Abstract
Diesel fueled compression ignition engines are widely used in power generation and freight transport owing to their high fuel conversion efficiency and ability to operate reliably for long periods of time at high loads. However, such engines generate significant amounts of carbon dioxide (CO2), nitrogen oxides (NOx), and particulate matter (PM) emissions. One solution to reduce the CO2and particulate matter emissions of diesel engines while maintaining their efficiency and reliability is natural gas (NG)-diesel dual-fuel combustion. In addition to methane emissions, the temperatures of the diesel injector tip and exhaust gas can also be concerns for dual-fuel engines at medium and high load operating conditions. In this study, a single cylinder NG-diesel dual-fuel research engine is operated at two high load conditions (75% and 100% load). NG fraction and diesel direct injection (DI) timing are two of the simplest control parameters for optimization of diesel engines converted to dual-fuel engines. In addition to studying the combined impact of these parameters on combustion and emissions performance, another unique aspect of this research is the measurement of the diesel injector tip temperature which can predict potential coking issues in dual-fuel engines. Results show that increasing NG fraction and advancing diesel direct injection timing can increase the injector tip temperature. With increasing NG fraction, while the methane emissions increase, the equivalent CO2emissions (cumulative greenhouse gas effect of CO2and CH4) of the engine decrease. Increasing NG fraction also improves the brake thermal efficiency of the engine though NOx emissions increase. By optimizing the combustion phasing through control of the DI timing, brake thermal efficiencies of the order of ∼42% can be achieved. At high loads, advanced diesel DI timings typically correspond to the higher maximum cylinder pressure, maximum pressure rise rate, brake thermal efficiency and NOx emissions, and lower soot, CO, and CO2-equivalent emissions.
Highlights
As part of the Paris Agreement on climate change, Canada has committed to 30% abatement of its greenhouse gas (GHG) emissions from the 2005 levels by the year 2030 (Government of Canada, 2016)
At αNG 0%, the first peak of heat release corresponds to premixed combustion of air/diesel mixture, followed by the second major peak corresponding to the mixing controlled diffusion combustion
The first peak on the heat release rate curve of each Natural gas (NG) fraction is related to premixed combustion of air/NG/diesel, followed by the diffusion combustion of remaining diesel and subsequent flame propagation of the background air/NG mixture
Summary
As part of the Paris Agreement on climate change, Canada has committed to 30% abatement of its greenhouse gas (GHG) emissions from the 2005 levels by the year 2030 (Government of Canada, 2016). Diesel fueled compression ignition (CI) engines are widely used in power generation and freight transport owing to their high fuel conversion efficiency and ability to operate reliably for long periods of time at high loads. Owing to their ubiquity and extent of use, the carbon dioxide (CO2), nitrogen. In addition to offsetting diesel consumption, the potential advantages of such a configuration are lower PM emissions and limited engine modifications (Sahoo et al, 2009) Such dual-fuel engines can operate as conventional diesel engines when NG is not available. The main sources of these methane emissions at medium to high load conditions are crevice regions (Yousefi et al, 2019)
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