Aircraft Propulsion, 2nd Edition

CHAPTER 6 Aircraft Engine Inlets and Nozzles

6.1 Introduction

Source: Reproduced with permission from Rolls-Royce plc

In this chapter, we study the aerothermodynamics of aircraft engine inlets and nozzles. These two components in an aircraft engine represent “duct” flows with internal losses and hence we propose to study them in a single chapter. Despite these similarities, the inlet flowfield bears no resemblance to the exhaust flowfield. The presence of adverse pressure gradient in an inlet diffuser leads to a stalling boundary layer behavior, whereas the favorable pressure gradient in a nozzle promotes attached boundary layer flows. Another dissimilarity between these two components is in the cooling requirements of an advanced exhaust system as compared with the inlets, which remain uncooled until well into the hypersonic flight Mach numbers.

The system requirements of an aircraft intake primarily depend on the aircraft mission specification. In general, an aircraft intake system has to be designed to many of the following qualities, namely

1. light weight and low cost to manufacture
2. provide the engine with adequate mass flow rate at a proper Mach number at the engine face throughout the flight envelope
3. provide spatially smooth flow into the engine compressor, that is, low steady-state distortion throughout the flight envelope
4. provide temporally smooth flow into the engine ...