Open Collections

Jaeger, Nicolas S. B.

University of British Columbia

Natural gas (NG) is a promising alternative to diesel fuel for industrial engine applications. NG can potentially reduce emissions of CO₂, NOₓ, SOₓ, and particulate matter when compared to diesel. NG is more cost effective than diesel and there is existing infrastructure that makes it a more feasible transitional fuel than other proposed alternatives. NG is comprised primarily of CH₄, which is a much more potent greenhouse gas than CO₂. If engine exhaust contains excessive quantities of CH₄, the potential environmental benefits of switching to NG cannot be realized. Diagnostic methods for characterizing CH₄ emissions in engine exhaust must, therefore, be implemented to develop informed emissions reduction strategies. This work presents a wavelength modulation spectroscopy (WMS) system that was developed to characterize CH₄ emissions from NG engines. WMS is a laser based absorption spectroscopy method that uses specialized signal generation and data processing techniques to provide accurate measurements. In this work a new on-line processing method is shown to provide continuous CH₄ measurements in near-real time, for up to three hours, while requiring less than 0.01% of the memory that was consumed by previous processing methods. Additionally, a more advanced data processing method is shown to make measurements more robust. Improved calibration strategies are then presented, including two simulation-based methods that are demonstrated to work in the temperature range 30-90◦C. The simulations are shown to model WMS signals across the instrument’s dynamic range to within 5.4% or 1.7%, respectively, when compared to physical WMS measurements that were validated with a Fourier transform infrared spectrometer. Finally, the WMS system’s ability to measure in-use CH₄ emissions is demonstrated on three NG engines, including two engines on cargo ferries operated by an industry partner. Measurements of steady-state CH₄ emissions from the marine engines were used to characterize emissions as functions of engine loads. In-use emissions were characterized in 10% load increments, providing superior resolution than regulatory standards in industry. Findings from this work have contributed to historical emissions data for these engines and have quantified the effects of various CH₄ reduction strategies.

Text

2023-07-14

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/85243

Mechanical Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/