2017 Vol. 32, No. 8

Display Method:
Experiment on combustion characteristics of aeroderivative gas turbine twins annular combustor
2017, 32(8): 1793-1800. doi: 10.13224/j.cnki.jasp.2017.08.001
Abstract:
The reaction characteristics of a kind of twins annual premixed swirler(TAPS) combustor were studied using No.0 diesel as fuel in order to satisfy the requirement of low emission of gas turbine for ground transportation. The results showed that, the total pressure recovery coefficient of the TAPS combustor reached more than 0.97, higher than classical single annual combustor due to the changes in air distribution characteristics. The minimum atmospheric ignition fuel-air ratio over 0.05 was higher than that using the aviation kerosene as fuel with the same combustor structure due to the influence of viscosity and flash point, but idle lean blow-out limit had no obvious change between 0.006 and 0.008. The fuel mixing was nonuniform due to pressure atomization at the pilot stage, which caused the lower combustion efficiency 0.99, but the outlet temperature distribution factor was less than 0.25, which can meet the requirement. For the pollution emissions, NOx dry volumn fraction was 1.76×10-5 significantly lower than the required index, but the CO dry volumn fraction was higher up to 5.02×10-4 due to use of the premixed pre-evaporation combustion. Through comprehensive comparison of various performance indicators, the combustor has advantages in ignition, lean blow-out, combustor outlet temperature distribution and NOx emissions, but the lower combustion efficiency and higher CO emission are still problems to be solved.
Statistical analysis on the forced dynamic of internally-staged-swirling stratified flame
2017, 32(8): 1801-1808. doi: 10.13224/j.cnki.jasp.2017.08.002
Abstract:
To understand the dynamic mechanism of internally-staged-swirling stratified flame used in civil aero-engine low emissions combustor, high-speed CH* chemiluminescence images of this swirling flame fueled with propane were recorded under the forced condition with 100Hz frequency. Then the temporal and spatial dynamic features of the flame could be extracted by using statistical analysis of proper orthogonal decomposition (POD). The analysis results indicated that the most important 4 dynamic modes in the swirling flame are axial vibration, radial vibration, flame shedding and asymmetric helical motion, respectively. And the axial vibration of mode 1 and radial vibration of mode 2 have significant correlation. The POD analysis could be an effective method for the mechanism exploration of combustion instability in the internally-staged lean premixed combustion.
Performance evaluation methods of two-stage axial swirlers:Ⅱ influence of swirler rear geometric structure
2017, 32(8): 1809-1814. doi: 10.13224/j.cnki.jasp.2017.08.003
Abstract:
Theoretical and numerical studies on the reaction flow field and combustion performance of two-stage axial swirler combustors were carried out. The effects of total swirl number and swirler rear (sleeve) geometric structure size on the reaction flow field and combustion performance were investigated numerically. Results showed that the swirling flow tended to break away from the sleeve throat wall, forming jet-like flow when the total swirl number was small. And the swirling flow intensity increased with the increasing sleeve divergence angle. Airflow divergence angle increased with the increasing sleeve divergence half angle in the range from 30° to 70°. It was found that there was a critical divergence half angle 73° of sleeve. When the angle was greater than the critical angle, the airflow broke away from the sleeve wall. In addition, an empirical formula for estimating the airflow divergence angle of sleeve exit was developed by theoretical method together with numerical simulation. Compared with experimental and numerical results, it is found that the formula can predict the flowfield development downstream the swirlers accurately, providing a practical and effective method for the design of multi-stage swirlers in the future.
Piezoelectric excitation property of multi-nozzle injector
2017, 32(8): 1815-1821. doi: 10.13224/j.cnki.jasp.2017.08.004
Abstract:
The piezoelectric excitation property of multi-nozzle injector was studied by numerical simulation. Pressure, mass flow rate and fluctuation of velocity of the injector were obtained. The results showed that the pressure fluctuation was mainly influenced by wall motion characteristics, and the pressure amplitude increased with the increasing excitation frequency in multi-nozzle injector. But in the obturated cavity, the pressure fluctuation mainly depended on change of the cavity cubage, and the pressure amplitude didn't vary with the excitation frequency. Thus theoretical method of obturated cavity could not nicely forecast the pressure fluctuation in injector. In the multi-nozzle injector, the mass flow rate amplitude at inlet and outlet was different. The pressure amplitude distributed non-uniformly in different positions, resulting in different velocity amplitudes at multi-nozzle outlet, and also different jet shapes.
Conversion methods for lean ignition performances among single-sector,multi-sector and full annular combustors
2017, 32(8): 1822-1826. doi: 10.13224/j.cnki.jasp.2017.08.005
Abstract:
A series of ignition tests were conducted to study the similarities and differences of lean ignition limits among single-sector, multi-sector and full annular combustors. Furthermore, major factors causing the differences were analyzed. Based on Lefebvres ignition model, empirical lean ignition limit correlations of different combustors were summarized by data fitting method, together with the conversion formulas there in. Results show that: different types of combustors exhibit similar lean ignition limit changing pattern, but the lean ignition fuel air ratio of full annular combustor are obviously lower than those of single-sector and multi-sector combustors under same conditions.
Boundary ghost cell method for gas heat radiation calculation of hypersonic re-entry spacecraft
2017, 32(8): 1827-1834. doi: 10.13224/j.cnki.jasp.2017.08.006
Abstract:
Targeting the shock layer radiation heating, the radiative transfer equation was calculated by finite volume method, in which a way of boundary treatment, called as ghost cell method, was introduced. Based on the chemical non-equilibrium flow field data, radiation heat flux at wall was computed. The analysis reveals that ghost cell method in dealing with radiative transfer boundary ensures that the boundary conditions fit the physical fact. Good convergence and accuracy within 2.5% have been achieved, validating the physical model and numerical methods. Radiation heating computation of spacecraft using ghost cell method shows that computational radiative heating results agree well with the other researchers' computational results.
Heat transfer prediction on film boiling of liquid hydrogen under normal gravity and microgravity environments
2017, 32(8): 1835-1843. doi: 10.13224/j.cnki.jasp.2017.08.007
Abstract:
The film boiling heat transfer of liquid hydrogen was investigated, and the associated film boiling heat transfer experimental data in literatures were selected and analyzed. To validate the applicability and the predictive accuracy of three typical correlations for calculating heat transfer coefficient of film boiling events, a series of comparative studies were conducted. Moreover, a mathematical correlation was proposed to predict the film boiling heat flux of liquid hydrogen under microgravity. It was concluded that under the normal gravity condition, the heater geometries and their directions cannot significantly influence the film boiling heat flux of liquid hydrogen, and Breen & Westwater correlation was recommended to predict the heat transfer coefficient. Analysis of the experimental data shows that gravity has a significant influence on the film boiling heat transfer, and a power law correlation could be obtained to link the heat flux under different gravity conditions. In addition, a comparative study shows the proposed power law correlation allows to get the film boiling heat flux under any gravity condition as long as the heat flux under a similar reference condition has been known, and the predictive deviation is within 15%.
Effect of film hole location on film-cooling effectiveness of squealer tip
2017, 32(8): 1844-1852. doi: 10.13224/j.cnki.jasp.2017.08.008
Abstract:
The effects of film hole location on squealer tip leakage flow field, film-cooling effectiveness and surface heat transfer coefficient were studied by solving the Reynolds averaged Navier-Stokes equations using standard two equation k-ε model. Three film hole location configurations: camber line film holes, suction side film holes, leading edge film holes were simulated. The effects of tip clearance height (t) and blowing ratio (M) were also considered. The results showed that the film hole location affected the film-cooling effectiveness of squealer tip greatly under the same cooling flow rate. The camber line film cooling squealer tip had better film coverage on the region between the camber line and the pressure side squealer. The suction side film cooling squealer tip had better film coverage on the given middle chord region between the suction side squealer and the camber line, as well as on the trailing edge region. The leading edge film cooling squealer tip had better film coverage on all the tip surface. The tip clearance height had different effects on different squealer tips. The tip film-cooling effectiveness of the leading edge film cooling squealer tip increased greatly when the blowing ratio increased if compared with the other two kinds of cooling squealer tips.
Experiment on atomization characteristics of pintle injectors
2017, 32(8): 1853-1860. doi: 10.13224/j.cnki.jasp.2017.08.009
Abstract:
To study the atomization characteristics of pintle injectors, the influences of structural parameters of pintle injectors on Sauter mean diameter (SMD), drop distribution homogeneity factors and atomization cone angles were obtained by using high-speed photography and Marvin measuring instrument. The results indicated that SMD kept constant along the injection axis direction, and increased along the radical direction. In addition, with the increase of gas-liquid mass flow ratio SMD decreased, but the drop distribution homogeneity factors reduced firstly and then increased. The product of drop distribution homogeneity factors and slit width kept constant, which was 0.35. When the gas-liquid mass flow ratio was larger than 0.206, with the effects of aerodynamic force, the atomization boundary could be divided into two zones, the upper zone as the contraction stage, and the lower zone as the equal-diameter stage. Moreover, when designing pintle injectors, the slit width should be chosen as small as possible, while the half cone angle of liquid film should be selected according to SMD and atomization cone angles.
Experiment on infrared signature of two dimensional convergent-divergent vectoring nozzle exhaust system
2017, 32(8): 1861-1868. doi: 10.13224/j.cnki.jasp.2017.08.010
Abstract:
Experiments was conducted to study the distribution of wall temperature and infrared radiation characteristics on two dimensional convergent-divergent (2D-CD) vectoring nozzle exhaust system in three geometric deflection states, deflection of 0, 10, 20 degrees, and the results were compared with the reference axisymmetric nozzle exhaust system. The experimental results show that the infrared radiation characteristics is significantly lower than the reference axisymmetric nozzle exhaust system with a decline of 10% in the tail direction. With the increase of geometric deflection angle, the temperature of heat shield wall, convergent section wall increase, and the temperature of pressure side wall in deflection section increase slightly, while the temperature of suction side wall in deflection section decrease slightly, where the maximum change value is 30K; the increasing angle also significantly enhances the infrared radiation intensity, especially, in the tail direction from 15° to 45° and from -15° to -60°, where the maximum increase reaches 70%.
Periodic expansion/fracture of bubbles in burning oil droplets by internal evaporation
2017, 32(8): 1869-1875. doi: 10.13224/j.cnki.jasp.2017.08.011
Abstract:
The following phenomena were captured in combustion process by high-speed microscopic camera technology: the periodic expansion/fracture of micro bubbles in aviation kerosene RP-3 suspended droplet. The phenomena that the micro bubbles sharply expanded and suddenly fractured were found inside the burning 1.25mm diameter droplet at environment temperature of 973K. Namely: (1) in 0.04s, the diameter of the micro bubbles increased by 41.6%; (2) in 0.01s, the expansion bubble was fractured inside the droplet, which stimulated the droplet's sharply oscillations; (3) the droplet resumed relatively stable evaporation and combustion,and the internal residuals of the micro bubbles were observed to start the second round of expansion/fracture; (4) the droplet burned away after three rounds of expansion/fracture. The following mechanism was speculated: the quartz fiber heated by high temperature induced the rapid evaporation effect inside the droplet, which was the driving force of the micro bubble periodic expansion/fracture. Moreover, surface tension was the restraint mechanism to restore and maintain the droplet stable combustion.
Numerical research on film cooling effectiveness with different mainstream pressure gradient
2017, 32(8): 1876-1885. doi: 10.13224/j.cnki.jasp.2017.08.012
Abstract:
Numerical simulations of film cooling under the condition of subsonic mainstream in convergent channel, expanded channel and straight channel were conducted. The flow fields and temperature fields of the mainstream and secondary streams were investigated under different streamwise pressure gradients and different flow blowing radios. The results showed that the mainstream boundary layer thickness, mixing intensity of shear layer and the counter-rotating vortex pair intensity and distributions were the main factors contributing to the changes of the film cooling effectiveness. Compared with the zero pressure gradient case, adverse pressure gradient increased the boundary layer thickness and strengthened the penetration of the secondary flow for the low blowing ratio (M=0.25) cases. Meanwhile, the intensity of the counter-rotating vortex pair was weak. As a result, the averaged film cooling effectivenesd increases by 4.91% at the low blowing ratio. For the high blowing ratio case (M=2), favorable pressure gradient restrained the development of mainstream boundary layer and depressed the penetrating ability of the secondary flow. At the same time, the accelerated mainstream made the counter-rotating vortex pair closer to the wall. These caused the film cooling effectiveness increase by 17.40% at the high blowing ratio.
Code verification of mesh free method with computation of derivatives
2017, 32(8): 1886-1899. doi: 10.13224/j.cnki.jasp.2017.08.013
Abstract:
In order to improve the approximation of spatial derivatives without meshes, a set of mesh free method for spatial derivatives was developed, which agreed well with the Cartesian, cylindrical and spherical coordinates. Based on the comparisons between numerical and theoretical solutions, the errors and convergences were assessed by a posteriori method, showing that the approximations for functions and derivatives were of the second order accurate, and the scale of the support domain had some influences on numerical errors but not on accuracy orders. With a discrete scale h being 0.01, the relative errors of the numerical simulation for the selected functions and their derivatives were within 0.65%.
Study on aerodynamic characteristics of different types of civil aircrafts with engine air intake and exhaust
2017, 32(8): 1900-1910. doi: 10.13224/j.cnki.jasp.2017.08.014
Abstract:
The aerodynamic characteristics of different types of civil aircrafts with turbofan engine air intake and exhaust were studied numerically by solving the Navier-Stokes equations based on mixed grids. The engine air intake face boundary conditions and jet exhaust boundary conditions were adopted to simulate the powered effects of the engine. The numerical methods were validated by the turbine powered simulator model. On this basis, the effects of engine air intake and exhaust were analyzed for the civil aircrafts with wing-mounted nacelles and back-mounted nacelles. The results indicate that the jet efffects of the engine play a major role in the lift characteristics of the wing-mounted civil aircraft. For the tail-suspended civil aircraft, the mass of air intake affects the wing aerodynamic characteristics directly and with the increase of air intake mass, the surface pressure coefficients on the upper surface of the wing are reduced and the location of the shock wave is shifted downstream. The mass of air intake also has great influence on the drag characteristics of different types of civil aircrafts. The aerodynamic interference between aircraft and engine must be valued highly in the aircraft design.
Research on the conceptual design of a civil aero-engine based on MDO strategies
2017, 32(8): 1911-1921. doi: 10.13224/j.cnki.jasp.2017.08.015
Abstract:
The conceptual design of a civil turbofan aero-engine was studied. Three subsystems were integrated and analyzed in detail including: overall performance (analysis of thermodynamic cycle, assessment of mass, noise, oxynitride emissions), fan (analysis of aerodynamics and strength), low pressure turbine (analysis of aerodynamics and strength). Multidisciplinary design optimization (MDO) of the engine conceptual design was carried out with different optimization strategies but for the same optimization objects, i.e.: specific fuel consumption, overall mass, overflight noise power level, approaching noise power level, and oxynitride emissions of the combustor. Optimization strategies including individual discipline feasible (IDF) optimization, collaborative optimization (CO) and asymmetric subspace optimization (ASO), were adopted in the MDO study of aero-engine. The modeling method of the MDO engine system, the data transmission and the decoupling method of the subsystems were discussed. Finally, the following conclusions were drawn: the efficiencies of the three optimization strategies were approximately equal, and the difference of the maximum time consumption between every two of them was 742s. Moreover, CO and ASO strategies had better optimization results in the MDO of aero-engine conceptual design, and their comprehensive evaluation index were reduced by 0.82% and 0.86% respectively.
Underwater thrust vectoring method based on cross second flow
2017, 32(8): 1922-1932. doi: 10.13224/j.cnki.jasp.2017.08.016
Abstract:
A novel underwater thrust vectoring method based on cross second flow was proposed. In this method,the main flow can be deflected by the flow field induced by the cross second flow. A mathematical model relating the thrust vectoring angle to the flow vectoring angle was established. This model validated the feasibility of thrust vectoring through flow deflection. The effects of the depth of the second flow,the volume ratio as well as the velocity ratio of second flow to the main flow on the deflection angle were studied through numerical method. The numerical results showed that the deflection angle of the main flow decreased with the increase of the depth because of the variation of the adverse pressure at the nozzle. With the decrease of the volume ratio the deflection angle increased. And when the volume ratio was lower than a specific value,the deflection angle didnt vary any more. The deflection angle increased with the velocity ratio,and at a certain velocity ratio,the magnitude of the velocity had no effect on the deflection angle. Based on these numerical results,an underwater thrust vectored propulsor was designed. The simulation about this propulsor reveals that the maximum deflection angle can be realized when all the second jets at the same side of the midship section of the main flow are activated simultaneously. The deflection direction of the main flow can be controlled through activating different groups of second jets.
Influence of viscosity on interior ballistics of high-pressure air ejection device
2017, 32(8): 1933-1942. doi: 10.13224/j.cnki.jasp.2017.08.017
Abstract:
The gas viscous flow in the high-pressure air ejection device causes energy dissipation and pressure loss,and may change the performance of the interior ballistics. An energy loss calculation method was obtained for the non-fully developed unsteady flow. An interior ballistic model was established on the basis of the real gas effects for the high-pressure air ejection device under the gas friction effects. The numerical experiments were performed. The results show that the gas friction effects cause little errors for the quick gas expansion,and the performance of the missile changes not too much. The gas friction effects can be ignored in the low precision system. However,the law curves show that the gas friction effects reduce the energy quality,and slow down the gas expansion rate. Besides,the gas friction effects make the pressure in the low pressure chamber unequal,and generate the mass flowrate fluctuation from high pressure chamber to low pressure chamber. The missile collision occurs because of the gas friction.
A third order lattice Boltzmann force model capable of recoving the Naveir-Stokes equations
2017, 32(8): 1943-1949. doi: 10.13224/j.cnki.jasp.2017.08.018
Abstract:
In order to design a third order lattice Boltzmann force model capable of recovering the Navier-Stokes equations applied to low viscosity flow, the force model proposed by Shan,et al were amended. The fluid velocity and total energy affected by force were redefined directly without any physical assumption. The Navier-Stokes equations (including the energy equation) were derived from lattice Bhatnagar-Gross-Krook(LBGK) equation via the Chapman-Enskog expansion without any error terms.
Pseudo-shock characteristics in the two-dimensional supersonic inlet diffuser
2017, 32(8): 1950-1961. doi: 10.13224/j.cnki.jasp.2017.08.019
Abstract:
For pseudo-shock characteristics in the two-dimensional supersonic inlet diffuser,the influences of the diffuser length, diffusing ratio and the center line offset were numerically studied. Results show that: within the scope of the study, the influences of the diffuser length and diffusing ratio on the pseudo-shock characteristics are more significant than the center line offset. Both the diffuser length and diffusing ratio affect the pseudo-shock characteristics by changing the shock train length and the scale of separation. Based on the numerical results of a series of diffuser geometries, a simple linear fitting formula to estimate the optimum diffusing ratio corresponding to the maximum diffusion performance has been proposed. These results are beneficial to the design of the supersonic inlet diffuser.
Research of civil aviation engine overhaul workscope based on genetic algorithm
2017, 32(8): 1962-1970. doi: 10.13224/j.cnki.jasp.2017.08.020
Abstract:
To support the creation of engine overhaul workscope during its life cycle, and reduce the overhaul cost in its life cycle, based on the engine maintenance management program provided by manufactures, by setting the overhaul interval which is less than the maximum overhaul interval, and taking account of the life of life limited parts and soft time of modules, an engine overhaul cost optimization model was presented in the paper for a modular engine, which took the overhaul interval as the variable and the least shop visit cost per flight hour as a target, the genetic algorithm was used to solve this optimization problem. Taking V2500 as an example, its shop visit workscope was optimized, it gave that 6 shop visits in 25 years have the lowest cost, and the repair levels of each module were also created for each shop visit. It can provide a reference method for airlines to make engine workcope for shop visit.
Heuristic search algorithm for opportunistic replacement strategy of multiple life-limited parts
2017, 32(8): 1971-1977. doi: 10.13224/j.cnki.jasp.2017.08.021
Abstract:
A heuristic search algorithm was proposed to solve the lack of fast and effective problem-solving algorithm of opportunistic replacement of multiple life-limited parts (LLPs). At first, an optimization model of the opportunistic replacement problem of multiple LLPs was established to minimize the total LLP cost in the whole life cycle, and the solution space was expressed as a tree structure. To improve the efficiency of the search algorithm, a child node generation method and a node number control method in single layer were proposed. Based on these, a heuristic search algorithm was proposed. Finally, the proposed algorithm was evaluated and validated by numerical experiments and an actual application case. The results show that there is a relationship between the consumed time, the solving effect and the generating coefficient of child node α as well as the maximum number of single layer node β; when selecting the appropriate α and β, the proposed algorithm can achieve good results in a relatively short period of time; the proposed algorithm can be applied to large-scale opportunistic replacement of multiple LLPs with the equipment total life of 200000 time units and including 100 LLPs.
Bayesian assessment on MTBF of aero-engine
2017, 32(8): 1978-1983. doi: 10.13224/j.cnki.jasp.2017.08.022
Abstract:
It is difficult to evaluate the mean time between failures (MTBF) of aero-engine with traditional mathematical mean time method because of its small samples. To solve this problem, the historical test information was regarded as prior information, and prior distribution was determined by the moment equivalent method, then field test data were combined with prior distribution through Bayesian theorem, lastly a Bayesian method to evaluate MTBF of aero-engine was presented. The information used in the new method to evaluate MTBF was expanded. An example showed the MTBF evaluation result with the new method was 302.68h, 18.7% higher than that with the traditional mathematical mean time method. The engineering experts believed that the new result is closer to the real value than that by the traditional method.It is feasible to use the new method to evaluate MTBF of aero-engine.
Small fatigue crack growth behavior of nickel-based alloy GH4169
2017, 32(8): 1984-1991. doi: 10.13224/j.cnki.jasp.2017.08.023
Abstract:
On the basis of surface replication method, a fast-curing material named RepliSet was applied to monitor the small fatigue crack initiation and growth behavior of single-edge-notch tension specimens fabricated by nickel-based alloy GH4169. Optical microscope was used to view the replicas. Results showed that the RepliSet material can effectively copy the morphology of specimen surface and record the small fatigue crack initiation and growth process. Small fatigue cracks of nickel-based alloy GH4169 initiated from surface inclusions. The early stage of small fatigue crack growth was influenced strongly by microstructures thus the growth rates had high fluctuations. A critical crack length of about 250μm existed during the small fatigue crack growth process. The crack lengths increased very slowly when the major crack lengths were shorter than 250μm. However, the major cracks grew rapidly into long cracks and resulted in the final fracture soon after exceeding 250μm. A linear relationship between the small crack growth rate and crack length can be found when plotted on double-logarithmic coordinate.
Multi-objective optimization method for high pressure turbine casing based on thermal-structure coupling analysis
2017, 32(8): 1992-1999. doi: 10.13224/j.cnki.jasp.2017.08.024
Abstract:

An axisymmetric parameterized high pressure turbine (HPT) casing model was established after HPT casing structure was analysed. Based on the thermal-structure coupling deformation and parameter sensitivity analysis result, 12 key structure parameters were selected as optimization variables. Taking the casing mass and the hook area average radial displacement as the multi-objective function, the second generation non-dominated sorting genetic algorithm (NSGA-Ⅱ) was adopted to solve this multi-objective optimization problem. The optimization result showed that the optimal strengthening ribs structure was more efficient at heat conduction, and other optimal structure was more efficient at losing weight. After the optimization, the model weight and radial displacement were lessened simultaneously.

Accurate simulation method for contact stress of aero-engine bearing
2017, 32(8): 2000-2008. doi: 10.13224/j.cnki.jasp.2017.08.025
Abstract:
The combination of steady state thermal analysis and dynamic contact mechanics analysis was used to improve the calculation accuracy, and the stress distribution was corrected by thermal analysis, meanwhile the variation characteristics of the bearing were obtained. The research shows that, the maximum dynamic contact stress is located on the bearing ball surface, while the stress of the inner is the minimum. The contact stress of bearing has obvious dynamic response characteristics, while its distribution has a random variation. The contact stress, which increases with the rotational speed and the axial load, is composed of the principal stress and the shear stress.
Tooth surface topology modification and processing parameters calculation for spiral bevel gears
2017, 32(8): 2009-2016. doi: 10.13224/j.cnki.jasp.2017.08.026
Abstract:
In order to control tooth meshing performance freely, a kind of tooth surface topology modification method for pinion was proposed. By means of second-order surface approximation for tooth surface deviations, the tooth surface topology modification can be divided into five parts: spiral angle correction, pressure angle correction, lengthwise curvature correction, profile curvature correction and longitudinal twist correction, by changing five modification factors the pinion tooth surface topology can be controlled freely. On this basis, the modified model between tooth surface deviations and processing parameters correction was established, and the pinion processing parameters allowing to acquire modified tooth surface can be calculated by constructing sensitivity matrix and least squares method. The meshing analysis for a pair of spiral bevel gears was carried out. The results demonstrate that by selecting lengthwise curvature modification factor 0.0001, profile curvature modification factor 0.0005, longitudinal twist modification factor 0.0003, the transmission error magnitude is changed to -25.60″, and the contact path orientation is changed to 54.7° after tooth surface topology modification, and the meshing performance is improved compared with initial result. The rolling test result agrees well with simulation result, verifying the effectiveness of modification method.
Two-dimensional domain structure of dynamical parameters of combining spiral gear transmission
2017, 32(8): 2017-2024. doi: 10.13224/j.cnki.jasp.2017.08.027
Abstract:
The nonlinear dynamical model including piecewise backlash was created for combining spiral gear train, the governing equations of motion was solved by employing variant-step Gills numerical algorithm. The cell-mapping technique was put forward to investigate the two dimensional basins of dynamic parameters. Parametric excitations covering the backlash, transmission error, time-varying mesh stiffness and damping ratio, were considered in basin planes in terms of steady solutions. The dynamical bifurcation behavior under the excitation of various parameters was performed by means of the phase portrait, Lyapunov exponent (LE), Poincaré section and fast Fourier transform (FFT). It is validated that Cell-mapping approach is effective in gear dynamic parameter design. The result shows that the system leads to chaos via period-doubling cascades under the backlash and transmission error while large damping ratio within the range ξ∈[0.025,0.225] is beneficial to periodic states of the system. Under the excitation of time-varying mesh stiffness, significant transition between periodic response and chaotic motion was exhibited, small changes nearby parametric domain boundary guided the attracter into another basin of attraction.
Dynamic uncertainty of the measuring instrument for ball bearings' contact angles
2017, 32(8): 2025-2031. doi: 10.13224/j.cnki.jasp.2017.08.028
Abstract:
The influences on the precision of the measuring instrument for ball bearings contact angle caused by the dynamic characteristic of the instrument, test speed and test load were taken into consideration, then the calculation model of the instruments dynamic uncertainty was established. Based on the measuring results of the small sample, the grey theory was applied to calculate the uncertainty of the measurement. The principle of the influence on the uncertainty of the measurement caused by the instrument's dynamic characteristic, test speed and test load was separated based on the uncertainty separation principle, and then the calculation model of the instruments dynamic uncertainty was established. After that, the calculation model was verified by the actual examples. The calculation model of the instruments dynamic uncertainty established could be used to predict the uncertainty of the measurement for contact angle under different conditions. With this help, the corresponding calibration could be done on the measuring instrument in time to raise the precision of the measurement for ball bearings contact angle.
Adaptive sliding mode control for uncertain aero-enginedistributed control system
2017, 32(8): 2032-2040. doi: 10.13224/j.cnki.jasp.2017.08.029
Abstract:
With a focus on the aero-engine distributed control system with parameter perturbation and external disturbance, a robust adaptive sliding mode controller was designed under the condition of time-varying input delay and unknown disturbance upper bound. Firstly, based on the theory of predictive control and matrix singular value, an equivalent linear transformation was conducted for the original aero-engine discrete distributed control system, and a normal form model was obtained, making it easier to solve the sliding mode surface parameters. Secondly, with a given H∞ performance index, the sufficient condition for the asymptotical stability of sliding mode motion was deduced considering the influence of mismatched uncertainties. The sliding mode surface design method in linear matrix inequality (LMI) form was thus obtained. Finally, the adaptive law with disturbance estimation function was designed, and the adaptive sliding mode controller was proposed accordingly. Simulation results show that the proposed controller could reduce the impact of external disturbance on the systems dynamic performance effectively. Under the function of the considered uncertain factors, the systems sliding mode motion presented ideal H∞ performance. When the external disturbance intensity changed, the controller exhibited better robustness. The state convergence time was shorter than 0.8s, and there was no chattering phenomenon.
STOVL aircraft engine multi-variable control method
2017, 32(8): 2041-2048. doi: 10.13224/j.cnki.jasp.2017.08.030
Abstract:
The multi-variable control method was already used in the short take off/vertical landing (STOVL) aircraft engine. The research on outputs selection and control structure design for STOVL aircraft engines three-variable control system was carried out in different operating modes based on the analysis of robust stability, condition number and block relative gain array. As for normal operating mode, a three-variable block decoupling control method based on multi-ojective optimum was proposed. The dynamic tracking and coupling suppression properties were achieved through index definition. As for the transition control between normal operating mode and vertical landing operating mode, a compound controller with lift fan power feedforward was proposed to suppress the influence of the varying load. The simulation results show that the decoupling control effect can be ensured in normal operating mode, and the smooth transition between different operating modes also can be achieved by proposed methods, presenting the effectiveness of the control methods.