英国论文代写：离心泵的工作原理
离心泵是一种利用离心力输送液体的泵，是由一种称为叶轮的高速旋转装置研制而成。离心泵的工作原理如图1所示。叶轮固定在由电动机驱动的泵轴上。吸入法兰与吸入管连接。液体通过底阀和吸入管被吸入泵中。在启动泵之前，泵箱内被泵满了液体。泵一开动，叶轮就由电动机驱动，以高速旋转。叶轮叶片间的液体随着叶轮高速运动。在离心力的作用下，液体被加速到叶轮外缘获得动能，进入泵的蜗壳，通过减慢液体的速度将动能转化为压力。液体以高压进入输送管道，在高压的作用下，液体可以被输送到其他地方。
当液体被移到叶轮的外缘后，叶轮中心形成真空。因此，液体罐上的大气压力大于泵壳内的压力。液体被连续地压入套管。只要叶轮处于工作状态，液体就可以不断地吸进和排出泵外。离心泵的两个独立特性决定了它的运行。一是泵头特性曲线。另一种是系统曲线(或管道阻力曲线)。图2为泵压头特性曲线和管道特性曲线。扬程特性是离心泵在一定转速下扬程与排量之间的关系，且扬程值的开度不变。如图2所示，低速率的增加会导致磁头下降。在阀门开度和泵速不变的情况下，流量主要取决于需水量。因此，水头特性反映了水头与需水量之间的关系。
英国论文代写：离心泵的工作原理
Centrifugal pump is a type of pump that transport liquid by centrifugal force which is developed by a high speed revolving device known as impeller. The operating principle of a centrifugal pump is shown as Figure 1 Centrifugal Pump Operating Principle. An impeller is fixed onto the pump shaft driven by a motor. A suction flange is connected with a suction pipe. The liquid is sucked into the pump through a foot valve and the suction pipe.Before starting the pump, there is full of liquid being pumped in the pump casing. As soon as the pump is operating, the impeller is driven by a motor to rotate at a high speed. The liquid between impeller blades moves with the impeller in high speed. Under the impact of the centrifugal force, the liquid is accelerated to the out rim of the impeller to gain kinetic energy and gets into the volute of the pump which converts kinetic energy into pressure by slowing down the speed of liquid. The liquid gets into the delivery pipe with a high pressure under the impact of which the liquid can be delivered to other place.
After the liquid is moved to the out rim of the impeller, a vacuum is formed in the center of the impeller. Therefore, the atmosphere pressure on the liquid tank is greater than the pressure inside the pump casing. The liquid is pressed into the casing continuously. As long as the impeller is operating, the liquid can be sucked into and discharged out of the pump continuously. Two independent characteristics define the operation of a centrifugal pump. One is the pump head characteristic curve. The other is system curve (or pipeline resistance curve). Figure 2 shows the pump head characteristic curve and the pipeline characteristic curve.Head characteristic is the relationship between the head and capacity of a centrifugal pump at a certain speed under the condition that the discharge value opening is unchanged. As shown in Figure 2, an increase in rate of low can lead to a head decrease. Under the condition that the valve opening and pump speed are unchanged, the flow of flow mainly depends on the water demand. Therefore, head characteristic reflects the relationship between the head and the flow rate of water demand.