Experimental and Numerical Analysis of an Active Pre-Chamber Engine Fuelled with Natural Gas

Abstract

<div class="section abstract"><div class="htmlview paragraph">Increasingly stringent pollutant and CO₂ emission standards require the car manufacturers to investigate innovative solutions to further improve the fuel economy and environmental impact of their fleets. Nowadays, NO_x emissions standards are stringent for spark-ignition (SI) internal combustion engines (ICEs) and many techniques are investigated to limit these emissions. Among these, an extremely lean combustion has a large potential to simultaneously reduce the NO_x raw emissions and the fuel consumption of SI ICEs. Engines with pre-chamber ignition system are promising solutions for realizing a high air-fuel ratio which is both ignitable and with an adequate combustion speed.</div><div class="htmlview paragraph">In this work, the combustion characteristics of an active pre-chamber system are experimentally investigated using a single-cylinder research engine. The engine under exam is a large bore heavy-duty unit with an active pre-chamber fuelled with compressed natural gas.</div><div class="htmlview paragraph">In first stage, an experimental campaign was carried out for four different conditions of load and air/fuel ratio, at the same engine speed, then a 3D CFD analysis was realised to evaluate the in-cylinder turbulence and pre-chamber pressure traces. Global engine operating parameters as well as cylinder pressure traces, inside main combustion chamber and pre-chamber, were recorded and analysed. Based on the available 3D and experimental data, a phenomenological model of this unconventional combustion system is developed and validated.</div><div class="htmlview paragraph">The model is implemented in a commercial 1D code. The proposed numerical approach shows the ability to simulate the experimental data with good accuracy, with no case-dependent tuning. The model demonstrates to correctly describe the behaviour of a pre-chamber combustion system under the four operating conditions and to capture the physics behind such an innovative combustion system concept.</div></div>