Analysis of the Driving Altitude and Ambient Temperature Impact on the Conversion Efficiency of Oxidation Catalysts

Abstract

Worldwide emission standards are extending their requirements to cover engine operation under extreme ambient conditions and fill the gap between the type-approval and real driving conditions. The new ambient boundaries affect the engine performance and raw emissions as well as the efficiency of the exhaust aftertreatment systems. This study evaluates the impact of high altitude and low ambient temperature on the light-off temperature and conversion efficiency of an oxidation catalyst. The results are compared in a common range of exhaust mass flow and temperature with the baseline sea-level operation at 20 °C. A reduction of CO and HC conversion efficiencies was found at 2500 m and −7 °C, with a relevant increase of the light-off temperature for both of the pollutants. The analysis of the experimental data was complemented with the use of a catalyst model to identify the causes leading to the deterioration of the CO and HC light-off. The use of the model allowed for identifying, for the same exhaust mass flow and temperature, the contributions to the variation of conversion efficiency caused by the change in engine-out emissions and tailpipe pressure, which are, in turn, manifested in the variation of the reactants partial pressure and dwell time as governing parameters.

Fuel consumption and aftertreatment thermal management synergy in compression ignition engines at variable altitude and ambient temperature

“…This was the case with the highest sensitivity due to the temperature range ( 190 − 210 ° C) around the light-off temperature. 17 This behaviour was also found in cold altitude operation. In this case, the residence time of the gas within the catalyst increased due to the lower boost pressure (lower exhaust mass flow) and the temperature moved to a higher range from 195°C to ~ 220 ° C (Figure 4).…”

“…As ambient temperature, the altitude variation, which implies different ambient pressures, also leads to relevant effects on the combustion, 14 the gas exchange processes 15 and the ATS performance 16,17 . Wang et al 18 found a progressive decrease in brake thermal efficiency with increasing altitude in a heavy duty diesel engine.…”

Analysis of Altitude and Ambient Temperature Effects on the Reactivity of Oxidation Catalysts in the Presence of H2

“…The initial phase of the study was based on tests conducted by Serrano et al [16] on an HSDI diesel Euro 6d-Temp engine installed in a test bench coupled with the Horiba MEDAS. The MEDAS system, an altitude simulator developed by CMT -Thermofluids & Clean Mobility [29,30], facilitated variable working pressure for the engine based on the designated driving altitude.…”

“…The experimental facility used as a base to conduct the first part of the study consisted of an HSDI diesel Euro 6d-Temp engine for passenger car application, whose detailed characteristics are described in [16]. The engine was installed in a test bench integrated with Horiba MEDAS which can handle altitudes from sea level to 5000 m and ambient temperatures from -15 to 45 • C [29].…”

“…The efficiency of these catalysts, however, is influenced by environmental conditions. A study by Serrano et al [16], examining a Euro 6d-Temp ICE at various altitudes (0 and 2500 m) and temperatures (20 • C and -7 • C), reported increased raw emissions of CO and HC and decreased OC efficiency at 2500 m and -7 • C. Additionally, increased CO and HC raw emissions at higher altitudes lead to higher inhibitory effects, damaging OC performance. Historical research, including studies by Voltz et al [17] and Oh et al [18], has established that CO and HC presence impairs the oxidation process, decreasing conversion efficiency.…”