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    Burner research for Propulsion grade fire testing – BATTLE OF THE BURNERS

    Historically, the Federal Aviation Administration (FAA) evaluated and approved a number of kerosene burners for use in aviation tests. Some of these burners have become obsolete or have been withdrawn. The list of approved burners has remained unchanged for approximately 40 years.

    Faced with difficulties in maintaining, calibrating, and the performance of some approved burner models, it was agreed that action should be taken to update the list and ensure standardisation of the burners used in fire performance testing, and homogenisation of these tests. 

    The FAA created a new burner several years ago, this was named the Sonic burner. It was intended to be easy to use, accurate, and repeatably calibrated. It was hoped that it would be globally adopted as the standardised burner.

    During a fire test, the burner is supposed to simulate certain fire conditions, and as such the flame properties should be robust and repeatable. The Sonic burner was to achieve this due to precise fuel and air controls. However, the current calibration criterion (ISO2685:1998 and AC20-135) does not ensure consistent flame properties.

    The sensitivity of the Sonic burner performance to air and fuel flow measured in relation to temperature and heat flux for calibration purposes can vary. The impact of varying fuel/air ratio and thermocouple sizes was studied by conducting fire tests on aluminium samples, and these show inadequacies in the current calibration standards.

    Resonate, in association with the FAA, undertook R&D work on the repeatability of the Sonic burner in comparison with the incumbent industry standard Carlin burner. A major concern was that the Sonic burner was not operating within the parameters set by the industry whereas the older Carlin burner was much more reliable.

    For several years now Resonate Testing have been carrying out comparison investigations of existing and new kerosene burners that used in fire testing of aircraft propulsion systems.

    A list of presentations given by Resonate testing can be found below. Initial studies were carried out in collaboration with the Aerospace Research Center in the National Research Council Canada.

    An Extended Study into the Comparison of the Carlin and Sonic Burner ABSTRACT| PRESENTATION (3.37 MB)

    Continued evaluation of Carlin and Sonic Burner calibration equivalences PDF(2.3 MB)

    Study of Modified Sonic Burner For Powerplant Fire Testing in Comparison to Existing Carlin Burner

    Study of Sonic Burner, Carlin Burner and Innovative Mapping Techniques for Powerplant Fire Testing PDF(1.6 MB)

    Initial Study of Modified Sonic Burner and Innovative Mapping Techniques PDF (5.6 MB)

    Available Burners for Propulsion Grade Fire Testing - A Review ABSTRACT| PRESENTATION (10.1MB)

    Sonic Burner Compared to Carlin for Propulsion Grade Fire Testing - How Equivalency can be Maintained? ABSTRACT | PRESENTATION (4.29MB)

    Aviation industry - Flame ingression investigations

    A nacelle is a streamlined casing on the outside of an aircraft engine. The design of the nacelle has developed over many years and steps can be taken to minimise risk and improve fire prevention. This is a high-risk area and is highly monitored as a result. These measures are normally achieved through the inclusion of drainage and ventilation within the nacelle design.

    Drainage is achieved with the inclusion of a flame arrestor in the form of a tube. There is a recognised industry convention within thermodynamics that a flame will not continue to travel through a tube that is 10x longer than its diameter (10L/D).

    Design of the nacelle is required to provide a 15-minute window before the structural integrity of the aircraft is compromised and a 5-minute window until the power is shut off.

    Flame ingression and flame arrestor testing is investigated by measuring the length of the flame inside the nacelle “box” set up. Resonate Testing performed trials for conditions while the aircraft is on the ground. Further tests were developed which simulated conditions within a typical flight profile.

    The Company conducted tests to measure flame length and temperature inside the box as an extension of its fire hazard minimisation development work. This test was developed to facilitate the investigation of auto-ignition temperatures in the zone immediately adjacent to the flame which is sucked through.

    The work has included the investigation of

    flame ingression through holes and slits which may be present in structure that acts as a fire proof barrier and essential for the isolation and containment in the event of a fire and

    flame arrestor testing with different sized tubes, differing geometries and conditions.

    The industry and authorities alike have a renewed interest on the impact of fire during both on-the-ground events and inflight where scrubbing flame can be drawn across surfaces. The impact of such events on any holes, slots and tubes information which to Resonate Testing knowledge is not in the public domain.

    Resonate Testing’s goal is to assess the lengths for flame ingression when considering physical variables such as circular holes, slots and tubes (Length/Diameters- L/D). Additional variables to be considered include functional pressure differentials (Negative pressure drawing the flames in) and the burner distances from the target location.

    Introducing a study into Flame Ingression through Holes in Firewall, Assessing Impact of Geometry, Pressure Differential and Flame Characteristics for Calibrated Kerosene Burners Including the Sonic Burner. PDF(641 KB)

    A Study into Flame Ingression and Flame Arrestor Testing PRESENTATION (2.79 MB)

    The BTU Heat Transfer Device: Adapting a Standard Tool in Aircraft Fire Testing to Small Scale Experiments

    Tanja Pelzmann, Department of Mechanical Engineering École Polytechnique Montreal

    Mary Kelly, Resonate Testing

    Fire protection tests are either performed on-site of the aircraft component manufacturer or in dedicated external fire laboratories to evaluate new materials and fire proofing strategies. For powerplant installation and propulsion system components, FAA Advisory Circular AC20-135 states most of the considerations for the burner design and test rig. Test procedures demand for a standard flame provided by an approved and calibrated burner. The burner calibration for heat flux is commonly done using a standard apparatus (BTU heat transfer device) as outlined by the FAA AC20-135, an approach also adopted by other standardization bodies. The concept of this apparatus is based on the principle of heat flow calorimetry: the heat transfer from the flame to a well-defined isothermal section of the apparatus is determined from the measured raise in temperature in that section. The geometry, conductivity and surface condition of the exposed are usually considered in a sole apparatus constant.

    A detailed review and experimental study have been performed to identify and assess the effect of key parameters potentially altering the heat flux obtained using such a calorimeter over the duration of certification tests. A critical limitation of this approach is scalability, as the geometry of the calorimeter is prescribed in the certification requirements. In this work we discuss the necessary modification to adapt the BTU heat transfer device to small scale experiments that can be conducted on coupons in the laboratory. The results presented are from both experiments under full scale certification conditions and from small-scale tests, to study the scalability and limiting effects of this burner calibration approach. The emphasis is on the identification of scope of application for the underlying assumptions as well as on the suggestion of mitigation strategies for its extension.

    ABSTRACT | PRESENTATION (57.5MB)

    Development of FAA Copper Tube Heat Flux Calorimeter for Parametric Study of Heat Flux Calibration

    FAA certification fire test guidance for oil burners includes requirements for both flame temperature and heat flux calibration to ensure that the resulting flame is qualified to simulate the severe fire conditions that can occur on aircraft or in a powerplant environment. Burner heat flux calibration is a regular issue of concern among transportation authorities.

    This work includes the development of the FAA copper tube heat flux calorimeter (“BTU heat transfer device”) as per the FAA design described in the FAA Powerplant Engineering Report no. 3A and in Section 11.3.3.2 of the FAA Fire Test Handbook.

    A sensitivity study will show the effect of undefined design parameters of the calorimeter on the heat flux measured, using both a Carlin type modified gun burner and the latest version of the FAA NexGen Burner. Once a final configuration of the copper tube calorimeter is selected, the heat flux density will be measured using a Gardon gauge, for comparison.

    In addition, The work includes a comparative evaluation of the burner characteristics for both burners in accordance with report FAA-RD-76-213.

    PRESENTATION (2.6 MB)

    Development of a Complex Shock Test Facility

    In recent years, as spacecraft have become more capable, more sophisticated and delicate components can be flown to maximize mission results. During launch and deployment operations, satellites are exposed to energetic shock environments that may damage the satellite structure or its payload. Pyrotechnic devices are used to separate launcher stages and they produce high frequency, high energy shocks. As a result, components must be shock-tested under qualification shock response spectra (SRS) that were previously recorded using shock-spectrum accelerometers to ensure mission reliability.

    Resonate Ltd have developed the first shock testing facility in Northern Ireland that can qualify spacecraft components under shock testing standards set by ECSS, NASA and ESA. Components are fixed at different points on a metal horizontal plate, where each position produces a different SRS that is a function of the shock test’s initial conditions (hammer mass, impact height, plate dimensions and plate material) A Numerical Model was developed in Abaqus that replicates the complex and highly dynamic behaviours observed in the STF.

    The Digital Twin was used to predict the SRS for a client verification test and determine the optimal setup. A method of developing this Digital Twin is described where nonlinear material behaviours such as Viscoelasticity were characterized in order to predict the Shock Response Spectrum (SRS) of the STF. Using the Digital Twin, an understanding was gained as to how the different Initial Conditions (IC) influence the SRS and a guide explaining their effect and how they can be used to tune the SRS is described. This new insight allowed for more efficient tuning of the STF and significantly reduced setup time.

    This new knowledge led to suggestions for how the current STF could be developed further to allow for greater tunability and accuracy.

    Cubesat shock and vibration testing

    We are delighted to have supported Queens University Belfast's School of Mechanical and Aerospace Engineering Departments in the development of several different Cube Sats. Resonate Testing supported MSc students using our vibration table to simulate actual vibration conditions during launch. We are keen to use the strong innovation and STEM culture that exists within the staff at Resonate to support the next generation of engineers and science graduates.

    Dr. Gasser Farouk Abdelal from Queens University's School of Mechanical and Aerospace Engineering mentored the MSc students in the development of the prototype and analytical tools for analysing Cube Sat technology, a project which has been embraced globally. Dr Abdelal reiterated the importance of providing physical test capability to support development of analytical tools.

    “The students have been provided a fabulous opportunity to hone analytical skills with physical test data, this type of cooperation provides superb learning opportunities for the students, ensuring that their entry into industry or academia is grounded in the application of best practice within industry and academia.”

    https://daro.qub.ac.uk/eirsat-1-irish-satellite

    The Inter Trade Ireland Fusion Project

    The project, supported by InterTradeIreland under the Fusion programme (now known as the Innovation Boost programme), aims to develop a joint fire & mechanical testing service of advanced composite materials on the island of Ireland.

    Throughout our partnership with Composites Testing Laboratory (CTL) in the Republic of Ireland we can offer a different range of mechanical testing to accompany our fire and flammability services.

    https://www.irishnews.com/business/2020/12/04/news/newry-testing-firm-resonate-links-up-with-galway-s-ctl-2150424/

    CTL is a wholly owned subsidiary owned by ÉireComposites Teo in Inverin Galway. CTL was established as an accredited testing laboratory for advanced composite materials and is the only independent test within in EU specialising in composite materials testing providing mechanical, environmental and physical testing as well as world class static, fatigue and impact testing.

    CTL offer customers a fast, flexible and cost competitive service which includes testing in the aerospace, renewable energy, automotive, medical device and space sectors. CTL is ISO 17025 and NADCAP approved testing laboratory.

    CTL test to all recognised international standards - EN, ASTM, ISO and SRM. Testing to OEM specific specifications such as BATS and AITM is also available. Below is a snapshot of the tests we perform:

    Tension (OHT and FHT)

    Compression (OHC and FHC)

    In-Plane Shear

    V-Notch Shear

    NDT

    Flexure (Monolithic and Sandwich)

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