Air Delivery System Research Articles

Experimental results of a 330 GW impedance-matched Marx generator

Impedance-matched Marx generators (IMGs) are considered next generation pulsed-power drivers because of their long lifetime (> 10,000 shots), repetition rate (> 0.1-Hz), fast rise time (~ 100-ns), and high-energy-delivery efficiency (~ 90%). “TITAN” is a 14-stage IMG designed to deliver 1-TW to a 2-Ω matched load. In this paper, design, simulation, and experimental results for six stages of TITAN including its triggering system, air delivery system, and pulse shaping are presented. To achieve efficiency over 85% and maximize the capability of an IMG, synchronized triggering, reduced pre-fire rate, and pulse shaping ability are crucial. In this paper, novel engineering solutions are introduced, tested, and proven to overcome those challenges. 6-stage TITAN, powered by 102 identical bricks and 102 field-distortion-triggered gas switches, could generate ~ 600-kA and ~ 700-kV across a ~ 0.9-Ω matched load when fully charged to ± 100-kV. In these experiments, 6-stage TITAN is tested up to ± 70-kV charge voltage which delivers a peak power of 330-GW to a 1.2-Ω resistive load.

Research Progress on Gas Supply System of Proton Exchange Membrane Fuel Cells

Proton exchange membrane fuel cells (PEMFCs) are attracting attention for their green, energy-saving, and high-efficiency advantages, becoming one of the future development trends of renewable energy utilization. However, there are still deficiencies in the gas supply system control strategy that plays a crucial role in PEMFCs, which limits the rapid development and application of PEMFCs. This paper provides a comprehensive and in-depth review of the PEMFC air delivery system (ADS) and hydrogen delivery system (HDS) operations. For the ADS, the advantages and disadvantages of the oxygen excess ratio (OER), oxygen pressure, and their decoupling control strategies are systematically described by the following three aspects: single control, hybrid control, and intelligent algorithm control. Additionally, the optimization strategies of the flow field or flow channel for oxygen supply speeds and distribution uniformity are compared and analyzed. For the HDS, a systematic review of hydrogen recirculation control strategies, purge strategies, and hydrogen flow control strategies is conducted. These strategies contribute a lot to improving hydrogen utilization rates. Furthermore, hydrogen supply pressure is summarized from the aspects of hybrid control and intelligent algorithm control. It is hoped to provide guidance or a reference for research on the HDS as well as the ADS control strategy and optimization strategy.

Ultraviolet Germicidal Irradiation Development Method for Transportation Disinfection Modelling

How do you continuously sanitise a coach/bus? Travelling on a coach during the COVID 19 pandemic was risky, and still is in some regions. There are many means of viral transfer: fomites, which is via contact after touching an infected surface; through direct droplet ballistics after a cough, and finally through aerosolization of the sputum into the air. Clean hands and masks reduce the former two. Mitigating viral load aerosol accumulation within the bus is of personal, commercial and societal interest. Done correctly, the passengers are safer; the transport organisation maintains hygienic business conditions and the society sees the viral spread reduction. Ultraviolet Germicidal Irradiation (UVGI) has been in use in operating theatres and water plants for over 100 years to reduce viral and bacterial load in the air and water. Valeo’s Thermal Commercial Vehicles (TCV) product group proposed, developed and now manufactures the most powerful coach/ bus UV Purifier module available. If the module is located within direct reach of the main air conditioning inlet, disinfected air is then delivered and entrained into the vehicle HVAC air delivery system. There it is cleanly distributed to the passengers and driver. During development two linked problems emerged:1. Where do you put the module(s) in retrofit?2. How do you keep the UV-C levels sufficiently high enough to kill the SARS Cov-2 virus but then low enough for continuous driver and passenger daily exposure?Computational Fluid Dynamics (CFD) provides the insight necessary to solve them. However, although high and low UV-C limits can be defined for the latter limit problem, devising a suitably representative model presented a novel challenge to Valeo TCV. This paper deals with the introduction of the radiation and viral field modelling into Valeo’s CFD toolset. Reformulating the InfraRed radiation model into essentially monochromatic UV-C band radiation, and with thoughtful design allowed us to develop a very high intensity virus killer that was also perfectly safe in the vehicle cabin. The modules are sold worldwide. Most importantly we use them daily on our team member transportation coaches to keep our employees safe to and from work at our production facilities.

Effects of the misalignment and axial gap on performance of a cover-plate pre-swirl system with impellers for gas turbine cooling

Impellers are designed and used in the cover-plate cavity of the pre-swirl system of modern gas turbines to keep the circumferential velocity of the airflow consistent with the local velocity of the rotor. This reduces the aerodynamic loss of the pre-swirl air delivery system for turbine cooling and further improves pre-swirl system performance. However, in practical applications, the cover-plate disk with impellers is usually installed and fixed to the turbine disk by buckles, which leads to the possibility of the circumferential position of impellers deviating from the design intention during installation and a certain axial gap between impellers and the turbine disk, resulting in deviations in cooling performance. In this work, low-radius cover-plate pre-swirl systems with and without impellers are compared through numerical simulations, and the effects of the impeller circumferential displacement angle (θ) in the range of −0.5° to 0.5° and the axial gap (Δ) in the range of 0%–25% of the cover-plate cavity width are investigated on the flow characteristics and system cooling performance. Results indicate that the impellers are sensitive to the manufacturing and installation deviations. The non-designed circumferential displacement of the impeller will misalign it with the rotating receiver holes and supply holes, hindering the airflow movement in the radial direction and increasing the back pressure of the impeller. Consequently, the severe vortices on the suction side downstream of the impeller leading edge can occur and the entropy production can increase. Numerical results show that when the impeller is displaced by 0.5° circumferentially, the temperature drop effectiveness decreases significantly, and is about 21% lower than that at the designed condition. Moreover, while the axial gap is small, the overall flow pattern and system temperature drop are only slightly affected. As the axial gap increases, there are more cooling airs flowing through the axial gap and not subject to the work of the impeller. Therefore, the temperature drop starts to fall and the swirl ratio declines. For the system studied, the temperature drop effectiveness decreases by around 7.8% when the axial gap reaches 25% of the cover-plate cavity width.

Performance Analysis and Testing of a Multi-Duct Orchard Sprayer

A multi-duct orchard sprayer is designed in this paper to address the problem of low droplet coverage during plant protection in walnut orchards in South Xinjiang, China. This spray comprises a base frame, a pesticide tank, an air delivery system, a copying base frame and a drive system. Effects of the sprayer structure on the flow field were simulated using computational fluid dynamics. Operation parameters were optimised using the response surface analysis and validated using a field test. The results demonstrated that five jet tubes in the simulation design could fulfil the design requirements of GB/T 32250.3-2022. The upper, middle and lower droplet coverages were 74.92%, 90.01% and 69.9%, respectively, when the sprayer’s advancing speed, the angle of jet tubes and the nozzle diameter were 0.53 m/s, 70.27° and 0.81 mm, respectively. The machine can effectively enhance the spraying efficiency and droplet coverage of each canopy during plant protection operations in the new walnut orchards of South Xinjiang, China, and provide references for designing and optimising fruit tree spraying machinery.

Clinical Issues - July 2023.

Use of clean versus sterile pneumatic tourniquet cuffs Key words: clean, sterile, pneumatic tourniquet, incision site, cuff placement. Active shooter crisis preparedness Key words: active shooter preparedness, emergency response, active shooter event, evacuate, barricade. Heating, ventilation, and air-conditioning parameters Key words: laminar airflow (LAF); unidirectional ultraclean air-delivery system; unidirectional downward airflow; turbulent; heating, ventilation, and air-conditioning (HVAC) system. Modifying directional air pressure settings Key words: directional air pressure, negative-pressure room, positive-pressure room, bronchoscopy, parameters.

Optimization of Diversion Device and Experiment on Air-assisted Sprayers in Orchards

In order to improve the velocity distribution of the airflow field generated by the air-assisted sprayer in the orchard, a flow field distribution model of the sprayer air delivery system based on CFD simulation is designed. The airflow field distribution of the air-assisted operation is obtained through FLUENT simulation. The calculation domain includes the internal flow field and external flow field of the fan. The simulation result guides the optimal installation angle of the flow guide device. The installation angle of the upper deflector is 50°, and the installation angle of the lower deflector is 25°, so that the airflow generated by the air-assisted sprayer is mainly concentrated at a height of 0.7–3 m when it reaches the pear tree canopy. The installation angle of the inner deflector 1 and inner deflector 2 is 35°, the installation angles of the inner deflector 3, inner deflector 4, and inner deflector 5 are all 45°, and the average speed is increased by 18.81% in the range of height 1.6–2.4 m. A velocity distribution experiment is designed to measure the airflow velocity to verify the accuracy of the CFD simulation model. The simulation value is basically consistent with the measured value, which provides guidance for optimizing the parameters of the flow guide device.

Neural network and URED observer based fast terminal integral sliding mode control for energy efficient polymer electrolyte membrane fuel cell used in vehicular technologies

In this research work, a Neural Network (NN) and Uniform Robust Exact Differentiator (URED) observer-based Fast Terminal Integral Sliding Mode Control (FTISMC) has been proposed for Oxygen Excess Ratio (OER) regulation of a Polymer Electrolyte Membrane Fuel Cell (PEMFC) power systems for vehicular applications. The controller uses URED as an observer for supply manifold pressure estimation. NN is used to estimate the stack temperature which is unavailable. The suggested control method increased the PEMFC’s effectiveness and durability while demonstrating the finite-time convergence of system trajectories. By controlling the air-delivery system in the presence of uncertain current requirements and measurement noise, the approach ensures maximum power efficiency. The Lyapunov stability theorem has been used to confirm the stability of the presented algorithm. In addition, the suggested method eliminated the chattering phenomenon and improved power efficiency. Given these noteworthy characteristics, the research has the potential to decrease sensor dependence and production costs while also improving the transient and steady-state response in vehicular applications.

Performance improvement in polymer electrolytic membrane fuel cell based on nonlinear control strategies-A comprehensive study.

A Polymer Electrolytic Membrane Fuel Cell (PEMFC) is an efficient power device for automobiles, but its efficiency and life span depend upon its air delivery system. To ensure improved performance of PEMFC, the air delivery system must ensure proper regulation of Oxygen Excess Ratio (OER). This paper proposes two nonlinear control strategies, namely Integral Sliding Mode Control (ISMC) and Fast Terminal ISMC (FTISMC). Both the controllers are designed to control the OER at a constant level under load disturbances while avoiding oxygen starvation. The derived controllers are implemented in MATLAB/ Simulink. The corresponding simulation results depict that FTISMC has faster tracking performance and lesser fluctuations due to load disturbances in output net power, stack voltage/power, error tracking, OER, and compressor motor voltage. Lesser fluctuations in these parameters ensure increased efficiency and thus extended life of a PEMFC. The results are also compared with super twisting algorithm STA to show the effectiveness of the proposed techniques. ISMC and FTISMC yield 7% and 20% improved performance as compared to STA. The proposed research finds potential applications in hydrogen-powered fuel cell electric vehicles.

3D printed transwell-integrated nose-on-chip model to evaluate effects of air flow-induced mechanical stresses on mucous secretion.

While there are many chip models that simulate the air-tissue interface of the respiratory system, only a few represent the upper respiratory system. These chips are restricted to unidirectional flow patterns that are not comparable to the highly dynamic and variable flow patterns found in the native nasal cavity. Here we describe the development of a tunable nose-on-chip device that mimics the air-mucosa interface and is coupled to an air delivery system that simulates natural breathing patterns through the generation of bi-directional air flow. Additionally, we employ computational modeling to demonstrate how the device design can be tuned to replicate desired mechanical characteristics within specific regions of the human nasal cavity. We also demonstrate how to culture human nasal epithelial cell line RPMI 2650 within the lab-on-chip (LOC) device. Lastly, Alcian Blue histological staining was performed to label mucin proteins, which play important roles in mucous secretion. Our results revealed that dynamic flow conditions can increase mucous secretion for RPMI 2650 cells, when compared to no flow, or stationary, conditions.

Operating Room Improvements Based on Environmental Quality Index Risk Prediction can help Reduce Surgical Site Infections

Importance: The role of the operating room (OR) airborne environment in the incidence of surgical site infections (SSI) has ranked behind patient and perioperative team-related factors associated with risk for SSI. Emerging evidence demonstrates that the design and performance of the OR environment impacts the airborne microbiome both within the sterile field and at tables where instruments and implants are exposed. However, the correlation between OR air quality and the risk of SSI continues to be challenged. Objective: To determine if improving the asepsis of the airborne environment in ORs contributes to reduced SSI rates. Design: The performance of air delivery systems in fourteen operating rooms was evaluated using the Environmental Quality Indicator (EQI) risk picture method to identify potential improvements to airflow management that reduce airborne contamination and operating costs. SSI rates for colon and abdominal hysterectomy procedures were tracked in these ORs for 39 months before and after improvements were implemented. SSI rates were also tracked for the same time frame for six control ORs in which no improvements were made. Airborne microbial data was collected. Setting: Twenty ORs in an academic medical center, Midwest USA. A convenience sample of all surgical patients, de-identified, was used in the twenty ORs studied. Results: SSI rate was reduced from 8.4% to 5.7% (p=.0039) in ORs in which improvements were implemented. Reduction of SSI rate in control ORs was not significant (p=.76). Fewer airborne microbes were detected in areas of OR with improvements (p<.0001). Conclusion: Areas for environmental quality improvement in ORs was identified and mapped by relative risk of contamination. Implementation of these improvements resulted in decreased microbial contamination and contributed to significant reduction in surgical site infection.

Performance evaluation of a hybrid heating system combined a groundwater source heat pump with an existing fuel oil heater for a horticultural greenhouse

ABSTRACT This paper reports a new hybrid heating system (HHS) installed in a horticultural greenhouse to lower the impact of high and unstable fuel prices on the greenhouse operation cost, to save the energy necessary to heat the greenhouse, and to reduce CO2 emissions. The HHS consisted of a groundwater source heat pump system for basic heating and an existing fuel oil heater for peak heating. The performance of the HHS, including the fuel oil and energy savings, and CO2 emissions reduction, was evaluated based on measurements during a heating period from November 2014 through May 2015. The results show that, comparing with only using the existing fuel oil heater to heat the greenhouse, the HHS can save 74.4% fuel oil and 22.8% energy, and reduce 35.5% CO2 emissions. In order to further increase the performance of the HHS, the operating control of the HHS, indoor hot air delivery system, and local thermal insulation of the greenhouse were improved. Performance evaluation based on measurements from November 2015 through May 2016 shows that the improved HHS can save 88.0% fuel oil and 35.9% energy, and reduce 48.7% CO2 emissions, which are significantly higher than those of the HHS before improved. Moreover, the comparison indicates that the performance of HHS was almost not changed with three different groundwater pumping rates tested herein. The proposed HHS is particularly suitable for transforming conventional fossil heating systems of horticultural greenhouses into a more energy-saving and thus sustainable heating system with a comparatively low initial cost.

Design and performance analysis of a vane shaped rotating receiver hole in high radius pre-swirl systems for gas turbine cooling

In a pre-swirl cooling air delivery system for gas turbine, the function of rotating receiver hole is to receive the highly swirled flow from pre-swirl nozzle and direct it to the turbine blade supply hole. The geometry of the receiver hole and its relative velocity to the airflow are critical to the aerodynamic losses and cooling performance of the system. Two vane shaped (VS) receiver hole, which can realize the smooth connecting and matching between the stationary pre-swirl nozzle and rotating turbine blade supply hole, were designed here. The performance comparison between these high radius systems with VS receiver hole and a traditional direct transfer system (Baseline) was carried out. The results show that the nondimensional static pressure in pre-swirl cavity for the Baseline is 1.06 and the temperature drop effectiveness (ηt) is 0.31. While the value of ηt for the system with VS receiver hole increases by 35%, and the nondimensional static pressure reduces to 1.03. Moreover, the improved model Case-2, in which the receiver hole and supply hole connected to each other and the cover cavity was removed, has the lowest nondimensional static pressure of 0.98 and the highest temperature drop effectiveness of 0.71, more than double that of the Baseline model. The matching of rotating-stationary components and rotating-rotating components was described and implemented through the design of VS receiver holes. Flow field analysis was performed out to reveal the mechanism of losses occurred at interfaces of components. A comparison of low radius pre-swirl and high radius pre-swirl systems was also carried out. In the design of high radius pre-swirl systems, the swirl ratio in the system cannot be adjusted by applying an impeller due to the lack of radial space. This makes the VS receiver hole particularly suitable for high radius systems, to help the system achieving dual advantages of high temperature drop and low outer seal leakage.

An automated pressure-swing absorption system to administer low oxygen therapy for persons with spinal cord injury

Mild episodes of breathing low oxygen (O2) (i.e., acute intermittent hypoxia, AIH) elicits rapid mechanisms of neural plasticity that enhance respiratory and non-respiratory motor function after spinal cord injury (SCI). Despite promising outcomes in humans and rodents with SCI, the translational potential of AIH as a clinical therapy remains dependent on a safer and more reliable air delivery system. The purpose of this study is to investigate the performance of a novel AIH delivery system to overcome inconsistencies in human AIH protocols using a hand-operated (manual) delivery system. Specifically, we characterized system performance of AIH delivery in terms of flow rate, O2 concentration, dose timing, and air temperature. Our data show that a novel ‘automated’ delivery system: i) produces reliable AIH with a goodness-of-fit at 98.1% of ‘ideal’; ii) eliminates dose timing errors via programmable solenoid switches; iii) reduces fluctuations in O2 to less than 0.01%; and iv) delivers 62.7% more air flow than the ‘manual’ delivery method. Automated physiological recordings, threshold detection, and visual feedback of the participant's blood O2 saturation, heart rate, and blood pressure ensures real-time user safety. In summary, the ‘automated’ system outperformed the ‘manual’ delivery method in terms of accuracy, reliability, and safety. The ‘automated’ system offers several design features that move the technology closer to a medically approved treatment for clinical and home use.

Calibrated Low-Order Transient Thermal and Flow Models for Robust Test Facility Design

This paper describes an upgrade to high temperature operation of the Engine Component AeroThermal (ECAT) facility, an established engine-parts facility at the University of Oxford. The facility is used for high-TRL research and development, new technology demonstration, and for component validation (typically large civil-engine HP NGVs). In current operation the facility allows Reynolds number, Mach number, and coolant-to-mainstream pressure ratio to be matched to engine conditions. Rich-burn or lean-burn temperature, swirl and turbulence profiles can also be simulated. The upgrade will increase the maximum inlet temperature to 600 K, allowing coolant-to-mainstream temperature ratio to be matched to engine conditions. This will allow direct validation of temperature ratio scaling methods in addition to providing a test bed in which all important non-dimensional parameters for aero-thermal behaviour are exactly matched. To accurately predict the operating conditions of the upgraded facility, a low order transient thermal model was developed in which the air delivery system and working section are modelled as a series of distributed thermal masses. Nusselt number correlations were used to calculate convective heat transfer to and from the fluid in the pipes and working section. The correlation was tuned and validated with experimental results taken from tests conducted in the existing facility. This modelling exercise informed a number of high-level facility design decisions, and provides an accurate estimate of the running conditions of the upgraded facility. We present detailed results from the low-order modelling, and discuss the key design decisions. We also present a discussion of challenges in the mechanical design of the working section, which is complicated by transient thermal stress induced in the working section components during facility start-up. The high-temperature core is unusually high-TRL for a research organisation, and we hope both the development and methodology will be of interest to engine designers and the research community.

The effect of rotating receiver hole shape on a gas turbine pre-swirl system

The life assessment and the efficiency of turbine cooling blades and vanes are seriously affected by the cooling air delivery system of a gas turbine. The pre-swirl system in a gas turbine plays an important role between the stationary and rotating parts to supply enough cooling air at the appropriate temperature at the expense of pressure drop. In the stationary part, the pre-swirl nozzle creates the flow angle in advance of the rotating orifice, called the receiver hole, to minimize energy loss. However, because of the sudden change of direction and area of the flow path, an energy loss occurs at the inlet of the receiver holes. The circumferential velocity at the receiver hole inlet decreases even though the circumferential velocity at the pre-swirl outlet is equal to the tangential velocity of the turbine rotor system. To reduce the energy loss at the pre-swirl system, various shape parameters can be applied to the receiver hole, and the area ratio between the pre-swirl nozzle throat area and the receiver hole cross-sectional area can also be varied considering the structure problem, mass flow rate, and pressure drop. In this study, the shape of the receiver holes and its effects were analyzed using a 3D CFD method that was validated by previous studies including experimental data. The edge shape, inclined angle, area ratio, and number of receiver holes were analyzed with the discharge coefficient, adiabatic effectiveness, and pressure drop. The pre-swirl system perform-ance increased as the area ratio increased, and under fixed area ratio, a large number of smalldiameter receiver holes showed better performance. The receiver hole edge fillet was the most influential shape parameter in pre-swirl performance.

Theory and analysis of the flow in a cooling air delivery system of turbine blade

Theory and analysis of the flow in a cooling air delivery system of turbine blade

Design, decision-making and trade-offs in the Centre for Sustainable Development (La Maison du développement durable) in Canada

In order to fight climate change and reduce carbon emissions, professionals in the construction sector often strive for optimal mechanical / technical solutions and assume that a “best” solution exists at a given time and in a given place. But what happens in sustainable building projects when different sustainability or project objectives run at odds with one another? The Maison du développement durable or Centre for Sustainable Development (CSD) – a LEED platinum certified building — is recognized as one of the most sustainable buildings in Canada. This mixed-use building, conceived to be a social and environmental hub in downtown Montreal, houses 3000 m2 of office space and conference rooms. The design included a series of innovations, such as a five-storey biofiltering wall and an under-floor air delivery system. In 2018, the Fayolle-Magil Construction Research Chair in Architecture, the Building Sector and Sustainability from Université de Montréal and the Canadian NGO Équiterre partnered to conduct a post-occupancy evaluation (POE) of the MDD. The study focused on six functional and architectural aspects of the MDD and involved analyzing 12 integrated design workshops, dozens of project documents, and specifically gathering new data. The results show that finding what is “best” is not what happened in reality. Instead, professionals were required to make a series of trade-offs in decision-making. Some examples of these tradeoffs include: adaptability vs. cost, air quality vs. energy performance, shared spaces vs. building floorplate efficiency, and innovation in the design phase vs. long-term operations. This paper shows that tradeoffs adopted during the design phase impacted the MDD’s performance. The results of this study are not only valuable to the project’s partners, but also to the construction industry in general, offering insight into design compromises in sustainable office buildings.

A model predictive control strategy to optimize the performance of radiant floor heating and cooling systems in office buildings

This paper introduces a smart operation strategy based on model predictive control (MPC) to optimize the performance of hydronic radiant floor systems in office buildings and presents results from its implementation in an actual building. Our MPC approach uses dynamic estimates and predictions of zone loads and temperatures, outdoor weather conditions, and HVAC system models to minimize energy consumption and cost while meeting equipment and thermal comfort constraints. It includes data-driven building models estimated and validated using data from an actual building, and deploys an optimizer based on constraint linear/quadratic programming with hard comfort bounds that yields a global minimum with predicted exogenous disturbances. The MPC results show 34% cost savings compared to baseline feedback control during the cooling season and 16% energy use reduction during the heating season. Also, the radiant floor system with the predictive controller shows 29–50% energy savings when compared with a baseline air delivery system serving two identical thermal zones located in the same building.

Acoustic levitation as a screening method for excipient selection in the development of dry powder vaccines

Spray drying is emerging as a promising technique to produce thermally stable powder vaccines containing viral vectors. One of the most important factors in developing dry powder vaccines is the selection of the excipient carrier, however this process is time intensive, and uses large amounts of costly viral material. In this work, an acoustic levitator modified with a hot air delivery system was evaluated for its ability to mimic spray drying and acts as a screening method for excipient selection. The ability of three binary excipient blends to stabilize a human type 5 adenovirus was evaluated through an in vitro activity assay based on the expression of green fluorescent protein. Dried particle size and shape, glass transition temperature, moisture content, and crystallinity of powders produced by levitation and spray drying were compared. The particles created in the acoustic levitator under moderate heat can be considered representative of the powders that would be produced via spray drying. Viral vector titre losses differ between the methods, however, the trends with respect to excipient performance remain the same. Key material characteristics such as particle morphology and thermal properties are conserved when using the levitator. The acoustic levitator is a good starting point for dry powder vaccine development, and can be used to identify promising excipients while consuming minimal amounts of the viral vector.