Effects of compression ratio on thermodynamic and sustainability parameters of a diesel engine fueled with methanol/diesel fuel blends containing 1-pentanol as a co-solvent

Abstract

Researchers are intensively seeking to meet the ever-increasing energy demand worldwide. In this context, it is known that many studies have been carried out. The utilization of alternative energy sources is important both in meeting the energy demand and in reducing environmental pollution. In this direction, it is recommended to use clean fuels that can be employed in internal combustion engines. One of these fuels is methanol. However, it is known that phase separation occurs when methanol is blended with diesel fuel due to its poor mixing capability, but it is possible to avoid this phase separation by using different techniques in practice. One of them is to use co-solvent. Pentanol (C5H12O) stands out as a fuel additive that helps to blend diesel-methanol blends in a stable structure due to its phase stability-enhancing properties. In other words, diesel/methanol/pentanol blends can form a stable, transparent, and homogeneous fuel mixture. In the literature, there are a limited number of studies using the above fuel combination. In addition, these studies have classically evaluated engine characteristic results and emission parameters without detailed thermodynamic analysis. Investigating the use of these fuels in engines in terms of thermodynamics and sustainability at different engine operating parameters can provide important information on whether these fuels can be used as an alternative. The present study deals with the thermodynamic and sustainability analyses of a single-cylinder DI diesel engine when it was operated at several compression ratios (CRs) (16:1 and 18:1) and engine loads (25 %, 50 %, 75 %, and 100 %) to analyze the engine characteristics and pollutants. In this study, 1-pentanol as a co-solvent is infused into methanol/diesel blends with the intention of avoiding phase separation. In this context, M5P5 (90 % diesel fuel, 5 % methanol, and 5 % 1-pentanol) and M10P10 (80 % diesel fuel, 10 % methanol, and 10 % 1-pentanol) fuel combinations were prepared. The results were compared with conventional diesel fuel aiming to present the novelty of the fuel blends. To conclude, the experimental results pointed out that the CI engine consumed more alternative fuel blends because of their lower calorific value as compared to diesel fuel to provide the same output power for each tested fuel sample. It can be exhibited that the augmentation of CR and load led to increasing the energetic-exergetic efficiency values for each fuel. In this regard, the highest energetic efficiencies for D100, MP5, and MP10 were calculated to be 35.28 %, 31.79 %, and 30.56 %, respectively at the maximum load and CR; meanwhile, the highest exergetic efficiencies were found to be 33.06 %, 29.81 %, and 28.63 %, respectively. At the aforementioned operating conditions, the exergy destruction was found to be 8.33 kW for D100, 10.00 kW for MP5, and 10.65 kW for MP10. The outcomes achieved from the analyses highlighted that the CI engine powered by MP5 and MP10 fuel blends caused similar trends with diesel fuel. Owing to the higher exergetic efficiency of D100, the maximum results in the sustainability index were found to be 1.49 at the most elevated operational conditions. For that reason, methanol/diesel fuel blends including 1-pentanol as a co-solvent will be evaluated to be an alternative fuel instead of traditional diesel fuel when some of the disadvantages are shortly removed. These disadvantages come to mind first and foremost are the costs of methanol and pentanol. The increase in production quantities and the increase in academic studies on this subject will overcome this problem in a short time.