Injection pump

Last updated
Injection pump for a 12-cylinder diesel engine 12Zyl-Reiheneinspritzpumpe.jpg
Injection pump for a 12-cylinder diesel engine

An Injection Pump is the device that pumps fuel into the cylinders of a diesel engine. Traditionally, the injection pump was driven indirectly from the crankshaft by gears, chains or a toothed belt (often the timing belt) that also drives the camshaft. It rotates at half crankshaft speed in a conventional four-stroke diesel engine. Its timing is such that the fuel is injected only very slightly before top dead centre of that cylinder's compression stroke. It is also common for the pump belt on gasoline engines to be driven directly from the camshaft. In some systems injection pressures can be as high as 620 bar (8992 psi) .

Contents

Safety

Because of the need for positive injection into a very high-pressure environment, the pump develops great pressuretypically 15,000 psi (100 MPa) or more on newer systems. This is a good reason to take great care when working on diesel systems; escaping fuel at this sort of pressure can easily penetrate skin and clothes, and be injected into body tissues with medical consequences serious enough to warrant amputation. [1]

Construction

Inline diesel injection pump Inline EDC pump.JPG
Inline diesel injection pump

Earlier diesel pumps used an in-line layout with a series of cam-operated injection cylinders in a line, rather like a miniature inline engine. The pistons have a constant stroke volume, and injection volume (i.e., throttling) is controlled by rotating the cylinders against a cut-off port that aligns with a helical slot in the cylinder. When all the cylinders are rotated at once, they simultaneously vary their injection volume to produce more or less power from the engine. Inline pumps still find favour on large multi-cylinder engines such as those on trucks, construction plant, static engines and agricultural vehicles.

Distributor diesel injection pump Distributor injection pump.jpg
Distributor diesel injection pump

For use on cars and light trucks, the rotary pump or distributor pump was developed. It uses a single injection cylinder driven from an axial cam plate, which injects into the individual fuel lines via a rotary distribution valve. Later incarnations such as the Bosch VE pump vary the injection timing with crankshaft speed to allow greater power at high crank speeds, and smoother, more economical running at slower revolution of crankshaft. Some VE variants have a pressure-based system that allows the injection volume to increase over normal to allow a turbocharger or supercharger equipped engine to develop more power under boost conditions.

Inline diesel metering pump Dosierpumpe.png
Inline diesel metering pump

All injection pumps incorporate a governor to cut fuel supply if the crankshaft rpm endangers the engine - the heavy moving parts of diesel engines do not tolerate overspeeding well, and catastrophic damage can occur if they are over-revved. Poorly maintained and worn engines can consume their lubrication oil through worn out crankcase ventilation systems and 'run away', causing increasing engine speed until the engine destroys itself. This is because most diesel engines only regulate their speed by fuel supply control and most don't have a throttle valve to control air intake, other than those with EGR systems.

New types

Mechanical pumps are gradually being phased out in order to comply with international emissions directives, and to increase performance and economy. From the 1990s an intermediate stage between full electronic control were pumps that used electronic control units to control some of the functions of the rotary pump but were still mechanically timed and powered by the engine. The first generation four and five cylinder VW/Audi TDI engines pioneered these pumps before switching to Unit Injectors. These pumps were used to provide better injection control and refinement for car diesel engines as they changed from indirect injection to much more efficient but inherently less refined direct injection engines in the 1990s. The ECUs could even vary the damping of hydraulic engine mounts to aid refinement. BOSCH VP30 VP37 VP44 are example pumps. Since then there has been a widespread change to common rail diesel systems and electronic unit direct injection systems. These allow for higher pressures to be developed, and for much finer control of injection volumes, and multiple injection stages compared to mechanical systems.

See also

Injection pressures during the whole process should be above 1000-1200 bar for a good spray formation and air fuel mixture a tendency in practice to 1600-1800 bar and higher is noted

Related Research Articles

<span class="mw-page-title-main">Two-stroke engine</span> Internal combustion engine type

A two-strokeengine is a type of internal combustion engine that completes a power cycle with two strokes of the piston during one power cycle, this power cycle being completed in one revolution of the crankshaft. A four-stroke engine requires four strokes of the piston to complete a power cycle during two crankshaft revolutions. In a two-stroke engine, the end of the combustion stroke and the beginning of the compression stroke happen simultaneously, with the intake and exhaust functions occurring at the same time.

<span class="mw-page-title-main">Fuel pump</span> Pump

A fuel pump is a component used in many liquid-fuelled engines to transfer the fuel from the fuel tank to the device where it is mixed with the intake air.

The GM Ecotec engine, also known by its codename L850, is a family of all-aluminium inline-four engines, displacing between 1.4 and 2.5 litres. While these engines were based on the GM Family II engine, the architecture was substantially re-engineered for the new Ecotec application produced since 2000. This engine family replaced the GM Family II engine, the GM 122 engine, the Saab H engine, and the Quad 4 engine. It is manufactured in multiple locations, to include Spring Hill Manufacturing, in Spring Hill, Tennessee while the engine block and cylinder heads are cast at Saginaw Metal Casting Operations in Saginaw, Michigan.

The Ford Endura-D engine is a 1.8 L (1,753 cc) inline-4 Diesel engine used in a variety of vehicles made by the Ford Motor Company, including the Ford Escort (Europe), Ford Focus, Ford Fiesta, Ford Mondeo, Ford Orion, Ford Sierra, Ford Transit Connect and Ford Ikon.

<span class="mw-page-title-main">Common rail</span> Engine fuel delivery method

Common rail direct fuel injection is a direct fuel injection system built around a high-pressure fuel rail feeding solenoid valves, as opposed to a low-pressure fuel pump feeding unit injectors. High-pressure injection delivers power and fuel consumption benefits over earlier lower pressure fuel injection, by injecting fuel as a larger number of smaller droplets, giving a much higher ratio of surface area to volume. This provides improved vaporization from the surface of the fuel droplets, and so more efficient combining of atmospheric oxygen with vaporized fuel delivering more complete combustion.

<span class="mw-page-title-main">Cummins B Series engine</span> Motor vehicle engine

The Cummins B Series is a family of diesel engines produced by American manufacturer Cummins. In production since 1984, the B series engine family is intended for multiple applications on and off-highway, light-duty, and medium-duty. In the automotive industry, it is best known for its use in school buses, public service buses in the United Kingdom, and Dodge/Ram pickup trucks.

<span class="mw-page-title-main">Valvetrain</span> Mechanical system in an internal combustion engine

A valvetrain or valve train is a mechanical system that controls the operation of the intake and exhaust valves in an internal combustion engine. The intake valves control the flow of air/fuel mixture into the combustion chamber, while the exhaust valves control the flow of spent exhaust gasses out of the combustion chamber once combustion is completed.

The L-series engine is an automotive diesel engine built by Powertrain Ltd, a sister company of MG Rover.

<span class="mw-page-title-main">Unit injector</span>

A unit injector (UI) is a high pressure integrated direct fuel injection system for diesel engines, combining the injector nozzle and the injection pump in a single component. The plunger pump used is usually driven by a shared camshaft. In a unit injector, the device is usually lubricated and cooled by the fuel itself.

Internal combustion engines come in a wide variety of types, but have certain family resemblances, and thus share many common types of components.

An electronically controlled unit injector (EUI) is a unit injector (UI) with electronic control. It performs the same function as a conventional unit injector in an internal combustion engine, such as in an on-road or off-road vehicle or a diesel-electric locomotive. The pressurized delivery of fuel is camshaft-driven, but the timing of the injector's internal operations are controlled by the engine control unit so as to achieve certain advantages.

<span class="mw-page-title-main">Internal combustion engine</span> Engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber

An internal combustion engine is a heat engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combustion engine, the expansion of the high-temperature and high-pressure gases produced by combustion applies direct force to some component of the engine. The force is typically applied to pistons, turbine blades, a rotor, or a nozzle. This force moves the component over a distance, transforming chemical energy into kinetic energy which is used to propel, move or power whatever the engine is attached to. This replaced the external combustion engine for applications where the weight or size of an engine were more important.

<span class="mw-page-title-main">4 VD 14,5/12-1 SRW</span> Motor vehicle engine

The 4 VD 14,5/12-1 SRW is an inline four-cylinder diesel engine produced by the VEB IFA Motorenwerke Nordhausen from 1967 to 1990. The engine was one of the standard modular engines for agricultural and industrial use in the Comecon-countries. Approximately one million units were made.

<span class="mw-page-title-main">Mercedes-Benz OM 138</span> Motor vehicle engine

The Mercedes-Benz OM 138 is a diesel engine manufactured by Daimler-Benz. In total, 5,719 units were produced between 1935 and 1940. It was the first diesel engine especially developed and made for a passenger car. The first vehicle powered by the OM 138 was the Mercedes-Benz W 138. The light Mercedes-Benz trucks L 1100 and L 1500 as well as the bus O 1500 were also offered with the OM 138 as an alternative to the standard Otto engine.

Manifold injection is a mixture formation system for internal combustion engines with external mixture formation. It is commonly used in engines with spark ignition that use petrol as fuel, such as the Otto engine, and the Wankel engine. In a manifold-injected engine, the fuel is injected into the intake manifold, where it begins forming a combustible air-fuel mixture with the air. As soon as the intake valve opens, the piston starts sucking in the still forming mixture. Usually, this mixture is relatively homogeneous, and, at least in production engines for passenger cars, approximately stoichiometric; this means that there is an even distribution of fuel and air across the combustion chamber, and enough, but not more air present than what is required for the fuel's complete combustion. The injection timing and measuring of the fuel amount can be controlled either mechanically, or electronically. Since the 1970s and 1980s, manifold injection has been replacing carburettors in passenger cars. However, since the late 1990s, car manufacturers have started using petrol direct injection, which caused a decline in manifold injection installation in newly produced cars.

<span class="mw-page-title-main">Volkswagen-Audi V8 engine</span> Motor vehicle engine

The Volkswagen-Audi V8 engine family is a series of mechanically similar, gasoline-powered and diesel-powered, V-8, internal combustion piston engines, developed and produced by the Volkswagen Group, in partnership with Audi, since 1988. They have been used in various Volkswagen Group models, and by numerous Volkswagen-owned companies. The first spark-ignition gasoline V-8 engine configuration was used in the 1988 Audi V8 model; and the first compression-ignition diesel V8 engine configuration was used in the 1999 Audi A8 3.3 TDI Quattro. The V8 gasoline and diesel engines have been used in most Audi, Volkswagen, Porsche, Bentley, and Lamborghini models ever since. The larger-displacement diesel V8 engine configuration has also been used in various Scania commercial vehicles; such as in trucks, buses, and marine (boat) applications.

References

  1. Maxwell, R. J.; Dixon, P. L. (1988). "High Pressure Injection Injuries of the Hand: A Report of Three Cases". ANZ Journal of Surgery. 420 (4): 344–346. doi:10.1111/j.1445-2197.1988.tb01068.x. PMID   3254139.