What happens inside a fireball: Sheffield researchers publish boundary-pushing new paper on infrared radiation thermometers

Researchers from the Departments of Electronic and Electrical Engineering and Civil and Structural Engineering have been carrying out research that provides crucial information about the inner workings of blasts.

Fireball stock photograph

You can read the paper discussed in this news piece, 'High-Speed Infrared Radiation Thermometer for the Investigation of Early Stage Explosive Development and Fireball Expansion',  at this link.

The characterisation of blast events, and how they impact on structures, is critical for the development of infrastructure. It provides information to engineers that allows them to protect such infrastructure from events such as explosions. 

You can’t mitigate what you can’t understand.

Dr. Matthew Hobbs

Lecturer in the Department of Electronic and Electrical Engineering

However, there is a lack of high quality data regarding the characterisation of blast events which take place within a confined space, in part due to the lack of suitable measurement instrumentation. 

This is where the research of Dr. Matthew Hobbs, Lecturer in the Department of Electronic and Electrical Engineering, comes in. This paper, led by Matthew, was published last year when he was working as a Research and Teaching Associate in the Department, alongside a team of other researchers, including Prof. Jon Willmott, Professor of Metrology.

The published paper was published in the journal MDPI Sensors, and is entitled “High-Speed Infrared Radiation Thermometer for the Investigation of Early Stage Explosive Development and Fireball Expansion”, and was featured on the journal’s title page.

Other authors on this paper included members of the Blast and Impact Group from the Department of Civil and Structural Engineering at the University of Sheffield.

Photograph of the infrared radiation thermometer created by the team
The infrared radiation thermometer created by the team

By incorporating a custom, high-speed, non-contact infrared radiation thermometer within a combined blast event measurement setup, the temperature of the explosive fireball can be accurately characterised. By combining their new approach with traditional pressure gauges, the team are able to discover new information regarding the early stages of fireballs as they expand and develop. 

The explosive research was carried out in world-leading facilities out in the sleepy fields above Buxton. None of the nearby sheep were disturbed, however, as the explosions were carried out in a rig within a controlled chamber. 

Photograph of the controlled chamber which contained the explosions
The controlled chamber that contained the explosions

The infrared thermometer created by the researchers breaks new ground in the world of blast events in regards to the characterisation of fireballs and explosions. Previously, because work is carried out within a confined space, and the explosions that are created are of a size that will destroy any recording camera in that space, the inner workings of these blasts have been hard to measure. The Blast group at Sheffield relied on traditional pressure gauges and numerical modelling of fireballs - this meant there were features in the first few microseconds that their sensors were too slow to pick up, and that the group only knew about these features from their models.

This new novel, non-contact temperature measurement instrument means that the microseconds immediately after an explosion can be analysed in great depth, and lead to discoveries that can aid engineers in protecting infrastructure from threats, such as targeted attacks.

Photograph of Dr. Matthew Hobbs working in the lab at the University of Sheffield, pictured with the infrared thermometer contained within its box
Dr. Matthew Hobbs working in the lab at the University of Sheffield, pictured with the infrared thermometer contained within its box

By working closely together, we were able to develop instrumentation capable of measuring the temperature of a confined blast event. Such research would not have been possible without the mutual expertise of the two research groups; we were able to apply our novel research within temperature measurements in their novel application of blast load characterisation.

Dr. Matthew Hobbs

Lecturer in the Department of Electronic and Electrical Engineering

Funding for this research came from a grant entitled Mechanisms and Characterisation of Explosions (MaCE) from the Engineering and Physical Sciences Research Council (EPSRC). Spin out company from the Department of Electronic and Electrical Engineering, PyrOptik, were also subcontracted to professionally engineer the design, taking it from a lab based environment to practical implementation. Working with PyrOptik has meant that the team are able to "scale up" such instrumentation for implementation within further applications, 

This publication is an exciting achievement for Matthew not only due to the exciting research within it, but also as it is the most recent paper Matthew has written prior to being appointed as Lecturer.  A detailed Q&A with Matthew about the paper can be found at this link, under the alumni section of our website.

Top 10 in the UK

We're in the top 10 UK Electronic and Electrical Engineering Departments (QS World University Rankings 2021).

Centres of excellence

The University's cross-faculty research centres harness our interdisciplinary expertise to solve the world's most pressing challenges.