2014 Vol. 29, No. 6

Display Method:
Solving steady-state temperature fields with axial conduction in moving media using Green’s function method
ZHAO Guo-chang, DU Xia, SONG Li-ping, LI Jing
2014, (6): 1249-1260. doi: 10.13224/j.cnki.jasp.2014.06.001
Abstract:
The Green's function method for solving axial conduction effects of moving media on its steady-state temperature field was introduced. The mathematical expression describing steady-state temperature fields under first and second classes of non-homogeneous boundary conditions was derived using eigenvalues and eigenvalue functions to obtain the Green's function solutions. It was confirmed that the steady-state heat transfer problems can be solved under the non-homogeneous boundary conditions by employing Green's function method. The heat transfer of the moving media between two parallel plates and within a circular tube was calculated under uniform heat flux conditions for semi-infinite and finite lengths and the analytical dimensionless temperature solutions were obtained. The relationship between the axial conduction effects of moving media and the Pe and x/H was also analyzed. The results show that: the larger Pe means the smaller dimensionless temperature for both cases of uniform heat flux conditions of semi-infinite and limited lengths; more intense temperature changes in the absence of surface heat flux and more mild temperature changes for the case of uniform wall heat flux of semi-infinite length are observed; in the case of limited length under uniform heat flux condition, significant differences compared with the case of uniform heating in semi-infinite region and more dramatic temperature changes in the whole computational domain are observed.
Thermal protection performances of metallic honeycomb panel structure at transient thermal shock environment
WU Da-fang, ZHOU An-feng, ZHENG Li-ming, PAN Bing, WANG Yue-wu
2014, (6): 1261-1271. doi: 10.13224/j.cnki.jasp.2014.06.002
Abstract:
By using a self-developed transient aerodynamic thermal simulation system of high-speed aircraft, the heat-shielding performance of metallic honeycomb panel structure was tested at different transient thermal shock rates ranging from 5℃/s to 30℃/s, with the maximum instantaneous temperature reaching 950℃. Furthermore, a three-dimensional finite element method was established to determine the heat-shielding performance of the metallic honeycomb panel structure at different simulation environments with high thermal shock rates. The numerical calculation results coincide with the corresponding experimental results, verifying the credibility and effectiveness of the experimental methods and the numerical calculation approach. The tested metallic honeycomb panel structure exhibited slight planar flexure and deformation after the experiment in the high-temperature (950℃) environment; thus, in the context of high-speed flight vehicles, this structure is particularly suitable for structural components that must be made of lightweight materials with slight deformation in a high-temperature environment.
Cooling performance and comparison of impingement/effusion cooling lamilloy used as heat shield
LIU You-hong, LI Ying, YANG Xu
2014, (6): 1272-1278. doi: 10.13224/j.cnki.jasp.2014.06.003
Abstract:
In order to study the cooling performance of impingement/effusion cooling lamilloy contrastively and demonstrate the possibility of using impingement/effusion cooling lamilloy as heat shield in afterburner, a series of three-dimensional numerical simulations using fluid/solid conjugated computation method of heat transfer were conducted under three different total pressure ratio of the primary fluid to the secondary fluid conditions, and contrastive studies were carried out with both a type of corrugated heat shield and a single flat plate heat shield. Contrastive results of cooling performance, coolant consumption, coolant heat load and total pressure loss coefficient of the secondary flow were acquired. The results show that impingement/effusion cooling lamilloy has good cooling performance, but it is most affected by the change of total pressure ratio. Compared with conventional corrugated heat shield, the coolant consumption of impingement/effusion cooling lamilloy decreases by 41.6% averagely, and the coolant heat load decreases by 65.9% averagely.
Experiment on effects of mainstream turbulence intensity on film cooling characteristics of turbine vane
ZHOU Zhi-xiang, LIU Cun-liang, ZHANG Zong-wei, ZHU Hui-ren, HE Yi-hong
2014, (6): 1279-1286. doi: 10.13224/j.cnki.jasp.2014.06.004
Abstract:
The effect rules of mainstream turbulence intensity on film cooling characteristics of cylindrical holes on the suction side of turbine vane were studied using the transient heat transfer measurement technique with narrow-band thermochromic liquid crystal in the whole region. The results show that the mainstream turbulence intensity increase from 0.59% to 6.85% in experimental conditions can make film sticking the wall and expand the lateral coverage area in the upstream region to improve the film coverage performance. But when the mainstream turbulence intensity is very large, the film cooling performance will rapidly deteriorate. In the downstream region of film injection, film cooling efficiency decreases gradually with the mainstream turbulence intensity increasing. Heat transfer on the smooth vane surface without film cooling can be enhanced by increasing the mainstream turbulence intensity. Under the conditions with film cooling, the effects of the heat transfer enhancement of vane surface caused by the film injection have distinctive regional characteristics with the mainstream turbulence intensity increasing. The heat transfer coefficient ratio firstly increases and then decreases in the upstream region, gradually decreases in the midstream region, and slightly increases in the downstream region.
Application of reduced chemical kinetic model for ethylene combustion in combustor calculation of HIFiRE
XIAO Bao-guo, ZHAO Hui-yong, YANG Shun-hua, XING Jian-wen
2014, (6): 1287-1294. doi: 10.13224/j.cnki.jasp.2014.06.005
Abstract:
In order to assess the influence of chemical kinetic models on the computational results of scramjet, a software package for reduced chemical kinetics (SPARCK) was used based on quasi-stationary state approximation and specifically developed for chemical reaction kinetics reduction, and a reduced chemical kinetic model with 20 species and 16 global reactions was achieved by reducing the detailed chemical kinetic model for ethylene combustion. Then, the ignition delay time of ethylene was calculated with the reduced model and another reduced model generated by Princeton University. The computational results showed two reduced models almost had the same ignition delay time, and achieved a good agreement with experimental results. Both models can describe the ignition characteristic of ethylene. The Hypersonic International Flight Research Experimentation (HIFiRE) direct-connect test was numerically simulated using two reduced chemical kinetic models. The computational results showed two reduced chemical kinetic models had big difference in the static temperature of combustor, with nearly 12% relative error in the flowpath thrust. The reduced model, obtained by SPARCK, showed better agreement with experimental data for wall pressure distribution, as compared with the Princeton University model, and could simulate accurately combustion phenomena in scramjet combustor.
Combustion performances of lean direct injection model combustor with three injectors
ZENG Qing-hua, KONG Wen-jun, AI Yu-hua, WANG Bao-rui
2014, (6): 1295-1300. doi: 10.13224/j.cnki.jasp.2014.06.006
Abstract:
A rectangular model combustor with three counter dual-swirl Venturi-premix (CDV) injectors was designed and its combustion characteristics and performances were also investigated. The results showed that, the combustion flames were blue, which were very similar to those of lean premixed gaseous combustion. And in the above-mentioned working condition, CO and NOx emission volume fraction converted to 15 percent oxygen were less than 10×10-6 and 50×10-6 respectively. In addition, the effect of inlet air temperature change on pollutant emissions of these three CDV injectors was also investigated. It was found that the CO emission concentration was more affected by the change of inlet air temperatures than that of NOx. And the reason about above-specified phenomenon was analyzed and revealed. Moreover, the study showed that, atomizer's performances greatly influenced the characteristics of lean direct injection combustion flames. Processing technology of the fuel atomizers should be improved to ensure long-term stability of their atomization performances.
Influence of turbine stator blade profiles and film cooling holes optimization on the aerodynamic and cooling performances
LU Shao-peng, CHI Zhong-ran, WANG Long-fei, CAI Le, WANG Song-tao, FENG Guo-tai, WANG Zhong-qi
2014, (6): 1301-1311. doi: 10.13224/j.cnki.jasp.2014.06.007
Abstract:
To study the influence of blade profiles and film cooling holes' parameter changes on the performance of the turbine blade, a blade stator with multi-row film cooling holes was optimized by multi-objective optimization algorithm to get the Pareto set; the overall performance of the blade was improved. The maximum aerodynamic efficiency increased by 0.35%; the maximum wall average temperature decrease was 0.74%; the maximum decrease of the high temperature function was 45.71%. The result shows that the increase of the backward curved angle can reduce the blade loss and second flow loss. The cooling effect improvement of the region near the leading edge is mainly due to the direction change of the film cooling holes near the leading edge stagnation point, as the direction change makes the cooling gas distribution reasonable.
Numerical study of influences of primary jets on turbulent flows and spray combustion in model combustor
XU Rong, ZHAO Jian-xing, WANG Suo-fang
2014, (6): 1312-1322. doi: 10.13224/j.cnki.jasp.2014.06.008
Abstract:
The influences of different primary jets on turbulent flows and spray combustion of a dual swirl model combustor were numerically studied. The three-dimensional block-structured grids were generated by the differential equation method and sub-regional method for a model combustor including a dump diffuser, cowl, dual-stage axial swirler, flame tube as well as outer and inner annuluses. In arbitrary curvilinear coordinates, a multi-zone coupling approach was used for model combustor flow field numerical investigation. RNG (re-normalization group) k-ε model and EBU (eddy break-up) turbulent combustion model were employed for turbulent combustion. The particle trajectory model was applied to simulating two-phase flows. Comparisons between predicted and experimental data show that simulation is appropriate for predicting turbulent cold and combustion flow field. The influences of different primary hole structure parameters on gas temperature distributions are more obvious than the size of recirculation zone and profiles of velocity, and profile of exit temperature of the primary hole Ⅱ is more rational than those of other primary holes.
Numerical investigation on effects of ambient and injection parameters on supercritical injection
JIN Le, FAN Wei, FAN Zhen-cen, ZHOU Zhou
2014, (6): 1323-1329. doi: 10.13224/j.cnki.jasp.2014.06.009
Abstract:
Based on the PR(Peng-Robinson) equation of state, two-dimensional axisymmetric governing equation of two-phase flow was introduced to establish a numerical model of supercritical injection by employing the mixing rule described in relevant references. And preconditioning method was used for solving, while n-decane was used as an alternative of liquid hydrocarbon fuel to investigate the supercritical injection characteristics in a quiescent supercritical nitrogen chamber. The jet length and jet spreading angle affected by ambient and injection parameters were separately analyzed. This demonstrates that jet length and jet spreading angle decrease with the increasing ambient pressure, but increase with the increasing ambient and injection temperature. The sensitivity of supercritical jet length affected by ambient and injection parameters is higher than jet spreading angle. It is deemed that the injection density ratio and injection momentum are two main influential factors to the supercritical injection, and the injection momentum is considered to be the dominant factor.
Effect of partial blockage inside film hole on film cooling characteristics
HUANG Ke-nan, ZHANG Jing-zhou, GUO Wen
2014, (6): 1330-1338. doi: 10.13224/j.cnki.jasp.2014.06.010
Abstract:
Numerical investigations were performed to study the effects of partial blockage inside discrete holes on coolant jet flow and film cooling characteristics over a flat plate from a row of inclined holes, under the blowing ratios of 0.3-1.5 and blockage ratios of 0.1-0.5. The influences of blockage ratio, blockage position and blowing ratio on adiabatic film cooling effectiveness were revealed. The results in parameter range show that the partial blockage located at the leading edge near film jet exit is beneficial for suppressing the motion of kidney vortex pair, resulting in enhancement of the adiabatic film cooling effectiveness, especially under higher blowing ratio and higher blockage ratio cases. The partial blockage located at the trailing or lateral edges near the film jet exit weaken the adiabatic film cooling effectiveness under higher blockage ratio cases. Compared to the corresponding case of partial blockage located near the film jet exit, the partial blockage located at the film jet inlet or middle position has less impact on the film cooling.
Numerical simulation of icing accretion and influence on three-dimensional wing configuration
LU Tian, SANG Wei-min, LIU Xiao-yu, XI Chao
2014, (6): 1339-1345. doi: 10.13224/j.cnki.jasp.2014.06.011
Abstract:
The structured grid was used to numerically simulate the icing accretion of M6 wing and wing-body-tail configuration to get the icing process and influence under icing weather conditions. Euler two-plase flow methods was used to solve droplets impingement characteristics for the simulation of icing process. Thermodynamic model of icing growth was based on the Messinger model. Then, it was researched that the droplet impingment, shape of the iced wing and the influence on aerodynamic characteristics. The result showed the mass of icing increased with the spanwise chord reduction, especially for high-aspect-ratio wing. Moreover, the front of fuselage was also vulnerable to serious icing.
Radial distribution and formation mechanism of thevoid fraction in an inclined circular tube
LIU Guo-qiang, SUN Li-cheng, YAN Chang-qi, TIAN Dao-gui
2014, (6): 1346-1351. doi: 10.13224/j.cnki.jasp.2014.06.012
Abstract:
Void fraction radial distribution of gas-liquid two phase flow in an inclined circular tube was investigated experimentally by using an optical fiber probe, and the reason for its formation was also illustrated. Experiments were conducted in an inclined circular tube made of perspex with inner diameter of 50 mm, and inclination angles of 5°, 15° and 30°. The specific liquid velocity was 0.071~0.284m/s and the specific gas velocity covered the range of 0~0.5m/s. The results show that, with increase of the inclined angle, the radial distribution of void fraction gradually shifts from the ‘core peak’ and ‘wall peak’ to the single ‘wall peak’ distribution. The analysis of the buoyancy component in radius and lateral lift forces as well as wall force acting on bubbles shows that the combined effects of these forces lead to the bubbles gathering around the radial position between 15 mm and 22 mm, resulting in the ‘wall peak’ distribution of the void fraction.
Experiment of ice accrection and shedding on rotating spinner
WANG Jian, HU Ya-ping, JI Hong-hu, CHEN Ning-li, CAO Guang-zhou
2014, (6): 1352-1357. doi: 10.13224/j.cnki.jasp.2014.06.013
Abstract:
The ice accretion on the rotating spinner was tested in the icing wind tunnel. The main portion of the icing equipment was installed in the test section of the icing wind tunnel, driven by the external portion with strap. The ice accrection characteristics on the rotating spinner were obtained through icing test under typical icing conditions. The test results showed that at the beginning, the ice accrection was relatively slow, resulting in evenly distributed glaze ice on the spinner surface. And then, the glaze ice was discontinuously covered with white rime ice like ‘feather’ and grew rapidly. Finally, a majority of the ‘feather’ shaped rime ice shed from the icing surface of the rotating spinner.
Effect of restricted domain and premixed gas initial temperature on the flame blow-out performance of surface flame on porous media surface
ZHANG Long, XU Quan-hong, ZHANG Chi, LIN Pei-hua, LIN Yu-zhen
2014, (6): 1358-1362. doi: 10.13224/j.cnki.jasp.2014.06.014
Abstract:
To optimize a micro combustor based on porous media dome, the influences of the restricted domain and initial temperature of premixed gas on the blow-out performance of surface flame on porous media surface were investigated experimentally. The premixed gas of methane and air was experimental subject. The results show that with the quartz glass restricted domain, surface flame on porous media surface can only be maintained when the speed of the premixed gas is low (0.188-0.436m/s). It is easier to be blown out when the speed of premixed gas is increasing. However, restricted domains with different lengths produce no differences. When the premixed gas initial temperature increases from 293K to 550K, the blow-out velocity of surface flame on porous media surface becomes higher. When the equivalence ratio equals 1.0, the blow-out velocity of initial premixed gas increased from 1.176m/s (293K) to 2.678m/s (550K). There are two rising processes with different slopes. In this condition, initial temperature of premixed gas doesn't yield essentially impact on the blow-out performance.
Self-calibration Kalman filter method
FU Hui-min, WU Yun-zhang, LOU Tai-shan, XIAO Qiang
2014, (6): 1363-1368. doi: 10.13224/j.cnki.jasp.2014.06.015
Abstract:
A self-calibration Kalman filter(SKF)method, whose model and recursive algorithm were established, was presented. In most practical cases, such as deep space exploration and engine fault diagnosis, because of the effect of unknown inputs, such as gust, fault and unknown system error, the well-known Kalman filter will lead to greater filtering error in recursive process. To solve this problem, the proposed SKF, which is applied to estimate and compensate the unknown inputs, efficiently reduces the effect of the unknown inputs and enhances filtering accuracy. For some spacecraft navigation simulation, the mean and variance of estimated state errors by SKF decreased by at least 400% and 300%, respectively. The SKF method can be effective to improve the performance of filter, simple to calculate and easy to apply in engineering.
Multidisciplinary design optimization of aero-engine turbine flow path in preliminary design phase
SHEN Xiu-li, LONG Dan, DONG Xiao-lin
2014, (6): 1369-1375. doi: 10.13224/j.cnki.jasp.2014.06.016
Abstract:
In the preliminary design phase of aero-engine turbine, the turbine flow path was designed. The complex constraining and balanced relations between aerodynamic performance and turbine blade and disc strength were synthetically analyzed to establish turbine multidisciplinary optimization system of flow path design and turbine strength calculation, and to achieve the multidisciplinary design optimization of turbine flow path, with efficiency and structural weight as design targets. The maximum value of radial stress and circumferential stress are respectively decreased by 4.62% and 10.63%,the mean value of radial stress and circumferential stress in dangerous area are also decreased by 42.99% and 3%,and the turbine comprehensive performance in aerodynamic and structural strength are improved by 3.41% after optimization.
Analysis and design of platform damper construction for high pressure turbine blade
WU Xiang-yu, HAN Xu-jun, ZHANG Hai-yang, WANG Jing, LUAN Xu
2014, (6): 1376-1381. doi: 10.13224/j.cnki.jasp.2014.06.017
Abstract:
Analyzed the damping effect of a real engine's platform damper structure of high pressure turbine blade (HPTB) through calculation and experiment, experimental results show that with the increase of positive pressure, damping ratio increase at first, then reduce, and then fluctuate within a certain range, peak of the damping ratio occurs between 100-280N. Calculated positive pressure under the condition of first order bending resonance is 123-158N, damping effect consist with experimental results. Classified the platform damper structures commonly used and compared their advantages and disadvantages.Improved the damper mass about 30% by increased thickness of the damping sheet, when excitation force is 1%, 3% and 5% mass of aerodynamic force, a reduction of vibration response is 31%, 21% and 16%.
Mechanism motion reliability calculation method considering correlative multi-failure modes
LI Chang, XUAN Cheng-ming, HAN Xing, SONG Hua
2014, (6): 1382-1387. doi: 10.13224/j.cnki.jasp.2014.06.018
Abstract:
There exists inevitably correlative multi-failure modes in a mechanism motion process; in most cases, they were described as random error functions. In order to analyze effectively these influences of correlative multi-failure modes on mechanism motion, a motion reliability calculation model was built by taking these multi-failure modes into account, and then the mechanism reliability results could be solved by this model. Taking type 6408 ball bearing as an example, the motion reliability value was 95.9989% after 100000 times sampling calculations. It showed that this method has high accuracy and is helpful to the theroretical research and practical applications.
Low cycle fatigue test of rotating disc under axial loading
LIU Da-cheng, HUANG Fu-zeng, LIU Chuang, HUO Cheng-min, LIU Hai
2014, (6): 1388-1394. doi: 10.13224/j.cnki.jasp.2014.06.019
Abstract:
In order to meet the outfield service requirement of the engine assembled in a aircraft, the research was conducted on low cycle fatigue test of aero-engine disc based on traditional safety life method. The stress state of disc under engine working conditions was calculated using finite element method, while the critical positions and the corresponding standard cycle were confirmed with failure analysis. According to the feature that the disc's stress state was affected by axial loading, the test parameters were confirmed through analogy, and the test rig was designed to apply axial loading to the disc under rotating condition. The research shows: the critical position of the disc is not only related to stress level, but also depends on structure and failure mode. Test design needs to consider the impact on the stress state by axial loading. By adjusting the amount of oil, the test rig can control the axial loading and meet the requirement of various tests with different parameters for the new disc and the used one after outfield service.
Reduced order computational method for analysis of mistuning bladed disk dynamics characteristic
WANG Pei-yi, LI Lin
2014, (6): 1395-1402. doi: 10.13224/j.cnki.jasp.2014.06.020
Abstract:
A reduced order method was proposed to analyze the dynamics characteristic of mistuning bladed disks. Based on cyclic symmetry and harmonic balance method, a non-linear iteration equation was formed, of which the matrix scale was the same to the matrix size of a single sector and was solved without any truncate error, consequently its efficiency was higher than the component mode synthesis method without losing any accuracy. The mathematical deduction was given based on cyclic periodicity theory. Furthermore, the efficiency and accuracy of this method were investigated by performing a numerical study on a finite element model of mistuning bladed disk. The results show that, compared with component mode synthesis method,the matrix size of the method proposed is reduced by 59.5%, the computational complexity is lowered by 93.4%, the computational time is saved by 57.4%.
Estimation method for fatigue life under multi-axial random loading
WU Zhi-rong, HU Xu-teng, SONG Ying-dong
2014, (6): 1403-1409. doi: 10.13224/j.cnki.jasp.2014.06.021
Abstract:
An estimation method for fatigue life under multi-axial random loading was proposed.Firstly the rain-flow counting method was used to identify shear strain cycles on each plane.The shear strain cycles were taken as a main control parameter of multi-axial fatigue damage.Then the maximum normal stress and normal strain range within each shear strain cycle were calculated as the second damage control parameter.The damage of each plane was calculated by multi-axial fatigue life model and the critical plane was identified as the plane with the maximum damage.The fatigue life was determined using the damage associated with the plane.The method for fatigue life under multi-axial random loading was evaluated and validated by the multi-axial random fatigue test datum of SNCM630 steel,304 stainless steel and S45C steel.The multi-axial random fatigue life prediction results of these materials are almost within a factor of two scatter band of the test results.
Analysis on the system bifurcation and coexistence of multiple solutions for typical airfoil section with freeplay
YIN Lei-lei, ZHANG Si-jin, WEN Gui-lin, XU Hui-dong
2014, (6): 1410-1416. doi: 10.13224/j.cnki.jasp.2014.06.022
Abstract:
The typical airfoil section system with freeplay described by a piecewise-stiffness model was studied. The pitch angle at the maximum amplitude was chosen as the quasi-Poincaré sections to obtain numerically the bifurcation diagram with change of flight speed. It was found the trans-critical flutter area was located on flight speed of Ma=0.71-0.75 and limit cycle oscillation area located on flight speed of Ma=0.75-0.95 based on the bifurcation diagram. The stability of limit cycle oscillation was analyzed through the constructed four-dimensional map. According to the stability and motion manifold theory, it was learnt that the attraction basin of the limit cycle oscillation was located in the interior region of limit cycle, which was validated by the numerical method at last. At the same time, the coexistence of multiple solutions and various forms of bifurcation phenomena were found in trans-critical flutter area, such as the direct transition from double periodic motion to chaos, the coexistence of multiple periodic motion and double periodic motion, and the phenomenon of jump on amplitude.
Geometric configuration on the performance of counterflow thrust vectoring nozzle
LIU Zhao-miao, XU Ying-li, SHEN Feng
2014, (6): 1417-1425. doi: 10.13224/j.cnki.jasp.2014.06.023
Abstract:
Numerical simulation was applied to study internal flow structure and performance of counterflow thrust vectoring nozzle with geometric configuration. Results indicate that thrust vectoring angle increased with the increasing of slot height and terminal angle when the jet was not attached to the collar, while resultant thrust ratio decreased. Suction second flow shifted from coflow to counterflow, while the mass flow rate increased. The thrust vectoring angle decreased with the increase of terminal angle; resultant thrust ratio firstly increased but then decreased. During the procedure of increasing terminal angle, suction second flow shifted from counterflow to coflow, and mass flow rate was less than 2%, but decreased and then increased.
Experiment on plasma body force of SDBD
TIAN Xi-hui, ZHOU Peng-hui, NIE Wan-sheng, LI Xiao-nan, CHE Xue-ke, HOU Zhi-yong
2014, (6): 1426-1433. doi: 10.13224/j.cnki.jasp.2014.06.024
Abstract:
Particle image velocimetry (PIV) technology was applied to obtain the flow field induced by high frequency and high voltage SDBD plasma aerodynamic actuation at pressures of 2200,4800,7300,14600Pa. The body force was calculated though N-S equation based on the velocity field, and the effects of air pressure and voltage on the plasma body force were analysed. Experiments showed that: at the same air pressure, the body force increased at a higher voltage, while at the same voltage, the body force decreased at a higher air pressure. The body force direction lines are consistent at the body force distribution region, and comparatively large body force area is located at the upstream region of the body force direction lines and comparatively fast velocity area is located at the downstream region of the body force direction lines.
Effect of geometric parameters of rotor on hovering performance of coaxial rotor
WANG Qiang, CHEN Ming, WANG Bao-bing, SU Bing-bing
2014, (6): 1434-1443. doi: 10.13224/j.cnki.jasp.2014.06.025
Abstract:
To study the effect of geometric parameter on hovering performance of coaxial rotor, the aerodynamic model of coaxial rotor based on free-wake method and second-order lifting-line theory was established, the performance with the rotor's airfoil, the ratio of the upper rotor's radius to the lower rotor's radius, the vertical separation of the rotor, the blade twist angle, and the rotor taper was calculated and analyzed, the comprehensive optimized rotor's geometric parameter was selected and analyzed in hovering based on the upper result at last. The results show that influences of the rotor's airfoil, the ratio of the upper rotor's radius to the lower rotor's radius, the blade twist angle, and the rotor taper are great, while there is almost no influence of the vertical separation on the hovering performance. The tension coefficient of 0.01 of the comprehensive optimized rotor can be reduced by 10.5% and the figure of merit can be increased by 9.5% comparing with the basic rotor.
Development of inverse characteristic method for matching design of high-speed aircraft forebody/inlet
QIAO Wen-you, HUANG Guo-ping, XIA Chen, WANG Ming-sheng
2014, (6): 1444-1452. doi: 10.13224/j.cnki.jasp.2014.06.026
Abstract:
In order to solve the problems of robustness and accuracy for the given shock's aerodynamic surface, a kind of inverse characteristic method was developed. This method could be used to generate the aerodynamic surface and dependent domain flow field for the given shock wave in a non-uniform upstream. Numerical verification indicated that the relative error of the cone shape (cone angle) gotten by inverse characteristic method was less than 0.5 ‰,when the conical shock was given at Mach number of 5; the calculations of two-stage axisymmetric shock showed that the two-stage compression cone corresponding to the flow field could be accurately acquired. Finally, three aerodynamic models were obtained with use of the method, including: Bump surface with two-stage shock wave and waverider forebody at Mach number of 4 and the integration of the wave precursor and inlet. The CFD calculation results show that these models are better designed and the inverse characteristic method proposed provides a way for aerodynamic design.
Performance calculation and analysis of intercooled recuperated aero-engine
GONG Hao, WANG Zhan-xue, KANG Yong, HUANG Hong-chao, LI Gang-tuan
2014, (6): 1453-1461. doi: 10.13224/j.cnki.jasp.2014.06.027
Abstract:
In combination with intercooler, recuperator and intercooler duct model, an intercooled recuperated aero-engine(IRA) performance simulation methodology was developed based on conventional cycle two-spool unmixed flow high bypass ratio turbofan engine model. And an IRA performance calculation program was compiled. The characteristics of the IRA with separate intercooler duct exhaust were calculated and analyzed for the altitude velocity and throttling. The results indicate that, heat exchange process of the recuperator can always take place and IRA can operate normally in the flight envelope. In different conditions, the net thrust of the IRA is close to or higher than that of the conventional turbofan engine, while the specific fuel consumption of the IRA is reduced by 9% to 20%.
Suppression of vortex shedding around main circular cylinder by another small control cylinder using immersed boundary method
SONG Li-wei, WU Song-ping
2014, (6): 1462-1467. doi: 10.13224/j.cnki.jasp.2014.06.028
Abstract:
Based on the immersed boundary method, the suppression of vortex shedding around a main circular cylinder by another small control cylinder was numerically studied. The flow was computed on non-body conformal Cartesian grid, which was suitable for problems with complex boundaries. The discrete forcing direct boundary condition imposition could impose boundary condition on immersed boundary accurately. An implicit fractional step method on collocated grid was used to solve the two-dimensional unsteady incompressible Navier-Stokes equations, and improve its computational efficiency by decoupling of velocity and pressure. The numerical simulations included the flow over a cylinder and the flow interference between a main circular cylinder and another small control cylinder located at two different positions. From analysis on the vortex structure of flow fields and the lift and drag coefficients, the delay and complete suppression of vortex shedding behind the main circular cylinder was found. All the calculated results agreed well with the previous experiment and numerical results, with the error not exceeding 5%. This indicates the immersed boundary method could be simply and efficiently used for numerical simulation on suppression of vortex shedding.
Influence of tip clearance and propeller separation space onaerodynamic performance of ducted propeller
SU Yun-de, YE Zheng-yin, XU He-yong
2014, (6): 1468-1475. doi: 10.13224/j.cnki.jasp.2014.06.029
Abstract:
The aerodynamics of flow field around the ducted propeller system in hover was simulated to investigate the influence of tip clearance and propeller separation space on aerodynamic performance individually around the unsteady Euler equations with unstructured sliding mesh technique. The tip clearance ratio varied between 0 and 1.37%, and the propeller separation space range was 0.25-0.65 times of propeller radius. The investigation shows that increasing tip clearance leads to decrease in total trust and power loading of ducted propeller. The critical tip clearance ratio is about 1.10%. The magnitude of leakage vortices increases dramatically at the critical tip clearance, causing significant change of the thrust sharing ratio between duct and propeller; the proportion of duct thrust to total trust decreases by 10.27%, and system aerodynamic performance worsens rapidly. The unsteady characteristic of tip clearance flow appears at large tip clearance ratio. Increasing propeller separation space can improve aerodynamic efficiency of ducted coaxial propeller. However, the influence is denotable as the relative variation in aerodynamic force is within 3%, due to the diffusion effect of duct on propeller slipstream.
Three-dimensional blade optimization considering effect of stator seal leakage on end-wall in compressor
HE Liu, JIANG Hong-de
2014, (6): 1476-1481. doi: 10.13224/j.cnki.jasp.2014.06.030
Abstract:
Considering the negative effect of the leakage of the labyrinth seal gap close to the stator root on the end-wall in the compressor, a two-stage axial compressor of the stator seal structure was chosen as the research subject. Genetic algorithm (GA) was applied to conduct numerical aerodynamic optimization of this two-stage axial compressor. The optimization variables included the stagger angles and the leading-edge angles of the airfoils close to the hub of the rear-stage stator, and the optimization object was to achieve the maximum isentropic efficiency of the two-stage axial compressor. After the optimization, the isentropic efficiency of the two-stage axial compressor in the design point increased by 0.2 percentage points, and the rear-stage stator obviously showed the end-bend blading close to the hub. The main reason for the improvement of the two-stage axial compressor performance is that after the root airfoils of the rear-stage stator have been modified by the optimization, the incidences of the upstream flow close to the end-wall are located close to the optimal design incidences of these airfoils.
Mechanism of effect of leading-edge geometry on theturbine blade cascade loss
BAI Tao, ZOU Zheng-ping, ZHANG Wei-hao, ZHOU Kun, LIU Huo-xing
2014, (6): 1482-1489. doi: 10.13224/j.cnki.jasp.2014.06.031
Abstract:
A research on the flow field around leading-edges of different geometries at design and off design incidence was done. It is found that the elliptical leading-edge exhibits better performance, since the elliptical edge can not only depress the pressure spike to successfully avoid the presence of separation bubble near the leading-edge in wide range of working condition, but also keep the boundary layer almost unchanged small in wide range of incidence. When the positive incidence is large, the separation bubble will emerge at the leading-edge of different shapes, inducing the boundary layer transition, however, the research shows that the elliptical leading-edge will bring about the boundary layer transition at larger incidence. The elliptic leading-edge blade decreased about 7% of profile loss compared to baseline blade profile at the insidence of 20°. The increase of the inlet turbulence intensity could depress but not completely suppress the separation bubble at leading-edge.
Mechanism of self-excited vibration and dynamic stability for pneumatic valves
WANG Jian-zhong, CHEN Er-feng, YU Wu-jiang, YE Chao, SONG Bi-feng
2014, (6): 1490-1497. doi: 10.13224/j.cnki.jasp.2014.06.032
Abstract:
Based on the disturbance response characteristics of spring oscillator, the mechanism of pneumatic valves' self-excited vibration due to fluid-structure interaction was developed. Moreover, adopted small signal stability analysis theory, the dynamic mathematics model and stability analysis model for a check valve were constructed, and the critical stable curve and the parameter impact rule of the check valve were obtained by solving the characteristics root of the linear equations. The validation of stability analysis model was preformed by the pneumatic experiment of a check valve.The results indicate that there is a critical stability curve of pressure and mass flow, and the critical mass flow is one-to-one corresponding to the working pressure. If the mass flow is less than the critical mass flow at a constant working pressure, the check valve become unstable which causes the cyclical motion of the spool excited by a very small distribution; otherwise, the check valve is stable and keeping a fixed opening. Moreover, increasing the damp coefficient and the inlet diameter or decreasing the spring stiffness partly enlarge the stable region, which can be used for the optimum design of check valve.
Turbo-fan engine fault diagnosis based on adaptive particle filtering
HUANG Jin-quan, FENG Min, LU Feng
2014, (6): 1498-1504. doi: 10.13224/j.cnki.jasp.2014.06.033
Abstract:
An adaptive particle filter was proposed for the gas path component abrupt fault diagnosis of turbo-fan engine characterized by a nonlinear non-Gaussian system. In order to reduce the computational burden and ensure the filtering accuracy, the relation between the filtering accuracy and the sampling number was analyzed. The number of particles was adjusted in the filtering process according to the variance of the state variables. The proposed method could reduce the number of particles in the filtering process and computation time while guaranteed the filtering accuracy. The extended Kalman filter (EKF) was introduced to update the particles and generate the importance probability density function helping to avoid the particle degeneracy to some extent. A series of simulations on a turbo-fan engine indicates that the root mean square error of the improved particle filter for the turbo-fan engine fault diagnosis is reduced by 50% than the conventional particle filter, and the computational burden is also reduced by 30%.