분사펌프의 구동관로의 위치변화에 따른 유동특성 연구

Abstract

A jet pump is a fluid carrying device which spouts fluid of high pressure from a driving engine pipe and absorbs fluid of high pressure whose pressure is increased through exchange of momentum with surrounding gas of low pressure. It is applied for various types of industries such as heat engines, water power and thermal power plants, ducts for air conditioning, chemical and petroleum chemistry, food and environment industry in that it provides smooth operation in absorbing solid as well as fluid and gas. Vapor-vapor jet pump are widely used for absorption, mixing and dehydration in industrial fields and fluid-gas jet pumps have been considered most important for air conditioners to control a variety of harmful gases and to create pleasant environment of structures. Jet pumps can be easily constructed and installed irregardless of size of systems, can be easily used at the places involved in fluid and have little need of maintenance, and its expense is reasonable. This study is to identify floating characteristics of jet pumps, mean velocity, distribution of total pressure through CFD analysis. For the purpose, it changed the ends of driving duct with diameter ratio of 1 : 3.21, 1 : 2.25, and 1 : 1.86, found optimal points of driving engine ducts in each diameter ratio and conducted the analysis through PIV experiment. The results are presented as follows: (1). When the ends of each driving duct with diameter ratios of 1:3.21, 1:2.25 and 1:1.86 were placed in 1.333, 1.213 and 1.133, the largest effect of absorption was found, but the effect was not related to velocity change. (2). For velocity distribution of the main duct when driving duct were placed at optimal points according to diameter ratios, more than 33% the velocity at the wall increased (3). This study analysed PIV at optimal points according to diameter ratios of jet pumps and found that CFD flowing is consistent with PIV flowing. As the diameter of driving duct increased, a large eddy flow occurred, which caused decreased efficiency. It was found that the efficiency decreased as the size of driving duct increased in the results of CFD. Through this result, we found that the results of CFD were consistent with those of actual PIV test. (4). For increased efficiency of flow quantity of jet pumps, we have to find optimal points of driving duct at each diameter ratio. Atoptimal points, flow quantity efficiency as well as absorption effect was the highest. (5). When the end of driving duct was located in the center of the absorption duct, average 11% of efficiency decreased compared to the case that it was placed at the optimal point. When it was extended over optimal point, mean 23% of efficiency deceased. As the driving duct was longer, flow quantity efficiency was lower, and when the end of driving duct was placed at optimal point, flow quantity efficiency was the best. (6) When a diameter condition of driving duct was 1 : 3.21, the efficiency was the best, and as inlet velocity was faster, the efficiency increased. The flow quantity efficiency of 1 : 3.21 was 32% higher than that of 1 : 2.25, and the flow uantity efficiency of 1 : 3.21 was 46% higher than that of. As the ratio of the expanded duct to driving duct increased, the efficiency decreased.