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

• 6x 6 cross-section

• Adjustable ramp

• Optical access 18x 6

2-D Supersonic Inlet

• Inlet designed for M=3.5

• Mixed compression

• 5leading ramp

• Additional 5 incremental ramp

• 9radius 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 (cv=3)

• Operating pressure range

(0.7 - 3 psia)

Jet Excitation System

• Industrial Grade Nitrogen

cylinder

• Regulator (max= 200psi)

• Stagnation chamber

• Four solenoids (cv= 3)

• Teflon tubing

– 1/4 inner diameter

Figure 1: Normalized pressure distribution

X / L

Pm/Po

0 0.25 0.5 0.75 1-0.1

-0.05

0

0.05

0.1

0.15

0.2

Without InjectionWith Injection

X / L

Pm/Po

0 0.25 0.5 0.75 1-0.1

-0.05

0

0.05

0.1

0.15

0.2

Without InjectionWith Injection

No blockage 20% blockage

0

0.1

0.2

p/p 0

tap 1 0

0.1

0.2

p/p 0

tap 7

0

0.1

0.2p/

p 0

tap 2 0

0.1

0.2

p/p 0

tap 8

0

0.1

0.2

p/p 0

tap 3 0

0.1

0.2

p/p 0

tap 9

0

0.1

0.2

p/p 0

tap 4 0

0.1

0.2

p/p 0

tap 10

0

0.1

0.2

p/p 0

tap 522 22.2 22.4 22.6 22.8 23

0

0.1

0.2

p/p 0

tap 11

t (s)

Static Pressure distribution without injection (20% blockage)

0

0.1

0.2

p/p 0

tap 1 0

0.1

0.2

p/p 0

tap 7

0

0.1

0.2p/

p 0

tap 2 0

0.1

0.2

p/p 0

tap 8

0

0.1

0.2

p/p 0

tap 30

0.1

0.2

p/p 0

tap 9

0

0.1

0.2

p/p 0

tap 4 0

0.1

0.2

p/p 0

tap 10

0

0.1

0.2

p/p 0

tap 519 19.2 19.4 19.6 19.8 20

0

0.1

0.2

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.