T-1000, a 10-Stage Axial Flow Turbine

[Toymaker]

This build thread will detail the design and construction of a 10-Stage, axial flow, Parson’s type turbine. The steam generator (aka, boiler) for this turbine will copy the SES Boiler-Burner design developed in the mid 1970’s for automotive use and has proven steam output of 10 LPM at 1000 F (538 C) at 1000 psi, and will be covered in a separate thread.

This turbine will use water as the working fluid, and will therefore need multiple rotor-stator stages to extract as much of the steam’s energy as possible. Modern power plants use steam turbines with 20 or more rotor-stator pairs which allow the steam to expand around 800 time. These turbines are very energy efficient, but they are also quite large and complex. My end use needs a mobile engine, so I've made a compromise between greatest efficiency and simplest, smallest design; 10 rotor-stator pairs should extract the majority of the steam's energy.

The high temperature & pressure I plan to use requires extensive use of stainless steel; the turbine case, nozzle, and stators are all made from 304 stainless. Heavy grid-lines in the drawing below are 1 inch.

I chose to use a split case design as it allows for easy assembly & diss-assembly and also provides for good visual checks of blade clearance, but of course the split case will also be a challenge to properly seal.

The finished case is made up from 4 separate pieces; top & bottom high-pressure section, which is welded to the top & bottom low-pressure section.

High pressure case halves were machined from a single block of 304 stainless, which was cut in half.

Each half was machined on my CNC mill and lathe.

 

[ddmckee54]

Is this another part of your ORC turbine project, or is this something new? Out of idle curiosity, what's your design max pressure?

 

[Toymaker]

I deemed the low pressure case for the last 6 rotor-stator pairs to be too large to reasonably machine from a solid block, so I paid a machine shop to roll the two halves from 3mm thick 304 stainless plate; judging from the appearance of the two halves, the shop made extensive use of a hammer to attain the final shape.

Clear plastic pieces were super glued to the cone to allow for mounting in a 4-jaw lathe chuck. Below photo shows inside of the low pressure case halves; the 5 grooves help to retain the stators.

Photo below shows top and bottom case halves after high and low pressure sections were welded together.

Outside of finished case halves, not screwed together.

Keeping high & low pressure sections perfectly aligned during welding was achieved by making & fitting 4 aluminum discs into the stator grooves and then bolting everything together before welding. No one will ever accuse me of making beautiful welds, but they are strong.

 

[Toymaker]

Is this another part of your ORC turbine project, or is this something new? Out of idle curiosity, what's your design max pressure?

The T-1000 project is an all new design and build using water as the working fluid. I still believe the use of ORC working fluids have many advantages over steam, but using them safely, with zero leaks, and low risk of exposure to hazardous gases is currently beyond what my home workshop is able to provide. So, at least for now, I will switch to steam.

Max pressure is 1000 psi at 1000 F (538 C); which is why I'm calling it T-1000. As I noted in the first post, the steam generator (aka, boiler) for this project will copy the SES Boiler-Burner design which was developed in the mid 1970’s for automotive use and which has proven steam output of 10 LPM at 1000 F (538 C) at 1000 psi.

I will start a separate thread in the Boilers Forum to discuss the SES Boiler.

 

[ddmckee54]

Yup, sealing that thing up at that pressure WILL be a challenge.

 

[Steamchick]

I really enjoy your ambition, and your machining looks excellent! I could offer advice, but you are in a league well beyond my experience, so I shall simply watch and learn from you, and others who are capable of offering advice. I think your idea to use a known design of steam boiler is practical, as you want a working solution in one step, instead of designing and developing everything from scratch!
WELL DONE!
K2

 

[Steamchick]

Incidentally, my Dad worked in a Power Station - on the steam turbines. (Full annual overhaul). They used Hylomar - a blue jointing paste - developed by Rolls Royce for their turbines, suitable for the steam pressures and temperatures involved. A very thin smear on the joint was adequate, as the bolted joint (like between your 2 halves) was a decent flat surface. The Hylomar compresses and squeezes out to a very thin smear, but seals the machining marks on the surface to prevent steam escape. The pressure it must withstand is below the 1000psi as the 1000psi starts at the first nozzles, and drops as the steam is accelerated (expands) through the initial nozzles, and thence through the turbine.
Hylomar was used by many British engine builders of all types from the development in the 1960s, as it replaced many previous chemistries of jointing compound for sealing flat machined joints.
But it says it is good for >250deg.C. Your steam starts at 538C... but what temperature after initial expansion through the first injection nozzles? - Would I be wrong to guess that 20 expansion stages (10 dynamic, 10 static?) reduce the temperature in 20 near-equal steps to the exhaust temperature? (Probably - I think!).
K2
https://hylomar.com/product/universal-blue/