About this Research Topic

Background

Due to their higher reliability and superior fuel conversion efficiency, compression-ignition diesel engines are the most common internal combustion engines. However, diesel engines still generate significant amounts of carbon dioxide (CO2) and particulate matter (PM) emissions because of the inherent fuel properties of diesel and diffusion combustion characteristics inside the cylinder. The Paris Agreement has set up a long-term goal to keep the increase in global average temperature to well below 2 °C above pre-industrial levels, to substantially reduce the risks and effects of climate change. Under the Paris Agreement, each country must determine, plan, and regularly report on the contribution that it undertakes to mitigate global warming. As a result, many countries have set up their goals to reduce and/or limit greenhouse gas (GHG) emissions. This has exerted pressure on industries generating significant amount of GHG emissions, such as those using diesel engines. Therefore, it is of great importance to further reduce GHG and engine-out PM emissions from diesel engines.

Natural gas (NG) is a low carbon fuel that is abundant and inexpensive. The combustion of NG generates less CO2 emissions than that of diesel. In addition, the combustion of NG generates much less PM emissions compared to that of diesel. Therefore, replacing diesel by NG can help reduce CO2 and PM emissions from diesel engines.

In order to replace diesel by NG, a diesel engine can be converted to either a spark-ignition NG engine or a compression-ignition NG - diesel dual fuel engine. Spark-ignition NG engines offer relatively lower fuel efficiency compared to diesel engines and usually have limit in power output.

NG - diesel dual fuel engines retain the higher fuel efficiency of diesel engines and can be used to haul loads as diesel engines, while replacing a significant amount of diesel with NG. Besides, a diesel engine can be easily converted to a NG - diesel dual fuel engine, which makes the technology suitable for both new engine manufacture and retrofitting existing diesel engines. Studies have shown that NG – diesel dual fuel engines do significantly reduce CO2 and engine-out PM emissions compared to diesel engines. However, there are still some issues that are limiting the wide application of the dual fuel engines. These include the limited replacement ratio, efficiency deterioration, and especially the incomplete combustion of methane at low load conditions.

The purpose of this Research Topic is to focus on compression-ignition NG- diesel dual fuel engines using NG as either preliminary or supplementary fuel. The Research Topic will cover all aspects in the development of NG – diesel dual fuel engines, including fundamental combustion and emissions mechanisms, and advanced technology development to improve engine performance and minimize exhaust emissions at various engine load and speed conditions. The latest development in the advanced Reactivity Controlled Compression Ignition (RCCI) technology, using NG as high octane number fuel, with the combustion process controlled by high cetane fuel will also be explored. Advanced exhaust-gas after treatment technologies aiming to reduce methane emissions will also been covered.

Keywords: Compression Ignition Diesel Engines, Dual Fuel Engines, Natural Gas, Greenhouse Gas Emissions, Particulate Matter

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