Highly efficient and small machines, water jet pumps transport fluid by means of the flow of another fluid. One prominent feature of these pumps is their capacity to use a centrifugal pump—akin to another pump but with a lower pressure—while preserving a better capacity. The flow rate may thus be raised by two or three times! Four main components make up a water jet pump: the motive nozzle, which creates a strong vacuum; the suction chamber, where the secondary flow is entrained; the mixing pipe, where the motive and suction streams are combined via momentum exchange, so transferring energy from the motive fluid to the sucked fluid; and the diffuser, which slows down the mixing flow to help pumping with minimum energy loss. Our study features from two valuable reference papers entitled

“ Investigation of Effects of Scale and Surface Roughness on Efficiency of Water Jet Pumps Using CFD “

&

“ COMPUTATIONAL AND EXPERIMENTAL STUDY ON THE WATER-JET PUMP PERFORMANCE UNDER DIFFERENT GEOMETRICAL AND OPERATIONAL PARAMETERS”.

Figure 1: longitude section of water jet pump, adopted from the reference paper

Simulation Process

Adopting a Axisymmetric method, the computational cost decrese by more that 50%. This assumption is taken due to symmetrical design of water jet pumps. Besided, the proper blocking in Design Modeler paves the way for generation of structured grid over the domain (30400cells). The flow of all fluids through the inlet and outlet of the pump are in the axial direction. In this type of water jet pump, the entrained rotational fluid enters symmetrically to the suction chamber and then the suction nozzle.

Figure 2: Structured grid for water jet pump

Post-processing

Based on the contours, the color range from blue (low velocity) to red (high velocity) shows the velocity curve, which goes along with the pressure distribution. Low speeds (blue) are seen at the entrance. As the flow enters the narrow nozzle, speeds quickly rise until they hit their peak (red) of up to 23.5 m/s. This fast-moving jet makes the low-pressure area that is necessary for the pump to work. The low pressure pulls in the secondary flow, which can be seen as a blue area around the fast jet. As the mixed flow goes through the mixing chamber, the speed slowly slows down, changing from red to green and then blue. This is because the pressure is rising again in the diffuser section. The simulation does a good job of showing how pressure and speed work together in the jet pump. It shows how pressure energy is changed into kinetic energy in the nozzle, how secondary flow is created, and how kinetic energy is changed back into pressure energy in the diffuser.