2017 Vol. 32, No. 6

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Film cooling performance comparison at different positions on blade suction side
2017, 32(6): 1281-1288. doi: 10.13224/j.cnki.jasp.2017.06.001
Abstract PDF(1182KB) icon1458 icon493
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Film cooling performances of two fan shaped film holes at different positions on blade suction side were experimentally studied in a linear transonic cascade. The film cooling effectiveness of the fan shaped film holes on blade suction side was measured at mainstream inlet Reynolds number of 3.7×105, different mainstream exit Mach number of 0.81, 0.91,1.01, and different blowing ratio of 0.6-2.1. Results shows the film hole 2 is at the position with higher curvature, where the mainstream forces the coolant to better flow along the surface, however, this has both advantages and disadvantages. At smaller blowing ratio, the jet of film hole can flow close to the wall itself, so the advantage of the mainstream isnt obvious, but the mainstream forces the coolant to flow downstream and the coolant will be difficult for spanwise flow, bringing about lower film cooling effectiveness. At higher blowing ratio, the jet of film hole has large vertical velocity component, the coolant can be easily lifted off, then coolant of the film hole 2 can be forced to get close to the wall, so the film cooling effectiveness is increased substantially.
PIV measurement for inner flowfield in aero turbine engine combustor
2017, 32(6): 1289-1295. doi: 10.13224/j.cnki.jasp.2017.06.002
Abstract PDF(1260KB) icon1573 icon544
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A high pressure particle generator based on cyclone separation principle was designed, and applied for PIV（particle image velocimetry） measurement of inner flowfield of high pressure aero turbine engine combustor successfully. With the combustion flow of hydrogen and oxygen, the research of measurement for complicated inner flowfield in the single sector combustor of aero turbine engine was carried out by PIV at 813K and 2.78MPa. The strong rotational and turbulent inner flowfield with wide velocity range was measured under conditions of high temperature and pressure, and the flowfield velocity and microscopic structure close to real work pressure of combustor were obtained. The results show that there are multiple vortices in the inner flowfield of the studied combustor, accompanied with relevant recirculation zones. The effect of swirler is strong, and there is big vortex clockwise in cross section. The jet effect of main combustion holes and dilution holes is obvious, the jet flows have deep penetration, and have distinct effect on the flowfield structure. The flow field structure under high temperature and pressure condition is similar to that under normal temperature and moderate pressure.
Numerical study on factors of interior ballistic for low-temperature gas-ejection
2017, 32(6): 1296-1306. doi: 10.13224/j.cnki.jasp.2017.06.003
Abstract PDF(1536KB) icon1379 icon549
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Regarding a low-temperature gas ejection mechanism, a simplified physical model of the secondary combustion was established, a renormalization group k-ε turbulence model was adopted to simulate the flow-field, and a finite rate/eddy dissipation model was used to simulate the gas phase combustion, meanwhile a dynamic mesh update method was employed to update the missile movement; the launch canister within the load and the interior ballistic properties were obtained through numerical analysis. Results show that: if the interior ballistic design condition is met, the range of the total temperature in the entrance section of the nozzle of gas generator is 0.538-1.231, and the time of secondary reaction and the time out of the barrel decreases with the rise of the total temperature, and the exit velocity increases accordingly. The range of the oxygen mass fraction of the launch canister is 0.07-0.30, and the begin time of secondary reaction and out of the canister of time decreases with the increase of the oxygen mass fraction, and the exit velocity increases with the increase of the oxygen mass fraction. Research results can be used as a reference for the interior ballistic and device structure.
Experiment on thermal cracking coke of aviation kerosene
2017, 32(6): 1307-1312. doi: 10.13224/j.cnki.jasp.2017.06.004
Abstract PDF(964KB) icon1504 icon455
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To reduce the coke deposition of aviation kerosene in the process of active thermal protection, some reaction principles of thermal cracking and coke deposition should be investigated. Thermal cracking and coke experiments were conducted to compare the difference of gaseous, liquid and coke amount under different conditions. The results showed that dimerization of olefins and condensation polymerization of aromatics were the main reactions in the coke process. With the enhancement of temperature, the reaction rates of dimerization and polymerization sped up, so the coke amount in the reactor was aggravated. Volumn fraction of gas products such as methane and ethylene increased. In the liquid products, mass fraction of alkane decreased but the aromatics mass fraction increased. The residence time of kerosene increased significantly with the growth of pressure, benefiting the coke formation and additional aromatics in the liquid products.
Numerical investigation of the impact of spherical ignition chamber on pulse detonation DDT process
2017, 32(6): 1313-1320. doi: 10.13224/j.cnki.jasp.2017.06.005
Abstract PDF(922KB) icon1573 icon465
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The length of deflagration to detonation transition (DDT) is the key influential parameter to the single cycle time of pulse detonation engines (PDE). In order to reduce PDEs single cycle time, a new type detonation tube was designed by adding a spherical ignition chamber at the head of traditional detonation tube, meanwhile propane and air were used as fuel to study the effect of spherical ignition chamber on DDT process by 2-D numerical simulation. The numerical simulation results show that, the compression wave were frequently reflected in the ignition chamber, and then the detonation wave was formed quickly in the straight detonation tube, the length of DDT was significantly shortened. Compared with the conventional straight detonation tube, the length and time of DDT process reduced about 14% and 16.26% respectively, when the spherical ignition chamber's diameter was 1.5 times of the straight pipe's diameter.
Modeled experiment on overall cooling effectiveness of effusion holes in front of outer liner of annular slinger combustor
2017, 32(6): 1321-1327. doi: 10.13224/j.cnki.jasp.2017.06.006
Abstract PDF(987KB) icon1157 icon453
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An experimental model for simulating the local primary flow field near the front of outer liner of annular slinger combustor was designed to study the effusion cooling performance. The surface temperature distribution on the perforated plate was measured by the infrared camera, and the effects of blowing ratio, effusion holes-array arrangement, hole diameter and perforated percentage on the overall cooling effectiveness were then compared. Three effusion holes-array arrangements including square-diamond mode, long-diamond mode and super-long-diamond mode were adopted. The hole diameter varied from 0.6mm to 1.0mm, the perforated percentage varied from 3% to 6% and the blowing ratio varied from 1 to 6. The results show that the overall cooling effectiveness increases firstly along the streamwise direction and then decreases downstream due to the existence of recirculation zone in the front of outer liner. The blowing ratio of 2 results in the highest overall cooling effectiveness and the long-diamond holes-array arrangement seems to be advantageous. The decrease of hole diameter is helpful for improving the overall cooling effectiveness under the same perforated percentage. When the perforated percentage increases from 3% to 4.8%, the overall cooling effectiveness is significantly enhanced.
Influence of outlet delta-chevrons on aerodynamic and infrared characteristics of spherical convergent two-dimensional nozzle
2017, 32(6): 1328-1334. doi: 10.13224/j.cnki.jasp.2017.06.007
Abstract PDF(1151KB) icon1329 icon486
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Numerical investigation was performed to study the influence of outlet delta-chevrons on the aerodynamic and infrared characteristics of a spherical convergent two-dimensional nozzle in turbofan engine exhaust system. Results showed that the trust coefficient and total pressure recovery coefficient decreased by the outlet shaped-chevrons in relative to the baseline nozzle, especially for the larger base angle of delta-chevron. By comparison, the inner-recessed-chevron mode had a least influence on the aerodynamic performance of exhaust system. However, it resulted in an obvious enhancement both for the exhaust plume and total infrared radiation at the detective angle in the vicinity of ±15°. The outer-extended-chevron mode had a most influence on the aerodynamic performance of exhaust system. The equal-area-chevron mode with a base angle of 30° seemed to be advantageous, as it had a weak influence on the trust coefficient and total pressure recovery coefficient, and also showed certain infrared radiation suppression in the detective angles of -30°-0° and 0°-30°.
Effect of nozzle damage on performance of annular backflow combustor
2017, 32(6): 1335-1341. doi: 10.13224/j.cnki.jasp.2017.06.008
Abstract PDF(1043KB) icon1332 icon525
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The effects of different atomization performance caused by nozzle damage on the annular backflow combustor performance were studied by using Fluent software. Three-dimensional two-phase spray combustion flow fields in a model annular backflow combustor were numerically simulated using realizable k-ε model, DPM (discrete phase model) with UDF(user defined function) subroutines tracking fuel trajectory, n-heptane as surrogate fuel and laminar flamelet model. The results reveal that the numerical method is reasonable to predict combustion flow of annular backflow combustor. The outlet temperature non-uniformity deterirated with the atomization performances change caused by nozzle damage. And the combustion efficiency also decreased.When the fuel flow rate was reduced by 19%, the performance of the combustor was not conformity with the operational requirements.
Mechanical properties of TC4 titanium alloy diffusion bonded joints
2017, 32(6): 1342-1348. doi: 10.13224/j.cnki.jasp.2017.06.009
Abstract PDF(1154KB) icon1312 icon457
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The diffusion bonding of TC4 titanium alloy plate was conducted under the condition of 910℃ temperature and 3.4MPa pressure. Specimens were cut from the gained joints to conduct metallographic analysis. It indicated that the sound joints can be achieved under selected process parameters, since several microscopic defect only existed within the depth of 1mm from the surface of the joints. Subsequently, the mechanical properties of diffusion bonded joints were studied. The static tensile test, fracture toughness test and nano indentation test were carried out for diffusion bonded joints. The results show that the yield strength of the gained diffusion bonded joints is 887MPa, its tensile strength is 948MPa and fracture toughness is 101.9MPa·m1/2，presenting little difference of properties with raw materials. The results of nano indentation tests indicate that the micro elastic modulus of the bond line and the based metal region are 180.2GPa and 178.0GPa respectively.
Investigation and design for HCF/LCF complex fatigue experiment method of fan shaft
2017, 32(6): 1349-1358. doi: 10.13224/j.cnki.jasp.2017.06.010
Abstract PDF(1404KB) icon1325 icon491
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In order to accomplish the fan shaft's high-cycle fatigue/low-cycle fatigue (HCF/LCF) complex fatigue experiment under combined loading of axial force, principal torsion, vibration torsion and rotating moment, the sample's boundary conditions was simulated truly without inducing other extra loading. A loading method under these conditions was proposed based on mechanism design skills, hydraulics kills and computer data acquisition technology, meanwhile four kinds of loading control and calibrated system were established, and a fan shaft fatigue experiment device of high bypass ratio turbofan engine was designed. Making use of computer measurement and control systems, this experiment device can achieve the harmonious loading of axial force, principal torsion, vibration torsion and rotating moment by signal extraction, electro-hydraulic servo valve and mechanism system. Result showed that the high circle loading frequency could reach to 9Hz, the precision of low circle fatigue, vibration torsion and 92.75% the rotating moment to be loaded was superior to than ±0.12%, ±2% and ±5%, respectively, the maximum error of rotating moment didnt exceed ±9%. This experiment device has well repeatability and linearity.
Experimental design and verification of hollow fan blade high cycle fatigue
2017, 32(6): 1359-1365. doi: 10.13224/j.cnki.jasp.2017.06.011
Abstract PDF(959KB) icon1573 icon588
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Based on the structure feature of wide chord blade of actual high bypass ratio turbo-fan engine, the design and manufacturing of hollow fan blade specimen were finished, followed by high cycle fatigue experimental design and emphasized verification of the fatigue endurance of hollow structure. The experiment results indicate that the design of fixture and fan blade specimen could accomplish the high cycle fatigue experiment on hollow fan blade. Meanwhile, the high cycle fatigue strength of the hollow fan blade which lies between 370MPa and 400MPa for 1×107 cycle could fulfill the high cycle fatigue design requirement that the hollow fan blade should have high cycle fatigue strength no less than 324MPa under maximum operating condition. However, due to the lack of sufficient quantity of specimens, high cycle fatigue data were only derived under limited stress levels. Further research could be carried out similarly with increased quantity to estimate the fatigue endurance and then construct the stress-fatigue curve, providing prime data base for engineering research.
Statistical energy analysis considering thermal effect based on FEM-PIM
2017, 32(6): 1366-1374. doi: 10.13224/j.cnki.jasp.2017.06.012
Abstract PDF(1174KB) icon1302 icon450
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With the combination of the finite element method (FEM) and the power injection method (PIM) under modal coordinate considering thermal effect, a statistical energy analysis method applicable of vibration analysis of complex structures under thermal environment was presented. A simply supported L-shaped folded plate under rain on the roof excitation was studied and the accuracy of proposed method was verified with numerical examples. The influence of thermal effect on the parameters in statistical energy analysis was investigated under three cases: (1) only the material properties were affected by the thermal effect; (2) only the additional stiffness due to thermal stresses was considered; (3) both (1) and (2) were considered. Results showed that the increasing temperature changed the material properties and decreasd the value of coupling loss factor, but had little influence on internal loss factor. The thermal stresses had great influence on the parameters in statistical energy analysis, the increasing temperature decreasd both internal loss factor and coupling loss factor. When both (1) and (2) were considered, the influence of thermal stresses was dominant, the internal loss factor and the coupling loss factor gradually decreased with the increase of temperature. Similar trend was found between the change of modal density and temperature.
Multi-scale stress-strain calculation model of laminated ceramic matrix composites
2017, 32(6): 1375-1380. doi: 10.13224/j.cnki.jasp.2017.06.013
Abstract PDF(879KB) icon1056 icon479
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The stress-strain behavior for laminated ceramic matrix composites (CMCs) was studied. A model of calculating the stress-strain behavior for CMCs directly from constituent parameters was presented based on multi-scale method. On the basis of the micromechanical model of unidirectional fiber reinforced CMCs, the nonlinear mechanical response of unidirectional laminate can be calculated from the mechanical parameters of constituents. Subsequently, the stress-strain response of the entire composites can be obtained from the response of unidirectional laminate by finite element methods. The predicted stress-strain curves of laminated CMCs under monotonic tensile and repeated loading were acceptable if compared with the experimental results. Among these curves and their corresponding experimental results, the biggest deviation was 19.61%.
Thermal fatigue behavior of nickle based superalloy GH536
2017, 32(6): 1381-1387. doi: 10.13224/j.cnki.jasp.2017.06.014
Abstract PDF(1192KB) icon1113 icon547
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The flame tube of combustion chamber is the key structure of the aero-engine, and subjected to complex cyclic temperature load which will cause thermal fatigue. The thermal fatigue behavior of nickle based superalloy GH536 always used in flame tube was investigated. According to the characteristic load and structure of the flame tube, the specimen of a flat plate with a central hole and the thermal fatigue test were designed to study the crack initiation, crack propagation and thermal fatigue damage mechanism of the GH536 plate specimen under the thermal fatigue load condition. The study indicates: (1) the thermal fatigue cracks initiate transgranularly, develop and propagate intergranularly; (2) the crack propagation rate becomes faster and the crack initiation life becomes shorter with the increase of upper temperature in the thermal fatigue test. Thermal fatigue crack initiation life at 800℃ is 4.5 times of the crack initiation life at 900℃.
Optimization design method for twin-web turbine disk/tenon structure based on static strength and life reliability
2017, 32(6): 1388-1393. doi: 10.13224/j.cnki.jasp.2017.06.015
Abstract PDF(971KB) icon1054 icon478
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In order to guarantee the fatigue life reliability of twin-web turbine disk/tenon, a method of optimization design based on static strength and life reliability was put forward. With introduction of the optimization strategy of the disk's axisymmetric model and the turbine disk/tenon three-dimensional model in turn, the static strength optimization was in progress. According to the material stress-life data, the life reliability of turbine disk/tenon structure already meeting the static strength criteria was analyzed in consideration of the size effect. Stress-life curves of different zones for a given reliability were established. The point stress criterion of the static strength optimization was modified according to the stress-life curves. On the premise that the disk wasnt broken, the complex optimization process based on life reliability was simplified based on stress standard. A typical example showed that the static strength optimization result could not meet the design requirements of life reliability. Through the life reliability optimization design, the structural life was prolonged by 47.28% and met the design requirement of reliability life. And on the basis of the turbine disk/tenon mass reduction by 16.66% during the static strength optimization, the total mass reduced 3.43% in life reliability optimization again. Under the conditions of ensuring the accuracy of the optimization.The method can significantly improve the optimization efficiency, enabling convenient engineering applications.
Test on static and temperature characteristics of gas foil bearing
2017, 32(6): 1394-1399. doi: 10.13224/j.cnki.jasp.2017.06.016
Abstract PDF(1050KB) icon1163 icon442
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A test rig was set up to check the static characteristics and temperature characteristics of the foil gas radial bearing. After applying different load and speed on the bearing, the bearing take off speed, friction moment and bearing temperature were measured respectively. Then, the bearing static characteristics and temperature characteristics in different load and speed were analyzed. Results showed that, since there was no gas film in the start-stop stage, the foil gas bearing friction torque peak appeared larger, but when reaching a certain speed (take off speed), the friction torque would drop to a pole small value, and the steady-state after take-off speed bearing torque increased with the applied load and speed. In addition, the bearing temperature stabilized at a certain temperature in the stable operation stage. The bearing temperature rise was very small and increased approximately linearly with the speed and load.
Analysis of dynamic characteristics and stability prediction of spherical spiral groove hybrid gas bearings
2017, 32(6): 1400-1411. doi: 10.13224/j.cnki.jasp.2017.06.017
Abstract PDF(1811KB) icon1146 icon417
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In order to research the spherical spiral groove hybrid gas bearings, the nonlinear dynamic lubrication analysis mathematical model of spherical spiral groove hybrid gas bearings was established, based on the parameters of axis instantaneous position and instantaneous displacement speed. The transient perturbation pressure distribution of three-dimensional gas film, stiffness and damping coefficients were numerically computed were solved by using the combination of derivative integration and finite difference method. The influence law of speed,eccentricity ratio and supply pressure on the dynamic characteristics of gas film was researched. The results show that the influence of bearings supply pressure, speed and eccentricity ratio on the stiffness and damping coefficient of gas film was significant. The prediction model to estimate stability of rotor-bearing system was established, helping to predict the stability of bearings by applying Routh-Hurwitz stability criterion. The research provides the theoretical foundation for controlling actively the bearing running stiffness and damping and stemming the instability of gas film.
Vibration reduction optimization of gear modification based on Kriging model and genetic algorithm
2017, 32(6): 1412-1418. doi: 10.13224/j.cnki.jasp.2017.06.018
Abstract PDF(977KB) icon1155 icon429
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To solves the problems of large computation, low precision and complicated operation during optimization of gear modification, an algorithm for optimization of gear modification was proposed based on Kriging model and genetic algorithm. Taking spur gear drive as the research object, optimization of gear modification was carried out. Firstly, in order to solve the problems of multiple responses and implicit function during optimization of gear modification, Kriging model was established by using Latin sampling method. Compared with the gear engaged stiffness of Kriging prediction and finite element, it was shown that the maximum errors of predicted stiffness parameters were 7.79×10-5, 1.20×10-3 and 1.30×10-4 respectively, therefore, the precision of Kriging multiple prediction was validated. Secondly, Kriging prediction was applied to dynamical differential equation of spur gear, and then fluctuation of dynamic transmission error was regarded as the goal of genetic algorithm optimization, so optimal parameters of gear modification was obtained. Example showed that the proposed method was better than ISO(International Standardization Organization) modification and no modification, therefore, the efficiency and correctness of the gear modification by using genetic algorithm and Kriging model was validated. Compared with gear modification by using finite element directly, the cost time of the proposed method changed from 26.91d to 2.24h, so the computational efficiency of the proposed method was verified.
Simulation of gear windage losses and its application
2017, 32(6): 1419-1424. doi: 10.13224/j.cnki.jasp.2017.06.019
Abstract PDF(924KB) icon1111 icon428
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Several different types of gears, yet with similar size, were simulated. The air flow around gear teeth and the pressure distribution on gear teeth surfaces were studied. The windage losses of a specific internal bevel gear adopted in an aero engine was calculated. Result showed that， gear windage losses were consist of pressure loss and viscous force loss, and viscous force loss occupied ratio of 4%-17%. 60% difference in windage losses of helical gears with opposite hand of helix suggests the effect of wall. Windage losses for internal bevel gear in aero engine occupied about 49% of total transmission losses.
Design and simulation of sliding mode regulator for turbo-fan engine parameter limit
2017, 32(6): 1425-1433. doi: 10.13224/j.cnki.jasp.2017.06.020
Abstract PDF(1575KB) icon1156 icon471
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A sliding mode (SM) regulator was proposed for the turbo fan engine parameter limit protection. The feedback gains of the SM were designed using the regional pole placement method based on the mixed norm synthesis. The overall asymptotic stability of the SM regulator was established. The SM regulator was verified and compared in the simulation with different sliding switch gains, of which one of the gains was used as the standard coefficient for the following simulations. The regulating effects between SM regulator and linear regulator were compared and analyzed. The results preliminarily show that, the parameter limit regulator acts as a main control regulator during engine transient state process based on sliding mode control theory, overcoming the drawback of linear parameter limit regulator which nearly can not work during the same process; the designed regulator can conduct the parameter limit protection function in 7 seconds during the engine transient state.
Anti-surge model and control strategy of fan in wind tunnel
2017, 32(6): 1434-1440. doi: 10.13224/j.cnki.jasp.2017.06.021
Abstract PDF(842KB) icon954 icon424
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Based on the application of multi-stage axial fan in continuous high speed wind tunnel, the flow rate condition of surge and flow rate characteristic of changeful wind tunnel test state was analyzed, and an anti-surge model based on inlet flow rate and pressure ratio was established. The fan flow similarity condition and a flow rate calculating method were given, the generalized characteristics and work curves of wind tunnel fan were determined, and the anti-surge cluster curves were set based on rotating speed range and work characteristic of fan. Based on PLC （programmable logic controller） and WinCC automation system, a multi-level redundant anti-surge control strategy was proposed and validated in wind tunnel test. The results show that the anti-surge model has satisfactory effect to reflect the operation situation and safety margin of fan caused by changeful wind tunnel test condition exactly; standard deviation of flow rate and pressure ratio acquired is 0.002 and 0.001, anti-surge control repeatability accuracy is 0.003, realizing real-time discrimination and automatic control of surge come true, and effectively preventing the surge.
Transmission delay/packet dropout robustness analysis of distributed control system of aero-engine
2017, 32(6): 1441-1446. doi: 10.13224/j.cnki.jasp.2017.06.022
Abstract PDF(787KB) icon1280 icon408
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Research on the robustness analysis of distributed engine control system was conducted to describe the robustness quantitatively. Stability criterion for control system model considering transmission delay/packet dropout was simultaneously presented in linear matrix inequality form. Gain matrix was designed utilizing regional poles assignment technology, and the delay/packet dropout margin of closed-loop systems with poles in various regions was solved and verified. Discussion was extended to the closed-loop poles region selection in terms of delay packet dropout robustness and dynamic performance. Simulation confirmed the validity of the stability criterion. Further analysis result showed that the strongest delay/packet dropout robustness was obtained when closed-loop poles were assigned near -4. Considering the control requirements of delay/packet dropout robustness and dynamic performance comprehensively, it was feasible to place closed-loop poles in disk area with center between -8 and -4 and radius of 1.
Simulation of hypersonic scramjet engine real-time model
2017, 32(6): 1447-1455. doi: 10.13224/j.cnki.jasp.2017.06.023
Abstract PDF(863KB) icon1179 icon470
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A method for establishing a hypersonic scramjet engine real-time model was presented.The engine model adopted the component level model based on characteristics,considering volume dynamics of the combustion chamber,and a method for calculating shock angle in the calculation of inlet parameters was given,enabling to get the shock angle at one time without numerical solution and simplify the calculation process with better accuracy.The engine model was completed by means of numerical integration, iteration was avoided with high speed of the model. Taking the modeling of a certain model as an example, the response time was about 1s and the overshoot was 0.5% in the dynamic process by close loop simulation experiment.Simulation results demonstrate that the modeling method meets the requirement of improving real-time performance and contributes to the dynamic process of such engine control study.
Inverse design approach for propfan aerodynamics based on compressible lifting surface theory
2017, 32(6): 1456-1469. doi: 10.13224/j.cnki.jasp.2017.06.024
Abstract PDF(1459KB) icon1130 icon458
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Two kinds of design methodologies of propfan were briefly discussed combined with its structure and flow features. Based on the compressible lifting surface theory, an inverse approach for propfan aerodynamics design was developed. Compared with the traditional lifting surface design method of propeller, the effects of blade rotation, compressibility, long chord length, large sweep angle and blade interference were treated strictly under the small distribution linearization assumption in rotating coordinate system. The features of the profan with hub but without casing were reflected. The kernel functions of loading-downwash angle and thickness-downwash angle for propfan design were given. The kernel functions were verified by comparing with the wing kernel functions and their convergences were studied. The chordwise and spanwise integrals of the kernel functions were discussed in detail. The ways of prescribing the distributions of design parameters, especially the optimum loading distribution, were discussed. A loss model to modify the effect of flow loss on inverse design was made. A design example was given and the accuracy of this inverse design approach was analyzed. Studies show, at some transonic sections, the prescribed chordwise loading distributions have some differences from those of numerical simulation of the designed blade due to the linearization assumption differing from the real flow nature. The prescribed element power coefficient distribution and the overall performance agree well with the numerical simulation.
Effect of tip leakage flow and ejection on stall mechanism of transonic tandem rotors
2017, 32(6): 1470-1480. doi: 10.13224/j.cnki.jasp.2017.06.025
Abstract PDF(1485KB) icon1161 icon495
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In order to investigate the stall mechanism of transonic tandem rotor, the transonic tandem rotor tip flow field in different tip clearance was studied. The results show that the flow field of zone two has a great effect on stall and it is determined by the tip leakage flow and ejection. Furthermore, the tip leakage flow and ejection are determined by the tip clearance. When the forward blade tip clearance is large, the tip leakage flow is much stronger and becomes the leading factor of zone two. Thus, forward blade becomes the stall position. When the forward blade tip clearance is reduced, ejection grows stronger and becomes the leading factor of zone two. This leads that the stagnation area of the tip leakage flow in zone two reduces and after blade becomes the stall position. The forward blade tip clearance has more effect on stall than the after blade tip clearance. Whats more, after blade tip clearance has little effect on the tandem rotor when forward blade is the stall position.
Numerical simulation on blade tip unsteady flow in transonic compressor rotor
2017, 32(6): 1481-1490. doi: 10.13224/j.cnki.jasp.2017.06.026
Abstract PDF(1404KB) icon1055 icon439
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The detailed three-dimensional unsteady numerical study was conducted in a transonic compressor rotor to deepen the understanding of unsteady flow phenomenon in rotor blade tip region. Unsteady numerical simulations were studied in single rotor under different inlet conditions and different mass flows, so as to investigate the complex flow structure in rotor blade tip region and the development of blade tip unsteady flow. Results showed that the structure of blade tip flow field varied under different inlet conditions. When inlet direction was non-axial, signal passage periodical form emerged for unsteady flow at blade tip, while an unsteady flow phenomenon like “rotating instability”, spreading along circumferential direction, occurred in blade tip region under axial inlet condition. And with the decrease of mass flow, the structural flow field of blade tip region changed correspondingly.
PIV velocity field measurement-based pressure gradient computation
2017, 32(6): 1491-1504. doi: 10.13224/j.cnki.jasp.2017.06.027
Abstract PDF(1596KB) icon1082 icon428
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A description of the basic operation principles of the (particle image velocimetry) PIV velocity field measurement-based pressure gradient calculations and three different methods were described in detail. Then, an analytic test case of the convection of a Gaussian vortex was considered to give insight into the influences of the discrete scheme, parameter setting and flow field characteristic on successful determination of the pressure gradient field. Results showed that the uncertainty of pressure gradient calculation was dominated by errors of PIV velocity measurements. The effect of 1% errors in velocity on the result was about two orders of magnitude higher than any other steps. Time and spatial resolution settings were not as high as possible, but there was a suitable intermediate value. The Lagrangian approach was superior to the Euler approach in most cases, but the former became worse when the flow structure was more complex, the pressure gradient calculation method should be selected according to the flow type and flow field characteristics.
Analysis and optimizations on aerodynamic interaction of tiltrotor aircraft multi-components on its wing
2017, 32(6): 1505-1514. doi: 10.13224/j.cnki.jasp.2017.06.028
Abstract PDF(1542KB) icon1113 icon501
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For revealing the aerodynamic interaction mechanism between the rotor/fuselage/nacelle and wing of the tiltrotor aircraft, a CFD solution was established. The unstructured hybrid mesh system consist of triangular prism and tetrahedron meshes suitable for solving flowfield of tiltrotor aircraft under multiple flight conditions were established. Three-dimensional Navier-Stokes equations was the main control equation and the momentum source method was used to simulate the flowfield of tiltrotor, and data sharing OpenMP parallel strategy was employed to accelerate the calculation as well. A new momentum source adding and searching method was proposed. The aerodynamic interactions of tiltrotor/fuselage/nacelle on wing were simulated respectively, and some valuable conclusions for optimization were obtained. The surrogate model based on radial basis function (RBF) was used for the tiltrotor aerodynamic optimization problem. Considering the interaction effects on different sections of wing, the wing airfoils were used as the design variables in the optimization design process of tiltrotor aircraft, and optimized life/drag were improved by 36.78% compared with the original model.
Reverse design of asymmetric nozzle based on given wall pressure distribution
2017, 32(6): 1515-1522. doi: 10.13224/j.cnki.jasp.2017.06.029
Abstract PDF(1052KB) icon1054 icon471
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Reverse design method based on given wall pressure distribution was proposed for the shortcoming of traditional design method of asymmetrical nozzle. The reverse design program of expansion surface was obtained, and optimization method was used to find the wall pressure distribution with better comprehensive performance. Comparisons were made between the nozzle based on given wall pressure distribution and maximum thrust nozzle. The result showed that: the thrust coefficient of the nozzle decreased by 0.102% than that of maximum thrust nozzle, while the lift and pitch moment increased by 2.295% and 15.774% respectively when flow was fully expanded, verifying the design method and providing an efficient design approach for asymmetrical nozzle.
Dynamic characteristics of fluid-filled pipe in liquid rocket engines considering fluid-structure interaction
2017, 32(6): 1523-1529. doi: 10.13224/j.cnki.jasp.2017.06.030
Abstract PDF(972KB) icon1107 icon445
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To study the influence of fluid-structure interaction (FSI) on the frequency characteristics of fluid-filled pipe in rocket engines, a dynamic characteristic model of spatial pipe was set up based on transfer matrix method(TMM). Targeting a real liquid rocket engine pipe, simulations by transfer matrix method as well as conventional finite element method (FEM) for fluid with added-mass (non-FSI) were proposed, and verification modal test was also carried out. Influences of parameters such as diameter and thickness of the pipe on the coupling effect were discussed. The results indicate that each resonant frequency declines and the corresponding amplitude increases under FSI effect. In addition, the influence of pipe thickness on low-order resonant frequencies is more significant than the pipe diameter. The example given hereto also demonstrate that the concerned 1st-order resonant frequency calculated by the non-FSI model offsets is over 10% when the pipe thickness exceeds 30% of the design value, so the coupling effect can not be ignored in this case. And the influence of pipe thickness on 1st-order resonant frequency is less than 8% within the range of calculation.
Numerical simulation of influences of solid rocket motor post-thrust on missile base drag
2017, 32(6): 1530-1536. doi: 10.13224/j.cnki.jasp.2017.06.031
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Abstract:
Coupled with two-dimensional axisymmetric N-S equation and turbulence model, integral flow field simulation models were established for solid rocket motor nozzle tail flow and missile outer flow. For a given missile model, numerical simulations were carried out under different combustion gas mass flow rates. Velocity and pressure contours were obtained and influences of solid rocket motor post-thrust on missile base drag were analyzed under different combustion gas mass flow rates. According to the results, compared with the case when the motor was in idle condition, the missile base pressure increased and base drag decreased under low combustion gas mass flow rate. As the combustion gas mass flow rate increased, the missile base pressure decreased first and then increased; on the contrary, the missile base drag increased first and then decreased. As the combustion gas mass flow rate increased, resultant force of post-thrust and base drag increased, and the proportion of momentum thrust increased gradually.

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