Investigation on Thermal Characteristics of the Oil-Circulating Hydraulic Energy Storage System for Hybrid Mining Trucks

Abstract

The improved hydraulic energy storage system (IHESS) is a novel compact hydraulic ESS with only 10% of oil and 64.78% of installation space of the regular ones. However, its novel circulating structure and lightweight material result in poor heat dissipation. The thermodynamic and heat transfer model of IHESS with an oil-circulating layout is proposed. Based on the mining trucks’ dynamic model, thermal characteristics of IHESSs with different parameters under the actual and simplified working conditions are studied and the factors causing overheating are analyzed. Finally, a feasible thermal design is put forward, and its efficiency is analyzed. The simulation shows that more accumulators and higher recovery power lead to higher system temperature and vice versa. Under the standard simplified working condition at 40°C ambient temperature, the highest oil temperature reached is 93.13°C. About 90% of the generated heat is converted into the internal energy of nitrogen and oil. On this basis, by adopting an energy-saving passive cooling system with a cooling power of 6.68 kW, the highest temperature of the oil drops to 52.79°C and 28% of the generated heat is released through the cooling system.