THERMAL STORAGE DEVICE FOR USE IN A FLUID FLOW SYSTEM
An exhaust system is provided that includes at least one exhaust aftertreatment unit provided in an exhaust fluid flow pathway and a thermal storage device disposed upstream from the exhaust aftertreatment unit. The thermal storage device is operable to store thermal mass and provide thermal insulation to enable a catalyst to maintain a minimum predetermined temperature for a minimum predetermined time. In one form, a heater is also provided proximate the thermal storage device, along with variations that include a secondary flow pathway for the thermal storage device.
1 . An exhaust system comprising:
at least one exhaust aftertreatment unit provided in an exhaust fluid flow pathway; and
a thermal storage device disposed upstream from the at least one exhaust aftertreatment unit, wherein the thermal storage device is operable to store thermal mass and provide thermal insulation to enable a catalyst to maintain a minimum predetermined temperature for a minimum predetermined time.
2 . The exhaust system according to claim 1 , wherein the minimum predetermined temperature is approximately 100° C. and the minimum predetermined time is about 8 hours.
3 . The exhaust system according to claim 1 , wherein the minimum predetermined temperature is approximately 180° C. and the minimum predetermined time is a time span for an FTP-75 test procedure.
4 . The exhaust system according to claim 3 further comprising a heater disposed proximate the thermal storage device.
5 . The exhaust system according to claim 4 , wherein the thermal storage device is operable to release thermal energy when the heater is turned off and when the fluid temperature surrounding the thermal storage device is lower than the temperature of the thermal storage device.
6 . The exhaust system according to claim 1 , wherein the at least one exhaust aftertreatment unit is selected from the group consisting of a catalytic converter, a diesel particulate filter, a selective catalytic reduction, a diesel oxidation catalyst, a lean nitrogen oxides (NOx) trap, an ammonia slip catalyst, reformers, a decomposition tube, and combinations thereof.
7 . The exhaust system according to claim 6 , wherein the thermal storage device is operable to assist with at least one of light-off and NO to NO 2 conversion in the diesel oxidation catalyst unit.
8 . The exhaust system according to claim 6 , wherein the thermal storage device is operable to assist with NOx conversion in the selective catalytic reduction unit.
9 . The exhaust system according to claim 6 , wherein the decomposition tube is disposed upstream of a selective catalytic reduction unit.
10 . The exhaust system according to claim 9 , wherein the thermal storage device is operable to assist with at least one of processing urea and NOx conversion in the decomposition tube.
11 . The exhaust system according to claim 1 further comprising a secondary flow pathway in fluid communication with the exhaust fluid pathway, wherein the thermal storage device is disposed within the secondary flow pathway.
12 . The exhaust system according to claim 11 further comprising a heater disposed proximate the secondary flow pathway and a flow control device actuated by the heater, wherein the flow control device is in communication with the secondary flow pathway.
13 . The exhaust system according to claim 12 , wherein the heater is disposed proximate the thermal storage device.
14 . The exhaust system according to claim 11 , wherein the secondary flow pathway functions to cool a flow of exhaust fluid when the exhaust fluid is above a predetermined temperature.
15 . The exhaust system according to claim 1 , wherein the thermal storage device comprises a phase change material.
16 . The exhaust system according to claim 15 , wherein the thermal storage device changes phase between a temperature of approximately 180° C. and 450° C.
17 . An exhaust system comprising:
at least one exhaust aftertreatment unit provided in an exhaust fluid flow pathway;
a thermal storage device disposed upstream from the at least one exhaust aftertreatment unit, wherein the thermal storage device is operable to store thermal mass and provide thermal insulation to enable a catalyst to maintain a minimum predetermined temperature for a minimum predetermined time; and
a heater disposed proximate the thermal storage device.
18 . The exhaust system according to claim 17 , wherein the thermal storage device is operable to release thermal energy when the heater is turned off and when the fluid temperature surrounding the thermal storage device is lower than the temperature of the thermal storage device.
19 . The exhaust system according to claim 17 further comprising a secondary flow pathway in fluid communication with the exhaust fluid pathway, wherein the thermal storage device is disposed within the secondary flow pathway.
20 . The exhaust system according to claim 17 , wherein the thermal storage device comprises a phase change material that changes phase between a temperature of approximately 180° C. and 450° C.