Презентация на тему "Internal combustion engine"

Содержание

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  Internal combustion engine

  By Nikolas nosenko Student ofgroupe immm-11-1 Mmfnmu

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  Invention Invention of the two-stroke cycle is attributed to Scottish engineer Dugald Clerk who in 1881 patented his design, his engine having a separate charging cylinder. Dugald Clerk

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  The two-stroke engine was most popular throughout the 20th century in motorcycles, small engined devices such as chainsaws and outboard motors and some cars. Due to their simple design (and resulting low cost) and higher power-to-weight ratios. 20th century

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  The internal combustion engine is an engine in which the combustion of fuel (generally, fossil fuel) occurs with an oxidizer (usually air) in a combustion chamber.

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  In an internal combustion engine the expansion of the high temperature and pressure gases, which are produced by the combustion, applies forcedirectly to a movable component of the engine, such as the pistons or turbine blades and by moving it over a distance, generates useful mechanical energy.

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  Engines can be classified in many different ways: By the engine cycle used,by the layout of the engine, source of energy, the use of the engine, or by the cooling system employed. But we are both interested in enging cycle classification.

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  1.Cylinder head 2.Cylinder 3.Piston 4.Rod 5.Cranked shaft 1 - головка цилиндра; 2 - цилиндр; 3 - поршень; 4 - шатун; 5 - коленчатый вал;

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  The two main parts of it are

  Two-stroke cycle Four-stroke cycle

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  Two-stroke cycle

  Let's start with the Two-stroke engine. Also it's named "the father of engines" A two-stroke engine is an internal combustion engine that completes the thermodynamic cycle in two movements of the piston compared to twice that number for a four-stroke engine. This increased efficiency is accomplished by using the beginning of the compression stroke and the end of the combustion stroke to perform simultaneously the intake and exhaust (or scavenging) functions. In this way two-stroke engines often provide strikingly high specific power.

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  A two-stroke engine, in this case with a tuned expansion pipe illustrate the effect of a reflected pressure wave on the fuel charge. This feature is essential for maximum charge pressure (volumetric efficiency) and fuel efficiency. It is used on most high-performance engine designs. Two-stroke engine

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  Four-stroke engine

  Today, internal combustion engines in cars, trucks, motorcycles, aircraft, construction machinery and many others, most commonly use a four-stroke cycle. The four strokes refer to intake, compression, combustion (power), and exhaust strokes that occur during two crankshaft rotations per working cycle of the gasoline engine and diesel engine. A less technical description of the four-stroke cycle is, "Suck, Squeeze, Bang, Blow" Four-stroke engine

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  The cycle begins at top dead center (TDC), when the piston is farthest away from the axis of the crankshaft. A stroke refers to the full travel of the piston from Top Dead Center (TDC) to Bottom Dead Center (BDC) Intake   During the intake stroke, the piston moves downward, drawing a fresh charge of vaporized fuel/air mixture. The illustrated engine features a poppet intake valve which is drawn open by the vacuum produced by the intake stroke. Some early engines worked this way; however, most modern engines incorporate an extra cam/lifter arrangement as seen on the exhaust valve. The exhaust valve is held shut by a spring . Compression   As the piston rises, the poppet valve is forced shut by the increased cylinder pressure. Flywheel momentum drives the piston upward, compressing the fuel/air mixture Power   At the top of the compression stroke, the spark plug fires, igniting the compressed fuel. As the fuel burns it expands, driving the piston downward. Exhaust   At the bottom of the power stroke, the exhaust valve is opened by the cam/lifter mechanism. The upward stroke of the piston drives the exhausted fuel out of the cylinder.

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  And let see how to increase the efficiency of these engines with the help of special mechanisms .

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  Supercharging

  One way to increase engine power is to force more air into the cylinder so that more power can be produced from each power stroke. This was originally done using a type of air compression device known as a supercharger, which is powered by the engine crankshaft.   Supercharging increases the power output limits of four-stroke engine, but the supercharger is always running. Continuous compression of the intake air requires some mechanical energy to accomplish, so the supercharger has a cost of reduced fuel efficiency when the engine is operating at low power levels or when the engine is simply unloaded and idling.

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  Turbocharging

  The turbocharger was designed as a part-time method of compressing more air into the cylinder head. It consists of a two piece, high-speed turbine assembly with one side that compresses the intake air, and the other side that is powered by the exhaust gas outflow.  

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  When idling, and at low-to-moderate speeds, the turbocharger is not engaged and the engine operates in a naturally-aspirated manner. When much more power output is required, the engine speed is increased until the exhaust gases are sufficient to 'spin up' the turbocharger's turbine to start compressing much more air than normal into the intake manifold.

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  Turbocharging allows for more efficient engine operation at low-to-moderate speeds, but there is a design limitation known as turbo lag. The increased engine power is not immediately available, due to the need to sharply increase engine RPM to spin up the turbo, before the turbo starts to do any useful air compression. Turbocharging allows for more efficient engine operation at low-to-moderate speeds, but there is a design limitation known as turbo lag. The increased engine power is not immediately available, due to the need to sharply increase engine RPM to spin up the turbo, before the turbo starts to do any useful air compression.