So I've been making more progress on the modeling and CFD for the hot section components.
Here's the final NGV design, 5.1 in^2 throat area, 20 vanes. Also made some adjustments to the NGV top ring's axial swirl vanes to produce a flow path consistent with the NGV vane angle. The NGV vanes have also been modified from the original design - now using 20 vanes instead of 18 and have done away with the rounded head shape to improve flow characteristics.
I have also done a good deal of work on the combustor.
And a new section view of the engine model:
At this point I have sourced a manufacturer who is machining the 3 hot section components: NGV Outer Ring, Axial NGV Top Ring, and Radial NGV. Parts are being made from 316SS - total cost is $435 to the door. Should have some nice pieces here in my hands within a week or so. YAY!
Thats a very reasonable price , 316 SS is just so slow to machine up when in big sections ..........the hours I've spent at the lathe making NGV bits , its gotta be the worst part of making an engine . You're certainly getting good at this modelling , nice graphics :-)
Just finished modeling the RR wheel and the freepower housing sections. I've got a few discrepancies in the turbine calculator spreadsheet I made a couple of years ago w/regards to the hub diameter for this turbine. I originally had it as 4.8" diameter but my wheel has a hub dia of 4.472" and I know this is going to throw the calcs off. Need to re-evaluate the spreadsheet and geometries to figure out exactly what diameter the RR wheel needs to be cut at. I plan to send the wheel over to a waterjet facility to have them cut the wheel to size, + a little extra and I'll do the final grinding on the lathe, but need to nail down the maths to get the proper trim diameter...... and keep in mind I'm not using the GT60 wheel...
Some more models.
I will be designing the geartrain for the FPT pretty soon but need to make a trip over to a buddy's shop where he does nothing but automatic transmission rebuilds. I'm wanting to look through a variety of planetary gear sets and start working on the mental model of what transmission pieces I'll be able to use for the redux...
Last Edit: Apr 14, 2012 15:32:35 GMT -5 by ashpowers
A few more sexy model images - just about everything short of the FPT geartrain.... and yes, the finished engine wont look much different than what you see here - that's kindof the whole idea of the models. ;-)
Theres just one concern with removing the tip seal on the C20 wheel and thats blade security , the interconnection provided by the rim seal prevents blade vibration allowing for a "lighter" blade, without the connection there will be a need for a substantial containment ring just in case the worst happens and you throw a blade . ..................thankfully we aren't flowing as much mass or expecting as high a power output as in its original scenario , so some blade stresses will be reduced
Possible design for bearing assembly: Tesla turbine mounted mid-length between the two angular contact duplexed bearing sets to act as a pressure booster to deliver the cooling air and fuel/oil mix back to two modified vaporizer tubes in the combustion chamber.
Not so sure I'm going to go this route though. It all depends on how well the fuel/oil mix is turned to mist and carried through the delivery tubes to the vaporizers. I tend to think the fuel/oil will want to wet out on the walls of the delivery tubing and cause inconsistent combustion.... hard to say though..
The bearing arrangement shown is very likely to be the route I'll end up going though. I've been playing around with a set of angular contact bearings I have here and when they are arranged face to face as shown in the model they sinch up all of the slop and turn incredibly smoothly. Having two pairs of these for the rotating group will provide dual axial support in both directions and these type of bearings are precision ground to produce preloads on the balls/races that they "like". Just really like the idea of the dual system - spreading the load across more bearings should improve service life and reduce possibility of catastrophic failures, which as a few of us here know, can get quite expensive and demoralizing, LOL.
I'll probably do away with the tesla turbine pump and just go with a large sump - I've got lots of room in the engine for a decent sump and de-aerator so I should be able to seperate the air and fuel/oil from each other to help reduce the complexity of external bits. Would be nice to allow the bleed air to open ventilate and simply return the fuel/oil mixture right back to the fuel tank.
I've spent my evening running down this tesla turbine idea which would be really cool to integrate but I dont think its going to pan out. I'm going to get my hands on another pair of these angular contact bearings and setup a rig to simulate the arrangement at operating conditions they will see in the actual motor to do some testing to see how they like the RPM, heat, and loading... This should be something that can be properly developed prior to putting several hundreds of dollars of real parts on the line..
One of the reasons I gave up on ball bearings and went back to the standard "off the shelf" brass bush ones.
Our TV94 turbocharger rotatives have shafting diameters etc designed for brass bush floating bearings that have inbuilt damping characteristics from the "thick" oil films , when the rotative is installed in "hard" ball bearings that damping is missing and has to be built into the bearing mount , this can mean a "spring" mount as the Rover car engine used with its radial inflow gas producer turbine, or a "thick" pressurised oil film surrounding the bearings OD.
On my FM-1 and 9/94 engines I had the ball bearings mounted in preloaded bronze cups for axial positioning , the bronze cups had O rings at each end of their OD and were a loose fit radially in the bearing housing , pressurised oil was fed to between the O rings, there being a circumfrential oil groove in the cups OD to distribute oil around the cup, small drill holes from that channel supplied the lubrication to the "oil jet" that sprayed onto the inner raceway, it being the raceway that is hardest to lubricate due to the centrifuging effects of the bearings rotation .
Combined with the pressure balancing seal behind the comp this setup seemed to cure the bearing problems I experienced with FM-1 , but with a lot of complication :-(
Half way around the world from each other and both you and I were tacking words out about exactly the same thing, at the same time. =) Gotta love the internet!
I'm referring to the lengthy email I just sent to you centered around exactly what your reply here is all about, so, check your mail.
In short, I'm working on modeling the design for the bearing assembly that is very similar to what you described above.
As for the rotor dynamics, I will be able to simulate this in solidworks. I've got a bit of a learning curve to go through with the FEA in solidworks but I doubt it is going to take long for me to navigate through it. If that aspect of computational modeling is anything similar to the CFD modeling, I'm REALLY looking forward to it. You can learn a lot from the difference of what your imagination may create for you about how a fluid moves through a body vs. what a CFD model reveals about the actuality of the situation.