2015 Vol. 30, No. 5

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Experiment on effect of misalignment on outlet flow field of double-swirler
HU Hao-sheng, JIANG Yao, LU Ke-qian, HU Jian
2015, 30(5): 1025-1031. doi: 10.13224/j.cnki.jasp.2015.05.001
Abstract PDF(1169KB) icon1189 icon829
Abstract:
In order to study the flow field characteristics downstream a double-swirler outlet, four double-swirler configurations with different misaligned dimensions (0,0.5,1.0,1.7mm) were designed. The no-reacting flow field of different misaligned dimensions was obtained by PIV. Expermental result shows that there is no significant difference in the flow field between misaligned dimension of 0mm and 0.5mm. In the configurations of misaligned dimension larger than 0.5mm, the double-vortex construction and the central recirculation zone downstream the double-swirler outlet become asymmetrical and narrow respectively. The flow filed show obvious deviation from the one of 0mm misaligned dimension. Misalignment has a pronounced influence on the radial velocity profile downstream the double-swirler outlet. The radial velocity around the axial location of X/D=0.5 is converted into peak and positive value when misaligned dimension is larger than 0.5mm.
Measurement of triple-stage swirler cup combustor flow field based on PIV technology
WANG Cheng-jun, JIANG Ping, XIN Xin, CHEN Bao-dong, CHEN Ke-hua
2015, 30(5): 1032-1039. doi: 10.13224/j.cnki.jasp.2015.05.002
Abstract PDF(1437KB) icon1647 icon1026
Abstract:
With reference to single-stage swirler design method, four kinds of third stage swirler of different blade numbers and installation angles in triple-stage swirler cup were designed. Triple-stage swirler cup combustor flow field was studied through the particle image velocity(PIV) technology. The experimental results show that with the increase of the third stage swirler blade number and installation angle, the axial velocity in main combustion zone decreases gradually, enhancing the effect of main combustion hole jet. Under the same blade number condition, the third stage swirler vortex intensity is boosted with the increase of the third stage swirle blade installation angle. For different third stage swirler blade installation angles, the flat trend of axial velocity increases with the increase of the third stage swirler blade number, making the effect of combustor flow disturbance decreases by main combustion hole jet and the mainstream flow more smoothly.
Effects of modified VOF method on gas-liquid two-phase flow oscillating flow and heat transfer calculation
ZHU Hai-rong, ZHANG Wei-zheng, YUAN Yan-peng
2015, 30(5): 1040-1046. doi: 10.13224/j.cnki.jasp.2015.05.003
Abstract PDF(909KB) icon1701 icon845
Abstract:
On the basis of VOF (volume of fluid) model, the level set function was introduced, and the CLSVOF (coupled level set volume of fluid) model was formed to numerically simulate the process of gas-liquid two-phase oscillating flow and heat transfer. The simulation results of CLSVOF model were compared with that of VOF model, and also compared with the experimental results. The results show that either for the oscillating flow and heat transfer process of two-phase flow in rectangular cavity, or for the oscillating cooling process of engine-oil in piston oil cooling gallery, CLSVOF model can more accurately simulate the oscillating flow rules of gas-liquid two-phase flow, and the calculation values of heat transfer coefficient consist with experimental results much better. For the oscillating cooling calculation of engine-oil in piston oil cooling gallery, with the increase of speed, i .e. Reynolds number, the error of calculation values of heat transfer coefficient increase accordingly. At the ultimate speed of 3000r/min, the error of CLSVOF model is 3.8%, and the error of VOF model is 7.5%; the error increase amplification of CLSVOF model is about 0.6%. The error increase amplification of CLSVOF model is relatively small and stable, so its higher calculation accuracy can be illustrated.
Windage heating experiment on rotating disc in cavity of rotor-stator system
ZHANG Da, LUO Xiang, XU Guo-qiang, HAN Jian-qiao
2015, 30(5): 1047-1056. doi: 10.13224/j.cnki.jasp.2015.05.004
Abstract PDF(1315KB) icon1679 icon1110
Abstract:
In order to investigate the windage heating effect on rotating disc in cavity of rotor-stator system, an experimental research was performed using infrared temperature measurement technology. A high-speed revolution test rig was developed to investigate the effect of flow parameters and rotor-stator gap ratio on the temperature rise along the radius on rotating disc surface respectively. The shrouded and unshrouded cases were both tested. The flow feature in the cavity of rotor-stator system was obtained by CFD simulation. The results show that the temperature rise on the rotating disc induced by the windage heating is difference between adiabatic wall temperature of rotating disc and environment temperature, which can be measured by the thermal infrared imager accurately. For the unshrouded case, the temperature rise of rotating disc is mainly affected by the rotation, and only for the small gap ratio case, the throughflow has influence on the windage heating. In general, the gap ratio has limited influence on temperature rise. Comparison of the shrounded case, the temperature rise occurs only for the small turbulence parameter case with shrouded stationary.
Ignition performance affected by axial position of primary holes at low pressure conditions
YANG Qian, LIN Yu-zhen, DAI Wei, ZHANG Chi, WANG Xiao-feng
2015, 30(5): 1057-1066. doi: 10.13224/j.cnki.jasp.2015.05.005
Abstract PDF(1033KB) icon1188 icon852
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Two structures of primary holes (staggered jets and aligned jets) were designed for reverse-flow liner. Experiments were conducted to study the combustor ignition performance affected by two structures of primary holes at different pressure conditions. The experiment result indicates that as the inlet air pressure of the reverse-flow combustor decreases, the fuel/air ratio at ignition boundary decreases at first and then increases. The ignition performance of aligned jets primary holes is better than that of staggered jets primary holes. Combined with numerical simulation results of liner cold flow field and ignition phenomena observed in the experiment, the area of recirculation zone is expanded and reference velocity of the liner is reduced due to the aligned jets primary holes. It is beneficial for decreasing the quenching probability of flame kernel and enhancing the stability of the flame. Thus ignition performance of the reverse-flow combustor is improved.
Conjugate heat transfer characteristics of brush seal based on local thermal non-equilibrium porous medium approach
QIU Bo, LI Jun
2015, 30(5): 1067-1075. doi: 10.13224/j.cnki.jasp.2015.05.006
Abstract PDF(1139KB) icon1817 icon808
Abstract:
Computational model was developed for multi-physics coupling simulation of the flowing, heat transfer, frictional contact of the brush seal. A dual-energy equation was proposed to describe the conjugate heat transfer in the brush seal under local thermal non-equilibrium condition. Both the heat convection between the bristle and airflow and the anisotropy of heat conduction in the bristle pack were considered in the dual-energy equation. The temperature distributions of brush seal were numerically predicted using the developed computational model at various pressure ratios and rotational speeds. Results show that a local high temperature region is formed around the bristle-rotor contact area due to frictional heat effect of brush seal. The high temperature region of bristles is mainly located under fence height. The temperature distribution of airflow is similar to that of bristles due to strong heat convection between leakage airflow and bristles. The maximum temperature of bristles increases with the increasing pressure ratio. The average temperature under fence height region of bristles decreases with the increasing pressure ratio. The maximum temperature and average temperature under fence height region of bristles increase with the increasing rotational speed. The temperature rise effect of leakage airflow arising from frictional heat effect makes the leakage rate of brush seal decrease with the increasing rotational speed.
Liner structure optimization based on pressure oscillation in combustor
QIN Hao, FU Zhen-bai, LIN Yu-zhen, LI Ji-bao
2015, 30(5): 1076-1083. doi: 10.13224/j.cnki.jasp.2015.05.007
Abstract PDF(853KB) icon1366 icon861
Abstract:
Pressure oscillation characteristics of combustor were tested and compared between double-plate liner and single liner, and the test results show that pressure oscillation amplitude of the former is minor under the same test conditions. Applicability of perforated resonators model based on superposition principle in analyzing pressure oscillation characteristics mentioned above was checked. After sensitivity analysis, liner structure improvements for decreasing pressure oscillation amplitude of combustor without changing cooling air allocation were investigated. Analysis results show that the hole number (or hole diameter) in linear wall is the key parameter in mitigating pressure oscillation in combustor in an engineering optimization way.
Experiments on film cooling with sonic injection into a supersonic flow
ZHANG Jia, SUN Bing
2015, 30(5): 1084-1091. doi: 10.13224/j.cnki.jasp.2015.05.008
Abstract PDF(959KB) icon1255 icon768
Abstract:
Film cooling experiments with sonic injection were conducted to investigate the effects of the number of the injection holes, the mass flow ratio, and the hole spacing on the film cooling effectiveness. The mainstream was obtained by the hydrogen-oxygen combustion, entering the experimental section at a Mach number of 2.0. The nitrogen with ambient temperature was injected into the experimental section at a sonic speed. The measured mainstream recovery temperature was approximately 910K. The mass flow ratio was regulated by varying the nitrogen injection pressure. The experimental results show that for the investigated cooling surface, the cooling effectiveness increases with the increase in the number of the injection holes with other parameters held constant. For a fixed cooling configuration, the cooling effectiveness increases with the increase in the mass flow ratio. Different from the subsonic film cooling, the optimal mass flow ratio is not observed. When the hole spacing is less than 4, no obvious difference is observed on the cooling effectiveness and lateral uniformity. With the mass flow ratio increasing further, this difference becomes much smaller. The shock wave also has an effect on the cooling effectiveness. Downstream the incident point of the shock wave, the cooling effectiveness is lower than that in the case without the shock wave.
Effects of swirl number of second stage radial swirler on combustor ignition and lean blow-out performances
DAI Wei, LIN Yu-zhen, ZHANG Chi
2015, 30(5): 1092-1098. doi: 10.13224/j.cnki.jasp.2015.05.009
Abstract PDF(926KB) icon1615 icon875
Abstract:
Twin-swirler is used as a major form in aero-engine combustor dome to make a recirculation zone. The effects of the swirl number of the second stage radial swirler on ignition and combustion stability performance were mainly studied. The numerical simulation results were validated well with the design parameters of the second stage radial swirler. Experimental studies show that the swirl number of the second stage radial swirler has no effect on the combustor ignition performance. However, the decrease of this swirl number will obviously improve the lean blow-out performance. The entrainment effect of swirl would impact the flame stabilization in the recirculation zone. Decreasing swirl number of the second stage radial swirler can increase the downstream entrainment and optimize the matching between the flow and flame in the recirculation zone, and this is more beneficial to improve the combustion stability.
Linear stability analysis of modal premixed combustor
FU Xiao, GUO Zhi-hui, YANG Fu-jiang
2015, 30(5): 1099-1105. doi: 10.13224/j.cnki.jasp.2015.05.010
Abstract PDF(941KB) icon1165 icon933
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Linear stability analysis was conducted in modal premixed combustor with bluff body flame holder. The software COMSOL Multiphysics was used to solve the three-dimensional Helmoholtz equation. The time lag model was the source term of equation. The periodic change of chemical reaction rate was studied by unsteady calculation for modal premixed combustor, and the unsteady heat release occurred at the top of the flame. The delay times of 0.6, 0.3, 0.9, 0.6ms were obtained for equivalence ratios of 0.72, 0.8, 0.88 and 0.97 respectively in four cases based on the phase difference of pressure and temperature signals. The linear stability analysis obtained the real part and imaginary part of frequency of longitudinal mode for modal premixed combustor, and the negative imaginary part represented linear instability. The results show that the second, third, and fourth longitudinal modes are linear instability in the first five longitudinal modes. The imaginary part of the third longitudinal mode has the largest absolute value, indicating the largest growth rate in small disturbance. So there is the biggest possibility to occur linear unstable and combustion instability for the third longitudinal mode in disturbance.
Effect of Knudsen number on similar characteristics of film cooling flow and heat transfer
GONG Dai-kun, ZHU Hui-ren, LIU Cun-liang, LU Cong-ming
2015, 30(5): 1106-1112. doi: 10.13224/j.cnki.jasp.2015.05.011
Abstract PDF(1121KB) icon1415 icon832
Abstract:
The effect of Knudsen number Kn on the similar characteristics between different scale film cooling flow and heat transfer was numerically studied. Single-row plate cylindrical hole film cooling models with aperture of 0.3, 3, 10mm were selected. Cooling effectiveness and discharge coefficient of models under condition of different Kn and the same Kn were calculated. Results show that small and large hole models have similar flow and heat transfer characteristics under the same value of Kn, resulting in little differences between cooling effectiveness and discharge coefficient. When Kn varies, the flow and heat transfer characteristics of these two models are different, bringing about different cooling effectiveness and discharge coefficients. Therefore it is necessary to make sure that small and large hole models should have the same Kn in similar amplification experiment of film cooling.
Effects of turning mixing duct on lobed mixer performance
YE Yu-chen, HUANG Yong, LIU Lei, WEI Fu-qing
2015, 30(5): 1113-1118. doi: 10.13224/j.cnki.jasp.2015.05.012
Abstract PDF(835KB) icon1115 icon754
Abstract:
Based on a series of numerical computations and model experiments on the lobed mixer, the effects of turning mixing duct on the lobed mixer performance were revealed. The experimental results show that a crescent-shaped high temperature flow area is formed at the outlet cross section caused by turning mixing duct if the length-diameter ratio of mixing duct is less than 2. And a backflow zone is also found in the center of this area which is disadvantageous to the pumping performance. However, the numerical results not only verify the air flow distribution, but also show that the turning mixing duct lower the pumping efficiency of lobed mixer, and the mixer duct length should be increased for better pumping performance. To achieve a satisfied lobed mixer performance, the length-diameter ratio should not be less than 2. The numerical results also show that the optimum length-diameter ratio of lobed mixer is 2, which may not vary with the area ratio. Compared with pipe mixer whose optimum length-diameter ratio is 6, the lobed mixer could shorten the mixing duct effectively. Furthermore, fitting relations between the pumping ratio and length-diameter ratio are also presented.
Numerical simulation on improved integrated afterburner scheme
WANG Wei-long, JIN Jie, JING Wen-ming, LIU Deng-huan, JI He-ming, YOU Qing-jiang, LI Jiang-ning
2015, 30(5): 1119-1124. doi: 10.13224/j.cnki.jasp.2015.05.013
Abstract PDF(848KB) icon1330 icon812
Abstract:
An improved integrated afterburner scheme was proposed to solve the problem of too large mass of traditional afterburner and too significant flow loss in non-augmentation condition. This scheme canceled the conventional stabilizer of blunt body, and a sudden expanding structure of central cone for stabilizing the flame was adopted. Numerical simulation was conducted to research its performance. The result indicates that the scheme is not sensitive to inlet parameters; total pressure recovery coefficients of three schemes on all cases are greater than 0.96; afterburner efficiency is close to 0.90; the scheme with lobed mixer has the best overall performance.
"Hot modes" of rotor vibrations and vibration reduction design for aero-engines
LIAO Ming-fu, CONG Pei-hong, WANG Juan, HE Yun, GAO Xiong-bing, SONG Ming-bo
2015, 30(5): 1125-1140. doi: 10.13224/j.cnki.jasp.2015.05.014
Abstract PDF(1279KB) icon1493 icon763
Abstract:
A concept of "hot modes" of aero-engines rotor was put forward to adapt to the design of rotor dynamics for variable speed operation of aero-engines. The "hot modes" were explained with two different models, and a procedure of rotor dynamics design under "hot modes" was developed. The ratios of critical speeds of rotor with elastic supports to those of the rotor with rigid supports were taken as design parameters for dynamic optimization of the rotor, which involved the influences of stiffness, mass of the rotor. Result shows that, when all "hot modes" are under the first mode of rotor with rigid supports, the critical speeds of the rotor should be lower than the first critical speed of the rotor with rigid supports. If the first "hot modes" under the first mode of rotor with rigid supports, and the second "hot modes" is between the first and the second modes of rotor with rigid supports, the second critical speed should be equal to the root mean square of the first and the second critical speeds of the rotor with rigid supports. Additionally, it is suggested that the residual imbalance should be kept orthogonal to the modes of the rotor with rigid supports.
Vibration characteristics analysis of blisk with cracking blades on axial flow compressor
CHEN Xiang, ZHU Jing, ZHANG Ya
2015, 30(5): 1141-1148. doi: 10.13224/j.cnki.jasp.2015.05.015
Abstract PDF(1206KB) icon1329 icon828
Abstract:
Crack fault of rotor blades occurred during performance experiment of an axial flow compressor. According to the structure characteristics of the compressor, the time-domain signal, frequency-domain signal of vibration response and high-frequency fluctuation were analyzed, and vibration characteristics of blisk with cracking blades on axial flow compressor were summarized. The results show that the blisk with cracking blades can cause vibration response of the axial flow compressor to present the nonlinear characteristics and the splitting of formant in the vibration frequency range, indicating the blade crack could induce mistuning of the first-stage rotor blisk of the axial flow compressor. With the rise of the speed, the frequencies of two formants fluctuate (periods of fluctuation about 8s and 9.2s respectively), and the blade crack grows and the number of cracking blades increases, so the mistuning extent of the blisk increases and modal localization of low order modes of the blisk appeares.
Method of roller bearing fault diagnosis based on feature fusion of EMD entropy
XIANG Dan, CEN Jian
2015, 30(5): 1149-1155. doi: 10.13224/j.cnki.jasp.2015.05.016
Abstract PDF(952KB) icon1518 icon797
Abstract:
The limitation of single fault signal for roller bearing fault diagnosis and nonlinear relation of fault features were studied. Starting from theory of information fusion, the method based on feature fusion of empirical mode decomposition (EMD) entropy was proposed using nonlinear dynamics parameters of entropy as features to deal with roller bearing fault diagnosis problem. Firstly, EMD was conducted for original signal, and on the basis of the property of adaptive multi-resolution for the EMD, different entropies of the intrinsic mode function (IMF) signal reconstructed by using the EMD were calculated. Secondly, the information fusion of the state features was further implemented by using the kernel principal component analysis (KPCA) to extract the complementary feature. Finally, the support vector machine (SVM) was employed to diagnose the fault by using the extracted fusion features. The experiment of rolling bearing fault diagnosis shows that the proposed method combines EMD, information entropy theory and strong nonlinear processing of KPAC, so it can be used for roller bearing fault diagnosis.
Low cycle fatigue life test of high pressure turbine disk based on safe life procedure
LIU Chuang, CHEN Guo-dong, LIU Da-cheng
2015, 30(5): 1156-1161. doi: 10.13224/j.cnki.jasp.2015.05.017
Abstract PDF(879KB) icon1512 icon809
Abstract:
The low cycle fatigue life test of high pressure turbine disk of an engine was studied by using safe life procedure based on Britain military standard Defence Standard 00971 safety requirements for disks. The finite element method was used for analyzing the stress field of high pressure turbine disk of engine under working conditions, and the effect of temperature field on stress distribution was considered. The critical position and reference cycle of high pressure turbine disk were determined according to Defence Standard 00971; then the test plan of low cycle fatigue life of high pressure turbine disk was formed, and the safe life assessment method of high pressure turbine disk based on test results was determined finally. The analysis shows that the stress factors of hub and bolt-hole are 1.0 and 1.017 respectively, which are within a reasonable scale; the test method of increasing rotation speed and cutting turbine blade simultaneously can simulate the effect of thermal stress on life effectively, giving important guidelines for low cycle fatigue life test of high pressure turbine disk.
Tensile properties of laminated composites with a hole under temperature conditions
WENG Jing-meng, WEN Wei-dong, XU Ying, ZHAO Yang
2015, 30(5): 1162-1170. doi: 10.13224/j.cnki.jasp.2015.05.018
Abstract PDF(1204KB) icon1476 icon723
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The stress analysis equations of laminated composites under temperature conditions was derived based on the virtual work principle of incremental form and the theory of unidirectional ply, and the progressive damage stress analysis method of laminated composites considering the effect of temperature was established by integrating the progressive damage analysis theory. On this basis, the tensile damage processes of laminated composites with a hole at 22, 80, 120℃ were predicted; compared with experimental results at 80℃ and 120℃, the maximum error of predicted strength was -2.28%. Research shows that the initial fiber damage strength and the failure strength of laminated composites with a hole are reduced with temperature rising, while the initial matrix damage strength rises gradually.
Optimizing design of composite spindle of aero-engine with hybrid algorithm consisting of genetic algorithm and enumeration algorithm
WANG Jie, LU Shan
2015, 30(5): 1171-1177. doi: 10.13224/j.cnki.jasp.2015.05.019
Abstract PDF(790KB) icon1404 icon728
Abstract:
For the case of coexistence of discrete and continuous variables in optimizing design of composite spindle, a hybrid algorithm consisting of genetic algorithm and enumeration algorithm was presented. From the prototype of an aero-engine low pressure turbine shaft, this hybrid algorithm was used to optimize ply angles and thickness of composite spindle for losing the weight of spindle under the premise of achieving the targets of static strength, critical speed and overall dimension. The results show that the hybrid algorithm can realize 5.54% and 3.87% extra weight loss for from 1 to 10 plies compared with full permutation algorithm and single genetic algorithm; and when plies numbers are greater than 6, the optimizing efficiency can be improved up to 3.1 times with using hybrid algorithm. Finally, the suggestion is given that the composite layer thickness is limited by strength and should not be too thin.
General transition arcs redesign and multivariable optimization of tenon-mortise joints
LEI Chi, WEN Wei-dong, CUI Hai-tao
2015, 30(5): 1178-1183. doi: 10.13224/j.cnki.jasp.2015.05.020
Abstract PDF(816KB) icon1436 icon767
Abstract:
In order to obtain a better structure type and reduce stress concentration to achieve better fatigue strength, the dual arcs transition on tenon-mortise joints was examined to find out its influence on stress distribution. Geometric restrictions on dual arcs transition were derived to support design optimization and modifications. Dual arcs transition were employed on two-teeth tenon-mortise joints of turbine disk and the stress assessment on the structure was performed. The dual arcs transition was proved effective in reducing stress concentration and improving structure strength. Multivariable optimization is carried out based on Isight platform using non-linear quadratic programming language (NLQPL) method. Better structural parameters are achieved to reduce stress concentration, and the maximum stress decreases by 19.98%.
Application of variable-camber inlet guide vanes in counter-rotating compressor
LIU Bo, ZHANG Guo-chen, WU Xiao-xiong, SONG Zhao-yun
2015, 30(5): 1184-1191. doi: 10.13224/j.cnki.jasp.2015.05.021
Abstract PDF(1237KB) icon1366 icon819
Abstract:
The flow of counter-rotating compressor was simulated by the NUMECA, and the flow structure and performance were obtained under different cambers of variable-camber inlet guide vanes (VIGVs). The total pressure ratio decreased and stability operating range became narrow when the camber of VIGV was positive. With the increasing camber of VIGVs, the total pressure ratio increased, and the point of blockage moved right-wards when the camber of VIGV was negative. The stability operating range was widest when the camber of VIGV was -15°. The results showed that it could adjust and improve the performance and flow structure of counter-rotating compressor by using VIGV. The reason is that the VIGVs could change incidence angle of rotors, and make incidence angle close to design incidence angle, thus improving the performance of compressor.
Experiment of an ultra-high-lift low pressure turbine performance at unsteady state
SUN Shuang, LEI Zhi-jun, LU Xin-gen, LI Wei, ZHU Jun-qiang
2015, 30(5): 1192-1199. doi: 10.13224/j.cnki.jasp.2015.05.022
Abstract PDF(1392KB) icon1255 icon723
Abstract:
The performance of an ultra-high-lift after loaded low pressure turbine (LPT) at steady and unsteady state has been investigated experimentally in the present paper. The experiment result show that both of the separation bubble and profile loss have been decreased by the wakes induced transition combined with the separation transition at low inlet Reynolds number and low inlet free stream turbulence intensity under the effect of upstream wakes. In one wake passing periodicity, the boundary layer separation is expanded and shrunken periodically due to the upstream wakes. It has also been seen that the wake is cut into 2 parts-a primary wake and a secondary wake, downstream the blade maximum camber. Even though the secondary wake can induce the transition, the suppression effect of separation is low due to the low wake intensity.
Tip clearance variation and its influence on a 3-stage low pressure fan performance in different operating conditions
YANG Dong, LI Qiu-shi, ZHANG Jian
2015, 30(5): 1200-1209. doi: 10.13224/j.cnki.jasp.2015.05.023
Abstract PDF(1383KB) icon1290 icon791
Abstract:
Tip clearance variation and its influence on a 3-stage low pressure fan performance in different operating conditions were studied using model and numerical simulation method. According to prediction results of tip clearance prediction model, the tip clearance variation of the 3-stage low pressure fan was mainly associated with the rotating speed, and the tip clearance variation from choke condition to near stall condition was small at the same rotating speed. Based on these characteristics, an evaluation method about the influence on the stability margin with tip clearance variation was found. The performance of a 3-stage low pressure fan was simulated in different operating conditions to allow a comparison by using the predicted tip clearance or not. The results show that the influence with tip clearance variation increases along with the growing rotating speed, and the tip clearance variations has a 0.5% impact on the calculated mass flow rate at inlet, 0.5% impact on the calculated maximum efficiency and 5% impact on the calculated stability margin at the 100% design rotating speed.
Improved empirical prediction model for multi-stage turbine noise
JI Liang, QIAO Wei-yang, WANG Liang-feng, YING Ji-yong
2015, 30(5): 1210-1218. doi: 10.13224/j.cnki.jasp.2015.05.024
Abstract PDF(994KB) icon1259 icon770
Abstract:
Based on early empirical prediction models and the test data of turbine noise, the key parameters of turbine which may influence the turbine noise were analyzed. And an improved empirical prediction model for multi-stage turbine noise was developed. This improved model was composed of three components: computation for single stage turbine noise, computation for the noise attenuation effect of each downstream turbine stage and superposition for the noise of each stage turbine. The calculation method for single stage turbine noise had been validated by use of turbine noise test data. Result shows that, the calculation deviation is less than 1.5 dB. An empirical prediction method fitting by experimental data for the propagation attenuation caused by downstream blade rows is also used in the improved multi-stage turbine noise prediction model. With comparison to early empirical prediction models, the calculation method of the improved model is more reasonable and the noise prediction result is more reliable.
Experiment of dynamic evolution characteristics of stall cells
MA Cai-dong, WU Yun, ZHANG Zhi-bo, ZONG Hao-hua, LI Yi-fan
2015, 30(5): 1219-1227. doi: 10.13224/j.cnki.jasp.2015.05.025
Abstract PDF(1531KB) icon1555 icon709
Abstract:
The throttling characteristics of a single-stage low-speed axial compressor were experimently investigated. Dynamic pressure signals were measured during the throttling process by dynamic pressure sensors in circumference. In order to analyze the dynamic evolution characteristics of stall cells during the throttling process, time domain analysis and frequency domain analysis were conducted combined with polar coordinate visualization. The results indicate that stall precursor type is modal wave and the frequency of modal wave is about 40% rotor rotation frequency; the compressor generates two stall cells at 349.5r in circumference at the early stage of stall, and two stall cells merge into one at 360r; one stall cell begins to split as the compressor runs into deep stall and splits into two stall cells at 410r; two stall cells merge into one again at 665r as the compressor exits stall, and finally the compressor exits the stall at 674.5r.
Calculation of pressure fluctuation within volute of hydraulic turbine under different guide vane numbers
SHI Guang-tai, YANG Jun-hu, MIAO Sen-chun, LI Tai-long
2015, 30(5): 1228-1235. doi: 10.13224/j.cnki.jasp.2015.05.026
Abstract PDF(1047KB) icon1462 icon634
Abstract:
Vibration phenomenon exists when centrifugal pump is operated as hydraulic turbine. In order to make hydraulic turbine operate stably, the volute outlet of hydraulic turbine was designed with different guide vane numbers; then, the geometric models were established using Pro/e software under different guide vane numbers; the monitoring points were set using ANSYS-CFD software along circumferential and radial directions of volute, and amplitudes of pressure fluctuation within volute of hydraulic turbine were calculated under different guide vane numbers; afterwards, the calculational results of pressure fluctuation were transformed by fast Fourier transform, and the distribution of frequency domain of pressure fluctuation in volute and vibration in hydraulic turbine were analyzed under different guide vane numbers. Investigation results show that the dominant frequency amplitude of pressure fluctuation is minimal along circumferential and radial directions of volute when the guide vane number is equal to 9. With the increase of flow rate, dominant frequency amplitude and maximum fluctuation amplitude of pressure fluctuation of monitorin points of valute along radial direction gradually increase, but the degree of increase gradually decreases with the increase of guide vane numbers. When the volute outlet of hydraulic turbine is designed with a set of guide vanes that the guide vane number is equal to 9, the vibration and noise within hydraulic turbine are effectively reduced, and the stability of hydraulic turbine is enhanced.
Influence of bump end wall on cascade flow of high turning-bowed compressor
CUI Ke, SONG Yan-ping, LIU Hua-ping, CHEN Fu
2015, 30(5): 1236-1243. doi: 10.13224/j.cnki.jasp.2015.05.027
Abstract PDF(1104KB) icon1084 icon633
Abstract:
The influence of bump end wall on flow cascade of high turning-bowed compressor was investigated. The result shows that the influence is better when the bump salient point is located on the pressure side, and the outlet total pressure loss obtains 5.8% reduction when the height of bump is 2% of the whole blade height. However, a poor result may be obtained as the salient bump point was located between the pressure side and the suction side. When the salient bump point of the end wall profile is 25% pitch away from the pressure side and the height of bump is 5% of the whole blade height, the outlet total pressure loss may get an increase of 3.4%, and the pressure gradient near the end wall changes from positive to negative, thus making the low energy fluid near the end wall of the pressure side transfer to the position of 10% of the whole blade height on the suction side and join into the low energy fluid near the suction side, strengthening the local secondary flow. As the angle of attack changes, the reverse differential pressure constructed by the lower bump end wall can still obviously reduce the intensity of the local secondary flow as well as the outlet total pressure loss; the outlet total pressure loss obtains a 5.6% reduction at the angle of attack of +3° and a 3.5% at the angle of attack of -3°. Meanwhile, the redistribution of the load along the radial direction due to this differential pressure will also change the flow near the upper end wall.
Research on heat load for main propulsion direct drive PMM of all-electric UAV
ZHANG Bing-yi, WANG Sen, FENG Gui-hong
2015, 30(5): 1244-1250. doi: 10.13224/j.cnki.jasp.2015.05.028
Abstract PDF(914KB) icon1135 icon698
Abstract:
Taking the main propulsion direct drive permanent magnet motor (PMM) of all-electric unmanned aerial vehicle (UAV) as the object of study, the heat load characteristics of main propulsion motor were analyzed in different working conditions. The fluid-solid coupled physical and mathematical models were established under strong cooling condition for the structure characteristics of open of main propulsion motor according to the fluid mechanics and heat transfer theory. The temperature rise of main propulsion motor was calculated in different heat loads and climbing angles. The changing rules of heat load and temperature rise of main propulsion motor were deeply analyzed under different working conditions. The wind tunnel and flight tests of main propulsion motor were performed. Result shows that, the highest temperature rise of motor is 124K when the heat load is 5500A2/(cm·mm2). Compared with the simulation value, the accuracy is within 2%, verifying the correctness of theoretical analysis. The heat load range of UAV main propulsion motor is between 3000A2/(cm·mm2) and 5500A2/(cm·mm2).
Compensation of springback error in a cold rotary forging method for hypoid gear
DANG Yu-gong, DENG Xiao-zhong, JIANG Chuang, NIE Shao-wu
2015, 30(5): 1251-1259. doi: 10.13224/j.cnki.jasp.2015.05.029
Abstract PDF(1454KB) icon1033 icon729
Abstract:
The authors put forward a cold rotary forging mthod, and the method simplifies the die structure, adopts the local line contact continuous plastic forming. The algorithm of displacement adjustment was used to construct the compensation iteration system of springback error, which was used to correct springback error of the rolling die. The feature of the system was first estimating the workpiece geometry using correction algorithm when the workpiece was assumed no springback, then obtaining the new rolling die with the design principle of rolling die. Based on the basic theory of elastic-plastic finite element method, instance of verification was carried out with the aid of finite element numerical simulation technology. The results of this research confirm the compensation iteration system of springback error just need three iterations to make the workpiece tolerances within the permitted scope, therefore it can greatly shorten the production cycle and cost.
Parameters effect on dual-path helical gear transmission dynamic load and load sharing characteristic
DONG Jin-cheng, WANG San-min, LIN He, WANG Lin-jie
2015, 30(5): 1260-1266. doi: 10.13224/j.cnki.jasp.2015.05.030
Abstract PDF(1027KB) icon1064 icon686
Abstract:
The lumped mass method was adopted to establish the dual-path helical gear transmission system dynamic model and dynamic equation; and considering the gear meshing deviation and time-varying meshing stiffness, change rule of the dynamic load coefficient and the load sharing coefficient of transmission system were studied in the case of different support stiffness and separated torque angles. The results show that: (1) the larger support stiffness is conducive to the transmission system load sharing characteristic and stability, and the load sharing characteristic is close to the ideal at the case of 16 times the initial support stiffness; (2) the dual-path helical gear transmission system's separated torque angle has a great influence on the dynamic load coefficient and the load sharing coefficient, and the system loading sharing characteristic gets the most optimal at the separated torque angle of 110 degree; (3) even 1μm meshing deviation has a great negative effect on the system loading sharing characteristic, so it should be strictly controlled.
High-precision prediction on unsteady aeroelastic loads of helicopter rotors under blade-vortex interaction condition
WANG Jun-yi, ZHAO Qi-jun, MA Li, LI Peng
2015, 30(5): 1267-1274. doi: 10.13224/j.cnki.jasp.2015.05.031
Abstract PDF(1233KB) icon1345 icon739
Abstract:
In order to obtain accurate aerodynamics loads of helicopter rotors under complex blade-vortex interaction (BVI) condition, blade deflections were introduced into rigid rotor CFD analysis and a computational fluid dynamics/computational structural dynamics (CFD/CSD) coupling method suitable for aerodynamic characteristics analysis of elastic rotors under BVI condition was developed. The CFD module solved Reynolds averaged Navier-Stokes (RANS)/Euler equations based on dual time-stepping algorithm and Baldwin-Lomax (B-L) turbulence model. The CSD module employed finite element model of moderate deflection beam theory, and the blade equations of motion were calculated by using Newmark-Beta method. Blade deformations were accomplished through algebraic grid deformation method and a CFD/CSD coupling strategy was developed for exchanging fluid/structure information. The established CFD and CSD modules were validated by UH-60A elastic blade respectively, and aerodynamics loads of UH-60A rotor were analyzed under BVI condition and compared with flight test data. The calculated results demonstrated that coupled CFD/CSD method can acquire more accurate aerodynamics loads under BVI condition than lifting-line method in rotor comprehensive analysis and rigid rotor CFD method, and the flow phenomena near azimuth of advancing blade and azimuth of retreating blade under BVI condition are well captured in detail. The calculated results of the lift's phase and amplitude caused by BVI agree well with the experimental data.
Aero-engine gas path fault diagnosis based on genetic algorithm of information fusion
CUI Wen-bin, YE Zhi-feng, PENG Li-fang
2015, 30(5): 1275-1280. doi: 10.13224/j.cnki.jasp.2015.05.032
Abstract PDF(755KB) icon1574 icon803
Abstract:
For the development trend of aero-engines from traditional regular maintenance to condition-based maintenance, the genetic algorithm was studied in the gas path performance parameters estimation, and the improved genetic algorithm based on information fusion was proposed. The multi-source information was fused with genetic algorithm to reduce search range of genetic algorithm. The simulation results prove that the situation that genetic algorithm might fall into local optimum in optimization process can be effectively overcome by multi-source information fusion. The estimation accuracy of gas path performance parameters can be improved evidently, and the estimation error can be controlled within 5% or less.

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