With the development in additive manufacturing, the use of surface treatments for gas turbine design applications has greatly expanded. An experimental investigation of the pressure loss and heat transfer characteristics within impingement jet arrays with arrays of target surface micro cooling units is presented. The discharge coefficient and Nusselt number are measured and determined for an evaluation of the pressure loss of the flow system and heat transfer level, respectively. Considered are effects of impingement jet Reynolds number ranging from 1000 to 15,000 and micro cooling units (square pin fin) height (h) with associated values of 0.01, 0.02, 0.05, 0.2, and 0.4 D, where D is the impingement hole diameter. Presented are variations of Nusselt number, and Nusselt number ratio, discharge coefficient, discharge coefficient ratio, discharge coefficient correlation. Depending upon the micro cooling unit height, discharge coefficient ratios slightly decrease with height, and the ratio values generally remain unit value (1.0). When Rej = 1000 and 2500 for several cooling units height values, discharge coefficient ratios show the pressure loss decreases about 2–18% and 3–6%, respectively, when compared to the data of a baseline smooth target surface plate. The observed phenomenon is due to the effects of flow blockage of micro cooing units, local flow separation, and near-wall viscous sublayer reattachment. Results also show that heat transfer levels increase 20–300% for some of the tested toughened target surface plates when compared to smooth target surface plates. The heat transfer level enhancement is because of an increase in thermal transport and near-wall mixing, as well as the increased wetted area. In addition, micro cooling units elements break the viscous sublayer and cause greater turbulence intensity when compared to the smooth target surface. Overall, results demonstrate that the target surface micro cooling units do not result in a visible increment in pressure loss and reduce pressure loss of the flow system for some of the tested patterns. Moreover, results show the significant ability of micro cooling units to enhance the surface heat transfer capability of impingement cooling relative to smooth target surfaces.
Overall cooling effectiveness was determined for a full-coverage effusion cooled surface which simulated a portion of a double wall cooling gas turbine blade. The overall cooling effectiveness was measured with high thermal-conductivity artificial marble using infrared thermography. The Biot number of artificial marble was matched to real gas turbine blade conditions. Blowing ratio ranged from 0.5 to 2.5 with the density ratio of DR = 1.5. A variation of cooling arrangements, including impingement-only, film cooling-only, film cooling with impingement, and film cooling with impingement and pins, as well as forward/backward film injection, was employed to provide a systematic understanding on their contribution to improve cooling efficiency. Also investigated was the effect of reducing wall thickness. Local, laterally averaged, and area-averaged overall cooling effectiveness were shown to illustrate the effects of cooling arrangements and wall thickness. Results showed that adding impingement and pins to film cooling, and decreasing wall thickness increase the cooling efficiency significantly. Also observed was that adopting backward injection for thin full-coverage effusion plate improves the cooling efficiency.
Tidal analysis requires only continuous pressure monitoring data and therefore is a cost-effective technique for estimating reservoir properties. Previous tidal analysis work focused on vertical wells. This study developed and solved tidal response models for a horizontal well considering skin effect and wellbore storage in three classical reservoir types: confined reservoir, semiconfined reservoir, and reservoir with mixed boundaries.
Green's function, source functions, Laplace transform, and Duhamel's principle were used to solve the models and obtain analytical solutions in Laplace space. Then, Laplace transform numerical inversion was utilized to invert the Laplace space solutions to time-domain solutions. Variable condition analysis was conducted to analyze the effects of different parameters (wellbore storage, skin effect, well length, well direction - horizontal or vertical, and vertical leakage) on tidal behavior:
For confined reservoirs, the influence of skin effect and wellbore storage (under the condition of positive skin effect) both tend to decrease the tidal amplitude ratio and increase the tidal phase lag. Longer wells lead to a smaller tidal amplitude ratio and lead to a larger tidal phase lag for small wellbore storage, and smaller tidal phase lag for large wellbore storage.
For reservoirs with mixed boundaries, the effect of wellbore storage depends on the value and sign of skin factor. A horizontal well with larger skin effect will have larger tidal phase lag and tidal amplitude attenuation.
For a semiconfined reservoir, the tidal amplitude ratio first increases with increasing vertical leakage but then decreases when there is a large vertical leakage. Vertical leakage tends to decrease the tidal phase lag or increase the tidal phase advance.
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