Fuel control system and method for gas engines

A method of controlling the supply of gaseous fuel to a gas engine, comprising:

• determining a desired first differential pressure setpoint between gaseous fuel and air pressures at air and fuel inlets, respectively, of an air/fuel mixing venturi which supplies an air/fuel mixture to an engine, the first differential pressure setpoint being varied based on a detected engine operating parameter;
• detecting actual fuel and air pressures at the fuel and air inlets, respectively, of the air/fuel mixing venturi;
• determining a differential pressure between the detected fuel and air pressures;
• comparing the first differential pressure setpoint to the detected differential pressure;
• and
• adjusting the fuel supply to the fuel inlet of the air/fuel mixing venturi in response to a detected difference between the first differential pressure setpoint and the detected differential pressure until the detected differential pressure is at least substantially equal to the first differential pressure setpoint.

A gaseous carburetor assembly for a gas engine, comprising:

• a single fuel control unit which is secured to an engine intake manifold of a gas engine, the control unit comprising at least a venturi mixer assembly, a fuel metering assembly, and an electronic control assembly which are secured together to form a single body;
• the venturi mixer assembly having a venturi body with a passage for air flow through the venturi body, an air inlet at one end of the passage, a fuel-air mixture outlet at a second end of the passage, a venturi throat of reduced cross-sectional area, and a fuel inlet to the venturi throat;
• the fuel metering assembly having an inlet connected to a gaseous fuel supply, a fuel supply passage which communicates with the venturi fuel inlet, and an adjustable metering valve which controls the area of the fuel supply passage;
• a differential pressure sensor which senses a differential pressure between the fuel supply to the venturi fuel inlet and the air supply at the venturi air inlet;
• and
• the electronic control assembly being connected directly to the fuel metering assembly and including a fuel pressure controller which controls the fuel supply to the venturi fuel inlet.

A gaseous carburetor apparatus, comprising:

• a venturi mixer assembly having a venturi body with a passage for air flow through the venturi having an air inlet at one end, an air/fuel outlet at an opposite end for connection to an engine intake module, a venturi throat of reduced cross-sectional area between the inlet and outlet, and at least one fuel inlet to the venturi throat;
• a fuel metering assembly having an inlet connected to a gaseous fuel supply, a fuel supply passage which communicates with the venturi fuel inlet, and an adjustable metering valve which controls the area of the fuel supply passage to vary the amount of fuel supplied to the venturi throat;
• an electronic control unit which controls the fuel metering assembly to adjust the fuel supply to the venturi fuel inlet;
• and
• the venturi mixer assembly further comprising a restriction of adjustable size between the fuel supply passage and the venturi fuel inlet, and an actuator for adjusting the size of the restriction to control the effective size of the venturi fuel inlet.

A fuel control system for a gas engine, comprising:

• an air/fuel mixing device which supplies an air/fuel mixture to a gas fuel engine, the mixing device having an air supply inlet, a gaseous fuel inlet, and an air/fuel mixture outlet;
• a fuel metering assembly which controls the supply of gaseous fuel to the gaseous fuel inlet;
• an air/fuel ratio control module which establishes a first gaseous fuel pressure set point,
• the first gaseous fuel pressure set point being adjusted as a function of an engine operating parameter;
• a first pressure sensor which detects the actual pressure of gaseous fuel supplied to the fuel inlet of an air/fuel mixing device;
• and
• a first pressure control module associated with the air/fuel ratio control module and first pressure sensor which controls the fuel metering assembly to vary the injection pressure of gaseous fuel supplied to the air/fuel mixing device based on a detected difference between the first gaseous fuel pressure set point and the detected fuel pressure.