Fuel Definition and 16 Discussions

A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work. The concept was originally applied solely to those materials capable of releasing chemical energy but has since also been applied to other sources of heat energy such as nuclear energy (via nuclear fission and nuclear fusion).
The heat energy released by reactions of fuels is converted into mechanical energy via a heat engine. Other times the heat itself is valued for warmth, cooking, or industrial processes, as well as the illumination that comes with combustion. Fuels are also used in the cells of organisms in a process known as cellular respiration, where organic molecules are oxidized to release usable energy. Hydrocarbons and related oxygen-containing molecules are by far the most common source of fuel used by humans, but other substances, including radioactive metals, are also utilized.
Fuels are contrasted with other substances or devices storing potential energy, such as those that directly release electrical energy (such as batteries and capacitors) or mechanical energy (such as flywheels, springs, compressed air, or water in a reservoir).

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  1. hilbert2

    Reactive metal wires in a fuel oxidizer mixture

    Suppose there's some slow burning pyrotechnic mixture like KNO##_3## with powdered charcoal, and several really thin threads/wires of magnesium metal (or zirconium or magnesium/aluminum alloy) are made go through a pile of that mixture. Now I would guess that because a mixture of finely powdered...
  2. gggnano

    What's wrong with this math: A lot of thrust and almost no fuel?

    So according to this if you need a force that can lift a human and even an extremely ultra-light craft (1500 N) and have a velocity of 200 m/s you can eject extremely small amount of fuel through the nozzle: 0.0007 or less kg per second for as long as you're using 15 MPa pressure which is doable...
  3. S

    Automotive Idling or turning the engine off?

    Hi all, I am aware that idling is fuel inefficient and a waste of fuel, but I guess that it is not always convenient to turn the engine off, since the turning on requires more energy than idling. So, I think that for long periods, turning the engine off is more fuel efficient than idling, but...
  4. R

    Void Coefficient

    Why is the void coefficient in enriched US reactors negative?
  5. Mackenzie Cobb

    Why isn't tungsten used in nuclear reactors?

    Me again, with another potentially ignorant nuclear science question: Why isn't tungsten used to prevent meltdown in nuclear reactors? If tungsten has a higher melting point of tungsten is almost 6200 degrees Fahrenheit, and nuclear meltdown happens when the uranium fuel is some 5200 degrees...
  6. A

    Could a spacecraft refuel from the atmosphere?

    https://phys.org/news/2018-03-world-first-air-breathing-electric-thruster.html If it dipped into the atmosphere temporarily on an elliptical orbit, could the air gathered be stored for a long flight? Then maybe get more fuel from another planet's atmosphere or moon for the return trip?
  7. J

    Could UV lasers be used to split CO2 and H2O?

    I was wondering whether intense UV light, tuned to the correct wavelength, could be used to split carbon dioxide and water molecules as a first step towards synthesizing liquid fuels.
  8. D

    Heat Transfer

    Hi there, I have a problem that I cannot find a solution too. In this problem I have a fuel (approximately natural gas) supply which is combusted when mixed with air inside a burner. The flame that is then generated is used to heat up a sealed cylindrical vessel (the flame is on the outside of...
  9. S

    Automotive Air fuel ratio effects in diesel vs. petrol engines

    I'm a mechanic who is currently doing a study automotive engineering. Being someone who worked on both diesel and petrol cars I know what a higher or lower air fuel ratio (AFR) will do for both engines. However I don't fully understand how the following is possible. "Adding fuel in a diesel...
  10. C

    Mass of Particulate from fuel exhaust

    I'd like to know that apart from Gases coming out of tailpipe of a vehicle, how much is Solid particle mass exhausted per gallon of fuel? I tried to search but I couldn't get exact answer. e.g. After 1 gallon of fuel burnout, exhaust pipe emits 1 gm or 10 gm or 100 gm of solid particles (PM10...
  11. drew wood

    Hydrogen fuel generation

    I would like to start experimenting with hydrogen as an electricity source, but I haven't been able to find any good resources for steps after the hydrogen generation. I've made some prototypes of small-scale hydrogen generation using electrolysis, so now I basically have two bags, one filled...
  12. D

    How do fuel pumps operate?

    I am not talking about the mechanics of them, I am talking about what factors influence how much fuel they pump in a given system(EFI return style) at a given time. What do numbers such as maximum pressure and free flow rate mean? Can you have a pump that is too powerful for a system like say...
  13. marcophys

    Miscible - acetone in petrol/oil & water?

    This refers to the addition of acetone in petrol and diesel, and the potential action on any water within the fuel. For interest: https://www.physicsforums.com/threads/adding-acetone-to-the-gasoline.366946/ The above provides an interesting live understanding of the benefits to be gained...
  14. K

    Fuel evaporation in a tank - Pressure calculation

    Hello everybody, I have the following problem: I have a fuel tank, with a liquid phase (the fuel) and gas phase at To and P0, where T is temperature and P pressure. I assume that the gas phase at the instant t=t0 is air. (Is this assumption correct?) The temperature of the liquid phase...
  15. C

    Efficient, carbon neutral fuel for cars

    Assuming that a carbon neutral fuel for cars has to be used, what would be most practical and efficient? (Assumption: there is electricity from hydropower/nuclear or possibility to grow plants for biofuels) 1) Hydrogen from water hydrolysis? (If I get it right, production is simple but the...
  16. D

    Carbon Emissions

    Hi there, Could someone explain to me why fossil fuels, such as coal and oil, produce fewer particulate matter emissions than natural gas? Also, how would you expect the combustion temperature of these fuels to affect particulate emissions? Would a higher temperature lead to a more complete...