VII PTNSS Congress - 27th-29th June 2017
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Numerical investigation on low calorific syngas combustion in the Opposed-Piston engine

The aim of this study was to investigate a possibility of using gaseous fuels of a low calorific value as a fuel for internal combustion engines. Such fuels can come from organic matter decomposition (biogas), oil production (flare gas) or gasification of materials containing carbon (syngas). The varying composition and low calorific value of these fuels usually do not meet standards defined by engine manufacturers. Additionally, when fuel is considered as a waste it needs to be utilized due to environmental regulations what raises additional costs. However, it might be possible to utilize these fuels for power generation with specific engine design and engine control measures. The barrel type Opposed-Piston (OP) engine arrangement is of particular interest for the authors because of its robust design, high mechanical efficiency and relatively easy incorporation of Variable Compression Ratio (VCR). With VCR it becomes possible to adjust compression ratio according to the composition of the fuel and apply Controlled Auto-Ignition (CAI) for high efficiency and low emission operation. In order to investigate engine operation on low calorific gaseous fuel authors performed 3D CFD numerical simulations of scavenging and combustion processes in the 2-stroke barrel type Opposed-Piston engine with use of the AVL Fire solver. Firstly, engine operation on natural gas with ignition from diesel pilot was analysed as a reference. Then, combustion of syngas in two different modes was investigated – with ignition from diesel pilot and with Controlled Auto-Ignition. Final engine operating points were specified and corresponding emissions were calculated and compared. Results suggest that engine operation on syngas might be limited due to misfire of diesel pilot or knocking combustion. A solution proposed by authors for syngas is CAI combustion which can be controlled with application of VCR and with adjustment of air excess ratio. Based on preformed simulations it was shown that low calorific syngas can be used as a fuel for power generation in the Opposed-Piston engine which is currently under development at Warsaw University of Technology.
Topic: Modelling and optimization of engine processes
Author: Rafał Pyszczek
Co-authors: Paweł Mazuro, Agnieszka Jach, Andrzej Teodorczyk