A gas engine is an internal combustion engine that runs on a fuel gas (a gas fuel), such as coal gas, producer gas, biogas, landfill gas, natural gas or hydrogen. In the United Kingdom and British English-speaking countries, the term is unambiguous. In the United States, due to the widespread use of "gas" as an abbreviation for gasoline (petrol), such an engine is sometimes called by a clarifying term, such as gaseous-fueled engine or natural gas engine.
Generally in modern usage, the term gas engine refers to a heavy-duty industrial engine capable of running continuously at full load for periods approaching a high fraction of 8,760 hours per year, unlike a gasoline automobile engine, which is lightweight, high-revving and typically runs for no more than 4,000 hours in its entire life. Typical power ranges from to .
History
Lenoir
There were many experiments with gas engines in the 19th century, but the first practical gas-fuelled internal combustion engine was built by the Belgian engineer Étienne Lenoir in 1860.
However, the Lenoir engine suffered from a low power output and high fuel consumption.
Otto and Langen
Lenoir's work was further researched and improved by a German engineer
Nicolaus Otto, who was later to invent the first four-stroke engine to efficiently burn fuel directly in a piston chamber. In August 1864 Otto met
Eugen Langen who, being technically trained, glimpsed the potential of Otto's development, and one month after the meeting, founded the first engine factory in the world, NA Otto & Cie, in Cologne. In 1867 Otto patented his improved design and it was awarded the Grand Prize at the 1867 Paris World Exhibition. This atmospheric engine worked by drawing a mixture of gas and air into a vertical cylinder. When the piston has risen about eight inches, the gas and air mixture is ignited by a small pilot flame burning outside, which forces the piston (which is connected to a toothed rack) upwards, creating a partial vacuum beneath it. No work is done on the upward stroke. The work is done when the piston and toothed rack descend under the effects of atmospheric pressure and their own weight, turning the main shaft and flywheels as they fall. Its advantage over the existing steam engine was its ability to be started and stopped on demand, making it ideal for intermittent work such as barge loading or unloading.
Four-stroke engine
The atmospheric gas engine was in turn replaced by Otto's four-stroke engine. The changeover to four-stroke engines was remarkably rapid, with the last atmospheric engines being made in 1877. Liquid-fuelled engines soon followed using diesel (around 1898) or gasoline (around 1900).
Crossley
The best-known builder of gas engines in the United Kingdom was
Crossley of Manchester, who in 1869 acquired the United Kingdom and world (except German) rights to the patents of Otto and Langen for the new gas-fuelled atmospheric engine. In 1876 they acquired the rights to the more efficient Otto four-stroke cycle engine.
Tangye
There were several other firms based in the
Manchester area as well.
Richard Tangye, of Smethwick, near Birmingham, sold its first gas engine, a 1 nominal horsepower two-cycle type, in 1881, and in 1890 the firm commenced manufacture of the four-cycle gas engine.
Preservation
The Anson Engine Museum in
Poynton, near
Stockport,
England, has a collection of engines that includes several working gas engines, including the largest running Crossley atmospheric engine ever made.
Current manufacturers
Manufacturers of gas engines include Hyundai Heavy Industries, Rolls-Royce with the
Bergen Marine, Kawasaki Heavy Industries,
Liebherr Group, MTU Friedrichshafen,
Jenbacher, Caterpillar Inc.,
Perkins Engines, MWM,
Cummins, Wärtsilä,
Waukesha Engine, Guascor Energy ,
Deutz AG, MTU, MAN,
Scania AB,
Fairbanks-Morse, Doosan, Eaton (successor to another former large market share holder, Cooper Industries), and
Yanmar. Output ranges from about
Cogeneration (CHP) to .
Generally speaking, the modern high-speed gas engine is very competitive with gas turbines up to about depending on circumstances, and the best ones are much more fuel efficient than the gas turbines. Rolls-Royce with the Bergen Engines, Caterpillar and many other manufacturers base their products on a diesel engine block and crankshaft. INNIO Jenbacher and Waukesha are the only two companies whose engines are designed and dedicated to gas alone.
Typical applications
Stationary
Typical applications are
base load or high-hour generation schemes, including
Cogeneration (for typical performance figures see
),
landfill gas,
mining gas,
oil well-head gas and
biogas, where the
waste heat from the engine may be used to warm the digesters. For typical biogas engine installation parameters see.
For parameters of a large gas engine CHP system, as fitted in a factory, see.
Gas engines are rarely used for standby applications, which remain largely the province of diesel engines. One exception to this is the small (<150 kW) emergency generator often installed by farms, museums, small businesses, and residences. Connected to either natural gas from the public utility or propane from on-site storage tanks, these generators can be arranged for automatic starting upon power failure.
Transport
Liquefied natural gas (LNG) engines are expanding into the marine market, as the lean-burn gas engine can meet the new emission requirements without any extra fuel treatment or exhaust cleaning systems. Use of engines running on compressed natural gas (CNG) is also growing in the
bus sector. Users in the United Kingdom include
Reading Buses. Use of gas buses is supported by the Gas Bus Alliance
and manufacturers include
Scania AB.
Use of gaseous methane or propane
Since
natural gas, chiefly
methane, has long been an economical and readily available fuel, many industrial engines are either designed or modified to use gas, as distinguished from
gasoline. Their operation produces less complex-hydrocarbon pollution, and the engines have fewer internal problems. One example is the liquefied petroleum gas, chiefly
propane. engine used in vast numbers of
forklift trucks. Common United States usage of "gas" to mean "gasoline" requires the explicit identification of a natural gas engine. There is also such a thing as "natural gasoline",
but this term, which refers to a subset of natural gas liquids, is very rarely observed outside the refining industry.
Technical details
Fuel-air mixing
A gas engine differs from a
petrol engine in the way the fuel and air are mixed. A petrol engine uses a
carburetor or
fuel injection. but a gas engine often uses a simple
Venturi effect system to introduce gas into the air flow. Early gas engines used a three-valve system, with separate inlet valves for air and gas.
Exhaust valves
The weak point of a gas engine compared to a
diesel engine is the exhaust valves, since the gas engine exhaust gases are much hotter for a given output, and this limits the power output. Thus, a diesel engine from a given manufacturer will usually have a higher maximum output than the same engine block size in the gas engine version. The diesel engine will generally have three different ratings — standby, prime, and continuous, a.k.a. 1-hour rating, 12-hour rating and continuous rating in the United Kingdom, whereas the gas engine will generally only have a continuous rating, which will be less than the diesel continuous rating.
Ignition
Various ignition systems have been used, including
and spark ignition. Some modern gas engines are essentially
Multifuel. The main source of energy is the gas-air mixture but it is ignited by the injection of a small volume of
diesel fuel.
Energy balance
Thermal efficiency
Gas engines that run on natural gas typically have a thermal efficiency between 35-45% (LHV basis).,
As of year 2018, the best engines can achieve a thermal efficiency up to 50% (LHV basis).
These gas engines are usually medium-speed engines
Bergen Engines Fuel energy arises at the output shaft, the remainder appears as waste heat.
Large engines are more efficient than small engines. Gas engines running on
biogas typically have a slightly lower efficiency (~1-2%) and
syngas reduces the efficiency further still. GE Jenbacher's recent J624 engine is the world's first high efficiency methane-fueled 24-cylinder gas engine.
When considering engine efficiency one should consider whether this is based on the lower heating value (LHV) or higher heating value (HHV) of the gas. Engine manufacturers will typically quote efficiencies based on the lower heating value of the gas, i.e. the efficiency after energy has been taken to evaporate the intrinsic moisture within the gas itself. Gas distribution networks will typically charge based upon the higher heating value of the gas. i.e., total energy content. A quoted engine efficiency based on LHV might be say 44% whereas the same engine might have an efficiency of 39.6% based on HHV on natural gas.
It is also important to ensure that efficiency comparisons are on a like-for-like basis. For example, some manufactures have mechanically driven pumps whereas other use electrically driven pumps to drive engine cooling water, and the electrical usage can sometimes be ignored giving a falsely high apparent efficiency compared to the direct drive engines.
Combined heat and power
Engine reject heat can be used for building heating or heating a process. In an engine, roughly half the waste heat arises (from the engine jacket, oil cooler and after-cooler circuits) as hot water, which can be at up to 110 °C. The remainder arises as high-temperature heat which can generate pressurised hot water or steam by the use of an exhaust gas
heat exchanger.
Engine cooling
Two most common engine types are an air-cooled engine or water cooled engine. Water cooled nowadays use
antifreeze in the internal combustion engine
Some engines (air or water) have an added Oil cooling
Cooling is required to remove excessive heat, as overheating can cause engine failure, usually from wear, cracking or warping.
Gas consumption formula
The formula shows the gas flow requirement of a gas engine in norm conditions at full load.
where:
-
is the gas flow in norm conditions
-
is the engine power
-
is the mechanical efficiency
-
LHV is the Low Heating Value of the gas
Gallery of historic gas engines
File:National gas engine (Rankin Kennedy, Modern Engines, Vol II).jpg|1905 National company's ordinary gas engine of 36 hp
File:Körting gas engine (Rankin Kennedy, Electrical Installations, Vol III, 1903).jpg|1903 Körting gas engine
File:Backus upright gas engine (New Catechism of the Steam Engine, 1904).jpg|Backus upright gas engine
File:Otto horizontal gas engine (New Catechism of the Steam Engine, 1904).jpg|Otto horizontal gas engine
File:Otto vertical gas engine (New Catechism of the Steam Engine, 1904).jpg|Otto vertical gas engine
File:Westinghouse gas engine, section (Rankin Kennedy, Electrical Installations, Vol III, 1903).jpg|Westinghouse gas engine
File:Crossley gas engine and dynamo (Rankin Kennedy, Electrical Installations, Vol III, 1903).jpg|Crossley gas engine and dynamo
File:Premier twin gas engine electric generating plant (Rankin Kennedy, Modern Engines, Vol III).jpg|Premier twin gas engine electric generating plant
File:125hp gas engine and dynamo (Rankin Kennedy, Electrical Installations, Vol III, 1903).jpg|125 hp gas engine and dynamo
File:Crossley engine.jpg|Crossley Brothers Ltd., 1886 No. 1 Engine, 4.5 hp single cylinder, 4-stroke gas engine, 160 rpm.
File:Crossley Gas Engine - Kelham Island Industrial Museum.jpg|1915 Crossley Gas Engine (type GE130 No75590), 150 hp.
File:Gas Engine in the Gas Museum - geograph.org.uk - 2120293.jpg|National Gas Engine
File:Premier tandem scavenging high-power gas engine (Rankin Kennedy, Modern Engines, Vol II).jpg|Premier tandem scavenging high-power gas engine
File:Blast furnace gas engine with blowing cylinder (Rankin Kennedy, Modern Engines, Vol II).jpg|Blast furnace gas engine with blowing cylinder
File:Stockport gas engine and belt-driven dynamo (Rankin Kennedy, Electrical Installations, Vol III, 1903).jpg|Stockport gas engine and belt-driven dynamo
See also
