When employing two-point control, we need an additional equation. This can be the same as the U _f equation except that the U _f = g(U _o ) constraint is replaced by a fixed temperature value.

(14–25)

Similar to Equation 14–23 , U _f also "propagates" from the fixed point to either side. The fixed locations are chosen on either side of the flame.

The two-point control method may facilitate computing solutions through the extinction turning point or may "jump" from the upper branch to the middle branch. In the latter case, one can use one-point control once a solution on the middle branch is obtained to trace back to the extinction point.