S. Senthilkumar

A Study on Effect of Piston Bowl Shape on Engine Performance and Emission Characteristics of a Diesel Engine

This paper presents a study on the effect of re-entrant piston bowl configuration on the emissions characteristics and engine performances of a direct injection (DI) diesel engine. In order to meet the emission norms, modern-day diesel engines rely on methods of in-cylinder emission reduction and expensive after treatment device. By using an effective piston bowl shape, one can reduce the in-cylinder emission and the cost increased for the after-treatment device with considerable increase in the engine lifetime. Six piston bowl shapes with various geometric configurations were selected for numerical simulations. Three-dimensional models of the piston bowl shapes and the combustion chamber were created using Pro-E and mesh was generated by using preprocessor ANSYS ICEM CFD. The flow characteristics inside the cylinder with these piston bowls were investigated under steady condition with the RNG k-e turbulent model using ANSYS Fluent. Numerical simulations under isothermal condition were carried out to select an optimum bowl shape. The mass flow boundary condition was used for inlet manifold and the value of this was measured from the experimental test. The CFD results of mean swirl velocity of the engine at different locations inside the combustion chamber were calculated. From the computational results, it was found that the average swirl number is increased from 0.87 (base shape) to 1.74 (modified bowl shape). It is well known that the swirl number is very important to enhance the homogeneity of air/fuel mixture inside the combustion chamber, which in turn improves the combustion efficiency. The experimental results shows that, as compared to the baseline engine 20 % reduced in hydrocarbons (HC) emissions and 24 % reduced in carbon monoxide (CO) for the engine with modified piston bowl shape. However, there is a small amount of reduction in engine performance. It is observed that the brake specific fuel consumption (BSFC) reduced significantly for all load conditions.

Control of Vortex Shedding Behind a Circular Cylinder Using a Combination of Slot and Control Plates

Present numerical study aims at suppression of vortex shedding formed over a circular cylinder using different combinations of slot and control plates. Unsteady, two–dimensional computations are carried out for laminar, isothermal conditions at a Reynolds number (Re) of 150 using commercially available CFD software ANSYS-FluentTM. Numerical simulations with different passive controlling methods have been carried out to reduce the vortex shedding frequency or to suppress it completely by using the configurations, such as cylinder with control plates, and cylinder with combinations of slots and control plates. By carefully comparing the numerical results of all the cases, it is found that cylinder with control plates at 5° angle is the best case where the vortex shedding is completely suppressed which in turn reduces the drag force significantly. However, in other cases, it was partially suppressed but increases the drag force due to vortex formed near to the control plates or not having any effect on vortex shedding. The results are presented in terms of vorticity and streamline contours, Cl, Cd and Strouhal number.

Numerical Simulation of Isothermal Cruciform Jet Flow

This paper presents the results from numerical simulation of jet flow emanating from a cruciform orifice. OpenFOAM is used for the simulations with RANS standard k-e turbulence model. The results are validated with the experimental data of Quinn [1]. Mean flow quantities and turbulent quantities are discussed in detail. The evolution of cruciform shape to circular shape is described with various contours of mean flow and turbulent quantities. Possible reasons for the evolution of cross sectional shapes are discussed.

Numerical Modeling of Solar Radiation Heat Transfer for a Truck Cabin

The temperature inside the vehicle cabin will be higher than the outside environment temperature in parked conditions due to radiative effects. This increased temperature is not uniformly spread within the driver cabin due to absorption capacities of the various materials used for construction and the angle of incidence of the incoming radiation. The objective of the work is to predict the accumulation of heat inside the cabin numerically and find hotspots throughout the cabin. The path of the sun in different seasons and timings on a particular location was calculated and is implemented for the angle of incidence of radiation on the cabin. The investigation provides the variations of temperature, transmitted solar radiation and amount of absorption by various components that are subjected to assessment. Thus the major contributing factor for the abrupt increase in temperature was found.