2013 Vol. 28, No. 4

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Study and test validation of turboshaft engine on-line performance monitoring technology
SHAN Xiao-ming, HUANG Jin-quan, ZHOU Wen-xiang, CAI Jian-bin, KUANG Gui-lan
2013, 28(4): 721-729.
Abstract PDF(835KB) icon2329 icon1715
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A model based on-line turboshaft engine(TSE) performance monitoring technology was studied, while an on-line TSE performance monitoring software was developed and subsequently applied to an actual TSE land rig test. Test results show that the software could automatically distinguish the working state of TSE on rig test. With use of the atmosphere pressure and temperature, gas turbine rotor speed and power turbine rotor speed, the software could calculate the TSE performance parameters such as compressor pressure ratio, power turbine inlet gas total temperature, output shaft power and specific fuel consumption et al. The calculation error of compressor pressure ratio between TSE model and the specific engine in rig test is less than 2.3%, which shows the significant performance difference between testing engine and baseline engine, and the effectiveness of the on-line TSE performance monitoring technology is confirmed.
Experiment on spooldown airstart performance of aero-turbofan engine in ATF
MA Qian-rong, GUO Xin, WU Hu
2013, 28(4): 730-735.
Abstract PDF(1003KB) icon1987 icon1448
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A aero-turbofan engine turbofan with great flow rate completed spooldown airstart tests in altitude test facility(ATF). The simulated altitude was at 5km, 8km and 10km. The results of test in AFT showed that simulated intake total pressure and exhaust pressure had obvious fluctuation during spooldown airstart process. So the engine operating condition of spooldown airstart test in ATF deviated from the real flight condition. Moreover, different airspeeds of 25-70km/h were obtained using a few calculation ways to analyze the test data. A performance evaluation method of spooldown airstart test in ATF was recommended based on the analysis results, namely, the simulation flight condition means the average in three seconds span from the beginning of the airstart sequence for the successful tests, or the average in the time from the rotor speed's return to drop down again for the failure tests. This is important to improve the performance evaluation level of test in ATF.
Experiments on metal bellows expansion joints in six-component balance
LUO Hua-yun, HOU Min-jie, WANG Yue-gui, YE Wei, LIU Zhi-gang
2013, 28(4): 736-742.
Abstract PDF(542KB) icon2022 icon1442
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The force test platform was coupled flexibly with the fixed air pipeline with stagnation points based on the mechanism of force balance,and analysed deeply in order to explore the relationship of elastic bellows and internal flow six-component force-measuring balance in nozzle test facility.The changes of balance output signal connecting expansion joints and added force of balance control body by pressure were compared under the principle of load distributed by stiffness,and this was investigated to match the expansion joint stiffness and effective area with the force test platform.The test results indicate that the effect of elongate fixing of expansion joints with stagnation point is evident,the coherence of effective area of expansion joints must be very good,and the whole lateral stiffness must be smaller especially in order to reduce the excursion of benchmark stagnation point of balance and increase the aerodynamic stability of the force measurement system.
Transition mechanism of an incompressible boundary layer on a flat plate
LI Ning, LUO Ji-sheng
2013, 28(4): 743-751.
Abstract PDF(1550KB) icon1800 icon1083
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Direct numerical simulation (DNS) was carried out for laminar-turbulent transition of an incompressible boundary layer on a flat plate based on disturbance N-S equation in spatial mode with Fourier pseudo-spectral and massage passing interface(MPI) methods.The statistical data were analyzed.Transition processes caused by disturbances with different initial amplitudes were compared.Results indicate: after the amplitude of disturbances in laminar flow grows,nonlinear effect modifies the profile of mean flow,with enlargement of performed by the enlarging unsteady zones.At the same time,more and more high frequency harmonic waves are generated.When the profiles of mean flow are modified to certain degree,the unstable zones are enlarged significantly.More harmonic waves are actived and grown rapidly,triggering the breakdown of transition process.During the breakdown of transition process,the rapid growth of many harmonic waves induces the rapid growth of disturbance energy,accelerating the modification of mean flow profiles.The phenomenon means that the instability characteristic of mean flow profile is changed.The reciprocal rapid growth makes laminar flow become turbulent flow rapidly.Therefore,change of instability characteristic of mean flow profile plays a key role during process of transition.
Computational investigation of hypersonic curved shock two-dimensional inlet with compression surface constant Mach number gradient
ZHANG Lin, ZHANG Kun-yuan, WANG Lei, LIU Yuan
2013, 28(4): 752-758.
Abstract PDF(915KB) icon2032 icon1132
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A type of curved compression surface with wall Mach number linear distribution was investigated,and a hypersonic curved shock two-dimensional inlet was designed.The performance was compared with normal three-ramp compression inlet designed under the same conditions.The result shows that:curved compression surface can be designed through rational characteristic linear theory according to the given wall Mach number linear distribution and pressure ratio.Compared with normal three-ramp compression,the new inlet has more stable boundary layer and much shorter external compression surface,but not very sensitive to the change of free stream Mach number.Especially,the inlet has an excellent performance under off-design conditions.The mass flow rate reaches 0.783 at relay point Mach number and is increased by 13.2% compared to normal three-ramp compression two-dimensional inlet, while the total pressure recovery of throat section is also increased by 4.5%.
Quasi-steady aerodynamic model of tilt rotor based on optimization algorithm
WU Da-wei, LI Shu
2013, 28(4): 759-764.
Abstract PDF(547KB) icon2298 icon1270
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There are many hypotheses and limitations about the flight condition and blade shape in the quasi-steady aerodynamic model of conventional helicopter rotor,and many of them were eliminated considering the special blade shape,hub structure and flight condition of tilt rotor.Aerodynamic loads were calculated through numerical integration based on the blade element theory,and flap coefficients of tilt rotor were solved through sequential quadratic programming (SQP) algorithm.Induced velocity distribution was adopted as the steady form of Pitt-Peters dynamic inflow model.The aerodynamic performance and flap coefficients of the rotor of XV-15 tilt rotor aircraft were predicted by this method.The theoretical results and wind tunnel tests data make good agreement with error less than 8% and this method has high calculation efficiency that one case can be solved within 5 minutes,therefore,this method is applicable for aerodynamic performance prediction in preliminary design of tilt rotor aircraft and suitable to set up its flight dynamics model.
Sensitivity analysis and optimization design of basic flowfield with controllable Mach number distribution
LI Yong-zhou, ZHANG Kun-yuan, WANG Lei, NAN Xiang-jun
2013, 28(4): 765-774.
Abstract PDF(1453KB) icon1807 icon1150
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The sensitivity analysis of the design parameters of axisymmetric basic flowfield was performed using the software Isight,and the design parameters' effect on the overall performance was obtained,which shows that the leading edge compression angle and coefficient c affect most.The overall performance of the optimized basic flowfield was improved by optimization of three objectives of the polynomial response surface at design point.The hypersonic inward turning inlet with circular shape intake was designed based on the optimized basic flowfield.The numerical simulation results from when Mach number are 4~7 indicate that the inlet has relatively good mass capture ratio and compression efficiency,total pressure recovery coefficients are 0.581 and 0.513, and pressure ratios are 20.01 and 24.73 when Mach number are 6 and 7 respectively; the flow coefficient is 0.880 at the relay point of Mach number is 4, which verifies the feasibility of the optimization method.
Research on aerodynamic characteristics of 2-D hypersonic inlet
TENG Jian, YUAN Hua-cheng
2013, 28(4): 775-782.
Abstract PDF(1372KB) icon1844 icon1150
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A kind of 2-D hypersonic variable geometry inlet with movable lip along flow direction was designed.Three-dimensional computational fluid dynamics computation was carried out to simulate the flowfield of the inlet.Comparison of the aerodynamics characteristics was made between variable geometry inlet and fixed geometry inlet.Results indicate:by translating lip upstream,the contraction ratio (CR) of the variable geometry inlet decreases from 1.80 to 1.57 and the self-start Mach number decreases from 4.9 to 3.4.Within the Mach number range of 4.0~7.0,no major difference of the isolator exit Mach number and static pressure ratio of both inlets are observed.The mass flow rate and total pressure recovery coefficient of variable geometry inlet are at most 21% and 9% higher respectively compared with fixed geometry inlet.The variable geometry inlet has superior aerodynamic performance.
Experiment of fuel distribution of pressure-swirl atomizers for aero-engine
LIU Cun-xi, LIU Fu-qiang, MAO Yan-hui, MU Yong, XU Gang
2013, 28(4): 783-791.
Abstract PDF(933KB) icon1756 icon1192
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The experimental unit and correction method for estimation of performance of fuel distribution based on planar laser induced fluorescence (PLIF) method were established, and the correction method was validated. The comparisons between results of PLIF method and planar laser scattering (PLS) method indicate that, the results of PLS method overrepresents droplet concentration for droplets less than 50μm and PLIF is suitable for fuel distribution measurement. To make sure the quality of machining and performances of the atomizers, the distributions of droplets were evaluated comprehensively by PLIF method in terms of spray cone angle, non-uniformity of circumferential distribution and patternation index, and then, the results of eccentricity and grooves of different sizes for the poor droplets distribution show that, the factors for non-uniformity include the roughness of internal flow wall, roundness of nozzle and coaxiality of parts. The opening processes of spray cones in the direction of ejection were visualized by PLIF method at pressure differential of 0.14, 0.25 and 2.5 MPa, respectively, and the droplets dispersed from annulus to round in cross-sectional plane with development of the spray. Furthermore, the rate of droplets dispersion increased with the growing pressure differential of fuel.
3-D simulation of rotating detonation wave in combustion chambers without inner wall
TANG Xin-meng, WANG Jian-ping, SHAO Ye-tao
2013, 28(4): 792-799.
Abstract PDF(893KB) icon1846 icon1350
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Based on summary and analysis of existing results and conclusions on rotating detonation wave in annular combustion chambers, an alternative model of chamber for rotating detonation engines was presented. It has no inner wall. We utilized one step chemistry kinetic model together with the Eular function in three-dimensional space to testify the possibility of continuous rotation. The simulation showing that the detonation spontaneously converged to a propagation structure of two central symmetric detonation waves. Under the present condition, the mass flow could reach as large as 450kg/m2s and the fuel-based impulse was 1900s, which is 5 percent lower than that in the annular combustion chamber.
Experiments on hydrocarbon fuel ignition for scramjet at Mach 4
ZHANG Wan-zhou, LE Jia-ling, YANG Shun-hua, CHENG Wen-ming, DENG Wei-xin, ZHOU Hua-bo
2013, 28(4): 800-806.
Abstract PDF(843KB) icon1797 icon1125
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Hydrocarbon fuel ignition experiments were performed on directly connected pulse combustion facility.The test inflow parameters included stagnation temperature of 935K and the Mach number of 4 at the entrance of isolator. Gaseous ethylene was ignited successfully and combustion was maintained stable by employing three combination assistant ignition methods: torch igniter combined with pilot hydrogen, self-combustion of pilot hydrogen and air throttle combined with pilot hydrogen. The experimental results indicate that when employing self-combustion of pilot hydrogen, the mass flow rate of hydrogen should be ranged from 0.43~12.61g/s, and higher mass flow rate of hydrogen isn't helpful to ignition; for air throttle combined with pilot hydrogen ignition method, the injection pressure of hydrogen should be set at 5MPa, and the throttle mass flow rate should be 10%~30% of inflow mass flow rate. At last the lean blow-out limit and rich operation limit of scramjet were researched with ethylene injected from upstream of cavity or cavity floor.The results show that two injection schemes have similar lean blow-out limits at equivalence ratio of 0.077, and the rich operation limits varies a lot at equivalence ratios of 0.327 and 0.471 respectively.
Fast prediction of ice shape based on proper orthogonal decomposition method
SHEN Xiao-bin, YU Jia, LIN Gui-ping, BU Xue-qin, ZENG Yu
2013, 28(4): 807-812.
Abstract PDF(521KB) icon2327 icon1144
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To predict the shapes of ice accretion on the airfoils quickly,a numerical simulation program based on the proper orthogonal decomposition (POD) method was established.Taking sample of the ice shapes from computational fluid dynamics (CFD) numerical calculation,in view of the change of icing temperature,the procedure of predicting the ice shapes by POD method was introduced.Considering the icing temperature,icing time and liquid water content,the ice shape's quick prediction was made through the POD method in the case of variation of single parameter,two parameters and three parameters separately.The calculation results indicate that the POD computation is completed in only a few seconds,and the ice shapes obtained by POD method are in good coincident with those acquired by CFD except for the ice horn.The conclusion is made that the ice shapes can be obtained quickly and accurately by the POD method.
Experiment on discrete holes supersonic gas film cooling in cylindrical pipe
ZHANG Jia, SUN Bing, ZHENG Li-ming
2013, 28(4): 813-818.
Abstract PDF(543KB) icon1615 icon1008
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Experiments were made by using supersonic,high temperature gas in a cylindrical pipe as the mainstream and nitrogen at normal temperature as the injection medium to determine the rules of discrete holes supersonic gas film cooling.Mainstream Mach number was 2,and injection Mach number varied from 1 to 3 . Results show that the mass flow of the injection is the most important influential factor.Film cooling effectiveness that could be fitted into a correlation equation is enhanced greatly along with the increase of blowing ratio or diameter of the injection hole,and the Mach number of the injection has little effect on it.Injection with angle 30 degree shows better effectiveness than the tangential injection at downstream distance far from the hole, but worse effectiveness dose by the hole.
Pressure and heat transfer measurement of vane surface in short duration wind tunnel
LI Hong-cai, ZHU Hui-ren, FU Meng
2013, 28(4): 819-824.
Abstract PDF(622KB) icon1535 icon1025
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Surface pressure and heat transfer measurements of an enlarged vane were conducted at engine's typical Reynolds numbers and pressure ratios.The pressure coefficients decreased and the lowest point of the suction surface moved backward with an increasing pressure ratio,while the Reynolds number had small effect on the surface pressure coefficients.With increase of the Reynolds number,the surface heat transfer coefficients rose,and the transition occurred earlier at suction surface.The pressure ratio mainly affected the heat transfer of suction surface.The transition occurred later when the pressure ratio increased in small Reynolds number state.When supersonic flow appeared at the suction's rear region in large Reynolds number state,the heat transfer coefficients at large pressure ratio were lower than those at small pressure ratio.The local adiabatic wall temperatures decreased with increase of pressure ratio.In the case of constant pressure ratio,the local adiabatic wall temperature of laminar flow was lower than that of turbulent flow.
Orthogonal experiment of effect of fin geometrical parameters on leakage of straight-through labyrinth seals
DU Fa-qing, JI Hong-hu, SHUAI Hai-shan, ZHANG Bo, WANG Ding, LU Hai-ying, DENG Ming-chun
2013, 28(4): 825-831.
Abstract PDF(583KB) icon1706 icon886
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An orthogonal experiment was made to study the influence of the geometry parameters of straight-through labyrinth seals on sealing characteristics.The geometry parameters studied include the fin tip thickness,seal clearance,fin height,fin pitch,fin front inclined angle and rear inclined angle.The experiment was made with 25 models that were designed according to the orthogonal test method.The results show that various parameters have different influences on discharge coefficient.The best combination of various geometry parameters for sealing in the test range is that fin tip thickness takes 0.1mm,seal clearance takes 0.3mm,fin height takes 3 mm,fin pitch takes 9 mm,fin front inclined angle takes 0 degree and rear inclined angle takes 15 degree .The rank of importance of each parameter's variation from its maximum to minimum value on sealing characteristics is fin pitch,seal clearance,rear inclined angle,fin tip thickness,fin height,fin front inclined angle.Fin pitch is the most important parameter,seal dearance is less important than fin pitch,rear inclined angle and fin tip thickness have certain impact on the sealing characteristics,while fin height and fin front inclined angle have little influence on it.
Effects of RP-3 coke deposition on heat transfer under supercritical pressure
YUAN Li-gong, DENG Hong-wu, XU Guo-qiang, JIA Zhou-xia, LI Yi-fan
2013, 28(4): 832-837.
Abstract PDF(593KB) icon1701 icon1001
Abstract:
The effect of coking deposition of RP-3 on heat transfer was investigated experimentally.The fuel flowing through miniature tube was heated from 127℃ to 450℃ at 5MPa,and the mass flow rate was maintained at 3g/s.The surface coking deposition was obtained by weighting method.Test results show that the effect of coking deposition on heat transfer could be divided into three regions due to differences of deposition:stable heat transfer region at low fuel temperature,deteriorated heat transfer region at peak coking deposition position and short term enhanced heat transfer region at high fuel temperature.Due to lower fuel temperature at the entrance region,the coking deposition amount was tiny and its effect on heat transfer could be ignored.At peak coking region,heat transfer resistance increased sharply with coke deposition,heat transfer coefficiency decreased by 36.1%,and heat transfer deterioration was observed in the whole time.In addition,short term enhanced heat transfer occurred due to the roughness increase by coke particles adhered to the inner surface of the pipe and chemical heat absorption caused by cracking coke deposition.As more and more coke particles adhered,the increasing heat transfer resistance resulted in heat transfer deterioration.
Numerical simulation and analysis of nitrogen-enriched air flow in multi-bay fuel tank
ZHANG Sheng-qi, WANG Xue-de, WANG Zhi-wei, LIU Wei-hua, WANG Xiao-ping
2013, 28(4): 838-843.
Abstract PDF(530KB) icon1609 icon934
Abstract:
According to the characteristic of multi-bay fuel tank,a numerical simulation method for nitrogen-enriched air (NEA) flow in multi-bay fuel tank was developed.Firstly,the correctness of this method was verified by comparing the inerting results from numerical simulation with the results of the engineering model and the test data from foreign literatures.Secondly,after analyzing the oxygen volume fraction in individual bay of the inerting process,it was found that the oxygen volume fraction distribution in individual bay tended to be even and the outflow oxygen volume fraction of one bay was approximately equal to the average oxygen volume fraction of that bay.Lastly,the simulated flow rates were compared with the cross-section flow areas between different bays.It is found that if the vents are placed symmetrically to the inlet of NEA,the flow rates can be weighted based on the cross-section flow areas; while if the vents are placed asymmetrically to the inlet of NEA,the flow pattern would be relatively complex.
Influence of axial length on rotating detonation engine
CHEN Jie, WANG Dong, MA Hu, DIAO Ji-yang, YU Dong-liang
2013, 28(4): 844-849.
Abstract PDF(696KB) icon1659 icon971
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Based on 9 species and 19-step reaction,without consideration of the effect of viscosity,heat transmission and diffusion on flow,mixtures of hydrogen and oxygen were used to simulate rotating detonation engine flow field to research the effect of axial length on engine performance.Research show that:within a certain range,axial length has little influence on specific impulse of engine,but if axial length is too long,it will decrease specific impulse of engine;axial length has great influence on detonation pressure and temperature;if axial length is too little,the pressure of detonation wave is not high;if axial length is too long,the oblique detonation may decay;with the increase of axial length,the pressure of outlet continues to decrease owing to expansion;when axial length is 200mm,the average speed and specific impulse of engine reach the maximum value;azimuthal velocity decreases obviously cuttingdown the harmful influence on engine;the maximum thrust density decreases gradually;density difference in before and after shock wave decreases gradually,so that the thrust eccentricity could continue to decrease,thus effectively reducing angle scatter harmful influence.
Frequency domain solution of 2-DOF torsional dry friction system
LI Lin, FAN Yu, DAI Guang-hao
2013, 28(4): 850-857.
Abstract PDF(1203KB) icon3014 icon1728
Abstract:
The forced vibration response of a two degree of freedom (DOF) torsional system with Coulomb friction was studied,with a full consideration of the pure-slip and stick-slip contact motions.First,the 2-DOF lumped parameter model of such nonlinear system was presented and derived into a non-dimensional form.Second,the harmonic balance approach was used to establish a general frame of solving the response under different contact motion.Accordingly,the critical condition as well as the harmonic expands of friction force of the pure-slip and stick-slip contact motions were presented.Finally,the procedure of dealing with frequency domain solution was proposed.Based on this method,a group of results were obtained under different normal pressures,and were validated by the numerical integration method with a very good agreement.The proposed semi-analytical method provides more clear insights of the torsional dry friction system and therefore has advantage in computational cost.
Vibration characteristic of composite laminates with delamination
QI Wen-kai, CHENG Bo, LIU Lei
2013, 28(4): 858-865.
Abstract PDF(766KB) icon1752 icon925
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A reasonable finite element model was established to simulate composite laminates with delamination by using the user-defined matrix element to simulate contacting element in delamination region for distortion mode of the upper and lower sublaminates,and the selection of connection stiffness values was studied as well.This article focuses on the vibration performance of composite laminates with delamination depth and delamination size.The comparison of numerical simulation and experimental results indicates that it is feasible to simulate the delamination of composite laminates with the user-defined matrix elements; the maximum error of the modal calculation and the experimental values is 10.67%, and the minimum error is 0.34%; delamination depth and size have significant effects on vibration characteristic of composite laminates, and the natural frequency of laminates declines up to 50% with change of delamination depth; the first to fourth order natural frequencies of laminates decrease up to 12% with change of delamination size.
Novel structural design of mixed-flow compressor with high structural efficiency
ZHANG Da-yi, HONG Jie, MA Yan-hong, LIANG Zhi-chao
2013, 28(4): 866-871.
Abstract PDF(547KB) icon1581 icon901
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Structural efficiency evaluation method was employed and improved in structural design of high-load mixed-flow compressor to meet the strict requirements and to optimize the bladed disk structure.Two novel structure schemes were put forward named type “C” and type “M” to increase the structural efficiency.The key items including average stress,vibration robust coefficient and rim deformation coordination coefficient were calculated,and structural efficiency coefficient was studied and evaluated contrastively.Finally,the advantages of the novel structure schemes are proved including low weight,high reliability and low loss at blade tips.The calculation result shows the “M” structure scheme could result in that 24.7% increase in average stress,20% decreasing in mass,37.9% decreasing in vibration response and 67.6% decreasing in rim deformation.
Load sharing characteristics analysis of power split system based on deflection compatibility and clearance floating
DONG Hao, FANG Zong-de, WNAG Bao-bin, DU Jin-fu
2013, 28(4): 872-877.
Abstract PDF(541KB) icon1720 icon952
Abstract:
In order to implement the uniform load distribution of the gear train with dual power spliting,a pseudo-static model was built firstly.And then,according to the system power flow closed-loop feature,the torsional angle deformation compatibility conditions were deduced,the moment equilibrium conditions and elastic support conditions was established to calculate each gear pair transmission torque,and finally the system load sharing coefficient was obtained.Next,the relationship of the installation error and system load sharing characteristics was analyzed in the static research,and the floating pinion based on clearance floating played an important role in the system load sharing. The results show that the clearance of 0.8mm could meet the pinion to floating under the influence of the gear 2 with installation error of 0.03mm, obtain the load sharing coefficient of 1.0038, the floating pinion can improve the load sharing characteristics. Through theoretical data compared with the experimental data, in the same error conditions, power distribution is respectively 53.88% and 53.50%, which verifies the correctness of the method proposed.
Dynamic model updating of an aero-engine casing
MA Shuang-chao, ZANG Chao-ping, LAN Hai-bo
2013, 28(4): 878-884.
Abstract PDF(960KB) icon1718 icon1039
Abstract:
Dynamic model updating technique was applied to update a finite element(FE) model of an aero-engine casing.The modal data obtained from conducting vibration modal test to the casing were used as a reference to update the FE model.Based on the sensitivity of frequencies with respect to the element stiffness,some regions to be adjusted were selected.Then,model updating of the aero-engine casing was conducted using a first-order optimization method.The result shows that prediction of the first 10 modes from the updated FE model of the aero-engine casing and that from the measured ones were within 2%,therefore,it is feasible to apply the model to the whole engine dynamic analysis.
Effects of boundary layer suction on counter-rotating compressor in multistage environment
LIU Bo, CAO Zhi-yuan, WEI Wei, SHI Lei
2013, 28(4): 885-892.
Abstract PDF(1279KB) icon1614 icon959
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In order to study the effects of boundary layer suction (BLS) on counter-rotating compressors in multistage environment, numerical investigations were performed on the rotors of a dual stage counter-rotating compressor with BLS method. Three different suction slots in chord direction were set up on the front rotor (R1) and rear rotor (R2) suction surface to study the effects of flow structure and performance on different suction ways, and independent suctions were carried out on R1 and R2 respectively at different suction locations and suction air rate in counter-rotating compressor. By BLS of individual R1, the efficiency increases with the rise of suction air rate. But the aerodynamic performance matching R1 with R2 becomes worse and makes R2 fall directly. The overall efficiency is also represented by the fluctuation from going up to down. The best suction location of R1 is near the trailing edge. By BLS of R2 individually, the efficiency of R2 keeps the trend from increase to reduction with the rise of suction rate, while the efficiency and flow field of R1 remain unchanged nearly. The best suction location of R2 is near the trailing edge. The deviation angles reduce obviously after the BLS. The above results demonstrate that matching of aerodynamic parameters between blades rows is a main factor to be considered after BLS in multistage environment.
Flow loss control of turbine based on “groove” and “dimple” technology with low Reynolds number
YANG Lin, QIAO Wei-yang, MU Zhong-qiang, LUO Hua-ling, HOU Wei-tao
2013, 28(4): 893-902.
Abstract PDF(968KB) icon1592 icon908
Abstract:
Based on “groove” and “dimple” technology, flow loss control of tubine with low Reynolds number was studied. For “groove” technology, three-dimensional large eddy simulation(LES) method was used to do analysis on control effect of groove position and Reynolds number, while control technology of “dimple” using experimental method. The results show: (1) both of increasing the perturbation amplitude or selecting appropriate disturbance frequency are given significant control effect; (2) two-dimensional span-wise groove processing plays a “disturbance generator” role; (3) three-dimension dimple plays the role of not only “disturbance generator” but also “vortex generator” . The high frequency of the generation and shed of the vortex in the wake of the dimple zone enhances the flow mixture and generates the disturbance that promotes the transition of the separation bubble.
Theory and analysis method based on vorticity dynamics for gas turbine compressor
WU Hong, JIANG Hong-de
2013, 28(4): 903-910.
Abstract PDF(868KB) icon1546 icon1058
Abstract:
Vorticity dynamics theory and analysis method for compressor of gas turbine was described, and the mathematical and physical relations of total performance parameters and two important vorticity parameters was constructed based on vortictity dynamics theory. The analysis and optimization method based on boundary vorticity flux(BVF) and circumferential vorticity(CV) was researched. The multi-stage axial compressor of gas turbine was designed firstly and then analyzed using this theory and method, and the improving way for the designed compressor was found. It is demonstrated that CV can probe the high loss region near solid boundary, and the loss will be controlled if CV peaks can be restricted in the region near solid boundary. The swirl distribution can be optimized to control CV distribution, and in the optimization of the transonic compressor rotor based on CV the peak efficiency is improved by 1.13%. On the other hand, it is shown that BVF can reflect the vorticity source on solid boundary, and the vorticity and flow separation are suppressed through controlling BVF, and the rotor peak efficiency can be increased by 1.12% in the optimization based on BVF.
Numerical analysis of centrifugal compressor performance and flow at low Reynolds number
HUO Lei, LIU Huo-xing
2013, 28(4): 911-920.
Abstract PDF(2303KB) icon1936 icon996
Abstract:
Three-dimensional numerical simulation was conducted for a low pressure centrifugal compressor at low Reynolds number.Influence of Reynolds number on the flow-field was analyzed.The results show that, the efficiency,rotating stall margin and flow capacity reduce with the decrease of Reynolds number.Change of the blade loading distribution reduces the working capability of the compressor.In the flow-field,the leading-edge separation is more obvious and the secondary flow is encouraged.Tip leakage losses of the splitter blade increases.The low velocity flow area near the suction surface of blade obviously increases and its beginning location also moves forward.These will also enhance the influence on the span-wise region.
Effect of blade leading edge on aerodynamic performance of turbine
CHEN Lei, CHEN Jiang, ZHAO Shi-lei, ZHANG Hui
2013, 28(4): 921-929.
Abstract PDF(1217KB) icon1703 icon946
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Geometry of turbine blade leading edge was altered from circular to non-circular by using the Bezier curves methods,based on which numerical analysis and comparison were made to illustrate how turbine cascade leading edges affected the aerodynamic performance under different attack angles.Within the normal operating range of attack angle (-15°~ +10°),the non-circular leading edge had a better performance as the gradual increase of the curvature radius of the non-circular leading edge reduced the normal pressure gradient of the leading edge,which further restrained the flow from excessively expanding and reduced the energy dissipation caused by the viscous stress,resulting in a decreased flow loss,and the bigger the curvature radius of the non-circular leading edge,the better the performance.Whereas under the large attack angle of the non-design condition,the gradual increase of the curvature radius would cause more severe cascade separation,which aggravated the loss,and it was exemplified by the case of a five-stage low pressure turbine.Numerical analysis has indicated that the non-circular leading edge can improve the flow features and increase the turbine efficiency.However,for the non-design condition estranging from the design point,the flow attack angle alters so substantially that it has negative effect on the turbine aerodynamic performance.
Safety evaluation for long stored SRM
SHEN Wei, WANG Wen, ZHANG Jun, HUANG Wei-dong
2013, 28(4): 930-934.
Abstract PDF(731KB) icon1487 icon882
Abstract:
The safety of a long stored solid rocket motor was evaluated.The solid rocket motor (SRM) stored 18 years was disassembled.The safety of the long stored SRM was evaluated experimentally.Firstly,the mechanical properties and the sensitivity of the propellant were measured,and the popping experiment of the propellant and grain was carried out.The propellant stored 4 years was adopted as comparative sample.This shows that the mechanical sensitivity of the propellant was increased.The aged propellant is broken up badly in popping experiment.The RSM stored 18 years has a tendency to explosion under the popping condition.The vulnerability of the SRM stored 18 years has a remarkable change.
Structural analysis of aged grain of solid rocket motor with crack
ZHANG Jian-wei, ZHI Shi-jun, SUN Bing
2013, 28(4): 935-940.
Abstract PDF(777KB) icon1662 icon855
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In order to study the structure stability of the solid rocket motor grain with a crack with different storage time,the theory of viscoelastic fracture mechanics and finite element method were adopted to calculate the J integral of the crack when the solid rocket motor was under the ejection load and the ignition load.The singular crack elements were employed when the J integral of the crack was calculated.The results of J integral of cracks with various shapes and in different storage time were discussed.The results show that the J integral of the crack decreases with storage time and crack propagation is not likely to happen when the motor is under the ejection load.However,when the motor is under the ignition load,the J integral of the crack increases with storage time and the crack is more instable and is more likely to propagate.
Calculation of experimental regression rate of hybrid rocket motor
WU Jun-feng, TIAN Hui, LI Jun-hai, YU Nan-jia, CAI Guo-biao
2013, 28(4): 941-946.
Abstract PDF(508KB) icon1476 icon1021
Abstract:
Combustion chamber pressure of hybrid rocket motor was estimated to be proportional to its oxidizer mass flow rate under the conditions of short work duration of less than 2s or minor variation of grain port diameter within 10%. The conclusion was deduced from the exponential relation between solid fuel regression rate of hybrid rocket motor and corresponding oxidizer mass flux. The oxidizer mass flow rate during motor throttling or shutdown was calculated through pressure curve from motor test and obtain the fuel mass consumed consequently. By eliminating the mass consumed during motor shutdown, the overestimated regression rate calculated from motor test through end point average method was improved. Regression rates of two sets of propellant were calculated through the improved method from test results. The rates reduce about 20% and the results between different motor sizes agree with the scale effect within an error of 5%. It is thusreasonable to apply the regression rate from small scale motor to the design of large scale motor design.
ESN-based combination method for aero-engine condition prediction
GUO Yang-ming, FU Lin-juan, RAN Cong-bao, MA Jie-zhong
2013, 28(4): 947-953.
Abstract PDF(602KB) icon1963 icon996
Abstract:
As a nonlinear time series prediction method,echo state network (ESN) attracts more attention because of its good approximation capability for the nonlinear system.Aiming at the characteristics of nonlinear time series in the aero-engine's condition prediction analysis,such as noise and presenting chaos,a combination method based on ESN was proposed.Firstly,the noise contained in nonlinear time series was reduced by the wavelet analysis.Then the training sample data were yielded via phase space reconstruction of the time series.After reducing the dimension of the training sample data by principal component analysis,all the remaining principal data were sent into the ESN prediction model.An actual dynamic pressure time series of aircraft power was conducted.The experiments compare the proposed method with traditional ESN prediction model on prediction accuracy and time cost.The results show that the prediction accuracy rate of proposed method within 5 steps and one-step are totally raised 66.97%, and the prediction of the mean square error, normalized root mean square error and normalized absolute error are also improved simultaneously. The proposed method is an effective nonlinear time series prediction method in practice.
Research of variable cycle engine modeling techniques
WANG Yuan, LI Qiu-hong, HUANG Xiang-hua
2013, 28(4): 954-960.
Abstract PDF(469KB) icon2617 icon2340
Abstract:
The component level model of variable cycle engine (VCE) was built based on analysis of engine structure, and with a reference to the modeling method of two-spool-turbofan engine. The model of fan was developed with separated characteristic of fan tip and hub sections. The model of core drive fan stage(CDFS) model was built to work under single bypass mode and double bypass mode. According to the specialty of VCE, the static and dynamic co-working equations were set up, reflecting the variation of variable geometry components. The results of numerical simulation indicate that the VCE model enables switching of the working modes. In double bypass mode at low altitude and low mach number, it represents higher thrust and lower specific fuel consumption just as turbofan engine, and in single bypass mode at high altitude and high mach number, it shows higher thrust and lower specific fuel consumption just as turbojet engine. The performance variation in simulation accords with the specialty of VCE, so the modeling method of VCE proposed is feasible.

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