Jan, are you talking abut air that is going in the gasifier? And how big is the engine?
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Yes, I have tested a little earlier with preheating the air into the unit, but have not seen any difference, but I am starting to wonder if I would not need a lot more surface area if something were to happen with the heat transfer, considering the cooling of the gas it takes up a lot of surface area to bring the temperature down.
But at the same time the car runs better when it is -10c, I don’t understand this.
Edit: s10 4,3liter
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The specific characteristics of wood gasification probably won’t help you much, but I’ll write them anyway:
-we have 1kg of dry wood
-for the complete combustion of this kg of wood, approximately 7 kg of air is needed
-for the formation of wood gas (which is then mixed with air 1:1) we need approximately 3.5 kg of air
- now let’s look at the ratio between the amount of wood gas and fresh air, which is (wood gas = fresh air + weight of wood) 4.5 : 3.5, here we can easily conclude that the energy of the exhaust gases is just right for preheating the air, but for drying the wood and the pyrolysis process, it must be added from elsewhere
-as an interesting fact: 3.5kg of air heated from 20°C to 500°C means energy of approximately 0.46 kWh
If we use air preheating, we can save 0.46 kWh for 1kg of wood (1kg of wood contains 4 kWh) , the amount of fresh air is reduced to approximately 3kg, and the volume-weight of the wood gas drops by 0.5 kg, while it has 0.45 kWh more energy, in other words, it becomes 20% more powerful.
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If we were to raise the temperature of the air to 500, how would that affect the size of the nozzles and the oxygen content?
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JanA. the evolved internal details of WayneK. system shows what happens.
It heats the incoming air in three steps to this and even metals damaging higher.
You must increase the size and numbers of air-nozzles much more to get that same needed number of oxygen molecules.
The air will be less dense. These air opening are no longer Jets, but flow allowing nozzles.
Then the downward distance they travel to the restriction plate is increased to allow for the needed residence time.
The benefits are the HOT, HOT energized air better reacts with the made mid and upper systems gases.
And you WILL use less solid wood fuel to create the needed internal heats.
The evolved found needed differences are to boost the incoming air so high.
Give the internal larger/longer space for the shifted biased combustion triad of Time-Tempurature-Turbulance.
And enable the internal metals to survive the abuse.
On your observation of my vehicle performs better at -10C . . . why?
I am convinced it is because really cold air cannot hold as much moisture. And excessive moisture thermally drags down woodgasifier performance.
Steve Unruh
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7kg is a measurement of weight? How do you measure weight of air? I realize I’m kind’a dumb.
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Steve, l agree with you. But also there is less moisture in the gas probably. Jan, do you collect more condensate in the cooler at this temp?
The thing is, at low pressure and relatively high temp, such as is our engine ready woodgas (cooled and filtered) it seems dry but in fact holds s lot of water vapour. 5-10% by volume to be exact, depending on specific situation. Thats a nother 5-10% balast added to all the nitrogen and unreacted CO2 we got in our woodgas.
Tone, exelnt explanation!
Its exactly this energy (air, fuel preheat) that turns the uncondensable 5-10% water vapour in our gas in to more hydrogen and CO.
Or, be lazy like me and mix some charcoal with the wood (sorry, l have to poke the wasp nest a bit😉), wich will get rid of the water without the complex heat exchangers and preheaters.
To be fair, this is cheating and l do loose overall wood efficiancy but at a bonus of more power and smaller, lighter, less complex gasifier.
Don, Tone did it the right, “chemist” way. Volume of air changes drasticly by pressure and temperature but mass is always the same. The A/F ratio meter on your dash does this too, the number 1/14.7 (stechiometric) means 1kg petrol is consuming 14.7kg of air.
To get volune of air, the mass of air is multiplyed by 1.3 and you get cubic meters. Roughly.
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Jan, you asked a simple question, but the answer is not so simple, but it tells a lot about how to design a hot zone. If the air is heated from 20 to 500°C, its volume increases by 2.6 times, and the viscosity also increases by 2 times, which means 5 times more resistance at a certain opening - the nozzle. My new gasifier should have a pressure drop of about 20 mbar at the nozzles when producing gas for about 30 kW. I personally intentionally sacrifice such a pressure loss here, because it allows for a “controlled” expansion and contraction of the glowing zone. How does this pressure loss affect the engine’s output power? With a CR 1:13 engine, this is negligible. In a tractor, the vacuum gauge while driving shows -0.1 bar at high rpm of 2500/min and a fully open throttle (this is the vacuum just before the intake valves), and at idle it shows -0.6 bar, so a drop of 0.02 bar represents only 20% at 0.1 bar, the rest of the resistance is elsewhere in the system.
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Thanks for the answer Tone, I learned something new today.
Next question for all of you, has anyone measured how hot the intake air is with a probe inserted into the air stream?
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I emptied the container from the coolers and from the hopper yesterday.
From the coolers I got about 1-2 liters and from the hopper about 7 -8 liters, about as usual.
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Jan, it is impossible to measure the air temperature at the nozzle of my gasifier, it is a complicated labyrinth through which the air travels. If you imagine the glowing tip of the nozzle through which the air enters, all the superheated metal of the hot zone along which the air travels, you can conclude that the air gets very hot before entering the process (I personally think it has a higher temperature than 500°C. Here is a picture when I emptied the smaller gasifier after a test run, the nozzle below was glowing.
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Now I got curious again, don’t you have any nozzles above the throttle?
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