Dimethyl ether (dme) enhanced gasoline engine

Abstract

An engine having DME pilot ignition is disclosed. DME Pilot ignition creates far more energy than a conventional spark plug, thus minimizes the possibility of misfire in the engine map. DME injection can be used in a number of ways. In one embodiment, DME injection replaces the conventional spark plug in an Otto cycle engine. In another embodiment, DME injection is used in addition to spark ignition to minimize the use of DME. In this embodiment, DME injection is only used during those portions of the engine map where misfire may occur, or during those times when a misfire sensor detects misfire. DME injection can also be used in conjunction with alcohol boosting in other embodiments.

1 . A turbocharged or supercharged internal combustion engine system having a compression ratio of greater than 10, comprising:
 a first tank for storing a primary fuel that power said engine system,   a second tank for storing a spark pilot compression ignition fluid, different than said primary fuel, and   a nozzle in a cylinder head of said engine, through which said pilot ignition fluid is injected, such that pilot ignition is used during a fraction of the engine operation, while conventional spark ignition is used during the remaining operation.   
     
     
         2 . The engine system of  claim 1 , wherein said pilot ignition is used at conditions of highly diluted mixtures. 
     
     
         3 . The engine system of  claim 1 , wherein said engine is an Otto-cycle engine, with flame propagation for combusting the primary fuel 
     
     
         4 . The engine system of  claim 1 , further comprising a third tank adapted to hold an alcohol fluid having a latent heat of vaporization greater than 0.5 MJ/kg, wherein an injector injects said alcohol during the first 70% of the compression stroke, and whereby said nozzle injects dimethyl ether as said pilot compression ignition fluid at some time during the last 30% of the compression stroke. 
     
     
         5 . The engine system of  claim 1 , wherein at least part of said primary fuel is supplied in either liquid or vapor form through a cylinder intake valve before the beginning of the compression stroke. 
     
     
         6 . The engine system of  claim 1 , further comprising a third tank adapted to store an anti-knock agent, wherein said agent is methyl or ethyl alcohol mixed with water. 
     
     
         7 . The engine system of  claim 3 , wherein combustion is initiated by compression ignition of DME. 
     
     
         8 . The engine system of  claim 1  where pilot ignition is used during cold start. 
     
     
         9 . An internal combustion engine system where a fuel is introduced into the engine from a first source and dimethyl ether (DME) is introduced into said engine from a second source and where EGR is used at high torque to prevent knock and where the level of EGR used to prevent knock would result in misfire without the introduction of DME into said engine. 
     
     
         10 . The engine system of  claim 9 , wherein DME use is minimized by only introducing it into said engine during high torque. 
     
     
         11 . The engine system of  claim 9 , wherein combustion is initiated by use of a spark plug in part of the engine operation range or when the DME is exhausted. 
     
     
         12 . The engine system of  claim 9 , wherein said engine does not contain a spark plug. 
     
     
         13 . The engine system of  claim 9 , further comprising a knock detector wherein closed loop control using said knock sensor is used to determine the amount of EGR that is needed and the amount of DME is determined by closed loop control using a misfire detector or by open loop control using an engine map. 
     
     
         14 . The engine system of  claim 9 , where the ratio of DME to said fuel increases with increasing torque. [This may not be very valuable it may be the opposite. We may be limited in how small an amount of DME we an inject, and injecting the minimum, the ratio of DME to primary fuel will decrease with increasing torque] 
     
     
         15 . The engine system of  claim 9 , where DME is directly injected. 
     
     
         16 . The engine system of  claim 9 , wherein combustion is initiated by compression ignition of DME. 
     
     
         17 . The engine system of  claim 9 , wherein combustion is initiated by a spark. 
     
     
         18 . The engine system of  claim 9 , wherein said DME is provided in containers that can be readily inserted and removed from a vehicle. 
     
     
         19 . The engine system of  claim 9 , wherein directly injected alcohol or alcohol-water mixture from a third source is used in addition to said DME. 
     
     
         20 . The engine system of  claim 19 , wherein said directly injected alcohol or alcohol-water mixture is used at higher values of torque than that at which heavy EGR operation is utilized. 
     
     
         21 . The engine system of  claim 9 , wherein said DME is used to prevent misfire at low loads. 
     
     
         22 . The engine system of  claim 21 , wherein the amount of DME that is introduced is determined by closed loop control using information from a misfire detector. 
     
     
         23 . The engine system of  claim 21 , wherein the torque-rpm region in which DME is introduced is varied so as to control the amount of DME consumption. 
     
     
         24 . The engine system of  claim 9 , wherein the ratio of air, said fuel and said DME are controlled to provide substantially stoichiometric fuel/air ratio when torque is varied.