Keywords: finite size thermodynamics, finite speed thermodynamics, speed of revolution, Stirling engine cycle, exergy, engineering constraints, analytical optimisation
An engineer–oriented optimisation of Stirling engine cycle with finite–size finite–speed of revolution thermodynamics
Finite–time thermodynamics takes into account exo–irreversibilities which are not managed by reversible thermodynamics, especially reservoir–to–gas temperature gaps. In today's works, thermodynamicists use the working gas mass as the main imposed parameter. In this paper, the study of the Stirling engine cycle is carried out with a motorist–oriented viewpoint: instead of the working gas mass, the reference parameters are those linked to engineering constraints; they are the maximum pressure, the maximum volume, the extreme temperatures and the overall thermal conductance; the adjustable parameters are the volumetric compression ratio, the hot–to–cold conductance ratio and the regenerator efficiency. Analytical normalised expressions of the operating characteristics of the engine, such as power, work, efficiency, speed and their optima are set up. Classical results of analytical optimisation are found back and new ones are established, leading to new conclusions. Some dimensionless and dimensional numbers are put into evidence.