Dispersion and vaporization of biofuels and conventional fuels in a crossflow pre-mixer

    Authors

    X. Gu; S. Basu;R. Kumar

    Comments

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    Abbreviated Journal Title

    Int. J. Heat Mass Transf.

    Keywords

    Biofuels; Mono-dispersed spray; Vaporization; Crossflow; Pre-heating; DROPLET VAPORIZATION; AIR-FLOW; COMBUSTION; EVAPORATION; SPRAYS; JET; Thermodynamics; Engineering, Mechanical; Mechanics

    Abstract

    In lean premixed pre-vaporized (LPP) combustion, controlled atomization, dispersion and vaporization of different types of liquid fuel in the premixer are the key factors required to stabilize the combustion process and improve the efficiency. The dispersion and vaporization process for biofuels and conventional fuels sprayed into a crossflow pre-mixer have been simulated and analyzed with respect to vaporization rate, degree of mixedness and homogeneity. Two major biofuels under investigation are Ethanol and Rapeseed Methyl Esters (RME), while conventional fuels are gasoline and jet-A. First, the numerical code is validated by comparing with the experimental data of single n-heptane and decane droplet evaporating under both moderate and high temperature convective air now. Next, the spray simulations were conducted with monodispersed droplets with an initial diameter of 80 mu m injected into a turbulent crossflow of air with a typical velocity of 10 m/s and temperature of around 800K. Vaporization time scales of different fuels are found to be very different. The droplet diameter reduction and surface temperature rise were found to be strongly dependent on the fuel properties. Gasoline droplet exhibited a much faster vaporization due a combination of higher vapor pressure and smaller latent heat of vaporization compared to other fuels. Mono-dispersed spray was adopted with the expectation of achieving more homogeneous fuel droplet size than poly-dispersed spray. However, the diameter histogram in the zone near the pre-mixer exit shows a large range of droplet diameter distributions for all the fuels. In order to improve the vaporization performance, fuels were pre-heated before injection. Results show that the Sauter mean diameter of ethanol improved from 52.8% of the initial injection size to 48.2%, while jet-A improved from 48.4% to 18.6% and RME improved from 63.5% to 31.3%. The diameter histogram showed improved vaporization performance of jet-A. (C) 2011 Elsevier Ltd. All rights reserved.

    Journal Title

    International Journal of Heat and Mass Transfer

    Volume

    55

    Issue/Number

    1-3

    Publication Date

    1-1-2012

    Document Type

    Article

    Language

    English

    First Page

    336

    Last Page

    346

    WOS Identifier

    WOS:000297429600033

    ISSN

    0017-9310

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