Fuel Injection Responses and Particulate Emissions of a CRDI Engine Fueled with Cocos nucifera Biodiesel

Yew Heng Teoh,Farooq Sher,Thanh Danh Le,Huu Tho Nguyen,Heoy Geok How,Haseeb Yaqoob

doi:10.3390/su13094930

Abstract

The objective of this paper is to study the effect of coconut oil biodiesel (COB)-diesel blends on exhaust particulate matter (PM) emissions and fuel injection responses in an unmodified turbocharged four-stroke common-rail direct injection (CRDI) diesel engine. Characterization of COB and their blends has been conducted to ascertain the applicability of these fuels for the existing engine. The test fuels used were fossil diesel fuel, COB10, COB20, COB30 and COB50 of biodiesel-diesel fuels. A test cycle which composed of 16 different steady-state modes at various loads and speed conditions was followed. Generally, the results showed a marginally advanced SOI timing and longer injection duration with increasing COB blends at higher load as compared to diesel fuel. Additionally, the lower calorific value (CV) and higher viscosity of the COB fuel blends have resulted in reduced turbo boost pressure and increased common-rail fuel injection pressure, respectively, across all engine speeds and loads. On the aspects of PM emissions characterization, results indicated that the blending of COB with conventional diesel had benefits over diesel in PM reduction. In fact, the largest achievable PM mass reduction of 38.55% was attained with COB50. In addition, it was noticed that the size of PM particles accumulated such that the granular size increased with higher diesel content in the blend. Additionally, the composition analysis on the PM collected by EDX spectroscopy has revealed that the C, O and Si as three main elements that made up the PM particles in descending order. Overall, the results indicated that COB biodiesel is a clean-burning alternative fuel and can be used satisfactorily in an unmodified diesel engine without the needs for engine remapping.

Highlights

Combustion of petroleum diesel in engines is known to produce emissions such as carbon monoxide, carbon dioxide, nitrogen oxides (NOx), particulate matters and more, which are pollutants that are detrimental to human health if inhaled [1]
Unlike mechanical fuel injection (MFI) systems with a tendency to advance fuel injection timing due to several factors such as bulk modulus, viscosity, fuel density and sound velocity which is well explained by Breda Kegl [43], the advancement of fuel injection timing in common-rail direct injection (CRDI) system is mainly due to its characteristics of the programmed fuel injection map in ECU based as a function of engine speed and load demand
The engine exhaust particulate matter (PM) and fuel injection parameter responses of baseline diesel, COB10, COB20, COB30 and COB50 biodiesel blended fuels have been experimentally tested in a medium-duty common-rail diesel engine under different speed and load conditions

Summary

Introduction

Combustion of petroleum diesel in engines is known to produce emissions such as carbon monoxide, carbon dioxide, nitrogen oxides (NOx), particulate matters and more, which are pollutants that are detrimental to human health if inhaled [1]. Over the last few years, researchers have attempted in accessing various energy sources including derivatives from hydrogen, alcohols, vegetable oils as alternatives to petroleum diesel [5,6,7,8,9]. Christian Karl Diesel himself had introduced and envisioned the use of pure vegetable oil as fuels to power diesel engines since petroleum was not widely available at that time [10,11].

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