Technical Session - 7

Title:           Investigation of the Fuel-Air Cycle Phases in a Modern Compression Ignition Engine under Multi-Injection Strategy
Authors:      Vu Hoang Nguyen, Phuong Xuan Pham
Abstract:     Special attention is necessary paid for charactering advanced injection strategies including multiinjection techniques in order to improve physical processes (i.e. atomization, evaporation, and mixing) as well as chemical mechanism (i.e. low temperature and high temperature auto-ignition) in compress ignition engines, especially when operating with renewable fuels like biodiesels. This work qualitatively investigates the fuel-air cycle phases in a compression ignition engine equipped with an advanced injection system. The engine used in this study is a modern 4-cylinder targeted-controlled-injection diesel engine, typical of those used in Hyundai Starex CVX vehicles. Single, double, triple, or quadruple injection modes are possible in this engine depending on its load and speed conditions. In addition, both pilot-and post-injection modes can be triggered in several operating conditions. The engine is operated with either fossil diesel or 20:80 blend of a biodiesel derived from palm oil residue with fossil diesel under a wide range of engine speed and load fractions. The outcomes show a capability of multi-injection strategy to shortening the ignition delay which is essentially important at low load fraction and/or low engine speed where the atomization and evaporation conditions are quite poor. The pilotinjection modes enhance the atomization and evaporation by pre-conditioning the combustion chamber prior to the main auto-ignition. Depending on the engine operating condition, the start of main auto-ignition of biodiesel blends could be identical, earlier or later with respect to that of fossil diesel. Since the longer ignition delay observed for the biodiesel blend regardless higher cetane value of biodiesel compared to diesel, this could be attributed to the unequal effect of multi-injection strategy on pre-conditioning the combustion chamber when using different fuel with different physicochemical properties. This important point needs to be noted to control the chamber conditions targeting to improve physical and chemical processes when utilize biodiesels and their blends in auto-ignition engines.

Keywords:    Multiple Injection, Pilot/Post Injection, Biodiesel, In-Cylinder Pressure, Net Heat Release Rate, Ignition Delay
Pages:         361-368

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