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Stationary engine
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A stationary engine is an engine whose framework does not move. It is normally used not to propel a vehicle but to drive a piece of immobile equipment such as a pump or power tool.
This article concentrates on oil-burning or internal combustion engines;
steam-powered engines are described separately in stationary steam engine.
ionary engines come in a wide variety of sizes and use a wide variety of technologies.
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A stationary engine is an engine whose framework does not move. It is normally used not to propel a vehicle but to drive a piece of immobile equipment such as a pump or power tool.
This article concentrates on oil-burning or internal combustion engines;
steam-powered engines are described separately in stationary steam engine.
Overview
Stationary engines come in a wide variety of sizes and use a wide variety of technologies. These include:
Types of stationary engine
Live steam models of stationary engines are popular among collectors and hobbyists.
Applications
Agriculture
Small stationary engines were frequently used on a farm to drive various kinds of power tools and equipment such as circular saws, pumps, and hay elevators. The engine was fitted to a wooden trolley with steel wheels so that it could be moved to where required, and was then coupled to the equipment by means of a flat belt.
The engines were usually powered by gasoline, but in some cases for economy it was possible to switch over to run on paraffin after the engine had warmed up - to achieve this required a part of the inlet tract to be heated by exhaust gases in order to vaporise the less volatile fuel. Very large stationary engines ran on a heavier type of fuel oil, but this type of engine was usually too large to be moved; typical applications were electricity generation and large-scale pumping.
Initially, such engines mirrored steam engine design in having the piston move horizontally, with the crank and valve gear exposed and employed a drip-feed total loss lubrication system. Later for safety, cleanliness and longevity the design moved towards enclosing the working parts and using sump lubrication.
The four-stroke cycle design was by far the most common, but Petter, a British manufacturer, developed a successful two-stroke cycle design.
A centripetal governor system was usually incorporated to regulate the engine's speed under varying loads. This is a simple negative feedback control system. The engine speed is sensed by a pair of weights that rotate with the crankshaft. As the speed increases, centripetal force causes the weights to move outward against the pressure of a retaining spring. This outward movement is used to restrict the engine power to limit the speed. If the engine slows down, the centrifugal force reduces and the weights are pulled inward by spring pressure, and this movement is used to increase the engine power to maintain speed under increasing load.
The governor can use one of two techniques for controlling speed. Today, most governors open and close a butterfly valve to control the amount of fuel-air mixture entering the engine. However, in earlier engines, the governor would cut off the fuel air mixture completely. These engines are often called "hit and miss" (variously called "hit or miss") because they do not fire on every available power stroke. When the engine is running above a certain rpm, the exhaust valve is held open, and the magneto is prevented from generating a spark. Once the speed drops, the governor allows the exhaust valve to close and the magneto to fire. The engine fires and speeds back up, causing the governor to keep the exhaust valve open again.
On a medium size engine such as a 6hp, the engine can be adjusted so that it only fires every 10 seconds or so when it is not under load. These engines generally drove a wide flat belt to run a firewood cutoff saw, a pump, a reciprocating log saw, etc.
Eventually such engines were rendered obsolete by the development of a universal power take off (PTO) system on tractors, which could drive stationary equipment as well as mounted implements with much higher outputs than the average small stationary engines. For non-PTO equipment the arrival of the reliable electric motor or the small, light, high-speed petrol engine meant that even small machines could be driven by their own motors, making dedicated power units unnecessary.
Electricity Generation
Before mains electricity and the formation of nationwide power grids, stationary engines were widely used for small-scale electricity generation. Whilst large power stations in cities used steam turbines or high-speed reciprocating steam engines, in rural areas petrol/gasoline, paraffin/kerosene or fuel oil powered internal combustion engines were cheaper to buy, install and operate, since they could be started and stopped quickly to meet demand, left running unattended for long periods of time and did not require a large dedicated engineering staff to operate and maintain. Due to their simplicity and economy, hot bulb engines were popular for high-power applications until the diesel engine took their place from the 1920s. Smaller units were generally powered by spark-ignition engines, which were cheaper to buy and required less space to install.
Most engines of the late-19th and early-20th centuries ran at speeds too low to drive a dynamo or alternator directly. As with other equipment, the generator was driven off the engine's flywheel by a broad flat belt. The pulley on the generator was much smaller than the flywheel, providing the required 'gearing up' effect. Later spark-ignition engines developed from the 1920s could be directly coupled.
Up to the 1930s most rural houses in Europe and North America needed their own generating equipment if electric light was fitted. Engines would often be installed in a dedicated 'engine house', which was usually an outbuilding separate from the main house to reduce the interference from the engine noise. The engine house would contain the engine, the generator, the necessary switchgear and fuses, as well as the engine's fuel supply and usually a dedicated workshop space with equipment to service and repair the engine. Wealthy households could afford to employ a dedicated engineer to maintain the equipment, but as the demand for electricity spread to smaller homes, manufacturers produced engines that required less maintenance and that did not need specialist training to operate.
Such generator sets were also used in industrial complexes and public buildings- anywhere where electricity was required but mains electricity was not available.
Most countries in the Western world completed large-scale rural electrification in the years following World War II, making individual generating plants obsolete for front-line use. However, even in countries with a reliable mains supply, many buildings are still fitted with modern diesel generators for emergency use, such as hospitals and pumping stations. This network of generators often forms a crucial part of the national electricity system's strategy for coping with periods of high demand.
Pumping stations
The development of water supply and sewage removal systems required the provision of many pumping stations. In these, some form of stationary engine (steam-powered for earlier installations) is used to drive one or more pumps, although electric motors are more conventionally used nowadays.
Transport
Transport use of stationary engines is mainly for pumping water, but also for driving machine tools and other applications similar to many areas of industry.
Canals
For canals, a distinct area of application concerned the powering of boat lifts and inclined planes. Where possible these would be arranged to utilise water and gravity in a balanced system, but in some cases additional power input was required from a stationary engine for the system to work. The vast majority of these were constructed (and in many cases, demolished again) before steam engines were supplanted by internal combustion alternatives.
Railways
Canal inclined planes were in use tens of years before the first steam-powered railways were built. Industrial railways in quarries and mines made use of similar cable railways based on the same inclined plane idea, and certain early passenger railways in the UK were planned with lengths of cable-haulage to overcome severe gradients.
For the first proper railway, the Liverpool and Manchester of 1830, it was not clear whether locomotive traction would work, and the railway was designed with steep 1 in 100 gradients concentrated on either side of Rainhill, just in case. Had cable haulage been necessary, then inconvenient and time-consuming shunting would obviously have been required to attach and detach the cables. Fortunately, the Rainhill gradients proved not to be a problem, and in the event, locomotive traction was determined to be a new technology with great potential for further development.
The steeper 1 in 50 grades from Liverpool down to the docks were operated by cable traction for several decades until locomotives improved. Cable haulage continued to be used where gradients were even steeper.
Cable haulage did prove viable where the gradients were exceptionally steep, such as the 1 in 8 gradients of the Cromford and High Peak Railway opened in 1830. Cable railways generally have two tracks with loaded wagons on one track partially balanced by empty wagons on the other, to minimise fuel costs for the stationary engine. Various kinds of rack railway were developed to overcome the lack of friction of conventional locomotives on steep gradients.
These early installations of stationary engines would all have been steam-powered initially.
Some manufacturers of stationary engines
Preserved stationary engines
In the UK there are few museums where visitors can see stationary engines in operation. Many museums have one or more engines but only a few specialise in the internal combustion stationary engines. Among these are the Internal Fire - Museum of Power, in Wales, and the Anson Engine Museum in Cheshire. The Amberley Working Museum in West Sussex also has a number of engines, as does Kew Bridge Steam Museum in London.
Many steam rallies, like the Great Dorset Steam Fair, include an exhibit section for internal combustion stationary engines. These engines have been restored by private individuals and often are exhibited in operation, powering water pumps, electric generators, hand tools, and the like.
See also
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