![]() ![]() Its purpose is to prepare the mixture for combustion by increasing its temperature and pressure. The intake stroke is succeeded by the compression stroke which effectively starts at the intake valve closure. The closing time of the intake valve(s) is a function of the design of the induction manifold, which influences the gas dynamics and volumetric efficiency of the engine, and engine speed. Effectively, the induction process starts with the opening of the intake valve just before top-dead-center (TDC) and ends when the intake valve (or valves in four-valve per-cylinder engines) closes shortly after BDC. The mixture is generated either by means of a carburetor (as in conventional engines) or by injection of gasoline at low pressure into the intake port through an eiectronically-controlled pintle-type injector (as in more advanced engines). The intake stroke is initiated by the downward movement of the piston, which draws into the cylinder fresh fuel/air mixture through the port/valve assembly, and ends when the piston reaches bottom-dead-center (BDC). Each engine cylinder requires four strokes of its piston which corresponds to two crankshaft revolutions to complete the sequence which lead to the production of power. The majority of reciprocating internal combustion engines operate on what is known as the four-stroke cycle ( Figure 1), which is subdivided into four processes: intake, compression, expansion/ power and exhaust. From all these types, the passenger car gasoline and diesel engines have a prominent position since they are, by far, the largest produced engines in the world as such, their influence on social and economic life is of paramount importance. Within these two extremes lie medium-speed diesel engines, heavy-duty automotive diesels, truck and passenger car engines, aircraft engines, motorcycle engines and small industrial engines. This implies that the size and characteristics of today's engines vary widely between large diesels having cylinder bores exceeding 1,000 mm and reciprocating at speeds as low as 100 rpm to small gasoline two-stroke engines with cylinder bores around 20 mm. Internal combustion engines are used in applications ranging from marine propulsion and power generating sets with capacity exceeding 100 MW to hand-held tools where the power delivered is less than 100 W. Although Gas Turbines satisfy the definition of an IC engine, the term has been traditionally associated with spark-ignition (sometimes called Otto, gasoline or petrol engines) and diesel engines (or compression-ignition engines). It is this specific point, that fuel is burned inside the work-producing part of the engine, that gives IC engines their name and distinguishes them from other types such as external combustion engines. ![]() Its purpose is to generate mechanical power from the chemical energy contained in the fuel and released through combustion of the fuel inside the engine. The internal combustion (IC) engine has been the dominant prime mover in our society since its invention in the last quarter of the 19th century. ![]()
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