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Institute for Powertrains and Automotive Technology
Vienna University of Technology 
Getreidemarkt 9
1060 Vienna, Austria
Phone: +43 1 58801 31500
Mail: info[at]

Office opening hours:
Mo-Fr: 8 am - 4 pm

Mixture formation

At the Institute for Powertrains & Automotive Technology a multi-component model fuel has been developed for best representation of the fuel distillation behaviour. Gasoline consists of a vast number of hydrocarbons with different physical and chemical properties. Therefore, gasoline has not a simple boiling point but a characteristic distillation curve that reaches over a wide temperature range, see Figure 1.

Figure 1: Measured distillation curve compared to a five-component model-fuel (left) and its composition (right)
Figure 2 shows the CFD results of an injection sequence with a central injector. As one can see, a certain amount of the injected fuel impinges on the combustion chamber walls and forms liquid film especially on the piston and liner.

Figure 2: Wall film formation on the piston and liner during an injection event
In contrast to the multi-component approach, the formed liquid film is noticeably underestimated with a simplified single-component fuel. This is due to the components with lower volatility that remain in the injected spray.

The distribution of lambda in two orthogonal sectional views through the combustion chamber is depicted in Figure 3. The result with the multi-component approach reveals that for the considered operating point the fuel distributed much more inhomogeneously compared the result with the single-component fuel. Especially in close proximity to the spark plug the air-fuel mixture is 12 % leaner what leads to a more critical evaluation of the combustion stability.

Figure 3: Effect of a realistic fuel representation on the mixture formation

Dipl.-Ing. Michael Heiss
Phone: +43 1 58801 31537
Mail: michael.heiss[at]


Heiss, M.; Bobicic, N.; Lauer, T.; Pritze, S.: Modellansatz zur Entstehung von Vorentflammungen. In: MTZ - Motortechnische Zeitschrift (2014), Vol. 75, Issue 1, pp 64-71.

Lauer, T.; Heiss, M.; Bobicic, N.; Pritze, S.: A Comprehensive Simulation Approach to Irregular Combustion. In: SAE Technical Paper (Published in April 2014).

Heiss, M.; Bobicic, N.; Lauer, T.: A Detailed Analysis of the Initiation of Abnormal Combustion with Reaction Kinetics and Multi-Cycle Simulation. In: Proceedings of the FISITA 2012 World Automotive Congress, Vol. 190, pp.1007-1018, Beijing (2013).

Heiss, M.; Lauer, T.; Geringer, B.: A detailed Analysis of Engine Knock Initiation by means of a Stochastic Reactor Model. In: European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS), Vienna (2012).

Heiss, M.; Lauer, T.: Simulation of the Mixture Preparation for an SI Engine using Multi-Component Fuels. In: STAR Global Conference, Amsterdam (2012).