LNG delivery system for gas powered vehicles

Abstract

The delivery system of the invention consists of a pair of LNG fuel tanks mounted on a vehicle. A solenoid valve associated with each tank allows the vehicle operator to select the tank from which LNG is to be delivered to the engine. An automatic override system is provided whereby if the pressure in the non-selected tank rises above a predetermined level, the operator's tank selection is overridden and gas from the non-selected tank is used until the pressure falls below the predetermined level. This override system eliminates the need to vent gas to the atmosphere to avoid pressure building up and thereby eliminates waste of the LNG. Each tank is also provided with a pressure building capability such that the gas will always be delivered to the engine with sufficient pressure. The system is designed such that LNG from a stationary low pressure storage tank can be delivered at high pressure to refuel the tanks. Finally, a variable insulation barrier is provided in the fuel tanks to minimize heat transfer between the LNG and gas head.

What is claimed is: 
     
       1. A natural gas delivery system, comprising: a) a first vehicle mounted tank for storing liquid natural gas and natural gas vapor;   b) a second vehicle mounted tank for storing liquid natural gas and natural gas vapor;   c) a use line connected to said first and second tanks for receiving natural gas from the first and second tanks and delivering natural gas vapor to the use device on said vehicle and means for pressurizing the natural gas in the use line;   d) means for selecting one of said first or second tanks to deliver natural gas to the use line; and   e) means for overriding said selecting means to deliver natural gas vapor to the use line from either of said tanks in response to detecting a pressure rise therein which exceeds a preselected maximum.   
     
     
       2. The delivery system according to claim 1, further including means for filling said first and second tanks. 
     
     
       3. The delivery system according to claim 2, wherein said means for filling includes a storage means for holding liquid natural gas at a low pressure and means for delivering the liquid natural gas to the first and second tanks at a higher pressure. 
     
     
       4. The delivery system according to claim 3, wherein liquid means for filling further includes means for venting high pressure gas from said first and second tanks to said storage means. 
     
     
       5. The delivery system according to claim 1, wherein said means for selecting one of said first and second tanks includes a manually activated valve associated with each of said first and second tanks. 
     
     
       6. The delivery system according to claim 1, wherein said use line includes a heat exchanger for vaporizing the liquid natural gas. 
     
     
       7. The delivery system according to claim 1, further including a means for pressurizing the first and second tanks. 
     
     
       8. The delivery system according to claim 1, further including means for minimizing heat transfer between the liquid natural gas and the natural gas vapor in the first and second tanks. .Iadd. 
     
     
       9.  A natural gas delivery system for a vehicle comprising: a) a first vehicle mounted tank for storing liquid natural gas and natural gas vapor under pressure;   b) a second vehicle mounted tank for storing liquid natural gas and natural gas vapor under pressure;   c) a use line connected to said first and second tanks for receiving natural gas from the first and second tanks and delivering natural gas vapor to the use device on said vehicle;   d) means for pressurizing the natural gas in the use line; and   e) means for delivering natural gas to the use line from either of said tanks, said means for delivering natural gas delivering the natural gas from the tank which has the higher pressure..Iaddend..Iadd.   
     
     
       10.  The delivery system of claim 9 further comprising means for filling said first and second tanks..Iaddend..Iadd.11. The delivery system of claim 10 wherein said means for filling includes storage means for holding liquid natural gas at a low pressure and means for delivering the liquid natural gas to the first and second tanks at a higher 
     
     
        pressure..Iaddend..Iadd.12.  The delivery system of claim 11 wherein said means for filling further includes means for venting high pressure gas from said first and second tanks to said storage means..Iaddend..Iadd.13. The delivery system of claim 9 further comprising means for pressurizing the first and second tanks..Iaddend..Iadd.14. The delivery system of claim 9 further comprising means for minimizing heat transfer between the liquid natural gas and the natural gas vapor in the first and second tanks..Iaddend.