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Research Papers: Alternative Energy Sources

J. Energy Resour. Technol. 2017;139(4):041201-041201-12. doi:10.1115/1.4035904.

This study analyzes the feasibility of placing modified exercise equipment in public places to enable human energy harnessing. By assessing the impacts as a system-level synthesis of economic, environmental, productivity, and health benefits, it is shown that introducing human-powered equipment (HPE) in public places would be feasible and beneficial both to society in general and to the specific stakeholders investing in this technology. This study develops a framework to evaluate applications of this technology using benefits to costs analyses. The benefits and challenges for successful implementation of HPE technology are also presented and evaluated in various case studies involving public places at airports and schools.

Commentary by Dr. Valentin Fuster

Research Papers: Energy Systems Analysis

J. Energy Resour. Technol. 2017;139(4):042001-042001-5. doi:10.1115/1.4035908.

In this work, the effect of temperature on the pressure loss for Newtonian fluid in fully eccentric annulus with pipe rotation is investigated. Extensive experiments with water are conducted at Izmir Katip Celebi University (IKCU), Civil Engineering Department for various flow velocities ranging between 0.7 m/s and 2.9 m/s, pipe rotation range between 0 rpm and 120 rpm. The effect of temperature on frictional pressure losses is also examined, and the temperature is varied from 20 °C to 65 °C. It was observed that, an increase in the fluid temperature in fully eccentric annulus results in a decrease in the pressure gradient. On the other hand, the influence of temperature on pressure gradient becomes more significant, as the Reynolds number is raised. Variation of Taylor number causes negligible changes on frictional pressure losses for all temperature conditions considered. By using regression analysis of the dataset obtained from the experimental work, a simple empirical frictional pressure losses correlation taking into account of temperature effect is proposed. Results showed that a good agreement between the measured and predicted values is achieved with almost 94% coefficient of determination.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2017;139(4):042002-042002-10. doi:10.1115/1.4035909.

In acidizing operations, the acid flows selectively through large pores to create wormholes. Wormhole propagation has been studied by many experts at macroscopic scale. In this paper, the lattice Boltzmann model (LBM), which is a mesoscopic scale method, is adopted to simulate the flow, acid–rock reaction, and rock dissolution in porous media at mesoscopic scale. In this model, a new method based on nonequilibrium extrapolation is proposed to deal with the reactive boundary. On the basis of the model, extensive simulations are conducted on the propagation behavior of wormholes, and the factors influencing wormhole propagation are investigated systematically. The results show that the LBM is a reliable numerical technique to study chemical dissolution in porous media at mesoscopic scale, and that the new method of dealing with the reaction boundary performs well. The breakthrough time decreases with the increase of acid concentration, but acid concentration does not affect the ultimate dissolution pattern. As the reaction rate constant increases, shorter wormholes are created. A higher hydrogen ion diffusion coefficient will result in shorter but wider wormholes. These findings agree well with the previous experimental and theoretical analyses. This study demonstrates the mechanism of wormholing that the unstable growth of pores by the acid rock reaction makes the acid selectively flow through a few large pores which finally form wormholes.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2017;139(4):042003-042003-12. doi:10.1115/1.4036045.

Thermocells convert heat energy directly into electrical energy through charge-transfer reactions at the electrode–electrolyte interface. To perform an analytical study on the behavior of thermocells, the Onsager flux relationship was applied to thermocells, which used aqueous copper II sulfate and aqueous potassium ferri/ferrocyanide as the electrolyte. The transport coefficient matrices were calculated for each electrolyte and applied to several simulations, which were subsequently validated through experimental testing and comparison to previous literature results. The simulation is shown to correctly predict the short circuit current, maximum power output, and power conversion efficiency. Validation demonstrates that the simulation model developed, using the Onsager flux equations, works for thermocells with different electrode materials (platinum, copper, charcoal, acetylene black, and carbon nanotube), electrode spacing, and temperature differentials. The power dependence of the thermocell on concentration and electrode spacing, with respect to the Seebeck coefficient, maximum power output, and relative efficiency, is also shown.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2017;139(4):042004-042004-7. doi:10.1115/1.4035829.

Turbine blades are cooled by a jet flow from expanded exit holes (EEH) forming a low-temperature film over the blade surface. Subsequent to our report on the suction-side (low-pressure, high-speed region), computational analyses are performed to examine the cooling effectiveness of the flow from EEH located at the leading edge as well as at the pressure-side (high-pressure, low-speed region). Unlike the case of the suction-side, the flow through EEH on the pressure-side is either subsonic or transonic with a weak shock front. The cooling effectiveness, η (defined as the temperature difference between the hot gas and the blade surface as a fraction of that between the hot gas and the cooling jet), is higher than the suction-side along the surface near the exit of EEH. However, its magnitude declines sharply with an increase in the distance from EEH. Significant effects on the magnitude of η are observed and discussed in detail of (1) the coolant mass flow rate (0.001, 0.002, and 0.004 (kg/s)), (2) EEH configurations at the leading edge (vertical EEH at the stagnation point, 50 deg into the leading-edge suction-side, and 50 deg into the leading-edge pressure-side), (3) EEH configurations in the midregion of the pressure-side (90 deg (perpendicular to the mainstream flow), 30 deg EEH tilt toward upstream, and 30 deg tilt toward downstream), and (4) the inclination angle of EEH.

Commentary by Dr. Valentin Fuster

Research Papers: Fuel Combustion

J. Energy Resour. Technol. 2017;139(4):042201-042201-10. doi:10.1115/1.4035886.

The present study explores the impact of ethanol on the performance and emission characteristics of a single cylinder indirect injection (IDI) Diesel engine fueled with Diesel–kerosene blends. Five percent ethanol is added to Diesel–kerosene blends in volumetric proportion. Ethanol addition to Diesel–kerosene blends significantly improved the brake thermal efficiency (BTE), brake specific energy consumption (BSEC), oxides of nitrogen (NOx), total hydrocarbon (THC), and carbon monoxide (CO) emission of the engine. Based on engine experimental data, an artificial neural network (ANN) model is formulated to accurately map the input (load, kerosene volume percentage, ethanol volume percentage) and output (BTE, BSEC, NOx, THC, CO) relationships. A (3-6-5) topology with Levenberg–Marquardt feed-forward back propagation (trainlm) is found to be optimal network than other training algorithms for predicting input and output relationship with acceptable error. The mean square error (MSE) of 0.000225, mean absolute percentage error (MAPE) of 2.88%, and regression coefficient (R) of 0.99893 are obtained from the developed model. The study also attempts to make clear the application of fuzzy-based analysis to optimize the network topology of ANN model.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2017;139(4):042202-042202-8. doi:10.1115/1.4036046.

Surfactants have the potential to reduce the interfacial tension between oil and water and mobilize the residual oil. An important process which makes the surfactant injection to be less effective is loss of surfactant to porous medium during surfactant flooding. This study highlights the results of a laboratory study on dynamic adsorption and desorption of Trigoonella foenum-graceum (TFG) as a new nonionic surfactant. The experiments were carried out at confining pressure of 3000 psi and temperature of 50 °C. Surfactant solutions were continuously injected into the core plug at an injection rate of 0.5 mL/min until the effluent concentration was the same as initial surfactant concentration. The surfactant injection was followed by distilled water injection until the effluent surfactant concentration was reduced to zero. The effluent concentrations of surfactant were measured by conductivity technique. Results showed that the adsorption of surfactant is characterized by a short period of rapid adsorption, followed by a long period of slower adsorption, and also, desorption process is characterized by a short, rapid desorption period followed by a longer, slow desorption period. The experimental adsorption and desorption data were modeled by four well-known models (pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Elovich models). The correlation coefficient of models revealed that the pseudo-second-order model predicted the experimental data with an acceptable accuracy.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2017;139(4):042203-042203-7. doi:10.1115/1.4036049.

The structural parameters of combustion chamber have great impacts on the process of air–fuel mixing, combustion, and emissions of diesel engine. The dynamic characteristics and emission performances could be improved by means of optimizing the parameters of the combustion chamber. In this paper, the key structure of a diesel engine combustion chamber is parameterized, and the influence of individual structural parameter on dynamic characteristics and emissions of the engine is simulated and analyzed by computational fluid dynamics (CFD) software avl-fire. The results show that under constant compression ratio, the in-cylinder peak pressure decreases with increasing inclination angle of the combustion chamber (α), while the height (Tm) and bowl radius (R) have little influence on the in-cylinder peak pressure. With increasing α, NO emissions decrease, and soot emissions first increase and then decrease. With increasing R, both NO and soot emissions decrease first and then increase. Therefore, the combustion chamber parameters could be optimized by comprehensive consideration of cylinder pressure, NO and soot emissions.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2017;139(4):042204-042204-7. doi:10.1115/1.4035752.

This manuscript presents experimental results on the reduction of sulfur oxide emissions from combustion of a high-sulfur content pulverized bituminous coal (Illinois #6 Macoupin) using a dry sorbent injection method. The coal particles were in the size range of 90–125 μm and were blended with calcium-, sodium-, potassium-, and magnesium-containing powdered sorbents at different proportions. The alkali/sulfur molar ratios were chosen to correspond to stoichiometric proportions (Ca/S = 1, Mg/S = 1, Na2/S = 1, and K2/S = 1) and the effectiveness of each alkali or alkali earth based sorbent was evaluated separately. Combustion of coal took place in a drop-tube furnace, electrically heated to 1400 K under fuel-lean conditions. The evolution of combustion effluent gases, such as NOx, SO2, and CO2 was monitored and compared among the different sorbent cases. The use of these sorbents helps to resolve the potential of different alkali metals for effective in-furnace sulfur oxide capture and possible NOx reduction. It also assesses the effectiveness of various chemical compounds of the alkalis, such as oxides, carbonates, peroxides, and acetates. Reductions in SO2 emissions were in the range of 5–72%, with sodium being the most effective metal followed by potassium, calcium, and then magnesium. Acetates were effective as dual SO2 and NOx reduction agents.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2017;139(4):042205-042205-8. doi:10.1115/1.4036044.

This paper explores the feasibility of using Syngas with low methane number as fuel for commercial turbocharged internal combustion engines. The effect of methane number (MN), compression ratio (CR), and intake pressure on auto-ignition tendency in spark ignition internal combustion engines was determined. A nondimensional model of the engine was performed by using kinetics mechanisms of 98 chemical species in order to simulate the combustion of the gaseous fuels produced from different thermochemical processes. An error function, which combines the Livengood–Wu with ignition delay time correlation, to estimate the knock occurrence crank angle (KOCA) was proposed. The results showed that the KOCA decreases significantly as the MN increases. Results also showed that Syngas obtained from coal gasification is not a suitable fuel for engines because auto-ignition takes place near the beginning of the combustion phase, but it could be used in internal combustion engines with reactivity controlled compression ignition (RCCI) technology. For the case of high compression ratio and a high inlet pressure at the engine's manifold, fuels with high MN are suitable for the operating conditions proposed.

Commentary by Dr. Valentin Fuster

Research Papers: Petroleum Engineering

J. Energy Resour. Technol. 2017;139(4):042901-042901-8. doi:10.1115/1.4036043.

At the end of 2015 the U.S. held 5.6% or approximately 369 Tcf of worldwide conventional natural gas proved reserves (British Petroleum Company, 2016, “BP Statistical Review of World Energy June 2016,” British Petroleum Co., London). If unconventional gas sources are considered, natural gas reserves rise steeply to 2276 Tcf. Shale gas alone accounts for approximately 750 Tcf of the technically recoverable gas reserves in the U.S. (U.S. Energy Information Administration, 2011, “Review of Emerging Resources: U.S. Shale Gas and Shale Oil plays,” U.S. Department of Energy, Washington, DC). However, this represents only a very small fraction of the gas associated with shale formations and is indicative of current technological limits. This manuscript addresses the question of recovery efficiency/recovery factor (RF) in fractured gas shales. Predictions of gas RF in fractured shale gas reservoirs are presented as a function of operating conditions, non-Darcy flow, gas slippage, proppant crushing, and proppant diagenesis. Recovery factors are simulated using a fully implicit, three-dimensional, two-phase, dual-porosity finite difference model that was developed specifically for this purpose. The results presented in this article provide clear insight into the range of recovery factors one can expect from a fractured shale gas formation, the impact that operation procedures and other phenomena have on these recovery factors, and the efficiency or inefficiency of contemporary shale gas production technology.

Commentary by Dr. Valentin Fuster

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