I C engines

• Effects of wind on the thermo-flow characteristics of cooling towers have been revealed. • Windbreaker types have been studied to decrease the negative effects of wind. • Results show that it is possible to use the momentum effect of wind. • Movable windbreakers should be used to change the direction according to the wind. A B S T R A C T Performance of natural draft dry cooling towers is significantly affected when the wind velocity is higher than a critical level according to their design and geometry. During this type of conditions, global electricity generation of power plants using especially dry type cooling towers is substantially reduced, up to as high as 40%. In order to decrease the reduction in electricity generation of power plants, it is possible to study on the dimensions of the cooling towers. Additionally, using different types of windbreakers can reduce the effects of unfavorable operating conditions. However, the direction of the wind changes with the seasons although the prevailing wind direction is nearly the same. In this study, internal flat and combination of internal flat–external rounded windbreakers have been analyzed by using the computational fluid dynamics approach. The combination of windbreakers, which is able to move axially around the cooling tower, has been propounded to arrange the flow characteristics during the windy days. The studies on the windbreakers in the literature have been aimed to decrease the negative effects of the wind; however, the design in this study provides also an increase in the air mass flowrate due to the momentum effect of the wind.

Bioethanol-gasoline blends represent for Otto-cycle engines a consolidated alternative in the attempts to reduce GHG emissions and to limit the use of fossil fuels. However, the use of alternative fuels can strongly influence the performance of engines.
The purpose of this study is to analyse the output and the pollutant emissions of a four-stroke SI engine fuelled with 0%, 50% and 80% bioethanol-gasoline blends. Tests were performed on a 3-kW engine used in broad applications. No specific modifications were applied to the carburetion system in order to evaluate its fuel flexibility capabilities.
The tests evidenced that the mixture tends to get lean with alcoholic fuels; the brake specific fuel consumption increased due to the lower LHV of bioethanol, while the highest brake thermal efficiency was obtained with E50. Minor torque and power reductions were recorded with the ethanol blends. The concentration of UHC decreased with E50 and E80 while NOx emissions reduced because of the lower combustion temperature due to the bioethanol cooling effect and the leaner mixture. In contrast, the concentration of CO increased because a poor homogenization of the charge and a lower combustion temperature had facilitated the formation of partial oxidation products.

Introduction of water into diesel/biodiesel could be an answer to simultaneous reduction of NOX and PM, with increased combustion efficiency. Micro explosion phenomenon plays a vital role in influencing the combustion and emission characteristics of the emulsion, which is explained in detail. The stability of water in oil emulsions is better explained by surfactant concentration, HLB of the surfactant, water concentration in the emulsion which are discussed in this paper. This review paper collects and discusses the recent advances in water in diesel and water in biodiesel emulsion fuel studies and their impact on the performance and emission of diesel engines.