CFD-Based Preliminary Combustion Analysis Of A Diesel-Like Piston Chamber

Nugroho, Yohanes Doniano Audi (2026) CFD-Based Preliminary Combustion Analysis Of A Diesel-Like Piston Chamber. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Studi Tugas akhir ini menyajikan analisis pembakaran awal berbasis Computational Fluid Dynamics (CFD) pada ruang piston diesel-like yang dikembangkan menggunakan model ANSYS Fluent yang disederhanakan. Tujuannya adalah membangun dan mengevaluasi alur kerja CFD yang bertahap dan terverifikasi sebelum beralih ke simulasi mesin diesel yang lebih realistis. Ruang dua dimensi planar berukuran 200 mm × 100 mm yang disederhanakan dimodelkan menggunakan solver transien berbasis tekanan, gerak piston dynamic mesh yang dikendalikan oleh User-Defined Function (UDF), injeksi bahan bakar n-heptane cair melalui Discrete Phase Model (DPM), penguapan droplet menjadi uap C7H16, transport spesies, serta reaksi pembakaran global satu langkah, C7H16 + 11 O2 → 7 CO2 + 8 H2O. Model disusun secara bertahap, dimulai dari verifikasi cold-flow, dilanjutkan dengan gerak piston, injeksi dan penguapan DPM, pengaturan pembakaran, penyesuaian chemistry solver, dan studi parametrik temperatur awal ruang. Hasil cold-flow dan dynamic mesh mereproduksi kenaikan tekanan dan temperatur yang diharapkan selama kompresi serta penurunannya selama ekspansi, sedangkan model DPM berhasil menghasilkan uap C7H16 melalui penguapan. Upaya reaksi awal belum menghasilkan produk yang jelas hingga chemistry solver diganti menjadi Relax to Chemical Equilibrium, yang kemudian memunculkan pembentukan CO2 dan H2O disertai konsumsi O2. Studi parametrik membandingkan temperatur awal 1000 K, 700 K, 500 K, dan 300 K dan menunjukkan pengaruh yang monoton: temperatur awal yang lebih tinggi menghasilkan konsumsi O2 yang lebih dalam (fraksi massa minimum dari sekitar 0,207 pada 300 K menjadi 0,175 pada 1000 K) serta pembentukan CO2 dan H2O yang lebih besar, sedangkan tekanan puncak menurun seiring kenaikan temperatur awal (sekitar 2,78 MPa pada 300 K menjadi 2,32 MPa pada 1000 K) karena tekanan puncak pada ruang tertutup ini didominasi oleh kompresi muatan awal. Karena geometri disederhanakan dan kimia mengandalkan relaksasi kesetimbangan, hasil diinterpretasikan secara kualitatif dan komparatif. Secara keseluruhan, penelitian ini menyediakan platform analisis pembakaran awal berbasis CFD yang menjadi fondasi bagi pengembangan simulasi pembakaran dan perpindahan panas mesin diesel yang lebih realistis.
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This This final project presents a Computational Fluid Dynamics (CFD)-based preliminary combustion analysis of a diesel-like piston chamber developed using a simplified ANSYS Fluent model. The objective is to build and evaluate a staged, verifiable CFD workflow before advancing toward a more realistic diesel engine simulation. A simplified 200 mm × 100 mm two-dimensional planar chamber was modeled using a pressure-based transient solver, dynamic-mesh piston motion driven by a User-Defined Function (UDF), liquid n-heptane fuel injection through the Discrete Phase Model (DPM), evaporation of the droplets into C7H16 vapor, species transport, and a one-step global combustion reaction, C7H16 + 11 O2 → 7 CO2 + 8 H2O. The model was constructed progressively, beginning with a cold-flow verification, followed by piston motion, DPM injection and evaporation, the combustion setup, the chemistry-solver adjustment, and an initial-chamber-temperature parametric study. The cold-flow and dynamic-mesh results reproduced the expected rise of pressure and temperature during compression and their decrease during expansion, while the DPM model successfully produced C7H16 vapor through evaporation. Early reacting attempts did not yield clear products until the chemistry solver was changed to Relax to Chemical Equilibrium, after which CO2 and H2O formation together with O2 consumption were observed. The parametric study compared initial temperatures of 1000 K, 700 K, 500 K, and 300 K and showed a monotonic effect: a higher initial temperature produced deeper O2 consumption (minimum mass fraction from about 0.207 at 300 K to 0.175 at 1000 K) and greater CO2 and H2O formation, whereas the peak pressure decreased with increasing initial temperature (about 2.78 MPa at 300 K to 2.32 MPa at 1000 K) because the pressure peak in this closed chamber is dominated by compression of the initial charge. Because the geometry is simplified and the chemistry relies on equilibrium relaxation, the results should be interpreted qualitatively and comparatively. Overall, this study provides a preliminary CFD combustion analysis platform that serves as a foundation for developing more realistic diesel engine combustion and heat-transfer simulations.

Item Type:	Thesis (Other)
Uncontrolled Keywords:	CFD, Discrete Phase Model, dynamic mesh, n-heptane, pembakaran diesel-like, diesel-like combustion
Subjects:	T Technology > TJ Mechanical engineering and machinery > TJ254.7 Combustion chambers T Technology > TJ Mechanical engineering and machinery > TJ797 Diesel motor--Fuel systems--Testing.
Divisions:	Faculty of Industrial Technology and Systems Engineering (INDSYS) > Mechanical Engineering > 21201-(S1) Undergraduate Thesis
Depositing User:	Yohanes Doniano Audi Nugroho
Date Deposited:	05 Aug 2026 07:22
Last Modified:	05 Aug 2026 07:22
URI:	http://repository.its.ac.id/id/eprint/144006

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