Review Article

J. Energy Resour. Technol. 2018;140(12):120801-120801-30. doi:10.1115/1.4040584.

Biodiesel has emerged as a suitable alternative to mineral diesel in compression ignition (CI) engines in order to ensure global energy security and to reduce engine out emissions in near future. Biodiesel derived from various feedstocks available worldwide fits well in the current fuel supply arrangement for transport sector. However, biodiesel as an alternative transportation fuel has been extensively investigated because of differences in its important fuel properties compared with baseline mineral diesel. Since fuel properties greatly influence spray development, combustion, and emission formation in internal combustion (IC) engines, a number of experimental and computational studies on biodiesel usage in CI engines have been performed to determine its brake thermal efficiency (BTE), gaseous emissions, durability, etc., by various researchers using variety of engines and feedstocks. In the present paper, a critical review of the effect of biodiesel's fuel properties on engine performance, emissions, and combustion characteristics in existing diesel engines vis-a-vis conventional diesel has been undertaken. In addition, the progress and advances of numerical modeling involving biodiesel are also reviewed to determine the effect of fuel properties on spray evolution and development of reaction mechanisms for biodiesel combustion simulations. Fuel properties are discussed in two categories: physical and chemical properties, which are key parameters affecting spray and combustion processes. Subsequent sections review spray, combustion, emissions, and performance characteristics of biodiesels under various engine operation conditions. In the last section of this review paper, numerical modeling of biodiesel covering recent numerical models and schemes to understand the behavior of biodiesel combustion and pollutants formation is included. This review paper comprehensively summarizes biodiesel fuel's (BDFs) spray, combustion, and emission characteristics using experimental and numerical approaches. Limitations and scope for future studies are discussed in each section.

Commentary by Dr. Valentin Fuster

Research Papers: Alternative Energy Sources

J. Energy Resour. Technol. 2018;140(12):121201-121201-7. doi:10.1115/1.4040506.

Darrieus type vertical axis wind turbines (VAWT) are being used commercially nowadays; however, they still need to improve in terms of performance as they work in an urban environment where the wind speeds are low and the gusts are frequent. The aerodynamic performance of Darrieus turbine is highly affected by the wingtip vortices. This paper attempts at analyzing and comparing the performance of Darrieus with the use of various wingtip devices. Attempts have also been made to find out optimal working parameters by studying the flow through turbines with different tip speed ratios and different inlet wind speeds. A comparative computational fluid dynamics (CFD) simulation was performed on a small-scale, straight-bladed Darrieus rotor vertical axis wind turbine, with a large stationary domain and a small rotating subdomain using sliding mesh technique. Comparison of the performance of end tip device that can be used against a baseline rotor configuration is done, with the aim of identifying the best tip architecture. The main focus lies on building an experimental setup to validate the results obtained with the CFD simulation and to compare the performance with and without wingtip device. VAWTs with wingtip device show very promising results compared to the baseline model.

Commentary by Dr. Valentin Fuster

Research Papers: Energy Systems Analysis

J. Energy Resour. Technol. 2018;140(12):122001-122001-10. doi:10.1115/1.4040530.

Water vapor adsorption and desorption isotherms and kinetics studies on three Sichuan Basin shale samples were performed at 298 K by an accurate gravimetric method. The adsorption equilibrium data were fitted using both Dent model and Modified Dent model to estimate the adsorption characteristic of water on the primary and secondary sites. The primary site adsorption is restricted to a monolayer while the secondary site adsorption is associated with multilayer sorption. A positive correlation was found between clay mineral content and monolayer sorption content. The isosteric heats of sorption of water were determined from the equilibrium data and they decreased with the increase of adsorption amount. The adsorption/desorption hysteresis were studied with the pore structure. The kinetics of water vapor adsorption was studied with the unipore model and linear driving force mass transfer (LDF) model. The effective diffusivity and kinetic rate constant varied with the increase of relative pressure, which suggested diffusion of water vapor on shale corresponding to a combination of adsorption on primary sites, adsorption on secondary sites, formation of water clusters, and capillary condensation.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2018;140(12):122002-122002-7. doi:10.1115/1.4040404.

Previous works have demonstrated that the distributed reaction regime improved the reformate product distribution, prevented soot formation, and favored higher hydrogen yields. The experimental data from these works and additional literature focusing on individual reactions provided an insight into how the distributed reaction regime influenced the reformate product composition. The distributed reaction regime was achieved through the controlled entrainment of hot reactive products (containing heat, carbon dioxide, steam and reactive radicals and species) into the premixed fuel air mixture, elongating the chemical time and length scales. High velocity jets enhanced mixing, while shortening the time and length scales associated with transport. As some steam and carbon dioxide will form in the reforming process, it was theorized that the mixing of the entrained flow (containing heat, carbon dioxide, and steam) into the premixed fuel air mixture promoted dry and steam reforming reactions, improving conversion. The available information on chemical kinetics of reformation is rather limited. In this work, the activity and timescales of these reactions were determined from the available experimental data. This was then used to assess which reactions were active under Distributed Reforming conditions. These data help in the design and development of advanced reformers using distributed reforming conditions.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2018;140(12):122003-122003-8. doi:10.1115/1.4040102.

This paper presents the results of a thermo-economic (TE), primary-energy-factor and CO2-equivalent (CO2 (eq)), emissions-sensitivity analysis for the preparation of sanitary hot water (SHW) in fourth-generation district-heating systems. The annual required additional heat for the SHW provided by a local heating unit, based on an air-to-water heat pump (AWHP), a natural-gas boiler (NG boiler), and an electrical resistance heater (ERH), was determined using a trnsys simulation. Additionally, the seasonal performance factor (SPF) of the HP under consideration was determined. The study considered three possible supply temperatures, i.e., 35, 40, and 45 °C. The results show that a local heating unit based on an AWHP is most efficient in terms of the used primary energy (PE) and CO2 (eq) emissions. This unit is also the second best in terms of TE performance. The unit based on a NG boiler is much more appropriate than an ERH unit in terms of both the primary energy factor (PEF) and the CO2 (eq) emission factors for an electricity generation mix (EGM) that has values higher than the average for the EU-28. The heat generated by this NG unit is also cheaper than the heat produced by an ERH based on the average price for electricity in the EU-28.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2018;140(12):122004-122004-5. doi:10.1115/1.4041090.

The effect of microalgae growth medium on power ultrasound treatment of microalgal biomass was investigated. Chlorella vulgaris was grown in Bold's basal medium (BBM), Bristol's medium, sueoka medium, and MiracleGro All Purpose Water Soluble Plant Food. These media showed statistically indistinguishable intrinsic growth rates, averaging 0.052/day. Power ultrasound treatment was applied at 9.5 W for 5 min. MiracleGro showed chemical oxygen demand (COD) solvation post-sonication of 66%, twice that of other growth media per cell ruptured; which was unexpected based on observed consistent biomass quality. Media differences do not appear to have an effect on ultrasound power transfer; thus, C. vulgaris grown in MiracleGro medium has a decreased strength in terms of resistance to rupture by ultrasound. These results suggest that while biomass productivity and composition are important for the efficiency of extraction, media effects on the susceptibility of cells to pretreatment should not be ignored in overall process design.

Topics: Ultrasound , Biomass
Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2018;140(12):122005-122005-13. doi:10.1115/1.4041093.

A thermodynamic and economic comparative analysis are presented for waste heat recovery (WHR) from the heavy oil production with steam-assisted gravity drainage (SAGD) process employing organic Rankine cycle (ORC) and Kalina cycle (KC). The liquefied natural gas (LNG) cold energy is employed as the cold source. Thus, a combined cooling heating and power system is proposed. The effect of key parameters on thermodynamic performance is investigated. The results showed that increasing the turbine inlet temperature (TIT), ORC is more appropriate for WHR in SAGD process than KC, but KC provides better energy use and exergy efficiency, while the reverse situation occurs when the evaporation pressure is increased. The compression ratio has little effect on the cold exergy recovery efficiency of the refrigeration cycles. In addition, the total exergy destruction and the total WHR efficiency in the combined SAGD/KC are slightly higher than these in the combined SAGD/ORC. Moreover, for the TIT below 180 °C and the evaporation pressure above 6 MPa, the SAGD/KC can obtain more energy return on investment (EROI) than SAGD/ORC. The results obtained through economic analysis show that the use of the SAGD/ORC is more economical. Through the thermos-economic comparison of the two combined systems, it helps to choose different combined cycles according to the different actual operation, which can facilitate the future engineering applications.

Commentary by Dr. Valentin Fuster

Research Papers: Fuel Combustion

J. Energy Resour. Technol. 2018;140(12):122201-122201-7. doi:10.1115/1.4040379.

Integration of a supply chain involves the design, planning, execution, control, and monitoring of delivery chain activities for creating net value. This includes building appropriate infrastructure, leveraging logistics, synchronizing supply with demand, and continually measuring/monitoring performance. The combination of advanced mining and beneficiation technologies and power plant improvement processes when integrated within a “whole-of-supply chain” promises great potential for creating step changes in the way that coal is delivered to its end user. When the supply chain involves a direct mine-to-power plant, the benefits may initially seem limited, but the adoption of a value-in-use model to determine costs incurred along the chain can show how changes in mining, beneficiation, and supply impact on power plant performance and, ultimately, total-supply chain costs. Uniper Technologies' proprietary Fuel Evaluation Tool as described in the paper is an expert value-in-use model, which combined with coal beneficiation modeling and expertise from Somerset International can show the potential improvements achievable by adopting a “whole-of-supply-chain” approach.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2018;140(12):122202-122202-15. doi:10.1115/1.4041543.

New induction manifold designs have been developed in this work to enhance the turbulence intensity and improve the mixing quality inside diesel engine cylinders. These new designs employ a spiral-helical shape with three different helical diameters (1D, 2D, 3D; where D is the inner diameter of the manifold) and three port outlet angles: 0 deg, 30 deg, and 60 deg. The new manifolds have been manufactured using three-dimensional printing technique. Computational fluid dynamics simulations have been conducted to estimate the turbulent kinetic energy (TKE) and the induction swirl generated by these new designs. The combustion characteristics that include the maximum pressure raise rate (dP/dθ) and the peak pressure inside the cylinder have been measured for a direct injection (DI) diesel engine utilizing these new manifold designs. In addition, engine performance and emissions have also been evaluated and compared with those of the normal manifold of the engine. It was found that the new manifolds with 1D helical diameter produce a high TKE and a reasonably strong induction swirl, while the ones with 2D and 3D generate lower TKEs and higher induction swirls than those of 1D. Therefore, dP/dθ and peak pressure were the highest with manifolds 1D, in particular manifold m (D, 30). Moreover, this manifold has provided the lowest fuel consumption with the engine load by about 28% reduction in comparison with the normal manifold. For engine emissions, m (D, 30) manifold has generated the lowest CO, SO2, and smoke emissions compared with the normal and other new manifolds as well, while the NO emission was the highest with this manifold.

Commentary by Dr. Valentin Fuster

Research Papers: Petroleum Engineering

J. Energy Resour. Technol. 2018;140(12):122901-122901-13. doi:10.1115/1.4040237.

Downhole casing leaks in oil and gas wells will highly impact the shallow water horizons and this will affect the environment and fresh water resources. Proactive measures and forecasting of this leak will help eliminate the consequences of downhole casing leaks and, in turn, will protect the environment. Additionally, downhole casing leaks may also cause seepage of toxic gases to the fresh water zones and to the surface through the casing annuli. In this paper, we introduced a risk-based methodology to predict the downhole casing leaks in oil and gas wells using advanced casing corrosion logs such as electromagnetic logs. Downhole casing corrosion was observed to assess the remaining well life. Electromagnetic (EM) corrosion logs are the current practice for monitoring the casing corrosion. The corrosion assessment from EM logs is insufficient because these logs cannot read in multiple casings in the well. EM tool gives average reading for the corrosion in the casing at a specific depth and it does not indicate the orientation of the corrosion. EM log does not assess the 360 deg corrosion profile in the casing and it only provides average value and this may lead to wrong decision. All of this makes EM logs uncertain tools to assess the corrosion in the downhole casing. A unified criterion to assess the corrosion in the casing and to decide workover operations or not has been identified to minimize the field challenges related to this issue. A new approach was introduced in this paper to enhance the EM logs to detect the downhole casing corrosion. Corrosion data were collected from different fields (around 500 data points) to build a probabilistic approach to assess the casing failure based on the average metal loss from the EM corrosion log. The failure model was used to set the ranges for the casing failure and the probability of casing failure for different casings. The prediction of probability of failure (PF) will act as proactive maintenance which will help prevent further or future casing leaks.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2018;140(12):122902-122902-13. doi:10.1115/1.4040531.

As a novel jet technology, liquid nitrogen jet (LNJ) is expected to effectively break rocks and further provide a high-efficiency method for drilling, especially geothermal drilling. Using this technology, rocks can be broken down by the coupled effects of cryogenic cooling and jet impingement. In this study, transient downhole jet flow field and heat transfer during drilling with LNJ were simulated. Then, the distributions of temperature (including LNJ and ambient rock), velocity, and pressure at different times were analyzed. Finally, the effects of the parameters on jet impingement and rock cooling performance were discussed. Results indicated that cryogenic LNJ could be efficiently generated in the downhole region. The temperature of the rock surface remarkably decreased as the LNJ reached the bottomhole. The high-speed LNJ caused axial impingement and radial shear effects on the bottomhole rock. The rock cooling performance caused by the LNJ was influenced by the initial rock temperature. With the increase of the initial rock temperature, the drop amplitude of the rock temperature also increased. The impingement capability of the LNJ was improved by increasing the nozzle diameter and the nozzle pressure drop. With the increase of standoff distance, the wall pressure and the radial velocity of the bottomhole decreased while increasing the impingement scope. The confining pressure hardly influenced the rock cooling performance and jet impingement capability, thereby indicating that LNJ could work even at high confining pressure conditions.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2018;140(12):122903-122903-10. doi:10.1115/1.4041089.

Artificial intelligence (AI) tools are used to explore the influence of shale barriers on steam-assisted gravity drainage (SAGD) production. The data are derived from synthetic SAGD reservoir simulations based on petrophysical properties and operational constraints gathered from the Suncor's Firebag project, which is representative of Athabasca oil sands reservoirs. The underlying reservoir simulation model is homogeneous and two-dimensional. Reservoir heterogeneities are modeled by superimposing sets of idealized shale barrier configurations on this homogeneous reservoir model. The individual shale barriers are categorized by their location relative to the SAGD well pair and by their geometry. SAGD production for a training set of shale barrier configurations was simulated. A network model based on AI tools was constructed to match the output of the reservoir simulation for this training set of shale barrier configurations, with a focus on the production rate and the steam-oil ratio (SOR). Then the trained AI proxy model was used to predict SAGD production profiles for arbitrary configurations of shale barriers. The predicted results were consistent with the results of the SAGD simulation model with the same shale barrier configurations. The results of this work demonstrate the capability and flexibility of the AI-based network model, and of the parametrization technique for representing the characteristics of the shale barriers, in capturing the effects of complex heterogeneities on SAGD production. It offers the significant potential of providing an indirect method for inferring the presence and distribution of heterogeneous reservoir features from SAGD field production data.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2018;140(12):122904-122904-8. doi:10.1115/1.4041091.

Recently, engineers and researchers reconsider honeycomb sandwich structures due to their vast application in industries and aviation arenas. In this study, a new honeycomb sandwich material was developed and tested. The purpose of the present work is to investigate numerically and experimentally with a comparative study on the effects of heat transfer on design parameters and geometry for different types of exotic honeycomb structures taking in account radiation within the cell and conduction in the cell walls. The numerical solution for temperature profiles for different types of exotic honeycomb structures and solid disk are performed in order to inspect the variation of heat transfer. The modeling results show a good agreement with the experimental results. The present work demonstrates that the temperature profile for reentrant is the highest one compared to splined and stiffened which reaches around 10% at temperature of the front surface Tin = 100 °C. It was found that the rib length enhances significantly heat transfer. Results showed also that stiffened honeycomb has a good insulation and metallic honeycomb core structure has a good thermal insulation characteristic for the highest instantaneous temperature, whereas reentrant honeycomb has a good heat transmission.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2018;140(12):122905-122905-9. doi:10.1115/1.4041542.

Underground injection of slurry in cycles with shut-in periods allows fracture closure and pressure dissipation which in turn prevents pressure accumulation and injection pressure increase from batch to batch. However, in many cases, the accumulation of solids on the fracture faces slows down the leak off which can delay the fracture closure up to several days. The objective in this study is to develop a new predictive method to monitor the stress increment evolution when well shut-in time between injection batches is not sufficient to allow fracture closure. The new technique predicts the fracture closure pressure from the instantaneous shut-in pressure (ISIP) and the injection formation petrophysical/mechanical properties including porosity, permeability, overburden stress, formation pore pressure, Young's modulus, and Poisson's ratio. Actual injection pressure data from a biosolids injector have been used to validate the new predictive technique. During the early well life, the match between the predicted fracture closure pressure values and those obtained from the G-function analysis was excellent, with an absolute error of less than 1%. In later injection batches, the predicted stress increment profile shows a clear trend consistent with the mechanisms of slurry injection and stress shadow analysis. Furthermore, the work shows that the injection operational parameters such as injection flow rate, injected volume per batch, and the volumetric solids concentration have strong impact on the predicted maximum disposal capacity which is reached when the injection zone in situ stress equalizes the upper barrier stress.

Commentary by Dr. Valentin Fuster

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