The search for alternative transport fuel with comparable performance to fossil fuels in powering internal combustion engines (ICEs) has been a topical research project for decades. This is important because ICE is a well-developed technology, but fossil fuels are a finite resource, yet their consumption causes environmental damage. The alternative fuel is therefore expected to overcome these limitations. Hydrogen gas has been on top of the list as the most suitable option, but it is widely proposed dilute it with other fuels for better performance. To understand the effects of diluents such as methane and propane on the combustion characteristics hydrogen gas, Particle Image Velocimetry (PIV) was employed in this study to compare the fundamental combustion characteristics of hydrogen, propane and methane as single fuels at similar conditions in a featureless Leeds University Ported Optical Engine, (LUPOE-2D). The experiments were carried out at low speed of 50 rpm and a boosted inlet pressure of 1.67 bar at port inlet closing, typical of a downsized engine. The mixtures were ignited during the compression stroke at 5 bar. The inlet air was heated, and the temperature of the cylinder head was slightly adjusted from room temperature of 25 ± 2°C for the different mixtures such that a temperature of 439K was obtained for the mixtures at spark pressure of 5 bar. The temperature was estimated using the first law of thermodynamics. Flame combustion characteristics such as flame wrinkling parameters, stretch rate, burning velocities, etc., were derived and compared. There is good agreement between the stretched laminar burning velocities derived from direct measurement of the flame speed and unburned gas velocities ahead of the flame front, extrapolated to the zero-stretch, the values derived from the products of the unstretched flame speeds and the density ratios, and Chemkin-computed values. The burning rates increased with increase in flame stretch except for H2 ϕ=0.5 which increased to a peak before declining in similar manner as the flame stretch reached a peak and declined before the influence of wall confinement. The flame sphericity and the flame wrinkling amplitude were used to compare their flame wrinkling characteristics of the flames. H2 ϕ=0.5 flames showed significant instability from the onset and became more winkled as the flame radius increased.
CORE (COnnecting REpositories)
CORE (COnnecting REpositories)