In the days before the internal combustion (IC) engine, John Ericsson, inventor of the ship propeller, also developed a highly successful ‘hot air’ engine.
This engine produced power by externally heating one cylinder and cooling another and was based on a thermodynamic cycle that has become known as the Ericsson cycle.
The Ericsson cycle consists of four processes: a constant-temperature compression, a constant-pressure heat transfer to the working fluid; a constant-temperature expansion, and a constant-pressure heat transfer out of the system.
The need for reduced emissions and fuel consumption has renewed interest in these engines which unlike IC engines, have continuous and low-pressure combustion that can be made very clean burning. The Ericsson Cycle also apparently has the potential to achieve Carnot Cycle efficiency, the highest possible thermodynamic efficiency.
With its Afterburning Ericsson Cycle Engine, Californian company, Proe Power Systems, claims to have adapted Ericsson’s concept to meet 21st century environmental requirements. Ericsson’s design has been modified with the addition of an afterburning combustion process, modern stainless steel materials, and a key component called the Proe 90 recuperator.
This component recovers over 90% of an engine’s exhaust heat and returns it to the engine, thus reducing fuel consumption and lowering emissions.
Richard Proeschel, Owner of Proe Power Systems, claims that this Engine/recuperator combination has 2/3 the fuel consumption of a corresponding microturbine along with a similar reduction in emissions.
Proeschel, who supervised Rockwell International’s Space Shuttle Fuel Cell group during the Space Shuttle program, also states that the low fuel consumption and clean exhaust of the engine is even competitive with fuel cells when using gasoline, natural gas or other commonly available fuels.
The real significance of this invention is that all the components of the new engine can be manufactured in any machine shop capable of rebuilding an automobile engine. According to Proeschel, ‘The Proe 90 recuperator and Afterburning Ericsson Cycle Engine now give smaller manufacturers low-cost competition against the big guys and their expensive microturbines or fuel cells.’
A 5.25 horsepower prototype engine will shortly begin a comprehensive test program.