Editing Stirling engine (section)

=== Early hot air engines ===
[[Robert Stirling]] is considered one of the fathers of hot air engines, along with earlier innovators such as [[Guillaume Amontons]],<ref name="haeamontons-s01" /> who built the first working hot air engine in 1699.<ref>{{Cite web|url=http://hotairengines.org/primitive-air-engine/amontons-1699|title=Guillaume Amontons &#124; Hot Air Engines|website=hotairengines.org}}</ref>

Amontons was later followed by Sir [[George Cayley]].<ref name="haecayley1807-s01" /> This engine type was of those in which the fire is enclosed, and fed by air pumped in beneath the grate in sufficient quantity to maintain combustion, while by far the largest portion of the air enters above the fire, to be heated and expanded; the whole, together with the products of combustion, then acts on the piston, and passes through the working cylinder; and the operation being one of simple mixture only, no heating surface of metal is required, the air to be heated being brought into immediate contact with the fire.{{citation needed|date=July 2020}}

Stirling came up with a first air engine in 1816.<ref name="haestirling1816-s01" /> The principle of the Stirling Air Engine differs from that of Sir [[George Cayley]] (1807), in which the air is forced through the furnace and exhausted, whereas in Stirling's engine the air works in a closed circuit. The inventor devoted most of his attention to that.{{citation needed|date=July 2020}}

A {{convert|2|hp|adj=on}} engine, built in 1818 for pumping water at an Ayrshire quarry, continued to work for some time until a careless attendant allowed the heater to overheat. This experiment proved to the inventor that, owing to the low working pressure obtainable, the engine could only be adapted to low power for which there was, at that time, no demand.{{citation needed|date=July 2020}}

The Stirling 1816 patent<ref name="haestirling1816-s02" /> was also about an "[[economizer|economiser]]," which is the predecessor of the regenerator. In this patent (# 4081) he describes the "economiser" technology and several applications where such technology can be used. Out of them came a new arrangement for a hot air engine.{{citation needed|date=July 2020}}

With his brother James, Stirling patented a second hot air engine in 1827.<ref name="haestirling1827-s01" /> They inverted the design so that the hot ends of the displacers were underneath the machinery, and they added a compressed air pump so the air within could be pressurised to around {{convert|20|atm}}.{{citation needed|date=July 2020}}

The Stirling brothers were followed shortly after (1828) by Parkinson & Crossley<ref name="haeparkinson&amp;crossley" /> and Arnott<ref name="haearnott-s01" /> in 1829.{{citation needed|date=July 2020}}

These precursors, including Ericsson,<ref name="haeericsson" /> have brought to the world the hot air engine technology and its enormous advantages over the steam engine.{{citation needed|date=August 2023}} Each came with his own specific technology, and although the Stirling engine and the Parkinson & Crossley engines were quite similar, Robert Stirling distinguished himself by inventing the regenerator.{{citation needed|date=July 2020}}

Parkinson and Crossley introduced the principle of using air of greater density than that of the atmosphere and so obtained an engine of greater power in the same compass. James Stirling followed this same idea when he built the famous Dundee engine.<ref name="haestirling1842" />

The Stirling patent of 1827 was the base of the Stirling third patent of 1840.<ref name="haestirling1842patent-2" /> The changes from the 1827 patent were minor but essential, and this third patent led to the Dundee engine.<ref name="haestirling1842-2" />

James Stirling presented his engine to the Institution of Civil Engineers in 1845, <ref name="haestirling1842-S03" /> the first engine of this kind which, after various modifications, was efficiently constructed and heated, had a cylinder of {{convert|12|inch|cm|order=flip|abbr=off}} in diameter, with a length of stroke of {{convert|2|ft|cm|order=flip|round=5}}, and made 40 strokes or revolutions in a minute (40&nbsp;rpm). This engine moved all the machinery at the Dundee Foundry Company's works for eight or ten months, and was previously found capable of raising 320,000&nbsp;kg (700,000&nbsp;lbs) 60&nbsp;cm (2&nbsp;ft) in a minute, a power of approximately {{convert|21|hp|kW|order=flip|abbr=off}}.{{citation needed|date=July 2020}}
Finding this power insufficient for their works, the Dundee Foundry Company erected the second engine with a cylinder of {{convert|16|inch|cm|order=flip|abbr=off|round=5}} in diameter, a stroke of {{convert|4|ft|m|order=flip|abbr=off}}, and making 28 strokes in a minute. When this engine had been in continuous operation for over two years it had not only performed the work of the foundry in the most satisfactory manner but had been tested (by a friction brake on a third mover) to the extent of lifting nearly {{convert|687|t|lb|lk=on|abbr=off|sigfig=2}}, approximately {{convert|45|hp|kW|order=flip|abbr=off}}.{{citation needed|date=July 2020}}
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This gives a consumption of {{convert|2.7|lb|kg|abbr=off|order=flip}} per horse-power per hour; but when the engine was not fully burdened, the consumption was considerably under {{convert|2.5|lb|kg|abbr=off|order=flip}} per horse-power per hour. This performance was at the level of the best steam engines whose efficiency was about 10%. After James Stirling, such efficiency was possible only thanks to the use of the economiser (or regenerator).{{citation needed|date=July 2020}}
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