Standalone thermal energy recycling device for engine after-treatment systems

Abstract

A standalone thermal energy recycling device in which exhaust air emitted from an internal combustion engine exchanges heat with that being heated during regeneration of after-treatment devices. By using the thermal energy recycling device, heat generated for regeneration is used to compensate energy loss during heat exchange rather than provide the overall energy needed for boosting exhaust flow temperature to target. Inside the thermal energy recycling device, heat exchanger is bypassed during normal engine operations for decreasing back pressure.

Description

[0001]This present application claims priority from U.S. provisional application No. 60 / 850,459 having the title of Engine Aftertreatment System with Thermal Energy Recycling and filed on Oct. 10, 2006.FIELD OF THE INVENTION[0002]The present invention relates to devices for effectively boosting and controlling temperature of exhaust gases emitted from an internal combustion engine to facilitate regeneration of after-treatment systems.BACKGROUND OF THE INVENTION[0003]Reducing oxides of nitrogen (NOx), carbon monoxide (CO), hyrdrocarbon (HC), and particulate matter (PM) in exhaust air from internal combustion engines is required in emission control. DOCs (Diesel Oxidation Catalyst) and three-way catalysts have been broadly used for reducing CO, HC, and NOx, while SCR (Selective Catalytic Reduction), LNT (Lean NOx Trap, a.k.a. NOx adsorber), LNC (Lean NOx Catalyst), and EGR (Exhaust Gas Recirculation) technology are used for achieving low NOx emissions. The PM in exhaust air usually is...

AI Technical Summary

Benefits of technology

[0014]In accordance to an advantageous feature of the invention, good fuel economy is achieved by burning less fuel in the DOC due to the exhaust flow at DOC inlet has a higher temperature.

[0024]Yet in another embodiment of the present invention, the after-treatment system comprises a DOC, a DPF, an LNT, and a heat exchange device, in which high temperature exhaust air emit from the LNT during desulfation exchanges heat with low temperature exhaust air. In accordance with an advantageous feature of the invention, during desulfation, the temperature dropping is minimized in rich cycle due to the energy exchange between the exchange device and exhaust air, and temperature rising time is shortened in lean cycle. Thereby, desulfation process is more effective.

Problems solved by technology

However, due to high exhaust flow rate, most of regeneration energy is actually used for increasing enthalpy of exhaust air instead of providing enough temperature for soot to be oxidized or for reducing metal sulfate.

Due to the large power needed in regeneration, resistive heating devices normally cannot be directly used for mobile applications without exhaust flow control, while fuel burners are complex and it is hard to control the regeneration temperature.

As a result, it is difficult to use DOCs for engines with low exhaust temperature, e.g. engines with two-stage turbochargers.

And in transient applications, e.g. vehicles stop and go frequently, when turbo outlet temperature frequently drops below light-off temperature, regeneration cannot be effectively performed.

Images