The QD-88 lives!!

[hinote]

Hello to my fellow forum members:

Today, I was able to accompllish the first runs of the QD-88 derivative--the HO (high-output) version of the QD pulsejet project that is software designed (by "M.") and built by me.

The previous version (as you may recall) was measured at almost EXACTLY its predicted thrust, and was subsequently turned into metallic taffy after an extended hot run, followed by a hot shutdown. A real PJ disaster, IMHO.

After cutting the poor beast apart and saving the useable pieces, the engine was reassembled with the necessary new components as well as the HO tailpipe mod.

The newly-predicted rating is 40 lbf nominal and 45 lbf max (BTW on the SAME fuel consumption as before).

Today, I went to my test site (in the middle of a local airport) and made the first runs with the current version (on the newly-modified thrust-measuring stand). Here's my latest report on the results:

There's GOOD news, and BAD news:

The BAD news is, I can't think of anything bad to report!

The GOOD news is, as follows:

1. The engine started (on its own), with nothing more than supplied fuel and spark --no supplemental air required. Bruce Simpson has also described this phenomenom, and I think it's a combination of the dynamics of a larger engine combined with some luck, and a propane feed that induces supporting air for the start.

2. The engine is throttleable over a HUGE range--easily in excess of a 10:1 turndown ratio. I'll let M. describe why this is so,--if he wants to.

3. The projected increase in thrust appears to be WAY too conservative, based on initial thrust measurements. I exceeded the nominal thrust ratings, with only a partial throttle setting. The thrust stand is still not satisfactory--the tension spring only works across a limited range of values. I'm probably going to "bite the bullet", and install a strain gauge to measure the thrust digitally, with stated/guaranteed repeatability. Plus, I can record the numbers to a datalogger for further evaluation. Luckily, my brother is in aerospace and is using just this kind of equipment in his current work.

I would again like to take this opportunity to thank M. for including me in his efforts to create advances in the PJ art/technology.

Stay tuned for more reports. My next effort is to create some TSFC numbers--in spite of the hinderance of using (difficult to measure) gaseous propane.

Bill H.
Acoustic Propulsion Concepts, Inc.

P.S.: M. doesn't (yet) know anything about this test, or this posting to the forum; it will be interesting to see what his reply will be.

[larry cottrill]

Bill -

My heartiest congratulations to you and M.!

That sounds like a wonderful achievement -- I especially like the news about throttleability, which has always seems to be a substantial practical problem in pulsejet design.

Yes, it will be fun to see how M. responds when he awakens to the news ...

All the best,
L Cottrill

[hinote]

-- I especially like the news about throttleability, which has always seems to be a substantial practical problem in pulsejet design.

I'm going to stretch my welcome with M. and tell everybody:

--it's a fuel-delivery issue. 'Nuf said!

I find it hard to believe that one person can have so much savvy about such an obscure technology as pulsejets, but I can assure you-all, M. really knows his stuff, PJ-wise.

Bill H.

[Mike Everman]

Congrats, Bill! I love posts like this. How cool! You guys are complete studs.

[milisavljevic]

DELETED.

[milisavljevic]

DELETED.

[resosys]

Impressive work!

Congratulations gentlemen.


Chris

[k.maynard]

I'm so jealous

[Anthony]

Being jealous is not the way, just enjoy the progress hehe!

[k.maynard]

yes.. you are right. i do enjoy the progress.

[Mark]

There's plenty of pain and suffering to go around and plenty of things to try.
Mark

[milisavljevic]

DELETED.

[Graham C. Williams]

The magnitude for an absolute maximum is 2.5, and an absolute minimum is 2.1.

Well done.

Graham.

[mk]

Congratulations again to you, Bill and Milsavljevic!!
REALLY impressive work!
Hearing (or rather reading) such "good news" in pj developement just makes these "fire pipes" more and more interesting...

[hinote]

Congratulations again to you, Bill and Milsavljevic!!
REALLY impressive work!
Hearing (or rather reading) such "good news" in pj developement just makes these "fire pipes" more and more interesting...

The QD series is a single-inlet design, and owes its heritage to the SNECMA Ecrevisse.

My experience with the 4-tube Kentfield, although positive, would lead me to recommend a single-inlet design if possible--to avoid the complications of construction and fuel feed.

Bill H.
Acoustic Propulsion Concepts