A New Concept of Externally Heated Engine—Comparisons with the Stirling Engine

This paper presents a new concept of the externally heated valve (EHV) engine. Air can be used as a working medium in the closed cycle of this engine. Heat delivered to the working air can come from a combustion chamber or another heat generator of an arbitrary type. The engine construction and the thermodynamic cycle performed by it are original and entirely different from the well-known Stirling engine. The main disadvantage of the Stirling engine is its low power density, that is the low power obtained per litre of the engine cylinder volume. In the case of the engine presented here it is possible to achieve power density and efficiency similar to those typical of advanced internal combustion engines. Comparisons between the power of the Stirling engine and the power of the new engine have been performed for the same engine capacity, rotational frequency and maximum and minimum temperatures of the cycle. At the same minimum pressure of the working gas in both engines, the power of the EHV engine is several times higher than that of the Stirling engine, while, on the other hand, at the same maximum pressure of the working gas in both engines, the power of the EHV engine is 20 per cent higher than that of the Stirling engine power. The efficiencies of both engines do not differ significantly from each other.