COMPUTATIONAL FLUID DYNAMICS ANALYSIS OF NOx AND OTHER POLLUTANTS IN THE MAN B&W 7S50MC MARINE ENGINE AND EFFECT OF EGR AND WATER ADDITION

Marine engines represent a significant contribution to global emissions. In order to overcome this problem, a great attention was given to reduce their exhaust emissions in the last years, and marine engines have to adapt to regional, national and international restrictions. In this regard, the purpose of this paper is to develop a numerical model to study NOx (oxides of nitrogen) and other pollutants in engines. EGR and water addition were studied too as measures to reduce NOx. The main advantage of this study is that it provides a cheap and fast method to analyze emissions, contrary to experimental setups which are too expensive and laborious. Particularly, a commercial marine engine was analyzed and validated with experimental data. Results showed that increasing EGR and water addition leads to reduce NOx, but increase carbon monoxide and unburnt hydrocarbons due to an incomplete combustion.

COMPUTATIONAL FLUID DYNAMICS ANALYSIS OF NOx REDUCTION BY AMMONIA INJECTION IN THE MAN B&W 7S50MC MARINE ENGINE

Taking into account the importance of NOx (nitrogen oxides) emissions from marine engines and the current increasingly restrictive legislation, this work aims to develop a numerical model to study NOx reduction. To this end, direct injection of NH3 (ammonia) into the combustion chamber was proposed in the MAN B&W 7S50MC marine engine. The numerical model was employed to analyze several injection temperatures, injection timings and ammonia to fuel ratios, obtaining NOx reductions of almost 60%. Besides, a comparison between ammonia injection and water injection was done. The results showed that ammonia is more efficient than water to reduce NOx with a negligible influence on other pollutants such as CO (carbon monoxide) and HC (hydrocarbons). Nevertheless, ammonia is efficient in a very restrictive temperature and injection timing range. This numerical model was compared with experimental measurements, obtaining satisfactory results which validate the work.

Plasma Gas Temperature Control Performance of Metal 3D-Printed Multi-Gas Temperature-Controllable Plasma Jet

The aim of the study was to design and build a multi-gas temperature-controllable plasma jet that can control the gas temperature of plasmas with various gas species, and evaluated its temperature control performance. In this device, a fluid at an arbitrary controlled temperature is circulated through the plasma jet body. The gas exchanges heat with the plasma jet body to control the plasma temperature. Based on this concept, a complex-shaped plasma jet with two channels in the plasma jet body, a temperature control fluid (TCF) channel, and a gas channel was designed. The temperature control performance of nitrogen gas was evaluated using computational fluid dynamics analysis, which found that the gas temperature changed proportionally to the TCF temperature. The designed plasma jet body was fabricated using metal 3D-printer technology. Using the fabricated plasma jet body, stable plasmas of argon, oxygen, carbon dioxide, and nitrogen were generated. By varying the plasma jet body temperature from −30 °C to 90 °C, the gas temperature was successfully controlled linearly in the range of 29–85 °C for all plasma gas species. This is expected to further expand the range of applications of atmospheric low temperature plasma and to improve the plasma treatment effect.

108 Atrial fibrillation effects on coronary perfusion across the different myocardial layers: a computational analysis

Aims Atrial fibrillation (AF) patients may present ischaemic chest pain in the absence of classical obstructive coronary disease. Among the possible causes, the direct haemodynamic effect exerted by the irregular arrhythmia has not been studied in detail. Methods and results A computational fluid dynamics analysis was performed by means of a 1D-0D multiscale model of the entire human cardiovascular system, characterized by a detailed mathematical modelling of the coronary arteries and their downstream distal microcirculatory districts (subepicardial, midwall, and subendocardial layers). Three mean ventricular rates were simulated in both sinus rhythm (SR) and AF: 75, 100, 125 b.p.m. We conducted inter-layer and inter-frequency analysis of the ratio between mean beat-to-beat blood flow in AF compared to SR (Q¯AP/Q¯SR Inter-layer analysis showed that, for each simulated ventricular rate, Q¯AP/Q¯SR progressively decreased from the epicardial to the endocardial layer in the distal left coronary artery districts (P-values < 0.001 for both left anterior descending artery—LAD, and left circumflex artery—LCx), while this was not the case for the distal right coronary artery (RCA) district. Inter-frequency analysis showed that, focusing on each myocardial layer, Q¯AP/Q¯SR progressively worsened as the ventricular rates increased in all investigated microcirculatory districts (LAD, LCx, and RCA) (P-values < 0.001 for all layer-specific comparisons). Conclusions AF exerts direct haemodynamic consequences on the coronary microcirculation, causing a reduction in microvascular coronary flow particularly at higher ventricular rates; the most prominent reduction was seen in the subendocardial layers perfused by left coronary arteries (LAD and LCx).

Aerodynamic Analysis of Spoiler at Varying Speeds and Angles

Spoilers have been there in practice since years for the purpose of improving aerodynamics of a car. The pressure drag created at the end of the vehicle, referred to as wake region affects handling of the vehicle. This could be hazardous for the cars at high speeds. By adding a spoiler to the rear of the car reduces that pressure drag and the enhanced downforce helps in better traction. The paper presents aerodynamic analysis of a spoiler through Computational Fluid Dynamics analysis. The spoiler is designed using Onshape software and analyzed through SIMSCALE software. The simulation is carried out by changing angles of attack and velocities. The simulation results of downforce and drag are compared on the basis of analytical method. Keywords: Designing a spoiler, Design and analysis of spoiler, Aerodynamics of spoiler, Aerodynamic analysis of spoiler, Computational fluid dynamics, CFD analysis, CFD analysis of spoiler, Spoiler at variable angles, Types of spoilers, Analytical aerodynamic analysis.

Effects of uniform injection and suction through perforated pentagonal cylinders on the flow and heat transfer

Purpose The purpose of this paper is to study the effects of uniform injection and suction through a perforated pentagonal cylinder on the flow field and heat transfer. Design/methodology/approach The finite-volume method has been used to solve the ensemble-averaged Navier-Stokes equations for incompressible flow at moderate Reynolds number (Re = 22,000) with the k-ɛ turbulence model equations. Findings A computational fluid dynamics analysis of turbulent flow past a non-regular pentagonal cylinder with three different aspect ratios aspect ratios has been carried out to investigate the effects of uniform injection/suction through the front and all surfaces of the cylinder. It is found that flow field parameters such as drag coefficient, pressure coefficient and Nusselt number are affected considerably in some cases depend on injection/suction rate (Γ) and perforated wall position. Research limitations/implications To optimize the efficiency of the injection and suction through a perforated surface, both wide-ranging and intensive further studies are required. Using various perforation ratios and injection/suction intensities are some possibilities. Practical implications Control of the vortex shedding and wake region behind bluff bodies is of vital interest in fluid dynamics. Therefore, applying uniform injection and suction from a perforated bluff body into the main flow can be used as a drag reduction mechanism, thermal protection and heat transfer enhancement. Originality/value This study provides unique insights into the active flow control method around pentagonal cylinders that can be useful for researchers in the field of fluid dynamics and aeronautics.