Abstract
In pursuing maximum energy efficiency, local utilization of various crude fuels came into view. The present paper compares the combustion characteristics of standard diesel oil and crude rapeseed oil; the latter is an excellent model for high-viscosity liquid fuels. The combustion tests were performed in a 15 kW atmospheric turbulent swirl burner; the liquid fuels were atomized by a plain-jet airblast atomizer. Firstly, the acoustic signal is evaluated, since the instabilities of swirl combustion are accompanied by characteristic pressure fluctuations. The spectral analysis was performed by Wavelet transform, which fits excellently to the acoustic spectrum of combustion noise. This multi-scale technique features increased spectral resolution at lower frequencies at the expense of lower temporal resolution, providing excellent performance at both low-frequency, well-localized components and high-frequency, broadband phenomena. The joint probability density function of two characteristic frequencies was plotted with the result that flame acoustics match for the two fuels. Secondly, their pollutant emissions were compared and evaluated under similar conditions with the conclusion that crude rapeseed oil can substitute diesel oil in a limited operating range. Note that the distinct material properties already mean differences in all atomization, evaporation, and mixing characteristics, hence, the latter result is not intuitive.
Highlights
Renewable liquid fuel utilization has a turbulent history with a general conclusion that our energy demand massively surpasses the potential of arable fields
Even though the loss during energy conversion is higher for combustion engines, the difference makes it evident that liquid fuels will remain in active use for decades in both transportation and aviation
Since the present study focuses on the combustion of crude rapeseed oil, its evaporation characteristics will not be covered in the latter part of this paper; it was published in an earlier study [36]
Summary
Renewable liquid fuel utilization has a turbulent history with a general conclusion that our energy demand massively surpasses the potential of arable fields. It is predicted by the IEA that oil utilization for power generation will drop in the future [2], biofuels for transportation are on a stable incline [3], highlighting aviation [4] These all can be realized by using waste-to-fuel technologies, like producing biodiesel from waste cooking oil [5], harvesting algae ponds [6], and using peak shaving to convert electricity into fuel when there is excessive power available from principally renewable sources [7]. The chemical conversion of crude vegetable oils to lighter fuel types [9] solves numerous operational problems, such as poor spray quality, insufficient evaporation and, inadequate fuel-air mixing These issues all lead to a bad fuel economy combined with increased pollutant emissions. The key challenges of HRF combustion are summarized in the following
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