• Energy Research

AbstractMicrocombustors are microscale combustion devices that can be used to power microelectromechanical systems. Many combustor configurations are reported in the literature and, among them, combustion in a microscale recirculating heat exchanger is a feasible option. In this work, a simple, double‐channel, recirculating heat exchanger is considered. The novelty of the present work lies in the heat transfer analysis approach to design a microcombustor. A combustor is designed using thermal resistance networks for a premixed fuel containing a methane–air mixture in stoichiometric ratio. The length of the combustor is designed based on the position of the combustion flame. Computational fluid dynamics is utilized to validate the theoretical results. The analysis is carried out for adiabatic and nonadiabatic conditions. The combustor lengths for adiabatic and nonadiabatic (ceramic) combustors vary from 39 to 242 mm and 49 to 276 mm, respectively, for variations in the mass flow rate of the premixed gases from 6 to 10 mg/s. A minimum limiting flow rate of 6 mg/s was identified. The average error in the maximum combustion gas temperatures between the theoretical and CFD results obtained in this work is 4.2%. The theoretical approach presented can be suitably applied to more complex geometries involving multichannels and variations in geometrical properties.

Biogas is an important renewable energy resource that has been considered as carbon neutral. The advantage that it can also reduce volumes of biowaste makes it an attractive option for secondary source of energy. In this scenario, large amounts of banana wastes are observed around the world with minimum work in anaerobic digestion. Hence, the present study demonstrates the anaerobic digestion of banana pseudo stem (BP) and cow dung (CD) feedstock by co-digesting them in different proportions (5 levels of BP – 0%, 30%, 50%, 70%, and 100%) and varying digester temperatures (3 levels: 42.5 °C, 45 °C, and 47.5 °C). Batch scale 1 liter feedstocks are prepared and digested for a period of 30 days. Initial studies suggested that the optimal temperature for digesting BP is between 40 and 50 °C which falls in the transition of mesophilic and thermophilic range. At all the digester temperatures, pure BP feedstock produced an average of 74% lower biogas as compared to CD feedstock. However, co-digesting CD with about 30% BP had a negligible loss in biogas production (1.2%). Further experimental data was subjected to regression, ANOVA, and optimization analyses. The optimization study results reveal that more than 5000 ml/liter of feedstock can be obtained for BP feedstock within 30-40% proportions if the temperature is maintained between 45 to 47 °C.

Two-stroke petrol engines find wide applications in the areas like chain saws, weed cutters, and power sprayers because of their compactness and higher power to weight ratio. In the present study, the feasibility of using vegetable-based lubricant instead of ordinary mineral 2 T oil is investigated. M15 (85% petrol + 15% methanol) and E15 (85% petrol + 15% ethanol) blend with gasoline are used as the fuel. Experiments were carried out in a two-stroke air-cooled engine equipped with a rope brake dynamometer. It is observed that the vegetable-based lubricant (sunflower oil) is miscible with the tested fuels. The frictional power for the vegetable-based lubricant was found to be less than that of mineral 2 T oil. The brake thermal efficiency improved and the brake-specific fuel consumption decreased for the sunflower oil-based lubricant. The combination of E15 + sunflower oil lubricant exhibited the greatest benefits, raising the brake thermal efficiency by 3.4% and reducing the brake-specific fuel consumption by 1.4%. Hydrocarbon and carbon monoxide emissions were lower for the vegetable-based lubricant than the 2 T mineral oil.

AbstractThe United Nations Sustainable Development Goals (SDGs) are imperative from the point of view of protecting the environment by employing sustainable options. Considerable research has been carried out in the transportation sector to meet this objective. Here, the influence is assessed of epoxidised gingelly oil methyl ester biolubricant with alumina (Al2O3) nanoparticles on the performance and emissions of a single cylinder 0.66-L capacity direct injection compression ignition engine driven by gingelly B20 biodiesel. Engine tests are carried out with gingelly B20 biodiesel as a fuel, and gingelly methyl ester (B100), epoxidised gingelly methyl ester (B100E), and epoxidised gingelly methyl ester (B100E) mixed with 0.5%, 1.0%, and 1.5% w/w alumina (Al2O3) nanoparticles as the lubricant combinations. The results are compared with baseline B20 biodiesel fuel-mineral lubricant operation. The findings indicate that brake thermal efficiency increases by 8.64% for epoxidised gingelly methyl ester (B100E) with 1.0% w/w alumina (Al2O3) nanoparticle biolubricant in comparison to baseline operation. Considerable reductions in emissions are detected; specifically, reductions of 52.4%, 22.0%, 20.0%, and 34.9%, respectively, are observed for CO, NOx, and HC concentrations and smoke opacity for the abovementioned combination as compared to baseline operation. The present work suggests that further research is merited on green fuel-green lubricant combinations. The findings of this study address the United Nations Sustainable Development Goals (SDGs) 7 and 13.

The use of ethanol blending for gasoline has been found to have a significant effect in reducing emissions without any loss in the performance of a spark ignition engine. However, an increase in the emissions of oxides of nitrogen (NOx) may be seen due to the increased oxygen content in the fuel. On the contrary, emulsifying fuel with hydrogen peroxide (H2O2) has shown a substantial effect in reducing all the emissions, including NOx in a compression ignition (CI) engine. In this study, 10% ethanol is blended with gasoline (E10) and further emulsified with H2O2 up to 1.5%. When compared to neat gasoline, a 4.8% increase in brake thermal efficiency (BTE) is obtained with 10% ethanol and 1.5% H2O2. The corresponding average decrease in the emissions of carbon monoxide (CO), hydrocarbons (HC), and NOx were 80%, 43%, and 17%, respectively. The results of the experimental trials are used to model an artificial neural network (ANN) to derive a relationship between the input factors of ethanol concentration, H2O2 concentration, and engine speeds with the output responses of BTE, CO, HC, and NOx. The ANN models of each response are optimized using a multi-objective particle swarm optimization (PSO) for maximizing BTE and minimizing emissions of CO, HC, and NOx. The PSO results showed that operating the engine at 2000 rpm using ethanol blending between 4 and 6% and H2O2 emulsification of 1.5% are the best optimal conditions.

Effectively utilizing agro residues, when abundantly available, can help energy conservation efforts and increase farmers’ incomes. This article highlights the effective utilization of agro and industrial biomass residues in the form of briquettes. The various types of feedstock used and the technologies adopted in the briquetting process are discussed. Process parameters and feedstock variables influencing briquetting are described. Combustion studies undertaken using briquettes are comprehensively detailed. This literature review reveals that the combustion characteristics of briquettes not only depend on the type of the feedstock but also on the density, moisture content, binder percentage, and method used for briquetting. Higher ash content lowers the calorific value. The ash formed during combustion causes slagging and fouling which in turn lead to corrosion. It is concluded that biomass briquettes can meet the energy demands for cooking and heating needs, especially in rural areas where abundant biomass feedstock is available. It is recommended that research focuses more on investigating emissions along with the combustion of briquettes manufactured from different origins.

AbstractIt is well known that lubricating oils can reduce the coefficient of friction between two contacting surfaces. Owing to their poor biodegradability and toxicity, petroleum lubricants are typically deemed unacceptably harmful to the environment. These oils have a significant negative impact on both human and plant life and contaminate air, soil, and drinking water. Consequently, the public’s concerns about a pollution-free environment are growing along with the demand for ecologically friendly lubricants. Because of their superior lubricity, biodegradability, viscosity-temperature properties, and low volatility, plant oils hold promise as basis fluids for lubricants. In the current work, jatropha and jojoba oil were converted into bio-lubricants by chemical modification processes such as transesterification and epoxidation using H2SO4 and HCl catalysts. The kinematic viscosity of jatropha ester increases by 12.93 and 123.22%, and that of jojoba ester increases by 15.91 and 104.24% at 32 and 90 °C, respectively, when the concentration of the catalyst is increased from 0.3 to 0.9 ml for H2SO4 catalyst. Similarly, for the HCl catalyst, the kinematic viscosity values of jatropha are increased by 5.43 and 30.25%, and for jojoba, 20.84 and 50.96% at 32 and 90 °C, respectively. The epoxidized jatropha had greater experimental flash and fire point values than the epoxidized jojoba. The anti-wear and friction-reduction qualities were tested using an Anton Paar TRB3 ball on a disk. In comparing the 0.9 ml concentration of jatropha bio-lubricant samples to the 0.3 ml concentrations, the percentage reduction in wear was 31.68% for epoxidized jatropha—HCl catalyst, and 33.95% for epoxidized jatropha—H2SO4 catalyst.