Design of a Scramjet Engine

Adam J. Resler

ME 566 – Aerospace Propulsion

Wed 04/29/15

Overview

• Scramjet Introduction

• Current State of Scramjet Technology

• Design Considerations

• Methods

• Results and Conclusions

• Questions & Comments

Scramjet Introduction

Scramjet Benefits

• Air-Breathing Engine – No oxidizer required to be carried onboard

• No moving parts

• Theoretical Specific Impulse between 1000 – 4000 seconds

• Escape velocity capable; Theoretical Range between Mach 5 and Mach 26 flight velocity

Scramjet Disadvantages

• Special materials requirements – High strength/weight – scramjet have high

payload mass fractions making weight a concern

– High thermal stress characteristics – heavy cooling burden; also loss of cooling ability as fuel is consumed

• Current designs typically start at Mach 5

• Poor thrust/weight ratio

• Low to very low lift/drag ratio

Scramjet Programs

• SCRAM: USA; Mach 4 – 10 • National Aerospace Plane (NASP): USA; Mach 17

Upper Limit; Mach 25 Possible; Current H2 Combustion Model (31 Reactions; 16 Species)

• HyShot: Australia; Flew at Mach 7.6 for 6 seconds; 10 vehicles; 40% Success Rate

• HyperX: USA; Mach 7 for 11 seconds (15 miles) 2004; Mach 10 in 2004;

• X-51 Waverider: USA; In 2013 flew for 240 seconds ~Mach 5.1 before running out of fuel

NASA X-43A HS Vehicle w/ Scramjet

Design Considerations

• Design Velocity: Mach 5

• Maximum Temperature: 2000 K

• Flight Altitude: 15 km

• Number of Inlet Shocks: 3

Design Method

• Solution of the simplified compressible, inviscid, Navier-Stokes equations with semi-perfect gas equations of state

• Generalized Quasi-1D Flow – takes into account area change, friction, and heat addition; however, no differential mass terms

• Complete combustion model (no dissociation, complete combustion prior to nozzle)

Results of Analysis

• Thrust: 405.7 kN (91,210 lbf)

• Isp: 174.1 s

• Efficiency: 0.83pr/0.56t/.47o

• TSFC: 0.01757 kg/kN-s

• T/ma: 0.572 kN-s/kg

• Time in engine: 0.0021 s

• Specific burn time: 9.82 s/m3

Results of Analysis

Property Diffuser Combustor Nozzle

Pressure Recovery

0.8355 0.5433 0.6724

Total Recovery

0.3053

Adiabatic Efficiency

0.9243 1.0 0.9127

Perspective

• Actual speed-over-land: ~0.9 to 1 mile/second

• New York to LA: 44.68 minutes

• Around Earth at Equator: 7.576 hours

• Destin, FL to New Orleans, LA: 5 minutes

• Compared to F-15 Eagle P&W F100-220 Turbofan Engine: ~3.8 times more thrust

Conclusions

• Low specific impulse - unexpected

• Engine not viable unless installed in a large vehicle

• Better combustion model required to study higher Mach numbers

Summary

• Scramjet Introduction

• Current State of Scramjet Technology

• Design Considerations

• Methods

• Results and Conclusions

• Questions & Comments

Q&C

• Scramjet CFD Model (1 min) https://www.youtube.com/watch?v=kaVDDm222H8

• Scramjet Engine Wind Tunnel Test (no apparent combustion): (40 sec)

https://www.youtube.com/watch?v=EfJp2luk_IY