Reducing fuel consumption and CO2 emissions by optimizing active intake systems for naturally aspirated and turbocharged engines

Abstract

Reducing fuel consumption and CO2 emissions by optimizing active intake … 170 Lower fuel consumption and fewer emissions – these are two of the key requirements of modern engines. A decisive and economically efficient influencing parameter in this context is improvement of the gas exchange process in engines through the opti-mization of active intake systems. Since the end of the 1980s, intensive work has been carried out on improving the gas exchange process for naturally aspirated gasoline en-gines through the use of optimally adapted intake systems. The pressure pulses of the air intake system caused by the gas exchange process are used to achieve high charge filling of the combustion chamber. To this end, the lengths, diameter and volumes of the intake manifold between the throttle body and the inlet valves are adapted to the desired engine speed range. In order to achieve optimal filling over a wide speed range, active intake manifolds were introduced that permit switchable flow paths for the intake air by means of active switching elements such as flaps and rotary valves. Typically, different resonance runner lengths or resonance volumes are employed. Figure 1: Reduction in CO2 emissions required by legislation The trend towards downsizing gasoline engines and turbocharging to improve perfor-mance in response to the stringent CO2 emissions legislation has led to a reduction in the complexity of intake systems in recent years. Higher filling levels, as in diesel en-gines, are no longer achieved by means of optimised pressure pulses in the intake run-ner, but through turbocharging and supercharging. The aim of optimising the gas ex-change process in turbocharged engines is therefore to minimise pressure losses and create an appropriate velocity distribution during inflow into the combustion chamber.