Ducted Fan Design
Volume 1

by F. Marc de Piolenc & George E. Wright, Jr.

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CONTENTS


 

Acknowledgements

 1

Foreword

 4

Introduction

 8

PART ONE—Theory, Applications and Design Procedure

Applications of Ducted Fans (warning: 1.5 MB)

 10
  • Why a Duct?
  • Applications
  • ...and Why Not

Basic Propulsion Physics

 18
  • Force and Momentum
  • Where Thrust Comes From
  • Power Required to Generate Thrust
  • Maximizing Thrust per Horsepower
  • Propulsive Efficiency

Ducted Fan Design Issues and Errors

 23
  • Copying Turbojet Inlets
  • Copying Turbofan Inlets
  • High Pressure Ratios
  • Unrealistic Performance Goals
  • Ignoring Powerplant Limitations
  • Inlet Design; Cheater Holes, Blow-In Doors and Other Atrocities
  • Fan Placement: Inlet, Throat or Exit?
  • Boundary Layer Ingestion vs Boundary Layer Bleed or Diversion

Duct Nomenclature and Design Principles

 30
  • Nomenclature
  • The Engineering Model of the Duct
  • Relations used in duct design
  • Velocity Change and Pressure Rise

Duct Design Procedure

 34
  • Tools
  • Outline of the Design Method
  • Estimate of Stage and Duct Efficiency
  • Engine Rating
  • Preliminary Fan Sizing
  • Mass Flow—First Estimate
  • Capture Area
  • Fan Entry Static Pressure
  • Fan Flow Speed
  • Duct Exit
  • Fan Swirl Parameter; Swirl Horsepower
  • Accounting for Swirl
  • Fan Delivery Pressure
  • Check: Power Required
  • Iteration: New Mass Flow Estimate
  • Tip Mach Number Check
  • Longitudinal Duct Profile
  • Duct Cross-Section Shapes
  • Bends
  • Inlet Design

Fan Design

 47
  • Design Method
  • Design Procedure—Blade Twist Distribution
  • Optimum Fan Blade Design
  • A Simple Stator—The NPL Straightener

Static Thrust Estimation

 58
  • Method I: Constant Mass Flow and Power
  • Method II: ACV Correlation Line

PART TWO— Engines, Fans and Aircraft

Engines

 62
  • Operating Cycles
  • Power Output
  • Available Engines

Ducted Fan Aircraft

 82
  • VTOL Aircraft Using Tilt-ducts
  • Flying Platforms Using Ducted Propellers/Fans
  • The Flying Jeeps
  • "Tunnel" Aircraft

PART THREE—Bibliography and Symbol Table

Bibliography

 140
  • Report Series and Sources

Symbols

 164

PART FOUR—Design Example

Duct Design Example

 166

Fan Design Example

 169

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