Method of starting a gas turbine engine including a bowed-rotor cooling phase

A gas turbine engine, the gas turbine engine comprising:

• a rotor surrounded by a casing;
• a turning motor system in operable communication with the rotor;
• a combustion section;
• and
• a controller configured to store and execute instructions for starting the gas turbine engine, the instructions comprising:
• accelerating the rotor during an acceleration phase, where the rotational speed of the rotor is increased toward a combustion speed to force air through the gas turbine engine;
• actively sensing vibrations during a condition monitoring phase during the acceleration phase, wherein vibrations are actively monitored while the rotational speed of the rotor is equal to or less than a critical speed of the rotor;
• actively sensing vibrations during a bowed rotor condition monitoring phase in the acceleration phase, where the rotor is monitored for a bowed rotor condition;
• maintaining a first rotational speed of the rotor, during a first bowed rotor cooling phase during the acceleration phase, below a non-contact speed below which the rotor does not contact the casing upon the presence of the bowed rotor condition;
• and
• maintaining a second rotational speed of the rotor during a second bowed rotor cooling phase following the first bowed rotor cooling phase, whereupon in the presence of the bowed rotor condition the rotational speed of the rotor continues to be maintained below the non-contact speed below which the rotor does not contact the casing, and wherein the second rotational speed of the rotor is greater than the first rotational speed,
• wherein at least a portion of the bowed rotor condition monitoring phase occurs after initiating the first bowed rotor cooling phase.

A gas turbine engine, the gas turbine engine comprising:

• a rotor surrounded by a casing;
• a turning motor system in operable communication with the rotor;
• a combustion section;
• and
• a controller configured to store and execute instructions for starting the gas turbine engine, the instructions comprising:
• initiating a first acceleration phase where the rotational speed of the rotor is increased toward a combustion speed to force air through the gas turbine engine;
• sensing vibrations during the first acceleration phase while the rotational speed of the rotor is equal to or less than a critical speed of the rotor;
• sensing a first bowed rotor condition during the first acceleration phase;
• initiating a first bowed rotor cooling phase during the first acceleration phase, where the rotational speed of the rotor is maintained below a first bowed rotor threshold speed until a first non-bowed rotor condition is satisfied, wherein the air forced through the gas turbine engine cools the rotor;
• sensing the first non-bowed rotor condition:
• thereafter, initiating a second acceleration phase, wherein the rotor speed is increased from at least the critical speed of the rotor toward the combustion speed;
• sensing a second bowed rotor condition during the second acceleration phase;
• initiating a second bowed rotor cooling phase during the second acceleration phase, where the rotational speed of the rotor is decelerated below a second bowed rotor threshold speed and above the first bowed rotor threshold speed until a second non-bowed rotor condition is satisfied, wherein the air forced through the gas turbine engine cools the rotor;
• sensing the second non-bowed rotor condition;
• and
• thereafter, initiating a combustion phase, where upon reaching the combustion speed during the combustion phase fuel is supplied to the combustion section and ignition is turned on.