Effects of Engine Operating Parameters on Lean Combustion Limit of Hydrogen Enhanced Natural Gas Engine

Abstract

An experimental study was conducted on a S.I. engine fueled by compressed natural gas and hydrogen blends (HCNG), in order to test different engine operating parameters that affect lean combustion limit (L.C.L) of HCNG engine. Firstly, constant ignition timing and ignition timing under maximum L.C.L (L.L.T) conditions were compared, then L.L.T conditions were adopted in this paper. The results indicated that for each condition, neither over-retarded nor over-advanced ignition timing are advised in order to achieve leaner combustion. L.C.L increases with hydrogen fraction in the blends, and slightly increases with throttle opening, while decreases when the engine speed is raised

Effect of Ignition Energy and Hydrogen Addition on Laminar Flame Speed, Ignition Delay Time, and Flame Rising Time of Lean Methane/Air Mixtures

“…Owing to the large burning velocity and lower flammability limit, hydrogen is a candidate fuel for stabilizing lean operations and reducing emissions of natural gas engines [12][13][14][15]. For instance, Ma et al [12] reported that the excess air ratio of purely natural gas at 105 kPa of manifold absolute pressure was 1.71 and could be extended to 1.82, 2.09, and 2.4 by adding 10%, 30%, and 50% in volume fraction of H 2 , respectively.…”