Facebook
Google
GitHub
Linkedin
Hi. We have recently performed an overhaul on a Nuovo Pignone GE10.2 gas turbine (single combustion chamber, Twin rotor). After overhaul, we attempted to start the unit (8 times so far) and failed.
The starter (which is a turbo expander) runs the GG rotor up to 7600 rpm. Up to this point everything looks normal. On GG speed of 2300, the ignition takes place and the flame holds on, On GG speed of 3900 the PT rotor starts spinning. On 7600 rpm GG and 2700 rpm PT the starter valves are closed, expecting that the unit is self-sustaining, but only after about 10 seconds the flame is lost and the unit trips.
At the point which the starter goes off, the compressor discharge pressure and temperature are normal (for start-up sequence), the exhaust temperature is around 20°C higher than expected. The wheel space temperatures are suspiciously uneven between left and right sides (60°C on first stage, 50°C on second, 100°C on third and 10°C on forth stage).
Vibrations, bearing temperatures and fuel pressure look normal. IGVs and NGVs are recalibrated and are functioning normally. All items regarding instruments, connections and control valves are double checked. The problem seems to be mechanical.
First I would like to hear any general advice on where and how to look for causes. Any similar experience and solution would be appreciated.
After that I have to make a confession. the new transition piece that we have used on this unit is not completely OK. The TP on GE10.2 units have two sides with a horizontal joint. The joint on our TP has some gapes that will result in some compressor discharge air to leak in to the hot gas flow. Of course the TP joints are not supposed to have a perfectly gastight joint (they also intentionally have some tiny holes to let the cool air in to cool the body) but the gaps on this TP is larger than expected. So our first suspect is this item, but we are not certain and like to consider any other possibility, mainly because there is a question here. If TP gap is the problem, why the flame goes off exactly after the starter shuts off, and why not any time sooner say at 4000 rpm?
The starter (which is a turbo expander) runs the GG rotor up to 7600 rpm. Up to this point everything looks normal. On GG speed of 2300, the ignition takes place and the flame holds on, On GG speed of 3900 the PT rotor starts spinning. On 7600 rpm GG and 2700 rpm PT the starter valves are closed, expecting that the unit is self-sustaining, but only after about 10 seconds the flame is lost and the unit trips.
At the point which the starter goes off, the compressor discharge pressure and temperature are normal (for start-up sequence), the exhaust temperature is around 20°C higher than expected. The wheel space temperatures are suspiciously uneven between left and right sides (60°C on first stage, 50°C on second, 100°C on third and 10°C on forth stage).
Vibrations, bearing temperatures and fuel pressure look normal. IGVs and NGVs are recalibrated and are functioning normally. All items regarding instruments, connections and control valves are double checked. The problem seems to be mechanical.
First I would like to hear any general advice on where and how to look for causes. Any similar experience and solution would be appreciated.
After that I have to make a confession. the new transition piece that we have used on this unit is not completely OK. The TP on GE10.2 units have two sides with a horizontal joint. The joint on our TP has some gapes that will result in some compressor discharge air to leak in to the hot gas flow. Of course the TP joints are not supposed to have a perfectly gastight joint (they also intentionally have some tiny holes to let the cool air in to cool the body) but the gaps on this TP is larger than expected. So our first suspect is this item, but we are not certain and like to consider any other possibility, mainly because there is a question here. If TP gap is the problem, why the flame goes off exactly after the starter shuts off, and why not any time sooner say at 4000 rpm?
