跨临界CO_2引射制冷系统控制性能

Control Performance of Transcritical CO_2 Ejector Refrigeration System

本文建立了两种控制器(单通道最优控制器(SCOC)和多变量线性二次高斯控制器(LQG))以改善跨临界CO_2引射制冷系统的运行效率。首先建立了SCOC,通过在线调节喷嘴喉部面积,搜索系统最优的气冷器压力;其次针对SCOC作用下制冷量不可控的缺点,设计了LQG以实现系统制冷量可调。将两种控制器分别应用于实验系统中,结果表明:SCOC能够驱使系统不断接近系统的最优气冷器压力,给定工况下获得最大制热系数COPh为3.15,但导致系统制冷量的不可控。在LQG的作用下,气冷器压力、系统制冷量得到独立控制,显示了很好的参数跟随性,然而LQG无法保证系统的稳态运行效率。研究指出两种控制器各有优缺点,若实现满足系统负荷需求的同时保持系统最高的运行效率,需要设计结合两种算法特点的新型控制器。

Two controllers （single channel optimal controller （SCOC） and muhivariable linear quadratic Gaussian controller （LQG）） are built to improve the performance of a transcritical CO2 refrigeration cycle. The SCOC is first proposed to search the optimal gas cooler pressure online by adjusting the nozzle throat area. Considering the uncontrollable cooling capacity by the SCOC, the second controller LQG is designed to achieve the controllable cooling capacity, Experimental results show that the optimal gas cooler pressure is actually achieved by the SCOC with a maximal COPh of about 3.15 under the given operating conditions. However, with the SCOC, the cooling capacity is changed passively and uncontrollably. Moreover, experiments with LQG indicate that the cooling capacity and gas cooler pressure are accurately tracked independently. However, LQG cannot ensure the maximal operating performance when the system becomes steady. This work points out that the two controllers have their own advantages and disadvantages. More work needs to be done to combine the two algorithms into one. This will achieve maximal efficiency under the desired cooling capacity.