Optical investigation of flash boiling and its effect on in-cylinder combustion for butanol isomers and iso-octane

Abstract

Performance of a gasoline direct injection engine significantly depends on the fuel injection phenomenon. It has been shown that variation in the fuel thermo-physical properties and in-cylinder thermodynamic conditions can adversely affect engine performance. Spray collapse due to flash boiling is the consequence of such varying in-cylinder thermodynamics. It has also been observed that gasoline direct injection engines have higher particulate matter emissions compared to port fuel injection engines. One of the possible reasons for this observation may be fuel impingement on the piston head and spray collapse at high fuel injector temperature. In the present work, experiments have been performed to understand spray characteristics under flash boiling conditions and ultimately its effect on in-cylinder combustion quality for the three different fuels: n-butanol, iso-butanol and iso-octane. To mimic in-cylinder conditions, hot fuel was introduced inside an optically accessible engine. It was observed that fuel temperature and their thermo-physical properties have a significant effect on piston head wetting and pool fire on the piston top. Butanol isomers showed significant reduction in sooty combustion with increase in fuel temperature. However, iso-octane showed higher wall wetting at elevated fuel temperature due to spray collapse.

Coupled in-nozzle flow and spray simulation of Engine Combustion Network Spray-G injector

“…30 Furthermore, significant plume-top-plume interactions show that the ambient ingestion into the spray is minimal which may result in increased chances of diffusion combustion due to localized fuel rich zones. 31 All these characteristics are qualitatively well captured in the simulations.…”

Potential of ethanol and butanol in reducing deposits of DISI engine injectors

“…The application of alcohol as a fuel admixture is very important because it provides several benefits, such as reducing greenhouse gas emissions, reducing emissions of toxic exhaust components, increasing energy safety, and improving many fuel performance properties, including knock combustion resistance [19]. Knock combustion is a major barrier to achieving higher thermal efficiency in reciprocating internal combustion engines [12,17,19]. The fuel atomization process heavily influences the performance of a spark-ignition (SI) engine, particularly a direct-injection engine fueled by a gasoline-alcohol blend.…”

Numerical Analysis of GDI Flash Boiling Sprays Using Different Fuels

“…With these benefits, new challenges manifest themselves requiring further optimization strategies in order to reduce soot and particulate matter emissions that may result from phenomena such as tip wetting and wall-impingement [4,5]. Thus, spray air interaction and mixture formation in GDI engines require great care as the effect on the subsequent combustion phase significantly impacts the engine's thermal efficiency [6]. Flash boiling, when the fuel is ejected in a superheated state into the cylinder, has been characterized with an intense atomization phase and high plume-to-plume interaction in multi-hole injectors [7].…”