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A Fundamental Study of the Relationship Between Altitude and Research Octane Number
Technical Paper
2002-01-1662
ISSN: 0148-7191, e-ISSN: 2688-3627
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English
Abstract
The influence of altitude (ambient pressure) on the auto-ignition phenomenon is a fuel property that has been studied indirectly in terms of octane-response studies involving large fleets of test vehicles. The magnitude of the measured altitude-octane response has varied from study to study and the phenomenon lacks a definitive answer. The present paper presents a simple theoretical analysis based on the response of the end-gas auto-ignition to pressure which is used to predict the altitude-octane effect. A series of tests were conducted using a standard CFR engine operating at an altitude of 1485 meters above sea-level to evaluate and confirm the theoretical findings which indicated clearly that the altitude-octane effect is an intrinsic fuel property. The magnitude of the effect was shown to vary depended on the fuel itself, but was typically in the range -1.0 to -1.5 ON/300 m for modern commercial fuels. Against this background, the altitude response of the combined automotive engine and fuel was investigated via the results of a recent 54-vehicle fleet study that was conducted in South Africa. A novel statistical analysis technique was used to determine the magnitude of the underlying altitude-octane effect, which was determined as -0.88 ON/300 m.
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Citation
Yates, A. and Cilliers, C., "A Fundamental Study of the Relationship Between Altitude and Research Octane Number," SAE Technical Paper 2002-01-1662, 2002, https://doi.org/10.4271/2002-01-1662.Also In
References
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