Patent Publication Number: US-10774820-B2

Title: Cryogenic pump

Description:
TECHNICAL FIELD 
     The present disclosure relates to a cryogenic pump for an engine fuel system. More particularly, the present disclosure relates to a drive arrangement for the cryogenic pump. 
     BACKGROUND 
     Cryogenic pumps are commonly used to pressurize a cryogenic liquid for use. For example, a cryogenic pump may be used to pressurize a cryogenic liquid, such as liquid natural gas (LNG), to be vaporized and used as fuel in an internal combustion engine. A vaporizer transfers heat to the fuel, converting the fuel from liquid state to gaseous state before supplying it to the engine. The cryogenic pump typically includes plungers or pistons to pressurize the liquid fuel. These plungers or pistons may be actuated or driven by mechanical or hydraulic actuators either directly or through additional components, such as push rods. Cryogenic pumps typically employ one or more seals to inhibit leakage of the cryogenic liquid past the plunger or piston. However, these seals are susceptible to damage from debris, which may eventually cause a leakage of the cryogenic liquid outside the pumping chamber, thereby reducing the efficiency of the pump, which is undesirable. 
     US Patent Publication no. 2008/0213110 (hereinafter referred to as the &#39;110 publication) relates to an apparatus and method for pressurizing a cryogenic media. The &#39;110 publication describes a compressor including a compressor chamber surrounded by a cylinder wall in which a compressor piston is moved in a linear manner, a suction valve and a pressure valve, which are arranged in the region of the lower end position of the compressor piston, and a liquid chamber which at least partially surrounds the compressor chamber. The cylinder wall defines at least one opening, which corresponds to the liquid chamber, and at least one opening, via which the gaseous medium can be extracted from the compressor chamber, where the openings are located at points on the cylinder wall that are passed by the compressor piston. 
     SUMMARY 
     In one aspect, a cryogenic pump for a fuel system of an engine is provided. The cryogenic pump includes a drive assembly and a pressurization assembly operatively coupled to the drive assembly. The drive assembly includes a housing having a sidewall and a piston slidably disposed within the housing. The sidewall and a first surface of the piston define an expansion chamber within the housing. The drive assembly further includes a fuel supply valve in fluid communication with a supply of liquid cryogenic fuel and configured to selectively provide liquid cryogenic fuel into the expansion chamber. Further, the drive assembly includes a heating element extending at least partially into the expansion chamber and configured to introduce thermal energy into the expansion chamber, thereby facilitating vaporization of the liquid cryogenic fuel. Vaporization of the liquid cryogenic fuel increases a pressure inside the expansion chamber causing the piston to move in a first direction. The pressurization assembly includes a barrel defining a bore and a plunger slidably disposed within the bore. The plunger defines a pressurization chamber within the bore. The pressurization chamber is configured to receive liquid cryogenic fuel therein. The plunger is operatively coupled to and driven by the piston. The movement of the piston in the first direction causes movement of the plunger to pressurize the cryogenic fuel within the pressurization chamber. 
     In another aspect of the present disclosure, a fuel system, for supplying a cryogenic fuel to an engine, is provided. The fuel system includes a cryogenic fuel tank and a cryogenic pump disposed within the cryogenic fuel tank. The cryogenic pump includes a drive assembly and a pressurization assembly operatively coupled to the drive assembly. The drive assembly includes a housing having a sidewall and a piston slidably disposed within the housing. The sidewall and a first surface of the piston define an expansion chamber within the housing. The drive assembly further includes a fuel supply valve in fluid communication with the cryogenic fuel tank and configured to selectively provide liquid cryogenic fuel into the expansion chamber. Further, the drive assembly includes a heating element extending at least partially into the expansion chamber and configured to introduce thermal energy into the expansion chamber, thereby facilitating vaporization of the liquid cryogenic fuel. Vaporization of the liquid cryogenic fuel increases a pressure inside the expansion chamber causing the piston to move in a first direction. The pressurization assembly includes a barrel defining a bore and a plunger slidably disposed within the bore. The plunger defines a pressurization chamber within the bore. The pressurization chamber is configured to receive liquid cryogenic fuel therein. The plunger is operatively coupled to and driven by the piston. The movement of the piston in the first direction causes movement of the plunger to pressurize the cryogenic fuel within the pressurization chamber. 
     In a yet another aspect of the present disclosure, an engine system is provided. The engine system includes an engine and a fuel system configured to supply cryogenic fuel to the engine. The fuel system includes a cryogenic fuel tank and a cryogenic pump disposed within the cryogenic fuel tank. The cryogenic pump includes a drive assembly and a pressurization assembly operatively coupled to the drive assembly. The drive assembly includes a housing having a sidewall and a piston slidably disposed within the housing. The sidewall and a first surface of the piston define an expansion chamber within the housing. The drive assembly further includes a fuel supply valve in fluid communication with the cryogenic fuel tank and configured to provide liquid cryogenic fuel into the expansion chamber. Further, the drive assembly includes a heating element extending at least partially into the expansion chamber and configured to introduce thermal energy into the expansion chamber, thereby facilitating vaporization of the liquid cryogenic fuel. Vaporization of the liquid cryogenic fuel increases a pressure inside the expansion chamber causing the piston to move in a first direction. The pressurization assembly includes a barrel defining a bore and a plunger slidably disposed within the bore. The plunger defines a pressurization chamber within the bore. The pressurization chamber is configured to receive liquid cryogenic fuel therein. The plunger is operatively coupled to and driven by the piston. The movement of the piston in the first direction causes movement of the plunger to pressurize the cryogenic fuel within the pressurization chamber. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic illustration of an exemplary engine system having a fuel system for supplying fuel to an engine, in accordance with an embodiment of the present disclosure; 
         FIG. 2  is a sectional view of an exemplary cryogenic pump disposed inside a cryogenic fuel tank, in accordance with an embodiment of the present disclosure; 
         FIG. 3  is a sectional view of an exemplary cryogenic pump disposed inside the cryogenic fuel tank, in accordance with an alternative embodiment of the present disclosure; and 
         FIG. 4  is a sectional view illustrating a pressurization stroke of the cryogenic pump of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     The present disclosure relates to a cryogenic pump for a cryogenic fuel system of an engine.  FIG. 1  illustrates a schematic illustration of an exemplary engine system  100  including a fuel system  101  for supplying fuel to an engine  102 . The fuel system  101  is configured as a cryogenic fuel system for supplying a gaseous fuel, stored in cryogenically cooled liquefied state, to the engine  102 . 
     The engine  102  may be mounted on a machine (not shown), such as a mining truck, a dump truck, a locomotive or the like. The engine  102  may be powered at least partly or fully by gaseous fuel, such as liquefied natural gas (LNG). In some implementations, the engine  102  may be a high-pressure natural gas engine that is configured to receive a quantity of gas by direct injection. In general, the engine  102  may use natural gas, propane gas, hydrogen gas, or any other suitable gaseous fuel, singularly or in combination with each other, to power the engine&#39;s operations. Alternatively, the engine  102  may be based on a dual-fuel engine system, or a spark ignited engine system. The engine  102  may embody a V-type, an in-line, or a varied configuration as is conventionally known. The engine  102  may be a multi-cylinder engine, although aspects of the present disclosure are applicable to engines with a single cylinder as well. Further, the engine  102  may be one of a two-stroke engine, a four-stroke engine, or a six-stroke engine. Although these configurations are disclosed, aspects of the present disclosure need not be limited to any particular engine type. For the sake of brevity, operation and other functional aspects of the conventionally known engines are not described in greater detail herein. 
     Referring to  FIG. 1 , the fuel system  101  includes a supply of cryogenic fuel, such as a cryogenic fuel tank  104 , a cryogenic pump  106 , and a vaporizer  108 . The cryogenic fuel tank  104 , hereinafter referred to as the tank  104 , stores the fuel in cryogenically cooled liquefied state and defines a tank storage volume  105 . For example, the tank  104  may store the fuel at a cryogenic temperature around −160° C. It will be appreciated that the temperature for storing the liquid fuel as described herein is merely exemplary and that other storage temperatures are also possible without deviating from the scope of the disclosed subject matter. The tank  104  may include an insulated, single or multi-walled configuration. For example, in the multi-walled configuration, the tank  104  may include an inner tank wall, an outer tank wall and an isolating material or a vacuum jacket provided between the inner tank wall and the outer tank wall (not shown). The structural configuration of the tank  104  is configured to insulate the tank  104  from external temperatures, thereby maintaining the liquid fuel in cryogenically cooled liquefied state. 
     The cryogenic pump  106 , hereinafter referred to as the pump  106 , is configured to pressurize and deliver the liquid fuel from the tank  104  to the vaporizer  108 . In an embodiment of the present disclosure, the pump  106  is a reciprocating piston type pump explained in further detail with reference to the  FIGS. 2 through 4 . Operational speed of the pump  106  is controlled based on a fuel demand of the engine  102 . The fuel demand of the engine  102  may be understood as an amount of fuel required by the engine  102  to produce a desired amount of power. The pump  106  is operated within a range of predefined maximum and minimum operational speeds in order to adjust the discharge output of the pump  106  based on the fuel demand of the engine  102 . 
     Furthermore, the fuel system  101  may include a controller  110  operatively coupled to the various components of the fuel system  101  (as shown by the broken lines in  FIG. 1 ), including the pump  106  and the engine  102 . The controller  110  disclosed herein may include various software and/or hardware components that are configured to perform functions consistent with the present disclosure. As such, the controller  110  of the present disclosure may be a stand-alone controller or may be configured to co-operate in conjunction with an existing electronic control module (ECM) of a vehicle to perform functions consistent with the present disclosure. Further, the controller  110  may embody a single microprocessor or multiple microprocessors that include components for selectively controlling operations of the fuel system  101  based on a number of operational parameters associated with the fuel system  101 . 
     According to an embodiment of the present disclosure, the controller  110  may determine the fuel demand of the engine  102  based on one or more operational parameters associated with the engine  102 , such as engine load, speed, torque, etc. The controller  110  may further determine a mass and/or a volumetric flow rate of the fuel that the engine  102  requires for producing a desired power output. The controller  110  accordingly may operate the pump  106  based on the determined mass and/or the volumetric fuel demand of the engine  102 . For example, the controller  110  may adjust the speed of the pump  106  to adjust the discharge output of the pump  106 . Therefore, for higher fuel demands of the engine  102 , the pump  106  is run at a higher speed and for lower fuel demands of the engine  102 , such as during low load and idle conditions, the pump  106  is run at a lower speed. The pump  106  may have a predefined range of rated minimum and maximum operating speed and the controller  110  operates the pump  106  within the predefined range to adjust the discharge output of the pump  106  based on the fuel demands of the engine  102 . 
       FIG. 2  illustrates an exemplary embodiment of the pump  106  disposed inside the tank  104 .  FIG. 3  illustrates an alternative embodiment of the pump  106  disposed inside the tank  104 . The tank  104  defines the tank storage volume  105  that is configured to store and maintain the liquid cryogenic fuel  201  in cryogenically cooled liquefied state. However, it may be contemplated that even though the tank  104  is insulated, ambient heat is naturally transferred to the tank storage volume  105 , causing a portion of the liquid cryogenic fuel  201  to vaporize to a saturated vapor state  203 , hereinafter referred to as the vaporized cryogenic fuel  203 . The vaporized cryogenic fuel  203  and the liquid cryogenic fuel  201  gradually reach an equilibrium within the tank  104 . Therefore, the tank storage volume  105  may include both the liquid cryogenic fuel  201  at the bottom as well as the vaporized cryogenic fuel  203  at the top of the tank  104 . 
     As illustrated in  FIGS. 2 to 4 , the pump  106  is positioned inside the tank  104  within a pump socket  202 . The pump socket  202  is configured to support and secure the pump  106  in place within the tank  104 . In an exemplary embodiment of the present disclosure, the pump socket  202  may include a conical baffle  205 . One or more liquid seals  207  may be provided between the pump socket  202  and the pump  106  to prevent liquid cryogenic fuel  201  from entering the pump socket  202 . 
     In an embodiment of the present disclosure, the pump  106  may include a pressurization assembly  204  configured to pressurize the cryogenic fuel and a drive assembly  206  configured to drive the pressurization assembly  204 . As shown in  FIGS. 2 to 4 , the drive assembly  206  may include a housing  208  having a sidewall  210 , a first end wall  211 , a second end wall  213  defining an internal volume of the housing  208 . As shown in  FIGS. 2 to 4 , the first end wall  211  may be a bottom end wall, whereas the second end wall  213  may be a top end wall. The drive assembly  206  further includes a piston  212  slidably disposed within the housing  208 , such that the piston  212  divides the internal volume of the housing  208  into an expansion chamber  214  and a buffer chamber  216 . 
     The piston  212  is configured to reciprocate within the housing  208  between a top dead center (TDC) position (as shown in  FIGS. 2 and 3 ) and a bottom dead center (BDC) position (as shown in  FIG. 4 ). The piston  212  includes a first surface  218 , such as a top surface or head end, and a second surface  220 , such as a bottom surface or rod end. In an exemplary embodiment, the first surface  218  of the piston  212  along with the sidewall  210  and the second end wall  213  of the housing  208  defines the expansion chamber  214 , and the second surface  220  of the piston  212  along with the sidewall  210  and the first end wall  211  of the housing  208  defines the buffer chamber  216 . Furthermore, the drive assembly  206  may include one or more seal rings  222  disposed about the body of the piston  212  and positioned between the piston  212  and the sidewall  210 , to prevent fluid communication and leakage between the expansion chamber  214  and the buffer chamber  216 . 
     In an embodiment of the present disclosure, the drive assembly  206  may further include a cryogenic fuel injection system  224  configured to selectively provide liquid cryogenic fuel  201  into the expansion chamber  214 . The cryogenic fuel injection system  224  includes a fuel supply valve  226  in fluid communication with a feed tube  228  that is in fluid communication with the tank  104 . In one example, the fuel supply valve  226  may be configured as a fuel injector, a solenoid operated admission valve, a solenoid or piezoelectric actuated valve, or any other remotely controllable valve known in the art. The fuel supply valve  226  is configured to selectively provide and control a predetermined amount of liquid cryogenic fuel from the feed tube  228  to the expansion chamber  214 . The cryogenic fuel injection timing, duration, and the predetermined amount of the liquid cryogenic fuel to be provided into the expansion chamber  214  may be controlled by the controller  110  based on the desired output and volumetric efficiency of the pump  106  in order to obtain a desired operational speed of the pump  106 . For example, the fuel supply valve  226  may be operatively connected to the controller  110  such that controller  110  switches the fuel supply valve  226  between an ON (open) state and an OFF (closed) state according to the injection timing and the predetermined amount of cryogenic fuel to be provided to the expansion chamber  214 . 
     In an exemplary embodiment of the present disclosure, the drive assembly  206  may further include a heating element  230  disposed on the second end wall  213  of the housing  208  and extending at least partially into the expansion chamber  214 . The heating element  230  is configured to introduce thermal energy into the expansion chamber  214  and facilitate vaporization of the liquid cryogenic fuel provided/injected by the fuel supply valve  226  therein. In one example, the heating element  230  may be configured to generate heat itself, such as in case of an electrically driven heater element. In another example, heated working fluid from the engine  102  may be used as the heating element  230  to supply heat to the expansion chamber  214  and the liquid cryogenic fuel therein. Although only two examples of heating element  230  are described herein, it may be contemplated that the scope of claims is not limited to only these two examples and that any other type of heating element may also be used to achieve similar result. 
     When the liquid cryogenic fuel is injected into the heated expansion chamber  214 , the thermal energy of the heating element  230  and the expansion chamber  214  is transferred to the liquid cryogenic fuel resulting in the vaporization of the liquid cryogenic fuel therein. The vaporization of the liquid cryogenic fuel causes an increase in pressure inside the expansion chamber  214  urging the piston  212  to move in a first direction, such as in a downward direction (as shown in  FIGS. 2 to 4 ), to effect a pressurization stroke of the drive assembly  206 . According to an exemplary embodiment of the present disclosure, the vaporization of the cryogenic fuel within the expansion chamber  214  may create a pressure of up to 4.6 mega pascals (MPa), which acting over an area of the first surface  218  of the piston  212 , produces a force, causing the piston  212  to move in a first direction, such as in a downward direction. 
     Further, the drive assembly  206  may include an exhaust valve  232  in fluid communication with the expansion chamber  214  and an accumulator  217 . In an embodiment, the exhaust valve  232  is disposed on the second end wall  213  of the housing  208 , and is configured to facilitate venting of the vaporized cryogenic fuel from the expansion chamber  214  to the accumulator  217 . For example, when a pressure PE within the expansion chamber  214  is greater than a pressure PA of the accumulator  217  and the exhaust valve  232  opens, the vaporized cryogenic fuel from the expansion chamber  214  is released into the low-pressure accumulator  217 . From the accumulator  217 , the vaporized cryogenic fuel may be further provided into air intake manifolds of the engine  102  and is used as fuel. In an embodiment, the exhaust valve  232  may also provide direct fluid communication between the expansion chamber  214  and an intake manifold (not shown) of the engine  102 . The exhaust valve  232  may be operatively coupled to the controller  110 , and the controller  110  may control an opening and closing of the exhaust valve  232 . It may be appreciated that the exhaust valve  232  may be opened during a return stroke of the piston  212  (the drive assembly  206 ) to allow the exit of the vaporized cryogenic fuel from the expansion chamber  214 . In an embodiment, the exhaust valve  232  may be opened when the piston  212  reaches the BDC position and remains open until the piston  212  reaches the TDC position. 
     The return stroke of the drive assembly  206  may be facilitated by a biasing force exerted on the second surface  220  of the piston  212  by a biasing member  234  disposed inside the buffer chamber  216 . The biasing member  234  is configured to move the piston  212  to the retracted position corresponding to the TDC position. In one example, as shown in  FIG. 2 , the biasing member  234  may be a spring  235  having a first end  236  in contact with the first end wall  211  of the housing  208  and a second end  240  in contact with the second surface  220  of the piston  212 . As the piston  212  moves towards the BDC position, the spring  235  is compressed, and therefore the spring  235  exerts the biasing force on the second surface  220  of the piston  212  to move the piston  212  towards the retracted position. However, as the force exerted on the first surface  218  of the piston  212  due to the pressure of vaporized cryogenic fuel in the expansion chamber  214  is greater than the biasing force exerted on the second surface  220  of the piston  212 , the piston  212  moves in the first direction, during the pressurization stroke of the drive assembly  206 . As the exhaust valve  232  is opened, the pressure of the vaporized cryogenic fuel in the expansion chamber  214  decreases due to an exit of the vaporized cryogenic fuel from the expansion chamber  214 . This causes a reduction of force acting on the first surface  218  of the piston  212  to a lower value than that of the biasing force exerted on the second surface  220  of the piston  212  by the spring  235 , thereby causing a movement of the piston  212  towards the retracted position. 
     Furthermore, in an embodiment, the drive assembly  206 , in addition to the spring  235 , may include a vapor inlet port  242  provided on the first end wall  211  of the housing  208  and in fluid communication with the buffer chamber  216  and the tank  104 . The vapor inlet port  242  is configured to facilitate inlet of a volume V of the vaporized cryogenic fuel  203 , present at the top of the tank  104 , into the buffer chamber  216 . The conical baffle  205  of the pump socket  202  along with the liquid seals  207  may provide a guided pathway to facilitate inlet of the vaporized cryogenic fuel  203  into the buffer chamber  216  through the vapor inlet port  242 . The vaporized cryogenic fuel  203  enters the buffer chamber  216  from the top of the tank  104  until the pressure inside the buffer chamber  216  equals to the pressure inside the tank  104 . In such a case, the spring  235  and the volume V of the vaporized cryogenic fuel introduced into the buffer chamber  216  through the vapor inlet port  242  collectively exert the biasing force on the second surface  220  of the piston  212  to move the piston  212  back to the retracted position after the pressurization stroke of the drive assembly  206 . 
     Alternatively, in the embodiment illustrated in  FIG. 3 , only the volume V of the vaporized cryogenic fuel introduced into the buffer chamber  216  through the vapor inlet port  242  exerts the biasing force on the second surface  220  of the piston  212  to move the piston  212  back to the retracted position after the pressurization stroke of the drive assembly  206 . As the exhaust valve  232  is opened at the end of the pressurization stroke of the drive assembly  206 , the pressure of the vaporized cryogenic fuel in the expansion chamber  214  decreases, while the pressure of saturate vapor fuel present inside the buffer chamber  216  remains relatively constant. The decrease in the pressure inside the expansion chamber  214  causes a decrease in the force acting on the first surface  218  of the piston  212  to a magnitude less than the magnitude of the biasing force exerted on the second surface  220  of the piston  212  by the volume V of the saturate vapor fuel. In this manner, the biasing force exerted by the volume V of the vaporized cryogenic fuel on the second surface  220  of the piston  212  causes the piston  212  to move to the retracted position. 
     The drive assembly  206  may be operatively connected to the pressurization assembly  204  and configured to drive the pressurization assembly  204 . As shown in  FIGS. 2 to 4 , the pressurization assembly  204  includes a barrel  244  having a bore  246  defined by an inner wall  247  and a head portion  249 . Further, the pressurization assembly  204  includes a plunger  248  slidably disposed within the bore  246 . As illustrated, the plunger  248  includes a plunger surface  250 . The plunger surface  250  along with the inner wall  247  and the head portion  249  define a pressurization chamber  252  for pressurizing liquid cryogenic fuel to be supplied to the vaporizer  108  and subsequently to the engine  102 . 
     The plunger  248  is operatively coupled to the piston  212  through a push rod  254  such that the movement of the piston  212  inside the housing  208  causes the movement of the plunger  248  within the bore  246 . As shown in  FIGS. 2 to 4 , the push rod  254  is connected to the second surface  220  of the piston  212  at one end and to the plunger  248  at the other end. The plunger  248  and the barrel  244  may be paired with a matched clearance fit to minimize leakage of the liquid cryogenic fuel out of the pressurization chamber  252  and past the plunger  248 . Alternatively, the plunger  248  may include one or more circumferential seals, such as the seals  222  disposed about the piston  212 , described previously. 
     The pressurization assembly  204  may further include a fuel inlet valve  256  provided in fluid communication with the tank  104  and the pressurization chamber  252 . For example, as illustrated in  FIGS. 2 to 4 , the fuel inlet valve  256  is provided on the head portion  249  of the barrel  244 . However, the positioning of the fuel inlet valve  256  is merely exemplary and may be varied to achieve similar results. The fuel inlet valve  256  may be configured to control flow of the liquid cryogenic fuel into the pressurization chamber  252  from the tank  104 . In an embodiment, the fuel inlet valve  256  may be a pressure actuated check valve configured to open and allow flow of the liquid cryogenic fuel from the tank  104  into the pressurization chamber  252  when the piston  212  and the plunger  248  move towards the retracted position (intake stroke of the pressurization assembly  204 ). Further, the fuel inlet valve  256  is configured to close when the pressurization chamber  252  is filled completely with the liquid cryogenic fuel and remain in closed position when the pressure within the pressurization chamber  252  increases during the pressurization stroke. 
     Furthermore, the pressurization assembly  204  may include a fuel discharge valve  258  in fluid communication with the pressurization chamber  252  and a discharge passage  260  defined within the barrel  244 . For example, the discharge passage  260  may be provided in fluid communication with the vaporizer  108  and is configured to facilitate outlet of the pressurized liquid cryogenic fuel from the pressurization chamber  252  to the vaporizer  108 , from where the gaseous fuel is subsequently supplied to the engine  102  for combustion. In an exemplary embodiment, the fuel discharge valve  258  may be a pressure actuated check valve to facilitate only outlet of the cryogenic fuel when the pressure inside the pressurization chamber  252  increases during the pressurization stroke. 
     INDUSTRIAL APPLICABILITY 
     The pump  106  according to the embodiments as disclosed herein may be used in the fuel system  101  to pressurize and supply cryogenic fuel from the tank  104  to the other components of the fuel system  101 , such as the vaporizer  108  and subsequently to the engine  102 . The pump  106  as disclosed herein eliminates the usage of a separate working fluid for operating the piston  212  and the plunger  248 , and hence the usage of a separate seal to separate the two fluids. Therefore, the pump  106  mitigates the risk of cross contamination of the working fluids and increases the life and efficiency of the pump  106 . 
     The operation of the pump  106  will now be described in greater detail with respect to  FIGS. 2 to 4  in the following description. Initially, the piston  212  is in a retracted position corresponding to the TDC position of the piston  212  (as shown in  FIG. 2  and  FIG. 3 ). At this time, the exhaust valve  232  is in a closed position and the heating element  230  is activated to introduce the thermal energy into the expansion chamber  214 . 
     To effect a pressurization stroke of the drive assembly  206 , the fuel supply valve  226  is actuated, allowing a predetermined amount of liquid cryogenic fuel to enter into the expansion chamber  214 . The controller  110  may control the operation of the fuel supply valve  226  to inject the cryogenic fuel according to the predefined injection timing and duration. As the cryogenic fuel is injected into the pre-heated expansion chamber  214 , the cryogenic fuel vaporizes and results in an increase in pressure inside the expansion chamber  214 . The pressure created inside the expansion chamber  214  acts on the first surface  218  of the piston  212  to produce a force F to move the piston  212  in a first direction, such as the downward direction, to effect the pressurization stroke of the drive assembly  206 . It may be contemplated that the piston  212  moves towards the BDC position, thereby increasing a volume of the expansion chamber  214  and decreasing a volume of the buffer chamber  216 . 
     The plunger  248  is operatively connected to the piston  212  by means of the push rod  254 . Therefore, the downward movement of the piston  212  causes the plunger  248  also to move in the downward direction, thereby resulting in pressurization of the cryogenic fuel present in the pressurization chamber  252 . This means that the pressurization stroke of the drive assembly  206  causes the pressurization stroke in the pressurization assembly  204 . 
     As the plunger  248  pressurizes the liquid cryogenic fuel inside the pressurization chamber  252 , the fuel discharge valve  258  opens to fluidly connect the pressurization chamber  252  with the discharge passage  260  and allow flow of the pressurized cryogenic fuel from the pump  106  to the other components of the fuel system  101 , such as the vaporizer  108 , via the discharge passage  260 . Meanwhile, as the plunger  248  pressurizes the liquid cryogenic fuel within the pressurization chamber  252 , the piston  212  moves towards the BDC position. Subsequently, as the piston  212  reaches the BDC position, the exhaust valve  232  is opened to fluidly connect the expansion chamber  214  to the accumulator  217 , thereby allowing venting of the vaporized cryogenic fuel from the expansion chamber  214  to the accumulator  217 . The gaseous cryogenic fuel, vented from the expansion chamber  214 , may be provided to the accumulator  217  through a separate fluid channel (not shown), for storage and subsequent supply to the engine  102 . The accumulator  217  may be at a relatively lower pressure than the expansion chamber  214 , thereby causing the vaporized cryogenic fuel to flow from the high-pressure expansion chamber  214  to the low-pressure accumulator  217  when the exhaust valve  232  opens. Alternatively, the vaporized cryogenic fuel exiting from the expansion chamber  214  may be returned to the tank  104  for future utilization. 
     Further, as the vaporized cryogenic fuel exits the expansion chamber  214 , the pressure within the expansion chamber  214  decreases thereby decreasing the force acting on the first surface  218  of the piston  212 . Further, as the vaporized cryogenic fuel exits the expansion chamber  214 , the pressure within the expansion chamber  214  decreases thereby causing the volume V of the vaporized cryogenic fuel  203 , present in the tank  104 , enter the buffer chamber  216  through the vapor inlet port  242  and exert a force on the second surface  220  of the piston  212 . In this embodiment, wherein the pump  106  is embodied as pump  106   a , the spring  235  is also connected to the second surface  220  of the piston  212 , which acts as the biasing force on the piston  212 . The biasing force exerted by the spring  235  acts in combination with the force exerted by the volume V of the vaporized cryogenic fuel  203  entering the buffer chamber  216  to move the piston  212  in the second direction, such as an upward direction, to move the piston  212  towards the retracted position. In an alternative embodiment, there may be no vapor inlet port  242  and the biasing force exerted by the spring  235  acts alone on the piston  212  to move it towards the retracted position. 
     In an alternative embodiment, as shown in  FIG. 3 , wherein the pump  106  is embodied as the pump  106   b , the spring  235  may not be present in the buffer chamber  216 , and the volume V of the vaporized cryogenic fuel introduced into the buffer chamber  216  through the vapor inlet port  242  acts as the sole biasing force on the second surface  220  of the piston  212 , causing the piston  212  to move in the upward direction towards the retracted position. 
     As the piston  212  moves towards the retracted position, i.e., the TDC position during the return stroke, the plunger  248  also moves along with the piston  212  in the upward direction. The upward movement of the plunger  248  creates a vacuum inside the pressurization chamber  252  thereby causing opening of the fuel inlet valve  256  thereby allowing intake of the liquid cryogenic fuel into the pressurization chamber  252  from the tank  104 . The upward movement of the plunger  248  reduces the pressure inside the pressurization chamber  252 , and the pressure of the tank  104  being relatively higher causes the fuel inlet valve  256  to open and fluidly connect the tank  104  with the pressurization chamber  252  thereby allowing the liquid cryogenic fuel to flow from the tank  104  to the low-pressure pressurization chamber  252 . 
     Subsequently, the pressurization stroke of the drive assembly  206  and the pressurization stroke of the pressurization assembly  204  may be repeated continuously, as required, to operate the pump  106  for supplying the pressurized cryogenic fuel to the vaporizer  108  and subsequently to the engine  102 . 
     While aspects of the present disclosure have been particularly depicted and described with reference to the embodiments above, it will be understood by those skilled in the art that various additional embodiments may be contemplated by the modification of the disclosed machines, systems and methods without departing from the spirit and scope of what is disclosed. Such embodiments should be understood to fall within the scope of the present disclosure as determined based upon the claims and any equivalents thereof.