Imran Nazir Unar

Tubercles at the leading edge (LE) of airfoils are used in maintaining the lift coefficient at the higher angle of attack (AoA) and delay stall. Previous research has documented the impact of varying the wavelength and amplitude of sinusoidal tubercles on the aerodynamic efficiency of various airfoil models, with a particular focus on changes at the leading edge. This study introduces a novel approach to tubercle design by analyzing the aerodynamic efficiency of a sinusoidal leading edge airfoil featuring a single, high-amplitude tubercle, offering a more realistic estimate of its effects. The research involves the development of three wing models – first, a baseline with a smooth leading edge; second, an airfoil with a tubercle labeled A3λ11; and third, an airfoil featuring a high-amplitude tubercle (A311λ11) on a sinusoidal leading edge. All airfoil models are developed using the NACA0021 airfoil profile and simulated at the 20° angle of attack. Large eddy simulations (LES) are conducted at a chord-based Reynolds number Re_c = 1.2 × 10⁵, and the results are validated against experimental data reported in the literature. Compared with the baseline airfoil, both tubercle airfoils show a substantial increase in the lift coefficient and a reduction in the drag coefficient. For the A3λ11 and A311λ11 airfoil models the lift coefficients increase by 34.8 and 12%, respectively. Moreover, reduction in the drag coefficient of about 10.3 and 23.6% are noticed for the A3λ11 and A311λ11 airfoil models, respectively. Additionally, the results reveal that the A311λ11 airfoil model exhibits a 14.9% reduction in the drag coefficient as compared to that of the sinusoidal A3λ11 airfoil model.

Thermochemical processes utilizing biomass demonstrate promising prospects for the generation of syngas. In this work, a gasification process employing combination of an indigenous low-grade coal with two distinct biomass sources, namely rice husk (RH) and wood sawdust (WS), was explored. The gasification of the selected feedstock was performed using a double-staged multi-opposite burner (MOB) gasifier. A 3D computational fluid dynamics (CFD) model was employed to analyze the effect of kinetic and diffusion rates on the overall gasification performance of an entrained flow biomass gasifier. DPM was employed to track the particles’ trajectory, while the gas phase was treated as the continuous phase, and its behavior was predicted using a standard k-epsilon turbulent model. To calculate both the homogeneous and heterogeneous reaction rates, the finite rate/eddy dissipation model was implemented. The findings indicate that the char conversion efficiency exceeded 95% across all instances. Among the different reaction schemes, scheme E (which involved complete volatile and char combustion reactions) produced better results in comparison with published results, with less than 1% error. Hence, scheme E was validated and utilized for the rest of the simulated cases. The feeding rate has an inverse effect on the overall performance of the gasifier. An increase in feed rate decreases the CO and H₂ composition in syngas. The maximum CO value was observed to be 57.59% at a 1.0 O/C ratio with a 0.005 kg/s feed rate, and the maximum H₂ value was observed to be 16.58% in the same conditions for Lakhra coal samples. In summary, Lakhra coal exhibited better performance than other biomass samples due to its better fixed carbon and volatiles in its composition.

Plastic waste accumulation has been recognized as one of the most critical challenges of modern societies worldwide. Traditional waste management practices include open burning, landfilling, and incineration, resulting in greenhouse gas emissions and economic loss. In contrast, emerging techniques for plastic waste management include microwave-assisted conversion, plasma-assisted conversion, supercritical water conversion, and photo reforming to obtain high-value products. Problems with poorly managed plastic waste are particularly serious in developing countries. This review article examines the emerging strategies and production of various high-value-added products from plastic waste. Additionally, the uses of plastic waste in different sectors, such as construction, fuel production, wastewater treatment, electrode materials, carbonaceous nanomaterials, and other high-value-added products are reviewed. It has been observed that there is a pressing need to utilize plastic waste for a circular economy and recycling for different value-added products. More specifically, there is limited knowledge on emerging plastic waste conversion mechanisms and efficiency. Therefore, this review will help to highlight the negative environmental impacts of plastic waste accumulation and the importance of modern techniques for waste management.

The thermochemical conversion of different feedstocks is a technology capable of reducing the amount of biowaste materials produced. In addition, the gasification of feedstock using steam as a gasifying agent also produces hydrogen, which is a clean energy fuel. This article aimed to encapsulate the current status of biowaste gasification and to explain, in detail, the advantages and limitations of gasification technologies. In this review paper, different gasifying agents such as steam, air, and oxygen, as well as their effects on the quality of syngas production, are discussed. In addition, the effects of reactor configuration and different operating parameters, such as temperature, pressure, equivalence ratio, and incorporation of a catalyst, as well as their effects on the ratio of H₂/CO, LHV, syngas yield, and tar production, were critically evaluated. Although gasification is a sustainable and ecologically sound biomass utilization technology, tar formation is the main problem in the biomass gasification process. Tar can condense in the reactor, and clog and contaminate equipment. It has been shown that an optimized gasifier and a high-activity catalyst can effectively reduce tar formation. However, key biowaste treatment technologies and concepts must first be improved and demonstrated at the market level to increase stakeholder confidence. Gasification can be the driving force of this integration, effectively replacing fossil fuels with produced gas. In addition, support policies are usually needed to make the integration of biomass gasification technology into the industry profitable with fully functional gasification plants. Therefore, to address such issues, this study focused on addressing these issues and an overview of gasification concepts.

Pakistan has proven huge coal reserves but still unable to harvest the energy due to unavailability of ingenious technology. Coal gasification is robust, efficient and environmental friendly technology but it is highly sensitive to the coal characteristics. Scant literature is available on the development of the coal gasification technology which suits the characteristics of indigenous coal reserves. This papers presents the simulation of entrained flow gasifier for using indigenous coal through process modeling software namely Aspen Plus® to evaluate various system flow steps within an entrained flow gasifier. General techniques have also been discussed for creating the equilibrium-bases simulations of gasification systems. Peng-Robinson equation was used to correlate the volume of species with respect to state variables (temperature and pressure). The effects of composition of different indigenous coals like Thar, Lakhra and Sonda were investigated through simulations along with O/C (Oxygen-to-Carbon) ratio. Parametric study revealed that the O/C ratio along with other related system parameters have great influence on the performance. Sulfur could be available in different forms in coal like pyrite, sulfate or organic sulfur so appropriate form of sulfur in feedstocks should be corrected for better accuracy of model results. The highest percentages of CO i.e. 44.2, 37.8, and 46.6% were obtained from Thar coal (air dried form), Lakhra coal and Sonda coal respectively at the 0.3 O/C ratio. The decrease in LHV and HHV (Lower and Higher Heating Values) of syngas was observed on increase of O/C ratio for all coal types. The composition of as received Thar coal gave maximum LHV (1.5x104 KJ/Kg) and HHV (1.78x104 KJ/Kg) at the 0.3 O/C ratio. The future work could be extended by simulating biomass composition in the developed model of gasifier in transient simulations.

The interest in the thermochemical conversion of biomass for producer gas production since last decade has increased because of the growing attention to the application of sustainable energy resources. Application of biomass resources is a valid alternative to fossil fuels as it is a renewable energy source. The valuable gaseous product obtained through thermochemical conversion of organic material is syngas, whereas the solid product obtained is char. This review deals with the state of the art of biomass gasification technologies and the quality of syngas gathered through the application of different gasifiers along with the effect of different operating parameters on the quality of producer gas. Main steps in gasification process including drying, oxidation, pyrolysis and reduction effects on syngas production and quality are presented in this review. An overview of various types of gasifiers used in lignocellulosic biomass gasification processes, fixed bed and fluidized bed and entrained flow gasifiers are discussed. The effects of various process parameters such as particle size, steam and biomass ratio, equivalence ratio, effects of temperature, pressure and gasifying agents are discussed. Depending on the priorities of several researchers, the optimum value of different anticipated productivities in the gasification process comprising better quality syngas production improved lower heating value, higher syngas production, improved cold gas efficiency, carbon conversion efficiency, production of char and tar have been reviewed.