System and method for sensor control of the fuel-air ratio in a burner

A system for controlling the fuel-air ratio of a burner of an external combustion engine having a heater head, based at least on the concentration of a gas in an exhaust gas product of a combustion chamber of the burner, the system comprising:

• a sensor for measuring the gas concentration in the exhaust gas product of the combustion chamber and for generating a sensor signal;
• a blower, governed by a blower drive signal, for injecting air into the burner;
• and
• a controller for receiving the sensor signal from the sensor and for adjusting the blower drive signal based at least on the sensor signal from the sensor and the sign of the derivative of the sensor signal with respect to the blower drive signal, to control the fuel-air ratio in the burner.

A method for controlling the fuel-air ratio of a fuel-air mixture in a burner of an external combustion engine having a heater head, the fuel-air mixture formed from a fuel and preheated air provided to the burner, the method comprising:

• determining the fuel-air ratio in the burner;
• determining a temperature of the preheated air;
• and
• adjusting an air flow rate to obtain a predetermined optimal fuel-air ratio, where the optimal fuel-air ratio is based on at least on the temperature of the preheated air.

A method for igniting a fuel-air mixture in a burner of an external combustion engine, the fuel-air mixture formed from a fuel and air provided to the burner and characterized by a fuel-air ratio, the method comprising:

• determining an optimal fuel-air ratio for igniting the fuel-air mixture based on at least the temperature of the air used in the fuel-air mixture;
• setting the fuel-air ratio to an initial ignition fuel-air ratio that contains a higher amount of fuel than the optimal fuel-air ratio by adjusting a fuel flow rate into the burner;
• maintaining the initial ignition fuel-air ratio until the fuel-air mixture ignites;
• and
• reducing the fuel flow rate to obtain the optimal fuel-air ratio.

A method for igniting a fuel-air mixture in a burner of an external combustion engine, the burner having a controller and the fuel-air mixture formed from a fuel and air provided to the burner and characterized by a fuel-air ratio, the method comprising:

• setting the fuel-air ratio of the fuel-air mixture to an ignition fuel-air ratio that is retrieved from a memory area of the controller of the burner;
• attempting to ignite the fuel-air mixture at the ignition fuel-air ratio;
• adjusting the fuel air ratio, if the fuel-air mixture does not ignite, by alternately increasing and decreasing the fuel-air ratio above and below the ignition fuel-air ratio until the fuel-air mixture ignites;
• and
• storing the fuel-air ratio at which the fuel-air mixture ignites in the memory area as the ignition fuel-air ratio.