# Questions tagged [combustion]

The tag has no usage guidance.

157 questions
Filter by
Sorted by
Tagged with
1 vote
57 views

### Why does a heated body emit a continuous spectrum of waves, while a burning body emits one color?

Why does a heated body emit a continuous spectrum of waves (as I understand it, that's why they burn red/white/blue), and a burning body is one color? as I understood it, for example, the green flame ...
• 13
2k views

### Will a piece of coal burn at the atomic level at room temperature?

If there is a piece of coal in the open air at room temperature, some of the molecules in the surrounding air will have sufficient velocity to oxidize the carbon in the coal. Will the surface of the ...
• 71
78 views

### Can we use Internal Combustion Engine exhaust to give heat for electrolysis to get hydrogen from water, to be used as fuel in the ICE?

Can we use exhaust from an Internal Combustion Engine to provide heat for the process of the electrolysis (to get hydrogen from water). And then use the H2 as fuel for the ICE so we use very little ...
1 vote
146 views

### General Doubt. My doubt about combustion

When we give flame to a newspaper it burns readily. What we need for a fire (fuel, heat, Oxygen) is also known as the fire triangle. But why does the paper not burn when we pour boiling water over it? ...
• 47
48 views

### How does the height of the hole on the bottle affect the burning time of the candles?

We took 3 identical bottles and drilled some holes on the side, each bottle had a hole but at different heights. Then we covered the burning candles with the 3 bottles and measured the burning time. ...
32 views

### If I burn a log & contain all the matter, will the burned log weigh $E/c^2$ less than the unburned log, with $E$ being the energy from light & heat? [duplicate]

I understand that the change in weight would be tiny even to a physicist and nothing for any practical purpose. I am also not talking about smoke and water vapor. I am only referring to energy given ...
1 vote
50 views

### Would a candle in very high gravity blow itself out?

A candle creates an upward draft of hot air, without which the flame would be spherical. The buoyancy generated is proportional to the density difference as well as the strength of gravity. Suppose a ...
• 6,531
71 views

### Does fire cause friction in the fuel?

It is possible to create fire by friction. For example - by striking a stone with another stone or by striking a matchstick on a rough surface. My question is: Can we say that, where there is fire ...
90 views

### Why does force decrease with increase in velocity in case power was constant?

Suppose an internal combustion engine burns the same amount of fuel every cycle (regardless of engine or car speed ) that means it creates the same pressure every cycle and the force on the piston due ...
• 103
1 vote
52 views

### Would there be a flame front in an air-fuel mixture? [closed]

Suppose a piston enclosing an amount of air-fuel mixture and then this piston compresses the mixture to the point of auto ignition, if every part of the mixture ignite simultaneously is it safe to say ...
• 103
164 views

### What's the $T$ around a candle?

I think most of you have already heard of the candle lift/elevator. It's a funny experiment that is easy to perform too. If you don't know what I'm talking about I would recommend you to watch the ...
3k views

### Can we call rusting of iron a combustion reaction?

In case of rusting of iron the chemical reaction is not fast enough. The oxygen used is not molecular oxygen from the atmosphere but it is the oxygen from water molecule. The reaction is not rapid and ...
• 1,357
1k views

### I don't understand why combustion releases energy?

So I've tried to wrap my head around fire. To keep it simple, I explain it with cellulose combustion. But to explain exothermic reactions, I show the example of methane combustion. Here is the detail ...
• 217
91 views

### If there is no oxygen in space what does the sunshine burn for fuel? [duplicate]

Since there is no oxygen in space how does the sun burn fuel?
148 views

### How does an internal combustion engine reduce the heat produced by burning fuel?

If I understand correctly, any heat produced by an internal combustion engine can be considered "waste heat"; energy from the fuel that did not get converted to mechanical energy. But if you ...
690 views

### Why do engines compress the air-fuel mixture prior to combustion?

In a basic Otto-cycle internal combustion engine, the air-fuel mixture that is drawn into the cylinder is compressed prior to the spark plug initiating the combustion process. Why is is beneficial to ...
• 101
1k views

### How does an exothermic reaction release energy? [closed]

When a reaction is exothermic it releases energy often denoted in kJ/mol. This is due to the total enthalpy of the reactant(s) being higher than the enthalpy of the product(s) and thus needs to ...
• 139
113 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 ...
• 159
79 views

### 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 ...
• 4,515
261 views

### 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 ...
• 161
72 views

### 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 ...
571 views

### 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 ...
• 912
1 vote
681 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 ...
• 65
70 views

### 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 ...
1 vote
26 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 ...
56 views

### 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: ...
• 2,659
1 vote
87 views

### 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 ...
147 views

### 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 ...
145 views

### 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 ...
• 101
375 views

### Why light comes from fire?

We know that light is produced when a charge particle accelerates. Fire doesn't have electric and magnetic field so how does light come from a fire?
1 vote
49 views

### 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?
• 13
577 views

### 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 ...
• 4,484
759 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 ...
• 4,484
43 views

### 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 ...
• 149
314 views

### 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 ...
• 60k
1 vote
58 views

### 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 ...
58 views

• 175
47 views

### 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 ...
• 143
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 ...
• 366