This work investigates the image quality achievable with a large-aperture endoscope system and high-speed cameras in terms of detecting the premixed flame boundary in spark-ignited engines by chemiluminescence imaging. The study is an extension of our previous work on endoscopic flame imaging [SAE 2014-01-1178]. In the present work, two different high-speed camera systems were used together with the endoscope system in two production engines to quantify the time-resolved flame propagation. The systems were cinematography with a CMOS-camera, both with and without an intensifier, the latter variation being used in a four-cylinder automotive engine as well as in a single-cylinder motorcycle engine. An algorithm with automatic dynamic thresholding was developed to detect the line-of-sight projected flame boundary despite artifacts caused by the spark and the large dynamic range in image brightness across each time series. A fundamental problem in evaluating the systems’ efficacy is that it is not clear what constitutes “correct” detection of flame boundary. To help clarify this question, the endoscopic results are compared among each other and to a “best-case scenario”, which was unintensified high-speed imaging with a large-aperture commercial camera lens in an engine with full optical access. We find that for the part-load operation examined here, broadband unintensified imaging through the endoscope yields useful and physically plausible results during all of the early flame propagation. Imaging is most challenging during inflammation, when the spark ignites the first small volume of mixture. For the conditions examined here, the chemiluminescence of the flame then is just at the level of the camera’s background-corrected read-out noise, while the spark in the immediate vicinity can still be very bright.

The proportion of nitrogen dioxide in the engine-out emissions of a Diesel engine is of great importance for the conversion of the total oxides of nitrogen (NOX) emissions in SCR catalysts. Particularly at lower engine loads and lower exhaust temperatures an increase of the already low NO2/NOX fraction will enhance the SCR operation significantly. For this purpose, the understanding of the NO2 formation during the Diesel combustion and expansion stroke is as substantial as being aware of the different thermodynamic impacts and engine operating parameters that affect the formation process.To determine the influences on the NO2 emission level several variation series were performed on a single-cylinder research engine. Especially the charge dilution parameters like the air-fuel ratio and the EGR rate as well as the injection parameters could be identified to be decisive for the NO2 formation.Empirical models were generated for different operating points by the use of statistical test plans in order to predict the impacts of those parameters on the NO2 emissions. The model behavior could be validated with test data and with results from the chemical kinetic modeling of the NO2 and NOX formation.In general, it turned out that the NO2 concentration always increases with the total NOX concentration, so the formation of NO also affects the formation of NO2. While nearly every measure that leads to an increase of NOX emissions, like earlier injection timings, higher rail pressures or lower EGR rates, leads to a disproportionately lower increase of the NO2 emissions, only the dilution with additional air has a greater influence on NO2 than on NO. This effect enables to adapt the NO2/NOX ratio without changing the total NOX emissions by simultaneous varying the air-fuel ratio against other parameters. The different application measures for this were mapped out and analyzed in the current work.

When it comes to covering the growing demand for cooling power worldwide, elastocalorics offer an environmentally friendly alternative to compressor-based cooling technology. The absence of harmful and flammable coolants makes elastocalorics suitable for energy applications such as battery cooling. Initial prototypes of elastocaloric systems, which transport heat by means of thermal conduction or convection, have already been developed. A particularly promising solution is the active elastocaloric heat pipe (AEH), which works with latent heat transfer by the evaporation and condensation of a fluid. This enables a fast and efficient heat transfer in a compression-based elastocaloric cooling system. In this publication, we present a simulation model of the AEH based on MATLAB-Simulink. The model showed very good agreement with the experimental data pertaining to the maximum temperature span and maximum cooling power. Hereby, non-measurable variables such as efficiency and heat fluxes in the cooling system are accessible, which allows the analysis of individual losses including the dissipation effects of the material, non-ideal isolation, losses in heat transfer from the elastocaloric material to the fluid, and other parasitic heat flux losses. In total, it can be shown that using this AEH-approach, an optimized system can achieve up to 67% of the material efficiency.

Auf dem Weg zu einer dekarbonisierten Mobilität kann der Wasserstoffmotor vor allem im Nutzfahrzeugsektor und auf der Langstrecke einen wertvollen Beitrag leisten. Durch die Verwendung von sauberem Wasserstoff als Brennstoff treten Stickoxide als praktisch einzig relevante Schadstoffemissionen auf, die durch motorische Maßnahmen gepaart mit einer Abgasreinigung im Abgasstrang minimiert werden können. Dieser Artikel gibt einen Überblick zu den Einflüssen verschiedener Motorbetriebszustände auf die Emissionen eines Wasserstoffmotors und zeigt aktuelle und zukünftige Möglichkeiten einer effizienten Abgasnachbehandlung auf.