Journal of Energy Engineering

In the study of wind‐induced motion of conductors of overhead power transmission lines, an indoor test span measuring 30 m or more is normally used. The span is generally excited into motion by an electrodynamic‐type exciter connected at a span end. This connection increases the stiffness of the span at the point of connection, which will affect the dynamic characteristics of the test span. A more exact simulation of the indoor test‐conductor motion is essential. Simulation of test‐conductor motion using the principle of electrodynamic forces between parallel, long conductors is proposed. Indoor test‐span motion by this method is equivalent to steady crosswinds excitation in the field as distinguished from galloping conductors resulting from a combination of wind direction, velocity, moisture, and temperature. Consequently, the results of vibration experiments also will be more exact. The principle employed in the new excitation system, the methods of excitation in indoor spans using the principle, and the advantages of the new excitation system as compared to the presently employed system are discussed in this paper.

The use of alternative fuels in the transportation industry has gained a strong support in recent years. In this paper an attempt was made to evaluate the use of liquefied petroleum gas (LPG) and compressed natural gas (NG) by 25 LPG‐bifuel and 14 NG‐bifuel vehicles that are operated by 33 transit systems throughout Nebraska. A set of performance measures such as average fuel efficiency in kilometers per liter, average fuel cost per kilometer, average oil consumption, and average operation and maintenance cost for alternatively fueled vehicles were calculated and compared with similar performance measures of gasoline powered vehicles. The results of the study showed that the average fuel efficiency of gasoline is greater than those of LPG and NG, and the average fuel costs (dollars per kilometer) for LPG and NG are smaller than those for gasoline for most of the vehicles under this study.

In situ gas hydrates have been found abundantly in the Arctic regions of the United States, Canada, and Russia. Gas recovery from such a hydrate reservoir under permafrost conditions is described in the present paper. The technique is based upon a finite‐element transient heat‐conduction model that includes the ability to handle phase change. That model is applied to field data available from the North Slope of Alaska for predicting natural‐gas production. Parametric studies have also been conducted to explore the effects of hydrate zone thickness, wellbore temperature, wellbore radius, porosity, etc., on the gas production rate. Comparisons of temperature distributions throughout the medium, and the propagation of the moving dissociation front with respect to time predicted by the present scheme and a finite‐difference scheme, show good agreement. The data generated in the present study may be useful in deciding on the most optimal technique for gas recovery from hydrates. Additionally, it may provide drilling engineers with valuable information to establish guidelines for safe drilling in the presence of hydrates.