This document summarizes different types of power cycles used in gas engines. It describes gas cycles where the working fluid remains in gas phase throughout, and vapor cycles where it exists in both gas and liquid phases. The main gas cycles discussed are Carnot, Otto, Diesel, Dual, and Brayton cycles. Carnot cycle acts as an ideal benchmark, while Otto cycle models spark ignition engines, Diesel cycle models compression ignition engines, and Brayton cycle models jet and turboprop engines.

1. GAS POWER
CYCLES
The devices or systems used to produce a
net power output are often called
engines, and the thermodynamic cycles
they operate on are called power cycles.

2. TYPES OF POWER CYCLES
GAS CYCLES:-
• In gas cycles, the working fluid remains in the gaseous
phase throughout the entire cycle.
VAPOUR CYCLES:-
• In vapour cycles, the working fluid exists in the vapour
phase during one part of the cycle and in the liquid
phase during another part.

3. AIR STANDARD ASSUMPTIONS
 The cycle is considered closed with the same ‘air’ always remaining in the
cylinder to repeat the cycle.
 In the cycle, all the processes are reversible.
 Mass of working fluid remains constant through entire cycle.
 The working fluid is homogenous throughout the cycle and no chemical
reaction takes place.
 The air behaves as an ideal gas and its specific heat is constant at all
temperatures.
 The working fluid is air.

4. TYPES OF GAS CYCLES
 Carnot cycle
 Otto cycle
 Diesel cycle
 Dual cycle
 Brayton cycle

5. CARNOT CYCLE
 This cycle is a hypothetical cycle
having highest possible efficiency.
Process 1-2 : Isothermal expansion
Process 2-3 : Adiabatic compression
Process 3-4 : Isothermal compression
Process 4-1 : Adiabatic compression

6. APPLICATIONS
 Carnot cycle is an idealization, since no
real engine processes are reversible.
 All real processes involves some increase
in entropy.
 Heat transfer into the engine in isothermal
process is too slow to be of practical value.

7. OTTO CYCLE
 It is a constant volume cycle.
Process 1-2 : Reversible adiabatic compression
Process 2-3 : Addition of heat at constant volume
Process 3-4 : Reversible adiabatic expansion
Process 4-1 : Rejection of heat at constant volume

8. APPLICATIONS
 Two Stroke Petrol Engine
 Spark Ignition Petrol Engine
 Four Stroke Petrol engine

9. DIESEL CYCLE
 It is a constant pressure cycle.
Process 1-2 : Reversible adiabatic compression
Process 2-3 : Addition of heat at constant pressure
Process 3-4 : Reversible adiabatic expansion
process 4-1 : Rejection of heat at constant volume

10. APPLICATIONS
 Compression Ignition Diesel Engine
 Two Stroke Diesel Engine
 Four Stroke Diesel Engine

11. DUAL CYCLE
Process 1-2 : Reversible adiabatic compression
Process 4-5 : Reversible adiabatic expansion
Process 3-4 : Addition of heat at constant pressure
Process 5-1 : Rejection of heat at constant volume
Process 2-3 : Addition of heat at constant volume

12. APPLICATIONS
 Dual Combustion Engine
 Used for mobile propulsion in
vehicles and portable machinery.
 In mobile equipment.
 In aircrafts, helicopters, large
ships and electric generators.

13. BRAYTON CYCLE
Process 2-3 : Heat addition at constant pressure
Process 1-2 : Reversible adiabatic compression
Process 4-1 : Heat rejection at constant pressure
Process 3-4 : Reversible adiabatic expansion

14. APPLICATIONS
 Jet Engine  Turboprop Engine

15. THE
END