Turbo Shaft Lawn Tractor Build

[Colin Heath]

Managed to tag on  little welding at the end of the day.

I was welding this turbo manifold up.





I then remembered grabbed some clamp ferrules for hygienic pipework which are almost same as a V band but with O Ring groove and welded one to the turbine flange.



This was purge welded so I could allow full penetration for strength (Forgot to purge for tacks but not for food so will be fine)




free flag images

So the combustion tube will have another flange on the end to drop over flame tube and also a further flange at the top with a solid stainless plate to allow swap out of fueling setups, position etc.

Still deciding whether to weld a bottom joint in with conical reducer and then have slip joint on parallel section of flame tube or have the entire flame tube a slip joint into turbo turbo flange.

[Colin Heath]

I am now looking at my entry to combustion chamber from the compressor and wondering what thoughts are in size of entry?

I have a 4” - 2.5” concentric reducer and was going to notch this to fit the 6” tube central as I am reading that tangential entry leads to issues.

I also have a 5” - 4” reducer but wondered if there is a limit to how much we want to open up the inlet tube?

Any thoughts on this much appreciated.

Also what book would you recommend for a beginner please? I have model jet engines by Kamps for an overview at present 🙂

[racket]

Hi Colin

the 4"-2.5" should be OK as long as theres good flow space between flametube and outer can , one of the reasons why I like to dump my air into the bottom of the outer can is because theres more flow space around the "funnel" between flametube cross section and scroll inlet

As for books ........my early edition Cohen and Rogers, Gas Turbine Theory, "educated" me

Cheers
John

[Colin Heath]

Jan 20, 2020 19:06:55 GMT -5 racket said:

Hi Colin

the 4"-2.5" should be OK as long as theres good flow space between flametube and outer can , one of the reasons why I like to dump my air into the bottom of the outer can is because theres more flow space around the "funnel" between flametube cross section and scroll inlet

As for books ........my early edition Cohen and Rogers, Gas Turbine Theory, "educated" me

Cheers
John

Thanks John and you answered a question I had brewing about placement and why lower on the chamber so that’s perfect.

I will look for that as my next book on the subject.

I’m one of those that learns better having applied the practical hence building while learning

[racket]

Hi Colin

The delivery tube needs to flow freely at the combustor wall otherwise it can put such excessive backpressure on the comp that it can surge .

On my Gt6041 build the delivery tube really is at the base plate jetandturbineowners.proboards.com/attachment/download/216 , this allows easy flow into a plenum , then as the air passes up the combustor, 50% is bled off at the Tertiary holes , this then allows the remaining air to travel slower facilitating easier entry into the Secondary holes and even easier and more even entry into the important Primary holes compared to a delivery tube mounted up near the top of the combustor.

Theres this overpriced copy on UK Ebay of my favourite book
www.ebay.com/itm/Acceptable-Gas-Turbine-Theory-H-Cohen-and-G-F-C-Rogers-1954-01-01-The-hinges/401750692717?hash=item5d8a35136d:g:kZAAAOSwNndctedu

Cheers
John

[racket]

Hi Colin

Another very good book to have www.amazon.com/Gas-Turbine-Engine-Development-Applications/dp/0801957532 , not much theory , but covers a large number of automotive turbine engines

Cheers
John

[Colin Heath]

Jan 21, 2020 18:21:03 GMT -5 racket said:

Hi Colin

The delivery tube needs to flow freely at the combustor wall otherwise it can put such excessive backpressure on the comp that it can surge .

On my Gt6041 build the delivery tube really is at the base plate jetandturbineowners.proboards.com/attachment/download/216 , this allows easy flow into a plenum , then as the air passes up the combustor, 50% is bled off at the Tertiary holes , this then allows the remaining air to travel slower facilitating easier entry into the Secondary holes and even easier and more even entry into the important Primary holes compared to a delivery tube mounted up near the top of the combustor.

Theres this overpriced copy on UK Ebay of my favourite book
www.ebay.com/itm/Acceptable-Gas-Turbine-Theory-H-Cohen-and-G-F-C-Rogers-1954-01-01-The-hinges/401750692717?hash=item5d8a35136d:g:kZAAAOSwNndctedu

Cheers
John

Thanks John, this now makes sense as the smaller holes will restrict higher speed gasses and cause huge turbulence I am guessing (more than required for mixing).

I see what you mean about back pressure and will kept this in mind when building the inlet such as keeping bends smooth where possible.

I picked up my own overpriced copy of this book from Amazon haha.

I will keep an eye out for the other book also.

[Colin Heath]

Well I managed to get the flame tube cut, rolled and welded today 






Here is a mockup of the top plate which will mount the flame tube into the combustion chamber. Holes above primary are for cooling and primary holes are placed at where the fuel will collide in the 45deg cone I have for the oil nozzle. I may put a couple of very small holes in the 1.5" tube between lid and flame tube but hopefully won't be needed. I also have some slots around top of flame tube lid to hopefully help with swirl. All the holes and slots add up to the primary area suggested in Jet Specs.

My flame tube is the length suggested by Jet specs and will be longer with the cone added. I wondered if the length includes cone or not? If so will a longer tube matter? I'm assuming longer tube will allow further cooling before hitting turbine but could be very wrong here




I now need to cut the 1.5" hole through combustion chamber lid and also figure out where my spark plug needs to go? I'm thinking the best place is in and around primary fuel contact zone? I wouldn't get the reach through top with spark plug so may make something from a long boiler spark probe.

Then move on to making the transition piece and slip joint.

[racket]

Hi Colin

Spark plug between Primary and Secondary holes , there are extra long reach spark plugs available , I needed one in my engine

Cheers
John

[Colin Heath]

Jan 25, 2020 15:53:03 GMT -5 racket said:

Hi Colin

Spark plug between Primary and Secondary holes , there are extra long reach spark plugs available , I needed one in my engine

Cheers
John

Thanks John,

Im thinking of putting a boss in side of combustion chamber and passing through a hole in flame tube rather than try and reach from top.

A long reach spark electrode should then take me well into flame tube.

[racket]

Hi Colin

NGK make one with a 26.5 mm long 14 mm thread , its a LFR5A-11, thats what I needed in the 12/118 engine ...............with the boss in the outer wall and the combustor assemble it easy to mark the flametube for plug hole , but remember theres lotsa axial expansion of the flametube as it runs hotter than the outer can, so some allowances required

Cheers
John

[Colin Heath]

Jan 25, 2020 18:02:47 GMT -5 racket said:

Hi Colin

NGK make one with a 26.5 mm long 14 mm thread , its a LFR5A-11, thats what I needed in the 12/118 engine ...............with the boss in the outer wall and the combustor assemble it easy to mark the flametube for plug hole , but remember theres lotsa axial expansion of the flametube as it runs hotter than the outer can, so some allowances required

Cheers
John

Thanks John, that’s a great help. I hadn’t considered axial expansion and although I will fit a slip joint, I hadn’t thought about axial allowance.

What sort of allowances do you work with for both axial and radial clearance please?

[racket]

Hi Colin

With the flametube fixed at the fuel injection end , we probably need to allow at least 1mm axial expansion at the sparkplug in the sidewall , 100mmm length X 500 C degrees X 0.00002 exp coef = 1 mm .

A lot will depend on just how hot the wall gets , but I've noticed several millimeters of witness mark at the flametubes scroll inlet slipjoint with my TV84 flametube .............radial expansions aren't a problem as the distances are smaller , on some flametubes I've had just the electrode poke through a hole in the wall with the face of the threaded section pressed hard against the FT wall to "seal" it , the flexibility of the sheeting used in the FT takes up the expansion..............with too much clearance around a plug the incoming air can blow fuel away from the plug gap making ignition harder

Cheers
John

[Colin Heath]

Jan 26, 2020 4:28:55 GMT -5 racket said:

Hi Colin

With the flametube fixed at the fuel injection end , we probably need to allow at least 1mm axial expansion at the sparkplug in the sidewall , 100mmm length X 500 C degrees X 0.00002 exp coef = 1 mm .

A lot will depend on just how hot the wall gets , but I've noticed several millimeters of witness mark at the flametubes scroll inlet slipjoint with my TV84 flametube .............radial expansions aren't a problem as the distances are smaller , on some flametubes I've had just the electrode poke through a hole in the wall with the face of the threaded section pressed hard against the FT wall to "seal" it , the flexibility of the sheeting used in the FT takes up the expansion..............with too much clearance around a plug the incoming air can blow fuel away from the plug gap making ignition harder

Cheers
John

Thanks John,

Hope to be ready to get spark plug mounted and other bits soon.

Keen to get this thing moving!

[Colin Heath]

Haven't got much done recently but working on the oil pump mounting / port plate for the Ford Escort pump.

For the fuel pump I have come across one of these on Ebay and wondered what peoples thoughts were for kerosene through a 7gph nozzle.

www.ebay.co.uk/p/2242649415?iid=401384838518&chn=ps&norover=1&mkevt=1&mkrid=710-134428-41853-0&mkcid=2&itemid=401384838518&targetid=855806132334&device=c&mktype=pla&googleloc=1006734&poi=&campaignid=7412990566&mkgroupid=94005539728&rlsatarget=aud-381667280803:pla-855806132334&abcId=1139356&merchantid=7442124&gclid=CjwKCAiA-P7xBRAvEiwAow-VacxduZuppm5C_xsDM1jVUgd9iQcCxEyG9vCSwuRZGgS3W89qpRakaxoC-GIQAvD_BwE

Failing that I was also looking at a hydraulic pump that can be regulated from 40-200bar