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This study investigates the experimental and theoretical impact of biodiesel obtained from hydrodynamic cavitation based waste cooking oil on the performance parameters while testing compression ignition engines. Due to the alarming energy security concerns and inadequacy of fossil fuels, biodiesel is seeking importance globally. Many countries have put forth different subsidies, incentives, and mechanisms, urging the usage of biodiesel. In the current research, nanotechnology is effectively used for enhancement of the blend properties of biodiesel, making them more suitable for compression ignition diesel engines. This investigation includes a comparative analysis of diesel to biodiesel blends with and without the addition of nanoparticles CuO and ZnO. To understand the performance characteristics of a four-stroke diesel engine, a single zone thermodynamic model is developed in it. Comparative readings are taken for the test blends with varying compression ratios of 16, 17, and 18. For each ratio, a variation in the cylinder volume is noted with reference to the rotation in the crank angle. The investigated parameters include net heat release, the rate of pressure rise, brake thermal efficiency, and the heat transfer coefficient. This study concluded that the theoretical results are in close consonance with the experimental results of the comparative analysis of diesel and biodiesel blends. Results obtained from this research paper can contribute to predict combustion process analysis and recommend the effectiveness of nano-additives in biodiesel enhancement.

The increment in the usage of automobiles is resulting in increased greenhouse gases (GHG) emissions continuously and there is a substantial need to reduce them effectively. The present research work investigates the emission behavior of waste cooking oil biodiesel doped with CuO nanoparticles during testing in Compression Ignition (CI) engines. This investigation is based on the effective emission reduction analysis emitted by diesel fuel during experimentation on CI engines. It suggests a cost effective modification of biodiesel as a fuel prepared from waste cooking oil (WCO) by a novel hydrodynamic cavitation technique which includes the hydrodynamic cavitation reaction mixture composed of 1.28 L of methanol and 10 g KOH and 5 L of preheated WCO at 45 °C in the cavitation reactor for 40 min. These reactants are synthesized utilizing the principle of cavitation and the final manufactured esterified oil is authenticated with ASTM Standard property measurement for suitability check. In the research work, two different investigations are carried out. In the first one, WCO biodiesel-diesel blends of 0, 30, and 100% (B0, B30, B100) ratio are prepared and the emission characteristics have investigated at 1500 rpm constant speed with varying load and indicated mean effective pressure (IMEP). In the second investigation, the emission suitable blend B30 is doped with CuO nanoparticles, keeping other parameters as per the previous setup, the emission characteristics investigated for the second one. For precise results, more experimental trials are needed to achieve this decrease in the emission of harmful gases. Using an amalgamation of L9 Taguchi and response surface methodology (RSM) the maximum emission control with a minimum number of experimental trials is achieved. The first investigation includes the predefined predictors as A (blend), B (load), and C (IMEP), where blends (0 ≤ A ≤ 100%), load (0 ≤ B ≤ 12 kg), IMEP (3.5 ≤ C ≤ 7.5 bar) are controllable features. Optimization process resulted into a minimum emission of CO, CO2, and NOx by appertaining the condemnatory merger of inputs such as blend B0 (Diesel), load 12 kg, and IMEP 3.48 bar in the first investigation, which has resulted into 0.08 ppm CO, 0.6 ppm CO2 and 30 ppm NOx emission. Taguchi analysis-based second experimental investigation includes the predefined predictors as A (CuO), B (load), and C (IMEP), including nanoparticles CuO in blend B30, and the prognosticated results of optimization are 0.03 ppm CO, 0.3 ppm CO2 and 21 ppm NOx emission. In current investigation, the percentage reduction is found to be 92.3%, 94.82%, and 96% compared to the emission of diesel in CO, CO2 and NOx gases, respectively. The coefficient of determination is almost equal to 1, which reveals the chosen optimization technique is very accurate in prediction. The investigation has provided suitable minimum emission characteristics in a cost-effective way.