Analisis Numerik Performa dan Emisi Co-firing LNG-Hidrogen dengan Variasi Rasio Kompresi untuk Beberapa Fraksi Mol Hidrogen pada Diesel Gas Engine

Yoga Ady Samudra, Ir. Fauzun, S.T., M.T., Ph.D., IPM., ASEAN Eng.

2026 | Tesis | S2 Teknik Mesin

Transisi energi menuju sistem kelistrikan rendah karbon menuntut pembangkit berbasis gas untuk menurunkan emisi tanpa mengurangi keandalan. Pada PLTDG bermesin dual-fuel diesel gas, penerapan co-firing hidrogen dengan LNG menjadi opsi strategis karena berpotensi meningkatkan efisiensi pembakaran dan menurunkan emisi karbon. Penelitian ini bertujuan menganalisis secara numerik pengaruh rasio kompresi 11,5; 11,7; dan 11,9 serta fraksi hidrogen 0%, 7%, 10%, dan 15% terhadap performa dan emisi diesel gas engine skala pembangkit.

Metode yang digunakan adalah simulasi CFD tiga dimensi pada ruang bakar mesin Wartsila 18V50DF dengan domain sektor 1/8 silinder. Kondisi batas dan parameter operasi mengacu pada data PLTDG Pesanggaran. Model turbulensi RANS RNG k–? dikombinasikan dengan model pembakaran premixed–pilot ignited dan mekanisme reaksi multi-spesies untuk memprediksi tekanan silinder, temperatur, performa, serta komposisi gas buang. Studi parametrik dilakukan dengan mengubah fraksi H? dan rasio kompresi melalui variasi ketebalan shim plate.

Hasil validasi menunjukkan model layak digunakan, dengan rata-rata error Pmax 1,24%, NOx 4,42%, dan CO 13,29%. Peningkatan fraksi H? dan rasio kompresi mempercepat pembakaran serta meningkatkan performa, tetapi menaikkan tekanan lokal dan NOx. Kombinasi rasio kompresi 11,9 dengan 15% H? menghasilkan efisiensi tertinggi 52,64?n ISFC 150,13 g/kWh, namun tidak direkomendasikan karena Pmax lokal 144,59 bar melewati alarm knocking 140 bar. Kondisi optimal diperoleh pada kombinasi rasio kompresi 11,7 dengan 10% H?, dengan efisiensi 52,33%, daya indikasi 930,36 kW, IMEP 19,61 bar, ISFC 152,90 g/kWh, NOx 82,83 ppm, CO 161,41 ppm, CO? 4,920%, CH? slip 26,43 ppm, dan Pmax lokal 134,61 bar.

The energy transition toward low-carbon systems requires gas power plants to reduce emissions without compromising reliability. In dual-fuel power plants, hydrogen co-firing with LNG is a promising strategy for improved combustion efficiency and lower carbon emissions. This study numerically investigates compression ratios of 11.5, 11.7, and 11.9, with hydrogen fractions of 0%, 7%, 10%, and 15%, on the performance and emissions of a power-scale engine.

The method uses three-dimensional CFD simulation of a Wartsila 18V50DF combustion chamber modeled as a 1/8-cylinder sector. Boundary conditions and operating parameters were based on PLTDG Pesanggaran data. The RANS RNG k–? turbulence model was combined with a premixed–pilot ignited combustion model and a multi-species reaction mechanism to predict cylinder pressure, temperature, engine performance, and exhaust gas composition. A parametric study was then performed by varying the hydrogen fraction and compression ratio through shim plate thickness modification.

The validation results show that the model is acceptable, with average errors of 1.24% for Pmax, 4.42% for NOx, and 13.29% for CO. Increasing hydrogen fraction and compression ratio accelerated combustion and improved performance, but also increased local pressure and NOx emissions. The combination of a compression ratio of 11.9 with 15% H? achieved the highest thermal efficiency of 52.64% and ISFC of 150.13 g/kWh, but was not recommended because its local Pmax reached 144.59 bar, exceeding the 140 bar knocking alarm limit. The optimal operating condition was obtained at a compression ratio of 11.7 with 10% H?, producing 52.33% thermal efficiency, 930.36 kW indicated power, 19.61 bar IMEP, 152.90 g/kWh ISFC, 82.83 ppm NOx, 161.41 ppm CO, 4.920% CO?, 26.43 ppm CH? slip, and 134.61 bar local Pmax.

Kata Kunci : Co-firing LNG-H2, Diesel Gas Engine, CFD, Fraksi H2, Rasio Kompresi