2015 Vol. 30, No. 11

Combustion Heat and Mass Transfer
Internal cooling passage of mist/steam two-phase flow enhanced cooling gas turbine blade
SHI Xiao-jun, SHUI Lin-qi, GAO Jian-min, LI Fa-jing
2015, 30(11): 2561-2567. doi: 10.13224/j.cnki.jasp.2015.11.001
Abstract:
A square channel of a geometry commonly used in heavy-duty gas turbine blade as forced convection cooling channel was experimentally studied. The effect of Reynolds number, wall heat flux and mist mass flow rate on the heat transfer characteristic of mist/steam cooling channel wall were analyzed. A experimental correlation of heat transfer was developed to account for mist flow working conditions and channel wall heating conditions. Results show the heat transfer coefficient of mist/steam two-phase flow is significantly higher than the pure steam. Heat transfer performance of mist/steam decreases with increasing of heat flux and increases with increasing of Reynolds number and mist mass flow ratio. The average heat transfer coefficient of upper wall surface is lower 13% than bottom wall surface under higher heat flux and lower mist mass flow ratio, while in the case of low heat flux and high mist mass flow ratio, this ratio increases to approximately 25%.
Gas analysis test and calculation method of aeroengine
WANG Ming-rui, XIAO Yang, HAN Bing, JIA Lin-yan
2015, 30(11): 2568-2574. doi: 10.13224/j.cnki.jasp.2015.11.002
Abstract:
Targeting gas analysis test in the aeroengine and combustion chamber experiments, the principle and system of gas analysis test were introduced. The computing method for Liquid fuel used was optimized, and the method for gas fuel was developed. The influence of the error about gas component test on the computation result of combusting parameter was analyzed. The effects of mixed sampling means and sampler structure were discussed, and the factors about judging rationality of mixed sampler structure were provided. The measurement results of gas analysis and general testing were compared. Excess air coefficient is better than 5% with reasonable mixed sampler structure and enough measuring points and reasonable gas analysis system. The deviation of combustion efficiency from thermocouple and gas analysis is analyzed.
Analysis of low-swirl injector emissions and combustion stabilization
ZHANG Chi, YU Bo-wen, YANG Qian, LIU Cheng-chuan, LIN Yu-zhen
2015, 30(11): 2575-2583. doi: 10.13224/j.cnki.jasp.2015.11.003
Abstract:
Low-swirl combustion technology based on low-swirl injector (LSI) has an ability of ultra-low emission. The principle of the low-swirl combustion stabilization and emissions reduction was analyzed; it was found that its special flowfield structure matching the turbulent flame propagation was a key factor for combustion stabilization and pollution emissions. Key parameters such as the vane angle, radius ratio and mass flow ratio, could impact the downstream flow characteristics of LSI, which would further affect the combustion performance. Fuels impact the combustion stabilization and pollution emissions of LSI by the flame speed and adiabatic flame temperature. To apply the liquid fuel in LSI, the premixed prevaporised combustion was adopted at present, and the experimental results indicated that it could reduce 10%-60% of NOx emissions compared with the traditional high swirl injector combustor, along with a risk of autoignition and flashback. And for LSI spray combustion, more basic researches on the liquid spray combustion in low-swirl flow shall be required. It is difficult to develop next-generation ultra-low emission combustor for aero-engines different from the traditional high-swirl combustion, unless solving the application problem of LSI using liquid fuel.
Improvement on one-dimensional flow model of rotor-stator cavity with central inlet
LIN Li, TAN Qin-xue, WU Kang, REN Jing
2015, 30(11): 2584-2591. doi: 10.13224/j.cnki.jasp.2015.11.004
Abstract:
The boundary layer entrainment mass flow of rotary disk was analyzed numerically in order to improve the performance of one-dimensional(1-D) flow model of rotor-stator cavity. The numerical results show that, 1/7 power law assumption of boundary layer velocity distribution underestimats the boundary layer entrainment mass flow of free disk, affecting the calculation of source region boundary position; the traditional correlations can not correlate the numerical results of boundary layer entrainment mass flow on rotary disk under different conditions well, affecting the calculation of swirl ratio in core region of 1-D flow model. Correlations of boundary layer entrainment mass flow on free disk and rotary disk in rotor-stator cavity were brought out by investigating the numerical results, and 1-D flow model was corrected accordingly. Moreover, the corrected 1-D flow model was verified by experiments, showing that the corrections improved the accuracy of 1-D flow model with respect to the radial pressure difference calculation.
Model experiment on pressure drop and thermal efficiency of double U-shaped tubes heat exchanger
LIU Xi-yue, ZHANG Jing-zhou, LI Gang-tuan, KANG Yong
2015, 30(11): 2592-2599. doi: 10.13224/j.cnki.jasp.2015.11.005
Abstract:
Pressure drop and thermal efficiency of double U-shaped tube heat exchanger, especially the effects of tube cross-sectional shape and heat exchanger inclined angle, were experimentally investigated in a low-speed wind tunnel. The results show that the internal pressure drop for the elliptical tube heat exchanger is bigger than the circular tube heat exchanger under the same averaged flow velocity inside the U-shaped tube. The difference between two different heat exchangers is more obvious under higher flow velocity inside the U-shaped tube. For the external flow, the pressure drop is significantly increased with the increase of the heat exchanger's inclined angle. Under small inclined angle, the external flow pressure drop for the elliptical tube heat exchanger is somewhat higher than the circular tube heat exchanger. However, the pressure drop outside the elliptical tube heat exchanger is significantly lower than the circular tube heat exchanger under big inclined angle. The overall heat transfer coefficient of heat exchanger with 30 degree inclination is about 50% higher than that with 10 degree. Under the density flow ratio of 0.4, the thermal efficiency of elliptical tube heat exchanger is increased about 6% in relative to the circular tube heat exchanger.
Instantaneous propagation characteristics of continuous rotating detonation wave
WANG Chao, LIU Wei-dong, LIU Shi-jie, LIN Zhi-yong, JIANG Lu-xin
2015, 30(11): 2600-2606. doi: 10.13224/j.cnki.jasp.2015.11.006
Abstract:
Experiments on continuous rotating detonation were performed using hydrogen/air. The instantaneous propagation frequency and velocity of the continuous rotating detonation wave (CRDW) were analyzed, and the relative standard deviation was obtained to describe the stability of detonation wave instantaneous propagation process. The effect of propellant mass flow rate on the CRDW instantaneous propagation characteristics was studied. The results showed that when the mass flow rate of air increased from 321g/s to 505g/s with the equivalence ratio of 1.0, the average propagation frequency of CRDW rose from 4.60kHz to 5.33kHz, and the average propagation velocity increased from 1445m/s to 1674m/s. Correspondingly, the relative standard deviation of instantaneous propagation frequency of CRDW decreased from 4.00% to 1.69%, indicating a more stable propagation process of CRDW at a higher propellant mass flow rate.
Cavitation characteristic in aviation fuel pump based on surrogate fuel
XIONG Ying-hua, LIU-Ying, LI Shu-lin, CHEN Tai-ran, WANG Guo-yu
2015, 30(11): 2607-2615. doi: 10.13224/j.cnki.jasp.2015.11.007
Abstract:
To study the cavitation characteristic in an aviation fuel pump with China Daqing RP-3 kerosene as flowing medium, the cavitating flows in the aviation fuel pump under high temperature and low pressure circumstance were researched based on the numerical simulations. Surrogate fuel was put forward to take the place of the kerosene in the complex components. A four-species surrogate fuel consisting in mole fraction of 74.5% dodecane,10% methylcyclohexane,10% toluene and 5.5% octane was selected to simulate the real Daqing RP-3 kerosene. Local swirling correction turbulence model derived from the standard k-ε two-equation model and Zwart-Gerber-Belamri cavitation model were applied into the numerical simulations. The numerical data were compared with the experimental results. The results show that this numerical method based on surrogate fuel and local swirling correction turbulence model can calculate the cavitation characteristic in the aviation fuel pump accurately. Thermodynamic effects of Daqing RP-3 kerosene can be ignored, but the temperature has an influence on cavitation characteristic of the aviation fuel pump. The cavitation characteristic of the aviation fuel pump is worse under 80℃. Rotational speed has a great influence on cavitation characteristic of the aviation fuel pump. The cavitation specific speed is the highest under 10000r/min, and the cavitation characteristic is the best.
Research of fouling deposition influence on heat transfer of blade surface
SHI Hui, LI Liang, FENG Zhen-ping
2015, 30(11): 2616-2622. doi: 10.13224/j.cnki.jasp.2015.11.008
Abstract:
Two turbine blades, the MARKⅡ vane and a high pressure turbine vane, were chosen in the study. The former blade surface was smooth and the latter was rough, covered with evenly spaced truncated cones. The CFD numerical simulation technique was used to calculate the cascade characteristics and blade surface heat transfer distribution. The reliability of the computational method was validated by comparing the calculated results with the experimental data. The results show that accurate prediction of the transition location and appropriate y+ value are key to calculate the heat transfer characteristics of the blade surfaces. The predicted results by using the shear stress transport(SST)transition model are most satisfactory. In the calculation of rough blade, the roughness model was verified and then fouling deposition effects on heat transfer characteristics were analyzed in detail. It is shown that the heat transfer coefficient on the rough blade surface is enlarged with the increase of surface roughness, due to the enhancement of near-wall turbulence.
Realization and verification of the flow characteristic experiment in rotating two-pass square duct with smooth walls
CHEN Hao, DENG Hong-wu, CHENG Jun-hua, LI Yang, TIAN Shu-qing
2015, 30(11): 2623-2629. doi: 10.13224/j.cnki.jasp.2015.11.009
Abstract:
In order to investigate the pressure and flow characteristics of the rotating channels, a new measurement system was invested and implemented in National Key Laboratory of Science and Technology on Aero-Engine Aero-Thermodynamics of Beijing University of Aeronautics and Astronautics. The new measurement system with high measurement accuracy and plural air channels could reach high Rotation numbers by increasing the back pressure of test section. The Reynolds and Rotation numbers ranged from 20000 to 70000 and 0 to 1.025 respectively. The investigation used different temperature ratio conditions to investigate the pressure and flow characteristics of the rotating two-pass square duct with smooth walls. The results proved the reliability and superiority of the measurement system by comparing with similar experiments in foreign countries. The result showed that the static flow resistance increased with the increasing Reynold number, and decreased when the Reynold number was high enough. In cold conditions, the flow resistance increased with the increasing Rotation number. In thermal state, the flow resistance showed no obvious change in low Rotation number, and increased significantly with the increasing Rotation number in high Rotation number.
Turbomachinery
Application of time-inclined method on the unsteady simulation of turbomachinery
GAO Li-min, LI Ping, CHEN Xuan, ZHOU Li
2015, 30(11): 2630-2637. doi: 10.13224/j.cnki.jasp.2015.11.010
Abstract:
The method of time-inclined was applied to deal with arbitrary pitch ratio for unsteady simulations. Through time and space conversion of the flow control equation, the unsteady time exact algorithm of two adjacent blade rows with unequal pitch at any speed was developed, so that the method was expanded to be suited to the unsteady flow calculation of turbomachinery with extraordinary rotor/rotor construction. On this basis, the programs of time-inclined algorithm and domain scaling algorithm were both written. The unsteady flow calculation of the stator/rotor interaction between an inlet guide vane and rotor shows that compared with domain scaling algorithm, time-inclined method using the original single-channel model truly reflects the unsteady flow field; at the same time, the amount of calculation is only 2/41 of the total channel simulation, greatly saving the cost calculation.
Investigations on desensitization of blade tip clearance variation in turbine blades
GAO Jie, ZHENG Qun, LIU Yun-ning, ZHAO Zhan
2015, 30(11): 2638-2646. doi: 10.13224/j.cnki.jasp.2015.11.011
Abstract:
Numerical investigation was performed to simulate the sensitivity of turbine performance to blade tip clearance variation for four different tips including flat tip and other three tips: cavity tip, flat tip with injection and cavity tip with injection; passive, active and compound clearance control methods were used respectively by solving Reynolds-averaged Navier-Stokes equations in conjunction with a standard k-ω two-equation turbulence model. The influences on the clearance flow structure and losses caused by tip clearance variation were analyzed. In addition, the variation of the turbine performance which changes by the different clearances was investigated. Furthermore, the sensitivities of the efficiency-gains caused by different clearance control methods to changes in incidence angles were assessed. Results show that, with different clearance control methods, the growth rate of the strength of tip leakage vortex slows down, especially for the compound clearance control method. This leads to the results that the compound clearance control method presents the lowest sensitivity of turbine performance to clearance variation. In addition, only the leakage flows over the front part of the blade are sensitive to incidence angle variation, which causes the best adaptability of cavity tip to incidence angle variation.
Stall of an axial-compressor rotor with casing treatment
FAN Lin
2015, 30(11): 2647-2657. doi: 10.13224/j.cnki.jasp.2015.11.012
Abstract:
For investigating the stall of compressor with casing treatment, using the unsteady Relynold averaged numerical simulation method, numerical simulations of an axial transonic rotor with a axial skewed slot casing treatment with back plenum were carried out. Then, the rotor characteristics at high/low speed were gained, accordingly, the flow fields at near stall points were analyzed as well. It was found that the main responsibility of the inception of stall under the condition of casing treatment is different from the condition of the solid casing. At the operation point of stall, due to that the casing treatment could not absorb any more low energy fluid at blade tip, the fluid with little streamwise momentum was accumulated near the trailing edge of suction surface at blade tip, and a serious flow blockage was formed, the stall was finally triggered, even though the negative influence of the blade tip leakage flow was still suppressed effectively.
Effects of vortex generator jet on the flow of bowed compressor cascades
LI Long-ting, SONG Yan-ping, LIU Hua-ping, CHEN Fu
2015, 30(11): 2658-2665. doi: 10.13224/j.cnki.jasp.2015.11.013
Abstract:
A numerical study of vortex generator jet application in bowed compressor cascades shows that, vortex generator jets with several kinds of parameters for both positively and negatively bowed blade can reduce the total loss at most by 2.5% and 8.8% respectively. Moreover, the result reveals that the jet can not only apply momentum to boundary layer, but also create a streamwise vortex, which can deflect the passage vortex to make it rotate away from the suction side. The streamwise vortex is dissipated in the flow passage at 60% axial chord length from the leading edge. For positively bowed blade, the flow separation disappears on the suction side, and the concentrated shedding vortex is weakened for negatively bowed blade. Besides, the jet increases the blade loading and turning angle.
Study on the frequency of partial surge and a frequency prediction method
PAN Tian-yu, HE Lei, WANG Zheng-he, LI Zhi-ping, LI Qiu-shi
2015, 30(11): 2666-2672. doi: 10.13224/j.cnki.jasp.2015.11.014
Abstract:
Partial surge was kind of axisymmetric, low-frequency, hub region initiated disturbance by experimental investigations in a transonic compressor. In term of physical mechanisms, partial surge was much similar to an oscillation in a Helmholtz system. By Duct-Compressor-Plenum model, the Helmholtz frequency of the system was estimated, which was very close to the frequency of partial surge. To further verify this link between the frequency of partial surge and the Helmholtz frequency, experimental investigations were carried out with variation of specific parameters of the Helmholtz system. The results present that the frequency of partial surge varies with the Helmholtz frequency of the system. And the values of both frequency are very close. Therefore, the frequency of partial surge is determined by the Helmholtz frequency of the system.
Aerothermodynamics and Aeroengine Design
Performance degradation and components deterioration degree estimation for a turboshaft engine
HUANG Kai-ming, LI Yi-Guang, ZHANG Wei, FENG Xing, CAI Jian-bing
2015, 30(11): 2673-2679. doi: 10.13224/j.cnki.jasp.2015.11.015
Abstract:
To monitor the performance and health conditions of a turboshaft engine during an endurance test, an engine mathematical model was set up and adapted to its real performance by adjusting component maps using a multiple-point performance adaption method. Gas path diagnostic analysis of the engine based on a non-linear gas path analysis (GPA) methodology was performed. In combination with field experiences, evaluation of the engine gas path component deterioration during an engine endurance test was carried out. The results indicated that the engine performance deviation and component deterioration varied over time. During initial phase of the test, the performance of the compressor and the compressor turbine deviated most rapidly then stabilized afterwards. As for the power turbine, the health was almost unchanged during the entire endurance test. The validation and experience of the GPA diagnostic technique prove that the technology can be applied into engine performance and health check for the evaluation of health of the turboshaft engine in its future service.
Analytical model of inlet distortion effect on aerodynamic stability of variable cycle engine
YAN Wei, HU Jun, TU Bao-feng, ZHANG Chen-kai, YIN Chao
2015, 30(11): 2680-2687. doi: 10.13224/j.cnki.jasp.2015.11.016
Abstract:
A theoretical model was established to assess the effect of circumferential inlet distortion on the aerodynamic stability of the variable cycle engine. The model incorporated source items into the two-dimensional unsteady Euler's equations to describe the flow through variable cycle engine. The source items were calculated according to the component characteristic and the equations were solved by time-advancing method. The circumferential inlet distortion transfer curve along the flow path and the critical distortion factor of the variable cycle engine were obtained. The results suggest that the model accomplishes the simulation of inlet distortion effect on aerodynamic stability of variable cycle engines. The inlet distortion experiences a great attenuation when passing through the core driven fan stage. The core driven fan stage is sensitive to distortion. It is the weakest link of the aerodynamic stability of the variable cycle engine.
3-D numerical simulation of dynamic process of twin nozzle STOVL aircraft lift loss
HONG Liang, Eriqitai, XU Jing-lei
2015, 30(11): 2688-2694. doi: 10.13224/j.cnki.jasp.2015.11.017
Abstract:
For twin nozzle short take off and vertical landing (STOVL) aircraft lift loss, Reynolds-averaged turbulence k-ε model was employed to simulate the aerodynamic flow field of STOVL aircraft and its lift loss. The effects of suck down and additional lift of STOVL aircraft on lift loss were studied, and curves of suck down during steady and dynamic processes were acquired. Results showed that suck down mainly depended on low pressure area generated by entrained flow, and additional lift had little effects on lift loss. When dimensionless height was lower than 3.5, suck down was larger than 10% of the aircraft lift. Dynamic and steady processes were compared, and suck down in the dynamic process was greater than that in the steady status, especially at dimensionless height 2, nearly 20.6% difference. The movement and development delay of main vortex was the cause of this difference of suck down during steady and dynamic processes.
Design and simulation of a dual-channel variable geometryturbine based combined cycle inlet
WANG De-peng, ZHUANG Yi, TAN Hui-jun, ZHANG Hong, DU Mo-chen, LI Guang-sheng
2015, 30(11): 2695-2704. doi: 10.13224/j.cnki.jasp.2015.11.018
Abstract:
To meet the demand of turbine based combined cycle (TBCC) engine, a design concept of external parallel dual-channel variable inlet was proposed. By rotating cowls of turbine channel and ramjet channel, the inlet can regulate mass flow capture height and realize mode transition. Besides, the inlet can obtain good performance in a wide Mach range by adjusting internal contraction ratio with the Multi-linkages mechanism under the lower wall of ramjet channel. Numerical simulation method was applied to investigate the flow characteristics and the performance of the inlet. The results reveal that the variable inlet can work in a wide Mach range with good performance in the work envelope. Compared with fixed geometry inlet, the variable geometry inlet can increase total pressure recovery coefficient up to 12.5%, 30.2% and 133.3% at Mach number is 2.5,3.0 and 4.0, respectively.
Investigation on wall modeled large eddy simulation of channel turbulent flow in high Reynolds number
LI Meng, TU Zheng-guang, XU Jing-lei
2015, 30(11): 2705-2712. doi: 10.13224/j.cnki.jasp.2015.11.019
Abstract:
The numerical simulation of plane channel flow was performed with various turbulent models, which were employed for wall modeled large eddy simulation. Large eddy simulation (LES), Spalart-Allmaras (S-A), detached eddy simulation (DES) and a dynamic hybrid model (Hybrid) were investigated. Using the Reynolds numbers ranging from 395 to 12000 based on friction velocity, three kinds of coarse grid were used, the grid numbers of wall-parallel directions were set as 37, 49 and 65, simultaneously.y+ (1)~1 was maintained in wall-normal direction. Mean velocity profile, Reynolds-shear stress and other turbulent statistics were predicted. It was shown that LES cannot provide accurate solutions at high Reynolds number and coarse grid conditions. Log layer mismatch was still a problem of DES. The simulation of Hybrid agreed well with direct numerical simulation (DNS), and the resolved stress accounted for 93% in log layer and about 99% in outer layer. Therefore, proper hybrid model may provide accurate solutions with cost effectiveness and has potential to solve engineering problem.
Autocontrol
Research on backup hydromechanical control plan of the turbo-shaft engine's control system
LIAO Guang-huang, HUANG Jin-quan
2015, 30(11): 2713-2720. doi: 10.13224/j.cnki.jasp.2015.11.020
Abstract:
Based on the research of the development and the maturity of turbo-shaft engine's control systems abroad, a control system scheme including a hydromechanical system as the backup was proposed. The module of backup hydromechanical control system could work synchronously with the digital control module, and switch to the main control system smoothly in case of failure of the digital control mode. This kind of design could achieve the function of backup control for the fuel and the compressor guide vane, and also guarantee the security for the engine's work and the return of helicopters. The design has been checked with the semi-physical simulation experiment and engine rig test after design and manufacturing. According to the verification result, the system has a control precision of ±0.5% for power turbin speed and precision of 4° for the guide vane, which insures the well application in engineering.
Robust design of external gear pump with trapped oil problem
WU Xiao-feng, LIU Chun-jie, GAN Wei-min, WANG Xiao-jun, HU Shao-gang, JI Jing-jing
2015, 30(11): 2721-2729. doi: 10.13224/j.cnki.jasp.2015.11.021
Abstract:
Based on the fluid dynamic characteristics of gear pump, a robust design method was proposed to solve the large noise, low volume efficiency in external gear pump caused by high pressure of trapped oil. A type of high pressure gear pump was used as the research object, modeled and simulated by CFD professional software PUMPLINX. The effects on trapped oil pressure by cat eye type unloading groove structure parameters, gear pump speed, load pressure and medium characteristics were analyzed. An approximate model of trapped oil pressure was built based on the design of experiments and response surface function methods. Finally, in order to reduce the impact of uncontrollable of factors such as pump speed, load pressure and medium characteristics on pump performance, the robust performance evaluation model was built to optimize the cat type unloading groove structure parameters and achieve the trapped oil pressure model subjecting to normal distribution in the case of the minimum mean square error. Besides, with the change of random and uncontrollable factors, the robust performance of trapped oil pressure was verified; the result displayed that the trapped oil pressure peak before robust design fluctuated from 40% to 18% after robust design, so the stability and reliability of working pump were improved.
Numerical simulation on fuel vapor core configuration in fuel vapor core pump with radial straight blades
WANG Bin, YU Ding-peng, YE Zhi-feng, GUAN Hua-sheng
2015, 30(11): 2730-2737. doi: 10.13224/j.cnki.jasp.2015.11.022
Abstract:
To obtain the establishment process and change rule of vapor core in the fuel vapor core pump, based on renormalization group (RNG) k-ε double-equation turbulence model and Schnerr-Sauer cavitation phase transition model, a fuel vapor core pump with radial straight blades was studied by overall three-dimensional geometry modeling and steady vapor-liquid two-phase numerical simulation. And the vapor phase region under the influences of rotation speed, throttle opening and outlet pressure was further analyzed. Results show that, the vapor core enlarges with the increasing rotation speed within a certain range of rotation speed, while the vapor core lessens as the outlet pressure increases at a constant rotation speed. When the vapor phase region expands to the limit position, namely passing through the impeller outlet, the vapor core pump runs under the unstable condition. Both RNG k-ε double-equation turbulence model and Schnerr-Sauer cavitation phase transition models can be applied to numerical simulation on vapor core configuration in the fuel vapor core pump.
New robust control method with guardian maps
LI Chen-liang, ZHANG Rui, LIU Meng-ying, LIU Yan-bin, LU Yu-ping
2015, 30(11): 2738-2745. doi: 10.13224/j.cnki.jasp.2015.11.023
Abstract:
According to uncertain characteristics of modern control system, a new robust control method based on guardian maps theory was proposed. In light of guardian maps theory, the constraints between the controller gain parameters and the closed loop system poles were set up by this algorithm. By the closed loop system poles assignment, the dynamic characteristics and the steady performances were to meet the expected performance requirements. The controller structure was fixed. As long as an initial gain parameter was given, the robust control of the system can be realized. Simulation results show that this algorithm can adaptively obtain the control gain parameters and meet the control requirements all along the entire domain for the second order system model with parameter. Meanwhlie,the Monte Carlo random experiment shows that the control gain parameters still satisfy the requirements of system control performance, so as to ensure the robustness of the control process under the random variation of system parameters.
Construction and experiment of intelligent temperature and humidity measurement system for freight spacecraft
CHEN Jun-guang, LI Yun-hua, LI Yun-ze, ZHANG Hong-sheng, ZHONG Ming-liang
2015, 30(11): 2746-2752. doi: 10.13224/j.cnki.jasp.2015.11.024
Abstract:
According to the requirement for temperature and humidity measurement in thermal equilibrium experiment of a freight spacecraft, a distributed measuring system based on controller area network(CAN) bus and SHT15 intelligent temperature and humidity sensor was designed and constructed. The collected data of measurement modules were transferred to the slave computer(SC) through concentrator, then sent to the personal computer (PC). Data calibration, display and storage were realized. The design concept and flow chart of software in the system were provided. Experiments of vacuum storage and calibration were conducted. The results show that the system has high reliability and accuracy. Measurement errors of relative humidity are less than 2%. Furthermore, the system is convenient to use and increase nodes. The system has been used in actual measurement.
Structure Strength and Vibration
Structure and dynamics analysis of rotor system in geared turbofan engine
MA Yan-hong, CAO Chong, HAO Yong, ZHANG Bo, HONG Jie
2015, 30(11): 2753-2761. doi: 10.13224/j.cnki.jasp.2015.11.025
Abstract:
Taking the coupling between fan and low-pressure rotors of geared turbo fan (GTF) engine into consideration, a simplified model of rotor system and a critical speed calculation method for the model were proposed. Differences of critical speed results between the overall rotor system and the single rotor system were clarified. Influence of typical parameters on critical speed and dynamics of the rotor system was discussed. From the results, calculating the fan and low-pressure rotors separately causes deviation of natural frequency and loss of critical speed. Increase of the gearbox support stiffness leads to rise of critical speeds, while keeping the stiffness value below 106N/m may provide better dynamic characteristics. The flexural rigidity of the torque transmission shaft and radial stiffness of the gearbox have less impact on system's dynamic characteristics.
Design method of squeeze film damper for aero-engine rotors
LIU Zhan-chi, LIAO Ming-fu, CONG Pei-hong, WANG Juan, WANG Si-ji, SHI Bin, LI Yan
2015, 30(11): 2762-2770. doi: 10.13224/j.cnki.jasp.2015.11.026
Abstract:
The design process and method of squeeze film damper (SFD) for aero-engine were proposed, in which the relationship between the dynamic characters of rotors and the SFD design parameters was taken in consideration. The rotor parameters include damping ratio, setting of critical speeds, maximum unbalance, vibration peak and force transmitted to foundations, etc, and the SFD design parameters include the eccentricity ratio, radial clearance and length of the film as well as rotor cage stiffness. The design was made for purpose of control of the critical peak value and force transmitted to foundations.The damping ratio and maximum unbalance of the rotor were found to be critical parameters for the SFD design. Numerical and experimental verification were carried out based on a rotor system. Results show that vibration attenuation of critical vibration peak can be reduced by 60%, and the correctness and effectiveness of the method provide a guideline for the SFD design.
Analysis of the effect of floating ring squeeze film damper on sudden unbalance response of low pressure rotor
XIA Ye-bao, REN Xing-min, QIN Wei-yang, DENG Wang-qun
2015, 30(11): 2771-2778. doi: 10.13224/j.cnki.jasp.2015.11.027
Abstract:
To research the depression effect of floating ring squeeze film damper on sudden unbalance response of low pressure rotor in turboshaft engine, a dynamical simplified model of low pressure rotor supported on floating ring squeeze film damper was built, considering multiple dynamical coupling. Its motion equations were derived and solved by the numerical method. The influence of some parameters, e .g ., mass ratio between floating ring and bearing, stiffness of elastic support, and film clearance, were analyzed. The main results are as follow: compared with traditional squeeze film damper, the floating ring squeeze film damper has better performance in depressing both critical transient responses and sudden unbalance responses in steady-state process or in accelerating process; with greater mass ratio between floating ring and bearing, smaller stiffness of elastic support and smaller film clearance, the floating ring squeeze film damper has better performance in depressing both transient amplitude and transient time of sudden unbalance responses; the speed range with large vibration of rotor system during passsing through the bistable region depends not only on the mass ratio between floating ring and bearing, but also on the film damper clearance; it decreases along with the mass ratio increases, and increases with the film clearance decreases.
Testability prior information fusion method based on uncertainty measure and supporting degree
ZHANG Xi-shan, HUANG Kao-li, YAN Peng-cheng, LIAN Guang-yao, LI Zhi-yu
2015, 30(11): 2779-2786. doi: 10.13224/j.cnki.jasp.2015.11.028
Abstract:
To overcome the shortcoming of subjectivity and unicity in those fusion methods, the uncertainty measure and supporting degree of prior distribution was introduced; and the prior information weighting fusion was proposed on the basis of the uncertainty measure combined with the supporting degree. First, the uncertainty of testability prior information was described using β distribution and the prior distribution hyper-parameter was determined by different prior information. Then, the uncertainty measure and supporting degree was proposed as the weight coefficient of prior information, and the corresponding fusion algorithm was designed. Finally, using the mixed prior distribution and combining with the testability field test data, the posterior results of Bayes fusion evaluation were caculated. This method considered both the proximity of the measure parameter to the real situation, and also the level of supporting degree between different prior information. The example shows that the lower limit of confidence estimation based on the proposed method increases 0.7% than the traditional method at the same confidence.
Rocket Engine
Rate-dependent cohesive zone model of the interface between HTPB propellant and insulation
CHEN Xiong, NIU Ran-ming, ZHENG Jian, JIA Deng
2015, 30(11): 2787-2793. doi: 10.13224/j.cnki.jasp.2015.11.029
Abstract:
In order to build up a rate-dependent cohesive zone model (CZM) of the interface between hydroxyl-terminated polybutadiene(HTPB) propellant and insulation, experimental method and inverse analysis were adopted. Improved single lap joints (SLJ) specimens were used to conduct the HTPB propellant and insulation interface debonding experiment, then a numerical analysis was conducted with cohesive elements method, and with an inverse program developed based on Hook-Jeeves optimizing algorithm, the inverse analysis was conducted for the SLJ specimens to calibrate the interface parameters in different loading rates. Considering the significant rate-dependency shown in the parameters, a rate-dependent damage function was built and then the rate-dependent interfacial type Ⅱ CZM of HTPB propellant and insulation was built based on the bilinear CZM. The correlation coefficient between the predicted result and the experimental result is bigger than 99%, illustrating the rate-dependent CZM referred herein can accurately describe the fracture properties of propellant and insulation interface for the loading rate of 5mm/min to 200mm/min.
Investigation on acquisition schemes of cryogenic propellant subcooling for long-term on-orbit storage
WANG Lei, LI Yan-zhong, MA Yuan, XU Meng-jian
2015, 30(11): 2794-2802. doi: 10.13224/j.cnki.jasp.2015.11.030
Abstract:
Increasing cryogenic propellant subcooling remarkably benefits the long-term on-orbit storage of cryogenic fuels. Literature research and theoretical analysis were conducted to study the working processes and research status for four subcooling schemes, and their advantages and disadvantages were also analyzed. On this basis, a research approach in this field was proposed for guiding the domestic researches. Several valuable conclusions were drawn as follows: (1) Based on the cost consideration, an operating procedure for subcooling operation after fuel filling process is suggested and the subcooling equipment should be located close to the target tank.(2) A liquid nitrogen pool boiling can be used to cool the cryogenic liquid oxygen and liquid methane.(3) Helium injection approach is only suggested to cool the small-scale liquid hydrogen since it costs massive helium gas.(4) Due to excellent characteristics including less total weight and energy input, thermodynamic cryogen subcooler (TCS) approach has a better application prospect in liquid hydrogen subcooling obtainment. This research provides a reference for the domestic researches of cryogenic propellant subcooling.
Power Transimission
Influence predictions of base parameters on noise radiations of face gear drives
LI Zheng-min-qing, CHEN Hong-shang, ZHU Ru-peng
2015, 30(11): 2803-2809. doi: 10.13224/j.cnki.jasp.2015.11.031
Abstract:
To investigate the dynamic behaviors and noise radiations of face gear drives, a calculation procession of noise radiations of face gear drives, which is based on lumped mass method, finite element method (FEM) and boundary element method (BEM), was proposed. Furthermore, a noise radiation of an example case was simulated, and the influences of base geometric parameters and operating conditions on noise radiations of face gear drives were discussed. The analytic results indicate increasing module and drive ratios would benefit to reduce noise radiations, and pressure angles would be insensitive for noise radiations, et al. These contributions would be helpful to improve the design of face gear drives associated with low noise radiations.
Optimum design of double-row angular-contact ball bearing with immune algorithm
CHENG Chao, WANG Jiu-gen
2015, 30(11): 2810-2816. doi: 10.13224/j.cnki.jasp.2015.11.032
Abstract:
The optimal design model of double-row angular-contact ball bearing was established. Dynamic load rating, static load rating and the weighted sum of these two load capacities were set as objective functions respectively, the bearings were optimally designed with immune algorithm. The design parameters included number of rolling elements in one row, the rolling element diameter, inner race groove curvature radii, outer race groove curvature radii and the pitch diameter. The optimal results of immune method were compared with those of genetic algorithm, and the immune algorithm achieved more efficient results. Furthermore, compared with the designs in the handbook of rolling bearings,dynamic load rating and static load rating of the optimized bearings(3210 and 3218) had an increase of more than 60%.