Fuel Stratification and Partially Premixed Combustion With Neat n-Butanol in a Compression Ignition Engine

Abstract

Homogeneous charge compression ignition (HCCI) has been considered as an ideal combustion mode for compression ignition (CI) engines due to its superb thermal efficiency and low emissions of nitrogen oxides (NOx) and particulate matter. However, a challenge that limits practical applications of HCCI is the lack of control over the combustion rate. Fuel stratification and partially premixed combustion (PPC) have considerably improved the control over the heat release profile with modulations of the ratio between premixed fuel and directly injected fuel, as well as injection timing for ignition initiation. It leverages the advantages of both conventional direct injection compression ignition and HCCI. In this study, neat n-butanol is employed to generate the fuel stratification and PPC in a single cylinder CI engine. A fuel such as n-butanol can provide additional benefits of even lower emissions and can potentially lead to a reduced carbon footprint and improved energy security if produced appropriately from biomass sources. Intake port fuel injection (PFI) of neat n-butanol is used for the delivery of the premixed fuel, while the direct injection (DI) of neat n-butanol is applied to generate the fuel stratification. Effects of PFI-DI fuel ratio, DI timing, and intake pressure on the combustion are studied in detail. Different conditions are identified at which clean and efficient combustion can be achieved at a baseline load of 6 bar IMEP. An extended load of 14 bar IMEP is demonstrated using stratified combustion with combustion phasing control.

Implementation of thermal and fuel stratification strategies to extend the load limit of HCCI engine

“…For the increased loading conditions where fuel supply is higher may increase the NOX emissions as the local rich ϕ zone possibly reach to stoichiometric. Early injection timing causes high PRR and Knock, while late DI results in high NOX emission (Dev et al 2018). For high load operation SCCI uses similar strategies to PCCI to achieve very high load operations with limiting emissions (Dev et al 2018;Vallinayagam et al 2017).…”

“…Early injection timing causes high PRR and Knock, while late DI results in high NOX emission (Dev et al 2018). For high load operation SCCI uses similar strategies to PCCI to achieve very high load operations with limiting emissions (Dev et al 2018;Vallinayagam et al 2017). The various strategies to extend the SCCI load limit are 1.…”

Combustion Stability, Performance and Emission Characteristics of a CI Engine Fueled with Diesel/n-Butanol Blends

“…Recently, however, it is butanol that attracts more attention than ethanol and methanol because its properties are similar to those of fossil fuels [15]. It is a fuel that can simultaneously reduce harmful engine emissions, and produced from biomass can potentially reduce the carbon footprint and improve energy security [16]. In addition, higher alcohols, such as butanol, are better suited to blending with diesel fuel than lower alcohols, such as methanol and ethanol, due to their higher energy content per unit of weight, blend stability, low corrosivity and lower miscibility with water [2].…”