Prospects and Challenges of DME Fueled Low-Temperature Combustion Engine Technology

Abstract

The ever-increasing demand for energy, the exhaustible nature of conventional fuels, and increasing pollution have led to an immediate search for clean, sustainable, and renewable alternative energy sources. DME is one such alternative fuel that is quite promising for internal combustion (IC) engines because of several advantages over conventional fuels. DME is the ultimate next-generation e-fuel since it can be produced from renewable feedstocks such as agricultural, municipal sewage waste, and many kinds of biomass fuels by direct and indirect synthesis. However, DME-fueled IC engines have few limitations, e.g., high NOx emissions, which need to be overcome to expand their usage in production-grade engines. In addition to environment-friendly fuel, there is also a need to investigate emerging, innovative combustion technologies capable of meeting fuel economy targets and complying with the prevailing stringent emission norms. Engines with low-temperature combustion (LTC) concepts are highly efficient and environmentally friendly and offer promising alternatives to conventional combustion engine technologies. Homogeneous charge compression ignition (HCCI), partially premixed charge compression ignition (PCCI), Reactivity controlled compression ignition (RCCI), and gasoline compression ignition (GCI) are a few of the LTC variant technologies, which should be investigated for DME to combine both cleaner and efficient engine technology and environment-friendly alternative fuel. HCCI engine technology is an ideal LTC engine technology with higher efficiency. However, there are some limitations of HCCI engine technology, such as limited operational range. Hence, other LTC engine technologies are being widely investigated. PCCI engine technology is one of them. Factors such as lean premixed charge, high compression ratio, and multi-point spontaneous ignition lead to excellent fuel economy and low NOx emissions. Another LTC engine technology is the RCCI, which uses two different fuel reactivities to achieve excellent engine efficiencies. Low reactivity fuels such as natural gas can be used along with high reactivity fuels such as DME, yielding lower NOx and PM emissions, reducing heat transfer loss, and increasing engine efficiency. Moreover, the RCCI technology leads to an elimination of the need for expensive exhaust gas after-treatment systems. This chapter examines the concepts of various LTC engine technologies and their performance and emission characteristics, underlying challenges, and way forward for using DME as a fuel in IC engines.