Optimized fuel management system for direct injection ethanol enhancement of gasoline engines

Abstract

Fuel management system for enhanced operation of a spark ignition gasoline engine. Injectors inject an anti-knock agent such as ethanol directly into a cylinder. It is preferred that the direct injection occur after the inlet valve is closed. It is also preferred that stoichiometric operation with a three way catalyst be used to minimize emissions. In addition, it is also preferred that the anti-knock agents have a heat of vaporization per unit of combustion energy that is at least three times that of gasoline.

1 - 5 . (canceled)  
   
   
       6 . A spark ignition engine which is turbocharged or supercharged and is fueled with gasoline from a first source and with direct injection of alcohol from a second source, comprising: 
 a spark ignition engine;    a turbocharger or supercharger;    means for fueling the engine with gasoline from the first source;    means for direct injection of the alcohol from the second source;    wherein during part of engine operating time, the engine is powered both by gasoline from the first source and the directly injected alcohol from the second source;    wherein under some operating conditions the instantaneous energy ratio of the alcohol to total fuel is at least 20%; and    wherein a fuel management system increases the alcohol/gasoline ratio to an amount that is sufficient to suppress knock as the turbocharger or supercharger increases the manifold pressure; and    wherein the fuel management system controls the amount of air to the turbocharger or supercharger, the amount of gasoline and the amount of the alcohol to obtain a substantially stoichiometric air/fuel ratio during some or all of the time that the second fuel is directly injected.    
   
   
       7 . The engine system of  claim 6  where substantially stoichiometric operation with the changing alcohol/gasoline ratio that occurs as the manifold pressure is increased is achieved by use of a control system which employs information from a knock sensor, an oxygen sensor and a look up table and where the control system enables use of a three way catalyst.  
   
   
       8 . The engine system of  claim 7  wherein the fuel management system minimizes the amount of the alcohol that is used to prevent knock and employs closed loop control using information from a knock sensor.  
   
   
       9 . The engine system of  claim 8  wherein spark retard is changed as a function of the amount of alcohol that has been used.  
   
   
       10 . The engine system of  claim 8  where the fuel in the second source is a mix of ethanol with another fuel and has variable characteristics and where during some of the operating time the ethanol energy fraction used in the engine is between 40 and 80%.  
   
   
       11 . The engine system of  claim 7  where the gasoline from the first source is directly injected using an independently controlled injector that is separate from an injector that directly injects the alcohol from the second source and the alcohol/gasoline ratio is controlled in a closed loop using information from a knock detector.  
   
   
       12 . The engine system of  claim 7  where the gasoline from the first source is directly injected using an injector that contains two nozzles where one is used for direct injection of the alcohol from the second source and where the alcohol/gasoline ratio is controlled in a closed loop using information from a knock detector.  
   
   
       13 . The engine system of  claim 7  where the gasoline from the first source and the alcohol from the second source are injected from the same injector and where their ratio is varied so as to prevent knock by use of a valving system which is upstream from the injector and the gasoline/alcohol ratio is controlled in a closed loop using information from a knock detector.  
   
   
       14 . The engine system of  claim 6  where during some operating conditions the alcohol energy fraction used in the engine is between 40 and 80% and the manifold pressure is at least 2 bar.  
   
   
       15 . The engine system of  claim 14  where the engine is downsized by at least a factor of two relative to an engine which uses port fuel injection of gasoline alone and operates with a drive cycle efficiency that is at least 20% greater.  
   
   
       16 . The engine system of  claim 14  where the fuel in the second source is an alcohol and the alcohol is mixed with water.  
   
   
       17 . The engine system of  claim 14  where the fuel in the second source is a mixture of ethanol and gasoline.  
   
   
       18 . The engine system of  claim 7  where the compression ratio is 11 or greater.  
   
   
       19 . The engine system of  claim 7  where the engine is started using only fuel from the first source.  
   
   
       20 . Sew) A spark ignition engine which is turbocharged or supercharged and is port fueled with gasoline from a first source and with direct injection of a liquid alcohol fuel from a second source comprising: 
 a spark ignition engine;    a turbocharger or supercharger;    means for port fueling the engine with gasoline from the first source;    means for direct injection of the alcohol from the second source;    wherein during part of engine operating time, the engine is powered both by gasoline from the first source and the directly injected alcohol from the second source;    wherein under some operating conditions the instantaneous energy ratio of the alcohol to total fuel is at least 20%; and    where a fuel management system increases the alcohol/gasoline ratio to an amount that is sufficient to suppress knock as the turbocharger or supercharger increases the manifold pressure; and    where the fuel management system controls the amount of air to the turbocharger or supercharger, the amount of gasoline and the amount of the second fuel to obtain a substantially stoichiometric air/fuel ratio during some or all of the time that the second fuel is directly injected and    where the substantially stoichiometric operation with the changing alcohol/gasoline ratio that occurs as the manifold pressure is increased is achieved by use of a control system which employs information from a knock sensor and an oxygen sensor and where the control system enables use of a three way catalyst.    
   
   
       21 . The engine system of  claim 20  where the control system also includes a look up table and where the fuel management system minimizes the amount of alcohol that is employed to prevent knock by means of closed loop control using information from a knock detector.  
   
   
       22 . The engine system of  claim 21  where the engine operates with a compression ratio of 11 or greater and 
 where the fuel in the second source is a mix of ethanol and another fuel and has variable characteristics and    where during some of the operating time the ethanol energy fraction used in the engine is between 40 and 80%.    
   
   
       23 . The engine system of  claim 20  where the alcohol is ethanol and where during some of the operating time the ethanol energy fraction in the engine is between 40 and 80%.  
   
   
       24 . The engine system of  claim 23  where t the manifold pressure is at least 2 bar.  
   
   
       25 . A turbocharged or supercharged spark ignition engine where alcohol and gasoline are directly injected at the same time into the engine cylinders and 
 where the fuel is directly injected in such a way as to provide a non uniform distribution with a greater concentration in the end gas region of the cylinder; and    where alcohol/gasoline ratio is sufficiently high so as to prevent knock and resulting in the alcohol/gasoline ratio being reduced as compared to a situation using a uniform distribution.    
   
   
       26 . The turbocharged or supercharged engine of  claim 25  where alcohol energy fraction in the engine varies and 
 where the alcohol energy fraction is less than 80% and the manifold pressure is greater than 2 bar.    
   
   
       27 . The turbocharged or supercharged spark ignition engine of  claim 24  further including a means for port fuel injection of the fuel.  
   
   
       28 . The turbocharged or supercharged engine of  claim 24  where the nonuniform distribution is used only part of the time and when it is employed the directly injected fuel is concentrated in the outside region of the engine cylinders.  
   
   
       29 . The turbocharged or supercharged spark ignition engine of  claim 28  where swirl is used.  
   
   
       30 . The turbocharged or supercharged engine of  claim 25  where fuel is directly injected after the inlet valve has closed.