Numerical analysis of zero-carbon HCCI engine fuelled with steam diluted H2/H2O2 blends

Abstract

The addition of hydrogen peroxide and steam to a hydrogen-fuelled HCCI engine was investigated at various fuel lean conditions ( ϕ e f f = 0.2–0.6) and compression ratios (15–20) using a 0-dimensional numerical model. The use of hydrogen peroxide as an ignition promoter demonstrated increased IMEP (16%–39%), thermal efficiency (up to 2%), and reduced NOx (50%–76%) when compared to the conventional method of intake charge heating. When hydrogen peroxide was used as an ignition promoter, a 15% addition of steam was sufficient to reduce NOx by 93%–97%, though this reduced IMEP and thermal efficiency slightly. When heat transfer was considered and steam addition was increased from 0%–10%, no increase in intake air heating was able to match the IMEP of 5% hydrogen peroxide addition without an increase in the equivalence ratio (up to 40%). The parametric space of hydrogen peroxide (0%–25%) and steam (0%–40%) addition was explored in view of engine performance metrics, showing the complete range of conditions possible through control of both inputs. A three-order reduction in NOx was possible through steam addition. An optimal balance of performance and emissions occurred at 5%–10% hydrogen peroxide and 10%–15% steam addition. In a study of compression ratio, very little hydrogen peroxide addition ( < 5%) was required to achieve 98% of the maximum efficiency at higher compression ratios (19–20), though at lower compression ratios ( < 17) impractical quantities of hydrogen peroxide were required. The 10% steam addition present at these conditions led to extremely low NOx levels for ϕ e f f of 0.3 and 0.4, though at ϕ e f f of 0.5 NOx levels would require some after-treatment. Maintaining constant a high or low load across steam additions was possible through reasonable adjustment of hydrogen peroxide addition. • Hydrogen Peroxide increased performance, lowered emissions of Hydrogen HCCI engine. • Three-order reduction of NOx possible through additional steam dilution. • Hydrogen Peroxide was preferable ignition promoter compared to glow plug method. • No exhaust treatment necessary at lean equivalence ratios. • 5%–10% Hydrogen Peroxide and 10%–15% steam dilution ideal for most conditions.