Patent Publication Number: US-9403588-B1

Title: Open loop cooling systems and methods for marine engines

Description:
FIELD 
     The present disclosure relates to marine engines, open loop cooling circuits for marine engines, and methods of cooling marine engines, including outboard motors. 
     BACKGROUND 
     The following U.S. Patents are incorporated herein by reference. 
     U.S. Pat. No. 7,370,611 discloses a cooling system for a marine propulsion device that provide a bypass loop around a cooling pump that allows the flow of cooling water through certain components to be reduced or increased as a function of the temperature of those components while causing a full flow of cooling water to flow through other selected heat emitting devices. Using this configuration of components and bypass conduits, the operating condition of the cooling water pump can be continually monitored, including the condition of its flexible vanes. By observing the effective cooling capacity of the system under conditions with the bypass valve open and closed, the effectiveness of the cooling water pump can be assessed and a suggestion of maintenance can be provided. 
     U.S. Pat. No. 7,476,135 discloses a cooling system for a marine vessel that is configured to allow all cooling water to flow out of the cooling circuit naturally and under the influence of gravity when the marine vessel is removed from the body of water. All conduits of the cooling circuit are sloped downwardly and rearwardly from within the marine vessel to an opening through its transom. Traps are avoided so that residual water is not retained within locations of the cooling system after the natural draining process is complete. The opening through the transom of the marine vessel is at or below all conduits of the cooling system in order to facilitate the natural draining of the cooling system under the influence of gravity and without the need for operator intervention. 
     U.S. Pat. No. 7,503,819 discloses a cooling system for a marine propulsion device that provides a closed portion of the cooling system, which recirculates coolant through the engine block and cylinder head, the exhaust manifold, and the exhaust elbow. It provides a pressure relief cap connected to the exhaust elbow and a low velocity portion of the coolant jacket of the exhaust elbow to facilitate the release of gas and coolant when pressures exceed a preselected magnitude. 
     U.S. Pat. No. 7,585,196 discloses a cooling system for a marine propulsion device that provides a transom opening that is sufficiently low with respect to other components of the marine propulsion device to allow automatic draining of all cooling water from the system when the marine vessel is removed from the body of water in which it had been operating. The engine cooling passages and other conduits and passages of the cooling system are all located at positions above the transom opening. The system provides automatic draining for a marine cooling system that is an open system and which contains no closed cooling portions. 
     U.S. Pat. No. 8,298,025 discloses cooling systems and methods for hybrid marine propulsion systems. A first cooling circuit is arranged to convey raw cooling water through an internal combustion engine and to at least one drive component of a drive unit for the marine propulsion system. A second control circuit is arranged to convey raw cooling water through an electric motor. The system is arranged such that raw cooling water in the second cooling circuit is conveyed to the first cooling circuit to cool the drive component without cooling the component of the internal combustion engine. 
     U.S. Pat. No. 8,402,930 discloses a cooling system for a marine engine that is provided with various cooling channels and passages which allow the rates of flow of its internal streams of water to be preselected so that heat can be advantageously removed at varying rates for different portions of the engine. In addition, the direction of flow of cooling water through the various passages assists in the removal of heat from different portions of the engine at different rates so that overheating can be avoided in certain areas, such as the exhaust manifold and cylinder head, while overcooling is avoided in other areas, such as the engine block. 
     U.S. Pat. No. 8,479,691 discloses a cooling system for a marine engine provided with various cooling channels which allow the advantageous removal of heat at different rates from different portions of the engine. A split flow of water is conducted through the cylinder head, in opposite directions, to individually cool the exhaust port and intake ports at different rates. This increases the velocity of coolant flow in the downward direction through the cylinder head to avoid the accumulation of air bubbles and the formation of air pockets that could otherwise cause hot spots within the cylinder head. A parallel coolant path is provided so that a certain quantity of water can bypass the engine block and avoid overcooling the cylinder walls. 
     U.S. Pat. No. 8,500,501 discloses an outboard marine drive that includes a cooling system drawing cooling water from a body of water in which the outboard marine drive is operating, and supplying the cooling water through cooling passages in an exhaust tube in the driveshaft housing, a catalyst housing, and an exhaust manifold, and thereafter through cooling passages in the cylinder head and the cylinder block of the engine. A 3-pass exhaust manifold is provided. A method is provided for preventing condensate formation in a cylinder head, catalyst housing, and exhaust manifold of an internal combustion engine of a powerhead in an outboard marine drive. 
     U.S. Pat. No. 8,540,536 discloses a cooling system for a marine engine having an elongated exhaust conduit comprising a first end receiving hot exhaust gas from the marine engine and a second end discharging the exhaust gas; and an elongated cooling water jacket extending adjacent to the exhaust conduit. The cooling water jacket receives raw cooling water at a location proximate to the second end of the exhaust conduit, conveys raw cooling water adjacent to the exhaust conduit to thereby cool the exhaust conduit and warm the raw cooling water, and thereafter discharges the warmed cooling water to cool the internal combustion engine. 
     SUMMARY 
     This Summary is provided to introduce a selection of concepts that are further described below in the Detailed Description. This Summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter. 
     In certain examples, systems are for cooling a marine engine that is operating in a body of water. The systems include an open loop cooling circuit for cooling the marine engine, wherein the open loop cooling circuit is configured to convey cooling water from the body of water to the marine engine so that heat is exchanged between the cooling water and the marine engine. A pump is configured to pump the cooling water from upstream to downstream through the open loop cooling circuit. The open loop cooling circuit comprises an upstream inlet that is configured to receive the cooling water from the body of water and a downstream outlet that is configured to discharge the cooling water back to the body of water after the heat has been exchanged between the cooling water and the marine engine. A heat exchanger is configured to cause an exchange of heat between the cooling water located upstream of the marine engine and the cooling water located downstream of the marine engine to thereby warm the cooling water located upstream of the marine engine prior to cooling the marine engine. Methods are for cooling the marine engine. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Examples of marine engines, open loop cooling circuits for marine engines, and methods of cooling marine engines, including outboard motors, are described with reference to the following figures. The same numbers are used throughout the figures to reference like features and like components. 
         FIG. 1  is a schematic of an open loop cooling system for a marine engine in an outboard motor. 
         FIG. 2  is a schematic of another embodiment of an open loop cooling system for a marine engine. 
         FIG. 3  is a schematic of another embodiment of an open loop cooling system for a marine engine. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
       FIG. 1  depicts one example of a system  10  for cooling a marine engine  12  that is operated in a body of water  14 . In this example, the marine engine  12  is part of an outboard motor  11 ; however the concepts of the present disclosure are not limited for use with outboard motors and can also be utilized with other propulsion devices for marine vessels, such as inboard motors, stem drives and/or the like. The marine engine  12  is an internal combustion engine having a cylinder block  16  and a cylinder head  18 . An exhaust manifold  20  conveys exhaust gases from the marine engine  12  to an exhaust tube  22  that extends into a midsection or drive shaft housing  24  of the outboard motor  11 . An oil sump  26  is located below the marine engine  12  and is configured to contain oil for lubrication of the marine engine  12 . The outboard motor  11  further includes a gear case housing  28  that depends from the drive shaft housing  24  and contains transmission gears (not shown) and a propeller shaft (not shown) for driving one or more propellers  29  into rotation based upon operation of the marine engine  12 . 
     The system  10  includes an open loop cooling circuit  30  that has one or more conduits and/or passages and/or cooling jackets that are connected together and configured to convey cooling water from the body of water  14  to the marine engine  12  so that heat is exchanged between the cooling water and the marine engine  12  and various components of the marine engine  12  and outboard motor  11  and then back to the body of water  14 . The open loop cooling circuit  30  includes and upstream inlet  32  that is configured to receive the cooling water from the body of water  14  and a downstream outlet  34  that is configured to discharge the cooling water back to the body of water  14  after the heat has been exchanged between the cooling water and the marine engine  12 . A pump  36  is configured to pump the cooling water from upstream to downstream, as shown at arrows  15 , through the open loop cooling circuit  30 . 
     In this example, the upstream inlet  32  and downstream outlet  34  both are located in the gear case housing  28 ; however the locations of the upstream inlet  32  and downstream outlet  34  can vary from that shown. The open loop cooling circuit  30  includes an exhaust tube cooling jacket  38  disposed on the exhaust tube  22 . The exhaust tube cooling jacket  38  is configured to convey the cooling water towards the marine engine  12  and adjacent to an outside surface of the exhaust tube  22  so that heat is exchanged between the cooling water contained in the exhaust tube cooling jacket  38  and the exhaust gases flowing through the exhaust tube  22 , thereby cooling the exhaust gases. The open loop cooling circuit  30  further includes an exhaust manifold cooling jacket  40  disposed on the exhaust manifold  20 . The exhaust manifold cooling jacket  40  is configured to convey the cooling water adjacent to an outside surface of the exhaust manifold  20  so that heat is exchanged between the cooling water in the exhaust manifold cooling jacket  40  and the exhaust gases flowing through the exhaust manifold  20 , thereby cooling the exhaust gases. Cooling systems incorporating these and other features are disclosed in U.S. Pat. Nos. 8,402,930; 8,479,691; and 8,540,536, which are incorporated herein by reference. 
     The open loop cooling circuit  30  further includes cooling passages  42  in the cylinder block  16  and cylinder head  18 . Examples of such cooling passages are provided in the incorporated U.S. Pat. Nos. 8,402,930 and 8,540,536. The cooling passages  42  are configured to carry cooling water through the cylinder block  16  and cylinder head  18  so that heat is exchanged between the cooling water in the cooling passages  42  and the cylinder block  16  and cylinder head  18 , to thereby cool the cylinder block  16  and cylinder head  18 . Once the cooling water is discharged from the cooling passages  42 , it flows through a thermostat  44 , which is configured to open and close based upon the temperature of the cooling water. The thermostat opens to allow flow of cooling water out of the cooling passages  42  and to the downstream outlet  34 , as shown at arrows  15 . 
     Through research and experimentation, the present inventors have determined that the cooling of the exhaust gases flowing through the exhaust manifold  20  and exhaust tube  22 , via the exhaust tube cooling jacket  38  and the exhaust manifold cooling jacket  40 , can cause condensation of water from the exhaust gases, which can accumulate in the exhaust manifold and/or exhaust tube  22 . Such accumulation of condensation has been found to adversely affect operation of the marine engine  12  and/or operation of one or more catalysts  41  disposed in the exhaust system for the marine engine  12  and/or operation of sensors  43  in the exhaust system, for example oxygen sensors associated with the one or more catalysts. The catalysts and associated sensors can be located in the exhaust manifold  20  or exhaust tube  22  or other conduits associated therewith. The inventors have recognized this problem and have therefore found it to be desirable to provide a system and method for controlling the temperature of the incoming cooling water conveyed through the noted exhaust tube cooling jacket  38  and exhaust manifold cooling jacket  40 , to thereby prevent such condensation and improve performance of the marine engine  12  and any catalyst and/or sensor associated therewith. 
     According to the present disclosure, the relatively hot cooling water exiting the marine engine  12  passes through a water-to-water heat exchanger  46  and thereby passes energy to the relatively cold cooling water that is pulled from the body of water  14  by the pump  36 . This transfer of energy allows the upstream cooling water to be pre-heated, for example prior to entering the exhaust tube cooling jacket  38 , exhaust manifold cooling jacket  40  and passages  42  in the marine engine  12 . The present inventors have recognized that water temperature will increase most under cold environmental or boundary conditions and at idle engine speed conditions and least under hot environmental or boundary conditions and high engine speed and load conditions. The low speed and temperature conditions provide lower flow rates, which increase water dwell time in the heat exchanger  46 , leading to a larger temperature gradient even with less heat exchange. The cold water temperatures provide a large temperature gradient between the upstream cooling water and the downstream (thermostat discharge) water leading to increased heat exchange, as well. 
     As shown in the example of  FIG. 1 , the system  10  includes a heat exchanger  46  that is configured to cause an exchange of heat between cooling water located upstream of the marine engine  12  and flowing towards the marine engine  12  and cooling water located downstream of the marine engine  12  and flowing away from the marine engine  12 , to thereby warm the cooling water located upstream of the marine engine  12  prior to its cooling of the marine engine  12 . This has been found by the inventors to reduce condensation of the exhaust gases. 
     The location of the heat exchanger  46  can vary. In the examples shown in  FIGS. 1 and 2 , the heat exchanger  46  is located in the midsection or drive shaft housing  24 . In another example the heat exchanger  46  is located in the gear case housing  28 . In another example, shown in  FIG. 3 , the heat exchanger  46  is located adjacent the exhaust tube cooling jacket  38 . In the example of  FIG. 3 , the heat exchanger  46  has shared walls with the exhaust tube cooling jacket  38 . The type of heat exchanger  46  also can vary. In one example, the heat exchanger  46  is a tube-in-tube heat exchanger. In another other example, the heat exchanger  46  is a tube-in-shell heat exchanger. In another example, the heat exchanger  46  is a flat plate counter-flow heat exchanger with or without fins. Other conventional types of heat exchanger  46  can be utilized within the scope of this disclosure. 
     The open loop cooling circuit  30  further includes a bypass passage  48  that conveys cooling water from the open loop cooling circuit  30  through a strainer  50 , past a fuel module  52  and out of a tell-tale  53  on the outboard motor  11 . The bypass passage  48  runs past the fuel module so that an exchange of heat is caused between cooling water in the bypass passage  48  and the fuel module  52 . Another bypass passage  54  carries cooling water from the bypass passage  48  to an exhaust sprayer for spraying cooling water into the exhaust gases carried through the exhaust tube  22 , thereby cooling the exhaust gases. Examples of such an exhaust sprayer are disclosed in the incorporated U.S. Pat. No. 8,540,536. 
     In the example of  FIG. 1 , the bypass passage  48  receives cooling water from the open loop cooling circuit  30  at a location that is downstream of the heat exchanger  46 . In contrast, in the example of  FIG. 2 , the bypass passage  48  receives cooling water from the open loop cooling circuit  30  at a location that is upstream of the heat exchanger  46 . Through experimentation the inventors have found that providing warm water to the bypass passage  48  adjacent the fuel module  52  can adversely affect the fuel module  52 . The example shown in  FIG. 2  eliminates this problem by connecting the bypass passage  54  to the bypass passage  48  at a location that is upstream of the heat exchanger  46 . The example in  FIG. 3  also eliminates this problem by locating the heat exchanger  46  on the exhaust tube  22  adjacent the exhaust tube cooling jacket  38 , as discussed above. The example in  FIG. 3  is also a more efficient use of space in the gear case housing  28 . 
     In the above description, certain terms have been used for brevity, clarity, and understanding. No unnecessary limitations are to be inferred therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed. The different systems and method steps described herein may be used alone or in combination with other systems and methods. It is to be expected that various equivalents, alternatives and modifications are possible within the scope of the appended claims. Each limitation in the appended claims is intended to invoke interpretation under 35 U.S.C. §112(f), only if the terms “means for” or “step for” are explicitly recited in the respective limitation.