Abstract
Ammonia is a toxic exhaust component emitted from internal combustion engines. Both pure ammonia and the products of its reaction with nitrogen and sulfur compounds, being the source of particulate matter (PM) emissions, are dangerous for human health and life. The aim of the article was to demonstrate that NH3 can be produced in exhaust gas after-treatment systems of spark-ignition (SI) engines used in light-duty vehicles. In some cases, NH3 occurs in high enough concentrations that can be harmful and dangerous. It would be reasonable to collect research data regarding this problem and consider the advisability of limiting these pollutant emissions in future regulations. The article presents the results of the spark-ignition engine testing on an engine test bench and discusses the impact of the air–fuel ratio regulation and some engine operating parameters on the concentration of NH3. It has been proven that in certain engine operating conditions and a combination of circumstances like the three-way catalytic reactor (TWC) temperature and periodic enrichment of the air–fuel mixture may lead to excessive NH3 emissions resulting from the NO conversion in the catalytic reactor. This is a clear disadvantage due to the lack of limitation of these pollutant emissions by the relevant type-approval regulations. This article should be a contribution to discussion among emissions researchers whether future emission regulations (e.g., Euro 7 or Euro VII) should include a provision to reduce NH3 emissions from all vehicles.
Highlights
Ammonia is a toxic substance classified by international regulations [1]
The aim of the testing was to determine the influence of selected engine parameters on NH3 emissions
Euro VI requirements for all limited exhaust gas components (CO, NOx, NMHC, particulate matter (PM), and particulate number emissions (PN)) in each tested variant, but its NH3 emission was clearly dependent on the air–fuel regulation and the three-way catalytic reactor (TWC) used
Summary
Ammonia is a toxic substance classified by international regulations [1]. US regulations allow for the NH3 concentration limit of 25 ppm during 8-h human exposure [2].NH3 is not a product forming itself inside the engine combustion chamber during the combustion process. Ammonia is a toxic substance classified by international regulations [1]. US regulations allow for the NH3 concentration limit of 25 ppm during 8-h human exposure [2]. In spark ignition (SI) engines, NH3 is formed in exhaust after-treatment systems during NO conversion in the presence of CO. NH3 may react with the acids contained in the exhaust gas, forming particulate matter (PM) and harmful aerosols. Ammonia causes more serious harm due to the toxicity to organisms living in water [3]. Regulation No 595/2009 for the value of NH3 concentration in Euro VI has set 10 ppm as the limit for NH3 concentration in the exhaust gas emitted from a heavy-duty vehicle [4]. There are no NH3 limits for light-duty vehicles
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