Performance improvement of underwater jet pump by optimal arrangement of primary jet stream

Abstract

In recent years, as a new application technology of jet pumps, attention is paid to a method of installing a jet pump at the bottom of a contaminated lake or a river to remove pollutants and promote purification. The large flow rate that can be generated by the jet pump supplies dissolved oxygen in the water to the stagnant area. As a result, underwater bacteria are activated, and contaminants are decomposed and removed by the activated bacteria. In this research, we aimed to pursue the structure and operating characteristics of a jet pump that consumes less power and can generate jet flow with larger flow rate. The jet pump used in this experiment consists of one or more primary nozzles and a secondary nozzle for flow amplification and is installed at the bottom of a large tank. By measuring the flow velocity distribution blown out from the secondary nozzle, the flow rate flowing out from the secondary nozzle is obtained, and the flow rate amplification factor which is the ratio with the injection flow rate of the primary nozzle can be calculated. In this research, the performance difference between a system consisting of one primary nozzle and a system consisting of two or more primary nozzles was experimentally investigated. As a result, knowledge on the optimum supply system of the primary jet was obtained.