Oscillating Flows in Inlets of Pulse Detonation Engines Presenter: Lerma, Nelson Graduate Assistant: Nori, Venkata Mentor: Dr. Corin, Segal

Introduction Supersonic Inlet (Mach 3.5) Multiple detonation tubes with a common inlet Inlet-combustion chamber interactions –Inlet response to downstream disturbances arising from valve operation

Experimental Setup Supersonic Wind Tunnel 2-D Supersonic Inlet Schlieren Vacuum System Jet excitation System Data acquisition –LabVIEW –Pressure Scanner –High speed transducers

Supersonic Tunnel Range Mach 1.5 to 4 6  x 6  cross-section Adjustable ramp Optical access 18  x 6 

2-D Supersonic Inlet Inlet designed for M=3.5 Mixed compression 5  leading ramp Additional 5  incremental ramp 9  radius of curvature cowl Four 3/8  injection channels Four exit channels Plexiglas side plates

Cowl Ramp Static taps Blockage plate Injection Channel

Schlieren Setup –Mercury short arc lamp 100W/1 (3 electrodes) –Collimating mirrors –knife edge –Power supply (C.C.) Flow visualization Tool –Density gradients Shocks Oscillations

Vacuum System Vacuum pump –Hp 1 1/2 4 Solenoids (c v =3) Operating pressure range ( psia)

Jet Excitation System Industrial Grade Nitrogen cylinder Regulator (max= 200psi) Stagnation chamber Four solenoids (c v = 3) Teflon tubing –1/4 inner diameter

Figure 1: Normalized pressure distribution No blockage20% blockage

p/p 0 tap p/p 0 tap p/p 0 tap p/p 0 tap p/p 0 tap p/p 0 tap p/p 0 tap p/p 0 tap p/p 0 tap p/p 0 tap 11 t (s) Static Pressure distribution without injection (20% blockage)

p/p 0 tap p/p 0 tap p/p 0 tap p/p 0 tap p/p 0 tap p/p 0 tap p/p 0 tap p/p 0 tap p/p 0 tap p/p 0 tap 11 t (s) Static Pressure distribution with injection (20% blockage)

Effect of Excitation Pressure drop during air injection. Oscillations of equal frequency to the injection solenoids were observed in the static taps. Lower frequencies produced larger oscillations in the flow. Greater exit area blockage lowered the pressure in the inlet. Injecting higher mass flow increased the oscillations. Coupling of solenoids also affected the flow oscillations.

Future Work Add additional static taps at the cowl surface to investigate if any separation is occurring inside the inlet. Introduce a stagnation tap at the exit in order to have a better understanding of the exit Mach number. If the inlet is supersonic as believed in the present, then further modifications to the inlet must be made in order to create a subsonic flow at the exit. Further modifications can also be made to the back body to increase the pressure in the inlet.