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the main unit in the starting system of an engine. A starter increases the speed of rotation of the engine shaft until the starting speed is reached. The starter comprises a motor or engine, a reduction gear, devices for engaging with and disengaging from the shaft of the main engine, and a starting device for internal use (for starters that are not self-contained, for example, gasoline and turbine starters).
Starters are classified according to their principle of operation as inertia, direct-coupled, or combined-drive. In inertia starters, a flywheel is brought to a speed of rotation at which it possesses energy sufficient to rotate the shaft of the main engine upon engagement. Direct-coupled starters are linked directly to the shaft of the main engine. Starters can be of the electric, turbine, compressed-air, hydraulic, or gasoline type.
Electric starters are usually direct-current high-speed motors (up to 13,000 rpm). Starter-generators are also classified as electric starters. During cranking, these units work as starters, but once the engine is in operation they function as generators of electric power. In contrast to other types of starters, starter-generators remain engaged to the shaft of the main engine after the engine has started. The rated power of electric starters can be up to 25 kilowatts (kW), or 35 hp; the operating voltage ranges from 12 to 112 volts (V).
In turbine starters, a turbine is used as the motor. The turbine is rotated by air or by the gases obtained from the combustion of fuel. Depending on the type of feed, turbine starters are classified as compressed-air, combustible-mixture, solid-fuel, and liquid-fuel starters. In compressed-air starters, pressurized air rotates the turbine; the power rating can be as high as 110 kW (150 hp). Combustible-mixture starters, which can be of the gas-turbine or centrifugal-turbine type, are small gas-turbine engines capable of developing a power of up to 300 kW (400 hp). In combustible-mixture turbine starters without compressors, the compressed air for fuel combustion is supplied from cylinders. In solid-fuel turbine starters, which can be of the powder-squib or turbine type, the turbine is driven by the combustion products of a powder charge. In liquid-fuel turbine starters, the turbine is driven by the combustion (decomposition) products of a single-component liquid fuel. The power ratings of solid-fuel and liquid-fuel turbine starters are up to 300 kW (400 hp).
Hydraulic and compressed-air starters are usually pumps or compressors that operate as motors when fed by a liquid or highly pressurized air.