Internal-combustion engines – Precombustion and main combustion chambers in series – Precombustion chamber mounting means
Reexamination Certificate
1999-10-19
2001-01-30
Kwon, John (Department: 3747)
Internal-combustion engines
Precombustion and main combustion chambers in series
Precombustion chamber mounting means
C123S276000, C123S279000
Reexamination Certificate
active
06178942
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Field of the Invention
This invention relates to a piston configuration for a reciprocating piston, direct injected internal combustion engine.
B. Related Technology
Various combustion chamber configurations for direct injected, reciprocating piston internal combustion engines are described and utilized in the prior art. In particular, pistons including a central recess or bowl for receiving the major portion of each fuel and air charge of each combustion cycle and into which the fuel is injected by a fuel injector are commonly utilized in diesel cycle (compression-ignition) and Otto cycle (spark-ignited) engines.
It is well known that the exhaust stream of diesel cycle engines in particular may contain high levels of particulate matter (p.m.) (i.e., soot and soluble hydrocarbons) that are observable as dark smoke discharged from the engine exhaust, such smoke containing various solids or particulates as well as gaseous substances, all of which contribute to undesirable atmospheric pollution. Government regulatory bodies have enacted various laws and regulations reducing the permitted amount of smoke and particulate matter that may be contained in a diesel engine exhaust stream with the objective of improving the quality of atmospheric air, particularly in urban areas or other areas exposed to high concentrations of pollutants caused by engine exhaust emissions.
Reducing the discharge of p.m. from such engines has become a major objective of diesel engine manufacturers world wide and various attempts have been made to achieve more complete combustion of the relatively heavy, high cetane fuels typically combusted in diesel cycle engines. Much attention, for example, has been given to the manner in which the fuel is injected and atomized in the combustion chamber of the engine and other approaches to the problem of unburned hydrocarbons have been taken with various results.
A specific combustion chamber arrangement that has been found to reduce smoke and particulate emissions from diesel engines is described in U.S. Pat. Nos. 4,898,135 granted Feb. 6, 1990, and U.S. Pat. No. 5,322,042 granted Jun. 21, 1994, both of which are assigned to the assignee of the present invention. In accordance with the aforesaid patents, one or more small reaction chambers are located adjacent the piston recess and communicate with the recess through openings that may be configured as slots or discrete orifices. The orifices are configured to produce a lag between gaseous flow of fuel and air into the reaction chamber and the discharge of partially reacted fuel radicals and intermediate species from the reaction chamber into the piston recess area. This produces a delayed infusion or “seeding” of radicals (the term radicals is always intended to include intermediate species) into the piston recess to the extent that a supply of radicals is produced in the reaction chamber in a first combustion cycle and part of the radicals are discharged into the next succeeding pre-ignition fuel air mixture to promote desirable ignition characteristics in the mixture and more complete combustion of the fuel of the mixture.
In accordance with the prior art as described in the aforesaid patents, the various arrangements of orifices produced a high degree of interaction between the reaction chamber and the piston recess area each combustion cycle and further produced a reduction in smoke and particulate emissions discharged into the exhaust stream of the engine. However, in order to meet increasingly stringent emission standards for diesel engines, further improvements were needed to promote more complete combustion of the fuel injected into the engine combustion chamber.
BRIEF SUMMARY OF THE INVENTION
The present invention provides an improvement over the prior art described in U.S. Pat. Nos. 4,898,135 and 5,322,042 in the form of an improved arrangement of discrete orifices that provide communication between the reaction chambers described in the previous patents and the piston recess or bowl area where most and usually all of the fuel is injected during each combustion cycle of the engine. In accordance with the present invention, the orifices are arranged in an array so as to provide at least a first row of aligned orifices extending along the central cross-sectional area of the respective reaction chamber with which they are associated and at least a second row of aligned orifices extending diagonally or vertically along the reaction chamber cross-sectional area, with the first and second aperture rows intersecting each other.
At least some of the orifices of the second or diagonal row are located for tangential communication with the curvilinear cross-section of the respective reaction chamber.
The manner of locating the orifices in the reaction chambers is where the present invention introduces the breaking of symmetry into the design process. Use of concepts from chaos theory for locating orifices allows a greater degree of control of reactions than previously possible for the partial oxidation process within the reaction chamber and greater control of timing of the issuing of the jets communicating with the piston recess. The net result is an appreciable improvement in soot reduction enabled by the jet interaction with the soot cloud formed in each fuel injection plume, as will be discussed below.
The emergence of the concept of “space” (where location or distance has significance) in which location or distance could not previously be perceived in an intrinsic manner is called “symmetry breaking”. One of the properties of such a system is the transition from simple random molecular behavior (where, within a simple system, the random behavior is the same with no opportunity to determine direction or location from the events taking place in the system) to a system with order and coherence (i.e., when a location can be determined due to fixed patterns of molecular behavior).
The advantage of symmetry breaking is that systems possessing this capability show perfect reproducibility, therefore stability in time for a repetitive process. Also of importance is that a region or system characterized by symmetry breaking is defined as a
Dissipative Structure
, which helps in characterizing the system under consideration. When dealing with dissipative structures we refer to the physics of far-from-equilibrium and self-organizational systems where under appropriate thermodynamic conditions a multitude of phenomena on a macroscopic scale can occur in the form of spatial patterns or temporal rhythms.
A combustion process using the distribution of reaction chambers interacting with the piston recess via the jet fluxes emanating from them is just one of many examples where thermal convection currents can drive chemical reactions to new auto-catalytic levels able to reduce soot and control NO formation well beyond levels previously attained.
The partial oxidization process in the relatively small piston reaction-chamber volume, where the volume of a reaction chamber in a single piston in a combustion chamber in which fuel is injected by a fuel injector having multiple orifices is given by:
k
(V
tdc
)
umber of injector orifices
where k is a number between 0.02 and 0.05 and V
tdc
is the total top dead center volume of the main combustion chamber and ranges from 0.3 to 0.9 cc, depending on engine size, is relatively easy to control compared to the actual combustion process in a large open combustion bowl or piston recess. The combustion bowl volume is typically at least 150 times the volume of the volume of a single reaction chamber. In the combustion bowl the elements related to control of combustion are relatively coarse or crude, for example, swirl, squish, compression ratio, injection pressure, number of injectors, injector location and use of Exhaust Gas Recirculation (ERG).
In the reaction chambers the elements allowing control of the speed of the partial oxidation process are volume, shape, material, as well as orifice size, location, number, and orifice length all of which also affect
di Priolo Carlo Leto
Pouring Andrew A.
Bacon & Thomas PLLC
Kwon John
Sonex Research Inc.
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