2019 Vol. 34, No. 11

Display Method:
Wind tunnel test of aerodynamic characteristics and parametric variation for rotor in vortex ring state
HUANG Mingqi, WANG Liangquan, HE Long
2019, 34(11): 2305-2315. doi: 10.13224/j.cnki.jasp.2019.11.001
In order to investigate the flowfield and aerodynamic characteristics of rotor in descent and vortex ring state, a BO-105 model rotor with tip Mach number similarity was tested in Φ5m vertical wind tunnel of China Aerodynamics Research and Development Center. Flowfields around blade tip in hover and descent flight were captured, and variations of rotor thrust and torque were obtained. The process of vorticity accumulation with the increase of rotor descent rate was observed through application of high speed PIV(particle image velocimetry) camera. When vertical descent rate was 0.9, rotor thrust and torque were at the lowestlevel, and the value was only 60% and 80%, respectively, of that in hovering state. The formation and break down of large scale vortex structure were observed in deep vortex ring state. Violent fluctuation of rotor thrust and torque in vortex ring state was caused by this phenomenon. Oblique descent had less thrust and torque loss than vertical descent. Aerodynamic characteristics of parabolic blade tip were similar with those of conventional rectangular blade tip in vertical descent.
Kinematics and dynamics simulation of thrust reverser
CHEN Yongqin, HE Jie, SU Sanmai
2019, 34(11): 2316-2323. doi: 10.13224/j.cnki.jasp.2019.11.002
In order to study the kinematics and dynamics characteristics of cascade type thrust reverser, the mechanism was simplified and the kinematics and dynamics mathematical model of thrust reverser was established according to the motion principle. Taking displacement of translating sleeve and pneumatic load of blocker door as the input, the displacement, velocity and force characteristic of thrust reverser were simulated, and the trajectory of feature points and the thrust everser load force under different size parameters were comparatively analyzed. The results showed that: the kinematics and dynamics simulation results were in conformity with the real working process. When the mechanism parameters of thrustreverser were selected unreasonably, the interference phenomenon occurred between components.The change of components parameters had a remarkable influence on the maximum load force; when the length of the AC segment of blocker door increased by 6% and the CB segment decreased by 9%, the positive maximum load force increased by 19.53% and the negative maximum load force increased by 12.67%. The model and research results can provide a reference for the kinematics and dynamics analysis and optimization design of the thrust reverser tructure.
Six-component stand design and vector thrust positioning
ZHANG You, ZHANG Binshan, WU Feng
2019, 34(11): 2324-2330. doi: 10.13224/j.cnki.jasp.2019.11.003
Based on the screw theory, some basic design principles of six-component thrust stand were described to ensure its effectiveness. This proved that it was improper mathematically to predict the vector thrust by multiplying the inverse static mapping matrix with the reading of sensors, and only three forces and three moments of the vector thrust can be obtained, but the action point cannot be accurately positioned. In order to find the action point, an experimental method denoted as circular deflection method was proposed, at least three tests about thrusts of same axial angle and different direction angles were needed.Finally, the validity of the proposed method was verified by examples. The numerical result showed that the weights of the engine and the floating frame seriously affected the positioning of action point, so the gravity influence must be eliminated before using this method.
Numerical simulation of flow field of concentric canister launcher based on k-ω SST turbulence model
ZHANG Cheng, XIA Zhixun, MA Chao
2019, 34(11): 2331-2338. doi: 10.13224/j.cnki.jasp.2019.11.004
The flow field of the concentric canister launcher and structural optimization was simulated numerically based on the axisymmetric Navier-Stokes(N-S)equation, the k-ω shear stress transfer (SST) turbulence model and the dynamic mesh update method named zone moving and dynamic laying. With reference to the initial scheme of the concentric canister launcher, the dynamic flow field of the launching process was studied. On this basis, the parameterization of the convergence angle of the convergent section of the inner cylinder and the expansion angle of the expansion section of the cylinder was studied. The results showed that the convergent section of the inner cylinder made the gas discharge guide smoother, the thermal environment inside the cylinder was improved, and the inner cylinder convergence section played a certain role of anti-spray. The larger convergence angle brought about the better thermal environment at the bottom of the cylinder. The expansion section of the nozzle had a significant change to the dynamic flow field during the launch process. When the convergence angle was 15 degrees and the expansion angle was 20 degrees, the thermal environment of the missile was the best from the start to the complete exit.
Flow separation unsteadiness in single expansion ramp nozzle
HE Chengjun, LI Jianqiang, FAN Zhaolin
2019, 34(11): 2339-2346. doi: 10.13224/j.cnki.jasp.2019.11.005
In combination with the focus schlieren and dynamic pressure measurement technology, the flow field and nozzle wall pressure were experimentally measured, under the different nozzle pressure ratios (NPR) of the single expansion ramp nozzle (SERN). Time and frequency domain analysis exhibited unsteady flow characteristics within the nozzle. Results showed that the flow field structure inside SERN was obvious asymmetrical. The flow separation mode on the upper wall of the nozzle was at restricted shock separation (RSS), and that on the lower wall at free shock separation (FSS); in RSS mode, the pressure on the wall near the outlet was sharply oscillated in relation to FSS mode. The pressure standard deviation of the upper and lower walls of the nozzle was peaked near the separation point, and the probability density function distribution was skewed to one side or showed double peaks. In RSS mode, the shock motion exhibited obvious low-requency characteristics. In FSS mode, the unsteady characteristics of the shock wave were not only affected by the pressure disturbance of the recirculation region, but also affected by the separated shear layer.
Strategy of calculating minimal-distance of engine pipelines based on point cloud data
FAN Jingjing, MA Liqun, SUN Anbin
2019, 34(11): 2347-2353. doi: 10.13224/j.cnki.jasp.2019.11.006
A strategy of calculating minimal-distance of engine pipelines based on point data was proposed to inspect whether the minimal-distance meets the design requirement. The strategy includes five steps: (1) the points belonging to the same pipeline was picked up and saved in a group. (2) A set of equal-interval grid was built along a coordinate direction in which the pipeline stretched longest. Then the point cloud data were divided into corresponding grid according to the coordinates. The center point of each grid was calculated and the trend-line data of pipeline were constituted. (3) On each trend-line point, a projection plane was built vertically to a straight line connecting the point and its adjacent point. Then point cloud data of pipeline were projected to the nearest projection plane. And a group of projected points in arc distribution were obtained on each projection plane. (4) The projected points on each projection plane were fitted into a circle using least square fitting method. And the center points of all circles constituted the center-line points of a pipeline. And the mean radius of each fitted circle was regarded as pipeline radius. (5) Traversing method was used to calculate minimal-distance between two groups of center-line points. And minimal-distance of two pipeline surfaces was calculated by subtracting radii of two pipelines from the minimal-distance of center-line points. Four groups of pipelines were examined to verify the proposed strategy. The results showed that the deviations of minimal-distance of two pipeline surfaces were within -0.35~0.46mm. And the deviations of pipeline radius were within -0.08~0.22mm. The proposed method is more robust than mostly used method and also meaningful for realizing digital inspection of pipeline distance.
Shape parameters optimization of hypersonic vehicle based on surrogate model
YI Chunlun, LIU Chunbin, CAO Rui
2019, 34(11): 2354-2365. doi: 10.13224/j.cnki.jasp.2019.11.007
In view of the complexity and difficulty of hypersonic vehicle analysis, a surrogate model was proposed to approximate the true model with complex disciplinary coupling in the process of performance analysis and optimization. According to the requirements of cruise mission, the objective of optimization was to optimize the static and dynamic performance and minimize the model difference. By means of sensitivity analysis, the surrogate model was established. The static and dynamic performance analysis of the surrogate model was carried out, and the results of the true model were compared to verify the accuracy of the surrogate model. It was found that the trend of the trimming characteristics of the two models was completely consistent, the difference of angle of attack was less than 3%, and the difference of elevator deflection angle was only about 20% when the lower angle of the front body was large. Based on the surrogate model and optimized performance index, the trimming performance optimization and gap metric optimization of the surrogate model’s shape parameters were compared with the optimization results of the true model and the optimization efficiency. It was found that the difference between the two results was less than 2%, but the optimization efficiency using surrogate model was improved by 456%. It was proved that the optimization based on the surrogate model can improve the optimization efficiency without compromise of the accuracy.
Aerodynamic performance comparison of a two-dimensional inlet for missile in an inverted “X”-type layout with classical layout
LUO Hao, JIN Zhiguang, ZHANG Kunyuan
2019, 34(11): 2366-2376. doi: 10.13224/j.cnki.jasp.2019.11.008
In order to raise the stability margin of “X”-type inlet system with incoming Mach number range from 2 to 4 at a high angle of attack, an inverted two-dimensional inlet was designed and compared with the classical inlet layout. Results indicate that the inverted inlet layout has better overall performance at incoming Mach number 2.3 to 3.5 with angle of attack from 0° to 6°. There is no obvious phenomenon of shock/boundary layer interactions, allowing to meet the design requirements. When the same inlet design scheme is adopted, the terminal shock location and overall performance parameters have little differences between windward and leeward inlets of the inverted layout. The critical total pressure recovery coefficient of the inverted layout isalmost equal to classical layout when the angle of attack is 0°, 2%-3% higher when the angle of attack is 4° and generally 19% higher when the angle of attack is 8°. The higher the incoming Mach number is, the more obvious the increase is. The total mass flow coefficient of the inverted layout is about 6% higher at angle of attack 8°. Moreover, the total drag force of inverted layout is lower than that of classical layout at low incoming Mach number, which is 1.7% lower when angle of attack is 4°. While at high incoming Mach number, the total drag force of inverted layout is higher than that of classical layout, which is 2.0% higher when angle of attack is 4°.
Numerical simulation of flow field under coaxial rigid rotor/fuselage interaction
LIU Jiaqi, CHEN Rongqian, CHENG Jiaming
2019, 34(11): 2377-2386. doi: 10.13224/j.cnki.jasp.2019.11.009
The method of solving the Navier-Stokes (RANS) equation by the sliding mesh technique was studied, and the interaction problem of the coaxial rigid rotor/fuselage was analyzed. The correctness of the numerical simulation of the flow field related to rotor was verified by the examples of Caradonna-Tung rotor, Robin helicopter, Maryland helicopter rotor/fuselage interaction, and Harrington 2 coaxial rotors. On this basis, with the Maryland fuselage as the model prototype, the interference characteristics between the coaxial rigid rotor with different pitches and the fuselage were analyzed. Results showed that numerical simulation method can simulate the aerodynamic interference characteristics of the coaxial rigid rotor/fuselage very well; the hovering efficiency of the rotor increased by about 5% due to the blockage of the airflow field of the coaxial rigid rotor., and the increase of the hovering efficiency was more obvious with the increase of the pulling coefficient; the increase of the hovering efficiency of the rotor was mainly related to the increase of the blade lift coefficient near the 0° azimuth of the lower rotor, and the increment of the tensile coefficient was gradually reduced from the root of the blade to the tip of the blade.
Optimization of port height of opposed-piston two-stroke diesel engine based on GA-SVM
LU Xuetian, ZHANG Fujun, ZHANG Zhenyu
2019, 34(11): 2387-2394. doi: 10.13224/j.cnki.jasp.2019.11.010
Taking fuel consumption as the optimization goal, the automatic optimization of the intake and exhaust port height of an opposed-piston two-stroke diesel engine prototype for various engine speeds was simulated experimentally by using the genetic-support vector machine method on the basis of one-dimensional simulation model. The results showed that under the low engine speed such as 1200r/min, the combination of optimized dimensionless intake and exhaust ports height was[0.075, 0.105], and the minimum fuel consumption was 220.32g/(kW·h). For the opposed-piston two-stroke diesel engine, the optimized port height for either intake port or exhaust port monotonically increased with the increasing engine speed. Exhaust port height increased more obviously than that of intake port for optimized port height under high engine speed (engine speed was greater than 1600r/min).
Mixed-mode fatigue crack propagation of titanium alloy diffusion bonded joints
LIU Xiaogang, ZHU Xiaolin
2019, 34(11): 2395-2402. doi: 10.13224/j.cnki.jasp.2019.11.011
Compact tensile shear(CTS) specimens of TC4 diffusion bonded joints were designed and processed. The fatigue crack propagation tests of Ⅰ-Ⅱ mixed mode under different loading angles were carried out. The test results showed that when the loading angle was less than 45 degrees, the cracks propagated along the weld line. When the loading angle was more than 45 degrees, the cracks started to propagate along base metal at certain angle. The a-N curves of crack propagation were obtained by electron microscopy in combination with potential method. Based on the test results, the interaction integral method was used to calculate the stress intensity factor, and the Ⅰ-Ⅱ mixed crack propagation process was analyzed based on the strain energy release rate. Finally, considering the weight of crack mode Ⅱ, the composite ratio was introduced. On this basis, a unified model of Ⅰ-Ⅱ mixed crack propagate rate of TC4 diffusion bonded joints under different loading angles and loads was established.
Mechanism and effect of “critical follower speed” on dual-rotor system of aero-engines
LI Yan, LIAO Mingfu, JIANG Yunfan
2019, 34(11): 2403-2413. doi: 10.13224/j.cnki.jasp.2019.11.012
In order to investigate the mechanism of “critical follower speed” which could lead to a sustained strong vibration of aero-engine, a dual-rotor dynamic model with intershaft bearing was established. The relationship of the dual-rotor parameters in the case of “critical follower speed” phenomenon was deduced. And the dynamic characteristics of the rotor system under “critical follower speed” were analyzed. The results of investigation revealed that: the phenomenon “critical follower speed” caused the failure of rotor system to cross the critical speed of disk-swing mode, which made vibration extremely sensitive to unbalanced mass distribution of the rotor system. And there were two ratio influential factors: the ratio of polar inertia moment to the diameter inertia moment by disks (simple named “inertia ratio”), and the increasing speed ratio of dual-rotor system. When the inertia ratio of the equivalent high-pressure-disk was equal to 1, or the increasing speed ratio was equal to the inertia ratio of any low-pressure-disk, the rotor system was excited by high-pressure rotor under the “critical follower speed” state. Besides, when the inertia ratio of the low-pressure-disk was equal to 1, or the product of increasing speed ratio and inertia ratio of equivalent high-pressure-disk was equal to 1, the rotor system was excited by low-pressure rotor under the “critical follower speed” state. Additionally, it is suggested that the equivalent inertia ratio design of the blade-disk on aero-engine and the speed increasing ratio of dual-rotor should be strictly controlled.
Sealing characteristics of aviation pipeline fittings and influence of fluid temperature
YAN Yangyang, ZHUANG Baoshun, GAO Peixin
2019, 34(11): 2414-2422. doi: 10.13224/j.cnki.jasp.2019.11.013
The multi-scale finite element simulation method was used to study the sealing characteristics of pipeline fittings. Based on the measured data of rough surfaces, the multi-scale model of pipeline fittings was modelled, sealing state and sealing performance of fittings were obtained by simulating the tightening process of fittings. The results showed that the calculation results based on the multi-scale model could really present seal characteristics of pipeline fittings, and improve the calculation accuracy of pipeline fittings assembly method. In addition, during the process of fittings tightening, thehigh stress zone between pipeline fittings and ferrule diffused to all sides through two high stress zones, and the change of sealing performance of pipeline fittings presented linear change. When the displacement of ferrule reached certain position, the pipeline fittings achieved the optimal assembly state, making it particularly important for the application of pipeline fittings. Besides, the fluid temperature in the allowable range had certain influence on the sealing characteristics of pipeline fittings.
Application of convolutional neural network and kurtosis in fault diagnosis of rolling bearing
LI Jun, LIU Yongbao, YU Youhong
2019, 34(11): 2423-2431. doi: 10.13224/j.cnki.jasp.2019.11.014
Traditional intelligent diagnosis method relying much on expert knowledge and manual extraction data features takes a lot of work. Based on the advantages of deep learning in feature extraction and processing of big data,a method of rolling bearing fault diagnosis based on convolution neural network and kurtosis was studied. This method was used to analyse four kinds of vibration signal of the normal state,the inner race fault,the outer race fault and the ball fault. The vibration signal was processed in segments to obtain kurtosis, which was converted into gray images by data-to-image method. Finally, these were fed into convolution neural network model to complete rolling bearing fault classification. In the case of rolling bearing fault diagnosis, the improved model had a diagnostic accuracy of 99.5%, which was higher than 95.8% of the traditional support vector machine (SVM) algorithm.
Faultdiagnosis of rolling bearing based on convolution gated recurrent network
YANG Ping, SU Yanchen
2019, 34(11): 2432-2439. doi: 10.13224/j.cnki.jasp.2019.11.015
In view of the phenomenon of the degraded diagnostic performance of many rolling bearing fault diagnosis methods based on deep learning under the small sample data set, a bearing fault diagnosis model based on convolution gated recurrent neural network was proposed. This model used a two-layer convolution network to extract features from the input signal, using the tanh function as the activation function, and the pooling layer used the large pooled kernel for overlapping downsampling. The extracted high-level features were connected to the bidirectional gated recurrent network. The last states of the forward and reverse directions of the recurrent network were combined, and a layer of fully connected layers was connected for output. The bearing fault data set of Case Western Reserve University was used to verify the diagnostic performance of the model under the small sample data set. The experimental results showed that the model still maintained 97% accuracy with only 20 training samples compared with other types of models.
Damping design technology of aero-engine supporting structure system
ZHANG Jian, MA Yanhong, WANG Yongfeng
2019, 34(11): 2440-2447. doi: 10.13224/j.cnki.jasp.2019.11.016
The vibration control method with dry friction damping was put forward for the supporting structure system in high thrust-mass ratio turbofan engine. A dry friction damper with vibration absorption function was designed to enhance the damping characteristic of the supporting structure without loss of stiffness, and achieve vibration response control for the system. Influences of friction contact characteristic and dry friction damper structure characteristic on the damping effect were acquired in theoretical analysis and simulation calculation, and the damping design flow for supporting structure was presented. Results exhibited that vibration response was attenuated with the dry friction damper, and the damping effect could be optimized with reasonable design of friction coefficients and claw's width, which helped attenuate resonance amplitude of bearing house by more than one order in the example.
Influence of rocket engine exit parameters on flow and radiation characteristics of exhaust plume
BAO Xingdong, YU Xilong, MAO Hongxia
2019, 34(11): 2448-2457. doi: 10.13224/j.cnki.jasp.2019.11.017
Based on the detailed chemical reaction mechanism, the flow and radiation of the plume were studied by the method of computational fluid dynamics (CFD) + line-by-line integration and light of sight method. The effects of different chemical reaction mechanisms on flow and radiation were compared and analyzed. The validity of the model was verified by optical measurement data. On this basis, the influence of rocket exit parameters on plume flow and radiation was analyzed in detail. The results showed that: the temperature of the nozzle exit had little effect on the structure of the flow field, but had a significant effect on the afterburning; the increase of pressure at the nozzle exit had an effect on the wave structure of the Maher disk, but had little effect on the afterburning; the infrared radiation intensity of the plume increased with the increase of the temperature and pressure of the nozzle exit, and the infrared radiation intensity was positively related to the thrust of the engine.
Influence of throat diameter ratio of two-stage nozzle on gas-steam ejection parameters
LI Renfeng, CHEN Shuai, HU Xiaolei
2019, 34(11): 2458-2465. doi: 10.13224/j.cnki.jasp.2019.11.018
The multi-phase flow models coupling with projectile motion and vaporization were established respectively under different conditions of throat diameter ratio. What’s more, the influence of throat diameter ratio on gas-steam ejection flow field, ejection device load and interior ballistics was studied. Results showed that increasing or decreasing the throat diameter ratio within a certain range led to the deterioration of ejection device flow field and launch stability. When the throat diameter ratio increased too large, the spray pressure difference meeting the working conditions could not be established. When the throat diameter ratio was too small, the shock wave upward movement eventually led to abnormity of the gas generator. When the throat diameter ratio was 1.46, the pressure difference of tail cover was the smallest and the launch stability was the best. The maximum temperature of launch tube was controlled within the design value of 800K, and the interior ballistic parameters could satisfy the design requirements.
Measurement and analysis of fuel average regression rate of solid fuel ramjet based on high-resolution data reconstruction
QIU Shuang, LI Yingkun, LI Weixuan
2019, 34(11): 2466-2477. doi: 10.13224/j.cnki.jasp.2019.11.019
A non-contact active scanning and structural grating projection positioning technique was used to reconstruct the three-dimensional point cloud data of combustion morphology of solid fuel ramjet grain after ground test using high density polyethylene (HDPE) as propellant. The three-dimensional distribution cloud map of mean local regression rate on the inner surface of solid fuel was obtained. The results showed that: (1) the error between the burning removal quality of the grain calculated by this method and the actual mass change after experiment was within 0.1%. The accuracy met the requirement of regression rate evaluation for solid fuel. (2) The reconstructed regression rate test method can truly reflect the change of fuel grain structure with certain applicability. (3) The relationship between mean local regression rate and total average regression rate was obtained by this method, and the relationship between regression rate and inflow air mass flux was obtained by linear fitting method. Through the validation and analysis of this method, it is concluded that the regression rate test method has a certain reference value for the further study of solid fuel ramjet gressionrate.
Influence of torsional stiffness on load sharing characteristics of power split transmission system
JIN Guanghu, REN Wei, ZHU Rupeng
2019, 34(11): 2478-2489. doi: 10.13224/j.cnki.jasp.2019.11.020
Considering factors such as the backlash, time-variant mesh stiffness, eccentricity errors, shaft torsion and support stiffness, a dynamic model of the system was developed. The rigid body displacement in the kinetic equation was eliminated by using the force closure feature of the transmission configuration and the method of converting the torsional angular displacement equivalent of the shaft into a linear displacement. The dynamic equations were solved by Runge-Kutta numerical simulation method, and the load-sharing coefficients of the system were obtained. The influence of the torsional stiffness of transmission shaft on the load sharing performance was studied. Results showed that torsional stiffness of input shaft and output shaft had little influence on load sharing performance of each transmission stage of the system; the load sharing coefficients were sensitive to the torsional stiffness of the compound shaft and the spilt torque shafts. Once the compound shaft met the strength requirement and the torsional stiffness took a small value, rationally configuring the torsional stiffness of left-branch and right-branch spilt torque shafts can improve dynamic load sharing performance of system.
Effect of sample size on evaluation of variation process of rolling bearing vibration performance
YE Liang, XIA Xintao, CHANG Zhen
2019, 34(11): 2490-2502. doi: 10.13224/j.cnki.jasp.2019.11.021
Based on the vibration time series during the life cycle of rolling bearings, a maximum entropy Poisson evaluation model was constructed to study the evolution process of rolling bearing vibration performance. The vibration time series were divided into different segments, and then the variation probability, vibration performance maintaining reliability and their variation speed and acceleration were calculated based on maximum entropy principle and Poisson process for each vibration time series in relation to the intrinsic series. The relationships between performance variation indexes and sample size were analyzed to select the appropriate sample size. Dynamic average uncertainty was used to analyze the uncertainty of evaluation results of performance maintaining reliability. Result showed that the sample sizes of 800-1000 and 500-900 were selected respectively, for case 1 and case 2, which can make the intrinsic series data sample contain enough vibration information, but also effectively evaluate the specific variation process of bearing vibration performance.
Thermal protection effectiveness of thermal barrier coatings in turbine blade applications
ZHU Jianqin, ZHAO Chaofan, QIU Lu
2019, 34(11): 2503-2508. doi: 10.13224/j.cnki.jasp.2019.11.022
A validity criterion of thermal barrier coating was developed by theoretical derivation based on a simplified heat transfer model of turbine blades with thermal barrier coating. Besides, the effectiveness of thermal protection was analyzed based on the validity criterion and engineering practice. Theoretical analysis and numerical experiments showed that the change of composite heat transfer coefficient caused by thermal barrier coating could greatly affect the thermal protection effect. For the front edge of the high pressure turbine blade in the high temperature zone, the maximum rate of change of the composite heat transfer coefficient caused by the thermal barrier coating should be range from 1.25% to 10.83% to meet the thermal protection effectiveness. In practice, special attention should be paid to the change of the composite heat transfer coefficient due to the application of the thermal barrier coating, otherwise it will cause thermal protection failure or even counter effect.
Rib influence on heat transfer and pressure drop in pin-fin array
BAI Wandong, LIANG Dong, CHEN Wei
2019, 34(11): 2509-2515. doi: 10.13224/j.cnki.jasp.2019.11.023
For the interaction between diverse internal cooling structures in turbine blades, various shaped ribs’ influences on pin-fin array heat transfer and pressure drop were investigated using a transient liquid crystals test. The 90°, 60°, V-shaped and W-shaped ribs were considered to compare the characteristic differences of pin-fin array heat transfer distribution, heat transfer enhancement and pressure drop levels. The results showed that upstream ribs made the spanwise variation of pin-fin endwalls heat transfer non-uniform. The vortices induced by upstream ribs appeared to enhance pin-fin array heat transfer but reduce pressure drop, leading to an overall thermal efficiency improvement. The W-shaped and 90° ribs made pin-fin arrays yield the best thermal efficiency and then the V-shaped and 60° ribs.
Effect of self-circulating treatment casing on rotor performance at different speeds
YAN Song, CHU Wuli
2019, 34(11): 2516-2528. doi: 10.13224/j.cnki.jasp.2019.11.024
Taking NASA Rotor 37 as the research object, the influence of the bleeding position of self-circulating treatment casing (SCT) on the rotor performance at different speeds was studied by numerical simulation. The researches show that the influences of the bleeding positions of the SCT and the rotor speed on the rotor performance are interactive. The essential reason lies in that, when the rotor is in near stall condition at different speeds, theflow condition is different in the rotor tip region, so that the relative position changes between the bleeding positions and the blade tip blockage as the rotor speed changes, resulting in an interactive effect on the rotor performance. Through the analysis of the influence of the bleeding positions of the SCT on the rotor stability at different speeds, it is found that when the bleeding position is at the trailing edge of the blade tip blockage region,there exists the best inhibition of the low-velocity blockage zone, greatly improving the flow ability of the rotor tip region, and contributing most to the stall margin improvement (SMI) of rotor. At 100%, 90% and 70% design speeds, the maximum value of the SMI is 7.46%,8.52% and 6.14%, respectively. In addition, through detailed analysis of the flow field at the rotor tip region, it is found that when the bleeding position of the SCT is located at the trailing edge of the blade tip blockage region of the near-stall operating condition of the rotor at different speeds, the highpecific entropy zone caused by the SCT is the least, bringing about minimal reduction in rotor efficiency, and making it most beneficial to the performance.