Fan Operation Research Articles

A novel time-current-temperature difference (T-I-T) defrosting control method for air source heat pump based on outdoor fan operation characteristics in space heating

In space heating, air source heat pumps (ASHPs) always encounter mal-defrosting incidents, resulting in significant energy waste. To improve the defrosting accuracy of ASHP, this paper proposes a novel Time-Current-Temperature difference (T-I-T) defrosting control method based on the characteristic parameter of outdoor fan operation (current). Through theoretical analysis and experimental tests, the influence of frosting on the characteristic parameters of outdoor fan operation was revealed. Then, based on the optimal defrosting control point theory, a method for selecting the defrosting current threshold close to the actual ASHP was proposed. Ultimately, a novel Time-Current-Temperature Difference (T-I-T) defrosting control method was developed, using the current increment to control the defrosting operation. The results showed that, the defrosting current thresholds decreased as the severity of frosting decreases, from 1.52 to 0.78 A. The T-I-T defrosting control method enables the ASHP unit to operate stably and efficiently in space heating. The defrosting frequency decreased from 0.93 to 0.56 times per hour, a reduction of 39.80 %; the average duration of the frosting/defrosting cycle increases from 64.30 to 106.90 min (an increase of 66.25 %), and the average COP of the ASHP unit increases by 10.60 % compared to the T-T defrosting control method.

An actuator-disk model augmentation for low-pressure axial fan simulation

Abstract Actuator-disk rotor models are important simulation tools for cost-effective industrial axial fan system analysis. Actuator-disk fan model performance, however, is constrained by the conventional use of 2D airfoil coefficient input data which limits the accuracy of the models to a narrow operating range free from significant secondary radial blade flow effects. Radial blade flow is characteristic of off-design fan operation which is often unavoidable within typical industrial fan system environments, so the enhancement of actuator-disk model performance for these conditions is desired. This paper accordingly presents a new means of robustly determining actuator-disk model coefficient inputs that are suitable for a wide range of fan operating conditions. The proposed Augmented Actuator-disk Method (AADM) capitalizes on new insights on the unique aerodynamic behavior of low-pressure axial fan rotors. The performance of the AADM is evaluated for two different industrial cooling fans and is shown to outperform existing actuator-disk coefficient formulations through computational fluid dynamics (CFD) simulations. The AADM is shown to better predict key fan performance metrics, spanwise blade force distributions, and to produce flow fields that are more physically representative (an important feature for industrial heat exchanger studies where the AADM is anticipated to be commonly applied). The AADM has been developed to be easily adopted in generic industrial fan analyses and is expected to serve as a valuable springboard for future actuator-disk fan model developments.

Prediction of Fan Array Performance with Polynomial and Support Vector Regression Models

The increasing utilisation of demand-controlled ventilation strategies leads to the frequent operation of fans under part-load conditions. To accurately predict the energy demand of a ventilation system with a fan array in the early design stages, models that calculate reliable results across the whole operating range are required. We present the comparison of a polynomial and a machine learning approach through support vector regression (SVR) to predict the fan performance over a wide range of typical operating points. For fitting and validation, we use experimental data. We investigate the extrapolation performance of both approaches. The SVR model achieves a slightly better representation of the experimental data with a lower error, especially when only sparse data are available. Both approaches yield similar results when the evaluation is conducted within the experimentally captured domain but deviates outside the domain. At operating points that are far from the experimentally captured domain, the polynomial models yield fan efficiencies that are physically plausible, while the SVR models drastically overpredict the fan efficiency. To rate the influence of such deviations towards modelling the actual energy demand, both approaches are applied to an operation simulation of a simplified office building. Both approaches yield similar results despite differing extrapolation capabilities.

An Optimization Approach for Enhancing Energy Efficiency, Reducing CO2 Emission, and Improving Lubrication Reliability in Roller Bearings using ABC Algorithm

Friction and energy waste pose significant challenges in various industrial processes. Lubrication plays a crucial role in reducing friction and optimizing energy consumption. This study focuses on analyzing, simulating and calculation the oil film thickness, friction levels, energy losses, and CO2 emissions. The objective is to optimize lubrication conditions to enhance performance, improve energy consumption, and maximize lubrication efficiency for rolling bearings in a centrifugal fan. The simulation utilizes ANSYS CFX software, MATLAB programming. The optimal oil viscosity grade is determined based on two objectives by using artificial bee colony algorithm (ABC): minimizing energy consumption (thus reducing CO2 emission) and achieving the optimal oil film thickness and viscosity ratio. The findings reveal that, under the current lubrication conditions and normal fan operation, energy losses due to oil friction amount to 36.3 MWh per year, with CO2 emissions resulting from power losses reaching 18,750 kilograms per year. By transitioning to the optimized oil grade, energy savings of 1.08 MWh per year and a corresponding reduction of 557 kilograms in CO2 emissions per year can be achieved.

Quality control of functioning of the structure “object-thermoelectric cooler-heat sink” of the system of providing thermal modes

The analysis of the mathematical model of the system of providing thermal modes with the use of thermoelectric cooling to assess the influence of the conditions of heat exchange of the heat sink with the medium on the main parameters, reliability indicators and dynamic characteristics of a single-cascade thermoelectric cooler at a given temperature level of cooling, medium temperature, geometry of branches of thermoelements for different current operating modes is considered. The results of calculations of the main significant parameters, reliability indicators, dynamic and energy characteristics of a single-cascade cooler and heat sink of the selected design at a given temperature level of cooling, medium temperature, thermal load, geometry of branches of thermoelements for various characteristic current operating modes are given, when the conditions of heat exchange on the heat sink of the given design under variation of the heat transfer coefficient. It is shown that with the increase of air flow velocity on the heat sink the heat transfer coefficient increases and thus the temperature drop on the heat sink of the thermoelectric cooler with the medium decreases, which allows to significantly reduce the relative failure rate of the cooler and thus increase the probability of failure-free operation of the whole device. When operating a system for providing thermal modes comprising a cooling device, a heat sink, and an electric fan used for dissipating heat output to the environment, different modes of operation of the electric fan (air flow rate) can be used. With the increase in air flow rate of the electric fan increases the velocity of air flow in the live section of the heat sink of a given design, which leads to an increase in the heat transfer coefficient. This, in turn, makes it possible to reduce the temperature drop at a given design of the system for ensuring thermal modes. The possibility of control of reliability indicators, namely, relative intensity of failures and probability of failure-free operation of thermal mode systems of different designs (current modes, number of thermocouples, surface area of the heat sink) at a given cooling level (medium temperature, thermal load, geometry of thermocouples) under changing conditions of heat exchange of the heat sink with the medium is considered.

Reverse Thrust Aerodynamics of Variable Pitch Fans with Inlet Distortion

Abstract Variable pitch fans can improve the operability of low pressure ratio fan systems by re-pitching the rotor blades. If a variable pitch fan can generate sufficient reverse thrust on landing it also eliminates the need for heavy, cascade-type thrust reversers. However, any reverse thrust generation is impacted by high levels of inlet distortion generated as air is drawn into the exhaust nozzle. This paper uses RANS computations and low-speed rig experiments to explore how a representative inlet distortion from the engine installation affects the aerodynamics and performance of a variable pitch fan operating in reverse thrust mode. The simulations and the experiments show that the distortion from the engine installation leads to a highly three-dimensional flow field with a large recirculation region within the bypass duct. The distortion substantially redistributes the mass flow, thrust and power in the engine. Streamline tracking combined with a power balance analysis reveals highly radial flow within the fan rotor, with almost all the fan power used to drive the recirculating flow in the bypass duct, generating high loss and high total temperature. The recirculation reduces the net mass flow through the engine to around 5% of a uniform inflow case and greatly reduces the effective reverse thrust. With uniform inflow, the net reverse thrust was found to be 35% of the nominal takeoff thrust. With inlet distortion, this was reduced to 20%. This demonstrates the importance of designing and operating variable pitch fan systems to minimise reverse thrust inlet distortion.

Predictive modelling of multi-domain factors on window, door, and fan status in naturally ventilated school classrooms

Most studies regarding the investigation of occupant behaviour (OB) in school classrooms addressed the environmental influence on window operation solely and were conducted in oceanic climates. This study aimed to identify and quantify the influence of multi-domain factors (including thermal, indoor air quality, contextual and multi-behaviour domains) on window, door, and fan status in naturally ventilated school classrooms in a humid subtropical climate, in order to predict OB. Environmental variables, manual operation of windows, doors and fans, and occupancy rate were monitored and questionnaires were applied in a set of classrooms of three public school buildings in the state of São Paulo, Brazil, during four rounds at two-month intervals, resulting in a comprehensive year-long study. During part of the physical monitoring, restrictive occupancy measures due to the COVID-19 pandemic were observed. Generalized Linear Mixed Models were applied to assess the influence of the recorded parameters on the window, door, and fan status and to generate OB predictive models. Results showed that indoor environmental variables influenced window, door, and fan status in school classrooms, with few exceptions. Yet, the models including school routines, social norms and teachers’ behaviour as predictors led to the highest accuracy. This suggests that, while a more complex model with additional predictors can provide more accurate predictions of OB, it also becomes more context-dependent and less generalizable. The trade-off between model complexity and generalizability is an important consideration in this research study, and it highlights the nuanced relationship between multi-domain factors affecting occupant behaviour in school buildings.

Identification of required power for air transport system of the cotton-picking machine MX-2.4

Abstract This article addresses the issues in the air transport system of semi-suspended MX-1.8 and MX-2.4 cotton pickers with a vertical spindle. Given that semi-suspended machines currently pick cotton crops with 60 cm row spacing, the goal is to eliminate the shortcomings of these machines and optimize the technological parameters of this machine. The power required for fan operation is calculated, taking into account the additional aerodynamic resistance caused by the complexity of the air transport system design. The results of the calculations are presented in the form of a histogram.

Tunnel Ventilation Silencer Replacement Project

Silencers play a major role on road and rail tunnel ventilation projects throughout North America and the globe. They are instrumental in acheving the required dBA levels; specifically for emergency announcements. Vibro-Acoustics was called to replace silencers that began rusting internally. This caused metal pieces to break off during fan operation. Blade strikes were discovered by maintenance personel which promped an entire replacement task. This was a challenge in itself to remove the existing silencers and install new ones in their place as many space restrictions were present. The new silencers had to be fabricated in a way to meet the stringent acoustic requirements but also for ease of installation. They consisted of 84" inlet and 144" discharge lengths to acheive the noise requirements both at the track level and nearly street level. The silencers consisted of 3/16" plate casings and G235 18 gauge baffles as per the engineers specification. This presentation will show the steps taken to remove the old silencers, the challenges of installing the new silencers, and the testing process for ceritfiying the acoustic performance by a third party acoustical consulant located in NYC. Vibro-Acoustics was involved throughout the entire project which dates back to 2018.

Noise control tactics to balance the demand for sustainable energy storage, community tranquility, and environmental regulatory compliance

As the construction of large-scale Battery Energy Storage System (BESS) facilities increases in California, their impact on urban sprawl is also becoming more pronounced. Projects involving BESS arrangements increasingly find themselves within or near residential land uses in California, providing greater challenges for noise control and abatement to comply with state and local operational noise thresholds. This paper presents case studies of what Dudek has found to be the most efficient noise control tactics related to lowering the noise emission of BESS facilities, particularly through the implementation of onsite noise walls, direct noise attenuation applied to BESS equipment (i.e., noise attenuation for battery thermal management systems involving the operation of ventilation fans and refrigeration system components), and modified BESS equipment arrangements. These strategies are essential for ensuring that BESS projects are not only compliant with environmental standards but also socially acceptable within residential communities. By presenting practical and efficient noise mitigation techniques, this paper aims to guide planners and developers in the sustainable development of BESS facilities, balancing the demand for energy storage with the preservation of community tranquility and compliance with regulatory noise limits.

Atmospheric alchemy: The energy and cost dynamics of direct air carbon capture

Abstract Amid a relentless global climate crisis, the 28th Conference of the Parties (COP28) spotlighted Direct Air Carbon Capture (DACC) as a key intervention to mitigate escalating temperatures and CO2 levels. The Intergovernmental Panel on Climate Change (IPCC) underscores the urgency of this challenge, stipulating the need for robust CO2 removal strategies. It sets a daunting yet crucial target: capture 85 million metric tons of CO2 by 2030, escalating to 980 million metric tons by 2050, to achieve net-zero emissions (IEA, Executive Summary—Direct Air Capture 2022—Analysis. https://www.iea.org/reports/direct-air-capture-2022/executive-summary). Despite this imperative, the existing 19 operational DAC facilities globally face significant barriers, including prohibitive costs and stringent regulations, which impede their large-scale application (Ozkan et al.). Current status and pillars of direct air capture technologies. Iscience (2022). While COP28 stopped short of delineating a definitive roadmap for DAC, this article addresses a vital aspect of this technology: DAC processes’ substantial energy and heat requirements, which are integral to their operational efficiency and economic viability. This article illuminates pathways for future technological evolution and cost optimization through an in-depth analysis of these requirements, thereby charting a course toward a more effective and scalable DAC infrastructure. Graphical abstract Highlights With atmospheric CO2 exceeding 420 ppm, the clock is ticking on the climate crisis. DAC offers a revolutionary approach to directly remove this excess CO2, acting as a critical tool in our fight for a sustainable future. However, current DAC systems face the challenge of high energy consumption. Continuous fan operation for air intake and sorbent material regeneration, consuming nearly 2000–3000 kWh per ton of CO2 captured, are major contributors. Optimizing these processes is crucial. Advancements in sorbent efficiency, system design that minimizes parasitic energy losses, and seamless integration with renewable energy sources are key to slashing DAC’s energy demands. By reducing its carbon footprint and enhancing economic viability, these advancements can unlock the full potential of DAC to become a game-changer in combating climate change and securing a cleaner future for our planet. Discussion Given the significant energy and heat requirements of DACC processes, what technological innovations are necessary to make these systems more energy efficient and economically viable? Considering the substantial energy demands of DACC processes, what are the most promising avenues for reducing these requirements to enhance the technology's scalability and cost-effectiveness? How can current technological limitations be overcome to scale up DACC effectively? What role could renewable energy sources play in meeting the energy and heat demands of DACC facilities, and how might this integration impact the overall carbon footprint of the carbon capture process? How do the energy and heat requirements of DACC technologies influence their location and infrastructure needs, particularly in relation to energy sources and heat sinks? What technological innovations or advancements are currently being explored to optimize the energy and heat efficiency of DACC processes, and what challenges do they face in terms of implementation and scaling? Given the significant role of DACC in achieving net-zero emissions targets, how can policy and regulatory frameworks be designed to support the development and deployment of energy-efficient DACC solutions?

A coronavirus disease 2019 outbreak in a residential living facility with suboptimal ventilation in resident rooms

We report a large outbreak of severe acute respiratory syndrome coronavirus 2 in a residential living facility. Measurements of carbon dioxide levels, aerosol particle clearance, and airflow were used to identify and remediate areas with suboptimal ventilation. A simple intervention involving continuous operation of bathroom fans was effective in significantly improving ventilation in resident rooms.

Determination of the possibilities of using the universal low-temperature rotary apparatus for the production of meat and vegetable products under the conditions of providing uniform heat supply

The object of research is the process of frying a meat-vegetable product in the developed universal low-temperature rotary apparatus. The problem of ensuring the uniformity of the temperature field during low-temperature processing of meat and vegetable products is solved in the developed universal low-temperature rotary apparatus. The expected effect during the approbation of the apparatus is predicted under the condition of eliminating high-temperature intermediate coolants (hot air, etc.) due to the use of a film-like resistive electronic heater of the radiating type. The temperature field is established, which confirms the uniformity of the temperature effect on meat and vegetable products, and a slight deviation within the limits of autonomous exhaust fans is not critical and within the permissible error. Also, the introduction of Peltier elements into the design of the rotary apparatus will allow converting thermal energy into a low-voltage supply voltage (3–6 W) and, already at 20 °C, ensure autonomous operation of fans. The obtained results in the form of practical implementation of the developed apparatus will allow to implement low-temperature processing of meat and vegetable products. This allows to maximally preserve the functional properties of meat raw materials and the physiological properties of vegetable semi-finished products with a high degree of readiness. The practical implementation of the universal low-temperature rotary apparatus from the side of constructive implementation due to the use of functional containers makes it possible to obtain a wide range of assortment of meat products, both in the shell and without the shell. The elimination of high-temperature intermediate heat carriers (hot air, steam, etc.), their technical networks and generating apparatuss ensures energy and metal-intensive resource savings. In addition, the introduction of multicomponent vegetable semi-finished products of a high degree of readiness (powders, pastes, etc.) into the recipes of meat products will lead to a partial replacement of the main recipe components and an increase in the functional properties of the finished products.

Design of a universal low-temperature rotary apparatus for making meat and vegetable products considering the integrated adaptive mechanism

The object of this study is the implementation of low-temperature processes for the production of meat and vegetable products under the conditions of adding a dried semi-finished product of a high degree of readiness to the recipe when using the designed universal rotary device of continuous action. The rotary device of continuous action for low-temperature processing of meat and vegetable products with a cylindrical working chamber is heated by a film-like resistive electronic heater of the radiating type. It has a stationary wall (with a technical door for unloading and loading the device) and a technical wall (with an opening angle of 90°). On the inner surfaces of the walls, inclined converging ribs with an angle of 25° are installed, which are covered with an electric heater. Semi-finished meat and vegetable products are loaded onto carts with technological containers and mounted on a frameless drum (rotation frequency 0.03...0.06 s–1). The device converts secondary thermal energy into low-voltage power supply voltage (~3...8 W) for autonomous operation of fans. The proposed integrated adaptive mechanism for the system of complex interaction of the agricultural, processing, and production sectors implies the formation of resource efficiency of production processes from "farm to table". The designed device implements the process of frying meat-vegetable bread under conditions of reaching 80 °C in the center of the product. The obtained temperature field data confirm the uniformity of the temperature field during frying of the product (cooking readiness of the product at the initial weight of 650±20 g – 4.0 hours). The introduction of a multicomponent dried fraction based on potatoes, Jerusalem artichokes, zucchini, and carrots into the recipe of meat-vegetable bread reduces the weight loss of the semi-finished product during frying by 12.3 %. It increases the content of calcium, phosphorus, vitamin C accompanied with a decrease in energy value by 28.1 %

Removal efficiency of restroom ventilation revisited for short-term evaluation

Ventilation efficiency or contaminant removal efficiency is often evaluated using the ratio between the concentrations in the exhaust air and the room air. This ratio does not truly represent the expectation of ventilation in restrooms, where dynamic airflow fields and sources are more typical. This study focuses on a short-term (10 min) pollutant removal percentage in a residential restroom featuring a dynamic airflow field, particularly with the onset of window-induced stack ventilation during toilet uses. Thirteen ventilation scenarios of a residential restroom were studied using the numerical method that was validated by a mock-up experiment. The scenarios differed in the operation of the exhaust fan and window. Results show that the 10-min pollutant removal percentage of a typical exhaust ventilation system at 10 h-1 air change rate (ACH) is only 68.5%. Under exhaust ventilation, opening the window can introduce both adverse short circuit and favorable stack ventilation depending on the difference between the indoor and outdoor temperatures. As the temperature difference increases from 0 to 12.5 °C, the removal percentage increases from below 50%, a drop due to short circuit, to above 98% thanks to a tripled ventilation rate. The human thermal plume has notable effect on the removal percentage, but its effect can be neglected with the presence of stack ventilation. The hybrid ventilation strategy has impact on perceived air quality and thermal comfort. When the outdoor air is colder, opening the window under exhaust ventilation may increase the current sitting user’s exposure to the self-produced pollutants but can reduce the exposure of the next immediate standing user. In addition, opening the window in cold days will make the toilet user thermally uncomfortable with reduced local temperatures and increased airflow velocities. The study highlights the importance of using the short-term removal percentage to evaluate the performance of restroom ventilation.

Constructing heterojunction on N-doped porous carbon nanofibers for Li-S batteries: Effect of built-in electric field on efficient catalytic transformation kinetics

In this study, the CoP-Co2P heterojunction nanoparticles embedded in N-doping porous carbon nanofibers (CoP-Co2P/NPCNFs) are designed and prepared. The highly conductive grid of NPCNFs can physically confining lithium polysulfide (LiPS) and provide facilitated channels for Li+ transport. Furthermore, due to the spontaneous built-in electric field (BIEF) based on at the formed heterogeneous interfaces of CoP-Co2P, the heterojunction can significantly catalyze bi-directional conversion of LiPS and chemically adsorb LiPS which confirmed by the DFT calculations, suppressing the “shuttle effect” of LiPS. Thus, the Li-S batteries with the CoP-Co2P/NPCNFs modified separators exhibit a high initial specific capacity of 1322.86 mAh g−1 at 1 mA cm−2 and stable 695 cycles with a low decay rate (0.069 %). More importantly, the assembled pouch cell also can run with ultra-low specific capacity decay rate. Additionally, the pouch battery can also be applied to the operation of fans, temperature and humidity meters, mobile phone charging, etc.

Energy modelling and analysis of variable speed series fan-powered terminal units (FPTUs) using energy management system (EMS) in EnergyPlus

The energy impact of constant and variable speed fan operations in series fan-powered terminal units (FPTUs) was investigated by simulating a small office building with four climates in EnergyPlus. While the existing module in EnergyPlus was used to model the performance of constant speed FPTUs, the performance model of variable speed FPTUs was implemented by using energy management system and user-defined modules. Compared with constant speed FPTUs, the variable speed FPTUs could save up to 90% of terminal unit fan energy, 4% of central supply fan energy, and 6% of central cooling coil energy although the heating energy increased due to reduction of fan motor heat gains. The overall savings in the HVAC system was in a range of 15–35% depending on local climates. The demonstration of modelling variable speed series FPTUs in EnergyPlus could increase the awareness of energy efficiency design and promote its incorporation into standard EnergyPlus modules.

Constant static pressure strategy for residential kitchen exhaust system: Deducing control parameters from required exhaust rate and non-distributed data transmission

Roof fans have gradually replaced the non-powered hood as supplementary power to increase exhaust rate in high-rise residential kitchen shafts. However, an effective control strategy for roof fans is lacking. This paper studies the constant static pressure strategy and deduces its control parameters based on required exhaust rate and non-distributed data transmission. First, the static pressure set value (SV) is investigated under the worst exhaust condition, considering variations in shaft heights and measuring positions (MP). Then, an on/off mechanism is set up based on the measured static pressure and the fan frequency when the exhaust rate is adequate. Results show that under the recommended shaft sizes and design concurrent usage rates, the SVs for users' exhaust rate reaching 500 m³/h are −60, −60, and 0 Pa for 10/18/26-floor shafts when the MP is at a shaft's outlet, and roof fans are turned on when the static pressure reaches 100, 90, and 90 Pa and turned off when the fan frequency is below 32, 30, and 22 Hz. The MP at the shafts' outlet can keep the shaft at a slightly negative pressure. Control parameters for specific applications can be obtained through the proposed calculation process. An 18-floor shaft study found that the constant static pressure strategy can achieve 50 % energy savings compared to the constant frequency operation of the roof fan. These findings contribute to reliable control without users' distributed data transmission and to lower energy consumption of the residential kitchen exhaust system.

Jet noise of a low bypass turbofan with internal mixing and external plug

Jet noise generated by turbofan engines which are designed for supersonic aircraft operation is expected to remain a challenge for the aerospace industry. For civil supersonic transport, low bypass ratio engines with internal mixing and external plugs are currently seen as promising exhaust architecture to meet aircraft mission and certification requirements. Measurements of the noise from a representative low-bypass ratio long duct mixed flow with external plug exhaust configuration were made, along with corresponding steady-RANS and LES analyses. The measured data showed excess high frequency noise across a wide range of operating conditions as compared to an equivalent single stream jet, or an equivalent uniform jet with internal plug. The absolute levels of the excess noise were relatively insensitive to forward flight, and the excess noise was most dominant when the primary and secondary streams had large velocity and temperature mismatch just upstream of the internal mixer. Preliminary indications from the LES analysis also indicated that significant pressure fluctuations, at the same frequencies which are insensitive to forward flight, develop inside the nozzle as the internal shear layer from the mixer grows and gets accelerated by the external plug. Parametric study test measurements on the fan and core operating conditions were performed, providing support for the hypothesis that the excess noise is generated as the internal shear layer, starting inside the nozzle, gets accelerated by the plug and passes through the weak shock at the nozzle exit where the flow accelerates more and turns over the external plug.

Effects of distortion on a BLI fan

Abstract The BLI (boundary layer ingestion) concept for propulsion seeks to improve the energy efficiency of aircraft propulsion. This is achieved by accelerating low momentum flow ingested from boundary layers and wakes developed over the fuselage through the fan. A major challenge that needs to be overcome to realise the benefits is that the fan needs to work efficiently in distorted flow. Understanding the effects of distortion on the aerodynamic performance and the distortion transfer through the fan is therefore essential to future designs. A BLI fan, designed at reduced scale, is used for analytic modelling and experiments in a rig designed for this purpose. The test rig replicates BLI conditions for a fan installed at the aircraft tail cone. An unsteady model that includes all blades and vanes of the fan, as well as the nacelle and the by-pass duct of the test rig is used for CFD (computational fluid dynamics) simulations. Test results are used to confirm that the CFD model is representative of the aerodynamics of the fan. The tests are conducted using varying fan operating conditions but also tests with an added distortion screen. Analysis results are then used to investigate the effects of distortion on the fan efficiency, as well as on the overall efficiency. The fan efficiency is found to be moderately decreased depending on the level of and extent of inlet circumferential distortion. In terms of overall energy efficiency, a net improvement over a similar fan in clean inlet flow is found.