5空气要求讲义.docVIP

5 Air Requirements空气要求 1 INTRODUCTIONThe selection of a fan, blower or compressor is probably one of the most important decisions to be made in the design and specification of a pneumatic conveying system. It is often the largest single item of capital expenditure and the potential conveying capacity of the plant is dependent upon the correct choice being made. The output capability of the air mover is a major consideration in selection. The rating of the fan, blower or compressor is expressed in terms of the supply pressure required and the volumetric flow rate. Any error in this specification will result in a system that is either over-rated or is not capable of achieving the desired material flow rate [1].通风机，鼓风机或压缩机的选择，可能是气力输送系统的设计和明细中所做的最重要的决定之一。它往往是投资中最大的单项目，而且装置的潜在输送能力取决于所做的正确的选择。 空气动力机械的输出能力是选择中的一个重要考虑。通风机，鼓风机或压缩机的等级体现在所要求的供气压力和体积流量上。规格选择的任何错误，将导致系统或者超过额定量，或着不能够实现所期望的物料流量[ 1 ] 。 For an existing pneumatic conveying system it is often necessary to check the performance, particularly if operating problems are encountered, or changes in material or conveying distance need to be considered. Here it is the conveying line inlet air velocity that is important. Since the determination of conveying line inlet air velocity and the specification of air requirements is so important for the successful operation of pneumatic conveying systems, all the appropriate models are derived and presented for reference purposes. In addition to the influence of pressure, temperature and pipeline bore, which are the primary variables, humidity is also considered. 对于现有的气力输送系统往往必要校核其性能，特别是遇到操作问题，需要考虑改变物料或输送距离。这里重要的是输送线进气速度。由于输送线入口空气流速的确定及空气的规格要求气力输送系统的成功操作非常重要，对所有的适当的模型进行推演，并提出以供参考。除了压力的影响外， 温度和管道口径是主要的变量，湿度还要加以考虑。 1.1 Supply Pressure供气压力 The delivery pressure, or vacuum, required depends essentially upon the working pressure drop needed over the length of the conveying pipeline. The pressure drop across the gas-solids separation device can usually be neglected, but if a blow tank is us