# US 11,078,869 B2 · Condensing Stirling cycle heat engine

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- Number: US 11,078,869 B2
- Document ID: US11078869B2
- Status: Granted
- Kind: B2
- Application number: 15/260,353
- Filed: 2016-09-09
- Published: 2016-12-29
- Granted: 2021-08-03
- Earliest claimed: 2016-09-09
- Applicants: Matthew David Marko
- Inventors: Matthew David Marko
- Web page: https://patentgrep.com/patent/US11078869B2

## CPC

- F02G 1/043: the engine being operated by expansion and contraction of a mass of working gas which is heated and cooled in one of a plurality of constantly communicating expansible chambers, e.g. Stirling cycle type engines
- F02G 2243/30: having their pistons and displacers each in separate cylinders
- F02G 2250/00: Special cycles or special engines
- F02G: HOT GAS OR COMBUSTION-PRODUCT POSITIVE-DISPLACEMENT ENGINE PLANTS (steam engine plants, special vapour plants, plants operating on either hot gas or combustion-product gases together with other fluid F01K; gas-turbine plants F02C; jet-propulsion plants F02K); USE OF WASTE HEAT OF COMBUSTION ENGINES; NOT OTHERWISE PROVIDED FOR

## Abstract

The inventor claims a heat engine that follows a modification of the Stirling thermodynamic heat engine cycle; the monatomic working fluid is a saturated gas at the beginning of the isothermal compression stage, and ends up a mixed-phase fluid at the end of the compression. A proximate piston compresses and expands surrounding ideal gas helium, to function as a regeneration mechanism of this Stirling cycle and minimize the temperature difference during heat transfer. This cycle takes advantage of the temperature-dependent attractive intermolecular forces of the working fluid to assist in compressing the working fluid partially into a liquid, reducing the input compression work and increasing the overall heat engine efficiency.

## Claims

### Claim 1

A method of operating a mechanical heat engine according to an internally reversible, thermodynamic cycle, comprising:
providing saturated argon gas at 120 K in a piston-cylinder system at bottom dead center;
isothermally compressing the argon at 120 K in the piston cylinder system to top dead center;
isochorically heating the argon in the piston cylinder system fixed at top dead center to a supercritical gas at 166 K temperature;
isothermally expanding the gas in the piston cylinder system at 166 K back to bottom dead center; and
isochorically cooling the argon in the piston-cylinder system fixed at bottom dead center to a saturated gas at 120 K.

### Claim 2 (depends on 1)

The method of claim 1, wherein the mechanical heat engine is surrounded by a 1 kg mass of ideal gas helium disposed proximate the piston cylinder system, to serve as a heat transfer medium from a heat exchanger;
during the process of isothermal expansion, this will provide a heating source at 166 K;
followed by providing a heat sink at 120 K for cooling the process of isothermal compression.

### Claim 3 (depends on 1)

The mechanical heat engine method as described in claim 1 wherein the engine further comprises;
a bore of 20 cm, a stroke of 40 cm, a compression ratio of 6.82 and a steel cylinder wall of 5 mm thickness, and containing 0.7575 kg of argon.

### Claim 4 (depends on 3)

The mechanical heat engine method of claim 3, wherein the cyclic motion moves for 90°, and then stops;
the heat engine piston-cylinder system is allowed to move from bottom dead center to top dead center during isothermal compression;
the heat engine piston-cylinder system is held motionless during isochoric heating; the heat engine piston-cylinder system is allowed to move from top dead center to bottom dead center during isothermal expansion;
the heat engine piston-cylinder system is held motionless during isochoric cooling; the motion control is actuated by a mechanical obstruction operated by a cam shaft.

### Claim 5 (depends on 2)

The method of claim 2, wherein the ideal gas helium average temperature is increased and decreased between 120 K and 166 K by compressing the 1 kg helium with a second piston-cylinder system;
providing the ideal gas helium at a temperature of 120 K at bottom dead center; providing the ideal gas helium at a temperature of 166 K at top dead center;
and with a compression ratio of 2.375.

### Claim 6 (depends on 5)

The method of claim 5, wherein the cyclic motion moves for 90°, and then stops;
the heat engine piston-cylinder system is held motionless during isothermal compression; the heat engine piston-cylinder system is allowed to move from bottom dead center to top dead center during isochoric heating;
the heat engine piston-cylinder system is held motionless during isothermal expansion;
the heat engine piston-cylinder system is allowed to move from top dead center to bottom dead center during isochoric cooling; the motion control is actuated by a mechanical obstruction operated by a cam shaft.