Biofuel Powering of Internal Combustion Engines: Production Routes, Effect on Performance and CFD Modeling of Combustion

Abstract

The use of liquid or gaseous biofuels in reciprocating internal combustion engines (ICEs) is today a relevant issue as these systems are largely diffused for both steady power generation and transportation due to their flexibility and easiness of use. The improvement and perfect control of the combustion process under non-conventional fueling is mandatory to achieve high-energy efficiency without substantial changes to the architecture or the fuel supply system. In this perspective, the detailed characterization of multiphase reacting systems achievable though computational fluid dynamics (CFD) may give a decisive contribution. However, the assessed combustion models used for fossil fuels (diesel oil, gasoline, methane), tuned on the ground of a massive amount of experimental data, often results poor in predicting the actual behavior of renewable fuels whose composition and properties may change also according to technology for their production. Present work aims at filling some existing gaps in biofuel combustion modeling by performing investigations on two representative engine cases, for their characterization and performance enhancement. Two approaches are followed, namely through reduced chemical kinetics coupled with turbulence within a coherent flame schematization, and through a turbulent species transport approach with detailed kinetics. Simulations are first carried out on a compression ignition (CI) ICE. The formulation of a 3D CFD model is described to reproduce the performance of this engine in a dual-fuel mode with premixed syngas from biomass gasification and a biodiesel pilot injection leading to self-ignition. Pollutants formation and energy efficiency are calculated as syngas amount and the biodiesel start of injection (SOI) are varied. Attention is then focused on the implementation of renewable alcohol fuels (ethanol and butanol), as these lasts are receiving large interest due to low production costs. A validated reduced kinetic mechanism for PRF-ethanol-butanol combustion performs well in multi-component oxidation conditions, as well as in neat fuel oxidation conditions, in terms of ignition delay time, laminar flame speed and HCCI combustion conditions. The paper shows that CFD, even at different level of approximation, may describe into detail the combustion process and provide important guidelines for the design of new generation ICEs fuelled by biofuels.

The “INNOVARE” Project: Innovative Plants for Distributed Poly-Generation by Residual Biomass

“…ICEs, on the other hand, are particularly suitable to syngas use over the micro-scale or small-scale of power due to their low cost, easy control, durability and suitability to frequent start-and-stop procedures [27,28]. Nevertheless, their use has been up to present derived mostly from natural gas engine design, with low or null modification to the combustion chamber or to the control strategy.…”

The Flex-OeCoS—a Novel Optically Accessible Test Rig for the Investigation of Advanced Combustion Processes under Engine-Like Conditions

“…Measured at TDC from piston top to the bottom of the head. 2 Normal operating range: 300-1200 rpm. 3 Controlled with an external unit.…”

“…Measured from the circular combustion chamber to the bottom of the head 2. Electrical heating, which can be switched off during experiments.…”

Acoustic analysis of a single-cylinder diesel engine using magnetized biodiesel-diesel fuel blends

“…Biodiesel is prepared from vegetable oils, food crops and waste feedstock by transesterification ( Khoobbakht et al., 2020a and b ) and has approximately similar characteristics to diesel fuel especially in terms of cetane number ( Costa and Piazzullo, 2018 ; Sindhanai Selvan et al., 2018 ).…”