Hi John
Good old out of the box engineering!!! I am glad to hear that is working good for you.
At first I was always referring to conversion charts as I drove (one more distraction), but now it,s all millivolts.
The GRATE is usually good to go at 7-10mV, cruising temp of 25-30mV depending on how fast weāre cruising.
The ASH PIT below the grate heats up sooner than the grate, but levels off about 10mV less than the grate. (Unless the ash is full, then it runs similar to the grate)
The HOPPER cruises at 3-4 mV. And itās time to re-load at 7mV. (unless I just reloaded and itās time for a bump)
The fresh air comming out of the HEAT EX hangs around 3mV which tells me I need to work on reclaiming more heat!
The O2 SENSOR cruises at 100-180 mV. Stepping on gas peddle (or letting up on it) will bump it up to 900mV instantly.
Itās all about millivolts.
John
Do you have different types of probes on the hopper and grate? Seems like 7 mv canāt represent the same temp on both of them.
Hey John,
Is it fun or what !!
Roll on !
Chris, what Iām saying is that from a cold start when I see 7mV itās good to switch over to wood gas. And when I see 7mV in the hopper itās time to add more wood. Both statements are true. I love all my numbers and instrumentation, and I agree with you that good gauges are like insurance: they let you āseeā right into the gasifier so you can correct trouble before it starts.
John
Ha! Ha! Yes fun, fun. Often absolute values are more confusing versus helpful. Unless they are āstandardizedā for all conditions pretty meaningless to share with others let alone compare what was happing last Summer with what is happening this Winter in a gasifier.
Now the RATIO of raw readings and RATE of changes ARE comparable and relevant.
Example: my wife recently moved her training school from a three party shared sub-leased area to a much better internally devided smaller but now exclusive to her use primary lease area. Her monthly cost went UP by XXXX a month. Sheās happy. I pointed out to her this expense as a percentage of her overall cost of operation just jumped up. You either have to now cut other spend out in other areas to offset OR now recruit and cycle XX more students a month threough your program or slowly cash flow bleed out dry.
One of the most impoertant conributions from MR Wayne has been his āwhen the sysem is working bestā pressure ratios and temperature ratios.
JohnB you are now doing the same in measured millivolts. Thanks for the useable info. I became real accuston about 30 years ago to having to always calculate my own percentages and rate changes for my own useage. Numbers crunchers were alway tring to hide the bad news in numbers confusion and overpromoting any supposed āgoodā numbers. So what if sales went up by thousands of units if the costs of sales went up faster as a percentage!! Personal finance, small business to General Motors you on a road to collapse and bankrupsy.
Heat and energy balances in a gasifier works the same way. IC engines the same way.
Regards
Steve Unruh
Wayne, I have to tell you, I do believe driving this Dakota on woodgas is the most fun and satisfaction Iāve had in many years (except,of course the fun stuff my wife and I do when we done woodgassing). We took our little vacation last week on woodgas. We took a beautiful route through the hills and lakes in central Minnesota. We drove 375 miles all on wood. And one peculiar thing happend. Since we never stopped at any service station, we never had a chance to buy snacks. My wife was nearly starving when we pulled off the road and pulled out the cooler to make lunch.
We had a great time driving past several Amish sawmills. I really wanted to stop and show off, but it was Sunday and they were in their buggies dressed in their finest bonnets and hats. All the little Amish kids waved at us, not even realizing that we were both driving sustainable rigs. But the fact was not lost on me, and I waved back with a big smile.
I did stop an āEnglishā sawmill the other and showed the rig to the owner. He was totally amazed! I told him about you and your sawmill and chunker and I could just see the wheels turning in his head.
Iāve got 1500 miles on the Dakota now on wood. I donāt ever use petrol except to start up, and it just runs beautifully!!! No trouble keeping up with traffic, and always looking for somewhere to go. Thanks a million for all your great ideas and experience!
Oh, and I like the pvc knob on your idle string, although I believe the water faucet knob would be a finer piece of instrumentation.
Thanks again
John
Steve, regarding the helpfulness of ratios offered by Wayne, I totally agree. I realized when I was shopping for vacuum gauges that I could build the 2:1 ratio between the 'rails" and the hopper right into the display. I have the ārailsā on a 30 inches dial and the hopper on a 15 inches dial. They are right next to each other on the dash. When the ratio between the two is 2:1, both needles point to the same angle, the needles are parallel. No need to read any numbers at all. I couldnāt do that with the manometers in the old van.
John
This morning while shopping I came across these glow plugs on clearance for $5.95 and they reminded me a lot of thermocouples so I did a little research when I got home and found out that they also put out a voltage when heated. That made me think of John Stoutās post here. I wonder if they would work in the heat ranges we are talking about in gasifiers. The one out of the box at the top of the photo is about 3 inches long beyond the threads.
Don Mannes
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I will get one and see what it puts out and what it can take.
Hey Don,
Thats Brilliant!
How high a temp are they good for?
I donāt know how high a temp they will survive in Terry, but maybe John S will tell us. I think they are designed to be in the air intake manifold of diesel engines somewhere near the air intake valves where the heat is not intense. That said, they do have to survive their own red hot/white hot heat that they produce when operating.
On one of my experiments I used a cheap type K thermocouple with ceramic cloth sheathed wires that I laid in and covered with fire clay mortar and that survived 14-1500 F temps.
It would be nice to know what grate temps are but in the history of woodgas, an extremely high percentage of miles have been traveled without grate temp readings. An experienced operator knows what other things to look for to make sure the right temps are achieved.
Don, I have finally bought a glow plug and just now have run a few tests. Very interesting! The glo plug seems to continue functioning at 960 C and produces a steady output of 16 mV. That is the thermocouple, reads 40 mV which is 960 C. And the gp fixed in the same MAP gas flame reads 16 mV. This temp is past the red line for gasifier grate.
Response time is a bit slower than the tc but still real time.
I didnāt burn it out yet so I donāt know how it lasts. But it is really a neat sensor! I will monkey with it some more to see ho well it stands up.
Where did you read that the gp puts out a current? I couldnāt find it when I searched last week. But Iād like to learn more about.
John
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Good job John! I got one too but I didnāt have a way to compare or measure temperatures like you do. I held a propane torch to the tip until it was red/orange hot and the readng went up to 29 mV and then held steady at 28 mV until I moved the flame away. How far into the char bed just above the grate would you poke these things to get a grate reading without overheating the shaft?
I did a Google search āusing glow plugs as thermocouplesā and got a few pages of things to look at and the most useful ones came from diesel forums and particularly from a guy whose handle is ācrossbonesā. Here is one sample
http://www.eng-tips.com/viewthread.cfm?qid=133986
Don
Don, Iām going to install my glow plug into my system SOMEWHERE tomorrow. And then see how long it lasts. Whatever numbers it produces will be appreciated for as long as they keep comming.
I read the link you sent and it looks like gloplugs are not engineered to give calibrated numbers. No matter, if it lasts it would be useful.
John
Is there any reason why these digital manometers would not work for gasifiers?
http://www.ebay.com/itm/Digital-Manometer-Differential-Air-Pressure-Meter-Gauge-/120658272340
If I read it right, it measures up to 55 inches H20 and should work well in the truck cab and even has backlit LCD for night visibility and they keep a log of readings with a time stampā¦ They are a little pricey but not too bad.
Good evening Mr. Don
Yes those look very interestingā¦if it was me I would Order one and compare it to the other analog gauges. See how it goesā¦Good find Sir
Here is a DIY version http://www.hayriv.com/arduino/gasifier-monitor so you can monitor more than one pressure at a time. Could be programmed to give you an alarm when values got outside your desired range.
Thanks a lot Don. Just a little late for me. I just put two regular gauges on my dash. The jug of water that I had sitting in my beverage tray as a manometer froze and broke.
OK I bit the bullet and ordered a couple of these http://www.ebay.com/itm/Digital-Manometer-Differential-Air-Pressure-Meter-Gauge-/120658272340 digital manometers. They explained these same units better on a different website and said that these also measure ādifferential pressureā. Differential pressure is defined as the difference in pressure between two points. This manometer has dual inputs for measuring differential pressure. So now I am asking myself - could we hook one input on the rails and the other on the hopper and get by with just one readout in differential pressure? We would have to learn to interpret the resulting readout - say if we had 10 inches on the rails and 3 on the hopper - would the differential reading be 7? Then as long as the gauge read somewhere between say 4 and 9 we would be in the sweet spot between char diarrhea and constipation. If this would work I would use the other one before and after the hay filter.