Syngas-Biogas-Hydrogen Flexible Fuel Supply Strategy for IC Engines Operating in Hybrid Renewable Energy System 

Bui Van Ga

University of Science and Technology, The University of Danang

buivanga@ac.udn.vn

Abstract: Developing efficient technologies for renewable energy production and utilization significantly contributes to advancing the energy transition process and implementing the Net-Zero roadmap. The hybrid solar-biomass renewable energy system effectively addresses the limitations associated with relying solely on an individual renewable energy source. This energy system generates electricity and syngas, biogas, hydrogen, which in turn power internal combustion engines to produce energy when solar energy from PV panels is insufficient. Due to the low air-to-fuel ratio and low heat value of syngas, power derating, typically in the range of 30%-50%, poses a significant challenge for engines fueled solely by neat syngas using traditional fuel supplying methods. To overcome this challenge, syngas should be enriched with high-heat value fuels, and an appropriate method should be applied to supply them to the engine. In the solar-biomass hybrid energy system, syngas is enriched with biogas and hydrogen. The present study introduces an innovative technology for syngas-biogas-hydrogen injection through a twinning injector system. This flexible technology allows for supplying gaseous fuels with a large variation in air/fuel ratio. Furthermore, in the case of direct injection, this method can simultaneously adjust the equivalence ratio and the mass of fresh gas, which is beneficial for enhancing the performance of syngas engines specifically, and engines utilizing lean fuels in general. The study considers the effects of nozzle diameter, injection pressure, and engine operating parameters. For spark-ignition engines, simulation results suggest that the twinning injector system, including two injectors with a 5mm nozzle diameter located close to the inlet port and operating at an 1-bar injection pressure, is suitable for a Honda GX200 engine fueled with syngas-biogas-hydrogen. For a dual-fuel engine converted from a Vikyno RV165 conventional diesel engine, simulation results reveal that the gaseous fuel direct-injection strategy significantly influences power derating at a fixed pilot diesel injection. Adjusting the start injection angle can reduce power derating for engines with minor variations in their loading regime. Conversely, changing the stop injection angle can reduce power derating for engines with larger variations in their loading regime. Direct injection of syngas using the twinning injector system with a 6mm nozzle diameter and injection pressure of 6 bar, combined with a suitable start/stop injector strategy, constitutes an appropriate solution for maintaining power derating in syngas-diesel dual-fuel engines converted from the Vikyno RV165 engine below an acceptable threshold of 10%.

Keywords: Renewable energy, Hybrid Renewable Energy System, Syngas, Biogas, Hydrogen, Internal Combustion Engine