STRATIFIED CHARGE ENGINE

Of many types of internal combustion engine, two types, namely diesel and petrol engine are well established. However each one of them has certain limitations. The petrol engine has very good full load power characteristic, but has rather poor part load efficiency, whereas the diesel engine has good part load characteristic but has poor air utilization, low smoke limited power and higher weight to power ratio. The use of higher compression ratio for better starting and good combustion over a wide range of engine operation are other requirement which pose additional problems of maintenance and high losses in diesel operation. For an automotive engine both part load efficiency and full load power are very important.
Therefore, there is a need to develop an engine which combines the advantages of both petrol and diesel engine and at the same time avoid as far as possible their disadvantages. Stratified engine is midway between the homogenous charge spark ignition engine and the heterogeneous charge compression ignition engine.
Charge stratified means provided different fuel air mixture strength at various places in the combustion chamber – a relatively rich mixture at and the vicinity of the spark plug and a leaner mixture in the rest of combustion chamber
The principle of the stratified charge engine is to deliver a mixture that is sufficiently rich for combustion in the immediate vicinity of the spark plug and in the remainder of the cylinder, a very lean mixture that is so low in fuel that it could not be used in a traditional engine. On an engine with stratified charge, the delivered power is no longer controlled by the quantity of admitted air, but by the quantity of petrol injected, as with a diesel engine.