Book contents
- Frontmatter
- Contents
- Preface
- Foreword
- Part I Cycle Analysis
- Part II Component Analysis
- 4 Diffusers
- 5 Nozzles
- 6 Axial Flow Compressors and Fans
- 7 Centrifugal Compressors
- 8 Axial Flow Turbines
- 9 Combustors and Afterburners
- 10 Ducts and Mixers
- Part III System Matching and Analysis
- Part IV Appendixes
- References
- Answers to Selected Problems
- Index
4 - Diffusers
Published online by Cambridge University Press: 05 June 2012
- Frontmatter
- Contents
- Preface
- Foreword
- Part I Cycle Analysis
- Part II Component Analysis
- 4 Diffusers
- 5 Nozzles
- 6 Axial Flow Compressors and Fans
- 7 Centrifugal Compressors
- 8 Axial Flow Turbines
- 9 Combustors and Afterburners
- 10 Ducts and Mixers
- Part III System Matching and Analysis
- Part IV Appendixes
- References
- Answers to Selected Problems
- Index
Summary
Introduction
The purposes of the diffuser or inlet are first to bring air smoothly into the engine, second to slow the fluid and to increase the pressure, and third to deliver a uniform flow to the compressor. As indicated by studies for cycle analyses in Chapters 2 and 3, engine performance improves with increasing pressure to the burner. The first component the air encounters is the diffuser, and the second component is the compressor. Thus, if the diffuser incurs a large total pressure loss, the total pressure into the burner will be reduced by the compressor total pressure ratio times this loss. For example, if 2 psia are lost in the diffuser, for a large engine this can result in 50 psia less in the burner.
The losses result from several processes and affect engine performance in several ways. First, losses in total pressure occur outside of the diffuser primarily as the result of shock interactions. The flow outside the diffuser can also actually affect the flow around the entire engine and add a drag to the aircraft. Second, ideally the flow inside the diffuser is uniform and the streamlines are smooth. However, because of the unfavorable pressure gradient, the boundary layer on the walls tends to grow and separate. This has three subeffects.
- Type
- Chapter
- Information
- Fundamentals of Jet Propulsion with Applications , pp. 209 - 243Publisher: Cambridge University PressPrint publication year: 2005