Akademik Veri Yönetim Sistemi
Tez Türü: Yüksek Lisans
Tezin Yürütüldüğü Kurum: Gazi Üniversitesi, Mühendislik Fakültesi, Makina Mühendisliği, Türkiye
Tez Danışmanı: Fatih Aktaş
Tezin Onay Tarihi: 2026
Tezin Dili: Türkçe
Özet:
In this thesis, the combustion and emission characteristics of a tri-fuel Reactivity Controlled Compression Ignition (RCCI) strategy employing hydrogen and methane alongside a diesel pilot in a heavy-duty engine were numerically investigated. A zero/one-dimensional (0/1-D) model developed in AVL CRUISE M provided initial boundary conditions, followed by three-dimensional CFD analyses performed with ANSYS Forte on a 1/8 sector model. Both models were validated against experimental data, with errors below 2% for performance parameters and 0.24% for maximum in-cylinder pressure. In the first stage, the effects of diesel pilot mass fractions of 5%, 10%, and 20% and injection timing on methane–diesel RCCI combustion were examined. Applying the diesel baseline injection timing directly in RCCI mode failed to sustain stable combustion; advancing to 710 °CA restored stability and increased indicated thermal efficiency from 7% to 30%. In the second stage, a parametric injection timing study over 706–716 °CA was conducted for the 5D-2.5H-92.5M and 10D-2.5H-87.5M compositions formed by adding 2.5% hydrogen by mass. At 706 °CA, the maximum pressure rise rate exceeded the knock threshold. The 710–712 °CA window was identified as the most balanced operating range, yielding 46–49% indicated thermal efficiency while offering the most favorable NOx and THC trade-off. Under early injection conditions, a three-stage heat release structure was observed, consisting of a cool flame, a diesel-ignited premixed combustion peak, and a methane-hydrogen main combustion peak. Contour analysis confirmed that NO formation is spatially correlated with the ~2500 K high-temperature zone, while CO and soot are concentrated in the locally rich regions near the diesel spray.