Here is the complete guide about Compression Ratio. Here we provides Compression Ratio working principle and Advantages of Higher Compression Ratio ect.
Compression Ratio is one of the essential specifications of an Internal Combustion engine. It is the ratio of the volume above the piston when it is at the bottom-most position (BDC) to the extent above the piston when it is at the top-maximum position (TDC). It indicates the quantity to which the air-gasoline mixture is compressed in the engine.
A compression ratio (CR) of an I C engine is the ratio of the total volume of the combustion chamber To the volume left after complete compression i.e. clearance volume. In easy words, it is the ratio among the total volume of the combustion chamber that is left when the piston is at its bottom dead middle and the volume left inside the combustion chamber whilst the piston actions to its top dead center.
Since Petrol may be very volatile, the ‘Compression Ratio’ for Petrol engines is generally lower. Thus, it varies from 10:1 to 14:1. The petrol engine compresses the air & gas with a ratio among 10:1 to 14:1. The petrol engine mixes petrol with air & compresses this mixture in the combustion chamber. The higher blending of air and gas with each other makes it homogeneous. An electric powered spark-plug then ignites the compressed air-gas mixture with a spark. Thus, it reasons the gas to burn absolutely and instantly.
In diesel engines, the ‘Compression-Ratio’ varies from 18:1 to 23:1, which depends on engine design & construction. The petrol engines use the ‘Spark Ignition’ method. However, the diesel engine technologies such as ‘Direct Injection’ & ‘InDirect Injection’ & ‘Common-rail Direct Injection’ use the ‘Compression Ignition‘ method. However, the compression ratio remains almost the same for both the petrol engine and diesel engine, respectively, regardless of the engine capacity/displacement.
The compression ratio (CR) of an I C engine is a design criterion that must be decided through the layout group at the same time as designing the engine; the CR is chosen in line with the output want of the engine as it directly affects the engine output and also the overall size of the engine.
The want of the CR is exclusive for diesel and petrol engines which can be as follows-
If we talk about 4-stroke petrol engine the compression ratio has its own significance that are-
When it comes to diesel engines the compression ratio has its greater significance as-
The better the compression-ratio, the better is the thermal efficiency of the engine. Thus, the engine can extract more mechanical strength from the given mass of the air-gas mixture. In that context, diesel engines have enhanced gas efficiency for the given amount of gas than petrol engines of the same size.
It means that let’s say; you compare the conventional petrol and diesel engines with the same engine capacity of 1.0L. Then, in the real world, the 1.0L diesel engine will consume much less gas than the 1.0L petrol engine. In other words, a automobile with a 1.0L diesel engine would give higher mileage in comparison to the only with a 1.0L petrol engine under similar driving conditions.