Two-stage precombustion chamber for large bore gas engines

Abstract

In certain embodiments, a two-stage precombustion chamber may be used to reduce engine NOx levels, with fueled precombustion chambers, while maintaining comparable engine power output and thermal efficiency. One or more fuel admission points may be located in either the first prechamber stage or the second prechamber stage. A more efficient overall combustion characterized by low levels of NOx formation may be achieved by a two-stage precombustion chamber system while generating very high energy flame jets emerging from the second prechamber stage into the main combustion chamber. A first prechamber stage may be substantially smaller than a second prechamber stage. The volumes and aspect ratios of the two prechamber stages, along with the location of the electrodes within the first stage prechamber, the hole patterns, angles and the separate fueling, may be selected to create a distribution of fuel concentration that is substantially higher in the first stage prechamber compared to the second prechamber stage.

We claim: 
     
         1 . A two-stage precombustion chamber comprising:
 a first prechamber stage enclosing a first prechamber volume, the first prechamber stage comprising:
 one or more first stage holes communicating between the first prechamber volume and a second prechamber volume; 
 a primary electrode disposed within the first prechamber volume; and 
 one or more ground electrodes disposed within the first prechamber volume and offset from the primary electrode to form one or more electrode gaps; and 
   a second prechamber stage enclosing the second prechamber volume, the second prechamber stage comprising:
 one or more second stage holes communicating between the second prechamber volume and a combustion chamber volume; 
   wherein the two-stage precombustion chamber further comprises at least one fuel admission point configured to admit fuel to the second prechamber volume; and   wherein the first prechamber volume is smaller than the second prechamber volume and the first prechamber stage and the second prechamber stage are arranged in a selected relationship with respect to each other, such as to generate a first fuel concentration in the first prechamber volume that is higher than a second fuel concentration in the second prechamber volume.   
     
     
         2 . The two-stage precombustion chamber of  claim 1 , wherein each of the one or more first stage holes comprise a penetration angle and a rotational offset and each of the one or more second stage holes comprise a hole angle that maintains proportionality of flow direction and flow momentum in each of the two stages. 
     
     
         3 . The two-stage precombustion chamber of  claim 1 , wherein the one or more first stage holes and the one or more second stage holes are arranged to maintain proportionality of flow direction and flow momentum in each of the two stages. 
     
     
         4 . The two-stage precombustion chamber of  claim 1 , wherein the first prechamber stage has a first shape and the second prechamber stage has a second shape and the first and second shapes are arranged to maintain proportionality of flow direction and flow momentum in each of the two stages. 
     
     
         5 . The two-stage precombustion chamber of  claim 1 , wherein the first prechamber stage is positioned relative to the second prechamber stage to maintain proportionality of flow direction and flow momentum in each of the two stages. 
     
     
         6 . The two-stage precombustion chamber of  claim 1 , wherein the first prechamber stage is positioned symmetrically on a center hole axis of the second prechamber stage to maintain proportionality of flow direction and flow momentum in each of the two stages. 
     
     
         7 . The two-stage precombustion chamber of  claim 1 , wherein the first fuel concentration is at least about 5% higher than the second fuel concentration. 
     
     
         8 . The two-stage precombustion chamber of  claim 1 , wherein the first prechamber volume is smaller than the second prechamber volume. 
     
     
         9 . The two-stage precombustion chamber of  claim 1 , wherein the first prechamber volume is less than about 50% of the second prechamber volume. 
     
     
         10 . The two-stage precombustion chamber of  claim 1 , wherein each of the one or more first stage holes defines a first stage hole axis and each of the one or more second stage holes defines a second stage hole axis and wherein each first stage hole axis and each second stage hole axis defines an index angle, a penetration angle and a rotational offset. 
     
     
         11 . The two-stage precombustion chamber of  claim 10 , wherein the index angle, the penetration angle and the rotational offset of the first stage holes and the second stage holes are selected to generate a first fuel concentration in the first prechamber volume that is higher than a second fuel concentration in the second prechamber volume. 
     
     
         12 . The two-stage precombustion chamber of  claim 1 , wherein the first stage prechamber comprises a passive prechamber spark plug with a heat range selected to maintain all surface temperatures of the passive prechamber spark plug below a thermal runaway point dictated by the air-fuel mixture composition and by the level of combustion mean effective pressure at which the engine operates. 
     
     
         13 . A two-stage precombustion chamber comprising:
 a first prechamber stage enclosing a first prechamber volume, the first prechamber stage comprising:
 one or more first stage holes communicating between the first prechamber volume and a second prechamber volume; 
 a primary electrode disposed within the first prechamber volume; and 
 one or more ground electrodes disposed within the first prechamber volume and offset from the primary electrode to form one or more electrode gaps; and 
   a second prechamber stage comprising:
 an external surface and an internal surface enclosing the second prechamber volume; 
 one or more second stage holes communicating between the internal surface and the external surface; and 
 a fuel admission point configured to admit fuel into the second prechamber volume 
   wherein the first prechamber stage and the second prechamber stage are flow-dynamically matched.   
     
     
         14 . The two-stage precombustion chamber of  claim 13 , wherein each of the one or more first stage holes comprise a penetration angle and a rotational offset and each of the one or more second stage holes comprise a hole angle that maintains proportionality of flow direction and flow momentum in each of the two stages. 
     
     
         15 . The two-stage precombustion chamber of  claim 13 , wherein the one or more first stage holes and the one or more second stage holes are arranged to maintain proportionality of flow direction and flow momentum in each of the two stages. 
     
     
         16 . The two-stage precombustion chamber of  claim 13 , wherein the first prechamber stage has a first shape and the second prechamber stage has a second shape and the first and second shapes are arranged to maintain proportionality of flow direction and flow momentum in each of the two stages. 
     
     
         17 . The two-stage precombustion chamber of  claim 13 , wherein the first prechamber stage is positioned relative to the second prechamber stage to maintain proportionality of flow direction and flow momentum in each of the two stages. 
     
     
         18 . The two-stage precombustion chamber of  claim 13 , wherein the first prechamber stage is positioned symmetrically on a center hole axis of the second prechamber stage to maintain proportionality of flow direction and flow momentum in each of the two stages. 
     
     
         19 . The two-stage precombustion chamber of  claim 13 , wherein a first fuel concentration in the first prechamber volume is higher than a second fuel concentration in the second prechamber volume. 
     
     
         20 . The two-stage precombustion chamber of  claim 19 , wherein the first fuel concentration is higher than the second fuel concentration before a spark is introduced. 
     
     
         21 . The two-stage precombustion chamber of  claim 19 , wherein the first fuel concentration is at least about 5% higher than the second fuel concentration. 
     
     
         22 . The two-stage precombustion chamber of  claim 13 , wherein the first prechamber volume is smaller than the second prechamber volume. 
     
     
         23 . The two-stage precombustion chamber of  claim 13 , wherein the first prechamber volume is less than about 50% of the second prechamber volume. 
     
     
         24 . The two-stage precombustion chamber of  claim 13 , wherein each of the one or more first stage holes defines a first stage hole axis and each of the one or more second stage holes defines a second stage hole axis and wherein each first stage hole axis and each second stage hole axis defines an index angle, a penetration angle and a rotational offset. 
     
     
         25 . The two-stage precombustion chamber of  claim 24 , wherein the index angle, the penetration angle and the rotational offset of the first stage holes and the second stage holes are selected to generate a first fuel concentration in the first prechamber volume that is higher than a second fuel concentration in the second prechamber volume. 
     
     
         26 . A method of reducing NOx levels in gas engines, comprising:
 providing a two-stage precombustion chamber comprising:
 a first prechamber stage enclosing a first prechamber volume, the first prechamber stage comprising:
 one or more first stage holes communicating between the first prechamber volume and a second prechamber volume; 
 a primary electrode disposed within the first prechamber volume; 
 one or more ground electrodes disposed within the first prechamber volume and offset from the primary electrode to form one or more electrode gaps; and 
 
 a second prechamber stage enclosing the second prechamber volume, the second prechamber stage comprising:
 one or more second stage holes communicating between the second prechamber volume and a combustion chamber volume; 
 wherein the first prechamber stage and the second prechamber stage are flow-dynamically matched; 
 
   introducing one or more fuel admission points to the second prechamber volume; and   generating a spark across at least one of the one or more electrode gaps to ignite a fuel-air mixture in the first prechamber volume.   
     
     
         27 . The method of  claim 26 , wherein each of the one or more first stage holes comprise a penetration angle and a rotational offset and each of the one or more second stage holes comprise a hole angle that maintain proportionality of flow direction and flow momentum in each of the two stages. 
     
     
         28 . The method of  claim 26 , wherein the one or more first stage holes and the one or more second stage holes are arranged to maintain proportionality of flow direction and flow momentum in each of the two stages. 
     
     
         29 . The method of  claim 26 , wherein the first prechamber stage has a first shape and the second prechamber stage has a second shape and the first and second shapes are arranged to maintain proportionality of flow direction and flow momentum in each of the two stages. 
     
     
         30 . The method of  claim 26 , wherein the first prechamber stage is positioned relative to the second prechamber stage to maintain proportionality of flow direction and flow momentum in each of the two stages. 
     
     
         31 . The method of  claim 26 , wherein the first prechamber stage is positioned symmetrically on a center hole axis of the second prechamber stage to maintain proportionality of flow direction and flow momentum in each of the two stages. 
     
     
         32 . The method of  claim 26 , wherein the first prechamber volume is smaller than the second prechamber volume. 
     
     
         33 . The method of  claim 26 , wherein the first prechamber volume is less than about 50% of the second prechamber volume. 
     
     
         34 . The method of  claim 26 , wherein the first prechamber volume contains a first fuel-air mixture with a first fuel concentration and the second prechamber volume contains a second fuel-air mixture with a second fuel concentration and wherein the first fuel concentration is higher than the second fuel concentration. 
     
     
         35 . The method of  claim 34 , wherein the first fuel concentration is higher than the second fuel concentration before the spark is generated. 
     
     
         36 . The method of  claim 34 , wherein the first fuel concentration is at least about 5% higher than the second fuel concentration. 
     
     
         37 . The method of  claim 26 , wherein each of the one or more first stage holes defines a first stage hole axis and each of the one or more second stage holes defines a second stage hole axis and wherein each first stage hole axis and each second stage hole axis defines an index angle, a penetration angle and a rotational offset. 
     
     
         38 . The method of  claim 37 , wherein the index angle, the penetration angle and the rotational offset of the first stage holes and the second stage holes are selected to generate a first fuel-air mixture in the first prechamber volume with a higher fuel concentration than a second fuel-air mixture in the second prechamber volume. 
     
     
         39 . The method of  claim 26 , further comprising:
 providing cooling to the first stage prechamber to maintain all surface temperatures of the first prechamber below a thermal runaway point dictated by the air-fuel mixture composition and by the level of combustion mean effective pressure at which the engine operates.   
     
     
         40 . The method of  claim 26 , further comprising:
 providing cooling to the second stage prechamber to maintain all surface temperatures of the second prechamber to prevent flame quenching and to promote flame propagation speed as dictated by the air-fuel mixture composition and flow dynamic.   
     
     
         41 . A method of reducing NOx levels in gas engines, comprising:
 providing a two-stage precombustion chamber comprising:
 a first prechamber stage enclosing a first prechamber volume, the first prechamber stage comprising:
 one or more first stage holes communicating between the first prechamber volume and a second prechamber volume; 
 a primary electrode disposed within the first prechamber volume; 
 one or more ground electrodes disposed within the first prechamber volume and offset from the primary electrode to form one or more electrode gaps; and 
 
 a second prechamber stage comprising:
 an external surface and an internal surface enclosing the second prechamber volume; and 
 one or more second stage holes communicating between the internal surface and the external surface; 
 
 wherein the first prechamber stage and the second prechamber stage are flow-dynamically matched; 
   introducing one or more fuel in-filling streams to the second prechamber volume; and   generating a spark across at least one of the one or more electrodes gaps to ignite a fuel-air mixture in the first prechamber volume.   
     
     
         42 . The method of  claim 41 , wherein each of the one or more first stage holes comprise a penetration angle and a rotational offset and each of the one or more second stage holes comprise a hole angle that maintains proportionality of flow direction and flow momentum in each of the two stages. 
     
     
         43 . The method of  claim 41 , wherein the one or more first stage holes and the one or more second stage holes are arranged to maintain proportionality of flow direction and flow momentum in each of the two stages. 
     
     
         44 . The method of  claim 41 , wherein the first prechamber stage has a first shape and the second prechamber stage has a second shape and the first and second shapes are arranged to maintain proportionality of flow direction and flow momentum in each of the two stages. 
     
     
         45 . The method of  claim 41 , wherein the first prechamber stage is positioned relative to the second prechamber stage to maintain proportionality of flow direction and flow momentum in each of the two stages. 
     
     
         46 . The method of  claim 41 , wherein the first prechamber stage is positioned symmetrically on a center hole axis of the second prechamber stage to maintain proportionality of flow direction and flow momentum in each of the two stages. 
     
     
         47 . The method of  claim 41 , wherein the first prechamber volume is smaller than the second prechamber volume. 
     
     
         48 . The method of  claim 41 , wherein the first prechamber volume is less than about 50% of the second prechamber volume. 
     
     
         49 . The method of  claim 41 , wherein the first prechamber volume contains a first fuel-air mixture with a first fuel concentration and the second prechamber volume contains a second fuel-air mixture with a second fuel concentration and wherein the first fuel concentration is higher than the second fuel concentration. 
     
     
         50 . The method of  claim 49 , wherein the first fuel concentration is higher than the second fuel concentration before the spark is generated. 
     
     
         51 . The method of  claim 49 , wherein the first fuel concentration is at least about 5% higher than the second fuel concentration. 
     
     
         52 . The method of  claim 41 , wherein each of the one or more first stage holes defines a first stage hole axis and each of the one or more second stage holes defines a second stage hole axis and wherein each first stage hole axis and each second stage hole axis defines an index angle, a penetration angle and a rotational offset. 
     
     
         53 . The method of  claim 52 , wherein the index angle, the penetration angle and the rotational offset of the first stage holes and the second stage holes are selected to generate a first fuel-air mixture in the first prechamber volume with a higher fuel concentration than a second fuel-air mixture in the second prechamber volume. 
     
     
         54 . A method for controlling the admission of fuel to a two-stage precombustion chamber utilizing an electrically actuated valve, comprising adjusting a quantity of fuel admitted and timing of admitting the quantity of fuel relative to engine position to achieve a desired fuel distribution in the two-stage precombustion chamber; wherein the two stages are flow-dynamically matched. 
     
     
         55 . The method of  claim 54 , wherein at least one of the quantity of fuel and the timing of admitting the fuel is adjusted utilizing a closed feedback loop based on one or more previous operating cycles and wherein the feedback loop includes feedback generated from the two-stage precombustion chamber or the main combustion chamber. 
     
     
         56 . A method for controlling and adjusting the characteristics of a spark discharge event within a two-stage precombustion chamber, comprising utilizing an electronically controlled ignition system to adjust the characteristics of a spark discharge event based on the fuel distribution present in a two-stage precombustion chamber; wherein the two stages are flow-dynamically matched. 
     
     
         57 . The method of  claim 56 , wherein the characteristics of the spark discharge are adjusted utilizing a closed feedback loop based on one or more previous operating cycles and wherein the feedback loop includes feedback generated from the two-stage precombustion chamber or the main combustion chamber.