Cycle-to-cycle variation in combustion phasing and combustion rate cause knock to occur differently in every cycle. This is found to be true even if the end gas thermo-chemical time history is the same. Three cycles are shown that have matched combustion phasing, combustion rate, and time of knock onset, but have knock intensity that differs by a factor of six. Thus, the prediction of knock intensity must include a stochastic component. It is shown that there is a relationship between the maximum possible knock intensity and the unburned fuel energy at the time of knock onset. Further, for a small window of unburned energy at knock onset, the probability density function of knock intensity is self similar when scaled by the 95th percentile of the cumulative distribution, and log-normal in shape. A methodology to predict the maximum possible knock intensity based on the volumetric expansion rate of the end gas was developed, and the expansion rate was modeled based on blast wave theory, which is proportional to the energy of the initial explosion. The results showed a comparable level of scatter as the measurements.


    Access

    Check access

    Check availability in my library

    Order at Subito €


    Export, share and cite



    Title :

    A Statistical Description of Knock Intensity and Its Prediction


    Additional title:

    Sae Technical Papers


    Contributors:

    Conference:

    WCX™ 17: SAE World Congress Experience ; 2017



    Publication date :

    2017-03-28




    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




    EFFECT OF KNOCK INTENSITY ON FUEL KNOCK RATINGS

    MacCoull, Neil | SAE Technical Papers | 1937


    AUDIBILITY ANTI-KNOCK TESTS AND KNOCK-INTENSITY EVALUATION

    ROESCH, DANIEL | SAE Technical Papers | 1926


    Comparison Between Heat Transfer and Knock Intensity on a Statistical Basis

    Ferraro, C. V. / Millo, F. / Marzano, M. R. et al. | SAE Technical Papers | 1996


    Comparison between Heat Transfer and Knock-Intensity on a Statistical Basis

    Ferraro, C. V. / CSAT | British Library Conference Proceedings | 1996


    Consideration for evaluating knock intensity

    Nakajima,Y. / Ohoda,M. / Nagai,T. et al. | Automotive engineering | 1982