Artificial intelligence (AI) can help improve many areas of waste management and biogas generation. The world has reached a state where waste generation is increasing daily, while an effective waste management system is essential for the sustainable development of a country. AI could be of great use in optimizing the waste management scheme by technical differentiation of all sorts and recycling techniques. AI can contribute to the improvement of waste segmentation, recycling, and disposal. Thus, by assessing availability and composition, AI can easily contribute to the selection of the most suitable feedstock for biogas generation. This paper will discuss the optimization of gasifier design, an important part of biogas production, to enhance gasification efficiency for more efficient syngas production. Several gains accrue from AI applications, and among them is the selection of feedstocks and gasifiers optimal for more efficient and sustainable waste management and use in the production of biogas systems. This review paper identifies the potential application areas in either waste management practices or biogas production and puts forward ways in which AI can be used in these areas.
To ensure the economic feasibility of shale oil and gas exploitation, large-scale hydraulic fracturing is essential for increasing recovery volumes by creating more efficient conductivity channels. However, China's continental shale reservoirs present complex geological conditions, making optimization through traditional hydraulic fracturing challenging. Thus, substituting CO2 for water in fracturing fluids to enhance shale reservoirs has garnered significant interest. An orthogonal experimental design was implemented to identify the optimal parameters for CO2 composite fracturing. Analysis of single-factor experiments led to the selection of four key variables: slickwater volume, slickwater displacement, pre- flush liquid CO2 volume, and proppant addition volume, resulting in 16 experimental configurations. Using numerical simulation of tight oil shale reservoirs, the effective stimulated reservoir volume for each parameter combination was calculated. Variance analysis revealed that increased slickwater volume significantly enhances fracture initiation and propagation. While variations in slickwater displacement and preflush liquid CO2 volume influence fracture network morphology and complexity, they have a lesser effect on the stimulated volume compared to slickwater volume. Proppant quantity primarily affects fracture conductivity with minimal impact on stimulated volume. This research underpins the optimization of constructional parameters for CO2 composite fracturing.
In this article, the detailed mechanism of isopentanol was simplified by direct relationship graph error propagation (DRGEP), generation rate analysis, reaction path optimization, and sensitivity analysis, and a comprehensive simplified mechanism of isopentanol/gasoline alternative fuels was obtained. Isopentanol/gasoline-characterized fuels with different blending ratios were investigated, and the results showed that blending of isopentanol promoted the autoignition of gasoline. It was found that blending isopentanol does not signifi- cantly affect the low-temperature reaction path of alkanes, but increases the reaction path fl ux from toluene to benzene. During combustion of isopentanol/gasoline alternative fuels, the isopentanol component exhibits a unique two-stage combustion phenomenon.
The aim of this research is to investigate the effect of intake closing timing (ICT) on the fl ow fi eld and combustion process in elliptical rotary engines. The model that can accurately describe the working process of the elliptical rotary engine was established, fi ve kinds of ICTs were designed, and the influence of ICT on the fl ow fi eld and combustion process was studied. The results show that the advance of the ICT can increase the intake mass fl ow- rate and reduce the back fl owrate, the volumetric efficiency is 86.1% at a 145-deg crank angle (degrees CA) before top dead center (BTDC), which is 7.6% higher than 125 degrees CA BTDC. The advance of the ICT improves the consumption speed, makes the combustion reaction more intense, and shortens the combustion time. When the ICT is 145 degrees CA BTDC, the crank angle when the burned mass fraction is 90% (CA90) is 19.4 degrees CA earlier than 125 degrees CA BTDC, the peak mass of hydroxy in a cylinder is 41.6% higher, and the peak pressure in a cylinder is 25.9% higher. With the advance of the ICT, the pressure and heat release in the cylinder are significantly increased, the peak temperature in the cylinder is increased, the rate of carbon monoxide generation is accelerated, and the mass of nitrogen oxide emission is significantly increased. However, advancing the ICT cannot improve the indicated thermal efficiency of the elliptical rotary engine. This analysis provides a comprehensive understanding of the ICT of elliptical rotary engines.
Horse manure is one of the highest potential biowastes for heat and power generation. This article investigates the experimental and mathematical modeling of thermochemical conversion for horse manure. As one type of thermochemical conversions, the pyrolysis process was carried out at eight different heating rates on horse manure using three parameters: the extent of reaction, the rate change of the extent of reaction, and differential thermal analysis (DTA), all used to determine kinetic data that will be validated with a mathematical model. Slow pyrolysis: below 15 degrees C/min showed optimistic results of obtaining exothermic reaction over a wide range of temperature which makes it self-sustainable with steady heat generation. Also, low heating rates allowed a quasi-equilibrium state through slow heating with a minimum delay in response for any transient error that could be generated from differential thermal gravimetry (DTG) device.
The identification of model parameters is complex and requires many approximations and laboratory investigations. Here, a novel approach to identifying these parameters is proposed, which uses experimental data, and a parameter estimation method to minimize a cost function made up of errors between the predicted and experimental deposit thickness. Parameters are determined for various ethanol-gasoline mixtures and lubricants. Simultaneously, the thermal and electrical properties of deposits are studied, and this information, coupled with the identified parameters, is utilized to infer potential deposit formation sources, mechanisms, and other elements that will influence the characteristics of the spark plug. It is found that the deposit formation model along with the identified parameters has the potential to reliably estimate the deposit growth with time as good correlations have been observed between measured and predicted spark plug deposit mass for all fuels and lubricants. The thermal and electrical conductivity of the spark plug deposit increases with a high ethanol fraction and high viscous oil, which results in increased chances of side sparking.
Despite the aluminized propellants offering a high specific impulse, the challenge of nozzle erosion adversely impacts the rocket's performance and its reusability potential. This study presents a numerical model aiming to predict the mechanical erosion of the propulsion chamber nozzle. The model employs an Eulerian-Lagrangian approach to simulate the complexity of the flow field within the rocket combustion chamber and the interactions between the continuous phase and particles. The model also emphasizes the importance of the aluminum particle combustion process and the secondary breakup phenomena in the erosion process. Experimental and numerical data from the literature were used to validate the numerical model. Subsequently, the model was utilized to explore the impacts of increasing propellant aluminum content and varying particles' injection velocities on the nozzle's mechanical erosion. The outcomes indicated that higher aluminum content leads to a 4-10% increase in nozzle erosion compared to the 15% content case. Furthermore, the aluminum particles tend not to fully burn within the combustion chamber and contribute to the nozzle's erosion. Lastly, particles with higher initial velocity at the inlet of the combustion chamber increase the nozzle mechanical erosion despite the observed decrease in incident mass flux.
The vertical-axis Savonius wind rotor is known for its design simplicity, better starting qualities, and direction independency despite its inferior efficiency when measured against certain other types of vertical-axis wind rotors. Despite a plethora of research work on Savonius rotors, an in-depth analysis of Reynolds number (Re) on aerodynamic and power coefficients of the Savonius rotors is scarce. This paper aims at exploring the influence of Re on the performance of a novel parabolic blade profile through unsteady two-dimensional (2D) computation. The Reynolds-averaged Navier-Stokes (RANS) equations are modeled using the ansys fluent by adopting a shear stress transport (SST) k-omega turbulence model. The computational results of the novel blade profile are then compared and analyzed with an established semicircular blade profile to draw some meaningful insights into the aerodynamic performance. In the tested range of Re = 5.3 x 10(4)-10.6 x 10(4), the novel parabolic blade profile outperformed the semicircular blade profile in terms of aerodynamic and performance coefficients.
Low-concentration coalbed methane is an efficient and clean unconventional natural gas with abundant reserves. It can greatly lessen the problem of energy scarcity when used to produce combustion power. Nevertheless, the engine finds it challenging to burn the CH4 directly due to its low and fluctuating concentration. This study suggests using a hydrogen jet to ignite low-concentration coalbed methane. The simulation method is used in this paper. To investigate the effects of various ignition injection strategies on the combustion characteristics of low concentration coalbed methane ignited by a hydrogen jet, a constant volume bomb model was developed. The results show that when the ignition and hydrogen injection interval is 2.0 ms, the cold jet of hydrogen does not burn immediately when it reaches the premixed flame, and there is a transition process from the premixed flame to the jet flame. The larger the interval between ignition and hydrogen injection, the more waste gas is produced after the premixed flame combustion, which has a certain inhibition effect on the formation of the jet flame. With the decrease in the interval between ignition and hydrogen injection, the combustion duration is obviously shortened. Therefore, the earlier hydrogen is involved in the ignition, the faster the combustion speed.
The fundamental objective of this study is to utilize a temperature dataset to achieve accurate rate estimation. This study introduces a graphical method, incorporating suitable assumptions, for predicting flowrates in single-phase vertical oil flow. The method takes into consideration the fouling factor and addresses the steady-state flow of heat in the wellbore, while also accounting for the transient heat conduction in the formation. To evaluate and validate the proposed model, two field cases are examined, and associated uncertainties are discussed. The model's predictions are compared with those obtained from Hassan and Kabir's approach, as well as actual separator flowrate data. The comparisons reveal that the model exhibits a high level of accuracy within its specified range of application. Statistical analyses indicate that most of the models perform comparably, although the suggested graphical model stands out for its higher accuracy and user-friendly nature. The performance of uncertainty is found to be more reliant on the accuracy of data measurement rather than the features of the model itself.
The transformer is the key oil-filled equipment in the power system, and its fire behavior seriously affects the safe operation of the power grid. In this article, to analyze the fire development process and combustion behavior of oil-filled equipment, a mesoscale model of transformer equipment was constructed, and fire simulation experiments of transformer equipment under the action of external ignition sources were conducted. The flame temperature, flame height, heat release rate, oil temperature, and pressure were measured. The experimental results show that the oil-filled equipment fire presents the characteristics of nonlinear development. The fire can be divided into three stages: the ignition stage, the stable growth stage, and the combustion mutation stage. The transformer oil near the wall is pyrolyzed by the external heat source, and the combustible gas and transformer oil form a gas-liquid two-phase flow, which is the main reason for the nonlinear development of oil-filled equipment fires. The experimental results are of great significance for the safe operation and fire control of power system oil-filled equipment.
Precisely forecasting the operational characteristics of oil pipelines is essential for developing rational design, production, and operation strategies, as well as reducing energy consumption and saving energy. Due to significant disparities in the computation outcomes of conventional mechanism models and the inadequate performance of machine learning models when handling limited sample data, their conclusions likewise lack tangible significance. In this study, a novel physics-guided neural network (PGNN) model, which integrates mechanisms with machine learning models, is introduced. The proposed model incorporates essential physical intermediate factors that impact the temperature and pressure of oil pipelines as artificial neurons within the loss function. Additionally, an adaptive moment estimate approach is employed to optimize the parameters of the model. Through a comparative analysis of various models' predictive capabilities on an oil pipeline, it was shown that PGNN has the highest level of accuracy in forecasting pipeline temperature and pressure. Furthermore, PGNN demonstrates the ability to generate satisfactory prediction outcomes even with a limited sample size. Simultaneously, the predictive outcomes of PGNN exhibit a stronger correlation with variables that have a direct impact on temperature and pressure.
Recently, an ejector refrigeration system (ERS) has been a promising cooling strategy with waste heat utilization and minimization of power consumption by evading the compressor. However, analyzing the intricate flow structure inside the ejector and the corresponding coefficient of performance enhancement are major challenges of an ERS. The type of working fluid, design specifications, and working conditions significantly affect the ejector behavior. The environmental issues caused by the leakage of the most popular high-GWP refrigerant R134a divulge the need for low-GWP alternatives. Moreover, the effect of critical design specifications such as area ratio (AR) and nozzle exit position (NXP) for these alternatives is not explored yet. Therefore, five low-GWP alternates for R134a, namely R1234yf, R1243zf, R152a, R513a, and R440a, are tested numerically under wide-ranging operating conditions. In addition, the ejector performance for all refrigerants is examined for seven distinct ARs and five different NXPs. The effect of the refrigerant variant and NXP on the internal flow structures of the ejector is also analyzed. Besides, the study is extended to find the optimal NXP at various operating temperatures using R1234yf refrigerant. In most cases, the higher entrainment ratio (ER) is obtained with R1234yf and R1243zf, and the increase in AR has a positive effect on the ER. The impact of the NXP is higher at condenser temperature with minimal waste heat in the generator. Irrespective of the operating conditions for R1234yf, the optimum NXP is obtained as 10 mm, which is 1.67 times the constant-area mixing chamber diameter.
The study aims to investigate the application of the organic Rankine cycle (ORC) in the bioenergy with carbon capture and storage (BECCS) using gasification of sewage sludge. The tool used in the investigation is the aspen plus software with refprop property methods for calculating fluid properties. The reason for this study is that a detailed analysis of the proposed BECCS process flow diagram indicates that a certain amount of waste heat is available in the exhaust gas from the high-to-intermediate pressure gas turbine. Some of this energy can be used by applying expansion in a low-pressure turbine, optionally by applying regenerative water heating, which is then redirected to the combustion chamber, or finally by incorporating the ORC into the main cycle. For the ORC cycle, different configurations are studied, with regeneration and using different working fluids. For the highest efficiency of the cycle, the regenerative heating of high-pressure water is applied and a suitable ORC working fluid with optimal saturation parameters and mass flow is selected. Such modified proposed BECCS power plant hybrid systems with ORC are compared to the reference case with lower pressure expansion. A study of the heat duty and temperature distribution in heat exchangers is carried out. Five ORC fluids were investigated, namely ethanol, refrigerants R236ea, R245fa, R1233zd(E), and water, which gave a net efficiency of the whole power plant of 39.71%, 40.02%, 40.26%, 40.34%, and 39.35% respectively, while the proposed BECCS reference case gave 38.89%.
Fluid starvation and congestion at the meshing area of external gear pumps (EGPs) happen inevitably as an intrinsic nature of these pumps. As a result, cavitation and excessive pressure pulsation are the two significant issues suffering the pump performance at almost any pump speed. Increasing speed or differential pressure exacerbates the situation, resulting in excessive noise, vibration, and damage to the pump or the hydraulic circuit, plus a significant reduction of pump efficiency. External gear pumps have tiny decompression grooves on the bearing blocks to alleviate these issues. However, these grooves cannot handle sufficient flow to prevent pressure drop at the intake side and pressure rise at the discharge side of the meshing area. This study presents analysis of an innovative core-feed inlets/outlets which effectively reduce cavitation and excessive pressure pulsation, even at extremely high speeds, by connecting the closed volumes of fluid at the gears meshing area to the main inlet/outlet through the center of gears. A computational fluid dynamics (CFD) analysis was performed to study the dynamic behavior of the pump. A fully functional prototype with secondary inlets and transparent components was built to validate the flow rate calculation against the experimental data and visualize the cavitation phenomena. The numerical results were in an excellent agreement with experimental data. The results show that the new pump can operate at much higher speeds with higher efficiency than a typical gear pump.
Bio-oxygenated fuels are expected to be used as a clean alternative energy source to improve the ignition behavior and pollutant emissions of RP-3 kerosene in compression ignition engines. In this study, the spray autoignition of PR-3 blended with different types of oxygenated fuels (including n-pentanol (PeOH), methyl propionate (MP), methyl ethyl ketone (MEK), 1,2-dimethoxyethane (1,2-DME), and 2-ethylhexyl nitrate (EHN)) was measured using a constant volume combustion chamber. Experiments were performed on three sets of blended fuels with different oxygen contents (2.5 wt%, 5 wt%, and 10 wt%) in the temperature range of 723-863 K and at ambient pressures of 2.2 and 4 MPa. A kinetic analysis utilized a merged RP-3 low-temperature kinetic model containing various oxygenated components. The ignition delay of blended fuels increases with the addition of PeOH, MP, and MEK, particularly PeOH, which demands more energy absorption at low temperatures due to its higher specific heat and latent heat of vaporization. As ambient pressure increased, the ignition delay period shortened for all blended fuels; however, PeOH and MEK demonstrated more significant low-temperature suppression. The combined kinetic model can reasonably predict the trend of the effect of oxygenated additives. 1,2-DME showed significantly more low-temperature reactivity versus PeOH, MP, and MEK. The variability is because the products of secondary O2 addition and isomerization of 1,2DME undergo low-temperature branched chain reactions, but other oxygenated fuels produce more inert components.
This study employs thermogravimetric analysis (TGA) to investigate the thermal degradation behavior of various components of refuse-derived fuel (RDF). The analysis is conducted individually for different RDF fractions, including cardboard, mixed papers, mixed plastics, other organics, and fines, alongside raw RDF. TGA experiments are performed in triplicate to ensure repeatability and homogeneity assessment. The results reveal distinct degradation profiles for each material, influenced by moisture content. Cardboard and mixed papers exhibit similar decomposition characteristics attributed to their cellulose content. Cardboard undergoes initial moisture-driven mass loss (5.52%), followed by cellulose and hemicellulose decomposition (58.86%) at 250-400 degrees C and lignin degradation (10.1%) at 400-500 degrees C. In contrast, mixed plastics, with an initial moisture content of 0.81%, manifest multiple decomposition steps: polyvinyl chloride (PVC) degradation (3.84%) at 200-335 degrees C, polystyrene (PS) degradation (6.63%) at 335-400 degrees C, polypropylene (PP) degradation (24.41%) at 400-450 degrees C, and high-density polyethylene (HDPE)/low-density polyethylene (LDPE) degradation (54.6%) at 400-500 degrees C. Other organics, with 1.47% initial moisture content, undergo cellulose decomposition (37.98%) at 200-381 degrees C and polyester/microfilament degradation (21.3%) at 381-450 degrees C. Fines display cellulose and hemicellulose decomposition (29.8%) at 200-383 degrees C and plastics/polyester degradation (43%) at 383-550 degrees C. LDPE in mixed plastics undergoes pure polymer decomposition at 483.6 degrees C.
Emission values have been limited and some levels must be compatible with human health and the environment. One of the most effective ways to achieve these levels is effective piston bowl geometry. The aim of designing the new combustion chamber (NCC) was to provide a multiaxial distribution of the fuel in the bowl. In the study, the new combustion chamber was compared with the standard combustion chamber (SCC). Both chambers were fi tted to the engine and the performance analysis was tested at different operation conditions. Then, 100-h tests were carried out to evaluate the effect of the piston bowl geometry on the surface of the cylinder liner by analyzing its microstructure. From the obtained results, the new combustion chamber geometry reduced HC, CO, and soot emissions while NO emissions slightly increased compared to the standard combustion chamber. It decreased brake-specific fuel consumption values by 4%, 5.53%, 7.02%, 6.4%, 5.55%, and 5.18% for 1700, 1800, 1900, 2000, 2100, and 2200 rpm, respectively. Torque values increased at all engine speeds. When the cylinder liners were evaluated as a result of long-term endurance, there were clearly fewer abrasive wear lines on the cylinder liners of NCC compared to SCC.
To improve the performance of traditional solar power generation systems, a new solar organic Rankine cycle system that can generate electricity and heat is proposed. The system incorporates the separation-flash process, regenerator, and ejector to enhance its efficiency. The optimization of the working fluid, pinch point temperature difference, evaporator outlet dryness, flash dryness, and entrainment ratio is conducted to achieve optimal performance. Aiming at maximum exergy efficiency and minimum levelized energy cost, the operating parameters are further optimized using a multi-objective optimization algorithm. R245fa is the optimal working fluid for the system, offering maximum net output power and thermal efficiency. The optimal performance can be achieved when the pinch point temperature difference is 1 K, evaporator outlet dryness is 0.6, flash dryness is 0.44, and entrainment ratio is 0.29. Moreover, the photovoltaic subsystem can further increase the net output power and thermal efficiency by 15.52% and 15.45%, achieving a maximum net output power and thermal efficiency of 33.95 kW and 10.61%, respectively. Additionally, when the solar hot water temperature is 100 degrees C, pinch point temperature difference is 1.8 K, evaporator outlet dryness is 0.6, flash dryness is 0.65, and entrainment ratio is 0.16, the system can achieve the optimal state of both performance and economy, exhibiting optimal exergy efficiency and levelized energy cost of 64.1% and 0.294 $/kWh, respectively. Finally, the payback period of the system is 3.43 years, indicating the potential for significant economic benefits.
