Dinesh, M.H.Pandey, J.K.Kumar, G.N.2026-02-042022International Journal of Hydrogen Energy, 2022, 47, 60, pp. 25391-254033603199https://doi.org/10.1016/j.ijhydene.2022.05.287https://idr.nitk.ac.in/handle/123456789/22504In the present paper, an experimental investigation has been performed under variable CR and 1400&1800RPM speed at a fixed spark timing of 24ºCA BTDC under wide-open throttle conditions. The hydrogen blending is performed based on energy fractions from 5% to 21% of the total fuel energy. With increasing compression ratio (CR), the flame development gets faster, and the flame propagation speed improves, leading to a short combustion period. Similarly, increasing hydrogen fraction improves combustion, resulting in a rapid rise in pressure and temperature. Despite a 13.64% decrease in volumetric efficiency from 5% to 21% hydrogen fraction at 1400 and 1800 RPM, BP and BTE increased by 16.89% and 33%, respectively. The slow-burning properties of NH<inf>3</inf> extend the combustion period, resulting in a long-delayed burning period. As a result, the temperature of the low-hydrogen fraction of the exhaust gas is higher. As the hydrogen fraction and CR increase, this effect decreases, resulting in lower EGT. The hydrogen addition increases the peak temperature; therefore, NO<inf>x</inf> increases continuously with increasing hydrogen despite reducing ammonia. Ammonia is a key element used to reduce NO<inf>x</inf> from vehicles. A practical solution for controlling the NO<inf>x</inf> due to the ammonia/hydrogen blend is selective catalytic reduction (SCR). © 2022 Hydrogen Energy Publications LLCBlendingCombustionEnginesNitrogen oxidesSelective catalytic reductionConditionEmission behaviorExperimental investigationsNO xNO x emissionPerformanceSI EnginesSpark timingVariable compression ratioWide open throttleAmmonia