Physical properties of a free-piston stirling engine with a reversible chemical reaction of dioxside nitrogen ↔ tetraoxside nitrogen in the working gas

Abstract

Simulation is used to study the properties of a free-piston Stirling engine in the isothermal approximation. The working substance is a chemically reacting gas mixture, in which mutual conversion of nitrogen dioxide and nitrogen tetroxide can occur in the reversible reaction 2NO2  N2O4. In the cooler, the exothermic reaction 2NO2 → N2O4 occurs, in the heater at a high temperature, the endothermic reaction N2O4 → 2NO2 occurs. Two cases are compared: 1) the above chemical reaction occurs in the working gas, and 2) the working gas is chemically inert. The engine efficiency eng is higher in the first case over the range of heater temperature change from 90 to 130C, and where eng increases from 0.345 to 0.383. In this case, eng turns out to be higher than that calculated using the Carnot formula with the same maximum and minimum temperatures. High efficiency is achieved thanks to the engine's ability to produce negative E. Schrödinger entropy.