Gas turbine engine with transmission and method of adjusting rotational speed

A method of adjusting rotational speeds of a gas turbine engine having independently rotatable low pressure and high pressure spools, the method comprising:

• selecting a first rotational speed for at least one high pressure compressor rotor and at least one high pressure turbine rotor of a core of the gas turbine engine;
• rotating the at least one high pressure compressor rotor with the at least one high pressure turbine rotor through the high pressure spool at the first rotational speed, a ratio between the first rotational speed and a rotational speed of the high pressure spool having a fixed value;
• selecting a second rotational speed for a load of the engine;
• selecting a third rotational speed for at least one low pressure compressor rotor of the engine;
• and
• adjusting a variable ratio of a continuously variable transmission including a first drive member coupled to the low pressure spool, a second drive member coupled to the at least one low pressure compressor rotor, at least one movable member drivingly engaged to the first and second drive members and having a relative position with respect to the first and second drive members, and an actuation mechanism connected to the at least one movable member, the variable ratio being adjusted to rotate the at least one low pressure compressor rotor at the third rotational speed while rotating the load at the second rotational speed with at least one low pressure turbine rotor of the engine through the low pressure spool, the variable ratio being adjusted by varying the relative position of the at least one movable member with the actuation mechanism, the relative position determining a variable rotational speed ratio between the rotational speeds of the first and second drive members, a ratio between the second rotational speed and a rotational speed of the low pressure spool having a fixed value.

A gas turbine engine comprising:

• a core engine having at least one high pressure turbine rotor and at least one high pressure compressor rotor connected to a high pressure spool such as to be in driving engagement therewith, the high pressure spool being rotatable, a first fixed rotational speed ratio being defined between a rotational speed of the at least one high pressure turbine rotor and a rotational speed of the at least one high pressure compressor rotor;
• a low pressure spool rotatable independently of the high pressure spool;
• at least one low pressure turbine rotor connected to the low pressure spool such as to be in driving engagement therewith, a second fixed rotational speed ratio being defined between a rotational speed of the at least one low pressure turbine rotor and a rotational speed of the low pressure spool, the at least one low pressure turbine rotor in fluid communication with the at least one high pressure turbine rotor;
• a rotatable load in driving engagement with the low pressure spool, a third fixed rotational speed ratio being defined between a rotational speed of the rotatable load and the rotational speed of the low pressure spool;
• and
• a low pressure compressor rotor in fluid communication with the at least one high pressure compressor rotor, the low pressure compressor rotor being in driving engagement with the low pressure spool through a continuously variable transmission, the continuously variable transmission defining a variable rotational speed
• ratio between the rotational speed of the low pressure spool and a rotational speed of the low pressure compressor rotor, the continuously variable transmission including a first drive member coupled to the low pressure spool, a second drive member coupled to the low pressure compressor, at least one movable member drivingly engaged to the first and second drive members, and an actuation mechanism connected to the at least
• one movable member, the at least one movable member having a relative position with respect to the first and second drive members, the relative position being variable, the relative position determining a variable rotational speed ratio between the rotational speeds of the first and second drive members, and the actuation mechanism determining the relative position.