Abstract:
A system for adjusting ambient air temperature shielding an engine. The system includes an engine having first and second ends and a heat generating source, and a shield having a substantially cylindrical portion defining an interior cavity. At least a portion of the heat generating source is disposed in the cavity. The shield has a heat reflecting interior surface facing the cavity and an opposing exterior surface. The interior surface reflects heat generated by the heat source.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention pertains to air breathing heat engines such as combustion turbines (CT) comprised of a compressor, combustor, and turbine, and, in particular, to a system for cooling such heat engines. 
         [0003]    2. Description of Related Art 
         [0004]    The aero-derivative and framed CTs are rapidly becoming the power generators of choice for electrical power and for direct drive. Earlier applications of CTs were configured to meet spikes in energy dispatch and to meet those spikes with very little regard for heat rates. Due to many favorable features of CTs such as being relatively environmental friendly, as well as improvement in heat rates and reduced capital costs, CTs are increasingly being employed in intermediate and base load generation and now likely will be the wave of the foreseeable future. 
         [0005]    It is obvious that when the compressor aspects of a CT are cooled, the work compressing the air mass is reduced. For the same reason, aero derivative CTs have greater power output when the aircraft say flying at 25,000 feet as days when the aircraft when flying at 5,000 feet. Likewise, when the dry bulb temperature falls the thermal efficiency of the turbine is improved. 
         [0006]    In stationary power generation mode, the current acoustical housing and/or enclosures are designed to absorb sound energy achieving free-field noise emission levels not exceeding 63 decibels at 200 feet and to provide for weather protection. These enclosures are structured around the power take-offs, the hot section of the turbine, the combustors, and the compressors. The engines aspects within the enclosure convect, conduct, and radiate at the rate of the thermal loss expressed as the over-all transformation efficiencies which can be calculated: 
         [0000]    
       
         
           
             
               
                 
                   Turbine 
                    
                   
                       
                   
                    
                   Heat 
                    
                   
                       
                   
                    
                   
                     Btus 
                      
                     
                       / 
                       # 
                     
                   
                 
                 sec 
               
               - 
               
                 
                   Compressor 
                    
                   
                       
                   
                    
                   Heat 
                    
                   
                       
                   
                    
                   
                     Btus 
                      
                     
                       / 
                       # 
                     
                   
                 
                 sec 
               
             
             
               
                 Combustor 
                  
                 
                     
                 
                  
                 Heat 
                  
                 
                     
                 
                  
                 
                   Btus 
                    
                   
                     / 
                     # 
                   
                 
               
               sec 
             
           
         
       
     
         [0007]    Energy Transformation in the Compressor Aspects: The rotating blades (or impellers) adiabatically transfer heat energy to the flow of the air (gas) as per the pressure ratio and the physical characteristics of the compressor. This mechanical work causes a temperature rise in the flow of air. Also when the radiation from the combustor aspects is reflected into the compressor aspects, it causes an additional temperature rise, all of which reduces the efficiencies of the compression of air (gas). 
         [0008]    Energy Transformation in the Combustor Aspects: The energy stored in the flow of air (gas) is increased by raising its temperature. This is a conversion of chemical energy to an enthalpy rise based upon the heating value of the fuel. The combustor aspects (basket metal temperature) along the axis will attain heat at temperatures that radiate off to the surrounds. This radiation of heat energy also is reflected into the compressor and turbine aspects affecting the thermal efficiencies of the CT. 
         [0009]    Energy Transformation in the Turbine Aspects: When the high pressure/high temperature air (gas) expands through the turbine, its energy is transferred from the air to the rotating blades. This combustion gas diffused and expanded into the turbine at a rate depending temperature drop, and when the radiated heat from the combustor is reflected into the turbine aspects, this reheat from combustor radiation hinders the drop in temperature along with slowing down the rate of gas expansion which essentially reduces the power thereby reducing the thermal efficiencies. 
         [0010]    Typical stationary mode CT thermal efficiency is affected when heat is radiated from the combustor back into the compressor and turbine aspects. This bounced, reflected, radiated heat from the combustor causes the compressor aspects to gain heat which causes a temperature rise beyond that which would have been attained simply from the heat of compression. This radiated heat, as an example, will cause a loss of thermal efficiency on a 90° F. day on average of a calculated 5% + , likewise the radiated heat reflected into the turbine could result in a loss in efficiency calculated at 4% + . 
         [0011]    The U.S. Pat. No. 6,082,094 entitled “Ventilation System for Acoustic Enclosures for Combustion Turbines and Air Breathing Heat Engines” teaches a method of cooling and ventilating in the acoustical box enclosure. While the radiated heat from the combustor can be shielded and reflected back into the combustor (at about 50,000 Btu/sq ft/hr) reduces the fuel burn slightly with a corresponding reduction in heat rate. A problem with the heat produced and convected in existing acoustic enclosures is the tendency to retain that heat being produced by the CT components. In particular, all things being equal, CTs shielded by high temperature air operate less efficiently than turbines shielded by cooler air. Although some of the heat produced in energy transformation by the CT is removed by oil cooling systems and engine exhausts, an appreciable amount of heat is transferred to the enclosure and the air contained therein. This transferred heat causes the air in the enclosure to increase in temperature, which tends to adversely affect CT efficiency. 
         [0012]    To offset the radiated, converted, and conducted energy from the operation of a CT confined to an acoustical enclosure and power take-off entrapments within the enclosure, the ambient is filtered air at a rate between 10-20 cfm per kilowatt and vented to the CT forcibly by blowers through the enclosure as a coolant. However, the cooling capabilities of such a configuration is less than desired and heat continues to be a problem with regard to the CTs with subsequent reduction in thermal efficiencies. 
         [0013]    In response to problems resulting from radiated and convected energy from operating the CT, the inventor of the present invention proposed an enclosure for the CT into which air, conditioned and cooled, was directed to cool the compressor portion of the CT. This proposition is disclosed in U.S. Pat. No. 6,082,094, issued to the inventor of the present invention on Jul. 4, 2000, and expressly incorporated herein by reference. However, such enclosures require a mechanism for removal of this heating from within the enclosure, which may increase the number of components and the cost of the system. 
         [0014]    CTs also experience overheating from the radiated and convected energy even if no enclosure is provided. An acoustical enclosure of the annular combustor aspects of the CT is such that it radiants heat energy emitted from the combustor in all radial directions. With such radial emission of heat, the compressor aspect of the CT absorbs heat that is reflected from the combustor, thereby creating a situation where the compressor aspects may become overheated by the radiated heat energy which negatively affects the CTs overall thermal efficiency. 
       SUMMARY OF THE INVENTION 
       [0015]    The present invention provides for the means to absorb the radiated and convected heat from compression aspects into a ducted stream of conditioned air. Further, the invention provides for the means to reflect the heat energy waves into the combustor aspects and shielding heat energy from the compressor and turbine aspects, all of which provides the means to enhance the overall thermal efficiencies of the CT. 
         [0016]    The present invention further provides a power generation system including an air breathing heat engine CT including an intake for delivery of air to the CT and an outlet for exhaustion of compression and combustion gases from the acoustical enclosure. The air breathing heat engine includes a heat generating source and a ducted shield defining an interior cavity in which the conditioned ambient air as a chillate absorbs the radiated heat energy and convects them into the ventilation of the enclosure. 
         [0017]    The present invention further provides the CT an air breathing heat engine with a reflector surrounding the combustor aspects that shield the compressor and turbine aspects from the reflected heat from the combustor. The curved reflective shield surrounding the combustor has at least one absorption surface with ducting for conditioned cooling by an air stream which will maintain a differential in the surface temperature between combustor and the absorptive reflective shield. The reflective shield is formed to reflect the radiated heat back into the combustor aspects while shielding the compressor and turbine aspects from the stray radiated heat. Reflecting the radiated heat back into the combustor aspects while shielding the compressor and turbine aspects provides for a more efficient use of fuel and thereby minimizing the overall heat rate. 
         [0018]    The present invention provides a method of adjusting a temperature within a power generation system including operating a prime mover having a motion impeller to create motion, connecting an electrical generator to the prime mover, generating electrical energy at the electrical generator by utilizing the motion of the prime mover, and shielding the generator to minimize the temperature of the generator. 
         [0019]    The invention further provides for the reflection of radiated heat from prime movers other than combustion turbines. The geometrics that shape the surround of prime movers (say electric motors) will conform so to reflect away from the prime mover the radiated heat energy. To direct the heat energy away from the reflective shield, means for keeping the shield cool may be implemented, such as a ducted, refrigerated cool air stream convecting the absorbed radiated heat away from the prime mover (motor). 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    The above mentioned and other advantages and objects of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawing, wherein: 
           [0021]      FIG. 1  is a schematic front view of a ventilating system for the housing of a combustion turbine; 
           [0022]      FIG. 2  is a sectional view of an existing combustion turbine which is part of a ventilation system of  FIG. 1 ; 
           [0023]      FIG. 3  is a sectional view of the combustion turbine of  FIG. 2  including a shield proximate the compressor portion in accordance with one embodiment of the present invention; and 
           [0024]      FIG. 4  is a schematic view of a combustion turbine including a shield in accordance with another embodiment of the present invention. 
       
    
    
       [0025]    Corresponding reference characters indicate corresponding parts throughout the several views. Although the drawings represent an embodiment of the present invention, the drawings are not necessarily to scale and certain features may be exaggerated in order to better illustrate and explain the present invention. The exemplification set out herein illustrates an embodiment of the invention and such exemplification is not to be construed as limiting the scope of the invention in any manner. 
       DESCRIPTION OF THE INVENTION 
       [0026]    For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. 
         [0027]    Referring now to  FIG. 1 , a combustion turbine, or air breathing heat engine, is schematically shown at  10 , and as is conventional with such gas turbines, includes compressor  16 , combustion portion  18 , and turbine  20 . Turbine  20  utilizes the gases from combustion portion  18  to drive shaft  12 , which is drivingly connected to generator  14  for power generation. Turbine  10  operates in the stationary mode in that, unlike the aero-related turbines on which its design is based and which are naturally moved while used in flight, the turbine is fixedly mounted to a support surface or on the ground during use. 
         [0028]    Intake air duct  28  supplies air to compressor  16  of turbine  10 . Ambient air entering into duct  28  passes sequentially through vapor condensing heat exchanger  22  and cooling heat exchanger  24  to be conditioned prior to entering turbine compressor  16 . The turbine exhaust is ported through conduit  26  to waste heat recovery unit and stack exhaust system  30  that exhausts to the atmosphere. Heat exchanger  32  positioned within a flue of the exhaust stack is used to draw heat off of the combustion gases being exhausted in order to power an absorption refrigeration unit, which is abstractly shown at  34 , that supplies chillate to the heat exchangers  22  and  24 . 
         [0029]    Proximate shoe  36  is proximal inlet opening  40  which is in air flow communication with the downstream end of an intake air duct, or shaft,  42 . Intake air duct  42  includes inlet end  44  that is open to the atmosphere and fans, or blowers,  45  are provided to force air into inlet end  44  and through the ventilation intake air duct  42 . Blowers  45  alternatively may be provided at other points along the ventilation system, including such as within the ventilation exhaust duct, to force or draw air through the system. Air entering duct  42  through inlet end  44  passes through a filter (not shown) and through a vapor condensing heat exchanger generally shown at  46  mounted within the interior of intake duct  42 . Although shown closer to inlet end  44  than shoe  36 , heat exchanger  46  may be alternatively positioned along the length of intake duct  42 , such as closer to or immediately adjacent inlet opening  40  within the scope of the present invention. 
         [0030]    Vapor condensing heat exchanger  46  may be of conventional design including a cooling coil over which air flows and which provides a circuitous path for relatively low temperature chillate being carried therethrough. The cooling coil includes cooling coil tube sections that are arranged in rows and columns in air duct  42  and that are oriented to be generally transverse to the flow of ambient air being conveyed through duct  42 . The cooling coil tube sections may be arranged, for example, to extend horizontally and with spacing between the cooling coil tube sections to provide a large surface area for contact with passing air. While single inlet and outlet chillate lines for heat exchanger  46  are shown, multiple inlet lines and outlet lines may be used and separately circuited to the coil tube sections within the scope of the present invention. 
         [0031]    Vapor condensing heat exchanger  46  removes the heat from the airstream by firstly condensing the vapor (rejecting 970 BTU per pound of water) followed by a cooling of the remainder of the vapor air mixture. This conditioning of the air results in better cooling capabilities of the ventilation system. 
         [0032]    By conditioning the air to a relatively low dry bulb and wet bulb temperature, the system is better cooled, and the efficiency of combustion turbine  10  is improved. By way of example to illustrate the benefits of cooler air, the specific heat in comparable air mixtures is, at sea level pressure, 20.16 BTU/ft 3  when at 55° F. @ 80% Relative Humidity (R.H.) and 54.74 BTU/ft 3  when at 95° F. @ 80% R.H. These numbers evidence that an air mixture of 55° F. @ 80% R.H. would have a calculated cooling advantage of 34.58 BTU/ft 3  over the air mixture at 95° F. @ 80% R.H. 
         [0033]    Vapor condensing heat exchanger  46  is preferably sized and arranged to condition the intake air flowing through air duct  42  such that air exiting heat exchanger  46  is cooled to between approximately 45° F. and 50° F., and preferably 45° F., and to one hundred percent relative humidity. Heat exchanger  46  may be configured to condition air to different air temperatures, including temperatures higher than these preferred values, provided such conditioned air temperatures are satisfactory to achieve suitable cooling of the system; the same configuration can be used to heat the system. 
         [0034]    Vapor condensing heat exchanger  46  is shown in  FIG. 1  being supplied with chillate that has already been circulated through heat exchangers  22  and  24  in air duct  20 . In particular, the exchangers may be plumbed in series such that chillate, for example water at 42° F., is introduced to the inlet of heat exchanger  24  through thermally insulated conduit  52  from absorption refrigeration system  34 , passes from heat exchanger  24  to heat exchanger  22  through thermally insulated conduit  54 , passes from heat exchanger  22  to vapor condensing heat exchanger  46  through thermally insulated conduit  56 , and is returned at a higher temperature from heat exchanger  46  to refrigeration system  90  through thermally insulated conduit  58 . In order to ensure the chillate delivered to heat exchanger  46  is adequately cold to suitably cool the ventilating air, in an alternate embodiment, chillate at between 42-44° F. may be provided directly from the refrigeration system to heat exchanger  46 . For example, heat exchangers  46 ,  22 , and  24  may be plumbed in parallel. 
         [0035]    The chillate may be provided by, and the conduits  52  and  58  may be connected to, an absorption refrigeration system of the type described in U.S. Pat. No. 4,936,109, the complete disclosure of which is incorporated fully herein by reference. This type of system, from an energy standpoint, is non-parasitic (that is, the refrigeration does not draw off the generated electricity). Other refrigeration processes which are known in the art may be used to provide chillate to the heat exchangers within the scope of the invention. For example, the chillate may be produced using a conventional vapor-compression refrigerator that may be, for example, powered by an external power source of conventional design so as to be an energy parasitic system. 
         [0036]    Although not shown, the ventilation ducts, and in particular the air intake duct  42 , may be equipped with a stop valve to selectively open and close off the ventilating system from the ambient air. For example, in cold weather, it is desirable to prevent an influx of cold air through duct  42  and, as a result, around shield  36  when the system is initially started. 
         [0037]    Heat absorbing shield  36  includes two main portions, cylindrical portion  48  and curved portion  50 , to cool compressor  16  of combustion turbine  10 . As shown in  FIG. 2 , radiant heat produced by combustion portion  18  is able to emanate from combustion portion  18  and to be absorbed to a certain extent by compressor  16 , as indicated by arrows  70 ,  72 , and  74 . As such, compressor  16  may absorb heat and may experience a decreased efficiency and greater wear due to that inefficiency. 
         [0038]    As shown in  FIG. 3 , shield  36  is placed over a portion of combustion turbine  10 , specifically compressor  16 , to absorb a portion of the excess heat and to reflect a portion of the excess heat coming from combustion portion  18 . Cylindrical portion  48  is structured to define interior cavity  68  between compressor  16  and cylindrical portion  48 . Cylindrical portion  48  has interior absorptive surface  60  which absorbs heat from compressor  16  as indicated by arrows  62 , that heat being received by compressor  16  from combustion portion  18 . By absorbing this heat, the heat is then not retained within compressor  16  to cause a reduction of efficiency, but is instead pulled away from compressor  16  to provide improved, or at least stable, efficiency. Shield  36  further includes curved portion  50  proximal combustion portion  18 . Curved portion  50  includes reflective surface  64  and absorbing surface  66  on a side of curved portion  50  opposite reflective surface  64 . As indicated by arrows  76 , the radiant heat from combustion portion  18  radiates outwardly toward compressor  16  but instead of being absorbed by compressor  16 , and surface  64  of curved portion  50  is structured and arranged to reflect the heat by back to combustion portion  18 . However, curved portion  50  does not abut compressor  16 , thus some radiant heat energy is capable of being absorbed by compressor  16 . Specifically, the radiant heat energy is able to enter interior cavity  68  and be absorbed by surface  60 , as indicated by arrow  62 , or alternatively be absorbed by surface  66  of curved portion  50 ; however, in either case the radiant heat energy is pulled away from compressor  16 . 
         [0039]    To further enable cooling of compressor  16 , air from inlet  44  and exiting at outlet  40 , is allowed to blow over cylindrical portion  48 . This air, which has been cooled to 42° F., cools cylindrical portion  48  so that heat which is absorbed by cylindrical portion  48  is then removed by natural heat exchange through cylindrical portion  48  being cooled to absorb further heat from compressor  16 . The same can be said of curved portion  50  which also is cooled by the air passing over it. Thus, by use of a less complex cylindrical portion and curved shield structure, compressor  16  is able to be cooled relatively easily and efficiently. 
         [0040]    Although shield  36  has been described as being used with combustion turbine  10 , other such electrical generating devices utilizing heat energy may be used with shield  36 . Whenever heat is generated for creation of electrical energy, heat may also be radiated therefrom and be absorbed by other related devices. Thus, the use of shield  36  would protect additional devices through its absorbing and reflecting of the radiant heat energy. Other such devices may include heat engines, other turbines, or other combustion related engines. 
         [0041]    Although not shown, automatic controls for the ducts and the heat exchanger, with appropriate sensors, may be provided in the shown ventilating system to insure compressor  16  is properly ventilated with cooled air from heat exchanger  46 . The inventive ventilating system, due to the improved cooling of compressor  16  by shield  36 , reduces the severity of creep in the engine components and improves CT aspects and the turbine efficiency. 
         [0042]    Referring now to  FIG. 4 , combustion turbine or air breathing heat engine  110  according to another embodiment of the present invention is schematically shown. Turbine  110  includes compressor  116 , combustion portion  118  and turbine  120 . Turbine  120  operates similar to turbine  10  in  FIGS. 1-3 . Intake air duct  128  supplies air to compressor  116  of turbine  110 . The air entering into duct  28  may be pre-conditioned prior to entering compressor  116  by any means including, for example, the method described in U.S. Pat. No. 4,936,109 issued on Jun. 26, 1990 to R. Longardner, the inventor of the present application, and hereby incorporated by reference. 
         [0043]    Heat absorbing shield  136  is positioned about combustion portion  118  and includes somewhat cylindrically-shaped barrel portion  136   c , first lip portion  136   a  and second lip portion  136   d . First and second lip portions  136   a ,  136   d  are disposed at opposite ends of barrel portion  136   c  and extend inwardly from barrel portion  136   c . Shield  136  includes interior surface  136   b  which is formed of a reflective material adapted reflect the heat emanating from combustion portion  118  back toward combustion portion  118  and away from compressor  116 , thereby preventing compressor  116  from overheating. Shield  136  may be formed of any material capable of reflecting the heat back to combustion portion  118 . For instance, shield  136  may be formed of a metal such as nickel, chrome, iron or alloys thereof such as Inconel. As illustrated in  FIG. 4 , barrel portion  136   a  bows outward to further aid in the reflection of heat toward combustion portion  118 . First lip portion  136   a  of shield  136  further blocks the heat emanating from combustion portion  118  from reaching compressor  116 . First lip portion  136   a  includes exterior surface  136   e , which may be adapted to absorb heat from compressor  116 , as described above with respect to shield  36  ( FIGS. 1-3 ). 
         [0044]    To further prevent the overheating of compressor  116 , air duct  142  is provided. Air duct  142  extends along the outside of turbine  110  from compressor  116  to turbine  120 . Air duct defines channel  145  and includes inlet  144  and outlet  140  in fluid communication with channel  145 . Channel  145  may be partially defined by the exterior surface of shield  136  such that the air flowing through channel  145  contacts the exterior surface of shield  136 . Alternatively, channel  145  may be partially defined by a wall (not illustrated) that abuts the exterior surface of shield  136 . Cooled ambient air is directed into air duct  142  via inlet  144 . The air entering inlet  144  may be pre-conditioned by any means including, for example, that disclosed in U.S. Pat. No. 6,082,094 issued on Jul. 4, 2000 to Robert Longardner et al., the inventor of the present invention and hereby incorporated by reference. This cooled air travels through duct  142  and exits duct  142  via outlet  140 . As the cooled air travels through duct  142  it contacts the exterior surface of shield  136  and cools barrel portion  148 . 
         [0045]    While this invention has been described as having exemplary structures, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.