2013 Vol. 28, No. 10

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Diagnosis method for crack-rubbing coupled fault in rotor system based on integration of information entropy distance
AI Yan-ting, FU Qi, TIAN Jing, CHEN Chao-long
2013, 28(10): 2161-2166.
Abstract PDF(1423KB) icon1497 icon1227
Abstract:
For the crack-rubbing coupled fault in rotor system, a fault diagnosis method was proposed. Firstly, the rubbing fault, crack fault and crack-rubbing coupled fault were simulated on rotor test rig. The acceleration signals of each fault were collected. The integration of information entropy distance was calculated for fault diagnosis using singular spectrum entropy in time-domain, power spectrum entropy in frequency domain, wavelet energy entropy and wavelet spatial characteristics spectral entropy in frequency-time domain. The case study showed that these four information entropies could evaluate rotor vibration state comprehensively. Information entropy distance curves in multiple points and multiple speeds can effectively improve the accuracy and distinguish single and coupled faults. The information entropy distance between the test signal and its corresponding fault is the least and the information entropy distance curve is located in the bottom of the axis, so its fault category can be diagnosed.
Mesoscopic mechanical constitutive relation of cyclic plasticity for nickel based polycrystalline superalloy
YU Duo-kui, YANG Xiao-guang, ZHANG Ke-shi
2013, 28(10): 2167-2173.
Abstract PDF(2062KB) icon1138 icon1640
Abstract:
Based on the constitutive relation in crystal plasticity,anisotropy of cyclic hardening of meso-plastic deformation flow and nonlinear movement of crystal slip was considered.Using the Voronoi polycrystalline as a representative volume element (RVE),the mesoscopic mechanical constitutive relation of nickel based polycrystalline superalloy was described by the theory of crystal plasticity.Calculations of both symmetric and asymmetric cycle analyses were conducted.The results of symmetric cyclic analyses indicate that the model is suitable to simulate the strain hardening phenomenon and Bauschinger effect.The results of asymmetric cycle analyses show that the model has the ability to describe ratchet behavior,back stress calculations have great impact on the evolution of slip shear strain rate,slip shear strain rate value largely depends on nonlinear evolution led by back stress hardening process.
Concurrent structural and material optimization of turbine frame in turbo-fan engine
GAO Xi-guang, LIU Xing-guo, ZHANG Hua-jun, SONG Ying-dong
2013, 28(10): 2174-2180.
Abstract PDF(4511KB) icon1463 icon1196
Abstract:
Based on the traditional structural optimization method,a structural/material optimization method for turbine frame was developed in consideration of the effects of structural parameters and properties of materials on the performance of turbine frame.The original optimization problem was decomposed into structure level and the material level.The first one was solved by feasible direction method while the second problem was solved by parallel genetic algorithms.A distributed computer system was designed by C language and employed to obtain the optimal material combination and structural parameters of one typical turbine frame.The result shows that the structure/material optimization may obtain better design than structure optimization.In the examples,compared with the worst material combination,the mass of the optimal material combination is reduced by 29.0%.
Aero-engine rotor-stator rubbing positions diagnosis rule acquisition based on support vector machine
LI Ai, CHEN Guo, YU Ming-yue
2013, 28(10): 2181-2193.
Abstract PDF(18554KB) icon6626 icon13106
Abstract:
The data mining technology based on support vector machine(SVM) was introduced,and aero-engine rotor-stator rubbing positions diagnosis rule acquisition was proposed based on SVM.Firstly,the rubbing experiment of 4 rubbing parts was simulated based on aero-engine rotor tester with the casing,and a large number of experimental data were obtained by using the strain test of 4 parts of the casing.A new approach was proposed to extract knowledge rules from support vector clustering (SVC).Then SVC algorithm was adopted to get the clustering distribution matrix of the sample data with chosen features.Secondly,hyper-rectangle rules were constructed on the basis of the clustering distribution matrix.In order to make the rules more concise and explainable,hyper-rectangle rules should further simplified by using such means as rules merger,dimension reduction and interval extension.Finally,using the data mining method based on SVM,aero-engine rotor-stator rubbing positions diagnosis rules were extracted from a large number of rubbing position experiment data,then explanation and validated accordingly.The recognition rates were more than 99%,showing that the method is corrective and effective,and embodies great practical values.
Experiment of foil friction effect on static stiffness and lift off speed of bump foil journal bearing
XU Fang-cheng, LIU Zhan-sheng, MA Rui-xian, YAN Jia-jia
2013, 28(10): 2194-2201.
Abstract PDF(13936KB) icon1519 icon1555
Abstract:
Two bump foil journal bearings with different surface roughness of bearing housing's cylindrical hole surface were manufactured.The test-bed was established by exploiting bump foil journal bearing to test the static stiffness and lift off speed of bump foil journal bearings using friction torque method.By comparing test results of each bump foil journal bearing,the effects of friction between bump foil and bearing housing on static stiffness and lift off speed of bump foil journal bearing were studied.The results indicate that reducing surface roughness of bearing housing's cylindrical hole surface can weaken the friction between bump foil and bearing housing,decrease the bearing static stiffness and lift off speed under the same bearing load capacity.It has engineering significance to improve the bearing structure design and extend the bearing life due to lower the wear of bearing surface.Moreover,the static stiffness of bump foil journal bearing has strong nonlinear characteristic,and increases with the increasing foil deformation,so it is necessary to consider the nonlinear foil structural stiffness when modeling the bump foil journal bearing.
Suppression of supersonic flutter of laminated composite panel using dynamic absorber device and its optimal design
ZHAO Hai, CAO Deng-qing, LONG Gang
2013, 28(10): 2202-2208.
Abstract PDF(9472KB) icon1288 icon1089
Abstract:
The problem of suppression of supersonic flutter of laminated composite panel using dynamic absorber device was investigated.The interaction forces between the panel and the dynamic absorber device were expressed as the functions of relative displacement and velocity of the panel and the absorber.Based on the von-Karman nonlinear deflection panel theory and the 3rd-order nonlinear piston theory,the equations of motion of the panel and the absorber were established according to the Hamilton principle and the Newton second law of motion.Then the assumed modal method was adopted in the discrete procedure,and the numerical simulation was conducted.The coordinate of the absorber was optimized.The simulation results indicate that the critical flutter dynamic pressure can be enhanced by 51.7% under certain parameters of the absorber,and the amplitude of the limit cycle oscillation can also be suppressed.
Measurement and analysis of helicopter control stick vibration characteristics
WANG Fang, CHEN Ming, XU Guan-feng
2013, 28(10): 2209-2215.
Abstract PDF(2259KB) icon1371 icon1223
Abstract:
A calculation model of the control stick vibration characteristics was set up. Based on the research of helicopter hinge moment, a calculation model of the swashplate control stick load was established. With reference to conventional airplane measurement cells, the measurement cell with enough strength and sensitivity was developed, solving the contradiction between measurement accuracy and flight safety by ground tests. The flight test was successfully conducted, and the important parameter of swashplate control stick load was obtained. The calculation results are basically consistent with experimental data, and the excitation force frequency is close to 1 and 2 times of the main rotor speed. Engineering computation requirement can be achieved, providing a reference for the design and test of helicopter control system.
Tensile stress-strain behavior of 2.5-D self-healing C/SiC composite
LIANG Shi-fei, JIAO Gui-qiong
2013, 28(10): 2216-2222.
Abstract PDF(1974KB) icon1283 icon1174
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According to the micro-structure of 2.5-D self-healing C/SiC composite, a tensile mechanical model in weft and warp directions were established based on the damage mechanism including interfacial crack and matrix crack. The tensile nonlinear stress-strain functions in weft and warp directions were gained, and the predicted stress-strain curve agreed with the experiment very well. The result shows that,the largest error of the predicted stress-strain curve in weft direction is 8% to 9%. The largest error of the predicted stress-strain curve in warp direction is 10%. The stress-strain curve in weft direction is different from that in warp direction. By adopting tangent elasticity modulus and average crack distance, mass work to obtain strain is not needed and the model is simplified.
Experiment on vibration reduction by elastic support/dry friction damper with piezoelectric ceramic
SONG Ming-bo, TAN Da-li, LIAO Ming-fu
2013, 28(10): 2223-2227.
Abstract PDF(1557KB) icon1331 icon1415
Abstract:
An elastic support/dry friction damper using piezoelectric ceramic was designed and its effectiveness of reducing rotor vibration was experimentally verified. Firstly, the basic operation mode of elastic support/dry friction damper was introduced. Then based on the previous structure using an electromagnet, an elastic support/dry friction damper using piezoelectric ceramic which was simpler and lighter was designed, and its effectiveness of reducing rotor vibration was experimentally verified. The experimental results show that the elastic support/dry friction damper using piezoelectric ceramic can significantly reduce vibration in a rotor system; the maximum reduction of vibration amplitude is about 66% at the critical speed. Compared with the previous design, the structure is much simpler, the weight is reduced by half and the power consumption is just 5W.
Sample points reused failure response curve method for structural reliability analysis
FENG Huan-huan, JIANG Xiang-hua
2013, 28(10): 2228-2234.
Abstract PDF(13073KB) icon5713 icon8698
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Based on the failure response curve method, and in order to fully utilize sample pionts in the iterative process,a sample points reused failure response curve (SPRFRC) method for a sample points reused failure response curve (SPRFRC) method for structural reliability analysis was developed,which regarded structural reliability index as convergence condition,selected sample points near the failure boundary from all sample points after convergence,then constructed failure curve response function and finally calculated the structural reliability by the Monte Carlo sampling method.Some examples show that the response function avoids simulation of performance function response surface,reduces the model dimension;and with introduction of the cross-term response function with rotation functionality,the function enable to approximate the failure curve,and effectively improve the reliability calculation accuracy.
Integrative design method of blisk considering structure strength and resonant vibration avoidance
YU Xue-ran, LU Shan
2013, 28(10): 2235-2239.
Abstract PDF(1610KB) icon1655 icon1404
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The parametric model of blisk was established based on the software of ANSYS.The blisk model with minimum mass and sufficient structure strength,along with stress criterion of the strength design for disk,was accomplished through optimization module of ANSYS.The vibration characteristics of blisk was analyzed,and the influence of the adjustment of disk parameters and blade profile parameters on the nature frequency of blisk were studied.On this basis,the structure design method of blisk considering avoidance of low order excitation was studied through the adjustment of different structural parameters,such as rim thickness,blade lean and blade profile thickness.According to the research statistics,the adjustment of disk parameters can increase the margin between the frequencies of low order coupled vibration and 4E excitation by 2.2% at the maximum rotation speed for the drum-constrained blisk,and the margin increase can be 8% by adjustment of blade profile parameters.The integration design method of blisk considering structure strength and resonant vibration avoidance is feasible,as the margin between the frequencies of 4E excitation and 1st vibration of the final blisk with the minimum mass is up to 10.8% with insulation from 5E excitation at the loss of 4.77% mass increase.
Numerical investigation on the influences of impingement holes on heat transfer of leading edge in lamilloy
WANG Ming, LU Yuan-li, JI Hong-hu
2013, 28(10): 2240-2247.
Abstract PDF(5997KB) icon1556 icon1361
Abstract:
According to the typical guide vane shape and the boundary conditions, numerical investigation was carried out to study the flow and heat transfer characteristics on simplified vane leading edge in lamilloy. Two arrangements of impingement holes, film holes and pin-fins, and two axis modes of impingement holes were analyzed, and re-normalization group(RNG)k-ε turbulent model was used. The results show that with the same arrangement of film holes and pin-fins, the models with different impingement holes have less than 1% of cooling flow rate varies. Besides, the model with more impingement holes and smaller diameter of impingement holes can achieve higher heat transfer coefficient and cooling effectiveness, by about 2%. The angle of impingement holes axis has little influence on heat transfer of leading edge in the same arrangement impingement holes.
Numerical simulation of internal thermal response of ablative thermal protection for reentry spacecraft
ZHANG Tao, CHEN De-jiang
2013, 28(10): 2248-2255.
Abstract PDF(4412KB) icon1470 icon1303
Abstract:
The thermal response simulation model and method of ablation thermal protection system were studied.Charred layer-pyrolysis surface-original material layer model was applied to establish physical and mathematical model of thermal response and the axis-symmetrical thermal response of thermal protection system of spacecraft was computed by finite element method.The calculational formulas of pyrolysis gas mass flux and mechanism of heat transfer during ablation course were studied and analyzed deeply.Convection heat transfer between pyrolysis gas and charred layer was treated as heat source and it could speed up convergence of temperature field calculation by keeping the conductance matrix and capacitance matrix positive definite symmetric.The calculation results demonstrate that the mass flow of prolysis gas in the direction of thickness is over 80%,and side direction part is very small. The ablation scale is approximately 10mm, so the carton-carton material with good anti-ablation performance must be used in the tip of target;the ablation scale of body is less than 2mm,so the carton-phenolic aldehyde of small density can be used in thermal protection system of body.
Effects of nozzle on flow field and performance of multi-cycle two-phase pulse detonation engines
WANG Yan-yan, WENG Chun-sheng
2013, 28(10): 2256-2266.
Abstract PDF(7013KB) icon1352 icon1076
Abstract:
The CE/SE(conservation element/solution element) method using adaptable unstructured meshes was derived and applied to calculate the inner and outer flow fields of multi-cycle two-phase pulse detonation engines(PDEs) with different types of nozzles.It was found that the propulsive performance of multi-cycle PDEs with nozzles differed a lot from that of one-cycle PDEs with nozzles.The Laval nozzle offered the highest average thrust in a cycle, while the plug-in-convergent-divergent nozzle provided the maximum impulse and fuel-specific impulse in the longest operation cycle when the nozzles were filled with fuel and the ambient pressure was 0.1MPa.
Experiment on pressure characteristics of dual rotating cavities
CAI Xu, LUO Xiang, XU Guo-qiang, LI Deng-chao, HUANG You-zhi
2013, 28(10): 2267-2275.
Abstract PDF(4218KB) icon1303 icon943
Abstract:
Pressure distribution and total pressure loss were measured by fixed transducers on proper positions of dual rotating cavities. The results show that with turbulent flow parameter varying from 0.1 to 0.4, the pressure on rotating disk decrease with the increasing rotational Reynolds number at first, and then increases with the increasing rotational Reynolds number. The critical turbulent flow parameters for these two cavities are different. Under the same turbulent flow parameter, rotational Reynolds number dominates the shape of pressure distribution curves on the rotating disk surfaces. When turbulent flow parameter increases, total pressure losses of two cavities become larger. But when rotational Reynolds number increases under the same turbulent flow parameter, total pressure losses of these two cavities are different.
Comparative ignition characteristics of ethylene and gasolene in multi-cycle pulse detonation engine
CHENG Xiao-jun, FAN Yu-xin, CAI Di, HAN Qi-xiang, WANG Jia-hua
2013, 28(10): 2276-2283.
Abstract PDF(7220KB) icon1296 icon1283
Abstract:
To investigate the influence of the structure of multi-cycle pulse detonation engine(PDE) on its operation performance,experiments of ethylene-air and gasoline-air mixtures initiation process in the aero-valve PDE of 1050mm length and 40mm inner diameter were performed.The results show that the detonation wave can be successfully initiated in the ethylene-air with frequency of 25,30Hz and 40Hz,and C-J(Chapman-Jouguet) detonation wave can be achieved at the frequency of 40Hz with detonation wave propagation velocity of 1724m/s(less 5.6% than the C-J detonation wave velocity theoretical value 1832.45m/s) and peak wave pressure of 3.01MPa(higher 7.88% than the C-J detonation wave pressure theoretical value 2.79MPa).While the deflagration to detonation transition failed to complete in gasolene-air.By comparison of the two results,it was found that the evaporation process dominated the initiation process in liquid fuels,thus slowering the flame acceleration process in the detonation tube.More novel and optimized-designed reinforced-combustion devices for accelerating the flame should be developed,which may cause higher total pressure loss.Thus,atomization and evaporation to improve the quality of the mixture is a key technology for detonation in the liquid fuel.
Numerical study on characteristics of temperature reduction and flow loss in radial pre-swirl system
ZHANG Jian-chao, WANG Suo-fang
2013, 28(10): 2284-2291.
Abstract PDF(16307KB) icon5239 icon7044
Abstract:
To explore new method of structure design based on‘preswirl temperature-reduction effect’in preswirl system of aero-engine,the characteristics of temperature reduction and flow losses in radial pre-swirl system were studied,and numerical investigation was carried out on a simplified radial pre-swirl system.Numerical method was validated by experimental results;flow structure in the radial pre-swirl system was analyzed.Characteristics of temperature reduction and pressure losses were investigated with changes of rotational Reynolds number and non-dimensioned mass flow rate.The computational results show that:the numerical results coincide with the experimental results,and relative error is not more than 20%,proving that the reliability of CFD method;under certain conditions of the study,at the given non-dimensional mass flow rate,the temperature reduction and pressure losses of radial pre-swirl system decrease as the rotating Reynolds number increases;with the given rotational Reynolds number,the temperature reduction and pressure losses increase as the non-dimensional mass flow rate increases.
Experiment on clearance leakage flow and aerodynamic performance in shrouded turbine cascade
LIU Yan, LIU Pan-nian, JIANG Wo-han, LU Hua-wei, ZHAO Peng-fei
2013, 28(10): 2292-2301.
Abstract PDF(4957KB) icon1554 icon1389
Abstract:
Flow structure at the exit of turbine cascades and aerodynamic performance were studied experimentally in a low speed wind tunnel for unshrouded and shrouded blades with a turning angle of 108.1°. The secondary structure, distribution of flow angles and total pressure loss coefficient on exit planes were investigated under various working conditions, including different clearances between the blade and the casing and different angles of incidence. Experimental results show that, compared with the unshrouded turbine cascades, the shroud can effectively control tip clearance leakage flow and reduce aerodynamic loss of cascade. With the growing clearance between the shroud and casing, the amount of leaked fluid increases. Consequently the mixing loss induced by the leaked fluid becomes larger. For the cascade studied hereto, the clearance should be less than 1% span of the blade. Variation of angle of incidence influences three-dimensional vortex structures and their intensity in cascade passages. Also it clearly affects static pressure distribution on the suction surface of the blade. Proper and positive angle of incidence helps improve the flow field, thus enhancing aerodynamics performance for cascades with large turning angles.
Analysis method of hot streak migration avenue
XUE Wei-peng, ZENG Jun, HUANG Kang-cai
2013, 28(10): 2302-2308.
Abstract PDF(4279KB) icon1218 icon972
Abstract:
An unsteady numerical simulation of turbine stage on the S1 flow surface with hot streak was performed firstly.After analysis of the results,some assumptions for the hot streak migration were made.And then a separate section calculation method and an integral calculation method for the hot streak migration avenue were presented.Comparison with the unsteady calculation,the results show that,these two methods have high precision on the prediction of the hot streak migration avenue,and the differences of migration in circumferential direction are within one degree.
Design of high Reynolds number compressor airfoil with early transition for heavy-duty gas turbine
QUE Xiao-bin, JIANG Hong-de
2013, 28(10): 2309-2315.
Abstract PDF(1807KB) icon1417 icon1202
Abstract:
A type of compressor airfoil, characterized by lower losses and wider operating range than conventional controlled diffusion airfoil (CDA), was developed for use in heavy-duty gas turbines, which considered the early boundary layer transition on blade surface induced by high Reynolds number. Direct design process was adopted, in which the parameterization of airfoil geometry and the blade to blade flow solver were integrated into genetic algorithm to facilitate automatic optimization of airfoil. The optimization object was considered as a compromise of airfoil loss and operating range of incidence, and a special airfoil geometry model correlating the thickness distribution with camber line was applied to reduce optimzation variables. The main characteristics of early transition airfoil by optimization are as follows: the suction side velocity maximum moves forward to around 10% of chord, and the velocity distribution in the rear portion is flat. Finally, the design strategy of this type of early transition airfoil was summarized according to the optimization results.
Aerodynamic performance of tip leakage flow of two different blade tips in transonic turbine
ZHONG Fang-pan, ZHOU Chao, ZHOU Kai
2013, 28(10): 2316-2325.
Abstract PDF(3526KB) icon1271 icon1045
Abstract:
The aerodynamic performance of the tip leakage flow of flat tip and cavity tip was investigated numerically in transonic turbine cascade. The Mach number within the tip gap of flat tip was higher than that of cavity tip. Oblique shock wave structure appeared within the tip gap of flat tip. For cavity tip, the oblique shock wave structure was not obvious because of low Mach number within the tip gap. The mass flow ratios of tip leakage flow to the mass flow at the inlet of the cascade for flap tip and cavity tip were 3.87% and 3.74%, respectively. The aerodynamic loss coefficient was 0.079 for flat tip and 0.072 for cavity tip. The study shows that the aerodynamic performance of cavity tip is better than that of flat tip.
Experimental validation of geometry of compressor intermediate casing
LI Bin, WU Ya-dong, TENG Jin-fang, DU Zhao-hui
2013, 28(10): 2326-2331.
Abstract PDF(8660KB) icon1272 icon1022
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Four kinds of intermediate casings were tested experimentally,including the original model,optimization model,and two models based on optimization model respectively.The length of the strut's chord and the flow path were changed for the last two models.Inlet and outlet total temperature,inlet and outlet total pressure,static pressure of outer and inner wall,static pressure of middle struct along 50% spanwise were measured by pneumatic intelligent pressure scanner and pressure probe,and the effects of the geometry structure on the intermediate casing's aerodynamic performance were evaluated.The results shows that:increase of the duct's axial distance can improve the performance of intermediate casing;the optimized intermediate casing profile can improve the pressure distribution in inlet and outlet;the inner wall profile has a significant impact on the acceleration and deceleration of flow,and optimized pressure distribution is relatively smooth;the geometry of the struts should be considered in optimization.
Half-inverse problem for design of S-shaped compressor transition duct
SHAN Peng, LÜ Zhen-tao
2013, 28(10): 2332-2342.
Abstract PDF(6658KB) icon1237 icon895
Abstract:
An aerodynamic design method of S-shaped transition duct between compressor components was studied. Based on the control of wall static pressure gradient of the transition duct, etc, a half-inverse problem design strategy was proposed, and the corresponding design code was developed. To verify the feasibility of the method, a transition duct for axial-centrifugal compressor was designed by the method mentioned above. The result shows that the static pressure distribution on inner wall along with its geometry can be controlled freely by adjusting the inverse design parameters. The designed static pressure distribution on inner wall can be realized through the numerical matching procedure of the outer wall geometry. The design method is practicable since the total pressure recovery coefficient of the axial-symmetric transition duct can be above 0.98 without searching the optimal static pressure gradient distribution on inner wall, when the duct parameters of inlet-height/length ratio is 0.138, and hub-radius-difference/length ratio is 0.485.
Rear lifting airfoil aerodynamic characteristic of F1 racing car
HE Yi-bin, LI Wei-ping, LIU Meng-xiang, LEI Ji-ping, YANG Zhen-yu
2013, 28(10): 2343-2347.
Abstract PDF(1899KB) icon2137 icon1915
Abstract:
Taking the rear lifting airfoil of scale of 1∶3 F1 racing car as the object of study, the influence law of angle of attack of rear lifting airfoil on the aerodynamic drag and lift of the F1 racing car was researched. When the angle of attack is 12°, the absolute value of aerodynamic lift and drag ratio reaches the maximum, and the angle is the optimum angle of attack of rear lifting airfoil for F1 racing car. Model wind test validated the conclusion.
Low temperature start testing of turbofan engine in altitude test cell
WU Feng, GONG Xiao-qi, QIAO Song-song
2013, 28(10): 2348-2354.
Abstract PDF(3987KB) icon1354 icon1374
Abstract:
A method of low temperature start testing of turbofan engine was presented.And an experimental investigation was performed in a altitude test cell,focusing on studying the method of engine cold-soak process.The low-temperature starting characteristics of the turbofan engine were successfully obtained in the simulated altitude test cell using the low-temperature start testing method,confirming the feasibility of the method used in this testing.The test results give some helpful suggestions for future low-temperature start testing of aero-engines.The results show that:(1) Although the engine windmilling has some disadvantages on cold-soak process,it is still an economic and high-effective cold-soak method.(2) It is difficult to meet requirements of heat preservation time defined in GJB241 during real low-temperature start testing. Thus,it's recommended that the low-temperature test status should be judged using the temperature of lubricating oil. (3) The low-temperature environment has greater influence on the starter than on the turbofan engine.
Design of vortex-controlled serpentine inlet based on NURBS curve
HUANG Chen, XIE Wen-zhong, JING Jian-peng
2013, 28(10): 2355-2363.
Abstract PDF(9203KB) icon1377 icon1028
Abstract:
A parametric description method was established using NURBS(non-uniform rational B-spline) curve,and effects of two key parameters on the inlet performance were studied by numerical simulation.Results show: (1) Controlled vortex induced by backswept convex pon the second S-duct can lead low momentum flow to side regions of AIP(aerodynamic interface plane),and the separation region can be reduced.The value of convex angle need to be selected appropriately,otherwise the convex angle is not conducive to the improvement of the vortex-controlled serpentine inlet performance. (2) Uplifting the lower wall of second S-duct properly could alleviate the adverse pressure gradient on the wall,which has positive effects on the flow within ducts. (3) While the design parameters are chosen appropriately,the total-pressure recovery coefficient of the vortex-controlled serpentine inlet is 0.9667 under design conditions,the distortion index is 0.2451,and the inlet performance has been significantly improved.
Defect accurate positioning method of solid rocket motor in volume space
ZHU Min, YU Guang-hui, LU Hong-yi, LI Peng
2013, 28(10): 2364-2369.
Abstract PDF(4681KB) icon1284 icon960
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On the basis of 3-D reconstruction of the solid rocket motor volume data,the three-dimensional similarity transformation templates compliant with the volume data features of debonding,bubbles and slag inclusion were built.The volume data fields of various defects were located by 3-D similarity transformation.The defect geometric center was selected as the mark point for defect accurate positioning,and the calculation method in volume space of the defect geometric center was given.The simulated solid rocket motor with preset typical defects was designed.Through the experiment,the ratio of the measured distance between the geometric center and the actual geometric center,to the maximum diameter is less than 10%.That's to say,the measured geometric center and the actual geometric center are very close,and the positioning of the geometric center of defects is accurate.
Estimation of relaxation modulus of composite solid propellant based on particle packing model
ZHANG Jian-wei, ZHI Shi-jun, SUN Bing
2013, 28(10): 2370-2375.
Abstract PDF(4327KB) icon1382 icon1111
Abstract:
To estimate more accurately the relaxation modulus of composite solid propellant with different particles volume fraction, the molecular dynamics method was adopted to construct solid propellant meso-scale models with different particle volume fraction. The mean stress of composite solid propellant meso-scale model varying with relaxation time was computed by finite element theory and mesomechanics homogenization method when the model was under a fixed strain load. So the effective relaxation modulus of composite solid propellant can be estimated. It can be seen clearly that the instantaneous modulus of composite solid propellant increases when particle volume fraction becomes larger and the influence of particles random distribution to the instantaneous modulus of composite solid propellant by the proposed method.When this method is applied to the design process of composite solid propellant, it can reduce the design cost and shorten the design cycle effectively.
Combustion instability at end of burning in a solid rocket motor
SU Wan-xing, LI Shi-peng, ZHANG Qiao, ZHAO Yan-dong, YE Qing-qing, WANG Ning-fei
2013, 28(10): 2376-2383.
Abstract PDF(11261KB) icon5616 icon6637
Abstract:
Based on a solid rocket motor (SRM),numerical simulation with linear prediction was carried out to study the pressure oscillation at the end of burning.Acoustic modes and natural acoustic frequencies of combustor chamber were obtained by finite element analysis (FEA) method.The results indicate that the first and second axial acoustic frequencies first decrease and then increase with the regression of the burning surface.The flow-field and pressure oscillation characteristics of the combustor were analyzed via large eddy simulation (LES) method.The oscillation frequency was well consistent with the experimental value,confirming that the SRM presented fundamental acoustic combustion instability.Then the damping effect of the motor was analyzed.It shows that the total damping continuously decrease with the regression of the burning surface.Finally,the pressure oscillation mechanism at the end of burning was explained via linear combustion instability theory.The decrease of the throat-to-port area ratio is a key factor that makes the SRM turn from linear stable state to linear unstable state.
Modeling of whole processes of mixing exhaust afterburner twin spool turbofan engine
SHI Rui-jun, ZHOU Jian-bo, ZHANG Qiu-gui, PI Xing, FAN Si-qi
2013, 28(10): 2384-2390.
Abstract PDF(2866KB) icon1663 icon1322
Abstract:
Firstly, a steady state mathematical model was developed for the mixing exhaust afterburner twin spool turbofan engine in full envelope. Secondly, a startup dynamic model was constructed by combining the effects of volume dynamics with the steady model. Then, by extending the volume dynamics theory to idle state, a whole process model was obtained to calculate the startup process, acceleration and deceleration process, turn on/off afterburner process and stop process. Finally, the altitude characteristic was presented with the proposed regulation law in full envelope of the engine; the whole processes from startup to stop were simulated with the designed control algorithm. The results show that the model is able to simulate the steady and dynamic states in full envelope, and correctly describes the whole process of mixing exhaust after burner twin spool turbofan engine including afterburning.
Technology analysis and system scheme for aero-engine distributed control system
SONG Jun-qiang, PAN Mu-xuan, HUANG Jin-quan
2013, 28(10): 2391-2400.
Abstract PDF(2258KB) icon1644 icon2946
Abstract:
The status, progress and technology readiness level of the system architecture, communication bus, smart components, high temperature electronic components and power bus for aero-engine distributed control system were analyzed and evaluated. The results show that the studies for aero-engine distributed control system are at fundamental phase and the technology readiness level (TRL) is TRL 1 to TRL 2. According to the analysis and evaluation aforementioned, two potential schemes of distributed control system for a turbofan were proposed, including transitionally distributed control and partially distributed control based on TTCAN bus, and the system architectures, control functions and communication traits were discussed, providing a reference for future development of the aero-engine distributed control system.

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