407 research outputs found

    Effect of char on the combustion process of multicomponent bio-fuel

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    Combustion of pyrolysis oil has attracted many attention in recent years as a renewable and environmental friendly fuel. However, pyrolysis oil as an multi-component fuel has some differences compared to conventional fossil fuels. One of the main differences is the formation of solid char in the droplet during evaporation. The goal of this work is to study the effect of the solid char on the combustion characteristics of multi-component fuel. An Euler-Lagrange model of three phase gas/liquid/solid combustion is developed to study the detailed information about every phenomena in the process such as: heat, mass and momentum transfer between droplet and gas phase, droplet evaporation, homogeneous and heterogeneous reactions. The results indicate that the presence of the solid char and consequently its combustion elongates significantly the combustion region in a typical spray injection chamber/burner. Moreover, the gas phase reaches higher temperatures as a result of char combustion that creates more heat by heterogeneous oxidation as a kind of afterburner

    Experimental Research on Flow Separation Control using Synthetic Jet Actuators

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    Airplane wings can suffer from flow separation, which greatly decreases their aerodynamic per-formance. The flow separates due to the bound-ary layer possessing insufficient momentum to engage the adverse pressure gradient along the airfoil surface. Flow separation control actively influences the flow such that flow separation is delayed and airfoil performance is improved. In this research flow separation control is ap-plied on a 2D wing with a NACA0018 section with a 0.165 m chord using tangentially direct-ed synthetic jets. The actuators are located in-side the wing and the jet exits from a slot in the upper wing surface. The synthetic jet inhales the low momentum air in the boundary layer during instroke and during the outstroke the air adds momentum to the boundary layer. The actuator, with a piezo-electric diaphragm, has a slot width of 0.25 mm. With this design jet velocities up to 65 m/s have been achieved at an optimum actuation frequency of 900 Hz. A spanwise row of ten actuators is placed inside the wing, such that the slots cover 66% of the wing's span. During wind tunnel experiments forces have been measured using a balance. The tests have been performed at a fixed free stream velocity of 25 m/s (Rec = 2.73×105) and for various actuation frequencies and jet velocities. It is shown that for given actuation frequency a higher jet velocity results in a higher maximum lift coefficient and a corresponding higher stall angle. However, for the performance of the syn-thetic jet actuation, actuation frequency proves to be of greater importance than jet velocity. The best actuation frequency in combination with the maximum jet velocity possible with the present actuator is a dimensionless frequency F+ of 5.9 (1300 Hz) and a momentum coefficient cμ of 0.0014 (maximum jet velocity 32.9 m/s and Velocity Ratio of 1.32). Using these actuation parameters the lift coefficient is increased by 12% and the stall angle by 22%

    Records of five bryozoan species from offshore gas platforms rare for the Dutch North Sea

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    This study reports on bryozoan species collected at three offshore gas platforms in the Dutch part of the North Sea. Four out of thirteen observed species are considered as rare in the Netherlands, whereas Cribrilina punctata is anew species for Dutch waters

    Review - Late toxicity of abdominal and pelvic radiotherapy for childhood cancer

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    As survival improves in childhood cancer, prevention of late treatment-related toxicity in survivors becomes increasingly relevant. Radiotherapy is an important contributor to late toxicity. Therefore, minimizing radiation exposure to normal tissues is an important step towards improving the long-term therapeutic window of childhood cancer treatment. Since children are growing and developing, they are particularly vulnerable to radiation exposure. This makes the 'as low as reasonably achievable (ALARA)' principle even more important. In order to guide and achieve clinically meaningful dose reductions through advanced and emerging radiation techniques, it is important to investigate age-dependent relationships between radiation exposure to healthy tissues and late radiation-induced toxicity. In this review, we provide an overview of literature on the association between radiotherapy dose and late toxicity after abdominal and pelvic irradiation in childhood cancer. With this information, we aim to aid in decision-making regarding radiotherapy for childhood cancer. (c) 2022 The Author(s). Published by Elsevier B.V. Radiotherapy and Oncology 170 (2022) 27-36 This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
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