Tec 9 Fuel Injector

[Enrichetta]

Fuel injection is the introduction of fuel in an internal combustion engine, most commonly automotive engines, by the means of an injector. This article focuses on fuel injection in reciprocating piston and Wankel rotary engines.

All compression-ignition engines (e.g. diesel engines), and many spark-ignition engines (i.e. petrol (gasoline) engines, such as Otto or Wankel), use fuel injection of one kind or another. Mass-produced diesel engines for passenger cars (such as the Mercedes-Benz OM 138) became available in the late 1930s and early 1940s, being the first fuel-injected engines for passenger car use.[1] In passenger car petrol engines, fuel injection was introduced in the early 1950s and gradually gained prevalence until it had largely replaced carburetors by the early 1990s.[2] The primary difference between carburetion and fuel injection is that fuel injection atomizes the fuel through a small nozzle under high pressure, while carburetion relies on suction created by intake air accelerated through a Venturi tube to draw fuel into the airstream.

The term "fuel injection" is vague and comprises various distinct systems with fundamentally different functional principles. Typically, the only thing all fuel injection systems have in common is a lack of carburetion. There are two main functional principles of mixture formation systems for internal combustion engines: internal mixture formation and external mixture formation. A fuel injection system that uses external mixture formation is called a manifold injection system. There exist two types of manifold injection systems: multi-point injection (or port injection) and single-point injection (or throttle body injection). Internal mixture formation systems can be separated into several different varieties of direct and indirect injection, the most common being the common-rail injection system, a variety of direct injection. The term "electronic fuel injection" refers to any fuel injection system controlled by an engine control unit.

Several early mechanical injection systems used relatively sophisticated helix-controlled injection pump(s) that both metered fuel and created injection pressure. Since the 1980s, electronic systems have been used to control the metering of fuel. More recent systems use an electronic engine control unit which meters the fuel, controls the ignition timing and controls various other engine functions.

The fuel injector is effectively a spray nozzle that performs the final stage in the delivery of fuel into the engine. The injector is located in the combustion chamber, inlet manifold or - less commonly - the throttle body.

Direct injection means that the fuel is injected into the main combustion chamber of each cylinder.[3] The air and fuel are mixed only inside the combustion chamber. Therefore, only air is sucked into the engine during the intake stroke. The injection scheme is always intermittent (either sequential or cylinder-individual).

This can be done either with a blast of air[4] or hydraulically, with the latter method being more common in automotive engines. Typically, hydraulic direct injection systems spray fuel into the air inside the cylinder or combustion chamber. Direct injection can be achieved with a conventional helix-controlled injection pump, unit injectors, or a sophisticated common-rail injection system. The latter is the most common system in modern automotive engines.

In a common rail system, fuel from the fuel tank is supplied to a common header (called the accumulator), and then sent through tubing to the injectors, which inject it into the combustion chamber. The accumulator has a high-pressure relief valve to maintain pressure and return the excess fuel to the fuel tank. The fuel is sprayed with the help of a nozzle that is opened and closed with a solenoid-operated needle valve.[5] Third-generation common rail diesels use piezoelectric injectors for increased precision, with fuel pressures up to 300 MPa or 44,000 psi.[6]

The M-System, used in some diesel engines from the 1960s to the 1980s, sprayed the fuel onto the walls of the combustion chamber,[12] as opposed to most other direct-injection systems which spray the fuel into the middle of the chamber.

Manifold injection systems are common in petrol-fuelled engines such as the Otto engine and the Wankel engine. In a manifold injection system, air and fuel are mixed outside the combustion chamber so that a mixture of air and fuel is sucked into the engine. The main types of manifold injections systems are multi-point injection and single-point injection.

These systems use either a continuous injection or an intermittent injection design.[13] In a continuous injection system, fuel flows at all times from the fuel injectors, but at a variable flow rate. The most common automotive continuous injection system is the Bosch K-Jetronic system, introduced in 1974 and used until the mid-1990s by various car manufacturers. Intermittent injection systems can be sequential, in which injection is timed to coincide with each cylinder's intake stroke; batched, in which fuel is injected to the cylinders in groups, without precise synchronization to any particular cylinder's intake stroke; simultaneous, in which fuel is injected at the same time to all the cylinders; or cylinder-individual, in which the engine control unit can adjust the injection for each cylinder individually.[13]

Multi-point injection (also called 'port injection') injects fuel into the intake ports just upstream of each cylinder's intake valve, rather than at a central point within an intake manifold.[14] Typically, multi-point injected systems use multiple fuel injectors,[15] but some systems, such as GM's central port injection system, use tubes with poppet valves fed by a central injector instead of multiple injectors.[16]

In indirect-injected diesel engines (as well as Akroyd engines), there are two combustion chambers: the main combustion chamber, and a pre-chamber (also called an ante-chamber)[18] that is connected to the main one. The fuel is injected only into the pre-chamber (where it begins to combust), and not directly into the main combustion chamber. Therefore, this principle is called indirect injection. There exist several slightly different indirect injection systems that have similar characteristics.[19]

In 1891, the British Herbert-Akroyd oil engine became the first engine to use a pressurised fuel injection system.[25][26] This design, called a hot-bulb engine used a 'jerk pump' to dispense fuel oil at high pressure to an injector. Another development in early diesel engines was the pre-combustion chamber, which was invented in 1919 by Prosper l'Orange[27] to avoid the drawbacks of air-blast injection systems. The pre-combustion chamber made it feasible to produce engines in size suitable for automobiles and MAN Truck & Bus presented the first direct-injected diesel engine for trucks in 1924.[20] Higher pressure diesel injection pumps were introduced by Bosch in 1927.

In 1898, German company Deutz AG started producing four-stroke petrol stationary engines[28] with manifold injection.[citation needed] The 1906 Antoinette 8V aircraft engine (the world's first V8 engine) was another early four-stroke engine that used manifold injection. The first petrol engine with direct-injection was a two-stroke aircraft engine designed by Otto Mader in 1916.[29] Another early spark-ignition engine to use direct-injection was the 1925 Hesselman engine, designed by Swedish engineer Jonas Hesselman.[30][31] This engine could run on a variety of fuels (such as oil, kerosene, petrol or diesel oil)[32] and used a stratified charge principle whereby fuel is injected towards the end of the compression stroke, then ignited with a spark plug.

The Cummins Model H diesel truck engine was introduced in America in 1933.[33] In 1936, the Mercedes-Benz OM 138 diesel engine (using a precombustion chamber) became one of the first fuel-injected engines used in a mass-production passenger car.[34]

During World War II, several petrol engines for aircraft used direct-injection systems, such as the European Junkers Jumo 210, Daimler-Benz DB 601, BMW 801, and the Shvetsov ASh-82FN (M-82FN). The German direct-injection systems were based on diesel injection systems used by Bosch, Deckel, Junkers and l'Orange.[35] By around 1943, the Rolls-Royce Merlin and Wright R-3350 had switched from traditional carburettors to fuel-injection (called "pressure carburettors" at the time), however these engines used throttle body manifold injection, rather than the direct-injection systems of the German engines. From 1940, the Mitsubishi Kinsei 60 series engine used a direct-injection system, along with the related Mitsubishi Kasei engine from 1941. In 1943, a low-pressure fuel injection system was added to the Nakajima Homare Model 23 radial engine.[36]

The first mass-produced petrol direct-injection system was developed by Bosch and initially used in small automotive two-stroke petrol engines. Introduced in the 1950 Goliath GP700 small saloon, it was also added to the Gutbrod Superior engine in 1952. This mechanically-controlled system was essentially a specially lubricated high-pressure diesel direct-injection pump of the type that is governed by the vacuum behind an intake throttle valve.[37] A Bosch mechanical direct-injection system was also used in the straight-eight used in the 1954 Mercedes-Benz W196 Formula One racing car. The first four-stroke direct-injection petrol engine for a passenger car was released the following year, in the Mercedes-Benz 300SL sports car.[38] However the engine suffered lubrication problems due to petrol diluting the engine oil,[39][40] and subsequent Mercedes-Benz engines switched to a manifold injection design. Likewise, most petrol injection systems prior to the 2000s used the less-expensive manifold injection design.

Throughout the 1950s, several manufacturers introduced their manifold injection systems for petrol engines. Lucas Industries had begun developing a fuel injection system in 1941 and by 1956 it was used in the Jaguar racing cars.[41] At the 1957 24 Hours of Le Mans, the 1st to 4th placed cars were Jaguar D-Type entries using a Lucas fuel injection system.[42] Also in 1957, General Motors introduced the Rochester Ramjet option, consisting of a fuel injection system for the V8 engine in the Chevrolet Corvette. During the 1960s, fuel injection systems were also produced by Hilborn,[43] SPICA[44] and Kugelfischer.

c80f0f1006