Optimisation of operating parameters on the performance characteristics of a free piston engine linear generator fuelled by CNG–H2 blends using the response surface methodology (RSM)

• Published in: International journal of hydrogen energy 2022-01, Vol.47 (3), p.1996-2016
• Main Authors: Raheem, Ahmed T., Aziz, A. Rashid A., Zulkifli, Saiful A., Baharom, Masri B., Rahem, Abdalrazak T., Ayandotun, Wasiu B.
• Format: Article
• Language: English
• Subjects: Engine performance; Linear free piston engine; Optimisation; Response surface methodology
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2021.10.125

The free piston engine linear generator (FPELG) is a simple engine structure with few components, making it a promising power generation system. However, because the engine works without a crankshaft, the handling of the piston motion control (PMC) is the main challenge influencing the stability and performance of FPELGs. In this article, the optimal operating parameters of FPELG for maximising engine performance and reducing exhaust gas emissions were studied. Moreover, the influence of adding hydrogen (H2) to compressed natural gas (CNG) fuel on FPELG performance was investigated. The influence of operating parameters on in-cylinder pressure was also analysed. The single-piston FPELG fuelled by CNG blended with H2 was used to run the experiments. The response surface methodology (RSM), including the central composite design (CCD), was used. Then, adequacy models were developed and verified by ANOVA. Three independent factors on seven responses were utilised for optimisation. Results showed that the optimal operating conditions of lambda, ignition velocity, and injection position were 0.96, 0.53 m/s, and −14.9 mm, respectively. The best-predicted values were as follows: indicated mean effective pressure (IMEP) of 7.6 bar, in-cylinder pressure of 27.87 bar, combustion efficiency of 39.64%, CO of 9531.41 ppm, CO2 of 2.4%, HC of 551.75 ppm, and NOX of 113.737 ppm. Furthermore, results showed that the experimental data could be fitted well with the predicted quadratic model. [Display omitted] •Three independent factors on seven responses were used for the optimisation.•The adequacy models were developed in RSM and verified by ANOVA.•The operating parameters of FPELG were optimised using RSM.•Maximum performance and minimum emission of FPELG were obtained.•The effect of operating parameters on FPELG performance was investigated.