Mechanical Engineering Ph.D. Dissertation

Abstract

Escalated pollutant emissions and dwindling natural resources put the most apparent combustion systems, i.e., internal combustion (IC) engines, under significant social pressure and governmental regulations. Research on combustion systems continues to improve the efficiency of energy conversion. The impending major upgrades of combustion engines to improve energy conversion efficiencies are higher operating pressure, lean-burn, and homogenous combustion (spatially distributed ignition). The work explores prechamber-assisted combustion (PCC) technology, reportedly capable of enabling significant upgrades for closed-cycle combustion systems simultaneously.

PCC enhances conventional ignition sources (glow plugs, spark plugs, microwaves, and laser igniters) by encapsulating them inside a small volume. This volume is maintained at thermochemical and fluid dynamic conditions suitable for combustion initiation using these ignition sources. This combustion within the confined space cascades to ignite the main chamber combustible mixture under harsher conditions (lean/high pressure). The interaction of the PCC combustion with the mixture to ignite happens through a nozzle with or without offices. The understanding of the aerothermochemistry of PCC igniter remains segmented. The work relies on a methane/ methanol fueled optical IC engine ignited using an active spark-assisted narrow-throat PCC and optical PCC to study the dynamics.

The primary objective of the work is to develop and implement laser diagnostic methods suitable to study PCC combustion physics (mixing, quenching, and velocity) in its various configurations. Classically, 10 Hz IC engine laser diagnostics provide single snapshot images of the transient combustion process lasting 3 to 10 msec in one revolution. These methods are unable to time resolve the combustion process. The difficult optical access to confined combustion chambers leads to additional laser light delivery and imaging challenges. The work relies on advancements in lasers and scientific imaging to explore the thermochemistry and gas dynamics of the prechamber with high spatiotemporal resolution.

Bio

Priybrat Sharma is a Ph.D. candidate in the Mechanical Engineering Program, in PSE division under the supervision of Prof. Gaetano Magnotti. His Ph.D. research is centered on planar laser induced fluorescence and scatting techniques to study gas dynamics and thermochemistry of prechamber-assisted combustion.