Gary D. Neely

New diesel emission control strategy to meet US tier 2 emissions regulations

The aim of this study was to establish a fully capable diesel exhaust treatment system (4-way catalyst system) based on a catalyzed diesel particulate filter (cDPF) and a Lean NOx trap (LNT) for meeting US Tier 2 emissions. In this study, two modified combustion technologies, LTC (Low Temperature Combustion) and PCCI (Premixed Controlled Compression Ignition), were used and improved to achieve high catalyst bed temperatures and to provide rich exhaust gas with low smoke to utilize a 4-way catalyst system. The LTC operation area was expanded to both lower and higher loads using a dual loop EGR system (high-and low-pressure-loop EGR). The effect of air-fuel ratio, injection timing, and intake manifold temperature on combustion stability and soot emissions of LTC were investigated. PCCI, characterized by increased and advanced pilot injection, combined with retarded main injection timings and without EGR was used to achieve low-smoke, rich combustion at medium loads. The effect of pilot and main injection timing, quantity, injection pressure, and EGR rate were investigated to reduce smoke. For the evaluation, a PSA DW10 diesel (4-cylinder, 2000cc) was used and NOx and CO 2 emissions were examined at five points representative of the FTP 75 test cycle. This study confirmed that LTC and PCCI can facilitate high NOx conversion efficiency with low engine-out smoke, sufficient combustion stability and minor fuel penalty at five FTP 75 representative points (BMEP: 0 to 8.2 bar). Estimated FTP 75 NOx emissions were 0.012 g/mile (fresh catalyst), and estimated CO 2 emissions were 1.7% above the baseline. The method to maintain very high catalyst temperatures and provide slightly rich gases was also examined for simultaneous DPF regeneration and LNT desulfation.

Experimental investigation of PCCI-DI combustion on emissions in a light-duty diesel engine

The combination of premixed charge compression ignition (PCCI) and conventional Dl diesel combustion was studied on a light-duty diesel engine equipped with EGR and a common rail fuel injection system. This combustion mode is referred to as PCCI-DI combustion. The main objectives of the study were to examine the emissions, performance and combustion characteristics of the engine operating under various levels of PCCI-DI combustion to determine if this mode of combustion was a viable in-cylinder NO x emissions reduction strategy. The premixed charge was obtained with early pilot injections (up to three) using a custom engine controller. The engine test conditions were limited to light and medium loads and moderate engine speeds. Engine tests consisted of sweeps of pilot injection timing and quantity, and number of pilot injections. The results of this study suggest the greatest potential for reducing NOx emissions with PCCI-DI combustion exists at light loads (below 30%) and medium to low speeds. At 1500 rpm and 17% load, moderate NO x reductions of up to 15% were achieved, while a 9% NO x reduction was achieved at 2600 rpm and 54% load.