Applied Mechanics and Materials Vols. 488-489

Abstract: This paper presents two nose cones models and their numerical calculation of aerodynamic noise in high speed airflow field combining the analysis theory of fluid dynamics with the acoustic boundary element analysis method. The noise sound pressure levels (SPL) of these two models are calculated under the different speed airflow. And we compare the SPL of the better model with that of commercial nose cone models. These simulated results show that the aerodynamic noise of the nose cone with a ellipsoid head has lower flow-induced noise than that of commercial nose cone models at relative high air flow velocities at most frequencies.

Abstract: This paper discusses utilizing Austempered Ductile Iron (ADI) to manufacture driving/driven spiral bevel gears for big-horsepower (under 350 Hp) heavy truck rear axles, which is a breakthrough in China. Through the carry out of focused research and experiments on main craft process key points of the components, and with all-round analysis to technical/quality outcome achieved, the authors have finally developed this new generation copper-niobium alloy ADI main/sub spiral bevel gear that is suitable for heavy truck (under 350 HP) rear axle uses. While being able to replace 22CrMo and 18CrMnTi alloy forged steels in use, this new gear has also achieved replacing forging & steel with casting & iron. Cutting of two main process steel-making and steel-rolling has not only raised production efficiency, but also lowered the its cost. At current, rear axle spiral bevel gears for automobiles in China are manufactured through forging, with 40Cr18CrMnTi22CrMo as key materials; cemented quenching and tempering techniques are applied in the production process.This method is also used in manufacturing of driving/driven spiral bevel gears for trucks rear axles. Such combination of high-quality steel and forging means high material cost, complicated process, and production inefficiency.

Abstract: In order to solve the problem of high voltage system which caused by an excess of system reactive power during the systems valleyload period,this paper described the methods of leading phase operation of generator to adjust the system voltage to the reasonable range, which is proved feasible and effective through the field test.

Abstract: The purpose of this research is to study the performance of axial fanof the porous thin plate. First, the area of the holes of the porous thin plate is changed to estimate the influence of the porous thin plate on the performance of the fan. This study is conducted by simulations and experiments to find out the factors that will impact the performance of the fan. The results show that if the area rate of the porous thin plate and the fan is smaller, the difference of the simulations and experiments will become greater. When the area rate is more than 80%, the difference of the simulations and experiments will turn to be 10% lower. The results of experiments show that the fan size and fan thickness are the two main factors that produce the influence on the porous thin plate. If the thickness of the bar of the porous thin plate is 2.0mm, the performance of the fan loss would be the smallest. As to the assembly position of the porous thin plate, unilateral assembly makes the performance of the fan better than bilateral assembly. This is in relation to the area size of the porous thin plate. Fan tray is bilateral assembled. The performance of the fan tray can be improved in the following two ways. To use the thicker fan as the static pressure is greater, or to use the fan with lower air flow as the loss will be lesser.

Abstract: Both the voltage critical clearing time (VCCT) and the voltage transient transmission capacity (VTTC) are always used to evaluate the stability of the system transient voltage, and their relationships are studied and clarified in the paper. The stability of the transient voltage is mainly depended on the dynamic reactive characteristics of load and the transmission characteristics of voltage and power. Based on the analysis on the dynamic reactive characteristics of load and the transmission characteristics of a power transmission network, the characteristics of the VCCT and the VTTC are studied in this paper. Finally, a conclusion, i.e. the margin of the VCCT and the VTTC has a nonlinear characteristic, is obtained by simulations on the actual power grid. According to the conclusion, the voltage stability cannot be exactly reflected by the VCCT margin.

Abstract: Nowadays, the image azimuth determination is an important content of image processing. At present, the image azimuth is determined by solar azimuth angle achieved by look-up table, but the method is imprecise and inconvenient. To overcome such drawbacks, a novel determination method was proposed in the paper. First, the solar declination at imaging time is calculated. Then, the shadow deflection is determined by comparing the solar declination with the latitude of imaging place. Finally, the solar azimuth angle is calculated to determine the image azimuth based on the relation between shadow feature and solar azimuth angle. The theoretical analysis shows that the proposed method is more effectual then traditional methods.

Abstract: A simulation method for fluid-structure interaction (FSI) in compressor blades was discussed to predict the aeroelastic stability of blades. Using the MFX, which is a Multi-Field Solver in ANSYS, the total force of computational fluid dynamics (CFD) have been interpolated to computational structural dynamics (CSD) grids, and then the vibration displacements of CSD nodes have been interpolated to CFD grids at the blade surface. In CFD analysis, the grid coordinates of the moveable region have been updated by multi-layer moving grid technique, and the finite volume method has been applied to calculate the Reynolds-averaged Navier-Stokes (RANS) equations closed by k-E turbulent model. For NASA Rotor 67, detect the displacement response of compressor blades at the design speed , and the aeroelastic stability of blades has been analyzed preliminarily. The study shows that the FSI procedure is feasible to predict the aeroelastic stability of compressor blades.

Abstract: In order to improve the performance of the diesel engine, the original engine fuel injection advance angle is optimized, and a new advance angle of fuel injection is proposed in this paper. By numerical calculation with simulation of software FIRE, the effect of different combustion chamber structures on the cylinder pressure, temperature, accumulated heat release and the parameters such as NOx mass fraction was analyzed. From the simulation results, the optimized fuel injection advance angle had greatly improved the diesel combustion and emission performance. Finally, via experimental verification, the engine with optimized fuel injection advance angle has better dynamic performance, as well as less emission than original machine.

Abstract: Using the phase shift of reflection coefficient of SH seismic wave at the interface of strata, we derived the lateral shift of total reflected SH-wave, drawn the curves of lateral shift. The results show that for glancing wave or angle of incidence being near the critical angle, the lateral shift are very large.angle of incidence the lateral shift is the same order of magnitude as the wavelength (period).

Abstract: The present paper provided a kind of numerical simulation method which was employed to guide the process of ultrasonic nondestructive testing and analyze the inspection results. The simulation concerning the propagation process of shear wave in the steel plate was carried out using the ANSYS, according to the mechanism of ultrasonic mode conversion. Then, the frequency, velocity and refraction angle were extracted from the time-domain date in order to verify the simulation. It is found that the result of simulation agrees well with the theoretical one, which shows that the present method is correct and reliable.