Ericsson cycle

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Thermodynamic cycles
Atkinson cycle Brayton/Joule cycle Carnot cycle Combined cycle Crower cycle Diesel cycle Ericsson cycle Hirn cycle Kalina cycle Lenoir Cycle Linde-Hampson cycle Miller cycle Mixed/Dual Cycle Otto cycle Porter/Brayton cycle Rankine cycle Scuderi cycle Stirling cycle Two-stroke cycle Wankel cycle
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The Ericsson Cycle is named after inventor John Ericsson. John Ericsson designed and built many unique heat engines based on various thermodynamic cycles. He is credited with inventing two unique heat engine cycles, and developing practical engines based on these cycles. His first cycle is very similar to what we now call the "Brayton Cycle". His second cycle we now call the "Ericsson Cycle".

Contents 1 Ericsson Cycle 2 Brayton Cycle 3 The Regenerator 4 History 5 References

[edit] Ericsson Cycle

The Ericsson engine, (see figure), is based on the Ericsson cycle, and is known as an "external combustion engine", because it is externally heated. To improve efficiency, the engine has a recuperator or regenerator between the compressor and the expander. The engine can be run open or closed cycle.

The Ericsson Cycle is often compared to the Stirling Cycle, since the engines based on these cycles are both external combustion engines with a regenerators. Theoretically, both of these cycles have so called ideal efficiency, which is the highest allowed by the Second law of thermodynamics. The most well known ideal cycle is the Carnot Cycle, although ironically, a real Carnot Engine is not known to have been invented.

The Ericsson Engine is comprised of an air compressor that pumps air into a tank. The heat loss from the tank essentially maintains a constant temperature, thus approximating isothermal compression. From the tank, the compressed air passes through the regenerator and picks-up heat on the way to the heated power cylinder. There the air is expanded at a constant temperature. Before the air is released as exhaust, it is passed back through the regenerator, thus heating the regenerator for the next cycle.

[edit] Brayton Cycle

The first cycle Ericsson developed, is now called the "Brayton Cycle", commonly applied to the rotary jet engines for airplanes.

[edit] The Regenerator

Ericsson coined the term "regenerator" for his invention; however, Rev. Robert Stirling had invented the same device, prior to Ericson, and called it a "recuperator", so the invention is credited to Stirling. Interestingly, the term "regenerator" is now the name given to the component in the Stirling Engine! Stirling's term "recuperator" now has a different meaning, used to refer to a counter-flow or counter-current heat exchanger for exhaust gases.

[edit] History

In 1791, before Ericsson, Barber proposed a similar engine, but it lacked a regenerator/recuperator. Ericsson invented and patented his first engine using the Brayton Cycle in 1833 (number 6409/1833 British). This was 18 years before Joule and 43 years before Brayton. Brayton engines were, for the most part, internal combustion versions of the Ericsson. The "Brayton Cycle" is now known as the gas turbine cycle, which differs from the original "Brayton Cycle" in the use of a turbine compressor and expander. The gas turbine cycle is used for all modern gas turbine and turbojet engines.

Ericsson eventually abandoned the open cycle in favor of the traditional closed Stirling cycle. Closing the cycle resulted in higher pressure working gas, thus increasing the engine's specific power.

The Ericsson Cycle Engine (The second of the two discussed here) was used to power a 2000 ton ship, The Caloric Ship Ericsson and the engine ran flawlessly for 73 hours. The combination engine produced about 300 horsepower. It had a combination of 4 dual-piston engines; the larger expansion piston/cylinder, at 4.267 meters or 14 feet in diameter, was perhaps the largest piston ever built. Rumor has it that tables were placed on top of those pistons and dinner was served and eaten, while the engine was running at full power. At 6.5 RPM the pressure was limited to 8 psi. The one sea trial was apparently perfectly successful; however, he never returned to that engine. No one knows why.

Ericsson designed and built a very great number of engines running on various cycles including steam, Stirling, Brayton, externally heated diesel air fluid cycle. He ran his engines on a great variety of fuels including coal and solar heat. Ericsson was a very brilliant and successful engineer and understood heat engine principals extensively.

Ericsson also introduced the twin-screw propeller for ship design, in the USS Princeton.

Cycle/Process	Compression	Heat Addition	Expansion	Heat Rejection
Ericsson (First, 1833)	adiabatic	isobaric	adiabatic	isobaric
Ericsson (Second, 1853)	isothermal	isobaric	isothermal	isobaric
Brayton (Turbine)	adiabatic	isobaric	adiabatic	isobaric

Compared to the Brayton cycle which uses adiabatic compression and expansion, the Ericsson cycle uses isothermal compression and expansion, thus producing more net work per stroke. Also the use of regeneration in the Ericsson cycle increases efficiency by reducing the required heat input. For futher comparisons of thermodynamic cycles, see Heat engine.

[edit] References

• Ericsson's patents. 1833 British and 1851 USA
• THE EVOLUTION OF THE HEAT ENGINE, by: IVO KOLIN Published Moriya Press, 1972 by Longman