the steady- and transient-state sea-level rotational speed characteristics and flight mission profile characteristics of an 8 MW propfan propulsion system were simulated. The numerical simulation results show that, this mathematics model can successfully simulate the detailed performance of the variable pitch angle and the angle of attack of propeller or propfan on the cooperating points, and also the steady- and transient-state characteristics including the thrust and the specific fuel consumption of thrust of turboprop engine, while the environmental and adjusted parameters like altitude, velocity and turbine inlet total temperature are varying.
Simulation on effect of throat contraction ratio and strake stagger angle on flow field and aerodynamic performance of scrampressor
YANG Ling, ZHONG Jing-jun, HAN Ji-ang
2017, 32(5): 1183-1194. doi: 10.13224/j.cnki.jasp.2017.05.020
Abstract PDF(1550KB) icon966 icon11
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The design methods of typical supersonic aircraft intakes and shock wave compression technology have been applied to ram-rotor, an attractive compression system. A ram-rotor is of a typical structure including the compression ramp, the throat and the subsonic diffuser; a scrampressor is similar to ram-rotor, the only difference is that scrampressor has no subsonic diffuser. The work was the continuation of the preparatory work. In order to further study the effect of throat contraction ratio and strake stagger angle on the flow field and performance of a scrampressor, the flow field of a scrampressor with a three-dimensional flow path was numerically simulated with different throat contraction ratios and strake stagger angles. Simulated results indicated that the optional aerodynamic performance of a scrampressor could be achieved with an adiabatic efficiency of 0.8413 a total pressure recovery coefficient of 0.8446, a total pressure ratio of 7.14 and a static pressure ratio of 5.17 for a throat contraction ratio of 0.6 and a strake stagger angle of 12°. It was therefore concluded that an appropriate decrease in throat contraction ratio and an increase in strake stagger angle could help the comprehensive improvement of a scrampressor in performance.
Comparison among three models for compressor internal flow
2017, 32(5): 1195-1206. doi: 10.13224/j.cnki.jasp.2017.05.021
Abstract PDF(1295KB) icon1048 icon18
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In order to simulate the flow of compressor better, mixing plane method, harmonic balance method and phase lag method for CFD of compressor internal flow were implemented into an inhouse finite volume code. Taking NASA Stage 35 compressor model as an example, results of three methods were compared with each other. Result indicates that, phase lag method ranks highest in terms of accuracy and mixing plane method ranks lowest; the result of phase lag method is as accurate as the result of half annulus simulation of the flow with the dual time stepping method, and a factor of 20 speedup could be achieved; compared with mixing plane method, harmonic balance method can simulate unsteady interference between rotor and stator and global parameters variation in inlet and outlet accurately; when the harmonic order is set more than or equal to 5, the result of harmonic method does not vary with the harmonic order and matches well with the result of phase lag method; computational efficiency of mixing plane is much higher than the other two methods, computational efficiency of phase lag method is nearly equal to harmonic balance method with a harmonic order of 5.
Performance prediction model of partial casing treatment
2017, 32(5): 1207-1215. doi: 10.13224/j.cnki.jasp.2017.05.022
Abstract PDF(1025KB) icon996 icon18
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Using the idea of inlet distortion parallel compressor theory dividing the compressor into some sub compressors, the partial casing treatment compressor was divided into casing treatment sub compressor and solid wall sub compressor. Then the outlet parameter of the partial casing treatment compressor was got according to the laws of momentum conservation and energy conservation, and the assumption of partial casing treatment performance prediction model was acquired based on the experimental conclusions of linear relationship between the mass flow of stall margin point and the casing treatment circumferential angle. Comparisons of the prediction results and the experimental results reveal that the curves of prediction characteristics and experimental characteristics are consistent in overall trend. Under supersonic condition at 98% design rotating speed, the peak efficiency prediction error is smaller than 0.5%, and the comprehensive margin prediction error is under 0.6%.
Performance evaluation of turbulence models for complex flows in Sajben diffuser
2017, 32(5): 1216-1223. doi: 10.13224/j.cnki.jasp.2017.05.023
Abstract PDF(1379KB) icon1079 icon11
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Eight turbulence models were employed in the detailed numerical investigations for transonic flows in the Sajben diffuser, so as to assess the predictive capabilities of the turbulence models for shock-wave/turbulent boundary layer interactions in internal flows, including the Spalart-Allmaras model, the standard k-ε model, the RNG(re-normalization group) k-ε model, the realizable k-ε model, the standard k-ω model, the SST (shear stress transport) k-ω model, the v2-f model, and the Reynolds stress model. The performance of these different turbulence models was systematically assessed by comparing the numerical results with the available experimental data. The v2-f model and the SST k-ω model performed much better than other models, and the SST k-ω model predicted a little better than the v2-f model for pressure on walls, while v2-f model predicted a little better than the SST k-ω model for separation location, reattachment location and separation length in strong shock case.
Models of aluminum agglomeration in solid propellants
2017, 32(5): 1224-1233. doi: 10.13224/j.cnki.jasp.2017.05.024
Abstract PDF(810KB) icon1281 icon44
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The research progress on the aluminum agglomeration in solid propellants was reviewed. The limitations of present studies was discussed, followed by the analysis of valuable research directions of agglomeration models in future. The physical process of aluminum agglomeration can be divided into three stages, accumulation, aggregation and agglomeration. The present agglomeration models may be classified to five categories, which are empirical model, pocket model, physical model, random packing model and condensed-layer model, respectively. Highly accurate and widely applicable models used to predict the aluminum agglomeration behavior is still lacking. Developing new agglomeration models which can predict the size distribution of the agglomerates with low computational expense will be a hot issue in future. Physical model is promising due to its capability of the description of agglomeration nature. The combustion experiments of aluminized propellants was conducted at pressure of 5MPa, and agglomerate diameters on the propellants burning surface were obtained by a high-speed camera coupled with a microscope. The experimental results were compared with the prediction results of Hermsen model and Salita model. The prediction errors of agglomeration diameter are 8.7% and 9.6% by Salita model, for propellants with burning rate of 5.1mm/s and 8.0mm/s, respectively, whereas the prediction error reachs 19.2% by Hermsen model for the high burning rate propellant. Overall, it is shown that Salita model has a more reasonable accuracy.
Fatigue properties of HTPB propellant at low temperature
2017, 32(5): 1234-1240. doi: 10.13224/j.cnki.jasp.2017.05.025
Abstract PDF(816KB) icon1022 icon13
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To obtain the fatigue properties of hydroxyl-terminated polybutadiene(HTPB) propellant at low temperature, high-cycle fatigue tests including variable strain amplitudes and frequencies were conducted by taking practical application of tactics missile into account.Test equipment was a dynamic mechanical analyzer and temperature was kept constant at -50℃, frequencies at 50, 100, 150Hz.Before cyclic loading, quasi-static loading was carried out to investigate the effect of small pre-strain on fatigue properties of HTPB propellant at low temperature.Also, axial tensile tests at constant strain rates were made to acquire mechanical parameters after fatigue tests.The results indicate that with the increasing strain amplitude and loading frequencies, the mechanical properties degradation degree and fatigue damage increase.Initial quasi-static loading has a negative effect on fatigue properties and fatigue damage evolution demonstrates the non-linear characteristics, while fatigue damage accumulation slows down along with the cyclic numbers.
An improved BP neural network algorithm for researching on stability of reverse unloading diaphragm pressure reducing regulator
2017, 32(5): 1241-1249. doi: 10.13224/j.cnki.jasp.2017.05.026
Abstract PDF(1151KB) icon910 icon8
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To investigate the stability of PRR(pressure reducing regulator) with adjusting multiple structure parameters simultaneously, BFGS (Broyden-Fletcher-Goldfarb-Shanno) quasi-Newton method and line search with Wolfe conditions were applied to optimize the BP (back propagation) algorithm. Results showed that the improved BP algorithm reduced number of iterations by 1-2 orders of magnitude, making it easy to reach a global minimal point. When the improved BP algorithm was used for reverse unloading diaphragm PRR, it could adapt to coupling of 2-3 structure parameters and predict the data set with more than 106 data points. It was easy to find a combination of structure parameters to stabilize PRR when multiple structure parameters change simultaneously. More importantly, when these parameters changed together, the stability of PRR was much better than the case with change of just one of the parameters.
Effect of swirl flows in combustion of solid fuel ramjet
2017, 32(5): 1250-1258. doi: 10.13224/j.cnki.jasp.2017.05.027
Abstract PDF(1240KB) icon1191 icon16
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To study the effect of swirl number on the combustion flow field of solid fuel ramjet, the experiments of connected pipe under different multiple swirl numbers (s=0.2, 0.4, 0.6) and non-swirl(s=0) were conducted. High-density polyethylene (HDPE) was used as a solid fuel. And simulations were conducted under conditions of s=0.6 and s=0. The results of simulation and experiment show that swirl flow is helpful to enhance the stability of flame and increase the regression rate of solid fuel and the pressure of afterburning chamber. For swirl case, the surface heat flux of solid fuel is higher than that of non-swirl case, and the chemical reaction in the combustion chamber is more efficient. Comprehensive analysis indicate that high intensity swirl flow helps to increase the combustion efficiency.
Tooth meshing simulation and analysis based on isometric mapping Ease-off surface
2017, 32(5): 1259-1265. doi: 10.13224/j.cnki.jasp.2017.05.028
Abstract PDF(768KB) icon1043 icon11
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Based on the isometric transformation of Ease-off surface,a method for the meshing simulation analysis of gear tooth was put forward. By using the parameters of curvature and torsion of surface geometry, both the definition on the 2nd order osculating surface and its topologic method were presented. Within the extent of 2nd order differential precise, the osculating surface was close to the original curve surface, making it possible to carry out the geometric analysis instead of the original scattered curve surface. By using the ordinate system transformation, the derivation of meshing equation and the establishment of universal model on generating spiral bevel gears were done respectively. Based on isometric mapping between two tooth meshing surfaces, the solutions to mismatched size of the relative point at surfaces of tooth were made, then the osculating surface of the Ease-off of tooth surface was set-up by means of the topology of original scattered surface using the least square method. Depending on the parameters of the set-up Ease-off osculating surface, the solving methods were presented on behavior parameters of tooth surface meshing such as contact area, contact path and transmission errors by the introduction of the isoheight line and the asymptotic behavior of the tooth surface contact. The results of analysis show that it is able to obtain directly the tooth meshing perfect information of gears by means of one-off constructing Ease-off surface, and increase the topologic precision of curve surface up to 0.1 μm. This presented method is not only more suitable for the reverse engineering and the numerical computing relative to the conventional methods of meshing simulation, but also more convenient for gaining the information of tooth surface contact.
Time-frequency feature extraction of rolling bearings early weak fault based on wavelet de-noising using neighboring coefficients
2017, 32(5): 1266-1272. doi: 10.13224/j.cnki.jasp.2017.05.029
Abstract PDF(1169KB) icon1056 icon13
Abstract:
The wavelet de-noising using neighboring coefficients and frequency slice wavelet transform (FSWT) were combined for weak fault time-frequency feature extraction of rolling bearing. Based on the analysis results of the vibration data of rolling element bearing's early weak fault, the strong background noise of rolling bearing can be decreased effectively by the wavelet de-nosing using neighboring coefficients method. Furthermore, the de-noised signal was handled by the FSWT method and better time-frequency feature extraction result was obtained compared with the method using FSWT directly, so the effectiveness of the proposed method was verified. Besides, the advantages of the proposed method were also verified by comparing with other time-frequency method such as spectral kurtosis.
A novel method for on-board propulsion system modelling under supersonic state
2017, 32(5): 1273-1280. doi: 10.13224/j.cnki.jasp.2017.05.030
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Abstract:
In order to meet the high requirements of precision, timeliness and data storage of on-board aero propulsion model, a new method of onboard modeling was proposed. The similarity criterions used in traditional on-board steady-state model were deeply discussed, and a similarity criterion with higher modeling accuracy was obtained. Based on the new similarity criterion, a high precision steady state variable model was established, which includes the nonlinear 2 order term in the Taylor expansion, and the inaccuracy problem of the traditional piece-wise linear method in the condition of large flight envelope and variable state was solved effectively. In order to solve the problem of the prominent difference between engine installed thrust and net thrust under supersonic state, the simplified inlet model considering the outflow characteristics is established, and a method is given to calculate the installed thrust, the part of the installed thrust compatible with the similarity criterion was computed by the above simplified engine model, while the spilled air fluid resistance, the deflation resistance and some part of engine net thrust incompatible with the similarity criterion were calculated by the simplified inlet model. The simulation results show that the error of the on-board propulsion system model based on the new similarity criterion has the advantages of large flight envelope and variable state adaptability, and the error of output parameters are within 0.5%.

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