TABLE OF CONTENTS In this chapter, the thermodynamic characteristics of basic engine cycles are explained. For each concept, the thermal efficiency is derived from thermodynamic equations.
A short introduction to thermodynamics is given in this section. It is essential to understand the thermodynamic processes for the different types of engine models explained in this book.
Ideal gases are always in a gaseous state and they behave according to the ideal gas equation:
| (2.1) |  |
where:
| p | is the pressure in N/ m 2 |
| V | is the volume in m 3 |
| m | is the mass in kg |
| R | is the gas constant R = 287.4 m 2/( s 2 K) |
| ? | is the absolute temperature in K |
The expression pV has the unit Joule and it depends on the mass and temperature of the gas.
The thermal energy is defined as:
| (2.2) |  |
where:
| q | is the thermal energy in J |
| c | is the specific heat constant in J/( kg K) |
This equation is valid for all kind of materials in solid, liquid and gaseous state. The specific heat constant is material depending. In gases, different state changes have to be distinguished which will be discussed in the next section.
| (2.3) |  |
| dq | is the differential change of thermal energy. Energy which is brought into the gas is positive. |
| du | is the differential change of internal energy. Internal energy which is brought into the gas is positive. |
| dw |
