Patent Publication Number: US-2010126437-A1

Title: Heat recovery system

Description:
FIELD OF THE INVENTION 
     The invention is directed to methods and systems for heating an engine, particularly during initial start-up. 
     BACKGROUND 
     Engines often have elevated levels of exhaust emissions during initial start-up as associated exhaust treatment devices have reached steady state operating temperatures. As such, the efficiency of removal or treatment of exhaust emissions is dependent upon the temperature of the engine exhaust gas and, inherently, the engine. In cooler operating conditions engines may have increased difficulty starting or have reduced fuel economy due to lower initial operating temperatures. Existing solutions that assist engine cold starts may be costly, with respect to necessary product and energy use, and can be cumbersome to use. Accordingly, there is a need for an improved system and method for providing heat to an engine before or during initial start-up of the engine. 
     SUMMARY OF THE INVENTION 
     An embodiment of the invention is directed towards methods and systems for heating an engine, particularly during initial start-up of the engine. In one exemplary embodiment, a heat storage and release system for an engine is provided. The system may include a material capable of being super cooled within the operating temperature range of the engine. The material is in thermal communication with the engine. In other non-limiting examples, the system also includes an energy input device associated with the material. The energy input device delivers energy to the super cooled material sufficient to initiate an exothermic phase change. During the phase change the material releases heat to the engine. 
     In another embodiment, a method of storing and releasing energy, in the form of heat, to an engine is provided. The method includes forming a structure having a cavity containing a material capable of super cooling within an operating temperature range of the engine and locating the structure in thermal communication with the engine. The method also includes absorbing heat generated by the engine with the material and inducing a phase change of the material from a super cooled state to thereby release the stored heat to the engine. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features, advantages and details appear, by way of example only, in the following detailed description of embodiments, the detailed description referring to the drawings in which: 
         FIG. 1  illustrates a schematic view of an engine with a heat recovery system of the present invention in a first mode of operation; 
         FIG. 2  illustrates a schematic view of an engine with the heat recovery system shown in  FIG. 1  in a second mode of operation; and 
         FIG. 3  illustrates a schematic view of an engine with the heat recovery system shown in  FIG. 1  in a third mode of operation. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     The present invention provides methods and systems for improving emissions, performance and efficiency of an engine during initial operation thereof. These and other benefits are achieved through the absorption, storage and release of potential energy, particularly heat, generated by an engine. In particular, a heat storage material capable of the absorption, storage and release of heat is provided. The material is in thermal communication with an engine and/or a coolant flowing therethrough. The heat storage material is configured to absorb heat generated by the engine during operation of the engine. Thereafter, as the engine cools the heat storage material retains at least a portion of the stored energy for later release, particularly during a subsequent start-up of the engine. When additional heat is desired for the engine, the heat storage material is caused to release the stored heat to the engine. 
     In one particular configuration of the heat storage material, during operation of the engine, the heat storage material absorbs heat generated by the engine causing the material to exist in a first physical state (e.g., liquid). The heat storage material remains super cooled in its first physical state after operation of the engine has been discontinued and the engine has cooled to ambient temperatures. Prior to, or during, a subsequent start-up of the engine, the heat storage material is caused to change to a second physical state (e.g., solid) wherein heat is released, generally in a steady-state manner, during and after transition of the heat storage material from the super cooled liquid state to the solid state. The release of heat lowers the heating time of the engine thereby providing improved emission reduction, performance and efficiency. 
     In one configuration, the heat storage material exists in a liquid physical state at or above its melting temperature and exists in a liquid or a solid physical state at or below its freezing temperature. When the heat storage material exists as a liquid below its freezing point, the heat storage material is commonly referred to as being super cooled or, in a super cooled state. In this super cooled state, the heat storage material requires additional energy to transform from a liquid state to a solid state (i.e., cause crystallization of the heat storage material). 
     The operating temperature of the engine ranges from the cold start temperature of the engine to a steady state operating temperature of the engine. While the cold start temperature of the engine will vary seasonally and regionally, the steady state operating temperature will be somewhat constant. It should be appreciated that the steady state operating temperature may vary by engine make, model, and operating conditions such as temperature and load. In general though, the operating temperature of an automotive internal combustion engine is generally between about −40° to 129° C. As such, the heat storage material of the present invention is also capable of super cooling within that range. 
     Suitable heat storage materials contemplated by the present invention include material capable of storing heat across the operating temperature range of an engine. In one exemplary embodiment, the heat storage material is capable of existing in a super cooled state within the operating temperature range of the engine. Such suitable heat storage materials include materials having a melting temperature below the steady state operating temperature of the engine and a freezing temperature above a cold start temperature of the engine. Further, the suitable materials will release heat (i.e. change phases from a super cooled liquid to a solid) at a temperature above the cold start temperature of the engine. As such, the suitable material melts during an operational temperature of the engine and is super cooled below steady state operational temperatures of the engine. When the super cooled material undergoes a phase change, the engine is heated due to the release of heat by the heat storage material. 
     Specific examples of suitable heat storage materials include sodium acetate, sodium ethanaote, disodium hydrogen phosphate dodecahydrate and the like. In one particular configuration, the heat storage material comprises a sodium salt of an acetic acid, such as sodium acetate. Sodium acetate comprises a material capable of relatively easily existing in more than one physical state within a given temperature range. For example, sodium acetate has a melting temperature above about 95° C. and a solidification, or freezing temperature of about 54° C. However, due to the inherent characteristics of sodium acetate, it can exist in a liquid phase at temperatures notably below 54° C., including ambient temperatures commonly encountered by engines, particularly vehicle engines. In order to initiate solidification of super cooled liquid sodium acetate the sodium acetate must be sufficiently activated or disturbed, such as through the energy input device. Upon disturbance, the sodium acetate changes phase from a liquid to a solid. During this exothermic phase change, the sodium acetate heats to a temperature of about 54° C. 
     Referring to  FIGS. 1-3 , schematic views of an exemplary embodiment of the present invention are shown. In this embodiment, a heat recovery system  10  is provided for absorption of heat from an engine  18  and for subsequent release of the absorbed heat to the engine. The heat recovery system  10  includes a structure  12  defining a cavity  14  that receives a heat storage material. The structure  12 , containing heat storage material  16 , is in thermal communication with an engine  18  and, more particularly, in one embodiment an engine block  20  or engine cylinder head  25 . The structure  12  containing the heat storage material  16  may also be in thermal communication with an engine coolant  22  flowing through a coolant flow path  24  defined by the engine block  20  and engine cylinder head  25 . 
     In one exemplary operation of the heat recovery system  10 , referring to  FIG. 1 , energy input device  26  induces an exothermic phase change in the heat storage material  16 . During the phase change, referring to  FIG. 2 , the heat storage material  16  transforms from a first physical state (super cooled liquid) to a second physical state (solid). This phase change results in the release of heat, by heat storage material  16 , causing the engine  18  and engine coolant  22  to be heated. The addition of heat is additive to the inherent heating capabilities of the engine  18  during operation. The heat generated by the engine  18  and the heat storage material  16  is circulated through the engine block  20 , via engine coolant  22 . Once the temperature of the engine  18  and engine coolant  22  reach suitable levels, see  FIG. 3 , the coolant is further circulated through an engine cooling system  28  which may include a radiator  30  or otherwise. During this time, or at any time when the temperature of the engine is greater than the temperature of the heat storage material  16 , the heat storage material  16  absorbs heat generated by the engine  18 . During heat absorption, the solid heat storage material  16  undergoes a physical phase change back to the liquid state. Upon termination of engine operation and cooling of the engine  18  to ambient temperatures, the heat storage material  16  enters a super cooled, liquid state. In this state the material  16  is again ready to release stored energy, in the form of heat, to the engine  18  upon subsequent operation of the energy input device  26 . 
     It should be appreciated that the engine  18  may include more than one heat recovery system  10 , each of which may function to provide simultaneous heating, sequential heating or other heating solutions. For example, in one configuration it is contemplated that one or more heat recovery systems  10  may be associated with each cylinder head  25  of the engine  18 . These heat recovery systems  10  may extend along all or a portion of the length or width of an engine. It should be appreciated that different configurations are available for obtaining a desired heating result. 
     As described, the exothermic phase change of the heat storage material  16  is initiated through an energy input device  26 . The device may be mechanical in function and may be located inside or outside of the structure  12  where it operates to deliver mechanical energy sufficient to initiate an the liquid to solid phase change in the heat storage material  16 . Such mechanical energy may be in the form of waves initiated through percussion, vibration or otherwise. It should be appreciated that various configurations may be used for the generation of waves or other mechanical energy to the heat storage material  16 . For example, in one configuration a moveable member maybe provided that is configured to strike the structure  12  containing the heat storage material  16  thereby transmitting energy waves through the material and initiating a phase change therein. Such movable members may comprise a pin, hammer, or other suitable percussion member and may move through the use of a solenoid (electrically driven, pneumatically driven or otherwise), or the like. In another configuration, the moveable member is configured to move the structure  12  with sufficient force to cause disturbance and initiate the phase change of the heat storage material  16 . Other configurations are contemplated. 
     The energy input device  26  may be activated at different times and through different activation devices  32 . The energy input device  26  may be activated during an operational cycle of the engine, during a non-operational cycle of the engine, or both. In one exemplary embodiment, the energy input device  26  is activated prior to ignition of the engine  18 . For example, the energy input device may be associated with a suitable controller for activation of the energy input device during approach of an operator to the vehicle, during unlocking of a vehicle door, upon placement in, or rotation of, a key in an ignition system of the engine  18 , or otherwise. In another configuration, the energy input device is activated during start-up of the engine. This may be through an activation device  32  or through the natural vibration of the engine  18  during starting. In still another exemplary embodiment, the energy input device  26  may be activated after initial ignition of the engine. In configurations where more than one energy input device  26  is used, it is contemplated that the energy input devices may be activated simultaneously or at different times, such as sequentially or otherwise. 
     The activation device  32  may comprise any suitable device capable of transmitting signals to the energy input device  26 . In one configuration, the activation device comprises a remote device, such as a remote keyless entry fob of a vehicle. In another configuration, the activation device  32  comprises a control device associated with a vehicle, such as an engine or vehicle controller. In this configuration, the controller may be in communication with the remote device, a sensor associated with the ignition, an entry handle of the vehicle or otherwise. It should be appreciated that other configurations are contemplated. 
     The heat storage material  16  is located within structure  12  that is in thermal communication with the engine  18  and optionally the engine coolant  22  in coolant flow path  24 . The structure  12  may be located adjacent to the coolant flow path  24  of the engine  18 . In one exemplary embodiment, the structure  12  comprises a portion of the engine  18 , such as engine block  20  or engine cylinder head  25 , and the cavity  14  is defined thereby. Hence, the structure  12  is integrally formed with the engine  18 . In this configuration, the heat storage material  16  is placed within the cavity  14  and the cavity is subsequently sealed. In another configuration, the structure  12  is formed separately from the engine block  18  or engine cylinder head  25  and is attached to, or otherwise placed in thermal communication therewith. In this configuration, the heat storage material  16  is placed in the cavity  14  and the structure  12  is subsequently brought into association with the engine  18 , such as placement within an opening thereof, or mounting to (e.g., mechanically fastened, welded or otherwise) the engine block  20 , engine cylinder head  25  or otherwise. Other configurations are possible. 
     The quantity of heat storage material  16  located within the cavity  14  is dependent upon the quantity of heat desired for the engine  18 . It should be appreciated that the more heat storage material  16  placed within the cavity  14  the more potential heat is available for delivery to the engine  18 . Accordingly, the quantity of heat storage material  16  may be based upon, or proportional to, the engines size and/or heating requirements. 
     Cavity  14  may comprise any suitable shape and/or size for holding a sufficient quantity of heat storage material  16 . In one configuration, the cavity  14  is symmetrically shaped, such as a cylinder to facilitate machining during production. In another configuration, the cavity  14  may be asymmetrically shaped. This latter configuration may be particularly advantageous where the cavity  14  is cast into a structure comprising an engine block  20  or engine cylinder head  25  and the cavity extends through all or a portion of the engine block  20 , engine cylinder head  25 , or otherwise. As such, the heat storage material may be located at various locations within the engine  18  to provide desired heat transfer to engine components and/or coolant. It should be appreciated that the cavity may be formed during casting of the engine block or engine head or may be subsequently machined therein. 
     In one detailed sequence of operation, the heat recovery system  10  is activated by activation device  32 , which operates energy input device  26 , prior to or during an initial start-up of the engine  18 . Upon activation the heat storage material  16  undergoes an exothermic phase change from a super cooled, liquid state to a solid state causing a release of heat to the engine  18 . During subsequent operation of the engine, the temperature of the engine  18  and engine coolant  22  rise to levels that exceed the melting point of the heat storage material  16  thereby causing a return to a liquid phase. Once the engine is no longer in operation, the engine  18 , engine coolant  22  and heat recovery system  10  cool to ambient conditions. However, due to inherent properties described, the heat storage material  16 , enclosed in the structure  12 , remains in a super cooled, liquid state upon cooling below its melting point temperature. At this point, the heat storage material  16  can be reactivated through the energy input device  26  to again deliver heat to the engine  18 . It should be appreciated that the heat recovery system  10  may be regenerated, as described, through the life of the vehicle without replenishment of the heat storage material  10 . 
     While exemplary embodiments have been described and shown, it will be understood by those skilled in the art that various changes may be made, and equivalents may be substituted, for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.