Turbo
The O2 conentration should be pretty much the same (% O2 : %N2 ...). Air density is a measure of the mass of gas molecules in some defined volume of air, like a cubic meter, at a given temp and pressure. The air pressure tends to compress the air molecules together. Heat mades the molecules move/vibrate apart and therefore take up more space.
Absolutely correct, just be sure that you know that its all the molecules not just o2...and its not really more space, its they're less dense, therfore less pressure
Now power is a function of how much fuel you can burn. As you know, the ideal fuel air ratio is somewhere around 1 part gas to 14 parts air at sea level, because the number of molecules of oxygen pretty much matches up with the amount of fuel. as you get higher, the air density (mass/unit volume) drops, which by definition, means that the air contains less mass (fewer molecules/ oxygen) than it did at sea level. You therefore need to compress larger quantities of air to provide enough oxygen to support the oxidation of the same amount if fuel needed to support the desired power level. The relative concentration of the different gasses is the same at any pressure, but the actual number of molecules of each gas drops as the ambient pressure drops and/or as the temp increases. In physics, the relationship is defined by the Ideal gas law.
That paragraph is 100% absolutely correct, and i love the way you said "You therefore need to compress larger quantities of air to provide enough oxygen to support the oxidation of the same amount if fuel needed to support the desired power level. "
You cannot maintain the rpm/power because the air density is lower AND because the lower density air contains fewer o2 molecules, which makes the mixture too rich, unless you can find more oxygen oxygen (through turbocharged compression) to maintain power.
Here ya lost it...You are correct up to a point, there is still the same amount of o2 per cubic meter that there is of any other gas in our atmosphere, at any given temperature, at any given density, and at any given pressure (read the ideal gas law you just mentioned). There is still the EXACT same percentages of o2 to nitrogen, argon, helium, xeon ect. I could give you the exact percentages, but there is no point to it. All i'm trying to say is stop thinking that oxygen becomes more concentrated as it goes through its different states of high and low pressure/density/temperature. And realize that regardless of what state that the air parcel is in its content are still the same.
If you take a piece of sky, we typically refer to them as slugs, you can refer to them however you want meters, feet, miles what ever. You take that and compress it, heat it, throw it up to the upper atmosphere and it will always, always, always, contain the exact same percentage of oxygen to the other gasses in the atmosphere. That is pure physics, it has nothing to do with fewer o2 molecules per, slug, because it is absolutely constant. You cannot separate them (well you can, but that is an absolutely entirely different process then compressing it). Wait till I get home and i'll send you some links and other information to help you out. I guess what i'm trying to say is that heat acts on the parcles of the air, as does the pressure, etc. not just o2 per give measurement.
Don't worry if you don't believe me because i've got students who i teach who have a hard time believing it too, and I had a bitch of a time believing it myself when I was first told...but it is none the less true. (if you think thats bad wait till I tell you that centricifal force doesn't exist...and I try to explain that one to ya...lol...and yeah i know about Newton..so don't try to use physics on that one either).
While on the subject, what is the temperature of the air at 32,000 ft?
Temperature goes from a standard lapse rate at 1,000MSL (it is for all basic scientific principles standard from sea level to 1,000 MSL) of 2 degrees C then at varying stages of the atmosphere it cools more rapidly and heats up and cools etc. For an exact i'd have to get a Winds Aloft Forecast and it'll tell you how cold it is for which city etc.
