Which of the following processes is NOT comprised by Diesel cycle?
Addition of heat at constant volume
Understanding the Diesel Cycle Processes
The Diesel cycle is a thermodynamic cycle that describes how internal combustion ignition engines operate. It is different from other cycles like the Otto cycle, particularly in how heat is added.
Key Processes in the Ideal Diesel Cycle
The ideal Diesel cycle consists of four distinct processes. These processes are typically represented on a Pressure-Volume (P-V) or Temperature-Entropy (T-S) diagram.
Here are the four processes that make up the ideal Diesel cycle:
- Process 1-2: Reversible Adiabatic Compression (Isentropic Compression)
- Process 2-3: Constant Pressure Heat Addition (Isobaric Heat Addition)
- Process 3-4: Reversible Adiabatic Expansion (Isentropic Expansion)
- Process 4-1: Constant Volume Heat Rejection (Isochoric Heat Rejection)
Analysing the Given Options
Let's examine each option provided and see if it is part of the ideal Diesel cycle.
| Option Description | Part of Ideal Diesel Cycle? | Notes |
|---|---|---|
| Addition of heat at constant volume | No | Heat addition in the Diesel cycle occurs at constant pressure. This process is characteristic of the Otto cycle. |
| Adiabatic expansion and compression | Yes | Processes 1-2 (compression) and 3-4 (expansion) in the Diesel cycle are adiabatic (isentropic). |
| Rejection of heat at constant volume | Yes | Process 4-1 in the Diesel cycle involves heat rejection at constant volume. |
| Addition of heat at constant pressure | Yes | Process 2-3 in the Diesel cycle involves heat addition at constant pressure. |
Based on this analysis, the process that is NOT comprised by the Diesel cycle is the "Addition of heat at constant volume". Heat addition in the ideal Diesel cycle happens at constant pressure.
Distinguishing Diesel Cycle from Otto Cycle
A key difference between the Diesel cycle and the Otto cycle (which represents petrol engines) lies in the heat addition process. In the Otto cycle, heat addition occurs at constant volume, while in the Diesel cycle, it occurs at constant pressure.
Therefore, any process involving "Addition of heat at constant volume" is not part of the Diesel cycle.
Important Questions from Diesel Cycle
The compression ratio of diesel engines normally have the range:
Which of the following is NOT related to a spark ignition engine?
In CI engines, the combustion is:
Which is the first stage of combustion in an SI engine?
An air standard Otto cycle consists of ______.
