EGR control on operation of a tar tolerant HCCI engine with simulated syngas from biomass. (1st October 2018)

• Record Type: Journal Article
• Authors: Bhaduri, Subir; Jeanmart, Hervé; Contino, Francesco
• Is Part Of: Applied energy. Volume 227(2018)
• Page Start: 159
• Page End: 167
• Publication Date: 2018-10-01
• Subjects: Homogeneous Charge Compression Ignition -- Biomass syngas -- Exhaust Gas Recirculation; Power (Mechanics) -- Periodicals; Energy conservation -- Periodicals; Energy conversion -- Periodicals; 621.042
• DOI: 10.1016/j.apenergy.2017.08.233
• Languages: English
• ISSNs: 0306-2619

Abstract

Highlights: Novel methodology to directly use unscrubbed biomass syngas in piston engines. Demonstration of EGR as an efficient control parameter for HCCI engines operated with synthetic syngas. For syngas combustion, EGR has mainly a thermal effect rather than chemical kinetic effect. The study spans a large range of conditions and improve by 30% the IMEP. Abstract: In combined heat and power plants operated with biomass syngas, the removal of condensible tars is a necessary but expensive step (up to one third of the installation and maintenance costs). This step is required because the syngas has to be cooled down to avoid knocking in the spark ignition engines traditionally used in such plants. To remove the tar condensation problem, we developed an alternative system based on an Homogeneous Charge Compression Ignition (HCCI) engine operated at intake temperatures above the tar dew point. To address the challenge of power derating of such engine setups, the current paper focuses on the application of Exhaust Gas Recirculation (EGR) as a control parameter that would indirectly allow the improvement of the engine performance. Based on a conservative estimate of tar dew points, HCCI combustion was studied at an intake temperature of 250 °C using synthetic biomass syngas and synthetic EGR on a mono-cylinder HCCI engine operated at 1000 RPM. The effects of charge dilution, thermal and kinetic damping due to the EGR gases were also analysed to understand their main effects. The use of EGR successfully increased the maximum achievable Indicated Mean Effective Pressure from 2.5 bar at EGR = 0% up to 3.3 bar at EGR = 25%, through damping the maximum pressure rise rate and allowing higher equivalence ratios.