Fundamentals of Jet Propulsion with Power Generation Applications

A nozzle is sometimes called the exhaust duct or tail pipe, and is the last component of a jet engine through which the air passes. Up to two parallel nozzles are present on an engine: primary and fan (or secondary). In this chapter, both converging and converging– diverging (CD) nozzle types are discussed, and the two nozzles can be any combination of the two types (i.e., converging and converging–diverging, converging and converging, etc.). Recall that the functions of the nozzles are to convert high-pressure, high-temperature energy (enthalpy) to kinetic energy and to straighten the flow so that it exits in the axial direction. It is from this conversion process that the thrust is derived. Because of the high temperatures that a nozzle experiences, materials used in nozzle construction are usually a nickel-based alloy, titanium alloy, or ceramic composite. In Chapter 2, the nonideal effects of nozzles are discussed. The reader is also encouraged to review Appendix C as many of the fundamentals are covered therein. In this chapter, these effects are covered in more detail along with other design considerations.