Exhaust aftertreatment system with ammonia gas generator

1. An exhaust aftertreatment system comprising:

a reductant tank;

a gaseous ammonia source;

an injector receiving liquid reductant from the reductant tank and gaseous ammonia from the gaseous ammonia source and injecting the liquid reductant into a stream of exhaust gas in a first mode, and injecting the gaseous ammonia into the stream of exhaust gas in a second mode;

a first conduit communicating liquid reductant from the reductant tank to the injector; and

a second conduit communicating gaseous ammonia from the gaseous ammonia source to the injector.

2. The exhaust aftertreatment system of claim 1 , wherein the injector simultaneously injects both of the liquid reductant and the gaseous ammonia into the stream of exhaust gas in a third mode.

3. The exhaust aftertreatment system of claim 2 , wherein the injector includes an outlet port through which a mixture of liquid reductant and gaseous ammonia are injected into the stream of exhaust gas.

4. The exhaust aftertreatment system of claim 3 , wherein the injector includes a pair of inlet ports fluidly connecting the first and second conduits with the outlet port.

5. The exhaust aftertreatment system of claim 1 , wherein the injector is fluidly coupled with an exhaust pipe at a location upstream of a catalyst in the stream of exhaust gas.

6. The exhaust aftertreatment system of claim 5 , wherein the injector includes a liquid reductant input to receive the liquid reductant and a gaseous ammonia input to receive the gaseous ammonia.

7. The exhaust aftertreatment system of claim 6 , wherein the catalyst is a selective catalytic reduction catalyst.

8. The exhaust aftertreatment system of claim 1 , further comprising an air source to facilitate injection of both the liquid reductant and the gaseous ammonia into the stream of exhaust gas.

9. The exhaust aftertreatment system of claim 8 , wherein the air source is in fluid communication with the injector via a third conduit, and wherein air flow through a passage in the injector cools the injector.

10. The exhaust aftertreatment system of claim 9 , further comprising a first valve disposed along the third conduit and controlling the fluid flow therethrough.

11. The exhaust aftertreatment system of claim 10 , wherein the injector includes a liquid-reductant outlet that is fluidly connected to a recirculation conduit coupled to a liquid reductant tank.

12. The exhaust aftertreatment system of claim 11 , wherein the liquid reductant from the reductant tank and the gaseous ammonia from the gaseous ammonia source is mixed in a chamber within the injector.

13. The exhaust aftertreatment system of claim 12 , further comprising an electrical heating element in a heat transfer relationship with the air tank.

14. The exhaust aftertreatment system of claim 13 , wherein the first conduit includes a second valve to prevent backwards flow of the liquid reductant.

15. The exhaust aftertreatment system of claim 14 , further comprising a control module controlling a position of the first valve and a rate of injection of a mixture of the liquid reductant and the gaseous ammonia.

16. An exhaust aftertreatment system comprising:

a reductant tank containing liquid reductant;

a gaseous ammonia source containing gaseous ammonia;

a pressurized air source facilitating injection of one or both of the liquid reductant and the gaseous ammonia into a stream of exhaust gas;

a first conduit communicating liquid reductant from the reductant tank to the stream of exhaust gas;

a second conduit communicating gaseous ammonia from the gaseous ammonia source to the stream of exhaust gas; and

a third conduit communicating pressurized air from the pressurized air source to the stream of exhaust gas.

17. The exhaust aftertreatment system of claim 16 , further comprising an injector that receives the gaseous ammonia from the second conduit and the pressurized air from the third conduit, wherein the second and third conduits are in communication with each other upstream of the injector.

18. The exhaust aftertreatment system of claim 16 , further comprising an electrical heating element in a heat transfer relationship with the pressurized air source.

19. The exhaust aftertreatment system of claim 16 , further comprising an injector in fluid communication with the first, second and third conduits, and wherein the injector includes a liquid-reductant outlet that is fluidly connected to a recirculation conduit coupled to the liquid reductant tank.

20. The exhaust aftertreatment system of claim 16 , wherein a first valve is disposed along the first conduit to prevent backward flow of the liquid reductant.

21. The exhaust aftertreatment system of claim 20 , wherein a second valve is disposed along the third conduit to control the fluid flow therethrough.

22. The exhaust aftertreatment system of claim 16 , further comprising an injector receiving the liquid reductant from the reductant tank via the first conduit and the gaseous ammonia from the gaseous ammonia source via the second conduit and injecting both the reductant and the gaseous ammonia into the stream of exhaust gas.

23. The exhaust aftertreatment system of claim 22 , wherein the liquid reductant from the reductant tank and the gaseous ammonia from the gaseous ammonia source mixes in a chamber within the injector.

24. An injector for an exhaust aftertreatment system, the injector comprising an injector body including a first port, a second port, a third port, a fourth port, and a fifth port, the first port in fluid communication with the third port and the fifth port, the second port in fluid communication with the fourth port, the second and fourth ports are fluidly isolated from the first, third and fifth ports, the injector body housing a pintle that is movable between a closed position preventing fluid flow through the fifth port and an open position allowing fluid flow through the fifth port.

25. The injector of claim 24 , wherein the first port is fluidly connected to a liquid reductant conduit, and the second port is fluidly connected to a conduit containing ammonia gas.

26. The injector of claim 25 , wherein the third port forms a liquid-reductant outlet that is fluidly connected to a recirculation conduit coupled to a liquid reductant tank.

27. The injector of claim 25 , wherein the fourth port is defined by an outer annular collar surrounding the fifth port.

28. The injector of claim 27 , further comprising an intermediate annular collar extending from the injector body, the intermediate annular collar is surrounded by the outer annular collar and cooperates with the outer annular collar to define the fourth port.

29. The injector of claim 28 , further comprising a tubular inner body that is surrounded by the intermediate annular collar, the tubular inner body cooperating with the intermediate annular collar to define an annular passageway in fluid communication with the first port, and wherein the tubular inner body defines an inner passageway in fluid communication with the third port.

30. The injector of claim 29 , wherein the pintle is disposed within the inner passageway.

31. An injector for an exhaust aftertreatment system, the injector comprising:

an outer body including a liquid inlet port receiving liquid reductant, a gas inlet port receiving gaseous ammonia, a liquid outlet port through which the liquid reductant exits the injector, and a gas outlet port through which the gaseous ammonia exits the injector; and

a pintle disposed within the outer body and movable between an open position allowing fluid flow through the liquid outlet port and a closed position preventing fluid flow through the liquid outlet port.

32. The injector of claim 31 , wherein the gas outlet port is formed in an annular collar that at least partially surrounds the liquid outlet port.

33. The injector of claim 32 , wherein the gas outlet port is an annular port that at least partially surrounds the liquid outlet port.

34. The injector of claim 32 , wherein the annular collar includes an annular recess that surrounds a portion of the pintle and is in fluid communication with the gas inlet port and the gas outlet port, and wherein the annular recess is axially spaced apart from the liquid outlet port.

35. The injector of claim 31 , wherein the outer body includes a liquid-recirculation outlet port.

36. The injector of claim 35 , wherein the liquid-recirculation port is in fluid communication with inner passage disposed within the outer body, wherein the pintle is at least partially disposed within the inner passage, wherein the outer body includes a first annular collar that defines a first annular passage surrounding a portion of the inner passage, wherein the first annular passage fluidly connects the liquid inlet port with the liquid outlet port, wherein the outer body includes a second annular collar that cooperates with the first annular collar to define the gas outlet port, and wherein the gas outlet port is a second annular passage that surrounds at least a portion of the first annular passage.

37. An exhaust aftertreatment system comprising:

a reductant tank;

a reactor system receiving reductant from the reductant tank and outputting gas comprising ammonia;

a storage tank receiving gas comprising ammonia from the reactor system and storing a volume of gas comprising ammonia;

a first conduit communicating gas comprising ammonia from the reactor system to a stream of exhaust gas, the first conduit bypassing the storage tank; a second conduit communicating gas comprising ammonia from the storage tank to the stream of exhaust gas;

a third conduit communicating gas comprising ammonia from the reactor system to the storage tank; and

a first heat exchanger in a heat transfer relationship with the reactor system, the first heat exchanger transferring heat from exhaust gas to the reactor system, further comprising a second heat exchanger in which heat is transferred from the stream of exhaust gas to a working fluid, wherein the first and second heat exchangers are fluidly coupled to each other to allow a first flow of the working fluid therebetween.