Towards in-cylinder chemical species tomography on large-bore IC engines with pre-chamber

Abstract

A feasibility study is presented and the achieved key design milestones towards the first application of Chemical Species Tomography by Near-IR Absorption Tomography on a heavy duty, large-bore marine engine to visualise relative mixture strength are described. The engine is equipped with pre-chamber ignition and operates using Liquefied Natural Gas with > 88.9 % methane content. Operation of the engine under maximum-load conditions is a key design requirement, with peak cylinder pressure and mean temperature exceeding 127,510 Torr (170 bar) and 850 K respectively. The near-IR spectroscopic behaviour of methane is examined for suitable absorption and reference regions for the above application. In particular, the spectroscopic absorption around the 2ν3 transition region near 1,666 nm is approximated by simulation using data from the HITRAN database under worst-case conditions. The simulation results are compared with methane spectra experimentally acquired at high temperature and ambient pressure. Interference from other chemical species as well as measurement linearity is also investigated. A 31-laser beam tomographic imaging array is proposed, which has been optimised to achieve higher spatial resolution performance in the vicinity of the pre-chamber’s orifices. To enable optical access, a novel, minimally-intrusive method is presented, utilising standard fibreoptics and collimator

Laser absorption spectroscopy for combustion diagnosis in reactive flows: A review

“…parallel (58,144,161,163,167) and fan-shaped (150,164,168,169) beam arrangements, the measurement space should be sampled evenly in spatial and angular dimensions to achieve the best image reconstruction results. Subject to the limits imposed by the physical size of the collimators and detectors, regular beam arrangements are often impractical in particular applications such as a multi-cylinder engine and a gas turbine engine (31,170). To visualize the properties of any beam geometry, Terzija et al first introduced sinogram space with one linear variable, s, and one angular variable, u (162).…”

“…This gives rise to a significant superiority of LAS that the sensor can be embedded in practical combustors with minimal intrusions. Therefore, LAS is most promising to be applied to the combustion diagnosis of steel engines in the practical operating conditions (31).…”

Optical Access Schemes for High Speed and Spatial Resolution Optical Absorption Tomography in Energy Engineering

“…The in-cylinder imaging technology was extended to image methane in marine engines [8]. Two beam array designs were proposed: a 26-beam regular array to image the entire cylinder cross-section and a 31-beam irregular array to specifically target the exit orifices of the engine's pre-chamber.…”

Spray Combustion Analysis of Humins

“…Recent research in large bore two-stroke diesel engines focusses on the in-cylinder processes. Various setups are deployed to visualize spray and combustion progress, including constant volume chambers [51][52][53][54][55] and optical accessible engines [56][57][58].…”