Study On The Exhaust Cooling Absorption System Of The Closed Cycle Diesel Engine

The closed cycle diesel system is used as main driving force in underwater power plants for it has many advantages such as little risk and low cost etc. And also the diesels' technology is mature. And the cooling of emissions and treatment of carbon dioxide are very important key technology.In order to improve the overall performance of the closed cycle diesel engine system, this paper starts to work for its research object is the exhaust cooling absorption system. Based on the simulation and calculation this paper designs the direct contact cooler and obtains the experimental verification. For the cross-flow rotating packed bed is used as the exhaust carbon dioxide absorption system this paper conducts the experimental study of its pressure drop and mass transfer characteristics and proposes the structure's improvement scheme in view of performance conditions, It also uses computational fluid dynamics software theory to analyze the feasibility of the scheme. The research contents are as follows:1. Using VOF multiphase flow model and ignoring the influence of wall heat and different concentrations of gas mixture on the cooler temperature field, this paper simulates and calculates the exhaust which is cooled via water by direct contact. The experimental value is lower than the calculated value. The cooling effect is a little more ideal and can satisfy the requirements of the closed cycle diesel engine system.2. Using experiment to study the varying relationship of pressure drop with the rotating speed and water flow and measure the varying relationship of carbon dioxide concentrations of gas inlet and outlet with the rotating speed and water flow in the cross-flow rotating packed bed. Then we can obtain the values of mass transfer efficiency by calculating. The experimental results show that the maximum mass transfer efficiency of this cross-flow rotating packed bed is 12%.3. This paper proposes an improvement scheme of the rotating packed bed's structure and simulates single-phase flow field and two-phase flow field of the axis-zigzag rotating packed bed. The resistance loss of gas phase is about 55Pa. The airflow rises in spiral shape along the "S" shaped channel in rotating packed bed on the whole. The theoretical analyses show that the best area for mass transfer is countercurrent contact zone. This paper chooses Eulerian multiphase flow model to simulate gas-liquid two phase flow of the rotating packed bed and obtains different sections' fluid dynamics distribution's situation such as pressure contours, velocity vector contours and phase holdup distribution contours, etc. The simulation result is a little more reasonable and it can truly reflect the distribution's situation of two-phase flow field in the rotating packed bed.This paper can provide certain theoretical basis for the exhaust cooling absorption system's research of the closed cycle diesel engine system by using computational fluid dynamics software, simplifying model reasonably and conducting numerical simulation on heat transfer and mass transfer of gas-liquid two phase flow.