Backside cooling has been around for a while. Its easier in a lean burn design (such as TAPS) due to the lower peak flame temperature in the dome area of the combustor.
What's necessary is good air impingement onto the backside of the combustor liner. It also helps to have finned channels to cool the hottest sections.
Eventually the cooling air must be dumped somewhere. Now, I haven't seen the GEnX cross section to that level of detail. (If you have a link please share), but its possible to bypass most fo the combustor before dumping the cooling air at either the Turbine inlet vane roots (to create a film at the ID
and OD, post combustion, to protect the turbine) or even to have it go into the turbine inlet vane.
You only care to keep the film air away from the dome and first 2/3rds of the combustor to prevent the quenching of CO
. Once enough residence time has been given to burn out the CO
, its ok to quench the combustor gases as they have to finish burning sometime.
1. Good backside cooling designs
2. Good Thermal barrier coatings
3. Good casting processes (to create the backside heat transfer enhancement)
4. I'm assuming its still a double wall combustor (with impingement jets). There has been a tremendous amount of work in this area.
What helps? Efficient compressors. The more efficient the compressor, the cooler the gas entering the combustor and thus the less cooling required.