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Ethyl tert‐butyl ether (ETBE) is a promising gasoline improver and this study shows its comparison with other prospective oxygenated fuel additives. ETBE synthesis and its economics are reviewed with emphasis on sustainable production. Furthermore, an experimental investigation is performed on the impact of employing relatively large proportions of ETBE in fuel blends and a particular emphasis is put on the magnitude of cyclic variations at different operating conditions. Tests involved a primary reference fuel (95PRF and two mixtures of ethyl tert‐butyl ether (ETBE) with 95PRF. To provide a baseline for comparison, a commercial gasoline fuel containing 5 % by volume of ethanol (E05) was also tested. The experiments were performed by using a well‐controlled single‐cylinder research engine, which has a disc‐shaped combustion chamber with a full‐bore overhead optical access. The pressure recording method was used simultaneously with natural‐light video photography for recording the flame propagation. To quantify the cyclic variations, the indicated mean effective pressure (IMEP), the peak pressure and the crank value at which it is attained, and the time for 90 % mass fraction burnt (MFB) were used. Increasing proportion of ETBE in the fuel has very little effect on both the average rate of combustion and its cyclic variability, regardless of what parameter is chosen to characterize the it.

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The combustion performance of a cylindrical burner accommodating up to six multiple pairs of opposing methane-air mixtures with a cross-flow of hydrogen was addressed. The cross-flow initially duplicated the stagnation impact and enriched the vortical structures. Aided by the resulting flow strain, the transport of heat and active species from the hydrogen oxidation zone to the methane reaction zones accelerated the combustion across the opposing premixed flames and reduced the peak temperature across the outer diffusion flame. Increasing the cross-flow/opposing jets' velocity ratio to 0.89 merged the two stagnation centers and maximized the shearing stress. By the slight increase in the velocity ratio to 1.07, the H and OH pools provided for methane combustion became closer to the ports such that a hydrogen/methane mass percent of 10.3% extended the stoichiometric blowout velocity from 28.3 to 35.7 m/s. Since the turbulent kinetic energy thus increased to 8.4 m 2 /s 2 , the firing intensity reached values as high as 48.2 MW/m 3. Not only was there a reduction in the residence time for NOx formation, but also the blowout velocity relative gain overrode the relative increase in the NOx formation rates such that the NOx emission index decreased to 17 g/MWhr. By the excessive increase in velocity ratio, the vortical structures shrank such that the NOx exponential increase became dominant above 21 ppm. With fuel-lean mixtures, the hydrogen was partially combusted by the excess air from the opposing flames but the blowout velocity decreased to 13.1 m/s at È ¼ 0.50. The hydrogen flame NOx emissions decreased by providing the excess air at larger jets' diameter/separation ratios, thus reducing the residence times for thermal NOx formation and simultaneously interrupting the prompt NOx formation. At the lean operational limit, tripling the number of opposing jets decreased the hydrogen flame length by 54% such that the NOx emissions decreased by 38.4%.

In the current study, potential improvements in both flow field and heat transfer characteristics of a prototype solar chimney for power generation through passive flow control approaches have been numerically examined. The numerical modeling was conducted for three different schemes to enhance the velocity magnitude at the entrance of the chimney. The first scheme is concerned with the effect of the number of turbulent generators on the maximum flow speed obtained while the second scheme deals with the effect of throat area at the entrance of the chimney. The last scheme is related to investigating the effect of making round edges having different radii at the entrance of the chimney.

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For the purpose of enhancing the heat transfer performance of cross-flow heat exchangers, extended surfaces are attached on the gas side, thus increasing the surface area and lowering the convection heat transfer resistance. Experiments have been carried out to evaluate the performance of four modules of cross flow heat exchangers. All heat exchanger modules have ten equally-spaced copper tubes in vertical alignment.A sheet of copper woven wire mesh was corrugated in the form of rectangular-shape. Then, it was press-fitted to the tube to form a wire mesh heat exchanger. One module has bare copper tubes. The other three wire mesh heat exchanger modules were manufactured with 2, 3, and 4 mm wire mesh layer-to-layer spacings for comparison purposes. Copper tubes containing hot distilled water flow of the heat exchanger modules, were subjected to external air flow forced convection heat transfer into an air duct having a 20 cm x 20 cm cross sectional inside area. The pressure drop in the air stream and the temperature of the hot water inlet and outlet were recorded. The significance of this experimental work is the use of a low cost and commercially available woven wire mesh sheet as extended heat transfer surface. A comparison was made between the results of this study and results of other enhanced cross-flow heat exchangers, obtained from open literature. Results showed an enhancement of the Nusselt number for all the wire mesh finned modules as compared to that of the bare module. Volumetric heat transfer coefficient results showed, an average increase of 113.9%, 91.5%, and 81.4% in the 3, 4, and 2 mm wire mesh heat exchangers, respectively, as compared to the bare heat exchanger module.

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