Development of centrifugal pump for electric vehicle battery thermal management system

Abstract

The demand for electric and hybrid vehicles is increasing day by day due to rapidly decreasing fossil energy sources and increasingly stringent emission regulations. Although electric vehicles are becoming more and more common, extending the vehicle's range and maintaining its performance throughout the range is still one of the biggest problems. One of the main reasons for this problem is the gradual decrease in battery performance and life due to the fact that the batteries are charged and discharged many times during the vehicle usage period. Heating that occurs in the battery cells along the life of the vehicle should be controlled by a suitable battery thermal management system (BTMS). Thanks to the cooling performance provided by BTMS , the heat generated in the battery cells during vehicle cycles is transferred to outside. In this way, battery life and vehicle performance are improved. In addition to the heating effect, cold environmental conditions have a critical importance in terms of battery cell life and vehicle performance. BTMS should not only prevent the battery from overheating during vehicle use, but also warm the battery to the optimum temperature at low temperatures. Under the 50° C degree temperature is required for battery life and it should be kept between 25-40° C temperature in operation cycle. BTSM has five main category which are air cooling, liquid cooling-heating, direct refrigerant cooling-heating, phase change material cooling-heating and thermo-electric cooling-heating. Among these five main topics, within the scope of this thesis, active liquid cooling was considered and a cooling pump was designed to provide enough coolant to thermal management system. In addition, in electric vehicles, there may be more than one coolant pump in different cooling lines inside the vehicle for the purpose of cooling the electronic components, electric motor and inverter. In order to design a cooling pump with high efficiency at the required flow rate and pressure that will meet the cooling needs of electric vehicles, each blade parameter that affecting the efficiency of the pump is handled separately and evaluated within the scope of the study. In the first place, a base pump was designed with turbomachinery design program. By performing computational fluid dynamics analysis of the designed base pump, pump efficiency and performance values were obtained. In the next steps of study, design parameters that affect pump performance and efficiency, such as blade wrap angle, cutwater diameter and surface roughness were investigated. After the numerical simulations, each blade parameter value that provides the highest efficiency was determined for the design point and these parameters were used during the new impeller geometry, which was desired to have an efficiency value above the base pump. In this context, we can examine the study in five main sections. In the first part, centrifugal pump fundamentals such as head, flow, efficiency and specific speed were explained.