Diesel engine swirl chamber

The nozzle throat through which fuel is injected into a swirl chamber is arranged so that a flame front which travels back through the plume of injected fuel is deflected and prevented from directly propagating thereinto. The orientation of the nozzle throat also reduces the amount of surface area of the throat against which the injected fuel impinges and reduces the amount of fuel which adheres thereto.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to diesel engines and more 
specifically to an improved swirl chamber arrangement for a swirl chamber 
type diesel engine. 
2. Description of the Prior Art 
FIG. 1 shows a prior art arrangement of the nature disclosed in 
JM-A-55-12054. As shown, this arrangement includes an essentially 
cylindrical or so called "disc" shaped swirl chamber 1 which is fluidly 
communicated with a main combustion chamber 2 via an angled transfer port 
4. The swirl chamber 1 is further is formed with a nozzle throat 6 through 
which a fuel injector 8 injects fuel, and a bore 10 in which a glow plug 
12 is disposed. 
The transfer port 4 is arranged to introduce the compressed charge from the 
main combustion chamber 2 in the swirl chamber 1 in a manner that the 
incoming flow follows the path denoted by the bold arrow A. As shown in 
the drawing, due to the above mentioned flow of the air, the plume of fuel 
which is sprayed into the swirl chamber by the injector 8, is deflected 
(as indicated by arrow a) in a manner to flow through the swirl chamber in 
the direction denoted by the bold arrow B. Some of the fuel impinges on a 
wall portion of the nozzle throat and is deflected as indicated by arrow 
b. 
However, this arrangement has suffered from the drawback that unacceptably 
large amounts of smoke tend to be formed during engine operation. 
Experiments performed have established that the reason for the large amount 
of smoke formation is due to the fact that, during engine operation the 
spontaneous ignition of the fuel within the swirl chamber tends to occur 
at the point denoted by *. 
Following the initial ignition, even though the swirl in the chamber is 
flowing in the opposite direction, the flame front travels rapidly back 
through the fuel spray in the direction denoted by the bold arrow C as 
well as propagating in the forward direction. This rearward propagation 
direction tends to cause the flame front to travel directy into the nozzle 
throat 6. 
As the mixing effect of the air which is induced to swirl in the swirl 
chamber 1, is very low in the nozzle throat 6, localized combustion of a 
pocket of poorly carburetted excessively rich mixture occurs and leads to 
the formation of a large amount of smoke. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a swirl chamber 
construction which obviates the combustion of excessively rich mixtures in 
the nozzle throat and therefore reduces the formation of smoke. 
In brief, the above object is achieved by a swirl chamber arrangement 
wherein the nozzle throat is arranged so that a flame front which travels 
back through the plume of injected fuel, is deflected and prevented from 
directly propagating into the nozzle throat. The orientation of the nozzle 
throat also reduces the amount of surface area of the throat against which 
the injected fuel impinges and reduces the amount of fuel which adheres 
thereto. 
More specifically, a first aspect of the present invention takes the form 
of an internal combustion engine which features: a swirl chamber, the 
swirl chamber being communicated with a main combustion chamber by way of 
a transfer passage, the transfer passage being arranged to, during the 
compression phase of the engine, introduce air into the swirl chamber in 
manner that it establishes a swirling air pattern therein; means defining 
nozzle throat through which fuel is injected into the swirl chamber; and a 
wall portion located adjacent the nozzle throat which deflects a flame 
front which propagates back through the fuel plume following ignition 
thereof, the wall portion being arranged to prevent the flame front from 
propagating directly into the nozzle throat. 
A second aspect of the present invention takes the form of a diesel engine 
which features: a main combustion chamber; an essentially cylindrically 
shaped swirl chamber; a transfer port, the transfer port communicating the 
main combustion chamber with the swirl chamber, the transfer port being 
oriented to induce a swirlying air pattern to form in the swirl chamber 
during the compression phase of the engine; means defining a nozzle throat 
which opens into the swirl chamber, the nozzle throat being oriented at a 
first predetermined angle with respect to the swirling air pattern which 
is established in the swirl chamber; a fuel injector; the fuel injector 
being arranged at a second predetermined angle with respect to the 
swirling air pattern which is established in the swirl chamber, the fuel 
injector being arranged to inject fuel into the swirl chamber through the 
nozzle throat in a manner that the fuel becomes admixed with the swirling 
air pattern, the difference between the first and second predetermined 
angles reducing the surface area of the nozzle throat upon which injected 
fuel tends to impinge; and a deflecting wall portion, the deflecting wall 
portion being located immediately adjacent the nozzle throat and on the 
downstream side thereof with respect to the direction in which the 
swirling air pattern swirls in the swirl chamber, the deflecting wall 
portion being arranged to deflect a flame front which propagates back 
through the fuel injected into the swirl chamber and prevent the flame 
front from directly propagating directly into the nozzle throat.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 2 shows an embodiment of the present invention. This arrangement is 
essentially similar to the prior art arrangement however features a nozzle 
throat 6' arrangement which is constructed and arranged such that the 
mouth of the throat is oriented in a direction which is close to normal to 
the direction in which the flame front propagates back through the fuel 
plume. This defines a deflection surface 100 between the nozzle throat 6' 
and the adjacent bore 10 in which the glow plug 12 is disposed. This 
deflection surface 100 is arranged at an angle to the flame front and 
substantially parallel to the swirl pattern, as shown in FIG. 2, to 
deflect the flame front at a location immediately upstream of the nozzle 
throat 6' (see bold arrow D) in a manner which prevents same from 
propagating directly into the nozzle throat and therefore obviates the 
problem encountered with the prior art wherein a pocket of poorly 
carburized/rich mixture undergoes combustion therein. 
The orientation of the nozzle throat also reduces the surface area of the 
wall portion 102 against which the injected fuel impinges and subsequently 
adheres. Viz., by comparing FIGS. 1 and 2 it will be noted that, with the 
present invention, due to the formation of the deflection surface 100, the 
wall portion 102 of the nozzle throat 6' is more sharply angled with 
respect to direction in which fuel is injected than the corresponding wall 
portion of the prior art. This results in the surface area of the nozzle 
throat 6' upon which fuel impinges being reduced. 
This area reduction in combination with the flame front deflection, 
promotes a further reduction in smoke formation.