High Pressure Shock Tube (TH3)

  Photograph of the TH3 experiment Copyright: © HGD

The investigation of the ignition behavior, in particular the ignition delay time, is for the characterization of gaseous and liquid fuels of great importance. The compression and heating of the gaseous fuel/air mixture to temperatures above the ignition temperature due to a shock occurs almost instantaneously and homogeneously. The ignition onset is deteced with fast pressure sensors and a photomultiplier tube (PMT), wherein the latter detects the light emission in the CH- or OH- band range. A high speed schlieren imaging with a frame rate up to 1 MHz allows for the visualization of the ignition process and the propagation of the flame front.

  schematic of the TH3 Experiment Copyright: © HGD

The high-pressure shock tube TH3 is ideally suited for ignition delay time measurements due to its large inner diameter of 140 mm and its total length of 16.1 m. A large inner diameter leads to less shock attenuation, resulting in well-defined experimental conditions. The TH3 is also designed for high operating pressures, whereby investigations of undiluted fuel/air mixtures up to ignition pressures of 100 bar are feasible. Prior to each experiment minimal residual amounts of gas are pumped out by a rotary vane pump and two turbo-molecular pumps. Depending on the experimental conditions stainless steel or aluminum membranes with different thickness are used.