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### Research Papers: Air Emissions From Fossil Fuel Combustion

J. Energy Resour. Technol. 2008;130(1):011101-011101-8. doi:10.1115/1.2824295.

This study investigated normal heptane ($N$-heptane)-diesel combustion and odorous emissions in a direct injection diesel engine during and after engine warmup at idling. The odor is a little worse with $N$-heptane and blends than that of diesel fuel due to overleaning of the mixture. In addition, formaldehyde (HCHO) and total hydrocarbon (THC) in the exhaust increase with increasing $N$-heptane content. However, 50% and 100% $N$-heptane showed lower eye irritation than neat diesel fuel. Due to low boiling point of $N$-heptane, adhering fuel on the combustion chamber wall is small and as a single-component $C7$ fuel, relatively high volatile components present in the exhaust are low. This may cause lower eye irritation. On the contrary, bulk in-cylinder gas temperature is lower and ignition delay significantly increases for 50% and 100% $N$-heptane due to the low boiling point, high latent heat of evaporation, and low bulk modulus of compressibility of $N$-heptane than standard diesel fuel. This longer ignition delay and lower bulk in-cylinder gas temperature of $N$-heptane blends deteriorate exhaust odor and emissions of HCHO and THC.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2008;130(1):011102-011102-11. doi:10.1115/1.2824286.

Diesel engines are critical in fulfilling transportation and mechanical/electrical power generation needs throughout the world. The engine’s combustion by-products spawn health and environmental concerns, so there is a responsibility to develop emission reduction strategies. However, difficulties arise since the minimization of one pollutant often bears undesirable side effects. Although legislated standards have promoted successful emission reduction strategies for larger engines, developments in smaller displacement engines has not progressed in a similar fashion. In this paper, a reduced-order dynamic model is presented and experimentally validated to demonstrate the use of cooled exhaust gas recirculation (EGR) to alleviate the tradeoff between oxides of nitrogen reduction and performance preservation in a small displacement diesel engine. EGR is an effective method for internal combustion engine oxides of nitrogen $(NOx)$ reduction, but its thermal throttling diminishes power efficiency. The capacity to cool exhaust gases prior to merging with intake air may achieve the desired pollutant effect while minimizing engine performance losses. Representative numerical results were validated with experimental data for a variety of speed, load, and EGR testing scenarios using a $0.697l$ three-cylinder diesel engine equipped with cooled EGR. Simulation and experimental results showed a 16% drop in $NOx$ emissions using EGR, but experienced a 7% loss in engine torque. However, the use of cooled EGR realized a 23% $NOx$ reduction while maintaining a smaller performance compromise. The concurrence between simulated and experimental trends establishes the simplified model as a predictive tool for diesel engine performance and emission studies. Further, the presented model may be considered in future control algorithms to optimize engine performance and thermal and emission characteristics.

Commentary by Dr. Valentin Fuster

### Research Papers: Energy From Biomass

J. Energy Resour. Technol. 2008;130(1):011801-011801-6. doi:10.1115/1.2824247.

In (bubbling) fluidized-bed combustion and gasification of biomass, several potential problems are associated with the inorganic components of the fuel. A major problem area is defluidization due to bed agglomeration. The most common found process leading to defluidization in commercial-scale installations is “coating-induced” agglomeration. During reactor operation, a coating is formed on the surface of bed material grains and at certain critical conditions (e.g., coating thickness or temperature) sintering of the coatings initiates the agglomeration. In an experimental approach, this work describes a fundamental study on the mechanisms of defluidization. For the studied process of bed defluidization due to sintering of grain-coating layers, it was found that the onset of the process depends on (a) a critical coating thickness, (b) on the fluidization velocity when it is below approximately four times the minimum fluidization velocity, and (c) on the viscosity (stickiness) of the outside of the grains (coating).

Commentary by Dr. Valentin Fuster

### Research Papers: Energy Systems Analysis

J. Energy Resour. Technol. 2008;130(1):012001-012001-8. doi:10.1115/1.2824296.

Despite the immense environmental, technical, and financial promise of distributed generation (DG) technologies, they still constitute a very small percentage of electricity capacity in the United States. This manuscript answers the apparently paradoxical question: Why do technologies that offer such impressive benefits also find the least use? Going beyond technical explanations of problems related to system control, higher capital costs, and environmental compliance, this paper focuses on sociotechnical barriers related to utility preferences, business practices, regulatory bias, and consumer values. The approach helps us understand the glossing over of DG technologies, and identifies the impediments that policymakers must overcome if they are to find wider use.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2008;130(1):012002-012002-7. doi:10.1115/1.2835614.

Energy management in the industrial context is an important factor to attain energy savings as well as environmental efficiency. Often, linear regression models quite well represent the consumption of energy carriers and statistical process control (SPC) techniques, such as the cumulative sum (CUSUM) plot and Shewhart-like control charts, are currently applied to identify when a system changes the way energy is consumed. Despite the fact that SPC is widely applied in many fields, there is a lack of published material in energy management. The purpose of this paper is to widen the SPC techniques to be applied to energy management. Particular emphasis is given to small- and medium-sized enterprises since energy data are limited and generally known at system level. The CUSUM of the recursive residuals is proposed as the main tool for the analysis of energy consumption data, both for the historical and the monitoring phases. In addition, tabular CUSUM and EWMA control charts are also included.

Commentary by Dr. Valentin Fuster

### Research Papers: Petroleum Wells-Drilling/Production/Construction

J. Energy Resour. Technol. 2008;130(1):013101-013101-7. doi:10.1115/1.2824261.

A new type of rotary steering stabilizer used in a common rotary bottom hole assembly (BHA) to control well path was developed. In order for design and use of this kind of BHA, mathematical models were proposed for 3D mechanical analysis of rotary steering BHA with small deflection. The mathematical models include (1) differential equations; (2) boundary conditions of drill bit, stabilizer, diameter change, tangent point, and bore hole wall; (3) methods for calculating lateral forces and deflection angles of the bit; and (4) models for determining navigation ability and navigation parameters. As an example, a given rotary steering BHA was studied.

Commentary by Dr. Valentin Fuster

### Research Papers: Underground Injection and Storage

J. Energy Resour. Technol. 2008;130(1):013301-013301-5. doi:10.1115/1.2825174.

Our previous coreflood experiments—injecting pure $CO2$ into carbonate cores—showed that the process is a win-win technology, sequestrating $CO2$ while recovering a significant amount of hitherto unrecoverable natural gas that could help defray the cost of $CO2$ sequestration. In this paper, we report our findings on the effect of “impurities” in flue gas—$N2$, $O2$, $H2O$, $SO2$, $NO2$, and CO—on the displacement of natural gas during $CO2$ sequestration. Results show that injection of $CO2$ with approximately less than $1mole%$ impurities would result in practically the same volume of $CO2$ being sequestered as injecting pure $CO2$. This gas would have the advantage of being a cheaper separation process compared to pure $CO2$ as not all the impurities are removed. Although separation of $CO2$ out of flue gas is a costly process, it appears that this is necessary to maximize $CO2$ sequestration volume, reduce compression costs of $N2$ (approximately 80% of the stream), and improve sweep efficiency and gas recovery in the reservoir.

Commentary by Dr. Valentin Fuster

### Technical Briefs

J. Energy Resour. Technol. 2008;130(1):014501-014501-6. doi:10.1115/1.2824297.

An experiment was performed to study air∕water slug frequency in a horizontal clear pipe by means of visual inspection and differential pressure measurement in the range of $0–1∕s$. Results showed that a simplified model for slug pressure drop allowed the differential pressure data to compare favorably with visual observations for slug frequency. It was concluded that this technique gives a proper estimation of slug frequency, given only basic flow information. It is recommended that this technique be used when constrained to differential pressure or used to analyze existing differential pressure data.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2008;130(1):014502-014502-4. doi:10.1115/1.2835616.

With today’s high prices for natural gas and oil, the demand for oil and country tubular goods (OCTGs) with superior performance properties is very high. Failures in OCTG can be attributed to numerous sources, for example, makeup torque, corrosion, and galling. Thread galling is the most common mode of failure. This failure often leads to leakage, corrosion of the material, and loss of mechanical integrity. The failure of OCTG eventually amounts to excessive operational costs for the gas and oil industry. Numerous approaches have been taken to improve the galling resistance of OCTG connections. The advocacy of these approaches is often achieved through experimental studies using galling testers. There is a need to design and use effective galling testers to understand and improve the performance of OCTG connections. Thus, the objective of this paper is to present a concise review of literature related to the galling testers that may have applications to OCTG.

Commentary by Dr. Valentin Fuster