Open Access

In industrial applications, the effects of explosions must be considered as important part of safety assessments. This is particularly crucial in applications involving explosives or pressurized containers. The evaluation of the effects of shock waves on the environment becomes essential in such scenarios and requires comprehensive experimental test series. This article therefore presents a test bench that can generate and record reproducible, adjustable shock waves with short set-up times. The presented data proves the quality and validity of this set-up to generate case relevant data, like overpressure in comparison to explosives and shock tubes, with load cases of high relevance. The presented free-field tests are carried out at BAM's Test Site Technical Safety (TTS) with a gas-operated shock wave generator. This shock wave generator consists of a pressure vessel (autoclave) that is operated with a detonable gas mixture or compressed air. The pressure is released through an orifice by the instantaneous bursting of a diaphragm. The aim is to develop further the novel test bench that generates shock waves on models in a generic scenario and offers several advantages to create a valid database for the effects of shock waves. In contrast to classic shock tubes, this test bench offers the advantage of realistic hemispherical shock wave propagation and scalability, both for the investigated model size and for the generation of load cases, so that different model variables can be investigated under different boundary conditions (mainly overpressure); at the same time, typical interference of a shock tube experiment due to reflections, blockage effects and the following fluid flow can be minimized. These negative influences are not realistic compared to the ideal event of a detonation.

A simple test bench was set up on the BAM test site to investigate shock waves caused by gas detonations. The aim was to build a simple mobile test bench that can be used for various applications, to demonstrate the vaildity and for comparison with other test benches. For this purpose a balloon filled with acetylene and oxygen at atmospheric pressure with an electric ignitor was used. The characteristics of the shock waves can be scaled via the gaseous mixture, the filling quantity of the balloon and the distance to the sensors. Pressure sensors were set up around the balloon at various distances to measure the shock. With the help of the high-speed recordings and the Rankine Hugoniot equations, the shock front pressure was estimated and compared with the results of the pressure sensors. In order to validate the results of this test bench, they were compared with an experiment using plastic explosive no. 4 . These agreed well with the results. Overall, symmetrical undisturbed scalable shock waves can be generated with the setup. Only the reproducibility, which is comparatively poor to open shock tubes due to the influence of wind, had to be improved.

In industriellen Prozessanlagen können Druckwellen bei unfallbedingten Ereignissen (z. B. Detonation oder Bersten von Druckbehältern) schwere Schäden verursachen. Die Norm EN ISO 4126 beschreibt daher Druckentlastungseinrichtungen, die in solchen Fällen wirksam eingreifen. Dabei entweicht das Gas nach dem Öffnen der Berstscheibe und belastet das Umfeld, wie zum Beispiel benachbarte Module oder Personal (Burgess et al 2013). Daher soll in dieser Arbeit das Strömungsfeld hinter solch einer Einrichtung betrachtet werden, um exemplarisch Daten zur Einschätzung der Gefährdung im Nahbereich hinter einer Berstscheibe zu geben. Zu diesem Zweck wurde auf dem BAM TTS ein Versuchskonzept entwickelt, bei dem ein druckfester Autoklav (Stoßwellengenerator, SWG) als zu entlastende Anlage dient. Damit lassen sich die Ausbreitung und die Impulsübertragung von Gasen und Druckwellen sowie deren Phänomenologie am offenen Ende mit verschiedenen Gasen untersuchen. In diesem Beitrag werden die Ergebnisse eines Gemischs aus Acetylen und Sauerstoff vorgestellt. Dieses Gemisch wurde gewählt, da es hohe Explosionsdrücke und Flammentemperaturen erreicht, die mit anderen Gasgemischen kaum möglich sind und somit ein Worst-Case-Szenario darstellt. Eine solche Untersuchung wurde bereits mit Wasserstoff durchgeführt (Kuang et al. 2024). Es wurden verschiedene Auslassgeometrien von Schutzarmaturen – etwa Entlastungsöffnungen, wie bereits von Heinrich publiziert (Heinrich et al. 1966) – untersucht, um eine fundierte Nahfeldbewertung zu ermöglichen. Die experimentellen Daten können beispielsweise zur Validierung von CFD- Simulationen dienen und erlauben, den Einfluss von Geometrie und Umgebungsbedingungen systematisch abzubilden, und liefern praxisrelevante Daten als Basis für Leitlinien für den Explosionsschutz und die Bewertung von Störfallauswirkungen in modularen Anlagen und tragen somit zur Steigerung der Anlagensicherheit bei.

The shock wave generator (SWG) is used to investigate the effects of blasts on humans and structures. Since its explosion characteristics deviate from the ideal characteristics in the form of excessively high impulse, various sensors were used to gain more detailed insights into the combustion and fluid mechanics inside the SWG. Two symmetrically arranged pressure sensors enabled the analysis of the almost identical but slightly shifted propagation of the shock waves inside the SWG, which differs by a few microseconds . The fluid then flows out of the SWG. In this way, it is detected in a smaller pipe section by a pressure sensor and a fast heat flux sensor. The innovative measurement technology used in this process enabled the detection of extremely high heat fluxes of over 100 MW/m² with dynamics in the range of MHz, thus allowing the local boundary layer development to be determined. After less than 100 microseconds, it changed from a laminar flow to a turbulent boundary layer. In addition, the combination of both sensors allows conclusions to be drawn about the non-ideal shock wave characteristics outside the SWG, i.e. in the area where the models to be investigated are positioned. This makes it possible to identify additional shock waves emerging from the SWG, providing valuable information for further developing and optimising the test setup.