Search Results

A new technique has been developed to allow engine performance engineers to visualize and communicate a wide range of thermodynamic issues and constraints in a single diagram. The technique, called Visual Thermodynamics, is the presentation of engine cycle data in logarithmic pressure and logarithmic temperature space, log(p)-log(T). Visual Thermodynamics is a thought organization and concept visualization tool. It is not intended to provide high-precision numerical results. The utility of the technique is in comparing engine concepts, assessing trends, identifying boundaries of operation and building a general understanding of engine system behavior. The technique provides a powerful mechanism for communicating engine thermodynamic issues to both technical and non-technical colleagues.

The influence of bowl offset on motored mean flow and turbulence in a direct injection diesel engine has been examined with the aid of a multi-dimensional flow code. Results are presented for three piston geometries. The bowl geometry of each piston was the same, while the offset between the bowl and the cylinder axis was varied from 0.0 to 9.6% of the bore. The swirl ratio at intake valve closing was also varied from 2.60 to 4.27. It was found that the angular momentum of the air at TDC was decreased by less than 8% when the bowl was offset. Nevertheless, the mean (squish and swirl) flows were strongly affected by the offset. In addition, the distribution of turbulent kinetic energy (predicted by the k-e model) was modified. Moderate increases (10% or less) in mass averaged turbulence intensity at TDC with offset were observed. However, the TDC turbulent diffusivity was changed less than 3% due to a slight decrease in turbulent length scale with increasing offset.