The problem of the forced film condensation heat transfer of pure steam and steam-air mixture flowing downward a tier of horizontal cylinders is investigated numerically and experimentally. Liquid and vapor-air mixture boundary layers were solved by an implicit finite difference scheme. The effects of the free stream non-condensable gas (air) concentration, free stream velocity (Reynolds number), cylinder diameter, temperature difference and angle of inclination on the condensation heat transfer are analyzed. Inline and staggered tubes arrangements are considered. The mathematical model takes into account the effect of staggering of the cylinders and how condensation is affected at the lower cylinders when condensate does not fall on to the center line of the cylinders. An experimental setup was also manufactured and mounted at METU workshop. A set of experiments were conducted to observe the condensation heat transfer phenomenon and to verify the theoretical results. Condensation heat transfer results are available in ranges from (U&amp / #61605 / = 1 - 30 m/s) for free stream velocity, (m1,&amp / #61605 / = 0.01 -0.8) for free stream air mass fraction, (d = 12.7 -50.8 mm) for cylinder diameter and (T&amp / #61605 / -Tw =10-40 K) for temperature difference. Results show that / a remarked reduction in the vapor side heat transfer coefficient is noticed when very small amounts of air mass fractions present in the vapor. In addition, it decreases by increasing in the cylinder diameter and the temperature difference. On the other hand, it increases by increasing the free stream velocity (Reynolds number). Average heat transfer coefficient at the middle and the bottom cylinders increases by increasing the angle of inclination, whereas, no significant change is observed for that of the upper cylinder. Although some discrepancies are noticed, the present study results are inline and in a reasonable agreement with the theory and experiment in the literature. Down the bank, a rapid decrease in the vapor side heat transfer coefficient is noticed. It may be resulted from the combined effects of inundation, decrease in the vapor velocity and increase in the non-condensable gas (air) at the bottom cylinders in the bank. Differences between the present study results and the theoretical and the experimental data may be resulted from the errors in the numerical schemes used. These errors include truncation and round off errors, approximations in the numerical differentiation for interfacial fluxes at the vapor-liquid interface, constant properties assumption and approximations in the initial profiles. Mixing and re-circulation in the steam-air mixture at the lower tubes may be the other reasons for these deviations.

Preliminary designs for the cylinder heads of Scania’s next generation Diesel Engine have been investigated by the means of PIV measurements on a steady test rig. General structures present in the flow have been investigated, with a specific focus on Swirl motion due to its well documented impact on combustion efficiency and pollution generation. The first set of measurements was acquired in the tumble plane. A method to perform efficiently PIV measurements was introduced, which consists in rotating the experimental setup rather than the PIV measurement instruments. As a consequence, a considerable amount of work is saved and a great number of measurement planes can be acquired. This method has allowed to reconstruct a 3D3C picture of the flow in the cylinder. Such 3D3C direct measurement of flow in a test rig cylinder had not been reported previously in the literature, as far as the author is aware of it. The second set of measurements was acquired in the swirl plane. General patterns in the swirl velocity fields have been identified. The author introduces the hypothesis that shifting down the measurement position may, to some extend, be equivalent to observing the flow evolve in time in the real engine situation. Measurement performed far enough under the valves exhibit clear and stable swirling vortex structure with the cylinder heads investigated. This may explain for the validity of the combustion models used in the industry that, despite apparent over simplification of the flow situation, have proved in good agreement with engine tests.

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