|
|
Post by propellanttech on Sept 1, 2011 19:45:16 GMT -5
Ok, so I"m starting a new thread for the JT84 engine I want to build. I took John's idea, but I want opinions. Will this cause problems? I took every third spoke, and I'm planning to port it to the tunnel and inner combustion chamber.  Tell me your thoughts, James |
|
|
|
Post by Johansson on Sept 1, 2011 23:22:16 GMT -5
A neat way of getting around the need for flow deflectors inside the engine!  A slight downside is that once you have made the diffusor there is no way you can alter the ratio of air going towards the shaft tunnel. (by the way, try to size the pictures so that you don´t have to scroll sideways while reading the thread.) |
|
|
|
Post by propellanttech on Sept 1, 2011 23:49:34 GMT -5
A neat way of getting around the need for flow deflectors inside the engine! A slight downside is that once you have made the diffusor there is no way you can alter the ratio of air going towards the shaft tunnel. (by the way, try to size the pictures so that you don´t have to scroll sideways while reading the thread.) Yeah...that is true, once the diffuser is machined, it would be hard to change the ratio. But I figure a 2 to 1 ratio should be suitable. I don't have to scroll.....sorry. I thought the board shrank the picture enough to prevent scrolling from side to side. I'll make them a size smaller. You will have to tell me when they are small enough. James |
|
|
|
Post by Johansson on Sept 2, 2011 2:35:29 GMT -5
I am running a 1/3 ratio on my engine, so stay tuned for a progress report. Pics looking good now, fits a normal sized computer screen. |
|
|
|
Post by propellanttech on Sept 2, 2011 12:28:55 GMT -5
I am running a 1/3 ratio on my engine, so stay tuned for a progress report. Pics looking good now, fits a normal sized computer screen. I'm going to finish the drawing.....and may have to modify the design later. Keep us updated on your spool up, I know everyone is patiently waiting. We all hope it goes well. James |
|
|
|
Post by propellanttech on Sept 2, 2011 17:42:39 GMT -5
I didn't take the time to finish the diffuser yet.....but I did do one major feat. I just finished a KJ66 turbine drawing. It was not easy. There are many facets of the wheel, which are complicated to get correct. One thing I added which was not on my drawings.......a raised circle for balancing. I think every turbine for home building should have one. There is actually one on each side.  James |
|
|
|
Post by Johansson on Sept 2, 2011 18:06:20 GMT -5
So you won´t make a sheet metal turbine for this engine? It would be really interesting to see a proper DIY build with home bent axial turbine blades. |
|
|
|
Post by propellanttech on Sept 2, 2011 18:15:30 GMT -5
So you won´t make a sheet metal turbine for this engine? It would be really interesting to see a proper DIY build with home bent axial turbine blades. Nope, can't say I will. I really don't like the idea of a turbine with blades bent from sheet metal. First, I don't think you could bend Inconel effectively, and stainless doesn't stand the heat very well. I say a video where a guy is TIG welding blades for a turbine. I'm actually quite scared of the whole idea. I am unfortunately going to use a cast turbine. James |
|
|
|
Post by propellanttech on Sept 3, 2011 3:42:23 GMT -5
Here is the core of the project....... The turbine isn't exactly the size for this design. The plans call for a 68mm, and this one is 66, but it's a good representation for now.  James |
|
|
|
Post by propellanttech on Sept 4, 2011 2:34:20 GMT -5
With the burner can.....  James |
|
|
|
Post by Johansson on Sept 4, 2011 12:47:03 GMT -5
Really nice drawings you are making! |
|
|
|
Post by propellanttech on Sept 4, 2011 14:30:30 GMT -5
Really nice drawings you are making! Well.....since I'm not building, I figured I would make sure the drawings were accurate. Everything but the diffuser, vaporizer tubes, and turbine are exactly as Ken Jacks plans call for. The diffuser is of my design (to insure the tunnel gets enough air flow and to reduce complexity of the radial vanes) and the turbine is of a KJ66 turbine. Ken Jack calls for his turbine of 68mm. I'm going to update the turbine to his dimensions. The vaporizer tubes have the added alternating squeeze to the tubes. The NGV is going to be somewhat difficult to insure correct. I do not have an accurate drawing of the blade geometry. But because it is a cast part, the blade geometry is not critical for the plans. But I am a perfectionist. I find the outer casing is somewhat strange on his design. It actually lets some air pass the NGV. I think this helps keep it cool. But I wonder how much it effects the efficiency of the turbine. I will post as I progress. James |
|
|
|
Post by propellanttech on Sept 21, 2011 0:38:36 GMT -5
Here is my latest assembly. It doesn't include the compressor, but does work out some design flaws of the prints I have. Something is wrong with the dimensions of the shaft tunnel. I think it's tail end is too long. I have checked the drawing numerous times, and it is drawn to print, but I have had to add length to the turbine spacer (2 mm).  I'm thinking of buying the new Levil 5 axis machine and do some custom NGV's and turbines. I have some other ideas for customers to justify the machine. I think a larger turbine would be better, but Inconel gets pretty expensive. 3.5 inch diameter rod is $1225.00 for 1 foot of material. That would only produce approximately 6 turbines, and 6 NGV's. The price gets real high for 5 inch diameter material. But the Levil machine would probably handle the 718 alloy fine. But the material would need to be hardened afterwards. James |
|
|
|
Post by Richard OConnell on Sept 21, 2011 15:47:38 GMT -5
Looks really good. You've put a lot of thought into this. Are you ready to settle on bearings yet or are you going to do some experimenting first?
|
|
|
|
Post by propellanttech on Sept 21, 2011 15:53:28 GMT -5
Looks really good. You've put a lot of thought into this. Are you ready to settle on bearings yet or are you going to do some experimenting first? The first iteration will be just standard run of the mill ceramic turbine bearings. I am adjusting some designs to implement air bearings in the future. I haven't finalized the actual size yet. This is a good test, and can be adjusted easily in CAD. After some calculating, I may adjust the size to a larger compressor and turbine. This is due to the possibility of a new 5 Axis in my shop. James |
|
