2020 Vol. 35, No. 3

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Experimental determination of leaning threshold at a certain aero piston engine
MENG Xianzhao, TANG Xiaobo
2020, 35(3): 449-456. doi: 10.13224/j.cnki.jasp.2020.03.001
Abstract PDF(2284KB) icon1213 icon615
Abstract:
In order to control the leaning range and obtain the convenient safety leaning threshold for engineering practice based on the case of a large number of exhaust valve ablations caused by excessive leaning in the operation of a certain aero piston engine, the corresponding relationship between valve operating temperature and exhaust gas temperature (EGT) at this engine was obtained by measuring the actual operating temperature of exhaust valve body near the sealing surface, and the engineering problem of indirectly measuring the actual operating temperature of valve body with EGT as parameter was solved. With the corresponding relation and by ensuring that the protective layer on the exhaust valve sealing surface was not damaged, the safety leaning threshold with 732℃ of EGT at this engine was obtained, and the reliability of this threshold was proved by practical test of 70000 flight hours.
Experiment on atomization characteristics of fan nozzle
DI Dong, LIU Yuchen, WANG Yajun
2020, 35(3): 457-470. doi: 10.13224/j.cnki.jasp.2020.03.002
Abstract PDF(6516KB) icon832 icon580
Abstract:
According to the requirements of the cone cavity ignition and the flame crossover in the afterburner, the fan nozzle for the cavity ignition and flame crossover was designed, and the corresponding atomization test was carried out to study the effect of the fuel supply pressure difference, fan angle and the fan exit height on the discharge and atomization characteristics of the fan nozzle and the effect of the temperature, speed and fuel supply pressure difference of the lateral airflow on the penetration depth and the Sauter mean diameter (SMD) under afterburning environment. Weighing method was used to test the discharge coefficient of the fan nozzles. And the Malvern laser particle size analyzer and high speed camera were used to measure the SMD of the droplets, spray angle and penetration depth, respectively. Results suggested that: (1) with the increase of fuel supply pressure difference, the discharge coefficient decreased first and then became insensitive to fuel supply pressure difference. (2) Under the same fuel sypply pressure difference, the discharge coefficient and spray angle increased with the increase of fan angle. (3) With the increase of fan exit height, the atomization effect became better. (4) In addition to the above mentioned results, the mounting position had less effect on the atomization characteristics of the fan nozzles. (5) As the oil supply pressure difference increased, the penetration depth of the fan nozzle increased, and the SMD decreased. (6) The greater lateral airflow speed and temperature, the smaller the penetration depth, and the oil mist field was closer to the downstream section. (7) As the lateral airflow temperature increased, the SMD decreased.
Ventilation process of variable exhaust valve of aviation piston two-stroke engine
GUO Dong, QIAN Jiance, ZHAO Zhenfeng
2020, 35(3): 471-481. doi: 10.13224/j.cnki.jasp.2020.03.003
Abstract PDF(4609KB) icon906 icon535
Abstract:
The ventilation process of the aviation piston two-stroke engine directly affects the engine performance, and the variable exhaust valve can improve the dynamic performance of engine. Through the GT-Power to build the one-dimensional engine model, simulation research about ventilation process of the engine at different speeds and different exhaust valve stages was carried out, and the influence of exhaust valve stage on the ventilation process was analyzed. On this basis, the stage of the exhaust valve under constant speed cruise conditions (speed of 6500r/min, 50% throttle opening) was also optimized. The results show that different exhaust valve stage can change the phase of pressure fluctuations during engine exhaust process, thereby affecting the engines ventilation quality and combustion process; under constant speed cruise conditions, when the exhaust valve is at medium stage (primary valve is closed, secondary valve is open), engine power performance is the best.
Experiment on primary atomization characteristics of planar prefilming nozzle
HE Changsheng, LIU Yunpeng, HAN Zongying
2020, 35(3): 482-492. doi: 10.13224/j.cnki.jasp.2020.03.004
Abstract PDF(5441KB) icon778 icon598
Abstract:
To understand the primary atomization characteristics of the planar prefilming nozzle, the atomization experiment was carried out to study the influence of different inlet conditions. The high-frequency imaging method of backlight illumination and sheet laser illumination was used to obtain the liquid film breakup morphology in top view and side view. At the same time, the optical image was processed using proper orthogonal decomposition(POD)statistical analysis and the liquid film edge position analysis method, three physical quantities of the primary atomization characteristics were obtained:the main frequency of the liquid film surface wave, the breakup length and the transversal wave length. The experiment results indicated that: (1) the three liquid film breakup morphologies in the planar prefilming nozzle primary atomization process were divided into end breaking, wave dropping and surface stripping based on the breakup morphology of side view and top view. The effect of inlet Weber number on breakup morphology of the prefilming nozzle was dominant. (2) The combination method of POD analysis and liquid film edge position analysis was applied to the post-processing analysis of the high-frequency non-contact optical image, as an effective data post-processing method. (3) The effect of inlet Weber number played an important role in liquid film breakup morphology. The primary atomization characteristics of the liquid film were mainly affected by the inlet Weber number and the gas-liquid momentum flux ratio. Both the breakup length and the transversal wave length decreased with the increase of the inlet Weber number, the frequency of the liquid film surface wave increased with the increase of the inlet Weber number and the obtained formula is in good agreement with the experiment data. The effect of the inlet parameters on the breakup morphology and atomization characteristics of the liquid film provides a basis for effectively optimizing the atomization quality of the prefilming nozzle.
Effects of mainstream angles of attack on film cooling characteristics of double-jet film cooling holes
HE Jianhong, ZHANG Ke, YANG Xi
2020, 35(3): 493-501. doi: 10.13224/j.cnki.jasp.2020.03.005
Abstract PDF(5193KB) icon825 icon573
Abstract:
Film cooling effectiveness of double-jet film cooling holes was measured using pressure sensitive paint at various mainstream angles of attack (i=-30°, -20°, -10°, 0°, 10°, 20°, 30°) on a flat plate, and the flow field obtained by computational fluid dynamics (CFD) was used to analyze the film cooling effectiveness. The dimension less spanwise distance was 0.5, the dismension less streamwise distance was 3; the density ratio was 1.0, and the blowing ratio varied as 0.5, 1.0, 1.5, 2.0. The results showed that, at small mainstream angles of attack (i=-10°, 0°, 10°), the film layer attached well with wall because of the anti-kidney vortex pair or the pressing effect in the flow field, contributing to the highest film cooling effectiveness; at large positive angles of attack (i=20°, 30°), the anti-kidney vortex pair degenerated though the coverage area of film was the largest, the film cooling effectiveness became lower; at large negative angles of attack (i=-20°, -30°), there existed kidney vortex pair, the lateral coverage of the film was limited and the film cooling effectiveness was lowest.
Influence of air entraining position on radial pre-swirl system
ZHANG Kai, WANG Suofang, HOU Xiaoting
2020, 35(3): 502-509. doi: 10.13224/j.cnki.jasp.2020.03.006
Abstract PDF(3238KB) icon2097 icon476
Abstract:
To reduce the flow loss in radial pre-swirl system, numerical simulation method was used to analyze the radial pre-swirl system with different air entraining positions of the cavity. The results showed that the swirl ratio of air flow at the pre-swirl nozzle outlet decreased, the temperature drop coefficient and total pressure loss coefficient increased with the increase of the radial air entraining position. When rotational Reynolds number was 7.9×106, the temperature drop coefficient increased by 525% and the total pressure loss coefficient increased by 3.93% when the air entrainment position changed from low to high. The specific entropy increment in the radial pre-swirl system mainly occurred in the pre-swirl nozzle and the co-rotating cavity, accounting for about 80% of the total specific entropy increment. With the increase of the radial air entraining position, the overall specific entropy increment decreased, and the specific entropy increment proportion of the pre-swirl nozzle increased. However, the spectific entropy increment proportion of co-rotating cavity decreased.
Optimum design and experiment of stator blade profile of a compressor
LI Xiaodong, ZHONG Jingjun
2020, 35(3): 510-518. doi: 10.13224/j.cnki.jasp.2020.03.007
Abstract PDF(3529KB) icon803 icon562
Abstract:
In order to obtain a more suitable blade profile for compressor stator to reduce aerodynamic loss, the blade profile at mid-span of stator was extracted. The loss characteristics of the original blade profile were obtained through linear cascade experiment, finding that the aerodynamic loss of original blade profile was relatively high, making it necessary to match the design parameters properly to reduce the loss. For this reason, a numerical optimization platform was built to search for blade profile with lower aerodynamic loss in constrained design space. The objective function was constructed by taking the total pressure loss coefficient at multiple incidence angles into account to improve the design and off-design performance. The optimization results showed that, the value of objective function was reduced by about 9%. Further experimental studies showed that the optimized blade profile had lower total pressure loss coefficient than the original one in the whole Mach numbers and incidence angles involved in the experiment. The total pressure loss coefficient in the design condition was reduced by 31.3% compared with the original one, and the stall resistance capacity of the blade profile near positive incidence angle boundary was improved, the airflow inflection angle increased by 1° at the design inlet Mach number with an incidence angle of 4°. The mechanism of blade profile performance improvement was explained through in-depth analysis of experimental results, and suggestions for the design and multi-objective optimization of blade profiles working in similar environment were given.
Uncertainty quantification of inlet incidence angle variation for turbine blade
XIA Zhiheng, LUO Jiaqi
2020, 35(3): 519-531. doi: 10.13224/j.cnki.jasp.2020.03.008
Abstract PDF(5362KB) icon643 icon579
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A non-intrusive polynomial chaos (NIPC) model was proposed to efficiently and accurately quantify turbine blade performance change caused by flow variations, and verified by function model. It was used to quantify the change of energy loss coefficient for transonic turbine cascade when the inlet incidence angle varied at different scales. Meanwhile, it was compared with the direct Monte Carlo simulation (MCS) and sensitivity-based evaluation method. The flow solutions were statistically analyzed to reveal the impact mechanism of inlet incidence angle variation. The results showed that the adaptive NIPC quantified the uncertainty of energy loss coefficient with high performance at different scales perturbation of inlet incidence angle. Besides, the energy loss coefficient variation was nonlinearly dependent on the inlet incidence perturbation. Moreover, the shock wave in blade passage was most sensitive to the inlet incidence angle variation, becoming the most contribution to energy loss coefficient uncertainty for the transonic turbine cascade.
Effects of inlet flow distortion on fan performance under nonuniform tip clearance
LI Jianxiong, CHEN Yingxiu, HOU Anping
2020, 35(3): 532-539. doi: 10.13224/j.cnki.jasp.2020.03.009
Abstract PDF(5610KB) icon635 icon526
Abstract:
Based on the real total pressure distortion, the influence of relative position of inlet distortion on fan flow field under nonuniform clearance was studied. The results showed that there was a phase lag between the rotor flow filed and the inlet flow distortion, which was about 90°. The total pressure distortion resulted in the most remarkable effect when it acted at the circumferential position with the worst flow of the original flow field, and the rotating stall was closely related to the sector with convergence clearance. It can be inferred that the stall will occur once the overflow with high entropy has not been dissipated during the propagation from large to small clearance region.
Effects of specific swirl distortion on performance of transonic compressor
WANG Jiale, CHENG Bangqin, ZHANG Lei
2020, 35(3): 540-551. doi: 10.13224/j.cnki.jasp.2020.03.010
Abstract PDF(7650KB) icon652 icon510
Abstract:
The StreamVane swirl distortion generator was combined with transonic compressor Stage 67 using numerical simulation to investigate the effect of swirl distortion generated by exit of S-duct inlet and hybrid wing body (HWB) on the performance and stability of compressor. The compressor characteristic map and flow field were obtained by this method and compared with characteristic map and flow field with uniform inflows. There existed a maximum decrease of pressure ratio, efficiency, stability mass flow rate and stability margin by 0.06%, 0.85%, 5.97% and 1.13%, respectively, with 100% corrected speed under the effect of the S-duct inlet swirl distortion. Both pressure ratio and efficiency characteristic lines moved to the lower left. There existed a maximum decrease of efficiency, stability mass flow rate and stability margin by 6.25%, 26.88%, 2.84% and a maximum increase pressure ratio by 6.61% respectively with 100% corrected speed under the effect of the HWB swirl distortion. The pressure ratio characteristic lines moved to the upper right, the efficiency characteristic lines moved to the lower right.
Fretting wear of discontinuous interface considering centrifugal force and thermal stress
YANG Lihua, WANG Zhenfa, XIE Kun
2020, 35(3): 552-559. doi: 10.13224/j.cnki.jasp.2020.03.011
Abstract PDF(2739KB) icon787 icon553
Abstract:
The disks of combined rotor of the rotating machines, such as aero-engine, heavy-duty gas turbine, are often joined by discontinuous interface, both structural analysis and thermal-structural coupling analysis were carried out for cold preloading and speedup stages as well as steady-state temperature field by establishing a two-wheel contact finite element model. The evolution of fretting parameters, including contact stress, the shear stress and fretting wear depth of the annular contact interface, was investigated. Results showed that the contact stress decreased gradually from the inner diameter to the outer diameter under the action of preloading force. The contact stress and shear stress were the largest at the inner diameter, and the fretting wear was the most serious. The maximum contact stress at the annular contact interface increased and the minimum contact stress decreased with the increase of the rotational speed and the centrifugal force, which caused the non-uniformity contact stress distribution and intensified the wear. The steady-state temperature field caused a large increase of the average contact stress, and it would seriously aggravate wear. Judging from the uniformity of the contact stress distribution and fretting wear condition, the thermal load is the main factor causing fretting wear on the discontinuous interface of combined rotor.
Oil film characteristic of two-phase flow squeeze film damper under extremely low oil supply pressure
ZHANG Wei, WANG Haojie, DING Qian
2020, 35(3): 560-568. doi: 10.13224/j.cnki.jasp.2020.03.012
Abstract PDF(3186KB) icon898 icon553
Abstract:
Influence of two-phase flow on the oil film characteristic of squeeze film damper(SFD) under extremely low oil supply pressure was investigated through tests. The test results showed that the oil film damping decreased with the increase of gas volume fraction when the gas volume fraction is under 0.9. As the gas volume fraction reached 0.9, the damping was 60% of the damping of pure oil. The damping decreased dramatically to negligible, as the gas volume fraction continued increasing beyond 0.9. The trend can not be predicted by the existing theoretical model. Based on the test results, the best-fitting model for the two-phase flow of SFDs was used to predict the damping coefficients of SFD, which can match the test results under both large and low oil supply pressures. The model can provide a reliable theoretical basis for the selection of SFD two-phase flow model.
Dynamic strain reconstruction method of rotating blades based on no-contact measurement
AO Chunyan, QIAO Baijie, LIU Meiru
2020, 35(3): 569-580. doi: 10.13224/j.cnki.jasp.2020.03.013
Abstract PDF(3481KB) icon905 icon578
Abstract:
A dynamic strain reconstruction method of rotating blade based on blade tip timing non-contact measurement and transmissibility concept was proposed. The transmissibility between displacement and strain of any point was derived in the frequency domain. The analytical formula of transmissibility with respect to mode shapes was obtained. The three-dimensional (3D) finite element model of rotating blade was established to conduct modal analysis considering rotating pre-stress effect. The displacement and strain mode shapes of blade were extracted and the transmissibility between displacement at blade tip and dynamic strain of critical point at blade root under any rotational speed was calculated. The test for high-rotating blade based on blade tip timing non-contact measurement was conducted. The Circumferential Fourier transform method was applied for analyzing blade-tip displacement at different rotational speeds in case of single mode resonance. Combining with the transmissibility, the dynamic strain of five blades at some critical points was reconstructed. Results showed that when the first mode resonance at rotational speed of 9000r/min and 13000r/min occurred, comparing with the measuring results of strain gages, the average relative error of dynamic strain reconstruction of three critical points on the blade root, such as the maximum-strain point, the secondary-strain point and the edge point, was less than 15%, showing the validity of the dynamic strain reconstruction method.
Experiment of gas plasma plume deflection by magnetic control
ZHAO Kai, HU Jianbo, LU Yongji
2020, 35(3): 581-588. doi: 10.13224/j.cnki.jasp.2020.03.014
Abstract PDF(2970KB) icon527 icon399
Abstract:
To investigate the deflection effect of gas plasma plume controlled by magnetic field, a novel experimental scheme was presented. The Cs2CO3 catalytic ionization seeds were injected into the combustion chamber to obtain gas plasma on a high temperature magneto hydrodynamic (MHD) experiment rig. The plasma jet was deflected under the action of an external magnetic field, resulting in a thrust-vector effect. Particle image velocimetry (PIV) collected two-dimensional images of jet flow field. Through image processing and velocity vector analysis, the jet deflection angle can be obtained quantitatively. At 1800-2500K, the jet deflection was verified experimentally under the condition of 0.45T magnetic field strength. The results indicate that the jet deflection angle increases gradually with the increase of gas temperature, and above 2200K, the jet deflection angle increase obviously. In the process of gas plasma jet, it is feasible to realize the jet deflection controlled by MHD by adding an external magnetic field.
Influence of jet deflector configuration on flow field and acoustics field of launch vehicle at lift-off
XING Chenglong, LE Guigao, SHEN Lin
2020, 35(3): 589-596. doi: 10.13224/j.cnki.jasp.2020.03.015
Abstract PDF(2993KB) icon711 icon454
Abstract:
To study the acoustics environment around the four-nozzle launch vehicle at lift-off, a two-component compressed flow model of gas/air was established. The second-order Roe scheme, SAS (scale-adaptive simulation) turbulence model and acoustic analogy method (FW-H) were used to solve the three-dimensional Navier-Stokes equation. Firstly, the jet and noise of single-nozzle launch vehicle were numerically simulated. The error between the numerical results and the experimental data was less than 3dB (relative error less than 1.6%), and then the configuration of the jet deflector on the acoustic environment of the four-nozzle launch vehicle was studied. Results showed that the overall sound pressure level of the one-sided jet deflector was larger than that of the two-sided jet deflector, and the maximum difference of the overall sound pressure level (OASPL) was 10.7dB. In addition, for one-sided jet deflector, the overall sound pressure level of the circumferential noise receiving points showed the symmetry of the center section of the one-sided jet deflector and the increasing trend along the direction of the jet deflector outlet. The research results provide some reference for the prediction of noise environment and noise control of launch vehicle.
Integration algorithm oriented modeling and performance evaluation on integrated liquid fuel ramjet
HAN Yongheng, LI Gaochun, QIANG Hongfu
2020, 35(3): 597-610. doi: 10.13224/j.cnki.jasp.2020.03.016
Abstract PDF(6040KB) icon695 icon439
Abstract:
The engineering prediction method of ramjet performance was developed,and an integration algorithm oriented model of integrated liquid fuel ramjet was established,which was compatible with group contribution method. The velocity-altitude characteristic,altitude-throttle characteristic,throttle-velocity characteristic and angle of attack characteristic of the specific impulse, thrust coefficient and fuel mass flow rate of the ramjet at angles of attack 0°~6°,altitude 0~18km,Mach number 2.0~3.5 and excess air coefficient 1.0~2.9 were analyzed. Results showed that,the model can predict the performance of ramjet engine without depending on the test data under the condition of integrated algorithm and within the allowable range of group contribution method. The relative error between the calculated results and the technical reference values was less than 14%. Thrust coefficient and specific impulse had basically the same velocity-altitude characteristics and similar altitude-throttle characteristics. The difference between throttle-velocity characteristics of thrust coefficient and specific impulse were obvious under the influence of gas composition.Different from the change of specific impulse and thrust coefficient showing a slowing trend after entering the stratosphere, fuel mass flow rate showed continuity.The higher the velocity, the lower the altitude and the smaller the excess air coefficient was,the higher the fuel mass flow rate was, and vice versa.Taking the angle of attack into account ,the larger the angle of attack was, the lower the specific impulse,thrust coefficient and the higher the inlet start Mach number was.The angle of attack-start Mach number curve was approximately linear in a small range,and the non-linearity was intensified when the angle of attack exceeded 5.6°.
Impacts of propeller installation effect on aerodynamic performances for UAV
SHI Wenbo, LI Jie
2020, 35(3): 611-619. doi: 10.13224/j.cnki.jasp.2020.03.017
Abstract PDF(4160KB) icon821 icon509
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Computational fluid dynamic (CFD) approaches were implemented on prop-uninstalled and prop-installed configurations of a flying wing unmannel aerial vehicle (UAV), so as to solve the problem of the decline of the maximum lift-drag ratio, and the results obtained through numerical methods were shown to be in good agreement with the test data. The impacts of the installation of the propeller on the aerodynamic performances of the aircraft were studied in depth on the basis of the collaborative experiment and numerical research. Detailed analysis of the numerical results indicated that the lowest pressure areas at the aft part of the airframe generated by the aerodynamic interactions between the propeller blades and airframe led to the increase of the drag and hence a decrease of around 30.7% in maximum lift-drag ratio. The feasibility of center shaft extension can effectively reduce the lowest pressure areas at the aft part of the airframe and increase the maximum lift-drag ratio of the aircraft by 17.3% and 15.4% at the angles of attack of 8° and 9°, respectively.
Influence of blade negative twist on aerodynamic performance of cycloidal propeller
ZENG Jianan, ZHU Qinghua, WANG Kun
2020, 35(3): 620-632. doi: 10.13224/j.cnki.jasp.2020.03.018
Abstract PDF(7833KB) icon498 icon435
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In order to improve the analysis accuracy of the influence of shape parameters on the aerodynamic performance of cycloidal propeller, a set of CFD methods suitable for the simulation of the cycloidal propeller flow field based on the dynamic overset mesh and Unsteady Reynolds time average method equation were established. The characteristics of the spanwise lift distribution and surface pressure distribution in case of different negative twist were provided. The influence of the negative twist on the aerodynamic performance of cycloidal propeller was emphasized. The results showed that, the change of negative twist caused the change of azimuth for cycloidal propeller lift. The larger the absolute value of negative twist, the lower the figure of merit of the cycloidal propeller; the smaller the negative twist, the more gentle the instantaneous aerodynamic fluctuation; the influence mechanism of negative twist on the aerodynamic performance of cycloidal propeller was generated from changing the non-uniform distribution of the cycloidal propeller's effective angle of
Flight test for turbo-shaft engine air-startingcharacteristic based on operational tasks
ZHAO Haigang, WANG Junqi, LIU Yu
2020, 35(3): 633-640. doi: 10.13224/j.cnki.jasp.2020.03.019
Abstract PDF(3690KB) icon953 icon455
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An air-starting flight test scheme of the turbo-shaft engine was designed to evaluate the urgent air-starting characteristics of turbo-shaft engine and the corresponding disposal measures in the situation of the engine accidental shutdown possibly encountered during combat flight. The air-starting flight test scheme was applied to the design appraisal flight test of a turbo-shaft engine in several different flight conditions. Results showed that the designed flight test scheme was reasonable and feasible, providing an effective way to evaluate the air-starting ability of turbo-shaft engine from the perspective of practical combating use. Above 4000m altitude, the helicopter average declining altitude was 670m and average engine-shutdown time was 185s in the engine restart processes. The flight test scheme and results are useful and provide references for the military pilots to deal with possible engine accidental shutdown.
Measured data reconciliation model for a certain type of turbofan engine
YANG Xuesen, YANG Qiao, ZHANG Weiya
2020, 35(3): 641-650. doi: 10.13224/j.cnki.jasp.2020.03.020
Abstract PDF(2177KB) icon712 icon436
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To improve the validity and reliability of the measured data, primal-dual interior point method was used to reconcile the measured data for a certain type of turbofan engine based on cooperative working equations. The performance of the model on reconciling mass flow rate, temperature and pressure was stidoed bu case when measured data had errors. The physical computation time was also tested using two starting value update methods under various flight conditions. The influence of constraint violation threshold on the precision of data reconciliation was studied. The predictive effect of dynamic data reconciliation on missing parameters was tested, and an approach to make further improvement of computation speed was proposed. Results showed that the uncertainties of measured and unmeasured data could be reduced to less than 1%, meanwhile, the processing time could also be reduced to 5s, providing a support for aero-engine state monitoring, sensor maintenance and generation of aero-engine control strategy in case of sensor failures.
Turbine characteristics conversion method of aeroengine
CHEN Zhenlai, SU Sanmai, LI Rong
2020, 35(3): 651-657. doi: 10.13224/j.cnki.jasp.2020.03.021
Abstract PDF(2568KB) icon944 icon545
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For the turbine characteristics expressed by taking the nozzle pressure ratio as the abscissa, the corrected mass flow and efficiency as the ordinate, and differentiated by different equal rotation speed lines, when the turbine works at critical state, the corrected mass flow of this form of turbine characteristics almost remain unchanged, and had the disadvantage of reducing computational efficiency in solving common working point when it was used in aeroengine mathematical model by interpolation of turbine characteristics. According to similarity theory and the corresponding relationship between turbine expansion work and nozzle pressure ratio under isentropic conditions, the calculation formula between turbine nozzle pressure ratio, turbine efficiency and turbine equivalent work was derived; combined with the parabolic interpolation method, a method for transforming turbine characteristics expressed in the above form was presented, the converted turbine characteristics were expressed by the equal rotation speed as the abscissa, the turbine equivalent work and efficiency as the ordinate, and differentiated by different equal corrected mass flow lines. The conversion calculation shows that with the proposed conversion calculation method, the relative error is less than 0.65% between two forms of turbine characteristics, which meets the engineering requirements, and can effectively avoid the disadvantage of previous turbine characteristics.
Vibration analysis of peeling fault of intermediate bearing outer ring based on whole aero-engine
CHEN Guo, HE Zhiyuan, WEI Xunkai
2020, 35(3): 658-672. doi: 10.13224/j.cnki.jasp.2020.03.022
Abstract PDF(5068KB) icon746 icon459
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In view of the problem of outer ring fatigue peeling fault diagnosis of intermediate bearing in a typical double-rotor aero-engine, based on the vibration coupling dynamic model of aero-engine, the early peeling fault model of outer ring of intermediate bearing was introduced, and the vibration response of aero-engine was obtained by numerical integration. The fault features of intermediate bearing with peeling off on outer ring were extracted and analyzed. It was found from the signal analysis that: (1) there were 4 times of the characteristic frequency of outer ring fault and the modulation sidebands with the outer ring rotation frequency taken as the interval on both sides. (2) With the increase of unbalance, the characteristic frequency component was basically unchanged, and the sidebands became more prominent. (3) With the increase of bearing clearance, the impact caused by outer ring fault was more intense, and the characteristic frequency and modulation sideband frequency were significantly increased. By comparing the fault characteristics of the signals from the bearing housing to the casing, the results showed that the impact caused by the early fatigue peeling of the intermediate bearing transmitted to the casing from the bearing housing could produce a great degree of attenuation, and the bearing fault characteristics basically disappeared in the casing measurement point signals.

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