Methods for improving transient response of diesel engines – influences of different electrically assisted turbocharging topologies

Abstract

The paper presents a comprehensive study on engine performance improvement attributable to application of different electrically assisted turbocharger topologies. Performance of a baseline turbocharged high-speed direct-injection (HSDI) diesel engine is compared to the performance of an engine utilizing an electrically assisted turbocharger, an engine utilizing a turbocharger with an additional electrically driven compressor, and an engine utilizing an electrically split turbocharger. Analyses are performed based on a validated physically based engine and vehicle model comprising detailed models of all vehicle components, thus ensuring adequacy of results. Analyses are performed for various driving conditions, including tip-in in the fixed gears and the new European drive cycle (NEDC). Results reveal that electrically assisted turbocharger topologies improve transient response of the engine and thus driveability of the vehicle. Additionally, over a limited period of time, electrically assisted turbocharger topologies are able to improve steady-state torque output of the engine with retained fuelling, which is made possible by the availability of energy in electric storage devices. It was also revealed that the utilization of electrically split turbocharger enables considerable reduction in fuel consumption when driven according to urban drive cycles.

An assessment of the impacts of low-pressure exhaust gas recirculation on the air path of a diesel engine equipped with electrically assisted turbochargers

“…In a similar finding, on an off-road heavy-duty diesel (HDD) engine, Terdich et al 8 proposed engine downsizing and downspeeding as a benefit derived from fast boost response enabled by a REAT system. Fuel savings from downspeeding/downsizing has been reported by several researchers in Terdich et al, 8 Jain et al, 9 Xue and Rutledge, 10 Katrasnik et al, 11 Burke, 12 and Tavcar et al 13 REAT systems provide the compressor power demand through a combination of electrical and exhaust turbine power. Hence, it is possible to operate the exhaust turbine at its most optimal condition, through an optimal VGT vane setting, by supplementing any power deficit using the electrical source.…”

“…These sweeps were conducted for fixed parameters: 1 22 , the total EGR rate _ m EGR _ m air + _ m EGR '0:4, T 1 = 300 K, and T 3 = 560 K. It is clear from Figure 7 that increasing h c *h tm leads to a reduction in PR, hence improving TC efficiency in conjunction with a wide open LP-EGR valve will reduce the adverse impact of LP-EGR on p 3 . Note that we can use equations (12) and (13) to derive equivalent conditions for the HP-EGR only case simply by setting _ m LP, EGR =0. This is because setting _ m LP, EGR = 0 implies _…”

Electric Boosting and Energy Recovery Systems for Engine Downsizing

“…In this turbocharger, the electric machine is connected to the electrically driven compressor and is not affected by the exhaust gas driven turbine. Thus, since the electric machine drives solely the compressor, the transient response is improved for low engine speed as the boost pressure build-up is made faster [83]. Moreover, according to Lee et al [81], the benefits of the topology are the low power consumption of the electric motor and inverter as well as the improvement of the steady state performance.…”

“…Results obtained by Moreover, the compressor is electrically driven by an electric machine which makes the control more flexible [81]. However, due to the incapability of this topology to generate energy itself, electrical energy has to be provided to the storage by an integrated starter generator (ISG) or the regenerative braking system [83]. In addition, according to Lee et al [81], the main drawback of this topology is the low system efficiency.…”

“…On the other hand, the main disadvantage of the TEDC is that the electric energy required to drive the compressor needs to be generated by generator/alternator powered by the engine shaft or regenerative braking system [83]. Furthermore, another major drawback that should be considered is the low system efficiency of the topology [81].…”