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2 2017

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Numerical simulations of n-heptane spray in high pressure and temperature environments

Smuga W., Kapusta Ł. J., Teodorczyk A.

Journal of Power Technologies

2017

Vol. 97, nr 1

1--6

In this study n-heptane spray in supercritical environments was simulated using commercial CFD (Computational Fluid Dynamic) software AVL Fire. The numerical results were analyzed in terms of global spray parameter, and spray penetration. The results obtained were compared with experimental data available at Sandia National Laboratories. N-heptane spray simulations were performed in the same conditions as in the Sandia experiments. The goal of the study was to assess whether the Lagrangian approach performs well in engine relevant conditions in terms of spray global parameters. Not included in this assessment was the influence of supercritical mixing on liquid-gas interphase. The major element was the potential for practical application of the commercial CFD code in terms of properly representing global spray parameters and thus mixture formation in supercritical conditions, which is one of the core aspects in whole engine process simulation. The key part of the study was mesh optimization. Therefore, the influence of mesh density on both the accuracy of calculations and the calculation time was determined, taking into consideration detailed experimental data as initial conditions for the subsequent calculations. This served as a basis to select the optimal mesh with regard to both accuracy of the results obtained and time duration of the calculations. As a determinant of accuracy, the difference within a range of evaporated fuel stream was used. Using selected mesh the set of numerical calculations were performed and the results were compared with experimental ones taken from the literature. Several spray parameters were compared: spray tip penetration, temperature of the gaseous phase and mixture fraction in the gaseous phase. The numerical results were very consistent in respect of spray tip penetration. The other parameters were influenced by specific features of the Lagrangian approach. Nevertheless the results obtained showed that the Lagrangian approach may be used for engine relevant conditions.

A 4-stroke spark-ignition engine fuelled with low quality gas

Brzeżański M., Mareczek M., Sutkowski M., Smuga W.

Combustion Engines

2017

R. 56, nr 1

122--124

Huge amount of by-products is still considered as waste and is simply disposed, for example by-product gas is usually flared. Political and social pressure to reduce air pollution and national needs for energy security make these waste fuels interesting for near-future power generation. Unfortunately most of these waste fuels, even when liquefied or gasified, have very low quality and can hardly be used in high-efficiency power systems. Among main challenges are low calorific value and composition fluctuation. Additionally very often there is a high content of sulphur, siloxanes, tars, etc., which have to be removed from the fuel. Modern 4-stroke gas engines designed for power generation applications provide very high efficiency, high reliability and availability. Unfortunately, these gas engines require high quality fuel with stable composition. Horus-Energia together with Cracow University of Technology developed a novel gas supply system HE-MUZG that can adapt to current gas quality and change engine settings accordingly.This article will present results from the HE-MUZG system tests on modern 4-stroke spark-ignition gas engine. Tests focus on low quality gas, such as gas with low calorific value, gas with very low methane number and gas with very big variations of calorific value. Test results compared with performance of that engine in the original configuration show huge improvements. Moreover the HE- MUZG system is easy to implement in commercial gensets.