Advanced Turbocharging Technologies for Heavy-Duty Diesel Engines

Heavy-duty diesel engines face increasingly stringent emissions regulations. The trade-off between fuel economy and NOx emissions and between NOx and particulate emissions is becoming even more critical. In the light of these regulations and the trade-off among many variables, air handling and exhaust gas recirculation (EGR) systems become increasingly important. Three advanced turbocharging technologies - variable nozzle turbochargers, integral EGR pump and an ultra-high pressure ratio, long life compressor are described. In this paper an overview of the designs and their impact on fuel economy, low speed torque, emissions and durability is described. It is shown that significant improvements in all four variables are readily possible with the use of these advanced turbocharging technologies. It is shown that variable nozzle (VNT) turbocharging reduces smoke particularly at low speeds by a factor of 5, improves torque at low engine speeds and improves fuel economy by about 3%. It is shown that the IEGR pump enables EGR without increasing back pressure on the engine. Finally, the ultra-high pressure ratio, long life compressor is shown to supply high pressure ratios (5-6:1) with wide flow range and fatigue life increases by factors of 100 or more. Later publications will present these three technologies individually and in greater detail.