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Air-cooled engine

March 17, 2024

Main article: Internal combustion engine cooling

Air-cooled engines rely on the circulation of air directly over heat dissipation fins or hot areas of the engine to cool them in order to keep the engine within operating temperatures. Air-cooled designs are far simpler than their liquid-cooled counterparts, which require a separate radiator, coolant reservoir, piping and pumps.

Air-cooled engines are widely seen in applications where weight or simplicity is the primary goal. Their simplicity makes them suited for uses in small applications like chainsaws and lawn mowers, as well as small generators and similar roles. These qualities also make them highly suitable for aviation use, where they are widely used in general aviation aircraft and as auxiliary power units on larger aircraft. Their simplicity, in particular, also makes them common on motorcycles.

A cylinder from an air-cooled aviation engine, a Continental C85. Notice the rows of fins on both the steel cylinder barrel and the aluminum cylinder head. The fins provide additional surface area for air to pass over the cylinder and absorb heat.

Introduction edit

Most modern internal combustion engines are cooled by a closed circuit carrying liquid coolant through channels in the engine block and cylinder head. A fluid in these channels absorbs heat and then flows to a heat exchanger or radiator where the coolant releases heat into the air (or raw water, in the case of marine engines). Thus, while they are not ultimately cooled by the liquid, as the heat is exchanged with some other fluid like air, because of the liquid-coolant circuit they are known as liquid-cooled.

In contrast, heat generated by an air-cooled engine is released directly into the air. Typically this is facilitated with metal fins covering the outside of the Cylinder Head and cylinders which increase the surface area that air can act on. Air may be force fed with the use of a fan and shroud to achieve efficient cooling with high volumes of air or simply by natural air flow with well designed and angled fins.

In all combustion engines, a great percentage of the heat generated, around 44%, escapes through the exhaust. Another 8% or so ends up in the oil, which itself has to be cooled in an oil cooler. This means less than half of the heat has to be removed through other systems. In an air-cooled engine, only about 12% of the heat flows out through the metal fins.[1] Air cooled engines usually run noisier, however it provides more simplicity which gives benefits when it comes to servicing and part replacement and is usually cheaper to be maintained.[2]

Applications edit

Road vehicles edit

 
Honda CB1100

Many motorcycles use air cooling for the sake of reducing weight and complexity. Few current production automobiles have air-cooled engines (such as Tatra 815), but historically it was common for many high-volume vehicles. The orientation of the engine cylinders is commonly found in either single-cylinder or coupled in groups of two, and cylinders are commonly oriented in a horizontal fashion as a Flat engine, while vertical Straight-four engine have been used. Examples of past air-cooled road vehicles, in roughly chronological order, include:

Aviation edit

During the 1920s and 30s there was a great debate in the aviation industry about the merits of air-cooled vs. liquid-cooled designs. At the beginning of this period, the liquid used for cooling was water at ambient pressure. The amount of heat carried away by a fluid is a function of its capacity and the difference in input and output temperatures. As the boiling point of water is reduced with lower pressure, and the water could not be efficiently pumped as steam, radiators had to have enough cooling power to account for the loss in cooling power as the aircraft climbed. The resulting radiators were quite large and caused a significant amount of aerodynamic drag.[4]

This placed the two designs roughly equal in terms of power to drag, but the air-cooled designs were almost always lighter and simpler. In 1921, the US Navy, largely due to the efforts of Commander Bruce G. Leighton, decided that the simplicity of the air-cooled design would result in less maintenance workload, which was paramount given the limited working area of aircraft carriers. Leighton's efforts led to the Navy underwriting air-cooled engine development at Pratt & Whitney and Wright Aeronautical.[4]

Most other groups, especially in Europe where aircraft performance was rapidly improving, were more concerned with the issue of drag. While air-cooled designs were common on light aircraft and trainers, as well as some transport aircraft and bombers, liquid-cooled designs remained much more common for fighters and high-performance bombers. The drag issue was upset by the 1929 introduction of the NACA cowl, which greatly reduced the drag of air-cooled engines in spite of their larger frontal area, and the drag related to cooling was at this point largely even.[4]

In the late 1920s into the 1930s, a number of European companies introduced cooling system that kept the water under pressure allowed it to reach much higher temperatures without boiling, carrying away more heat and thus reducing the volume of water required and the size of the radiator by as much as 30%. They could also eliminate the radiator entirely using evaporative cooling, allowing it to turn to steam and running the steam through tubes located just under the skin of the wings and fuselage, where the fast moving outside air condensed it back to water. While this concept was used on a number of record-setting aircraft in the late 1930s, it always proved impractical for production aircraft for a wide variety of reasons.[5]

In 1929, Curtiss began experiments replacing water with ethylene glycol in a Curtiss D-12 engine. Glycol could run up to 250 C and reduced the radiator size by 50% compared to water cooled designs. The experiments were extremely successful and by 1932 the company had switched all future designs to this coolant. At the time, Union Carbide held a monopoly on the industrial process to make glycol, so it was initially used only in the US, with Allison Engines picking it up soon after. It was not until the mid-1930s that Rolls-Royce adopted it as supplies improved, converting all of their engines to glycol. With the much smaller radiators and less fluid in the system, the weight and drag of these designs was well below contemporary air-cooled designs. On a weight basis, these liquid-cooled designs offered as much as 30% better performance.[6]

In the late- and post-war era, the high-performance field quickly moved to jet engines. This took away the primary market for late-model liquid-cooled engines. Those roles that remained with piston power were mostly slower designs and civilian aircraft. In these roles, the simplicity and reduction in servicing needs is far more important that drag, and from the end of the war on almost all piston aviation engines have been air-cooled, with few exceptions.[6]

As of 2020, most of the engines manufactured by Lycoming and Continental are used by major manufacturers of light aircraft Cirrus, Cessna and so on. Other engine manufactures using air-cooled engine technology are ULPower and Jabiru, more active in the Light-Sport Aircraft (LSA) and ultralight aircraft market. Rotax uses a combination of air-cooled cylinders and liquid-cooled cylinder heads.

Diesel engines edit

Some small diesel engines, e.g. those made by Deutz AG and Lister Petter are air-cooled. Probably the only big Euro 5 truck air-cooled engine (V8 320 kW power 2100 N·m torque one) is being produced by Tatra.

Stationary or portable engines edit

Stationary or portable engines were commercially introduced early in the 1900s. The first commercial production was by the New Way Motor Company of Lansing, Michigan, US. The company produced air-cooled engines in single and twin cylinders in both horizontal and vertical cylinder format. Subsequent to their initial production which was exported worldwide, other companies took up the advantages of this cooling method, especially in small portable engines. Applications include mowers, generators, outboard motors, pump sets, saw benches and auxiliary power plants and more.

References edit

  1. ^ Thomas, Kas (1997-02-19). . AVWeb. Aviation Publishing Group. Archived from the original on 2008-12-02.
  2. ^ YouMotorcycle (2015-12-19). "Air Cooled vs. Liquid Cooled Motorcycle Engines". YouMotorcycle. Retrieved 2020-04-23.
  3. ^ Sloan 1964, pp. 71–94, Chapter 5, "The copper-cooled engine"
  4. ^ a b c Taylor 1971, p. 53.
  5. ^ Taylor 1971, p. 55.
  6. ^ a b Taylor 1971, p. 56.

Bibliography edit

Cited sources edit

  • Sloan, Alfred P. (1964), McDonald, John (ed.), My Years with General Motors, Garden City, NY, US: Doubleday, LCCN 64011306, OCLC 802024. Republished in 1990 with a new introduction by Peter Drucker (ISBN 978-0385042352).
  • Taylor, C. Fayette (1971). Aircraft Propulsion. Smithsonian Institution.

Further reading edit

  • Biermann, A. E. (1941). "The design of fins for air-cooled cylinders" (pdf). Report Nº 726. NACA.[permanent dead link]
  • P V Lamarque, "The design of cooling fins for Motor-Cycle Engines". Report of the Automobile Research Committee, Institution of Automobile Engineers Magazine, March 1943 issue, and also in "The Institution of Automobile Engineers. Proceedings XXXVII, Session 1942-1943, pp 99-134 and 309-312.
  • Julius Mackerle, "Air-cooled Automotive Engines", Charles Griffin & Company Ltd., London 1972.

March 17, 2024
cooled, engine, this, article, multiple, issues, please, help, improve, discuss, these, issues, talk, page, learn, when, remove, these, template, messages, this, article, need, rewritten, comply, with, wikipedia, quality, standards, help, talk, page, contain, . This article has multiple issues Please help improve it or discuss these issues on the talk page Learn how and when to remove these template messages This article may need to be rewritten to comply with Wikipedia s quality standards You can help The talk page may contain suggestions June 2012 This article relies largely or entirely on a single source Relevant discussion may be found on the talk page Please help improve this article by introducing citations to additional sources Find sources Air cooled engine news newspapers books scholar JSTOR June 2012 Learn how and when to remove this template message Main article Internal combustion engine cooling Air cooled engines rely on the circulation of air directly over heat dissipation fins or hot areas of the engine to cool them in order to keep the engine within operating temperatures Air cooled designs are far simpler than their liquid cooled counterparts which require a separate radiator coolant reservoir piping and pumps Air cooled engines are widely seen in applications where weight or simplicity is the primary goal Their simplicity makes them suited for uses in small applications like chainsaws and lawn mowers as well as small generators and similar roles These qualities also make them highly suitable for aviation use where they are widely used in general aviation aircraft and as auxiliary power units on larger aircraft Their simplicity in particular also makes them common on motorcycles A cylinder from an air cooled aviation engine a Continental C85 Notice the rows of fins on both the steel cylinder barrel and the aluminum cylinder head The fins provide additional surface area for air to pass over the cylinder and absorb heat Contents 1 Introduction 2 Applications 2 1 Road vehicles 2 2 Aviation 2 3 Diesel engines 2 4 Stationary or portable engines 3 References 4 Bibliography 4 1 Cited sources 4 2 Further readingIntroduction editMost modern internal combustion engines are cooled by a closed circuit carrying liquid coolant through channels in the engine block and cylinder head A fluid in these channels absorbs heat and then flows to a heat exchanger or radiator where the coolant releases heat into the air or raw water in the case of marine engines Thus while they are not ultimately cooled by the liquid as the heat is exchanged with some other fluid like air because of the liquid coolant circuit they are known as liquid cooled In contrast heat generated by an air cooled engine is released directly into the air Typically this is facilitated with metal fins covering the outside of the Cylinder Head and cylinders which increase the surface area that air can act on Air may be force fed with the use of a fan and shroud to achieve efficient cooling with high volumes of air or simply by natural air flow with well designed and angled fins In all combustion engines a great percentage of the heat generated around 44 escapes through the exhaust Another 8 or so ends up in the oil which itself has to be cooled in an oil cooler This means less than half of the heat has to be removed through other systems In an air cooled engine only about 12 of the heat flows out through the metal fins 1 Air cooled engines usually run noisier however it provides more simplicity which gives benefits when it comes to servicing and part replacement and is usually cheaper to be maintained 2 Applications editRoad vehicles edit nbsp Honda CB1100Many motorcycles use air cooling for the sake of reducing weight and complexity Few current production automobiles have air cooled engines such as Tatra 815 but historically it was common for many high volume vehicles The orientation of the engine cylinders is commonly found in either single cylinder or coupled in groups of two and cylinders are commonly oriented in a horizontal fashion as a Flat engine while vertical Straight four engine have been used Examples of past air cooled road vehicles in roughly chronological order include Franklin 1902 1934 New Way 1905 limited production run out from the CLARKMOBILE Chevrolet Series M Copper Cooled 1921 1923 very few built 3 Tatra all wheel drive military trucks Tatra 11 1923 1927 and subsequent models Tatra T77 1934 1938 Tatra T87 1936 1950 Tatra T97 1936 1939 Tatra T600 Tatraplan 1946 1952 Tatra T603 1955 1975 Tatra T613 1974 1996 Tatra T700 1996 1999 Crosley 1939 1945 The East German Trabant 1957 1991 Trabant 500 1957 1962 Trabant 600 1962 1965 Trabant 601 1964 1989 ZAZ Zaporozhets 1958 1994 Fiat 500 1957 1975 Fiat 126 1972 1987 Porsche 356 1948 1965 Porsche 911 1964 1998 Porsche 912 1965 1969 1976 VW Porsche 914 1969 1976 The Volkswagen Beetle Type 2 SP2 Karmann Ghia and Type 3 all utilized the same air cooled engine 1938 2013 with various displacements Volkswagen Type 2 T3 1979 1982 Volkswagen Type 4 1968 1974 Volkswagen Gol G1 1980 1986 Toyota U engine 1961 1976 Chevrolet Corvair 1960 1969 Citroen 2CV 1948 1990 Featured a high pressure oil cooling system and used a fan bolted to the crankshaft end Citroen GS and GSA Honda 1300 1969 1973 NSU Prinz Royal Enfield Motorcycles India The 350cc and 500cc Twinspark motorcycle engines are air cooled Oltcit Club 1981 1995 T13 653 G11 631 and VO36 630 Demak Dzm 200 2015Aviation edit During the 1920s and 30s there was a great debate in the aviation industry about the merits of air cooled vs liquid cooled designs At the beginning of this period the liquid used for cooling was water at ambient pressure The amount of heat carried away by a fluid is a function of its capacity and the difference in input and output temperatures As the boiling point of water is reduced with lower pressure and the water could not be efficiently pumped as steam radiators had to have enough cooling power to account for the loss in cooling power as the aircraft climbed The resulting radiators were quite large and caused a significant amount of aerodynamic drag 4 This placed the two designs roughly equal in terms of power to drag but the air cooled designs were almost always lighter and simpler In 1921 the US Navy largely due to the efforts of Commander Bruce G Leighton decided that the simplicity of the air cooled design would result in less maintenance workload which was paramount given the limited working area of aircraft carriers Leighton s efforts led to the Navy underwriting air cooled engine development at Pratt amp Whitney and Wright Aeronautical 4 Most other groups especially in Europe where aircraft performance was rapidly improving were more concerned with the issue of drag While air cooled designs were common on light aircraft and trainers as well as some transport aircraft and bombers liquid cooled designs remained much more common for fighters and high performance bombers The drag issue was upset by the 1929 introduction of the NACA cowl which greatly reduced the drag of air cooled engines in spite of their larger frontal area and the drag related to cooling was at this point largely even 4 In the late 1920s into the 1930s a number of European companies introduced cooling system that kept the water under pressure allowed it to reach much higher temperatures without boiling carrying away more heat and thus reducing the volume of water required and the size of the radiator by as much as 30 They could also eliminate the radiator entirely using evaporative cooling allowing it to turn to steam and running the steam through tubes located just under the skin of the wings and fuselage where the fast moving outside air condensed it back to water While this concept was used on a number of record setting aircraft in the late 1930s it always proved impractical for production aircraft for a wide variety of reasons 5 In 1929 Curtiss began experiments replacing water with ethylene glycol in a Curtiss D 12 engine Glycol could run up to 250 C and reduced the radiator size by 50 compared to water cooled designs The experiments were extremely successful and by 1932 the company had switched all future designs to this coolant At the time Union Carbide held a monopoly on the industrial process to make glycol so it was initially used only in the US with Allison Engines picking it up soon after It was not until the mid 1930s that Rolls Royce adopted it as supplies improved converting all of their engines to glycol With the much smaller radiators and less fluid in the system the weight and drag of these designs was well below contemporary air cooled designs On a weight basis these liquid cooled designs offered as much as 30 better performance 6 In the late and post war era the high performance field quickly moved to jet engines This took away the primary market for late model liquid cooled engines Those roles that remained with piston power were mostly slower designs and civilian aircraft In these roles the simplicity and reduction in servicing needs is far more important that drag and from the end of the war on almost all piston aviation engines have been air cooled with few exceptions 6 As of 2020 update most of the engines manufactured by Lycoming and Continental are used by major manufacturers of light aircraft Cirrus Cessna and so on Other engine manufactures using air cooled engine technology are ULPower and Jabiru more active in the Light Sport Aircraft LSA and ultralight aircraft market Rotax uses a combination of air cooled cylinders and liquid cooled cylinder heads Diesel engines edit Some small diesel engines e g those made by Deutz AG and Lister Petter are air cooled Probably the only big Euro 5 truck air cooled engine V8 320 kW power 2100 N m torque one is being produced by Tatra Stationary or portable engines edit Stationary or portable engines were commercially introduced early in the 1900s The first commercial production was by the New Way Motor Company of Lansing Michigan US The company produced air cooled engines in single and twin cylinders in both horizontal and vertical cylinder format Subsequent to their initial production which was exported worldwide other companies took up the advantages of this cooling method especially in small portable engines Applications include mowers generators outboard motors pump sets saw benches and auxiliary power plants and more References edit Thomas Kas 1997 02 19 Shock Cooling Myth or Reality AVWeb Aviation Publishing Group Archived from the original on 2008 12 02 YouMotorcycle 2015 12 19 Air Cooled vs Liquid Cooled Motorcycle Engines YouMotorcycle Retrieved 2020 04 23 Sloan 1964 pp 71 94 Chapter 5 The copper cooled engine a b c Taylor 1971 p 53 Taylor 1971 p 55 a b Taylor 1971 p 56 Bibliography editCited sources edit Sloan Alfred P 1964 McDonald John ed My Years with General Motors Garden City NY US Doubleday LCCN 64011306 OCLC 802024 Republished in 1990 with a new introduction by Peter Drucker ISBN 978 0385042352 Taylor C Fayette 1971 Aircraft Propulsion Smithsonian Institution Further reading edit Biermann A E 1941 The design of fins for air cooled cylinders pdf Report Nº 726 NACA permanent dead link P V Lamarque The design of cooling fins for Motor Cycle Engines Report of the Automobile Research Committee Institution of Automobile Engineers Magazine March 1943 issue and also in The Institution of Automobile Engineers Proceedings XXXVII Session 1942 1943 pp 99 134 and 309 312 Julius Mackerle Air cooled Automotive Engines Charles Griffin amp Company Ltd London 1972 Retrieved from https en wikipedia org w index php title Air cooled engine amp oldid 1211230845, wikipedia, wiki, book, books, library,

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