Hydraulic Machines Essay Example | Topics and Well Written Essays - 1000 words - 1

Hydraulic Machines - Essay Example The former types of machines are called turbines and the latter, pumps. A combination of both pump and turbine is used in fluid couplings and torque converters for the transmission of power smoothly through a fluid medium. The analysis of impact of fluid jets on vanes is typically involved in the design of an efficient turbo-machine. When a vane moves away from the jet as shown in the below figure, the mass flow arriving at the vane is considerably reduced because some of the mass leaving the nozzle results in a growing column of fluid between the jet and the nozzle. This is what happens in turbines where the vanes are part of a revolving wheel. We need only consider the simplest case of movement in a straight line in the direction of the jet. Assuming the velocity of the jet is v and the velocity of the vane is u as shown above, the velocity of the fluid arriving would be v - u. This is the relative velocity, that is, relative to the plate. The mass flow rate arriving on the plate is then calculated as The true velocity of the fluid leaving the nozzle is v1 and velocity of the vane is u. The fluid arrives on the vane with relative velocity v1-u as before, which is shown in the above figure. This is a relative velocity with respect to someone moving with the vane. In the absence of friction, the velocity of the fluid over the surface of the vane will be v1-u at all points. At the tip where the fluid leaves the vane, it will have two velocities. The fluid will be flowing at v1-u over the vane but also at velocity u in the forward direction. The true velocity v2 at the exit as shown above must be the vector sum of these two. The vector diagram is illustrated below: If only the force acting on the vane in the direction of movement is required, then the horizontal component of v2 must be determined. Because this direction is the direction in which the vane is whirling around the centre of the wheel, it is