This is somewhat contrary to my understanding. I always thought that hottest temperatures were reached at equivalence ratios just over 1 (in English that means with just a little bit more fuel than is needed to react all of the available oxygen/oxidizer). I believe in car engines for example, maximum power is obtained by running slightly rich, maximum fuel economy by running slightly lean.
I ran several cases through an equilibrium* combustion code: Hydrogen/Air, Hydrogen/Oxygen, Methane/Air, and Jet-A/Air, varying the fuel to air ratio around perfect stoichiometry. In each of these cases the maximum flame temperature was calculated with a somewhat rich fuel/oxidizer mixture.
I’m glad someone noticed this! It means I’m not the only combustion maniac here.
This is resulting from a simplification I made in the article for readability, where I tried to omit getting into a detailed discussion on dissociation. For those who are wondering, the phenomenon of dissociation means that in the series of reactions and chemical processes in the flame, some small portion of the fuel is effectively un-combusting due to the heat of the reaction. That is, some CO2 becomes CO and O2, some H2O becomes H2 and O2, some H2O2, etc. This ends up reducing the heat, and thus the temperature, of the reaction.
This typically is only seen as the temperatures get really high (above 2700 to 2950 F, depending on the type of fuel), and for backyard-type burners I would think the effect is very small. So I geared my answer towards someone who might have a simple butane lighter or one of those long butane torches.
However, even with a simplification my point about practical flames still stands IRL with both low and high-temperature flames - that is, because of the realities of mixing and getting enough air with the fuel, the highest temperatures are typically with flames that are slightly lean. If nothing else, you really would want to avoid forming large amounts of CO, which you can get as you cross over the equivalence ratio.
In simplest terms, temperature is approximately the amount of energy you have per particle, while heat is the total amount of energy. So, for instance, you’ll have more heat in a bathtub full of ice water than in one cup of hot coffee, just because you have more particles in the bathtub.
The maximum amount you can heat something with a flame will be determined by the temperature of the flame (your steak can never get to a higher temperature than the flame), but if you have more heat in the flame, you can heat your steak quicker.
Think about it this way. You’ve got two huge insulated bins of dry ice (at about -80 degrees Celsius). Pour your bathtub of ice water (say, 100 liters at about 0 degress) into one, the cup of coffee (about 300 milliliters at, I dunno, 70 degrees) into the other. How much dry ice will be sublimated (evaporated) in each bin before the mixture reaches thermal equilibrium at -80? Obviously, the bathtub of ice water will have a lot more of an effect on the dry ice than the teeny cup of coffee! It sounds weird to say the bathtub of ice water contains more heat, but that’s because it’s colder than most things we’d like to heat up, and heat always flows from the higher-temperature to the lower-temperature object. (Put the cup of coffee in the bathtub, and it loses heat to the bathtub until both objects are the same temperature.) But when you take something colder than both to compare with, it makes a lot more sense.
How about this: If each Chinese person has one dollar and each citizen of New Orleans, Louisiana has ten dollars, will China have more or less money in total than New Orleans?
Temperature relates to how much money each person has (how much energy each particle has), heat relates to how much money the whole area has (how much energy the entire body contains).
