Session: Technical Posters

Paper Number: 111707

111707 - Cfd Model Development for Highly Dilute Stoichiometric Heavy-Duty Natural Gas Engines 

Increasingly stringent emission regulations and continuously depleting fossil fuel resources have necessitated the development of engines with improved efficiency and low emission levels. One of the popular methods to achieve this is the use of lean air-fuel mixtures, which reduces the specific fuel consumption and lowers exhaust emissions. But lean fuel operation leads to reduced combustion stability due to lower flame speeds, resulting in misfires and increased unburned hydrocarbon (HC) emissions. Therefore, lean fuel operation requires enhanced high ignition-energy technologies like plasma ignition, laser-induced ignition or corona discharge-based spark ignition systems. Another promising technology that has the potential to achieve reliable lean burn operation is the turbulent jet ignition (TJI) which uses chemically active turbulent jets generated from combustion inside a prechamber to initiate combustion of the diluted mixture inside the main combustion chamber. The present work focusses on developing computational fluid dynamics (CFD) models of prechamber-assisted combustion for the stoichiometric operation of a heavy-duty internal combustion engine running on natural gas. The simulations were carried out using CONVERGE CFD software and the models were validated against the data generated from experiments on a single cylinder Cummins N-14 optical diesel engine that was modified to include an existing prechamber design. The pressure traces and the apparent heat release rate (AHRR) were the primary parameters considered for validation of the CFD models. Three different levels of mixture dilution were evaluated, and it was observed that the peak pressure and AHRR in the main combustion chamber reduces as the dilution level increases. It was also observed that the peak pressure inside the prechamber is similar for the different dilution levels considered, although the duration of prechamber combustion increases as the dilution level increases. With increased dilution, a larger delay in the initiation of pressure rise in the main chamber is observed, which is further augmented by quenching effects as the flame passes into the main chamber through the orifices. This quenching of the flame was accounted explicitly modelling the turbulence chemistry interactions available in CONVERGE v3.1 and it was found that the model provided satisfactory predictions of the pressure rise and AHRR for all the cases considered in the present work. This CFD model has been further used to evaluate the influence of parameters such as spark plug location and flow characteristics on flame development inside the prechamber.

Presenting Author: Arun Ravi Varma Carnegie Mellon University

Presenting Author Biography: Arun Ravi Varma is currently pursuing his PhD in Mechanical Engineering at Carnegie Mellon University under the esteemed supervision of Professor Satbir Singh. The primary focus of his research work involves the development of CFD models for accurate prediction of the combustion characteristics in highly dilute heavy-duty natural gas engines operating under stoichiometric conditions. Prior to his doctoral studies, Arun completed his MPhil degree in 2021 from Newcastle University, UK where his research work involved DNS of premixed combustion. Previously, Arun has also worked in the automotive industry in India as a CAE analyst from 2012 to 2019. During this period, he gained valuable experience in thermomechanical and NVH simulations using FEA and CFD. Driven by a passion for innovation and a commitment to advancing the field of IC engine combustion, Arun is dedicated towards contributing to the development of cleaner and more efficient combustion technologies.