23-12-2010, 03:43 PM
Prepared by:Shashikumar C.M
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EFFECT OF CCD
The effect of combustion chamber deposits include octane requirement increase, decreased volumetric efficiency, combustion chamber deposit interference (CCDI)
Combustion chamber deposit interference is the result of physical contact between deposits on the piston top and cylinder head
combustion chamber deposits increases engine-out emissions of pollutants such as unburned hydrocarbons and nitric oxides
EFFECT OF WALL TEMPERATURE ON CCD
Formation of fuel deposits is due to the condensation of components like aromatics
With increased wall temperature hydrocarbon condensation decreases, deposit formation reduces
PURPOSE OF THIS STUDY
An experimental study was conducted to investigate the effect of elevated wall temperature on deposit growth
This study monitors CCD growth as a function of metal wall temperature
Attempts are made to determine critical wall temperature for no growth
CONTROL & MEASUREMENT OF PISTON SURFACE TEMPERATURES
A composite piston design was developed
By varying the thickness of the ceramic wafer, the surface temperature of the cap could be increased
CONTROL & MEASUREMENT OF PISTON SURFACE TEMPERATURES
THERMOCOUPLE LOCATION ON THE CAP
MONITORING OF DEPOSIT GROWTH
A technique for monitoring deposit growth is through the measurement of local surface temperature using thermocouples
As deposit buildup on the surface, forms insulation barrier, reduces heat flow, reduces wall’s surface temperature
Rate of change of wall surface temperature is indicative of rate of deposit growth
REGIONS WHERE MEASUREMENTS WERE TAKEN
CORRELATION B/N AVERAGE PST & AVERAGE DEPOSIT GROWTH
The average deposit thickness was found to decrease at 3.38µm per mm of ceramic insulation
CHEMICAL ANALYSIS
According to test data, the deposits in the end gas region have highest fuel content. It is due to the deposition of unburned hydrocarbon products
The region b/n sparkplug and intake valve have lower fuel content. This is due to fuel vaporization (16ºC more hotter)
Deposits in the cap’s edge have highest oil content
EFFECT OF WALL SURFACE TEMPERATURE ON C/H RATIO
Increase in ST-decrease in concentration of carbon
Increase in ST-decrease in C/H ratio
Deposits on high temperature CC walls were composed of inorganic compounds
CONCLUSION
Elevating piston temperature critically affected deposit formation in SI engine combustion chamber
No deposit growth was obtained when operating with a WST of 320°C
Test using unleaded fuel with reformer bottoms yielded a 55% increase in deposit growth
Elevating WT, decrease C/H ratio of deposits
