Naslov
Calculation of Vibe Parameters for HCCI Combustion by Using a Six-zone Detail Chemical Kinetics Model

Autori
Kozarac, Darko ; Sjerić, Momir ; Tomić, Rudolf

Vrsta, podvrsta i kategorija rada
Radovi u zbornicima skupova, cjeloviti rad (in extenso), znanstveni

Izvornik
5th AVL AST International User Conference / - , 2011

Skup
5th AVL Advanced Simulation Technologies International User Conference

Mjesto i datum
Graz, Austrija, 28.06.2011. - 30.06.2011

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Nije recenziran

Ključne riječi
HCCI; Boost; Vibe parameters; Ethanol

Sažetak
Homogeneous charge compression ignition [1, 2] is a relatively new type of combustion which offers a possibility to combine the benefits of Diesel and Gasoline engines. It has a potential to achieve very high efficiencies with low NOx and particulate emissions [3]. Main current limitations that prevent the commercial application of HCCI combustion are low power density and control of combustion timing. One of the recent trends for achieving high power densities is high boosting levels of these engines [4]. Nevertheless, control of combustion timing still remains an issue. For the control of combustion timing there are several proposed strategies that can be used: fast thermal management, recirculation of exhaust gases, exhaust gases re-breathing, residual gas trapping, variable compression ratio, variation of fuel blend, etc. In order to be able to asses the potentials of these strategies and to be able to develop control algorithms for these strategies, fast simulation models of HCCI engines are required. In recent years several control oriented models have been developed [5-14]. Some of them are mean value models and some of them are crank angle resolved models. In most of the models the well known integral functions (Arrhenius rate, knock integral, etc.) are used for a definition of start of combustion, and combustion progress is modeled by Vibe functions with mostly constant parameters. The use of integral functions means that for each fuel a specific function has to be defined, or there is a need for ignition delay data over the large possible operating conditions. Also, these models are individually developed and are not available to wide combustion research community. The work presented here is a part of the wider research work whose aim is to define steps necessary to build a fast HCCI engine model by using available commercial software. The idea is that a model could use Vibe combustion, which is fast enough, whose parameters are functions of operating conditions. In the first part of this work the analysis of state factors which are influencing the Vibe combustion parameters is made, and the regression functions which calculate combustion parameters on the basis of defined state factors are derived. By using these functions one can calculate Vibe parameters on the basis of state in the cylinder at a certain moment and use them during combustion event. These functions are shown to be valid in a stable HCCI operating region. In order to have a fully flexible model a definition of boundaries of the HCCI operating region has to be defined which is a second part of the overall work, and is not presented here. All the data that are used in the analysis and in calculations of the regression functions are obtained by a calculation with six-zone HCCI combustion model which uses detailed chemical kinetics and is implemented into the AVL Boost. Ethanol is used as a fuel, i.e. the reaction mechanism of ethanol with 58 species and 310 reactions. Parameters of double Vibe combustion are analyzed instead of standard Vibe, but the procedure could be applied for a single Vibe also. Final results show that by using double Vibe parameters calculated by regression functions it is possible to simulate pressure trace reasonably well. Since this simulation is several hundreds of times faster than the detail kinetics one the use in calculation of transients is enabled. Also since double Vibe combustion model is available in commercial cycle simulation software, like AVL Boost, this approach is available to wide combustion research community.

Izvorni jezik
Engleski

Znanstvena područja
Strojarstvo

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