一种特殊形状制件的成形工艺

对弹匣前口板这种特殊形状制件成形工艺进行了讨论,找到了一种具有较高材料利用率,较高生产效率及简便易行的成形方法.     

Numerical investigation of flow erosion and flow induced displacement of gas well relief line

High-pressure particle-laden gas flow should be discharged through relief line of gas well timely to ensure safe test and exploitation. Erosion and vibration usually take place on the bend in relief lines, bringing a potential safety hazard to field operation. The majority of this paper investigates the factors affecting the erosion of bend and displacement of relief line in the downstream of bend using the computational fluid dynamics (CFD) methodology. A three-dimensional elbow pipe is selected as computational domain in this investigation. The kinematics and trajectory of discrete solid particles and liquid droplets are described by discrete phase model (DPM) while the hydrodynamic characteristics of continuous phase are obtained based on Reynolds-Averaged-Navier-Stokes (RANS) equations. An empirical erosion model is employed to predict the erosion rate of bend, and a fluid–structure interaction (FSI) model is adopted to calculate the displacement of relief line. The effects of types of multiphase flow (such as gas–solid two-phase flow and gas–liquid–solid three-phase flow), inlet flow rate and pipe diameter on erosion and displacement are discussed. The results show that large displacement and severe erosion present with large inlet flow rate in minor diameter pipe. The increase in liquid droplet content has less effect on flow erosion than that by the same increase in sand particle content.     

High resolution numerical simulation of methane explosion in bend ducts

In this paper we developed a parallel code, adopting a fifth-order weighted essentially non-oscillatory (WENO) scheme with a third-order TVD Runge-Kutta time stepping method for the two-dimensional reactive Euler equations, to investigate the propagation process of methane explosion in bend ducts. In the simulations, an inverse Lax-Wendroff procedure is adopted to construct a high order boundary in order to treat the complex boundaries. The numerical results show that when the bend angle is 30° and 45°, it cannot inhibit the propagation of the detonation wave; while when the angle reaches 60° and 75°, the detonation wave finally attenuates to the shock wave. It indicates that the propagation of the detonation wave can be inhibited. Furthermore, the temperature and the pressure at the entrance of the bend are low. When the angle arrives at 90°, the detonation wave evolves into cellular detonation when it passes through the bend. When the angle is larger than 90°, the detonation wave dramatically attenuates at the diffracting point, and later some hot spots can be formed, which can ignite the combustible gas nearby. Thus the second explosion occurs and finally the detonation is formed. When the angle is larger than or equal to 90°, the temperature and the pressure at the entrance of the bend is too high that the rescue efforts in the methane explosion accidents will encounter great difficulties. Hence, the laneway with 60° and 75° bend can inhibit the propagation of the detonation wave, and the temperature and the pressure at the entrance of the bend is not too high as well. All the results above can provide an important basis for the design and optimization of the mine laneway.     

桥式起重机主梁下挠的矫正

介绍了桥式起重机主梁下挠的产生原因,对几种下挠矫正方法进行了对比,并详细叙述了1998年3月对2#桥式起重机主梁下挠矫正的过程,分析了通过矫正所取得的技术经济效果。     

Flame acceleration in pipes containing bends of different angles

Bend structures are common in process industries. These bends containing three typical angles (90°, obtuse angle and acute angle) are often incorporated into pipes or ducts at different positions. In our experiments, the effect of both the bend angle and bend position on flame acceleration was studied. Flame acceleration in a pipe bend can be divided into three stages. The flame speeds increased before the bend and increased again after decreasing for a short distance in the bend. Flame reversing decreased the flame speeds in the bend and led to additional turbulence, which enhanced flame acceleration after the bend. The flame acceleration in three different pipe bend angles had similar trends. The decreasing amplitude of the flame speed in the bend increased with a decrease in the bend angles. The flame speeds in the bend were ordered such that 52° <90° <145°. However, the maximum flame speeds in the pipe were in the opposite order. Additionally, both the flame speeds in the bends and the maximum flame speeds in the whole pipes increased as the bend’s position away from ignition point increased.