Piston for prechamber-type gas engine and prechamber-type gas engine

Patent metadata

Field	Value
Publication number	US-10024221-B2
Application number	US-201415024829-A
Country	US
Kind code	B2
Filing date	Oct 8, 2014
Priority date	Oct 9, 2013
Publication date	Jul 17, 2018
Grant date	Jul 17, 2018

Abstract

Particular embodiments may provide a piston for a prechamber-type gas engine and a prechamber-type gas engine taking into consideration the shape of the piston top surface portion so that the region where flame propagation due to torch jet is delayed, a piston for a prechamber-type gas engine where torch jet formed by combustion a prechamber fuel in a precombustion chamber is injected to a main combustion chamber through a plurality of injection holes, may include a piston top surface portion comprising a land portion formed in a first region extending between axis line directions of adjacent injection holes, and the first region is positioned at a higher position than a second region extending across the axis line direction. The land portion may be formed on a cavity formed in the piston top surface portion. A plurality of land portions are provided corresponding to the plurality of injection holes, and the plurality of land portions are provided so as to be offset toward a same direction from a middle position between axis line directions of adjacent injection holes.

First claim

The invention claimed is:

1. A prechamber-type gas engine utilizing a torch jet formed by combusting a prechamber fuel in a precombustion chamber to be injected into a main combustion chamber through a plurality of injection holes, comprising:
the precombustion chamber on which the plurality of injection holes are provided, and
a piston which includes a piston top surface portion to define the main combustion chamber together with a cylinder head and a cylinder liner,
wherein the piston top surface portion comprises a cavity formed substantially concentric with the piston, the cavity comprising a bottom portion such that the cavity comprises a concave curved surface and comprises a depth which increases as a radial position becomes closer to the center position of the piston from a circumferential edge portion and wherein the depth is largest at the center position of the piston,
wherein the piston top surface portion comprises a land portion formed in a first region extending between axis line directions of adjacent injection holes among the plurality of injection holes, the first region being positioned at a higher position than a second region extending across the axis line direction, and
wherein the bottom portion of the cavity comprises the concave curved surface such that a part of the bottom portion of the cavity on an axis line through the center of the piston and a tip portion of the land portion comprises a larger curvature than another part of the bottom portion of the cavity on an axis line through the center of the piston and not through the tip portion.

2. The piston for a prechamber-type gas engine according to claim 1 ,
wherein the land portion is formed on the cavity, and
wherein a distance from a circumferential edge portion of the cavity in the first region to a central axis is smaller than a distance from a circumferential edge portion of the cavity in the second region to the central axis.

3. The prechamber-type gas engine according to claim 1 ,
wherein a plurality of land portions are provided corresponding to the plurality of injection holes, and
wherein the plurality of land portions are provided so as to be offset toward a same direction from a middle position between axis line directions of adjacent injection holes among the plurality of injection holes.

4. The prechamber-type gas engine according to claim 1 ,
wherein the land portion comprises a concave curved surface facing the injection hole.

5. The prechamber-type gas engine according to claim 4 ,
wherein the concave curved surface comprises a curvature defined based, at least in part, on an arc centered at a tip of a potential core of the torch jet and comprising a radius of Lprop which is a minimum flame propagation distance defined by the expression:
L prop= R−L ×sin θ t

where R is a radius of the cavity, L is a length of the potential core of the torch jet, and θt is an injection angle.

Assignees

• Mitsubishi Heavy Ind Engine & Turbocharger Ltd

Inventors

• Nomura Kazutoshi
• Hiraoka Kenji
• Yuuki Akihiro
• Yamada Satoshi

Classifications

• F02B19/1019

  with only one pre-combustion chamber (F02B19/1004 take precedence) · CPC title

• F02B2023/108

  Swirl flow, i.e. the axis of rotation of the main charge flow motion is vertical · CPC title

• F02B23/0636

  the combustion space having a substantially flat and horizontal bottom · CPC title

• F02B19/16

  Chamber shapes or constructions not specific to sub-groups F02B19/02 - F02B19/10 · CPC title

• F02B23/08

  with positive ignition · CPC title