What is the cut off ratio of a diesel engine?

Answer 1

The thermodynamic cycle which powers a diesel engine has four steps: 1. Adiabatic compression (compression with no heat transfer into or out of the reaction cylinder). 2. Heating at constant pressure. In a diesel engine, the heat generated by the compression step is so great that fuel spontaneously combusts as it's injected into the cylinder; however, this combustion is not instantaneous, so the gases inside the cylinder heat up and expand at constant pressure as the fuel burns. 3. Adiabatic expansion (this is the part where the cylinder is doing work on whatever the engine is hooked up to). 4. Cooling at constant pressure (the exhaust is expelled from the cylinder). The compression ratio is the ratio between the initial volume and the volume at the end of Step 1. The cutoff ratio is the ratio of the volume at the end of Step 1 (BEFORE the fuel is injected and burned) to the volume at the end of Step 2 (AFTER the fuel is injected and burned). The expansion ratio is the ratio of the volume at the end of Step 2 to to volume at the end of Step 3. In case this clarifies, (compression ratio) = (cutoff ratio) * (expansion ratio).