Hi everyone, looking for some help/info

[joeshmoe_44883]

I Want to start off first by introducing myself. im joe, i live in ohio here in the USA. keepin it short, i built my first turbo based turbine about 6 years ago, i still have it, just kinda got put on the back burner. I was a member of the yahoo group for awhile, got tired of always deleting e-mails so i unsubscribed, since then i've followed this forum from time to time. I also kept a close eye on don at rcdon.com, and i loved ash powers work.

Getting onto the subject of the post, we operate a drainage company that has some rather large equipment with large diesel engines. although diesel engine technology has done wonders in cold weather startup, it still isnt enough when the engine has to turn over 11 hydraulic pumps that are pumping really cold hydraulic oil. often times we have pickup trucks with jumper cables hooked up to get the engine enough electrical power to turn over.

While doing this i always thought a turboshaft gt would be a perfect tool for this. basically a small turbo is used to spin-up the wheel of a larger turbo without the compressor. somehow a belt pulley is fastened onto the shaft, and will either run through a reduction gearbox first or direct drive a big alternator and a water pump. the gas producer will suck diesel out of the machines fuel tank for power, spin the power turbine that not only keeps the batteries charged, but 1) blows heat onto the engine/hydraulic pumps, and 2) powers the water pump that will circulate the machines engine coolant through a coil in the exhaust and back into the motor to get the engine block temperature up.
I have a really small turbo with an inducer diameter of just 36cm, hub of 13mm, that'd i'd like to use as the gas producer, and several larger semi-truck turbos, even one schwitzer from a tank, that could be used as the power turbine.

I wanted to ask all the professionals on here what sort of equations or math i need to do to properly size what freepower turbine i should look for? I thought i remember at one point that the free power should approx be 5x bigger than the gas producer? is this correct? It doesnt need to be perfect, its only going to run for about 15-20 minutes at a time and as long as it does it job, i'll be happy. i've already ran the jet specs program, and done don giodomenico's combustor formula to figure out the flame tube. Also, if i remember right i think john wallis?, made a freepower go kart that used a turbo to drive a chain and sprocket, i could be wrong. i was just wondering how they fastened the chain sprocket to the shaft. If anyone has any advice or opinion to help please speak up! I've had one turbine for play, how cool i think it would be to have one that is an actual tool! and in case anyone is wondering or wants to say, we work in the middle of fields where theres no power for battery chargers/ block heaters or anything.

[racketmotorman]

Hi Joe

Bit cold up your way at the moment )

Generally you only need a freepower with ~2 times the gas producer flow areas , but a very small gas producer like your 36mm inducered one might need slightly more than twice because small turbos have poorer component efficiencies than larger ones so theres less thermodynamic energy exiting them which means slower gas speeds thru the freepower turbine than what one would normally design for .

A simple way of getting something close to a decent match is to build the gas producer as a pure jet engine , get it sorted with a jetnozzle on it so that TOTs are safe and then measure the jetnozzle area .

Your 36mm inducered turbo will probably need a jetnozzle of maybe 33-35mm dia .

All you need to do is find a larger turbo ,( single port job , no "split" housing ones as their efficiency is low ,) with its scroll nozzle area a bit larger than your jetnozzle area , the scrolls nozzle area "A" is the narrowest part of the scroll inlet just where the scroll port winds back on itself ...............Fig 2 http://www.turbobygarrett.com/turbobyga ... ch102.html .

You'll probably find that the turbine stage from even a Cummins ST50 like RC Don is using for his gas producer will be a little too big even with the smallest A/R turb housing on it when used with the 36mm inducered turbo . , .....................what you could do is use a larger A/R split/twin port turb scroll housing but only feed the outflow from the gas producer to one port , the other being blanked off , this way you'd have the advantage of the larger diameter turb wheel with "lower??" rpm than you would with a smaller diameter turb stage .

The freepower I used on my kart http://www.racketmotorman.turbinebuilde ... hp?album=4 was a Cummins " W shaft" wheel , the comp end of which had a "rough" sleeve silver soldered on and which was machined to fit the karting sprocket , the shaft was run on ball races supplied with total loss drip feed lube and some bleed air to force the lube thru the bearings and into the turb and exhaust whilst cooling the turb end bearing , karting sprockets were 10T on freepower to 81 T on axle giving ~2,000 axle rpm at ~16,000 freepower rpm . .....................you'd probably be better using toothed belting redux if they can take the cold .

Your idea should work )

Cheers
John

[joeshmoe_44883]

I was also thinking of a toothed belt reduction unit driving a serpentine belt system to drive the alternator and water pump. While driving an idea hit me for the coolant heating system, instead of using a coil to warm up the engine coolant, would it be better to use an EGR cooler off say a semi or something? its almost perfect, it would save lots of time and money experimenting and its already made to withstand the heat. Speaking of heat, what would you suggest would be a good TOT to achieve if one is planning on adding a freepower? I like your idea of using the split scroll turbine, mostly because thats what my old gt used, if i could recycle it and reuse it that would be great, if not, theres always ebay.

It seems like lately i've been seeing alot of people using vapor sticks/tubes in their combustors. any advantages over using direct injection? my previous engine used a big home heating fuel oil pump that fed 200psi of diesel to a 4gph nozzle. It didnt reach full rpm but it was a simple setup and easy to fab up that started easy. I was planning on going this route again unless theres advantages using the vapor sticks/tubes. Without going back to the yahoo group and signing up again, is there anyway i can get some formula's or anything to kinda get an idea of fuel burn and what size fuel nozzle im gonna need?

[racketmotorman]

Hi Joe

EGR cooler sounds good .

TOT , or more correctly ITT ( inter turbine temp) of ~600C - 1100 F is OK , it can be higher than this but with less safety margin in case something isn't "right", I have run ITTs of up to 800 C -1450F but only for short periods , your longer running times at full power probably would best be done at the lower temps, also, as you are using a small turbo , they often have "undersized" turbine stages used in conjunction with a wastegate , this combination doesn't like high temps due to turb stage choking at the higher temps .

TOTs should be the same whether theres a correct sized jet nozzle or freepower downstream of the gas producer , it can't tell the differance , all it feels is a restriction to outflow

If you have a marginal sized turb stage your mass flow rate could be less than the theoretical air flow of ~ 0.25 to 0.3 lbs/sec , this would normally need ~0.25 - 0.3 lbs/minute of fuel , or ~15 lbs/hour , this will be ~2.5 US gph max , so if your fuel pump is capable of 200psi , you'll only need a 1.75 GPH hollow cone pattern fuel spray nozzle .

Evaporators allow the use of relatively low fuel pressures ,an automotive EFI pump is sufficient , but spray nozzles require higher fuel pressures if they are to achieve fine atomisation and good combustion , ideally up around 500psi fuel pressure at full power , at lower fuel pressures we need larger flametube volumes to slow the dwell time so combustion can be completed before the turbine is contacted .

Cheers
John

[joeshmoe_44883]

Amazing, i wish i knew half of everything you've forgotten haha. I'm sure you've read a few books for turbine math, any you recommend? I've already bought and read kamps book, i should probably re-read it again to refresh myself. a few years ago i bought some 9th edition of turbomachinery or something, way way too advanced for me, i ended up just looking at pictures, trying to decipher the velocity triangles. tricky stuff it is.

I think i'm just going to use my fuel oil pump and direct injection nozzle since i already have all the parts. I must admit i'm a lil excited to be starting on another project, its been years since i last touched my engine. in fact the last occurance could of ended badly when i tried to start on acetylene, NOT a good idea. once i blew the air and it hit the sparkplug BOOM! windows shook and my ears rang for a day. luckily it was just a reminder of what kind of unstable chemicals and unpredictable situations surround this hobby.

[racketmotorman]

Hi Joe

Theres not much written about designing turbines using a radial inflow wheel , most of the examples use axial turb wheels which are somewhat different, but the same, if you know what I mean .

Kamps book is as good as any , even the expensive turbine books have examples that don't quite workout correctly .

LOL.......leave the acetylene for the oxy torch , far too dangerous for or machines , and the engine wouldn't give any more power even if you could use it in place of kero/diesel , power is "fixed" by comp tip speed and a safe TIT .

Cheers
John