2017 Vol. 32, No. 4

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Fatigue life prediction of fiber reinforced composites turbine shaft structure
2017, 32(4): 769-779. doi: 10.13224/j.cnki.jasp.2017.04.001
Abstract PDF(1146KB) icon992 icon462
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The method of estimating the fatigue life of the low pressure turbine shaft structure made of continuous fiber reinforced composite material under given low cycle loading was studied. Structural characteristics of continuous fiber reinforced composites were considered, low cycle fatigue life prediction method based on the local stress strain theory was studied, and the efficiency of the method was proved. A certain type of low pressure turbine shaft of the engine was selected for reference, the maximum stress, strain and fatigue life were calculated with the method. Result showed that, the fatigue life value of the 45° angle of composites layer was the biggest within the scope of the 0°-90°; when the thickness of the metal remained unchanged, the composite material fatigue life of outer metal and the first layer increased with the increasing thickness of the composites; when the shaft wall thickness was 6 mm, if reducing the thickness of the composites layer, and increasing the inner or the outer metal coating thickness, the structure fatigue life decreased as composites layer thickness decreased; the life of the outer metal coating was longer than the fatigue life of the first layers composite materials.
Research on excitability of the wake of stator in aero-engine to high order resonance of bladed-disk
2017, 32(4): 780-790. doi: 10.13224/j.cnki.jasp.2017.04.002
Abstract PDF(1280KB) icon969 icon502
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Targeting the forced vibration of bladed-disk in aero-engine, the impact of the severity of resonances induced by flow-wake of stator was studied. On the basis of the numerical simulation of unsteady stator-rotor interface flow, both frequency spectrum and spatial spectrum of aerodynamic pressure on the rotor surface were obtained respectively by fast Fourier transformation. Meanwhile, the excitability of wake was defined as the projection of aerodynamic pressure on the modal space, also called modal force, so as to evaluate the strength of resonant response of bladed disk. The analysis shows that the excitability of wake to a non-primary resonance is much less than a primary resonance. As a result, it is reasonable that in the operating speed region of aero-engine, the existence of high-order resonances with small complementary angle between aerodynamic force and modal displacement of bladed disk (small excitability), should be accepted.
Numerical study on static and dynamic characteristics of negative dislocated seal
2017, 32(4): 791-799. doi: 10.13224/j.cnki.jasp.2017.04.003
Abstract PDF(1280KB) icon964 icon484
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A kind of negative dislocated seal based on the dislocated bearing theory was presented to eliminate hydrodynamic effects and reduce air induced force. The static and dynamic characteristics of negative dislocated seals based on computational fluid dynamic (CFD) moving-gird technology were put forward. The effects of the eccentricity ratio and dislocation ratio on the leakage, circumferential pressure distribution, air force, rotor dynamic characteristics coefficients, and seal rotor stability were analyzed. Results show the seal leakage increases with the eccentricity ratio and dislocation ratio; the seal gap fluid circumferential pressure distribution satisfies the sine law. Compared with the traditional cylinder seals, the negative dislocated seal has divergent wedge gap, and reduces the hydrodynamic pressure effects, circumferential pressure difference and seal tangential force. This is the main reason for the negative dislocated seal suppression of air force. With the increase of the eccentricity ratio, the seal absolute value of stiffness and the cross-coupled damping increase and the direct damping decreases. This seal can effectively reduce the cross-coupled stiffness and increase the direct damping coefficients, the effective stiffness and effective damping so that the seal stability improves.
Application of a friction damper in blisk structure
2017, 32(4): 800-807. doi: 10.13224/j.cnki.jasp.2017.04.004
Abstract PDF(1191KB) icon999 icon472
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A fraction damper for integrally bladed disk(blisks) was introduced. The design was based on a friction pin located in a hole underneath the rim of the blisk. In operation, friction occurred between the pin and the rim due to centrifugal load, so the vibration energy was dissipated. This friction pin damper was applied into two turbine blisks to reduce the blade dynamic stress. Test results revealed that damping efficiency varied intensely. Through numerical simulation, it was proven that damping efficiency of this damper was closely related to vibration energy transfer between blades and disks. For strong coupling blade-disk mode, this damper could be highly efficient and blade vibration stress reduces about 70%, while for weak coupling blade-disk mode, the blade vibration stress reduces only a little.
Field balancing technology for low pressure rotors ofhigh bypass ratio turbofan engines
2017, 32(4): 808-819. doi: 10.13224/j.cnki.jasp.2017.04.005
Abstract PDF(1313KB) icon1078 icon585
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For high bypass ratio turbofan engines, a field balancing method for low pressure rotors was established based on least-square influence coefficient, and a testing system for dynamic balancing was developed. After a model rotor experiment rig was built up, relevant calculation of dynamic characteristics and balancing experiments were conducted. And the correctness, validity and reliability of the field balancing technology were verified in a bench experiment of actual engine. Results indicated that using the method of tracking high pulse and transforming square wave according to fixed proportion can identify the high-tooth signal, and integral period interception, interpolation processing and multiple times averaging of vibration signals can ensure the accuracy and stability of speed and phase measurement. The No.1 support was more sensitive to the fan unbalance, and the No.5 support was more sensitive to the turbine unbalance, while the No.2 support was sensitive to both unbalances, and the sensitivity to the fan unbalance was greater. Under the premise of ensuring the balancing effectiveness, when compared with the three-circle balancing method, the field balancing technology for low pressure rotors can also facilitate the operational convenience, decrease the number of startups and shutdowns, and achieve less time consumption with a bright prospect in engineering application.
Research on nonlinear vibration analytical model of rotor-system
2017, 32(4): 820-827. doi: 10.13224/j.cnki.jasp.2017.04.006
Abstract PDF(2157KB) icon890 icon464
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An analytical vibration model was proposed to analyze a series of typical nonlinear behaviors of flexible rotor-system, such as resonance and oscillation coursed by couple interaction between linear and nonlinear forces during the speeding-up process. By introducing a nonlinear scaling factor ε, the model mainly probed into nonlinear response characteristics. Multi-scale method was applied to deduce the analytical pass-band solution of nonlinear rotor-vibration as a Fourier series form, and then obtain the nonlinear natural frequency and the fundamental-frequency frequency-response equation (FRE). A confirmatory experiment was made to verify the nonlinear characteristics of the analytical pass-band solution and the fundamental-frequency FRE under equal-scale condition (ε=1), and also verify the rationality and effectiveness of the analytical couple-vibration model and the analytical pass-bomd solution.
Plastic strain energy-life model of turbine disk under various stress ratios
2017, 32(4): 828-834. doi: 10.13224/j.cnki.jasp.2017.04.007
Abstract PDF(888KB) icon847 icon440
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The area of cyclic stress-strain curve deviated from elastic line due to plastic deformation in the first cycle was taken as fatigue damage parameter, and the plastic strain energy-life model was established from the perspective of energy. With the method of quadratic interpolation for stress ratio, the relation of plastic strain energy and fatigue life under various stress ratios could be obtained. The testing results of the simulated bolt-hole specimens of a turbine disk and the simulated runway-hole specimens of an interstage disk were used for comparison and validation. Results show that the method of quadratic interpolation is more accurate compared with linear interpolation for stress ratio when using the plastic strain energy-life model. The calculated life of simulated bolt-hole specimen is 9.42% less than testing life; meanwhile the calculated life is just 1.88% larger than testing life for the runway-hole specimen. In general, the results of the plastic strain energy-life model fit well with testing life, showing a higher accuracy.
Modeling and response analysis of dual-rotor system under maneuvering flight
2017, 32(4): 835-849. doi: 10.13224/j.cnki.jasp.2017.04.008
Abstract PDF(2122KB) icon935 icon616
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Considering the coupling effect of intershaft bearing and the influence of gyroscopic moments, a dynamic model of a dual-rotor-ball bearing coupling system under maneuvering flight was established by using Lagranges equation, whilst theoretical and experimental study were both carried out. It is shown that with the increase of speed ratio of inner and outer rotors, the vibration amplitude decreases and the speed of bifurcation point grows with a maximum rate about 67.49%. The rotors vibration amplitude increases and more frequencies appear under maneuvering flight. With the increase of leaping flight speed, the outer rotors vibration amplitude increases obviously with a maximum rate about 409.24%, the speed of bifurcation point grows at the same time. During rolling flight, the rotors period doubling bifurcation point disappears in contrast to the system without maneuvering flight, but the vibration amplitude increases obviously. By using a model experiment rig of a dual-rotor system under maneuvering flight, parts of dynamic characteristics of outer rotor have been studied, and the experimental and numerical simulation results are in good agreement.
Curved compression surface with wall pressure and Mach number distribution using geometric combination
2017, 32(4): 850-857. doi: 10.13224/j.cnki.jasp.2017.04.009
Abstract PDF(1687KB) icon852 icon10
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The curved compression surface with wall pressure and Mach number distribution by geometric combination was investigated according to the reverse design method of compression surface with the given wall parameters distribution. The parameter distribution and performance of compression surface were analyzed. The curved compression surface was applied to design two-dimensional inlet under the same conditions as the reference inlet. And the performance was analyzed and compared with the reference inlet. Numerical results show that the advantages of curved compression surface designed by a single parameter were achieved using geometric combination. The wall parameter distributions were improved effectively and tended to be more reasonable. Compared with the reference two-dimensional inlet, the inlet length with combination compression surface was increased. But its throat total pressure recovery coefficient was improved significantly within the incoming Mach number range of 4~6. The throat total pressure recovery coefficient of inlet with combination compression surface was increased by 10% at incoming Mach number of 6, and increased by 9.6% at incoming Mach number of 4.
Aerodynamic performance of time asymmetric flapping of a three-dimensional flapping hovering bionic wing
2017, 32(4): 858-864. doi: 10.13224/j.cnki.jasp.2017.04.0010
Abstract PDF(1128KB) icon1079 icon410
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Based on the analysis of the bumblebees flight, the kinematic model of time asymmetric flapping hovering wing was established, and the effect of different time asymmetric flapping on the aerodynamic performance of the wing was numerically studied by solving three-dimensional laminar Navier-Stokes (N-S) equation. The results show that the wing with appropriate time asymmetric flapping possesses enhancement aerodynamic performance. Through the analysis of flow field of different time asymmetric flapping wings, it was also found that the enhancement rotational circulation, stronger leading edge vortex and spanwise flow were observed for the wing with appropriate time asymmetric flapping, hence leading to enhancement aerodynamic performance.
Effects of bypass ratio on the cost and environmental performance of large civil aircraft
2017, 32(4): 865-873. doi: 10.13224/j.cnki.jasp.2017.04.011
Abstract PDF(947KB) icon878 icon460
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In order to assess the effects of bypass ratio on the cost and environmental performance of the civil aircraft with consideration of engine installation, a multidisciplinary analysis procedure was established, in which propulsion,geometry, aerodynamics, mass, mission performance,cost,noise and emissions analysis module were integrated. A typical wide body civil aircraft was used to illustrate the procedure, in which the cost and enviromental performance of wide body aircraft was analyzed with different engine bypass ratios ranging from 8 to 14. The results show that the civil aircraft with the highest bypass ratio engine achieves the lowest noise and landing-takeoff NOx emissions. However, the civil aircraft with the engine of moderate bypass ratio (around 11) has the lowest cash operating cost and flight NOx emissions.
Lift loss of short/vertical takeoff and landing aircraft proximity of ground based on response surface method
2017, 32(4): 874-881. doi: 10.13224/j.cnki.jasp.2017.04.012
Abstract PDF(1180KB) icon963 icon431
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The lift loss flow field calculation model of short/vertical takeoff and landing (S/VTOL) aircraft proximity of the ground was built. The two order response surface function of lift loss about nozzle pressure ratio(NPR), velocity of the cross wind and height of the plane above ground, as well as the key factors affecting the lift loss significantly at multi working states proximity of the ground were obtained by response surface method. The interaction effect of NPR, velocity of the cross wind and height of the plane above ground on the lift loss was analyzed and the minimum lift loss in certain range of working state was optimized. The study shows that the lift loss reduces with the increasing height of the plane above ground and NPR and increases with the velocity of the cross wind when considering single factor; the interaction effect on the lift loss exists between height of the plane above ground and NPR, velocity of the cross wind and NPR, the interaction effect on the lift loss doesnt exist between height of the plane above ground and velocity of the cross wind, the minimum lift loss obtained by optimization is at height of the plane above ground of 9D (D is nozzle diameter), nozzle pressure ratio of 3, velocity of the cross wind of 0m/s working state, and the corresponding lift loss is 1.3%.
Analytical method of rotor aerodynamic characteristics by coupling a high-efficiency trim strategy
2017, 32(4): 882-889. doi: 10.13224/j.cnki.jasp.2017.04.013
Abstract PDF(1039KB) icon997 icon446
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A numerical analytical methodology was developed for aerodynamic characteristics analysis of helicopter rotor by coupling a high-efficiency trim strategy and the computational fluid dynamics（CFD) technology. Firstly, using the CFD solver to calculate the Jacobin matrix and rotor flowfield, an analytical methodology with direct trim method was established. Then, by employing the “delta method”, the computation of Jacobin matrix was simplified and a delta trim method was developed such that the calculation time of rotor performances was significantly decreased. For the calculation of rotor flowfield, the Navier-Stokes equation was selected as the governing equation, and a second-order upwind scheme, i.e. Roe scheme, was used for spatial discretization. Implicit lower-upper symmetric Gauss-Seidel (LU-SGS) scheme was adopted for time marching, and the Baldwin-Lomax （B-L） model was selected as the turbulence model. The computation efficiency and accuracy of the “delta” trim method was compared with that of the direct trim method by numerical calculations based on experimental states of “AH-1G” and “Helishape 7A” rotors. In addition, effects of the background grid quantity on rotor trimming were also analyzed. It is shown that, compared with the direct trim method, the delta trim method can save at least sixty percent of computing time to make the trimming procedure converged. A coarse background grid is not helpful for the capture of flowfield details, but has nearly the same accuracy as a refined background grid in the calculation of rotor control settings; furthermore, the computing efficiency of a coarse grid is higher than that of a refined grid due to the lower grid quantity.
Effect of flow capture shape on the geometry and aerodynamic characteristics for inward turning inlet's external compression segment
2017, 32(4): 890-899. doi: 10.13224/j.cnki.jasp.2017.04.014
Abstract PDF(1184KB) icon838 icon454
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Taking the constant slope internal cone flow as the basic flowfield, a program was constructed to design and quickly analyze the external compression segment performance of inward turning inlet (ITI). Then taking the rectangular capture shape for example, the effects of three outline and position determinant parameters, including center distance, rotation angle and aspect ratio, on the external compression segment's geometry and aerodynamic characteristic were studied. At last, external compression segments with different flow capture shapes (FCS) (rectangular, rounded rectangular and circular) were compared. The results show that the average radius of flow capture shape can be used as an important geometric parameter to evaluate the total pressure recovery; as the average radius increases, the total pressure recovery goes higher. For rectangular capture shape, as the center distance increases, the length and arc length of external compression segment along with the wetted surface area increase monotonically, the external contraction ratio decreases monotonically, while the effect of the rotation angle and aspect ratio on the external compression segment is relatively complicated. Besides, among the three parameters, the center distance is the most sensitive parameter for total pressure recovery. In addition, if the center distance and capture area keep invariant, the fillet radius has little effect on the geometry and performance parameters of the external compression segment.
Numerical research on aerodynamic characteristics and flow fields of airfoil with serrated trailing edge
2017, 32(4): 900-908. doi: 10.13224/j.cnki.jasp.2017.04.015
Abstract PDF(1468KB) icon882 icon410
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To research the aerodynamic characteristics and unsteady flow fields of NACA 0018 airfoil with or without serrated trailing edge based on large eddy simulation, the influences or rules were discussed by changing relative wave length and relative wave amplitude of trailing edge serrations. It was found that the effect of trailing edge serration parameters on aerodynamic performance of airfoil was a complex nonlinear process, lift-drag ratio increased at special angle of attack, the stall occured when the critical angle of attack of the bionic blade with trailing edge serrations was smaller. As an example, the lift-drag ratios of serrated trailing edge blades with different relative wave lengths were higher than original blade when angle of attack was between 9.4°and 14.8°, but there wasn’t a linear relationship between the lift-drag ratios and relative wave length.The findings showed that the trailing edge serrations could delay boundary layer separation of airfoil, promote wake flow mixing and energy diffusion, and change the structure of unsteady vortex and vortex shedding frequency. Changes of wave amplitude of trailing edge serrations influenced the unsteady flow characteristics more significantly. The turbulent jet and the counter-rotating vortices on suction surface occurred by the trailing edge serrations changed the circulation of the original blade, therefore aerodynamic characteristics and flow field of bionic blade with serrated trailing edge were influenced extremely.
Mathematical model of performance prediction of axisymmetric vectoring nozzle based on numerical simulations
2017, 32(4): 909-916. doi: 10.13224/j.cnki.jasp.2017.04.016
Abstract PDF(1414KB) icon872 icon409
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A series of axisymmetric vectoring nozzles with different divergent geometrical parameters were studied based on 3D numerical simulations, and each nozzle's flow field was simulated under different working conditions. The effects of divergent angle and divergent wall length on nozzle performance were analyzed. Through the method of least square surface fitting, a mathematical model taking divergent angle, divergent length/throat height, nozzle pressure ratio/designed nozzle pressure ratio and vector angle as its independent variables was established. Through comparison of performance predictions with the experimental data, result showed that, the error of thrust coefficient was under 0.41%, the error of flow coefficient was under 1.58% and the error of vectoring angle was under 1.76°. The mathematical model was built to predict performances of nozzle with different geometrical parameters, presenting strong commonality and engineering significance.
Large eddy simulation of flow structure in combustor with axial triple swirler
2017, 32(4): 917-925. doi: 10.13224/j.cnki.jasp.2017.04.017
Abstract PDF(1927KB) icon906 icon480
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To gain an improved understanding of the complex flow field structures in practical aero-engine combustor, LES(large eddy simulation) with dynamic Smagorinsky sub-grid model on self-developed CFD platform was made to explore the cold flow field in single rectangle dome of triple swirler under 0.5MPa. The complex geometric configuration including all about 2000 film cooling holes on liner was fully simulated without any conventional simplification in order to reduce the modeling errors. The capability of the CFD code to simulate very complicated flow was validated by the calculation. Unsteady process of the turbulent swirling flow developing from static to statistically stationary status was totally reproduced. Interaction between mainstream and transverse jet was investigated and swirling flow characteristics like vortex breakdown were well captured. Turbulent kinetic energy spectrum predicted by calculation was in reasonable agreement with the -5/3 law in classic turbulence theory, while time-averaged flow field predicted by LES fitted well with PIV （particle image velocimetry）measurement. It shows that the high fidelity mesh and large eddy simulation can be applied in the simulation of full annular combustor of aero-engine.
Semi-theoretical prediction of air core diameter and averaged spray cone angle at simplex swirl atomizer exit
2017, 32(4): 926-931. doi: 10.13224/j.cnki.jasp.2017.04.018
Abstract PDF(805KB) icon1100 icon454
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Influence of the liquid viscosity on air core size in the pressure swirl atomizer was investigated. And theoretical analysis model was established in a control volume with the conservation law of angular momentum in the particles system. Eventually, the semi-theoretical prediction formula was derived, and used to calculate air core size and spray cone angle. In addition, validity of the prediction formula was verified by experimental data under different operation conditions. Results show that the present prediction formula can availably and accurately calculate air core size and averaged spray cone angle, exhibiting a prediction uncertainty of ±13% for air core diameter calculation and from －20% to 6% for spray cone angle determination.
Simulation and characteristics of the coolant feeding tubes in tip clearance control system
2017, 32(4): 932-941. doi: 10.13224/j.cnki.jasp.2017.04.019
Abstract PDF(1087KB) icon979 icon491
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Typical coolant feeding tubes of low pressure turbine tip clearance control system were numerically and experimentally investigated with three-dimensional calculations and full size experimental section, i.e. 90° curved round-section coolant feeding tubes. The outflow characteristic of impingement holes on coolant feeding tubes was studied, and the inlet parameters, arrangement of impingement holes were changed to examine the rules of inner flow and flow rate distribution of coolant feeding tubes. The effective inlet total pressure of impingement holes was defined, then one-dimensional flow net caculation model was established according to this new assumption. Finally the assemblies of coolant feeding tubes of low pressure turbine tip clearance control system were studied by this one-dimensional flow net model and experiments. It was found that with the increase of central angle, the outflow rate and the discharge coefficient increased. The outflow rate through the coolant feeding tube increased with the increasing of inlet Reynolds number，however the discharge coefficients of the impingement hole remained consistent. The comparison between numerical results and experimental data indicates that reasonable flow characteristics of the coolant feeding tubes can be obtained by the one-dimensional flow net model. The maximum relative error between calculation results and experiment data is 4.5%. All the results show that the one-dimensional flow net model has a reasonable accuracy and good application in the complex fluid nets like the tip clearance control system.
Numerical simulation of shock wave imploding detonation initiation in two-stage pulse detonation engine
2017, 32(4): 942-948. doi: 10.13224/j.cnki.jasp.2017.04.020
Abstract PDF(1001KB) icon885 icon416
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Ignition method and periodic pulse in two-stage pulse detonation engine(PDE) were computed by numerical simulation. Results showed that two zones with high temperature and high pressure were engendered by shock wave imploding in engine. Temperature and pressure of the second zone became much higher than the first one, which was the key point of ignition. Depending on temperature, pressure or Mach number improvement, detonation appeared in the unfired condition. With precondition of successful ignition, modulating was still necessary to get appropriate inlet condition which can keep periodic pulse. Periodic pulse with frequency of 300Hz appeared by the inlet temperature of 600 K, Mach number of 2.0 and pressure of 150kPa.
Experimental measurement of solubility of carbon dioxide in RP-3 jet fuel
2017, 32(4): 949-954. doi: 10.13224/j.cnki.jasp.2017.04.021
Abstract PDF(918KB) icon880 icon422
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The actually used RP-3 jet fuel containing additives was employed as the study object to measure its density and the solubility of CO2 from 5℃ to 40℃ under three pressure ranges via a experiment apparatus based on the pressure reduction method. The experimental solubility was compared with the theoretical solubility calculated by a relative density method provided in the standard of ASTM D2780-92. The result reveals that there exists a large deviation between experimental solubility and the calculated solubility. The deviation rises with the increase of the temperature or the decrease of the pressure, and the maximum deviation is over 106%. Hence, the formula to calculate the Ostwald coefficient depicted in ASTM D2780-92 is linearly corrected via the experimental data and the deviation is within 10% after this correction. The study results can provide a reference for the design of the green on-board inert gas generation system.
Numerical simulation of effect of parabolic nozzle contour parameters on flow separation
2017, 32(4): 955-960. doi: 10.13224/j.cnki.jasp.2017.04.022
Abstract PDF(662KB) icon795 icon399
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To investigate how the parabolic nozzle flow separation process is affected by three contour parameters, namely initial expansion curve radius, inlet angle and exit angle, the flow field parameters under different contour parameter combinations were numerically simulated, the changing processes of the nozzle flow separation position and separation mode with the increases of gas chamber pressure were obtained. The flow separation mode variation process with chamber pressure was gained. Results show that these three parameters can influence the development of nozzle flow field during engine starting, the flow separation mode transition nozzle pressure ratio(NPR) keeps a positive relationship with the initial expansion curve radius within a certain range. Restricted shock separation can be put off and shortened by suitable design of inlet angle and exit angle. The conclusion provides a possible way to solve the side load problem.
Influence of inlet angle and injection water law on gas-steam ejection
2017, 32(4): 961-969. doi: 10.13224/j.cnki.jasp.2017.04.023
Abstract PDF(931KB) icon820 icon400
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To study the influence of inlet angle and injection water law on flow field and interior ballistics, the Mixture multi-phase flow model, Renormalization group (RNG) k-ε turbulence model and dynamic mesh technology were adopted to build gas-steam ejection numeric calculation model. Comparing the calculation results with the literature data, it proved that the numerical method was effective. And on this basis, the influences of inlet angle and injection water law on gas-steam ejection power system were analyzed. The results show that when inlet angle is 60°, it can make the most use of the gas-steam medium energy and the launcher temperature is more uniform. Moreover, under the condition of the same water quantity, slow water injection can obtain short time out of tube but its acceleration is larger; on the contrary, quick water injection enables steady launching but the time out of tube is longer. The result can provide reference for gas-steam ejection power system design.
Characterization and measurement of doubly charged ions in xenon ion thruster beam
2017, 32(4): 970-975. doi: 10.13224/j.cnki.jasp.2017.04.024
Abstract PDF(759KB) icon814 icon400
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In order to evaluate the proportion of double ion ratio in ion engine beam rapidly, discharge chamber parameters were obtained through empirical theory, ratio of doubly/singly charged ions in beam was derived based on different generating processes of singly and doubly charged xenon ions. 20cm xenon ion thruster of Lanzhou Institute of Physics was tested and average fraction of doubly charged ions was acquired through E×B spectrometer. Xe++/Xe+ ratio under standard condition was measured to be 0.077, which was in good agreement with the analysis result of 0.071.
Influence of temperature on torque properties of miniature flexible joint
2017, 32(4): 976-982. doi: 10.13224/j.cnki.jasp.2017.04.025
Abstract PDF(965KB) icon715 icon406
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In order to study the properties of flexible joint torque at a certain motor pressure, a miniature flexible joint made of silicone rubber elastomer was designed. The dynamic characteristics of flexible joint under 0.1MPa vessel pressure were tested and the curves of torque versus vector angle for the flexible joint at different temperatures were obtained. The friction torque was obtained through the 0° vector angle torque .The spring torque was calculated by the near-linear part of the torque versus vector angle curve. In addition, the influences of temperature on the three kinds of torque were studied. Results show that the torque decreases as temperature increases while temperature has little influence on the torque. The coulomb friction torque increases with the temperature rise. The spring torque and the total ratio torque decrease as the temperature increases and then increase within a certain range caused by thermo-elastic inversion phenomenon. The dynamic elastic modulus and coefficient of loss decrease with the temperature rise. The energy loss decreases as the temperature and frequency increase due to the influence of dynamic elastic modulus and coefficient of loss.
Mechanism of affecting ability of stability enhancement with varying axial position of self-recirculating casing treatment
2017, 32(4): 983-989. doi: 10.13224/j.cnki.jasp.2017.04.026
Abstract PDF(1096KB) icon745 icon348
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The unsteady numerical investigation of three kinds of self-recirculating casing treatments was performed to explore the mechanism of affecting the ability of improving compressor stall margin with changing axial position of casing treatment(CT). Results showed that the ability of improving stall margin was best when the injecting part of CT was close to the blade tip leading edge, and also located in upstream blade inlet. The ability became low by changing the axial position of CT to make the injecting part above the blade tip leading edge. It became lower by moving the injecting part away from the blade tip leading edge along upstream direction, and the corresponding stall margin improvement gained with three kinds of casing treatments was 9.40%, 7.09% and 5.49% respectively. When the injecting part of CT was close to the blade tip leading edge, and located in upstream blade inlet, the level of positive effect created by CT was highest in the blade tip leading edge and the stall of rotor happened in this pivotal zone. Consequently the inlet blockage caused by the low energy tip clearance leakage flow was restrained most effectively, and the corresponding ability of increasing rotor stable operating range was highest among three kinds of casing treatments.
Numerical study on influence of coolant injection on the aerodynamic performance of high pressure turbine
2017, 32(4): 990-1000. doi: 10.13224/j.cnki.jasp.2017.04.027
Abstract PDF(2042KB) icon762 icon385
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Influence of coolant injection on the aerodynamic performance of high pressure turbine and secondary flow structure in cascade channel were numerically simulated. The results indicate that cooling high-pressure turbine vane and rotor load decreased, vane inlet and outlet Mach number decreased, rotor outlet relative Mach number increased in the radial region from 0 to 0.55, but decreased in the radial region from 0.55 to 1.0 with the increase of cooling air mass flow. Vane inlet and outlet flow angle was less affected by cooling air mass flow change. Cooling air mass flow increased from 4.83% to 14.49% of compressor inlet mass flow, rotor inlet relative flow angle increased in the radial region from 0.05 to 0.95, but outlet relative flow angle decreased in the radial region from 0.6 to 1.0; adiabatic wall cooling efficiency of vane first increased and then decreased while adiabatic wall cooling efficiency of rotor gradually improved by 19.33%. Hub and case sealing gas entered into the rotor cascade channel in bundles, with cavity sealing gas flow was greater affected by the pump effect of rotating wall.
Controlling mechanisms of bowed and swept of rotor in transonic axial compressor
2017, 32(4): 1001-1011. doi: 10.13224/j.cnki.jasp.2017.04.028
Abstract PDF(1294KB) icon818 icon364
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In a 1.5-stage transonic axial compressor, the controlling mechanism of bowed and swept blades was researched by 3-D numerical simulation when the compressor was working at different conditions. Results show that the combined scheme of sweepforward and positive bow is better than the combined scheme of sweepback and negative bow at the design speed, but its completely opposite at the part speed, because the controlling mechanisms of different bowed and swept schemes are different at the design speed and the part speed. The intensity and position of shock can be changed by the bowed and swept blades at the design speed, the same as the leakage vortex in the shroud gap and the spanwise C-shape pressure distribution; so the surge margin of compressor could be improved by combined action of three changed factors, but followed with the decrease of efficiency. However, the shock disappeared at the part speed, the reverse pressure gradient of the suction surface at the top of blade and the spanwise C-shape pressure distribution are changed, improving the aerodynamic stability of compressor and cutting down the efficiency.
Design method and analysis of differential planetary gear mechanism for contra-rotating propellers/propfans
2017, 32(4): 1012-1017. doi: 10.13224/j.cnki.jasp.2017.04.029
Abstract PDF(846KB) icon839 icon448
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A design and analysis method of the differential planetary gear decelerating mechanism for driving the type of loading of aerodynamic turbo-machinery, especially the co-axial contra-rotating propellers or propfans, was put forward. Differing from the ordinary path, this integral performance method considered the kinetic parameters first and solved the speed ratios, radii, steady exerting forces last, then the correlations among those parameters of the transmission mechanism were established by equations. The conceivable design principles, utilizing types, suitable prime mover aero-engines of the mechanism were discussed. An analytical case of modern turboprop was provided for obtaining the variable intervals of the propfan and mechanism, the features and the importance of those design parameters. Result shows that this method can reveal the domains of feasible solution and the optimal designs of all stable parameters of the mechanism and serve as a theoretical model in the overall simulation of the off-design characteristic of a propulsion system.
Theoretical analysis for manufacturing face gear by plane cutter
2017, 32(4): 1018-1024. doi: 10.13224/j.cnki.jasp.2017.04.030
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Abstract:
The application of the plane cutter in face gear manufacturing is able to improve the generality and decrease the design and manufacturing cost of the cutter. Firstly, based on the simulation of the Gleason Works'method, it pointed out that the ideal tooth surface cannot be obtained by only the application of higher order roll ratio. Then an additional motion was proposed: through the additional motion and higher order roll ratio, the exact simulation of suppositional involute can be realized in the cutters motion. Thirdly, the method for determining the polynomial coefficients of the higher order roll ratio and additional motion was proposed. Fourthly the equations of the generating plane of the plane cutter and the tooth surface of the face gear were derived. Finally, the numerical simulation of the roll ratio, motion rule, tooth contact analysis were performed. The results show that: in the numerical example, the maximum tooth surface error is -1.05 mm, the contact path is tilted, the maximum length of contact ellipse is 11.2 mm, transmission errors is about 0″, the meshing between the generated face gear and the standard pinion demonstrates good features of ‘quasi conjugate’. Hence the manufacturing method for rough cutting, and finish grinding has perfect feasibility and practicability.

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