Self-draining ullage fuel tank systems and related methods

Abstract

Self-draining ullage fuel tank system and related methods are described. An example fuel tank apparatus includes a fuel tank and a ullage tank positioned at an elevation relative to the fuel tank. The example fuel tank apparatus also includes a fluid path to fluidly couple a cavity of the fuel tank and a cavity of the ullage tank. The fluid path having a first end coupled to the cavity of the fuel tank. The fluid path having a second end extending through an opening of an upper wall of the ullage tank and having an opening positioned adjacent a bottom surface of the cavity of the ullage tank.

What is claimed is: 
     
         1 . A fuel tank apparatus, comprising:
 a fuel tank;   a ullage tank positioned at an elevation relative to the fuel tank; and   a fluid path to fluidly couple a cavity of the fuel tank and a cavity of the ullage tank, the fluid path having a first end coupled to the cavity of the fuel tank, the fluid path having a second end extending through an opening of an upper wall of the ullage tank and having an opening positioned adjacent a bottom surface of the cavity of the ullage tank.   
     
     
         2 . The fuel tank apparatus of  claim 1 , wherein the fluid path is to provide a siphon effect that is initiated when the first end of the fluid path is primed to start liquid flow. 
     
     
         3 . The fuel tank apparatus of  claim 2 , wherein the siphon effect is to draw fuel from the cavity of the ullage tank toward the cavity of the fuel tank. 
     
     
         4 . The fuel tank apparatus of  claim 1 , wherein the bottom surface of the cavity of the ullage tank has a convex shape. 
     
     
         5 . The fuel tank apparatus of  claim 1 , wherein the opening is positioned adjacent an apex of the bottom surface of the cavity of the ullage tank. 
     
     
         6 . The fuel tank apparatus of  claim 1 , further comprising a second fluid path to fluidly couple the cavity of the ullage tank and a vent, the second fluid path being coupled to the upper wall of the ullage tank. 
     
     
         7 . An apparatus, comprising:
 a ullage tank defining a cavity to contain excess fuel from a cavity of a fuel tank; and   a fluid path to fluidly couple the cavity of the ullage tank and the cavity of the fuel tank, the fluid path positioned through an upper wall of the ullage tank, at least a portion of the fluid path positioned adjacent a bottom wall in the cavity of the ullage tank, the bottom wall being opposite the upper wall.   
     
     
         8 . The apparatus of  claim 7 , wherein the cavity of the ullage tank is positioned at an elevation relative to the fuel tank. 
     
     
         9 . The apparatus of  claim 8 , wherein a first end of the fluid path is primed to start liquid flow via a vacuum to draw excess fuel from the cavity of the ullage tank to the cavity of the fuel tank, the first end of the fluid path being coupled to the fuel tank. 
     
     
         10 . The apparatus of  claim 7 , wherein the bottom wall of the ullage tank has an inverted conical-like shape. 
     
     
         11 . The apparatus of  claim 10 , wherein a second end of the fluid path has an opening positioned in the cavity adjacent an apex of the conical-like shape. 
     
     
         12 . The apparatus of  claim 7 , further comprising a second fluid path coupled to the upper wall of the ullage tank, the second fluid path to fluidly couple the cavity of the ullage tank and the atmosphere. 
     
     
         13 . A fuel tank apparatus, comprising:
 first means for containing fluid;   second means for containing fluid positioned at an elevation relative to the first means for containing fluid, the second means for containing fluid being fluidly coupled to and configured to receive fuel from the first means for containing fluid; and   means for fluidly coupling the first and second means for containing fluid, the means for fluidly coupling passing through an opening in an upper wall of the second means for containing fluid and having a portion extending into a cavity of the second means for containing fluid and positioned adjacent a bottom portion of the second means for containing fluid.   
     
     
         14 . The apparatus of  claim 13 , further comprising means for supporting the portion of the means for fluidly coupling extending into the cavity of the second means for fluidly coupling. 
     
     
         15 . The apparatus of  claim 14 , further comprising means for attaching the portion of the means for fluidly coupling that extends into the cavity to an upper wall of the second means for fluidly coupling. 
     
     
         16 . The apparatus of  claim 13 , further comprising means for venting, the means for venting to fluidly couple the cavity of the second means for fluidly coupling and the atmosphere. 
     
     
         17 . A method for coupling a fuel tank assembly, comprising:
 providing a fuel tank;   providing a ullage tank;   positioning the ullage tank at a height relative to the fuel tank; and   fluidly coupling a cavity defined by the fuel tank and a cavity defined by the ullage tank via a fluid path, a first end of the fluid path being coupled to the fuel tank, a second end of the fluid path being positioned through an upper wall of the ullage tank and at least partially positioned in the cavity of the ullage tank.   
     
     
         18 . The method of  claim 17 , wherein positioning the fluid path at least partially in the cavity of the ullage tank comprises positioning the second end of the fluid path adjacent a bottom portion of the ullage tank. 
     
     
         19 . The method of  claim 18 , further comprising fluidly coupling the cavity of the ullage tank and the atmosphere via a vent. 
     
     
         20 . The method of  claim 18 , further comprising securing the second end of the fluid path adjacent the bottom portion of the ullage tank via a coupling.