Studi Eksperimental Pengaruh Variasi Waktu Injeksi Pilot pada Mesin Diesel Dual Fuel Berbahan Bakar Biodiesel-CNG terhadap Proses Pembakaran dan Pembentukan Emisi

Trihatmojo, Ahmad Arbi (2019) Studi Eksperimental Pengaruh Variasi Waktu Injeksi Pilot pada Mesin Diesel Dual Fuel Berbahan Bakar Biodiesel-CNG terhadap Proses Pembakaran dan Pembentukan Emisi. Masters thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Biodiesel dan CNG (compressed natural gas) merupakan salah satu bahan bakar alternatif yang dapat digunakan pada mesin diesel dual fuel. Pada penelitian ini, bahan bakar biodiesel digunakan sebagai pilot pembakaran, dan CNG digunakan sebagai bahan bakar substitusi yang diinjeksikan ke dalam intake manifold. Pada mesin diesel dual fuel, waktu injeksi pilot memiliki peran penting dalam mengontrol awal proses pembakaran. Hal tersebut dikarenakan ignition delay pada mesin diesel dual fuel lebih lama dibandingkan dengan mesin diesel single fuel. Selain itu, untuk mempertahankan puncak tekanan silinder berada pada rentang 10 – 15 °CA ATDC, perlu dilakukan pengaturan waktu injeksi pilot, sehingga performa mesin tetap optimal dan emisi gas buang yang dihasilkan lebih rendah. Penelitian ini bertujuan untuk mengkaji proses pembakaran dan pembentukan emisi dengan melakukan variasi waktu injeksi pilot pada mesin diesel dual fuel berbahan bakar biodiesel-CNG. Proses eksperimen dilakukan dengan cara mengganti paking pompa bahan bakar pilot sesuai dengan waktu injeksi yang digunakan. Untuk pengujian mode single fuel menggunakan waktu injeksi standar yaitu 13 ºCA BTDC, dan untuk mode dual fuel menggunakan lima variasi waktu injeksi pilot, yaitu 11, 13, 15, 17, dan 19 ºCA BTDC. Bahan bakar CNG diinjeksikan pada 110 ºCA ATDC, dan durasi injeksi CNG 70 ºCA pada beban rendah, 90 ºCA pada beban menengah, dan 110 ºCA pada beban tinggi. Mesin dioperasikan pada putaran konstan 2000 rpm dan diberi beban 1000 – 4000 Watt dengan interval 500 Watt. Pada setiap variasi waktu injeksi pilot tersebut akan diukur beberapa parameter eksperimen, seperti tekanan silinder dan laju pelepasan panas yang diukur menggunakan combustion analyzer, serta emisi gas buang seperti CO, HC, dan Smoke yang diukur menggunakan gas analyzer dan smoke meter. Selain itu juga dilakukan proses penghitungan untuk memperoleh data unjuk kerja mesin seperti daya, torsi, bmep, sfc, thermal efficiency, air fuel ratio, dan persentase substitusi CNG. Data yang diperoleh dari proses pengukuran dan penghitungan tersebut dianalisis dan disajikan dalam bentuk grafik untuk setiap parameter eksperimen. Hasil analisis data menunjukkan bahwa, dengan memajukan waktu injeksi pilot pada mode dual fuel dapat meningkatkan tekanan silinder sebesar 24,15% dan puncak tekanan silinder berada pada rentang 10 – 17 °CA ATDC. Pada beban tinggi, mode dual fuel dengan waktu injeksi pilot standar menghasilkan puncak tekanan silinder dan puncak laju pelepasan panas lebih tinggi dibandingkan dengan mode single fuel. Secara keseluruhan, thermal efficiency mode dual fuel lebih rendah dibandingkan dengan mode single fuel. Untuk semua kondisi operasi mesin, thermal efficiency dan persentase substitusi CNG tertinggi dihasilkan pada waktu injeksi pilot 17 °CA BTDC. Dalam aspek emisi gas buang, mode dual fuel dengan waktu injeksi pilot 17 °CA BTDC menghasilkan emisi smoke 26,41% dan emisi HC 14,52% lebih rendah dibandingkan dengan variasi waktu injeksi pilot standar. Namun pada beban tinggi, emisi CO terendah diperoleh pada waktu injeksi pilot 19 °CA BTDC.
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Biodiesel and CNG (compressed natural gas) are alternative fuels that can be used in dual-fuel diesel engine. In this study, biodiesel was used as combustion pilot, and CNG was used as substitution fuel which injected into the intake manifold. In dual-fuel diesel engine, pilot injection timing has an important role in controlling the initial combustion process. It is caused by ignition delay of dual-fuel diesel engine longer than single-fuel diesel engine. Furthermore, in order to maintain the peak of cylinder pressure in the range of 10 – 15 °CA ATDC, it is necessary to adjust pilot injection timing, so that engine performance remains optimum and produces low exhaust emissions. Therefore, this study aims to examine the combustion process and emission formation with varying the pilot injection timing on dual-fuel diesel engine using biodiesel-CNG. The experimental process was carried out by replacing the gasket of pilot fuel pump according to the injection time used. Single fuel mode used standard injection timing 13 ºCA BTDC, and dual fuel mode used five variations of pilot injection timing, namely 11, 13, 15, 17, and 19 ºCA BTDC. CNG was injected at 110 ºCA ATDC, and CNG injection duration was 70 ºCA at low load, 90 ºCA at medium load, as well as the 110 ºCA at high load. Engine was operated at constant speed of 2000 rpm and was given series of load of 1000 - 4000 Watt with an interval of 500 Watt. In each variation of pilot injection timing was measured by several experimental parameters, such as cylinder pressure and heat release rate which measured by combustion analyzer, as well as the exhaust emissions such as CO, HC, and Smoke measured by gas analyzer and smoke meter. In addition, calculation process was also made to obtain engine performance data such as power, torque, bmep, sfc, thermal efficiency, air fuel ratio, and percentage of CNG substitution. Data obtained from measurement and calculation process was analyzed and presented in graph for each experimental parameter. The results of data analysis show that with advanced pilot injection timing in dual fuel mode can increase cylinder pressure 24.15% and the peak of cylinder pressure in the range of 10 – 17 °CA ATDC. At high load, dual fuel mode with standard pilot injection timing produces the peak of cylinder pressure and the peak of heat release rate greater than single fuel mode. Overall, thermal efficiency of dual fuel mode is lower than single fuel mode. For all engine operating conditions, the highest thermal efficiency and CNG substitution rate was produced at pilot injection timing 17 °CA BTDC. In the aspect of exhaust emissions, dual fuel mode with pilot injection timing 17 °CA BTDC produces Smoke emission 26.41% and HC emission 14.52% lower than standard pilot injection timing. However at high load, the lowest CO emission was obtained by pilot injection timing 19 °CA BTDC.

Item Type:	Thesis (Masters)
Uncontrolled Keywords:	pilot injection timing, diesel dual fuel, biodiesel-CNG, combustion process, emission formation.
Subjects:	T Technology > TJ Mechanical engineering and machinery > TJ324.5 Fuel systems T Technology > TJ Mechanical engineering and machinery > TJ799 Diesel motor--Electronic control.
Divisions:	Faculty of Industrial Technology > Mechanical Engineering > 21101-(S2) Master Thesis
Depositing User:	Ahmad Arbi Trihatmojo
Date Deposited:	21 Jul 2026 08:31
Last Modified:	21 Jul 2026 08:31
URI:	http://repository.its.ac.id/id/eprint/67948

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