Potential of hydrogen/diesel reactivity controlled compression ignition (RCCI) combustion from the perspective of the second law of thermodynamics

Abstract

The potential of reactivity controlled compression ignition (RCCI) combustion fueled with hydrogen and diesel (i.e. hydrogen/diesel RCCI) was evaluated using multi-dimensional simulations embedded with a reduced chemical mechanism. In hydrogen/diesel RCCI, the premixed hydrogen is ignited by the diesel, which is directly injected into the cylinder well before the top dead center. To investigate the potential benefits of hydrogen/diesel RCCI, its combustion characteristics were compared with that of gasoline/diesel RCCI from the perspective of the second law of thermodynamics. Meanwhile, the impacts of premixed energy ratio and initial pressure on the exergy distribution for hydrogen/diesel RCCI were explored. The results show that hydrogen/diesel RCCI has an advantage over gasoline/diesel RCCI in the reduction of exergy destruction due to higher combustion temperature, shorter combustion duration, and the distinctive oxidation pathways between hydrogen and gasoline. A higher proportion of exergy output work can be achieved for hydrogen/diesel RCCI under the conditions with the same total input energy and 50% heat release (CA50) point. Moreover, a larger premixed energy ratio (i.e. larger hydrogen proportion) is helpful to elevate exergy output work and reduce exergy destruction owing to higher combustion temperature and the undergoing oxidation pathways of hydrogen with less exergy destruction. A higher initial pressure yields raised exergy destruction because of lower combustion temperature and longer combustion duration, but exergy output work is increased owing to the significantly reduced exergy transfer through heat transfer.

A numerical study of piston bowl geometry and diesel injection timing in a heavy-duty diesel/syngas RCCI engine

“…Using high-depth piston bowls can noticeably enhance Turbulence Kinetic Energy (TKE) of in-cylinder flow during the compression stroke. 6 Conversely, the use of dual-swirl chamber led to lower maximum swirl ratio compared to stock chamber which can be related to in-cylinder flow separation into two sections which deteriorated TKE. Additionally, by using the wide-shallow chamber, the in-cylinder maximum swirl ratio dramatically decreased compared to other piston bowls, as shown in Figure 4.…”

Introduction to the current and future use of H2 and H2-based e-fuels in combustion engines and fuel cells Special Issue

“…The papers in this category include studies of: the use of anode off-gas of a methane-fueled solid oxide fuel cell system in an internal combustion engine, 7,8 the effect of compression ratio and bore/stroke ratio on methanol-fueled spark-ignition engine operation, 9,10 the role of hydrogen enrichment for diesel-pilot combustion in a high-speed compression ignition engine and in a spark-ignited large-bore engine, 11,12 the effect of oxymethylene ether on emissions and aftertreatment system design for ultra-low emission compression-ignition engine concepts, 13 the potential of Miller cycle in combination with synthetic fuels for heavy-duty engine applications 14 and the potential of hydrogen/diesel compared to gasoline/diesel reactivity-controlled compression ignition combustion utilizing a second law analysis. 15 The Editors hope you find this issue interesting and that the papers can spark a dialog on the important topic of hydrogen utilization in engines and fuel cells in the field of mobile and stationary applications.…”

“…the potential of hydrogen/diesel compared to gasoline/diesel reactivity-controlled compression ignition combustion utilizing a second law analysis. 15…”

Maximum reduction in greenhouse gas emissions by complete replacement of natural gas with pure hydrogen as a sole low reactive fuel in a RCCI engine

“…Hence, some limited studies related to the use of pure hydrogen as a sole low reactive fuel in diesel engines under dual-fuel mode of combustion and more recently under RCCI combustion has been conducted. [46][47][48] Therefore, this study seeks to assess the performance of a heavy-duty diesel engine under RCCI combustion fueled with diesel fuel/pure hydrogen. For this purpose, a single-cylinder heavy-duty diesel engine with bathtub piston bowl geometry is set to operate under RCCI combustion at its Mid-Load range from 9.4 to 13.5 bar gross IMEPs.…”

“…Hence, some limited studies related to the use of pure hydrogen as a sole low reactive fuel in diesel engines under dual-fuel mode of combustion and more recently under RCCI combustion has been conducted. 46–48…”