120kW级燃料电池可变喉口引射器的设计及特性

A Variable-nozzle Ejector for a 120kW PEMFC Stack: Design and Performance

摘要:

引射器是质子交换膜燃料电池氢气循环系统中的关键部件，依靠超音速流动的射流工质实现阳极排气的再循环。传统的固定结构引射器通常针对电堆额定工况设计，工作在非设计工况时性能较差；而可变喉口引射器可以动态地改变其喉口大小，有效扩大其工作范围。基于Sokolov设计理论，搭建了引射器的一维模型并探究了其工作特性，在此基础上提出了一种可变喉口引射器的设计方法。研究结果表明，引射器的工作特性主要受其操作压力、喉口直径和混合室直径影响；通过缩小喉口、提高工作流体压力可以使工作喷嘴保持临界状态，这对大负载下的引射性能影响较小，但能够有效提高电堆小负载下的引射比，并使引射器的工作范围向小负载扩展。

Abstract:

The ejector acts as a critical component in the hydrogen recirculation system for proton exchange membrane fuel cells which realizes anode exhaust recirculation via a supersonic jet. Traditional fixed-geometry ejectors are commonly designed according to the stack’s rated condition and achieve poor performance in off-design conditions. In contrast， variable-nozzle ejectors can adjust the throat’s opening dynamically and enlarge the operating range. Based on Sokolov’s theory， a one-dimensional model for the ejector was built to study its working characteristics， and a design methodology for the variable-nozzle ejector was later proposed. The results show that the ejector’s performance is mainly affected by its operating pressure， the throat diameter， and the mixing chamber’s diameter. By shrinking the throat and raising primary pressure， the working nozzle can be kept critical， which has little effect on entraining performance under high stack load. However， under low stack load， the entrainment ratio can be significantly improved， and the operating range expands toward low stack load.