Patent Publication Number: US-2002005269-A1

Title: Engine coolant cooler

Description:
FIELD OF THE INVENTION  
       [0001] The present invention relates to an improved engine coolant cooler, for cooling a marine engine, which marine engine is used to drive a water jet.  
       SUMMARY OF THE INVENTION  
       [0002] It is an object of the present invention to provide a marine engine coolant cooler in which the above disadvantages are reduced or substantially obviated. It is a further object of the present invention to provide an improved method of cooling marine engine cooling coolant.  
       [0003] In accordance with a first aspect of the invention, there is provided a heat exchanger for cooling the coolant of a marine engine used to drive a water jet, characterized in that the heat exchanger comprises a stator of the water jet, the stator having at least one stator vane, which stator vane is hollow and has an inlet for hot coolant from the marine engine and an outlet for cooled coolant.  
       [0004] In a preferred embodiment of the heat exchanger, the stator comprises a plurality of substantially circumferentially equi-spaced stator vanes projecting generally radially outwardly from a central region, each of the vanes comprising a duct extending from a radially outer end of the vane to a radially inner end of the vane through which the engine coolant can flow. Preferably the heat exchanger further comprises an inlet manifold for receiving hot coolant from the engine and an outlet manifold for receiving cooled coolant from the stator. The arrangement may be such that the inlet manifold is in fluid connection with the radially outer end of the ducts of some of the vanes, and the outlet manifold is in fluid connection with the radially outer end of the ducts of the remainder of the vanes, the radially inner ends of the ducts of all the vanes being fluidly interconnected such that engine coolant can flow from the inlet manifold to the outlet manifold through the vanes.  
       [0005] It is also preferred that the or each stator vane is made of aluminum. In a particularly preferred embodiment the stator is cast.  
       [0006] The marine engine coolant may be any suitable fluid, for example water or a water/glycol mixture.  
       [0007] In accordance with a second aspect of the invention, there is provided a method of cooling the coolant of a marine engine used to drive a water jet, the water jet having a stator and the method comprising passing the engine coolant through a stator vane of the stator.  
       [0008] The invention further provides a stator adapted for use in the heat exchanger according to the first aspect of the invention or for use in the method of cooling the coolant of a marine engine according to the second aspect of the invention.  
       [0009] A marine engine coolant cooler in accordance with the invention has a large surface area for effective cooling and is less susceptible to cooling passage blockage by marine debris than known coolers. It is also an advantage that the position of the stator in the water jet ensures a supply of high velocity, high turbulence raw water flow over the vane(s) providing for extremely efficient heat transfer in the heat exchanger. Furthermore, integration of the cooler into the jet drive saves weight and space compared to the use of a separate cooler.  
       [0010] Other applications of the present invention will become apparent to those skilled in the art when the following description of the best mode contemplated for practicing the invention is read in conjunction with the accompanying drawings. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0011] The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein:  
     [0012] An embodiment of a marine engine coolant cooler will now be described, by way of example only, with reference to the accompanying drawings, in which:  
     [0013]FIG. 1 is a schematic drawing of an embodiment of a marine engine coolant cooler shown in a cooling system with a marine engine; and  
     [0014]FIG. 2 is a section on the line A-A of FIG. 1, showing the stator in detail. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
     [0015] As can be seen from FIG. 1, a marine drive system shown generally at  10  comprises a marine engine  2 , an impeller  4  and a drive shaft  6 , one end of which is attached to the output of the marine engine  2  and the other end of which is drivingly attached to the impeller  4 . A jet pump shown generally at  8  comprises a housing  12  surrounding a duct  14  in which the impeller  4  is located. The duct  14  comprises a duct inlet  16  located upstream of the impeller  4  and a duct outlet  18  located downstream of the impeller  4 . The direction of water flow in the duct  14  is shown by arrows.  
     [0016] A stator  20 , made of aluminum or aluminum alloy, is fixedly mounted in the duct  14  between the impeller  4  and the duct outlet  18  and comprises a set of hollow vanes  26 . Preferably, the stator is cast but it can also be made from sheet material. The construction of the stator  20  is shown in more detail in FIG. 2. The hollow portions of the vanes  26  form a series of ducts  28 . The ducts  28  in the vanes  26  radiating from one side of the stator  20  are connected to a first manifold  30  with an inlet  22  for receiving an incoming flow of hot engine coolant coming from the engine  2 . All of the ducts  28  are connected about a central manifold  34  positioned axially in the duct  14 . The ducts  28  in the vanes  26  radiating from the other side of the stator  20  are connected to a second manifold  32  with an outlet  24 , for returning an outgoing flow of cooled engine coolant to the engine. The engine coolant is preferably either water or a mixture of water and glycol, but may be of any suitable liquid.  
     [0017] In operation, the marine engine  2  drives the drive shaft  6  either directly or via a gear box (not shown). As the drive shaft  6  rotates, it drives the impeller  4  which generates a flow of water along the duct  14 , through the stator  20  and out through the outlet  18 . The vessel in which the drive system  10  is installed is thus propelled through the water. Therefore whenever the vessel is moving through water, cold water from the river, lake or other expanse of water in which the vessel is floating, passes over the stator  20 . In some water jets, there may be more than one stator  20 .  
     [0018] Engine coolant is pumped from an outlet of the engine  2  through the inlet  22  of the first manifold  30 , into the series of ducts  28  linked by the central manifold  34 , into the second manifold  32 , and then out through the outlet  24  and back to an inlet of the engine. A closed circulating path between the engine  2  and the stator  20  thus operates as a heat exchanger, allowing hot engine coolant entering the stator  20  at the coolant inlet  22  to be cooled by the water in the duct  14  before it leaves the stator  20  at the coolant outlet  24 .  
     [0019] The high flow rate of raw water in the duct  14  means that the temperature of the raw cooling water in contact with the cooling vanes  26  of the stator  20  is substantially always at the ambient temperature of the raw water. Therefore the temperature differential between the engine coolant and the raw cooling water is maximized for maximum heat transfer. Furthermore, the number of vanes in the stator provides a large surface area for effective heat transfer.  
     [0020] Due to the closed circulating path between the engine  2  and the stator  20 , the engine coolant is not easily contaminated, and the high flow rate of raw water in the duct  14  helps to prevent blockages from water borne debris.  
     [0021] While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.