2020 Vol. 35, No. 9

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Effect of fuel temperature on atomization characteristics of centrifugal nozzle
LIU Aiguo, WANG Dong, YU Haoyang
2020, 35(9): 1793-1800. doi: 10.13224/j.cnki.jasp.2020.09.001
Abstract PDF(2687KB) icon810 icon687
Abstract:
Taking the centrifugal pressure atomizer as the research object, the effects of fuel temperature on the atomization characteristics of aviation kerosene under different pressures were experimentally tested and numerically simulated. The atomization characteristics of the fuel within the range of -20 ℃ to 50 ℃ were studied experimentally. The flow and atomization characteristics of the fuel within the range of -50 ℃ to 50 ℃ were simulated by numerical simulation. Results showed that the fuel pressure had little effect on the atomization characteristics; within the studied temperature range, the increase of temperature led to the increase of atomization angle, the decrease of Sauter mean diameter(SMD) and the increase of the non-uniformity of circumferential distribution. When the temperature rose from -20 ℃ to 50 ℃, the SMD decreased from 45 μm to 30 μm; the thickness of oil film increased with the decrease of fuel temperature, which was conducive to the improvement of the uniformity of fuel circumferential distribution, but led to the straight atomization droplets Track enlargement.
Combustion characteristics of gasoline-aviation kerosene in spark ignition aviation piston engine,
WANG Lei, ZHAO Zhenfeng, YU Chuncun
2020, 35(9): 1801-1811. doi: 10.13224/j.cnki.jasp.2020.09.002
Abstract PDF(4560KB) icon876 icon456
Abstract:
In order to study the combustion characteristics of aviation kerosene in the spark ignition aviation piston engine, an aviation piston engine test rig capable of simultaneously burning gasoline-aviation kerosene was reconstructed. And a three-dimensional simulation model of the engine combustion chamber was established. Using the combination of test and three-dimensional simulation, the difference of combustion characteristics between gasoline and aviation kerosene was studied. The result showed that under the condition of low speed and small load, the indicated mean effective pressure (IMEP) was less than 05 MPa; by adjusting the operating parameters such as ignition timing, the aviation kerosene can reach the combustion characteristics similar to gasoline; as the engine speed and load increased, the aviation kerosene combustion characteristics presented the extended flame retardation, the increased combustion duration, the reduced maximum pressure, and the burning center of gravity moved backward, accompanied by obvious knocking. Under high speed conditions, aviation kerosene combustion was affected by knocking, and the load can only be increased to 21%.
Model of spatial SMD distribution of spray at the near-field of swirl cup
GAO Zhao, LIU Yuying, GU Pengcheng
2020, 35(9): 1812-1821. doi: 10.13224/j.cnki.jasp.2020.09.003
Abstract PDF(2576KB) icon383 icon434
Abstract:
A semi-empirical model of spatial SMD distribution at the near-field of swirl cup was proposed based on the physical process of swirl cup atomization and the characteristics of spatial Sauter mean diameter (SMD) distribution. The swirl cup spray at the near-field was divided into central zone and border zone, the hybrid atomization model of pressure swirl with primary air blast atomizer was used for the central zone, and the prefilming airblast atomization model of Ventruri tube was used for the border zone spray. The SMD and SMD spatial distributions of the spray were combined with Gaussian distribution simultaneously. According to the difference of air pressure drop, two types of semi-empirical models: pressure swirl atomization dominated model and airblast atomization dominated model, were validated respectively. Furthermore, the influences of liquid pressure and air pressure drop on the spatial SMD distribution were predicted and analyzed. Pediction results show that: the SMD decrease with the increase of liquid pressure or air pressure drop.
Atomization performance on fuel slinger with pulsed digital holography,
XUE Zhiliang, JIANG Zhi, LI Feng
2020, 35(9): 1822-1830. doi: 10.13224/j.cnki.jasp.2020.09.004
Abstract PDF(3136KB) icon362 icon336
Abstract:
The measurement system of atomization field was built on a centrifugal fuel slinger test bench. A suction hood with multi-well plate was used to prevent the oil mist spill, and its flow field was calculated by simulation. Performance parameters such as fuel droplet space distribution, size distribution and atomization cone angle were measured by pulsed digital holography under different rotary speeds. Results indicated that the radial velocity of suction hood was uniform, the velocity field near the fuel slinger was an order of magnitude lower than the droplet velocity, so its influence on the atomization field was small. The 20 μm peak droplet size of atomization field accounted for 20%-30%. With increase of the rotary speed, droplet size Sauter mean diameter (SMD) gradually decreased, atomization field was centralized to axial direction and atomization cone angle was reduced. At the same rotary speed, with the increasing distance away from the nozzle outlet, the droplet size SMD rose, and when the speed increased, the amplitude diminished.
Thermodynamic parameters calculating method of gas and its application in convective heat transfer over turbine cascade
XUE Yu, LIU Jingyuan
2020, 35(9): 1831-1844. doi: 10.13224/j.cnki.jasp.2020.09.005
Abstract PDF(5159KB) icon525 icon395
Abstract:
To investigate the influence of thermodynamic parameters of combustion gas on convective heat transfer, a method of calculating thermodynamic parameters of multicomponent combustion gas was proposed for hydrocarbon-air combustion system in aero-engine system. The certain thermodynamic parameters derived by the method were then applied to simulate the convective heat transfer over flat plates and turbine cascades under different inlet temperatures and compare with the numerical results with air as working substance. Results showed that local convective heat transfer coefficients of the gas as the working substance were greater than the coefficients of the air for the flat plate and turbine cascade respectively, and with the rise of inlet temperature, the differences of the local Nusselt number of air and gas increased gradually under the same input conditions except different working substances for the flat plate and turbine cascade respectively. Within given inlet temperature range, the local Nusselt number of the flat plate rose from 28% to 30%, and the turbine cascade increased from 725% to 969%.
Flow field characteristics of single round hole pulsed jet based on PIV technology
SHEN Xinyao, MAO Junkui, LIU Fangyuan
2020, 35(9): 1845-1855. doi: 10.13224/j.cnki.jasp.2020.09.006
Abstract PDF(5675KB) icon464 icon387
Abstract:
The flow field characteristic structure of steady and pulsed jet impinging on the target plate was investigated. High frequency particle image velocity measurement technology was used to measure a steady jet and a pulsed jet with a frequency of 20 Hz. Besides, the distance between the jet nozzle and the target plate was 6 times the diameter of the nozzle, and the steady jet inlet Reynolds number was 6 000 for both steady and pulsed jet flows. The experiment obtained velocity distribution of the core jet zone, the wall jet zone, and the stagnation zone. The results show that: (1) due to the shear action of the jet, maximum axial fluctuation velocity in the core jet zone of the pulsed jet was nearly three times that of the steady jet. (2) In the stagnation zone, the maximum gradient of the axial velocity of the pulsed jet was approximately twice that of the steady jet, which resulted from the shear action of the jet and the stagnation action of the wall. Furthermore, the maximum fluctuation velocity in the stagnation zone was nearly three times that of the steady jet. (3) The entrainment of the pulsed jet and the propagation of the vortex led to the destruction of the velocity boundary layer in the wall jet region. Compared with the steady jet, the flow field of the pulsed jet increased the energy of the turbulent coherent structure and generated periodic large-scale vortex.
Analysis on oxygen volume fraction control index in aircraft fuel tank inerting
ZHOU Penghe, LIU Wenyi, LIU Weihua
2020, 35(9): 1856-1865. doi: 10.13224/j.cnki.jasp.2020.09.007
Abstract PDF(2958KB) icon592 icon371
Abstract:
The current standard test methods for limiting oxygen volume fraction, theoretical and test research results on limiting oxygen volume fraction for aircraft fuel were systematically summarized, then some suggestions were presented by extensively drawing on previous research results: (1) When N2 inerting was adopted on the ground, 12% oxygen volume fraction can be used as the control index of oxygen volume fraction in the fuel tank for RP-3 fuel. (2) For civil aircraft, the control index of oxygen volume fraction in the fuel tank within the flight envelope can be determined, indicating that the limited oxygen volume fraction in the ullage of fuel tank at sea level through 3 048 m was approximately within 12%, with a linear increase from 12% at 3 048 m to approximately 145% at 12 192 m; for military aircraft, it can be considered to add a 20% safety margin on the civilian aircraft standard, the limited oxygen volume fraction increased linearly from 9% at sea level to 12% at 12 192 m. (3) At present, in the development of the inerting system of domestic military aircraft, the requirement of controlling the oxygen volume fraction in the ullage of fuel tank within 9% during the whole flight envelope was debatable, which would directly lead to excessive compensation loss caused by excessive protection.
Effects of humidity ratio on lean blowout performance of piloted vaporization flameholder
FENG Yuhua, LIU Yuying, DENG Yuanhao
2020, 35(9): 1866-1874. doi: 10.13224/j.cnki.jasp.2020.09.008
Abstract PDF(2488KB) icon393 icon355
Abstract:
A modified model of Lefebvre lean blowout fuel/air ratio containing humidity ratio was proposed based on cold flow field numerical simulation and analysis of humidity ratio effect on the combustion load parameters, combustion reaction and fuel atomization of piloted vaporization flameholder, under the conditions of 300-483 K incoming temperature, 014-03 incoming Mach number and 0-016 humidity ratio. The effect of humidity ratio on the lean blowout performance of piloted vaporization flameholder was discussed. It was found that the combustion loading parameters increased with the increase of humidity ratio, and the lean blowout fuel/air ratio increased significantly with the increase of humidity ratio. Therefore, the combustion loading parameter makes it difficult to describe the change of lean blowout fuel/air ratio itself alone, and the effect of humidity ratio on the fuel atomization can not be ignored.
Effect of fuel distribution on combustion performance for micro gas turbine combustor,
CHEN Xuanren, LIU Aiguo, HU Jian
2020, 35(9): 1875-1883. doi: 10.13224/j.cnki.jasp.2020.09.009
Abstract PDF(2750KB) icon621 icon364
Abstract:
A dry low emission (DLE) micro gas turbine combustor with variable nozzle position and multi-point fuel injection was put forward. In order to gain the effect of different fuel-staged methods on the combustion performance for the combustor, and the effect of fuel distribution mode between pilot and primary on combustion performance, different distribution modes of the combustor were experimentally studied by numerical simulation. Results showed that: the change of fuel nozzle position had little effect on the emissions. With the increase of two-stage fuel distribution ratio, the NOx emissions decreased first and then increased, and there existed an optimal fuel distribution ratio to minimize NOx emissions. There existed obviously a primary recirculation zone (PRZ) in combustor, helping to facilitate ignition and propagation of flame. The amount of thermal NOx produced was directly related to the size of the region above 1 950 K and the highest gas temperature. The NOx emissions of the designed combustion can be reduced to below 50 mg/m3 under all working conditions with natural gas as fuel, which can reach the level of low-emission combustion (less than 50 mg/m3).
Numerical investigation on influence of sealing clearance on sealing performance
ZHANG Qingcai, TAN Xiaoming, LUO Qingyang
2020, 35(9): 1884-1892. doi: 10.13224/j.cnki.jasp.2020.09.010
Abstract PDF(3854KB) icon548 icon487
Abstract:
A three-dimensional numerical simulation of the rim seal of a high-pressure turbine was carried out. To reveal the sealing efficiency and the flow field characteristics in the cavity,different parameters of axial and radial clearances were analyzed. Results showed that the sealing ring divided the disk cavity into an outer cavity and an inner cavity. The outer cavity could effectively resist the mainstream gas,therefore the inner cavity had a higher sealing efficiency. With the increase of axial clearance,the overlap length and the resistance of the coolant flow decreased,so the sealing efficiency of the disk cavity was improved. With a constant axial clearance,the radial distance of the outer cavity decreased as the radial distance decreased. The sealing efficiency at the lower radial region could be improved.
Effect of condensation phase transient on Reynold number test for cryogenic wind tunnel
SUN Wan, XU Tao, LIU Xiufan
2020, 35(9): 1893-1899. doi: 10.13224/j.cnki.jasp.2020.09.011
Abstract PDF(2798KB) icon414 icon347
Abstract:
In order to investigate the condensation effect on Reynold number test for the cryogenic wind tunnel, a two-phase condensing flow model was established based on the Fluent software. The classic nucleation theory considering the non-isothermal effect and Gyarmathy droplet growth theory were employed for the prediction of spontaneous condensation. Under varying inflow pressures and testing Reynold numbers, the numerical simulations of nitrogen flowing around the NACA 0012 airfoil were carried out. The simulation results showed that the decrease of incoming flow temperature resulted in rapid expansion and the gas supercooled state at region near the airfoil surface. With further reduction of the incoming flow temperature, significant change of local flow fields affected by condensation was observed at a macroscopic level. The release of latent heat heated up the nitrogen flow and thus resulted in a deceleration of Mach number and a deviation of pressure coefficient in comparison with the case without condensation. Without destroying the airfoil aerodynamic performance test, it was feasible to make full use of gas supercooling for reducing the incoming flow pressure, which also meant few cost of driving power and liquid nitrogen injection. Alternatively, keeping the incoming flow pressure constant increased the testing Reynold number of the cryogenic wind tunnel.
Boundary layer blowing characteristics of bump inlet by wind-tunnel test
ZHAO Haigang, LIU Yu, REN Dingding
2020, 35(9): 1900-1908. doi: 10.13224/j.cnki.jasp.2020.09.012
Abstract PDF(4572KB) icon573 icon436
Abstract:
Based on the low and high speed wind tunnel，a test system for measuring the boundary layer blowing characteristics of the bump inlet at a wind tunnel was designed and set up. The boundary layer blowing characteristics were studied by test at different incoming Mach numbers and flow ratios. Through analysis of the test data, calculation and comparison of the flight test results of the same type, the boundary layer blowing characteristics of the bump inlet were studied. Results showed that the boundary layer blowing ability of the bump inlet gradually decreased with the increase of the flow ratio at the same incoming Mach number.Within the wide range of the flow ratio at subsonic, the pressure coefficient of the bump inlet surface was symmetric along the center line with high pressure gradient, and it increased along the mainstream. The bulge structure showed a relatively strong blowing ability of the boundary layer. The flow ratio range with effective blowing ability at supersonic was significantly smaller than that at subsonic. At supersonic the bow-shaped shock wave of the inlet lip was the main factor affecting the pressure gradient change at different positions on the bump surface and the boundary layer blowing ability. Under the flight conditions near Mach number 18 and above, the boundary layer blowing ability was decreased, and the separation of the boundary layer flowing was strengthened, causing large loss and distortion of the inlet pressure.
Inverse design method of airfoil based on deep learning
HE Lei, QIAN Weiqi, LIU Tao
2020, 35(9): 1909-1917. doi: 10.13224/j.cnki.jasp.2020.09.013
Abstract PDF(3283KB) icon650 icon306
Abstract:
An inverse design method of airfoil based on deep learning was proposed, and the pressure distribution image and airfoil curve were taken as the learning objects to build the prediction model. It can obtain the airfoil curve by using convolutional neural network to extract geometric features from pressure distribution image, while avoiding the time-consuming process of traditional numerical calculation method. In the test case, 6 000 samples of pressure distribution images and airfoil curves were used to train the prediction model, and the other 561 samples were used for validation with validation time only 67 s. The average relative error between the predicted and CFD results was 055%. In the comparison test, noise was added to the pressure distribution curve and the output layer size was changed to further validate the performance of the model. The results show that the proposed inverse design method of airfoil has strong robustness and prediction accuracy. The method can greatly reduce the computation time and improve the design efficiency of airfoil with satisfactory design accuracy.
Modeling and optimal design of stratospheric airship propulsion system based on energy balance
WANG Dongchen, SONG Bifeng, WANG Haifeng
2020, 35(9): 1918-1926. doi: 10.13224/j.cnki.jasp.2020.09.014
Abstract PDF(2693KB) icon711 icon220
Abstract:
An modeling and optimal design method of stratospheric airship propulsion system based on energy balance was proposed to achieve both high efficiency and light weight goals.Efficiency and weight surrogate models of motor and propeller were individually established using design of experiments method and surrogate model technology. A weight calculation model for airship energy system containing solar cells and energy storage batteries was also built. Based on the multi-island genetic algorithm, the optimal design model of airship propulsion system was established with the energy and thrust balance as the constraints,and the minimum total weight of the propulsion and energy system as the goal. Optimization design of an example was carried out. The results show that the efficiency of the optimized propulsion system is increased by 23%,and the total weight of the propulsion and energy system is reduced by 340 kg,verifying the feasibility and application value of the modeling and optimal design method of stratospheric airship propulsion system.
Effect of unilateral blade tip fillet structure on blade tip clearance flow of compressor cascade
GAO Limin, WANG Haoha, ZHAO Lei
2020, 35(9): 1927-1935. doi: 10.13224/j.cnki.jasp.2020.09.015
Abstract PDF(4455KB) icon381 icon274
Abstract:
A method of compressor cascade blade tip leakage flow control was presented. By using a small-scale fillet structure in the pressure side of the blade tip region, the flow condition in the tip clearance of the diffuser cascade was improved.The effects of blade tip fillet on the aerodynamic performance of compressor cascade were investigated by numerical method. Through analysis of the control effects of three different tip fillet structures (3%, 4%, 6% of the maximum blade thickness), the simulation showed that the blade tip fillet structure can weaken the tip separation vortex with the decrease of total pressure loss coefficient of tip clearance passage and affect the vortex system structure in the region of tip clearance. The method showed a good ability to improve the flow conditions in the blade tip region and undermined the effect of blockage in blade tip passage. However, an increase in the leakage mass flow rate with a loss for the efficiency was observed because of the mixing of leakage flow and main flow. The conclusion shows that the appropriate blade tip fillet structure could improve the aerodynamic performance and the fillet radius of 3% of the maximum blade thickness has a good effect compared with other radiuses.
Basic geometric theory and volume calculation of double-tooth gas circulation pump
FENG Shiyu, ZHOU Libiao, ZHU Zhenyu
2020, 35(9): 1936-1942. doi: 10.13224/j.cnki.jasp.2020.09.016
Abstract PDF(1397KB) icon283 icon214
Abstract:
Based on the mathematical geometry theory,the basic profile equations of the female-male rotor were derived through coordinate transformation and envelope conditions,and the mathematical model of the double-tooth gas circulation pump was established.The relationship between the position of the meshing point and the rotor angle of the female rotor with the meshing of the male and female rotors was studied.The calculation method of line integral was used to derive the relationship between the elementary area of the working volume and the rotor angle, which can simplify the calculation difficulty of the working volume.Results showed that when the rotor angles were 0 and π,the female and male rotors formed a closed invalid area,which led to the sudden rise and fall of the element area of the working cavity during the change of the rotor angle.At the end of inhalation,the suction chamber had an additional part connected to the suction port compared with the exhaust chamber,resulting in a sudden drop in the element area.The establishment of these basic geometric theories can lay a certain theoretical foundation for the application of double-tooth gas circulation pumps.
Coupling effect of boundary layer ingestion on rectangular-to-circular intake and fan
WEI Wei, REN Siyuan, DA Xingya
2020, 35(9): 1943-1953. doi: 10.13224/j.cnki.jasp.2020.09.017
Abstract PDF(4525KB) icon497 icon259
Abstract:
Focusing on the boundary layer ingestion effects on the rectangular-to-circular S-shaped intake and fan coupling aerodynamic performance, steady and unsteady computational fluid dynamics (CFD) numerical simulation methods were used to analyze the intake and the fan’s aerodynamic performance and the fluid features. The numerical simulation and analysis results revealed the primary effects of the inlet boundary layer ingestion. With the increase of intake boundary layer ingestion thickness, the steady circumferential total pressure distortion index of the intake outlet, the total pressure defect and the relative airflow angle of the distortion regions rose, and the flow coefficient decreased within the total pressure distortion region. However, the size of the intake distortion region changed little, and the inlet boundary layer thickness made minimal effects on the total aerodynamic performance of the intake and the fan. Due to the pressurization effect of the fan, the outlet airflow parameters distortion among circumferential direction was weakened effectively.
Vibration measurement of turbine rotor blades of aero-engine based on blade tip-timing
LIU Meiru, TENG Guangrong, XIAO Xiao
2020, 35(9): 1954-1963. doi: 10.13224/j.cnki.jasp.2020.09.018
Abstract PDF(3161KB) icon799 icon343
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The difficulty of vibration non-contact measurement of the turbine rotor blade based on tip-timing was introduced. Breakthrough progress was made on the structure design, the installation on the casing and the cooling strategy of high temperature optical tip-timing sensor. The timing signal of H profile of turbine blades was acquired by setting signal hold time of the system for avoiding the secondary trigger, and a method of determining the revolution speed for the blade tip-timing system was proposed for core-engine. Such a tip-timing system was successfully used in the vibration monitoring of the turbine blades of core engine. The tip magnitudes and natural frequencies of the blades were successfully determined by the tip-timing system, and compared with the dynamic strain results from the traditional strain gage. The comparison results demonstrated that the non-contact measurement based on tip-timing and the contract measurement based on strain gage can successfully identify the vibration of turbine blades. The 1st bending mode of the turbine blades at about 8 200 r/min on was caused by engine order of 12. The relative error of the two methods in determining the 1st bending natural frequency of blades was less than 4%.
Combination resonance characteristics of a dual-rotor system with a local defect of inter-shaft ,bearing inner ring
YI Haiming, HOU Lei, GAO Peng
2020, 35(9): 1964-1976. doi: 10.13224/j.cnki.jasp.2020.09.019
Abstract PDF(5306KB) icon484 icon250
Abstract:
A simplified dynamic model of aero-engine with dual-rotor system was established. Considering the non-linear factors such as Hertz contact force and radial clearance of the intermediate bearing, the local defect of the inner ring of the inter-shaft bearing was simulated as an inverted isosceles trapezoidal groove. The Runge-Kutta method of order 4 was used to simulate the fault system and draw the bifurcation diagram. The combination resonance characteristics of the bifurcation region were analyzed emphatically, and the results showed that there were three bifurcation regions in the bifurcation diagram of a dual-rotor system with local defect of inter-shaft bearing. Vibration response analysis showed that the first two bifurcation phenomena were caused by the combined resonance of inner-ring fault, and the last bifurcation phenomenon was caused by the induced resonance of inner-ring fault. In the bifurcation region, the periodicity of system motion would change correspondingly, mainly from approximate single-periodic motion to almost periodic motion and then to approximate single-periodic motion.
Reliability assessment of bearings with incomplete performance degradation data under small and non-failure samples
XU Lingtian, SHEN Xuejin, JIANG Shuang
2020, 35(9): 1977-1987. doi: 10.13224/j.cnki.jasp.2020.09.020
Abstract PDF(1172KB) icon573 icon221
Abstract:
A reliability assessment with incomplete performance degradation data under small and non-failure samples was made. A data-based random number simulation method proposed by Taylor and Thompson was used to complete the missing sample degradation data,the Bootstrap method was used to expand the sample size,and the reliability assessment of the bearings was analyzed based on the degradation trajectory-based method. The vibration degradation of 7 groups of tested bearings was selected and analyzed under the conditions of complete and incomplete performance degradation data,respectively. It was found that the method proposed can obtain accurate reliability assessment and the absolute value difference between two results was controlled within 01. The above results were compared with the results obtained by analyzing the lifetime data through the weighted E-Bayes method and the maximum likelihood estimation. It was found that the results obtained by the method were better,and the actual error was within 10% compared with the actual test,showing positive practical significance for improving the evaluation accuracy and reducing the test cost.
Effect of cabin layout on vacuum plume of Hall thruster based on particle simulation
WANG Junwei, ZHANG Lei, GONG Jie
2020, 35(9): 1988-1994. doi: 10.13224/j.cnki.jasp.2020.09.021
Abstract PDF(3978KB) icon392 icon230
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The plume field in a vacuum facility for Hall thruster ground testing was investigated in detail through a series of simulations using direct simulation Monte Carlo (DSMC) code. The focus here was put on the effects of vacuum plume flow field in testing facility under different distributions of the xenon pump and beam baffle. The results showed that the position of xenon pump had little influence on the plume flow field. However, it should be considered that the xenon pump should be uniformly arranged to prevent locally excessive increase of pressure and formation of resistance. The beam baffle had an obvious inhibitory effect on the backflow particles, and had a good protection function for xenon pump. However, it also changed the plume flow field distribution, even the discharge characteristic and performances of Hall thruster. There were also some considerations for distribution of process equipments to reach a better and real testing environment. The numerical simulation is great beneficial to the design and layout optimization of test facility, which provides a more effective test environment for ground tests of electric propulsion.
Influence of propellant composition on performance of solid fuel ramjet
QIU Shuang, SU Yingli, YANG Haitao
2020, 35(9): 1995-2005. doi: 10.13224/j.cnki.jasp.2020.09.022
Abstract PDF(5173KB) icon449 icon249
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In order to investigate the influence of different component propellants on the performance of solid fuel ramjet(SFRJ), experiments were conducted on connected pipe facility for ignition of a SFRJ using polyethylene(PE) with paraffin, carbon black and carbon fiber as propellant. The combustion surface morphology was observed by SEM. The three-dimensional distribution of regression rate was obtained by using three-dimensional scanner and data reconstruction method. According to the data obtained from the experiment, the performance parameters of SFRJ under different working conditions were further calculated. Results indicated that: addition of 5% Carbon fiber could hinder the mechanical erosion of combustion surface of the polyethylene-based propellant and affect the pyrolysis process, making it impossible for self-sustaining combustion. The Kelvin-Helmholtz instability was found through the three-dimensional distribution of burning rate. Adding carbon black and paraffin to the polyethylene-based propellant could improve the regression rate, and the influence of paraffin was more obvious. The mass fraction of paraffin of 30%, 50% paraffin and pure paraffin were 375%, 514% and 544% higher than those of PE respectively. Finally, the relationship between the average regression rate of the polyethylene-based propellant and the mass fraction of paraffin was obtained.
Turbofan engine abrupt gas path fault diagnosis method based on improved K-SVD dictionary training and sparse theory
LI Kui, HU Yu, SUN Zhensheng
2020, 35(9): 2006-2016. doi: 10.13224/j.cnki.jasp.2020.09.023
Abstract PDF(3452KB) icon507 icon293
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The characteristic atomic group of turbofan engine components was classified and exploited to the K-SVD(K-singular value decomposition) based on the sparse characteristics of gas path abrupt fault signals,then an improved K-SVD dictionary training algorithm was proposed and used for abrupt fault diagnosis. The compared results with EKF(extended Kalman filter) and UKF (unscented Kalman filter) showed that the improved K-SVD method was accurate for fault location,and the change of health parameters of no fault components was 0,which can improve the identification of fault components effectively and avoid misdiagnosis;the calculation time was basically the same as EKF method;under similar accuracy,the time consumption of this method was only 03% of UKF method,which can be adapted for engine gas path parameter tracking and abrupt faults diagnosis.

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