Fluid Dynamics and Efficacy of Swirling Flow in a Solid Fuel Ramjet Engine Samuel R. Carr University of Virginia Region I Student Conference, April 7-8, 2017 Charlottesville, Virginia

Swirling Flow – State of the Art Solid Fuel vs. Liquid Fuel Variable Bypass Secondary Gaseous Injection Inlet Swirler SFRJ has advantage for medium- to long-range missiles because of design simplicity and lower life-cycle costs Disadvantage: self-throttling disposition over a limited operating envelope Variable bypass: increases fuel loading and control of fuel regression rate, but efficiency also depends on air mass flux Could also lead to flow coupling between combustor and bypass duct, leading to undesirable flow/pressure oscillations Gas Injection (air, oxygen, gaseous fuel, combustion catalysts): Small amts of oxygen added to fuel rich regions seems to enhance combustion *Swirl in their case was effective for limited increase in fuel regression rate, but highly dependent on the geometry of the motor Swirl sometimes would prevent ignition by taking away the fuel rich recirculation zone that would normally act as a flameholder Our SIMPLISTIC swirler tries to offer the advantages of each of these solutions while minimizing the disadvantages

Using Computational Fluid Dynamics (CFD) to model fluid flow Summary of Project Using Computational Fluid Dynamics (CFD) to model fluid flow 2D Analysis Proof of Concept phase Vary inlet flow angle Hope to achieve strong recirculation zone 3D Analysis Replicate effects produced in 2D analysis Cooperation with Aerojet-Rocketdyne

Geometry, velocity fields, scalar profiles 2D Analysis

Simplified axisymmetric model Inlet air angle can be varied 2D Geometry & Set-up Simplified axisymmetric model Inlet air angle can be varied Constant fuel regression We had to create an axisymmetric model Rectangle on the left will be used as an inlet for the air Rectangle on top will be used as an inlet for the fuel Inlet velocity was known for air, velocity for fuel was calculated from regression rate Simplified nozzle on right side to use for an outlet (just so we have something)

Constant axial velocity Recirculation zone Preliminary 2D Results Inlet angle: 70° Constant axial velocity Recirculation zone Showcasing recirculation zone Fuel grain is towards the very right of this screenshot Introduce swirl numbers: 1x swirl = azimuthal is half axial, 2x swirl = azimuthal is axial, etc.

Preliminary 2D Results Added an analysis plane towards the end of the combustor, shown is a scalar profile for varying swirl numbers 8x swirl is at the top – ignore due to divergence 7x and 9x swirl have bumps – ignore due to likely being too high of a swirl value Decide to go with 6x swirl – equates to approximately 70 degree inlet angle

Geometry, Particle Traces, Scalar Profile, Velocity Profile 3d Analysis

Cylindrical base has a “bullet” shape 6 blades 3D Geometry SPECIFICALLY simplistic Airfoil chosen to be symmetric, 6-series also means it is maximized for laminar flow 70 degrees was changed to 60 degrees bc 70 led to too much backdraft More blades meant not enough spacing between airfoil extrusions Less blades were not as effective Cylindrical base has a “bullet” shape 6 blades NACA 64 A010 airfoil shape 60°relative to centerline

Particle Traces Give brief discussion on what particle traces are in CFD Colors denote magnitude of velocity Give frame of reference Talk about rotational swirl seen here Flow straightens out by the time it enters the fuel grain Slower as it hits the fuel grain

Particle Traces Walk through it

Scalar Profile Similar to 2D analysis, but instead of analysis plane at one point, we’re going to follow the profile through the fuel grain By approximately 50% of the way through the fuel grain, we already achieve at minimum, 65% fuel

Velocity Profiles Note that these are projections: define coordinate system Relate to 2D analysis Obvious recirculation zones Recirculation zone seems to stop before we get to the fuel grain

Velocity Profile Taken approximately a quarter of the way through the fuel grain Note that most of the velocity vector here is directed INTO the board, this is a projection

Dr. Pat Hewitt, Aerojet-Rocketdyne Acknowledgements Dr. Rita Schnipke, Department of Mechanical and Aerospace Engineering at the University of Virginia Dr. Pat Hewitt, Aerojet-Rocketdyne Mark Friedlander, Aerojet-Rocketdyne

Questions?

Backup slides

Pressure

2D Scalar Profile Integral Swirl Characteristics Trapezoidal Integral of Scalar Profile No inlet tube (0x swirl) 0.1004 No inlet tube – half inlet (1x swirl) 0.1036 2x swirl 0.1301 4x swirl 0.1893 6x swirl 0.2318