Journal of Energy Engineering

From the raindrops of lightning to atomized droplets used in many fields, research on electrostatic spray technology has both a natural basis and practical significance. The utilization of electrostatic spray technology has covered the biological, food, pharmaceutical, industrial, agricultural, chemical, and manufacturing industries. To provide comprehensive information about the technology, this review presents a typical electrostatic spray system in terms of its atomization mechanism, electrostatic spray modes, and several kinds of basic parameters. This review focuses on the applications of electrostatic spray technology in the fields of nanomaterial preparation, agricultural plant protection, wet flue gas desulfurization (WFGD), and fuel combustion. This paper comprehensively surveys already well-established or future potential applications of electrostatic spray technology.

This paper presents a numerical study of swirl flow effects on the combustion and emissions in single-cylinder spark ignition engine. First, a three-dimensional (3D) computational fluid dynamics (CFD) simulation was performed at two engine operating points to obtain the reference results of in-cylinder flow quantities required for the verification of a new $\mathit{K}\text{-}\mathit{k}\text{-}\epsilon$ turbulence model integrated with a cycle simulation. Then a zero-dimensional (0D) (quasi-dimensional) combustion model was used to analyze the swirl flow variations on the combustion and emissions where experimental results of 6 operating points were used to calibrate combustion and emission submodels in a cycle simulation. The coupling of the new turbulence and combustion model enabled the reconstruction of ordered in-cylinder swirl flow and the application of velocity operators on flame particles. The double swirl ratio increased the peak cylinder pressure by approximately 20%, and nitrogen oxide emissions were approximately 44% higher, while hydrocarbon (HC) emissions decreased by 44%. The twice lower swirl ratio decreased peak pressure by approximately 6%, and nitrogen oxide emissions were around 15% lower, while HC emissions were increased by 28%. If knock-limited spark advance is found for a double swirl ratio, the engine indicated that efficiency can be increased by 8.7% while HC emissions can be reduced by 20%.

Under current changing climatic conditions, there has been a growing interest in green energy to mitigate carbon emissions. As such, proper management and planning of electricity are essential to mitigating climate change. This paper presents a hybrid inexact credibility constraint programming (ICCP) model for planning and optimization in the electricity sector for Ontario, Canada. The model considers the costs and emissions of electricity generated from six sources over a planning horizon of $30\mathrm{years}$, minimizing system cost while meeting provincial emission goals. The ICCP method addresses uncertainties by transforming fuzzy variables into crisp equivalents with credibility levels, allowing decision-makers to address uncertainties in planning by tackling uncertainties as intervals through an interactive two-step algorithm. This model was applied to electricity planning in Ontario to address uncertainties due to demand predictions, technological advancements, and shifting energy consumption. The cap-and-trade program was compared to the federal carbon pricing backstop program, and the results over the planning horizon were similar. Through this model, expansion options to address future demands were also compared to minimize emissions while meeting electricity demand.

Utilizing the organic Rankine cycle (ORC) for waste heat recovery is an important energy conversion method. Some faults may occur in the ORC in actual operation, but few studies have focused on the fault detection and diagnosis of the whole ORC system. Fault detection detects whether a fault occurs in the system and fault diagnosis diagnoses where the fault is. This paper investigated a fault detection and diagnosis scheme of the ORC system for waste heat recovery based on machine learning. First, a thermodynamic ORC model was established. Three kinds of faults (expander fault, pump fault, and heat exchanger fault) and three kinds of algorithms [logistic regression, softmax regression, and support vector machines (SVMs)] were described. The data of four major important faults (fouling fault of the evaporator and of the condenser, looseness of the mechanical moving parts in the expander, and blocking of the pump) were generated from the thermodynamic ORC model and used to train the fault detection and diagnosis schemes. To evaluate the accuracy of the fault detection and diagnosis schemes, a set of experimental data was employed to test the schemes. The accuracy scores of fault detection using logistic regression and support vector machines were 77.42% and 96.77%, respectively. The accuracy scores of fault diagnosis using softmax regression and SVM were 91.78% and 94.52%, respectively. The test times of fault diagnosis using softmax regression and SVM were 0.0099 and 0.0085 s, respectively. The results demonstrated that machine learning–based fault detection and diagnosis schemes for the ORC have high accuracy and immediacy. Therefore, the proposed schemes are promising tools for fault detection and diagnosis of the ORC system for waste heat recovery.

Thermal management is of great significance to ensure that a battery pack works at a reasonable temperature and avoids thermal runaway. In this study, three different designs of liquid cooling-based lithium-ion battery modules with wavy tubes are proposed. A three-dimensional transient simulation of the designed structure is carried out. The effects of the coolant mass flow rate, separated dual tube structure, connection mode of adjacent tube lines (series mode and parallel mode), and coolant flow direction are discussed. The results show that increasing the mass flow rate of coolant in the range of ${0–0.01\mathrm{kg}·\mathrm{s}}^{-1}$ can significantly reduce the maximum temperature of the battery module. On the contrary, the temperature difference increases markedly with the rise of the mass flow rate. Until the mass flow rate is greater than $0.006\mathrm{kg}·{\mathrm{s}}^{-1}$, the temperature difference of the battery module changes less and stabilizes at 4.2°C–4.4°C. In addition, compared with the series mode, the parallel mode can improve the thermal performance of the battery module, especially in reducing the maximum temperature. The reverse flow of coolant on both sides of the battery with a separated dual tube structure can obtain the optimal cooling effect. This study provides a new way to optimize the cooling capacity of the thermal management system for a cylindrical lithium-ion battery module.

Low-temperature combustion (LTC) is a new combustion mode, and low cetane number fuels may be more appropriate for the LTC. Fuel properties play important roles both in the physical process of fuel-air mixing and the chemical process of combustion in the cylinder of diesel engines. Alcohol additives in diesel will definitely change its fuel properties. In this paper, an experiment was conducted to investigate the combined impact of alcohol fuel properties on the performance and emissions characteristics of a diesel engine operated at the LTC mode. A total of 20% ethanol, 20% propanol, and 20% n-butanol by volume were added in the diesel (represented as E20, Pr20, and Bu20), respectively, at different exhaust gas recirculation (EGR) rates. The results show that when the EGR rate reaches up to 35%, the CA50 phase obviously retards for E20, while the corresponding EGR rates are 40% for Pr20 and 45% for Bu20. The effects of fuel properties on cycle-to-cycle variations may be random or stochastic. Medium EGR rates may be the best choice for the LTC. Fuel properties have little effect on CO, THC, and ${\mathrm{NO}}_x$ emissions. But E20 can reduce soot emissions greatly within medium EGR regions. That is, E20 may be more proper as diesel LTC fuel.

Fully premixed burners are widely used in the field of gas boilers, and the excess air rate is a crucial parameter to control. In this paper, a low-cost solution for monitoring the excess air rate based on the flame ionization current is applied to premixed burners. The ion signal measurement system is independently developed by the authors’ research group to convert a weak ion signal into a measurable detection voltage. The detection voltage of the metal fiber (MF) and stainless steel (SS) are compared. When the excess air rate is in the range of 1.1–1.5, the detection voltage of the MF and SS burner decreases from 1.914 to $1.217\mathrm{V}$ and $1.342\mathrm{V}$ to $0.693\mathrm{V}$. Moreover, the function is established because both of them have a strong linear relationship. Based on Class 5 of ${\mathrm{NO}}_x$ emissions (with a minimum value of 40 ppm) with respect to the European norm (EN 677), the detection voltage of the MF and SS burner is lower than 1.810 and $1.216\mathrm{V}$, as the heat load is $24\mathrm{kW}$, respectively.

This paper assesses the thermal performance of reinforced Typha-fibers unfired clay bricks. Various Typha additive proportions (0%, 1%, 3%, 7%, 15%, and 20%), by weight in a fibrous form, have been prepared for experimental testing. X-ray diffraction and fluorescence analysis showed that exploited clay is suitable for construction purposes with a predominant quartz (${\mathrm{SiO}}_2$) content. Collected findings showed that higher Typha-fiber proportions produced brick samples with higher porosity levels. The highest recorded porosity, 14.95%, was obtained with the incorporation of a 20% additive, compared to a 1.14% porosity percentage for reference samples. This resulted in the production of more porous bricks with improved thermal properties. In fact, at a 20% Typha-fibers additive content, $0.29\mathrm{W}/\mathrm{m}·\mathrm{K}$ and $0.76\mathrm{kJ}/\mathrm{k}\mathrm{g}·\mathrm{K}$ respective thermal conductivity and specific heat capacity values were recorded, compared to $0.51\mathrm{W}/\mathrm{m}·\mathrm{K}$ and $0.59\mathrm{kJ}/\mathrm{k}\mathrm{g}·\mathrm{K}$ at the reference samples. This represents 43% and 23% gains in thermal conductivity and specific heat capacity, respectively. A dynamic thermal inertia simulation was also carried out in the TRNSYS Type 56 software to evaluate the time lag and decrement factor parameters of prepared specimens as walling structures of a reference house. A total of 38% and 45% gains in the time lag and decrement factor were obtained with the incorporation of the highest additive proportion, 20%, compared to reference samples. Finally, four mathematical models are used to evaluate the thermal performance, in terms of thermal conductivity and specific heat capacity, of the studied specimens as a function of the measured porosity. The comparison drawn between the models’ theoretically predicted thermal properties and experimentally measured ones reflected a positive association between the two as the obtained correlation coefficient $R$ was found to be very close to 1.

Centralized generation-expansion planning is one of the well-known problems in the literature, and usually a static power transmission network is considered for this problem. As power systems are moving toward renewable sources of energy, static transmission networks no longer provide efficient transmission solutions. Dynamic-line rating and transmission switching are two alternatives to static transmission network, especially in power systems integrated with renewable energy sources. These alternatives have not been explored for generation-expansion planning. This paper integrated dynamic-line rating and transmission switching into the generation-expansion planning problem. Transmission planning was incorporated into the generation-expansion model to obtain more-competitive solutions. This addition resulted in a mixed-integer nonlinear problem. The nonlinear problem was linearized into a mixed-integer linear problem which was solved by a commercial solver. The proposed model was demonstrated with two test power systems, and the efficiency of dynamic-line rating and transmission switching in renewable sources planning was evaluated through numerical experiments.

Because of the many nanoscale pores in shale gas reservoirs (SGRs), the fluid transport mechanisms in shale are complex. Also, previous research has shown that there exists water in the shale plays. Hence, two-phase gas-water transport model construction becomes very important so as to increase accuracy in numerical simulation work. However, most of the current study is still focused on single-phase gas transport. In this paper, based on the second slip model coupled with the fluid single-pipe flow equation, the Knudsen and surface diffusions, and combined with the fractal theory, the relative permeability model for gas-water in shale was constructed. The model reliability was proven by using the available two-phase gas-water relative permeability data. A sensitivity analysis has been carried out based on the proposed model. The results show that with the pressure decreasing, the relative permeability of gas increases. The increase of the pore size distribution fractal dimensions ($D_f$) and fractal dimension ($D_T$) caused the gas relative permeability ($K_{rg}$) to increase. The $K_{rg}$ increases with the increase of $D_f$ and $D_T$. The influence of the viscous slip flow, Knudsen diffusion, and surface diffusion are trade-offs, which are mainly controlled by water saturation ($S_W$) and pressure ($P$). The $K_{rg}$ is extremely sensitive when $P<1\mathrm{MPa}$. Under low pressure and low water saturation, the effect of viscous slip flow is secondary. And its contribution increases gradually and becomes the main role with the increase of water saturation or pressure. The effect of the Knudsen diffusion is negligible when $P>1\mathrm{MPa}$ and the water saturation $S_W>40\%$. However, it cannot be ignored under other conditions. The influence of surface diffusion reached 21.64%–72.78% when $P<1\mathrm{MPa}$ and $S_W<10\%$. A surface diffusion contribution of less than 4.25% was obtained when $P>1\mathrm{MPa}$ and $S_W>70\%$.

The US Midwest successfully generates wind power at a hub height of $80–90\mathrm{m}$ and the use of tall towers can reduce the wind energy cost. However, the lack of reliable wind data and production estimates at elevated heights hamper this effort. In this paper, wind resources and annual energy production (AEP) are studied using wind data up to $200\mathrm{m}$ above ground to estimate and validate AEP as a function of hub height at multiple sites. The AEP results show that energy production can increase by about 10% when the hub height is increased to $100\mathrm{m}$. It also suggests that the optimal elevated hub height for a given region is not constant. A suitable site-specific height is desirable to minimize the levelized cost of energy (LCOE). Wind information from the National Renewable Energy Laboratory Wind Integration National Dataset (WIND) Toolkit is used as an alternative for estimating AEPs at elevated hub heights. This approach produced somewhat conservative results, confirming its use for wind farm planning purposes when measured wind data are not available.

In this paper, a parabolic trough collector (PTC) is studied, and its thermal performance is compared to that of an integrated collector storage solar water heater (ICSSWH). The effect of the concentration technology is so investigated using computational fluid dynamics (CFD) simulations. Results show that the PTC presents higher useful heat and, consequently, higher water temperature relative to the ICSSWH. It is also shown that its main disadvantage is its fast temperature drop and, thus, its high night losses. This drawback can be limited by covering the storage tank with a particular material layer. Phase change materials (PCM) are so introduced, and a PTC in which the storage tank is covered with a PCM layer is studied. Three different materials, respectively, durene, methyl bromobenzoate, and octatricontane, and three PCM radiuses, respectively, 0.03, 0.04, and 0.04 m, are considered. Simulation results show that the latent heat storage unit presents better thermal performance than the sensible one. Concerning the phase change, it is noted that for methyl bromobenzoate, the melting temperature that is relatively the highest in comparison with other PCM is not reached, and the phase change does not occur. The thermal behavior is similar to that in the sensible unit in which the water temperature increases, reaches its maximum value, and decreases next. However, for the other PCM, the melting temperature is reached, and the solid/liquid transition occurs. We notice that in an isothermal behavior during all this period and even after its end, the water temperature decreases very slightly during the rest of the night. Durene can be so selected as the most appropriate PCM for this PTC’s design relative to octatricontane as it allows higher useful heat and lower night losses. The effect of the PCM’s radius shows that the best performance corresponds to the lowest value, which is 0.03 m.

As a result of anthropocentric climate change, there is an urgent need to decarbonize the supply of energy. Organic biomass, referred to as feedstock, can be converted into biofuels that have the potential to decarbonize transport. However, biofuels are typically not carbon neutral because the preparation of feedstocks and the production of biofuels require energy currently supplied by fossil fuels, which involve carbon emissions. This work aimed to bring biofuel research up to date with current UK policy of net zero carbon emissions by examining the volume of carbon-neutral advanced biofuels that could be produced from sustainable feedstocks generated in the UK. By analyzing relevant data, it is estimated that between 667 and 1,791 million litres (Mltr) of carbon-neutral biodiesel equivalent could be produced with the energy content of 22.7–60.9 PJ, corresponding to 8.1%–21.7% of current diesel consumption by heavy goods vehicles in the UK.

The presence of blockages in the flow field (FF) of proton exchange membrane fuel cells (PEMFCs) increases the mass transport of reactants toward the catalyst layer regions and improves cell performance. In this paper, the effects of channel blockage in a conventional interdigitated FF of PEMFCs are investigated both numerically and experimentally. The tested cell contains a $25\text{-}{\mathrm{cm}}^2$ active area tested at four air flow rates—0.4, 0.7, 1.0, and 1.5 standard liters per minute (slpm). For numerical modeling, a three-dimensional simulation of a repeating unit of a whole cell was used. Blocks were placed in a staggered arrangement along the neighboring flow channels in order to push reacting species into the gas diffusion layer uniformly. The numerical and experimental data showed good agreement. In this paper, the influence of flow channel blockages is analyzed on velocity contours, the distribution of reactants and local current density over catalyst layer, and polarization and power density curves. Blockages increase the pressure drop along the flow channels and also balance of plant pumping power that drives the working fluid within the FF. Hence, the effect of indentation on pressure drop and pumping power is also measured. The results show that channels blocking at 1.5 slpm improve the limiting current density by 9% and enhance the maximum net power (generated power from which the pumping power is subtracted) by 22%.

Oxycombustion allied with flue gas recirculation is a promising combustion technology owing to its potential to enhance combustion while reducing pollutant emissions. This numerical work investigated the effects of ${\mathrm{CO}}_2$ dilution under oxygen enrichment conditions on the flame structure and soot precursor formation in an $n$-heptane coflow diffusion flame. The numerical approach considered kinetic chemistry, thermal and transport properties, and a radiative heat transfer model. The oxygen content in the oxidizer stream was varied from 30% to 60% ${\mathrm{O}}_2$ (molar basis) with ${\mathrm{N}}_2$ or ${\mathrm{CO}}_2$ as diluent. The chemical effect of ${\mathrm{CO}}_2$ diluent was isolated numerically from its total thermal effect using an inert counterpart fictitious ${\mathrm{CO}}_2$. Results demonstrated that increasing ${\mathrm{O}}_2$ concentration significantly increased the flame temperature and soot precursor species, whereas a notable reduction of flame height occurred with increasing ${\mathrm{O}}_2$. Soot precursors were suppressed by replacing ${\mathrm{N}}_2$ with ${\mathrm{CO}}_2$ in the coflow oxidizer through not only thermal effects but also through chemical effects. The primary pathway for the chemical effect of ${\mathrm{CO}}_2$ is the reaction ${\mathrm{CO}}_2+\mathrm{H}=\mathrm{CO}+\mathrm{OH}$, which decreases H radicals. The results also showed that ${\mathrm{CO}}_2$ the effect of ${\mathrm{CO}}_2$ was more profound at lower oxygen conditions, indicating that the inhibition effect of ${\mathrm{CO}}_2$ could be restricted in higher oxygen conditions.

A hollow-structured bilayer coating system was developed to reduce heat loss through windowpanes. It was formed by two separate polymer films with stable air gaps in between. The outer surface was enhanced by a low-emissivity layer. Following ASTM C1199, ASTM C518, NFRC-100, and NFRC-102, the heat transfer measurement indicated that a 3-mm-thick bilayer coating could significantly reduce the $U$-factor from 5.8 to $2.9\mathrm{W}/({\mathrm{m}}^2·\mathrm{K})$. The $U$-factor could be further lowered if the coating thickness was increased. The overall visual transmittance, haze, and structural integrity were satisfactory.