Combustion modelling for direct injection diesel engines

Abstract

Successful modelling of combustion systems depends on an adequate as well as a computationally eYcient description of the reaction mechanisms. For a typical medium speed compression ignition direct injection (CIDI ) engine under normal operating conditions, from 70 to 95 per cent of the injected fuel is in the vapour phase at the start of combustion and 10-35 per cent of the vaporized fuel has mixed to within ammability limits. This indicates that both a premixed combustion mechanism and a diVusion combustion mechanism are important to model CIDI engines. In the early stages of combustion, a premixed combustion mechanism should be utilized while, late in the combustion process, a diVusion-based mechanism will be dominant. The former is chemically based, while the latter is physically based. In this article, the two combustion mechanisms mentioned above and various combinations of the two mechanisms for the intermediate stages of combustion are investigated. The study was done on a Caterpillar 3401 diesel engine. It was found that by utilizing a hybrid scheme whereby the premixed combustion mechanism is employed up to a user-speci ed crank angle, beyond which point a diVusion combustion method is utilized, reasonable agreement for both in-cylinder pressure and heat release rate with experimental data could be obtained.

Computational Modeling of Diesel Spray Combustion with Multiple Injections

“…Turbulence modeling is still one of the most, if not the most, critical issues when approaching engineering CFD simulations of practical interest. Despite the fact that the standard − model has been and is still widely used in combustion vessel and Diesel engine simulations [15][16][17], the recognition that it cannot provide satisfactory prediction of streamline curvature and flow separation in the near wall region, which has significant effects in IC engines due to the combination of high Reynolds number and complex geometries, has pushed researchers towards more reliable turbulence models [16,18,19]. A possible alternative is the − SST (Shear Stress Transport) model proposed in [20,21] using the original − in the near wall region and gradually switching to standard − model in the wake region and free shear layers, which also introduces a modification to eddy viscosity to account for the transport of the principle turbulent shear stress, having the potential to better describe the entrainment and mixing rates after the flame-wall contact [22].…”

Multi-zone diesel fuel spray combustion model for the simulation of a diesel engine running on biofuel

“…6. The instance of time τ k when the CPF, which reached the control cross-section of the spray, has been injected is computed using equations (1), (5), (13), and (15). 7.…”

“…For example, CFD simulations using KIVA were carried out in references [10] to [13] to analyse engine's performance. Modelling of fuel combustion in marine diesel engines was carried out in reference [14] using Star-CD software.…”