exhaust temp of 1000 are damn close and a good estimate

 

SWEET!

 

It's an estimate. Headers glow red - over 900 degrees. Drag cars used to (maybe still do) use aluminum headers - aluminum melts at ~1100 degrees.

 

how sure are you about what kind of pressure there is after the cylinder fires? keep in mind the gasses completely change.

The only (relatively easy) way I can see getting an accurate idea of all the information you want would be to set up the system in EES. Other than that its sorta a rough estimate.

 

what do you mean that these gases completely change? Do you think that the molarity of the gas after combustion is that much different. I would assume that the molarity change is negligible. or do you mean that this mixture does not follow the idea gas law?

 

lol....why do you need to know this in the first place?

 

^ That's why.

 

Well if you want to be exact, I would account pressure of each different gas at a given mass, volume and temp. If you want to neglect it, then neglect it, its probably not a huge variable.

Either way, regarless... the simplest way to get ALL of the information you want, would be to set up the cycle in EES. Its a great tool, and I assume if you have advanced fluid dynamics programs, then your school should definitly have EES. My teacher gave it out for free to all the students.

If you use EES, the program knows all the properties of all the gases, so you just have to plug in what you know. I was able to design a fuel cell/ micro turbine hybrid power plant and know the exact pressure, temp, gas concentration, mass flow rate, exergy, etc etc etc of all 20 stages of the power plant. It would be cake for a single combustion chamber.

 

[QUOTE=marks_lude,Jun 25 2008, 11:30 AM]how sure are you about what kind of pressure there is after the cylinder fires?

 

Im not talking about that at all...

Im talking about the duration of the cycle where the valves are closed. the piston comes up, compresses, fires, and the gas expands due to 1) temp increase, and 2) possibly expansion due to change in gases as well... all be for the exhaust valves open as the pistion is pushed back down creating power as well as the chamber pressure which determines the exit speed.

Like I said, I'm not sure #2 is significant or not, but If you plug it into EES it takes care of all the thinking for you.

All Im saying, is if you sit down and do a page of hand calcs, you've already done more work to get less accurate numbers than if you know what your doing at all in ESS. Sounds like your school has resources, and this would be a fantastic opertunity to learn the program, plus it would be solid "R" (from the term R&D) that could stand behind your design.