# Combustion temperature and pressure

1. Feb 21, 2016

### yousaf nasir

hi
i have a cylinder whose volume, intake and exhaust area is known. i know the amount of air entering into the combustion chamber(cylinder) and the amount of fuel entering into the combustion chamber. i am taking an ideal approach and assuming stoichiometric combustion (LPG). is there any formulation or method for me to find out temperature, pressure or anyone of these properties in combustion chamber????

2. Feb 21, 2016

### Staff: Mentor

Are the intake and exhaust closed during the combustion? Is the volume of the cylinder constant during the combustion? Have you had a course in thermodynamics yet?

3. Feb 22, 2016

### yousaf nasir

it is a pulsejet (valveless type) and i am an engineering student, so yes i have attended the course. it is a constant volume combustion because the cycle momentarily stops and at that moment combustion occurs, so yes we can say that intake and exhaust are closed because there is no flow at that moment. i know how to get the adiabatic flame temperature for constant volume through which i can get pressure but through various research papers and blogs i know the compression ratio remains in range of 1.2-1.3. if i follow the correct method through wihich i find enthalpies of products and reactants, the pressure it shows is quite large ( way off ) than the experimental values. i want to know what to do

4. Feb 22, 2016

### Staff: Mentor

I don't have much experience in this area, but I'll try to help. It's hard to know what the problem is without knowing more of the details. Are you trying to determine the conditions before the power stroke or at the end of the power stroke? Is that where you have the measurements of the pressure and temperature? What do you estimate for the pressure and what is the observed value? Can you provide a sample calculation?

Chet

5. Feb 22, 2016

### Nidum

Pulse jets work on a modified Lenoir cycle

There are many research studies relating to the thermodynamics and practical design of pulse jets .

There is a modern day resurgence of interest in this type of engine .

Last edited: Feb 22, 2016
6. Feb 22, 2016

### Nidum

Just as a point of interest pulse jet like combustion can occur as an unwanted effect in turbojet engines .

If you are lucky the engine blows out and not much harm done but just a few seconds of sustained pulsed combustion can be highly destructive .

This type of unstable combustion was a significant problem in the pioneer days of turbojet engine development .

Rarely a problem with modern engines .