Stationary engine

A stationary engine is an engine whose framework does not move. They are used to drive immobile equipment, such as pumps, generators, mills or factory machinery. The term usually refers to large immobile reciprocating engines, principally stationary steam engines and, to some extent, stationary internal combustion engines. Other large immobile power sources, such as steam turbines, gas turbines, and large electric motors, are categorized separately.

Stationary engines were once widespread in the era when each factory or mill generated its own power, and power transmission was mechanical (via line shafts, belts, gear trains, and clutches). Applications for stationary engines have declined since electrification has become widespread; most industrial uses today draw electricity from an electrical grid and distribute it to various individual electric motors instead.

Engines that operate in one place, but can be moved to another place for later operation, are called portable engines. Although stationary engines and portable engines are both "" (not moving) while running, preferred usage (for clarity's sake) reserves the term "stationary engine" to the permanently immobile type, and "portable engine" to the mobile type.

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.

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