Bi-fuel Engine Using Hydrogen

Abstract

A method is disclosed for making a transition from fueling an engine with hydrogen to another fuel. That other fuel may be gasoline, a gasoline and alcohol mixture, or gaseous fuels, as examples. The other fuel has the capability of providing higher BMEP than the hydrogen because of better air utilization and because the other fuel occupies less volume of the combustion chamber. Because a desirable equivalence ratio to burn hydrogen is at 0.5 or less and a desirable equivalence ratio to burn other fuel is at 1.0, when a demand for BMEP that leads to a transition change from hydrogen fuel to the other fuel, the amount of air supplied to the engine is decreased to provide more torque and vice versa. During a transition in which liquid fuel supply is initiated, it may desirable to continue to provide some hydrogen, not leaner than 0.1 hydrogen equivalence ratio.

1 . A method to transition from a first to a second operating mode in an internal combustion engine, comprising:
 decreasing air supply substantially, said decrease starting at transition initiation; decreasing an amount of a first fuel supplied to the engine at transition initiation;   initiating supply of a second fuel to the engine at transition initiation; and increasing supply of the second fuel abruptly in an amount to cause equivalence ratio to increase abruptly to 1.0 wherein the increasing is performed in response to equivalence ratio exceeding a threshold equivalence ratio.   
   
   
       2 . The method of  claim 1  wherein said first fuel is substantially 100% hydrogen and said second fuel is primarily comprised of hydrocarbons. 
   
   
       3 . The method of  claim 1 , further comprising:
 decreasing continually a supplied amount of said first fuel during said transition wherein at termination of said transition said first fuel is no longer being supplied to the engine; and.   
   
   
       4 . The method of  claim 1  wherein said second fuel is a liquid fuel. 
   
   
       5 . The method of  claim 1  wherein said first fuel is hydrogen and said transition is initiated in response to a demand for a torque increase when said equivalence ratio is roughly 0.5. 
   
   
       6 . The method of  claim 1  wherein said threshold equivalence ratio is about 0.85. 
   
   
       7 . The method of  claim 1  wherein said air supply is decreased by 30-60% during the transition. 
   
   
       8 . The method of  claim 1  wherein the transition is initiated in response to engine piston speed exceeding a threshold. 
   
   
       9 . The method of  claim 1  wherein said transition is initiated in response to BMEP demand exceeding a threshold. 
   
   
       10 . A method to transition between two operating modes in an internal combustion engine, comprising:
 conducting the transition in a transition initiation phase followed by a transition completion phase wherein an equivalence ratio of 1.0 is maintained during the transition initiation phase and equivalence ratio decreases during the transition completion phase;   the transition initiation phase comprising:   increasing air supply;   initiating supply of a first fuel, hydrogen, to the engine; and   decreasing supply of a second fuel to the engine; and   the transition completion phase comprising further decreasing supply of the second fuel abruptly in an amount to cause equivalence ratio to decrease abruptly to an equivalence ratio below a threshold equivalence ratio.   
   
   
       11 . The method of  claim 10  wherein said transition is initiated in response to a demand for a torque decrease below a threshold BMEP. 
   
   
       12 - 13 . (canceled) 
   
   
       14 . The method of  claim 10  wherein the equivalence ratio threshold is about 0.85. 
   
   
       15 . The method of  claim 10  wherein said supply of hydrogen to the engine during the transition termination phase causes the equivalence ratio with respect to only the hydrogen fuel to be at least 0.1. 
   
   
       16 . The method of  claim 10  wherein said second fuel is a liquid fuel. 
   
   
       17 . A method to transition from a first to a second operating mode in an internal combustion engine, comprising:
 conducting the transition in a transition initiation phase followed by a transition completion phase with an equivalence ratio of 1.0 being maintained during the transition completion phase and maintaining an equivalence ratio less than a threshold equivalence ratio being maintained during the transition initiation phase wherein said threshold equivalence ratio is an equivalence ratio at which NO x  production exceeds a corresponding threshold;   the transition initiation phase comprising:   decreasing air supply to the engine;   decreasing an amount of hydrogen supplied to the engine; and   initiating supply of a liquid fuel to the engine; and the transition completion phase comprising:
 abruptly increasing supply of the liquid fuel; and 
 decreasing supply of hydrogen continually through the transition completion phase. 
   
   
   
       18 . The method of  claim 17  wherein said transition is initiated based on a demand for increased BMEP that causes said hydrogen equivalence ratio to exceed about 0.5. 
   
   
       19 . The method of  claim 17  wherein the equivalence ratio threshold is about 0.85. 
   
   
       20 . The method of  claim 17  wherein said transition is initiated in response to BMEP demand exceeding a threshold. 
   
   
       21 . A method for controlling an internal combustion engine during transitions between hydrogen fuel and a hydrocarbon fuel, the method comprising:
 supplying hydrocarbon fuel to the engine in an amount to produce an equivalence ratio that is either below a first threshold equivalence ratio or above a second equivalence ratio.   
   
   
       22 . The method of  claim 21  wherein the first and second equivalence ratios correspond to equivalence ratios associated with NO x  production exceeding a predetermined NO x  threshold. 
   
   
       23 . The method of  claim 21  wherein the first equivalence ratio threshold is about 0.85 and the second equivalence ratio threshold is 1.0.