Even though this ICAO data is for emissions, it is also valid for fuel consumption. So far it is the best fuel burn data that I have come across.
Now let us look at a comparison between twin spool and triple spool engine fuel consumption as applicable to a B777-200ER.
GE90-94B
Take-off - 3.513 kg/s
Climb-out - 2.831 kg/s
Approach - 0.876 kg/s
Idle - 0.284 kg/s
Trent 895
Take-off - 4.03 kg/s
Climb-out - 3.19 kg/s
Approach - 1.05 kg/s
Idle - 0.33 kg/s
Pratt 4090
Take-off - 3.898 kg/s
Climb-out - 2.977 kg/s
Approach - 0.957 kg/s
Idle - 0.268 kg/s