2.1 Introduction

The operation of gas turbine engines and of rocket motors is governed by the laws of mechanics and thermodynamics. The field of mechanics includes the mechanics of both fluids and solids. However, since the process occurring in most propulsion devices involves a flowing fluid, our emphasis will be on fluid mechanics or, more specifically, gas dynamics.

Understanding and predicting the basic performance of gas turbine engines and rocket motors requires a closed set of governing equations (e.g., conservation of mass, energy, momentum, and entropy). For transparency, understanding, and capturing the basic physical phenomena, we model the gas as a perfect gas and the flow as one-dimensional flow, in which the fluid properties are constant across the flow and vary only in the direction of flow (axial direction).

This chapter is intended as a review of thermodynamics and one-dimensional gas dynamics that are the foundation of this textbook. We include new material from Hypersonic Airbreathing Propulsion by Heiser and Pratt13 on the graphical solution and description of one-dimensional gas dynamics in Section 2.8 to improve the reader's comprehension of this fundamental material.

This chapter concludes with a short section on chemical reactions to provide the fundamentals needed to understand reacting flows (e.g., combustion). With this material, we will predict the equilibrium state of reacting flows and the performance of liquid-fuel rocket motors. For further study, the student is directed to references such as Ref. 14.

2.2 Equations of State and Conservation of Mass

The state of...