Listening to the Flow: KTH Researcher Develops New Methods for Compressor Noise Characterization
Heavy-duty trucks are the backbone of modern logistics, transporting the goods that sustain industries and everyday life. While advances in turbocharging technology have significantly improved engine efficiency and reduced emissions, compressor noise has emerged as a growing challenge. The characteristic hum and whine generated by turbocharger compressors contributes to urban noise pollution and impacts driver comfort. As regulations become increasingly stringent and industry seeks quieter transport solutions, understanding and mitigating compressor noise has become an important research priority. KTH Doctoral Researcher Janakiraman Thiyagarajan, from the HPT division at the Department of Energy Technology, has been addressing this challenge through his doctoral research that combines aerodynamics, thermodynamics, and aeroacoustics to support the development of quieter and more efficient compressor designs for future heavy-duty vehicles.
Jana's doctoral journey was shaped by close collaboration between academia and industry. The research began at Lund University under the supervision of Magnus Genrup , with Jens Fridh serving as co-supervisor from KTH. As the project later transitioned to KTH, Jens Fridh took on the role of main supervisor alongside Mauricio Gutierrez as co-supervisor. Launched as an Industrial PhD project with Scania CV AB/Traton AB in 2022, Jana's research initially focused on the aero-thermodynamic performance of centrifugal compressors, with the aim of developing methods to evaluate existing designs, identifying opportunities for redesign, and supporting the creation of tailor-made solutions through simulation-driven design. However, as the project evolved, the scope expanded to investigate the aero-acoustic behaviour of centrifugal compressors, particularly the mechanisms behind tonal Blade Passing Frequency (BPF) noise and the development of practical methods for identifying quieter compressor designs. While conventional theories largely link tonal noise generation to unsteady blade loading, Jana’s research revisited the underlying physics by exploring the relationship between flow-field energy and tonal noise production. Through measurements of unsteady pressure fluctuations at the inlet and outlet of compressor components, the work provided new insights into how aerodynamic interactions generate acoustic emissions within turbomachinery.
Inspired by studies of the silent flight mechanisms of barn owls, the research introduced three novel noise prediction factors designed to quantify the impulsiveness of circumferential static pressure variations within compressors. These indicators, namely the Acoustic Crest Factor (ACF), Outlet quasi-unSteadiness fActor of an Impeller (OSAI1), and Quasi-unsteady Impeller outlEt facTor (QuIET), offer simplified yet effective approaches for estimating tonal noise using low-fidelity Reynolds-Averaged Navier-Stokes (RANS) simulations. The work introduced detailed instrumentation approaches for assessing component-level performance and resulted in new methodologies to extract impeller design parameters directly from experimental data, as well as improved methods for matching the volute to the impeller and diffuser. To support this work, Kiel probes were calibrated in the KTH wind tunnel while extensive compressor testing was conducted at Scania’s gas stand, providing valuable experimental data for model validation and performance assessment.
Jana’s work highlights KTH’s continued commitment to advancing industrially relevant research that combines fundamental scientific understanding with practical engineering solutions. By providing new insights into compressor aeroacoustics and developing tools that enable the design of quieter and more efficient turbomachinery, the research supports ongoing efforts to create cleaner, more comfortable, and more sustainable heavy-duty transportation systems for the future.
👉 To learn more about Jana's research on centrifugal compressor aero-thermodynamics and aeroacoustics, or to explore collaboration opportunities in turbomachinery research at KTH's Heat and Power Technology division, kindly contact our team.
