Method and apparatus for controlling exhaust gas flow rate

Abstract

An exhaust emissions control system includes a valve in an exhaust stream portion of a mainstream exhaust ahead of an aftertreatment element such as a catalytic converter. The valve controls the amount of exhaust flowing into a hydrocarbon reformer. A bi-directional acoustical air meter in the exhaust stream portion ahead of the reformer measures the velocity of the exhaust stream portion, and a computer determines the amount of combustion needed in the converter at all times, adjusts the amount of hydrocarbon fuel provided to the reformer, and adjusts the position of the valve to provide the optimum amount of exhaust gas flow into the reformer to achieve a desired temperature in the converter.

1 . A system for aftertreatment of an exhaust gas stream, comprising: 
 a) a valve for controlling a second gas stream portion of said exhaust gas stream;    b) an after treatment element disposed in a first gas stream portion of said exhaust gas stream for receiving at least said first gas stream portion;    c) a reformer for receiving said second gas stream portion and for reforming hydrocarbon fuel from said second gas stream portion to form a reformate, said reformate being provided into said aftertreatment element; and    d) a gas flow meter for controlling the flow of said second gas stream portion into said reformer.    
   
   
       2 . A system in accordance with  claim 1  wherein said gas flow meter is an acoustical gas flow meter.  
   
   
       3 . A system in accordance with  claim 2  wherein said acoustical flow meter is a bi-directional acoustical gas flow meter.  
   
   
       4 . A system in accordance with  claim 1  wherein said gas flow meter is located in said second gas stream portion.  
   
   
       5 . A system in accordance with  claim 1  further including a programmable controller.  
   
   
       6 . A system in accordance with  claim 5  wherein said programmable controller is a computer.  
   
   
       7 . A system in accordance with  claim 1  wherein said aftertreatment element is selected from a group consisting of a NOx adsorber, a particulate trap, and an oxygen catalyst.  
   
   
       8 . A system for reforming hydrocarbon fuel from the exhaust gas stream of an internal combustion engine, comprising: 
 a) a hydrocarbon reformer; and    b) a bi-directional acoustical gas flow meter located in said gas stream for controlling the flow of exhaust gas into said reformer.    
   
   
       9 . A system in accordance with  claim 8  wherein said engine is selected from the group consisting of spark-ignited and diesel.  
   
   
       10 . An internal combustion engine having a system for catalytically modifying the exhaust gas stream of the engine, said engine comprising: 
 a) a valve for controlling a second gas stream portion of said exhaust gas stream;    b) an after treatment element disposed in a first gas stream portion of said exhaust gas stream for receiving at least said first gas stream portion;    c) a reformer for receiving said second gas stream portion and for reforming hydrocarbon fuel from said second gas stream portion to form a reformate, said reformate being provided into said aftertreatment element for combustion therein; and    d) a gas flow meter for controlling the flow of said second gas stream portion into said reformer.    
   
   
       11 . A system for treatment of an exhaust gas stream, comprising: 
 a) an exhaust producing energy source for producing said exhaust gas stream; and    b) a bi-directional acoustical gas flow meter for measuring the flow of said exhaust gas stream.    
   
   
       12 . A system in accordance with  claim 11  further including an emission control device disposed in flow communication with said exhaust producing energy source for receiving said exhaust gas stream, wherein said bi-directional acoustical gas flow meter measures the flow of said exhaust gas stream into said emission control device.  
   
   
       13 . A system in accordance with  claim 11  wherein said exhaust producing energy source is selected from the group consisting of power train reformer, fuel cell, spark-ignited internal combustion engine and compression-ignited internal combustion engine.  
   
   
       14 . A system in accordance with  claim 11  further including a reformer for receiving said exhaust gas stream and for reforming hydrocarbon fuel from said exhaust gas stream, said bi-directional acoustical gas flow meter disposed in flow communication with said reformer for measuring the flow of said exhaust stream into said reformer.