Fuel Injection Strategies in Opposed-Piston Engines with Multiple Fuel Injectors

Abstract

In an opposed-piston engine, two or more fuel injectors are mounted to a cylinder for direct side injection into the cylinder. The injectors are controlled so as to inject either a single fuel pulse or a plurality of fuel pulses per cycle of engine operation in order to initiate combustion during varying engine speeds and operating conditions.

1 . A method of operating fuel injectors located for direct side injection of fuel into a cylinder of an opposed-piston engine, comprising:
 causing a pair of opposed pistons to move in the cylinder; and,   injecting fuel from first and second fuel injectors into a combustion chamber of the engine defined between the end surfaces of the pistons as the pistons approach top dead center locations, such that fuel injected by the first fuel injector includes at least a pilot injection followed by a main injection, and fuel injected by the second fuel injector includes at least a pilot injection followed by a main injection.   
     
     
         2 . The method of  claim 1 , wherein each pilot injection is separated in time from its following main injection by at least an inter-pulse gap (IPG). 
     
     
         3 . The method of  claim 2 , wherein the pilot injections injected by the first and second fuel injectors are offset by an amount of time less than the IPG. 
     
     
         4 . The method of  claim 3 , wherein the main injections injected by the first and second fuel injectors are substantially simultaneous. 
     
     
         5 . The method of  claim 1 , wherein fuel injected by the first fuel injector includes a first pilot injection and a second pilot injection delayed from the first pilot injection by at least an inter-pulse gap (IPG), and the main injection is delayed from the second pilot injection. 
     
     
         6 . The method of  claim 5 , wherein the pilot injection injected by the second fuel injector occurs in time between the first and second pilot injections of the first fuel injector. 
     
     
         7 . The method of  claim 6 , wherein the main injections of the first and second fuel injectors occur substantially simultaneously in time. 
     
     
         8 . The method of  claim 6 , wherein the main injections of the first and second fuel injectors overlap in time. 
     
     
         9 . The method of  claim 1 , wherein fuel injected by the first fuel injector further includes at least one post injection following the main injection. 
     
     
         10 . The method of  claim 1 , wherein fuel injected by the second fuel injector further includes at least one post injection following the main injection. 
     
     
         11 . A method of operating fuel injectors located for direct side injection of fuel into a cylinder of an opposed-piston engine, comprising:
 causing a pair of opposed pistons to move in the cylinder; and,   injecting fuel from first and second fuel injectors between the end surfaces of the pistons as the pistons approach top dead center locations, in which fuel is injected by the first fuel injector with a first split injection, and fuel is injected by the second fuel injector with a second split injection.   
     
     
         12 . The method of  claim 11 , wherein each of the first and second split injections includes a pilot injection separated in time from a following main injection by at least a minimum interval. 
     
     
         13 . The method of  claim 12 , wherein the pilot injection of the first split injection is offset from the pilot injection of the second split injection by an amount of time less than the minimum interval. 
     
     
         14 . The method of  claim 13 , wherein the main injections of the first and second injections are substantially simultaneous. 
     
     
         15 . The method of  claim 11 , wherein the first split injection includes a first pilot injection and a second pilot injection delayed from the first pilot injection by at least a minimum interval, and the main injection is delayed from the second pilot injection. 
     
     
         16 . The method of  claim 15 , wherein the pilot injection of the second split injection occurs in time between the first and second pilot injections of the first split injection. 
     
     
         17 . The method of  claim 16 , wherein the main injections of the first and second split injections occur substantially simultaneously in time. 
     
     
         18 . The method of  claim 16 , wherein the main injections of the first and second split injections overlap in time. 
     
     
         19 . The method of  claim 11 , wherein the first split injection further includes at least one post injection following the main injection. 
     
     
         20 . The method of  claim 11 , wherein the second split injection further includes at least one post injection following the main injection. 
     
     
         21 . A fuel injection system for an opposed-piston engine, comprising:
 at least one cylinder with a pair of pistons disposed in opposition for movement between top and bottom dead center positions therein;   a plurality of fuel injectors positioned for direct side injection of fuel into the cylinder, between the pistons;   a control unit responsive to engine operating conditions for generating fuel injection control signals; and,   an injector driver responsive to first control signals for generating fuel injector actuation signals operative to cause a first fuel injector to emit a first split injection and to cause a second fuel injector to emit a second split injection.   
     
     
         22 . The fuel injection system of  claim 21 , wherein each of the first and second split injections includes a pilot injection separated in time from a following main injection by at least a minimum interval. 
     
     
         23 . The fuel injection system of  claim 22 , wherein the first and second split injections overlap. 
     
     
         24 . The fuel injection system of  claim 22 , wherein the pilot injection of the first split injection is offset from the pilot injection of the second split injection by an amount of time less than the minimum interval. 
     
     
         25 . The fuel injection system of  claim 21 , wherein the injector driver is further responsive to second control signals for causing each of the first and second fuel injectors to emit a single injection. 
     
     
         26 . A fuel injection system for an opposed-piston engine, comprising:
 at least one cylinder with a pair of pistons disposed in opposition for movement between top and bottom dead center positions therein;   a plurality of fuel injectors positioned for direct side injection of fuel into the cylinder, between the pistons;   a control unit responsive to engine operating conditions for generating fuel injection control signals when the pistons are near top dead center locations in the cylinder; and,   an injector driver responsive to first control signals for generating first fuel injector actuation signals operative to cause a single fuel injector to inject fuel into the cylinder and for generating second fuel injector actuation signals operative to cause at least two fuel injectors to inject fuel into the cylinder.   
     
     
         27 . The fuel injection system of  claim 26 , wherein the first fuel injector actuation signals are further operative to cause the single fuel injector to inject fuel into the cylinder by a split injection. 
     
     
         28 . The fuel injection system of  claim 26 , wherein the second fuel injector actuation signals are further operative to cause each fuel injector to inject fuel into the cylinder by a split injection.