Kerosene adalah satu bahan api penerbangan yang digunakan secara global.Walau bagaimanapun, masalah pemanasan global dan kekurangan sumber bahan api fosil telah meningkatkan kesedaran terhadap sumber tenaga yang baru, mesra alam sekitar dan mudah diperolehi. Biodiesel adalah salah satu bahan api yang boleh diperbaharui dan mempunyai beberapa kelebihan kepada alam sekitar.Penggunaan biodiesel dapat mengurangkan gas pencemaran seperti hidrokarbon (HC) dan pelepasan karbon monoksida (CO). Justeru itu, kajian ini dijalankan untuk mengkaji sifat-sifat kerosene dan biodiesel yang dicampur mengikut peratusan yang berbeza-beza. Kajian ini mengkaji kesan campuran biodiesel dan kerosene tersebut terhadap panjang nyalaan api, taburan suhu nyalaan dan prestasi dalam enjin kapal terbang berkipas.
Sampel utama bahan api yang diuji adalah kerosene (JP-4) dan B100 biodiesel (Minyak Palm) dan nisbah campuran yang berbeza untuk kedua-dua bahan api. Dalam kajian ini analisis dibahagikan kepada tiga bahagian. Bahagian pertama merangkumi kajian sifat-sifat bahan api. Bahagian kedua mengkaji taburan suhu dalam enjin untuk tiga nisbah udara kepada bahan api. Bahagian ketiga menguji bahan api tersebut dalam enjin turbofan dengan menggunakan simulasi Gas Turbine Program untuk mengkaji prestasi bahan api dalam enjin kapal terbang berkipas dan penghasilan NOX dan CO.
Dalam keputusan bahagian pertama, biodiesel didapati kelikatan kinematik, ketumpatan dan tahap meledak yang tertinggi dalam semua sampel bahan api. Peningkatan dalam peratusan biodiesel dalam kerosene meningkatkan sifat-sifat tersebut. Untuk ujian nilai keletupan bahan api, biodiesel mempunya nilai yang terendah manakala kerosene merupakan yang tertinggi. Peningkatan dalam peratusan biodiesel dalam kerosene menurunkan nilai tersebut. Dalam hasil analisa berkomputer CFD, biodiesel mempunyai perambatan api yang terpanjang dalam ketiga-tiga nisbah manakala kerosene mempunyai yang paling pendik. Peningkatan dalam peratusan biodiesel dalam kerosene memanjangkan perambatan apai.
Akhir sekali, dalam bahagian ketiga analisis GSP biodiesel mempunyai suhu pembakaran terendah dalam enjin turbofan manakala kerosene merupakan yang tertinggi. Pelepasan gas NOX adalah terendah di kalangan semua campuran bahan api manakala kerosene adalah yang tertinggi. Ini adalah kerana kerosene mempunyai nilai keletupan yang tertinggi. Semakin tinggi nilai keletupan tersebut, lebih banyak gas NOX pelepasan tetapi kekurangan gas CO dan gas kabut pelepasan.
Beberapa cadangan dapat disyorkan untuk memperbaiki kajian ini. Titisan trajektori dan pengagihan saiz titisan campuran biodiesel dan kerosene dapat dikajikan kerana faktor ini adalah penting kerana ia akan menentukan kadar penyejatan dan pembentukan gas CO. Selain itu, panjang nyalaan api dan taburan suhu nyalaan campuran biodiesel dan kerosene dapat dikaji secara eksperimen dengan menggunakan C492 Combustion Laboratory Unit untuk mengesahkan keputusan simulasi.
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Kerosene fuel is an aviation fuel globally used. In the early years, kerosene was the largest selling and most important products in petroleum industry. However, global warming problem and lack of fossil fuel resources have increased the demand of new sources of energy, which should be renewable, environmental friendly and locally available. Biodiesel is one of renewable fuel which provides several advantages to the environmental. Use of biodiesel lead to reduction of gas pollutants such as hydrocarbon (HC) and carbon monoxide (CO) emissions. This research reviews the fuel properties of different mixture of kerosene fuel and biodiesel to study their effect on flame propagation, temperature distribution and performance inside a turbofan engine.
The main sample of fuels tested are kerosene (JP-4) and biodiesel B100 (Palm Oil) and will be blended into several composition: 100% Biodiesel (100%BD), 20% Kerosene-80% Biodiesel (20%KE 80% BD), 40% Kerosene-60% Biodiesel (40%KE 60%BD), 60% Kerosene-40% Biodiesel (60%KE 40%BD), 80% Kerosene-20% Biodiesel (80%KE 20%BD), 100% Kerosene (100%KE). This study is conducted into three sections. Firstly, the thermo-chemical properties of the fuel mixtures are tested. Secondly, the flame propagation and temperature distribution of the fuel mixtures are analysed for three different air to fuel ratio which are stoichiometric, lean and rich through Computational Fluid Dynamics software. Finally, the fuel mixtures are analysed in a
turbofan engine using Gas Turbine Simulation Program to determine the engine performance and the generation of NOX and CO.
Results obtained from the thermo-chemical properties test showed that biodiesel is found to have the highest kinematic viscosity, flash point and density while kerosene is the lowest. Increasing percentage of biodiesel in kerosene increased these properties. However for heating value test, biodiesel is the lowest while kerosene is the highest. In comparison to kerosene, longer chain length, oxygen content and unsaturated acid content in the biodiesel are the main reason associated to the lower heating value. The evaluation of flame propagation shows that biodiesel has the longest flame propagation in all three difference air to fuel ratio while kerosene shows the shortest. Increasing percentage of biodiesel in kerosene prolong the flame propagation. Viscosity is found to be the main factor influences the flame propagation. As biodiesel has the higher viscosity, the flame propagation of the fuel is the longest compared to kerosene and other fuel mixtures. Finally, from GSP analysis, biodiesel is found to have the lowest combustion temperature while kerosene has the highest combustion temperature. NOX emissions of biodiesel is lowest among all fuel mixtures while kerosene is the highest due to its highest caloric value. The higher the caloric value, higher combustion temperature generated thus the more NOX emissions but the lesser CO.
Several recommendations are recommended in order to improve this study. The effect of caloric value in CFD analysis can be analysed by setting same mass flow rate for all fuel mixtures. To further analyse the effect of fuel properties on the combustion characteristics, fuel droplets trajectory and distribution of droplets size of fuel mixtures in the combustion chamber is essential as it will determine evaporation rate and CO
formation. Additionally, the flame propagation studied in this work can be visually explained through experiment work using C492 Combustion Laboratory Unit to further validate the CFD simulation.
Study on the effect of biodiesel-kerosene mixture on flame propagation, flame temperature distribution and aircraft engine performance / Ng Wei Xuan