Combustion process investigations in an optically accessible DISI engine fuelled with n-butanol during part load operation. (May 2015)

• Record Type: Journal Article
• Authors: Irimescu, A.; Marchitto, L.; Merola, S.S.; Tornatore, C.; Valentino, G.
• Is Part Of: Renewable energy. Volume 77(2015)
• Page Start: 363
• Page End: 376
• Publication Date: 2015-05
• Subjects: Spark ignition engines -- Direct injection -- Butanol -- Optical investigations; Renewable energy sources -- Periodicals; Power resources -- Periodicals; Énergies renouvelables -- Périodiques; Ressources énergétiques -- Périodiques; 333.794
• DOI: 10.1016/j.renene.2014.12.029
• Languages: English
• ISSNs: 0960-1481

Abstract

Abstract: The effect of n-butanol on the combustion process in a DISI engine was investigated through in-cylinder pressure measurements and optical data. An optical engine was equipped with a commercial head and with high pressure wall guided injection system. 2000 rpm engine speed was chosen as representative for mid-road load automotive use. Two partially open throttle conditions were tested. All trials were performed at close to stoichiometric air–fuel ratio. Optical diagnostics based on UV–visible imaging and natural emission spectroscopy were applied to study the combustion process from spark ignition to exhaust valve opening. A custom post-detection procedure applied to digital imaging data allowed evaluating the flame area. Results were correlated with volume fraction burned obtained through thermodynamic analysis. UV–visible spectroscopy was applied to investigate formation and evolution of the main chemical compounds characterizing spark ignition and combustion processes. Pollutant measurements (HC, CO, NO x, opacity) at undiluted exhaust, for gasoline and butanol, were correlated with pressure data and in-cylinder optical results. Overall engine operation was found to be similar for both energy sources, with the alternative fuel providing a slight improvement in performance compared to gasoline, for both loads; a significant reduction of NO x and soot was also obtained for alcohol fuelling. Highlights: n-butanol induces little increase in performance and reduction of smoke opacity and NO x . This study allowed a better understanding of alcohol fuel effect on flame front propagation. n-butanol is featured by higher flame speed than gasoline but slower flame kernel evolution. At fixed load, butanol shows comparable OH emission with lower CO–O and CH intensity than gasoline.