IGNITION SYSTEM ( Function and Requirements)

-
IGNITION SYSTEM

FUNCTION

The function of the ignition system is to produce a spark in the engine cylinder towards the end of the compression stroke. In a four-stroke engine, a spark should occur in each cylinder after two revolutions of the crankshaft, whereas in a two-stroke engine a spark in each cylinder is required every revolution of the crankshaft. Thus, for instance, in a 6-cylinder 4 stroke engine running at 5000 r.p.m., the number of sparks required per minute will be 15000 and these have to be timed very accurately.


REQUIREMENTS OF AN IGNITION SYSTEM

1. Spark at the plug electrodes must be regular and synchronously timed with respect to the cylinder-piston position at all speeds and loads on the engine.

2. The spark should be sufficiently strong so as to start ignition of the charge. Since lean air fuel mixtures are less conductive, they require higher ignition voltages. Thus on modem emission-controlled engines that use lean-mixtures, higher-voltage ignition system is required. Moreover , due to higher secondary voltage in these systems, it becomes necessary to increase the electrical insulation

3. The spark duration should be sufficient to establish burning of the air-fuel mixture under all conditions.

4. It should have the ability to produce spark even when a shunt is established over the spark plug electrodes, possibly due to carbon, oil or lead deposits, liquid fuel or water condensation.

5. The power consumed to produce spark should be minimum.

6. It should have service life at least equal to that of the engine.

7. The system must be easy to maintain. .

8. It must not cause radio interference

9. It should be light and compact.

10. It should be adaptable to mass production.

Popular posts from this blog

INTRODUCTION TO ENGINE

-
Image
Engine : It acts as the power unit. The internal combustion engine is the most commonly used in automobiles. It is of two types ; (i) Spark ignition (ii) Compression ignition.         Both engines are called heat engines. A steam engine is an external combustion engine because the fuel is burned outside the engine. The principle of working of an external combustion engine is shown in the figure below. COMPARISON BETWEEN INTERNAL AND EXTERNAL COMBUSTION ENGINES      The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber. In an internal combustion engine the expansion of the high temperature and pressure gases, which are produced by the combustion, directly applies force to a movable component of the engine, such as the pistons and by moving it over a distance, generate useful mechanical energy.          The internal combustion engine...
Read more

FOUR STROKE SPARK IGNITION (PETROL) ENGINE

-
Image
FOUR STROKE PETROL ENGINE MAIN PARTS 1. PISTON 2. CYLINDER 3. CONNECTING ROD 4. INLET VALVE 5. EXHAUST VALVE 6. SPARK PLUG 7. CRANK SHAFT 8. FLY WHEEL 9. CAM SHAFT CONSTRUCTION A four stroke petrol engine have a piston, connecting rod, crank shaft, inlet valve, exhaust valve and a spark plug. The connecting rod is used to connect the piston and crank shaft. The spark plug and valves are mounted in the cylinder head. Also the valves are operated by cam shaft which is connected to the crank. In this type of engines, there would be a power stroke for every two rotations of crank shaft. It is also known as otto cycle. Each full rotation of crank having two strokes. So one stroke is  180° rotation of flywheel. A four stroke petrol engine having the following strokes. WORKING Induction stroke : The crankshaft moves the piston downwards (TDC to BDC). The inlet valve is open and a mixture of fuel and air is sucked into the combustion chamber. It is also known suction stroke. In this strok...
Read more

MAJOR PARTS OF AN IC ENGINE

-
Image
ENGINE COMPONENTS 1. CYLINDER BLOCK      The cylinder block is the main body of the engine. Cylinder head is mounted on the cylinder block. It houses iniet and exhaus valves. Crank case is attached to the bottom of the cylinder block. Crank case supports the crank shaft. Oil pan is attached to the bottom of the crank case. Cylinder block contains large cylindrical holes called cylinder bore. The cylinders are accurately finished to accommodate pistons. The space above the piston inside the cylinder at TDC called the combustion chamber. Combustion of fuel inside this space, high pressure and temperature will be developed inside the cylinder. Therefore, it should be made of material which can resist high pressure and temperature (2800°C). In water jackets has around the cylinders for the circulation cooling water to absorb the temperature while running of an engine. 2. CYLINDER HEAD Cylinder head is a separate casting placed on top of the cylinder block by studs and nuts. I...
Read more