Investigation into an ultra-high efficiency liquid-piston compressor

以气体压缩和膨胀为目的的储能必须具有非常高的效率。在压缩空气储能的情况下，存储周期的往返效率被限制在c乘以e。如果压缩机和膨胀机的效率都是90%，那么往返效率肯定会低于81%。对于涉及泵送热量的储能，往返效率对压缩和膨胀过程中的损失更为敏感。通常用于抽热应用，“热”与“冷”温度的比例为2.5（即5/2）。在这种情况下，每3J的净火能传入存储器，5J的功在压缩机中完成，2J的功从膨胀机中回收。反之，从存储中回收能量时，从膨胀机中回收5J的功，而将2J的功输入压缩机。总的来说，对于像这样的抽水蓄能系统，如果机械效率为99%（即损耗为1%），则充电时的损耗为2.333%，放电时的损耗也为2.333%，因此总往返损耗约为4.666%。本项目将探索开发一种利用液体活塞技术的超高效率压缩机。现有设计中存在的最重要的损耗机制将被确定，并提出修改后的设计，以保留原设计的吸引力，但实现更高的性能。损失的来源包括：(a)气体和压缩机部件之间的热传递，(b)阀门和管道上的压降，(c)机器内部的热传递，(d)机器置换部分的摩擦损失，(e)通过置换活塞和压缩机不同体室之间的漏油损失，以及(f)与油运动有关的粘性损失。

Gas compression and expansion for the purposes of energy storage must necessarily be very high efficiency. In the case of compressed air energy storage, the round-trip efficiency of the storage cycle is limited to c times e. If both compression and expansion machines had efficiencies of 90%, then the round-trip efficiency would definitely be below 81%. For energy storage involving pumped heat, the round-trip efficiency is much more sensitive to losses in the compression and expansion processes. Typically for pumped-heat applications, the ratio of "hot" to "cold" temperatures is 2.5 (i.e. 5/2). In that case, for every 3J of net exergy passed into storage 5J of work is done in a compressor and 2J of work is recovered from an expander. The converse is true during energy recovery from storage: 5J of work is recovered from the expander while 2J of work is put into the compressor. Overall, for a pumped thermal energy storage system like this, if the machinery is 99% efficient (i.e. losses are 1%), then the losses during charging are 2.333% and losses during discharging are also 2.333% so total round-trip losses are around 4.666%. This project will explore the development of an ultra-high efficiency compressor exploiting liquid-piston technology. The most important loss mechanisms present in an existing design will be identified and a revised design will be put forward that retains the attractions of the original design but achieves higher performance. Sources of loss include: (a) heat transfer between gas and compressor components, (b) pressure-drops across valves and pipe-work, (c) heat transfer within the body of the machine itself, (d) friction losses in the displacer part of the machine, (e) oil leakage losses past the pistons of the displacer and between the different body chambers of the compressor and (f) viscous losses associated with oil motions.