System and method for fuel nozzle cleaning during engine operation

A heat engine, the heat engine comprising:

• a compressor section configured to provide a flow of oxidizer to a combustion chamber;
• a fuel nozzle comprising a plurality of fuel injection openings, wherein the fuel nozzle is configured to provide a first fuel flow to the combustion chamber through one or more of the fuel injection openings and a second fuel flow to the combustion chamber through one or more of the fuel injection openings different from the first fuel flow;
• a fuel system configured to provide the first fuel flow through the fuel nozzle variably and separate from the second fuel flow through the fuel nozzle;
• and
• a controller configured to execute operations, the operations comprising:
• operating the compressor section to provide the flow of oxidizer at a first oxidizer flow condition to the combustion chamber, wherein the first oxidizer flow condition comprises an environmental parameter, wherein the environmental parameter comprises a temperature parameter and a pressure parameter;
• operating the fuel system at a first fuel flow condition to produce a fuel-oxidizer ratio at the combustion chamber;
• comparing the environmental parameter to a first environmental parameter threshold;
• comparing the environmental parameter to a second environmental parameter threshold;
• and
• transitioning the fuel system to a second fuel flow condition corresponding to a cleaning condition at the fuel nozzle if (i) the environmental parameter is equal to or greater than the first environmental parameter threshold, and (ii) the environmental parameter is less than or equal to the second environmental parameter threshold,
• wherein the first environmental parameter threshold corresponds to one or more of a temperature of the flow of oxidizer of 550° F. or greater or a pressure of 135 psi or greater downstream of the compressor section and upstream of the combustion chamber.