2014 Vol. 29, No. 7

Display Method:
Structure dynamics design method of aero-engine high pressure rotor
LIAO Ming-fu, TAN Da-li, GENG Jian-ming, SONG Ming-bo, LÜ Pin
2014, (7): 1505-1519. doi: 10.13224/j.cnki.jasp.2014.07.001
Abstract:
Taking all design parameters into account, this model was applied for dynamic design of aero-engine high pressure rotors in practice. The influences of design parameters on the vibration features of the rotors were revealed, and an estimation method of critical speeds of rotor was theoretically proven, giving a clear limit value estimation of critical speeds of rotor. A design criterion of the stiffness was suggested with different effects two orders critical responses. A special phenomenon of critical speeds was observed, and a certain combination of rotor parameters can result in an additional critical speed, at which the damper will not reduce the vibration and the vibration peak will reach a very high level. This critical speed is defined as parameter critical speed. The parameter conditions corresponding to this critical speed were obtained, giving important guidelines for the design of high pressure rotors of aero-engines.
Numerical simulation of effect of high temperature oxidation on stress field distribution of EB-PVD thermal barrier coating
HAO Yong, QI Hong-yu, MA Li-qiang
2014, (7): 1520-1526. doi: 10.13224/j.cnki.jasp.2014.07.002
Abstract:
Targeting the characteristics of thermal barrier coatings (TBCs) prepared by electron beam-physical vapor deposition (EB-PVD) of complex structure, the Walker viscoplastic constitutive model was used to realize the accurate description of the high temperature mechanical behavior of TBCs structure. Tube specimens with blade curvature feature were selected for numerical analysis with reference to the actual engine load characteristics. The effect of the interface shape and the thickness of thermal growth oxide (TGO) on stress field of EB-PVD coating were focused on. The calculating results show that the stress field of TBCs structure changes little at the linear interface, while the amplitude of stress field can be changed up to 2 times at the cosine interface. The absolute value of stress at top coat increases due to the presence of the TGO. The valley at the interface is always subject to radial compressive stress no matter of circulation to the highest temperature 1050℃ or cooling to 100℃, therefore the valley is not easy to be damaged; while the stress at the peak is relatively large, furthermore, the stress state is easy to form part of the damage. As a result, the peak is a point for easy failure and destruction of the ceramic layer.
Imbalance response of rotor system with nonlinear bearing stiffness
MA Yan-hong, HE Tian-yuan, ZHANG Da-yi, HONG Jie
2014, (7): 1527-1534. doi: 10.13224/j.cnki.jasp.2014.07.003
Abstract:
According to the nonlinearity of bearing stiffness in aero-engine, a computational method for imbalance response of multi-degree-of-freedom rotor system was developed based on the harmonic balance method. Numerical simulation of imbalance response of the double-disc rotor system with nonlinear bearing was carried out. Important laws and key parameters having impact on the response of nonlinear rotor system were founded. Result shows that the nonlinear characteristics of imbalance response are closely related with the vibration mode; the peak frequency and peak amplitude of rotor increases with the growing bearing stiffness nonlinearity and the imbalance; the third order and fifth order response occurs with nonlinear bearing.
Method of fault feature extraction based on EMD sample entropy and LLTSA
XIANG Dan, GE Shuang
2014, (7): 1535-1542. doi: 10.13224/j.cnki.jasp.2014.07.004
Abstract:
A fault feature extraction method based on the empirical mode decomposition (EMD), sample entropy and manifold learning was presented to account for a range of issues of the vibration signal, e.g. Nonlinearities, non-stationary and weak fault features hard to extract. The proposed method combined the EMD, sample entropy and manifold learning techniques. Firstly, on the basis of the property of adaptive multi-resolution for the EMD technique, the sample entropy of the IMF (intrinsic mode function) signal reconstructed by using the EMD was calculated, and the state features of the rolling bearing were preliminarily extracted. Secondly, the extraction performance of the state features was further implemented by using the manifold learning technique. Finally, the SVM(support vector machine) was employed to classify and to evaluate the feature extraction method. Moreover, the proposed method was applied to the experiment of the rolling bearing fault diagnosis. The experimental results show that the proposed fault feature extraction method has more robust clustering performance than the fault diagnosis method based on the sample entropy of wavelet packets. Furthermore, a relatively high precision, namely, 100% of classification result for the SVM, can be obtained. The proposed method not only decreases the complexity of the feature data, but also enhances the classification performance of fault diagnosis and pattern recognition, thus bringing about certain superiority.
Vibration of bending-torsion coupling gear-rotor-rolling bearing transmission system
LI Chao-feng, ZHOU Shi-hua, LIU Wen-ming, REN Zhao-hui, WEN Bang-chun
2014, (7): 1543-1555. doi: 10.13224/j.cnki.jasp.2014.07.005
Abstract:
A nonlinear dynamic model of bending-torsion coupling for gear-rotor-rolling bearing transmission system was estabished, with consideration of the gear meshing, torsion effect, input/output, and bending/torsion vibration of gear shaft. The dynamic differential equation was deuced based on the imbalanced gear-rotor-rolling bearing of bending-torsion coupling. Considering the gear eccentricity and nonlinear contact of rolling bearing, the influence law of parameters, including the speed, eccentric distance and bearing clearance, etc, on the system vibration response was analyzed. Result show that, an obvious component of rotational frequency of driven shaft existed in the driving shaft, due to the effects of bending-torsion coupling. However, the frequency of every rotation and engagement of shaft was more obvious in the torsional vibration. Given the rolling bearing's own resonance frequency, the effect of the variable stiffness frequency of rolling bearings on the system should be avoided during the system design. The change of gear eccentric distance also affects the time and frequency response of system. Besides, the bearing clearance also affects vibration response of the system. So a suitable bearing clearance is suggested to reduce the vibration amplitude of every part of system.
Approach for civil aero-engine repair objective determination based on life limited parts
FU Xu-yun, CHEN Yin, ZHONG Shi-sheng
2014, (7): 1556-1561. doi: 10.13224/j.cnki.jasp.2014.07.006
Abstract:
To make a scientific and reasonable maintenance workscope, an approach for civil aero-engine repair objective determination oriented towards the life cycle based on life limited parts was proposed. At first, a multi-objective optimization model was established to minimize shop visit times and total life limited parts cost, and maximize total objective time on wing in the life cycle. On the basis of the analysis of every optimization objective, a solution based on the step-by-step strategy was put forward. Finally, the approach for repair objective determination was validated by the actual data of a civil aero-engine from an airline. Validation results show that the proposed approach can achieve a balance between shop visit times and total life limited parts cost in the life cycle, based on a compromise coefficient and every weight of optimization objectives. The approach can provide decision support for aero-engine repair objective determination and avoid the randomness of making repair objective.
Comparison of bilinear process method and group test method for performance degradation
WANG Zhi-hua, FU Hui-min, HUANG Rong, ZHANG Yong-bo
2014, (7): 1562-1566. doi: 10.13224/j.cnki.jasp.2014.07.007
Abstract:
For the performance degradation reliability analysis, comparison of bilinear process method and group test method was conducted. The modeling procedure of these two methods was theoretically discussed. It can be found consequently that, the analysis precision of bilinear process method can be improved based on the one-stage estimation process, helping to avoid information waste. A reported window wiper switch performance degradation test was then considered to verify these two methods. Comparative analysis of the 10th percentile curve indicates that, the bilinear process method with 2.5% upper test data, can derive more reasonable results, compared with the group test method with 15% upper test data. In addition, model validation based on the residual analysis illustrates the effectiveness of the bilinear process method.
High-temperature ultra-high cycle fatigue test of TC17 titanium alloy
LI Jiu-kai, LIU Yong-jie, WANG Qing-yuan, HOU Fang
2014, (7): 1567-1573. doi: 10.13224/j.cnki.jasp.2014.07.008
Abstract:
A high-temperature ultrasonic fatigue testing system was self-developed to evaluate the ultra-high cycle fatigue properties of TC17 titanium alloy. Ultrasonic (20 kHz) fatigue tests were performed at room temperature, 200℃ and 350℃, respectively. The result shows that dynamic modulus of elasticity of TC17 titanium alloy decreases linearly with increasing temperature. The S-N curve presents a continuously descending shape at room temperature. While at 200℃ and 350℃, inflexion points of S-N curves can be observed clearly at fatigue life of 107 cycles. In addition, the results show that the fatigue cracks initiate from the surface or sub-surface of specimen and the interior crack initiation is not found. It indicates that the crack initiation of TC17 titanium alloy can be independent of interior inclusion or defect. Both the crack initiation and the crack propagation are promoted at high-temperature.
Prediction method on equivalent thermal conductivity coefficient of plain braided C/SiC composites material based on finite element method
LU Si-da, GAO Xi-guang, SONG Ying-dong
2014, (7): 1574-1582. doi: 10.13224/j.cnki.jasp.2014.07.009
Abstract:
A computing method on equivalent thermal conductivity of plain braided C/SiC composites material was proposed based on finite element method. Mesoscopic structure of materials was studied firstly, including microscopic model of carbon fiber bundles with matrix and single-cell model. Effects of porosity on the matrix equivalent thermal conductivity coefficient were calculated using random-pore single-cell model. The equivalent thermal conductivity coefficient of carbon fiber bundles with matrix and composites material was calculated under the condition of three sets of boundary conditions. Finally with the proposed method, the relationship between equivalent thermal conductivity coefficient and fiber volume fraction/porosity was studied in detail. The results indicate that the equivalent thermal conductivity coefficient of the composites material decreases linearly with the increase of fiber volume fraction. While fiber volume fraction increases from 54% to 78%, the equivalent thermal conductivity coefficient in y axis direction declines by 12.8% and that in x and z axis directions by 8.6%. The equivalent thermal conductivity coefficient of the composites material presents an accelerating downward trend during the porosity's rising process. While the porosity increases from 0% to 30%, the equivalent thermal conductivity coefficient declines by 22.91% in x and z axis directions and 34.66% in y axis direction.
Taguchi method based tolerance design for rotor system dynamics
YANG Jun, ZANG Chao-ping, LIU Yong-quan, WANG Xiao-wei, FENG Guo-quan
2014, (7): 1583-1590. doi: 10.13224/j.cnki.jasp.2014.07.010
Abstract:
A novel method based on Taguchi's method was proposed for tolerance design for rotor system dynamics. It reduces structural dynamic response variation of rotor system due to uncertainties of design parameters and assembly process, by tolerance design of manufacturing and assembly parameters. The approach was performed by the following steps:(1) Design parameters through orthogonal array experiments and ANOVA(analysis of variance), initially determining level combination of design parameters meeting design requirements;(2) Determine initial nominal value and range of design parameters for tolerance design, set up objective function and form multi-objective optimization;(3) Solve the multi-objective optimization problem by genetic algorithm and get the tolerance design results. A tolerance design of initial unbalanced discs assembly for a twin-spool aero-engine was carried out. The results show that bearing vibration response can be decreased by matching of initial unbalance amplitude and phase angle differences, and qualified rate of maximum bearing vibration response is increased from 17.7% to 97%, which can verify the feasibility of the method.
Experiment on friction and wear performance of textured port plate pair
LI Yang, DENG Hai-shun, WANG Xiao-lei
2014, (7): 1591-1597. doi: 10.13224/j.cnki.jasp.2014.07.011
Abstract:
To improve the friction and wear performance of port plate pair of axial piston pump, textured port plate pair were obtained by lithography and electrolysis technique, and the tests were carried out on the port plate pair's friction and wear tester. The results show that the textured port plate pairs can effectively reduce the friction coefficient, and their average wear sectional area and surface roughness are much less than the untextured ones. More severe adhesive wear is formed on the untextured port plate pair and only more serious abrasive wear on the textured ones with diameter of micro-dimples ranging from 100 μm to 300 μm, whose average wear sectional area was 4.54%-7.14% of untextured ones. There exists a good correlation between friction coefficient and average wear surface sectional area.
Performance investigation of intercooler operating in wet condition using distributed parameter model
ZHOU Ya-feng, LIU Gui-lin, HAN Ya-hui, YANG Chun-xin, ZHU Zhi-li
2014, (7): 1598-1605. doi: 10.13224/j.cnki.jasp.2014.07.012
Abstract:
The performance of a marine gas turbine intercooler operating in wet condition was evaluated. The intercooler was a cross-flow plate-fin heat exchanger that used air and pure water as its working fluids at the hot and cold sides, respectively. The heat transfer performance and the water vapor condensation were investigated for a relative humidity of the inlet air that reached 100% during warship cruise. The condensation of the water vapors increased the hot side outlet temperature by a certain amount, which could in turn influence the performance of the compressor downstream. The condensate film thickness and the void fraction were calculated based on an annular two-phase flow model. It is found that water vapor condensation in hot flow channel increases the outlet temperature with a maximum value of 7.3℃ in the case of 100% relative humidity. The calculated liquid film thickness reaches a maximum value of 4 μm, which indicates negligible thermal resistance to heat transfer. The results of liquid film thicknesses also provide a qualitative prediction of the diameter distribution of the condensate water droplets.
Mixing characteristics of hyperburner with a lobed mixer
CHENG Xiao-jun, FAN Yu-xin, CAI Di, WANG Jia-hua
2014, (7): 1606-1614. doi: 10.13224/j.cnki.jasp.2014.07.013
Abstract:
A simple structure square lobed mixer with high mixing efficiency and low resistance was designed to turbofan by pass flow with ram bypass flow thoroughly in turbine based combined cycle engine hyperburner. Numerical simulation of square lobed mixer and comparative analysis with conventional mixer were made; the results indicate that square lobed mixer with high mixing efficiency and low resistance of the streamwise vortices of daisy lobed mixer. Numerical simulation results of various mixer structure parameters' influence on mixing characteristics show that expansion angle dominates the thermal mixing efficiency, and the export height of the mixer has little effect on it. The square lobed mixer has the characteristics of high mixing efficiency and low resistance when the wavelength ratio is 1.0.
Effect of rib orientation on film cooling performance
LUO Jian-xia, ZHU Hui-ren, LIU Cun-liang, JIA Guang-sen
2014, (7): 1615-1622. doi: 10.13224/j.cnki.jasp.2014.07.014
Abstract:
Based on the smooth secondary flow crossflow channel case, two ribbed channels (135° ribs and 45° ribs) were compared to find out the orientation effect on film cooling performances. The heat transfer coefficient ratio and local film cooling effectiveness were measured by a transient liquid crystal technique. Reynolds averaged Navier Stokes (RANS) simulations with realizable k-ε turbulence model and enhanced wall treatment were performed using a commercial code Fluent. In the smooth secondary flow channel case, a helical motion of secondary flow was observed in the film hole, and this motion induced strong velocity separation and flow loss. The cooling air jet was divided into two parts, one consisting of a pair of skewed vortices. In the 135° ribs case, the vortex in the upper half region of the secondary flow channel rotates clockwise, inducing the coolant much easier to flow into the film hole, and straight stream lines in film hole are observed in this case. In the 45° ribs case, the vortex close to the film hole rotates counter clockwise, which enhances the vortices in the film hole. Flowing into the film hole, the flow structure of the coolant in the 45° ribs case is similar with the smooth crossflow channel case. The highest film cooling effectiveness and lowest heat transfer coefficient ratio is observed in the 135° ribs case.
Modeling and simulation of general fuel tank thermal model
LAN Jiang, ZHU Lei, ZHAO Jing-quan
2014, (7): 1623-1630. doi: 10.13224/j.cnki.jasp.2014.07.015
Abstract:
Heat balance differential equations were built for fuel tank wall, gas inside the fuel tank and fuel by considering comprehensive heat transfer processes. Then general simulation model of fuel tank was further developed on the Flowmaster platform with C# language. Dynamic simulations of a fuel system were subsequently performed over a typical flight profile to get dynamic curves of fuel mass, recirculation fuel mass flow rate and fuel temperature, so that quantitative analyses on the cooling ability of fuel could be conducted, and then appropriate circulation mass flow rates, and cooling capacity of the fuel radiator were obtained. Results show that the maximum heat load which can be carried away by the fuel is about 50 kW of this fuel system. For a higher heat load of 70 kW, circulation mass flow rates between the supply and transport tanks(front and back) are 0.3 kg/s and 0.1 kg/s, and the cooling capacity of the fuel radiator is 12 kW.
Feature-parameter-criterion for predicting lean blowout limit of aero-engine combustor
ZHANG Zhi-bo, ZHENG Hong-tao, LING Rui
2014, (7): 1631-1638. doi: 10.13224/j.cnki.jasp.2014.07.016
Abstract:
Core principle and forecasting process of feature-parameter-criterion (FPC) were expounded firstly. A CFD software FLUENT was used to simulate the process of lean blowout (LBO) of an aero-engine annular combustor. "M" flame was proposed as the portent of blowout and its cause was given. The effects of velocity and temperature of inlet air on the LBO limit of aero-engine combustor were discussed by use of FPC. The results show that lean blowout fuel air ratio decreases with the increase of velocity of inlet air. When temperature of inlet air is less than 395 K, lean blowout fuel air ratio decreases with the increase of temperature of inlet air. And when temperature of inlet air is more than 395 K, lean blowout fuel air ratio remains unchanged.
Influence of improved structure of bluff-body on combustion flow characteristics in advanced vortex combustor
SUN Hai-jun, ZENG Zhuo-xiong, XU Yi-hua, HU Chun-bo
2014, (7): 1639-1646. doi: 10.13224/j.cnki.jasp.2014.07.017
Abstract:
In order to study the mechanism of flame stabilization in cavity of advanced vortex combustor, an improvement program of after bluff-body structure was introduced, and the combustion characteristics of improved combustor under the conditions of premixed and non-premixed combustion were numerically simulated. The results show that under the condition of premixed combustion, the improved bluff-body structure can enhance the intensity and temperature of vortex flow in cavity, and make the temperature distribution more evenly no matter if equivalence ratio is 0.6 or equal to 1.0. In addition, the cavity temperature increases with the increasing premixed inlet velocity, and changes little when the velocity reaches a certain value. Under the condition of non-premixed combustion, the improved bluff-body structure ameliorates the vortex flow and temperature distribution in cavity, and the cavity maintains relatively high temperature under the condition of lean burning. The improved lightweight combustor can provide certain reference for engineering application.
Effect of baffle plate of rotating limited lamilloy on flow heat transfer of lamilboy
BAI Guo-qiang, CHANG Hai-ping
2014, (7): 1647-1653. doi: 10.13224/j.cnki.jasp.2014.07.018
Abstract:
Using numerical simulation method, the effect of baffle plate on the flow heat transfer capacity of coolant air in rotating limited lamilloy was researched. The results show that the heat transfer capacity of lamilloy is enhanced evidently by baffle plate. Nu of the rotating limited lamilloy is 18% higher than that of unlimited transverse flow impact lamilloy, and 15% higher than that of the unlimited transverse flow impact lamilloy. The Nu in heat conduction baffle plate is 10% to 15% higher than that in heat insulation baffle plate. In the rotating limited lamilloy, the heat transfer capacity declines with the increase of the rotation number of impingment hole close to the rotating center, and increases with increasing rotation number of impingement hole far away from the rotating center. Rotation can effectively reduce the temperature of high temperature regions of the target surface because of the baffle plate. Rotating limited lamilloy is more suitable for turbine rotor.
Effect of porous media structure parameters on surface flame blow-out performance
ZHANG Long, XU Quan-hong, ZHANG Chi, LIN Pei-hua, LIN Yu-zhen
2014, (7): 1654-1659. doi: 10.13224/j.cnki.jasp.2014.07.019
Abstract:
To optimize a micro combustor with dome made of porous media, the influences of porous media structure parameters (equivalent aperture, porosity) on the surface flame blow-out performance were investigated experimentally under different premixed gas initial temperatures. Methane and air premixed gas was used as fuel in this experiment. The results show that both two sides of the porous media surface flame go out at the same time when equivalent aperture equals 120 μm. One side goes out firstly when equivalent aperture equals 80 μm. With the decrease of equivalent aperture or porosity, equivalent ratio equals 1.0, premixed gas initial temperature equals 300K, the blow-out velocity increases. When equivalent aperture equals 80 μm, and porosities equal 0.55, 0.50 and 0.45, the blow-out velocities of porous media surface flame turn out to be 1.11, 1.22 and 1.31 m/s, respectively. When porosity equals 0.50, and equivalent apertures equal 120, 80 μm, equivalent ratio equals 1.0, premixed gas initial temperature equals 300K, the blow-out velocities turn out to be 0.73 m/s and 1.22 m/s, respectively. The increase of premixed gas initial temperature has obvious influence on porous media with equivalent aperture of 120 μm or porosity of 0.45. When the premixed gas initial temperature increases from 300K to 500K, the blow-out velocities increase by 120% and 76%, respectively.
Experiment on inlet pressure distortion of high-pressure compressor
WU Hui, ZHANG Guo-wang, YANG Ming-sui
2014, (7): 1660-1666. doi: 10.13224/j.cnki.jasp.2014.07.020
Abstract:
A series of relevant experiments were carried out for assessing high-pressure compressor distortion characteristics accurately. Inlet pressure distortion experiment methods of high-pressure compressor were emphasized, and targets of characteristic parameters such as complex distortion index, dynamic and steady state distortion components, threshold value, distortion contours as well as test concept and experimental data processing method were proposed. Furthermore, as the inlet pressure distortion experiment for a kind of high-pressure compressor was accomplished, and the effect on the performance of this high-pressure compressor by total pressure distortion along with the assessment data for relative stability was obtained. Experiment results show that high-pressure compressor has significantly higher pressure distortion sensitive coefficient, weaker anti-distortion ability than fans under off-design speed; high-pressure compressor is identical with fan in pressure distortion sensitive coefficient under design speed, showing strong anti-distortion ability and aerodynamic stability.
Aerodynamic design of three-stage vaneless counter-rotating turbine
ZHOU Kun, LIU Huo-xing, ZOU Zheng-ping, WANG Lei
2014, (7): 1667-1679. doi: 10.13224/j.cnki.jasp.2014.07.021
Abstract:
An aerodynamic design criterion was discussed for the 1+3/2 counter-rotating turbine by analyzing the velocity triangles. There are 8 key aerodynamic parameters in the criterion, based on the consideration of aerodynamic efficiency and some strength requirements. Then, an aerodynamic design for the 1+3/2 counter-rotating turbine was made according to the criterion, and a three-dimensional simulation was conducted for it. Finally, the conclusions were obtained. The criterion containing 8 key aerodynamic parameters is verified rationally and the efficiency of the turbine reaches 91%. The aerodynamic characteristics of 1+3/2 counter-rotating turbine are mainly decided by the load coefficient, and due to an optimal power distribution coefficient of the low pressure turbine, the efficiency of the low pressure turbine can be best.
Dynamics mechanism of tip leakage flow trajectory movement in rotor
LIU Dong-jian, LI Jun, LI Jian-wei, LUO Zhi-huang, LI Fan-yu
2014, (7): 1680-1687. doi: 10.13224/j.cnki.jasp.2014.07.022
Abstract:
In order to uncover the evolutionary tendency of the tip clearance flow in a subsonic axial-flow compressor rotor as well as its associated flow mechanism, the unsteady three-dimensional multi-passage numerical simulations were carried out to investigate the flow field of the compressor rotor. The computational results show that as the compressor rotor's mass flow decreases, the axial momentum of the incoming flow reduces, and that of the tip leakage flow increases under the impact of the pressure gradient between the pressure side and suction side of the tip clearance block combined with the secondary leakage flow, thus increasing the axial momentum ratio of the tip leakage flow to the approach flow in the clearance region. The consequence is a movement of the interface between the incoming flow and the tip leakage backflow toward the leading edge of the rotor. As the strength of the axial reversed flow is increased from design status to near stall, the flow blockage zone in the rotor tip region becomes more severe and moves further upstream, which plays a role in triggering the compressor stall.
Numerical investigation on effect of heat transfer on tip clearance flow in micro centrifugal impellers
SUN Qian-wei, LI Qiu-shi, LI Zhi-ping
2014, (7): 1688-1694. doi: 10.13224/j.cnki.jasp.2014.07.023
Abstract:
Three-dimensional numerical simulations were carried out on a centrifugal micro impeller under adiabatic and isothermal wall temperature boundary conditions in order to compare the impeller performance and the detailed flow features affected by heat transfer. The comparison was especially focused on the heat transfer effect on tip clearance flow in micro centrifugal impeller. It is found out that the performance of impeller is mainly attributed to the influence of heat transfer on tip clearance flow. The trajectory of tip clearance flow develops along the suction side of the blade towards impeller outlet under adiabatic condition, while the tip clearance flow is driven away from the suction side of the blade towards the pressure side of the adjacent blade when heat transfer is involved. Meanwhile, heat transfer also lead to the increase of mixing between tip clearance flow and the main flow resulted in greater loss. Although heat transfer can reduce the pressure gradient within blade passage to certain extent as compared with adiabatic condition, it eventually causes more tip blockage in impeller passage as the initial tip clearance blockage was enlarged due to heat addition.
Numerical investigation of effect of tip clearance on stress of high pressure turbine rotor
LI Yu-jie, LIU Yong-bao
2014, (7): 1695-1700. doi: 10.13224/j.cnki.jasp.2014.07.024
Abstract:
For the problem that tip clearance of the high pressure turbine rotors has a significant effect on the aerodynamic characteristic and structural reliability, numerical simulation based on conjugate heat transfer method of turbine rotors with different tip clearance sizes was performed. Coupled caculation of the energy transferred from physical interface between fluid and solid was made. The effects of leadage vortex flow on the distribution of temperature and pressure were presented, and the effects of thermal stress and aerodynamic stress on the structure intensity of blades were analyzed. It showed that, with the increase of tip clearance height, the leakage flow velocity increased and the thermal stress changed significantly. The maximum equivalent stress increased by 2.6% increase while the tip clearance height changed from 0.3% to 3.0%. The acquired results can provide a theoretical basis for tip clearance control.
Feature analysis on US military aircraft engine advanced technology programs
LIANG Chun-hua, SUN Ming-xia, LIU Hong-xia
2014, (7): 1701-1709. doi: 10.13224/j.cnki.jasp.2014.07.025
Abstract:
US military aircraft engine advanced technology programs were overviewed and analyzed from light weight gas generator (LWGG) program initiated in 1960s through integrated high performance turbine engine technology (IHPTET) program started in 1980s, then to versatile affordable advanced turbine engine (VAATE) program. Some features and trends were summarized and concluded by literature statistics method, such as teams based on closely corporation among government, industries and academics, goals oriented with national defence strategies and weapon system development requirements, engineering manufacture and development including all relative disciplines and areas, verification measured by technology readiness level, the application extending to military aircraft engine, civilian engine, gas turbine and space vehicle, etc. The experience and lessons obtained can provide reference and guide for technology research and engineering manufacture and development of military aircraft engines in the world.
One-dimensional unsteady calculational method of secondary air system
LI Peng, WU Hong, TAO Zhi
2014, (7): 1710-1720. doi: 10.13224/j.cnki.jasp.2014.07.026
Abstract:
The unsteady calculational method of secondary air system in gas turbines was studied. The whole system was divided into several length correlated parts and discrete loss parts. The method of characteristic line was adopted for single length correlated parts, while partial differential equations of continuity, momentum and energy were transformed to ordinary differential equations under specified conditions, so the interaction of flow and heat transfer inside the parts itself could be taken into account. When the method of flow network based on pressure correction was used for discrete losses parts, momentum equations were solved prior to the calculation of respective energy equation. The process of data transfer on the interfaces between the mentioned two types of parts was discussed. With the method of time step definition and improved analytical models for different parts adopted, unsteady analysis of secondary air system was achieved. The program was validated against steady experimental data of the whole system and unsteady calculational data of individual parts; in 10s' calculational process, the result achieved by the program deviates 10.2% from that by CFD. The results indicate that the program can satisfy the need of unsteady calculation on secondary air system.
Flight dynamics characteristics of miniature unmanned ducted vehicle
ZHAO Hong, LI Jian-bo, CUI Zhao
2014, (7): 1721-1728. doi: 10.13224/j.cnki.jasp.2014.07.027
Abstract:
To investigate the flight characteristics of unmanned ducted vehicle, a full-scale ducted propeller wind tunnel test was conducted to build the aerodynamic model and analyze the aerodynamic characteristics of ducted propeller. On these foundations, the flight dynamic mathematical model of the vehicle was established to investigate the characteristics trimming and stability of unmanned ducted vehicle.The results indicate that the aerodynamic characteristics of the ducted-propeller are strongly influenced by the forward speed and attitude angle, leading to significant variations in stability and maneuverability of the unmanned ducted vehicle at different forward speeds. This unmanned ducted vehicle is an unstable body similar to inverted pendulum in hover and low forward speed. The aerodynamic damping is small, while the speed and attitude angle diverge quickly, with double amplitude in 0.5 s. The flight stability is improved due to the increase of aerodynamic damping at high forward speed. The reverse control brings difficulties to flight control the unmanned ducted vehicle.
Optimal guaranteed cost fault-tolerant control with bi-index constraints for aero-engine distributed control system
WANG Lei, XIE Shou-sheng, PENG Jing-bo, YANG Yong, REN Li-tong
2014, (7): 1729-1737. doi: 10.13224/j.cnki.jasp.2014.07.028
Abstract:
The passive fault-tolerant control was studied for aero-engine distributed control system with parameter perturbation, Markov time-delay, data dropout and external disturbance when interval random actuator faults occurred. An optimal guaranteed cost fault-tolerant controller was designed under double constran of H and cost performance index. At the beginning, uncertain parameters were described quantitatively. Based on the description a closed-loop augmented model was built. Then sufficient conditions for asymptotic stability with bi-index constraints of the augmented system were derived. The design approach of guaranteed cost fault-tolerant controller was proposed. Finally the optimal guaranteed cost fault-tolerant controller was designed based on consistency theory. Simulation results show that the devised controller ensures the closed-loop system asymptotically stable when interval random actuator faults occur, and have a certain H performance. Besides, when low-pressure rotor speed has 1% step change, the maximum main fuel mass flow and throat area in this controller are 16.03% and 16.93%, respectively, of that in optimal robust H fault-tolerant controller.
Real-time obstacle avoidance trajectory planning for missile borne air vehicle based on constrained artificial potential field method
WANG Wei, WANG Hua
2014, (7): 1738-1743. doi: 10.13224/j.cnki.jasp.2014.07.029
Abstract:
A three-dimensional constrained artificial potential field method was proposed for planning of real-time obstacle avoidance trajectory for the missile-borne air vehicle, due to the low altitude and needing real-time obstacle avoidance. Combined with a potential field—height adjust potential field and the dynamic constraints of the missile-borne air vehicle, the artificial potential field method was extended to three-dimensional space. The new method not only inherited the advantages of fast calculation and less memory, but also could ensure the flight performance of planning trajectory for the missile-borne air vehicle. The simulation results show that the constrained artificial field method has the following advantages compared with the traditional artificial potential field method: the planning trajectory presents flight performance; the swing phenomenon near the obstacle is significantly reduced; the oscillatory phenomenon in narrow passage is significantly improved; it is easier to escape from the local minimum point.
Design and simulation of a control scheme for turbo-shaft engine in helicopter autorotation training process
YAN Chang-kai, ZHOU Xiao, ZHANG Hai-bo
2014, (7): 1744-1751. doi: 10.13224/j.cnki.jasp.2014.07.030
Abstract:
According to the special need of turbo-shaft engines for fast response in helicopter autorotaion training process, a robust control scheme for turbo-shaft engines, including both fuel mass flow and guided vanes angle control, was proposed and designed to reduce the turbine speed transient droop. Firstly, an improved comprehensive model of UH-60 helicopter/T700 engines, which can simulate autorotation decent and autorotation recovery, was presented. Secondly, robust control scheme for turbo-shaft engine based on fuel mass flow and guided vanes adjustment was preset in the simulation cases. The result shows clearly that the turbine speed transient droop, controlled by the proposed robust control scheme, is sharply reduced to 3% than traditional method only exploring fuel mass flow control, while the variation of fuel mass flow is much slower and the operation condition of the actuator is improved.
Pre-control and experiment method of meshing performance for face gear drives
LEI Bao-zhen, LI Da-qing, WANG Xun-wei, DENG Xiao-zhong
2014, (7): 1752-1760. doi: 10.13224/j.cnki.jasp.2014.07.031
Abstract:
To enhance the meshing performance of face gear drives, based on the generation process of grinding of face gear and three-dimensional topology modification theory of pinion, the expressions of tooth face equations of face gear drives were derived respectively. The influence of 5 modification coefficients on the meshing performance were analyzed, and theory for meshing performance pre-controlled was proposed, which can be realized by optimizing the modification coefficients. The three-dimensional topology modification theory presented was verified by the experimental results.The results show that: the modification coefficient of tooth profile is the major pre-control parameters which affect the width of contact area along the direction of tooth height obviously. The modification parabolic coefficient of tooth length affect the width of contact area along the direction of tooth length, and different values of these two parameters can significantly affects the tilt of contact line and the shape and the size of contact area.Contact area and transmission error can be pre-controlled effectively by three-dimensional topology modification theory of pinion and the sensitivity of the installation error of face gear drives can be reduced effectively.