Diesel Engine Cycle
The Diesel Engine Cycle
- A diesel engine cycle is not that different from a petrol engine cycle
- It still consists of 4 strokes, but they work differently
The four 'strokes' of the diesel engine cycle
- In the induction (or intake) stroke, only air is drawn into the cylinder (compared to a petrol-air mixture in the petrol engine)
- This means there is no fuel in the cylinder during compression
- During the compression stroke, the air is compressed at a high temperature which vapourises and ignites the diesel fuel (as a fine spray) pumped directly into the cylinder through an injector
- The expansion and exhaust stages are similar
Indicator Diagrams
- This theoretical diagram would look like this:
Theoretical indicator diagram for a four-stroke diesel engine
- From A to B:
- The gas is compressed adiabatically
- From B to C:
- Heat is supplied and the pressure is kept constant
- From C to D:
- The gas expands adiabatically (cooling)
- From D to E:
- The system is cooled at a constant volume
- The actual indicator diagram looks like:
- The biggest difference is from B to C - there is no sharp peak at the start of the expansion stroke
