CH3NO2
Senior Member
Joined: March 2017
Posts: 455
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Post by CH3NO2 on Jan 27, 2019 23:07:52 GMT -5
... Its a diffent case with our "turbo" gas producers though , its possible to swap around the pressure drops to better suit the wheel/NGV physical sizes which aren't always whats optimal .... Hi John, How do you determine pressure drop location/spread for a particular wheel/NGV combo? Rules of wheel trim, area ratios, total pressure? Something more complicated? Thanks, Tony
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Post by racket on Jan 28, 2019 0:23:37 GMT -5
Hi Tony
LOL............I go back to basics , workout the amount of power required to get the compression we want at the efficiency given on the map or make a guesstimate , then convert that into whats needed in the way of pressure drop at the turb stage and see how the turb map handles it and/or if no map, make a judgement call on whether the turb wheel/stage is under or over sized and then think about whats possibly the best way to split up the pressure drop.
With a fairly efficient comp stage and modest PR we won't need to choke anything , just keep the gas velocities as low as possible to optimise eficiency whilst producing the required gas deflection/power.
But if theres a very large/oversized turbine wheel involved with lotsa flow area we might need to use the scroll/NGV throat area to keep mass flow under control and stop the comp flowing in the inefficient choke region , in which case the pressure drops are biased towards the scroll/NGV and little in the turb wheel which might be running less "efficiently" , reducing the overall stages efficiency.
The reverse might be the case with an undersized wheel where we might need to get the gases into the wheel with less expansion to keep them denser, then expand them in the wheel and choke the exducer with sonic velocities which will produce the required deflection/power.
Theres lotsa variables when we are required to use "off the shelf" bits , it gets easier with our "micro" engines as we can scale the NGV throats a bit easier than changing scrolls, even if available.
Then theres the differences between old and newer designs of comp wheels which throws up a whole new set of variables to consider ...................I just stumble along hoping I make the right decisions :-)
Cheers John
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Post by azwood on Jan 28, 2019 6:42:17 GMT -5
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Post by azwood on Jan 31, 2019 18:21:56 GMT -5
In the process of doing the drive line just trying to settle on a gear ratio I e got a 40 tooth on the axle and 13 front I'm thinking 6.5 to one to run that I don't want it to do 200kph just accelerate well and do maybe 150kph
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Post by turboron on Jan 31, 2019 20:53:38 GMT -5
Aaron, nice work on the turbine scroll. How many pieces in the fabricatin?
Thanks, Ron
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Post by racket on Jan 31, 2019 21:49:09 GMT -5
6.5:1 would be OK , the higher the ratio the better though , I used an ~8:1 on my kart when using karting chain 10/80 teeth
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Post by azwood on Feb 4, 2019 3:14:07 GMT -5
Aaron, nice work on the turbine scroll. How many pieces in the fabricatin? Thanks, Ron Sorry had internet problems.the housing has about 35 parts if you include the vains the outer scrolls probably got 10 parts.
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Post by azwood on Feb 4, 2019 3:17:35 GMT -5
6.5:1 would be OK , the higher the ratio the better though , I used an ~8:1 on my kart when using karting chain 10/80 teeth I’ll shoot for 8/1 I’m after acceleration still working away on it wherever I have time.i have all the parts theirs just a lot of turning to do it’s a fair process as I’m sure you know haha
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Post by azwood on Feb 10, 2019 17:36:38 GMT -5
A few pics
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Post by azwood on Feb 10, 2019 19:37:28 GMT -5
One concern is the bearings a press fit to both the shaft and the housing and is a little firm to spin
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Post by azwood on Feb 11, 2019 6:23:22 GMT -5
I might take a little out from the housing to free up the bearing.next job is to get a keyway cut to couple the shaft and to make the outer tube over it and mount the diff to the frame.
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Post by azwood on Feb 28, 2019 3:27:22 GMT -5
Things have been a bit crazy lately with a baby on the way in the next week.but I did get this turbo beanie its mate here is Australia looks like it's well made might contact them and see if I can have one made for the housing I made
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Post by azwood on Mar 2, 2019 22:49:39 GMT -5
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CH3NO2
Senior Member
Joined: March 2017
Posts: 455
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Post by CH3NO2 on Mar 3, 2019 17:20:24 GMT -5
That is going to be a boatload of fun when you get it running.
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Post by azwood on Mar 3, 2019 18:41:11 GMT -5
That is going to be a boatload of fun when you get it running. I sure hope so it's taken a lot of time and effort.but having never driven a turbine vercle before I have no idea what to expect.but the kart had a 100cc motor before and went well so I'd say it will be scarry.
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