Which of the following stages describe the physical and chemical progression of combustion inside a Compression Ignition (CI) diesel engine cylinder?
Options:
(A) Ignition delay period (physical atomization and chemical pre-ignition preparation)
(B) Period of rapid uncontrolled combustion (premixed combustion)
(C) Period of controlled combustion (mixing-controlled diffusion combustion)
(D) Isothermal expansion phase
Answer Key:
A, B, C
Step-by-Step Solution & Explanation
The four distinct stages of CI combustion (Ricardo's classical model) are:
1. **Ignition delay period:** Time between start of injection and start of combustion.
2. **Period of rapid uncontrolled combustion:** Fuel accumulated during delay burns rapidly, causing steep pressure rise.
3. **Period of controlled combustion:** Rate of burning is governed by rate of fuel injection and air-fuel mixing.
4. **Period of after-burning:** Unburnt fuel soot and CO continue to burn along the expansion stroke.
- There is no isothermal expansion phase.