Operating a gaseous fuel injector

Abstract

Fuel injection accuracy of gaseous fuel injectors is important for efficient engine operation. However, the performance of the injectors varies from part to part and across their lifetime, and when an injector is under performing according to its specification it is often unknown what is causing the problem. An apparatus for operating a gaseous fuel injector in an engine comprises a mass flow sensor that generates a signal representative of the mass flow rate of the gaseous fuel in a supply conduit in the engine. A controller connected with the injector and the mass flow sensor is programmed to actuate the injector to introduce gaseous fuel into the engine; determine the actual mass flow rate of the gaseous fuel based on the signal representative of the mass flow rate; calculate a difference between the actual mass flow rate and a desired mass flow rate; and adjust at least one of on-time of the gaseous fuel injector and a magnitude of an injector activation signal by respective amounts based on the difference when the absolute value of the difference is greater than a predetermined value.

What is claimed is: 
     
       1. An apparatus for operating a gaseous fuel injector in an internal combustion engine comprising:
 a supply of gaseous fuel; 
 a conduit delivering gaseous fuel to the gaseous fuel injector from the supply of gaseous fuel; 
 a mass flow sensor associated with the conduit generating a signal representative of a mass flow rate of the gaseous fuel; and 
 a controller operatively connected with the gaseous fuel injector and the mass flow sensor and programmed to: 
 actuate the gaseous fuel injector to introduce gaseous fuel into the internal combustion engine; 
 determine an actual mass flow rate of the gaseous fuel based on the signal representative of the mass flow rate; 
 calculate a difference between the actual mass flow rate and a desired mass flow rate; and 
 adjust at least one of on-time of the gaseous fuel injector and a magnitude of an injector activation signal by respective amounts based on the difference when an absolute value of the difference is greater than a predetermined value; 
 wherein the adjust at least one of on-time of the gaseous fuel injector and a magnitude of an injector activation signal results in an actual injection mass injected into the internal combustion engine by the gaseous fuel injector to equal a desired injection mass to within a predetermined tolerance. 
 
     
     
       2. The apparatus of  claim 1 , wherein the gaseous fuel injector is located to introduce the gaseous fuel directly into a cylinder of the internal combustion engine. 
     
     
       3. The apparatus of  claim 1 , wherein the controller is further programmed to adjust at least one of the on-time and the magnitude during a same cycle as the determination of the actual mass flow rate. 
     
     
       4. The apparatus of  claim 1 , wherein the mass flow sensor comprises:
 a membrane; 
 first and second temperature sensors arranged on a sensing surface of the membrane; and 
 a heater connected with the membrane and arranged between the first and second temperature sensors. 
 
     
     
       5. The apparatus of  claim 4 , wherein the controller is operatively connected with the first and second temperature sensors to receive first and second temperature signals respectively representative of the mass flow rate of the gaseous fuel. 
     
     
       6. The apparatus of  claim 4 , wherein the controller is a first controller, the mass flow sensor further comprising a second controller operatively connected with the first controller and the first and second temperature sensors, the second controller programmed to receive temperature information from the first and second temperature sensors and to transmit the first and second temperature signals representative of the mass flow rate of the gaseous fuel to the first controller. 
     
     
       7. The apparatus of  claim 1 , wherein the mass flow sensor is located within the conduit. 
     
     
       8. The apparatus of  claim 7 , further comprising one of:
 a flow redirecting conduit operatively arranged with the mass flow sensor to redirect a portion of gaseous fuel flow in the conduit to the mass flow sensor; and 
 a locating member to space mass flow sensor apart from an inner surface of the conduit. 
 
     
     
       9. The apparatus of  claim 1 , further comprising a sampling conduit adjacent to and in fluid communication with the conduit, wherein the mass flow sensor is mounted within the sampling conduit, and a flow redirecting member in the conduit to redirect a portion of gaseous fuel flow to the sampling conduit. 
     
     
       10. The apparatus of  claim 1 , wherein the controller is further programmed to report performance of the gaseous fuel injector in a diagnostic system, wherein the performance comprises at least one of the actual mass flow rate, a rate of increase of the actual mass flow rate, a leaking indication, an under-flowing indication and an over-flowing indication. 
     
     
       11. A method for operating a gaseous fuel injector in an internal combustion engine comprising:
 actuating the gaseous fuel injector to inject gaseous fuel; 
 measuring actual mass flow rate of the gaseous fuel upstream from the gaseous fuel injector; 
 calculating a difference between the actual mass flow rate and a desired mass flow rate; and 
 adjusting at least one of on-time of the gaseous fuel injector and a magnitude of an injector activation signal by respective amounts based on the difference when an absolute value of the difference is greater than a predetermined value; 
 wherein the adjust at least one of on-time of the gaseous fuel injector and a magnitude of an injector activation signal results in an actual injection mass injected into the internal combustion engine by the gaseous fuel injector to equal a desired injection mass to within a predetermined tolerance. 
 
     
     
       12. The method of  claim 11 , wherein at least one of:
 the on-time is adjusted during a same cycle as the measurement of the actual mass flow rate; and 
 the magnitude of the injector activation signal is adjusted during the same cycle as the measurement of the actual mass flow rate. 
 
     
     
       13. The method of  claim 11 , wherein when the actual mass flow rate is below a predetermined mass flow rate value, the method further comprises increasing at least one of the on-time of the injector and the magnitude of the activation signal until the actual mass flow rate is above the predetermined mass flow rate value. 
     
     
       14. The method of  claim 11 , further comprising:
 determining a rate of increase in actual mass flow rate when the gaseous fuel injector is actuated; and 
 determining that the opening of the gaseous fuel injector is slow when the rate of increase is below a predetermined value; 
 wherein the at least one of the on-time and the magnitude of the gaseous fuel injector activation signal is adjusted to compensate for the slow opening of the gaseous fuel injector. 
 
     
     
       15. The method of  claim 11 , further comprising reporting performance of the gaseous fuel injector in a diagnostic system, wherein the performance comprises at least one of the actual mass flow rate, a rate of increase of the actual mass flow rate, a leaking indication, an under-flowing indication and an over-flowing indication. 
     
     
       16. The method of  claim 11 , wherein a plurality of gaseous fuel injectors are operated, the method further comprising:
 calculating an average mass flow rate as a function of the actual mass flow rates for each gaseous fuel injector; 
 for each gaseous fuel injector at least one of; 
 determining whether the gaseous fuel injector is under-flowing wherein the actual mass flow rate is less than the average mass flow rate by a predetermined margin; and 
 determining whether the gaseous fuel injector is over-flowing wherein the actual mass flow rate is greater than the average mass flow rate by a predetermined margin. 
 
     
     
       17. The method of  claim 16 , further comprising determining a pressure regulator is under-flowing gaseous fuel when the actual mass flow rates for each injector are equal to within a predetermined range of tolerance and less than a desired mass flow rate by a predetermined value; and reporting the performance of the pressure regulator in a diagnostic system. 
     
     
       18. The method of  claim 11 , further comprising:
 heating a space in the flow of gaseous fuel; 
 measuring an upstream temperature and a downstream temperature; and 
 calculating the actual mass flow rate as a function of a difference between the upstream temperature and the downstream temperature. 
 
     
     
       19. The method of  claim 11 , further comprising redirecting a portion of gaseous fuel flow in a gaseous fuel conduit towards a sensing surface of a gaseous fuel mass flow sensor. 
     
     
       20. The method of  claim 11 , wherein the gaseous fuel comprises at least one of biogas, butane, ethane, hydrogen, landfill gas, methane, natural gas, propane, and combinations of these fuels.