Marine propulsion – Means for accomodating or moving engine fluids – Means for handling exhaust gas
Reexamination Certificate
1999-07-08
2001-08-14
Morano, S. Joseph (Department: 3617)
Marine propulsion
Means for accomodating or moving engine fluids
Means for handling exhaust gas
C181S220000, C181S260000
Reexamination Certificate
active
06273772
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of The Invention
The present invention relates generally to devices and methods for silencing engines and, more particularly, to silencers for engines used in a marine environment that employ water cooling of the exhaust gas.
1. Related Art
One technique for silencing engines, particularly those used in a marine environment, is to add water (usually the engine cooling water) to the engine's exhaust gas. Typical applications are marine propulsion engines and electric generators for use in a marine environment. Discharge of the resulting mixture of exhaust gas and water is straightforward in applications in which the engine is situated above the waterline. In these cases, the water and gas mixture may simply be downwardly directed through a pipe for discharge through the vessel's hull. The downward angling of the pipe is provided so that water does not flow back through the pipe and into the engine.
However, in some applications the engine is located below the waterline, such as in some sailboats or displacement power boats. In those applications in which water is not mixed with the exhaust gas, and thus the cooling and silencing benefits of mixing with water are foregone, the hot gas may simply be directed upward and discharged above the waterline. Typically, before discharge, the hot gas is silenced by a device that may be similar to an automotive muffler. In those applications in which water is mixed with the exhaust gas at the engine, the resulting mixture must be lifted above the waterline and then directed downward for discharge through the hull. The vertical distance that the mixture must be lifted may vary between a few inches to ten feet or more.
A device commonly referred to as a “waterlift silencer” has been developed to cool and silence the exhaust gas and to lift the mixture of exhaust gas and water above the waterline. In a waterlift silencer, the mixture is introduced into a chamber (or series of chambers). The expansion of the mixture into the volume of the chamber reduces the acoustic energy of the exhaust. An exit tube conventionally is provided through which the mixture is expelled from the chamber.
One such conventional waterlift silencer is described in U.S. Pat. No. 3,296,997 to Hoiby, et. al. In the Hoiby device, the mixture of cooling water and exhaust gas is introduced into a chamber through an inlet pipe. An exit tube extends vertically through the top of the chamber. The bottom of the exit tube is spaced from the bottom of the chamber so that the mixture may enter the bottom of the tube and be expelled. As described by Hoiby, the gas separates from the water in the chamber and, when the dynamic pressure in the chamber is such as to depress the water level to the bottom of the tube, the gas escapes in a high velocity flow through the bottom of the tube and out of the chamber. The kinetic energy of the gas escaping through the tube partially atomizes the water, according to Hoiby, and entrains the atomized liquid particles. The entrained liquid is thus carried, along with the exhaust gas, up through the exit tube. A similar design is shown in U.S. Pat. No. 5,554,058 to LeQuire.
U.S. Pat. No. 2,360,429 to Leadbetter is one type of silencer that uses water to silence exhaust gas and includes multiple chambers. Other designs of marine silencers employing water silencing using multiple chambers are described in U.S. Pat. No. 5,147,232 to Miles, et al. (including a list of patents related to silencers for marine engines; see column
1
). In the silencers described in Miles, multiple intermediate exhaust tubes are provided for carrying exhaust gas between chambers, and multiple outlet exhaust passageways are provided for expelling exhaust gas from the silencer. The silencer described in U.S. Pat. No. 2,498,979 to Bourne also shows multiple chambers and multiple pipes for expelling exhaust gas.
SUMMARY OF THE INVENTION
In some embodiments, the present invention is a waterlift silencer for reducing the acoustic energy of a fluid mixture of exhaust gas and a liquid coolant, and for expelling the mixture from above the silencer. These embodiments are particularly well suited for limiting back pressure in applications in which the exhaust gas flow rate may vary, as it typically does with engine speed. Often, the exhaust gas is produced by a marine engine or a generator used in a marine environment, but the source of the exhaust gas may be any of a variety of devices. For convenience, reference hereafter often is made to the speed of an engine, back pressure exerted on an engine, and so on. It will be understood, however, that the word “engine” is used broadly to refer to any device generating the exhaust gas operated upon by the waterlift silencer.
The waterlift silencer of these embodiments includes a holding chamber that holds the fluid mixture. The silencer also has first and second first mixture-expelling conduits, each of which has a bottom portion disposed within the holding chamber. The fluid mixture may be dynamically lifted out of the holding chamber and silencer through the conduits so that, typically, the mixture may be expelled from a point above the waterline. Thus, a usual application is one in which an engine is located below the waterline of a marine vessel. Also included in the waterlift silencer are means for sequentially operating the first and second mixture-expelling conduits.
The word “dynamic,” and grammatical variants thereof, are used in this context to mean that the fluid mixture, in a partially atomized state, is lifted up into a mixture-expelling conduit due to dynamic effects, as further described below. Even when these dynamic effects are not present, the fluid mixture may nonetheless rise to a certain level in the conduit as determined by the static pressure in the holding chamber. The fluid mixture may even be forced to flow through the conduit if the static pressure is high enough. In these cases, however, fluid droplets typically are not partially atomized, and the flow is substantially due to static effects. In contrast, dynamic lifting occurs when the velocity of the exhaust gas at the bottom opening of a conduit is high enough to partially atomize fluid droplets and entrain them in the flow. Dynamic effects at the inlet of the conduit determine the water level that the fluid mixture will reach in this partially atomized state such that, if the exhaust gas flow velocity is high enough, the fluid mixture is lifted up and flows through the conduit. Thus, the fluid mixture may be lifted above the silencer so that, for example, it may be expelled above the waterline in a marine environment. As noted below, the flow velocity of the exhaust gas generally is directly proportional to the exhaust gas volume flow rate into the holding chamber, which generally increases with increasing engine speed. Thus, the fluid mixture will be dynamically lifted upward and out of the holding chamber and the silencer in a partially atomized state at sufficiently high engine speeds, i.e., when the exhaust gas volume flow rate is high enough to create dynamic effects at the inlet of a conduit. Under these conditions, a mixture-expelling conduit may be referred to herein as being “dynamically operative.”
Typically as used herein, the phrase “sequentially operating,” and grammatical variants thereof, mean that first a first mixture-expelling conduit is dynamically operative, then a second mixture-expelling conduit is dynamically operative while the first mixture-expelling conduit may or may not continue to be dynamically operative. If additional mixture-expelling conduits are present in an embodiment, then a third mixture-expelling conduit is dynamically operative while both the first and second mixture-expelling conduits may or may not continue to be dynamically operative, and so on. Most generally, mixture-expelling conduits that are described herein as being sequentially operative may illustratively be assumed to be not exclusively dynamically operative. However, in some implementations, mixture-expelling co
Morano S. Joseph
Smullin Corporation
Wolf Greenfield & Sacks P.C.
Wright Andrew
LandOfFree
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