Experimental Study of the Effect of Hydrotreated Vegetable Oil and Oxymethylene Ethers on Main Spray and Combustion Characteristics under Engine Combustion Network Spray A Conditions

• Main Authors: José V. Pastor, José M. García-Oliver, Carlos Micó, Alba A. García-Carrero, Arantzazu Gómez
• Format: Article
• Language: English
• Published: MDPI AG 2020-08-01
• Series: Applied Sciences
• Subjects: hydrotreated vegetal oil; oxymethylene ethers; ignition delay; liquid length; lift-off length; soot
• Online Access: https://www.mdpi.com/2076-3417/10/16/5460

The stringent emission regulations have motivated the development of cleaner fuels as diesel surrogates. However, their different physical-chemical properties make the study of their behavior in compression ignition engines essential. In this sense, optical techniques are a very effective tool for determining the spray evolution and combustion characteristics occurring in the combustion chamber. In this work, quantitative parameters describing the evolution of diesel-like sprays such as liquid length, spray penetration, ignition delay, lift-off length and flame penetration as well as the soot formation were tested in a constant high pressure and high temperature installation using schlieren, OH∗ chemiluminescence and diffused back-illumination extinction imaging techniques. Boundary conditions such as rail pressure, chamber density and temperature were defined using guidelines from the Engine Combustion Network (ECN). Two paraffinic fuels (dodecane and a renewable hydrotreated vegetable oil (HVO)) and two oxygenated fuels (methylal identified as OME₁ and a blend of oxymethylene ethers, identified as OME_x) were tested and compared to a conventional diesel fuel used as reference. Results showed that paraffinic fuels and OME_x sprays have similar behavior in terms of global combustion metrics. In the case of OME₁, a shorter liquid length, but longer ignition delay time and flame lift-off length were observed. However, in terms of soot formation, a big difference between paraffinic and oxygenated fuels could be appreciated. While paraffinic fuels did not show any significant decrease of soot formation when compared to diesel fuel, soot formed by OME₁ and OME_x was below the detection threshold in all tested conditions.