Research Topic

Modeling and Unsteady Simulation of Multi-phase flow including Fuel Injection in IC-Engines

Schematic of Gasoline Engine

In internal combustion engines (ICE), researchers have to face with stringent regulations concerning pollutants while improving engine thermal efficiency, making the engine design a complex task. To meet these requirements an understanding of the salient features of all the engine processes are very important. Being the primitive process of engine operations, fuel injection influences the whole engine cycle via air-fuel mixture preparation, thereby the combustion behavior and subsequently the emission performance. The inhospitable environment inside a combustion chamber makes the experimental investigations become complex and expensive. In contrast, a CFD based investigation can provide comprehensive insight about in-cylinder flow field, spray injection phenomena as encountered in IC-engine

Collision model comparison for hollow cone in Z-plane: (left: CV based with model artifact), (right: collision kernel, artifact removed)
Wall impingement: splashing with various wall parameters (K, T*)

In the present study, a CFD tool that enables to investigate the real unsteady behavior of realistic engine configuration is developed by coupling Large Eddy Simulation (LES) together with a spray module with KIVA-4 Code. It is based on an Eulerian-Lagrangian framework to describe the spray evolution including primary and secondary atomization. A linear instability sheet atomization (LISA) based sub-model is integrated to represents the primary atomization. The secondary atomization is modeled by an available Taylor analogy break-up (TAB) model. In dense spray region, the droplet-droplet interactions considerably influences the overall spray dynamics. The first novelty of the proposed methodology is to include droplet-droplet interaction processes via an appropriate collision sub-model that is independent of mesh size and type. Thereby, taking account of different regimes, such as, bouncing, separation, stretching separation, reflective separation and coalescence. The formation of wall film on hot cylinder surface is a critical process in an IC-engine, since it largely influences the engine performance and emission characteristics. The second novelty of this spray module is improved wall film model that includes the combined effects of droplet kinetic energy and wall temperature is into KIVA4-mpi code.

Mesh generation for complex 4-canted valve engine configuration
Velocity profile on Y-plane during intake stroke ( 150° CA)

To perform an IC-engine simulation, a good quality mesh generation in ICEM-CFD for an engine geometry is challenging task. The KIVA4-mpi is compatible only with block structured mesh without any use of O-grid. Due to this reason, only certain degree of mesh refinement is possible. This makes it difficult to achieve a good quality fine mesh required for LES simulation. In the present study a new meshing strategy is proposed to generate suitable mesh for real IC-engine configurations. The new method clearly demonstrates the improvement in resolving the in-cylinder flow structures. First, the simulated results for motored case (no fuel injection and no combustion) are compared with the experimental data for a transparent combustion chamber (TCC) engine configuration from Engine Combustion Network (ECN). Second to demonstrate the importance of fuel injection sub-models, further simulations are carried out including the evolution of evaporating fuel spray with wall impingement. Third, using the new meshing strategy, simulation is also performed for a real complex canted 4-valve engine configuration. Simulated results are compared well with the available experimental data

Recent work

Key Research Area

Multi-Physics, Multi-Phase flow, CFD, IC Engine Simulation

Contact

Kaushal Nishad, M.Sc.

Address:

Dolivostraße 15

D-64293 Darmstadt

Germany

Phone:

+49 6151 16 - 24401 or 24402

Fax:

+49 6151 16 - 24404

Office:

S4|10-210

Email:

nishad (at) gsc.tu...

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