2015 SUMMER

The major air pollutants emitted by petrol & diesel engines are CO2, CO, HC, NOx, SO2, smoke & lead vapour. Effect of CO: (1) Carbon monoxide combines with hemoglobin forming carboy hemoglobin ,which reduces oxygen carrying capacity of blood. (2) This leads to laziness, exhaustion of body & headache. (3) Prolong exposure can even leads to death. (4) It also affects cardiovascular system, thereby causing heart problem Effect of CO2: Causes respiratory disorder & suffocation.

The loud pulsating noise heard within the engine cylinder is known as detonation. The following are the certain factors which causes detonation. (1) The shape of the combustion chamber. (2) The relative position of the sparking plugs in case of petrol engines. (3) The chemical nature of the fuel. (4) The initial temp & pressure of fuel (5) The rate of combustion of that portion of fuel which is the first to ignite. This portion of fuel in heating up , compresses the remaining unburnt fuel, thus producing the condition for auto ignition to occur.

Necessity of multistage compression i) As index of compression ‘n’ increases it increases compression work. ii) Increase in pressure ratio (P2/P1) it increases work as well as size of cylinder. iii) Increment in pressure ratio (P2/P1) beyond certain limit, volumetric efficiency decreases while it increases leakage loss on either sides the piston and valves. Due to above pointes and for higher pressure ratio compressor needs multistaging.