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Advances in Industrial Fan Technologies

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A special issue of International Journal of Turbomachinery, Propulsion and Power (ISSN 2504-186X).

Deadline for manuscript submissions: closed (30 September 2025) | Viewed by 10887

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Special Issue Editors

Dr. Massimo Masi

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Guest Editor

Department of Management and Engineering, DTG—University of Padova, 36100 Vicenza, Italy
Interests: low-speed fan aerodynamic design and analysis
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Thomas Carolus

E-Mail Website1 Website2
Guest Editor

1. Steinbeis-Transfer Center FLOWTRANS, 57250 Netphen, Germany
2. Chair of Applied Fluid Mechanics and Turbomachinery, Universität Siegen, 57068 Siegen, Germany
Interests: aerodynamics and aeroacoustics of isothermal turbomachinery (incompressible gases); industrial fans; wind turbines; turbines for ocean energy harvesting (wave and tidal); dynamic models of systems
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Special Issue Information

Dear Colleagues,

The design of industrial fans has evolved to meet the ever-increasing demands for higher-efficiency machines, combined with the requirements for lower noise and high availability. Numerical simulation techniques are important parts of the aerodynamic and acoustic design process and are increasingly coupled to optimization methods. In addition, connectivity, internet of things, and digitalization in general open new opportunities for highly efficient, low noise, and safe operation of fans in complex systems.

The aim of this new Special Issue on fans and fan systems is to promote the recent advances in technology and provide insight into the development and operation of industrial fans for a wide range of applications.

The paper submissions for the Special Issue can cover some of the following aspects, but submissions on other related topics are also welcome.

Fan Noise

Aerodynamic fan noise-generation mechanisms;
Structure-borne noise;
Dynamic force transmission;
Experimental methods for characterizing noise sources;
Noise source localization;
Design for low-noise fans;
Noise prediction by analytical/numerical models;
Optimization of fan installation to reduce noise;
Psychoacoustics;
Fan integration in HVAC unit.

Fan Aerodynamics

Aerodynamic design methods;
Practical design examples of new-generation industrial fans;
Advancements in traditional testing of fan aerodynamics;
Experimental techniques and computational methods for the detailed analysis of fan aerodynamics;
Artificial intelligence and aerodynamic performance optimization techniques;
Improving fan sizing/selection;
Unsteady phenomena and flow non-uniformities in actual fan operation;
Effects of flow characteristics and geometrical non-similarities affecting fan scaling law;
New design and analysis methods based on artificial intelligence or machine learning.

Fan Application and Systems

Compliance with legislation and regulations;
Harmonization of fan standards worldwide;
Connectivity technologies;
Digital services and new business models;
Predictive maintenance;
Operation and maintenance considerations;
Motors and drives;
Specialized fans for niche applications;
Retrofit and upgrading existing fan installations;
Fan system effect;
Energy-related topics (e.g., air curtain effectiveness);
Case studies (e.g., tunnel ventilation).

"Papers submitted for this Special Issue are also expected to come from the 5th International Conference FAN2025 (https://www.fan2025.org/) that is scheduled to take place in April 2025 in Antibes - Juan-Les-Pins, France."

Dr. Massimo Masi
Prof. Dr. Thomas Carolus
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 250 words) can be sent to the Editorial Office for assessment.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. International Journal of Turbomachinery, Propulsion and Power is an international peer-reviewed open access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

industrial fans
fan noise
aerodynamics
optimization

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Published Papers (10 papers)

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Editorial

Jump to: Research

2 pages, 137 KB

Open AccessEditorial

Fans: Noise, Aerodynamics, Applications and Systems—The Best of the International Conference FAN2025

by Thomas Helmut Carolus and Massimo Masi

Int. J. Turbomach. Propuls. Power 2025, 10(3), 30; https://doi.org/10.3390/ijtpp10030030 - 19 Sep 2025

Viewed by 983

Abstract

Industrial fans are indispensable components in modern engineering systems [...] Full article

(This article belongs to the Special Issue Advances in Industrial Fan Technologies)

Research

Jump to: Editorial

16 pages, 1180 KB

Open AccessArticle

Calculation of Total Tone-to-Noise Ratio and Total Prominence Ratio for Small Fan Noise and Determination of Subjective Annoyance Thresholds

by Takefumi Nakano and Gaku Minorikawa

Int. J. Turbomach. Propuls. Power 2026, 11(2), 20; https://doi.org/10.3390/ijtpp11020020 - 12 May 2026

Viewed by 288

Abstract

Fan noise from small cooling fans often contains multiple coexisting tonal components whose combined perceptual impact cannot be fully represented by conventional single-tone metrics. While the Tone-to-Noise Ratio (TNR) and Prominence Ratio (PR) defined in ECMA-418-1 are established measures for evaluating individual tonal components, their direct application under multi-tone conditions may be insufficient to characterize cumulative tonal influence. To address this issue, the Total Tone-to-Noise Ratio (TTNR) and the Total Prominence Ratio (TPR) have been proposed as cumulative extensions of the ECMA framework. In this study, calculation procedures for TTNR and TPR were systematically examined for projector operating noise containing multiple tonal components, and subjective annoyance thresholds were determined using controlled jury ranking tests with 20 participants. Detection parameters for tonal extraction were adjusted within the ECMA-418-1 framework to reflect realistic product conditions. The resulting annoyance thresholds were 11.6 dB for TTNR and 14.3 dB for TPR. These findings indicate that cumulative tonal evaluation can be performed within the existing standardized framework and that TTNR and TPR provide practical tools for assessing multi-tone noise in technical products equipped with small cooling fans. Full article

(This article belongs to the Special Issue Advances in Industrial Fan Technologies)

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15 pages, 3240 KB

Open AccessArticle

Aeroacoustic Prediction and Optimization of Unevenly Spaced Blades in Axial Fans

by Samir Assaf, Thibaut Gras and Jacques Ferhat

Int. J. Turbomach. Propuls. Power 2026, 11(2), 17; https://doi.org/10.3390/ijtpp11020017 - 4 Apr 2026

Viewed by 851

Abstract

A common solution for reducing the tonal noise annoyance caused by fans is to change the circumferential blade spacing from even to uneven. However, this technique requires predictive tools to simulate and assess their acoustic performance at a lower cost compared to experimental tests, which remain very costly. In this study, a hybrid analytic/numeric (HAN) approach for predicting the tonal noise of fans is proposed. It is based on the acoustic interference law, which is applied to the sound pressure generated by each blade, and Computational Aeroacoustics (CAA). This model allows for the analytical construction of a fan’s acoustic pressure spectrum from the numerically computed response of a single blade, significantly reducing computation time. An optimization procedure is then implemented to minimize the prominence of tonal noise peaks, where the decision variables are the blades’ angular positions and the constraints are rotor balance and the minimum angular distance between adjacent blades. The results show that the developed method may help designers reduce tonal noise annoyance by optimizing blade spacing. Full article

(This article belongs to the Special Issue Advances in Industrial Fan Technologies)

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11 pages, 2532 KB

Open AccessArticle

Numerical Investigation of Scaling Effects on the Performance Characteristics of Large-Scale Axial-Flow Fans

by Tristan Oliver Le Roux, Chris Meyer and Sybrand Johannes van der Spuy

Int. J. Turbomach. Propuls. Power 2026, 11(1), 15; https://doi.org/10.3390/ijtpp11010015 - 3 Mar 2026

Viewed by 974

Abstract

Large-diameter axial-flow fans are predominantly used for cooling purposes, such as in air-cooled heat exchangers. Since it is difficult to experimentally test large-scale fans in the controlled environments provided by fan test facilities, smaller scaled-down versions of the fans are tested instead. Scaling laws, also called affinity laws, are then used to determine the performance characteristics of the large-scale fan. The size difference between the two scaled fans means that it is not possible to match their Reynolds numbers when testing with the same test fluid. A comparison is conducted using experimental results and four numerical models for two different fans, which are scaled to different fan sizes: 0.63 m, 1.542 m, 3.658 m and 7.315 m, to determine the effect of Reynolds number on the performance characteristics of an axial-flow fan. The numerical geometries are based on the M- and B2a-fans, and are tested in the A-type experimental setup fan test facility at Stellenbosch University, which is used to obtain the experimental results. It was found that the numerical approach discussed within this paper, namely a Reynolds-Averaged Navier–Stokes (RANS) approach, can predict the performance of multiple fan sizes without relying on turbomachinery or blade-specific empirical correlations. This approach accelerates the evaluation of fan performance while enabling the parameterization of fan configurations. Full article

(This article belongs to the Special Issue Advances in Industrial Fan Technologies)

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15 pages, 85864 KB

Open AccessFeature PaperArticle

An Overview of the Benchmark Case for the Aeroacoustics and Structural Acoustics of an Enclosed Centrifugal Fan

by Felix Czwielong, Patrick Heidegger, Manuel Lauber, Christoph Heigl, Andreas Wurzinger, Marco Fritzsche, Stefan Schoder, Manfred Kaltenbacher and Stefan Becker

Int. J. Turbomach. Propuls. Power 2026, 11(1), 10; https://doi.org/10.3390/ijtpp11010010 - 3 Feb 2026

Viewed by 1096

Abstract

As part of a joint research project between the Institute of Fluid Mechanics (LSTM) and the Institute of Fundamentals and Theory of Electrical Engineering (IGTE), an international benchmark case for fluid–structure–acoustic interaction was developed. The research focused on an enclosed centrifugal fan, and its aerodynamic, aeroacoustic and structure–acoustic properties were characterised through experimental measurements. This paper provides an overview of the centrifugal fan, its enclosure and the test rig used for the experimental investigations. Rather than interpreting the results, the focus is on presenting the benchmark case and providing an overview of the available data. The entire benchmark dataset is listed and freely accessible via the Zenodo European platform in the EAA benchmark data collection. Full article

(This article belongs to the Special Issue Advances in Industrial Fan Technologies)

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12 pages, 7536 KB

Open AccessFeature PaperArticle

On the Effect of Tip Flow on the Noise of a Ducted Rotor

by Jose Rendón-Arredondo and Stéphane Moreau

Int. J. Turbomach. Propuls. Power 2026, 11(1), 5; https://doi.org/10.3390/ijtpp11010005 - 5 Jan 2026

Cited by 1 | Viewed by 1109

Abstract

This study focuses on the aeroacoustic aspects of ducted rotors that could possibly be used in future electrically driven helicopter tail rotor systems. It provides a comprehensive understanding of the tip flow evolution, and of the interaction with the stator stage. High-fidelity compressible numerical simulations are performed and compared with experimental results. A periodic variation is seen in the aerodynamic performance of the rotor blades, which is associated to a potential-interaction phenomenon. Additionally, the convection of the tip vortices and further impingement in the stator vanes generate torque fluctuations on these elements. Dilatation fields and

P_{r m s}

contours confirm a noise source generated by the tip-vortex–stator interaction. Finally, excellent far-field noise comparisons between the numerical and experimental results are obtained for both tonal and broadband noise. Full article

(This article belongs to the Special Issue Advances in Industrial Fan Technologies)

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21 pages, 12257 KB

Open AccessArticle

The Characterization of the Installation Effects on the Flow and Sound Field of Automotive Cooling Modules

by Tayyab Akhtar, Safouane Tebib, Stéphane Moreau and Manuel Henner

Int. J. Turbomach. Propuls. Power 2026, 11(1), 1; https://doi.org/10.3390/ijtpp11010001 - 19 Dec 2025

Viewed by 815

Abstract

This study investigates the aerodynamic and aeroacoustics behavior of automotive cooling modules in both conventional internal combustion engine (ICE) vehicles and electric vehicles (EVs), with a particular focus on installation effects. Numerical simulations based on the Lattice Boltzmann Method (LBM) are conducted to analyze noise generation mechanisms and flow characteristics across four configurations. The study highlights the challenges of adapting classical cooling module components to EV setups, emphasizing the influence of heat exchanger (HE) placement and duct geometry on noise levels and flow dynamics. The results show that the presence of the HE smooths the upstream flow, improves rotor loading distribution and disrupts long, coherent vortical structures, thereby reducing tonal noise. However, the additional resistance introduced by the HE leads to increased rotor loading and enhanced leakage flow through the shroud-rotor gap. Despite these effects, the overall sound pressure level (OASPL) remains largely unchanged, maintaining a similar magnitude and dipolar directivity pattern as the configuration without the HE. In EV modules, the inclusion of ducts introduces significant flow disturbances and localized pressure fluctuations, leading to regions of high flow rate and rotor loading. These non-uniform flow conditions excite duct modes, resulting in troughs and humps in the acoustic spectrum and potentially causing resonance at the blade-passing frequency, which increases the amplitude in the lower frequency range. Analysis of the loading force components reveals that rotor loading is primarily driven by thrust forces, while duct loading is dominated by lateral forces. Across all configurations, fluctuations at the leading and trailing edges of the rotor are observed, originating from the blade tip and extending to approximately mid-span. These fluctuations are more pronounced in the EV module, identifying it as the dominant source of pressure disturbances. The numerical results are validated against experimental data obtained in the anechoic chamber at the University of Sherbrooke and show good agreement. The relative trends are accurately predicted at lower frequencies, with slight over-prediction, and closely match the experimental data at mid-frequencies. Full article

(This article belongs to the Special Issue Advances in Industrial Fan Technologies)

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16 pages, 12081 KB

Open AccessArticle

Numerical and Experimental Investigations of the Sound Generation and Possible Optimization Techniques of Wires for Fan Guard Grilles

by Sandra Hub and Frieder Lörcher

Int. J. Turbomach. Propuls. Power 2025, 10(4), 45; https://doi.org/10.3390/ijtpp10040045 - 21 Nov 2025

Viewed by 966

Abstract

For modern axial fans optimized for low self-noise, additional noise emission from guard grilles mounted downstream of the fan can become one of the dominant sources of sound. In the present case, the overall sound power level increases by up to 6 dB. Based on narrow-band acoustic measurements and numerical Lattice-Boltzmann simulations of wind tunnel setups using round wires, it is observed that periodic flow separations behind the wires (von Kármán vortex street) lead to a pronounced hump in the noise spectrum. This occurs in a frequency range that corresponds to the grille-induced noise increase observed with an axial fan under comparable flow conditions. By examining various wire geometries, it was found that disrupting the von Kármán vortex street along the longitudinal direction of the wire and reducing the homogeneity of flow separation can significantly decrease sound generation. As a result, a guard grille prototype incorporating the most promising structures was manufactured for a modern low-noise axial fan. Comparative experimental results for the fan are presented. Full article

(This article belongs to the Special Issue Advances in Industrial Fan Technologies)

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21 pages, 3301 KB

Open AccessArticle

Toward the Detection of Flow Separation for Operating Airfoils Using Machine Learning

by Kathrin Stahl, Arnaud Le Floc’h, Britta Pester, Paul L. Ebert, Alexandre Suryadi, Nan Hu and Michaela Herr

Int. J. Turbomach. Propuls. Power 2025, 10(4), 41; https://doi.org/10.3390/ijtpp10040041 - 3 Nov 2025

Cited by 2 | Viewed by 1312

Abstract

Turbulent flow separation over lifting surfaces impacts high-lift systems such as aircraft, wind turbines, and turbomachinery, and contributes to noise, lift loss, and vibrations. Accurate detection of flow separation is therefore essential to enable active control strategies and to mitigate its adverse effects. Several machine learning models are compared for detecting flow separation from surface pressure fluctuations. The models were trained on experimental data covering various airfoils, angles of attack (0°–23°), and Reynolds numbers, with

{Re}_{c} = 0.8 - 4.5 \times 10^{6}

. For supervised learning, the ground-truth binary labels (attached or separated flow) were derived from static pressure distributions, lift coefficients, and the power spectral densities of surface pressure fluctuations. Three machine learning techniques (multilayer perceptron, support vector machine, logistic regression) were utilized with fine-tuned hyperparameters. Promising results are obtained, with the support vector machine achieving the highest performance (accuracy 0.985, Matthews correlation coefficient 0.975), comparable to other models, with advantages in runtime and model size. However, most misclassifications occur near separation onset due to gradual transition, suggesting areas for model refinement. Sensitivity to database parameters is discussed alongside flow physics and data quality. Full article

(This article belongs to the Special Issue Advances in Industrial Fan Technologies)

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12 pages, 765 KB

Open AccessArticle

Optimising Ventilation System Preplanning: Duct Sizing and Fan Layout Using Mixed-Integer Programming

by Julius H. P. Breuer and Peter F. Pelz

Int. J. Turbomach. Propuls. Power 2025, 10(4), 32; https://doi.org/10.3390/ijtpp10040032 - 1 Oct 2025

Cited by 1 | Viewed by 1077

Abstract

Traditionally, duct sizing in ventilation systems is based on balancing pressure losses across all branches, with fan selection performed subsequently. However, this sequential approach is inadequate for systems with distributed fans in the central duct network, where pressure losses can vary significantly. Consequently, when designing the system topology, fan placement and duct sizing must be considered together. Recent research has demonstrated that discrete optimisation methods can account for multiple load cases and produce ventilation layouts that are both cost- and energy-efficient. However, existing approaches usually concentrate on component placement and assume that duct sizing has already been finalised. While this is sufficient for later design stages, it is unsuitable for the early stages of planning, when numerous system configurations must be evaluated quickly. In this work, we present a novel methodology that simultaneously optimises duct sizing, fan placement, and volume flow controller configuration to minimise life-cycle costs. To achieve this, we exploit the structure of the problem and formulate a mixed-integer linear program (MILP), which, unlike existing non-linear models, significantly reduces computation time while introducing only minor approximation errors. The resulting model enables fast and robust early-stage planning, providing optimal solutions in a matter of seconds to minutes, as demonstrated by a case study. The methodology is demonstrated on a case study, yielding an optimal configuration with distributed fans in the central fan station and achieving a 5% reduction in life-cycle costs compared to conventional central designs. The MILP formulation achieves these results within seconds, with linearisation errors in electrical power consumption below 1.4%, confirming the approach’s accuracy and suitability for early-stage planning. Full article

(This article belongs to the Special Issue Advances in Industrial Fan Technologies)

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