M Buenijo

I am corresponding with the folks at gyroscope.com. They make a fairly large Tesla turbine with an integrated PMA that is rated for 1400 watts. The turbine is supposedly designed for saturated or slightly superheated steam up to 150 psig. They DO NOT have testing data on steam which I consider a red flag. So, I declined to purchase. But I offered to test the unit if they send me a unit. Note they are in the UK. I'm skeptical. But I will test it thoroughly if they send me a unit. My steam generator is almost perfectly sized for this unit.

Michael Galloway wrote:Hi everyone

First time poster so please let me know if I mess up the posting process.

I'm curious what you'll think of this:
Mackwell
Mackwell Youtube channel

I'm working for a startup working to displace diesel with advanced steam power. We're learning from the successes and failures of the steam age along with the best of it that was never widely implemented, and improving on that in areas where we can.

Our boiler are safe with no explosion risk, no sparks and no smoke when running. We'll have a 35 hp engine for sale by the end of the year and the first one is under construction now.

The boiler's are entirely mechanical in operation, though an electric fan speeds the startup. The boiler is self regulating and stable. They're designed for a long service life and easy maintenance.

I'd be very interested to hear any of your thoughts.
thanks
Michael

I became aware of this operation a couple years back. The combination of a gasification furnace and monotube steam generator was a critically important decision for making a practical system - along with optimizing expander efficiency (especially with more superheat, higher expansion, and piston valves). In my opinion, the generator platform seems too large and unnecessarily complicated. But I think the tractor once fully developed can be brilliant in some settings. I second your enthusiasm for making use of locally sourced fuels like wood that require minimal processing. I consider the best application for modern small scale steam power to be combined heat and power with low cost fuel (especially where minimal processing is required like wood chips, shredded household waste, and waste oils).

M Buenijo wrote:
DISCLAIMER: The "theoretical" efficiency figures I listed here were, shall I say, grossly estimated (sort of a thumb rule estimate - calculating a precise figure is a real PITA). Any engineers, please don't bother with a rebuttal (I know it is flawed). That noted, the cycle efficiencies reported by the two uniflow engines considered here were MEASURED.

I decided to check these figures more closely comparing the measured efficiency with the theoretical maximum "Rankine" cycle efficiency. All the data points for the White Cliffs engine showed 70-75% of Rankine cycle efficiency. Whereas, the Richard Smith engine I mentioned came in at around 57% of maximum. This is fantastic considering the best engineered large piston steam engines of the early 1900's were a bit over 80% and while using lower pressure and lower temperature steam.

In my opinion, the main reason Smith's engine came in lower is because there was no condenser and the steam supply pressure was relatively low. You have to expand the steam to get high efficiency. But the uniflow exhausts the steam through ports in the cylinder wall like a two stroke gas engine. Well, when the steam supply pressure is relatively low, and the steam exhaust pressure is relatively high (i.e. no condenser), then expansion must be more limited - otherwise, there will be not enough pressure to exhaust enough steam on each cycle. If this engine were to add a vacuum condenser, then getting 15%+ cycle efficiency would be possible - and without having to take pressure beyond 200 psig. In fact, I had considered previously to install a larger steam cylinder and operate at a lower pressure and lower rpm. But it would be difficult to get the power I want under this condition. Besided, my design can handle high pressure - and it's a CHP engine, so the condenser pressure can't get too low or the temperature gets too low to be useful.  

D Fujito wrote:1 we are currently using saturated wet steam to power our turbine , steam quality can fall all the way to saturated liquid and our turbine is still expected to run

2 we are testing , will get back to you on that

3 also under testing but we have an idea . Its turbine specific and dependa upon blade configuration.


If you can identify the required toqrue requirements of your fan,  i can help you size an appropriate turbine

A big problem with these Tesla turbines is the dearth of rigorous test data. Also, it's frustrating to see so many testing these units on compressed air. This is simply not useful. Steam is really the only practical working fluid for such a system (because low grade heat and water are cheap). I imagine quite a few folks are interested in your test results.

NOTE your steam generator must have temperature control to ensure the vapor is fully saturated as a wet steam will be less useful for thermal efficiency measurements. Preferably, the steam should be slightly superheated to ensure there is no condensate. What I would like to see is a "water rate" measurement where steam flows through the turbine to a condenser. Once the turbine output stabilizes, then the power will be recorded and the condensate from the steam that flows through the unit during the test period is collected and weighed. This is the simplest way to measure the quantity of heat used during the test with thermal efficiency as shaft work / heat input.

I am interested to power a typical whole house fan normally 100-300 watts mechanical. Ideally, the turbine could provide enough torque at low speeds to directly couple to the fan (around 3000 rpm). However, this is a tall order. I could gear down with a pulley/belt. But the lower the turbine speed the better. If the thermal efficiency were shown to be optimal at a significantly higher speed, then it would be better to just power a small generator directly. In such a case, I would be interested to direct steam engine exhaust through the unit to boost overall generator efficiency.

D Fujito wrote:

I bought the 4 inch 500 watt turbine of eBay for $120. So far it is working great with our flash boiler. Good torque and rpm this weekend hooking up to a 300 watt generator. Will post photos and updates.

I sent you a mooseage that included my cell number. Feel free to call anytime. I'm interested in whatever data you are able to collect from testing this turbine. Note I am primarily interested to direct steam exhausted from my piston expander through a small Tesla turbine to power auxiliary systems.

NOTE: I had independently considered that much household "waste" can be used as a fuel source in my system. Shredded paper waste and plastics can be supplemented to a wood chip gasification furnace along with dry shredded biomass products other than wood (provided wood remains as the majority of the fuel).

M Buenijo wrote:Just making an update for anyone who might be interested in this project of mine.

I tested the steam generator again yesterday. No problems. I'm confident it's working as designed. So, I will advance to the next step. I just purchased the alternator that will load the crankshaft. It will directly couple to the crankshaft, and I will load the alternator with a heating element installed in my pot still. You can check the unit here if you're interested: http://www.motenergy.com/mepmge.html . I will mount it using an adapter plate. A small oil pump will mount to the plate and get driven by the camshaft via a rod extension that penetrates the crankcase cover. I'll start assembling steam expanders after this is done. I'm going to try a design that does not require oil lubrication. But other designs call for oil (hence the oil pump).

My alternator arrived today! That was fast! I was expecting a couple weeks. Anyway, I need to do some basic machine work including cutting down the shafts (both the alternator and the crankshaft PTO). I'm going to use a clamping coupling to avoid having to cut a new keyway. This will take a minute as my tools are primitive.

M Buenijo wrote:

I'm going to contact them this week. I'll get back to you. I need to feel them out and see if they're legit. I need specs.

I called several times on different days and left email. No reply.

Just making an update for anyone who might be interested in this project of mine.

I tested the steam generator again yesterday. No problems. I'm confident it's working as designed. So, I will advance to the next step. I just purchased the alternator that will load the crankshaft. It will directly couple to the crankshaft, and I will load the alternator with a heating element installed in my pot still. You can check the unit here if you're interested: http://www.motenergy.com/mepmge.html . I will mount it using an adapter plate. A small oil pump will mount to the plate and get driven by the camshaft via a rod extension that penetrates the crankcase cover. I'll start assembling steam expanders after this is done. I'm going to try a design that does not require oil lubrication. But other designs call for oil (hence the oil pump).

M Buenijo wrote:http://kimmelsteam.com/smith-petersen-work.html

If you reference this page and scroll down a bit, you will see some data on testing a Mercury outboard two-stroke engine converted to a steam engine using bump valves. The data provided is as follows:

“Merc” 4 cylinder Engine on
cradle type E, Fan Brake for test,
Pressure: ~200 psig
Temp:     ~390° F.
RPM:     ~200
Exhaust Pressure – Atmospheric: (14.7)
Water Rate this test: 23.7 lbs/H.P. HR
—R.Smith

Assuming the data is accurate (and based on Smith's work I imagine it's reasonable), this puts the cycle efficiency at around 10.5% which is approximately 75% of theoretical maximum Rankine cycle efficiency. The reader may not likely appreciate this, but I'll just say this is pretty nuts for a small steam engine. A typical double-acting slide valve steam engine expander would show around 50-55% of theoretical maximum under these conditions. So, a good single-acting uniflow can provide 50% MORE work from the exact same steam source. Furthermore, the uniflow design is simpler mechanically.

The White Cliffs engine using saturated steam at around 550 psig (about 480F) and exhausting to a partial vacuum at around 5 psia showed around 73% of theoretical maximum (actual cycle efficiency was 16%). The cycle efficiency increases as the steam temperature increases (i.e. more superheat). However, the % of theoretical maximum tends to fall mostly due to clearance volume losses. For example, the White Cliffs engine showed about 65% of theoretical maximum efficiency when the steam temperature increased to 780F (cycle efficiency was measured at 21.9%). Furthermore, the efficiency gains start to flatline after about 150F superheat.

The lesson I got from this is don't bother trying to use crazy hot steam. You get diminishing returns and the additional thermal stress on the engine isn't worth it. I plan to operate at about 500 psig and no higher than 700F. This can yield a cycle efficiency of 20%.

DISCLAIMER: The "theoretical" efficiency figures I listed here were, shall I say, grossly estimated (sort of a thumb rule estimate - calculating a precise figure is a real PITA). Any engineers, please don't bother with a rebuttal (I know it is flawed). That noted, the cycle efficiencies reported by the two uniflow engines considered here were MEASURED.

John C Daley wrote:Can you explain what this CHP system is please?

John, "CHP" means Combined Heat and Power. It refers to a system designed to provide electricity while also harvesting otherwise wasted heat for useful purposes (i.e. water heating, space heating, etc.).