Teilprojekt C03 Janicka/Sadiki

Teilprojekt C03 Hasse/Sadiki

LES-based investigation of flame-wall interactions for internal combustion engines

Motivation

In the context of global warming the necessity of efficient and low emission combustion applications arises. In addition to the use of alternative fuels, the current tendency is towards smaller internal combustion engines, which enable higher pressure ratios and, therefore, reach higher efficiencies. However, this evolution increases the surface to volume ratio, which leads to a growing influence of near wall phenomena on the overall combustion process.

The interaction of the flame with the surrounding walls has a crucial influence on the overall efficiency. Due to heat-losses at the cold walls, the chemical reaction within the flame stagnates. This leads to incomplete combustion in close vicinity to the walls, which has a major impact on pollutant formation.

To develop new features for the optimization of geometries and operating conditions in modern, low emission internal combustion engines the understanding of the underlying processes of the chemical reacting near wall flow is essential.

Objectives

The insights obtained during the first funding period regarding the flow and combustion processes of simple fuels in close vicinity to walls will be extended to alternative fuels.

Additionally, the impact of pressure on wall-related mechanisms, the influence of mixture inhomogeneities as well as turbulence-chemistry interaction is investigated to enable the simulation of realistic engine applications. The experiments performed in A04 (side-wall quenching burner) serve as validation data.

The findings allow the modeling of the processes in towed and fired engine operation, which can be used for the detailed investigation of near-wall flow, combustion and pollutant formation in internal combustion engines. The focus lies on the optical motor in TP C01.

Previous Findings

The simulation of the laminar SWQ burner (AP04) using detailed chemistry revealed the crucial role of near-wall diffusion processes on combustion in the vicinity of walls, especially concerning pollutant formation.

Even though classical tabulation approaches (FGM) using stationary flamelets predict the flame structure and main species accurately, minority species such as CO show a significant deviation. This deviation could be associated with errors in the scalar dissipation rates.

Based on these findings,, requirements for the development of improved chemistry modeling were deduced before a wall-adapted, reduced chemistry model was derived with REDIM (B06).

Turbulenten-Flamme-Wand-Interaktion sowie der motorischen Konfiguration werden Large Eddy Simulation (LES) mit ausschließlich tabellierter Chemie durchgeführt.

Die Analyse der Wechselwirkung der Modelle in einem komplexen Anwendungsfeld, wie dem Verbrennungsmotor, stellt eine wichtige Herausforderung des Teilprojekts dar.

Approach

The generic SWQ configuration (A04), as well as the IC motor (C01), are simulated using the open source software library OpenFOAM.

For the SWQ burner (AP04) the combustion processes are modeled using detailed and tabulated chemistry. In the case of turbulent flows, Large Eddy Simulations (LES) with tabulated chemistry are performed to investigate the turbulent flame-wall interactions in the SWQ burner and the IC motor.

The investigation of the interaction between the mathematical models in a complex application, such as the IC engine, represents an important challenge of this subproject.

Current Work

In the SWQ configuration (A04) alternative fuels (DME) and mixture inhomogeneities are investigated.

Additionally, for turbulent combustion, the influence of higher pressure is examined. These findings will then be applied in the engine simulations.

The near-wall flow in the IC engine is examined in the trailed operation using LES. Thereafter, fired homogeneous and inhomogeneous direct injection operations are investigated. The interaction of tumble flows with the boundary layer is of particular interest. The simulated configurations are based on the experimental work from C01.

Cooperation

In the SWQ configuration (A04) alternative fuels (DME) and mixture inhomogeneities are investigated.

Additionally, for turbulent combustion, the influence of higher pressure is examined. These findings will then be applied in the engine simulations.

The near-wall flow in the IC engine is examined in the trailed operation using LES. Thereafter, fired homogeneous and inhomogeneous direct injection operations are investigated. The interaction of tumble flows with the boundary layer is of particular interest. The simulated configurations are based on the experimental work from C01.

Selected Publications

  • Ganter, S., Heinrich, A., Meier, T., Kuenne, G., Jainski, C., C. Rißmann, M., Dreizler, A., Janicka, J.: Numerical analysis of laminar methane–air side-wall-quenching. Combust. Flame 186, 299–310 (2017).
  • Ganter, S., Straßacker, C., Kuenne, G., Meier, T., Heinrich, A., Maas, U., Janicka, J.: Laminar near-wall combustion. Int. J. Heat Fluid Flow 70, 259–270 (2018)
  • Heinrich, A., Ganter, S., Kuenne, G., Jainski, C., Dreizler, A., Janicka, J.: 3D Numerical Simulation of a Laminar Experimental SWQ Burner with Tabulated Chemistry. Flow Turb. Combust. 100(2), 535–559 (2018).
  • Heinrich, A., Ries, F., Kuenne, G., Ganter, S., Hasse, C., Sadiki, A., Janicka, J.: Large Eddy Simulation with tabulated chemistry of an experimental sidewall quenching burner. Int. J. Heat Fluid Flow 71, 95–110 (2018).