Studies on the effects of methane fraction and injection strategies in a biogas diesel common rail dual fuel engine. (15th January 2019)

• Record Type: Journal Article
• Authors: Rahman, K. Abdul; Ramesh, A.
• Is Part Of: Fuel. Volume 236(2019)
• Page Start: 147
• Page End: 165
• Publication Date: 2019-01-15
• Subjects: Biogas composition -- Dual fuel engines -- Alternative fuels -- Multiple pulse in dual fuel engines -- Post injection -- Pilot injection; BDDF biogas diesel dual fuel -- BGES biogas energy share -- BMEP brake mean effective pressure -- BTE brake thermal efficiency -- CA crank angle -- CA50 crank angle at which 50% mass burn occurs -- CE combustion efficiency -- CH4 methane -- CI compression ignited -- CNG compressed natural gas -- CO carbon monoxide -- CO2 carbon dioxide -- COV coefficient of variance -- DAQ data acquisition system -- DP double pulse -- ECU engine control unit -- EGR exhaust gas recirculation -- EGT exhaust gas temperature -- EPi.I early pilot injection -- FID flame ionization detector -- FSN filter smoke number -- H2 hydrogen -- H2S hydrogen sulphide -- HC hydrocarbon -- HCCI homogenous charge compression ignition -- HRR heat release rate -- ICT intake charge temperature -- IMEP indicated mean effective pressure -- kW kilowatt -- Max. ROPR maximum rate of pressure rise -- MBD mass burn duration -- MBT maximum brake torque -- MI main injection -- NDIR nondispersive infrared detector -- NO nitric oxide -- NOx oxides of nitrogen -- °aTDC degree after compression top dead center -- °bTDC degree before compression top dead center -- O2 oxygen -- PI post injection -- PM particulate matter -- ppm parts per million -- RCCI reactivity controlled compression ignition -- SI spark ignited -- SOC start of combustion -- SOIT start of injection timing -- SP single pulse -- THC total hydrocarbon -- Vol % volume percent -- η efficiency; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2018.08.091
• Languages: English
• ISSNs: 0016-2361

Abstract

Highlights: Proper selection of injection timing is important for utilizing biogas with varying compositions. Up to an energy share of 60% even very low proportions of methane can be used in a biogas dual fuel engine. Low proportions of methane and high energy shares reduce NO emission. Simulation indicated that thermal effect of CO2 is more dominant than the dilution effect. The pilot plus main injection strategy can reduce smoke levels. Abstract: Biogas is an environment friendly renewable fuel which is a valuable resource in the current context of increased energy requirement and sustainability. The quality or the proportion of methane in biogas can vary significantly based on the raw material and method of production. This experimental work was aimed at evaluating the influence of such variations in composition on the energy conversion efficiency and emissions of a common rail dual fuel engine under different output conditions. The effects of post and pilot injection of diesel were also studied in this mode. Biogas with methane proportions in the range 24–68% could be utilized without significant changes in efficiency and emissions till a biogas energy share (BGES) of 60% when the injection timing of diesel was suitably adjusted. Higher than normal methane concentrations (normal: 51–53%) only elevated the NO levels with little impact on efficiency. However, when low proportions of methane were used NO could be controlled effectively particularly at low BGES. Simulation studies indicated that this reduction in NO is due to the lowered in-cylinder temperature rather than the reduced concentration of oxygen as a result of increased CO2 . When the proportion of methane was decreased from 68% to 24% the start of injection of diesel had to be advanced by 3 °CA (at a BGES of 60%) to compensate for the increase in ignition delay and reduction in combustion rate. With pilot injection there was a reduction in smoke emission because of improved charge homogeneity due to the split injection process. However, post injection which is generally effective in diesel engines was not advantageous in the biogas diesel dual fuel (BDDF) mode because of the diffusion combustion the post injected fuel undergoes.