My new Engine

[ganuganu]

Hello everyone its been long time for any new post, now here i have made an engine with 3.2 inches diameter with a aim to produce 20pounds thrust. I was doing this project from 9/02/2012 and completed fabricating the engine and tested for thrust today it gave only 8.8pounds of thrust. Here is the picture of the engine, now i planned to remove the straight pipe near the cone and join the cone with the pipe located below.

Take a look at the video. There are large flames coming out from the intake pipe.

http://youtu.be/qW6N6N2h050

[ganuganu]

Can anyone help me out here iam just struck here, i made a new design with 3.2inches diameter take a look at the picture. And i made a test run yesterday evening i couldnt guess what is the problem with my engine. Please someone log in and post a suggestion.

http://youtu.be/nlafjj_Nk08

http://imageshack.us/photo/my-images/204/32inches.png/

[PyroJoe]

The design only has approximate 5 calibers of non expanded tailpipe. Typically 9 calibers are needed. Even the 5 calibers have a slight expansion from 44 to 47.

In my own terminology I would say you expanded the tail to early and have reduced the primary pump length by near 40%. So the the primary pump is only working at about the 60% level.

[ganuganu]

The design only has approximate 5 calibers of non expanded tailpipe. Typically 9 calibers are needed. Even the 5 calibers have a slight expansion from 44 to 47.

In my own terminology I would say you expanded the tail to early and have reduced the primary pump length by near 40%. So the the primary pump is only working at about the 60% level.

i have added an straight pipe after the first cone and tried to start it, i could get some good bang sounds and some roars but not getting started. Here is the modified drawing.

http://imageshack.us/f/254/32inchesnew.png/

[PyroJoe]

The tail is about 2.5 calibers long in length. It would need about 106mm cut from the back of the tail to be near 20 calibers in length.

Also the CC is a little small in diameter. 2 calibers diameter CC would have given 88mm. If it continues to give problems cut about 8mm off the front length of the CC. That should true up the Helmholtz volume a small amount.

[ganuganu]

I made the modifications as you said i can see small improvement and i used three point injector is it ok. And here are some modification made by me, now iam in a confusion to whether keep the cone after the straight pipe or remove it.

forgot to say this point: I just tried to start with different injector positions when i keep the injector deep then the engine gives good response.

http://imageshack.us/f/14/32inchesnewnew.png/

[PyroJoe]

That is interesting work.
I am curious to know how much flame is pouring out the intake after your modifications. Your very first video on the topic showed about 200mm of flame pouring out the intake. It represents considerable pressure being lost. I almost expected to see an augnmenter added, but it was good to see the cone added instead.

The extra length of the pump in this one makes it on the border line of what I call "fraction" engines. The extra tail pump length matches the CC length a little better.
Good work

[ganuganu]

That is interesting work.
I am curious to know how much flame is pouring out the intake after your modifications. Your very first video on the topic showed about 200mm of flame pouring out the intake. It represents considerable pressure being lost. I almost expected to see an augnmenter added, but it was good to see the cone added instead.

The extra length of the pump in this one makes it on the border line of what I call "fraction" engines. The extra tail pump length matches the CC length a little better.
Good work

The first engine on this topic is the worst welding i have ever done in pulsejets there were many leaks and cuts and joints, i thought to modify more but couldnt do anything so i left it back and made a new engine. But on the other side i was surprised that atleast it pushed 4kg of thrust.

[ganuganu]

hello joe i made this new modification today morning and iam 100% sure that it was trying to start i can hear the alternate roars but suddenly switched off dont know why. Here is the modification. One more point the last 4inches diameter straight pipe(150mm length) was tack welded will that be the problem.

http://imageshack.us/f/443/32inchesstart.png/

[PyroJoe]

The tail is to long again. Before the 150mm modification was made the tail was about 23 calibers. Just 3 calibers over the 20 calibers defined by the recipe. With the modification the tail becomes 25 calibers.

The returning tail pressure/compression wave is delayed along with the ignition.
If it were my engine I would cut the entire 150mm off and test it. You may have already run it like that?

[ganuganu]

my bad luck today neighbours stopped me from starting my engine. So i WILL go to my collage and start my engine.

[ganuganu]

Made this new engine it was able to produce a thrust of 1.5kg without augmenter but after augmentation it just pushed 0.5kg of thrust any suggestions please. Here is the drawing. This is for my collage(final year) project.

[PyroJoe]

Augmenter was applied to end of the tail pipe?

[ganuganu]

sorry forgot to say about that augmenter was placed at tailpipe and at a distance of 76mm

[PyroJoe]

The "combined" intake to tail diameter ratio is approximately 0.558 This typically results in the CC is starved for air, and is not completely driving the tail pipe. Adding more trapped mass behind the tail pipe only increases the problem.
Some injector setup can entrain more air and help produce better results, but 0.558 represents a large quantity of entrainment to balance.

Looks like the minimum intake length is very short also, adding to the intake leakage.