Questions tagged [combustion]

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Combustion test of gases for boiler use [closed]

How to mix to gases in specific proportions (e.g. 25 per cent hydrogen and 75 per cent hydrogen)? Thanks in advance I researched using various research papers and texts but nowhere I could find the ...
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-2 votes
2 answers
47 views

May the chemical energy of combustion be wholly released as photon only?

It may be the burning of wood, LPG gas, hydrogen, gasoline. The energy is released wholly as photon and it is the absorption of photon by matter that heats up everything else increasing their kinetic ...
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If the human eye can see green so well, why don't flames and such that emit a broad rangecof wavelengths ever appear green?

Similar questions have been posted many, many times before, but.... If a black body at the correct (average) temperature is 'centered' on the green, and human eyes our retinal cones) see best in the ...
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2 votes
5 answers
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Is there an 'intuitive' explanation for "Which burns more?"

In helping a friend's son with his grade 10 science homework, I came across a question that essentially asked the following: "If two objects of equal mass but different specific heat capacities ...
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A combustion engine uses cylinders to compress air and fuel before igniting it

The piston moves up to compress the mixture before exploding and sending the piston down with great force. Would there be any improvement if the piston were turned upside-down? This would mean the ...
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1 answer
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Why does air not flow backwards in Jet Engines in the combustion chamber? [duplicate]

In jet engines air is taken in, compressed and then fuel is injected and then ignited forcing the turbine to spin powering the compressor. What I am curious about is why the combusted air isn't forced ...
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1 vote
1 answer
57 views

Why do internal combustion engines use adiabatic expansion and combustion?

In the gasoline engine, the gasoline mixture is heated at constant volume, followed by adiabatic expansion. In the diesel engine, the mixture is heated at constant pressure, and this is followed by ...
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2 answers
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Can I use combustion gases for heating?

What is the temperature of the carbon dioxide gas released from combustion of wood? If I let the gases escape directly, then only some heat is transferred by the gas to the heating drum and the rest ...
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1 vote
1 answer
25 views

Adding extra gas to a high velocity burner but the temperature in the vessel won't rise

So I'm doing a refractory dryout of a vessel and I'm stuck at 350°C. Normally I would add some more gas to the burner and the temperature would go up, but now it just stays at the same level. I've ...
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0 votes
1 answer
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Why is all heat released by a deflagration wave conducted upstream?

I'm having some trouble understanding the phenomenological analysis used to calculate the thickness of a 1D deflagration wave (Combustion Theory by Williams, page 135). I quote the text below: ...
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2 answers
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Can carbohydrates in powdered form provide a more 'energy efficient' alternative solution to traditional combustion engines?

In my high school chemistry class I am studying the affect of surface area over the rate of reaction. In this case, using Collision Theory to describe how a high surface area to volume ratio ...
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1 answer
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How sound waves are generated in IC engine?

I have found the source of sound in the IC engine as aerodynamic, combustion, and mechanical. But I want to know which among the 3 is the major source. Also what happens during the combustion of fuel ...
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1 answer
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Why does a gunpowder makes sound when it burns but not like a candle?

My class teacher asked this question, when a fire-cracker ( which has gunpowder in it) burns, it explodes and make a sound while when a candle is burnt it doesn't, and I also want to know why does ...
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2 answers
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Why light comes from fire?

We know that light is produced when a charge particle accelerate. Fire doesn't have electric and magnetic field so how do light comes from fire
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1 answer
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Can ionizing particles cause ignition of flammable material?

For example, can high energy $\alpha$ or $\beta$ particle cause ignition of $H_2/O_2$ mixture below critical conditions?
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3 answers
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Why is the burning temperature of different species of wood so different? [closed]

If you have read Farenheit 451, you may have the idea that paper (or perhaps wood in general) burns at 451F. However, in fact, different species of wood burn at widely different temperatures. Here is ...
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2 answers
87 views

How much oxygen does it take to burn a log of wood?

How much oxygen does it take to burn a log of wood? This is kind of a complex question because the wood itself contains oxygen, so it is not as simple to just compute how much carbon is in the wood ...
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2 votes
0 answers
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What happens to the composition of a mixed gas plasma when de-ionizes back into a gas

I've been thinking about this question for the past few days, but I'm not very well versed in plasma physics. I am an aerospace engineering student in my senior year of college. A little while ago, I ...
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2 answers
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Is combustion a phase transition?

Is combustion a phase transition? Premise If we take a chemical reaction $$ A + B \leftrightarrow AB, $$ we expect all the three chemicals, $A,B, AB$ to be present in the mixture, in the proportions ...
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1 vote
2 answers
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How actually Gave and wax candle works? [duplicate]

I have seen a candle and gave (diya) burning. But how exactly they work. Because in candle we use wax but we also use a thread like structure to burn it, although if we try to burn simple wax by ...
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Why is the the temperature change due to the combustion of paraffin wax so high (10000 Kelvin)?

I'm trying to work out the temperature change (I got something like 10k Kelvin,hotter than the Sun's core...) caused by the combustion of paraffin wax which has a molar enthalpy of combustion $E^{wax}...
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3 votes
1 answer
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Does burning something with higher temperature make the burning faster?

Like if I burn wood at 500 C, or 1000 C, is there a relationship? Any equation that model this? Thanks
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12 votes
5 answers
5k views

Fire caused by friction with water

Friction causes heat and heat causes fire, but could something catch in fire because of friction with a high speed water stream? If so, what material would it be and how fast would the water speed ...
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1 answer
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Minimum temperature of a smouldering fire? Read below

What is the lowest temperature in the hottest part of the ember of an oxygen starved low temperature smouldering fire the hypothetical fire glows a dull and faint orange at night, not red but orange, ...
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4 votes
2 answers
426 views

How are "cold sparks" possible?

At raves, nightclubs, and parties, sometimes there are "cold fireworks" machines that spew out a dense bunch of really bright sparks. The odd thing is that these machines are apparently safe ...
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5 votes
3 answers
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Color of a flame [duplicate]

I use an LPG (liquefied petroleum gas) gas stove at home for cooking purposes. I notice that, in the flame, the bottom part is almost always blue but the top has a yellowish-orange color. Why is that? ...
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0 votes
1 answer
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How will the compression ratio increase thermal effeciency of otto cycle while Win is higher?

Why the ideal otto cycle thermal effeciency increase with compression ratio although that will increase work input? While the temperature difference in the combustion chamber could be low,the overall ...
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17 votes
5 answers
4k views

Does fire emit black-body radiation?

Question: Can the radiation emitted by fire be approximated by black body spectrum? It has been discussed in this community that black-body spectrum mostly serves as an approximation to actual spectra ...
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31 votes
8 answers
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If air is a bad conductor, how does fire heat up a room?

If air is a bad heat conductor, how does fire heat up a room? Could someone help me, as I really don't get this?
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0 votes
1 answer
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Absolute entropy of methane at 111 K

I have to analyse a combustion process. One of the inputs of the process is methane at 1 bar and 111 K. To apply the second law of themodynamics I have to calculate $\overline{s}(111 K, 1 bar)$. By ...
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2 votes
1 answer
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Why does hot oil inflame when windows are opened?

A Japanese Youtuber posted a video on her survival from burns on one side of her face. She said left oil heating on the stove and noticed it producing lots of black smoke- hit the smoke temperature ...
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7 votes
7 answers
5k views

Can I burn a piece of wood by emitting only one photon per second on it?

Can I burn a piece of wood by emitting single photons on it? (for example by emitting only one photon per second or per milisecond etc to the wood). How much should be the rate of emitting single ...
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1 answer
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Why combustion need oxygen?

Why actually oxygen is needed for combustion?, can combustion take place with other element? Or oxygen is the only gas involving in this chemical reaction?
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6 votes
2 answers
858 views

The process of burning and increasing weight

I saw a movie in which an object (a kind of steel wool in kitchens) was burning on the kitchen scale. When the burning process began, the weight of the object began to increase. Can anyone explain the ...
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0 votes
1 answer
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Do gas-powered plants use Higher Heating Value(s) (HHV) or Lower Heating Value(s) (LHV)?

Does anyone know if natural gas power plants, and other utilities for that matter, obtain as much energy as (reasonably) possible from burning methane (or coal, or whatever)? Where would one find that ...
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14 votes
6 answers
10k views

What happens to the mass of a burned object?

If I were to burn a pile of wood weighing a hundred kilograms and I would have a big sack hanging over the burning pile. In this sack I would catch all the smoke that came from the burning pile, if ...
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0 votes
1 answer
15 views

Is incineration of a solid fuel complete or incomplete?

If I have some solid material like biomass and incinerate it at 1000 Celsius degrees for 15 minutes in an oxidized atmosphere within an incineration oven. As an output it gives me ash. Is the ...
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1 answer
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Could you survive on hydrox in at 10 atmospheres?

I was told that hydrox is incredibly dangerous, that pure oxygen will combust without any source of ignition at 3 to 4 atmospheres of pressure, and that because humans are hydrocarbons they will act ...
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1 vote
2 answers
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Engine rotating a generator at its rated speed, but engine power exceeds power required?

What would occur if a gasoline engine would be driving a generator (specifically, a permanent-magnet synchronous AC 3-phase sinusoidal generator) as its only load at the output shaft and if that ...
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1 vote
2 answers
83 views

Understanding thermolysis vs. combustion

While thinking about Will "water" glow at very high temperatures? it made me realize another gap in my understanding of physics/chemistry. To mean these two things seem paradoxical: if you ...
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1 vote
2 answers
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Thermodynamics of a Fire Piston and the First Law

I'm trying to understand how a Fire Piston works, in the context of the First Law of Thermodynamics. The First Law states that $$ \Delta U = q + w = 0 \text{ (for an isolated system)} $$ Where "...
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9 votes
8 answers
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Does more fire create a hotter fire?

If we lit a single fire that was fueled by a substance that burns at 500°F, then around that fire we lit directly against it another fire surrounding the original one. This second fire's fuel also ...
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1 answer
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Calculating dust concentration

How can I determine the concentration of dust? Let's say it's for general forest residue chips (biofuel). Perhaps the question is vague, but I am not sure. I am still new to the site, so I am not sure ...
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-2 votes
2 answers
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Can we burn Ash? [closed]

Can we burn ash at any temperature ? Will it melt ? If i am talking about ash of paper. I actually collected several samples of ashes and tried to burn it but it didn't. Tell me wil ash change its ...
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1 vote
1 answer
337 views

What decides the color of a flame?

Flame color can in part be decided by metal emission spectrums, that I know. But supposedly, the color could also be affected by the heat of the combustion, black body radiation. I’m wondering how ...
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2 votes
1 answer
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Problem from the Open Latvian Physics Olympiad 2019: "Reactive Reaction"

A rockets engine is supplied with a mass $m$ of hydrogen every second and just enough oxygen to burn all of the hydrogen. Determine the thrust force of the engine given that the exhaust openings cross-...
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2 votes
0 answers
49 views

Hydrogen discharge tube emission spectrum different from emission during burning

In "How is it possible some substances burn with an invisible flame" it is stated that light emitted from burning hydrogen is almost invisible, more precisely: You say that hydrogen flames are ...
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1 answer
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Fighting wild fires with sub zero air

I understand this is probably too costly to be practical, but was intrigued how one might use the mechanism of fire combustion against itself. Fires produce their own retardants (water and carbon ...
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42 votes
7 answers
5k views

Bush fires and heat waves, the real mechanics?

Like many others, I have been following the sad development of the bush/forest fires in Australia recently. A claim that gets repeated is that one of the contributors to this blaze is the ongoing >45°...
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1 vote
2 answers
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Why doesn't NASA try using high-explosives to fuel rockets?

For a smoothly burning liquid-vapor mixture, I understand that burning hydrogen and oxygen is the best possible solution, not just for now but even theoretically. (?) But I read about ideas, that ...
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