Internal-combustion engines – Precombustion and main combustion chambers in series – Having combustible mixture forming means
Patent
1991-12-06
1993-05-11
Wolfe, Willis R.
Internal-combustion engines
Precombustion and main combustion chambers in series
Having combustible mixture forming means
123257, F02B 1910
Patent
active
052092003
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the combustion process in internal combustion engines particularly two stroke cycle engines and specifically relates to the fuel/air preparation within the engine and distribution of fuel and air mixture in the combustion chamber.
In the control of contaminates in the exhaust gas of an internal combustion engine, it is desirable to obtain effective distribution of the fuel in the dilutant charge within the cylinder, the dilutant charge being made up of air or a mixture of air and retained exhaust gas. However, in the preparation of the combustible charge, by the introduction of fuel into the dilutant charge, it is desirable to prevent the fuel being distributed to parts of the combustion chamber distant from the point of ignition Wide distribution of the fuel in the dilutant charge creates local fuel charge mixtures which are lean and therefore difficult to ignite and/or maintain the combustion. Combustible lean mixtures promote the production of NOx, as combustion is taking place in an oxidant rich mixture, and non-combustible lean mixtures lead to the emissions of hydrocarbons in the form of unburned fuel in the exhaust gas.
The distribution of the fuel in the combustion chamber is of particular importance under low engine load conditions when the quantity of fuel being delivered per cycle is relatively small and therefore the distribution thereof must be contained in order to establish an effectively ignitable and combustible mixture. However under high engine loads it is desirable to burn up substantially all oxidant in the dilutant charge which may be achieved by obtaining a greater degree of distribution of the fuel within the dilutant charge so that the fuel is exposed to sufficient oxidant providing combustible fuel charge mixtures, to maximise air utilisation and achieve effective combustion of the relatively greater quantity of fuel delivered to the engine per cycle at the high engine loads.
It has previously been proposed to endeavour to control the distribution of the fuel in a premixed charged engine by controlling the movement of the charge upon entry into the combustion chamber so that a degree of stratification of the fuel is obtained in the combustion chamber. This control of the premixed charge is difficult to obtain in a two stroke cycle engine as the gas movement in the combustion chamber is complex, and may experience many changes within that part of the engine cycle during which the air and fuel mixture is entering the combustion chamber, while at the same time the exhaust gases are leaving the combustion chamber.
There has been proposed in the applicant's prior U.S. Pat. No. 4,719,880, wherein the fuel is injected directly into the engine combustion chamber and a cavity is provided in the cylinder head with the fuel being injected into that cavity. In that prior proposal, the fuel injector system is of a low penetration type so that the fuel is substantially contained within the cavity in the cylinder head.
Further the cavity in the cylinder head is shaped to establish a circular motion of the charge in the cylinder so the fuel as it enters the cavity is carried by the air motion from the injector to the point of ignition. This combustion system limits the distribution of the fuel within the engine combustion chamber so that the fuel/air mixture presented to the point of ignition is of a readily ignitable and combustible character.
The combustion system as proposed in the above referred to U.S. Patent is particularly effective under light to medium engine load conditions where the fuelling rate is comparatively low. However, as the fuelling rate increases to meet higher engine loads, it is necessary to obtain a greater degree of distribution of the fuel within the combustion chamber so that the fuel is exposed to substantially all the oxidant throughout the combustion chamber, or at least sufficient oxidant, providing combustible fuel charge mixtures to effect complete combustion of the fuel whilst also containing the fuel to provide a readily ignitable and
REFERENCES:
patent: 2851019 (1958-09-01), Fleming et al.
patent: 3452726 (1969-07-01), Szymanski
patent: 3937188 (1976-02-01), Wrigley
patent: 4091772 (1978-05-01), Heater et al.
patent: 4719880 (1988-01-01), Schlunke et al.
Ahern Steven R.
da Silva Jorge M. P.
Orbital Engine Company (Australia) Pty. Limited
Wolfe Willis R.
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