DME Combustion at Diesel Engine Conditions

Sponsors: NSF-DOE

Statement: Use of DME, a natural-gas derived liquid fuel, in the ICE has significant advantages with traditional fuels (gasoline and diesel) on an energy equivalent basis, yielding low emissions and zero PM, and improved efficiency. Shortcomings include highly energy intensive processes for gas-to-liquid conversion and much lower energy density on a volume basis. Use of DME in advanced engine concepts with high efficiency will pursue lean-burn combustion, high injection pressures, and high EGR. This proposal aims for a fundamental, phenomenological, and quantitative study on the energy conversion method over a wide range of pressures and temperatures, utilizing state-of-the-art experimentation along with strong synergistic theoretical and computational efforts.

Intellectual Merits:  DME combustion yields very low NOx but higher CO and HC emissionsdue to much higher DME volatility and reactivity. Limited engine testing has shown that with the use of high injection pressures, DME offers the potential to meet 2010 HD diesel emission standards without any aftertreatment system while maintaining very high engine efficiencies. For future engine strategies to extend the DME application use of (i) higher injection pressures, much capable pressures compared to the present day 300 bar operation, and (ii) low temperature combustion strategies, such as lean-burn and high EGR concepts are envisioned. The system is not limited by soot formation, thereby facilitating very high EGR levels for NOx reduction. These unique combustion properties under highly diluent mixture conditions however raise many questions about DME use as a fuel for ICE application, including:

  • Are inherent characteristics of DME sprays, i.e., atomization, ignition, and flame properties advantageous or disadvantageous for use in ICE’s under diluent conditions? How do these characteristics affect burning rates, quenching limits, and emissions such as NOx, UHC in engines?
  • Are DME characteristics encouraged or suppressed by changing air-fuel mixing strength, amount of EGR, pressure and temperature? Is the behavior of high-temperature DME autoignition similar to that under low-temperature conditions?
  • How do DME spray characteristics of liquid length and penetration influence fuel-air mixing, especially under low temperature conditions at varying injection pressure?
  • What is the proper injection pressure to obtain low emissions and high efficiency? What advancements in DME injector technology are required to produce these pressures?

In this joint effort between MTU, Argonne, Alternative Fuel Technology, and Navistar, the experimental facilities and expertise of individual partners will be leveraged to characterize the low temperature combustion of DME. The net outcome of this effort will be fourfold: (i) a comprehensive characterization of DME high-pressure spray combustion; (ii) a comprehensive determination of highly dilute DME autoignition; (iii) development of CFD predictive tool for emissions and combustion efficiency; and (iv) optimization of high pressure DME fuel system validated through MTU-CV and ANL-RCM. The ultimate goal of this project is to further develop a highly efficient engine combustion strategy that uses dilution and high boost pressures.

Broader Impacts: This proposed research will have important broader impacts on high school, undergraduate, and graduate education, while enhancing the involvement of underrepresented students in science and engineering. The project will support one graduate student and one undergraduate student who will become experts in the modeling and analysis of multi-physics combustion problems. The unique part of this plan is an integrated approach whereby research, education, and service are simultaneously integrated and undertaken. Throughout this joint program, the students will benefit from performing research in close collaboration with national laboratory and industrial scientists. For example, the PI and graduate students along with industrial scientists will continuously develop demonstrations and presentations to give to science and math classes that illustrate, in a visually appealing and interesting manner, principals or material being taught to instill interest in math and science. This provides the graduate students and scientists with teaching experience, community service, and social exposure while exciting young students, motivating them to pursue a career in engineering and science.

NSF-DOE Advanced Engine Combustion Project Outline