Bir Katamaran Motoryat Dizel Motorunda Bir Islak Egzoz Sisteminin İki Fazlı Sayısal Modellenmesi

Öz

Bu çalışmada, bir yat dizel motorunda kapsamlı sayısal model kullanılarak ıslak egzoz sisteminden çok fazlı sıcaklık dağılımları ve hacim fraksiyonları 3 boyutlu olarak incelenmiştir. Bu amaçla sayısal model olarak Volume of Fluid çok fazlı modeli seçilmiştir. Yakıt egzozları, modern bir yat görünümü sağlamak ve egzoz gürültüsünü en aza indirmek için genellikle su altında bulunmaktadır. Su basıncını, egzoz gazlarını ve soğutma suyu akış dağıtımını yönetmek için katamaran yat egzozunun üzerine bir muhafaza yerleştirilmiştir. Bununla birlikte, nozulda kullanılan sıcak egzoz gazı ve soğutma suyu olmak üzere iki tip akışkan kullanılmıştır. Tasarım Ansys SpaceClaim kullanılarak oluşturulmuştur ve soğutma suyu nozulun 60° ucundan püskürtülecek şekilde ele alınmıştır. Dahası simülasyonda kullanılan yapısal ağ 1.405.113 elemana ve 523.125 düğüme sahiptir ve ortalama yapısal ağın çarpıklığı 0,46, meshin ortalama ortogonal kalitesi 0,64'tür. Simülasyonlarda Realizable k-ε türbülans modeli kullanılmıştır. Sonuçlar incelendiğinde, 1,5 saniye sonra akış tam olarak gelişmekte ve su nozulu, suyu boru boyunca püskürtmekte ve egzoz gazlarını soğutmaktadır. Ayrıca hız konturları ve hız vektörleri incelendiğinde borunun dirsek bağlantı noktasında meydana gelen durma noktaları dikkat çekicidir.

Anahtar Kelimeler

• Islak egzoz sistemi
• Deniz dizel motoru
• CFD
• Termal performans
• İki fazlı akış.

Two-Phase Numerical Modelling of a Wet Exhaust System in a Catamaran Motor Yacht Diesel Engine

Abstract

In this study, the multiphase temperature distributions and volume fractions through wet exhaust system were investigated as 3D by using comprehensive numerical model in a yacht diesel engine. For this purpose, Volume of Fluid multiphase model was selected as the numerical model. Fuel exhausts are generally located underwater to ensure a modern yacht appearance and minimize exhaust noise. To manage water pressure, exhaust gases, and cooling water flow distribution, a scoop is positioned above the catamaran yacht exhaust. Besides, two types of fluids have been used one of which is the hot exhaust gas the other one is the cooling water used in the nozzle. The design has been created using Ansys SpaceClaim and the cooling water is sprayed from the 60° tip of the nozzle. Moreover, the mesh used in the simulation has 1,405,113 elements and 523,125 nodes and the average mesh skewness is 0.46, the average orthogonal quality of the mesh is 0.64. Realizable k-ε turbulence model has been used in the simulations. According to results, the flow fully develops after the time of 1.5 seconds and the water nozzle sprays the water along the tube cools the exhaust gases. Also, the stagnation points occurring at the elbow fitting of the tube are striking when the velocity contours and velocity vectors are examined.

Keywords

• Wet exhaust system
• Marine diesel engine
• CFD
• Thermal performance
• Two-phase flow.

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