Optical investigation on impacts of component ratio on spray, combustion and flame structure of isopropanol-butanol-ethanol (IBE)/diesel blends

Abstract

Isopropanol-butanol-ethanol (IBE) is a clean and renewable biofuel, but its component ratio effects on the spray combustion process of diesel have not been reported to date. In this study, IBE mixtures with different component ratios (6:3:1, 3:6:1 and 0:10:0) were separately blended into diesel at the volumetric ratio of 20% and then tested in a constant volume chamber. The experimental results show that isopropanol in IBE plays leading role on the spray combustion characteristics of IBE/diesel blends; the more isopropanol in the IBE blend, the shorter the liquid penetration is. Furthermore, the IBE/diesel blends containing more isopropanol always exhibit a long ignition delay but a short combustion duration. Results also show that regardless of whatever type of IBE/diesel blends, the flame lift-off length (FLOL) prolongs and the spatial integrated natural flame luminosity (SINL) reduces. However, the magnitudes of reduction of the SINL for the IBE/diesel blends vary with the component ratio of IBE. The IBE/diesel blends containing more isopropanol always present a noticeably lower SINL. Compared with pure diesel, the fuel blends containing more isopropanol are capable of reducing the time integrated natural luminosity (TINL) almost by half in most test conditions. That is to say, increasing isopropanol ratio in IBE can reduce the soot formation of IBE/diesel blends but the increase of the butanol ratio has an opposing trend.