Exhaust system having a pre-heater

Abstract

An exhaust system for a machine is disclosed. The exhaust system may have a first conduit configured to receive a first portion of an exhaust flow from an engine. The exhaust system may further have a second conduit configured to receive a remaining portion of the exhaust flow from the engine. The exhaust system may also have a diffuser connected at downstream ends of the first and the second conduits. In addition, the exhaust system may have an after-treatment component fluidly connected downstream of the diffuser. The exhaust system may also have a pre-heater configured to heat exhaust in the second conduit.

What is claimed is: 
     
         1 . An exhaust system, comprising:
 a first conduit configured to receive a first portion of an exhaust flow from an engine;   a second conduit configured to receive a remaining portion of the exhaust flow from the engine;   a diffuser connected at downstream ends of the first and the second conduits;   an after-treatment component fluidly connected downstream of the diffuser; and   a pre-heater configured to heat exhaust in the second conduit.   
     
     
         2 . The exhaust system of  claim 1 , further including a valve controllable to selectively direct the remaining portion of the exhaust flow from the engine to the second conduit. 
     
     
         3 . The exhaust system of  claim 2 , further including a controller configured to control the valve and to activate the pre-heater when the temperature of exhaust flowing out of the diffuser is below a first threshold temperature. 
     
     
         4 . The exhaust system of  claim 3 , wherein the pre-heater includes:
 a heating portion disposed outside the diffuser and configured to heat exhaust in the second conduit; and   a heater tube disposed within the diffuser.   
     
     
         5 . The exhaust system of  claim 4 , wherein exhaust enters the diffuser from the first conduit in a direction generally orthogonal to a direction of exhaust entering the diffuser from the second conduit. 
     
     
         6 . The exhaust system of  claim 5 , wherein the after-treatment component includes:
 a diesel oxidation catalyst; and   a diesel particulate filter located downstream of the diesel oxidation catalyst.   
     
     
         7 . The exhaust system of  claim 6 , wherein the pre-heater is configured to heat exhaust from the second conduit above a light-off temperature of the diesel oxidation catalyst. 
     
     
         8 . The exhaust system of  claim 7 , wherein the diesel oxidation catalyst is configured to heat exhaust in the after-treatment component above a regeneration temperature of the diesel particulate filter. 
     
     
         9 . A method of pre-heating exhaust, comprising:
 selectively directing a first portion of exhaust from an engine into a first conduit;   selectively directing a remaining portion of the exhaust from the engine into a second conduit;   heating exhaust in the second conduit;   transferring the heated exhaust to a diffuser connected at downstream ends of the first and the second conduits; and   treating the heated exhaust in an after-treatment component at a location downstream of the diffuser.   
     
     
         10 . The method of  claim 9 , wherein:
 heating includes heating the exhaust in a heating portion of the second conduit outside of the diffuser; and   transferring the heated exhaust to a heater tube disposed within the diffuser.   
     
     
         11 . The method of  claim 10 , further including mixing the heated exhaust from the heater tube with exhaust from the first conduit to produce a generally uniformly heated exhaust in the diffuser. 
     
     
         12 . The method of  claim 11 , further including adjusting at least one of a flow rate of exhaust in the second conduit and heating of exhaust in the second conduit such that a temperature of exhaust flowing out of the diffuser is greater than a first threshold temperature. 
     
     
         13 . The method of  claim 12 , further including:
 heating exhaust in the after-treatment component to a second threshold temperature.   
     
     
         14 . The method of  claim 13 , wherein the first threshold temperature is about 240 to 280° C. 
     
     
         15 . The method of  claim 14 , wherein the second threshold temperature is about 500 to 650° C. 
     
     
         16 . A machine comprising:
 an engine having a plurality of cylinders;   an exhaust system configured to receive exhaust from the plurality of cylinders, treat exhaust, and direct exhaust to atmosphere, the exhaust system including:
 a first conduit configured to receive a first portion of an exhaust flow from the engine; 
 a second conduit configured to receive a remaining portion of the exhaust flow from the engine; 
 a diffuser connected at downstream ends of the first and the second conduits; 
 an after-treatment component fluidly connected downstream of the diffuser; and 
 a pre-heater configured to heat exhaust in the second conduit; 
   a valve controllable to selectively direct the portion of the exhaust flow from the engine to the first conduit; and   a controller to control the valve and activate the pre-heater when a temperature of exhaust flowing out of the diffuser is below a first threshold temperature.   
     
     
         17 . The machine of  claim 16 , wherein the pre-heater further includes:
 a heating portion disposed outside the diffuser and configured to heat exhaust from the second conduit; and   a heater tube disposed within the diffuser and configured to transfer the heated exhaust to the diffuser.   
     
     
         18 . The machine of  claim 17 , wherein exhaust enters the diffuser from the first conduit in a direction generally orthogonal to a direction of exhaust entering the diffuser from the second conduit. 
     
     
         19 . The machine of  claim 18 , wherein the after-treatment component includes:
 a diesel oxidation catalyst; and   a diesel particulate filter.   
     
     
         20 . The machine of  claim 19 , wherein the diesel oxidation catalyst is configured to heat exhaust in the after-treatment component to a second threshold temperature.