# How do you determine what the temperature will be in the combustion chamber of a rocket engine?

I am guessing it is dependent on the fuel and oxidiser and the chamber pressure but is there an equation that would calculate the chamber temperature?

The process of calculating chamber temperature is complicated by the fact that the chemical reaction rates involved depend on the chamber temperature...thus the process is iterative.

The book Aerothermodynamics of Gas Turbine and Rocket Propulsion by Oates outlines the process in Chapter 3.6

Here is a scan of the page:

---Notes---

Subscript $$_c$$ indicates the combustion chamber exit

Subscript $$_{in}$$ indicates the combustion chamber entrance

Subscript $$_d$$ indicates the intermediate value

Subscript $$_p$$ indicates combustion products

Subscript $$_R$$ indicates reactants

$$H$$ = enthalpy

$$\Delta H^\circ_{fTd}$$ = standard heat of formation

You have to look the equilibrium constants up in a table; the book includes a table for a simplified oxygen/hydrogen reaction. It also includes a sample calculation so it's well worth working through it if you want to understand the process.

• Wow I didn’t realise it was this complicated! I’ve never used it but I’ve heard Propep can calculate the temperatures, is this true? – EdwardJ Mar 8 at 9:01
• I don't know that program, but there is no reason the calculations can't be programmed...I learned about this while writing an engine simulation myself. Approximations can also be made if the range of operations is limited. – Organic Marble Mar 8 at 13:29
• @Edward You might be interested in this video detailing SpaceX's combustion sims: youtu.be/txk-VO1hzBY – 0xDBFB7 Mar 11 at 4:33