Gas Cycle

Types of gas cycles

Otto Cycle : Ideal cycle for spark-ignition engine

Diesel Cycle : Ideal cycle for compression-ignition engine

Brayton Cycle : Ideal cycle for gas-turbine engine

Jet-propulsion cycle.

Otto Cycle

r = compression ratio

= vmax/vmin

k = cp/cv

Diesel Cycle

1-2 : isentropic compression

2-3 : constant pressure heat addition

3-4 : isentropic expansion

4-1 : constant volume heat rejection

rc = v3 / v2 (cut-off ratio)

Otto Cycle vs. Diesel Cycle

For the same compression ratio,

However, Diesel cycle operates at higher compression ratio; resulting higher efficiency

Brayton Cycle

Brayton Cycle

Example: Simple Ideal Brayton Cycle

Combined Gas Steam Power Plant

Jet-Propulsion Cycle

In jet engine, high-temperature and high-pressure gases leaving the turbine are accelerated in nozzle to provide thrust

Turbojet Engine

Exercises