Fuel system with dual fuel injectors for internal combustion engines

An apparatus for controlling the delivery of gaseous fuel to an internal combustion engine, said engine having an intake manifold for receiving a fuel-air mixture and a plurality of cylinders for facilitating combustion of said fuel-air mixture, each of said plurality of cylinders having a lean misfire limit, said apparatus comprising:

• at least one fuel supply for storing and dispensing gaseous fuel;
• at least one primary fuel injector in fluid flow communication with said at least one fuel supply;
• a fuel-air mixer in fluid flow communication with said at least one primary fuel injector and said intake manifold, said fuel-air mixer being located upstream of said intake manifold, said fuel-air mixer having an air intake port for receiving air and a fuel port for receiving a primary amount of said fuel from said at least one primary fuel injector, said primary amount of said fuel being a majority of the total fuel required for combustion in said plurality of cylinders, said air and said primary amount of said fuel forming a primary fuel-air mixture;
• a plurality of secondary fuel injectors respectively located adjacent each of said plurality of cylinders, said plurality of secondary fuel injectors being in liquid flow communication with said at least one fuel supply and said fuel-air mixer, each of said plurality of secondary fuel injectors being adapted for injecting a secondary amount of said fuel to be mixed with said primary fuel-air mixture and ingested into each respective one of said plurality of cylinders;
• a plurality of misfire detection sensors respectively provided for each of said plurality of cylinders, each of said plurality of misfire detection sensors being capable of producing a signal representative of the lean misfire limit of each respective one of said plurality of cylinders, said plurality of misfire detection sensors being selected from the group consisting of spark-plug ionization sensors, instantaneous crank-angle velocity sensors, in-cylinder pressure sensors, in-cylinder temperature sensors, piezoelectric sensors, and fiber-optic sensors;
• and
• an electronic control module electrically connected to said at least one primary fuel injector, said plurality of secondary fuel injectors, and said plurality of misfire detection sensors for controlling said primary and secondary amounts of said fuel;
• wherein said electronic control module is capable of adjusting said secondary amount of said fuel in response to said signal for each of said plurality of cylinders such that each of said plurality of cylinders receives a fuel-air mixture having a specified margin from the lean misfire limit of each respective one of said plurality of cylinders.

A method of controlling the delivery of fuel to an internal combustion engine from at least one fuel supply;

• said engine having an intake manifold for receiving a fuel-air mixture and a plurality of cylinders for facilitating combustion of said fuel-air mixture;
• said method comprising the following steps:
• (a) distributing fuel from said at least one fuel supply to at least one primary fuel injector located upstream from said intake manifold;
• (b) injecting a primary amount of said fuel from said at least one primary fuel injector into a fuel-air mixer, said primary amount of said fuel being a majority of the total fuel required for combustion in said plurality of cylinders;
• (c) mixing said primary amount of said fuel with air in said fuel-air mixer to form a primary fuel-air mixture;
• (d) distributing fuel from said at least one fuel supply to a plurality of secondary fuel injectors respectively located adjacent said plurality of cylinders;
• (e) injecting a secondary amount of said fuel from each of said plurality of secondary fuel injectors into said primary fuel-air mixture to form a final fuel-air mixture for each of said plurality of cylinders, said secondary amount of said fuel being tailored for each respective one of said plurality of cylinders such that the final fuel-air mixture for each of said plurality of cylinders is appropriate for combustion;
• and
• (f) respectively passing said final fuel-air mixture to each of said plurality of cylinders.

A method of controlling the delivery of gaseous fuel to an internal combustion engine from at least one fuel supply;

• said engine having an intake manifold for receiving a fuel-air mixture and a plurality of cylinders for facilitating combustion of said fuel-air mixture, each of said plurality of cylinders having a lean misfire limit;
• said method comprising the following steps:
• (a) distributing gaseous fuel from said at least one fuel supply to at least one primary fuel injector located upstream from said intake manifold;
• (b) injecting a primary amount of said fuel from said at least one primary fuel injector into a fuel-air mixer, said primary amount of said fuel being a majority of the total fuel required for combustion in said plurality of cylinders;
• (c) mixing said primary amount of said fuel with air in said fuel-air mixer to form a primary fuel-air mixture;
• (d) distributing gaseous fuel from said at least one fuel supply to a plurality of secondary fuel injectors respectively located adjacent said plurality of cylinders;
• (e) injecting a secondary amount of said fuel from each of said plurality of secondary fuel injectors into said primary fuel-air mixture to form a final fuel-air mixture for each of said plurality of cylinders, said secondary amount of said fuel being tailored for each respective one of said plurality of cylinders such that the final fuel-air mixture for each of said plurality of cylinders has a specified margin from the lean misfire limit of each respective one of said plurality of cylinders;
• (f) respectively passing said final fuel-air mixture to each of said plurality of cylinders for combustion;
• (g) monitoring the lean misfire limit for each of said plurality of cylinders during said combustion process;
• and
• (h) adjusting said secondary amount of said fuel for each of said plurality of cylinders based on the respective lean misfire limit to maintain said specified margin.