Automotive electronics
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- Hydraulic starter
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- Self starting
Pneumatic starterSome gas turbine engines and Diesel engines, particularly on trucks, use a pneumatic self-starter. The system consists of a geared turbine, an air compressor and a pressure tank. Compressed air released from the tank is used to spin the turbine, and through a set of reduction gears, engages the ring gear on the flywheel, much like an electric starter. The engine, once running, powers the compressor to recharge the tank. Aircraft with large gas turbine engines are typically started using a large volume of low-pressure compressed air, supplied from a very small engine referred to as an auxiliary power unit, located elsewhere in the aircraft. After starting the main engines, the APU often continues to operate, supplying additional power to operate aircraft equipment. Alternately, aircraft engines can be rapidly started using a mobile ground-based pneumatic starting engine, referred to as a start cart or air start cart. On larger diesel generators found in large shore installations and especially on ships, a pneumatic starting gear is used. The air motor is normally powered by compressed air at pressures of 10–30 bar. The air motor is made up of a center drum about the size of a soup can with four or more slots cut into it to allow for the vanes to be placed radially on the drum to form chambers around the drum. The drum is offset inside a round casing so that the inlet air for starting is admitted at the area where the drum and vanes form a small chamber compared to the others. The compressed air can only expand by rotating the drum which allows the small chamber to become larger and puts another one of the cambers in the air inlet. The air motor spins much too fast to be used directly on the flywheel of the engine, instead a large gearing reduction such as a planetary gear is used to lower the output speed. A Bendix gear is used to engage the flywheel. On large diesel generators and almost all diesel engines used as the prime mover of ships will use compressed air acting directly on the cylinder head. This is not ideal for smaller diesels as it provides too much cooling on starting. Also the cylinder head needs to have enough space to support an extra valve for the air start system. The air start system operates very similar to a distributor in a car. There is an air distributor that is geared to the camshaft of the diesel engine, on the top of the air distributor is a single lobe similar to what is found on a camshaft. Arranged radially around this lobe are roller tip followers for every cylinder. When the lobe of the air distributor hits one of the followers it will send an air signal that acts upon the back of the air start valve located in the cylinder head causing it to open. The actual compressed air is provided from a large reservoir that feeds into a header located along the engine. As soon as the air start valve is opened the compressed air is admitted and the engine will begin turning. It can be used on 2-cycle and 4-cycle engines and on reversing engines. On large 2-stroke engines less than one revolution of the crankshaft is needed for starting. Since large trucks typically use air brakes, the system does double duty, supplying compressed air to the brake system. Pneumatic starters have the advantages of delivering high torque, mechanical simplicity and reliability. They eliminate the need for oversized, heavy storage batteries in prime mover electrical systems. Hydraulic starterSome diesel engines from 6 to 16 cylinders are started by means of a hydraulic motor. Hydraulic starters and the associated systems provide a sparkless, reliable method of engine starting at a wide temperature range. Typically hydraulic starters are found in applications such as remote generators, lifeboat propulsion engines, offshore fire pumping engines, and hydraulic fracturing rigs. The system used to support the hydraulic starter includes valves, pumps, filters, a reservoir, and piston accumulators. The operator can manually recharge the hydraulic system; this cannot readily be done with air or electric starting systems, so hydraulic starting systems are favored in applications wherein emergency starting is a requirement.
Other methodsBefore the advent of the starter motor, engines were started by various methods including wind-up springs, gun powder cylinders, and human-powered techniques such as a removable crank handle which engaged the front of the crankshaft, pulling on an airplane propeller, or pulling a cord that was wound around an open-face pulley. The behavior of an engine during starting is not always predictable. The engine can kick back, causing sudden reverse rotation. Many manual starters included a one-directional slip or release provision so that once engine rotation began, the starter would disengage from the engine. In the event of a kickback, the reverse rotation of the engine could suddenly engage the starter, causing the crank to unexpectedly and violently jerk, possibly injuring the operator. For cord-wound starters, a kickback could pull the operator towards the engine or machine, or swing the starter cord and handle at high speed around the starter pulley. Self startingSome modern gasoline engines with twelve or more cylinders always have at least one piston at the beginning of its power stroke and are able to start by injecting fuel into that cylinder and igniting it. ********************************************* Directory: images images -> Pelan pentaksiran kursus images -> Military callsign list as of dec 2010 images -> For Date: 02/01/2013 Friday Call Number Time Call Reason Action 13-768 0008 motor vehicle stop warning Issued images -> New embedded S images -> Creating Buy-In – Building Relationships images -> Deadline: Saturday, March 12th, 2016 images -> News items from Raising Our Voices images -> Last year four of the best Afrikaans Christian singers joined forces to tour Down Under with the production ‘Manne wat Glo’ images -> World-renowned vocal ensemble sweet honey in the rock images -> Peoples Voice Café History Download 142.31 Kb. Share with your friends:
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