Simulation of High Altitude Effects on Heavy-Duty Diesel Emissions

Abstract

<div class="htmlview paragraph">Exhaust emissions from heavy-duty diesel engines operating at high altitude are of concern. EPA and Colorado Department of Health sponsored this project to characterize regulated and selected unregulated emissions from a naturally-aspirated Caterpillar 3208 and a turbocharged Cummins NTCC-350 diesel engine at both low altitude and simulated high attitude conditions (≈ 6000 ft). Emissions testing was performed over cold- and hot-start transient Heavy-Duty-Federal Test Procedure (HD-FTP) cycles as well as selected steady-state modes. In addition, the turbocharged engine was operated with mechanically variable and (fixed) retarded fuel injection timing to represent “normal” and “malfunction” conditions, respectively.</div> <div class="htmlview paragraph">High altitude operation generally reduced NO<sub>x</sub> emissions about 10 percent for both engines. Average composite HD-FTP emissions of HC, CO, particulate matter, and aldehydes measured at high altitude for the naturally-aspirated engine were 2 to 4 times the levels noted for low altitude conditions. The same emission constituents from the turbocharged engine at high altitude with “normal” timing were 1.2 to 2 times the low altitude levels, but were 2 to 4 times the low altitude levels with “malfunction” timing.</div>