Method and apparatus for reducing NOx emissions

Abstract

In one embodiment, a reductant system comprises: a high pressure reductant pump in operable communication with a power source, wherein the reductant pump comprises a reductant chamber and is capable of pressurizing reductant to a pressure of greater than or equal to 500 psi; a reductant reservoir in fluid communication with the reductant chamber; and an atomizer in fluid communication the reductant chamber. In another embodiment, the reductant system comprises: a reductant pump; system pump in operable communication the reductant pump, a reductant reservoir in fluid communication with the reductant chamber, and an atomizer in fluid communication the reductant chamber. The system pump is configured to provide motive power via a pressurized fluid to the reductant pump, and the system pump is fluidly isolated from a reductant chamber in the reductant pump.

1 . A reductant system, comprising: 
 a reductant pump in operable communication with a power source, wherein the reductant pump comprises a reductant chamber and is capable of pressurizing reductant to a pressure of greater than or equal to 500 psi;    a reductant reservoir in fluid communication with the reductant chamber; and    an atomizer in fluid communication the reductant chamber.    
   
   
       2 . The reductant system of  claim 1 , wherein the power source is a system pump, wherein the system pump can provide motive power via a pressurized fluid to the reductant pump, and wherein the system pump is fluidly isolated from the reductant chamber.  
   
   
       3 . The reductant system of  claim 1 , wherein the reductant reservoir is in thermal communication with a reductant heater.  
   
   
       4 . The reductant system of  claim 1 , wherein the reductant reservoir comprises an expansion bladder.  
   
   
       5 . The reductant system of  claim 1 , further comprising: 
 a vent in fluid communication with the reductant reservoir and the reductant chamber; and    a purge bypass valve in fluid communication with the atomizer and the reductant reservoir for directing fluid from the reductant chamber to at least one of the atomizer and the reductant reservoir.    
   
   
       6 . The reductant system of  claim 1 , further comprising a control unit capable of varying an output of the reductant pump in response to a signal from a temperature sensor in thermal communication with an exhaust treatment device.  
   
   
       7 . The reductant system of  claim 1 , further comprising: 
 a first NOx sensor located upstream of the exhaust treatment device;    a second NOx sensor located downstream of the exhaust treatment device; and    an ammonia sensor located downstream of the exhaust treatment device.    
   
   
       8 . The reductant system of  claim 1 , wherein the reductant pump further comprises: 
 a piston, the piston comprising a first actuating surface, a second actuating surface, and a reductant pressurizing surface;    wherein the reductant chamber is in fluid communication with an inlet check valve and an outlet check valve, and is in fluid communication with the reductant pressurizing surface;    a first actuating chamber in fluid communication with the first actuating surface and in fluid communication with a first port; and    a second actuating chamber in fluid communication with the second actuating surface and in fluid communication with a second port;    wherein movement of the piston in a direction will increase the pressure of fluid received in the reductant chamber.    
   
   
       9 . The reductant system of  claim 8 , further comprising a spacer chamber disposed between the second actuating chamber and the reductant chamber such that a fluid leaking from the second actuating chamber will escape from the reductant pump and will not enter the reductant chamber, and reductant leaking from the reductant chamber will escape from the reductant pump and will not enter the second actuating chamber.  
   
   
       10 . A reductant system, comprising: 
 a reductant pump;    system pump in operable communication the reductant pump, wherein the system pump is configured to provide motive power via a pressurized fluid to the reductant pump, and wherein the system pump is fluidly isolated from a reductant chamber in the reductant pump;    a reductant reservoir in fluid communication with the reductant chamber; and    an atomizer in fluid communication the reductant chamber.    
   
   
       11 . A method for providing a reductant to an exhaust system, comprising: 
 introducing the reductant to a reductant chamber of a reductant pump;    powering the reductant pump with pressurized fluid from a system pump;    pressurizing the reductant to a pressure of greater than or equal to about 500 psi; and    passing the pressurized reductant through an atomizer and into an exhaust flowpath.    
   
   
       12 . The method of  claim 11 , further comprising introducing the reductant upstream of an exhaust treatment device.  
   
   
       13 . The method of  claim 11 , wherein the pressurized reductant is injected without a carrier fluid.  
   
   
       14 . The method of  claim 11 , further comprising purging a reductant system by 
 introducing a purge fluid to the reductant chamber;    powering the reductant pump with the pressurized fluid from a system pump;    pressurizing the purge fluid;    purging a flow path between the reductant pump and the atomizer with the pressurized purge fluid; and    purging a flow path between the reductant pump and a reductant reservoir with the pressurized purge fluid.    
   
   
       15 . The method of  claim 14 , comprising purging the reductant system of reductant when an ambient temperature is below a setpoint.  
   
   
       16 . The method of  claim 14 , further comprising pumping the pressurized reductant into an accumulator prior to injecting it into the exhaust flow path.  
   
   
       17 . A reductant system, comprising: a reductant pump comprising 
 a motor comprising a rotatable shaft;    a threaded piston keyed into a pump housing, a first end of the threaded piston comprising a first pressurizing surface in fluid communication with a first pressurizing chamber, and a second end of the threaded piston disposed opposite the first end, the second end comprising a second pressurizing surface in fluid communication with a second pressurizing chamber; and    a threaded nut in operable communication with threads on the threaded piston;    wherein rotatable shaft rotation rotates the threaded nut producing axial movement of the threaded piston; and    wherein axial movement of the threaded piston in a first direction increases pressure of a first fluid in the first pressurizing chamber and creates a vacuum in the second pressurizing chamber, and wherein axial movement of the threaded piston in a second direction increases pressure of a second fluid in the second pressurizing chamber and creates a vacuum in the first pressurizing chamber.    
   
   
       18 . The reductant system of  claim 17 , further comprising: 
 a reductant reservoir in fluid communication with the first pressurizing chamber and the second pressurizing chamber;    an accumulator in fluid communication with the first pressurizing chamber and the second pressurizing chamber; and    an atomizer in fluid communication the accumulator.    
   
   
       19 . The reductant system of  claim 17 , further comprising a reductant heater in thermal communication with the reductant reservoir.  
   
   
       20 . The reductant system of  claim 17 , wherein the reductant reservoir comprises an expansion bladder.  
   
   
       21 . The reductant system of  claim 17 , wherein the reductant pump further comprises: 
 a worm gear disposed on an outer surface of the rotatable shaft;    a first bevel gear in operable communication with the worm gear; and    a second bevel gear in operable communication with the first bevel gear, and annularly affixed to an outer surface of the threaded nut.