Numerical comparative study of hydrogen addition on combustion and emission characteristics of a natural-gas/dimethyl-ether RCCI engine with pre-chamber

Reactivity controlled compression ignition (RCCI) strategy uses two different fuels with independent reactivates which impacts combustion characteristics such as gross work, start of combustion (SOC) and burn duration as well as engines emissions. Effects of hydrogen addition have been numerically investigated on a RCCI natural-gas/di-methyl ether engine. For this purpose, six different percentages of H-2 (i.e.0,10,20,30,40 and 50%) has been evaluated. In all case studies total-heating values was kept constant. Numerical results showed increase in total gross work with the increase of hydrogen and up-to 19.7% boost by adding 50% of hydrogen. In the direction of adding hydrogen there are ascend in cumulative heat release which is about 15.9% with 50% of hydrogen. According to DME decomposition process, more than 10% of it was decomposed to its products, specially CH4 before SOC which affects fuel mixture Cetane number and in-cylinder heat release. Results showed advancement in combustion start about 5 CAD in 50% H-2, it is about 7.8 CAD for CA50. Burn duration of using 50% H-2 decreased about 6 CAD, approximately. Released CO and UHC descended 5.5 and 9.7 gr/kWh, respectively in 30% H-2. Temperature and pressure also increased during hydrogen addition with 16.3 and 25.6% in 50% of hydrogen. (C) 2019 Elsevier Ltd. All rights reserved.