Fuel separation via fuel vapor management systems

Abstract

Systems and methods for separating higher octane fuel from a fuel mixture are presented. In one example, fuel vapors may be limited or constrained from migrating to fuel tanks storing lower octane fuels. The systems may vent fuel vapors from a plurality of fuel tanks to a single fuel vapor storage canister. Alternatively, the systems may vent fuel vapors from the plurality of fuel tanks to a plurality of fuel vapor storage canisters.

1 . A fuel storage system, comprising:
 a first fuel tank;   a second fuel tank;   a first fuel vapor storage canister;   a second fuel vapor storage canister;   a first conduit coupled to the first fuel tank and the first fuel vapor storage canister;   a second conduit not coupled to the first conduit, the second conduit coupled to the first fuel tank and the second fuel vapor storage canister; and   a valve positioned along the second conduit.   
     
     
         2 . The fuel storage system of  claim 1 , where the first fuel tank stores a fuel having a higher octane number than a fuel stored in the second fuel tank, and where the first conduit provides fluidic communication between the first fuel tank and the first fuel vapor storage canister, and where the second conduit provides fluidic communication between the first fuel tank and the second fuel vapor storage canister. 
     
     
         3 . The fuel storage system of  claim 1 , further comprising a third conduit coupled to the second fuel tank and the second fuel vapor storage canister. 
     
     
         4 . The fuel storage system of  claim 3 , further comprising a valve positioned along the third conduit. 
     
     
         5 . The fuel storage system of  claim 4 , further comprising a fourth conduit, the fourth conduit coupled to an engine intake system and the second fuel vapor storage canister. 
     
     
         6 . The fuel storage system of  claim 1 , further comprising a controller including executable instructions stored in non-transitory memory for limiting return of fuel vapors from the second fuel vapor storage canister to the second fuel tank. 
     
     
         7 . The fuel storage system of  claim 1 , further comprising a conduit coupled to an engine waste heat exchanger and one or more of the two or more fuel tanks. 
     
     
         8 . A fuel storage system, comprising:
 two or more fuel tanks, a first fuel tank of the two or more fuel tanks storing a fuel having a higher octane number than a remainder of the two or more fuel tanks;   a conduit coupled to the first fuel tank and one of the remainder of the two or more fuel tanks; and   a check valve positioned along the conduit biased to limit flow from the first fuel tank to the remainder of the two or more fuel tanks.   
     
     
         9 . The fuel storage system of  claim 8 , further comprising a fuel vapor storage canister and a conduit coupled to the fuel vapor storage canister and the first fuel tank, and where the conduit coupled to the fuel vapor storage canister is a sole conduit coupled to the fuel vapor storage canister and the two or more fuel tanks. 
     
     
         10 . The fuel storage system of  claim 9 , further comprising a conduit coupled to an engine waste heat exchanger and one or more of the two or more fuel tanks. 
     
     
         11 . The fuel storage system of  claim 9 , further comprising a fuel pump in fluidic communication with the first fuel tank and a first fuel injector. 
     
     
         12 . The fuel storage system of method of  claim 11 , further comprising a fuel pump in fluidic communication with one of the two or more fuel tanks other than the first fuel tank and a second fuel injector. 
     
     
         13 . A fuel storage system, comprising:
 a first fuel tank storing a first fuel;   a second fuel tank storing a second fuel, the second fuel including a lower octane number than the first fuel;   a first fuel vapor storage canister in fluidic communication with the first fuel tank; and   a controller including executable instructions stored in non-transitory memory for limiting flow of fuel vapors from the first fuel tank to the second fuel tank.   
     
     
         14 . The fuel storage system of  claim 13 , further comprising a valve, and where limiting flow of fuel vapors is achieved via closing the valve. 
     
     
         15 . The fuel storage system of  claim 13 , further comprising a first conduit coupled to the first fuel vapor storage canister and the first fuel tank, and a second conduit coupled to the first fuel vapor storage canister and the second fuel tank. 
     
     
         16 . The fuel storage system of  claim 13 , further comprising a second fuel vapor storage canister, the second fuel vapor storage canister in fluidic communication with the second fuel tank and not in fluidic communication with the first fuel tank outside of an engine intake. 
     
     
         17 . The fuel storage system of  claim 16 , further comprising two fuel vapor purge valves, a first fuel vapor purge valve of the two fuel vapor purge valves in fluidic communication with the first fuel vapor storage canister and the engine intake. 
     
     
         18 . The fuel storage system of  claim 17 , further comprising a second fuel vapor purge valve of the two fuel vapor purge valves in fluidic communication with the second fuel vapor storage canister and the engine intake. 
     
     
         19 . The fuel storage system of  claim 13 , further comprising additional controller instructions for allowing flow of fuel vapors from the second fuel tank to the first fuel tank during diurnal cooling of the fuel vapor storage system. 
     
     
         20 . The fuel storage system of  claim 13 , further comprising additional controller instructions to inject condensed fuel in the first fuel tank to an engine, and where the condensed fuel originated from the second fuel tank.