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Research Papers: Fuel Combustion

J. Energy Resour. Technol. 2012;135(2):021001-021001-9. doi:10.1115/1.4007911.

This study presents fundamentals of spray and partially premixed combustion characteristics of directly injected methane in a constant volume combustion chamber (CVCC). The constant volume vessel is a cylinder with inside diameter of 135 mm and inside height of 135 mm. Two end of the vessel are equipped with optical windows. A high speed complementary metal oxide semiconductor (CMOS) camera capable of capturing pictures up to 40,000 frames per second is used to observe flow conditions inside the chamber. The injected fuel jet generates turbulence in the vessel and forms a turbulent heterogeneous fuel–air mixture in the vessel, similar to that in a compressed natural gas (CNG) direct-injection (DI) engine. The fuel–air mixture is ignited by centrally located electrodes at a given spark delay timing of 1, 40, 75, and 110 ms. In addition to the four delay times, a 5 min waiting period was used in order to make sure of having laminar homogeneous combustion. Spray development and characterization including spray tip penetration (STP), spray cone angle (SCA), and overall equivalence ratio were investigated under 30–90 bar fuel pressures and 1–5 bar chamber pressure. Flame propagation images and combustion characteristics were determined via pressure-derived parameters and analyzed at a fuel pressure of 90 bar and a chamber pressure of 1 bar at different stratification ratios (S.R.) (from 0% to 100%) at overall equivalence ratios of 0.6, 0.8, and 1.0. Shorter combustion duration and higher combustion pressure were observed in direct injection-type combustion at all fuel air equivalence ratios compared to those of homogeneous combustion.

Commentary by Dr. Valentin Fuster

Research Papers: Alternative Energy Sources

J. Energy Resour. Technol. 2013;135(2):021201-021201-11. doi:10.1115/1.4023173.

In the future energy pathway, characterized by flexibility of technologies and fuels, biogas could represent an alternative to conventional natural gas in feeding multiple types of technologies, both traditional thermal machines (chemical reactions), and innovative electrochemical generators such as fuel cells (electrochemical reactions). To compare the two pathways of energy production, two criteria are considered: (a) environmental analysis (emissions) and (b) exergy analysis. The results of the environmental and exergy comparison are presented and discussed in case of two selected transformation processes: partially premixed flames (PPFs, for chemical processes) and solid oxide fuel cells (SOFCs, for electrochemical processes), for a range of operating conditions. From an environmental point of view, the PPF exhaust stream has significant traces of NOx and C2H2, which are precursors of atmosphere pollution, while the SOFC exhaust stream does not contain such chemical species due to the absence of combustion. From a exergy point of view, the utilisation of the biogas in form of electrochemical oxidation in a SOFC indicates significantly higher exergetic efficiency compared to the chemical oxidation in partially premixed flames.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2014;135(2):021202-021202-1. doi:10.1115/1.4023170.

The above referenced paper is being retracted from the Journal of Energy Resources Technology because of unrebutted allegations that it contains confidential and proprietary information used without permission.

Commentary by Dr. Valentin Fuster

Research Papers: Energy Systems Analysis

J. Energy Resour. Technol. 2013;135(2):022001-022001-9. doi:10.1115/1.4023097.

With the rising cost of fuel and increasing demand for clean energy, solid-state thermoelectric (TE) devices are an attractive option for reducing fuel consumption and CO2 emissions. Although they are reliable energy converters, there are several barriers that have limited their implementation into wide market acceptance for automotive applications. These barriers include: the unsuitability of conventional thermoelectric materials for the automotive waste heat recovery temperature range; the rarity and toxicity of some otherwise suitable materials; and the limited ability to mass-manufacture thermoelectric devices from certain materials. One class of material that has demonstrated significant promise in the waste heat recovery temperature range is skutterudites. These materials have little toxicity, are relatively abundant, and have been investigated by NASA-JPL for the past twenty years as possible thermoelectric materials for space applications. In a recent collaboration between Michigan State University (MSU) and NASA-JPL, the first skutterudite-based 100 W thermoelectric generator (TEG) was constructed. In this paper, we will describe the efforts that have been directed towards: (a) enhancing the technology-readiness level of skutterudites to facilitate mass manufacturing similar to that of Bi2Te3, (b) optimizing skutterudites to improve thermal-to-electric conversion efficiencies for class 8 truck applications, and (c) describing how temperature cycling, oxidation, sublimation, and other barriers to wide market acceptance must be managed. To obtain the maximum performance from these devices, effective heat transfer systems need to be developed for integration of thermoelectric modules into practical generators.

Commentary by Dr. Valentin Fuster

Research Papers: Environmental Aspect of Energy Sources

J. Energy Resour. Technol. 2013;135(2):022101-022101-11. doi:10.1115/1.4023176.

Medical and health researchers have shown that fatalities during heat waves are most commonly due to respiratory and cardiovascular diseases, primarily from heat's negative effect on the cardiovascular system. In an attempt to control one's internal temperature, the body’s natural instinct is to circulate large quantities of blood to the skin. However, to perform this protective measure against overheating actually harms the body by inducing extra strain on the heart. This excess strain has the potential to trigger a cardiac event in those with chronic health problems, such as the elderly, Cui et al. Frumkin showed that the relationship of mortality and temperature creates a J-shaped function, showing a steeper slope at higher temperatures. Records show that more casualties have resulted from heat waves than hurricanes, floods, and tornadoes together. This statistic’s significance is that extreme heat events (EHEs) are becoming more frequent, as shown by Stone et al. Their analysis shows a growth trend of EHEs by 0.20 days/year in U.S. cities between 1956 and 2005, with a 95% confidence interval and uncertainty of ±0.6. This means that there were 10 more days of extreme heat conditions in 2005 than in 1956. Studies held from 1989 to 2000 in 50 U.S. cities recorded a rise of 5.7% in mortality during heat waves. The research of Schifano et al. revealed that Rome’s elderly population endures a higher mortality rate during heat waves, at 8% excess for the 65–74 age group and 15% for above 74. Even more staggering is findings of Dousset et al. on French cities during the 2003 heat wave. Small towns saw an average excess mortality rate of 40%, while Paris witnessed an increase of 141%. During this period, a 0.5 °C increase above the average minimum nighttime temperature doubled the risk of death in the elderly. Heat-related illnesses and mortality rates have slightly decreased since 1980, regardless of the increase in temperatures. Statistics from the U.S. Census state that the U.S. population without air conditioning saw a drop of 32% from 1978 to 2005, resting at 15%. Despite the increase in air conditioning use, a study done by Kalkstein through 2007 proved that the shielding effects of air conditioning reached their terminal effect in the mid-1990s. Kan et al. hypothesize in their study of Shanghai that the significant difference in fatalities from the 1998 and 2003 heat waves was due to the increase in use of air conditioning. Protective factors have mitigated the danger of heat on those vulnerable to it, however projecting forward the heat increment related to sprawl may exceed physiologic adaptation thresholds. It has been studied and reported that urban heat islands (UHI) exist in the following world cities and their countries and/or states: Tel-Aviv, Israel, Newark, NJ, Madrid, Spain, London, UK, Athens, Greece, Taipei, Taiwan, San Juan, Puerto Rico, Osaka, Japan, Hong Kong, China, Beijing, China, Pyongyang, North Korea, Bangkok, Thailand, Manila, Philippines, Ho Chi Minh City, Vietnam, Seoul, South Korea, Muscat, Oman, Singapore, Houston, USA, Shanghai, China, Wroclaw, Poland, Mexico City, Mexico, Arkansas, Atlanta, USA, Buenos Aires, Argentina, Kenya, Brisbane, Australia, Moscow, Russia, Los Angeles, USA, Washington, DC, USA, San Diego, USA, New York, USA, Chicago, USA, Budapest, Hungary, Miami, USA, Istanbul, Turkey, Mumbai, India, Shenzen, China, Thessaloniki, Greece, Rotterdam, Netherlands, Akure, Nigeria, Bucharest, Romania, Birmingham, UK, Bangladesh, and Delhi, India. The strongest being Shanghai, Bangkok, Beijing, Tel-Aviv, and Tokyo with UHI intensities (UHII) of 3.5–7.0, 3.0–8.0, 5.5–10, 10, and 12 °C, respectively. Of the above world cities, Hong Kong, Bangkok, Delhi, Bangladesh, London, Kyoto, Osaka, and Berlin have been linked to increased mortality rates due to the heightened temperatures of nonheat wave periods. Chan et al. studied excess mortalities in cities such as Hong Kong, Bangkok, and Delhi, which currently observe mortality increases ranging from 4.1% to 5.8% per 1 °C over a temperature threshold of approximately 29 °C. Goggins et al. found similar data for the urban area of Bangladesh, which showed an increase of 7.5% in mortality for every 1 °C the mean temperature was above a similar threshold. In the same study, while observing microregions of Montreal portraying heat island characteristics, mortality was found to be 28% higher in heat island zones on days with a mean temperature of 26 °C opposed to 20 °C compared to a 13% increase in colder areas.

Topics: Heat , Temperature , Cities
Commentary by Dr. Valentin Fuster

Research Papers: Petroleum Engineering

J. Energy Resour. Technol. 2012;135(2):022901-022901-4. doi:10.1115/1.4023005.

Carbonate rocks have well-developed macropore and micropore systems, it is necessary to study the dual pore characteristics in carbonate rocks. In this paper, based on the original macropore network and micropore network, a stochastic upscaling method is used to build the dual pore network with the integration of macropores and micropores properties in carbonates together and upscale the dual pore network to a larger scale. This method is verified by geometry-topology and flow parameters comparison, which provides an important tool to microscopic flow research in carbonate media.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2013;135(2):022902-022902-12. doi:10.1115/1.4023169.

The Oriskany sandstone formation has been a prolific producer of natural gas in the Appalachian basin since 1930s. Lot of production wells have been converted to gas storage wells for the ease of operation. Natural gas storage industry is a vital part of North American energy driven economy because of the fluctuation in seasonal demand and in maintaining the reliability of supply needed to meet the demands of the consumer. However, the storage wells suffer from an annual deliverability loss of 5% owing to the various damage mechanisms. A lot of work pertaining to the issue of identification of damage mechanisms and subsequent development of stimulation technology in order to mitigate the damage and restore the wells deliverability have been done in a joint effort between The Gas Research Institute, Department of Energy, American Gas Association and the various other operator companies involved in the storage industry. Operators mostly rely on traditional methods such as blowing, washing, reperforating, acidizing, infill drilling to restore wells deliverability. These traditional methods do provide short term benefits, but the longevity is not sustained and the overall situation remains same. Hydraulic fracturing is not preferred in terms of legitimate concerns over excessive vertical height growth, long fracture fluid cleanup times, lack of expertise and cost. This research study was carried out to understand the various damage mechanisms affecting the Oriskany wells, with a focus on gas storage wells. We then developed a dataset of reservoir properties, rock properties and fracture treatment data for Oriskany based on a complete literature review and calculations from a sonic log. Parametrical studies were carried out to investigate the effect of type of fracture fluids, injection rate, types of proppant, treatment volume, reservoir pressure and treatment schedule on fracture geometries in the Oriskany formation. Based on the results, we developed new stimulation methods that lead to increased well deliverability, fracture height containment, and higher average fracture conductivity. This new understanding and knowledge help in practicing engineers design better treatments in stimulating Oriskany wells.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2013;135(2):022903-022903-7. doi:10.1115/1.4023100.

Sandstone formations are exposed to a variety of high pH fluids, including: hydraulic fracturing using high pH borate gels, alkaline-based chemical enhanced oil recovery (EOR) methods, water-based drilling fluids, and cementing filtrate. High pH values can trigger fines migration, and subsequent loss of permeability and well productivity. An aluminum/zirconium-based (Al/Zr) clay stabilizer was developed to control fines migration at high pH applications. The objective of this study is to assess the effectiveness of this new stabilizer and compare its performance with commercially available stabilizers. Laboratory studies were performed using Berea sandstone (8 wt. % clays; mainly kaolinite) cores, 6 in. length and 1.5 in. diameter. Tetramethyl ammonium chloride (TMAC) and choline chloride were used for comparison as two commercial clay stabilizers. Various coreflood experiments were conducted to determine the effect of the three stabilizers on core permeability (from 64 to 100 mD) at various temperatures up to 300 °F. In these experiments, a preflush that included 2 wt. % stabilizer was injected, followed by injection of 2 wt. % NaOH solution. The latter represented high pH filtrate that can invade the formation during any treatment that includes alkaline fluids. The pressure drop across the core was measured and samples of the core effluent were collected. Inductively coupled plasma optical emission spectrometry (winlab32 software) was used to measure the concentrations of Al, Zr, Fe, Ca, and Mg. ZetaPALS (BIC software) was used to measure the surface charge on the kaolinite particles. Lab results indicated that the new clay stabilizer worked effectively up to 300 °F following 2 wt. % NaOH. No reduction in permeability was noted in any of coreflood tests using sandstone cores of various initial permeabilities. The concentrations of various cations were found to be a function of core mineralogy. TMAC and choline chloride were not effective when followed by fresh water and incompatible with the high pH fluids. The new stabilizer is environmentally friendly, and can be used in hydraulic fracturing, and alkaline-based chemical EOR methods to mitigate clay related problems.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2013;135(2):022904-022904-10. doi:10.1115/1.4023329.

In this study, swing rates of drum boilers are investigated in regard to maintaining proper drum level limits. The nonlinear boiler model employed in study investigations was validated by comparing simulated results against literature data. Experimental field data was recorded for variations in firing, steam, and feedwater flow rates in addition to drum pressure and water level were obtained from a Saudi Aramco power plant. The experimental results were used also for tuning the water level control loop and finding the proportional and integral gains of the boiler model that was simulated using matlab. Influence of steam demand perturbations on water drum levels was tested using four different perturbation schemes and in all cases the levels were found to be within the allowable limits. The time variation of drum water level in response to 40% ramp increase in steam demand occurring at the four different input perturbations was obtained. The considered values of swing rates of steam flow were eight steps of 5% per minute, four steps of 10% per minute, two steps of 20% per minute, or one step of 40% per minute. Although the maximum transient water level overshoot is attained due to the one step of 40% per minute perturbation, still remains within the allowable limits of either the low or high levels according to the boiler manufacturer specifications. The present results indicate that the allowable swing rates are much lower in the case of drop in steam demand in comparison to the case of rise in steam demand.

Commentary by Dr. Valentin Fuster

research-article

J. Energy Resour. Technol. 2013;135(2):021601-021601-11. doi:10.1115/1.4023098.

The paper presents the results of a research regarding the application of cogeneration plants, based on organic rankine cycle (ORC), fed with wood residuals. In the first part of the paper an energy audit of the companies in a furniture industry district, located in the North-East of Italy, is presented. On the basis of these data a typical electricity/thermal demand profile dependent on the number of employees has been determined. In order to evaluate the potential savings achievable with an ORC cogeneration plant, a numerical simulation model has been developed to analyse the energy balances of the components as well as the whole ORC power plant performance. The effects on the system energy and exergy efficiencies of different binary and ternary mixtures of polisiloxane as working fluid and of different operating modes (cogeneration or pure electricity production) have been analysed, also in off-design conditions.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2013;135(2):021602-021602-10. doi:10.1115/1.4023099.

In a wide variety of thermal energy systems, the high integration among components derives from the need to correctly exploit all the internal heat sources by a proper matching with the internal heat sinks. According to what has been suggested in previous works to address this problem in a general way, a “basic configuration” can be extracted from the system flowsheet including all components but the heat exchangers, in order to exploit the internal heat integration between hot and cold thermal streams through process integration techniques. It was also shown how the comprehension of the advanced thermodynamic cycles can be strongly facilitated by decomposing the system into elementary thermodynamic cycles which can be analyzed separately. The advantages of the combination of these approaches are summarized in this paper using the steam injected gas turbine (STIG) cycle and its evolution towards more complex system configurations as an example of application. The new concept of “baseline thermal efficiency” is introduced to combine the efficiencies of the elementary cycles making up the overall system, which demonstrates to be a useful reference to quantify the performance improvement deriving from heat integration between elementary cycles within the system.

Commentary by Dr. Valentin Fuster

Technical Briefs

J. Energy Resour. Technol. 2013;135(2):024501-024501-6. doi:10.1115/1.4023174.

Blended fuels such as biodiesel–diesel blends are being extensively used in practical devises such as engines. The burning characteristics of blended fuels are quite different than that of the individual fuels and need to be understood. In this study, a semiempirical analysis concerning the mass burning rate characteristics of biodiesel–diesel blends is presented based on the data measured using porous sphere experiments. Finally, a correlation for evaluating instantaneous burning rate of biodiesel–diesel blended fuels has been proposed for practical applications. Further, using this correlation, transient burning characteristics of blended biodiesel–diesel droplet in suspended mode have been studied for different blend compositions. Multiple modes of burning regimes are identified for the blended fuels.

Commentary by Dr. Valentin Fuster

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