|
Post by finiteparts on Mar 16, 2014 15:17:49 GMT -5
That is really cool. The variable nozzle vanes allow you to really control the turbine back pressure, just like a throttle for the turbine flow...where all of us with the fixed AR housings are stuck with a single nozzle area and thus a single range of back pressures for system mass flow rates.
So now you have an additional control variable, nozzle area...hummmm...Since you have a boost pressure gauge it should allow you to map the compressor operation somewhat...you could set the fuel flow, then vary the turbine nozzle area and record the compressor discharge pressure. If you had a compressor map, you could figure out how close you were to the surge line. Is that a truck turbo? If so, some of those have a shaft speed pickup that you could read with an oscilloscope to directly measure the shaft RPM too.
Also a EGT would be interesting...you could use the variable nozzle to map the turbine EGT at a fixed fuel flow...by recording the compressor pressure ratios and EGTs, you might be able to find the most efficient operating point....If you don't have one, you can buy a Harbor Freight multimeter with a type K thermocouple for like $15 and just immerse the thermocouple in the exhaust stream to get the EGT...lots of possibilities! I look forward to see how things go for you with this.
|
|
|
Post by racket on Mar 16, 2014 16:09:48 GMT -5
Hi Blake
When you do your high pressure runs be careful about using the variable nozzle control , you could send the engine into overspeed at what appears to be a "lowish boost" if the flow is in the choke region , you really need a tach on her .
Max "efficient" P2 would be at ~40psi , any higher and the compressor efficiency generally starts to drop off which negates any benefits from the higher pressure ratio , there will be some variation depending on the compressor wheel design,.......... BUT, that 40 psi is with the engine running with the compressor flowing in the middle of the efficiency islands , if over to the right hand side of the comp map in the high flow choke region you could be overspeeding at 30 psi P2 .
As for potential thrust ..........~70-80 lbs ............ if the gas producers flow was fed thru a suitable freepower turbine and transmission it would produce ~80 hp .
Please be careful with the VNT control whilst running to high P2s until you have a tach on the engine.
Cheers John
|
|
|
Post by finiteparts on Mar 16, 2014 20:11:30 GMT -5
Another thing that I noticed in your video is that you are spraying something in the inlet...I assume that is water...just make sure that you don't get any large drops because you can erode the compressor vanes leading edges... since water is incompressible it is essentially like spraying in small rocks...if the size of the droplets gets above a certain size, they will be too heavy to ride along with the airflow into the compressor...if there is a marked difference in velocities between the air and the drops, they will impact on the leading edges and produce plastic deformation. I would just check the leading edges carefully to make sure that the mist isn't damaging the leading edges...just a suggestion.
One thought on the varying the vane angles...can you "set" it at a certain angle and run there for a while or is it on a spring so that it is open or closed?
Looks like fun! Thanks for posting the vids!
~ Chris
|
|
|
Post by areacombustor51 on Mar 16, 2014 20:23:03 GMT -5
The clear liquid is Ethanol aka moonshine. It doesn't seem to have any effect so I haven't been using it and won't be. Thank You. The the spring cable. I will disconnect the spring/cable and run it and see what happens. I assume by disconnecting my cable the vanes will open automatically. I'll run it and see what happens.
|
|
|
Post by racket on Mar 16, 2014 21:48:46 GMT -5
Hi Blake
I'd imagine the vanes would be configured to open automatically if something went wrong , this would be the safest direction , if they closed up it would be possible for the diesel engine to very easily overspeed the turbo as well as overboost the engine .
Cheers John
|
|
|
Post by finiteparts on Mar 16, 2014 23:02:38 GMT -5
If they are like my Garrett VNT-15s, they will be free to rotate and likely go full open as John has suggested, but I would be worried that they would flap like a flag in the breeze and potentially damage the vanes...I would leave the cable attached and build some sort of locking device so that you could lock it in various nozzle settings.
If you try it without the cable, you might keep a close eye on the bellcrank to make sure that it isn't flapping and damaging the vanes.
Is it as cold there as it is here in Ohio? If so the ethanol wouldn't do much...wait till summer though...it may be worth a retry.
You got me curious!
|
|
|
Post by areacombustor51 on Mar 17, 2014 10:09:53 GMT -5
Haha ya it's cold here. Diesel Engine Exhaust Vane Nozzle??http://www.powerstroke.org/forum/6-0l-performance-parts-discussion/527481-i-need-bigger-turbo-myths-how-drive-vgt-turbo-turbo-lag.html Variable Geometry Animation: m.youtube.com/watch?v=t2GrVS-sGdQm.youtube.com/watch?v=-Vb4yzEeIZASo from what I've tested I haven't even opened up my vanes. I have them slightly open for start up spool and it's peaking to 15 psi. By disconnecting cable vanes should open up automatically set to most efficient range. Seems that I've probably been running turbo hot do to not opening the vanes to match the higher rpms and air flow. With the vanes closed turbine wheel at peak rpm boost spike turbine looses vacuum turbine wheel boost spike turbine looses suction and center point of journal bearing. Turbine wheel becomes unstable. Acts like the turbo has hit a choke point. Opening the vanes corrects problem? Any one using a Wideband 02 sensor? I installed mine in the chamber to read premix air fuel values. Works great. Propane AF ratio value set at 15.5
|
|
|
Post by racket on Mar 17, 2014 16:08:41 GMT -5
Hi Blake
Be careful about using information relating to the turbo behavior on a diesel engine and its gas turbine use, they are different animals.
If the vanes are closed too far you'll send the compressor wheel into surge ( low intermittent flow) which can wreck the turbo ( bent shaft) , if the vanes are opened too far the engine will flow in the high flow choke region and you'll have high temperatures going into the turbine , a mid point is probably a good starting point.
To check if the vanes are in the "best" position you'll need to measure a number of parameters , T2 in relation to P2 to determine compression efficiency , this will tell you if you're operating with the flow in the centre of the efficiency island ...............a thrust measurement in conjunction with the jet nozzle area will tell you if the engine is operating at its optimum , ..........the use of a pitot tube in the jetpipe to measure jetpipe total pressure when combined with the TOT will provide the potential jet efflux velocity ,which can be cross referenced with the thrust and jet nozzle sizing to get more concrete results as to whether or not the engine flow is what it should be .
Unlike a turbo on a diesel engine where there is a sealed blockage ( valves) between compressor and turbine stages our gas turbines are directly connected , so everything is influenced by everything before or after .................change those NGVs and it changes everything from the compressor wheel inducer airflow speed to the jet nozzle exhaust velocity , including T2 , P2 , T I T , rpm , TOT , P4t , etc etc ........
Those variable vanes can be a blessing but also a potential disaster , so play safe and don't close them up , set them at mid point and do some testing .
It is possible to theoretically workout a jet nozzle diameter that should suit your comp inducer diameter ,...........then if the NGVs are set in the correct position to maintain the optimum mass flow at the design T I T/TOT the engine will produce its full potential .
Cheers John
|
|
|
Post by areacombustor51 on Mar 17, 2014 16:38:42 GMT -5
Very interesting run. After sustained I pulled the vanes open slightly and 10 psi dropped to 3-5psi but still had had stable power. The turbo went from making a vacuum noise, to a whole lot of air velocity noise. Slowly open vanes with fuel noticed a huge difference in the sound of the exhaust jet pipe. Sounds like it flows a ton of more air. Turbine shaft becomes unstable with vanes almost closed while adding fuel. Opening vanes while adding fuel corrects unstable turbine wheel. I noticed while opening the vanes with high fuel you could hear the the turbine slow down and air velocity increases.
|
|
|
Post by finiteparts on Mar 17, 2014 19:16:50 GMT -5
I am not clear on what you are saying...are you saying that you can physically see the turbine shaft become unstable? I would be careful around that condition...damage due to rubs can happen quickly and remember that you are scrubbing the bearings before you scrub the housings. Is your oil staying pretty cool? As oil heats up, the viscosity drops and thus the load capability of the bearing also drops. If you keep your runs short, the oil won't get too hot...but if it gets hot and you run the turbo into some kind of unstable rotordynamic condition, your probability for damage goes up.
I was actually thinking that the sudden pressure changes caused by vane actuation will cause you to rapidly change the load on the thrust bearing also...this might cause the unstable condition...or wear out your thrust bearing, since they are notorious weak links on some turbos.
As for the sound change that makes sense because you are effecting the pressure ratio of the engine...I vote for another video!
|
|
|
Post by racket on Mar 17, 2014 20:35:47 GMT -5
Hi Blake That unstable turbine shaft is SURGE ,..............DO NOT GO THERE ...............IT WILL WRECK YOUR ENGINE !!
Please set your vanes at mid point and collect the data I recommended, if you keep on closing those vanes you WILL end up with a bent shaft .
Cheers John
|
|
|
Post by finiteparts on Mar 17, 2014 22:50:03 GMT -5
Wow...good catch there John...I totally read that wrong and missed it. Agreed, you are surging the compressor and this is not good. I grabbed a VNT-15 compressor map to show you... If you are sitting at the black circle and start to add fuel, the rotor doesn't respond fast enough and probably couldn't work against the back pressure caused by the closed vanes...but the other major factor is that the combustion process can respond fast. So you suddenly add a ton of heat which reduces the gas density. That means to get the mass flow through the back end you need to speed it up. mass flow = density x area x velocity or rearranged, velocity = mass flow / (density x area) So if the mass flow (due to flow inertia) and the area can't instantly change, as density goes down velocity goes up. But it can only go up till it reaches the speed of sound...once it reaches the speed of sound it chokes! The choked flow in the turbine feeds back and causes the flow across the compressor blades to stall like the flow on an airplane wing and it surges. So the flow in the compressor follows the red line and you move across the surge boundary! You can get some pressure rise due to the increased backpressure... I wouldn't do that...It can bend blades, break blades, wear the thrust bearing out quickly due to the back and forth thrust load, cause rotor rubs and even wipe out bearings, since the rotor can slow down and thus the fluid wedge in the bearing breaks down for a short time. But if you want to keep doing it...make a video so we can watch! Ha! ~ Chris
|
|
|
Post by areacombustor51 on Jun 17, 2014 18:44:24 GMT -5
The How To Building A Turbo Jet Powered Datsun 520. Motive Progress. Cleaned out the compressor housing. turbine wheel is an excellent condition. Shaft play feels yep still freely spinning. The gauge in the exhaust is a grill temp gauge.
|
|
|
Post by areacombustor51 on Jun 18, 2014 16:44:38 GMT -5
So I've figured there is two ways to plumb the turbo jet into the the vehicle engine.
Each option will require a 4 stroke engine camshaft timing modification. Two stroke engines require no mods and are already great stream/compressed air engines. The intake lobe must be mirrored to the opposite side of the camshaft. Nobody knows for sure if this is correct but YouTube shows proof. Exhaust lobe is still unknown. Rather than a lobe a circle which would allow the valve to remain slightly open during the 4 stokes. The pro of this is its a set leak allowing the combustion camber to breath freely. Could possibly work as an energy absorbing vehicle deceleration brake. I think this is what's called a "Jake Brake" and tractor trailer semis use it.
A. Plumb the turbo through the engine. Compressor charge pipe leads to the intake manifold. Exhaust manifold leads to the inlet of the combustion camber. Jet pipe is the exhaust
B. Steam Nozzle??? Plumb turbine jet exhaust into the engine intake. Heat from exhaust creates water vapor and the air creates mist/steam. The steam nozzle will look like the design of my first combustion camber design. Air velocity and hear will mix with the h20 molecules. Vehicle engine manifold is the exhaust . Correct Method Diesel Engine .
|
|
|
Post by areacombustor51 on Jun 21, 2014 11:21:48 GMT -5
|
|