Methods and systems for managing a clearance gap in a piston engine

Abstract

A piston engine may include a piston assembly, which may include a piston having a self-centering feature. The piston assembly may be configured to translate in a bore of the cylinder, and contact a combustion section and/or gas driver section. The self-centering feature may use a flow of blow-by gas in a clearance gap to provide a self-centering force on the piston assembly. The self-centering feature may include one or more slotted pockets, a step, a tapered portion, any other suitable feature, or a combination thereof. Optionally, a piston assembly may include a feature that aids in self-centering such as, for example, a labyrinth seal.

What is claimed is: 
     
         1 . A piston and cylinder assembly comprising:
 a cylinder having a bore;   a combustion section located within the bore of the cylinder, wherein the combustion section is capable of containing a combustion gas;   a piston configured to translate axially within the bore, wherein blow-by gas from the combustion section flows axially away from the combustion section through a clearance gap between the piston and the bore, and wherein the piston comprises a feature that provides self-centering using the flow of blow-by gas.   
     
     
         2 . The piston and cylinder assembly of  claim 1 , wherein the feature that provides the self-centering is selected from the group consisting of one or more slotted pockets, a step, a tapered portion, and any combination thereof. 
     
     
         3 . The piston and cylinder assembly of  claim 1 , wherein the combustion section has an operating pressure between 20 and 800 bar. 
     
     
         4 . The piston and cylinder assembly of  claim 1 , wherein the piston further comprises a labyrinth seal. 
     
     
         5 . The piston and cylinder assembly of  claim 4 , wherein the one or more features comprise a plurality of circumferential grooves positioned behind the self-centering feature relative to the combustion section. 
     
     
         6 . A piston and cylinder assembly comprising:
 a cylinder having a bore;   a gas driver section located within the cylinder, wherein the gas driver section is capable of containing a driver gas;   a piston configured to translate axially within the bore, wherein blow-by gas from the gas driver section flows axially away from the gas driver section through a clearance gap between the piston and the bore, and wherein the piston comprises a feature that provides self-centering using the flow of blow-by gas.   
     
     
         7 . The piston and cylinder assembly of  claim 6 , wherein the feature that provides the self-centering is selected from the group consisting of one or more slotted pockets, a step, a tapered portion, and any combination thereof. 
     
     
         8 . The piston and cylinder assembly of  claim 6 , wherein the gas driver section has an operating pressure between 20 and 800 bar. 
     
     
         9 . The piston and cylinder assembly of  claim 6 , wherein the piston further comprises one or more features that are not substantially self-centering, wherein the one or more features aid in centering of the piston. 
     
     
         10 . The piston and cylinder assembly of  claim 9 , wherein the one or more features comprise a plurality of circumferential grooves positioned behind the self-centering feature relative to the gas driver section. 
     
     
         11 . A piston assembly comprising:
 a piston having piston face configured to contact at least one of a combustion section and a gas driver section of a piston engine; and   a feature configured to provide self-centering of the piston assembly in a bore of the piston engine.   
     
     
         12 . The piston assembly of  claim 11 , wherein the feature configured to provide the self-centering is selected from the group consisting of one or more slotted pockets, a step, a tapered portion, and any combination thereof. 
     
     
         13 . The piston assembly of  claim 11 , wherein the piston face is further configured to contact the at least one of the combustion section and the gas driver section of the piston engine having an operating pressure between 20 and 800 bar. 
     
     
         14 . The piston assembly of  claim 11 , wherein the piston assembly further comprises piston labyrinth seal. 
     
     
         15 . The piston assembly of  claim 14 , wherein the one or more features comprise a plurality of circumferential grooves positioned behind the self-centering feature relative to the piston face. 
     
     
         16 . The piston assembly of  claim 11 , wherein the piston face is configured to contact the combustion section, and wherein the feature is further configured to use a flow of blow-by gas from the combustion section to provide the self-centering. 
     
     
         17 . The piston assembly of  claim 11 , wherein the piston face is configured to contact the gas driver section, and wherein the feature is further configured to use a flow of blow-by gas from a gas driver section of the piston engine to provide the self-centering. 
     
     
         18 . The piston assembly of  claim 11 , wherein the feature configured to provide the self-centering is a machined feature of the piston assembly. 
     
     
         19 . The piston assembly of  claim 11 , further comprising a bearing element, wherein the feature configured to provide the self-centering is a machined feature of the bearing element. 
     
     
         20 . The piston assembly of  claim 11 , further comprising one or more internal passages configured to route a flow of blow-by gas from the at least one of the combustion section and the gas driver section.