电动车跨临界CO_(2)热系统充注定量需求规律及非适充系统失稳特性

Charging Requirements and Unstable Characteristics of Automotive CO_(2) Thermal Management Systems

跨临界CO_(2)热系统是解决电动车“低温续航衰减”和“热系统工质温室效应强”主要问题的最佳技术之一,而电动车多变场景耦合跨临界循环复杂性,系统性能及运行稳定性强依赖于充注量。通过仿真研究了跨临界CO_(2)热系统在不同工况下的CO_(2)充注量定量需求变化规律。重点研究了环境温度、室内风量和室外风速这3个关键因素对不同模式下的系统制冷剂需求量的影响机理和定量表征;并探讨了在非适充场景下的系统动态特性。结果表明:热泵模式下,制冷剂需求下限随环境温度的升高、室内风量的降低和室外风速的增加而增大,其定量影响幅度为18.6%、6.16%和18.9%。制冷模式下,制冷剂需求下限则随环境温度的降低、室内风量的降低和室外风速的增加而增大,其定量影响幅度为7.03%、7.85%和2.27%。在非适充工况下,因非适充下的系统控制量与目标量作用关系发生潜在变化,导致系统出现失控,需要通过制冷剂分布调控缓解特殊工况的系统不稳定性。研究结果对于优化电动汽车空调系统储液器设计、提高其能效和舒适性具有重要参考价值。

Transcritical CO_(2) thermal systems have emerged as leading solutions to addressing challenges such as"range anxiety in winter"and pronounced greenhouse effects associated with the working fluid in electric vehicle thermal systems.Nevertheless,the intricate interplay of transcritical cycles in the varied scenarios of electric vehicles introduces complexity,with performance and operational stability intricately linked to the refrigerant charge.This study conducts simulations to investigate the variability in refrigerant charging requirements for transcritical CO_(2) thermal management systems under diverse operating conditions.We specifically examined the impact of three critical factors,namely ambient temperature,indoor airflow rate,and outdoor air velocity,on refrigerant requirements in different modes and their underlying mechanisms.In the heat pump mode,the demand for refrigerant charge increases with ambient temperatures and wind speed and decreases with cabinet air flow rate,with changes of 18.6%,18.9%,and 6.16%,respectively.In the cooling mode,the refrigerant charge requirement decreases with ambient temperatures and cabinet air flow rate and increases with outdoor wind speeds,with changes of 7.03%,7.85%,and 2.27%,respectively.In situations of nonoptimal charging,potential alterations in the interaction between system control variables and target variables contribute to system instability.This necessitates adjustments to refrigerant distribution to mitigate instability under specific operating conditions.The research outcomes hold substantial reference value for the optimization of electric vehicle air-conditioning accumulator designs,enhancement of energy efficiency,and improvement of overall thermal comfort.