ANALYSIS OF STIRLING ENGINE CHARACTERISTICS BY SCHMIDT’S THEORY Ing. Jan MACHÁ ˇ CEK, Doctoral Degree Programme (2) Dept. of Electrical Power Engineering, FEEC, BUT e-mail: xmacha08@stud.feec.vutbr.cz Supervised by: Dr. Jan Gregor ABSTRACT This article deals with problems associated with its operating characteristics. The Stirling engine’s parameters depend on both theoretical analysis applying Schmidt’s The- ory, which mathematically describes the Stirling cycle, and on experimental measurements, which reveal its actual properties. The design and contraction of the Stirling engine should be based on results of theoretical calculations and applied physics as well as data derived from practical measurements. 1 ANALYSIS OF CHARACTERISTICS BY SCHMIDT’S THEORY In 1861, E. Schmidt carried out mathematical modeling and Stirling engine analysis. His theory is based on harmonic pistons and device nodes movements, ideal isothermal expansion and compression and ideal regeneration. This method is considerably closer to realization of Stirling engine, even though some idealization of process is included, than purely theoretical approach resulting from Stirling cycle. Schmidt’s theory assumptions: – Processes of regeneration are ideal; there is a perfect regeneration. – Instant value of system pressure is constant. – Conditions of the working gas is changed as an ideal gas. – Gas volume changes are sinusoidal. – Temperature of cylinder walls and piston is constant. – Temperature of used material/gas is constant. – Device revolves at the constant rate. – The expansion process and the compression process changes isothermal. – The regenerator gas temperature is an average of the expansion gas temperature and the compression gas temperature. – The amount of working gas is constant.