Search Results

A transparent HSDI CI engine was used together with a high speed camera to analyze the liquid phase spray geometry of the fuel types: Swedish environmental class 1 Diesel fuel (MK1), Soy Methyl Ester (B100), n-Heptane (PRF0) and a gas-to-liquid derivate (GTL) with a distillation range similar to B100. The study of the transient liquid-phase spray propagation was performed at gas temperatures and pressures typical for start of injection conditions of a conventional HSDI CI engine. Inert gas was supplied to the transparent engine in order to avoid self-ignition at these cylinder gas conditions. Observed differences in liquid phase spray geometry were correlated to relevant fuel properties. An empirical relation was derived for predicting liquid spray cone angle and length prior to ignition.

The main goal of this paper is to acquire more insight into the relationship between wall and piston impingement of liquid fuel and unburnt hydrocarbon emissions (UHC) emissions, under early direct injection (EDI) premixed charge compression ignition (PCCI) operating conditions. To this end, the vaporization process is modeled for various operating conditions using a commercial CFD code (StarCD). Predicted values for liquid core penetration, or liquid length LL , have been successfully checked against experimental data from literature over a wide range of operating conditions. Next, the correlation between the CFD results for wall and piston impingement and measured UHC emissions is studied. The diesel fuel used in the experiments is modeled as n-dodecane and n-heptadecane, representing the low and high end of the diesel boiling range, respectively. A distinction is made between liquid spray impingement on the piston surface and cylinder liner.

A study on the modeling of fuel sprays in diesel engines will be presented. First, modeling of non-reacting diesel spray formation is studied in Fluent and Star-CD. The main objective however is to model combustion of the spray using a generic approach. This is achieved by applying a detailed chemistry tabulation method, called FGM (Flamelet Generated Manifold). Using this approach will make additional ignition modeling, which is conventional, obsolete. The FGM method is implemented in Fluent and Star-CD. Subsequently, constant volume spray combustion and full engine cycle simulations are performed. Spray formation is modeled with Lagrangian type models that are available in Fluent and Star-CD, and also with a 1D Euler-Euler spray model that is implemented and applied in 3D Fluent simulations. The results are compared with EHPC (Eindhoven High Pressure Cell) experiments, data from Sandia National Laboratories and IFP (Institut Français du Pétrole).

An HSDI Diesel engine was fuelled with standard Swedish environmental class 1 Diesel fuel (MK1), Soy methyl ester (B100) and n-heptane (PRF0) to study the effects of both operating conditions and fuel properties on engine performance, resulting emissions and spray characteristics. All experiments were based on single injection diesel combustion. A load sweep was carried out between 2 and 10 bar IMEPg. For B100, a loss in combustion efficiency as well as ITE was observed at low load conditions. Observed differences in exhaust emissions were related to differences in mixing properties and spray characteristics. For B100, the emission results differed strongest at low load conditions but converged to MK1-like results with increasing load and increasing intake pressures. For these cases, spray geometry calculations indicated a longer spray tip penetration length. For low-density fuels (PRF0) the spray spreading angle was higher.