Internal-combustion engines – Two-cycle – Rear compression
Patent
1987-03-11
1988-12-13
Myhre, Charles J.
Internal-combustion engines
Two-cycle
Rear compression
123305, F02B 3304
Patent
active
047902701
DESCRIPTION:
BRIEF SUMMARY
This application relates to delivering fuel to an engine by injecting the fuel directly into the combustion chamber.
In order to maintain the exhaust emissions of an engine within the prescribed limit it is desirable to effectively distribute the fuel within the combustion chamber. One mode of reducing exhaust emissions is to ensure that the fuel is exposed to sufficient air to burn the fuel and so avoid release of unburnt hydrocarbons in the exhaust.
This problem is more pronounced in engines operating on the two stroke cycle because of the late timing of the closure of the exhaust port in the compression stroke. If the fuel is delivered a significant time before final closing of the exhaust port, some fresh fuel may escape to the exhaust, particularly at low engine speeds. However if injection is delayed until after the exhaust port is fully closed, there is limited time available to effect delivery and obtain effective dispersion of the fuel within the combustion chamber before ignition. This is of importance at high fuelling rates, and particularly at high engine speed which creates a further restraint.
Characteristics of the spray of the fuel droplets issuing from a nozzle into a combustion chamber also have a major effect on the efficiency of the burning of the fuel, which in turn affects the stability of the operation of the engine, the fuel efficiency and the exhaust emissions.
In order to optimise these features in a spark ignited engine the desirable characteristics of the spray pattern of the fuel issuing from a nozzle include small fuel droplet size, controlled penetration of the fuel spray into the combustion chamber and, at least at low engine loads, a relatively rich mixture in the vicinity of the spark plug. More specifically in the control of the harmful components of the engine exhaust, it is desirable to control the placement of the fuel within the gas charge in the combustion chamber to meet a number of different parameters. Ideally the fuel should be distributed in the gas charge so that the resultant fuel-air mixture is readily ignitable at the spark plug, all the fuel has access to sufficient air to burn completely, and the flame is at a sufficient temperature to extend to all the fuel before being extinguished. There are other factors that must also be considered, such as combustion temperatures that may promote detonation, or the formation of undesirable contaminants in the exhaust gas.
It is therefore the principle object of the present invention to provide a method and apparatus for delivering fuel to an internal combustion engine that will assist in achieving the required level of fuel economy and exhaust emissions.
With this object in view there is provided a method of feulling a two stroke cycle spark ignited engine having a cylinder in which a combustable charge is prepared, and a cylinder head closing one end of said cylinder and having a cavity therein communicating with the cylinder, an ignition means to ignite the combustable charge in said cavity, a piston supported to reciprocate in said cylinder, and an exhaust port in said cylinder spaced from said cylinder head, said method comprising injecting a metered quantity of fuel into the cylinder at a location between the level of the exhaust port and the cylinder head and in a manner to direct part of the fuel in a direction to enter the cavity in the cylinder head and to direct another part of the fuel into that part of the cylinder on the opposite side of a diametral plane of the cylinder at the location of injection of the fuel to the cylinder.
Conveniently the fuel is divided into a number of streams extending into the cylinder, one said stream delivering fuel towards the cylinder head, to enter the cavity and at least one said stream being directed downwardly and across the cylinder.
The injection of the fuel may be effected through the side wall of the cylinder through an injector nozzle at a location which will result in the nozzle being covered by the piston during a portion of the engine cycle.
The nozzle may be of
REFERENCES:
patent: 1903381 (1933-04-01), Kennedy
patent: 2164234 (1939-06-01), Erren
patent: 3687118 (1972-08-01), Nomura
patent: 3881454 (1975-05-01), Jaulmes
patent: 4068629 (1978-01-01), Hooper
patent: 4579093 (1986-04-01), Eanes
Ahern Steven R.
McKay Michael L.
Myhre Charles J.
Okonsky David A.
Orbital Engine Company Proprietary Limited
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