Patent Publication Number: US-2023159013-A1

Title: Gas Turbine Engine Heaters

Description:
RELATED APPLICATION 
     This application claims priority to U.S. Provisional Patent Application No. 63/283,171, filed on Nov. 24, 2021, the entirety of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     Engine heaters maintain a temperature of an internal combustion engine. For example, fuel fired heaters are used onboard vehicles, such as locomotives, trucks, automobiles, ships, etc. in order to maintain the combustion engines within a desired temperature range. Moreover, reciprocating compressors maintain an air pressure of an air brake system. For example, slow speed reciprocating piston compressors, screw compressors, or other positive displacement compressors are used onboard vehicles in order to maintain an air pressure of an air brake system. 
     Locomotive idling is an unfortunate necessity. Besides additional fuel consumption and increased costs, idling produces emissions at the engine&#39;s least efficient operating point. Idling also produces noise. However, idling is necessary for the following reasons 1) to prevent the air brake system pressure from dropping below 90 psi, 2) to keep locomotive batteries charged, 3) to prevent the locomotive coolant from freezing in cold climates, 4) to keep oil from increasing in viscosity, and 5) to provide power for operator comfort systems. 
     Additionally, auxiliary load requirements have increased with the implementation of electronic monitoring equipment such as Positive Train Control (PTC). Presently locomotives are outfitted with Automatic Engine Start Stop Systems (AESS). The AESS will restart the engine for conditions where the engine temperature is too low (risk of freezing), and air brake pressure is too low (risk of brake release). The AESS will also stop the engine after 30 minutes of idling. Moreover, the AESS will restart the engine if a battery charge drops below a threshold. 
     Air brake pressure drop is the main reason for engine idling. Modern train systems lose up to 1 psi per minute at a rate of 60 cfm to 90 cfm per regulations set by AAR (Association of American Railroads). The regulations also state that the engine must restart if the brake line air pressure drops below 90 psi. Thus, a restart is likely every 50 minutes given this requirement. After multiple restarts the AESS will switch to remain idling. 
     In some onboard applications, fuel fired heaters may employ parasitic loads to maintain the engines within a desired temperature range. For example, fuel fired heaters may employ a fan and a pump to maintain the combustion engines within a desired temperature range. However, the fan and the pump may be parasitic loads on a battery of the vehicle. For example, the fan and the pump of the fuel fired heater may be powered by the battery of the vehicle, thereby reducing a charge of the battery of the vehicle. 
     Thus, there remains a need to develop new fuel fired heaters that provide compressed air, are more efficient, and are not a parasitic load on the vehicle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The detailed description is described with reference to the accompanying figures. The use of the same reference numbers in different figures indicates similar or identical items. 
         FIG.  1    illustrates an example engine heater system for heating a diesel engine of a vehicle, according to an embodiment in this disclosure. 
         FIG.  2    illustrates another example engine heater system for supplying compressed air to an air brake of a vehicle, according to an embodiment in this disclosure. 
         FIG.  3    illustrates another example engine heater system for supplying compressed air to an air brake of a vehicle, according to an embodiment in this disclosure. 
         FIGS.  4 A and  4 B  collectively illustrate an example process that the engine heater system of  FIG.  3    may implement to supply compressed air to an air brake of a vehicle and maintain a diesel engine of the vehicle within a desired temperature, according to an embodiment in this disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Overview 
     As noted above, reciprocating compressors may be employed for maintaining an air pressure of an air brake system of vehicles. This disclosure is directed to engine heater systems (e.g., microturbine auxiliary power units (APUs)) maintaining a diesel engine of a vehicle within a desired temperature and/or supplying compressed air to air brakes of the vehicle. Compared to conventional techniques, the engine heater systems described herein may be more efficient than running a main engine of a vehicle employed to do the same. 
     An example of an engine heater system that maintains a diesel engine of a vehicle within a desired temperature and/or supplies compressed air to air brakes of the vehicle may be an engine heater system like that seen in the figures. In some instances, the engine heater system may include a gas turbine and a compressor. The compressor may be fluidly coupled to an air reservoir of the vehicle, and the air reservoir may be fluidly coupled to the air brake of the vehicle. During rotation of the gas turbine, the compressor rotates and thereby supplies compressed air to the air reservoir of the vehicle. In turn, the air supplied to the air reservoir may be used to operate the air brake of the vehicle. Accordingly, this disclosure describes engine heater systems that may result in a more efficient operation of the vehicle. 
     While this application describes implementations that are described in the context of an onboard engine heater system for maintaining a diesel engine of a vehicle within a desired temperature and/or an air brake system of the vehicle within a desired pressure, the implementations described herein may be used in other environments and may be applicable in other contexts. For example, the engine heater systems may be located at any desired location, including with a generator (e.g., backup generator) located at a server farm, a hospital, a high-rise building, remote cell tower site, an urban cell tower site, an oil site, a gas site, etc. 
     Example Engine Heaters 
       FIG.  1    illustrates an example engine heater system  100  for heating a diesel engine of a vehicle  102 . While  FIG.  1    illustrates the vehicle  102  is a locomotive (e.g., a diesel electric locomotive), the vehicle  102  may be a ship, a truck, a car, etc. The engine heater system  100  may be onboard the vehicle  102 . For example, the engine heater system  100  may be arranged on the vehicle  102  for heating the diesel engine of the vehicle  102  and/or for maintaining an air brake system of the vehicle  102  within a desired pressure. 
     The engine heater system  100  may include a gas turbine  104 . A heat exchanger  106  may be fluidly coupled to an exhaust  108  of the gas turbine  104 . An electric generator  110  may include connection members  112  may be coupled to a battery  114  of the vehicle  102 . The battery  114  may be a battery bank of the vehicle  102 . A shaft  116  may be rotatably attached between the gas turbine  104  and the electric generator  110 . 
     A combustor  118  may be disposed proximate to the gas turbine  104 . The combustor  118  is configured to heat air that is provided to the gas turbine  104 . As such, the combustor  118  may be fluidly coupled to the gas turbine  104 . The combustor  118  may use multiple different fuels. In an example, the combustor  118  may comprise a combustor that utilizes diesel fuel. The heated air acts on the blades of the gas turbine  104  to rotate the gas turbine  104 . Rotation of the gas turbine  104  correspondingly rotates the shaft  116 . When the gas turbine  104  rotates the shaft  116 , the electric generator  110  charges the battery  114 . Moreover, the heat exchanger  106  utilizes the exhaust  108  of the gas turbine  104  to keep the diesel engine of the vehicle  102  within a desired temperature range. The heat exchanger  106  may comprise a cross-flow heat exchanger, a counterflow heat exchanger, etc. 
     In one example, the heat exchanger  106  may utilize the exhaust  108  of the gas turbine  104  to heat engine coolant of the diesel engine of the vehicle  102  to keep the diesel engine within the desired temperature range. Additionally or alternatively, the heat exchanger  106  may utilize the exhaust  108  of the gas turbine  104  to heat engine oil of the diesel engine of the vehicle  102  to keep the diesel engine within the desired temperature range. Additionally or alternatively, the heat exchanger  106  may utilize the exhaust  108  of the gas turbine  104  to heat an engine coolant of the diesel engine of the vehicle  102  to keep a cab of the vehicle  102  at a desired temperature. As such, the exhaust  108  may be usable for beneficial purposes. 
       FIG.  1    illustrates that the engine heater system  100  may include a compressor  120 . The compressor  120  may be a multistage air compressor (e.g., a two-spool multistage air compressor). The compressor  120  may be disposed proximate to the gas turbine  104  and may be attached to the shaft  116 . The compressor  120  may force air  122  into the combustor  118 . A fuel pump disposed with the combustor  118  may spray fuel (e.g., diesel fuel) into the combustor  118 , where the sprayed fuel mixes with air and ignites. When the gas turbine  104  rotates the shaft  116 , the shaft  116  rotates the compressor  120  to force the air  122  to the combustor  118 . The compressor  120  may be fluidly coupled to an air reservoir (not shown in  FIG.  1   ) of the vehicle  102 . The air reservoir is fluidly coupled to the air brake of the vehicle  102  and during rotation of the gas turbine  104 , the compressor  120  rotates to supply compressed air to the air reservoir of the vehicle  102  for operating the air brake of the vehicle  102  (discussed in more detail below). 
     The connection members  112  may further couple the electric generator  110  to an electric motor  124  of a coolant pump  126 . When the gas turbine  104  rotates the shaft  116 , the electric generator  110  may power the electric motor  124  of the coolant pump  126 . The coolant pump  126  may force engine coolant  128  through the heat exchanger  106 . The exhaust  108  of the gas turbine  104  may then heat the engine coolant  128  forced through the heat exchanger  106  by the coolant pump  126 . In turn, the heated engine coolant  128  may be used to keep the diesel engine within the desired temperature range. 
     While  FIG.  1    illustrates the coolant pump  126  that supplies the engine coolant  128  through the heat exchanger  106 , additionally or alternatively, an oil pump (not shown) may be powered by the electric generator  110  to supply engine oil through the heat exchanger  106 . In such an embodiment, the exhaust  108  of the gas turbine  104  may heat the engine oil and therein, the heated engine oil may be used to keep the diesel engine within the desired temperature range. 
     The heat exchanger  106  may be further fluidly coupled to an exhaust pipe  130  for venting the exhaust. While  FIG.  1    illustrates the exhaust  108  of the gas turbine  104  heating an engine oil, the exhaust  108  of the gas turbine  104  may additionally or alternatively heat a hydraulic oil, a fuel (e.g., diesel fuel), etc. 
     Because the engine heater system  100  includes the gas turbine  104  that rotates the compressor  120  (via the shaft  116 ), charges the battery  114 , and powers the coolant pump  126 , rather than drawing power from the battery  114 , the engine heater system  100  does not represent a parasitic load on the battery  114  of the vehicle  102 . Consequently, the engine heater system  100  may be more efficient that traditional techniques. For example, because the gas turbine  104  rotates the compressor  120  and powers the coolant pump  126 , the engine heater system  100  does not require power from the battery  114  to run the compressor  120  and/or the coolant pump  126 , and instead charges the battery  114 . Moreover, because the compressor  120  is rotated by the gas turbine  104  to supply compressed air to the air reservoir of the vehicle  102  for operating the air brake, the engine heater system  100  may be more efficient at supplying compressed air to the air brake of the vehicle  102  as compared to slow speed reciprocating piston compressors. Further, because the compressor  120  utilizes a high-speed rotating fan that utilizes centrifugal force to compress air, the compressor  120  may be physically smaller compared to slow speed compressors that are physically larger in size to displace the required air for high-flow and high-pressure requirements of the vehicle  102 . 
     Another Example Engine Heater 
       FIG.  2    illustrates an embodiment of an engine heater system  200 , similar to the engine heater system  100  in  FIG.  1   . However, the engine heater system  200  includes a multistage air compressor  202 , according to an embodiment in this disclosure. Inasmuch as other components of the engine heater system  200  are similar to those of engine heater system  100 , the reference numbers remain the same on the same parts for convenience. 
     The multistage air compressor  202  may comprise a two-spool multistage air compressor, for example. The multistage air compressor  202  may provide compressed air  204  to an air brake  206  of the vehicle  102  through a main air reservoir  208  of the vehicle  102 . For example, the main air reservoir  208  of the vehicle  102  may be fluidly coupled to the air brake  206  of the vehicle  102 , and the multistage air compressor  202  may provide compressed air  204  to the main air reservoir  208  fluidly coupled to the air brake  206  of the vehicle  102 . The air brake  206  of the vehicle  102  may comprise a train air brake pipe. The multistage air compressor  202  may provide for maintaining air brake pressure while maintaining engine temperature without the main engine of a vehicle running. For example, the multistage air compressor  202  may provide for reduced idling and/or start-up of a main engine (main combustion engine) of a vehicle, where the main engine needs to be maintained within a desired temperature for operation and/or to maintain an air pressure of an airbrake system to prevent vehicle runaway. 
     The multistage air compressor  202  may be fluidly coupled to the train air brake pipe and/or a locomotive air compressor. The multistage air compressor  202  may be arranged with the compressor  120 , the combustor  118 , and/or the gas turbine  104 . For example, the multistage air compressor  202  may be attached to the shaft  116  along with the compressor  120 , the combustor  118 , and/or the gas turbine  104 . When the gas turbine  104  rotates the shaft  116 , the shaft  116  rotates the multistage air compressor  202  to provide the compressed air  204  to the main air reservoir  208  of the vehicle  102  for operating the air brake  206  of the vehicle  102 . While  FIG.  2    illustrates the engine heater system  200  includes one shaft (e.g., shaft  116 ) the engine heater system  200  may include more than one shaft. For example, the engine heater system  200  may include a low-speed shaft and a high-speed shaft. 
     Another Example Engine Heater 
       FIG.  3    illustrates an embodiment of an engine heater system  300 , similar to the engine heater system  100  in  FIG.  1    and the engine heater system  200  in  FIG.  2   . However, the engine heater system  300  includes a two-spool multistage air compressor  302 , according to an embodiment in this disclosure. Inasmuch as other components of the engine heater system  300  are similar to those of engine heater systems  100  and  200 , the reference numbers remain the same on the same parts for convenience. 
     The two-spool multistage air compressor  302  will burn significantly less fuel than a locomotive prime mover engine while keeping the train ready for service and not idling the prime mover engine. The two-spool multistage air compressor  302  will make compressed air and enough heat in a compact package. The two-spool multistage air compressor  302  has the advantage over a reciprocating piston engine because the two-spool multistage air compressor  302  produces more power in a smaller and lightweight package as compared to the larger and heavier reciprocating piston engine producing less power. The two-spool multistage air compressor  302  used in a combined heat and power (CHP) application can be as high as 90% efficient use of the fuel energy potential. The two-spool multistage air compressor  302  has significantly lower emissions than a reciprocating piston engine. 
     The two-spool multistage air compressor  302  includes a low-speed spool  304  and a high-speed spool  306 . The low-speed spool  304  includes a low-speed shaft  308  operably coupled between a low-speed compressor  310  and a low-speed turbine  312 . The high-speed spool  306  includes a high-speed shaft  314  operably coupled between a high-speed compressor  316  and a high-speed turbine  318 . The low-speed turbine  312  includes an intake side  320  opposite an exhaust side  322 . The high-speed turbine  318  includes an intake side  324  opposite an exhaust side  326 . The low-speed compressor  310  includes an inlet side  328  opposite an outlet side  330 . The high-speed compressor  316  includes an inlet side  332  opposite an outlet side  334 . 
     A combustor  336  may be disposed proximate to the intake side  324  of the high-speed turbine  318  and/or the intake side  320  of the low-speed turbine  312 . The combustor  336  is configured to provide heated air to the high-speed turbine  318  and/or the low-speed turbine  312 . The outlet side  334  of the high-speed compressor  316  may be disposed proximate to the combustor  336  and fluidly coupled via a valve  338  to the air reservoir  208  of the vehicle  102  fluidly coupled to the air brake  206  of the vehicle  102 . Where during rotation of the high-speed shaft  314  via the high-speed turbine  318 , the high-speed shaft  314  rotates the high-speed compressor  316 , thereby increasing pressure at the outlet side  334  of the high-speed compressor  316  and supplying compressed air to the air reservoir  208  of the vehicle  102  for operating the air brake  206  of the vehicle  102 . The high-speed compressor  316  may supply about 90 cfm at about 90-100 psi to the air brake  206  of the vehicle  102 . As discussed above, regulations state that the main engine of a locomotive must restart if the brake line air pressure drops below 90 psi. Thus, because the high-speed compressor  316  may supply about 90 cfm at about 90-100 psi to the air brake  206  of the vehicle  102 , the engine heater system  300  reduces main engine start-ups. 
     The high-speed shaft  314  may be operably coupled to the electric generator  110 . Where the electric generator  110  is configured to charge the battery  114  as the high-speed turbine  318  rotates the high-speed shaft  314 . While  FIG.  3    illustrates the electric generator  110  operably coupled to the high-speed shaft  314 , the electric generator  110  may be operably coupled to the low-speed shaft  308 . 
     A heat exchanger  340  may be fluidly coupled to the outlet side  334  of the high-speed compressor  316 . For example, the heat exchanger  340  may be fluidly coupled to the outlet side  334  of the high-speed compressor  316 , via the valve  338 . The heat exchanger  340  is configured to remove heat from the compressed air for heating an engine coolant and/or heating an engine oil. Because air increases in temperature when compressed, the air exiting the outlet side  334  of the high-speed compressor  316  may have an exit air temperature that is very high (e.g., about  437 K or about  163 C). The high temperature air exiting the outlet side  334  of the high-speed compressor  316  may provide for improved brake performance by preventing brake line freezing in cold temperatures. For example, subsequent to the heat exchanger  340  removing heat from the compressed air for heating an engine coolant and/or an engine oil, the elevated temperature heated air supplied to the air reservoir  208  of the vehicle  102  fluidly coupled to the air brake  206  of the vehicle may prevent brake line freezing in cold temperatures. 
     A recuperator  342  may be fluidly coupled to the outlet side  334  of the high-speed compressor  316 . For example, the recuperator  342  may be fluidly coupled to the outlet side  334  of the high-speed compressor  316 , via the valve  338 , upstream of the combustor  336 . The recuperator  342  may add heat to the compressed air before it enters the combustor  336 . Because the recuperator  342  adds heat to the compressed air before it enters the combustor  336 , the recuperator  342  may provide for reduced fuel consumption by the combustor  336 . The valve  338  may be a pressure relief valve that splits the compressed air between the heat exchanger  340  and the recuperator  342 . The compressed air produced by the high-speed compressor  316  may include a product air mass flow of about 0.038 kg/s (at standard temp of 20F and pressure of 14.7 psia), which equates to about 60 cfm flow, at about 100 psig pressure, and at about 120C. 
     A heat exchanger  344  may be fluidly coupled to the recuperator  342 . Similar to the heat exchanger  106 , the heat exchanger  344  may utilize an exhaust of the low-speed turbine  312  and/or the high-speed turbine  318  to keep the diesel engine of the vehicle  102  within a desired temperature range. 
     An intercooler  346  may be fluidly coupled between the low-speed compressor  310  and the high-speed compressor  316 . The intercooler  346  may be a radiator heat exchanger configured to cool the compressed air downstream of the low-speed compressor  310 , before the compressed air enters the high-speed compressor  316 . The heat removed from the compressed air downstream of the low-speed compressor  310  may be used elsewhere. For example, the heat captured by the intercooler  346  may be used for cabin heating, engine oil heating, engine coolant heating, etc. 
     While  FIG.  3    illustrates the engine heater system  300  includes a two-spool multistage air compressor, the engine heater system  300  may include other types of gas turbines (e.g., recuperated gas turbines). For example, the engine heater system  300  may include a two-spool with overhung high pressure (HP) spool turbine, a single shaft axi-centrifugal turbine, etc. 
     Compressed air may be required to maintain brake line pressure of the vehicle  102 . Low brake pressure will result in a locomotive engine and attached air compressor restarting to charge the air pressure. The two-spool multistage air compressor  302  can be used to maintain brake line pressure and prevent locomotive engine and attached air compressor restarts to charge the air pressure. The two-spool multistage air compressor  302  can be used as a safety feature to prevent runaway trains when a main engine restart is not possible. Because the two-spool multistage air compressor  302  is relatively smaller in physical size and is relatively lighter in weight than a reciprocating engine compressor of similar power, weight savings and size savings are realized. 
     Example Engine Heater Process 
       FIGS.  4 A and  4 B  collectively illustrate an example process  400  that the engine heater system  300  may implement to supply compressed air to an air brake (e.g., air brake  206 ) of a vehicle (e.g., vehicle  102 ) and maintain a diesel engine of the vehicle within a desired temperature. Those having ordinary skill in the art will readily recognize that certain steps or operations illustrated in the figures above may be eliminated, combined, or performed in an alternate order. Any steps or operations may be performed serially or in parallel. Furthermore, the order in which the operations are described is not intended to be construed as a limitation. In some instances, the process described herein may be performed, in whole or in part, by the engine heater system  100 , the engine heater system  200 , and/or a combination thereof. 
     At an operation  402 , air may enter the low-speed compressor  310 . For instance, outside air may enter the inlet side  328  of the low-speed compressor  310 . 
     An operation  404  represents the low-speed compressor  310  compressing the air. For example, operation  404  may represent a first stage of air compression by the low-speed compressor  310 . As a result of the low-speed compressor  310  compressing the air, the temperature of the air increases. 
     An operation  406  represents the compressed air exiting the low-speed compressor  310 . For example, operation  406  may represent the compressed air exiting the first compression stage. 
     An operation  408  represents the intercooler  346  cooling the air. For example, the intercooler  346  may cool the compressed air downstream of the low-speed compressor  310 , before the compressed air enters the high-speed compressor  316 . The heat captured by the intercooler  346  may be used elsewhere in vehicle  102 . For example, the heat captured by the intercooler  346  may be used for heating a cabin of the vehicle, heating an engine oil of the vehicle, heating an engine coolant of the vehicle. 
     An operation  410  represents the cooled air entering the high-speed compressor  316 . For example, operation  410  may represent the cooled air entering a second stage of compression of the air via the high-speed compressor  316 . 
     An operation  412  represents the high-speed compressor  316  compressing the air. For example, operation  412  may represent a second stage of air compression by the high-speed compressor  316 . As a result of the high-speed compressor  316  compressing the air, the temperature of the air increases. Operation  412  may further represent the high-speed shaft  314  rotating the electric generator  110 . Where the electric generator  110  may generate electricity to charge the battery  114 , power the electric motor  124  of the coolant pump, power an electric motor of an oil pump, and/or power battery charger loads. 
     An operation  414  represents air exiting the high-speed compressor  316 . For example, operation  414  may represent the compressed air exiting the second compression stage. During rotation of the high-speed shaft  314  via the high-speed turbine  318 , the high-speed shaft  314  rotates the high-speed compressor  316 , thereby increasing pressure at the outlet side  334  of the high-speed compressor  316  so that the air exits the high-speed compressor at the outlet side  334  of the high-speed compressor  316  to at least supply compressed air to the air reservoir  208  of the vehicle  102  for operating the air brake  206  of the vehicle  102 . 
     An operation  416  represents routing the air exiting the high-speed compressor  316 . For example, operation  416  may represent the valve  338  splitting the compressed air exiting the high-speed compressor  316  between the heat exchanger  340  and the recuperator  342 . 
     An operation  418  represents heating the air. For example, operation  418  may represent the air routed to the recuperator  342  is heated by the recuperator  342 . For example, the air routed to the recuperator  342  may be heated by heat energy removed, via the recuperator  342 , from an exhaust exiting the exhaust side  322  of the low-speed turbine  312  to preheat the air before it enters the combustor  336 . 
     An operation  420  represents providing heated air to the high-speed turbine  318 . For example, operation  420  may represent the combustor  336  is configured to provide heated air to the high-speed turbine  318 . For example, the combustor  336  may burn fuel (e.g., diesel fuel) to heat the air to add more energy to the air and provide the heated air to the intake side  324  of the high-speed turbine  318 . 
     An operation  422  represents rotating the high-speed shaft  314 . For example, operation  422  may represent the high-speed turbine  318  on the high-speed shaft  314  removing energy from the air and converting the energy to torque to spin the high-speed shaft  314 . 
     An operation  424  represents rotating the low-speed shaft  308 . For example, operation  424  may represent the low-speed turbine  312  on the low-speed shaft  308  removing energy from the air and converting the energy to torque to spin the low-speed shaft  308 . 
     An operation  426  represents cooling the air. For example, operation  426  may represent the air (e.g., exhaust) exiting the exhaust side  322  of the low-speed turbine  312  is routed to the recuperator  342  and is cooled by the recuperator  342 . For example, the air from the low-speed turbine  312  may be very hot (e.g., about 800K or about 526C), which is routed to the recuperator  342  to be cooled, via the recuperator  342 , such that the air/exhaust heat energy is recovered by the recuperator  342  and transferred to the combustion air to reduce fuel consumption. 
     An operation  428  represents the air exiting the recuperator  342 . For example, operation  428  may represent exhaust air leaving the two-spool multistage air compressor  302 . 
     An operation  430  represents cooling the air. For example, operation  430  may represent the heat exchanger  106  removing heat from the exhaust air to heat engine coolant and/or engine oil. For example, coolant and/or oil pumps may move fluid through the heat exchanger  106  to remove heat from the exhaust air to heat the engine coolant and/or engine oil. 
     Conclusion 
     Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as example forms of implementing the claims.