Jet Fuel Thermal Oxidation Test Equipment

Abstract

Jet fuels' thermal oxidation characteristics are evaluated via the Standard Test Method for Thermal Stability of Aviation Turbine Fuels. This test method mimics the thermal stress conditions encountered by jet fuel in operation and is often carried out by laboratory devices, known as rigs. The rigs include a test section having a sleeve and a heater tube arranged therein. A pair of bus bars secure the test section to the rig and apply a current to the heater tube. The applied current heats the heater tube and subjects the sample jet fuels that are flowing in the volume between the sleeve and heater tube to high temperatures, which may produce thermal oxidation deposits on the heater tube. Heater tubes are difficult to install, however, and a gauge may be used to ensure accurate placement of the heater tube within the sleeve. In addition, the fuel sample must be prepared via an aeration process, and systems are disclosed for automating the aeration process such that the sample is prepared precisely according to the test standard. Moreover, the rig includes a pump system that moves the fuel sample through the test section, and a pump system is provided in a double syringe arrangement that optimizes fuel flow through the test section without fluctuation. Finally, the rigs include cooling systems for cooling the bus bars and maintaining an appropriate thermal profile within the heater tube, and cooling systems may be provided that independently control the temperature of each bus bar.

1 . A temperature system for independently controlling a temperature of a bus bar to improve a thermal profile of a heater tube in a thermal oxidation rig, the temperature system comprising:
 a heat sink arranged proximate to a base of the bus bar that secures the bus bar to the thermal oxidation rig,   a cooling element that interposes the heat sink and the base of the bus bar,   a forced convection device,   a thermocouple arranged at an end of the bus bar that is opposite the base and proximate to the heater tube, wherein the thermocouple measures the temperature of the bus bar, and   a controller that is associated with the cooling element and the forced convection device, wherein the controller controls the cooling element and the forced convection device based on the temperature measured by the thermocouple.   
     
     
         2 . The temperature systems of  claim 1 , wherein the base bar includes a bore extending from the base that receives a heat pipe. 
     
     
         3 . A thermal oxidation rig for analyzing a fuel sample, the thermal oxidation rig comprising:
 a test section comprising a sleeve and heater tube assembly supported by a pair of bus bars, wherein the sleeve and heater tube assembly is secured within a clamping assembly arranged in each of the bus bars, wherein the sleeve and heater tube assembly comprises   a sleeve, wherein the sleeve is hollow and is open at opposed ends;   a heater tube secured within the sleeve and hermetically sealed therein;   a fuel inlet and a fuel outlet arranged on the sleeve between the open ends of the sleeve;   the temperature system of  claim 1  for independently controlling a temperature of a said bus bar to improve a thermal profile of the heater tube in the thermal oxidation   
     
     
         4 . The thermal oxidation rig of  claim 3 , wherein the bus bar includes a bore extending from the base that receives a heat pipe. 
     
     
         5 . The thermal oxidation rig of  claim 3 , further comprising a pumping system for moving the fuel sample from a sample container, into the fuel inlet, and through the test section,
 the pumping system comprising:   a first and second syringe assembly, each syringe assembly having a hollow barrel that defines a volume for holding the fuel sample, a tip disposed at an upper end of the barrel, an open end disposed at a lower end of the barrel, each syringe assembly having an inlet valve and an outlet valve;   a pair of pistons that are each arranged to slide within one of the barrel volumes, each piston having shaft that extends into the volume through the open end of the barrel and connects to a head portion that abuts an interior wall of the hollow barrel so that the volume is sealed from the open end of the barrel, and   a pair of motors, each of the motors is coupled to one of the pistons and independently controlled so that a flow rate of the fuel sample remains constant, wherein each of the motors controls a stroke of its respective piston such that the pistons accelerate and decelerate simultaneously.   
     
     
         6 . A system for automatically aerating a fuel sample, the system comprising: a pump for facilitating an airflow, an flowmeter that measures the airflow, and a sample container into which the airflow is injected, wherein the pump further comprises a controller that is associated with the flowmeter and automatically maintains the airflow at a constant rate via a control loop. 
     
     
         7 . The system of  claim 6 , wherein the system further comprises an air desiccant that removes moisture from the airflow. 
     
     
         8 . The system of  claim 7 , wherein the system further comprises a humidity sensor arranged to sample the airflow passing through the air desiccant. 
     
     
         9 . The system of  claim 6 , wherein the sample container further comprises a diffuser arranged therein. 
     
     
         10 . The system of  claim 6 , wherein the constant rate is 1.5 liters per minute. 
     
     
         11 . The system of  claim 6 , wherein the system further comprises a filter that filters the airflow before passing through the pump. 
     
     
         12 . A gauge for positioning a heater tube within a sleeve, the gauge comprising a body having a first and a second end and a bore that extends from the first end into the body for a length, wherein the bore has a diameter that is sized to receive an open end of the sleeve, wherein the heater tube includes a pair of shoulders interposed by a thin portion and the shoulders extend away from the thin portion from a lip, and wherein one of the shoulders extends through the sleeve and into the length of the bore such that lip is positioned proximate to an outlet of the sleeve. 
     
     
         13 . The gauge of  claim 12 , wherein the bore of the gauge extends from the first end for a length that is shorter than the body. 
     
     
         14 . The gauge of  claim 12 , wherein the gauge further comprises a shoulder that is radially disposed along the bore at a location spaced from the first end by a distance equal to the length. 
     
     
         15 . The gauge of  claim 14 , wherein the bore extends from the first end to the second end of the body. 
     
     
         16 . The gauge of  claim 12 , wherein a portion of the bore proximate to the first end of the body is threaded. 
     
     
         17 . (canceled) 
     
     
         18 . A temperature system for independently controlling a temperature of a bus bar to improve a thermal profile of a heater tube in a thermal oxidation rig, the temperature system comprising:
 a heat sink arranged proximate to a base of the bus bar that secures the bus bar to the thermal oxidation rig,   a cooling element that interposes the heat sink and the base of the bus bar,   a forced convection device,   a thermocouple arranged at an end of the bus bar that is opposite the base and proximate to the heater tube, wherein the thermocouple measures the temperature of the bus bar, and   a controller that is associated with the cooling element and the forced convection device, wherein the controller controls the cooling element and the forced convection device based on the temperature measured by the thermocouple.   
     
     
         19 . The temperature systems of  claim 18 , wherein the base bar includes a bore extending from the base that receives a heat pipe. 
     
     
         20 . A clamping system for securing a heater tube to a bus bar of a thermal oxidation rig, the clamping system comprising:
 a bore extending into an end of the bus bar and terminating at an inner face of the bus bar;   a pair of prongs extending from the inner face to the end of the bus bar, the prongs defining a gap that extends with the bore;   a plate arranged to slide within the gap in an axial direction, and   a screw arranged within the bore and coupled to the plate, wherein rotation of the screw translates to displacement of the plate in the axial direction.   
     
     
         21 . A thermal oxidation rig for analyzing a fuel sample, the thermal oxidation rig comprising:
 a test section comprising a sleeve and heater tube assembly supported by a pair of bus bars, wherein the sleeve and heater tube assembly is secured within a clamping assembly arranged in each of the bus bars, wherein the sleeve and heater tube assembly further comprises:
 a gauge for positioning a heater tube of the heater tube assembly within a sleeve of the heater tube assembly, the gauge comprising a body having a first and a second end and a bore that extends from the first end into the body for a length, wherein the bore has a diameter that is sized to receive an open end of the sleeve, wherein the heater tube includes a pair of shoulders interposed by a thin portion and the shoulders extend away from the thin portion from a lip, and wherein one of the shoulders extends through the sleeve and into the length of the bore such that lip is positioned proximate to an outlet of the sleeve, 
   wherein the clamping assembly secures the heater tube to the bus bar and further comprises:
 a bore extending into an end of the bus bar and terminating at an inner face of the bus bar, 
 a pair of prongs extending from the inner face to the end of the bus bar, the prongs defining a gap that extends with the bore, 
 a plate arranged to slide within the gap in an axial direction, and 
 a screw arranged within the bore and coupled to the plate, wherein rotation of the screw translates to displacement of the plate in the axial direction; 
   a pumping system for moving the fuel sample from the sample container and through the test section, the pumping system comprising:
 a first and second syringe assembly, each syringe assembly having a hollow barrel that defines a volume for holding the fuel sample, a tip disposed at an upper end of the barrel, an open end disposed at a lower end of the barrel, each syringe assembly having an inlet valve and an outlet valve, 
 a pair of pistons that are each arranged to slide within one of the barrel volumes, each piston having shaft that extends into the volume through the open end of the barrel and connects to a head portion that abuts an interior wall of the hollow barrel so that the volume is sealed from the open end of the barrel, and 
 a pair of motors, each of the motors is coupled to one of the pistons and independently controlled so that a flow rate of the fuel sample remains constant, wherein each of the motors controls a stroke of its respective piston such that the pistons accelerate and decelerate simultaneously; 
   an aeration system for aerating the fuel sample in the sample container, the aeration system including a pump, a flowmeter for measuring airflow generated by the pump and injected into the sample container, wherein the pump further comprises a controller that is associated with the flowmeter and automatically maintains the airflow at a constant rate via a control loop; and   a temperature control system of  claim 1  for independently controlling a temperature of a said bus bar to improve a thermal profile of the heater tube in the thermal oxidation rig.