Passive Pre-Chamber Ignition with Varying Nozzle Sizes for Internal Combustion Engine

Abstract

A passive ignition pre-chamber for an internal combustion engine. The pre-chamber is typically implemented as a cap on the electrode end of a spark plug, and encloses a pre-chamber volume in which fuel is mixed with air to form a consistently ignitable mixture. The pre-chamber is passive in the sense that gas exchange with the engine's main combustion chamber is realized by local flow fields near nozzles into the main chamber and by pressure differences between the pre-chamber and the main chamber. The nozzles are sized such that at least one of the nozzles has a larger diameter than the remaining nozzles, as optimized using flow field and pre-chamber turbulence analysis.

1 . An ignition pre-chamber for an internal combustion engine, the engine having cylinders each with a spark plug with an electrode end and a combustion chamber, the engine being equipped for exhaust gas recirculation (EGR), comprising:
 a pre-chamber housing that encloses a volume between the electrode end of the spark plug and the combustion chamber;   a bottom wall of the pre-chamber housing having a number of nozzles that provide flow between the pre-chamber housing and the combustion chamber; and   wherein the number, size(s), and arrangement of the nozzles is manufactured by the following process: modeling the ignition pre-chamber at a desired engine operating point. the pre-chamber having a candidate configuration of nozzles, the configuration having a specific number of nozzles, size of each nozzle, and location of each nozzle, mapping. the EGR residual content during a compression stroke of the engine as a function of crank angles of the engine, repeating the modeling and mapping steps for a number of candidate configurations, and selecting a candidate configuration on the basis of EGR residual content.   
     
     
         2 . The pre-chamber of  claim 1 , wherein the pre-chamber housing is implemented as a cap at the electrode end of the spark plug. 
     
     
         3 . The pre-chamber of  claim 1 , wherein the spark plug has a center electrode and wherein a nozzle under the center electrode end has a larger diameter than the remaining nozzles. 
     
     
         4 . The pre-chamber of  claim 1 , wherein the spark plug generates a tumble flow field when activated, and wherein one or more nozzles aligned with the tumble flow field have a larger diameter than the remaining nozzles. 
     
     
         5 . The pre-chamber of  claim 1 , wherein the spark plug generates a tumble flow field when activated, and wherein one or more nozzles orthogonal to the tumble flow field have a larger diameter than the remaining nozzles. 
     
     
         6 . (canceled) 
     
     
         7 . (canceled) 
     
     
         8 . The pre-chamber of  claim 1 , wherein the spark plug has a J″ electrode that extends under the center electrode. 
     
     
         9 . A method of manufacturing an ignition pre-chamber for an internal combustion engine, the engine having cylinders each with a spark plug with an electrode end and a combustion chamber, comprising:
 modeling a pre-chamber having a housing that encloses a volume between the electrode end of the spark plug and the combustion chamber; a bottom wall of the pre-chamber housing having a number of nozzles that provide flow between the pre-chamber housing and the combustion chamber;   using computational fluid dynamics modeling to evaluate the pre-chamber with nozzles having varying nozzle diameters; and   selecting nozzle diameters based on the step of using computational fluid dynamics modeling.   
     
     
         10 . The method of  claim 9 , wherein the pre-chamber housing is modeled as a cap at the electrode end of the spark plug. 
     
     
         11 . The method of  claim 9 , wherein the spark plug has a center electrode and wherein a nozzle under the center electrode end has a larger diameter than the remaining nozzles. 
     
     
         12 . The method of  claim 9 , wherein the spark plug generates a tumble flow field when activated, and wherein one or more nozzles aligned with the tumble flow field have a larger diameter than the remaining nozzles. 
     
     
         13 . The method of  claim 9 , wherein the computational fluid dynamics modeling models residual gasses in the pre-chamber during a late portion of a compression stroke of the cylinder. 
     
     
         14 . The method of  claim 9 , wherein the spark plug has a J″ electrode that extends under the center electrode. 
     
     
         15 . A method of operating an internal combustion engine, the engine having cylinders each with a spark plug with an electrode end and a combustion chamber, comprising:
 placing a pre-chamber housing at the electrode end of the spark plug, such that the pre-chamber encloses a volume between the electrode end of the spark plug and the combustion chamber;   wherein the bottom wall of the pre-chamber housing has a number of nozzles that provide flow between the pre-chamber housing and the combustion chamber; and   sizing the diameter of the nozzles to have varying diameters based on computational fluid dynamics modeling of residual gasses in the pre-chamber during activation of the spark plug.