Studi Eksperimen Karakteristik Aliran Di Dalam Symmetric Flat-Walled Octagonal Diffuser 8 Derajat Pada Circuit Wind Tunnel

Palupi, Anastia Erina (2015) Studi Eksperimen Karakteristik Aliran Di Dalam Symmetric Flat-Walled Octagonal Diffuser 8 Derajat Pada Circuit Wind Tunnel. Undergraduate thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Diffuser merupakan suatu bentuk saluran tertutup yang mengalami pembesaran luas penampang melintang sepanjang arah aliran fluida. Pembesaran luas penampang diffuser menyebabkan aliran fluida mengalami penurunan kecepatan yang berakibat meningkatnya tekanan aliran. Peningkatan tekanan tersebut menyebabkan terjadinya adverse pressure gradient (APG) yang berpengaruh terhadap perkembangan boundary layer. Semakin besar APG yang terjadi maka aliran semakin mudah terseparasi. Terjadinya separasi merupakan salah satu faktor yang mempengaruhi turunnya nilai koefisien tekanan (pressure coefficient, Cp). Nilai Cp menjadi parameter penting untuk dianalisa dalam konteks penerapannya pada diffuser. Perancangan sebuah diffuser yang baik akan menghasilkan pressure recovery coefficient (Cpr) yang maksimum. Oleh karena itu penelitian mengenai diffuser perlu dilakukan. Penelitian mengenai diffuser ini menggunakan metode eksperimen dengan alat uji close circuit wind tunnel. Diffuser yang digunakan pada penelitian ini adalah symmetric flat-walled octagonal diffuser yang memiliki sudut divergensi (2θ) = 8°. Diffuser ini memiliki geometri panjang diffuser, L1 = 1500 mm, panjang upstream channel, L2 = 600 mm dan panjang downstream channel, L3 = 500 mm, lebar span inlet (b1) = 300 mm, lebar span outlet (b2) = 518,8 mm, dan lebar span inlet fan vi Tugas Akhir Institut Teknologi Sepuluh Nopember (b3) = 500 mm serta memiliki t inggi inlet diffuser (W1) = 300 mm, tinggi outlet diffuser (W2) = 518,8 mm dan tinggi inlet fan (W3) = 500 mm. Pada penelitian ini digunakan ketiga bilangan Reynolds berdasarkan diameter hidrolik yaitu ReDh = 1,98 x 105, ReDh = 3,86 x 105 dan ReDh = 5,85 x 105. Hasil yang didapatkan pada penelitian ini adalah tidak terjadinya separasi untuk ketiga bilangan Reynolds dan menghasilkan pressure recovery coefficient (Cpr) yang paling tinggi pada ReDh = 1,98 x 105. Peningkatan bilangan Reynolds tidak memberikan pengaruh yang signifikan pada peningkatan nilai coefficient pressure (Cp) serta besarnya nilai loss coefficient (K) yang paling tinggi terletak pada ReDh = 5,85 x 105. Hasil eksperimen ini juga menunjukkan bahwa intensitas turbulensi di dalam diffuser tidak seragam. Pada sisi inlet diffuser intensitas turbulensi sebesar 0,49 % sedangkan pada sisi outlet diffuser intensitas turbulensi sebesar 1,36 %. =============================================================================================== Diffuser is a closed channel which has cross section enlargement along the flow direction. Diffuser cross section enlargement causes fluid flow to decrease speed, resulting in increased pressure flow. Increased pressure causes the occurrence of adverse pressure gradient (APG) that influences the development of the boundary layer. The greater the APG, the easier separation will occured. The occurrence of separation is one of the factors that affect decreasing pressure coefficient (Cp). Pressure coefficient (Cp) values become important parameters to be analyzed in the context of its application to the diffuser. Designing a good diffuser will generate maximum pressure recovery coefficient (Cpr). Therefore, research on the diffuser needs to be done. Experiment method is used in this research by means of closed circuit wind tunnel test. Diffuser used in this study was symmetric flat-walled octagonal diffuser which has a divergence angle (2θ) =8°. It has long diffuser geometry diffuser, L1 = 1500 mm, length upstream channel, L2 = 600 mm and the length of the downstream channel, L3 = 500 mm, width span inlet (b1) = 300 mm, width span outlet (b2) = 518,8 mm, and width of the span inlet fan (b3) = 500 mm and has a height of inlet diffuser (W1) = 300 mm, height diffuser outlet (W2) = 518,8 mm and height of fan inlet (W3) = 500 mm. In this experiment, three Reynolds viii Tugas Akhir Institut Teknologi Sepuluh Nopember number are used based on the hyd raulic diameter which are ReDh = 1,98x105, ReDh = 3,86x105 and ReDh = 5,85x105. The results obtained in this study is that the separation in three Reynolds numbers and its pressure recovery coefficient (Cpr) are highest in ReDh =1,98x105. An increase in the Reynolds number does not have a significant influence in increasing the value of pressure coefficient (Cp) and the value of the loss coefficient (K) which at its highest in ReDh = 5,85x105. The experimental result also shows that the intensity of the turbulence in the diffuser was not uniform, with inlet diffuser turbulence intensity 0,49% and outlet side diffuser turbulence intensity of 1.36%.

Item Type: Thesis (Undergraduate)
Additional Information: RSM 620.106 4 Pal s
Uncontrolled Keywords: symmetric flat-walled diffuser, pressure recovery coefficient, loss coefficient, closed circuit wind tunnel
Subjects: T Technology > TJ Mechanical engineering and machinery > TJ935 Pipe--Fluid dynamics.
Divisions: Faculty of Industrial Technology > Mechanical Engineering > 21201-(S1) Undergraduate Thesis
Depositing User: Mr. Marsudiyana -
Date Deposited: 12 Dec 2019 07:27
Last Modified: 12 Dec 2019 07:27
URI: http://repository.its.ac.id/id/eprint/72348

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