Ultra high-speed camera tests fuel-injectors

The LTT has an international reputation for building and running injection chambers to investigate the transient spray processes within fuel-injectors used in internal combustion engines. Employing an experimental approach of continuously flushed chambers enables high injection rates and therefore time efficient experiments. This, in combination with the wide range of variable operation parameters, such as chamber pressure, chamber temperature, fuel pressure, fuel temperature, makes the chambers attractive both for fundamental research and testing under application conditions.

Conventional high-speed imaging techniques are already well-established in spray research, but are not able to resolve very fast processes such as spray fluctuations or the injector opening in high spatial resolution, as the fuel leaves the nozzle with up to 300m/s in gasoline injection and even higher velocities when using diesel fuel.

The Kirana Ultra High-Speed camera from Specialised Imaging closes this gap, being able to take 180 consecutive high quality images at frame rates of up to 5MHz. The full resolution of the Kirana camera is maintained independently of its frame rate, enabling it to achieve high spatial and temporal resolution at the same time.

The Kirana camera was used to visualise the opening of two experimental injectors, a gasoline and a diesel design, using a long distance microscope to achieve high magnifications and focus on the effects directly at the nozzle hole. The transient opening and closing behaviour of fuel-injectors is specifically relevant in application, since it causes a throttled flow that significantly alters the nozzle behaviour which can lead to tip wetting, jet-to-jet interaction and other phenomena.

The use of the Kirana ultra-high-speed camera not only reduced the measurement time by several orders of magnitude but also provided information about the temporal course of the highly turbulent flow that have not been accessible before. In the Diesel fuel injection experiments, the transition from throttled pre-jet to full needle lift is clearly visible.

Due to the convincing quality of the results achieved using the Kirana camera, further applications for ultra-high-speed measurements in spray research are currently under investigation at the LTT.

Incorporating a proprietary hybrid camera sensor, the compact Kirana ultra high speed video camera can deliver high resolution and high speed (up to 5 million frames per second) in a no-compromise design. The full resolution of this video camera is maintained at all speeds. Comprehensive triggering facilities, highly accurate timing control and a wide range of output signals, coupled with a software package, simplifies image capture and analysis. Full remote operation using Ethernet connectivity comes standard enabling the Kirana to be easily integrated into almost any environment. The Kirana offers the performance, ease-of-use and operational flexibility that enables users to record and deliver impressive slow-motion video images in just about any material scientific research application.