Expansion of optical measurement technology for research into diesel engine mixture formation, ignition and combustion

Project name

Extension of optical measurement technology for research into diesel engine mixture formation, ignition and combustion

Project duration

01.11.2013 - 31.12.2013

Brief description

In recent years, the Chair of Internal Combustion Engines at TU Dresden has acquired a high level of expertise in the visualization of diesel engine mixture formation and combustion. The existing optics laboratory enables the sub-processes of injection, mixture formation and combustion to be optically recorded and evaluated with the aid of high-speed cameras. Typically, images in the size 384 x 384 (pixel x pixel) are recorded with a time interval of 20µs. This means that 50,000 images per second are stored. With the previous tools, the diesel engine injection in a "hot chamber", a test setup with which the thermodynamic conditions (combustion chamber pressure and temperature) in the engine are simulated, can be separated out as a separate event and then only the injection and vaporization can be evaluated under an inert gas atmosphere. The same test vehicle can also be used to visualize "swirl-free" combustion, for which the gas atmosphere must be set so that oxygen is still present at the time of injection. Another test vehicle in the optics laboratory is a single-cylinder transparent engine. This makes it possible to observe injection and combustion in real engine operation. The interactions with the air mass movement (swirl) in the combustion chamber can also be seen here.
With the help of the image intensifier acquired as part of this project, the gap between injection/evaporation and combustion can be closed at the combustion engine department and it is now possible to visualize the phenomena of pre-ignition. This pre-ignition can be detected by the presence of OH radicals and the OH radicals emit light in the wavelength range of approx. 306-308nm, which is in the ultraviolet range. The visible wavelength range is from approx. 380nm (violet) to approx. 780nm (red). The purchased image intensifier is sensitive in a wide wavelength range, so that other luminescences can also be detected. This means that the intrinsic CH luminescence can also be measured in the future. With the image intensifier, the previous recording frequency (50 kHz) can also be maintained in the ultraviolet range, which now makes it possible to detect "shot-to-shot" deviations (cycle fluctuations).

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