Fuel Injection on the Lockwood-Hiller?

[Parker]

Hello,

I know that this is a pretty mundane and ofter posted question, yet I am still confused. I have searched and read all I could about this topic, but I am still not a 100% sure of it in its full details. If anyone has any helpful hints, ideas, and proven ways of setting up fuel injection, I would me very very thankful. I am GOING to actually build the 55 lbs locky this winter break from college. I have all necessary tools and materials and resources available, I am just lacking know how and experiance, especially the fuel injection part. I will post pics and hopefully video if I can truly understand the fuel injection area of production. I do plan on using propane (isn't it supposed to be the easiest?) Any comments or suggestions, I mean any! :) ,would be greatly appreciated. Thankyou all so much.

Parker

[hinote]

Hello,

I know that this is a pretty mundane and ofter posted question, yet I am still confused. I have searched and read all I could about this topic, but I am still not a 100% sure of it in its full details. If anyone has any helpful hints, ideas, and proven ways of setting up fuel injection, I would me very very thankful. I am GOING to actually build the 55 lbs locky this winter break from college. I have all necessary tools and materials and resources available, I am just lacking know how and experiance, especially the fuel injection part. I will post pics and hopefully video if I can truly understand the fuel injection area of production. I do plan on using propane (isn't it supposed to be the easiest?) Any comments or suggestions, I mean any! :) ,would be greatly appreciated. Thankyou all so much.

Parker

Hey Parker--I've been down the road you're starting to travel. I don't think there's enough guys on this forum who understand how big the liquid-fueling problem is.

I'm just starting to get "out of the woods" on this subject, after a pretty big expenditure of time and money.

Please, DO start by running your project on (gaseous!) propane. I can provide you with a usable orifice size to start with if you need. There's several more experienced guys here that can help you, if you want one-on-one experience with your L-H 55. I'm sure that many of us are willing to help you to your success.

Good luck on your project. If you get it to run, you will be in a still-exclusive club, even on this forum.

Bill H.
Acoustic Propulsion Concepts, Inc.

[Parker]

Yes, any type of information would be greatly appreciated, I am so greatful to all of you. I am studying Aerospace Engineering and Physics at the University of Missouri-Columbia, and Jet engines are my life. I have of yet, found no other person that feels the same about of Jets as I at school. I even brought my dynajet redhead to class one day, not even one person was interested! My proffessor knew what it was, he even had one. But, what really confused me was that he was just going to throw it away. I find myself checking this forum at least once an hour, its kinda obesessive. I have found out how finicky aspiration fuel jet engines can be, so I figured that that would be my biggest hurdle in making a running valveless. Again, any help would make my year.

Parker

[resosys]

Hello,

I know that this is a pretty mundane and ofter posted question, yet I am still confused. I have searched and read all I could about this topic, but I am still not a 100% sure of it in its full details.

Any comments or suggestions, I mean any! :) ,would be greatly appreciated. Thankyou all so much.

Parker

Parker,

Maybe I'm a lucky soul or maybe I'm doing things right, but 14 of my LH engines run fine and they all run on propane. On my smaller engines, the trick I use is to place a single fuel inlet pipe on the cone closest to the intake tube, at 90 degrees to the center line of the engine. The attached image is of the very first test engine we built (we being myself, some friends, and my wife). You can see the copper line on the right side going to the cone. Welded to the cone is a piece of 1/4" water pipe, cut to fit the angle of the cone.

On my larger engines, I've used two inlet pipes at 90 degrees to each other, in the same location on the front cone. The engines will run with only one of them on, but the throttle response is much better with both pipes flowing.

I'm working on a liquid fuel injected LH engine now. We're hoping to use a diesel/gasoline mixture. We've experimented with misting nozzles at various pressures and have been able to get some nice atomized fuel patterns into the combustion chamber.

Chris

[Bruno Ogorelec]

Hey, that's a nice running engine. Most of combustion at just the right place. Cool intake stack. Very good.

[Mike Everman]

Yeah, Chris, nice photo! got any more? And greetings from Santa Barbara. I used to live in Davis and Sac for what it's worth. By any chance are you following Moller's untethered VTOL test? (him being so close and all...)

[Graham C. Williams]

Gary Robinson had his injection point just a few cm further back than this photo. Gary had it just where the front cone and the combustion chamber met.
Graham.

[hinote]

Maybe I'm a lucky soul or maybe I'm doing things right, but 14 of my LH engines run fine and they all run on propane. On my smaller engines, the trick I use is to place a single fuel inlet pipe on the cone closest to the intake tube, at 90 degrees to the center line of the engine.

Chris

I think that 90 degree thing is a good detail. I did essentially the same thing on my Kentfield 4-tube engine, and it really runs smooth on propane.

The direction of the propane jet forces good mixing with the incoming fresh air, in my opinion. You can't just throw propane and fresh air into a can and hope something will happen--they HAVE to be mixed properly.

The combustion zone looks really good--if you compare it to the some other operating L-H engines posted here, the primary heat zone is confined to the "combustion chamber", and doesn't extend down the tailpipe.

Good job!

Bill H.
Acoustic Propulsion Concepts, Inc.

[resosys]

Yeah, Chris, nice photo! got any more? And greetings from Santa Barbara. I used to live in Davis and Sac for what it's worth. By any chance are you following Moller's untethered VTOL test? (him being so close and all...)

Thanks all, for the kind words.

I have a lot more photos, hopefully some video, and not enough time. Actually, I'm getting it all together to put up on the net.

I'm not familiar with Moller's project. I just started reading this forum after seeing SRL's V1 run last week and getting the motivational push to work on more engine projects.

Sacramento is a nice place, no matter what Arnold says. We've invited the fire department over for pulsejet runs and they love us.


Chris

[resosys]

I think that 90 degree thing is a good detail. I did essentially the same thing on my Kentfield 4-tube engine, and it really runs smooth on propane

The direction of the propane jet forces good mixing with the incoming fresh air, in my opinion. You can't just throw propane and fresh air into a can and hope something will happen--they HAVE to be mixed properly..

I think the propane gas pushing across the highly turbulent intake rush makes for a good mixture. I agree that you can't just throw it in. I've had issues with engines that were a LOT out of tune being terribly picky about exactly how much propane we put in.

The combustion zone looks really good--if you compare it to the some other operating L-H engines posted here, the primary heat zone is confined to the "combustion chamber", and doesn't extend down the tailpipe.

Good job!

Thanks. That image is the second ever run of that engine. We did get the entire tailpipe red hot a few times running liquid propane in.

BTW, that being our first test engine, we tried to kill it. It has some pretty bad welds on it. We took it out to a secluded test site and ran it until is drooped from the heat. The welds breached and when it flamed out, small flames would pop out of all the holes. A pop with the air gun and it would fire right back up. It wouldn't fail.

Chris

[Graham C. Williams]

Dear all.
The following is from an S.N.E.C.M.A. paper.
'Long practical experience with pulsejets has convinced us that the nature and quality of atomisation of fuel have only a secondary influence on performance whereas the positioning of the injector is critical. For the "Ecrevisse" pulsejets the change in injector position of 3mm. in an engine total length greater than 2 metres sufficed to change the thrust by more than 20%'

They don't answer the question 'Why is the position critical'?

Our work with the BCVP/Phoneix motors confirms everything the SNECMA say. I'd go further and say that a small change in the fuel injection location can make the difference between a motor working and not working.
As to answering the question, I wouldn't like to say. Like you I have some ideas, many similar to yours, but look at the powdered coal burning non-steady combustors what's going on in these then? Perhaps we have to think in terms of the non-steady flow stripping off layers of fuel from a core and mixing this in the turbulent region just before combustion. Such a model would fit the SNECMA findings.

Graham.

[Bruno Ogorelec]

I have always thought that injecting fuel into the combustion chamber was wrong. My first ideas concentrated on the best propane-air mixer I know of -- the Bunsen burner. We already have a similar structure in valveless pulsejets -- the intake stack. I thought injecting fuel into the intake stack might just be the best thing of them all. It would use the length of the stack to achieve proper mixing and also utilize the energy contained in the pressurized propane to accelerate the mixture into the chamber and achieve a minor level of superchage.

Yet, for some reason, nine designers out of ten have chosen to inject fuel into the chamber. To my eyes, this is illogical, but only two people I can think of have agreed with me so far. One is J.A. Melenric of the Thermojet fame and the other is F.H. Reynst. Both built successful pulsating combustors that received their fuel at the pressure anti-node, at the mouth of the intake. Reynst argued that this was the best place of all and indeed, his engines would run much better with such 'outside' supply of fuel than with injection into the chamber.

The NRL and the 'Chinese' are a halfway house -- they let fuel in at a point well inside the intake stack but also well before the chamber. Some 'Chinese' engines I have seen inject fuel like the Thermojet, into the intake mouth.

OK, by injecting into the intake you lose the convenience of having the internal pressure cut off the fuel flow duruing most of combustion, increasing fuel efficiency, but I guess it's a problem that can (and should) be handled separately.

[hinote]

Dear all.
The following is from an S.N.E.C.M.A. paper.
'Long practical experience with pulsejets has convinced us that the nature and quality of atomisation of fuel have only a secondary influence on performance whereas the positioning of the injector is critical. For the "Ecrevisse" pulsejets the change in injector position of 3mm. in an engine total length greater than 2 metres sufficed to change the thrust by more than 20%'

They don't answer the question 'Why is the position critical'?

Graham.

Another interesting perspective on the same issue is contained in SAE paper #840422:

Here, the authors have designed and built a supposedly-advanced engine of roughly the L-H type, and successfully operated it on propane.

As reported in the paper they never got it to run on liquid fuel, in spite of the installation of what would appear to be a sophisticated atomizer system.

As I've said before, fuel systems are possibly the biggest hurdle to successful PJ operation (assuming you want to run on something other than propane).

Bill H.
Acoustic Propulsion Concepts, Inc.

[hinote]

They don't answer the question 'Why is the position critical'?



Graham.

Graham--Do YOU have an answer to that question?

[hinote]

I have always thought that injecting fuel into the combustion chamber was wrong. My first ideas concentrated on the best propane-air mixer I know of -- the Bunsen burner. We already have a similar structure in valveless pulsejets -- the intake stack. I thought injecting fuel into the intake stack might just be the best thing of them all. It would use the length of the stack to achieve proper mixing and also utilize the energy contained in the pressurized propane to accelerate the mixture into the chamber and achieve a minor level of superchage.

Yet, for some reason, nine designers out of ten have chosen to inject fuel into the chamber.

The following probably refers only to liquid-fuel delivery issues:

Of course I don't (yet) know for sure, but it sure seems that the fuel delivery located at the mouth of the intake(s) is asking for a huge chunk of trouble.

Not only is it going to be entrained excessively in the outflow--but it will never be able to take advantage of the latent heat farther down, for conversion from atomized liquid to vaporized mixture.

Also, the joint between the intake(s) and the combustion chamber HAS to be highly turbulent, due to the discontinuous area changes there--and this contributes significantly to the mixing of fuel and air.

As even this excellent example of a Locky shows, the primary combustion zone is at least part-way down the chamber, and gives room for good fuel preparation at the head-end.

I think it would be an excellent technical effort for somebody to experiment with and record the results of changes in fuel-supply locations--all with the same engine. Lots of work.

Bill H.
Acoustic Propulsion Concepts, Inc.