The student Sergio Fernández Resines obtained an EXCELLENT CUM LAUDE

The student Sergio Fernández Resines obtained an EXCELLENT CUM LAUDE

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• Thesis title: Particle Emissions from Car Brakes: Development of a Laboratory-Scale Test for Accelerated Material Screening Based on UN GTR No. 24

Court:

• Presidency: Agustí Sin Xicola (UNITO)
• Vocal: Yezhe Lyu (Lund University)
• Secretary: Andrea Aginagalde Lopez (Mondragon Unibertsitatea)

Abstract:

Rising levels of particulate matter in urban areas pose a serious threat to human health, affecting both the cardiovascular and respiratory systems. While exhaust emissions have long been identified as the primary cause of traffic-related PM10 emissions, recognition of the significant contribution of non exhaust emissions is also growing. Among these emissions, brake wear has emerged as a major contributor, accounting for a substantial 55% of total non-exhaust emissions. Against this backdrop, the next EURO 7 emissions standard is set to become the first regulatory framework for controlling these emissions. To ensure compliance with the standard, the United Nations (UN) Global Technical Regulation (GTR) No. 24 defines a global methodology for measuring brake wear particle emissions from light-duty vehicles using brake dynamometer benches. Given that the GCI brake discs commonly used in current vehicles are not expected to comply with the upcoming regulatory requirements, the brake disc industry is compelled to seek technically and economically feasible solutions to comply with the new standard. This process requires extensive experimental work, but the limited availability of validated dynamometer benches, combined with the complexity of brake emission testing, has led to significant delays in evaluating new materials. 

In this context, the main objective of this thesis is to develop a laboratory-scale infrastructure for characterizing particulate emissions from braking systems, enabling faster and more cost-effective material screening by adapting the official WLTP Brake Cycle standard and correlating results with dynamometer bench testing.

To this end, a methodology and experimental framework were developed to implement the WLTP Brake Cycle on a PoD tribometer, enabling controlled testing of brake particle emissions at laboratory scale. The implementation successfully replicated the dynamic, thermal, and energy behaviour of full-scale tests, achieving excellent agreement in particle mass emissions, with deviations within 5% compared to dynamometer benchmarks. However, applying the full WLTP protocol according to UN GTR No. 24 proved time-consuming on the tribometer, limiting its usefulness as a rapid screening tool.

To overcome this limitation, three acceleration strategies were evaluated: reducing the number of braking events, minimising the duration of cruise phases, and implementing full test automation. Among these, the combination of a simplified Trip#10-based protocol (Trip#10-R5) combined with full automation emerged as the most effective. This configuration enabled a 150% increase in test throughput compared to dynamometer-based procedures, allowing two tests per day while maintaining consistency with full WLTP emission results.

Finally, the tribometer was validated across a range of mitigation strategies. Using standard GCI disc as a reference, two low-emission alternatives were evaluated: ferritic nitrocarburizing (FNC) and hard-coated (HSLC) discs. Tribometer results showed strong agreement with dynamometer measurements across all materials, covering emission levels from 10 mg/km (GCI) to 1 mg/km (HSLC). These findings demonstrate its effectiveness in ranking materials over the full emission performance range, supporting its use in early-stage development and regulatory alignment under Euro 7 targets.