Internal-combustion engines – Two-cycle – Whirl through piston-controlled ports
Patent
1989-12-06
1991-09-17
Okonsky, David A.
Internal-combustion engines
Two-cycle
Whirl through piston-controlled ports
123 73PP, 123 73AA, 123316, F02B 7502
Patent
active
050484737
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a method and apparatus for equipping a two-stroke internal combustion (ic) engine of the type having reciprocating pistons and self supercharging by a post-charging effect, and in particular, although not exclusively, an engine having at least one single-acting cylinder.
2. Prior Art
In the prior art, a large number of proposals already exist for using the direct action of the gases leaving a cylinder to compress and introduce a reserve of air into a cylinder at an appropriate moment in the cycle in order to supercharge it.
Most of these proposals make use of the direct action of the exhaust gases from one cylinder, and vice versa, with the angular phase difference between the cylinders communicating in this way being judiciously selected (see Swiss patent No. CH 593.420).
Proposals for making the energy of exhaust gases in a cylinder act directly on an air reserve for improving the charging and efficiency of the same cylinder are much rarer, particularly if, for obvious reasons of efficiency, account is taken only of those proposals which enable the phases of transferring pressure from the cylinder to the air reserve and then to the cylinder to take place in a closed space within the system under consideration, in order to avoid any loss of energy to the outside.
For reasons of convenience, the set of components constituting the above-mentioned system is referred to below as a "compressor system".
In general, the term "scavenging air" is used below to specify the scavenging agent used for renewing the burnt gases in a cylinder, regardless of whether it is constituted by pure air or by some other mixture of fuel and oxidizer.
The number of proposals is even smaller if account is taken solely of those which provide a post-charging effect as opposed to a compression of the entire gas quantity admitted to the cylinder (which is difficult to achieve in a two-stroke cycle unless the exhaust back pressure is simultaneously increased).
The term "post-charging" is used to mean injecting an additional quantity of air into the cylinder after scavenging, and after the exhaust ports have been closed.
The advantage of post-charging has been known for a long time, in particular, for use in the two-stroke cycle.
For a given amount of external compression work applied to the quantity of air, post-charging provides an increased overall charging by raising air purity. This is because the mass of residual gases not expelled at the end of the scavenging phase remains unaltered during the post-charging phase and therefore becomes relatively smaller compared with the total mass of air contained in the cylinder after the post-charging effect. This is equivalent to improving the scavenging efficiency and to making better utilization of the scavenging air.
One such apparatus for a single cylinder post-charging two-stroke engine is described in U.S. Pat. No. 1,362,080 and is shown in FIG. 5 thereof.
In said apparatus, the compressor system comprises a supply of air external to the engine and connected at one of its ends to a volume constituting an anti-chamber to said air reserve and to a duct communicating with a source of scavenging air (via a three-way valve), and at its other end to the admission pipe leading to the admission port of the cylinder (controlled by fluid-flow control means, e.g. of the valve type, housed in the cylinder head), and to a first exhaust duct for evacuating the exhaust gases to the outside (again via a three-way valve), after they have been used.
The volume forming an anti-chamber to the air reserve is itself connected at its upstream end to a non-return valve located immediately downstream from a pre-exhaust opening connected to a pre-exhaust port (controlled by an opening provided in the liner) which is distinct from the exhaust port per se (also controlled by an opening provided in the liner) opening out to a second exhaust duct which is the exhaust duct from the cylinder.
Following the various sequences
REFERENCES:
patent: 1362080 (1920-12-01), Chorlton
patent: 2041708 (1936-05-01), Harper
patent: 4091775 (1978-05-01), Curtil
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