Perubahan Preheat Zone Thickness dan Bilangan Karlovitz pada Fenomena Flame lift-up Pembakaran Premix Gas Propana

I Made Kartika Dhiputra, Bambang Sugiarto, Yulianto S. Nugroho, Cokorda Prapti Mahandari




Abstract


It has been found a phenomenon of flame lift-up on the experiment employing a Bunsen burner. Flame lift-up is the occurrence of flame jumping from the tip burner to the ring that inserting above the burner. Fundamental research on flames did not elaborate the cause of flame jumping. Using flame stretch approach, an initial research on dimensionless number to predict the occasion of this phenomenon was discussed to determine preheat zone thickness and Karlovitz number. Preheat zone thickness was calculated based on temperature distribution of flame axes. Karlovitz number was determined from preheat zone thickness, burning velocity and stretch rate. The occurrence of flame lift-up was less then a second. Therefore the two parameters will be evaluated on two different conditions which are just before and just after lift-up happened. It was found that after lift-up, preheat zone thickness and burning velocity decreased. Karlovitz number just before and after lift-up occurred is about 2.5. This number can be considered as the initial prediction that flame lift-up will be appeared on Karlovitz number 2.5.


Abstract in Bahasa Indonesia:

Fenomena lompatan nyala api atau flame lift-up ditemukan pada penelitian menggunakan burner Bunsen. Flame lift-up adalah kejadian melompatnya nyala dari ujung burner ke ring yang berada di atas ujung burner. Penelitian dasar tentang nyala api belum banyak membahas penyebab melompatnya nyala api. Dengan pendekatan konsep regangan nyala, kajian awal untuk menentukan bilangan tanpa dimensi penyebab munculnya fenomena ini dibahas dengan menentukan perubahan preheat zone thickness kemudian Bilangan Karlovitz. Preheat zone thickness ditentukan berdasarkan gradien maksimum dari distribusi temperatur pada sumbu nyala. Sedangkan Bilangan Karlovitz dihitung berdasarkan preheat zone thickness, kecepatan nyala dan laju regangan nyala. Peristiwa melompatnya nyala api yang hanya sesaat dianalisis dengan membandingkan kedua parameter pada dua kondisi yakni sesaat sebelum lift-up dan sesaat setelah terjadinya lift-up. Hasil penelitian menunjukkan bahwa ketebalan daerah pemanasan awal dan kecepatan nyala laminar setelah lift-up menurun sedangkan Bilangan Karlovitz sebelum dan setelah lift-up cenderung tetap yakni sekitar 2.5. Nilai ini dapat dijadikan prediksi awal bahwa lompatan nyala api akan terjadi pada Bilangan Karlovitz 2.5.

Kata kunci: Lift-up, preheat zone thickness, karlovitz number.


Keywords


Lift-up, preheat zone thickness, karlovitz number

Full Text: PDF

The Journal is published by The Institute of Research & Community Outreach - Petra Christian University. It available online supported by Directorate General of Higher Education - Ministry of National Education - Republic of Indonesia.

©All right reserved 2016.Jurnal Teknik Mesin, ISSN: 1410-9867

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