Karakteristik Pembakaran Dan Pembentukan Emisi Mesin diesel Dual Fuel Biodiesel Dan CNG

Yuvenda, Dori (2020) Karakteristik Pembakaran Dan Pembentukan Emisi Mesin diesel Dual Fuel Biodiesel Dan CNG. Doctoral thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Ketersediaan bahan bakar baru dan terbaru (EBT) seperti bahan bakar biodiesel crude palm oil (CPO) dan compressed natural gas (CNG) menjadi solusi dalam kelangkaan bahan bakar minyak fosil. Pemanfaatan bahan bakar biodiesel CPO dan CNG pada mesin diesel menggunakan teknologi sistem dual fuel yang telah terbukti dapat menurunkan konsumsi bahan bakar minyak fosil dan emisi nitrogen oxide (NOx), particulate matter (PM) dan juga carbon dioxide (CO2) yang merupakan sumber utama terjadinya global warming. Namun, mesin diesel dual fuel masih menemui permasalahan terkait dengan penurunan performa mesin dan peningkatan emisi hidrokarbon (HC) dan karbon monoksida (CO) dari mesin diesel standar. Penyebab utama adalah penurunan jumlah udara murni di dalam silinder karena sebagian udara digantikan oleh bahan bakar CNG yang diinjeksikan melalui saluran masuk, sehingga terjadi peningkatan kapasitas panas spesifik dari campuran bahan bakar CNG-udara dan penurunan tekanan parsial oksigen yang mengakibatkan terjadi penurunan tekanan dan temperatur pada akhir langkah kompresi dan ketika bahan bakar pematik (pilot) diinjeksikan maka kondisi flammability limit lebih lama tercapai sehingga periode ignition delay terlalu lama, maka awal pembakaran menjadi tertunda dan mengakibatkan pembakaran maksimum terjadi pada langkah ekspansi yang menghasilkan penurunan performa pembakaran seperti tekanan silinder, laju pelepasan panas dan peningkatan durasi pembakaran serta perlambatan pembentukan emisi. Penelitian ini dilakukan pengaturan secara komprehensif antara waktu injeksi CNG, durasi injeksi CNG, waktu injeksi pilot dan penambahan udara pembakaran sehingga proses pembakaran bisa optimal pada segala kondisi operasi mesin. Penelitian ini dilakukan pada mesin diesel dual fuel model injection port berbahan bakar biodiesel CPO (B100) dan CNG yang dilengkapi dengan sistem kontrol diesel dual fuel programmable yang dapat diprogram sesuai kondisi operasi mesin. Pengaturan waktu injeksi CNG (700-1500 ATDC dengan interval 200), durasi injeksi CNG (700-1500 CA dengan interval 200) dan waktu injeksi pilot (110-190 BTDC dengan interval 20) serta penambahan udara pembakaran menggunakan electrical supercharger (0,007074kg/s - 0,007836 kg/s). Kemudian juga, dilakukan optimasi multi respon menggunakan permodelan back propagation naural network (BPNN) dan genetic algorithm (GA) yang digunakan untuk menentukan pengaturan kombinasi parameter operasional yang dapat memaksimalkan performa mesin dan meminimalkan emisi gas buang. Hasil penelitian menunjukkan bahwa penggunaan bahan bakar biodiesel CPO sebagai pilot pada mesin diesel dual fuel dapat memperbaiki proses pembakaran dan penurunan emisi. Hal ini dikarenakan kandungan oksigen yang tinggi sehingga memperbaiki kualitas rasio udara dan bahan bakar dan tingginya nilai angka setana dapat menurunkan periode ignition delay sehingga mempercepat awal pembakaran pada mesin diesel dual fuel. Kemudian melalui pengaturan parameter operasional secara komprehensif dengan memundurkan waktu injeksi CNG (1100 ATDC) menghasilkan stratifikasi campuran udara-CNG yang lebih baik di dalam silinder sehingga pembakaran premix dari bahan bakar CNG meningkat yang menghasilkan kenaikan efisiensi termal hingga 2,82% dan penurunan emisi CO sampai 31,09%, dan pengkondisian jumlah CNG di dalam silinder melalui pengaturan durasi injeksi CNG (1100 CA) dapat meminimalisir kehilangan panas yang terlalu besar akibat penyerapan panas oleh bahan bakar CNG sehingga menghasilkan kenaikan efisiensi termal hingga 7,21% dan menurunkan emisi CO sampai 58,53%, dan kemudian memajukan waktu injeksi pilot (170 BTDC) dapat menyediakan waktu bercampur antara bahan bakar biodiesel CPO dengan campuran CNG-udara lebih lama sehingga campuran tersebut lebih homogen yang menghasilkan peningkatan jumlah titik-titik penyalaan dan tersebar luas di area ruang bakar sehingga laju pembakaran premix dari bahan bakar biodiesel CPO menjadi meningkat maka bahan bakar CNG lebih banyak terbakar yang ditandai dengan kenaikan efisiensi termal hingga 10,79% dan menurunkan emisi CO sampai 60,97%. Selanjutnya, dengan penambahan udara pembakaran (0,007836 kg/s) dapat memperbaiki rasio udara dan bahan bakar sehingga pembakaran menjadi sempurna yang menghasilkan peningkatan efisiensi termal hingga 12,49% dan menurunkan emisi CO sampai 61,58% pada kondisi beban mesin tinggi. Hal ini diketahui dari karakteristik pembakaran seperti peningkatan tekanan silinder hingga 15,66%, laju pelepasan panas hingga 7,84% dan penurunan ignition delay sampai 6,25% serta durasi pembakaran sampai 24,44% pada beban tinggi. Peningkatan proses pembakaran tersebut juga diikuti dengan peningkatan temperatur pembakaran yang mempercepat proses penguraian dan oksidasi bahan bakar yang berpotensi meningkatkan emisi CO2 dan NOx sehingga trennya bertolak belakang (tradeoff) dengan peningkatan performa mesin. Dengan kondisi tersebut metode optimasi prediksi BPNN-GA berperan dalam mendapatkan parameter optimal. Metode permodelan prediksi BPNN yang digunakan memiliki kinerja yang baik dalam memprediksi nilai performa mesin dan emisi yang dievaluasi dengan nilai mean square error (MSE) < 0,01 dan kemudian dilakukan optimasi multi respon dengan metode GA didapatkan kombinasi parameter operasional yang menghasilkan performa mesin dan emisi yang optimum yang dievaluasi dengan uji konfirmasi eksperimen. ============================================================================================================ The availability of new and renewable energy (NRE) such as crude palm oil (CPO) biodiesel and compressed natural gas (CNG) is a solution to the scarcity of fossil fuels. The use of CPO biodiesel and CNG fuels in diesel engine uses dual fuel system technology which has been proven to reduce fossil fuel consumption and emissions of nitrogen oxide (NOx), particulate matter (PM), and also carbon dioxide (CO2) which is the main source of occurrence global warming. However, diesel dual fuel engine still encounters problems related to reduced engine performance and increased hydrocarbon (HC) and carbon monoxide (CO) emissions from standard diesel engine. The main cause is a decrease in the amount of pure air in the cylinder because some of the air is replaced by CNG fuel which is injected through the intake manifold, resulting in an increase in the specific heat capacity of the CNG-air fuel mixture and a decrease in oxygen partial pressure which results in a decrease in pressure and temperature at the end of the compression stroke and when the pilot fuel is injected, the longer flammability limit is reached so that the ignition delay period is too long so the start of combustion is delayed and causes maximum combustion to occur in the expansion stroke which results in a decrease in combustion performance such as cylinder pressure, heat release rate and increased combustion duration as well as slowing down emissions formation. This research carried out a comprehensive arrangement between CNG injection timing, CNG injection duration, pilot injection timing, and the addition of combustion air so that the combustion process can be optimal in all engine operating conditions. This research was conducted on a diesel dual fuel engine with an injection port model fueled by CPO biodiesel (B100) and CNG which is equipped with a diesel dual fuel programmable control system that can be programmed according to engine operating conditions. Setting the CNG injection timing (700-1500 ATDC with 200 intervals), CNG injection duration (700-1500 CA with 200 intervals) and pilot injection timing (110-190 BTDC with intervals of 20) and addition of combustion air using an electrical supercharger (0.007074kg/s - 0.007836 kg/s). Then also, multi-response optimization is carried out using the backpropagation neural network (BPNN) modeling and genetic algorithm (GA) which are used to determine the combination of operational parameters that can maximize engine performances and minimize exhaust emissions. The results showed that the use of CPO biodiesel fuel as a pilot in a diesel dual fuel engine could improve the combustion process and reduce emissions. This is because the high oxygen content improves the quality of the air fuel ratio and the high cetane number value can reduce the ignition delay period so as to accelerate the start of combustion on a diesel dual fuel engine. Then through setting the operational parameters comprehensively by retarding the injection timing of CNG (1100 ATDC) results in better stratification of the air-CNG mixture in the cylinder so that the premix combustion of CNG fuel increases resulting in an increase in thermal efficiency of up to 2.82% and a reduction in CO emissions of up to 31.09%, and conditioning the amount of CNG in the cylinder through setting the injection duration of CNG (1100 CA) can minimize excessive heat loss due to heat absorption by CNG fuel resulting in an increase in thermal efficiency of up to 7.21% and lower CO emissions of up to 58.53%, and then advancing the pilot injection timing (170 BTDC) can provide longer mixing time between CPO biodiesel fuel and the CNG-air mixture so that the mixture is more homogeneous which results in an increase in the number of ignition kernel and is widespread in the combustion chamber area so that the premix combustion rate of CPO biodiesel fuel become increased so that the CNG fuel burns more, which is indicated by an increase in thermal efficiency of up to 10.79% and a decrease in CO emissions of up to 60.97%. Furthermore, with the addition of combustion air (0.007836 kg/s) can improve the air ratio and fuel so that combustion becomes complete which results in an increase in thermal efficiency of up to 12.49% and reduces CO emissions by up to 61.58% under high engine load conditions. This is known from the combustion characteristics such as an increase in cylinder pressure of up to 15.66%, heat release rate of up to 7.84%, and a decrease in ignition delay of up to 6.25% and combustion duration of up to 24.44% under high load. The increase in the combustion process is also followed by an increase in combustion temperature which accelerates the decomposition of fuel and oxidation process which has the potential to increase CO2 and NOx emissions so that the trend is a tradeoff condition with increased engine performance. Under these conditions, the BPNN-GA prediction optimization method plays a role in obtaining the optimal parameters. The BPNN prediction modeling method used has a good performance in predicting the value of engine performances and emissions which are evaluated with a mean square error (MSE) < 0.01 and then a multi-response optimization is carried out using the GA method to obtain a combination of operational parameters that results in optimum engine performance and emissions which was evaluated by an experimental confirmation test.

Item Type: Thesis (Doctoral)
Uncontrolled Keywords: diesel dual fuel, biodiesel CPO, performa mesin, emisi, waktu injeksi CNG, durasi injeksi CNG, waktu injeksi pilot, udara pembakaran, BPNN, GA =================================================================================================== diesel dual fuel, CPO biodiesel, engine performances, emissions, CNG injection timing, CNG injection duration, pilot injection timing, combustion air, BPNN, GA
Subjects: T Technology > TJ Mechanical engineering and machinery > TJ324.5 Fuel systems
T Technology > TL Motor vehicles. Aeronautics. Astronautics > TL229.D5 Diesel automobiles
Divisions: Faculty of Industrial Technology > Mechanical Engineering > 21001-(S3) PhD Thesis
Depositing User: Dori Yuvenda
Date Deposited: 11 Sep 2020 05:21
Last Modified: 11 Sep 2020 05:21
URI: https://repository.its.ac.id/id/eprint/81866

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