Thanks Terry. That’s the first analog air to fuel mixture gauge I’ve seen. So you hooked it up to the factory O2 sensor? If so, that’s neat and very good setup imo.
Drove 50 miles on wood yesterday and the wood is soaked now. It never gets a chance to dry out with 96% humidity and 5 inches of rain over night. I keep a stack of 2x4 scraps in the garage to keep dry for start ups.
I had nearly the same problem with my first thermocouples. The acid from the wood gas ate up the wire and started giving all kinds of weird readings. The shielded one has lasted almost 10 months now and still looks OK.
The gasifier killer on this end was the heavy loads we were trying to pull. The wet wood hasn’t been a problem. We have several different ways of dealing with the wet stuff. In the Ranger if I load the bed up with wood the thing heats up more than when empty. There are times when heat makes more of a difference depending on the state of the gasifier.
sean, have you ever thought of trying to use oxygen sensors as a “crude and cheap” way of measuring gasifier operation, i believe since you have a wealth of thermocouples you could observe changes in temperature and compare to O2 sensor readings, they might be able to be pretty close to the burner, cooling rack, or after the hay filter, i think if it were to work it could be a cheap alternative means of instrumentation, but i can see them getting plugged easily, since woodgas isnt engine exhaust,
Brent
I think that measuring the gasifier temp is extremely important. And the probes and displays I use are dead on accurate well worth the money for what your getting. I have used these same probes for years now they never fail. Do you know something about o2 sensors I don’t because as far as I know they don’t respond to heat only flammables. Below is a test to see if a sensor is bad or not. Sean
i actually dont know a lot about them, and yes im sure having a accurate and precise (those are two very different adjectives) temp reading is the best you can get, if O2 sensors are looking for a varying amount of O2 (not sure of this but the name implies this), i would hypothesize that the O2 levels would increase as a gasifier was running low on fuel, i figured since you have a very good feel for your equipment, and have watched it perform over and over again that adding an O2 sensor and comparing its readings with your gasifiers usual behavior and the actual temp readings that you might be able to see trends between the O2 sensor readings and your temp readings, the only reason i ask or suggest is bc i have a bunch of those laying around and i know they work, and im a budget minded individual, anything i can get for free ill take it, and i was thinking about how i would go about instrumenting my unit, bc i dont want to melt the thing down out in the middle of nowhere or something, ill look into this more, i just figured since they are used in exhaust applications they could take the heat, and even soot/tar, but i think it could be likely they would gumm up after a few thousand miles
Brent
Yes your are on the right thinking path however the temps will rise instantly as soon as the unit runs out of fuel. The next will be weak gas at this point the temps are already to hot and risk damaging the unit. So I wouldn’t try or rely on it next the o2 sensor in the gas stream is not going to hold up over time it will carbon up and you will constantly be cleaning it. My probes tell me lots of information not just out of fuel. Also overall gasifier conditions and leaks in the system. More on this later
if you want to experiment there is nothing wrong with that if you want something that is tried tested and proved the probes are here for you. It comes down to how much is your time worth to you. Sean
yea i watched the video, thats neat and i didnt know that, and yea i bet they do gum up, if you had to pick a basic and reliable set of thermocouples, and their locations in a standard burner+cyclone+cooler+filter unit and their temp ranges what would you suggest? just me thinking again i would say one right around the grate area and right around the entrance to the cooling rack, do you think reliable operation from those two thermocouple locations and a few vacuum guages between systems would give the user enough information to run with out too much worry? also what temp ranges for the needed locations? you said earlier 4000deg f for the burner area and then maybe like a 100-600 deg f for the cooling rack area?
Hi Brent,
We were asked in a machine design class, “What’s the difference between precision and accuracy?”. Lots of puzzled looks including mine. Suppose a program is set to drill a series of holes in a plate. Precision is drilling every hole in the exact same place every time. Accuracy is making sure those that those holes are located in the correct location in reference to the plate.
I’m at a point where I want to monitor temps in my gasifier so this is great info for me, but you are technically heads and tails above me, but the monitoring is fascinating. I’m at the beginner laser pointer level and not sure if that’s worthwhile information.
That’s a sharp looking PU.
Pepe
thanks pepe, i always remember by thinking about rulers, where the distance between the hash marks being as close to equal as possible determining the precision of the tool, and then if you measure an inch with this ruler and it is infact an actual inch then the tool would be considered accurate, yes your analogy is right on, and thanks about my truck!
Hi Guys
Yes O2 sensors do measure the “Remaining” oxygen in an exhaust stream. Narrow band type only designed as a feed back sensor around a very narrow range.The single wire (two wire and some three wire) snesors do this outputting a variable self made voltage signal from the inside of a ceramic tube closed end tube exposed to the outside air versus outside of the tube exposed to the exhaust gases. The tube surfaces are coated with rare metals. This style has to be heated to work and yes is easily contaminated from either side of the tube.
The wide band types can be either be in external testing instruments or exhaust stream mounted. Tney are ussally designed to measure oxygen from zero to ~22%. To do this they are always self heater heated, and most use an oxegen changing variable resistance element tech. So they must have an outside power supply for the heater element, a very precice fixed input voltage or amperage external supply. Measurement changes are in monitoring circuit voltage or amperage changes created by the oxegen present changed sensor resistance. They are also easily contaminated. A lot more electronics involved and software logic in these.
Varying pulse width tech can also be used. These have always had a very high in field failure rate. Lab rat stuff.
Temp monitoring is much more reliable and direct and durable for the operating conditions. Pressure monitoring good outside the core hot zones.
In our conversation regarding my request for a temperature adjustable controller to operate an emergency light, buzzer or shut down, you described that your current system already has this feature.
I think you may have forgot to mention this on your thread. Definitely a newbe gasifier saver.
Hi Peter,
Yes I forgot to mention that my devices come with the capability to turn other devices on/off. At a pre. set temp. zone the sky is limit here the system is fully adjustable. The hard part is the programing my units also come out with all programing taken care of. On the ranger project I used a really good t-probe and a cheap display unit this worked but could have worked much better with a quality display. Sean
Hi Sean,
I got a good deal on one of those 1000C thermocouples that look like the ones you use, but this one is on the short side (like 5 inches or so). I attempted to measure my gas exit temp at an elbow, but could only place it after 5-1/2 inches of piping past the “grate”. The last inch or so of the thermocouple probe was really carbon coated. It measured just over 800F there, so I am not sure if that is due to the probe being buried in char, measuring equilibrium or my burn chamber temp being low - so I plan to run the probe right into the char bed to see if I can measure the temps you are seeing for char and reduction zone. This will probably end badly for the thermocouple because the heat in the chamber is hotter than anything I ever messed with.
Can I use a 12v PID controller for anything ? It will alert if the process temperature goes above or below a set limit. That picks or drops a relay depending on how it is programmed. These type of devices go for about 36 bucks on ebay. I could put a standard thermocouple in the fuel bin and monitor that temperature real time and have a warning light if it gets too high (or cut ignition, etc)
Hi Gary,
My probes are set to the center of the restriction 1" above the grate. If those probes have any beef to them they should hold up the problem is the length it has to be center of the burntube. Second issue is the cheap displays don’t measure temps. like the quality ones do (slower react times) So you have built a false sense of security by the time it takes the probe the react to the temp rise it is normally too late and the gasifier has died. So you can have the best probe made to man and a cheap display and learn zero. I hate to say it but you get what you pay for. I can’t say for sure if the $30.00 pids will tell you what mine tell me when events happen in the gasifier. Sean
Hi Sean,
Thanks for the tips… I am to the point where I am asking a lot of “is this normal” questions because I really want to run an engine, but feel like I have to make this tar cracking temp measurement first. Was hoping to profile the chamber temps at full blast then see what happens when I back the flow down really low.
I went outside for a bit of time on the gassifier tonight and tried the chamber temp measurement. I had some issues with a packed char bed, since this is the most char I have left in it a day or two and we had rain overnight so I am sure some moisture was absorbed in the char and that may have been causing me some packing problems. Tonight was the first night ever that I could not get it to flare. Just was not happening… I was able to measure up to 1400F in the burn chamber near a nozzle for what that is worth, but as I said, it was not flaring properly so I am hoping that it is running a bit hotter than that. The external temps were about 100 degrees lower than I measured on the last run, so I am sure it has to be hotter than 1400F when it is cranked up.
I put a cutoff wheel in between the SS probe cover and the conduit metal connector housing to protect it. It remained cool to the touch as long as there was fuel to cover the hot charcoal. Anyways, I will clean it all out, dry the char and try again to see what temps this thing is running.
BTW… how hot is “too hot” above the grate or below the nozzles ? Have you noted any temps just before something goes bad ? Honestly, I have been looking for failure points on this setup and am not sure how close to the edge it may be running.
Hi Gary,
I don’t think gasifiers and normal fit in the same sentence. With my pids watching I don’t like the grate much above 1600 f. Gas exit temp into the heat x-changer 600-850f. Hopper refill 250-700 f refuel on the 700 mark. It has been a long time since anything has gone really bad on either trucks. With the temps. noted above the gasifier should be able to perform all work necessary. Also small scale is great to learn from getting the basics down for woodgas but running a vehicle down the road is a new type of learning. Sean
Thanks Sean,
I can see that monitoring a gasifier would be a lot to keep an eye on while driving. That is why I like digital gauges… for speed reading !
I re-ran my test tonight and measured the burn chamber around 1500 and up to 1700 as fuel started to run out, then pushed it into charcoal only (all fuel spent, but lots of hot charcoal in the fire tube) and the temps easily went over 2000F. Man that is hot. So I am sure the “small scale” unit is producing tar cracking temps and not warping or melting anything (it boils my condensate though). Each time I think running an engine is next, I learn something else that needs attention. I am going to do some more tuning on my choke assembly to see if I can conquer the issue of char packing after a shutdown. That seems to be a pellet fuel issue because the pellet char falls apart into tiny pieces (almost like sand) rather than really light ash. I have not burned much wood except in a fireplace and fire pit, but the pellet char seems to act differently than natural wood char.
Yes the first time you see all the gauges it can be a bit overwhelming. That’s why driving is the best way to practice as normal as breathing now.
I would say those temp readouts are plenty hot enough. On a cold start my grate temp will be around 500F and climb up to 1450f. With conditions optimized in the gasifier I can add as much throttle to the engine to maintain speed and the temps will stop climbing even start to cool down. I pay more attention to temp spikes rather than min./max. temp readings. A sudden temp change will alert me that the char in the gasifer has shifted allowing oxygen to travel closer to the grate or a seal/valve on the system has broken allowing oxygen to leak in where it should not be. Good luck with the pellets I have heard they turn to mush on shut down. Sean
Hello all,
So back to the narrowband/wideband conversation. If I am understanding right, and I think I am, wide band is better because of its tighter tollerances (if you will). I bought a SunPro CP 8210 AFR gauge, (cheapy 28 bucks) and wired it up on my 89 Toyota and it does not work. According to Autozone it is a narrowband gauge. Sean (thanks for your input) mentioned over in the materials section to me that the reason my gauge don’t work is because I am trying to combine OBD1 with OBD2. So I am trying to figuer out why, and making the assumption because OBD2 is on the newer vehicles and wideband is better that newer trucks have wideband systems and older OBD1 trucks have narrow band systems. So if this cheap gauge is truly a narrow band gauge, and I have a OBD1 vehicle I would guess it should work, unless…I have the wrong O2 sensor on but, in looking up the wiring colors for the sensor on a Toyota tech forum all appears right. It is a 4 wire O2 sensor with 2 wires for a preheater, one wire for input power from the computer, and one for output signal from the sensor. Could the sensor be trouble even though the truck runs fine and I have no check engine light?
I thought I would put this out there on this thread so more people could see it, and hopefully help enlighten me and us all.
Thanks all for your input.
David S.
