Passive scalar interface in a spatially evolving mixing layer (A. Attili and D. Denker)

Quartz nozzle sampling (D. Felsmann)

Dissipation element analysis of a planar diffusion flame (D. Denker)

Turbulent/non-turbulent interface in a temporally evolving jet (D. Denker)

Dissipation elements crossing a flame front (D. Denker and B. Hentschel)

Particle laden flow (E. Varea)

Turbulent flame surface in non-premixed methane jet flame (D. Denker)

DNS of primary break up (M. Bode)

Diffusion flame in a slot Bunsen burner (S. Kruse)

Various quantities in spatially evolving jet diffusion flame (D. Denker)

Engine Experiments


Basics

At first, investigations in a one-cylinder diesel engine have been done regarding the effect of inserting water and hydrogen peroxide into the combustion space on the emission of pollutants, especially soot. Here, emulsion injection - where diesel fuel and water/hydrogen peroxide are emulsified by a mixer before the injection pump and injected afterwards into the combustion space - has proven a very effective method for reducing soot and NOx. It is known that by inserting water into the combustion space, a lowering of temperature takes place, which reduces the  formation of thermally created NOx. In engine combustion, this kind of NOx makes up about 90% of the entire NOx-emissions. But the reduction of soot cannot be achieved by this lowering of temperature. On the contrary, soot emission increases here, as with lower temperatures fewer radicals (OH) are available and, therefore, the post oxidation of soot runs more slowly. This effect can be seen with the insertion of water by air-pipe jetting, for example. Therefore, other effect have to play a decisive part in the reduction of soot through emulsion injection.


Measurements

In this project, the effectiveness of emulsion injection will be inspected further with the help of two optical measurement processes on the one hand and an indicator for the injection law on the other hand, as well as the usual inspection and exhaust gas measurements. In the first optical process, jet diffusion in the engine was measured with high temporal and local dissolution using a Cu-steam-laser and a high-speed barrel camera. The temporal dissolution approximated 2000 rpm 0.4°KW, whereby a detailed evaluation of the injection process was made possible. The second optical measurement used is an expansion of the Integral Light Conduction technique, the cycle-to-cycle-resolved emission spectroscopy. With this technique it is possible to integrally capture soot and OH radiation during combustion temporally resolved.


Results

There is a good correlation between the classic index procedures  and the optical procedures. With the help of optical measurements it can be shown that soot reduction in diesel/water emulsion injection is gained particularly by a better mixture formation due to  a very good spraying of fuel. The good mixture formation is caused by the water contained in the fuel lacerating the jet through its higher density and, therefore, its higher impulse. The measurements were conducted with a VW transport engine 1.91 TDI and with a 1-cylinder research engine. Several fuels and fuel/water-ratios were investigated for their injection behaviour.  Further investigations on a 4-cylinder complete engine are planned. These contain exhaust-gas and index measurements, as well as emission spectroscopy at emulsion injection.

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