APPLIED THERMAL ENGINEERING IMPORTANT QUESTIONS

1. P-V and T-s Diagrams of Diesel Cycle:

p-V Diagram	T-s Diagram

Otto cycle is a gas power cycle that is used in spark-ignition internal combustion engines (modern petrol engines). This cycle was introduced by Dr. Nikolaus August Otto, a German Engineer.

An Otto cycle consists of four processes:

1. Two isentropic (reversible adiabatic) processes
2. Two isochoric (constant volume) processes

These processes can be easily understood if we understand p-V (Pressure-Volume) and T-s (Temperature-Entropy) diagrams of Otto cycle.

2. P-V and T-s Diagrams of Otto Cycle:

p-V Diagram	T-s Diagram

Note:

In the above diagrams,

p → Pressure

V → Volume

T → Temperature

s → Entropy

Vc → Clearance Volume

Vs → Stroke Volume

3. DUAL Cycle:

The cycle is the equivalent air cycle for reciprocating high speed compression ignition engines. The P-V and T-s diagrams are shown in Figs.12 and 13. In the cycle, compression and expansion processes are isentropic; heat addition is partly at constant volume and partly at constant pressure while heat rejection is at constant volume as in the case of the Otto and Diesel cycles.

4. Baryton Cycle:

The Brayton cycle is a theoretical cycle for simple gas turbine. This cycle consists of two

isentropic and two constant pressure processes. Figure.4.10 shows the Brayton cycle

on p-v and T-s coordinates. The cycle is similar to the Diesel cycle in compression and

heat addition. The isentropic expansion of the Diesel cycle is further extended followed

by constant pressure heat rejection. The thermal efficiency is given by,

ηth = Heat added - Heat rejected / Heat added