Influence of engine operating conditions on combustion parameters in a spark ignited internal combustion engine fueled with blends of methane and hydrogen

• Published in: Energy conversion and management 2019-02, Vol.181, p.414-424
• Main Authors: Amador Diaz, German J., Gómez Montoya, Juan P., Corredor Martinez, Lesme A., Olsen, Daniel B., Salazar Navarro, Adalberto
• Format: Article
• Language: English
• Subjects: Combustion; Combustion parameters; Compression; Compression ratio; Design of experiments; Empirical analysis; Equivalence ratio; Factor analysis; Factorial design; Form factors; Hydrogen; Indicator diagrams; Inlet pressure; Internal combustion engine; Internal combustion engines; Knock; Methane; Parameter estimation; Pressure; Pressure effects; Statistical analysis; Variance analysis
• ISSN: 0196-8904; 1879-2227
• DOI: 10.1016/j.enconman.2018.12.026

•Combustion parameters were estimated from the indicator diagram.•It was demonstrated that the fuel blends composition, ∅ and θIT influence KOCA.•Polytropic coefficient depend strongly on the compression ratio.•Correlations to estimate KOCA, ΔθCD and CCR were proposed.•Experimental MFB traces were fitted with the Wiebe constants a = 2.8 and m = 2.4. An experimental study of the effects of hydrogen and methane proportions, Compression Ratio (CR) and equivalence ratio (∅) on the Knock Occurrence Crank Angle (KOCA), the Combustion Duration (ΔθCD) and the compression Polytropic coefficient (n) is carried out in this paper. These parameters were estimated through an alternative method that uses the average engine indicator diagram and the first derivative concept. The tests were conducted in a 2 kW Cooperative Fuel Research Engine (CFR) wherein the effect of inlet pressure on KOCA was also studied. To evaluate these effects, a factorial design of experiment and an one-factor Analysis of Variance (ANOVA) were conducted. According to the statistical analysis the evaluated engine operating conditions significantly influence the combustion parameters; however, the analysis revealed that the inlet pressure does not influence KOCA. Moreover, validated empirical correlations to estimate KOCA, ΔθCD and Critical Compression Ratio (CCR) as a function of engine operating conditions were proposed. It was demonstrated that actual Mass Fraction Burned (MFB) curves can be fitted with a = 2.8 and m = 2.4 which are the so-called efficiency and form factors of the Wiebe function, respectively. These values for hydrogen and methane mixtures are different from the values widely used for conventional fuels, i.e. a = 5.0 and m = 2.0. In the present study, the compression polytropic coefficients as a function of engine operating conditions were reported and were found to be ranging from 1.21 to1.25.