Schwitzer 4LF-504 build

[desp]

I was directed to this forum from Racketmotorman on DIY Gas Turbines, as for some reason I'm not able to post over there, and the yahoo group is an antiquated interface anyway, even this orange forum is better!

So here's where I'm at - I bought this Schwitzer turbo off of ebay about 7 years ago with the hopes of building a jet engine out of it, except I didn't have the tools or money to do it. Well in between that time and now I have a lot more tools and ability to work on it, plus the constant teasing by my friends on "How's the jet engine going", I figured it was time to build it.



The Turbocharger is a Schwitzer 4LF-504, P/N 180290R. I can't find any info on it. I bought it on ebay and I believe it was a reman, I got it for $50 shipped, which is why I bought it so long ago. It appears to be in excellent condition, except some surface rust on the housing from sitting. The oil holes have been plugged this entire time.

I took everything apart to look at how it worked and assess the condition, it all appears good, I should probably give it a thorough cleaning before firing it up for the first time, so any suggestions on re-assembly and cleaning practice would be appreciated.

I have a cheap pump that's rated at 50 PSI, 300 GPH, it's going to pull the oil from the tank, through the oil cooler, then push it through the oil filter and into the turbo. I'm not sure if 50 PSI is enough oil pressure though, I haven't been able to find any documentation on the turbo.

The turbo's inducer is 2.5" at the smallest part of the blades, and the exducer(?) is 3" at the smallest part. Using the calculations from Jetspecs I created my flame tube, although it's slightly smaller than what was called for, I used what I had.

The flame tube is 3 1/4" ID, and the combustion chamber is 4 3/8" ID. The holes are drilled according to the jet spec calculation.

I was originally going to use a spark plug, but instead of trying to get the circuit to work with my ignition coil I decided just to get a glow plug. I found an AC Delco 60G that is rated at continuous duty, so I shouldn't have to worry about burning it up.

My nozzles are HAAG misting nozzles from McMasterCarr, rated at 10 GPH at 100 PSI. I was going to run two at a lower PSI, but I probably won't get good atomization much lower. At around 50 PSI they seemed to be misting well, but higher PSI will probably be better so I'll just end up using one.

I have a Walbro, 140 PSI, 255LPH fuel pump I'm using, I have an adjustable fuel bypass to adjust the PSI going to the nozzles, I'm considering also using a PWM to adjust the fuel pump speed and be able to make adjustments on the fly a little bit easier.

Here's where I'm at with the testing.

Exhaust from a shop vac connected to the combustion chamber, heat up glow plug and then start fuel pump, diesel ignites right away and I have a good flame, except I have a significant amount of unburnt diesel dripping out the end. As Racketmotorman pointed out to me, the nozzle I'm using with a shop vac or leaf blower is dumping way more fuel than it needs.

Some other possible design flaws:

Flame tube is too small
Fuel nozzle is to the side, and not in the middle
Should probably use propane to start then switch to liquid fuel

Suggestions on...

Will my small diameter flame tube be able to work, can I slow down the axial flow to allow the diesel to fully burn?

If I get the flame tube hot enough with propane, will my off set diesel nozzle work?

[stoffe64]

hello there!

welcome aboard i must start with!
nice with a new build in here!
your combustor is way too skinny i believe, what are the comp wheel inducer area? and the turbine wheels exducer area?, those two are the most important to start with, have you looked at jetspecs on the yahoo diy group? there you can get calculations for a working combustor right off from the start, the turbine wheel exducer should be about 25% larger than the comp wheel inducer area, that was just the beginning but there are lots of people in here helping out so you will get started soon!!
cheers/stephan

[desp]

Hi Stephan,

Yes I used Jetspecs - I was hoping I would be able to keep the total volume the same and use a smaller diameter flame tube since that was what I had on hand.

My Inducer is 2.5", with an area calculated by jetspecs of 4.908

The flame tube it calls for is 5" Diameter and 15" long. I made mine 24" long so I'd have the same volume but it appears that theory may not hold up to working, since the air velocity will be too high?

[stoffe64]

no you can not have a smaller flame tube, you can make them a bit shorter BUT you can not make them long and skinny, yes air velocity becomes too high, the one i build will use a 5" flametube about 35 centimeters tall
cheers/stephan

[desp]

Mar 19, 2013 10:17:00 GMT -5 stoffe64 said:

no you can not have a smaller flame tube, you can make them a bit shorter BUT you can not make them long and skinny, yes air velocity becomes too high, the one i build will use a 5" flametube about 35 centimeters tall
cheers/stephan

Is there a workaround for high air velocity problems, can I preheat the fuel to create a faster burn rate, can I baffle the airflow somehow to reduce the speed?

What kind of problems am I looking at here, loss of efficiency or simply not working at all?

My end goal is to mount the setup on a riding lawn mower and drive it down the street, show all of the haters that I built a jet engine that said I never would, and then probably be done with it and go back to working on my other 50 projects I haven't finished yet.

[Johansson]

Hi and welcome!

You will have problems with such a thin flame tube unfortunately, if I were you I would probably try to run it on propane since you´ve already built it but with a close check on the exhaust temps. I don´t think you should even consider feeding it diesel.

The best way is of course to build a new combustor after the Jetspecs design, then you know it will work.

If you want to really impress the assholes on your street you should try to build a power turbine for the lawnmover once the gas producer is up and running, even the crudest one possible will still give you more power than jet thrust will ever do.

Keep up the good work!
/Anders

[racket]

Hi Jordon

Good to see you here on JATO :-)

We really can't get around the high axial velocities other than increasing flametube crossectional area .

With a crossection of ~3 times inducer area , which for you would be 4.33 inch ID for the flametube , the length can be reduced to about 4 inducer diameters long , so 10 inches for you

Jetspecs was created to prevent guys building engines with skinny combustors that caused them no end of combustion problems.

You will probably get the engine to run on propane due to its very high speed flammability.

Cheers
John

[stoffe64]

hello Jordon!

sorry to say but your combustor as it is now probably dont work so good, maybe with propane as fuel as John and Anders also said but you should really build a new combustor following the jetspecs(atleast when it comes to the outer diameters) the length can be somewhat reduced but basically follow the recommendations from John and Anders, that was a good rule with 4 times inducer area as the length, that is what i build myself with my scaniaten turbojet.
cheers/stephan

[desp]

I'll start finding the parts to assemble a new combustor.

In the mean time I'll assemble this with propane and see if I can get it to start. Any suggestions on assembling the turbo to make sure it's all clean, since it's been sitting for so long?

What's the minimum oil PSI I can use with this turbo, anyone know?

[Johansson]

If the oil ports have been plugged it should be ok, pour a bit of oil through the bearings and spin it by hand. If it spins freely without any rubbing it is fine, also check the axial and radial play by pushing the comp nut in and out and to each side.

There should not be any axial play, and the radial play is ok as long as the compressor doesen´t scrape the housing if it is rotated while pushing the comp nut to one side.

50 psi should be enough, just make sure it doesen´t drop much below that when the oil starts to heat up.

Cheers!
/Anders

[desp]

I am looking for a new combustor, thinking about finding an empty oxygen or acetylene tank. If Jetspecs calls for a 5" flame tube, how much larger can it be without negatively effecting it?

[racket]

Hi Jordon

A 1" radial gap is more than adequate , you could get away with as little as 5/8" radially , the radial gap can't be too large but it can be too small .

A lot of us have used "7 inch" stainless "air over water" fire extinguishers for our outer cans , they're pressure tested to 300 psi and normally used at ~100psi , so plenty strong enough yet very lightweight .

I used one for my "Two shaft kart" ..................theres a build Thread here in the DIY section .

Cheers
John

[desp]

Mar 21, 2013 16:50:11 GMT -5 racket said:

Hi Jordon

A 1" radial gap is more than adequate , you could get away with as little as 5/8" radially , the radial gap can't be too large but it can be too small .

A lot of us have used "7 inch" stainless "air over water" fire extinguishers for our outer cans , they're pressure tested to 300 psi and normally used at ~100psi , so plenty strong enough yet very lightweight .

I used one for my "Two shaft kart" ..................theres a build Thread here in the DIY section .

Cheers
John

I've been looking at those, what did you end up using with that combo for a flame tube?

[racket]

Hi Jordon

I used a piece of stainless steel sheet 0.5mm - 0.020" and rolled to shape, I wouldn't recommend going that thin as its subject to pressure differential induced warpage when overheated, better to use 1mm- 0.040" stainless or even 1.2mm -0.048" as it has more structural strength and is easier to weld .

Cheers
John

[desp]

Mar 21, 2013 19:16:58 GMT -5 racket said:

Hi Jordon

I used a piece of stainless steel sheet 0.5mm - 0.020" and rolled to shape, I wouldn't recommend going that thin as its subject to pressure differential induced warpage when overheated, better to use 1mm- 0.040" stainless or even 1.2mm -0.048" as it has more structural strength and is easier to weld .

Cheers
John

What's your advice on this. Jetspec called for 15" Long, 5" diameter flame tube.

I've found some 6" pipe and 8" pipe. Can I do a 6" flame tube with a 8" combustion chamber around it, and make it shorter? If so how much shorter?