Two engine system with a gaseous fuel stored in liquefied form

1. A gaseous fuelled two-engine system comprising:

(a) a storage tank that is thermally insulated for holding a gaseous fuel in liquefied form;

(b) a first outlet associated with a lower portion of said storage tank for delivering said gaseous fuel in liquefied form;

(c) a second outlet associated with an upper portion of said storage tank for delivering said gaseous fuel in vaporized form;

(d) a cryogenic pump comprising a suction inlet fluidly connected to said first outlet;

(e) a drive for said cryogenic pump comprising a power supply;

(f) a vaporizer having a fuel inlet fluidly connected to a discharge outlet of said cryogenic pump;

(g) a first engine that is a direct injection gaseous-fuelled internal combustion engine comprising a fuel injector for injecting said gaseous fuel directly into a combustion chamber at pressures greater than 200 bar, said fuel injector receiving said gaseous fuel through a pipe that is in fluid communication with a vaporizer fuel outlet; and

(h) a second engine that is a fumigated gaseous-fuelled internal combustion engine comprising a fuel injector for injecting said gaseous fuel into an intake air manifold that delivers intake air to a combustion chamber of said second engine, wherein said gaseous fuel that is supplied to said second engine is delivered through a pipe that is in fluid communication with said second outlet, and wherein said second engine is said power supply for said cryogenic pump drive.

2. The gaseous fuelled two-engine system of claim 1 , wherein said second engine comprises a throttle in an intake air passage and a spark plug in said combustion chamber to trigger ignition of said gaseous fuel.

3. The gaseous fuelled two-engine system of claim 1 , wherein said system is mounted on a vehicle with said first engine being a primary source of motive power to said vehicle.

4. The gaseous fuelled two-engine system of claim 1 , wherein said second engine is also a power supply for at least one other auxiliary device selected from the group consisting of electrical generators, air conditioners, refrigeration equipment and hydraulic drives.

5. The gaseous fuelled two-engine system of claim 1 , further comprising an accumulator in fluid communication with said vaporizer outlet for storing vaporized gas.

6. The gaseous fuelled two-engine system of claim 5 , further comprising a pipe and a pressure reducing valve associated therewith for directing a portion of said gaseous fuel from said accumulator to said second engine.

7. The gaseous fuelled two-engine system of claim 1 , further comprising a pipe and a pressure reducing valve associated therewith for directing a portion of said gaseous fuel from said vaporizer outlet to said second engine.

8. The gaseous fuelled two-engine system of claim 1 , further comprising a second vaporizer, said second vaporizer comprising an inlet in direct fluid communication with said lower portion of said storage tank and an outlet fluidly connected to supply gaseous fuel to said second engine.

9. The gaseous fuelled two-engine system of claim 1 , wherein said second engine is located in thermal contact with said vaporizer.

10. The gaseous fuelled two-engine system of claim 1 , wherein said gaseous fuel is natural gas.

11. The gaseous fuelled two-engine system of claim 1 , further comprising a coolant subsystem for said second engine, said coolant subsystem comprising a cooling circuit in thermal communication with said vaporizer.

12. A vehicle comprising the gaseous fuelled two-engine system of claim 1 .

13. The vehicle of claim 12 , wherein said vehicle is one of a ship, a locomotive and a truck.

14. A method of supplying a gaseous fuel in said gaseous fuelled two-engine system of claim 1 , the method comprising:

(a) fuelling said second engine with vaporized fuel from said storage tank;

(b) driving said cryogenic pump with power supplied by said second engine; vaporizing said fuel in said vaporizer; and

(c) fuelling said first engine with vaporized fuel pumped from said storage tank from said cryogenic pump.

15. The method of claim 14 , further comprising supplementally fueling said second engine with said gaseous fuel pumped from said storage tank by said cryogenic pump.

16. The method of claim 14 , further comprising heating said vaporizer with heat generated by said second engine.

17. The method of claim 16 , wherein said second engine is located in thermal contact with said vaporizer whereby heat generated by said second engine is transferred to said vaporizer by conduction.

18. The method of claim 14 , further comprising regulating the speed of said second engine according to demand for said gaseous fuel from said gaseous fuelled two-engine system.

19. A vehicle powered by a gaseous fuelled two-engine system comprising:

(a) a first engine that is a high pressure direct injection internal combustion engine that provides on average at least 90% of the total power output of said system when said vehicle is moving;

(b) a second engine that is a fumigated internal combustion engine providing, on average, no more than 10% of the total power output of said system when said vehicle is moving;

(c) a fuel storage tank that stores a gaseous fuel in liquefied form at cryogenic temperatures;

(d) a cryogenic pump and piping connecting a lower portion of said fuel storage tank to a fuel injector for injecting fuel directly into a combustion chamber of said first engine;

(e) piping connecting an upper portion of said fuel storage tank to a low pressure fuel injector for injecting said gaseous fuel into an intake air manifold or intake port associated with a combustion chamber of said second engine.

20. The vehicle of claim 19 , wherein said vehicle is one of a ship, a locomotive and a truck.