Abstract: The invention is a positive displacement heat engine; where the engine cycle comprises the steps of Ericsson (isothermal) compression, recuperative heat addition, Brayton (adiabatic) expansion, and recuperative heat removal; whose principle is heat addition to the cycle by an afterburner in which fuel is burned with the low pressure air working fluid exhausted by the expander. The resulting combustion gases are used in a counterflow heat exchange recuperator to continually heat the high pressure air compressed by the compressor. All moving parts are only exposed to clean air, and the expander valves can be operated at temperatures comparable to current internal combustion engines. Liquid, solid or gaseous fuels can be used and control of speed and power is simple, based on keeping engine temperatures constant. The low-pressure continuous combustion avoids fuel pressurization problems and allows high efficiency, low emission combustion processes.

Abstract: An annular flow concentric tube heat exchanger for heating two counter flowing fluid streams has been devised. Although capable of heating gases or liquids, the primary purpose of the invention is to function as an improved recuperator for recovering exhaust heat from a Brayton Cycle gas turbine engine, Ericsson Cycle engine or similar recuperated engine. The basic element of the recuperator is a concentric tube assembly that, in the preferred embodiment, is comprised of four concentric tubes that enclose three concentric annular flow passages. The low pressure exhaust flows through the inner and outer annular passages while the high pressure compressor exit air flows through the annular passage that is between the two low pressure passages. The high and low pressure flows are in opposite directions to achieve the high effectiveness that is only available with a counterflow heat exchanger.

Abstract: This invention is a heat engine operating on the afterburning Ericsson cycle whose principle is heat addition to the cycle by an afterburner in which fuel is burned with the low-pressure air working fluid exhausted by the expander. The resulting combustion gases are used in a countercurrent heat exchanger continually heating (1) the air expanding in the expander and (2) further upstream the high-pressure air (compressed by the compressor) in the regenerator. The ideal efficiency of this cycle is the Carnot cycle efficiency between the same top and bottom temperatures. Practical engines are more efficient than those in which heat addition takes place upstream of the expander. All moving parts are only exposed to clean air, and expander valves can be operated at temperatures comparable to current internal combustion engines. Liquid or gaseous fuels can be used and control of speed and power is simple, based on keeping engine temperatures constant.