2017 Vol. 32, No. 10

  Previous Issue | Next Issue 
Display Method:
Application of entropy equation in the judgement of flow direction in transient air system
2017, 32(10): 2305-2313. doi: 10.13224/j.cnki.jasp.2017.10.001
Abstract PDF(953KB) icon810 icon511
Abstract:
The entropy equation of the nonequilibrium state was applied to the solution of air system. An expression of the change rate of entropy production in the pipe element and throttle element were derived. And the flow direction of the fluid was judged by the nonnegativity of the entropy production. Combined with the think of modular modeling, the fluid network simulation program of the transient air system was established. The Shock tube model and double cavity model were used to verify the algorithm accuracy. The simulation results are in good agreement with the experimental results, which show that the nonequilibrium entropy production can accurately determine the flow direction in the transient air system, overcome the limitation of the total pressure judgment and accelerate the convergence of the air system.
A new surrogate fuel of RP3 kerosene
2017, 32(10): 2314-2320. doi: 10.13224/j.cnki.jasp.2017.10.002
Abstract PDF(710KB) icon1106 icon541
Abstract:
In order to select the surrogate fuel with the same physical and chemical properties as RP-3 kerosene, the physical and chemical properties of RP3 kerosene were analyzed. According to the physical and chemical properties of RP3 kerosene, the selection criterions of the RP3 kerosene surrogate fuel (including the molecular mass, hydrogencarbon ratio, cetane number and lower heating value) were determined. Based on the selection criterions, a fivecomponent RP-3 kerosene surrogate fuel comprising ndecane, n-dodecane, iso-cetane, methylcyclohexane and toluene was presented, and the mole fractions of these five components were optimized. Furthermore, the densities and kinematic viscosities of the surrogate fuel and RP3 kerosene were contrastively analyzed at different temperatures. The results show that the molecular mass, hydrogencarbon ratio, cetane number and lower heating value of the surrogate fuel, which comprise 14% ndecane/10% ndodecane/30% isocetane/36% methylcyclohexane/10% toluene (mole fraction), agree well with the corresponding criterions of RP3 kerosene. At the same time, the variation trends of the densities and kinematic viscosities of the surrogate fuel agree well with the corresponding experimental data of RP3 kerosene at different temperatures.
Impact of depth of deflector on shock wave focusing processes in wedgeshaped cavity
2017, 32(10): 2321-2329. doi: 10.13224/j.cnki.jasp.2017.10.003
Abstract PDF(1019KB) icon991 icon493
Abstract:
In order to obtain the influence of the depth of deflector on the process of shock wave focusing in a wedgeshaped cavity, tests and numerical simulation studies were carried out to investigate shock focusing on a test section where the depth of deflector was 0, 5, 10,15mm. CCD(charge coupled device) camera was used to obtain the schlieren photos of the flow field. Pressure sensors were used to record the pressure histories. The numerical simulation of the process was carried out by using the numerical method with high accuracy. The shock wave focusing processes of different deflectors were compared. Result showed that, with the increase of depth, the time between leading shock focusing and compressional wave focusing decreased. Because of that, the strength of shock wave focusing and the peak of pressure in bottom of cavity increased. The depth of deflector can determine the forming time of secondary shock and its degree of development, and then influence the disorder degree of the flow field during the shock wave focusing process.
Onedimensional model of flow and heat transfer of supercritical hydrocarbon fuel
2017, 32(10): 2330-2337. doi: 10.13224/j.cnki.jasp.2017.10.004
Abstract PDF(832KB) icon1063 icon532
Abstract:
Considering the mutual influence between fuel flow and heat transfer process and pyrolysis reaction and coking process in horizontal circular tube, a onedimensional steadystate model was proposed to study the coupling characteristics of hydrocarbon fuel flow and heat transfer process and pyrolysis reaction. ndecane was chosen as the alternative fuel, pyrolysis reaction used onestep chemical reaction model and coking process used a onedimensional coking engineering model for numerical simulation. The overall results showed that the pyrolysis reaction can strengthen heat transfer, and different wall heat flux, inlet pressure and mass flow rate were chosen to simulate the typical working conditions. The overall results showed that flow and heat transfer process influenced fuels pyrolysis reaction rate and dwell time in the tube, thus affecting pyrolysis ratio. The comparisons of the calculated results with the experimental data show the reliability of the program, which can be applied to swift engineering calculation combined with the advantage of high calculation efficiency, and will provide a support for threedimensional numerical simulation.
Effect of flowing area ratio on the spray velocity field of a swirl cup
2017, 32(10): 2338-2343. doi: 10.13224/j.cnki.jasp.2017.10.005
Abstract PDF(877KB) icon883 icon469
Abstract:
Swirl cups with three different flowing area ratios were designed. The spray velocity fields of the swirl cups were firstly studied by particle imagine velocity (PIV) under selfstimulated condition of air pressure. The effects of the flowing area ratio on the spray velocity field and the distributions of velocity were studied and analyzed, respectively. The results shows that the area and length of central recirculation zone gradually become smaller and shorter, and the recirculated velocity of central recirculation zone and the angle of spray are tended to be higher and smaller with the increase of the flowing area ratios. In addition, it can be seen that the capacity of antideviation increases with the increase of flowing ratios according to the radial distribution of spray velocity.
Stable hydraulic computation method for fuel pipe system based on the graph theory
2017, 32(10): 2344-2354. doi: 10.13224/j.cnki.jasp.2017.10.006
Abstract PDF(917KB) icon896 icon533
Abstract:
Using nodal analysis model, a treatment for evaluating the local losses by merging them into relevant pipes was proposed and equations for computing total losses were deduced. Consequently, a method considering both friction and local losses was developed for stable fuel piping system. Then, it was applied to a practical simplified aeroengine fuel piping system. A software based on this algorithm was developed with VBNET language. Besides, threedimensional numerical simulations were conducted for the fuel piping system as well. Results showed that local loss affected the flow distribution a lot and directly determined the results. When solutions of the present method and numerical simulation were compared, they presented well agreement with each other with an error of ±10%.
Performance of ramjet combustor based on cavity/strut structure
2017, 32(10): 2355-2363. doi: 10.13224/j.cnki.jasp.2017.10.007
Abstract PDF(981KB) icon975 icon476
Abstract:
Strut injection was proposed to replace wall injection in ramjet combustaor, in order to promote the combustion efficiency and avoid the problem of inhomogeneous mixing of fuel and mainstream, which was caused by fuel centralized near the wall with wall injection in ramjet combustor based on cavity flameholder. The distribution of fuel and flow field structure in ramjet combustor based on cavity/strut structure was simulated. The effects of strut on mixing and performance of ramjet combustor were studied. It was found that the strut made homogeneous fuel distribution in the whole flow channel, enhanced the mixing of fuel and air, enhanced the mixing efficiency and combustion efficiency of the combustor exit by 214% and 205% respectively, although it reduced the total pressure recovery coefficient of the combustor exit by 63% compared with that under the wall injection method. The improvement of combustion efficiency made up the additional total pressure loss, and increased the specific impulse of the combustor exit by 396% under the strut injection method. Therefore, it is good for improving the combustor performance when the cavity/strut structure is used in ramjet combustor.
Experimental system of constant volume combustion bomb and measurement of C7 fuels flame speeds
2017, 32(10): 2364-2370. doi: 10.13224/j.cnki.jasp.2017.10.008
Abstract PDF(859KB) icon1074 icon558
Abstract:
The experimental system of constant volume combustion bomb for measuring laminar flame speed under the conditions of high temperature and pressure was designed and built. The composition and function of main subsystems, and the data processing method were introduced in detail. Moreover, at 400K temperature and 01,03MPa pressures the laminar flame speeds of C7 Fuels including toluene/methylcyclohexane/nheptane were measured, and compared with existing literature results. Results indicate that the experimental system has high reliability. Using this experimental system, laminar flame speeds can be accurately measured at high temperatures and elevated pressures, meanwhile the range of equivalence ratios can be extended.
Measurement on instantaneous flow fields of a sparkexcited synthetic jet
2017, 32(10): 2371-2377. doi: 10.13224/j.cnki.jasp.2017.10.009
Abstract PDF(1025KB) icon794 icon457
Abstract:
Phaseresolved instantaneous flow fields were experimentally measured by using particle image velocimetry (PIV) for the synthetic jets, which were excited by a specific sparkdischarge actuator. The unsteady flow structures of the sparkexcited synthetic jet during the developing process were captured. Meanwhile, the instantaneous velocities of the sparkexcited synthetic jet at some fixed axial positions downstream the nozzle were measured by using the hotwire anemometer. The effects of the spark-excitation parameters (such as discharge frequency and capacitance energy storage) on the synthetic jet were preliminarily analyzed. It was revealed that the sparkexcited synthetic jet took on sphericalshape diffusion near the jet nozzle at the initial stage of synthetic jet formation. As the synthetic jet developed, a series of vortices were induced by the shear and entrainment actions of the synthetic jet. The maximum peak normalvelocity appeared about 005T after pulsed discharge. From this moment the synthetic jet diffused rapidly, resulting in the decrease of peak velocity and vorticity. For the present sparkexcited actuator and the excitation parameters, the sparkexcited synthetic jet was strengthened with the increase of excitation frequency and capacitance energy storage.
Estimating isentropic exponent for nitrogen and fire extinguishing agent vapor using PR equation
2017, 32(10): 2378-2383. doi: 10.13224/j.cnki.jasp.2017.10.010
Abstract PDF(762KB) icon899 icon524
Abstract:
The variation of volumetric isentropic exponent and temperature isentropic exponent of the gas mixture of nitrogen (N2) and fire extinguishing agent vapor with pressurized pressure and temperature are a key influential factor to the fire extinguishing agent discharge progress for the aircraft fire extinguishing system. Based on the PR(PengRobinson) equation associated with the classical van der Waals mixing rule, a program was developed to estimate volumetric isentropic exponent and temperature isentropic exponent for the mixture of N2 and fire extinguishing agent vapor. The curves of volumetric isentropic exponent and temperature isentropic exponent varying with temperature were calculated with the pressurized pressure of 42MPa and 25MPa and initial temperature of 293K for the binary system of N2/HFC227ea, N2/CF3I and N2/CF3Br. The results showed that volumetric isentropic exponent and temperature isentropic exponent decreased as temperature increased and the relation was nearly linear. The volumetric isentropic exponent and temperature isentropic exponent of all the three binary systems had a higher value with pressurized pressure of 42MPa than with 25MPa at the same temperature. When pressurized to an equal pressure at same temperature, isentropic exponent of N2/CF3I had a largest value followed by the results of N2/HFC227ea and N2/CF3Br.
Experimental and numerical studies on the film cooling characteristics of anisotropic composite plates
2017, 32(10): 2384-2393. doi: 10.13224/j.cnki.jasp.2017.10.011
Abstract PDF(1162KB) icon1085 icon480
Abstract:
Experimental studies were carried out on the film cooling of the composite plates formatted through different weaving modes. An infrared radiation camera was used to capture the temperature distributions on hot side wall, and the effects of thermal conductivity, blowing ratio, and mainstream temperature on the overall cooling effectiveness were analyzed. Numerical simulations on the anisotropic composite plates with a single film hole were further conducted to explore the individual influence of thermal conductivity along the X, Y, and Z directions on the wall temperature distribution as well as the overall cooling effectiveness. Results show that the film cooling effectiveness increases with the enhancement of the blowing ratio and decreases with the increase of the main stream temperature. Among the three anisotropic composite plates, 25D composite plate produces the highest film cooling effectiveness while 3D composite plate gives the lowest cooling effectiveness. The increase of thermal conductivity along X and Z directions can improve the film cooling efficiency while the increase of thermal conductivity along Y direction has little influence on the film cooling efficiency.
Numerical investigation of a thermal barrier coated vane using conjugate heat transfer approach
2017, 32(10): 2394-2402. doi: 10.13224/j.cnki.jasp.2017.10.012
Abstract PDF(1089KB) icon880 icon464
Abstract:
Based on conjugate heat transfer, numerical investigation was carried out on a highly integrated first stage vane with thermal barrier coating (TBC). The numerical results showed that, under the condition close to real engine operation where temperature and pressure were very high, the effect of TBC on the areodynamic features in the cascade can be neglected. However, as the mass flow rate of cooling air decreased within a certain range, TBC could still reduced the temperature and heat transfer coefficient near the leading edge conspicuously. With the decrease of the coolant flow rate, the effect of TBC on the trailing edge of pressure side dropped heavily, but slowly on suction side. A quantitative comparison of the metal temperature averaged over three spanwise sections indicates that, with the equivalent overall cooling effectiveness achieved, TBC with a thickness of 015mm can save the mass flow rate of coolant by 20%-30%.
Investigation on the performance of bionic wick flat heat pipes
2017, 32(10): 2403-2309. doi: 10.13224/j.cnki.jasp.2017.10.013
Abstract PDF(1368KB) icon954 icon778
Abstract:
To solve the thermal management problem of electronic equipments, according to the micro convex structure of the hydrophilic plant, three flat heat pipes: normal evaporator (No1), superhydrophilic evaporator (No2), the matched superhydrophilic evaporator and superhydrophobic condenser (No3) were constructed with conical capillary wicks, using electrolytic copper powder of the particle diameter 75μm as sintering material. Experiments were conducted to study the effect of heating power Q and tilt angle on the three flat heat pipes with deionized water as the working fluid. The results show that angle almost has no effect on the three flat heat pipes, namely, the three flat heat pipes all have good antigravity performance. The No3 flat heat pipe has the best thermal performance; when tilt angle of 0° and Q=1404W, the central point temperature of the evaporation is just 670℃. The No3 flat heat pipe has not only the smallest evaporation thermal resistance, but also the smallest condensation thermal resistance, which can reach to 005K/W, 002K/W, respectively.
Influence of piezoelectric network on aerodynamic damping of bladed disk structure
2017, 32(10): 2410-2418. doi: 10.13224/j.cnki.jasp.2017.10.014
Abstract PDF(883KB) icon885 icon434
Abstract:
Firstly, by introducing the aerodynamic influence coefficient, a linear relation between aerodynamic force and the vibrating displacement was established. Based on this relation, a linear vibration equation of aeroelastic coupling of bladed disk structure was deduced. Then, the piezoelectric network was introduced into the bladed disk structure, and the fluidmechanicelectro coupling dynamic equation was established. The lumped parameter equivalent model was adopted to study the influence of the piezoelectric network on the aerodynamic damping of the bladed disk, and the eigenvalue problem of the fluidmechanicelectro coupling system was solved. The aerodynamic damping ratio of the system was obtained as the criterion of the aeroelastic stability of the system. The results show that the piezoelectric network can effectively improve the aeroelastic stability of the bladed disk vibrating in nodal diameter modes, which are main vibrating modes of the bladed disk; the electrical parameters of the piezoelectric network can be optimized to extend the flutter boundary in a large frequency domain of the bladed disk; the aerodynamic damping of the bending vibration of the blade is better than that of the coupled bending and torsional vibration.
Fatigue life evaluation procedure and its application for turbine disk
2017, 32(10): 2419-2426. doi: 10.13224/j.cnki.jasp.2017.10.015
Abstract PDF(877KB) icon1215 icon458
Abstract:
A fatigue life evaluation procedure of a turbine disk was established, and illustrated with a turbine rotor model, meanwhile a simulating test design method of turbine disk assessment sites was explored. The results show that the established life evaluation procedure has good engineering practicability. The developed method of determining the equation parameters could take advantage of the material experimental data effectively, and a group of parameters could be obtained by this method. Precision of the prediction life by using the method lied in two times scatter band. The stress gradient was the key influential factor to the fatigue life near the bore, bolt hole and transitional fillet of the turbine disk, for which enough attention should be paid in the design stage. Stress gradient features of the critical positions in the turbine disk were simulated using a plate model with notches, and the simulation results agreed well with the test results. A modeling test design method was provided for life evaluation of the turbine disk test pieces with notches.
Probabilistic thermal analysis of ceramic matrix composite turbine vane with anisotropic thermal conductivity
2017, 32(10): 2427-2437. doi: 10.13224/j.cnki.jasp.2017.10.016
Abstract PDF(1080KB) icon974 icon473
Abstract:
Considering the anisotropy and dispersion of thermal conductivity for ceramic matrix composites (CMC), a probabilistic thermal analysis model was established for predicting the temperature field of hot components made of CMC. Taking the cooling configuration of Mark Ⅱ turbine vane as an example, and assuming it was made of anisotropic CMC, the mean value and variation of the blades temperature field by the finite element method coupled with Monte Carlo simulations was analyzed. In this work, anisotropic thermal conductivities were applied as the random input parameters, the effects of thermal conductivities dispersion and anisotropy on the temperature field of CMC turbine vane were investigated. Furthermore the temperature fluctuations of leading edge stagnation point and trailing edge were studied, and the hot spot with temperature higher than 900K (T>900K) was discussed. The temperatures of leading edge stagnation point and trailing edge were distributed normally, when the thermal conductivity exhibited a normal distribution. The maximum standard deviation of temperature of stagnation point appeared when the variation coefficient of thermal conductivity equaled 01, and the thermal conductivity ratio was 2. There was a probability of 16% to exceed the mean value (12731K) by 913K. Regarding the trailing edge, the maximum standard deviation was obtained, when the variation coefficient of thermal conductivity equaled 01 and the thermal conductivity ratio remained 10. There was a probability of 16% to exceed the mean value (11529K) by 527K. The results show that the dispersion of thermal conductivity leads to the increase of hot spot, and the relative rate of increment ΔShot rises with the increase of thermal conductivitys variation coefficient. In this study, the maximum ΔShot was 48%, when the variation coefficient of thermal conductivity was 01, and the thermal conductivity ratio remained 2.
Simulation and experiment of dynamic characteristics for oilline electrostatic sensor
2017, 32(10): 2438-2446. doi: 10.13224/j.cnki.jasp.2017.10.017
Abstract PDF(955KB) icon917 icon451
Abstract:
In order to investigate the lack of characteristic parameters and verification method of the electrostatic sensor for online debris monitoring in aeroengine lubricated system, the corresponding characteristic parameters were proposed according to the basic principle of electrostatic induction and the structure of sensor. Sensing model of ring probe was used for simulation, and the rig of electrostatic sensor experiment system was designed and built. Dynamic characteristics of the oilline electrostatic sensor were analyzed and validated by experiments. Results showed that the proposed parameters can effectively reflect the dynamic characteristics of the electrostatic sensor. The ratio of length to diameter was an important structural parameter of the ring oilline electrostatic sensor, and the sensor efficiency increased with the increasing ratio of length to diameter. The effective field of view of the sensor also increased with the increasing size of the probe. Furthermore, the experiment rig can be applied to the analysis and experiment of the dynamic characteristic of the actual sensor with good repeatability. The simulation and experimental results have important guiding significance for the design and application of the oilline electrostatic sensor.
Interval multiobjective optimization for the specific power of a helicopters main reducer planetary gear trains
2017, 32(10): 2447-2455. doi: 10.13224/j.cnki.jasp.2017.10.018
Abstract PDF(862KB) icon939 icon446
Abstract:
The interval multiobjective optimization objective functions and constraint functions for the optimization problem of the specific power of a certain helicopters main reducer planetary gear trains with uncertain parameters of density and friction coefficient were established. The optimal parameter interval of objective functions and the design variables were obtained by using the improved interval multiobjective hierarchical optimization method, then the helicopters optimal main reducer planetary gear trains were compared and analyzed. Finally the experiment scheme for the efficiency of helicopters main reducer planetary gear trains was designed according to the optimization results. The results showed that: the gearing efficiency was improved by 214%, while the weight declined by 62% after the interval multiobjective optimization of the helicopters main reducer planetary gear trains, and the trend of the efficiency curves was more smooth and steady under the highspeed and heavyduty working conditions, illustrating the effectiveness of the interval multiobjective optimization method used in the specific power optimization of a certain helicopters main reducer planetary gear trains.
Vibration parameter stability of high contact ratio gear transimission system
2017, 32(10): 2456-2466. doi: 10.13224/j.cnki.jasp.2017.10.019
Abstract PDF(1156KB) icon909 icon471
Abstract:
The vibration intensity stability and movement orbit stability of high contact ratio gear rotor-rolling bearing transimission system was studied. By using the stability domain of vibration intensity parameter, the contribution of high contact ratio gear pair to enhance the stability of the gear rotor-rolling bearing system was quantified. The results revealed that under the condition of small mass eccentricity of the rotor, high contact ratio gear pair was able to improve the systems vibration intensity stability significantly, but high contact ratio gear pair played a limited role to improve the systems vibration intensity stability under the condition of large mass eccentricity of the rotor. The global bifurcation diagram of systems movement orbit stability with the parameters were calculated, the influence rules of clearance of rolling bearing and mass eccentricity of rotor on system's movement orbit stability were obtained. The mapping relation of several key parameters and all kinds of stable periodic orbits and nonperiodic orbits were gotten.
Application of adaptive tunable Qfactor wavelet transform on incipient fault diagnosis of bearing
2017, 32(10): 2467-2475. doi: 10.13224/j.cnki.jasp.2017.10.020
Abstract PDF(940KB) icon1080 icon477
Abstract:
The shift invariant characteristic of tunable Qfactor wavelet transform (TQWT) was analyzed, and verified through simulated signal. A method named adaptive tunable Qfactor wavelet transform (ATQWT) based on timefrequency kurtosis index optimization was proposed to solve the problem of incipient fault diagnosis of rolling bearing. Firstly, the timefrequency kurtosis index was used to search for the quality factor and the redundancy factor of TQWT； after the optimal influencing parameters were confirmed, the parameters of TQWT were set according to the obtained results and the original signal was processed, then the corresponding signal components could be acquired and the optimal signal component could be confirmed. The envelope demodulation process was performed on the optimal signal component. Finally, the condition of the bearing could be judged by analyzing the frequency components of the envelope spectrum. The analysis results of the experiment signals show the timefrequency kurtosis index by the proposed method is more reliable, and robustrness is better. This method could accurately separate the weak feature from the original signal at low signal to noise ratio, and effectively judge the incipient fault of bearing.
Condition monitoring of friction fault of plain bearings by introducing sparse atoms feature fusion
2017, 32(10): 2476-2483. doi: 10.13224/j.cnki.jasp.2017.10.021
Abstract PDF(841KB) icon922 icon436
Abstract:
Starting from the theory of information fusion, a algorithm of bearing friction fault feature fusion was proposed based on Kmeans singular value decomposition (KSVD) and maximum relevance minimum redundancy (mRMR) principle. First, in order to represent the nonlinear fault information, the algorithm uses KSVD to sparse the signals, and the dictionary atoms corresponding to the sparse coefficients were used as the parameters of the feature fusion. Second, in order to optimize the selection of dictionary atomic set, a criterion based on mutual information mRMR was proposed to determine the number of atoms in the optimal atomic set. Finally, the sparse coefficients were fused by maximizing the principle to extract the valid information for fault condition monitoring. The results of simulation experiment of bearing friction fault show that the proposed method can better integrate the feature information of the redundancy and complementarity. Compared with the single feature and other fusion method, the proposed method can improve fault recognition rate about 12%.
Rotor aerodynamic characteristics analysis and helicopter trimming
2017, 32(10): 2484-2490. doi: 10.13224/j.cnki.jasp.2017.10.022
Abstract PDF(972KB) icon1464 icon553
Abstract:
The UH60A rotor aerodynamic model suited to accurately predict the detail of rotor aerodynamic characteristics and helicopter trimming was established. The momentum element theory and the proposed rotor aerodynamic model were respectively embedded into the trimming procedure and applied to trim UH60A helicopter, the comparison among the computational results, test data and the referenced data indicated that the model was effective and more precise. On this basis, the distributions of induced velocity, angle of attack and liftdrag ratio on the rotor disk at various advance ratios were analyzed. The results show that with the increase of the advance ratios, the induced velocity distribution on rotor disk is more asymmetric and the rotor sideward incline is intensified. At high advance ratio, the flow separation region on the retreating blade side becomes large, the angle of attack distribution exhibits rapid change on the boundary of the reverse flow region. Due to effects of air compressibility and the reverse flow region, at high advance ratio, the lift to drag ratio is relatively low in the tip area of the advancing blade and the reverse flow region.
Experiment of influence of the nozzle pressure ratio on the interaction between the external flow and nozzle flow of hypersonic aerocraft
2017, 32(10): 2491-2497. doi: 10.13224/j.cnki.jasp.2017.10.023
Abstract PDF(930KB) icon1014 icon441
Abstract:
To find out the effect of nozzle plume on aerocraft aerodynamic performance, a pressure measurement experimental study on different nozzle pressure ratios (NPR) of nozzle plume was carried out at a freestream Mach number of 50 and 60 in the 05m hypersonic wind tunnel of China Aerodynamics Research and Development Center (CARDC).The structure of the nozzle plume interaction area was obtained by using schlieren photography. The result showed obvious different pressure distribution of aerocraft afterbody area at a high NPR. When the NPR was high, the nozzle plume interaction area became bigger with a higher pressure. The schlieren pictures also showed that cross interaction shocks became stronger and the extending of the shear layer tended to be more obvious. Interaction area has affected the pressure distribution of the wings, which would affect the control ability of the aerocraft.
Aircraft/engine performance integrated analysis on combined cycle engine
2017, 32(10): 2498-2508. doi: 10.13224/j.cnki.jasp.2017.10.024
Abstract PDF(1603KB) icon1125 icon496
Abstract:
Two cases of combined cycle engines（case 1:turbine engine/ramjet/dual mode scramjet, case 2:turbine engine/ejector ramjet/dual mode scramjet）were comparatively studied by using aircraft/engine performance integrated analysis method. Constraint analysis and mission analysis were conducted based on a given mission of the hypersonic vehicle capable of Mach number of 65 cruise. The optimal thrust loading and wing loading satisfying the constraint were obtained, and the corresponding takeoff gross mass and sealevel takeoff thrust were further obtained. Results indicated that under the condition of completing the mission of hypersonic vehicle, case 1 had a comparable takeoff mass with case 2. The takeoff mass of case 1 was 26% lower than case 2, and the takeoff thrust of case 1 was 103% higher than case 2. Considering the stateoftheart of turbine engines, two 129kNthrust turbine engines and two 119kNthrust turbine engines were used for case1 and case 2, respectively. In addition, the takeoff mass increased shapely with the cruise distance. The takeoff masses will be about 85t for both cases when the cruise distance is 4000km.
Compressor model and modal control based on unsteady air injection
2017, 32(10): 2509-2515. doi: 10.13224/j.cnki.jasp.2017.10.025
Abstract PDF(693KB) icon871 icon422
Abstract:
Based on the multidimensional compressor model with steady air injection, and in consideration of the mass and momentum effects and the unsteady influence introduced by the unsteady flow, the multidimensional compressor model with unsteady air injection was established. The principle of compressor modal control was analyzed, and modal control law using unsteady air injection was derived. Taking an axial compressor as example, modal control with different modes were simulated under stall condition. It indicates that using unsteady air injection, the same effect is achieved with only 57%-80% injected mass flow compared with steady and continual air injection, the extended stability range reaches 2.34% with the first four mode control, and also the stability range extends with the increment of mode number controlled.
SANNWA-PF algorithm of aeroengine gas path fault diagnosis
2017, 32(10): 2516-2525. doi: 10.13224/j.cnki.jasp.2017.10.026
Abstract PDF(1091KB) icon806 icon441
Abstract:
A selfadaptive neural network weight adjustment particle filter algorithm was proposed for aeroengine gas path fault diagnosis of the nonlinear and nonGaussian properties of aeroengine. Number of particles split and adjusted was determined by the distribution of particles. Then particles were spilt by the way of normal distribution and adjusted by back propagation (BP) neural network, which avoided the degradation and impoverishment of particles and had stronger selfadaptive and tracking ability. The simulation results of onedimensional nonlinear tracking model and aeroengine gas path fault diagnosis show that selfadaptive neural network weight adjustmentparticle filter (SANNWAPF) algorithm has a good nonGaussian performance. Compared with normal particle filter, SANNWAPF improved 21% in accuracy of onedimensional nonlinear tracking model, 30% with Gaussian noise and 26% with nonGaussian noise in aeroengine gas path fault diagnosis; and the diagnosis speed improved about 7 times with Gaussian noise and 10 times with nonGaussian noise.
A modeling method of propeller based on the propeller component characteristic
2017, 32(10): 2526-2535. doi: 10.13224/j.cnki.jasp.2017.10.027
Abstract PDF(1062KB) icon876 icon444
Abstract:
The studied propeller components characteristic was obtained by use of the general components characteristic of the propeller by scaling method. Under the condition of the nonezone flight speed, the algorithm on the propeller mathematical model was presented. At the same time, by use of the scaled characteristics of propeller, the working performance curve of the fixed blade angle and the aerodynamic principle of propeller, the interaction relationships of propeller power coefficient, force coefficient, blade angle, static thrust advance ratio threshold and the designed geometric parameters of propeller were analyzed, and the algorithm on the propeller mathematical model under the state of the static force was proposed. The simulation data of the above algorithms by digital simulation was verified with the comparison of the simulation data of Gas Turbine Simulation Program (GSP) software. The results show that the proposed algorithm on the propeller model was valid. When the propeller was in the advanced state, the maximum relative error of propeller force was no more than 66059×10-6, the maximum relative error of propeller power demanded did not exceed 55098×10-6, the maximum relative error of propeller efficiency was not more than 66955×10-6.
Intelligent optimization of turbine rotor blade assembly sequence
2017, 32(10) doi: 10.13224/j.cnki.jasp.2017.10.028
Abstract PDF(780KB) icon910 icon437
Abstract:
There are some problems such as “large unbalance value, aggregations of blades mass or massradins product and unstable assembly sequence of special blade” in rotor blades assembly sequences in a factory, which lead to ultra gaps arising between intermediates and shroud rings during the rotor blades installation. Based on a brief analysis of rotor blades assembly and weighing principle, an intelligent optimization method of rotor blades installation sort was presented in combination with the overall optimization and rapid convergence of genetic algorithm. According to fitup gaps of a certain grade rotor blade and test data of rotor dynamic balance, the optimization algorithm improved the qualification rate of fitup gap of the whole grade blade from 683% to 866%, reduced the rotor balancing counterweight block by about 492%, and decreased the journal vibration value by about 252% when the rotor rotated at 3000r/min.
Modification and validation of twozone model in centrifugal compressor
2017, 32(10): 2544-2552. doi: 10.13224/j.cnki.jasp.2017.10.029
Abstract PDF(1010KB) icon892 icon467
Abstract:
In onedimensional preliminary design of centrifugal compressor, high accuracy performance prediction could shorten the design cycle and improve the design efficiency. In order to improve the accuracy of performance prediction, a model of diffusion ratio based on the conventional twozone model was proposed with consideration of the effects of import external energy and impeller rotation. The twozone model was used in prediction of vaneless diffuser performance prediction by taking account of characteristics of vaneless diffuser. Validation of the model was performed against compressor maps and geometries available in the literature. The results showed that it could effectively reduce dependence on engineering experience by using the proposed model, and could be suitable for predicting performance of centrifugal compressor with different pressure ratios and backsweep angles. Predicted performance by the proposed model agreed fairly well with experiment and the percent difference was within 4%.
Effect of matrix material properties on the mechanical behavior of HTPB composite propellant
2017, 32(10): 2553-2560. doi: 10.13224/j.cnki.jasp.2017.10.030
Abstract PDF(780KB) icon881 icon411
Abstract:
The matrix material of hydroxylterminated polybutadiene (HTPB) composite propellant was manufactured according to the requirement of production process. To obtain the matrix material with different relaxation characteristics, the relaxation tests of material specimens were conducted under different temperatures (-50, -35, -20, 0, 20,35℃), and the test results were fitted by Prony series. The experimental results provided necessary parameters for the followup simulation calculation. Then the mesoscale model of the composite propellant was generated by combining molecular dynamics method with cohesive element. To verify the applicability of the random packing numerical model, the relaxation tests of HTPB propellant were conducted under room temperature. The simulation results agreed well with the real relaxation tests and the error between the two curves was less than 20%. This shows that the developed mesoscale numerical model is capable of reflecting the mechanical behavior of HTPB propellant. Finally, the numerical simulation of HTPB propellant with different random spatial distributions and matrix material properties was conducted on the Abaqus program. The results show that the random distribution of particles does not affect the macroscopic mechanical properties of HTPB propellant. However, the matrix properties have a significant impact on macroscopic mechanical behavior of HTPB propellant, and the relationship between macroscopic mechanical parameters (initial modules, elongation and strength) and the environment temperatures of binder follows the rule of exponential equation.

Copyright © 《Journal of Aerospace Power》 All Rights Reserved.

Supported by: Beijing Renhe Information Technology Co., Ltd.