Operation of a Compression Ignition Engine at Idling Load under Simulated Cold Weather Conditions

In colder climates, heavy-duty compression ignition (CI) engines and exhaust aftertreatment systems (EATS) may struggle to reach ideal operating temperatures under idling and low load conditions. This may lead to high emissions of pollutants, especially nitrogen oxides (NO_x). The objective of this study is to evaluate performance of a heavy-duty CI engine operating at various idling conditions and determine suitability for EATS operation. Steady state tests are conducted at engine speeds of 650 and 1100 rpm, and cold weather operation is simulated by operating engine at sub-optimal coolant, lubricant, and intake air temperatures. These engine speeds correspond to two-mode Clean Idle Test (CIT) as specified in the United States' (US) Code of Federal Regulations (CFR). The steady state tests are used to determine suitable diesel injection timing for performing CIT under standard and simulated cold weather conditions. At lowest load and 650 rpm idling speed, use of multiple injections and exhaust gas recirculation (EGR) are insufficient for raising exhaust gas temperature above 200°C. A combination of higher load, EGR, and 1100 rpm idling speed can create conditions for light-off selective catalytic reduction (LO-SCR) operation at the expense of higher fuel consumption. The modified CIT results show that optional Clean Idle NO_x emission standards can be met with the use of EGR at both test modes. The Mode 2 conditions at 1100 rpm may allow LO-SCR activation as well. There are also distinct differences between results under fully and partially warmed-up conditions.