A method for improving partial load efficiency in a gas turbine engine comprising a compressor, operating burners, a high pressure turbine and a low pressure turbine, the method comprising:
- operating the gas turbine engine by regulating at least:
- an air mass flow rate, and
- a flame temperature,
- controlling at least:
- the air mass flow rate supplied to a combustion chamber from the compressor;
- a number of the operating burners;
- and
- a change in an enthalpy drop between the high and low pressure turbine to control the air mass flow rate;
- wherein
- the air mass flow rate supplied to the combustion chamber from the compressor comprises a bleed that extracts a fraction of the air mass flow rate of the compressor at a compressor stage more upstream of a discharge, to limit a loss of work, in which a bleed flow rate supplied to the combustion chamber is modified, and
- the number of the operating burners comprises an annular combustor staging, in which the number of operating burners is modified, and
- the change in the enthalpy drop between the high and low pressure turbine to control the air mass flow rate comprises a nozzle guide vane control, in which the change in the enthalpy drop between the high and low pressure turbine is modified, allowing for regulation of the air mass flow rate, and
- at a lower load range, less than a first separating load value, operating the gas turbine engine by only controlling the bleed flow rate so as to limit the loss of work,
- at an intermediate load range, more than the first separating load value and less than a second separating load value, operating the gas turbine engine by only controlling the annular combustor staging so as to limit a thermal distortion of hot gas path components,
- at an upper load range, more than the second separating load value and less than a full operating load value, operating the gas turbine engine by only controlling a plurality of nozzle guide vanes, so as to regulate the air mass flow rate.