Direct Generation of Compressed Air from Waste Heat by Reciprocating Thermocompressors

压缩空气是最重要的技术能源之一，但也是最昂贵的技术能源之一，因为由于各种转换和传输损耗，从发电到消耗的效率通常仅为5%左右。因此，从经济和环境的角度来看，通过至少部分地用其他技术替代由电驱动压缩机产生的传统压缩空气，可以实现相当大的节省，所述其他技术的特征在于减少的或可能为零的初级能量消耗。- 由热流-优选地由废热-通过级联的SO-直接产生压缩空气，所谓的振荡热压缩机是这个项目的目标。热压缩的基本原理在很长一段时间内从斯特林循环中已知，并且早在1935年就在美国获得了“布什热压缩机”的专利，但到目前为止仅针对少数低压利基应用进行了探索。其有利地通过双作用置换器活塞来实现，所述双作用置换器活塞通过周期性地移动过程气体（在这种情况下是待压缩的空气）在恒定的总循环体积下经由回热器（并且因此在理想情况下可逆地）在“热”和“冷”气缸体积之间来回移动而引起压力波动。因此，通过止回阀，可以直接且非常有效地产生压缩空气，而无需通过电能或机械能，利用可用的热流。为了使这种系统达到技术上可用的压力水平，需要将级联中的几个压缩机级串联连接。这可以通过组合相同设计和尺寸的单元来经济地实现，尽管空气的状态变量在入口和出口压力之间变化很大。为了进一步简化，使用了所谓的过驱动自由活塞，这种活塞是自驱动的，不需要任何外部的辅助能源。在项目的第一阶段，开发了一种方法，利用分析和数值模型来模拟和设计这种叶栅的一个单级。为此，迄今为止主要为封闭回热式气体循环开发的理论原理和模拟工具被转移到迄今为止几乎没有研究的开放阀控循环领域。对为此目的而建造的一个试验性可变热力压气机级进行的初步初步试验构成了第一项目阶段的结束，拟议的第二项目阶段的目的是根据这些初步试验的结果实现多级级联。该级联计划加热和冷却的温度控制传热介质回路，以调查和优化预期的自我调节性能在这样的级联机的操作过程中，并将它们与分析考虑和模拟的结果进行比较。

Compressed air is one of the most important, but also one of the most expensive technical energy sources, as the efficiency from generation to consumption is typically only about 5% due to various conversion and transmission losses. Therefore, considerable savings from both an economic and an environmental point of view can be achieved by substituting conventional compressed air generation by electrically driven compressors at least partially by other techniques, which feature a reduced or possibly zero primary energy consumption.For this purpose, the direct generation of compressed air from heat flows - preferably from waste heat - by a cascade of so-called oscillating thermocompressors is the objective of this project. The underlying principle of thermal compression has in principle been known from the Stirling cycle for a long time and was patented as "Bush Thermocompressor” in the USA as early as 1935, but has so far only been explored for a few low-pressure niche applications. It is advantageously implemented by double-acting displacer pistons that cause pressure fluctuations by periodically moving the process gas - in this case the air to be compressed - back and forth between a "hot" and a "cold" cylinder volume via a regenerator (and thus reversibly in the ideal case) at a constant overall cycle volume. By means of check valves, compressed air can thus be generated directly and very efficiently without any detours via electrical or mechanical energy, utilizing an available heat flow. In order to achieve technically usable pressure levels with such a system, a series connection of several compressor stages in a cascade is necessary. This can be achieved cost-effectively by combining units of identical design and size, despite the fact that the state variables of the air vary significantly between the inlet and the outlet pressure. As a further simplification, so-called overdriven free pistons are used, which are self-actuated without any external supply of auxiliary energy.In a first project phase, a method was developed to simulate and design one single stage of such a cascade using both analytical and numerical models. For this purpose, the theoretical principles and simulation tools mainly developed for closed regenerative gas cycles so far were transferred to this so far scarcely investigated field of open, valve-controlled cycles. Initial preliminary tests with a single, experimentally variable thermal compressor stage constructed for this purpose constitute the end of the first project phase.The aim of the proposed second project phase is to realize a cascade of several stages based on the findings of these preliminary tests. This cascade is planned to be heated and cooled with temperature-controlled heat transfer medium circuits in order to investigate and optimize the expected self-regulating properties during operation of such a cascaded machine and to compare them with the results of analytical considerations and simulations.