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Multi Attribute Optimization: Fuel Consumption, Emissions and Driveability
Abstract:
In making our products more attractive, it is becoming increasingly important to balance multiple areas of performance, such as fuel economy, emissions and drivability. Customer expectations and government legislations, to protect global environment, strongly increase the work complexity of auto firms in order to release high quality and eco-friendly vehicles. The balancing between several target is becoming a key factor in the car design:
- respect current (and anticipate future) emission limits
- optimization of fuel consumption
- insure high level of drivability
- maintain acceptable(or increase) performances
- sustain acceptable cost, reliability, etc.
From recent emissions limitations, engine cold start (at the beginning of driving cycle) plays a major role in the total amount of pollutants. Especially, achievements of HC limitations are a big challenge for vehicles with a conventional spark ignition engine. Several options are studied by auto firms such as (but not limited):
- down-sizing
- additional technologies on injection systems (for example direct injections)
- additional technologies on post-treatment systems (for example secondary air injection or HC/NOx trap, etc.)
- additional technologies on the engine actuators and geometries (for example Variable Valve Timing, Variable Valve Actuation, Variable Valve Lift, variable compression ratio, variable tumble systems, etc.)
- additional technologies on the air path systems (for example overcharging, low pressure EGR loop, etc.)
These options need to be evaluated from auto firms with respect to the final cost, development time, complexity, reliability, etc… For this kind of compromise, system simulation physical model based becomes helpful. This paper describes about the development of a multi attribute full vehicle model and a new approach to find the best compromise between performance, fuel consumption and emissions.