"Fat Boy" 12/118 thrust engine

[racket]

Hi Ron

No rule of thumb , too many variables , more just a guesstimate based on what we've been using and the various engine calcs I've done over the years , the gas speeds are going to vary depending on the gas producers configuration, their densities as well , so flow areas will vary even for the same mass flow rate, every engine will be different.

Our 212mm dia 4th stage Allison wheels are good for ~30,000 , but with Anders new JU-02 engine his freepower gas inlet pressures are going to be higher than "ideal" and his wheel speeds will be limiting power to some extent , he needs probably 35,000 or a tad higher to take full advantage of those higher gas speeds

Cheers
John

[azwood]

Aug 9, 2018 20:46:49 GMT -5 racket said:

Hi Ron

No rule of thumb , too many variables , more just a guesstimate based on what we've been using and the various engine calcs I've done over the years , the gas speeds are going to vary depending on the gas producers configuration, their densities as well , so flow areas will vary even for the same mass flow rate, every engine will be different.

Our 212mm dia 4th stage Allison wheels are good for ~30,000 , but with Anders new JU-02 engine his freepower gas inlet pressures are going to be higher than "ideal" and his wheel speeds will be limiting power to some extent , he needs probably 35,000 or a tad higher to take full advantage of those higher gas speeds

Cheers
John

What do you use to work out what wheel to use?

[racket]

We need to run the engine as a pure jet and measure jetpipe temperature and total pressure with a pitot tube , then use them in conjunction with the jet nozzle size and the thrust produced to determine the mass flow .

Once we have the "numbers" we can then think about the size of the freepower required , but as we're rather limited in the freepower wheels available for 100+ HP outputs , we need to "fiddle" the numbers a bit by "adjusting" the NGV throat size and discharge angle .

Ideally we can simply square root the jetpipe total pressure ratio , get some gas velocity numbers from their pressure drop , and in conjunction with the gas density and the annulus area determine whats required ............its just a case of doing some rough maths

Cheers
John

[racket]

Further to the above email ,

I was checking for some sizes/flows if using the 2nd stage Allison C20 turb wheel( 163 mm dia) and NGV , and it appears they're good for ~85 HP if using a turbo based engine supplying ~1.3 lbs/sec at ~10 psit of pressure at 727 C - 1000 K , wheel rpm ~45,000 .

For 100+ HP the 3rd stage wheel is required , and 150+ HP the 4th stage wheel , with flows of >1.5 lbs/sec and >2 lbs/sec ..............these again are rough numbers and would vary with the gas producer configuration , the "small" second stage wheel , which is a beautiful bit of gear could be made to produce >100 HP if we could increase the supply pressure to it , which in turn would increase the gas velocities and along with those the wheel rpm , .............the horsepower developed is a product of gas deflection and wheel blade speed , the wheel is good for 52,000 .

Cheers
John

[Chuks]

Hi John,
an off question please?
Using two different gas turbine engines with separate oil pump, fuel pump etc, (let's say they don't depend on each other to run) with one freestage turbine
Incase someone is scared of falling from the sky.
What do we gain or loose?
Will it improve the fuel efficiency?

[azwood]

Thnks i understand how its done now

Aug 10, 2018 17:01:51 GMT -5 racket said:

We need to run the engine as a pure jet and measure jetpipe temperature and total pressure with a pitot tube , then use them in conjunction with the jet nozzle size and the thrust produced to determine the mass flow .

Once we have the "numbers" we can then think about the size of the freepower required , but as we're rather limited in the freepower wheels available for 100+ HP outputs , we need to "fiddle" the numbers a bit by "adjusting" the NGV throat size and discharge angle .

Ideally we can simply square root the jetpipe total pressure ratio , get some gas velocity numbers from their pressure drop , and in conjunction with the gas density and the annulus area determine whats required ............its just a case of doing some rough maths

Cheers
John

[racket]

Hi Chuks

One freepower wheel stage with two gas producers feeding it , one "hemisphere" of the NGV each , it will work , but efficiency will probably suffer a tad , but thats offset by the fact you only have the single freepower wheel and gearbox ..........a compromise .

As for fuel efficiency of the two gas producers , they shouldn't change as long as they are operated to their optimum , but any losses will be in the freepower stage , but they might be offset by other improvements from running a single larger/slower revving wheel .............too many unknowns.

Some of the locomotive turbos with axial turb wheels run "split" NGVs to maximise the pulse energy from their slow revving engines , half the cylinders to one hemisphere and half to the other.

Cheers
John

[Chuks]

Thanks John,
I didn't even think of splitting the NGV. New lesson... "One hemisphere each" two different exhaust pipe so that if one engine fails, the running engine won't loose power into the other dead one.
Thanks John.

[turboron]

John, I use a flow factor for turbine calculations. It is also used by Garrett for their turbochargers. It is (mass flow (lbs/min)) times (Square root of Turbine inlet temperature in degrees R divided by 519) divided by the (ratio of Turbine inlet pressure in psia to 14.7). When this formula is applied to the Allison 250 Series II engine I get the following flow factors:


1st Stage 2nd Stage 3rd Stage 4th Stage

55 90 140 200

I recently saw a flow factor for the TV94 turbine of 90. Do you agree that the Allison 2nd stage could be used instead of the TV94 power turbine?

Thanks, Ron

[racket]

Hi Ron

The 2nd stage Allison NGV I measured has a "marked" flow area of 5.2 ( square inches) , the actual measured flow area of the throats is generally bigger by maybe up to 10% , the wheel has a marked flow area 5.87 ( sq ins) but measured close to 6 .

The TV91/4 F Trim wheel with 129 mm inducer and 106 mm exducer has exducer throat areas varying from 6.6 sq ins to 7.85 sq ins depending on the brand and clipping of the exducer .

The Garrett wheel flows more than the Allison wheel , the Garrett map I have for the TV91 turb wheel indicates a Corrected Mass Flow at a 2:1 PR of 85 lbs with the 1.46 A/R and 90 lbs with the 1.70 A/R , I think these flows are with choked scrolls as the flow "flat lines" at higher PRs , by comparison the GT6041 flows 88 lbs Corrected at 2:1 but ~95 lbs at 3:1 with a 1.47 A/R scroll .

As our freepowers generally see PRs well below 2:1 I think I'd go for the larger flow areas , though the larger diameter of the Allison would mean lower rpm and he possibility of sourcing a NGV would make construction easier than using the Garrett.

The Allison wheel is a nice bit of Inco , www.ebay.com/itm/Scrap-High-Nickel-Turbine-Engine-Wheel-only-for-collectors-art/122473544473?hash=item1c83fdfb19%3Ag%3AzwUAAOSwtGlZB0uD&_sacat=293&_nkw=turbine+wheel+collector&_from=R40&rt=nc&_trksid=p2062648.m570.l1313.TR0.TRC0.A0.H0.Xturbine+wheel+collector.TRS1 but with "too many blades" its flow area lets it down , these 2nd stage wheels have been around for a long time but I've never been able to find a use for them , I tried doing the "numbers" for using the wheel as the gas producers turbine but its diameter and flow would require an extremely low Trim comp wheel , and an engine with limited power producing capabilities .

I think their best use would be for a freepower , with gearbox to maximise its rpm potential , but with the expectation of ~100 HP as a maximum output if used with a well developed high PR gas producer flowing ~1.3 lbs/sec .

Cheers
John

[turboron]

John, how do you get a copy of the kts turbo catalogue? I spent 30 minutes on Google and their website with no success.

Thanks, Ron

[racket]

Hi Ron

Go to KTS www.ktsturbobilletx.com/

On the top left hand side theres 3 bars , hit that.

On the next page that comes up theres 04 Downloads , hit Catalogue

Its a 3.9 mb download and you'll need a "modern Windows" to open it , I can't on my old computor but can on the newer one .

LOL...........what wheel are you looking for ??

Cheers
John

[turboron]

John, thanks, that worked.

I wanted to see what the compressor map of Anders kts x846 looked like compared to a TV94 compressor map. However, a quick look at the catalogue does not show any maps. Are the mass flows the same at a given rpm and pressure ratio? Does the performance improvement just come from turbine the rotor faster to take advantage of the forging?

Thanks, Ron

[racket]

Hi Ron

Nope , no maps , just lotsa guesstimates , Garrett is the only one with available comp maps

As the KTS wheels are made for high PRs the inducer should be transonic , so I "scaled" off the new generation Garrett comp wheels www.turbobygarrett.com/turbobygarrett/turbochargers/gtx5533r-gen-ii , I used the 48Trim comp wheel as a guide , and as we're using diffuser vanes rather than a vaneless diffuser our efficiencies should be better at the top end of the map .

The measured inducer tip angle is conducive to high flow/PR work

The X846 has a 107 mm inducer vs the TV94s 98 mm so plenty of extra "hole area" to start with , then we're going for ~1,900 ft/sec comp tip speed to give us the higher PR as well as more mass flow

Lotsa unknowns until Anders runs his performance testing of the engine at 5:1 PR , if the thrust is ~100 kgs-220 lbs ,then we know we're in the ballpark with my guesstimates.

Cheers
John

[azwood]

Nice website lots of wheel options

Aug 13, 2018 16:12:07 GMT -5 racket said:

Hi Ron

Go to KTS www.ktsturbobilletx.com/

On the top left hand side theres 3 bars , hit that.

On the next page that comes up theres 04 Downloads , hit Catalogue

Its a 3.9 mb download and you'll need a "modern Windows" to open it , I can't on my old computor but can on the newer one .

LOL...........what wheel are you looking for ??

Cheers
John