CCRC Seminar - 17 November 2022

The talks are on:

Title: Active and Passive Pre-chamber Assisted Engine Combustion: Simultaneous 50 kHz Formaldehyde PLIF and OH* Visualization

Priybrat Sharma 

Ph.D. Student, supervised by Prof. Gaetano Magnotti

Abstract:  Pre-chamber-assisted internal combustion engines allow lean limit extension by replacing the spark plug with multiple, high-temperature, radical-rich jets that entrain and ignite the main chamber charge. This work reports active ultra-lean, passive, and active rich pre-chamber operation through cycle-resolved measurements. The experiments are simultaneous single-shot, 50 kHz cycle resolved formaldehyde planer laser-induced fluorescence (PLIF) and OH* imaging in a heavy-duty optical engine operating at 1200 rpm under active ultra-lean, rich, and passive conditions. The third harmonic of a burst mode laser (355 nm) provided the excitation source for formaldehyde PLIF, and a high-speed CMOS camera collected the fluorescence signal from the side window of the engine. Bottom-view imaging of OH* chemiluminescence was achieved using an intensified high-speed camera. The high-speed image sequence of the pre-chamber jet formaldehyde layer and OH* captured the main chamber heat release stages and the interaction between the moving piston and the pre-chamber jet. The prechamber-assisted combustion process in the main chamber exhibit three phases: initial jet, jet sustained combustion and jet un-sustained combustion. The second phase starts with the main chamber heat release following the piston pre-chamber jet interaction. At this stage, large eddies are formed that travel upstream and sustain the combustion by entraining fresh flammable mixture in the prechamber jet. The passive pre-chamber shows a different ignition process, starting with mostly formaldehyde radicle jet impinging on the piston and then flame growth towards both the prechamber and cylinder wall. The rich main chamber leads to a thin formaldehyde layer.

Bio: Priybrat Sharma is a Ph.D. candidate in the Mechanical Engineering Program at King Abdullah University of Science and Technology, supervised by Professor Gaetano Magnotti. He graduated with M.S. (by Research) from the Indian Institute of Technology Mandi, India, in 2017 while working as a Junior Research Fellow (JRF) for a Government of India (GOI) DST project on the synergetic application of hydrogen in an internal combustion engine. His Ph.D. research focuses on developing and implementing laser-based diagnostics techniques for reciprocating internal combustion engines. 

Title: Electric Fields in a Counterflow Nonpremixed Flame: Measurement and Simulation

Jin Park 

Ph.D. Student, supervised by Prof. Min Suk Cha

Abstract: In electric field modified flames, the electric body force on fluid elements can play a role in modifying the flow field, affecting flame characteristics by the altered bulk flow motion. Numerical studies have developed ion kinetic mechanisms and appropriate transport models for charged species, validating them with a voltage-current trend only in 1D premixed flames. Recent experimental approaches have measured the electric field by adopting the Electric Field Induced Second Harmonic generation (EFISH) technique. We present experimental results comparing numerical results on the electric field profile and flame structure with an inhouse multi-physics CFD (Computational Fluid Dynamics) code. Overall, the quantified electric fields agreed well with those from numerical simulation, specifically capturing null electric fields near the flame in the sub-saturated regime due to the electric field screening effect of electrons and ions produced in the flame. In the saturated regime, notable discrepancy was found in a fuel stream when electrons moved through it: experiment indicated a significant number of negative ions in the fuel stream, whereas numerical results predicted negligible negative ions, due to the implemented ion-mechanism. This suggested that the experimentally obtained electric fields may serve as validation data for modeling studies to improve transport models and ion-mechanism. In-situ measurement of charged species in the presence of external electric fields should be the work of the future. 

Bio: Jin Park obtained his BS and MS degree in Mechanical Engineering at Chungnam National University (South Korea). He joined the Plasma Assisted Combustion Laboratory at CCRC in 2019 as a PhD student. His current research focuses on the fundamental characteristics of plasma at atmospheric pressure and its formation mechanism. He is also interested in fuel reforming using plasma, laser diagnostics technics, and chemi-ionization mechanisms.

Event Quick Information

17 Nov, 2022
12:00 PM - 01:00 PM