Re: Caterpillar engine high exhaust back pressure
Posted: Sun Nov 11, 2012 9:28 am
Its best we put the units of 800mmWG into a unit we can understand and for this purpose we can assume 28 inches of water head is eqaul to 1psi. We are talking about a pressure in the duct that is one tenth of atmosphere. Very difficult to measure this in a boosted engine room. Certainly nothing will burst. A human being can blow 28 inches of water out the manometer without effort.
Its been stated the exhaust pipes have laminar flow inside, this is not correct and only Naval Architects think that. All along the wall of the exhaust pipe the flow is turbulent and this area is called the boundary layer. The thickness of the Boundary Layer is variable and depends on the condition of the wall of the duct. Normal dry soot allows a reasonable thickness of boundary layer and an acceptable laminar flow. Oils/acids in the exhaust duct due to viscosity can cause a large increase in the thickness of the boundary layer and a serious reduction in the laminar flow. This type of turbulence causes high exhaust temperature and increased back pressure.
Check the crankcase pressure in your engine, look at the crankcase vent. Problems in the crankcase in a medium speed, cause oil carrying through the scrapers. Check the lub oil purifier, put off the auto blow and see how often it needs cleaning.
regards
Its been stated the exhaust pipes have laminar flow inside, this is not correct and only Naval Architects think that. All along the wall of the exhaust pipe the flow is turbulent and this area is called the boundary layer. The thickness of the Boundary Layer is variable and depends on the condition of the wall of the duct. Normal dry soot allows a reasonable thickness of boundary layer and an acceptable laminar flow. Oils/acids in the exhaust duct due to viscosity can cause a large increase in the thickness of the boundary layer and a serious reduction in the laminar flow. This type of turbulence causes high exhaust temperature and increased back pressure.
Check the crankcase pressure in your engine, look at the crankcase vent. Problems in the crankcase in a medium speed, cause oil carrying through the scrapers. Check the lub oil purifier, put off the auto blow and see how often it needs cleaning.
regards