Assemblies for engines
The present disclosure relates to assemblies for engines such as pre-combustion chamber assemblies for spark ignition engines. It is known to provide a spark ignition engine with a pre-combustion chamber but it can be difficult to provide a system with good knock performance at high speed with high loads while still having reliable ignition at low speed with low load. In particular, at low speed with low load, there may be a relatively high percentage of exhaust gas residuals (EGR) in a pre-combustion chamber which can prevent ignition especially when the ignition timing is retarded during catalyst heating. Aspects of the disclosure aim to alleviate at least to a certain extent the problems of the prior art. According to a first aspect there is provided a pre-combustion chamber assembly for a spark ignition engine, the assembly having: an ignition chamber adapted to contain at least one electrode of a spark generator; the ignition chamber being adapted to communicate with a main engine combustion chamber via at least one pre-chamber port; wherein the ignition chamber communicates for removal therefrom of exhaust gas residuals. The exhaust gas residuals are preferably removed to a distinct storage chamber, more preferably via a transfer port.
1. A pre-combustion chamber assembly for a spark ignition engine, the assembly having: an ignition chamber adapted to contain at least one electrode of a spark generator; the ignition chamber being adapted to communicate with a main engine combustion chamber via a plurality of cylindrical pre-chamber ports; wherein the ignition chamber communicates for removal therefrom of exhaust gas residuals to a distinct storage chamber via at least one transfer port, wherein the ignition chamber includes a single substantially cylindrical entrance channel leading from said pre-chamber ports in a direction towards an ignition region of the ignition chamber, the ignition region having a larger cross-section than the entrance channel, and wherein the entrance channel and ignition region are joined by a flaring chamber connector wall; and wherein the ignition chamber includes a tumble feature adapted to promote flow tumble, and the tumble feature is located in the region of the flaring chamber wall.
2. An assembly as claimed in claim 1 in which the ignition region is substantially circularly cylindrical.
3. An assembly as claimed in claim 2 in which the ignition region has a diameter between 2 to 5 times that of the entrance channel.
4. An assembly as claimed in claim 1 in which the tumble feature is a step surface; the tumble feature preferably being adapted to be generally radially aligned with a ground electrode of the spark generator to be mounted with the pre-combustion chamber assembly.
5. An assembly as claimed in claim 1 in which the ignition chamber has a longitudinal direction and is adapted to connect at one end thereof to a substantially coaxially oriented spark generator in the form of a spark plug, in which the ignition chamber is adapted to contain a tip of a ground electrode of a spark plug substantially in the centre of the ignition region.
6. An assembly as claimed in claim 1 , in which wall features of the ignition chamber near where a spark generator is to be contained are of a copper-beryllium material.
7. An assembly as claimed in claim 1 , in which wall features of the ignition chamber distal from where a spark generator is to be contained are of steel, and optionally are 316 stainless steel.
8. An assembly as claimed in claim 2 , in which said pre-chamber ports are configured in an equispaced pattern, in which the pre-chamber ports diverge from one another in a direction away from the ignition chamber.
9. An assembly as claimed in claim 7 , in which the pre-chamber ports are straight cylindrical tubes each orientated at an angle diverging from a longitudinal direction of the ignition chamber of about 30 to 60°.
10. An assembly as claimed in claim 7 , in which there are six said pre-chamber ports and the diameter of the entrance channel is about 2 to 4 times the diameter of each pre-chamber port.
11. An assembly as claimed in claim 7 , in which each pre-chamber port interfaces with a surface of the main combustion chamber which is convexly domed.
12. An assembly as claimed in claim 1 , in which the storage chamber is adapted to communicate only with the ignition chamber, otherwise being fully sealed.
13. An assembly as claimed in claim 1 , in which the storage chamber is a toroidal ring in shape, and the storage chamber is adapted to be located within a cylinder head assembly for an engine.
14. An assembly as claimed in claim 1 , in which the ignition chamber has a larger volume than the storage chamber, such as above 2 to 10 times larger, e.g. about 4 to 6 times larger.
15. An assembly as claimed in claim 1 , which includes a series of said transfer ports communicating at spaced apart locations into the ignition chamber; at least one said transfer port communicating into the ignition chamber at a first longitudinal position of the ignition chamber, at least one electrode tip of a spark generator being longitudinally between the first longitudinal location and a pre-chamber port of said pre-chamber ports.
16. An assembly as claimed in claim 1 in which each said at least one transfer port has a cross dimension or diameter which is between 5% and 20%, e.g. about 10% of a cross dimension of diameter of the ignition region of the ignition chamber.
17. An assembly as claimed in claim 1 , in which each said at least one transfer port is arranged in a direction which is a substantially radial direction, or having a tangential component, when viewed along a longitudinal direction of the assembly.
18. An assembly as claimed in claim 1 , which is passive, having no port for direct fuel injection into the ignition chamber.
19. An engine having a cylinder head, the cylinder head including an assembly as claimed in claim 1 .
20. An engine as claimed in claim 19 which has a gasoline direction injection (GDI) injector communicating directly into a main combustion chamber thereof; optionally including a port fuel injection (PFI) injector communicating directly into an air inlet port for the main combustion chamber.
21. An engine as claimed in claim 19 which has no ignition generator for the main combustion chamber to which the pre-combustion chamber assembly is connected other than a single ignition generator connected with at least one ignition electrode thereof located inside the ignition chamber.
22. A motor vehicle including an engine as claimed in claim 19 .
23. A pre-combustion chamber assembly for a spark ignition engine, the assembly having: an ignition chamber adapted to contain at least one electrode of a spark generator; the ignition chamber being adapted to communicate with a main engine combustion chamber via at least one pre-chamber port; wherein the ignition chamber communicates for removal therefrom of exhaust gas residuals to a distinct storage chamber via a plurality of transfer ports, and wherein the distinct storage chamber is adapted to communicate only with the ignition chamber, otherwise being fully sealed.
24. A pre-combustion chamber assembly for a spark ignition engine, the assembly having: an ignition chamber adapted to contain at least one electrode of a spark generator; the ignition chamber being adapted to communicate with a main engine combustion chamber via a plurality of cylindrical pre-chamber ports; wherein the ignition chamber communicates for removal therefrom of exhaust gas residuals to a distinct storage chamber via at least one transfer port, wherein the ignition chamber includes a single entrance channel leading from said pre-chamber ports in a direction towards an ignition region of the ignition chamber, the ignition region having a larger cross-section than the entrance channel, and wherein the entrance channel and ignition region are joined by a flaring chamber connector wall; and wherein the ignition chamber includes a tumble feature adapted to promote flow tumble, wherein the tumble feature is located in the region of the flaring chamber wall and the tumble feature is a step surface.