Turbo vs blower
12-03-2007, 09:31 AM
#102
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The problem with using a centrifugal blower in a driven (rather than turbo application) is that the boost is proportional to speed, this means that the low speed boost is poor when compared with a conventional supercharger.
You are right in that the efficiency of a centrifugal blower when on boost is significantly better than any rotating lobed supercharger but you do lose out on low end boost unless you have a variable speed ratio to drive your centrifugal blower. I'd imagine this would affect your on to plane performance compared with a coventional blower.
Variable drive ratio blowers are being developed (we're developing one at our company at the moment) but these are all being aimed at downsizing engines in the European market. eg 2-3l high boost and fast response.
You are right in that the efficiency of a centrifugal blower when on boost is significantly better than any rotating lobed supercharger but you do lose out on low end boost unless you have a variable speed ratio to drive your centrifugal blower. I'd imagine this would affect your on to plane performance compared with a coventional blower.
Variable drive ratio blowers are being developed (we're developing one at our company at the moment) but these are all being aimed at downsizing engines in the European market. eg 2-3l high boost and fast response.
Ruaraidh: When McCullogh first introduced the centrifugal blower that became the Paxton, it came with a planetary transmission that was downshifted by engine oil pressure when the accelerator was depressed at low RPM. This was necessary because the impellers weren't that good yet. The transmission was bigger than the compressor. As impellers improved the transmission was dropped.
I saw a two speed transmission for that small compressor from Denmark at PRI two years ago. Is that yours? Our problem is we would need the transmission to handle about 200 HP for our twin blower system. For us it makes more sense to put a transmission behind the engine.
We have put centrifugal blowers in boats that are going 160+ mph with one speed. You are not going to win a drag race with this setup but that isn't how the boats are used. Class 1 boats run between 4500-7500 RPM during a race. Poker run boats typically line up at 100 mph. In both scenarios low RPM response is not an issue. I would still like the transmission though.
Tom
12-03-2007, 11:02 AM
#103
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You're talking about Rotrex.
I see what you mean, if that's the case and performance out of the hole is not an issue then definitely there would be no disadvantage to using a centrifugal device with a single ratio. That said, you're still giving away a little boost at lower speeds if the ratio is set only for max power.
The device we're developing for smaller cars (we're calling it boosted hybridisation) is SuperGen, see here. Not really applicable to large powerboats but interesting all the same as it shows what can be done. We can generate full boost from idle at 1500rpm in 0.2s.....
Of course the ultimate here is the centrifugal blower that was fitted to the Messerschmidt ME109 (yes really) it had a variable drive (essentially a small torque converter) to the blower where the oil level (and thus boost) was varied as a function of altitude. Automated boost control all the way back in the 40s and it had gasoline direct injection... Wonderful thing about engineering is there's nothing new under the sun!! This is a fun thread!
I see what you mean, if that's the case and performance out of the hole is not an issue then definitely there would be no disadvantage to using a centrifugal device with a single ratio. That said, you're still giving away a little boost at lower speeds if the ratio is set only for max power.
The device we're developing for smaller cars (we're calling it boosted hybridisation) is SuperGen, see here. Not really applicable to large powerboats but interesting all the same as it shows what can be done. We can generate full boost from idle at 1500rpm in 0.2s.....
Of course the ultimate here is the centrifugal blower that was fitted to the Messerschmidt ME109 (yes really) it had a variable drive (essentially a small torque converter) to the blower where the oil level (and thus boost) was varied as a function of altitude. Automated boost control all the way back in the 40s and it had gasoline direct injection... Wonderful thing about engineering is there's nothing new under the sun!! This is a fun thread!
Last edited by Ruaraidh; 12-03-2007 at 11:05 AM.
12-03-2007, 11:38 AM
#104
Have never raced a boat from a stand still was always on plane. Dont think it will be necessary for my initial build but I can drop it into 1st gear to get on plane or spool up the turbos.
I did do an air impringement turbo were a shot of compreses air was aimed at the compressor wheel to help speed it up quicker. Also eliminated smoke. There were some that used oil shot at a paddle in the bearing hsg to help with spool up also.
We did the first ceramic turbine wheels too. There big issue was back spacing of the turbine wheel had to be increased to keep particulates from damaging the wheel which reduced efficency. We didnt realy want the warinty issues incured with the ceramic stuff on over the road trucks.
I did do an air impringement turbo were a shot of compreses air was aimed at the compressor wheel to help speed it up quicker. Also eliminated smoke. There were some that used oil shot at a paddle in the bearing hsg to help with spool up also.
We did the first ceramic turbine wheels too. There big issue was back spacing of the turbine wheel had to be increased to keep particulates from damaging the wheel which reduced efficency. We didnt realy want the warinty issues incured with the ceramic stuff on over the road trucks.
12-03-2007, 01:06 PM
#105
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Ah, WWII now we're really talking! Your right they were engineering marvels! All the things we talk about here are nothing more than rehashing some things first done 60+ years ago.
This really is great!
Do any of you remember the Cummins Hyper-Bar 903 engines for the Israeli tanks many years ago? I want to see if anyone knows them before I spill my limited knowledge of them. They were very cool!
This really is great!
Do any of you remember the Cummins Hyper-Bar 903 engines for the Israeli tanks many years ago? I want to see if anyone knows them before I spill my limited knowledge of them. They were very cool!
12-03-2007, 05:26 PM
#107
Ah, WWII now we're really talking! Your right they were engineering marvels! All the things we talk about here are nothing more than rehashing some things first done 60+ years ago.
This really is great!
Do any of you remember the Cummins Hyper-Bar 903 engines for the Israeli tanks many years ago? I want to see if anyone knows them before I spill my limited knowledge of them. They were very cool!
This really is great!
Do any of you remember the Cummins Hyper-Bar 903 engines for the Israeli tanks many years ago? I want to see if anyone knows them before I spill my limited knowledge of them. They were very cool!
Were they were the twin foot turbos if so I designed them back around 68 69. Did some redesign on them in the late 80s
12-03-2007, 07:41 PM
#108
Registered
The reason I mentioned those 903 tank engines was because there was mention here of shooting the turbo with air or oil to make them spool up quicker.
Now think about this - your sitting in a tank all hunkered down pretty much buried in sand with camo on top of it so the enemy can't stop you. Your just waiting out in the sand.
Your engine is turned off because the heat trail will give you away, but you need to run all the electonics.
Your radar picks up an incoming, you go to start the engine and if it starts because your running everything, like any other big diesel it takes a moment or two to build up boost which you can't build until you put a load on the engine. Well that extra time makes you a sitting duck and the missle hits you - you're all dead!!!!
I only seen one of these one type out at Columbus outside the dyno alley and this is how it worked. The turbo had a very long shaft with a small turbine engine driving it. They would ignite the turbine and run that while they were sitting still. The trubine would drive the trubo charger and keep boost on the engine while it was off. The turbine also dove a small hi-hertz generator that would keep the tank supplied with power because batteries go dead quickly. The heat trails from that could be ducked down and were small enough not to make a real differnce.
When they spotted an incoming they could hit the starter and the engine fired up with near full boost to get instant power to pull it ouy of the hole and away from the incoming.
When I looked at it all I could see was piping all over the place, but Carl Kuner if you guys know him from Cummins was explaining it and I just was like "What?"
Almost 15 years later and those little mirco-turbines made it into production. Elliot Magnetek build a plant is Stuart, Fl to build these things around 1998 and these were directly from the 1100hp Cummins 903 tank engines.
There are a few missing deatils here but its the theory and application that matters.
turbo2256b who did you work for? I don't know what twin foot turbos are unless they are compounds?
Now think about this - your sitting in a tank all hunkered down pretty much buried in sand with camo on top of it so the enemy can't stop you. Your just waiting out in the sand.
Your engine is turned off because the heat trail will give you away, but you need to run all the electonics.
Your radar picks up an incoming, you go to start the engine and if it starts because your running everything, like any other big diesel it takes a moment or two to build up boost which you can't build until you put a load on the engine. Well that extra time makes you a sitting duck and the missle hits you - you're all dead!!!!
I only seen one of these one type out at Columbus outside the dyno alley and this is how it worked. The turbo had a very long shaft with a small turbine engine driving it. They would ignite the turbine and run that while they were sitting still. The trubine would drive the trubo charger and keep boost on the engine while it was off. The turbine also dove a small hi-hertz generator that would keep the tank supplied with power because batteries go dead quickly. The heat trails from that could be ducked down and were small enough not to make a real differnce.
When they spotted an incoming they could hit the starter and the engine fired up with near full boost to get instant power to pull it ouy of the hole and away from the incoming.
When I looked at it all I could see was piping all over the place, but Carl Kuner if you guys know him from Cummins was explaining it and I just was like "What?"
Almost 15 years later and those little mirco-turbines made it into production. Elliot Magnetek build a plant is Stuart, Fl to build these things around 1998 and these were directly from the 1100hp Cummins 903 tank engines.
There are a few missing deatils here but its the theory and application that matters.
turbo2256b who did you work for? I don't know what twin foot turbos are unless they are compounds?
Last edited by HabanaJoe; 12-03-2007 at 07:43 PM.
