| Electric drive mining trucks,which are of heavy loads and high efficiencies,are widely used for off-road applications such as large-scale open-pit metal mines,coal mines,and water conservancy constructions.Unlike on-road trucks,off-road mining trucks usually work with fixed routes and in the mode of full-load uphill and no-load downhill along a high slope.The recoverable potential energy accounts for more than one-third of the uphill driving work.If this part of the energy can be recovered and reused,the vehicle fuel consumption and CO2 emission can be significantly reduced.As most of China's large open-pit mines are located in cold areas,the low temperature will aggravate the degradation mechanism of the batteries,resulting in the high cost of the mining dump truck with a battery energy storage system.Therefore,it is necessary to develop a new energy storage system with large capacity,high power,high efficiency,and low-temperature resistance.This paper takes the high-capacity composite pressure energy storage systems as the research objects,analyzes the influence of layouts on the performance of energy storage systems,and puts forward the method of using the oil-circulating hydro-pneumatic energy storage system to recover the downhill potential energy of mining trucks through layout comparison study;The thermal process model of circulating hydro-pneumatic energy storage system is established,its thermal effect mechanism is explored,and an effective coupling heat dissipation method with low energy consumption is proposed;Then,the multi-objective nested optimization method based on the adaptive hybrid surrogate model is used to obtain the optimal structure of circulating hydro-pneumatic energy storage system under the corresponding optimal energy management strategy with less computation cost;Finally,through the real vehicle test of the electric mining truck and the bench test of its composite powertrain,it is verified that the optimal structure and energy management strategy of the system can effectively reduce the fuel consumption and CO2 emission of the mining truck.Firstly,based on the hydraulic and compressed air energy storage systems,four basic hydro-pneumatic energy storage layouts are established:open volume layout,open mass layout,closed volume layout,and closed mass layout.Taking energy density and minimum specific power as the evaluation indicators,the energy and power characteristics of four basic layouts are analyzed,and their vehicle applicability is evaluated.According to the demand for braking energy recovery and energy storage of mining trucks in cold areas,the circulating hydro-pneumatic energy storage system model is established.The analysis results show that the system has good power and energy characteristics at the same time,which provides a feasible method for energy recovery and utilization of large mining trucks in cold environments.Aiming at the overheating problem of circulating hydro-pneumatic energy storage system during high-capacity and high-power energy recovery,the thermal process model of the energy storage system is established,the factors that lead to overheating are explored,and the coupling heat dissipation method is proposed.By combining the surplus cold potential in the downhill process and the surplus heat potential in the uphill process of the mining truck,the temperature potential coupling heat dissipation is realized in the way of low energy consumption.The calculation results show that the maximum temperature of hydraulic oil is reduced to 52.79?,and 28%of heat can be released through the cooling system,which effectively solves the overheating problem in the energy storage process of circulating hydro-pneumatic energy storage system.Aiming at the efficient energy recovery and utilization of the system in the uphill process of the mining truck,an energy management strategy of the circulating hydro-pneumatic energy storage system is proposed.Aiming at the minimum fuel consumption of the whole vehicle,the power distribution strategy of the composite powertrain is obtained based on the dynamic programming algorithm.Through the real vehicle test of the electric mining truck under its working conditions and the bench test of its composite powertrain,it is verified that the energy management strategy can effectively reduce the fuel consumption of the mining truck.Finally,to further improve the energy density of the circulating hydro-pneumatic energy storage system,the nested optimization method based on the adaptive hybrid surrogate model is adopted by using the Pareto optimal solution set.And combining the contradictory objectives of energy density and energy storage efficiency into the global normalized optimization objective,the optimal structure of the circulating hydro-pneumatic energy storage is obtained with less computation cost,which provides a basis for the design and application of the energy storage system for mining trucks. |
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