Reciprocating engine development toward better performance (less consumption and/or raw gaseous emissions) is asking for more accurate tools of investigation. During the last years, the Computational Fluid Dynamic (CFD) approach has become one of the most used numerical tool to study the fluid dynamic behaviour of Internal Combustion Engines (ICE) and to optimise their thermo physical behaviour. In particular, recently, thanks to computer evolution, the application and the development of Large Edddy Simulatio (LES) methods to reciprocating Internal Combustion Engine have become stronger and wider since their potential have become clear. With respect to RANS approach, LES approach is expected to be successful in predicting momentum transfer since the rate controlling-processes are dominated by the large scales of motion thus, most of the large scale unsteadiness is directly solved. LES characteristics make this approach a strong candidate to be an unavoidable tool to perform detailed fluid dynamic analysis of unsteady flows inside ICE. Nevertheless, for a LES simulation an accurate numerical set-up must be performed in order to achieve accurate and grounded numerical results. This paper would contribute in bridging LES toward industrial application showing capabilities, potential and limits. The aim of this paper is to present the application of the LES simulation approach for the analysis of a real airbox flow of an high performance race car. High performance race car efficiency is based on a very fine equilibrium between aerodynamic efficiency, engine performance and chassis behaviour. In order to maximize the overall performance of a naturally aspirated engine, it is necessary to optimise the boosting capability of the air box. It must be noted that air box must convert the external flow dynamic pressure into static pressure thus increasing the air density available over trumpets. Moreover it should minimize the unsteady effects induced by the intake process of each cylinders by a proper design. Thus as a first step of the development, the air box is analysed under “steady” flow conditions, checking its capability to increase air density from the ambient value taken as reference. The airbox simulations consider a non-reactive flow in a fixed grid. In order to guarantee realistic fluid dynamic conditions on the airbox inlet section, a part of the car body was considered too. The airbox simulations were performed by using the commercial CFD code Fluent v6.3. Since LES results are strongly affected by the numerical setup used and by the wall-bounded flow condition typical of real flows, a robust LES methodology was previously defined by the authors on a Backward Facing Step (BFS) test case and subsequently tested on an IC engine-like intake flow.
Brusiani F., Bianchi G. M., Baritaud T. Bianchi D'Espinosa A. (2008). Toward the Use of LES in Industrial Application. PARIGI : IFP.
Toward the Use of LES in Industrial Application
BRUSIANI, FEDERICO;BIANCHI, GIAN MARCO;
2008
Abstract
Reciprocating engine development toward better performance (less consumption and/or raw gaseous emissions) is asking for more accurate tools of investigation. During the last years, the Computational Fluid Dynamic (CFD) approach has become one of the most used numerical tool to study the fluid dynamic behaviour of Internal Combustion Engines (ICE) and to optimise their thermo physical behaviour. In particular, recently, thanks to computer evolution, the application and the development of Large Edddy Simulatio (LES) methods to reciprocating Internal Combustion Engine have become stronger and wider since their potential have become clear. With respect to RANS approach, LES approach is expected to be successful in predicting momentum transfer since the rate controlling-processes are dominated by the large scales of motion thus, most of the large scale unsteadiness is directly solved. LES characteristics make this approach a strong candidate to be an unavoidable tool to perform detailed fluid dynamic analysis of unsteady flows inside ICE. Nevertheless, for a LES simulation an accurate numerical set-up must be performed in order to achieve accurate and grounded numerical results. This paper would contribute in bridging LES toward industrial application showing capabilities, potential and limits. The aim of this paper is to present the application of the LES simulation approach for the analysis of a real airbox flow of an high performance race car. High performance race car efficiency is based on a very fine equilibrium between aerodynamic efficiency, engine performance and chassis behaviour. In order to maximize the overall performance of a naturally aspirated engine, it is necessary to optimise the boosting capability of the air box. It must be noted that air box must convert the external flow dynamic pressure into static pressure thus increasing the air density available over trumpets. Moreover it should minimize the unsteady effects induced by the intake process of each cylinders by a proper design. Thus as a first step of the development, the air box is analysed under “steady” flow conditions, checking its capability to increase air density from the ambient value taken as reference. The airbox simulations consider a non-reactive flow in a fixed grid. In order to guarantee realistic fluid dynamic conditions on the airbox inlet section, a part of the car body was considered too. The airbox simulations were performed by using the commercial CFD code Fluent v6.3. Since LES results are strongly affected by the numerical setup used and by the wall-bounded flow condition typical of real flows, a robust LES methodology was previously defined by the authors on a Backward Facing Step (BFS) test case and subsequently tested on an IC engine-like intake flow.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
