GT3788VA Variable nozzle turbojet build

[racket]

Hi Mitch

Those temp changes could have been a minor fuel supply/pump problem in that case .

The main thing is that the engine has fired up and its time to be "tuned" :-)

Cheers
John

[mitch]

Hopefully this weekend I can rig up some type of prototype water injection system. I will probably just fit a nozzle somewhere in the intake tube, before the combustion chamber.

[mitch]

Does anyone know anything about using a 12v battery charger as a power supply? For now, I have no need to use batteries to power the oil, fuel, and water injection pumps on my setup, so can I just use a 12v battery charger to directly power the 12v pumps? I have done it before, but I just want to double check so I don't damage any of my pumps, as they aren't cheap.

[mitch]

After doing some thinking I have decided that I am going to be re-doing my combustion chamber. Since this will be used on a bike, I want it to be as reliable, powerful, and efficient as possible. I'm getting some ideas down and starting on the new chamber soon.

[mitch]

[mitch]

Getting the base plates/ mounting plates drilled for the injector couplings and spark plug

[mitch]

Got the evap mount system nearly finished, the liquid fuel and gaseous fuel couplings welded in place (fairly straight, too!), just a few more things to finish with the new combustion chamber.





The stand with turbo sitting while the new combustion chamber is made. The old combustion chamber was not nearly large enough for this size turbo.

[mitch]

www.flickr.com/photos/67398173@N02/15949571412/in/photostream/

For higher resolution pictures of the build

[mitch]

Made some more progress tonight, got the spark plug placed in the bottom of what will be the combustion chamber, and got some other little things done.

As of now, Jetspecs calls for a 15 inch long combustion chamber... After measuring it out, that seems huge. I'll include a pic of what it would look like. Also, how much longer should the combustion chamber be than the flame tube?

[racket]

Hi Mitch

The outer can just needs to be long enough to provide adequate airflows around the flametube.

I'm having difficulties working out what the flametube is in the pic , whats the long plain section of tube at the bottom??

Have you allowed for the "funnel" between flametube and scroll inlet ??

Cheers
John

[mitch]

Hey racket, what you see in that pic is my old flame tube ( which was far too small) on top of a similar piece of 5" diameter tube, done just to use as a reference to show how large it would be. And no, that was not including the "funnel" section. It just looks large compared to other people's turbojet builds I have seen, even with similar sized turbos.

[racket]

Hi Mitch

Jetspecs produces a "generously proportioned" flametube which won't suffer problems virtually no matter how poorly things are made , with greater care and sophistication of fuel/air delivery and mixing its possible to reduce the relative volume generally by making it shorter , whatever you do , don't reduce the diameter as you need low air speeds in the critical primary zone for combustion of liquid fuels .

Cheers
John

[mitch]

ahhh okay that makes sense. I will keep it close to jetspec's specifications. As of now, I will have a 1/2" gap between the flame tube and the combustion chamber. Is there any special formula for finding how long my evaporator tube should be?

[racket]

Hi Mitch

I make my total evaporator/s inlet flow area ~10% of the inducer area and the total surface area of the evaporator/s 6 times the inducer area , the inlet area of the evaporator/s needs to be taken into account with regards Primary Zone hole area , so 1/3rd of Primary Zone hole area , the remaining 2/3rds in the wall holes .

Cheers
John

[mitch]

Got some tubing from the steel store today to finish the flame tube and combustion chamber. Also rigged up my homemade arduino controlled thermocouple with an lcd output to fit into a portable box, so I can use it to monitor turbine inlet temps during the first run with the new combustion chamber. It was fairly cheap to build the thermocouple compared to buying a diesel egt setup, and is good to 1800 degrees Fahrenheit, with 2 degrees of accuracy.