1992-02-01

Characterization of Knock and Its Effect on Surface Temperatures 920514

Knock in a spark-ignition engine was characterized in terms of its occurrence and magnitude or intensity. Cylinder pressure data from 90 consecutive individual cycles were generated from a single-cylinder engine of disc chamber design at about 72kHz sampling rate over a range of operating conditions between no knock and 100% of the cycles knocking. Mean values and distribution of following parameters were analysed: knock occurrence crank angle, knock intensity, combustion rate and the end-gas thermodynamic state. The effects of fuel octane number and inlet air temperature on these parameters were studied. The thermal imaging technique has been applied to record two-dimensional surface temperatures of cylinder head and piston simultaneously. The change in surface temperatures during knocking and non-knocking cycles was thus studied.
As expected, increase in the inlet air temperature or decrease in the fuel octane number caused the knock onset to occur at less advanced spark timing. For a given octane number fuel and inlet air temperature, the difference in spark timing between no knock and 100% of the cycles knocking was about 10 degree crank angle. On the individual cycle basis, the non-knocking cycles were among the slower burning cycles and knock occurrence crank angle correlated well with the combustion rate, especially the pressure at individual 50% burn crank angle. However they did not correlate well with end gas temperature in present experiments. The individual cycle knock intensity did not correlate well with any parameters used though it showed a trend of increase as the combustion rate and pressure at 50% burn crank angle increased and knok occurred earlier. The thermal images recorded showed the increased surface temperatures during knocking operations.

SAE MOBILUS

Subscribers can view annotate, and download all of SAE's content. Learn More »

Access SAE MOBILUS »

Members save up to 18% off list price.
Login to see discount.
Special Offer: Download multiple Technical Papers each year? TechSelect is a cost-effective subscription option to select and download 12-100 full-text Technical Papers per year. Find more information here.
We also recommend:
TECHNICAL PAPER

The Effect of Knock on the Heat Transfer in an SI Engine: Thermal Boundary Layer Investigation using CARS Temperature Measurements and Heat Flux Measurements

2000-01-2831

View Details

TECHNICAL PAPER

Piston Pin Related Noise - Quantification Procedure and Influence of Pin Bore Geometry

2005-01-3967

View Details

TECHNICAL PAPER

Gasoline Engine Piston Pin Tick Noise

2007-01-2290

View Details

X