A proposed methodology for estimating transient engine-out temperature and emissions from steady-state maps

Abstract

Many vehicle systems simulations utilize engine maps constructed from steadystate dynamometer measurements to estimate exhaust temperature and emissions as functions of engine speed and load. Unfortunately, steady-state engine behaviour is often significantly different from actual behaviour under transient driving conditions. This is particularly true for vehicles that undergo repeated engine shutdown and restart (e.g. electric hybrids). The authors propose a methodology for estimating transient engine exhaust properties and fuel economy based on corrections to steady-state maps. The suggested methodology has been implemented in the Powertrain Systems Analysis Toolkit (PSAT) and this implementation is used to demonstrate good agreement with experimental measurements for both a light-duty diesel and a flex-fuel gasoline/ethanol engine. Specific procedures are also recommended for setting key parameters required by the proposed methodology and possible directions for further improvements are suggested.

Perodua Myvi engine fuel consumption map and fuel economy vehicle simulation on the drive cycles based on Malaysian roads

“…The fuel consumption engine map used in the simulation records the fuel consumption when the engine reaches steady state torques and speeds. The difference of results between the steady-state and transient were mentioned by Z. Gao [9]. However, for estimation purpose, this simulation method is adequate as shown by the small difference in the simulation and the actual fuel economy results.…”

Investigation of the LTC fuel performance index for oxygenated reference fuel blends

“…The approach presented here is also unable to predict transient phenomena in the engine between the operating points, or switching from SI to HCCI operation. Gao et al [79] developed a methodology to estimate transient effects from steady-state engine data, and used this to improve predictions of fuel consumption and emissions in vehicle driving cycle simulations. Nüesch et al [80] also developed a model to predict transient effects from switching between the SI and HCCI combustion modes, finding that fuel consumption increased during transitions enough to nearly cancel out the HCCI improvements, and determined optimal timing delays to reduce these negative effects.…”

Optimization of Hybrid Power Trains by Mechanistic System Simulations

“…On the system level, there is a great challenge in establishing an appropriate balance between the level of detail of the model and its prediction accuracy [1]. This is particularly challenging for models of internal combustion engines [1].…”

“…On the system level, there is a great challenge in establishing an appropriate balance between the level of detail of the model and its prediction accuracy [1]. This is particularly challenging for models of internal combustion engines [1]. Frequently, nonmechanistic engine model approaches like maps [2,3] or surrogate models [4] are used to model the internal combustion engines.…”

“…Frequently, nonmechanistic engine model approaches like maps [2,3] or surrogate models [4] are used to model the internal combustion engines. Such models might have significant limitations when applied to transient conditions that are far from steady-state [1,5,6]. However, also more sophisticated methodologies for estimating transient engine performance from steady-state maps [1], might not be sufficiently accurate, since during transient operation performance and particularly emissions of the engines significantly differ from the corresponding steady-state values as presented in [7][8][9].…”