2017 Vol. 32, No. 2

  Previous Issue | Next Issue 
Display Method:
Wall temperature calculation on integrated combustion and nozzle in TBCC
2017, 32(2): 257-267. doi: 10.13224/j.cnki.jasp.2017.02.001
Abstract PDF(1138KB) icon1042 icon445
Abstract:
Based on the Navier Stokes(N-S) equations, the numerical simulation of coupling gas and heat on the integrated computational domain of combustion and nozzle in TBCC(turbine based combined cycle), including the heat shield, internal and external flow of the heat shield and the outer flow field, was carried out, inconsideration of the gas composition and the radiation heat transfer. The wall temperature distribution of the cylinder and heat shield in the integrated computational domain of combustion and nozzle in TBCC under certain flight condition was mainly studied in addition to the radiation heat flux distribution of heat shield. Results showed that the wall temperature along the intersection of the symmetry and cylinder changed slightly within the range of axial distance from 0.5m to 2.6m. The wall temperature rapidly increased within the range of axial distance from 2.6m to 3.1m, and dramatically decreased within the range of axial distance from 3.1m to 3.5m.Then the wall temperature along the upper intersection decreased gradually, while the wall temperature along the lower intersection increased first and then decreased. The highest wall temperature point(1577K) of the cylinder was contraction section of lower adjusting plate of nozzle. The radiation heat flux of inner wall of the heat shield changed from 370kW/m2 to 500kW/m2, the radiation heat flux decreased first and then increased along the flow, the radiation heat flux of the two intersections was more than 300kW/m2 compare with outer wall,the radiation heat flux of outer wall of the heat shield changed from 50kW/m2 to 200kW/m2.
Analysis on groundbased inerting performance of a fuel tank green onboard inert gas generation system
2017, 32(2): 268-274. doi: 10.13224/j.cnki.jasp.2017.02.002
Abstract PDF(896KB) icon843 icon450
Abstract:
Based on the description of the operating principle of a green onboard inert gas generation system (GOBIGGS), which could decrease the oxygen volume fraction on ullage of a fuel tank via the injection of the inerting gas produced by a catalytic combustion reactor, a GOBIGGS flow was designed and its mathematical model was setup. GOBISGGS was compared with the onboard inert gas generation system (OBIGGS) in which the inerting process was realized via the injection of the nitrogen enriched air (NEA) separated by a hollow finer membrane module. The result reveals that if the flow rate of the exhaust gas from the fuel tank in GOBIGGS is identical with that of NEA in OBIGGS, the inerting effect of GOBIGGS is much more positive than that of OBIGGS. Additionally, the performance GOBIGGS affected by the efficiency of the catalytic combustion reactor and the allocation proportion of the preheating gas were investigated. It is found that the increase of the efficiency could shorten the inerting time to the maximum safe oxygen volume fraction and reduce the ultimate oxygen volume fraction, and the power consumption of the system could decrease if a proper allocation proportion of the preheating gas is chosen.
Analysis on heat transfer performance of a microminiature flat heat pipe
2017, 32(2): 275-279. doi: 10.13224/j.cnki.jasp.2017.02.003
Abstract PDF(781KB) icon823 icon447
Abstract:
An experimental investigation was conducted for heat transfer performance of a microminiature flat heat pipe under natural and forced convection cooling. Effects of heating power and cooling intensity on the heat transfer performance of the heat pipe were analyzed. Heat transfer performance of an aluminum plate with the same dimensions was also investigated experimentally and compared. Result shows that,the flat heat pipe has good startup characteristics and uniform temperature distribution. The equivalent heat conductivity coefficient of the flat heat pipe can be 12.7 times higher than that of the aluminum plate. The flat heat pipe is convenient for large area machining with high mechanical strength, and thus has good application prospect in heat dissipation for electronic equipment.
Experimental investigations on breakup characteristic of single droplet in the core/bag breakup regime inthe continuous uniform heating airflow
2017, 32(2): 280-288. doi: 10.13224/j.cnki.jasp.2017.02.004
Abstract PDF(1038KB) icon906 icon438
Abstract:
In order to obtain characteristics of single droplet deformation and breakage in a continuous and uniform air jet flow, the highspeed cameras were applied to measure the single droplet deformation and breakage. In the experimental conditions, experimental results show that: (1) The process of droplet deformation and breakage in the core/bag breakup regime is caused by the combination effects of liquidflow and external aerodynamics. It can be divided into umbrella-type breakup regime and dipper-type breakup regime. (2) The reduction of original diameters of droplet and the increase of airflow temperature could decrease the minimum requirements of aerodynamic force on the core/bag breakup. (3) The characteristic time of droplet breakup has a negative relationship with the aerodynamics, while its value and change gradient are both positively associated with the original droplet diameter. (4) The percentage of sub droplet quality raises with the increase of aerodynamics, but decreases with the increase of droplet original diameter.（5) The spatial dispersion of quality percentage of sub droplet increases with the rise of aerodynamics.
Surface dynamic thermal radiation of highspeed flying projectile
2017, 32(2): 289-297. doi: 10.13224/j.cnki.jasp.2017.02.005
Abstract PDF(1000KB) icon925 icon467
Abstract:
In view of the key problems of the infrared system in tracking and acquisition of the highspeed flying projectile target in realtime, a method for solving the dynamic infrared radiation(IR) characteristics of the overall trajectory was proposed. Using 155 mm aperture uncontrolled projectile as the object, the 6degree of freedom (DOF) rigid body ballistic simulation model was established based on Simulink, and the trajectory data were calculated and analyzed. With method by thermal network, a physical model of coupling heat transfer of dynamic IR field was built. The aerodynamic heating calculation model of highspeed rotatable flying projectile was deduced, and the effect of the environmental thermal radiation was considered by Monte-Carlo(M-C) method. The nodes thermal balance equations were solved using RungeKutta method, the distributions of dynamic aerodynamic heating transfer coefficient and temperature and IR fields were obtained, and then the flying projectile IR characteristics in whole fling process on the different positions and wave bands intervals were analyzed. Results showed that the surface temperature increased rapidly when the projectile was launched in a short time. The more closer to the warhead means the faster the temperature rise rate, and the higher the peak temperature. The IR characteristics was obvious before 20 seconds in its flight trajectory. However, with the flight velocity decay resulted in rapid loss of heat, the radiation intensity weakened and mainly focused on 8～14μm wave bands.
Experimental investigation on leakage characteristics of small size brush seal with low front plate
2017, 32(2): 298-305. doi: 10.13224/j.cnki.jasp.2017.02.006
Abstract PDF(906KB) icon843 icon434
Abstract:
Experimental research on rotors axis locus and leakage characteristics of brush seal with low front plate at clearance/transition/interference fit states was carried out. The rotors axis locus was measured by using eddy current sensor. The results showed that: rotors axis locus became smaller with increase of differential pressure when the differential pressure was less than 0.4MPa. Rotor's axis locus didn't vary with differential pressure when the differential pressure exceeded 0.4MPa. Rotor's axis locus didn't affect the leakage characteristics of brush seals for different fit states if wear was not taken into account. This could ensure the safety and effectiveness of the experiment rig. Based on this, the effects of rotational speed, differential pressure and sealing clearance on leakage characteristics were studied. The result shows that: leakage coefficients increase with the increment of the rotational speed. Brush seals have obvious hysteresis under clearance fit and inconspicuous hysteresis under interference fit. The effect of wear on leakage characteristics is obvious at interference fit state. Leakage coefficients of brush seal increase with the increment of differential pressure ranging from 0.1 to 0.2MPa under clearance fit, and decrease when the differential pressure is 0.3MPa, and tend to be stable when the differential pressure exceeds 0.3MPa. Leakage coefficients of brush seal show an increasing trend with the increment of differential pressure under clearance fit, and the increasing trend slows down and leakage coefficients enter into a stable state when the differential pressure ranges from 0.3 to 0.5MPa.
Effects of outer swirl number on flow characteristics of tripleswirlers
2017, 32(2): 306-313. doi: 10.13224/j.cnki.jasp.2017.02.007
Abstract PDF(1102KB) icon902 icon504
Abstract:
The twodimensionalparticle image velocimetry (2D-PIV) planar structure was utilized to measure the flow field of different tripleswirlers under the same inlet condition, helping to analyze the effects of outer swirl number on flow characteristics. The experimental results show that: the swirl intensity of outer swirler is not the critical factor for the formation of central toroidal recirculation zone (CTRZ); the increment of CTRZ length, recirculated mass flowrate ratio, and the decrement of maximum recirculated velocity correspond to the increment of outer swirl number, as the cores of the vortexes move upward and outward; the shape of CTRZ is affected by both outer and inner swirl numbers, and an obvious CTRZ tail can be obtained for swirler with higher outer swirl number; a higher turbulence intensity of the flow generated by tripleswirlers with lower outer swirl number occurs near the swirler exit.
Design and experiment of multi spark capacitor discharge ignition system
2017, 32(2): 314-321. doi: 10.13224/j.cnki.jasp.2017.02.008
Abstract PDF(940KB) icon886 icon467
Abstract:
A multi spark discharge ignition mode with a single capacitor for a two stroke airassisted direct injection spark ignition engine fueled with diesel was proposed, and a direct current multi spark capacitor discharge ignition system was developed, in which the multi spark ignition mode was verified and ignition energies were tested. On these basis, the engine tests of cold start and low load at 3000r/min under 6℃ ambient temperature were conducted. The test results show that, applying 5 times capacitor discharge ignition is able to make a successful engine cold start, and under the low load condition, increasing the ignition times promotes the combustion in cylinder; 4 times ignition is obviously more beneficial to improve the power performance, fuel economy and emissions performance than 2 times ignition with the ignition advance angle between 10° crank angle before top dead center and 20° rank angle before top dead center ; the improvement effects gradually become small with the ignition timing angle advanced to 30° crank angle before top dead center.
Effects of asynchronous ignition phase on knock combustion of two stroke engine
2017, 32(2): 322-329. doi: 10.13224/j.cnki.jasp.2017.02.009
Abstract PDF(1063KB) icon828 icon444
Abstract:
In order to understand the impact of asynchronous ignition phase on the knock of twostroke kerosene aeropiston engine, a calculation model of the combustion chamber was established by using fire software. And the validity of the model was verified by the test data. The simulation and test results show that: at 5000r/min, full load and equivalence ratio of the mixture under 11 conditions, ignition energy at 3564mJ conditions, when one of the spark plugs ignition time is fixed at before top dead center crank angle is 29°, another ignition time is set ahead of crank angle is 1°, 3° and 5° relatively; with the increase of the phase difference of the double spark ignition, the average pressure, heat release rate and the accumulated heat release rate have decreased. The turbulent kinetic energy of the two spark plugs increases, the flame propagation velocity rises, the flame development period is shortened, and the concentration of the knock intensity is reduced gradually.
Effects of swirling flow on characteristics of water ramjet engine
2017, 32(2): 330-336. doi: 10.13224/j.cnki.jasp.2017.02.010
Abstract PDF(942KB) icon828 icon448
Abstract:
A swirlingstyle propellant water ramjet model was established on the basis of a particular model of columnstyle propellant water ramjet. The effect of swirling flow on the flow and reaction characteristics in the water ramjet was simulated by Fluent software. Turbulent flow simulation was performed using the standard kε two equation functions, and combustion reaction was calculated by finiterate/eddydissipation model. The functions were solved by implicit coupling calculation method based on the density. Results show that,adding swirling vanes and increasing the swirling angle can improve the maximum temperature, the average temperature, the outlet velocity and the specific impulse, which proves that adding swirling vanes make drastic improvements of flow and combustion reaction in the water ramjet engine, and the greater swirling angle means the better results.
Numerical research on infrared radiation characteristics of plume of engine influenced by crossflow injecting forms
2017, 32(2): 337-343. doi: 10.13224/j.cnki.jasp.2017.02.011
Abstract PDF(1035KB) icon814 icon450
Abstract:
Numerical study was done under the circumstances of the same total mass flow rate and the total temperature of inlet at 840 K to research the suppression effect of infrared radiation of plume of the engine in different kinds of crossflow injecting forms. The crossflow device was designed at the orifice of axisymmetric convergent nozzle. The injection of crossflow intensified the mixing of plume and outer air flow and thus decreased the length of hightemperature region. It is found that the mixing effect is distinctly worse than single or double oppositely injected when crossflow is circumferentially injected. At side detection plane, the suppression effect of infrared radiation of single and double opposite injecting comes very close when azimuthal angle is bigger than 20°, but the latter one is slightly better and has a maximum drop of 71.6%. At underneath detection plane, the infrared radiation intensity of single and double opposite injecting is stronger than that at side detection plane, and the latter has a close value when crossflow is circumferentially injected. At above detection plane, compared with other injecting forms, the infrared radiation intensity of single injecting is relatively weak and reaches a maximum drop of 78.4%.
Flight characteristic comparison of STS and DTSbased on mathematical model
2017, 32(2): 344-353. doi: 10.13224/j.cnki.jasp.2017.02.012
Abstract PDF(1368KB) icon763 icon486
Abstract:
A componentlevel characteristic simulation method for singlestage turbocharging reciprocating engine propeller propulsion system (STS) was studied. A regulating method of STS was proposed, the jointworking equations of STS were solved, and the altitudevelocity characteristic of STS were simulated. The flying characteristics of overall performance and each component were compared between a STS and a dualstage turbocharging reciprocating engine propeller propulsion system (DTS). Result shows that, the regulating method of STS can meet the design objectives, the full power holding altitude of STS can achieve 5.5km while that of the DTS is 12.5km. When selecting the same propeller and engine, the characteristics of each component between STS and DTS are similar, and the variation ranges of the altitude and velocity of the propulsion efficiency, specific fuel consumption, total efficiency of STS are narrower than those of the DTS.
Aerodynamic performance of propeller with two design points
2017, 32(2): 354-363. doi: 10.13224/j.cnki.jasp.2017.02.013
Abstract PDF(904KB) icon761 icon423
Abstract:
Considering the overall requirement of the propeller for a vertical takeoff and landing (VTOL) small unmanned air vehicle (SUAV), the difficulty of propeller design with two operating points was analyzed; the designed requirement of propeller performance was verified; the effect of two operating points on the propeller performance was studied; and the instructive conclusions were finally obtained. With CFX software as a tool, hovering and cruising models were calculated and compared with the results of truckmounted experiment. It showed that the propeller can meet the need and the results of simulation agree with the experiments basically with errors less than 11%. The effect of two operating points and the parameters were analyzed through comparison between the designed propeller and the propeller with single operating point. The results show that the performance reduction happens in relation to two operating points, and reducing the total weight and cruise velocity, or increasing number of propulsion and power to decrease the difference between two points can facilitate the design and reduce the performance loss.
Unsteady aerodynamic characteristic analysis of rotor airfoil under variational free stream velocity condition
2017, 32(2): 364-372. doi: 10.13224/j.cnki.jasp.2017.02.014
Abstract PDF(1203KB) icon842 icon557
Abstract:
In order to analyze the aerodynamic characteristics of airfoil under the condition of unsteady free stream velocity, the movingembedded grid method was employed to simulate the fluctuating velocity. Based on this method, the URANS(unsteady Reynoldsaveraged Navier-Stokes) equations coupling with the implicit scheme of LU-SGS(lowerupper symmetric Gauss-Seidel) was used to simulate the unsteady aerodynamic characteristics of the SC1095 airfoil under the condition of steady angle of attack with unsteady free stream velocity and under the condition of unsteady angle of attack with unsteady free stream velocity. It was discovered by comparing the calculated results that the unsteady characteristics, including hysteresis phenomenon, fluctuation and leading edge vortex induced by the unsteady free stream velocity, were observed under these conditions, and the unsteady characteristics were more obvious as the fluctuating velocity increased. By comparing the characteristics of airfoil at different basic velocities, it was found that the peaks of aerodynamic force curves enlarged as the basic velocity increased, and the unsteady vortex formed more early when the angle of attack increased. Considering the actual work environment of helicopter rotor, the aerodynamic loads of airfoil under dynamic stall were weakened at the large angle of attack and enhanced at the small angle of attack under the unsteady free stream velocity condition.
A full states performance model for aero engine
2017, 32(2): 373-381. doi: 10.13224/j.cnki.jasp.2017.02.015
Abstract PDF(920KB) icon971 icon490
Abstract:
A full states performance simulation model for aero engine was established by using the parametric representation based on the backbone characteristics of compressor and turbine. Part loading performance of a turbojet engine at sea level static condition was simulated through the model. Compared with the traditional model, results showed the average errors of the main parameters were no more than 07%, indicating the full states model had the same precision as the traditional model above idle speed. The simulations for windmill state, ground starting and acceleration to maximum power, and deceleration from maximum power to zero were performed respectively by using the full states model. The ability of simulating full states performance of engine was verified. The results are qualitatively consistent with the operative characteristics and physical laws of the engine.
Numerical simulation of twophase flow in inlet particle separator based on probabilistic bounce model
2017, 32(2): 382-389. doi: 10.13224/j.cnki.jasp.2017.02.016
Abstract PDF(1009KB) icon854 icon407
Abstract:
A probabilistic approach for the integral inlet separator particle trajectory simulations by fitting probability functions with five points Gauss-Hermite methods was presented, and its impact on particle tracking accuracy was performed as compared with deterministic particle rebound model and elastic bounce model. Results show that,the above three bounce models perform well in the prediction of separation efficiency for AC coarse sand; for Cspec sand, results based on elastic bounce model deviates from reality; the deterministic particle rebound model overpredicts the separation efficiency of Cspec sand, especially for the swirling inlet particle separator, and the probabilistic bounce model achieves an intermediate value in good agreement with experimental data.
Investigation on aerodynamic and infrared performance of a spherical convergent two-dimensional vectoring nozzle:simulating high altitude status
2017, 32(2): 390-397. doi: 10.13224/j.cnki.jasp.2017.02.017
Abstract PDF(959KB) icon958 icon514
Abstract:
A numerical investigation was performed to study the effects of pitching angle on the aerodynamic and infrared performances of a spherical convergent twodimensional vectoring nozzle under high attitude status. In the present research, the comparison with the ground status simulation was also taken into consideration. The results show that the pitch deflection has a very weak impact on the thrust coefficient and total pressure recovery coefficient of exhaust system under the pitching angle ranging from 0 degree to 20 degree. The aerodynamic vectoring angle is nearly the same as the geometric vectoring angle. The thrust coefficient and total pressure recovery coefficient of exhaust nozzle under high attitude status decrease 0.5% and 1.1%, respectively. As the total infrared radiation of exhaust system in 3-5μm band is concerned, the peak infrared radiation intensity of plume under high attitude status is only 12-24 percent of the corresponding values under ground status. For the total infrared radiation of exhaust system, the ratio of high attitude status to ground status is among 0.35 and 0.45. In general, the peak number of nozzle's infrared performance is continuously decreasing with the increase of vector angle.
Reliability analysis of engine blade under varied environment with competing risk model
2017, 32(2): 398-404. doi: 10.13224/j.cnki.jasp.2017.02.018
Abstract PDF(770KB) icon817 icon415
Abstract:
The complicated working condition results in the existence of multiple failure modes in aeroengine blade, and the failure rate of those failures is closely related with the operating environment, so, it is difficult to analyze the reliability of engine blades and control its risk. To solve the problem, firstly, based on the characteristics of wear and thermal crack failure modes commonly existing in rotor blades, the wear and thermal crack failure models with variable environment were researched, respectively. Secondly, a reliability analysis method based on competing risk model for rotor blades was proposed, and the corresponding algorithm was given. Finally, a high pressure turbine（HPT） rotor blade was analyzed and studied as an example. And the result showed that the risk was higher under single failure model compared with the competing risk model. When the competing risk model was employed in the reliability analysis, if the impact of thrust was not considered, the risk increased by 33% given the unreliability of 0.1, verifying the practicability of the proposed method.
Updating technology based on uncorrelated mode shapes
2017, 32(2): 405-415. doi: 10.13224/j.cnki.jasp.2017.02.019
Abstract PDF(1445KB) icon778 icon422
Abstract:
In order to make full use of the test measurement results, a method of FE (finite element) model updating with adoption of both correlated and uncorrelated modes for updating was put forward, and successfully applied in a certain type of modern high thrustweight ratio turbofan engine. The calculated values of the modified model were close to the test values by the correction calculation. The error was close to 0 and the MAC (model assurance criteria) value close to 1. Result showed that, the proposed method was found to successfully update an FE model yielding correct estimates of the updating parameters in the presence of uncorrelated modes, and the updated FE model had a high calculation precision.
Maximum entropy quantile estimation and dual optimization method
2017, 32(2): 416-423. doi: 10.13224/j.cnki.jasp.2017.02.020
Abstract PDF(785KB) icon837 icon428
Abstract:
Based on high nonlinearity, low computational accuracy, or hard convergence of Lagrangian calculation in the classic maximum entropy quantile function, a new method called dualsequential updating method was proposed. Dual expression of optimization function was established on the basis of Lagrangian dual approach. Further sequential updating method was proposed based on the constraint by the probability weighted moments. After analyzing several common distributions and a complex distribution by dual maximum entropy quantile function and classic maximum entropy quantile function, result showed that,dual maximum entropy quantile function had advantage of low nonlinearity and simple form, and dualsequential updating method had good computational accuracy and optimization convergence.
Behavior of fatigue life variability of nickelbased powder metallurgy superalloy FGH96 at elevated temperature
2017, 32(2): 424-428. doi: 10.13224/j.cnki.jasp.2017.02.021
Abstract PDF(780KB) icon935 icon438
Abstract:
The effects of defects on fatigue life variability of nickelbased powder metallurgy superalloy FGH96 were investigated by conducting fatigue tests in large sample case at different stress levels. The fatigue life distribution characteristics of FGH96 were obtained. The fatigue fracture analysis of all the tests by scanning electron microscopy showed: (1) the defects contributing to fatigue failure mainly were nonmetallic inclusions; (2) under higher stress levels (1200, 1100MPa), inclusion in the surface was the lifelimiting factor, resulting larger life variability; (3) in the middle stress levels (1000MPa), crack initiation in the internal inclusion did not affect the fatigue life variability; (4) under lower stress level (900MPa), fatigue crack was initiated in the internally, there were no effects of internal inclusions on fatigue life variability. Therefore, the defects need to be considered in the life prediction at higher stress level.
A life prediction method for size effects on notched fatigue
2017, 32(2): 429-437. doi: 10.13224/j.cnki.jasp.2017.02.022
Abstract PDF(785KB) icon842 icon442
Abstract:
By use of the normalized stress distribution at the notch root of a specimen, and based on a notched fatigue life prediction method with consideration of the effects of stress gradient, a life prediction method for fatigue of notched specimen was constructed by taking mean stress, stress gradient and size effect into account with focus on the influence of size effect on the fatigue life of notched specimen. The developed method was verified by use of fatigue test data of TC4 alloy notched specimen, and the prediction results were comparatively analyzed with those of several commonlyused local stressstrain approaches, indicating that those local stressstrain approaches overconservatively predicted the fatigue life of notched specimen. The developed method can predict the result more precisely with almost all the prediction results within the scatter band of 3 and more than three quarters of the results within the scatter band of 2.
Aero-thermal optimization of gas turbine blade airfoil
2017, 32(2): 438-445. doi: 10.13224/j.cnki.jasp.2017.02.023
Abstract PDF(932KB) icon800 icon384
Abstract:
A twostep optimization method was presented to improve the aerothermal characteristics of turbine blade airfoil. The first step was to construct turbine airfoil by polynomial lines. Design parameters were screened by design of experiment (DOE) and factorized sensitive analysis for best performance obtained from CFD simulations. The second step was to optimize airfoil, which was parameterized in Bezier lines for minimum flow loss and surface heat transfer in a weighted objective function. Result of design sample shows that increased stagger angle leads to lowered heat transfer along the pressure side surface, and larger leading edge radius reduces the local heat transfer around stagnation point. Reforming the polynomial shaped airfoil provides possible delay of the transition on the blade suction side surface and reduces whole heat transfer rate. Twostep method has relatively low computation requirement and good convergence, which is valuable for engineering purposes.
Numerical simulation on flow field of axial compressor after bleeding
2017, 32(2): 446-454. doi: 10.13224/j.cnki.jasp.2017.02.024
Abstract PDF(1087KB) icon755 icon389
Abstract:
By analyzing the transonic singlestage compressors NASA Stage 35, the results of numerical simulation and the experimental results were combined, proving the veracity of numerical simulation. The hole and slot bleeding were calculated by two ways, and the same results were got. At last, the results of hole bleeding and the slot were compared. Result showed that, the slot bleeding was better. The bleeding/cooling block of NUMECA software was easy to realize the bleeding, another way increased the difficulty and complexity of numerical simulation, but it agreed with the fact of bleeding on compressor. Before the bleeding, the efficiency improved, and the total pressure ratio declined little. At same time, stall margin was enhanced.
An optimal design of a turbine exhaust volute
2017, 32(2): 455-461. doi: 10.13224/j.cnki.jasp.2017.02.025
Abstract PDF(875KB) icon885 icon462
Abstract:
In order to improve the aerodynamic performance of a gas turbine exhaust volute, a collectionshell type volute was numerically studied and the source of flow losses was presented. Based on that, a flow separation layer design was put forward without changing the geometry size of the exhaust volute, and the comparisons of the effects between this design and two common methods were carried out. The numerical simulation results show that the flow separation layer design can at most decrease the total pressure loss coefficient by 3212% and increase the static pressure recovery coefficient by 48.73% on the design point; this is better than the result of adjusting arc lines of the diffusing structure, but worse than that of the wall profile modification of the collector. Accordingly, the mechanism of how the separation layer can improve the aerodynamic performance of the volute was revealed.
Effects of adverse pressure gradient on Reynolds stresses inturbulent boundary layers
LUO Xiao tian, ZHANG Ce, MA Wei, TENG Jin fang
2017, 32(2): 462-469. doi: 10.13224/j.cnki.jasp.2017.02.026
Abstract PDF(870KB) icon713 icon360
Abstract:
The effects of adverse pressure gradient (APG) on Reynolds stresses in turbulent boundary layers (TBLs) with APG were analyzed. The difficulty of this work was attributable to the Reynolds stresses in TBLs with APG under two combined effects, i.e.: effect of upstream flow and effect of APG. The effect of upstream flow is an inherent effect no matter pressure gradient exists or not. The individual effect was analyzed from absolute developments of Reynolds stresses in TBLs with zero pressure gradient (ZPG) firstly. Effect of APG was then analyzed from absolute developments of Reynolds stresses in TBLs with APG. Result showed that, for absolute development of mean streamwise Reynolds stresses, APG accelerated its development in TBL with ZPG; for absolute development of mean normal or shear Reynolds stresses, APG increased their magnitude in the outer part, and decreased their extent of large value region.
CT local reconstruction of solid rocket motor based on PI-POCS-TVM
LU Hong yi, CHEN Qing gui, ZHU Min, LI Peng, ZHAO Ru yan, WANG Bin
2017, 32(2): 470-476. doi: 10.13224/j.cnki.jasp.2017.02.027
Abstract PDF(840KB) icon741 icon414
Abstract:
In order to test the defects of solid rocket motor (SRM) accurately and efficiently, the computed tomography (CT) inspection scheme for SRM's defects was investigated and a CT local reconstruction algorithm called prior informationprojection onto convex setstotal variation minimization (PI-POCS-TVM) was developed. The SRM was first inspected by industrial CT (ICT) to generate a lowresolution SRM image used as the prior information, then highresolution local inspection was carried out for SRM's defects. To validate the effectiveness of the CT inspection scheme for SRM's defects, one SRM was inspected by a narrow fan beam ICT system. Filtered back projection (FBP) algorithm, POCS, POCS-TVM and PI-POCS-TVM algorithms were applied to reconstruct CT images. The performance of these algorithms was also compared. Results demonstrated the effectiveness of the CT inspection scheme for SRM's defects. Moreover, the PI-POCS-TVM algorithm has better local reconstruction image quality than the other three algorithms, showing great significance for accurate measurement of SRM's defects.
Underwater thrust characteristic of solid rocket motor
2017, 32(2): 477-485. doi: 10.13224/j.cnki.jasp.2017.02.028
Abstract PDF(1061KB) icon1240 icon449
Abstract:
The underwater performance characteristics of solid rocket motors (SRM) are different from those in the air as they are surrounded with high density medium water. In order to have a deep understanding into the performance characteristics of underwater SRM, the impact of the change of the flow structure on thrust was analyzed. A 2D axial symmetry model was adopted to simulate underwater SRM in different working conditions, and the figures of thrust oscillations were obtained. After analyzing the changes of thrust in different stages, the relationship of thrust peak value and neck breaking was studied, and the thrust oscillation amplitude and frequency changing with working environment were studied. The research results show that the thrust oscillation occurs due to the periodic neck breaking induced by the shock wave. In addition, as a result of the action of gas bulge and backattack, the jet thrust takes on a multistage frequency and peak value. According to the conclusion that the bulges are in the middlefrequency band, researches on the first four order frequency show that the gas bulge is related to the back attack.
Identification of flexible joint hysteresis damping characteristics
2017, 32(2): 486-491. doi: 10.13224/j.cnki.jasp.2017.02.029
Abstract PDF(715KB) icon728 icon391
Abstract:
In order to model and analyze the dynamics of flexible joint, the method of identifying flexible joint hysteresis damping characteristics was studied. The dynamic characteristics of flexible joint at different amplitudes and frequencies were tested. The elastic force and damping force at different frequency parameters were identified based on the method of variable stiffness and damping. Therefore the relationships between the frequency and stiffness coefficient and damping coefficient were discovered, and a nonlinear dynamic model of flexible joint was established. The calculated dynamic properties of the amplitude dependence for the joint with the proposed model were compared with experiment. Result shows that a good agreement is obtained and the torque increase a little with the increase of the frequency. Elastic moment is linear with the pendulum angle in the small amplitude, and it gradually becomes nonlinear with the increase of the amplitude.
Dynamic load reduction design for intershaft bearing of aircraft engine
2017, 32(2): 492-499. doi: 10.13224/j.cnki.jasp.2017.02.030
Abstract PDF(807KB) icon802 icon408
Abstract:
Based on statistics of 30 test run data of three typical intershaft bearing of aircraft engine, a principle to avoid synchronous impact was acquired. The statistics of test run data shows that it is dangerous area when integer multiple of the frequency of aerodynamic force and fault characteristic frequency of intershaft bearings are close in range of 2%,aircraft engine should not work under this state for long. Afterwards, a optimization iterative dynamics design approach for rotor with intershaft bearings was proposed. Blade number or high/low pressure rotor speeds ratio should be adjusted until the range of the dangerous area less than 10% of aircraft engines running range. The approach can reduce intershaft bearings dynamic load, let it free from synchronous impact, and eventually increase its fatigue life.
Variable predictive model based RBF class discriminate method
2017, 32(2): 500-506. doi: 10.13224/j.cnki.jasp.2017.02.031
Abstract PDF(840KB) icon762 icon378
Abstract:
Considering that the defect of four kinds of mathematical models can not reflect the complex relationship between the features in variable predictive model based class discriminate method, a variable predictive model based radial basis function (VPMRBF) method was put forward., Firstly, the abstracted features were input into VPMRBF classifier, and then the training samples were used to establish radial basis function models, which could reflect the complex relationship between features; finally, the established radial basis function prediction models were used to predict the features of those test samples, and the sum of squares prediction error could be employed as a basis for necessary classification. Experimental results of roller bearing fault diagnosis showed that the recognition rate of VPMRBF increased by 4.75%, 1.75% and 5.25% respectively, compared with the radial basis function neural network, the support vector machine and variable predictive model based class discrimination method. By making full use of and effectively combining the advantages of radial basis function and variable predictive model based class discrimination method, this realized entire diagnosis from fault feature extraction to fault identification.
Noise airworthiness assessment of turbofan aero-engine turbine
2017, 32(2): 507-512. doi: 10.13224/j.cnki.jasp.2017.02.032
Abstract PDF(691KB) icon958 icon441
Abstract:
A model for noise level assessment of turbofan engine turbine was established and a program was written by studying the mechanism of noise generation and the main influential factors of the turbine; after using the static test noise of a type of engine to verify the model established, the turbine noise assessment on airworthiness certification was carried out at different rotation speeds based on the static test noise of that engine and the airworthiness certification regulation. Result showed that, turbine noise contributed a lot to this engine total noise when the engine rotation speed was at the stage of approaching and this turbine noise airworthiness certification required that number of low pressure turbine blades of this type of engine should be less than 50 or greater than 100, and the low pressure turbine blade diameter should be less than 0.9m.

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

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