Nanosoft's annular jet

Moderator: Mike Everman

tufty
Posts: 846
Joined: Wed Dec 24, 2003 12:12 pm
Antipspambot question: 0
Location: France
Contact:

Re: Nanosoft's annular jet

Post by tufty » Thu Aug 26, 2004 4:23 pm

NanoSoft wrote:One thing that i am now taking into great consideration is how many fuel injectors should i have.
How about an annular spraybar?

Simon

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

Re: Nanosoft's annular jet

Post by Bruno Ogorelec » Thu Aug 26, 2004 4:38 pm

NanoSoft wrote:One thing that i am now taking into great consideration is how many fuel injectors should i have. I'm thinking four. I think that if there was only one it wouldn't be able to fill both sides of CC. But with four the fuel should be evenly spread through out the CC.
Yes, with the annular configuration, this becomes a problem. Four should do it, however.

NanoSoft
Posts: 261
Joined: Fri Feb 20, 2004 5:08 am
Antipspambot question: 125

Re: Nanosoft's annular jet

Post by NanoSoft » Thu Aug 26, 2004 8:13 pm

A annular spray bar is a good idea although because of the extremely small size of the jet it would be hard to find a place to put it were it would not cause a disturbance. Plus i am going to want to try gasoline eventually and a spray bar wouldn't vaporize enough. I'll go with four injectors. If i build a bigger annular LH i will try to fit a spray bar into the design.

Here are pictures of the completed nose piece. Looks very nice if i do say so myself. I'm going to start on the outside of CC next.

Nanosoft
Attachments
100_0028.jpg
Finished nose piece to Nano's annular LH
100_0028.jpg (163.5 KiB) Viewed 7016 times
100_0029.jpg
Finished nose piece to Nano's annular LH
100_0029.jpg (149.31 KiB) Viewed 7016 times
100_0030.jpg
Finished nose piece to Nano's annular LH
100_0030.jpg (146.97 KiB) Viewed 7016 times

Stephen H
Posts: 328
Joined: Mon Oct 06, 2003 6:51 pm
Antipspambot question: 125
Location: New Zealand

Re: Nanosoft's annular jet

Post by Stephen H » Thu Aug 26, 2004 9:26 pm

that looks very nice but it does look really small ???

NanoSoft
Posts: 261
Joined: Fri Feb 20, 2004 5:08 am
Antipspambot question: 125

Re: Nanosoft's annular jet

Post by NanoSoft » Thu Aug 26, 2004 10:42 pm

The diameter od the piece shown is 2.7in. Small, maybe but it looks cool plus if it doesn't work i'll just make a bigger one. Maybe i will try to make a escopette annular. That would be cool.

Nanosoft

Stuart
Posts: 83
Joined: Fri Oct 24, 2003 9:35 pm

Re: Nanosoft's annular jet

Post by Stuart » Fri Aug 27, 2004 1:42 am

For annular designs, remember there is a lot more friction from "boundary layer" effects. That is, viscous frictions along the walls and annular designs have much more such boundary area. So, I suspect you will have to enlarge the thinnest passageways. Of course, with these engines it could always be the opposite for some unknown reason, but enlarging would be my first guess.
I'm writing an automated airplane designer in java, useful later when you guys get ready to bolt a p-jet onto some wings

NanoSoft
Posts: 261
Joined: Fri Feb 20, 2004 5:08 am
Antipspambot question: 125

Re: Nanosoft's annular jet

Post by NanoSoft » Fri Aug 27, 2004 1:55 am

Thank you stuart for the recomendation. I am using the smallest grain sand paper i have to polish the surfaces as to reduce the frictional coefficent. I also am trying to make all the pieces very thick so i can shave a little more off the insides to make them bigger. And if need be, nothing is welded together so i can switch pieces. Such as maybe puting a new CC on that longer or is shaped different. I'm trying to give myself as many options as possible.

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

Re: Nanosoft's annular jet

Post by Bruno Ogorelec » Fri Aug 27, 2004 3:51 am

NanoSoft wrote:Thank you stuart for the recomendation. I am using the smallest grain sand paper i have to polish the surfaces as to reduce the frictional coefficent. I also am trying to make all the pieces very thick so i can shave a little more off the insides to make them bigger. And if need be, nothing is welded together so i can switch pieces. Such as maybe puting a new CC on that longer or is shaped different. I'm trying to give myself as many options as possible.
A very good approach when one is building pulsejets. I hope the large area/strong friction factor will not hurt. Mike Everman has shown with his Kazoo family pulsejets that pushing gases through rather narrow passages can work.

What worries me the most is the geometry of the annulus-to-cylinder transition between the combustion chamber and the exhaust. I think that it is the big unknown of this machine. That and the fuel distribution through the annular chamber.

My guess would be that fuel should be distributed early on, perhaps on the transition (frustum) between the intake and the chamber, so that the sudden enlargement of the passage, which will create turbulence, will help distribute fuel more evenly.

NanoSoft
Posts: 261
Joined: Fri Feb 20, 2004 5:08 am
Antipspambot question: 125

Re: Nanosoft's annular jet

Post by NanoSoft » Fri Aug 27, 2004 4:39 am

Thank you all for the advice. I have almost finished the outer shell of the combustion chamber. Sorry for not having pictures of it. When I finish it I will post the pictures.

I have taken into consideration the CC to exhaust bend. You can see in the last pictures the four small bolts in the inside. These are going mount the inner CC/exhaust to every thing else. In between the exhaust and nose are going to be little spacers on the bolts so I can change the size of that gap. I hope that made since and if not, tough luck. Actually you'll see what i mean when I take pictures of it finished.

I have also decided not to lathe the tailpipe out because that would take forever. Instead I was thinking of making an inner mold on the lathe and using it to pound into a pipe to make the exhaust. I figure this will be easy with a torch and a big hammer.

Another point is that to start his engine its probably going to take compressed air blowing into it from 2 sides. That is if it starts which i highly doubt it will. This project is more of a learning step of getting used to lathing and finding all the secrets. Then hopefully I will go on to make a much bigger annular. Maybe the LH 5.25 or the escopette. Both would be very interesting.

Anyways thanks for the support.

Nanosoft

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

Re: Nanosoft's annular jet

Post by Bruno Ogorelec » Fri Aug 27, 2004 5:06 am

NanoSoft wrote:hopefully I will go on to make a much bigger annular. Maybe the LH 5.25 or the escopette.
I'd go for Bruce's BIG Lockwood.

NanoSoft
Posts: 261
Joined: Fri Feb 20, 2004 5:08 am
Antipspambot question: 125

Re: Nanosoft's annular jet

Post by NanoSoft » Fri Aug 27, 2004 5:14 am

Bruce's may be just a tad to big to lathe out very easly or quickly. I was thinking while looking throught the form and i saw the Emachine shop topic and read it. Maybe i should let them build this thing for me. They would probaly do it ten times faster and alot for accurate. To late now.

Nanosoft

Stuart
Posts: 83
Joined: Fri Oct 24, 2003 9:35 pm

Re: Nanosoft's annular jet

Post by Stuart » Fri Aug 27, 2004 11:30 am

Just to add some edumacation, boundary layer effects are not strongly affected by surface roughness, so smoothing the walls in an annular will not completely compensate for the added surface area. - I used the word friction before but it is really the viscous action in the fluid that causes a velocity variation from zero at the wall parabolically to the free stream velocity. What happens in passages under half an inch is that the boundary layers from opposing walls overlap, so dimensions in a small annular will never be equivalent to those in linear designs. That said, your results will vary because the intake passage flows in both directions, so energy loses in one direction MAY compensate loses in the other (who knows?).
I'm writing an automated airplane designer in java, useful later when you guys get ready to bolt a p-jet onto some wings

skyfrog
Posts: 539
Joined: Fri Jul 23, 2004 11:39 am
Antipspambot question: 0
Location: Kaohsiung, Taiwan
Contact:

Re: Nanosoft's annular jet

Post by skyfrog » Fri Aug 27, 2004 11:43 am

Stuart wrote:What happens in passages under half an inch is that the boundary layers from opposing walls overlap, so dimensions in a small annular will never be equivalent to those in linear designs.
This is exactly the case of my engine, in which the passage dimension = 10mm. If my engine cannot pass the validating test, I suggest that Nanosoft should make a bigger engine, otherwise both of us will be trapped by the same devil.
Long live jet engine !
Horace
Jetbeetle

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

Re: Nanosoft's annular jet

Post by Bruno Ogorelec » Fri Aug 27, 2004 11:46 am

Stuart wrote:Just to add some edumacation, boundary layer effects are not strongly affected by surface roughness, so smoothing the walls in an annular will not completely compensate for the added surface area. - I used the word friction before but it is really the viscous action in the fluid that causes a velocity variation from zero at the wall parabolically to the free stream velocity. What happens in passages under half an inch is that the boundary layers from opposing walls overlap, so dimensions in a small annular will never be equivalent to those in linear designs. That said, your results will vary because the intake passage flows in both directions, so energy loses in one direction MAY compensate loses in the other (who knows?).
Stuart, what would you say to making the ducts shorter to compensate for greater drag (or quasi-drag)? After all, the narrowness of the ducts, as opposed to the chamber, is there to provide confinement. We are providing increased confinement here by viscous drag. It stands to reason that the length might safely be shorter. Overall, the performance might suffer, but shorter length, greater frequency, lower mass etc. might still offer a quite acceptable compromise.

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

Re: Nanosoft's annular jet

Post by Bruno Ogorelec » Fri Aug 27, 2004 11:49 am

skyfrog wrote:This is exactly the case of my engine, in which the passage dimension = 10mm. If my engine cannot pass the validating test, I suggest that Nanosoft should make a bigger engine, otherwise both of us will be trapped by the same devil.
Narrower passages than 10 mm have worked -- ask Mike Everman. If everything else is OK, the engine will pump through the narrow passage. It may not perform brilliantly, but that's too much to expect of any engine the first time out.

Post Reply