EFFECT OF ELEVATED PISTON TEMPERATURE ON COMBUSTION

CHAMBER DEPOSIT GROWTH

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

OUTLINE

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 CCDThe 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 STUDYAn 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

GROWTHThe 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 carbonIncrease in ST-decrease in C/H ratioDeposits on high temperature CC walls were composed of inorganic

compounds

CONCLUSIONElevating piston temperature critically affected deposit formation in SI

engine combustion chamber

No deposit growth was obtained when operating with a WST of 320°CTest 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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