Measurement of Heat of Vaporization for Research Gasolines and Ethanol Blends by DSC/TGA [electronic resource]

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Tác giả:

Ngôn ngữ: eng

Ký hiệu phân loại: 621.425 Applied physics

Thông tin xuất bản: Washington, D.C. : Oak Ridge, Tenn. : United States. Office of the Assistant Secretary of Energy Efficiency and Renewable Energy ; Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2018

Mô tả vật lý: Size: p. 12607-12616 : , digital, PDF file.

Bộ sưu tập: Metadata

ID: 266403

The heat of vaporization (HOV) is a relatively poorly studied fuel property that can be related to a fuel's evaporation characteristics and knock resistance and, therefore, the emissions and efficiency of direct-injection spark-ignition engines. Methods for measuring the HOV of complex gasoline mixtures and blends of gasoline with ethanol and other oxygenates require additional development. Recently, we described a differential scanning calorimetry/thermogravimetric (DSC/TGA) method to perform HOV measurements. Herein we describe a detailed investigation of factors affecting the precision and accuracy of the DSC/TGA method and examine enthalpy evolution and mass loss rate for research gasolines as a function of fraction evaporated. Examination of n-hexane evaporation using several DSC/TGA pan/lid configurations showed that initial sample loss can be reduced using a well-fitting pinhole lid on the sample pan, which reduces the evaporation rate during the balance of the experiment. However, additional experiments with research gasolines revealed that tight lid placement on the pans is not always achieved. Nevertheless, accurate total HOV measurements, with less than 10% initial sample loss, could be achieved for low volatility gasolines regardless of lid placement. A higher mass loss might be expected for higher vapor pressure (wintertime) gasolines. Because of variations in pan lids and their placement and their significant impact on results, quantitative comparisons between different samples of mass loss rate and heat flow curves versus time or fraction evaporated are not yet possible. However, features in the mass loss rate and heat flow curves are reproducible. Furthermore, results show that ethanol-gasoline blend evaporation is highly influenced by the formation of near-azeotropic mixtures of ethanol and specific gasoline components, causing a flattening of the mass and heat curves, with a sharp evaporation rate reduction after the ethanol is evaporated.
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