Electric ducted fan to boost diesel turbo

[cobaltdan]

I am interested in using an electric ducted fan as an inline induction blower on a full scale 180hp diesel aircraft engine which we are working with.

The purpose would be to help the engine's turbocharger spool up faster.

Rough calculations predict we require a 700scfm blower capable of putting out 1 psi.

Can any one recommend a brand of EDF to look at? Without having much experience with them I am guessing that they are capable of about 1/3 to 1/2 psi and that 2-3 stages should work for 1 psi. Total power required on the motor should be about 3kw, and it would only run for about 30 seconds on take off.

Any recommendations would be appreciated.

Daniel Preston
Atair Aerospace
www.atairaerospace.com

[turbonut]

Hummm where to start?.. how much experiance with turbos do you have?..I think you are going about this the wrong way!..Edf does not work well with any back preasure involved...I asume you are building some type of aircraft...why would you need to prespool a turbo?...I have been building turbo powered engines for almost 20 years...I dont think you need to put something in the intake system that will just cause more problems that it will solve...I would like to hear more about your project..But this will be way off anything for the fourm.....Pm me for more info if you like...Our web site is nine11design.com
Scott

[cobaltdan]

The engine is a special turbo and supercharged diesel used in a paraglider UAV we manufacture. The reason for the desired prespool is to shorten the take off roll. We have demonstrated take off rolls with 2200 pound+ UAV's of only 20' using gasoline engines. With this new diesel full power is not immediately developed and generates about a 100' take off roll. We believe the simplest solution for a fast spool up on take off could be with a electric supercharger of sorts.

This idea has been discussed with the engine's manufacturer and we are working with them to test the concept.

I have googled for OEM electric superchargers but have not found anything that would fit our specs. I believe building our own is the best approach but would like to utilize if possible existing R/C ducted fan components and brushless motor technology.

[JetPlaneFlyer]

If the engine already has a mechanically driven supercharger what added benefit would a second electric one have?.. Or will the electric blower replace the existing mechanical one?

I'm no expert on superchargers but I would very much suspect that using axial fans was not the best approach. I would have thought that if you must have and electric drive then a proven Roots or Screw type supercharger would be the obvious way to go but driven by an electric motor rather than a pulley off the crankshaft.

The whole concept appears a bit illogical to me though... why not take the power directly from the crankshaft rather than driving a (big, heavy) alternator to charge a (big, heavy) battery to power a (big, heavy) electric motor which in turn spins the supercharger... Far more logical surely just to drive the supercharger directly from the crankshaft and do away with all the (big, heavy, inefficient) ancillary components :rolleyes: This is especially true in aircraft application where weight needs to be minimised.

If the engine takes a little while to get to full power then why not some decent brakes so you can build up thrust before the roll begins.. Or even better a variable pitch prop so the engine can get up to peak RPM without generating any thrust. Would these not be simpler solutions and without the weight penalty?

[cobaltdan]

for a faster power ramp up on take off we could change the gearing on the integrated supercharger to run faster but this would then sacrifice fuel efficiency for the rest of the flight. does not make sense when all we need is seconds of boost for take off.

as to why not use a roots/screw/lobe type: inertia these designs can not instanteneously spin up. axial compressors are more efficient and much lower weight and rotational inertia.

the alternator does not enter into the picture at all as the electric supercharger will only be used for take off and less than 30 sec. the entire device should weigh less than 8 pounds (the all up weight of the uav is 3600 pounds).

[JetPlaneFlyer]

for a faster power ramp up on take off we could change the gearing on the integrated supercharger to run faster but this would then sacrifice fuel efficiency for the rest of the flight. does not make sense when all we need is seconds of boost for take off.

as to why not use a roots/screw/lobe type: inertia these designs can not instanteneously spin up. axial compressors are more efficient and much lower weight and rotational inertia.



Roots type compressors appear to spin up pretty damn fast is the top fuel dragsters I've seen... Certainly no problem getting off the line with those babies ;)

[corsair nut]

sounds like you need a smaller turbo for better spool time. big turbo's=big lag. also, if there isnt much load on the motor, the turbo will spool slower, but mostl is due to the size of the turbo. decrese the exhaust turbine, and increse spool, but you will loose some top end power. but on a deisel, im not so sure that will be a issue. :) ive built a couple turbo cars(2.3L SOHC for motors) turbos are alot of fun, but theres also alot to choosing the right size for the aplication.

[Gregor32]

what about a scuba tank to presurise/ supply air for take off?
just a thought.
Greg

[Whistling Watts]

Stick a disposable rocket on it, simple cheap, why be overly technical if you only need the power on takeoff? If its a uav its not likely to land out and need a rocket at the other base.

[Air Head]

Why not hold the brakes until you have the power pumping out of the engine?

[Air Head]

hold the brakes

[Whistling Watts]

Yes, but you are going to burn the fuel. Rocket would give you climb with lower engine powet and extended cruisr. If its a commercial uav, air time is $ time, forget the wheels, ramp on go and skid on return.

[turbonut]

One other option is to use Nitrious oxide..We have used it to spool up a turboed engine before and it works quite well...you could even drop the tank after take off...But I think RATO might be a easy answer also..
Scott

[Aceshigh84]

With the diesel you could even just use LP gas instead of nitrous oxide. A company called Bully Dog makes a kit for the big Ford, Dodge, and Chevy diesel pickups.

[corsair nut]

just put a stock turbo coupe t-bird IHI on that sucker...it will spool almost instantly! the one on my t-bird spooled at about 1,500rpm, and by 1,800 it was full boost, but it really ran out of flow past 4,000. on my last 2.3 i put a t3-t4 on the 2.3, didnt build boost until it got to 3grand, then didnt make full boost until about 3,700, but it pulled like freight train to 6,000+. that car on the dyno made 270hp and 305FT LBS of torque at the wheels, thats around 310hp and 340ft lbs of torque at the flywheel at 18psi. i still had stock injectors and stock computer, only had a bigger pump and adj fuel pres regulator..if i had a real fuel management sys, i could have ran 25+ PSI and made around 400hp on 105oct. i swapped that into a 87 notchback lx mustang, converted over to V8 brakes, tubular suspension, koni's, coil overs, poly bushings, bump steer kit, only weighed 2800 lbs..that was a fun street car, suprised alot of people, and really handled well, had about a 50/50 weight, ....oh wait...back to the thread..sorry guys!

slap some rockets on that sucker, or go back to gas :)

[Joe 1320]

Using an electic impeller on a turbo engine to spool the turbo faster is an idea that has been hashed over and over on many of the auto forums. Bottom line, it's not very effecient and likely would cause a restriction when the turbo does spool. There are several options that would work. The first is a two stage turbo system consisting of a small one for a quick spool combined with a larger one for higher flow once you are rolling. The next option is a small hit of N20 that is shut off once the turbo has spooled. This can be shut off by an rpm switch or a pressure switch. The latter is probably your best option as is sounds like your system would see limited times under boost.

A correctly sized turbo can be selected to give the best mix of fast spool and acceptable flow at speed. The bigger the turbo, the more exhaust flow required to spool it.

[kriptonic]

Bungee launch the sucker..... then you don't need no stinky runway. (pun intended)

Gene

[ronmeister]

I am interested in using an electric ducted fan as an inline induction blower on a full scale 180hp diesel aircraft engine which we are working with.

The purpose would be to help the engine's turbocharger spool up faster.

Rough calculations predict we require a 700scfm blower capable of putting out 1 psi.

Can any one recommend a brand of EDF to look at? Without having much experience with them I am guessing that they are capable of about 1/3 to 1/2 psi and that 2-3 stages should work for 1 psi. Total power required on the motor should be about 3kw, and it would only run for about 30 seconds on take off.

Any recommendations would be appreciated.

Daniel Preston
Atair Aerospace
www.atairaerospace.com
I remember reading through a thread on www.nasioc.com where they used a electric supercharger (like what you are planning to make/use), and had no visible effect of decreasing spool time.
They said that the design of the compressor makes it so that the air from the E/S pretty much bypasses the compressor directly into the intake hoses.

[RCAV8R13]

OK, here's what you do. Remove the generator from your aircraft. Install a oneway spraig clutch on the supercharger where its gets power from the engine to turn it. Mount a powerfull motor on the cluch to turn the supercharger faster than the engine can to spool it up. Once engine is up to it's full potential, shut off the motor and let the engine turn the motor into your new generator. No added weight. You simply remove one component, replace it with another and make it pull double duty.
RCA

[Whistling Watts]

"Slap some rockets on that sucker, or go back to gas"

Just realised that this is a paraglider uav. A rocket would make for an interesting somersault!

Ok, back to the workshop so I can post something relevent on another thread!

Good luck with the project guys.

[monkamarm2000]

if you just want a few seconds of simple boost just use nitrous. All the parts are already in place, its exceptionally tunable, and at a few seconds burst a small bottle would last a few take offs. And no development time and money wasted, its a proven system.

Barry

[winmodels]

......Rough calculations predict we require a 700scfm blower capable of putting out 1 psi. Daniel Preston Atair Aerospace
www.atairaerospace.com

Hi Daniel

too much noise and no substance....

this is easy to calculate: 700cfm = 1.1m^3/s and 1psi ~ 720Pa

Power required = [rho]*Q*[delta]H = 1.225 * 1.1 * 1440 = 1940W

The pressure is so low that a single stage is completly sufficient. However, the required mass flow is considerably larger than any standard EDF could supply. Large EDFs typically produce around half the flow rate for comparison.
Have a look at:
http://www.rcgroups.com/forums/showthread.php?t=378979&page=30#post6771099
for a large EDF. The WM2000 will supply around 0.8m^3 with a power input of 4000W, but in an EDF most of the power is used to increase the exit velocity, not the "static" pressure.

Have fun with fans

Klaus

[JetPlaneFlyer]

Would a 1psi boost result in any meaninfull increase in power???... All the turbos and superchargers I'm aware of give a much higher boost.

Assuming power output is proportional to inlet manifold pressure 1 psi will only give 6.8% increase in power (in the real world I would suspect it would be less). This is not going to reduce the take off run by much, or is there something I'm missing :confused:

[winmodels]

Would a 1psi boost result in any meaninfull increase in power???... All the turbos and superchargers I'm aware of give a much higher boost. Assuming power output is proportional to inlet manifold pressure 1 psi will only give 6.8% increase in power (in the real world I would suspect it would be less). This is not going to reduce the take off run by much, or is there something I'm missing :confused:

it will not provide a direct increase in power boost, i.e the fan is not used for charging the engine but to overcome duct resistance at start up when the suction of the turbo is very low. It would be interesting to know the correct air requirement however, because the 700cfm seem to be very high.
A 2.5 litre engine at 3600rpm has a requirement of "only" 150cfm without charging and about twice that at a boost of 29" HG, so the max. would be 300cfm, which is more likely in my view.
A little EDF on a car engine decreases the accelleration time from stand to 100mph by about 20% - every little helps.

Have fun with fans

Klaus

[rcgroupie]

Klaus,

For a 2500 cc car engine, what would be a good EDF combo?

Thanks!

[kriptonic]

What the :censored: does this have to do with EDF Jets?

Gene

[rcgroupie]

What the :censored: does this have to do with EDF Jets?

Gene

Not much. That's probably why it was moved.

[cobaltdan]

What the :censored: does this have to do with EDF Jets?

Gene


i thought this would be a good place to get recommendations of edf manufacturers to look into.

so far not one recommendation... :(

[cobaltdan]

it will not provide a direct increase in power boost, i.e the fan is not used for charging the engine but to overcome duct resistance at start up when the suction of the turbo is very low. It would be interesting to know the correct air requirement however, because the 700cfm seem to be very high.
A 2.5 litre engine at 3600rpm has a requirement of "only" 150cfm without charging and about twice that at a boost of 29" HG, so the max. would be 300cfm, which is more likely in my view.
A little EDF on a car engine decreases the accelleration time from stand to 100mph by about 20% - every little helps.

Have fun with fans

Klaus


700 cfm is a high estimate on my part.

btw, your estimate is actually very close to mine: but you are basing your numbers on a 4 stroke engine, our diesel is a 2 stroke.

[vintage1]

If you want a modest short duration power boost..as obviosuly you can select a stick turbo for any particular boost at any particular RPM - then what is wrong with a tank of compressed air..or as has been said, nitrous?

Or stick a motor on the turbo itself to spool it up a little before whatever time you need to get the power.

I am fairly sure that driven blowers do better as centrifugal or Rootes type than axial flow anyway..certainly for pressure they do..at higher flow rates and lower pressures the axials are good I believe.

Still who makes big EDFs? Wemotec I guess..Vasa? .dunno. spool a big EDF up to 40-50k and it will suck a kilowatt or so,.no idea how much air at what pressure it will deliver tho.

[Accu157]

nevermind... I need to read.

Saab does the same thing in one of their cars (response to first post) Reduces lag. Just use a motor to spin up the turbo, don't use an accessory EDF.

[JetPlaneFlyer]

nevermind... I need to read.

Saab does the same thing in one of their cars (response to first post) Reduces lag. Just use a motor to spin up the turbo, don't use an accessory EDF.

Are you sure about this?... Which model?

Are you perhaps getting mixed up with Electric / Internal combustion hybrid car?... In these the electric motor is provided power direct to the wheels... not to a turbo.