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The development of new high power diesel engines is continually going for increased mean effective pressures and consequently increased thermal loads on combustion chamber walls close to the limits of endurance. Therefore accurate CFD simulation of conjugate heat transfer on the walls becomes a very important part of the development. In this study the heat transfer and temperature on piston surface was studied using conjugate heat transfer model along with a variety of near wall treatments for turbulence. New wall functions that account for variable density were implemented and tested against standard wall functions and against the hybrid near wall treatment readily available in a CFD software Star-CD.

This study is presenting a comparative spray study of modern large bore medium speed diesel engine common rail injectors. One subject of paper is to focus on nozzles with same nominal flow rate, but different machining. The other subject is penetration velocity measurements, which have a new approach when trying to understand the early phase of transient spray. A new method to use velocimetry for spray tip penetration measurements is here introduced. The length where spray penetration velocity is changed is found. This length seems to have clear connection to volume fraction of droplets at gas. These measurements also give a tool to divide the development of spray into acceleration region and deceleration region, which is one approach to spray penetration. The measurements were performed with backlight imaging in pressurized injection test rig at non-evaporative conditions. Gas density and injection pressure were matched to normal diesel engine operational conditions.

The discrete droplet model is widely used to describe two-phase flows such as high-velocity dense sprays. The interaction between the liquid and the gas phase is modeled via appropriate source terms in the gas phase equations. This approach can lead to a strong dependence of the liquid-gas coupling on the spatial resolution of the gas phase. The liquid-gas coupling requires the computation of source terms using the gas phase properties, and, subsequently, these sources are then distributed onto the gas phase mesh. In this study, a Lagrange polynomial interpolation method has been developed to evaluate the source terms and also to distribute these source terms onto the gas mesh. The focus of this investigation has been on the momentum exchange between the two phases. The Lagrange polynomial interpolation and source term distribution methods are evaluated for non-evaporating sprays using KIVA3 as a modeling platform.

Non-evaporating diesel sprays have been simulated utilizing the ETAB and the WAVE atomization and breakup models and have been compared with experimental data. The experimental penetrations and widths were determined from back-lit spray images and the droplet sizes have been measured by means of a Malvern particle sizer. The model evaluation criteria include the spray penetration, the spray width and the local droplet size. The comparisons have been performed for variations of the injection pressure, the gas density and the fuel viscosity. The fuel nozzle exit velocities used in the simulations have been computed with a special code that considers the effect of in-nozzle cavitation. The simulations showed good overall agreement with experimental data. However, the capabilities of the models to predict the droplet size for different fuels could be improved.

This investigation is a continuation of a previous study by these authors in which a Lagrange polynomial interpolation method was developed to evaluate spray source terms and also to distribute the source terms onto the gas mesh; the method was applied to the liquid-gas momentum exchange. For this investigation, the method has been extended to the mass exchange between the liquid and gas phases due to evaporation. The Lagrange polynomial interpolation and source term distribution methods are applied to the liquid-gas mass and momentum exchange and are evaluated for evaporating sprays using KIVA3 as a modeling platform. These methods are compared with the standard “nearest neighbor” method of KIVA3, and experimental data are used to establish their validity. The evaluation criteria used include the liquid and vapor spray penetration, gas velocities and the computational stability.

The objective of this study was to build up an optical access into a large bore medium-speed research engine and carry out the first fuel spray Particle Image Velocimetry (PIV) measurements in the running large bore medium-speed engine in high pressure environment. The aim was also to measure spray penetration with same optical access and apparatus. The measurements were performed in a single-cylinder large bore medium-speed research engine, the Extreme Value Engine (EVE) with optical access into the combustion chamber. The authors are not aware of any other studies on optical spray measurements in large bore medium-speed diesel engines. Successful optical measurements of the fuel spray penetration and the velocity fields were carried out. This confirms that the exceptional component design and laser sheet alignment used in this study proved to be valid for optical fuel spray measurements in large-bore medium-speed diesel engines.