On-Line Mass Spectrometric Characterization of Hydrocarbons in Engine Exhaust Gases

Abstract

+ass spectrometryprovides a powerful and versatile method for the characterization of the unburnt and also theqyolyse&and partially oxidized gaseous hydrocarbon species present in exhaust gases. Flame ionization detection, the usual analysis meth6d for measuring exhaust hydrocarhons, can give only a total hydrocarbonfigure when used on-line. A mass spectrometer can perform the on-line characterization of the individual gaseous hydrocarbon species in the exhaust and can detect any trends in their concentrations. This permits the rapid assessment of experimental approaches for reducing these pollutants. In the present work exhaust gases have been sampled from the exhaust of a Ricardo E6 research engine pass to the analysis equipment via heated sample lines. The gases can be analysed as discrete samples spectrometry (GC-MS) in order to identify the components, or can be continuously monitored by ma order to measure any trends in the component concentrations. These mass spectrometric analysis techniques have been compayd with other ga$ analysis and general data acquisition methods, and have permitted the collection of much information about enginqexhaust emissionbThis information has been related to engine operating parameters with special reference to the,fuel-air ratio.The results from this work show that not only does the combustion result in an increase in the relative amounts of NO and CO, , but also suggest that the gubstituted aromatic hydrocarbon$way be products of combustion. Continuous monitoring of specijied exhaust components has been performed mass spectrometrically and related to the air-fuel ratio used for the engine. With lean fuels, the hydrocarbons are not totally combusled, but those that are burnt are combusted with reasonable eficiency. On the other hand, rich mixtures are associated with not only ineficient combustion, but also incomplete oxidation (that is CO-CO, ratio is increased), and an increase in the substituted aromatic hydrocarbons.@toichiometric)mixtures have been found to be associated with most eflcient combustion (highest C0,-CO ratio) and minimal hydrocbrbon emissions.

On-Line Mass Spectrometry: A Faster Route to Process Monitoring and Control

“…92 Another important class of examples is the analysis of engine exhaust for real-time monitoring of the effects of varying engine parameters (like the fuelto-air ratio). A wide range of emissions can be monitored, including unburnt fuel, pyrolyzed or partially oxidized hydrocarbons, 93 and sulfur-containing species (for which some selectivity can be achieved using a xenon chemical ionization source 34 ). These are extremely complex systems, in many cases requiring a concurrent chromatographic separation step (e.g., ref 94).…”