Meeting the particle (PN) emissions limits in dynamic vehicle test sequences needs specific attention on each power variation event occurring in the internal combustion engine (ICE).
Such transients arise from engine start onwards along the entire test drive. In hybrid systems, there is one further source for transient ICE response: each power shift between E-motor (EM) and ICE introduces gas flow variations with subsequent temperature response in the ICE and in the engine aftertreatment system (EAS). This bears consequences for engine out emissions as well as for the EAS efficiency and even for the durability of a catalytic converter.
As system calibration engineers must decide on numerous actuator parameters, their decisions, finally, are crucial for meeting legislative limits under the boundary conditions given by the ICE’s hybrid and drive environment.
The paper reports on a methodology to measure - on a degree crank angle basis - and evaluate the ICE and EAS response to the vehicle drive requirements and the power shift dynamics between EM and ICE.
Focus, in particular, is given to
1. particle emissions peaks at each engine start and torque variation with measurement of in-cylinder soot formation events and their impact on tailpipe PN emissions.
2. the response of the three way catalytic converter (TWC) temperature to each cylinder’s exhaust gas pulses with an evaluation of temperature and thermoshock risks.
Both topics are related to the ICE’s individual combustion cycles’ mixture formation and gasflow characteristics as the ICE operates in response to the hybrid power system requirements. Consequently, in-cylinder soot formation, TWC temperature, tailpipe PN flow are recorded together with the power output of EM and ICE.
The result of any test drive yields the usual emissions and performance data. The deg CA resolved in-cylinder and TWC signals, furthermore, provide the insight into combustion and gas flow phenomena relevant for PN emissions as well as TWC durability. This allows system development and calibration to benefit from such direct insight into ICE events, as any parameter variation’s effect is instantly recognized in the measurement system’s evaluation procedures.
Ernst Winklhofer, Alois Hirsch, Harald Philipp, Michael Trifterer, Manuel Berglez
AVL LIST GmbH
14th International Conference on Engines & Vehicles