Transcript effect of elevated piston temperature on combustion chamber

 Combustion Chamber Deposits
Effect of Combustion chamber deposits
Effect of wall temperature on CCD
Control & Measurement Of Piston Surface Temperatures
Thermocouple Location On The Cap
Monitoring Of Deposit Growth
Chemical Analysis
Combustion chamber deposits
are recognized as a major
contributor to the deterioration
of SI engine performance
Their build-up leads to increased
charge emissions, and increased
tendency for knock
The factors influencing deposit
formation are changes in fuel
composition, coolant
temperatures, engine speed
and load, and spark timing
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
Formation of fuel deposits is due to the condensation of
components like aromatics
With increased wall temperature hydrocarbon condensation
decreases, deposit formation reduces
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
A composite piston design
was developed
By varying the thickness of
the ceramic wafer, the surface
temperature of the cap could be
increased
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
The average
deposit thickness
was found to
decrease at 3.38µm
per mm of ceramic
insulation
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
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
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
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