Performance and emissions analysis of a diesel engine fuelled with biodiesel and waste recycling fuelUntitled Item
Creators: name: Billah, A G M Mustayen
Publisher: name: University of Tasmania
Year: 2024

description: Owing to its reliability and fuel efficiency, diesel engine has been extensively utilised in hybrid systems along with renewable energy (RE) sources (e.g. solar and wind) to generate power for remote areas and island communities in recent years. Nowadays, hybrid systems are attempting to reduce diesel engine dependency by integrating maximum renewable penetration because of the rapid increase in fuel cost and environmental issues. However, diesel engines are still a key component in hybrid systems given their unpredictability and the intermittent nature of RE sources. In this regard, low load (below 30% of maximum rated power) and variable speed diesel operation achieve the highest possible RE source penetration. Furthermore, alternative sources, such as biodiesel and waste recycling fuels, could substitute diesel in the power generation sectors because of depleting fossil fuel sources and emissions. The first objective of this thesis is to distinguish the key parameters responsible for improving engine performance and reducing emissions. The second objective is to validate a developed single-zone thermodynamic model using commercial diesel fuel and jojoba biodiesel blends with diesel at variable speeds and loading conditions. The third focus is to evaluate the potential of using plastic-made diesel (PMD) produced by pyrolysis via a distillation process from mixed waste plastic to replace diesel as an alternative fuel. The fourth objective is to validate a two-zone thermodynamic model that uses PMD blends at variable speeds under low load conditions.<br>This study first outlined an extensive review of the aspects of diesel power generation in hybrid (renewable diesel) systems for remote areas and islands. The performance and emission characteristics of diesel engines fuelled with standard diesel fuels, edible–nonedible biodiesels and landfill waste oils were reported. Various techniques (e.g. injection timing and rate, exhaust gas recirculation (EGR) systems and turbocharging and supercharging) used for improving engine performance, such as brake thermal efficiency (BTE), power and torque under various speeds and loading conditions, were discussed along with their disadvantages and benefits. The use of biodiesels made from edible, non[1]edible, landfill waste and their blends with diesel resulted in substantial reductions in CO and HC emissions but increased NOx emissions. In addition, biodiesel blends showed no significant changes in terms of engine performance at any operating conditions (e.g. speeds and loads). This review highlighted the current research status and future research directions for diesel engines, which were studied in the next few chapters.<br>Subsequently, a single-zone thermodynamic model was developed to predict engine combustion (e.g. in-cylinder pressure and temperature and heat release rate) and performance, such as BP, torque, BTE, BSFC and ID times under variable speeds and loading conditions, especially under low loads. Low heat release rate, BP, BT and higher BSFC were observed at low load operations (15% and 25%) compared with higher ranges. The ID correlations were evaluated to identify the suitable ID model for low load ranges and to analyse the impact on engine performance characteristics.<br>A fully automated, four-cylinder, four-stroke, liquid-cooled direct injection 3.7-L diesel engine was used in the experimental study fuelled with standard diesel and three different blends (e.g. JB5, JB10 and JB20) of Jojoba biodiesel with diesel at different speeds (i.e. 1200 to 2400 rpm) and loads (e.g. 25%–100%) to validate the single-zone model. A fine-quality jojoba biodiesel extracted from crude esterified jojoba oil utilised without additional chemical treatments was used. Under all operating conditions, remarkable agreements were observed between the measured and predicted values of engine performance characteristics, such as BP, torque, BTE and BSFC. A minimum error of 3.7% for BP was observed at 2000 rpm and 100% load for D100. However, the maximum error of 19.2% for BP was observed at 1200 rpm and 25% loading condition for JB10. A noticeable reduction of 7.55% and 6.65% for CO was observed for JB20 at 1200 rpm and 25% load compared with standard diesel, respectively. However, NOx increased to 10.25% under any given operating conditions.<br>With the success of using biodiesel, the research further focused on the recycling of waste plastic products. The utilisation of waste recycling energy in diesel generation sectors become attractive because of its pyroelectric properties. This study evaluated the potential of converting waste plastic to produce diesel engine fuel. Pyrolysis experiments were conducted to obtain mixed waste plastic crude oil (MWPCO) from mixed waste plastics, considering high-density polyethylene, polypropylene and polystyrene, which were described in this research. PMD was produced from MWPCO via a vacuum distillation technique. The pyrochemical properties of PMD were tested and tabulated after distillation. Diesel engine tests were conducted using three different ratios (5%, 10% and 20%) of PMD with ultra[1]low sulphur diesel (ULSD) to investigate its performance and emission characteristics at variable speeds (e.g. 1200, 1500, 1800 and 2100 rpm) and loads (e.g. 25%, 50%, 70% and 100%). The BP, torque and BTE of the engine with PMD20 were 2.9%–3.84%, 3.01%–3.21% and 3.9%–4.74% higher than those with ULSD at all tested conditions. The BSFC for PMD20 indicated a 3.77% less fuel usage at various load circumstances than the ULSD. The CO emissions for PMD20 were 14.51% lower than ULSD. In addition, CO emissions were 7.8% and 4.22% lower than those of PMD5 and PMD10 at all loading operations. The HC emissions of PMD20 were recorded at all loading operations, which were approximately 15.1%–18.7% lower than ULSD. A significant outcome was observed with NOx emissions, which decreased by 2.06%, 3.01% and 3.95% for PMD5, PMD10 and PMD20 compared with ULSD at different speeds and loading operations. This finding demonstrated that the PMD can be used to replace conventional diesel with better thermal and emission performance.<br>To provide useful information for future research in this field, a two-zone thermodynamic model was developed and validated using engine performance and emission characteristics with experimental results using plastic derived diesel (PDD) blends under low loads (e.g. 5%, 10%, 15%, 20%, 25% and 30%) at different speeds (1200, 1500, 1800 and 2100 rpm). The results showed good agreement between the simulation and experimental data. Compared with ULSD fuel, PDD blends showed a significant improvement in BP, torque, BTE and BSFC. The maximum BP variation of 9.85% is observed for PDD20 at 1200 rpm under 5% load. Moreover, the minimum BSFC variation of 4.15% is observed for ULSD at 1500 rpm, and a 25% load was reported. Compared with the commercial ULSD fuel, PDD20 exhibited maximum reductions of 4.75%, 5.95%, 4.45% and 4.35% in NOx, CO2, CO and HC emissions under any tested conditions, respectively. Considering that up to 20% of the PDD blends were tested in this study, further investigation should be conducted to try more than 20% of PDD blends to draw a conclusion. This study provides a new way of recycling waste plastic into beneficial diesel, thereby reducing reliance on fossil fuels and its negative impact on the environment.<br>