Method and apparatus for reducing emissions in diesel engines

1. A method of reducing emissions from a diesel engine, comprising the steps of:

providing an injector to an exhaust outlet of the diesel engine, the injector having an orifice with a diameter of about 0.006 inch or less;

providing a reagent to the injector at an inlet pressure between about 120 psi and about 60 psi;

actuating the injector on and off at a frequency between about 10 Hz and about 1 Hz with an on-time of about 1% or more;

injecting the reagent via the orifice into the exhaust outlet at an injection rate; and

wherein varying at least two of the inlet pressure, the frequency, and the on-time achieves a turn-down ratio of a maximum injection rate to a minimum injection rate of at least about 31:1.

2. The method according to claim 1 , wherein the injection rate is between about 0.2 grams/minute and about 25 grams/minute.

3. The method according to claim 1 , wherein the reagent includes at least one of a urea solution and a hydrocarbon solution.

4. The method according to claim 1 , wherein the at least two consists of the frequency and the on-time.

5. The method according to claim 4 , further comprising the step of:

maintaining a constant inlet pressure of about 80 psi.

6. The method according to claim 1 ,

wherein the diameter is 0.005 inch or less; and

wherein varying each of the inlet pressure, the frequency, and the on-time achieves a turn-down ratio of at least 100:1.

7. The method according to claim 1 , further comprising the step of:

adjusting the inlet pressure until the reagent is injected with droplet sizes between about 40μ and about 100μ SMD.

8. The method according to claim 1 , wherein the reagent is provided to the injector from a reagent tank, wherein the method further includes a step of recirculating at least a portion of the reagent back to the reagent tank.

9. The method according to claim 8 , wherein a recirculation flow rate is greater than the injection rate.

10. The method according to claim 1 , wherein the reagent is provided at a flow rate between about 2.5 gallons/hour and about 10 gallons/hour.

11. The method according to claim 10 , wherein the minimum injection rate is about 0.2 grams/minute and the maximum injection rate is about 25 grams/minute.

12. The method according to claim 1 , wherein the reagent is provided at a flow rate between about 7 gallons/hour and about 25 gallons/hour.

13. The method according to claim 12 , wherein the minimum injection rate is about 20 grams/minute and the maximum injection rate is about 600 grams/minute.

14. A method of reducing emissions from a diesel engine, comprising the steps of:

providing a reagent injector in communication with an exhaust outlet of the diesel engine, the injector having an orifice with a diameter less than about 0.035 inch;

providing a reagent to the injector at an inlet pressure;

actuating the injector on and off at a frequency to inject the reagent via the orifice into the exhaust outlet at an injection rate;

adjusting an on-time of the injector between about 85% and about 5%;

adjusting the inlet pressure between a first inlet pressure and a second inlet pressure;

wherein said steps of adjusting the on-time and adjusting the inlet pressure achieve a turn-down ratio of a maximum injection rate to a minimum injection rate greater than 10:1.

15. The method according to claim 14 ,

wherein the diameter is about 0.03 inch or less; and

wherein maximum injection rate is about 800 grams/minute.

16. The method according to claim 14 , further comprising the step of:

adjusting the frequency between a first frequency of about 10 Hz and a second frequency of about 1.5 Hz and adjusting the on-time to about 1% or less to achieve a turn-down ratio of at least about 50:1.

17. The method according to claim 16 , wherein the first inlet pressure is about 120 psi and the second inlet pressure is about 80 psi.

18. The method according to claim 17 ,

wherein the orifice diameter is 0.005 inch or less; and

wherein the turn-down ratio is at least about 100:1.

19. The method according to claim 14 , wherein the first inlet pressure is about 120 psi and the second inlet pressure is about 60 psi.

20. The method according to claim 14 , wherein the first inlet pressure is about 140 psi and the second inlet pressure is about 40 psi.

21. The method according to claim 14 , wherein the turn-down ratio is at least about 43:1.

22. A method of reducing emissions from a diesel engine, comprising the steps of:

providing a reagent injector to an exhaust outlet of the diesel engine, the injector having an orifice with a diameter not greater than about 0.006 inch;

supplying a reagent to the injector at an inlet pressure of about 80 psi or less;

actuating the injector on and off at a frequency not greater than about 1.5 Hz;

wherein said actuating injects the reagent via the orifice into the exhaust outlet at an injection rate of about 3.3 grams/minute or less; and

wherein the injector has an on-time less than 10.5%.

23. The method according to claim 22 ,

wherein the injector has an on-time less than 5%; and

wherein said actuating injects the reagent via the orifice into the exhaust outlet at an injection rate of about 1.5 grams/minute or less.

24. The method according to claim 22 ,

wherein the injector has an on-time of about 1% or less; and

wherein said actuating injects the reagent via the orifice into the exhaust outlet at an injection rate of about 0.8 grams/minute or less.

25. The method according to claim 22 , wherein the frequency is 1.0 Hz or less.

26. The method according to claim 22 , wherein the injection rate is between about 0.2 grams/minute and about 3 grams/minute.

27. The method according to claim 22 , wherein the on-time is about 1% or less.

28. The method according to claim 22 , wherein the reagent includes at least one of a urea solution and a hydrocarbon solution.