Fuel nozzles. A clogged nozzle shows in the temperatures first.

1. 01What it does. Each nozzle sprays its share of the fuel into the combustor in a fixed pattern. On a standard combustor the nozzles handle gas, liquid or both. On DLE engines premixers mix fuel and air before the flame in two or three rings, so the control can stage the fuel for low emissions. All nozzles on one engine have to flow alike: the temperature profile into the turbine depends on it.
2. 02Where it sits. Around the combustor casing, fed from a manifold through shrouded feeder tubes. LM2500 and LM6000 engines with a standard combustor use dual fuel or gas nozzles, some with water or steam injection for NOx. LM2500 and LM6000 DLE engines use premixers.
3. 03What goes wrong. Clogging and coking from dirty or wet fuel, liquid fuel left standing in the nozzle after a fuel changeover, eroded tips and leaking connections. We find clogged nozzles at end users more often than anything else in the hot section. It shows as a wider T48 spread, a cold or hot spot that moves with load, harder starts, and on DLE engines dynamics and emissions that drift. The control or the thermocouples often get the blame first.
4. 04How we check it on site. The individual thermocouple readings and the spread from the datalog to locate the burner, the measurement chain checked so a bad probe is ruled out, a borescope look, fuel supply and filters, then replacement per position or as a set. The mechanical work is done with an experienced crew; we do the checks, the restart and the control side, and prove the spread and the emissions afterwards.

Related: T48 thermocouples · LM2500 · LM6000