Dave,
My only concern with your piece of copper is that it may not be long enough to transfer enough heat to a cooler region. The one i used extended to the outside of the reactor. The guy that tipped me off about copper smelting tuyeres said that extending it outside was necessary to prevent it from burning the end off. But if you could make a good tight connection to a longer piece of aluminum it would transfer enough heat away. I think your refractory cement is a winner.
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Has anyone played with brass? lots of scrap faucets out there. Most have 1/2 pipe thread on them.
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Jim,
Brass doesnât conduct heat like copper. Brass conducts about twice the heat of steel but only about one third of the heat that copper conducts.
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Aluminum is about 1/2 as conductive as copper. The only metal that beats copper is silver, but not by much.
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but how does it resist oxidation?
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I donât know that we can entirely rule out melting as a source of nozzle failure. Here is what Wikipedia says:
âCharcoal burns at intense temperatures, up to 2,700 °C (4,890 °F).By comparison the melting point of iron is approximately 1,200 to 1,550 °C (2,190 to 2,820 °F).â
That sounds awfully high, and no citation is given.
In comparison, this is what I found about regular coal:
âAccording to âMarksâ Standard Handbook for Mechanical Engineersâ, 10th, coal gas burns at about 3,590°F (1,977°C) under 100% air conditions.â
So, it sounds to me that we cannot have a high degree of confidence that temperatures at the nozzle are not exceeding the melting point of steel.
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Carbon Monoxide has a flame temperature of 2121 C when combusted with air.
http://www.engineeringtoolbox.com/flame-temperatures-gases-d_422.html
Kyle thatâs why I decided to go with the ceramic ,they are much more forgiving if you should happen to run out of water or forget to do your exhaust return correctly , all the steel nozzles ( and copper ) I made melted , some real quick others a few runs later .
Lost count of the number of runs I do with no water drip , and always seem to get away with very long runs with no issues .
I guess unless you push things in the first place you never know what you can or cant do , I am at a point now where its very predictable , and i will drive the 5 miles to the station to collect my wife from work in the evenings and leave it all running away on its own .
Dave
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Yes we may be able to reach melting temperatures, but when we hold the temp below 1200C with EGR, the end of the stainless steel nozzle still corrodes away.
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Dave - Did you ever try just threading a Tig nozzle on the end of a steel nipple, without any refractory cement or anything?
Bruce - How are you judging your nozzle temperature?
I thought about sticking a thermocouple in the nozzle, but didnât want to risk melting that too.
Kyle,
I have burned a few thermocouples in gasifiers, but when I used a probe that was rated for 1100C and adjusted the EGR for temps between 900 and 1000C the probe was unaffected.
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I used the thermocouple to get a visual idea of what that 900-1000C looks like then adjusted by eye after that. If you want to play it safe use a titanium tube to shield the thermocouple.
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Once adjusted to the right temperature.
Is the nozzle temperature fairly constant?
Should often check the temperature?
If the RPM changes, should correct the EGR?
Thierry
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Since there is a close relationship between the RPM and the volume of gas being drawn thru the reactor there is an assumption that setting the egr at moderate throttle/rpm will give a consistent ratio of exhaust entering to control the temp. This has been my general observation on my generator. I hope to check this theory by watching reaction temp from my driverâs seat.
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I worked with what was on hand at the time ,and was not able to get a good enough air tight seal between the steel nipple and the TIG nozzle and didnât have a machine shop on hand to make my machine thread end , I was also advised at the time that the different expansion rate of the 2 materials will cause a problem on such a small piece if they were tightly joined .
I have tried just a TIG nozzle on its own on a smaller unit not too long ago and that seemed to work ok , but I have not put the hours on that system as yet .
Dave
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Dave - I am tempted to have the end of a pipe nipple turned to fit the TIG nozzle, just to see if you could run it that way. A friend of mine can do it for not much expense. I looked up the rate of thermal expansion for steel. I think the pipe would expand about .03" per thousand degrees C. I am assuming the nozzle expansion would be less. But the temperature gradient over the length of the nozzle might be enough narrow the gap. I was thinking about having it âloose threadedâ and then putting some high temp dope on the threads (2000 F).
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I am back in town.
Did I mention how much I hate waiting on Amazon?
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A loose fitting thread would be the way to go , Don also cut small expansion slits in it too that would also help I think .
You donât have to tell me about waiting for online goodies , I waited nearly 6 months for my dc power generator to be tested and sent from china ,and so it was a happy day when they dropped it at my door .
Last week I bought and paid for 3 petrol engine dc 24volt battery chargers from china , at a cost of $140 us each ,luckily I had someone I know bringing in a container load of farm equipment close by , so this time I will only have to wait a couple of weeks fingers crossed .
Dave
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Which 24V Battery charger did you get?
Let me know how those work out.
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