Double wall mixer with active heat transfer

Patent metadata

Field	Value
Publication number	US-10577995-B2
Application number	US-201715686220-A
Country	US
Kind code	B2
Filing date	Aug 25, 2017
Priority date	Aug 25, 2017
Publication date	Mar 3, 2020
Grant date	Mar 3, 2020

Abstract

A vehicle exhaust system includes an outer housing defining an internal cavity surrounding an axis, an inlet baffle configured to direct engine exhaust gas into the internal cavity, an injector that is configured to spray a fluid into the internal cavity to mix with engine exhaust gas, and an inner wall spaced radially inward of an inner surface of the outer housing to define a gap. The inner wall has an impingement side facing the axis and a non-impingement side facing the gap. At least one heating element is associated with the non-impingement side to actively heat the inner wall to reduce spray deposit formation on the impingement side.

First claim

The invention claimed is:

1. A vehicle exhaust system comprising:
an outer housing defining an internal cavity surrounding an axis;
an inlet baffle configured to direct engine exhaust gas into the internal cavity;
an injector that is configured to spray a fluid into the internal cavity downstream of the inlet baffle to mix with engine exhaust gas;
an inner wall spaced radially inward of an inner surface of the outer housing to define a gap, wherein the inner wall has an impingement side facing the axis and a non-impingement side facing the gap;
at least one opening formed in the inlet baffle to direct exhaust gas flow into the gap; and
at least one heating element associated with the non-impingement side to actively heat the inner wall to reduce spray deposit formation on the impingement side.

2. The vehicle exhaust system according to claim 1 wherein the outer housing comprises a curved housing and wherein the inner wall comprises a curved wall portion that is spaced radially inward of the inner surface of the outer housing such that a radially outer exhaust gas passage is formed in the gap between the outer housing and the inner wall and a radially inner exhaust gas passage is defined at least in part by the impingement side of the inner wall, and wherein the at least one heating element comprises an electric heater that is positioned within the radially outer exhaust gas passage and is attached to the non-impingement side of the curved wall portion.

3. The vehicle exhaust system according to claim 1 wherein the at least one heating element comprises a ceramic heater.

4. The vehicle exhaust system according to claim 1 including an outlet baffle positioned downstream of the inlet baffle, and wherein the fluid is injected into the internal cavity between the inlet and the outlet baffles.

5. The vehicle exhaust system according to claim 1 wherein the at least one heating element comprises a thick film heater.

6. The vehicle exhaust system according to claim 5 wherein the thick film heater comprises a positive temperature coefficient resister heater.

7. The vehicle exhaust system according to claim 6 including a power source coupled to the positive temperature coefficient resister heater, and wherein the power source provides a first power level when the inner wall is below a predetermined temperature and a second power level that is less than the first power level when the inner wall is above the predetermined temperature.

8. The vehicle exhaust system according to claim 1 wherein the at least one heating element comprises an electric heater positioned within the gap and including a power source attached to the electric heater with at least one electrical connection.

9. The vehicle exhaust system according to claim 8 including at least one shield to protect a connection interface of the electrical connection to the electric heater.

10. The vehicle exhaust system according to claim 8 wherein the inner wall is comprised of a metal material and wherein the power source provides a first power level when a temperature of the metal material is below a predetermined temperature and a second power level that is less than the first power level when the metal material is above the predetermined temperature.

11. A vehicle exhaust system comprising:
an outer housing defining an internal cavity surrounding an axis;
an inlet baffle configured to direct engine exhaust gas into the internal cavity;
an injector that is configured to spray a fluid into the internal cavity downstream of the inlet baffle to mix with engine exhaust gas;
an inner wall spaced radially inward of an inner surface of the outer housing to define a gap, wherein the inner wall has an impingement side facing the axis and a non-impingement side facing the gap; and
at least one heating element associated with the non-impingement side to actively heat the inner wall to reduce spray deposit formation on the impingement side, wherein the at least one heating element is a thick film heater that comprises a positive temperature coefficient resister heater, and wherein the positive temperature coefficient resister heater is applied along a predetermined length of the non-impingement side of the inner wall, and wherein the predetermined length is positioned opposite the injector.

12. A vehicle exhaust system comprising:
an outer housing defining an internal cavity surrounding an axis;
an inlet baffle configured to direct engine exhaust gas into the internal cavity;
an injector that is configured to spray a fluid into the internal cavity to mix with engine exhaust gas;
an inner wall spaced radially inward of an inner surface of the outer housing to define a gap, wherein the inner wall has an impingement side facing the axis and a non-impingement side facing the gap;
the outer housing comprises a curved housing and the inner wall comprises a curved wall portion that is spaced radially inward of the inner surface of the outer housing such that a radially outer exhaust gas passage is formed in the gap between the outer housing and the inner wall and a radially inner exhaust gas passage is defined at least in part by the impingement side of the inner wall;
wherein the inlet baffle includes at least one opening into the radially inner exhaust gas passage and at least one opening into the radially outer exhaust gas passage; and
at least one heating element associated with the non-impingement side to actively heat the inner wall to reduce spray deposit formation on the impingement side, wherein the at least one heating element comprises an electric heater that is positioned within the radially outer exhaust gas passage and is attached to the non-impingement side of the curved wall portion.

13. A vehicle exhaust system comprising:
an outer housing defining an internal cavity surrounding an axis;
an inlet baffle configured to direct engine exhaust gas into the internal cavity;
an injector that is configured to spray a fluid into the internal cavity downstream of the inlet baffle to mix with engine exhaust gas;
an inner wall spaced radially inward of an inner surface of the outer housing to define a gap, wherein the inner wall has an impingement side facing the axis and a non-impingement side facing the gap, wherein the inner wall extends only partially about the axis; and
at least one heating element associated with the non-impingement side to actively heat the inner wall to reduce spray deposit formation on the impingement side.

14. A method of reducing spray deposit formation in a mixer of a vehicle exhaust system comprising:
providing an outer housing defining an internal cavity surrounding an axis;
positioning an inlet baffle relative to the outer housing to direct engine exhaust gas into the internal cavity;
mounting an injector to the outer housing such that the injector injects a fluid into the internal cavity downstream of the inlet baffle to mix with engine exhaust gas;
spacing an inner wall radially inward of an inner surface of the outer housing to define a gap, wherein the inner wall has an impingement side facing the axis and a non-impingement side facing the gap;
forming at least one opening in the inlet baffle to direct exhaust gas flow into the gap; and
associating at least one heating element with the non-impingement side to actively heat the inner wall to reduce spray deposit formation on the impingement side.

15. The method according to claim 14 including positioning an outlet baffle downstream of the inlet baffle and injecting the fluid into the internal cavity between the inlet and the outlet baffles.

16

Assignees

• Faurecia Emissions Control Technologies Usa Llc

Inventors

• Ker Eric
• Rohde John G

Classifications

• F01N2900/1811

  Temperature · CPC title

• F01N3/2066

  Selective catalytic reduction [SCR] · CPC title

• F01N2240/16

  an electric heater, i.e. a resistance heater · CPC title

• F01N2610/02

  the substance being ammonia or urea · CPC title

• F01N2260/06

  for improving exhaust evacuation or circulation, or reducing back-pressure · CPC title