Varying Ignition Quality of a Fuel for a HCCI Engine Using a Photochemically-Controlled Additive: The Development of a ‘Smart’ Fuel

David Emberson,Judit Sandquist,Inge Saanum,Alessandro Schönborn,Terese Løvås

doi:10.3390/en14051470

Abstract

This study examines the possibility to provide control over ignition timing in a homogeneous charge compression ignition engine (HCCI) using a fuel additive whose molecular structure can be adapted upon exposure to UV light. The UV adapted molecule has a greater influence on retarding ignition than the original molecule, hence the ignition time can be modulated upon expose to UV light. The new fuel is referred to as a ‘smart fuel’. The fuel additive is in the form of 1,3-cyclohexadiene (CHD), upon UV exposure it undergoes electro-cyclic ring opening to form 1,3,5-hexatriene (HT). Various solutions of iso-octane, n-heptane and CHD have been irradiated by UV light for different amounts of time. CHD to HT conversion was examined using gas chromatography coupled with mass spectrometry. A primary reference fuel (PRF) mixture of 90% iso-octane and 10% n-heptane was used as a baseline in an optically accessible combustion chamber in a large bore, single cylinder compression ignition engine. The engine was operated in HCCI mode, using early injection to provide homogeneous mixture and utilized heated and compressed air intake. Following this a PRF with 5% CHD was used in the engine. A PRF with 5% CHD was then irradiated with UV light for 240 min, resulting in a PRF mixture containing 1.72% HT, this was then used in the engine. The HT containing PRF had a much later start of combustion compared with the CHD containing PRF, which in turn had a later start of combustion compared with the PRF baseline. This study has successfully validated the concept of using a photo-chemical ‘smart’ fuel to significantly change the ignition quality of a fuel in HCCI mode combustion and demonstrated the concept of on-board ‘smart fuel’ applications for ICE.

Highlights

Introduction published maps and institutional affilIn an effort to reduce regulated emissions and increase thermal efficiency of internal combustion engines (ICE), new equipment, fuels and combustion strategies are under investigation
This study examines a similar photo-chemically active fuel additive which is applied to a homogeneous charge compression ignition engine (HCCI) engine to achieve an element of control over the ignition timing
The final product concentration was calculated by integrating the area below the curves from the Gas chromatographic coupled with mass spectrometric analyses (GCMS) for the two isomers and adding them together

Summary

Introduction

In an effort to reduce regulated emissions and increase thermal efficiency of internal combustion engines (ICE), new equipment, fuels and combustion strategies are under investigation. To reduce NOx it is desirable to reduce peak flame temperatures, achievable by having an overall fuel lean mixture, avoiding any regions of stoichiometric mixture formation. A portion of exhaust particulate matter (PM), it is desirable to have a homogeneous mixture, with no fuel rich regions. In traditional compression ignition (CI) engines, there will always be some regions of high peak flame temperature and fuel rich regions due to fuel–air mixing in the cylinder; thermal efficiency is high due to the higher compression ratios used. In traditional spark ignition (SI) engines, there will be an overall homogeneous, stoichiometric fuel–air mixture, so soot is largely avoided. There will be regions of high flame temperature as the flame front progresses through the stoichiometric mixture resulting in high levels of iations

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Results

Conclusion