Types Of Engine used In Mechanical Applications
Types Of Engine used In Mechanical Applications
A heat engine is a device which transforms the chemical energy of a fuel into thermal energy and uses this energy to produce mechanical work. It is classified into two types-
(a) External combustion engine
(b) Internal combustion engine
External combustion engine:
In this engine, the products of combustion of air and fuel transfer heat to a second fluid which is the working fluid of the cycle.
- In the steam engine or a steam turbine plant, the heat of combustion is employed to generate steam which is used in a piston engine (reciprocating type engine) or a turbine (rotary type engine) for useful work.
- In a closed cycle gas turbine, the heat of combustion in an external furnace is transferred to gas, usually air which the working fluid of the cycle.
Internal combustion engine:
- In this engine, the combustion of air and fuels take place inside the cylinder and are used as the direct motive force. It can be classified into the following types:
1. According to the basic engine design-
(a) Reciprocating engine (Use of cylinder piston arrangement),-
Engine has one or more cylinders in which pistons reciprocate back and forth. The combustion chamber is located in the closed end of each cylinder. Power is delivered to a rotating output crankshaft by mechanical linkage with the pistons.
(b) Rotary engine (Use of turbine)-
It also called as wankle engine. you can read more information about rotary engine here: Seminar report on wankle-rotary engine
2. According to the type of fuel used-
(a) Petrol engine,
(b) diesel engine,
(c) gas engine (CNG, LPG),
(d) Alcohol engine (ethanol, methanol etc)
3. According to the number of strokes per cycle-
(a) Four stroke and –
A four-stroke cycle experiences four piston movements over two engine revolutions for each cycle
(b) Two stroke engine-
A two-stroke cycle has two piston movements over one revolution for each cycle.
4. According to the method of igniting the fuel-
(a) Spark ignition engine-
An SI engine starts the combustion process in each cycle by use of a spark plug. The spark plug gives a high-voltage electrical discharge between two electrodes which ignites the air-fuel mixture in the combustion chamber surrounding the plug. In early engine development, before the invention of the electric spark plug, many forms of torch holes were used to initiate combustion from an external flame.
(b) compression ignition engine –
The combustion process in a CI engine starts when the air-fuel mixture self-ignites due to high temperature in the combustion chamber caused by high compression.
(c) hot spot ignition engine
5. According to the working cycle-
(a) Otto cycle (constant volume cycle) engine,
(b) diesel cycle (constant pressure cycle) engine,
(c) dual combustion cycle (semi diesel cycle) engine.
6. According to the fuel supply and mixture preparation-
(a) Carburetted type (fuel supplied through the carburettor),
(b) Injection type (fuel injected into inlet ports or inlet manifold, fuel injected into the cylinder just before ignition).
7. According to the number of cylinder-
a) Single cylinder and -Engine has one cylinder and piston connected to the crankshaft.
(b) multi-cylinder engine
8. Method of cooling–water cooled or air cooled
9. Speed of the engine-Slow speed, medium speed and high speed engine
10. Cylinder arrangement-
Cylinders are positioned in a straight line, one behind the other along the length of the crankshaft. They can consist of 2 to 11 cylinders or possibly more. In-line four-cylinder engines are very common for automobile and other applications. In-line six and eight cylinders are historically
common automobile engines. In-line engines are sometimes called straight (e.g., straight six or straight eight).
Two banks of cylinders at an angle with each other along a single crankshaft. The angle between the banks of cylinders can be anywhere from 15°to 120°, with 60°-90° being common. V engines have even numbers of cylinders from 2 to 20 or more. V6s and V8s are common automobile engines, with V12s and V16s (historic) found in some luxury and high-performance vehicles.
Engine with pistons positioned in a circular plane around the central crankshaft. The connecting rods of the pistons are connected to a master rod which, in turn, is connected to the crankshaft. A bank of cylinders on a radial engine always has an odd number of cylinders ranging from 3 to 13 or more. Operating on a four-stroke cycle, every other cylinder fires and has a power stroke as the crankshaft rotates, giving a smooth operation. Many medium- and large-size propeller-driven aircraft use radial engines. For large aircraft, two or more banks of cylinders are mounted together, one behind the other on a single crankshaft, making one powerful, smooth engine. Very large ship engines exist with up to 54 cylinders, six banks of 9 cylinders each.
f) opposed cylinder or piston engines.
Two banks of cylinders opposite each other on a single crankshaft (a V engine with a 180°V). These are common on small aircraft and some automobiles with an even number of cylinders from two to eight or more. These engines are often called flat engines (e.g., flat four).
11) According to Valve Location:
(a) Valves in head (overhead valve), also called I Head engine.
(b) Valves in block (flat head), also called L Head engine.
Some historic engines with valves in block had the intake valve on one side of the cylinder and the exhaust valve on the other side. These were called T Head engines.
c) One valve in head (usually intake) and one in block, also called F Head engine; this is much less common.
12) Air Intake Process
(a) Naturally Aspirated. No intake air pressure boost system.
(b) Supercharged. Intake air pressure increased with the compressor driven off of the engine crankshaft
Intake air pressure increased with the turbine-compressor driven by the engine exhaust gases
(d) Crankcase Compressed.
Two-stroke cycle engine which uses the crankcase as the intake air compressor. Limited development work has also been done on design and construction of four-stroke cycle engines with crankcase compression.
13 ) Method of Fuel Input for SI Engines
(b) Multipoint Port Fuel Injection. One or more injectors at each cylinder intake.
(c) Throttle Body Fuel Injection. Injectors upstream in intake manifold
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