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Post by azwood on Jan 6, 2019 0:00:37 GMT -5
Been busy machining parts got the shaft tonal done bearing in and a nice snug fit I left it few microns smaller that worked well.still need and oil seal ring to suit the shaft it wasn’t there when I got the turbine not sure what my options are there.still need to find a way to turn down the shaft so the bearing seats next to the oil slinger and has good support near the end but it’s coming along it’s sure not a small job as John said harder than building the rest of the gas producer
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Post by azwood on Jan 8, 2019 0:26:39 GMT -5
At the point where I need to make the exducer for the turbine its fairly simple just a hollow pipe with a few degrees tapered.which reminded me of something turboron I think said about machining it more like a normal turbo and reducing it down a bit to try get a bit more drive off the end of the blades not sure how much it would take to make a difference but it makes sence with the wheel so big.
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Post by turboron on Jan 8, 2019 8:25:43 GMT -5
Aaron, can you post a rough hand sketch so we can comment?
Thanks, Ron
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Post by azwood on Jan 8, 2019 16:40:15 GMT -5
Aaron, can you post a rough hand sketch so we can comment? Thanks, Ron OK I'll take pics tonight and do a sketch.
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Post by azwood on Jan 9, 2019 5:53:30 GMT -5
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Post by turboron on Jan 9, 2019 8:05:06 GMT -5
Arron, this helps. You have what is termed a "mixed flow" radial inflow turbine in that the incoming flow has an axial as well as a radial component. Can you add the IGV and vaneless space to the sketch in the proper axial position? Also, what is the diameter of the inducer?
Thanks, Ron
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Post by azwood on Jan 9, 2019 16:09:55 GMT -5
Arron, this helps. You have what is termed a "mixed flow" radial inflow turbine in that the incoming flow has an axial as well as a radial component. Can you add the IGV and vaneless space to the sketch in the proper axial position? Also, what is the diameter of the inducer? Thanks, Ron The igv is 40mm wide and 40scm inducer area the turbine is 190mm
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Post by turboron on Jan 9, 2019 16:41:22 GMT -5
Aaron, I understand you to mean that the axial width of the IGV vanes is 40mm and the sketch shows the radial inflow turbine inducer have an axial blade height of 40mm. Good practice is to have a vaneless space about 10% larger that the turbine inducer diameter. This means that the minimum IGV vane diameter is approximately 1.1(190mm) = 209mm. The flow accelerates as the area decreases with the reduction in diameter. The turbine backplate ideally would be a little behind the vaneless passage so there is no rearward facing step to the flow.
Have you run the gasifier rotor (compressor, combustor and turbine combination) with the nozzle enough to establish the mass flow and the backpressure at the gasifer's exit before the nozzle?
Thanks, Ron
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Post by azwood on Jan 9, 2019 17:18:34 GMT -5
Aaron, I understand you to mean that the axial width of the IGV vanes is 40mm and the sketch shows the radial inflow turbine inducer have an axial blade height of 40mm. Good practice is to have a vaneless space about 10% larger that the turbine inducer diameter. This means that the minimum IGV vane diameter is approximately 1.1(190mm) = 209mm. The flow accelerates as the area decreases with the reduction in diameter. The turbine backplate ideally would be a little behind the vaneless passage so there is no rearward facing step to the flow. Have you run the gasifier rotor (compressor, combustor and turbine combination) with the nozzle enough to establish the mass flow and the backpressure at the gasifer's exit before the nozzle? Thanks, Ron Yep with a 68mm nozzle I got 5psi from the pitot
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Post by turboron on Jan 9, 2019 18:43:17 GMT -5
Aaron, on page 9 of your thread you said the gasifier compressor inducer was 82mm(3.23") in diameter. An approximation of air flow is 11 pounds per minute per square inch of the inducer. The estimated airflow area is then .785(3.23)3.23 = 8.2 square inches. The air flow equals 8.2(11) = 90 lbs/min or 1.5 lbs/sec. Assuming a turbine inlet temperature of 1450 degrees F and a pressure ratio of 3.0/1 and your 5 psig nozzle inlet pressure we can make some horsepower numbers. I will do some calculations tomorrow if I have the time. If you have better numbers for your turbine inlet temperature and pressure ratio it would help.
Thanks, Ron
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Post by azwood on Jan 10, 2019 0:31:01 GMT -5
Aaron, on page 9 of your thread you said the gasifier compressor inducer was 82mm(3.23") in diameter. An approximation of air flow is 11 pounds per minute per square inch of the inducer. The estimated airflow area is then .785(3.23)3.23 = 8.2 square inches. The air flow equals 8.2(11) = 90 lbs/min or 1.5 lbs/sec. Assuming a turbine inlet temperature of 1450 degrees F and a pressure ratio of 3.0/1 and your 5 psig nozzle inlet pressure we can make some horsepower numbers. I will do some calculations tomorrow if I have the time. If you have better numbers for your turbine inlet temperature and pressure ratio it would help. Thanks, Ron Sounds great ok my tots where around 12/1350f depending on rpm I've made the igv 40scm not the 34 that the nozzle was in case I had any restrictions but I can tune that more.I just get a feeling the wheel need a smaller exit area to make use of the axial flow part of the turbine. Thanks in advance for helping work this out.
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Post by turboron on Jan 10, 2019 21:36:11 GMT -5
Aaron, made some power turbine numbers this evening. Everything approximate as follows:
Compressor Pressure Ratio - 3.0 3.5 Compressor Inlet Temperature deg F - 60 60 Mass flow pounds per minute - 90 90 Compressor Discharge Temperature deg F - 354 381 Gasifier Turbine Inlet Temperature - deg - 1525 1650 Gasifier Turbine Outlet Temperature - deg F - 1225 1330 Power turbine inlet pressure - psig - 5.0 5.0 Power Turbine Outlet Temperature - deg F - 1093 1191 Power turbine horsepower w/o bear losses - 66 71
I assume compressor and turbine efficiencies of 70%. Note that the 1650 deg F is risky for our old DIY units.
Thanks, Ron
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Post by azwood on Jan 11, 2019 5:02:18 GMT -5
Aaron, made some power turbine numbers this evening. Everything approximate as follows: Compressor Pressure Ratio - 3.0 3.5 Compressor Inlet Temperature deg F - 60 60 Mass flow pounds per minute - 90 90 Compressor Discharge Temperature deg F - 354 381 Gasifier Turbine Inlet Temperature - deg - 1525 1650 Gasifier Turbine Outlet Temperature - deg F - 1225 1330 Power turbine inlet pressure - psig - 5.0 5.0 Power Turbine Outlet Temperature - deg F - 1093 1191 Power turbine horsepower w/o bear losses - 66 71 I assume compressor and turbine efficiencies of 70%. Note that the 1650 deg F is risky for our old DIY units. Thanks, Ron Thanks heaps I think my thurmacouple may read a little high I have no red glow at all on the turbine so far it’s been rock solid those numbers are not far from rackets original numbers when I started. I’ll keep moving forward with the drivetrain anyway I’ll post more pics soon.thanks everybody
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Post by turboron on Jan 11, 2019 7:56:23 GMT -5
Aaron, the difference between racket's numbers and mine are the difference in our assumptions. For example, he probably assumed a 4/1 pressure ratio and higher component efficiencies. We are in the right ball park.
Thanks, Ron
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Post by turboron on Jan 11, 2019 11:30:52 GMT -5
Aaron, I calculated a power turbine rpm for the 1650 deg F performance point.
Method is to set the head in feet from the mass flow and temperature drop equal to the head from the Euler equation. So if we use the Euler equation in the form Head = Slip times tip speed squared we can calculate an power turbine speed. For radial blades slip = .85 so we have tip speed squared = 32.2 (feet/sec squared) times 37,160 feet/.85 the square root is 1186 ft/sec. 32.2 is the gravity constant. We then calculate the power turbine rpm from the tip speed converting the 190mm diameter to inches(7.48"). N = 720(1186)/3.14(7.48) = 36,257 rpm. The 720 is just a conversion factor so you can use diameter in inches and the tip speed in ft/sec.
Bottom line is that the power turbine speed should be around 36,000 rpm at power with your 190mm turbine inducer.
Thanks, Ron
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