Research and development of combustion engines with sustainable and zero-carbon fuels

Abstract

As governments worldwide address the increasing levels of CO2 emissions, the automotive industry faces a significant challenge in mitigating climate change. To this end, the industry is exploring various solutions, including electrification and battery electric vehicles, as well as the adoption of low-carbon and zero-carbon fuels in Internal Combustion (IC) engines. While the electrification of vehicles has grown in popularity, it has challenges, such as the high cost of batteries, limited driving range, and the need for charging infrastructure. In light of this, there is also growing interest in using low-carbon and zero-carbon fuels, such as biofuels, hydrogen, and synthetic fuels, in IC engines. These fuels represent a promising approach to achieving net zero-carbon transportation and reducing the industry’s carbon footprint. Biofuels, for example, can be produced from renewable sources and significantly reduce greenhouse gas emissions compared to conventional fossil fuels. Hydrogen, meanwhile, can power internal combustion engines with zero emissions when produced using renewable energy sources. Synthetic fuels, produced with renewable energy, provide a more sustainable alternative to traditional fossil fuels. Adopting low-carbon and zero-carbon fuels in IC engines offers an effective and accessible pathway towards a more sustainable future. While electrification gains momentum, using sustainable fuels in IC engines provides a promising approach to achieving net zero-carbon transportation and reducing the industry’s carbon footprint. The present study confidently investigates two key solutions for accomplishing net-zero targets. Firstly, it explores the feasibility of second-generation biofuels with varying ethanol and Research Octan numbers as immediate drop-in replacements for fossil fuels. The study meticulously examines injection strategies for mitigating particulate matter emissions associated with these fuels. The study revealed that biogasoline fuel from 2nd generation feedstock could be used seamlessly in existing spark ignition engines without hardware modifications. This research emphasizes the significance of biofuels in attaining a zero-carbon future. Nevertheless, it is crucial to ensure sustainable biofuel production to offer low-carbon alternatives to conventional fossil fuels while considering land use, water consumption, and biodiversity conservation. The research findings provide strong evidence that biogasoline, due to its heavier components, is more likely to generate higher levels of PM emissions. However, it has been proven that deploying the right split injection methods can significantly minimise PM emissions. Secondly, the study focuses on hydrogen as the primary power source for ICE platforms. Through a comprehensive analysis of various injection methods and proportions, the study showcases the full potential of hydrogen as a substitute for gasoline. Additionally, the study confidently addresses performance and emission concerns by investigating NOx and CO2/Hc emissions associated with lubricants, using a novel method to identify the potential of considering H2ICE as a zero-carbon solution. The findings of this study are expected to confidently contribute to achieving net-zero targets. Hydrogen fuel has many advantages, such as running engines efficiently in lean conditions and maintaining stable combustion while achieving up to lambda 3.8. This translates to higher thermal efficiency, lower cyclic variability, and zero NOx emissions. Additionally, hydrogen combustion is an eco-friendly source of fuel, emitting no HC, CO, and CO2. Even under low load, exhaust hydrogen slip remains below 1000 ppm, which drops below 500 ppm with increased load. These remarkable results suggest that hydrogen would be an ideal fuel to replace gasoline and natural gas in a spark ignition engine with superior efficiency, zero emissions and greater engine performance. The study found that centrally-mounted (CDI) and side-mounted direct injection (SDI) direct injection systems had zero CO2, CO, and HC emissions during the steady state operations. The CDI and SDI setups demonstrated stable engine operations over a broad range of air-to-fuel ratios, with CDI having a more extensive range of lean-burn operations. CDI also had notably higher thermal efficiencies than SDI. The study identified the optimal operational settings for each system. It showed that CDI and SDI had similar emissions characteristics at low and mid-load, with SDI producing higher NOx and hydrogen emissions than CDI. After analysing NOx and lubricant emissions, it has been determined that NOx emissions are nearly non-existent within the lambda range of 2.75 to 3.7. Furthermore, it has been discovered that hydrogen emits 13.8% less NOx emissions than gasoline during stoichiometric operation. Lastly, the comprehensive NOx time analysis indicates that hydrogen exhibits greater consistency in NOx emissions than gasoline. The CO2/HC averaged emissions are nearly zero, while the peak spikes are less than 18 ppm.