Heat Engine :

(Power Plant of an Automobile) 

A device which is used to convert one form of energy into mechanical energy is called an Engine. The heat energy produced by burning of the fuel is converted into mechanical power, then it is called a Heat Engine. 

Heat engines are classified into two types. 

1.External Combustion Engine 

2.Internal Combustion Engine 

1. External Combustion Engine 

An external combustion engine is a Heat engine where a working fluid, is heated by combustion in an external source like Boiler. The fluid then, by expanding and acting on the mechanism of the engine, produces motion and usable work. The combustion process takes place outside the mechanical engine system.

 Eg. Steam Engines, Ancient Marine Engines 

2.Internal Combustion Engine 

An internal combustion engine (ICE) is a Heat engine where the combustion of a fuel and air occurs inside the engine combustion chamber that is an integral part of an engine. 

ENGINE CLASSIFICATION

Internal combustion engines can be classified in a number of different ways: 

Types of Ignition

 (a) Spark Ignition (SI).

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 airfuel mixture in the combustion chamber surrounding the plug

(b) Compression Ignition (CI).

The combustion process in a Cl engine starts when the air-fuel mixture self-ignites due to high temperature in the combustion chamber caused by high compression 

Engine Cycle 

(a)Four-Stroke Cycle. A four-stroke cycle experiences four times piston movements over two engine revolutions for each cycle. 

(b) Two-Stroke Cycle. A two-stroke cycle has two times piston movements over one revolution for each cycle 

Valve Location

 (a) Valves in head (overhead valve), also called I Head engine.

 (b) Valves in block (flat head), also called L Head engine.

 (c) One valve in head (usually intake) and one in block, also called F Head engine

 Basic Design 

a) Reciprocating. 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. 

b) Rotary. Engine is made of a block (stator) built around a large non-concentric rotor and crankshaft. The combustion chambers are built into the nonrotating block

Position and Number of Cylinders of Reciprocating Engines 

(a) Single Cylinder. Engine has one cylinder and piston connected to the crankshaft.

(b) In-Line. Cylinders are positioned in a straight line. In-line engines are sometimes called straight Which are one behind the other along the length of the crankshaft. 

(c) V Engine. 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.

 (d) Opposed Cylinder Engine. 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) W Engine. Same as a V engine except with three banks of cylinders on the same crankshaft. Not common, but some have been developed for racing automobiles, both modern and historic. Usually 12 cylinders with about a 60° angle between each bank. 

(f) Opposed Piston Engine. Two pistons in each cylinder with the combustion chamber in the center between the pistons. A single combustion process causes two power strokes at the same time, with each piston being pushed away from the center and delivering power to a separate crankshaft at each end of the cylinder. Engine output is either on two rotating crankshafts or on one crankshaft incorporating complex mechanical linkage. 

(g) Radial Engine. 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. 

Air Intake Process 

(a) Naturally Aspirated. No intake air pressure boost system.

(b) Supercharger. Intake air pressure with the compressor driven off of crankshaft which gives fast response changes but adds load to engine. 

(c)Turbocharger. Intake air pressure increased with the turbine-compressor driven b engine exhaust gases.it is used to in inlet air pressure to engine. Turbine that compressor is powered by exhaust flow engine. This adds no load to the engine results in turbo lag, a slower respo engine speed changes. (discussed intopic) 

(d) Crankcase Compressed. Two-stroke cycle engine which uses the crankcase as the intake
air compressor. 

Method of Fuel Input for SI Engines

 (a) Carburetted. 

(b) Multipoint Port Fuel Injection. One or more injectors at each cylinder intake. 

(c) Throttle Body Fuel Injection. Injectors upstream in intake manifold. 

Fuel Used 

(a) Petrol/Gasoline. 

(b) Diesel Oil or Fuel Oil. 

(c) Gas, Natural Gas, Methane. 

(d) LPG. (e) Alcohol-Ethyl, Methyl. 

(f) Dual Fuel. 

(g) Gasohol. (Common fuel consisting of 90% gasoline and 10% alcohol.) Note- There are a number of engines that use a combination of two or more fuels. Some, usually large, CI engines use a combination of methane and diesel fuel. 

These are attractive in developing third-world countries because of the high cost of diesel fuel. Combine gasoline-alcohol fuels are becoming" common as an alternative to straight gun automobile engine fuel.

Application

(a) Automobile, Truck, Bus. 

(b) Locomotive, ( Railway ) 

(c) Stationary.

(d) Marine

(e) Aircraft

(f) Small Portable,Chain Snaw,Model Airplane.

Types Of Cooling:

(a)Air Cooled

(b) Liquid Cooled/Water Cooled