Combustion method and internal combustion engine

Patent metadata

Field	Value
Publication number	US-9476346-B2
Application number	US-201214360108-A
Country	US
Kind code	B2
Filing date	Oct 27, 2012
Priority date	Nov 23, 2011
Publication date	Oct 25, 2016
Grant date	Oct 25, 2016

Abstract

A combustion process with auto-ignition for direct-injection internal combustion engines involves dividing injection jets at a jet divider contour into a first partial quantity, a second partial quantity, and third partial quantities. The first partial quantity enters into the piston cavity, the second partial quantity enters via the piston step into a region between the piston crown and the cylinder head, and the third partial quantities, starting from the respective injection jet, spread out on both sides in the peripheral direction in opposite directions along the piston step, and the respective third partial quantities collide with one another between two adjacent injection jets within the piston step and are deflected radially inwardly. The first partial quantity and the second partial quantity form a first combustion front and a second combustion front, and the partial quantities which in each case are jointly deflected inwardly form a third combustion front radially inwardly into a gap between the injection jets. The injection jets are deflected upstream from the jet divider contour in the direction of the piston by means of a resultant flow formed essentially from a swirl, a squish gap flow, and a jet flow.

First claim

The invention claimed is:

1. A combustion method having auto-ignition for direct-injection internal combustion engines, comprising:
the internal combustion engine having at least one cylinder with a combustion chamber laterally delimited by a cylinder wall, and is delimited axially on one side by a cylinder head, and is delimited axially on a second side by an adjustable-stroke piston in the cylinder,
the piston having an annular circumferential piston step axially recessed in the piston relative to an annular circumferential piston crown, and which via an annular circumferential jet divider contour merges into a piston cavity axially recessed in the piston relative to the piston step,
an injection nozzle situated in the cylinder head being associated with the particular cylinder,
wherein for a combustion operation in auto-ignition mode the injection nozzle simultaneously injects multiple injection jets into the combustion chamber in a star-shaped pattern,
wherein the injection jets are each divided at the jet divider contour into a first partial quantity, a second partial quantity, and third partial quantities,
the first partial quantity entering into the piston cavity, the second partial quantity entering via the piston step into a region between the piston crown and the cylinder head, and the third partial quantities, starting from the respective injection jet, spreading out on both sides in the peripheral direction in opposite directions along the piston step, and the respective third partial quantities colliding with one another between two adjacent injection jets within the piston step and being deflected radially inwardly,
the first partial quantity and the second partial quantity forming a first combustion front and a second combustion front, and the partial quantities which in each case are jointly deflected inwardly forming a third combustion front radially inwardly into a gap between the injection jets, and
wherein the injection jets are deflected above the piston cavity upstream from the jet divider contour in a direction of the piston by a resulting flow formed essentially from a swirl flow, a squish gap flow, and a jet flow, wherein a flow vector of the resulting flow includes a portion that forms above the piston cavity and coaxially with respect to a longitudinal center axis of the cylinder in a direction of the piston cavity.

2. The method of claim 1 , wherein the injection jets first strike the jet divider contour off-center and offset toward the piston cavity, during the injection spread over the center of the jet divider contour, and strike the jet divider contour offset toward the piston step.

3. The method of claim 1 , wherein the injection jets initially strike the jet divider contour off-center and offset toward the piston cavity, and in the course of the injection subsequently strike the jet divider contour.

4. The method of claim 1 , wherein the injection nozzle produces 10 to 12 injection jets at the same time.

5. The method of claim 1 , wherein the injection jet is introduced during an injection duration of 40 crankshaft angle degrees maximum.

6. The method of claim 1 , wherein the injection jets are injected at a spray cone angle in an angular range of 152°±1°.

7. The method of claim 6 , wherein the spray cone angle spreads out essentially coaxially with respect to the piston.

8. The method of claim 1 , wherein the injection jets are introduced into the combustion chamber at an injection pressure of 500 bar to 2800 bar.

9. The method of claim 1 , wherein the first partial quantity is deflected in an undercut in the piston cavity.

10. The method of claim 9 , wherein the undercut is up to 3% of a piston diameter.

11. An internal combustion engine, comprising:
a cylinder having combustion chamber laterally delimited by a cylinder wall, and axially delimited on one side by a cylinder head and on second by an adjustable-stroke piston in the cylinder;
an injection nozzle situated in the cylinder head,
wherein the piston has an annular circumferential piston step axially recessed in the piston relative to an annular circumferential piston crown, and which via an annular circumferential jet divider contour merges into a piston cavity axially recessed in the piston relative to the piston step,
wherein, for a combustion operation in auto-ignition mode, the injection nozzle is configured to simultaneously inject multiple injection jets into the combustion chamber in a star-shaped pattern,
wherein the injection jets are each divided at the jet divider contour into a first partial quantity, a second partial quantity, and third partial quantities,
wherein the first partial quantity enter into the piston cavity, the second partial quantity enter via the piston step into a region between the piston crown and the cylinder head, and the third partial quantities, starting from the respective injection jet, spread out on both sides in the peripheral direction in opposite directions along the piston step, and the respective third partial quantities colliding with one another between two adjacent injection jets within the piston step and being deflected radially inwardly,
wherein the first partial quantity and the second partial quantity form a first combustion front and a second combustion front, and the partial quantities which in each case are jointly deflected inwardly forming a third combustion front radially inwardly into a gap between the injection jets,
wherein a resulting flow, which is formed essentially from a swirl flow, a squish gap flow, and a jet flow, deflects the injection jets above the piston cavity upstream from the jet divider contour in the direction of the piston, wherein a flow vector of the resulting flow includes a portion that forms above the piston cavity and coaxially with respect to a longitudinal center axis of the cylinder in a direction of the piston cavity.

12. The internal combustion engine of claim 11 , wherein the swirl flow has an i-theta of 4.5 maximum.

13. The internal combustion engine of claim 12 , wherein the swirl flow is changeable corresponding to operating conditions.

14. The internal combustion engine of claim 11 , wherein the cylinder includes a squish gap at top dead center of the piston, axially between the piston crown and the cylinder head, wherein the squish gap has an axial height in a range of approximately 0.4% to approximately 1.2% of the piston diameter, or has a radial length in a range of approximately 9% to approximately 14% of the piston diameter.

15. The internal combustion engine of claim 11 , wherein the piston step has a radial extension of 4% to approximately 20% of a piston diameter, and an axial height of approximately 2.5% to 7% of the piston diameter.

16. The internal combustion engine of claim 11 , wherein the injection nozzle multiple injection holes, each having a ratio of a hole length to a hole diameter which is in a range of approximately 4 to approximately 8.

17. The internal combustion engine of claim 16 , wherein the injection holes have a conical design and taper from an intake side to an exhaust side.

18. The internal combustion engine of claim 17 , wherein a hole diameter at the intake side, is larger than a hole diameter at the exhaust side in a range of approximately 5% to approximately 15%.

19. The internal combustion engine of claim 11 , wherein the piston is equipped with a piston cone situated coaxially and centrally in the piston cavity and which has a cone angle of approximately 124°±5°.

20. The internal combustion

Assignees

• Daimler Ag

Inventors

• Zoeller Herbert
• Seddouk Naima

Classifications

• F02B23/0621

  Squish flow · CPC title

• F02B17/005 Primary

  having direct injection in the combustion chamber · CPC title

• F02B23/0693

  the combustion space consisting of step-wise widened multiple zones of different depth · CPC title

• F02B23/0651 Primary

  the fuel spray impinging on reflecting surfaces or being specially guided throughout the combustion space · CPC title

• Y02T10/125

  Cross-Sectional Technologies · mapped topic