EFFECT OF ELEVATED PISTON TEMPERATURE ON COMBUSTION CHAMBER DEPOSIT GROWTH

OUTLINE 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

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

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