Abstract
Dual fuel engines using diesel and fuels that are gaseous at normal conditions are receiving increasing attention. They permit to achieve the same (or better) than diesel power density and efficiency, steady-state, and substantially similar transient performances. They also permit to deliver better than diesel engine-out emissions for CO2, as well as particulate matter, unburned hydrocarbons, and nitrous oxides. The adoption of injection in the liquid phase permits to further improve the power density as well as the fuel conversion efficiency. Here, a model is developed to study a high-pressure, 1600 bar, liquid phase injector for liquefied natural gas (LNG) in a high compression ratio, high boost engine. The engine features two direct injectors per cylinder, one for the diesel and one for the LNG. The engine also uses mechanically assisted turbocharging (super-turbocharging) to improve the steady-state and transient performances of the engine, decoupling the power supply at the turbine from the power demand at the compressor. Results of steady-state simulations show the ability of the engine to deliver top fuel conversion efficiency, above 48%, and high efficiencies, above 40% over the most part of the engine load and speed range. The novelty of this work is the opportunity to use very high pressure (1600 bar) LNG injection in a dual fuel diesel-LNG engine. It is shown that this high pressure permits to increase the flow rate per unit area; thus, permitting smaller and lighter injectors, of faster actuation, for enhanced injector-shaping capabilities. Without fully exploring the many opportunities to shape the heat release rate curve, simulations suggest two-point improvements in fuel conversion efficiency by increasing the injection pressure.
Highlights
Renewable energy, that is practically ony wind and solar, cannot cover the world’s total primary energy supply by 2050
Engine performance simulations are performed by using state of the art computer-aided engineering (CAE) computer codes modeling the steady-state operation of super-turbocharged diesel and methane engines
Reference [4] presents the results for the baseline engine and the dual fuel diesel liquefied natural gas (LNG) engine with a lower pressure direct injector
Summary
That is practically ony wind and solar, cannot cover the world’s total primary energy supply by 2050. Not many are working on engines anymore; despite this fact, the world’s growing total primary energy supply is still covered—by more than 90%—by combustion fuels, oil, coal, natural gas, biomass, and waste [1]. In addition to the limited opportunities to grow their installed capacity, there are even more limited opportunities to grow the energy storage needed to compensate wind and solar intermittency and unpredictability [2,3]. It still makes a lot of Processes 2020, 8, 261; doi:10.3390/pr8030261 www.mdpi.com/journal/processes
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