No abstract

Penggunaan bahan bakar alternatif selalu berkaitan dengan dua masalah global, yaitu meningkatnya penggunaan minyak mentah dan cadangan minyak yang semakin menurun. Disamping itu, sumber energi alternatif menjadi topik yang menarik untuk terus dikaji. Indonesia adalah salah satu negara penghasil minyak kelapa sawit terbesar di dunia dengan nilai produksi mencapai 51,8 juta ton pada tahun 2019. Salah satu sumber energi alternatif yang dapat diolah dari minyak sawit adalah biodiesel. Biodiesel dapat digunakan secara langsung sebagai bahan bakar untuk mesin diesel. Tetapi biodiesel memiliki karakteristik yang berbeda dengan solar sehingga akan mempengaruhi unjuk kerja dan hal lainnya pada mesin. Oleh karena itu, penelitian ini akan menentukan pengaruh penggunaan biodiesel terhadap unjuk kerja mesin yang mencakup daya mesin, torsi, konsumsi bahan bakar spesifik (SFC), dan efisiensi termal. Bahan bakar yang digunakan adalah B100 (100% biodiesel minyak sawit) dan bahan bakar B20 (20% biodiesel minyak sawit + 80% solar) sebagai pembandingnya. Pengujian dilakukan selama 300 jam operasi, dengan beban konstan berupa lampu halogen sebesar 4 kW. Menurut hasil penelitian, mesin berbahan bakar B100 menghasilkan daya, torsi, dan efisiensi termal yang lebih rendah masing-masing sebesar 2,17%; 0,76%; dan 1,25% serta menghasilkan SFC yang lebih tinggi sebesar 14,61% bila dibandingkan dengan mesin berbahan bakar B20. Hal tersebut dikarenakan karakteristik bahan bakar B100 yang memiliki nilai kalor lebih rendah dan viskositas serta densitas lebih tinggi dibandingkan bahan bakar B20.

No abstract

LPG-air mixture enriched with oxygen is usually used for generating heat in industry sector. However, it is possible that LPG-oxygen will mix and react independently and the mixture could generate detonation wave. This condition could harm people, environment, and piping system, thus detonation quenching to guarantee safety becomes very important. The present study aims to investigate the characteristics of the detonation wave after propagating through the porous media model. The experiments used a detonation test tube with 50 mm of inner diameter and 6 m of total length. The test tube consists of two sections, 1 m long driver section and 5 m long driven section. The driver section and driven section are separated by Mylar film to prevent mixing between driver gas and driven gas, which consists of different gas mixture with different pressure. The driver section contained a stoichiometric H2-O2 mixture at constant initial pressure, which function as a direct initiator for detonation in the driven section. Besides, the driven section contained a stoichiometric mixture of LPG-oxygen and LPG-air at the initial pressure varied from 20 kPa to 100 kPa with an interval of 10 kPa. The stainless-steel porous media with masses of 15 g and 20 g were inserted in a cylindrical case which had been perforated with small holes on its cross-sectional surface to enable detonation wave to propagate through it. The observation of detonation wave propagation was conducted at upstream and downstream of the model. Two mechanisms of detonation wave propagation were observed in the downstream of the porous media model for combustion of the LPG-oxygen mixture; they are detonation re-initiation and detonation transmission. However, the LPG-air mixture could not generate a detonation wave. Additionally, the 5 g increments of the stainless-steel porous media mass only significantly increase the re-initiation distance of detonation (Dri) for mixture with low initial pressure, 20 kPa up to 50 kPa and did not significantly influence re-initiation distance of detonation for mixture with a high initial pressure of 60 kPa to 100 kPa.