Ignition properties of fuels - Combustion prediction by Diesel-RK

The work was based on Diesel-RK software code developed in Bauman Moscow State Technical University and it was carried out as a subcontract to VTT by the software group of the university. The actors were Dr. Andrey Kuleshov, Dr. Andrey Kozlov, and Dipl. Eng. Yury Fadeev. The work is reported in Appendix 1. The idea to use Diesel-RK code rose from the fact that Diesel-RK can handle spray and combustion chamber geometry unlike many 1D-simulation codes. Many alternative fuels like pyrolysis oils and alcohols have poor ignitability and need pilot injection in the engine. Dual spray systems, however, have complicated interaction and the geometry must be taken into account. Diesel-RK had originally possibility to use only one injector per cylinder. That's why the firsts step in the task was to add a second injection system to the code. For an example simulation case one was selected, where methanol is used as main fuel and light fuel oil as pilot. A wish was also set to be able to lean on Wärtsilä's combustion bomb (CRU) results for estimating ignition delay. The adding of second injection system to Diesel-RK succeeded well. The angles and bore diameters of all injection holes can now be selected freely, as well as start and end times of each injection. It appeared not to be easy to use the data gathered with CRU in the simulation model. During the work, it was leaned merely on the engine tests results, which were gained in the frame of WP4. Finally a model, which gives ignition delays and heat release curves reasonably well for the example case, was created. There are in the code, however, many parameters which must be correctly set for each fuel to get right results. Critical data are also fuel injection velocities into the cylinder. Unfortunately they are very difficult to estimate. As a conclusion, it seems that Diesel-RK is one tool, which can help to describe the behaviour of a fuel(s) in the engine, but the original target to be able to predict the ignition delay and heat release of a new fuel in the engine basing merely on bomb tests was not reached.