page_title: Stirling engine
section_title: Lubricants and friction
hierarchical_section_title: Stirling engine / Theory / Lubricants and friction
caption_attribution_description: English: Copied from en.wiki Original caption is as follows: A Stirling engine and induction generator set. This is a 55 kW (electrical) generator set for combined heat and power applications. The total enclosure length is about 2.5 metres, and this assembly has a mass of about 1300 kg. At the right side is the combustion chamber and heat exchanger. The four-cylinder regenerative Stirling engine is adjacent to the combustor, with the swash-plate drive housing obscured by the center post of the enclosure. At the left of the picture is a 55 kW induction motor used as a generator and to start the Stirling engine. Below the induction generator terminal box (black cable going to left) is an electrolyzer used to replenish the hydrogen gas working fluid of the engine. To the right of the electrolyzer is a small blower to force combustion air into the burner assembly. The blue hoses circulate cooling water through the cool-side heat exchanger - a hose connection point for cooling water is just above at the right end of the induction generator. The Stirling engine/generator set shown here is made by STM Power Inc. and is intended for auxiliary power and heat production at large farms, or for plants that produce waste flammable oils. This engine can also be adapted to run on low-heat-value landfill gas or biofuel digester gas. A photo I (user Wtshymanski) took and that I release to the public domain.
context_page_description: A Stirling engine is a heat engine that is operated by a cyclic compression and expansion of air or other gas at different temperatures, resulting in a net conversion of heat energy to mechanical work. More specifically, the Stirling engine is a closed-cycle regenerative heat engine with a permanent gaseous working fluid. Closed-cycle, in this context, means a thermodynamic system in which the working fluid is permanently contained within the system, and regenerative describes the use of a specific type of internal heat exchanger and thermal store, known as the regenerator. Strictly speaking, the inclusion of the regenerator is what differentiates a Stirling engine from other closed cycle hot air engines.
  Originally conceived in 1816 as an industrial prime mover to rival the steam engine, its practical use was largely confined to low-power domestic applications for over a century.
context_section_description: At high temperatures and pressures, the oxygen in air-pressurized crankcases, or in the working gas of hot air engines, can combine with the engine's lubricating oil and explode. At least one person has died in such an explosion.
  Lubricants can also clog heat exchangers, especially the regenerator. For these reasons, designers prefer non-lubricated, low-coefficient of friction materials (such as rulon or graphite), with low normal forces on the moving parts, especially for sliding seals. Some designs avoid sliding surfaces altogether by using diaphragms for sealed pistons. These are some of the factors that allow Stirling engines to have lower maintenance requirements and longer life than internal-combustion engines.
caption: A modern Stirling engine and generator set with 55 kW electrical output, for combined heat and power applications.
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