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Research Papers

J. Energy Resour. Technol. 2012;134(2):021001-021001-6. doi:10.1115/1.4005775.

This paper provides an overview of the development and optimization of abrasive-slurry-jet methods for completion and stimulation applications. Abrasive particles added to the fluid dramatically reduced the system pressure requirements. The paper discusses the technical capabilities of cutting through various materials and formations and also discusses improvements and proven applications. Abrasive fluid-jet systems are capable of cutting through rocks of all types, and with greater location control that is not susceptible to the geologically induced deviations encountered with mechanical methods. Abrasive fluid-jets drill rock through the erosion induced by very small particles which individually remove only small fragments but are in such numbers that the drilling rate is at or above that of conventional tools. The particles are powered by the velocity of the supporting fluid, generated in turn by pumps on the surface. The cutting occurs ahead of the nozzle body allowing the nozzle assembly to be fed in the tunnel to create drain-holes. Fluid-jet methods have the potential of improving completion and stimulation efficiency in heterogeneous formations such as fractured and/or vuggy carbonate reservoirs. Application for completion, stimulation and, even, well/platform abandonment has been successful.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2012;134(2):021002-021002-9. doi:10.1115/1.4006042.

The performance characteristics of a rice husk based integrated gasification combined cycle (IGCC) plant has been developed at the variable operating conditions of gasifier. A thermo-chemical model developed by the authors has been applied for wet fuel (fuel with moisture) for predicting the gas composition, gas generation per kg of fuel, plant efficiency and power generation capacity, and NOx and CO2 emissions. The effect of the relative air fuel ratio (RAFR), steam fuel ratio (SFR), and gasifier pressure has been examined on the plant electrical efficiency, power output, and NOx and CO2 emissions of the plant with and without supplementary firing (SF) between gas turbine (GT) outlet and heat recovery steam generator (HRSG). The optimum working conditions for efficient running of the IGCC plant are 0.25 RAFR, 0.5 SFR, and 11 bar gasifier pressure at the GT inlet temperature of 1200 °C. The optimum operational conditions of the gasifier for maximum efficiency condition are different compared to maximum power condition. The current IGCC plant results 264.5 MW of electric power with the compressor air flow rate of 375 kg/s at the existed conventional combined cycle plant conditions (Srinivas , 2011, “Parametric Simulation of Combined Cycle Power Plant: A Case Study,” Int. J. Thermodyn. 14 (1), pp. 29–36). The optimum compressor pressure ratio increases with increase in GT inlet temperature and decreases with addition of SF.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2012;134(2):021003-021003-9. doi:10.1115/1.4006041.

This paper investigates the effect of near-wall turbulence on selective removal of small-size particulate matter from sand beds deposited in pipelines. In an effort to develop effective strategies for in-line fines separation, experimental data on selective particle removal by burst-sweep turbulent structures have been gathered. A 3¾″ (0.095 m) diameter—15 m long flow loop together with a particle image velocimetry (PIV) system has been commissioned and used for observations of turbulent burst activities. The flow loop was also equipped with bottom extractors to allow real time sampling of deposited particles which are then analyzed for determining particle size distribution changes with time. In this work, the alteration of size-composition during turbulent transportation of moving (sand) bed was assumed to be the effect of burst-sweep activity (coherent structures). The frequency of coherent burst structures was measured at various distances from the pipe wall, during the radial dissipation, and results were compared with existing literature. The experimental results indicated that when a bed of particles with 0.1–50 μm size range is exposed to burst-sweep activities during turbulent pipe flow, the concentration of fine particles within the bed increases with time (i.e., coarser particles are preferentially removed).

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2012;134(2):021004-021004-5. doi:10.1115/1.4006046.

Biofuels, such as canola methyl ester (CME) and soy-methyl ester (SME) derived from vegetable oil, are alternative sources of energy that have been developed to reduce the dependence on petroleum-based fuels. In the present study, CME, SME, and commercial Jet-A fuel were tested in a porous-media burner at an equivalence ratio of 0.8 at the burner entrance. The measured combustion characteristics included NOx and CO emission indices, radiative fraction of heat release, and axial temperature profile in the surface stabilized and extended flame. The effects of fuel on the injector and porous-media durability were also documented. The NOx emission index was higher for the SME and CME flames than that of the Jet-A flame. Furthermore, the axial temperature profiles were similar for all the flames. The prolonged use of CME and SME resulted in more solid-particle deposition on the interior walls of the injector and within the structure of the porous medium than for Jet-A fuel, thereby increasing the restriction to the fuel/air flow and pressure drop across the burner.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2012;134(2):021005-021005-9. doi:10.1115/1.4006043.

Governments are pursuing a variety of measures to reach common and more efficient environmental and energetic policies: Nonetheless, the effort has shown to be not sufficient, since the objectives stated in the European Union (EU) Directive 2009/28/EC on energy efficiency seem quite distant to be reached. A greater attention has obviously been paid toward the industrial sector, which utilizes a major share of primary energy consumption: Till now several actions have been taken to achieve the energy performance of buildings, but very few are in operations. Nonetheless, in order to be most effective, governments should focus their attention not only on energy intensive large enterprises (LEs) but also on nonenergy intensive small and medium enterprises (SMEs) that represent the majority of the total number of industries, cover a consistent share of the energy consumption of a whole domestic industrial sector, and are usually less efficient than LEs. This paper aims to highlight the most effective energy savings opportunities (ESOs) for reducing energy consumption in industrial operations that have been successfully implemented in a large number of SMEs case studies investigated in North America and Italy, showing a correspondence (in terms of savings and costs) between the two databases. This paper analyzes the ESOs, characterized by best available technologies and practices (BAT/Ps), with a cross-analysis within three manufacturing sectors, i.e., primary metals, plastics, and textiles, and considering different subsizes among SMEs, in order to show commonalities and differences among the sample. The ESOs have been analyzed and ranked according to different criteria of importance, highlighting the most diffused, those having the highest energy savings, and those with the shortest pay-back time. The scope of the elaboration of these criteria is twofold: on one side, it allows to be closer to the entrepreneurial sensibility, guiding entrepreneurs in evaluating a possible investment in energy efficiency; on the other side, it provides important suggestions for a public local authority that, through financial support and/or other policies, aims at diffusing the adoption of BAT/Ps and increasing the sectors’ energy efficiency and competitiveness.

Commentary by Dr. Valentin Fuster

Energy Conversion/Systems

J. Energy Resour. Technol. 2012;134(2):021901-021901-10. doi:10.1115/1.4005659.

The temperature and pressure variation limits within the cavern of a compressed air energy storage (CAES) plant affect the compressor and turbine works, the required fuel consumption and therefore the overall plant performance. In the present work, the thermodynamic response of adiabatic cavern reservoirs to charge/discharge cycles of CAES plants are studied. Solutions for the air cavern temperature and pressure variations were derived from the mass and energy conservation equations, and applied to three different gas state equations, namely, ideal, real, and a self-developed simplified gas models. Sensitivity analyses were conducted to identify the dominant parameters that affect the storage temperature and pressure fluctuations. It is demonstrated that a simplified gas model can adequately represent the air thermodynamic properties. The stored air maximal to minimal temperature and pressure ratios were found to depend primarily on, both the ratio of the injected to the initial cavern air mass, and the reservoir mean pressure. The results also indicate that the storage volume is highly dependent on the air maximum to minimum pressure ratio. Its value should preferably be in between 1.2 and 1.8, where the exact selection should account for design and economic criteria.

Commentary by Dr. Valentin Fuster

Energy Systems Analysis

J. Energy Resour. Technol. 2012;134(2):022001-022001-6. doi:10.1115/1.4006435.

In this study, it is aimed to compare the efficiency of ultrasonic wave technology on asphaltene flocculation inhibition of crude oils with different American Petroleum Institute (API) gravities. A set of confocal microscopy test is performed and a series of statistical analysis is done. According to the results of this study, there is an optimum radiation time for both crudes at which the viscosity and the flocculation rate of asphaltenic crude oils reduces to its minimum. This optimum appears at later times of radiation for extra heavy oil. Also, it is shown that the rate of changes in the properties measured in this study is sharper for extra heavy crude oil. It could be concluded that the alternations caused by this technology is more significant for Kouh-e-Mond, which is heavier oil than Sarvak crude oil. Derjaguin–Ladau–Verwey–Overbeek (DLVO) kinetic model was also studied and it was understood that this model cannot be a validate model for radiated samples.

Commentary by Dr. Valentin Fuster

Fuel Combustion

J. Energy Resour. Technol. 2012;134(2):022201-022201-12. doi:10.1115/1.4005698.

In this study, first and second law analyses of a new combined power cycle based on wet ethanol fuelled homogeneous charge compression ignition (HCCI) engine and an organic Rankine cycle are presented. A computational analysis is performed to evaluate first and second law efficiencies, with the latter providing good guidance for performance improvement. The effect of changing turbocharger pressure ratio, organic Rankine cycle (ORC) evaporator pinch point temperature, turbocharger compressor efficiency, and ambient temperature have been observed on cycle’s first law efficiency, second law efficiency, and exergy destruction in each of its component. A first law efficiency of 41.5% and second law efficiency of 36.9% were obtained for the operating conditions (T0  = 300 K, rp  = 3, ηT  = 80%). The first law efficiency and second law efficiency of the combined power cycle significantly vary with the change in the turbocharger pressure ratio, but the change in pinch point temperature, turbocharger efficiency, and ambient temperature shows small variations in these efficiencies. Second law analysis demonstrates well how the fuel exergy is used, lost, and reused in all of the cycle components. It was found that 78.9% of the total input exergy is lost: 2.0% to the environment in the flue and 76.9% due to irreversibilities in the components. The biggest exergy loss occurs in the HCCI engine which is 68.7%, and the second largest exergy loss occurs in catalytic converter, i.e., nearly 3.13%. Results clearly show that performance evaluation based on first law analysis alone is not adequate, and hence more meaningful evaluation must include second law analysis.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2012;134(2):022202-022202-11. doi:10.1115/1.4005660.

Biofuels are a promising alternative to petroleum-based fuels. This paper investigates the performance, combustion, and exhaust emissions of a single cylinder diesel engine operated on baseline diesel and biofuel produced by vegetable oil and processing animal fat. The vegetable oil is called PODL20, which is a blend of palm oil and D -Limonen in proportion of 80% and 20%, respectively. The second biofuel is synthesized from the animal fat wastes (WAF) after transesterification process. Both experimental and numerical investigations are achieved in this work. The experiments are conducted at constant engine speed mode (1800 rpm) with applied loads on a wide domain. The CFD code converge is used to simulate the in-cylinder combustion for all the tested fuels. Comparative measures of brake thermal efficiency, break specific fuel consumption (bsfc), exhaust gas temperature, volumetric efficiency, and pollution (THC, CO2 , CO, NO, NOx) are presented and discussed. Also, a step is achieved with in-cylinder CFD simulation of biofuel combustion. The obtained results indicate that the combustion characteristics are slightly changed when comparing neat diesel to biofuels. Some of the results obtained in this work indicate that WAF fuel decreases the total unburned fuel as well as the nitrogen oxides (NOx) emissions. The numerical results are in logic agreement with those obtained experimentally, which promotes more detailed investigations and combustion characteristics optimization in forthcoming works.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2012;134(2):022203-022203-8. doi:10.1115/1.4005699.

The turbocharged direct injection stoichiometric spark ignition gasoline engine has less than diesel full load brake engine thermal efficiencies and much larger than diesel penalties in brake engine thermal efficiencies reducing the load. This engine has, however, a much better power density, and therefore may operate at much higher brake mean effective pressure (BMEP) values over driving cycles thus reducing the fuel economy penalty of the vehicle. This engine also has the advantage of the very well developed three way catalytic (TWC) converter after treatment to meet future emission regulations. Replacement of fossil gasoline with renewable gasoline-like fuels has major advantages. Ethanol and methanol have larger than gasoline resistance to knock and heat of vaporization, and this ultimately translates in larger than gasoline compression ratio and boost pressure and spark advances closer to maximum brake torque producing better efficiencies both full and part load. For the specific of these novel turbocharged direct injection stoichiometric spark ignition renewable gasoline-like engines coupled to a hybrid-electric power train, the paper considers the option to boost the total fuel conversion efficiency generating both mechanical and electric energy. When the internal combustion engine operates, significant fuel energy is lost in both the exhaust and the coolant. Part of this energy is recovered here by using organic Rankine cycle (ORC) systems fitted to both the exhaust and the coolant, with their expanders driving generators charging the battery of the car. The exhaust and the coolant organic Rankine cycle are effective in increasing the amount of fuel energy converted in usable power over the full range of loads and speeds. The organic Rankine cycle system fitted on the exhaust permits to increase the usable power versus the fuel energy flow rate of a 3.4% on average, with top improvements up to 6.4%. The system is effective particularly at high speeds and loads. The organic Rankine cycle system fitted on the coolant permits to increase the usable power versus the fuel energy flow rate of a 1.7% on average, with top improvements up to 2.8%. The system is effective particularly at low speeds and loads. The two combined organic Rankine cycle systems permit to increase the usable power versus the fuel energy flow rate of a 5.1% on average, with top improvements up to 8.2%.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2012;134(2):022204-022204-8. doi:10.1115/1.4005700.

The combustion stability of a single-cylinder homogeneous charge compression ignition (HCCI) engine operated with n-heptane was experimentally investigated over a range of engine speeds (N), intake temperatures and pressures, compression ratios (CR), air/fuel ratios (AFR), and exhaust gas recirculation (EGR) rates. These parameters were varied to alter the combustion phasing from an overly advanced condition where engine knock occurred to an overly retarded condition where incomplete combustion was observed with excessive emissions of carbon monoxide (CO) and unburned hydrocarbons (UHC). The combustion stability was quantified by the coefficients of variation in indicated mean effective pressure (COVimep ) and peak cylinder pressure (COVPmax ). Cycle-to-cycle variations in the HCCI combustion behavior of this engine were shown to depend strongly on the combustion phasing, defined in this study as the crank angle position where 50% of the energy was released (CA50). In general, combustion instability increased significantly when the combustion phasing was overly retarded. The combustion phasing was limited to conditions where the COVimep was 5% or less as engine operation became difficult to control beyond this point. Based on the experimental data, the combustion phasing limit was approximately a linear function of the amount of fuel inducted in each cycle. Stable HCCI combustion could be obtained with progressively retarded combustion phasing as the fuel flow rate increased. In comparison, stable HCCI combustion was only obtained under very advanced combustion phasing for low load operating conditions. Investigation of the experimental data reveals that the cyclic variations in HCCI combustion were due to cycle-to-cycle variations in total heat release (THR). The combustion completeness of the previous cycle affected the in-cylinder bulk mixture conditions and resultant heat release process of the following engine cycle.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2012;134(2):022205-022205-6. doi:10.1115/1.4006480.

The laminar burning speeds of Jet-A/air and three different samples of jet propellant (JP-8)/air mixtures have been measured and the onset of auto-ignition in JP-8/air premixed mixtures has been determined. The experiments were made in a constant volume spherical vessel, which can withstand high pressures up to 400 atm. Burning speed was calculated from dynamic pressure rise due to the combustion process in the vessel. A thermodynamic model based on the pressure rise was used to determine the burning speed. The burning speeds were measured in lean mixtures for pressures of 1–4.5 atm and temperatures of 493–700 K. The onset of auto-ignition of JP-8 fuels was evaluated by observing intense fluctuations of pressure data during the explosion of the unburned gas. It was revealed that Jet-A and JP-8 have very similar burning speeds; however, auto-ignition temperatures of various samples of JP-8 were slightly different from each other. Auto-ignition of these fuels was much more sensitive to temperature rather than pressure.

Commentary by Dr. Valentin Fuster

Petroleum Engineering

J. Energy Resour. Technol. 2012;134(2):022901-022901-7. doi:10.1115/1.4005661.

Deconvolution method is generally used to eliminate wellbore storage dominant period of well testing. Common Deconvolution techniques require knowledge of both pressure and rate variations within test duration. Unfortunately, accurate rate data are not always available. In this case, blind deconvolution method is used. In this work, we present a new approach to improve the ability of blind deconvolution method in well testing. We examined the behavior of rate data by comparing it with a special class of images and employed their common properties to represent gross behavior of extracted rate data. Results of examinations show ability of our developed algorithm to remove the effect of wellbore storage from pressure data. Our Algorithm can deal with different cases where wellbore storage has made two different reservoirs behave identical in pressure response. Even if there is no wellbore effect or after wellbore storage period is passed, proposed algorithm can work routinely without any problem.

Commentary by Dr. Valentin Fuster

Petroleum Transport/Pipelines/Multiphase Flow

J. Energy Resour. Technol. 2012;134(2):023001-023001-9. doi:10.1115/1.4005658.

A summary of all available correlations and mechanistic models for the prediction of slug liquid holdup is presented. Additionally, an experimental data base for slug liquid holdup has been collected from available literature. A comparison between the predictions of available models and correlations against the data base is presented, identifying the range of applicability of the different methods. The correlations have been tuned against the new data by calculating new values of their constant parameters, showing an improved performance. Also, the uncertainties of the correlations parameters are evaluated and presented. A recommendation for the best method of predicting the slug liquid holdup is provided.

Commentary by Dr. Valentin Fuster

Technical Briefs

J. Energy Resour. Technol. 2012;134(2):024501-024501-6. doi:10.1115/1.4005697.

The process of pressure reduction and gas leakage rate (discharge characteristics) of a hole has so far been accomplished by utilizing some zero-dimensional models. In these models, the effects of complex boundaries are ignored. The major aim of this study is simulating the process of pipeline gas leakage by the aid of a modified one-dimensional characteristics model. This model, beside the possibility of modeling the impact of leakage on one-dimensional compressible flow, benefits from introducing a variety of boundary conditions to flow zone. In this approach, hole is considered as an orifice, which makes a path for gas to release in a lower pressure ambient. Also, in this study, the effects of four kinds of boundary conditions at the ends of the pipeline on gas discharge characteristics are investigated.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2012;134(2):024502-024502-5. doi:10.1115/1.4006045.

For an 11 W proton exchange membrane (PEM) fuel cell, the exergy analysis at different channel geometry and internal parameters such as temperature, pressure, and mass flow rate are investigated experimentally. The geometry of the cell is rectangular, elliptical, and triangular. A PEM fuel cell with $25cm2$ active area and Nafion 117 membrane with 4 mg Pt $cm-2$ for the anode and cathode is employed as a membrane electrode assembly. The results show that when the geometry of the cell is rectangular, the irreversibility of the cell is at lower value and the exergy efficiency is at higher value. Also, the results show that with the increase of hydrogen, oxygen, and cell temperature, the exergy efficiencies of the cell increase and irreversibilities decrease.

Commentary by Dr. Valentin Fuster