Determination of ignition delay times of different hydrocarbons in a new high pressure shock tube

Abstract

The impending scarcity of fossil fuel in the future requires continued development in hydrocarbon combustion research. Biofuels offer a promising alternative to traditional fossil fuel-based combustion. To optimize engine design for biofuels, adequate combustion characteristics for new fuels have to be known. In this study, a new high pressure stainless steel shock tube for measuring ignition delay times is presented. When compared with other shock tubes for investigating ignition delays, the new tube provides superior maximum working pressures and geometric properties. Shock tube performance is determined by reference experiments with air as driven gas. These experiments allow to determine the available test time and the influence of shock attenuation. Owing to the large inner diameter of the shock tube, shock attenuation is <1% as it is typical for low pressure shock tubes. However, contrast to typical low pressure shock tubes, non-diluted fuel–air mixtures at high pressures can be investigated in the new shock tube due to the high allowable working pressure. First experiments concerning the ignition delay time have been performed with methane and n-heptane. The results of these experiments show a good agreement to literature data. As a first biofuel ethanol has been investigated at elevated pressures up to 40 bar.