Monotube Flash Boiler Design

[Toymaker]

Do you have safety valving in place yet?

Hopefully, this one will arrive be end of week; it's adjustable from 28 to 40 Bar. Then I will need to plumb it in.

Seeems to me...

If you do then a restriction at the boilers exit, such as a venturi or delaval, would let you build back pressure and provide a set exit speed for the steam, if you design it right.

A venturi would let you use a manometer to measure vacuum and derive mass flow

A de laval would let you use pages of equations, but would be the loudest therfore the most fun.

From that you could calculate the mass flow.

www.engineeringtoolbox.com/amp/speed-sound-d_519.html

https://www.efunda.com/formulae/fluids/venturi_flowmeter.cfm

Good info,...Thanks

 

[Steamchick]

This may be useful?
https://toolbox.tlv.com/global/UK/calculator/steam-flow-rate-through-orifice.html
K2

 

[The Ignoble Troll]

Chinese marketing,...all too common to inflate the specs.



No. The pump housing (actually the swash plate housing) also served as the front plate for the motor, and contained the front bearing. Since the original motor no longer had a front plate or bearing, I tossed it to a motor recycling collector.


This is the only marking I could find; FB-2. Does it mean anything to you??
View attachment 155938



Good advice, thanks

No sorry, fb-2 is probably just the sand mold number. Sorry I couldn't be of more help.

 

[The Ignoble Troll]

Have you adjusted your unloader valve on the pump yet? If you drop it waaaay down then it will at least stop pushing water against excessive back pressure.

You probably want a couple psi between the unloader setting and the over pressure valve. At least with hydraulics this is done to prevent oscillating action between two similarly set pressure reduction valves.

 

[Toymaker]

Have you adjusted your unloader valve on the pump yet? If you drop it waaaay down then it will at least stop pushing water against excessive back pressure.

You probably want a couple psi between the unloader setting and the over pressure valve. At least with hydraulics this is done to prevent oscillating action between two similarly set pressure reduction valves.

I adjusted the unloader valve to it's lowest setting when I was still using it as a pressure washer,....it was still pushing over 1200 psi. I wont be going over 500 psi in the boiler application, so unless I want to try replacing the load spring , the unloader is pretty useless. :-(

 

[The Ignoble Troll]

I adjusted the unloader valve to it's lowest setting when I was still using it as a pressure washer,....it was still pushing over 1200 psi. I wont be going over 500 psi in the boiler application, so unless I want to try replacing the load spring , the unloader is pretty useless. :-(

Too bad!

But not the end of that road:

An inline unloader with the return pumped back to your reservoir would be even better!


Such as:
https://northstarhotsy.com/product/parts/unloaders/hypro-500-87126890/


Just make sure the return line to your reservoir is submerged as water splashing in your reservoir will increase dissolved air and increase cavitation risks.

Once you have multiple safety controls, why not use the turbine as the restriction.


You extensively, if memory serves, mathed out it's inefficiencies running on steam.

If that's the case then it should be able to demonstrate those reduced numbers efficiency wise. If it's output on steam matches your math, you'll be much further ahead with reducing design assumptions.



Does liquid slugging matter to such a turbine? If so how are you planning on dealing with it?

 

[Toymaker]

<snip>
Does liquid slugging matter to such a turbine? If so how are you planning on dealing with it?

Yes & No.

I've talked about two very different types of turbines here on HMM; the current main power turbine I may use is a 3-stage design that looks a lot like my avatar, having blades on the discs and stators. I've read that wet steam will eventually destroy the blades on this type of turbine; I have no experience with how fast blade erosion occurs, but given that my blades are made of aluminum, not steel, I expect blade life would be somewhat short using wet steam; probably not a good choice for the first set of tests.

The second type of turbine I've built & tested (with compressed air) is a much smaller, hybrid turbine incorporating tiny impulse blading located on the circumference of typical Tesla turbine disks; that thread starts here: DIY Tesla Impulse Turbine. From my reading, the disks of a Tesla turbines are mostly impervious to wet steam,...but I have no knowledge of how impulse blades will hold up. I will most likely begin testing using this turbine. Depending on how well testing goes, I will build a slightly larger version of this hybrid Tesla design, capable of using the boiler's max output.

A few stats: the cross sectional area of the hole in an AN-10 fitting, where the steam exits my boiler, = 0.178 sq in.
The total nozzle cross sectional area of my Tesla turbine = 0.076 sq in.
Therefore, I should be able to keep boiler power at a low level for initial testing, while still building 200, 300, up to 400 psi.

 

[The Ignoble Troll]

I thought the bladed turbine was stainless! High tempurature freon gasses and aluminum are highly incompatible.

You get ANY decomposition products and that lump of aluminum will heat up to *thousands of degrees* as it gobbles up the halogens. It will form a self autocataltic violent reaction.

You can't fathom the violence of a halogen aluminum runaway reaction unless you've seen it.

Highly suggest you re-machine out of a compatable material and reassign your aluminum turbine to low tempurature testing.

Either that or revisit a heat exchanger that heats the freon safely. Adding a water loop might be extra weight but getting any decomposed freon on aluminum that's bathed in freon will give far poorer fuel efficiency. Actually it will give one good impulse but you'll probably only get a vertical lift of a couple dozen feet.

Adding a water loop might actually give better efficiency despite the weight.

This would let you store excess heat in a pressurized heat insulated reservoir. That would give your turbine low end torque, rather then waiting for it to spool up with on demand plumbing.


I'd also look at a liquid/gas seperator before the turbine, this would prevent slugging which in fast moving systems is the fluid equivalent of firing cannon balls into your turbine.


I did see the thread on the tesla turbine, it looked promising.

 

[Toymaker]

I thought the bladed turbine was stainless! High tempurature freon gasses and aluminum are highly incompatible.

You get ANY decomposition products and that lump of aluminum will heat up to *thousands of degrees* as it gobbles up the halogens. It will form a self autocataltic violent reaction.

You can't fathom the violence of a halogen aluminum runaway reaction unless you've seen it.

I do appreciate your cautions as I suspect a halogen reaction is similar to dropping a chunk of sodium into a bucket of water. However, per the safety data sheet, R-123 is only slightly reactive with freshly abraded aluminum, ie, don't scratch off the aluminum oxide layer while in contact with R-123. It's also worth noting that many refrigeration components, such as compressors, and condensing coils are made of aluminum and in direct contact with very hot R-123. I've attached a data sheet for R-123 which you may find of interest.

Highly suggest you re-machine out of a compatable material and reassign your aluminum turbine to low tempurature testing.

Either that or revisit a heat exchanger that heats the freon safely. Adding a water loop might be extra weight but getting any decomposed freon on aluminum that's bathed in freon will give far poorer fuel efficiency. Actually it will give one good impulse but you'll probably only get a vertical lift of a couple dozen feet.

Adding a water loop might actually give better efficiency despite the weight.

This would let you store excess heat in a pressurized heat insulated reservoir. That would give your turbine low end torque, rather then waiting for it to spool up with on demand plumbing.

I'd also look at a liquid/gas seperator before the turbine, this would prevent slugging which in fast moving systems is the fluid equivalent of firing cannon balls into your turbine.

I did see the thread on the tesla turbine, it looked promising.

I suspect that firing cannon balls at an impulse turbine would transfer far more torque into the rotor as compared to dry steam. Now, once those watery cannon balls splash off the flat surface of the impulse blades and are forced inward between the rotor discs, there's no further expansion of the liquid water, so seems likely the water will add drag and act to slow rotor rotation. Best to stick with dry steam for now

Finally, if the hybrid Tesla Turbine works as well as I believe it will, I will, for now, shelve the use of Freon and switch to water as the working fluid, as the main reason for using a Freon will be gone.

 

[Steamchick]

I have commented on wet steam and Tesla turbines in your thread on your hybrid design. I don't really know what effect it has but postulate "nothing useful".
Simply. I don't think water droplets add much but will extract more energy from the system, so dry steam is much preferable. - But aluminium and dry (superheated) steam do not match well either... Maybe anodise the aluminium after finish machining? Make the rotor in stainless steel?
I can't compute what the Hybrid design will do, but it does feel like adding the handicaps of both systems will out-weigh any perceived advantage.
Impulse turbines lose efficiency when the blades are moving above gas half gas velocity (momentum exchange re: difference of speed), but Tesla turbines lose efficiency from just below gas velocity or slower.. so the extra power from the "Tesla effect" (to call it something) will accelerate the turbine to lose "impulse effect", yet never get to true "Tesla effect" to really make that useful. At best, hardly any improvement on the poor Impulse design. A refined Impulse design would be likely to be better overall, IMHO? But the blades need to be shaped to maximise the impulse effect.
Also. High precision machining and de-burring is required to achieve "perfect" turbine balance, or vibration at high speed and excessive friction will prevent it performing as required. Small turbines run at 30.000rpm, effectively, not just a few thousand rpm. as I understand?
K2

 

[Steamchick]

I found this:
"Impulse blades are always the first stage of the turbine and are moved by a steam impacting them from nozzles. The reactive blades (subsequent stages) are actually nozzles. They are propelled by the reactive force generated by steam exiting from them.
Impulse blades are semi-circular & reaction blades are of aerofoil shapes in cross-section."
But I think you know all that from your turbine experience. - Bits already manufactured.
K2

 

[Steamchick]

I also found this comment:
"The blades of an impulse turbine are usually bucket-shaped so they catch the fluid and direct it off at an angle or sometimes even back the way it came (because that gives the most efficient transfer of energy from the fluid to the turbine)."
IF the direction of the steam jet is reversed from the impulse blade... (Max. efficiency), then the direction of steam is contrary to that to encourage the "Tesla" part of the turbine to work.
Actually, I suspect a Tesla turbine without the impulse blades may be more effective than the hybrid one you have made? - OR, as achieving the high rpm for a Tesla turbine to really become good is very difficult, a proper curved blade Impulse turbine is the best option?
How about it?
K2

 

[Steamchick]

Useful to anyone?
https://toolbox.tlv.com/global/UK/calculator/steam-flow-rate-through-orifice.html
K2

 

[The Ignoble Troll]

I do appreciate your cautions as I suspect a halogen reaction is similar to dropping a chunk of sodium into a bucket of water. However, per the safety data sheet, R-123 is only slightly reactive with freshly abraded aluminum, ie, don't scratch off the aluminum oxide layer while in contact with R-123. It's also worth noting that many refrigeration components, such as compressors, and condensing coils are made of aluminum and in direct contact with very hot R-123. I've attached a data sheet for R-123 which you may find of interest.

Decomposition products include hydrochloric and hydrofloric. Which would remove the oxide layer instantly.

A halogen reaction is more like pouring melted potassium into boiling sulfuric acid.


The attached picture is of halogens reacting with magnesium. The same reaction with aluminum is only -slightly- less exothermic.

 

[Toymaker]

I have commented on wet steam and Tesla turbines in your thread on your hybrid design. I don't really know what effect it has but postulate "nothing useful".
Simply. I don't think water droplets add much but will extract more energy from the system, so dry steam is much preferable. - But aluminium and dry (superheated) steam do not match well either... Maybe anodise the aluminium after finish machining? Make the rotor in stainless steel?

The tensile strength temperature knee for 6061 aluminum is 200 C. Sure, stainless will allow for much higher steam temperatures, but it's also more expensive and much harder to work with, so for this first prototype, aluminum was my preferred choice. If test results prove the idea to be a good one, then I will invest the time and money in either stainless or titanium.

I can't compute what the Hybrid design will do, but it does feel like adding the handicaps of both systems will out-weigh any perceived advantage.

One very noticeable advantage of the Hybrid design is the high torque at start-up demonstrated by the near instantaneous spool-up shown in the videos I've posted. Note also the centrifugal water pump was totally immersed in water during all the tests, which added significant resistance to spool-up.

Impulse turbines lose efficiency when the blades are moving above gas half gas velocity (momentum exchange re: difference of speed), but Tesla turbines lose efficiency from just below gas velocity or slower.. so the extra power from the "Tesla effect" (to call it something) will accelerate the turbine to lose "impulse effect", yet never get to true "Tesla effect" to really make that useful. At best, hardly any improvement on the poor Impulse design. A refined Impulse design would be likely to be better overall, IMHO? But the blades need to be shaped to maximise the impulse effect.
Also. High precision machining and de-burring is required to achieve "perfect" turbine balance, or vibration at high speed and excessive friction will prevent it performing as required. Small turbines run at 30.000rpm, effectively, not just a few thousand rpm. as I understand?
K2

Typical automotive turbochargers, (which are turbines with aluminum compressors), typically spin in the 300,000 rpm range. I expect my Tesla turbine with it's 61mm diameter rotors will spin in the 200,000 rpm range, providing the bearings don't fail.

 

[The Ignoble Troll]

A working tesla system would make you a very rich man, I can't imagine all of the possible applications. You'd potentially be able to replace a lot of rotary vane motors with motors that would no longer wear out.

 

[Toymaker]

Useful to anyone?
https://toolbox.tlv.com/global/UK/calculator/steam-flow-rate-through-orifice.html
K2

Not right away,...perhaps in the future when I have more data points to plug in.

 

[Toymaker]

I also found this comment:
"The blades of an impulse turbine are usually bucket-shaped so they catch the fluid and direct it off at an angle or sometimes even back the way it came (because that gives the most efficient transfer of energy from the fluid to the turbine)."
IF the direction of the steam jet is reversed from the impulse blade... (Max. efficiency), then the direction of steam is contrary to that to encourage the "Tesla" part of the turbine to work.
Actually, I suspect a Tesla turbine without the impulse blades may be more effective than the hybrid one you have made? - OR, as achieving the high rpm for a Tesla turbine to really become good is very difficult, a proper curved blade Impulse turbine is the best option?
How about it?
K2

I suggest we move all Tesla Turbine discussions over to the DIY Tesla Impulse Turbine thread, which is where I will answer your above questions.

 

[The Ignoble Troll]

Something I've always wondered about is popping a wee small axial turbine on the exaust of a tesla turbine and using it to run an oil pump for the tesla bearings. It wouldn't need to scaveng much power... with your CNC abilities, maybe you can do something to take advantage of the wasted energy.


A second tesla turbine, in series, designed to be condensing and put out water, not steam, would also be a feat. Given that there are now some solid papers on spacing the blades, maybe Making the blades have a mated divergent profile would let you plan for a dT through the turbine that's sufficient to make it act like a condenser?

A two stage system like that may be key to unlocking the full potential.


If you're impulse idea does not give you the increase in power that it might, maybe it would give an increase in efficiency as a tesla blower and be suitable as your burner blower?


Edit: posted this before your post came in on moving the discussion, my apologies.

 

[Toymaker]

Something I've always wondered about is popping a wee small axial turbine on the exaust of a tesla turbine and using it to run an oil pump for the tesla bearings. It wouldn't need to scaveng much power... with your CNC abilities, maybe you can do something to take advantage of the wasted energy.


A second tesla turbine, in series, designed to be condensing and put out water, not steam, would also be a feat. Given that there are now some solid papers on spacing the blades, maybe Making the blades have a mated divergent profile would let you plan for a dT through the turbine that's sufficient to make it act like a condenser?

A two stage system like that may be key to unlocking the full potential.


If you're impulse idea does not give you the increase in power that it might, maybe it would give an increase in efficiency as a tesla blower and be suitable as your burner blower?


Edit: posted this before your post came in on moving the discussion, my apologies.

Answered in the DIY Tesla Impulse Turbine thread.