Test: Combustion & Combustion Chambers Of IC Engine - 2 - Mechanical Engineering MCQ

F - head type have E valve in head and I valve in the cylinder block which are separately actuated by two cams mounted on two camshafts driven by the crankshaft through gears.

Factors affecting the delay period:
(i) Compression ratio
(ii) Engine speed
(iii) Output
(iv) Atomization of fuel injection duration
(v) Injection timing
(vi) Quality of the fuel
(vii) Intake temperature
(viii) Intake pressure

The delay period increases with increase in injection advance which favour knocking tendency.

Characteristics tending to reduce detonation or knock

In shallow depth chamber, the depth of the cavity provided in the piston is quite small. The squish is negligible due to very large cavity diameter. All these types are direct-injection chamber.

Advantages

• Injection pressure required is low
• Direction of spraying is not very important

Disadvantages

• Poor cold starting performance requiring heater plugs
• Sfc is high because there is a less of pressure due to air motion through the duct and heat less due to large heat transfer area.

Self ignition temperature of diesel is around 450°C and for petrol is around 550°C.

The silencer of an internal combustion engine is a device to reduce the noise level of engine so that it does’t harm the people.

At the end of the expansion stroke, the combustion chamber of a two-stroke engine is left full of combustion product. This is because, unlike four-stroke engine there is no exhaust stroke available to clear the cylinder of burnt gases.
The process of clearing the cylinder, after the expansion stroke is called scavenging process.

Squish is the flow of air, radially inwards towards the combustion recess by squeezing it out from the piston and cylinder head as they approach to each other at the end of stroke.

With no dissociation maximum temperature is attained with chemically correct fuel air mixture while with dissociation maximum temperature is obtained when mixture is about 10% rich.

As quantity of air increases, the cycle tends towards the air standard cycle since in air standard cycle working fluid is air only.

Due to less amount of fuel and more amount of air thermal efficiency at leaner mixture will be high but due to less amount of fuel heat generated will be less and hence less power output.