Hi folks, Yesterday evening, I ran Paraffin (Kerosene) on my Optimus Hiker+. I primed it with Meths and boiled 600ml of tap water in my Weekend HE pot. It took 3 minutes and 30 seconds for a rolling boil. That was with the standard flame spreader. I thought that I'd try it with a burner cap (the QuietStove Model 600) and it did the same thing but was even a couple of seconds faster, I thought. Allowing for me moving and pressing buttons, etc, I'd say they were both the exact same results. Now the interesting thing! I thought that I'd try it on Petrol (Aspen 4) this evening with the same set-up. A full rolling boil time took just under 5 minutes. I thought that it was the burner cap slowing the Petrol down for some reason so I changed back to the flame spreader - exact same result. So, to double check, I refuelled with Paraffin, purged the pipes with it and ran - back to 3 minutes and 30 seconds. Does Kerosene burn that much hotter than Petrol? Or maybe it's this particular stove's Nova burner and jet which makes it happen? I can hardly believe the results, I'd have thought Petrol would blow Kerosene away with a much faster performance, never mind so much a difference only the other way around? Mark
Kerosene contains 135,000 BTU/gal and gasoline contains 125,000 BTU/gal. So kerosene produces 8% more heat than gasoline. Yet in your tests kerosene boiled water 30% quicker. So the increased heat output of kerosene is only part of the answer. The rest must must lie in the stove design. Apparently it's optimized for kerosene and burns gasoline less efficiently. Ben
Indeed! The only thing I would say in the Aspen 4 Petrol's defence is that it is super clean and produces virtually no soot or dirt. The Paraffin left the burner area and cap fairly black and the pot bottom showed some blackness when I wiped it down too. So I'd still choose the Aspen 4 if I wanted to run cleaner. Mark
The 111 stove has had a number of variants burning paraffin (kerosene), then gasoline (Coleman Fuel, etc.), then the multifuel adding alcohol to the accepted fuels (111, 111B, 111/7, 111T, 111C, 111D, Hiker, Hiker+, Nova, Nova+) Which is the best of that range of stoves? To me it is the original 111 burning the paraffin that it was designed to use. Bomb-proof, reliable, easy to control and hot as hell when needed. The good news is that the original 111 can be purchased for a lot less than its fancy successors.
Kerosene contains 135,000 BTU/gal and gasoline contains 125,000 BTU/gal. So kerosene produces 8% more heat than gasoline. That 8% assumes fuel is being consumed at same rate. Fit a flow meter to the fuel line?
Jon's point is a good one. Also, heat output per gram of fuel burned (rather than vol) should be pretty close since gasoline has slightly more BTUs per gram than kerosene. The Nova burner used in the Hiker+ has a compromise jet size so it is a little too large for Kero and a little too small for the lighter Naptha-based fuels. White gasoline, because it burns cleanest, is what Optimus recommends in the paperwork that came with my stove. So I guess safety is of lesser importance to Optimus on this one. I agree with Trevor on the 111. Still, I have a Hiker+ and Nova because why not.
Disclosure: I'm not an expert on this, but you shouldn't need a flow meter. The flow of a gas through a small-diameter orifice is limited (by the orifice) to the speed of sound. (I have seen applications where volume of air passing through a space is regulated in this manner.) I'm guessing that the different sized orifices for gasoline and kerosene are to ensure that fuel is consumed at the same rate. Hopefully someone more knowledgeable than me will contribute to this thread. ....Arch
Interesting about the sub-sonic limitations to gas flow through jets. I wonder if, in any stoves we use, those limits are ever approached? The fact that adding pressure will increase stove output only up to a point means that pressure is limiting at low pressure, but something else becomes limiting at high pressure. It would be fun to think it is the speed of sound. I think the suggestion of the flow meter was more figurative than literal. The heat output is dependent on the rate of fuel consumption (if the stove is working correctly), and we don't know how that changes with different fuels. It is safe to say, however, that kerosene is probably being consumed faster since it heated the water faster. I suspect that the main effect of different jet sizes in multifuel stoves is to adjust the fuelir ratio -- kerosene requires more oxygen, hence with a smaller jet it burns cleaner. Changing the jet is easier than modifying other parts of the burner, although we do see attempts at that with restrictor tubes, etc. As to jet size and fuel flow. It is interesting that for the Coleman 550B, Coleman rates its BTU output with white gas higher than kerosene. This at first seems backwards but makes sense because of the larger jet used with white gas. If one used the same kero generator for both white gas and kerosene, the results might be similar to what Mark sees with the Hiker+.
Ur right. I didn't ever think an in line flow meter would work... but it does seem to be a required measurement here!
Thanks for all the replies, folks. Next run out, I'm going to try the same boil tests with my MSR Whisperlite Universal. As you know, the Hiker+ is one jet for all fuels so I'm curious to see the rolling boil time results with various specific sized fuel jets. I'd suspect they'll be much more similar? A pity I haven't different Optimus jets to try on the Hiker+! I have their Polaris stove but it is a one jet only burner too. Mark
fuel efficiency is quite easy to measure just weighting stove before and after boil test, at list, I do so. suggestions welcome.
https://classiccampstoves.com/threads/what-dictates-a-stoves-power.16249/#post-163656 https://classiccampstoves.com/threads/calculated-stove-powers.9572/ Best Regards, Kerophile.
I'm a new member on this forum and thought that digging this old thread up would be a good place to start. The question is really, what determines the amount of energy that passes the jet. I don't think this has been sorted out. The fuel passes the jet in the form of a gas. The amount of fuel is determined by its volume. Now the volume of a gas is simply given by the temperature, pressure and number of molecules. It's linear too, so if you double the number of molecules you get double the pressure or double the volume. Note that the size or weight of the molecules doesn't matter, the same number (more or less) of them will pass the nozzle regardless if you are burning hydrogen (very small molecule) or kerosene. But after passing the jet, the whole molecule will be burnt. So one H2 molecule will be burnt to 1xH20, but a kerosene molecule say maybe C10H22 will be 10xCO2+11xH20. Which gives a lot more energy. This is the main reason kerosene will have maybe 30-40% more power than petrol or white gas, because the molecules are larger. The fuels are mixtures of different molecules so it's hard to determine the power exactly but this is the governing mechanism. You should be able to calculate more exactly the difference between say propane and butane, and possibly methanol vs ethanol, but fuels like kerosene and petrol are soups of many different molecules. You would need to know the average molecule weight. Another thing to note is that by weight, the fuels will have about the same energy content, around 44 MJ/kg or 12 kWh/kg (1 J being 1 Ws, so one Wh is 3600 J). Except for alcohols, they have the OH part that is basically a halfburnt hydrogen atom already, and maybe the lightest gases like methane, which have a higher proportion of hydrogen because its so small. I hope this is helpful.
Bernoulli's principle states that an increase in the speed of a fluid occurs simultaneously with a decrease in pressure or a decrease in the in the fluid's potential energy. The experiment to do would be get a jet designed for white gas and a jet designed for kerosene. One would find the different fuels would be far more efficient. MSR provides different jets for each fuel. With this setup the fuels are more efficient. Granted it is an inconvenience to change the jets but your stove will perform much better. Of course I could be off base with my thinking but it wouldn't be the first time. Cheers, Norman
I've never heard anywhere that kero has 30-40% more energy than petrol/white gas, and I've been here a long time. Some small increment, yes..... I'd be interested in more info on that subject.
Welcome Radfahrer, Nice first post and you hoped it was helpful. It was, thank you. My take away was be mindful liquid fuel (specifications) and same fuel vaporized F/A mix differ significantly (as does gaseous container vs liquid). AND I also thank you for *"note that by weight, the fuels will have about the same energy content"... w/exceptions noted. That is noteworthy re energy density and tests (above) suggesting results defined by the weight of fuel consumed. *I had never heard that, a good thing to be mindful of. edit: I hadn't seen Ben's reply above as I typed this. Ben, Ed, all, Ed never heard "...that kero has 30-40% more energy than petrol/white gas" (I am still not hearing that anywhere fwiw). I consider Ben quite fuel knowledgeable, certainly more than I. He noted 30% quicker boil test and also he is not defining kero in this instance imo, he is quantifying OP's unexpected boil test result. Boil test, absent wind = stove maximum heat output/ heat transfer to water in a covered pot. 1 liter usually, cool water (note water & air temps helps). 30% more energy is re energy density and your impression is accurate energy density kero vs white gas is a much smaller increment than 30%. I'd guess closer to 5% or even lower and figures vary slightly among sources. OP shared an experience/experiment, he closed with "I can hardly believe the results, I'd have thought Petrol would blow Kerosene away with a much faster performance, never mind so much a difference only the other way around?" I share his surprise w/these results. He hasn't followed up but Norman notes a major variable w/his testing is efficiency of burner (for fuel). I will add IF considering burner efficiency, hi vs low setting is a key factor to note. Despite those who happen to disagree I find boil tests are very helpful if comparing camp stoves. Boil test results of most interest are quantifying stove performance (not fuel). Above is re fuel and factors are not discussed w/any consistency. Fuel energy density, test environment, efficiency of burner for it's fuel etc etc. BTU is most often an efficiency rating (for apparatus / fuel...), a given in tests measuring BTU is optimal consumption (an efficient burner for test criteria). thx omc tag @Radfahrer
A little higher I think. According to the Engineering Toolbox website the energy content of kerosene is 135,000 Btu/gal. That means kerosene has 8.9% more energy than gasoline. According to this U.S. specification sheet Coleman fuel contains 17,900 Btu/lb. which converts to 111,875 Btu/gal. Which means kerosene has 20.6% more energy than Coleman fuel. Ben
Hi Ben, White gas 111,875 Btu/gal I did not know that. I see our cleaner WG differs from gasoline (at 124,00 Btu/gal) on your chart. Above I had taken into consideration the widely published gasoline specification (vs white gasoline). Although that difference is no surprise, if I attempted to explain the why and how that is I'd surely butcher that. I was remiss above, along with numbers that vary slightly depending on source, as you have shared, I too did not find it represented in percentages. So along with you knowing more re many various fuels / flammables / combustibles. I defer all such math equations to you as well (20.6 % ok) with your better grasp of our topic. thx omc
