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On Sun, Mar 18, 2012 at 4:59 PM, William Wilson <fluffysheap@gmail.com> wrote:
You always want the highest A/R you can get. The charts and quotes for street use are intermittent power, and in an aircraft you need continuous power. Lower A/R makes the turbo not only spin up faster but also makes it less efficient, which means more heat dumped into the intake air, more thermal stress on the turbo and less margin against ignition-related bummers.
The charts are also intended for sea level use. Turbos work harder at high altitude. At 14,000 feet, your turbo is working twice as hard as it would be at sea level to produce the same HP.
The main benefit of a lower A/R is faster spooling time. Almost irrelevant in an aircraft. High A/R has major benefits.
On Sun, Mar 18, 2012 at 2:11 PM, <shipchief@aol.com> wrote:
Kelly;
I'm on the Turbonetics chart to size a turbo to an engine application. It's a matrix chart, which shows To4E-50 STG V .63 A/R as feeding a 4.5 liter engine 10 psi boost and giving 350 HP.
My TO4 60-1 P trim @ .81 A/R would be for a 5.0 liter 10 psi boost and 450-500 HP.
Yet I followed the salesman's advise for fitting. What is it about a rotary?
I checked the RX-7 site, 60-1 is a common enough application, albeit with a tighter A/R housing for street driving.
When I check the compressor map, I seem to be operating in the lower left hand corner, low turbine RPM, and not far from the surge line based on estimated airflow and pressure ratio.
I'm thinking that the exhaust blast of a rotary is much stronger, due to the port being wide open, where a piston engine has a poppet valve throttling the exhaust blast. Perhaps the high exhaust temp coupled with the high energy exhaust blast requires a bigger turbine to let it out in pulsations rather than pressurized flow?
I think the Q trim turbine wheel is the 68mm that you have, the P trim that I have is the smaller 65mm. These measurements being the outside diameter of smaller exducer part of the turbine wheel.
So it would seem to me that your turbine is larger than mine, offering less restriction to exaust flow, also with a 'looser' A/R turbine housing which additionally lets exhaust thru with less restriction.
Add to that, your 50 series compressor is smaller than my 60-1 compressor, and pulls less of a load on the turbine.
Very interesting. You may get a lower pressure ratio, exhaust pressure : intake pressure. Less exhaust back pressure for the boost you get.
Sent: Sun, Mar 18, 2012 8:10 am Subject: [FlyRotary] Re: Turbo charger setup
My Turbonetics TO4E-50 has the F1-65 turbine wheel but I chose the really loose 1.15 a/r housing to avoid compressor
surge and over speed at hoped for relatively high altitude cruising.............
Kelly Troyer
On Sun, Mar 18, 2012 at 7:45 AM, Ed Anderson <eanderson@carolina.rr.com> wrote:
I understand, some decisions have to be made before you know all the factors. An a/r of 0.81 may work fine, just wanted to caution you if it was 0.69 as I truly believe that is a bit on the small size for aircraft application - particularly if you do not have any active boost control.
Ed
Sent: Saturday, March 17, 2012 10:14 PM
Subject: [FlyRotary] Re: Turbo charger setup
Ed;
While you were answering my post, I was on the Turbonetics site, trying to recall what was in my 60-1 turbo.
I have the 'on center' housing, due to not knowing which way I was going to face the turbo at the time. This sets the possible A/R choices. The turbinescome in 2 sizes, F1-62 & F1-65.
Of those, the on-center housings' A/R start @ .58, .69, .81 That's it for the F1-62 wheel.
The F1-65 wheel continues on to .96 and 1.30.
I mistankenly said in the last post that the A/R is .61. I'm thinking it's actaully .81, the loosest choice for the F1-62 wheel, and the median choice if I have the F1-65 wheel.
Now I need to check.
I want to set up loose for first flights. I didn't know much about sizing a turbo when I bought this one, so I called and had the saleman set me up for a 13b turbo jetboat to be run at high altitude lakes with a tight engine cover....
Sent: Sat, Mar 17, 2012 6:41 pm
Subject: [FlyRotary] Re: Turbo charger setup
I would be hesitant to fly with a 0.68 a/r ratio turbine housing. A small a/r gives you tremendous (and rapid) boost - that "kick in the seat" sports car feel. However, at high rpm/power settings several things occur if no way of controlling the boost.
1. The small a/r will tend to overspeed the turbine - especially at altitude and can lead to surging.
2. The small a/r will produce a large amount of backpressure and heat from the turbine housing back to the engine - and add to your heat load - simply because it can not escape as readily as with an larger a/r.
3. The boost pressure may well exceed what your system is designed for
4. You will not produce as much HP at the higher rpm because the overall air mass flow will be less.
Most have found that if using an uncontrolled turbocharger that an a/r around 1.0 produces better and safer results. With a Turbonetics 60--1, you should have no problem acquiring a turbine housing closer to 1.0
There are several good books around on turbocharger and a/r selection - might want to browse through a few.
Good luck
Ed
Sent: Saturday, March 17, 2012 6:58 PM
Subject: [FlyRotary] Re: Turbo charger setup
Looks like March 7 was a busy day for this forum!
I'm ground running my RV-8 at the airport now. I even did a TAXI TEST to the end of the runway and back.
I have a Turbo 13b, with a Turbonetics 60-1. I'm at work now, so I can't give the particulars on the turbo, but someone on this forum told me that my exhaust housing is pretty tight for not having an intercooler, wastegate or blow off valve. (.61 A/R??)
Last week I ran the engine up while the aircraft was tied down as I have done in the past. But now that I have wings and brakes etc, and at the airport, I've been increasing the power output.
I did briefly get a boost reading of 44 " Hg, at about 5000RPM. The oil temp was climbing fast as Len says. I pulled back @ 200F, but it went for a few seconds to 206 before it came down. Good thing the oil and water cool well at lower settings.
I'm thinking aboout your comments on using excess boost air to operate auxilliary equipment.
I don't think you can do that in a practical way due to weight and space constraints in the 'engine room'.
I can barely fit all my 13b turbo stuff inside an RV-8 cowl, and I don't have the nose gear version.
I could eventually fit a remote wastegate, and an intercooler if needed, but servicing the engine would be difficult, as I would have to remove some layers to get to the core engine.
Remember, "Add lightness and simplicate" !!
I think I'm getting good power. The CATTO 2 blade prop is a left hand turnig version of his standard for O-360 Lycoming 180 HP engines. I got it up to 2280 RPM static. That seems up to 200 RPM higher that RV's are getting. I just don't know if I can do that for any sustained length of time.
I worry about high inlet air temp,and oil temp too.
The engine seems to respond well to throttle command while taxi, so as soon as I get some more wires pulled and the wing tips on, I could try some faster taxi tests...
I am planning on using the turbine of a turbo to spin a generator. I want the
muffler action. I don't want the added weight/drag of the "Turbo setup" which
can be quite large when factoring in all the components.
I plan to do most of my flying below 10k so it doesn't make sense to have the
boosted air. On the other hand - having electronic engine control and electronic
flying instruments electricity is becoming increasing important to me at all
flight regimes.
What I fly for a living has a similar electrical demand - so there are two
primary generators and a third powered off an APU, just in case. But those only
provide electricity to the instruments and mission equipment. The engines have
small alternators on them for providing primary power to the engine control
units. Redundancy is the name of the game.
So my plan right now is to have an alternator providing power to the EC3 and
EM3. and then a generator providing power to the glass cockpit and avionics. of
course the two will be redundant to each other.
Then for full redundancy - the glass cockpit has their own backup battery and
the airframe battery provides backup for the engine control and monitoring.
I am still very early in the process though - but I believe there is a lot of
energy to harness out of the exhaust of the rotary. But as you mentioned there
is something to be said for the muffler action being harnessed for something
useful.
Your plan though seems to work in theory - I would probably use that as a Turbo
Normalized setup though.
Mark
On Mar 7, 2012, at 6:26 PM, Ernest Christley wrote:
> On 03/07/2012 06:51 PM, Patrick wrote:
>> I'm planning to use a turbo on a 20B, primarily as a muffler, but would like
to set it for 3-5 psi boost.
>> A lot of current techniques are based on street car experience, which are not
always directly applicable to airplanes, ie. no need for rapid throttle response
(usually) and run at high % power continuously.
>>
>> I'm thinking of a setup modeling refrigeration techniques:
>>
>> * Run all exhaust through turbo, no waste-gate, larger A/R
>> * Compress higher than needed, which makes air very hot
>> * Run through intercooler, which is more efficient with higher temp delta
>> * Allow to expand using larger pipe and blow-off valve to regulate
>> pressure before intake
>>
>> The result "should be" cooler intake air at a slight boost.
>>
>> What am I missing?
>>
> The energy cost of compressing all that air and then throwing it away?
Though, like Tracy has said, pressurized air is hard to get on an airplane. It
wouldn't be so bad if you could use it for something. The two things that
spring to my mind are:
> 1) engine cooling: blow it through a radiator. The drawback is that you'll
want more boost on climbout, and that is when you'd want the extra air through
the radiator.
> 2) exhaust cooling/thrust: push the extra cool air into/around the exhaust.
As I understand it, rotary mufflers die quickly because of a combination of heat
and sonic pounding. Cooling it will reduce both, and if there might be a slight
amount of thrust available if everything is set up just right.
>
> --
> Homepage: http://www.flyrotary.com/
-- Kelly Troyer Dyke Delta_"Eventually" 13B_RD1C_EC2_EM2
--
Kelly Troyer
Dyke Delta_"Eventually"
13B_RD1C_EC2_EM2
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