Methods and systems relating to fuel delivery in combustion turbine engines

A method of controlling the delivery of fuel to a combustor of a combustion turbine engine, wherein a fuel delivery system of the combustion turbine engine includes:

• a fuel line having a fuel compressor positioned between a first connection to a fuel source and a second connection to the combustor of the combustion turbine engine, wherein the fuel line further comprises parallel branches downstream of the fuel compressor:
• a cold branch that includes an after-cooler;
• and a hot branch that bypasses the after-cooler;
• a rapid heating value meter configured to measure the heating value of the fuel from the fuel source and transmit heating value data relating to the measurements;
• wherein the rapid heating value meter comprises a device that provides heating value test results in less than approximately 30 seconds of beginning the testing process;
• and wherein the fuel delivery system is configured to test the fuel at regular intervals, the regular intervals being less than approximately 30 seconds;
• means for controlling the amount of fuel being directed through the cold branch and the amount of fuel being directed through the hot branch;
• and a fuel-mixing junction positioned in close proximity to the a combustor gas control valve at which the cold branch and the hot branch converge;
• the method including the steps of:
• measuring the heating value of the fuel with the rapid heating value meter;
• determining a target temperature range for the fuel based on the measured heating value and a target Modified Wobbe Index range of the combustor;
• and
• controlling the flow of fuel through the cold branch and the hot branch such that the temperature of the fuel being delivered to the combustor comprises a temperature within the target temperature range;
• wherein the fuel line further comprises a hot compressor bypass, which connects to the fuel line at a position upstream of the fuel compressor and is configured such that a flow of fuel therethrough bypasses the fuel compressor and is carried to a heater and heated, and from the heater, the hot compressor bypass connects to the hot branch at a position upstream of the fuel-mixing junction;
• and wherein the fuel line further comprises a cold compressor bypass, which connects to the fuel line at a position upstream of the fuel compressor and is configured such that a flow of fuel therethrough bypasses the fuel compressor and the heater and connects to the cold branch at a position upstream of the fuel-mixing junction and downstream of the after-cooler;
• and
• wherein the fuel delivery system further comprises a plurality of temperature measuring devices that are configured to measure fuel temperature, the plurality of temperature measuring devices being disposed along the fuel line at several locations to measure at least:
• a compressed fuel temperature that comprises the temperature of the fuel after being compressed by the fuel compressor;
• a cooled fuel temperature that comprises the temperature of the fuel after being cooled by the after-cooler;
• a heated fuel temperature that comprises the temperature of the fuel after being heated by the heater;
• a raw fuel temperature that comprises the temperature of the fuel in the cold compressor bypass;
• and a mixed fuel temperature that comprises the temperature of the fuel downstream of the fuel-mixing junction;
• further comprising the steps of:
• periodically measuring the compressed fuel temperature, the cooled fuel temperature, the heated fuel temperature, the raw fuel temperature, and the mixed fuel temperature;
• and
• based on the heating value measurement and the temperature measurements, controlling the flow of fuel such that a desired portion of the fuel is directed through the cold branch, a desired portion of the fuel is directed through the hot branch, a desired portion of fuel is directed through the hot compressor bypass, and a desired portion of fuel is directed through the cold compressor bypass so that the mixed fuel temperature downstream of the fuel-mixing junction achieves the target temperature range.