Diesel engine arrangement and method for varnish build-up control

Abstract

A method is provided for controlling varnish build-up in a variable geometry turbine (VGT) of a diesel engine turbocharger. According to the method, it is determined whether an operation parameter is at a level established for initiating a varnish build-up control sequence. Upon determining that the operation parameter is at the established level, the varnish build-up control sequence is initiated. The sequence comprises increasing exhaust temperature upstream of the VGT to a first exhaust temperature, and changing an opening size of a VGT nozzle between a smaller and a larger opening size in association with increasing the exhaust temperature to the first exhaust temperature. A diesel engine arrangement is also provided.

1 . A method for controlling varnish build-up in a variable geometry turbine (VGT) of a diesel engine turbocharger, comprising:
 determining whether an operation parameter is at a level established for initiating a varnish build-up control sequence; and   upon determining that the operation parameter is at the established level, initiating the varnish build-up control sequence, the sequence comprising
 increasing exhaust temperature upstream of the VGT to a first exhaust temperature, and 
 changing an opening size of a VGT nozzle between a smaller and a larger opening size while increasing the exhaust temperature to the first exhaust temperature. 
   
     
     
         2 . The method for controlling varnish build-up as set forth in  claim 1 , wherein the operation parameter comprises one or more of an estimated level of varnish build-up, an actual level of varnish build-up, force required to change nozzle opening size in the VGT, a period of engine operation, a period of engine operation at idle, an ambient temperature, a engine coolant temperature, detection of faulty hardware, cylinder temperature, intake manifold temperature, injection pressure. 
     
     
         3 . The method for controlling varnish build-up as set forth in  claim 1 , comprising cycling the exhaust temperature between the first exhaust temperature and a second, lower exhaust temperature through a plurality of temperature cycles. 
     
     
         4 . The method for controlling varnish build-up as set forth in  claim 1 , comprising changing the opening size of the VGT nozzle between the smaller and larger opening size after cycling the exhaust temperature through the plurality of temperature cycles. 
     
     
         5 . The method for controlling varnish build-up as set forth in  claim 1 , comprising changing the opening size of the VGT nozzle between the smaller and larger opening size by cycling the nozzle between the smaller and larger opening size through a plurality of nozzle opening and closing cycles. 
     
     
         6 . The method for controlling varnish build-up as set forth in  claim 1 , wherein the first exhaust temperature is a temperature sufficient to cause accumulated varnish accumulated on the VGT to turn into soot flakes. 
     
     
         7 . The method for controlling varnish build-up as set forth in  claim 1 , wherein the first exhaust temperature is approximately 175° C. or greater. 
     
     
         8 . The method for controlling varnish build-up as set forth in  claim 1 , wherein the first exhaust temperature is approximately 350° C. or greater. 
     
     
         9 . The method for controlling varnish build-up as set forth in  claim 1 , comprising maintaining the exhaust temperature at the first exhaust temperature for a predetermined length of time. 
     
     
         10 . The method for controlling varnish build-up as set forth in  claim 1 , comprising changing the opening size of the VGT nozzle between a 0% and a 100% opening size. 
     
     
         11 . The method for controlling varnish build-up as set forth in  claim 10 , comprising keeping the opening size of the VGT nozzle at a predetermined opening size when engine coolant temperature is above a predetermined engine coolant temperature. 
     
     
         12 . The method for controlling varnish build-up as set forth in  claim 1 , wherein the operation parameter comprises an ambient temperature at or below a predetermined ambient temperature and a period of operation at or exceeding a predetermined length of time, and wherein the varnish build-up control sequence comprises cycling the exhaust temperature between the first exhaust temperature and a second, lower exhaust temperature through a plurality of temperature cycles. 
     
     
         13 . The method for controlling varnish build-up as set forth in  claim 1 , the operation parameter comprises operation of the engine at extended idle, and wherein the varnish build-up control sequence is initiated upon determination that the engine has operated at extended idle for a predetermined length of time. 
     
     
         14 . The method for controlling varnish build-up as set forth in  claim 1 , comprising increasing exhaust temperature to the first exhaust temperature by one or more of reducing VGT nozzle opening size, retarding injection timing, reducing fuel injection pressure, increasing engine speed, and seventh injector dosing. 
     
     
         15 . The method for controlling varnish build-up as set forth in  claim 1 , comprising one or more of cycling the exhaust temperature between the first exhaust temperature and a second, lower exhaust temperature through a sufficient number of temperature cycles and changing the opening size of the VGT nozzle between the smaller and larger opening size a sufficient number of times so that a force required to change the opening size in the VGT is below a predetermined value. 
     
     
         16 . A diesel engine arrangement, comprising:
 a diesel engine;   a turbocharger, the turbocharger comprising a variable geometry turbine (VGT) downstream of the engine;   means for determining whether an operation parameter is at a level established for initiating a varnish build-up control sequence for controlling varnish build-up on the VGT; and   a controller arranged to initiate the varnish build-up control sequence when the determining means determines that the operation parameter is at the established level, the varnish build-up control sequence comprising
 increasing exhaust temperature upstream of the VGT to a first exhaust temperature, and 
 changing an opening size of a VGT nozzle between a smaller and a larger opening size while increasing the exhaust temperature to the first exhaust temperature. 
   
     
     
         17 . The diesel engine arrangement as set forth in  claim 16 , wherein the operation parameter comprises one or more of an estimated level of varnish build-up, an actual level of varnish build-up, force required to change opening size of the VGT nozzle, a period of engine operation, a period of engine operation at idle, an ambient temperature, and a engine coolant temperature. 
     
     
         18 . The diesel engine arrangement as set forth in  claim 16 , wherein the controller is arranged to increase exhaust temperature to the first exhaust temperature by one or more of reducing VGT nozzle opening size, retarding injection timing, reducing fuel injection pressure, increasing engine speed, and dosing via a seventh injector. 
     
     
         19 . The diesel engine arrangement as set forth in  claim 16 , wherein the determining means determines whether a force required to change the opening size of the VGT nozzle exceeds a predetermined value, and the controller is arranged to at least one of cycle the exhaust temperature between the first exhaust temperature and a second, lower exhaust temperature through a sufficient number of temperature cycles and change the opening size of the VGT nozzle between the smaller and larger opening size a sufficient number of times so that the force required to change the opening size of the VGT nozzle changes to a value below the predetermined value. 
     
     
         20 . The diesel engine arrangement as set forth in  claim 16 , wherein the controller is arranged to at least one of increase the exhaust temperature to the first exhaust temperature from a second, lower exhaust temperature through a sufficient number of temperature cycles and change the opening size of the VGT nozzle between the smaller and larger opening size a sufficient number of times so that a force required to change the opening size of the VGT nozzle remains below a predetermined value.