How to Calculate the Size of a Thrust Augmenter

And Safety Blurbs

Moderator: Mike Everman

Post Reply
Bruno Ogorelec
Posts: 3542
Joined: Sat Oct 04, 2003 7:31 am
Antipspambot question: 0
Location: Zagreb, Croatia

How to Calculate the Size of a Thrust Augmenter

Post by Bruno Ogorelec » Tue Aug 24, 2004 5:38 pm

The thrust augmenter is a device that mixes cool air into the hot gas jet of a pulsejet and greatly increases its thrust. It is simple to build and not terribly sensitive to exact measures. A reasonable approximation of the relations given here will be sufficient. Look at the illustration at the bottom to locate the elements depicted by the following symbols:

dj = Exhaust tube diameter

D = Ejector tube diameter

𝛿 = Distance between exhaust tube and augmenter mouth (sorry, this program does not appear to support greek letters)

R = Radius of the augmenter lip

L = Length of augmenter


dj is the starting parameter. Others are calculated from its value as follows:

𝛿 = 2 dj

D = 2.5 to 3 dj

L = 10 dj

R = 0.25 D

The end of the ejector can be flared (to an arbitrary fraction of L -- indeed, even the entire duct can be conical) and the internal angle of flare should not be more than 5 degrees from centerline.
You do not have the required permissions to view the files attached to this post.

Post Reply