Duct Shape Research Articles

Aircraft Ducted Heat Exchanger Aerodynamic Shape and Thermal Optimization

Abstract Interest in aircraft electrification and hydrogen fuel cells is driving demand for efficient waste heat management systems. Ultimately, most of the heat must be rejected to the freestream air. Ducted heat exchangers, also called ducted radiators, are the most common and effective way to do this. Engineers manually design ducted heat exchangers by adjusting the duct's shape and heat exchanger's configuration to reduce drag and transfer sufficient heat. This manual approach misses potential performance improvements because engineers cannot simultaneously consider all of the complex interactions between the detailed duct shape, heat exchanger design, and operating conditions. To find these potential gains, we apply gradient-based optimization to a three-dimensional ducted heat exchanger computational fluid dynamics (CFD) model. The optimizer determines the duct shape, heat exchanger size, heater exchanger channel geometry, and coolant flowrate that minimize the ducted heat exchanger's power requirements while rejecting enough heat. Gradient-based optimization enables the use of nearly 100 shape design variables, creating a large design space and allowing fine-tuning of the optimal design. When applied to an arbitrary, poorly performing baseline, our method produces a nuanced and sophisticated ducted heat exchanger design with five times less cruise drag. Employing this method in the design of electric and fuel cell aircraft thermal management could uncover performance not achievable with manual design practices.

Compact Heat Exchangers With Curved Fins for Hydrogen Turbofan Intercooling

Abstract Hydrogen is being considered as a possible path toward carbon-neutral aviation. There are additional advantages besides its main benefit of CO2-free combustion. One application is to use it for aero engine heat management due to its cryogenic temperature and high heat capacity, including intercooling and exhaust heat recuperation. The focus of this paper is on the design of a compact heat exchanger (HEX) integrated into an intermediate compressor duct (ICD), which could decrease compression work and specific fuel consumption (SFC). This compact heat exchanger features curved fins to promote flow turning and decrease pressure losses compared to more conventional straight fin heat exchangers. Conceptual design and duct shape optimization has been carried out which produced integrated ICD heat exchanger designs with significantly lower air-side total pressure losses compared to their conventional straight fin counterparts, which could improve system level integration and engine performance. A direct outcome of this study is a pressure loss correlation, which can be used in future engine system-level trade studies.

Near-Surface Thermodynamic Influences on Evaporation Duct Shape

This study utilizes in situ measurements and numerical weather prediction forecasts curated during the Coupled Air–Sea Processes Electromagnetic Ducting Research (CASPER) east field campaign to assess how thermodynamic properties in the marine atmospheric surface layer influence evaporation duct shape independent of duct height. More specifically, we investigate evaporation duct shape through a duct shape parameter, a parameter known to affect the propagation of X-band radar signals and is directly related to the curvature of the duct. Relationships between this duct shape parameter and air sea temperature difference (ASTD) reveal that during unstable periods (ASTD < 0), the duct shape parameter is generally larger than in near-neutral or stable atmospheric conditions, indicating tighter curvature of the M-profile. Furthermore, for any specific duct height, a strong linear relationship between the near-surface-specific humidity gradient and the duct shape parameter is found, suggesting that it is primarily driven by near-surface humidity gradients. The results demonstrate that an a priori estimate of duct shape, for a given duct height, is possible if the near-surface humidity gradient is known.

Improving inactivation performance of in-duct ultraviolet germicidal irradiation system with ribbed duct walls by optimizing UVC distribution

The in-duct ultraviolet germicidal irradiation system (ID-UVs) with ribs has been revealed to be effective in reducing the risk of biological contamination, and optimization of its UV radiation distribution is expected to further improve the inactivation performance. In this study, the Critical Survival Fraction Probability (CSFP) and Maximal Bearable UVC Dose (MBUD) methods were synergistically employed as evaluation indicators, and Computational Fluid Dynamics (CFD) was used to optimize the lamp array, duct shape, liner reflectivity and number of UV lamps. Results indicated that the optimal lamp array was positioned at 0° to the airflow direction, and square-section ducts were preferred over circular-section ducts. Ribs obstructed the transmission of specular reflected radiation, while diffuse reflection helps to overcome the obstruction. Reducing the number of lamps alone from four to one increased the volume-averaged irradiance by 14.4–25.3 % in the main irradiated region. For renovation projects, ID-UVs equipped with one lamp and galvanized steel ribs proved optimal, exhibiting increased inactivation efficiencies of 39.7 % (CSFP) and 239.4 % (MBUD) against highly UVC-susceptible MS2 Bacteriophage (K = 0.038 J/m2), and up to 341.1 % (MBUD) against low UVC-susceptible MS2 Bacteriophage (K = 0.028 J/m2) compared to the ID-UVs without ribs and featuring four lamps. Moreover, in comparison to conventional conditions that provide equivalent air-cleaning levels, the optimal ID-UVs allowed for a 60–70 % increase in air handling capacity while achieving at least an 83.6 % reduction in annual energy costs. These findings contribute towards advancing practical applications of ID-UVs with ribbed duct walls.

Analysis and optimization of the coupling effect for duct-rotor based on aerodynamic performance

The duct has the potential to provide additional thrust, which can enhance the overall aerodynamic performance of the system. Nonetheless, since the duct and the rotor interact with each other, it is crucial to consider their interaction while optimizing the system for improved performance. This paper presents a parameterization approach for the duct and rotor. Primarily, a rotor space characterization and parameter modeling method that utilizes Bezier curves, class functions/shape functions, and Bernstein polynomials is proposed. Next, the aerodynamic performance of different key factors of the duct-rotor system is calculated and analyzed using a numerical calculation method. The study found that the coupling effect of camber yf and chord length parameter Bc3 had a significant impact on the thrust coefficient, with a contribution rate of 7.3 %. Correspondingly, the coupling effect of camber yf and torsion angle parameter Ba3 had a great influence on the Figure of Merit (FM), with a contribution rate of 7.1 %. The thrust coefficient and FM of the rotor-duct system were optimized by taking the coupling effect into consideration, and the optimized ducted rotor was verified by experimental measurement. The test results shows that the high thrust case achieves a 25.60 % increase in thrust coefficient, while the high-FM case establishes an 8.89 % increase in the FM. This implies that the collaborative optimization based on the coupling effect of duct and rotor shape parameters can effectively improve the system's performance, such as thrust coefficient and Figure of Merit.

Simulation of expansion and contraction for sudden plastic flow of Bingham cement grout and Newtonian fluids in a rectangular duct, using the lattice Boltzmann method

Bingham-type fluids are crucial in many industries and in geology. This study examines their behavior in reinforcing fractured rocks. Rheological properties were derived from experimental data of a water-cement mixture. Computational simulations were conducted using Lattice Boltzmann Method, with a modification to the relaxation parameter. Behavior of these mixtures in narrow ducts that widen and narrow suddenly, common in fractured rocks, was analyzed. Comparing Bingham and Newtonian fluids in various duct shapes provided insight into pressure distribution. Findings demonstrate that both cement-water mixtures, with or without addition of cement, adhere to Forchheimer flow patterns. Furthermore, it is observed that Newtonian fluids generate more intense vortices in expansive and contractive areas, resulting in higher pressure drops compared to Bingham plastics. The ultimate goal is to propose a predictive model based on mortar reinforcement for fractured rocks, taking into account rheological properties and water-cement ratio, thus reducing the need for costly experiments.

FEM MODEL OF AN UNDERWATER VEHICLE THRUSTER PROPELLER

Propulsion research has been done within the context of the project for the design and optimisation of the Remotely Operated Vehicle (ROV). CFD and FEM simulations that took the undersea vehicle's properties into consideration supported the whole project. Optimising the semi-open duct for horizontal propellers—a quantifiable system that offered controllability and propulsion in a horizontal plane—was one of the goals. It was required to examine the construction of propellers with nozzles and contra-rotating propellers, as well as the numerical approach of propeller design, in order to build a model for this work. Theoretical solutions were presented to it, one of which included operating the examined propeller close to an underwater vehicle. Additionally, first qualitative studies of a streamlined system with a semi-open duct and contra-rotating propellers were performed. Making a choice on the ROVs duct shape was made possible by the findings acquired. An actual propeller model was created using the SLS (Selective Laser Sintering) fast prototyping technique. This meant that the propeller's FEM model, which was based on the load determined by the CFD model, had to be verified. The features of the investigated ROV, the theoretical foundation for propeller design for the situations under analysis, and the outcomes of CFD and FEM simulations are all included in this paper.

Design an Optimum Air Duct for Oscillating Water Column Wave Energy Device

Oscillating Water Column (OWC) is a technology that harvests wave energy to generate electricity. It works by harnessing the wave-induced pressure oscillation in the opening mouth of OWC. The oscillation of the pressurised air is extracted using a turbine placed at the top of the OWC structure. Although OWC has been studied for many years, designing an optimum air duct for such devices is still an open research area. The air duct plays a crucial role in the energy conversion process, as it is responsible for directing the airflow towards the turbine, and its design can greatly affect the performance and efficiency of the system. The article aims to study how the air duct design impacts the power output form. Moreover, the result will be compared with the conventional air duct design. The OWC performance is analysed using Computational Fluid Dynamic (CFD) software to identify which shape of the air duct has high efficiency. Autodesk Inventor is used to design the OWC devices modified from the basis design. Then these designs are imported into CFD software to simulate and obtain the energy extraction result. The CFD software is chosen to simulate the hydrodynamics problem. In this study, the oval design shows significant improvement in the energy extraction performance compared to the basis design. The oval design managed to produce 9.81, 10.02, and 11.66 J/kg of mechanical energy compared to 9.81, 9.82, and 10.04J/kg as prompted by the basis air duct design at the wave height of 0.2505, 0.75, and 2.25m, respectively. The result shows that the non-edge produces higher air pressure than the sharp edge of the air duct shape. Thus, the oval air duct design is more efficient, and it may increase the performance of the OWC wave energy converter device at a low wave height of 0.75 m.

Effect of insert plate on the inlet pressure distortion of the aero-engine

The shape of the inlet duct and other factors cause distortion of the total pressure, leading to a decrease in engine stability. This article inserts flat plate into the inlet port of a certain type of aviation turbojet engine to conduct an inlet distortion test on the entire engine. The characteristics of entire flow field after inserting the board are obtained through experiments and numerical simulations, and it is concluded that the depth of the board is positively correlated with the reflux area and total pressure loss. The area of the insertion plate increase leads to an increase in the distortion index, and a decrease in engine flow rate. Meanwhile, angle plate device is designed to simulate inlet distortion caused by elevation takeoff. Summarize the relationship between the depth of the insertion plate and the intake distortion, a comprehensive distortion index simulation formula is fitted. The distortion simulation device designed by combining prediction formulas can achieve continuous adjustment of comprehensive distortion index 2%–13%, meeting the distortion index requirements for aircraft engine anti distortion testing. This device can replace complex intake systems to save test costs and cycles, and quickly and effectively carry out aircraft engine related distortion testing.

Experimental study of natural heat transfer from finned heat exchanger fixed in variable shape of duct

The work was an experimental study of natural heat transfer from heated cylinders fixed in variable shape air duct, made from Pyrex glass. Two finned cylinders made from mild iron, outer diameter (12) mm, inner diameter (10) mm, rectangle fins dimensions (70*40) mm. The angle of two walls from the duct was changed to five angles α:(0°,3°,5°,10°,15°) with vertical to make converge shape. The cylinders were fixed inside the duct at top, centre and bottom. The cylinders were heated by supply variable power of constant heat flux (88,177,390 and 680) W/m2. The study was done with Rayleigh numbers (15x103 to 14x104). The heat was carried by free convection by atmosphere air. The results of experimental found for top location, the value of Nusselt number increased by 7.8% at ԛ•= 88 W/ m2 when increase the value of angle from 0° to 5°, and increased by 20% at ԛ•= 680 W/ m2 when increased the value of angle from 0° to 15°.For centre location, the value of Nusselt number increased by 25 % at ԛ•= 88 W/ m2 when increase the value of angle from 0° to 3°, and increase by 21 % at ԛ•= 680 W/ m2 when increase the value of angle from 0° to 10°.For bottom location, the value of Nusselt number increased by 35 % at ԛ•= 88 W/ m2 when increase the value of angle from 0° to 3°,and increased by 30 % at ԛ•= 680 W/ m2 when increasing the value of angle from 0° to 10°.The best location for the heat exchanger was at the bottom, and the best angle was 15°.

Numerical investigation of the effect of using louver baffles on thermal performance in solar air collectors

AbstractConventional flat plate solar air collectors have advantages such as low cost and simple design. However, their thermal efficiency is lower than that of other designs. The thermal efficiency of these collectors can be increased by detailed examination of parameters such as the shape, size, arrangement and material of the air duct. In this study, it is aimed to improve the thermal efficiency of solar air collectors. The effect of louver baffles, which were not previously used in solar air collectors, on thermal efficiency was investigated numerically via computational fluid dynamics. Three different solar air collectors with flat plates, segmented baffles, and louver baffles were compared in terms of thermal efficiency. In addition, pressure drops in solar air collectors were investigated. The mass flow rate of the air in all collectors is assumed to be 0.04 kg/s. Analyzes were carried out between 09:00 and 16:00. The thermal efficiency values obtained during the day for solar air collectors with flat plate, segmented baffles and louver baffles are 27.66%–56.35%, 29.57%–58.82% and 30.09%–59.47%, respectively. The daily thermal efficiency values obtained for solar air collectors with flat plate, segmented baffles and louver baffles are 46.98%, 49.18% and 49.87%, respectively. The pressure drop for solar air collectors with flat plate, segmented baffles and louver baffles were found to be 4.62, 18.82 and 5.96 Pa, respectively. Based on the data obtained from this study, louver baffles are recommended for use in solar heating applications due to their high thermal efficiency and low pressure drop.

Three-dimensional CFD analysis of solar air heaters for improving thermal performance using converged air ducts

ABSTRACT In this work, a CFD analysis is carried out for improving the plane solar air heater performance using a converged air channel in the construction of these types of solar collectors. The inclined position of the glass cover with respect to the black absorber provides the nozzle configuration of the air duct. The accelerated flow along the converged duct prevents the growth of the thermal boundary layer and enhances the rate of convection heat transfer. It is observed from the numerical findings that the nozzle shape of the air duct provides a higher rate of heat transfer. This concept is examined numerically by the solution of the turbulent airflow equations with the conduction equation for solid parts using the finite element method and the COMSOL Multi-physics. The RANS model is employed to capture the turbulent nature of the airflow. The efficiency improvement for the test case with the contraction ratio of 2.5 is obtained by about 10% compared to the base model. The obtained numerical results are compared with experimental and theoretical data published in the literature, and good consistency is found.

CFD studies of the effect of holes and angles of upstream duct of horizontal axis wind turbines

This work presents an approach to the analysis of duct-augmented wind turbines using Computational Fluid Dynamics (CFD). The main objective is to find the optimum duct shape and design that gives maximum boost to the performance of wind turbines. A duct surrounding the rotor is able to increase the power coefficient above the Betz limit, so it has attracted great attention for many years. In this work, an extensive analysis of the performance of duct augmented wind turbines is presented, considering the influence of various duct angles and axial holes in the diffuser on the efficiency, in which a new formulation for the far-wake velocity is proposed. This study consists of two main parts. The first part compares the experimental performance of a conventional wind turbine with the identical turbine modeled and solved using CFD. Once the CFD results are validated, the second part presents an extensive parametric study by integrating a convergent duct with different parametric designs into the wind turbine model. The study reveals that the CFD results are in close agreement with the experimental results. It is found that the presence of holes in the duct has a detrimental effect on performance. However, the increase in the angle of the duct enhanced the performance, and there was an average increase in power output by 96% with a duct angle of 20°.

Molecular and Morphological Characterization of Tylenchus Zeae n. Sp. (Nematoda: Tylenchida) from Corn (Zea Mays) in South Carolina.

Specimens of a tylenchid nematode were recovered in 2019 from soil samples collected from a corn field, located in Pickens County, South Carolina, USA. A moderate number of Tylenchus sp. adults (females and males) were recovered. Extracted nematodes were examined morphologically and molecularly for species identification, which indicated that the specimens of the tylenchid adults were a new species, described herein as Tylenchus zeae n. sp. Morphological examination and the morphometric details of the specimens were very close to the original descriptions of Tylenchus sherianus and T. rex. However, females of the new species can be differentiated from these species by body shape and length, shape of excretory duct, distance between anterior end and esophageal intestinal valve, and a few other characteristics given in the diagnosis. Males of the new species can be differentiated from the two closely related species by tail, spicules, and gubernaculum length. Cryo-scanning electron microscopy confirmed head bearing five or six annules; four to six cephalic sensilla represented by small pits at the rounded corners of the labial plate; a small, round oral plate; and a large, pit-like amphidial opening confined to the labial plate and extending three to four annules beyond it. Phylogenetic analysis of 18S rRNA gene sequences placed Tylenchus zeae n. sp. in a clade with Tylenchus arcuatus and several Filenchus spp., and the mitochondrial cytochrome oxidase c subunit 1 (COI) gene region separated the new species from T. arcuatus and other tylenchid species. In the 28S tree, T. zeae n. sp. showed a high level of sequence divergence and was positioned outside of the main Tylenchus-Filenchus clade.

A study on optimization of duct shape of electric hubless rim-driven propeller

A study on optimization of duct shape of electric hubless rim-driven propeller

Selection of the cross-section area shape of the ducts used in the shelter ventilation systems – analysis

Ventilation ducts are the basic element of any ventilation system. The paper presents three shapes of ventilation ducts used in industry and discusses them with particular emphasis on the possibility of using them in the con-struction of shelters. Circle ducts, rectangular ducts, and rectangular ducts with rounded corners. The flow and strength parameters of the indicated ducts were analyzed, and the advantages and disadvantages of individual so-lutions were presented. Based on the conducted analysis, knowledge gaps were identified.

Designing of non circular air intakes for subsonic gas-turbine engines

The subject matter of the article is the process of subsonic air intake shaping for gas-turbine engines at the airplane preliminarily design stage. The goal is to develop a mathematical model for non-circular air intake shaping for gas-turbine engines on the base of V. I. Polikovskii method of subsonic air intake shaping for high-bypass ratio turbofan. The tasks to be solved are: to consider the possibility of non-circular shape of the external outline of the engine nacelle; to take into account the possibility of non-circular shape of the internal air intake duct (in the first approximation, the shape of internal air intake duct cross-section is defined in the form of a rectangular with possible four different radiuses in its corners); to consider the engine inlet spinner presence. The methods used are: analytical and digital mathematical methods, implemented in MathCAD and Microsoft Visual Studio systems. The following results were obtained: On the base of the proposed method, new calculation module for the Power Unit software version 11.8 has been developed (С-language Win32 UNICODE application) having a friendly user interface. Conclusions. The scientific novelty of the results obtained is as follows: 1) mathematical model (algorithm and its program implementation) for non-circular air intake shaping for gas-turbine engines has been developed considering non-circular shape of the external outline of the engine nacelle, non-circular shape of the air intake duct internal outline, presence of engine inlet spinner, and zero expansion angle in the diffuser outlet cross-section; 2) adequacy of calculation results by the developed mathematical model is shown by means of comparison with the shape of real air intake, developed by the Antonov Company. For the following improvement of the mathematical model, it is desirable to add the possibility of considering S‑shape of the air intake duct, defining its length from designer’s considerations, defining a bigger radius of curvature of the air intake lip, and considering the presence of boundary layer bleeding devices in front of the air intake.

Optimization of Duct Shape for Improving Aerodynamic Performance of Ducted Tail Rotor

Optimization of Duct Shape for Improving Aerodynamic Performance of Ducted Tail Rotor

Recovery of gland function after endoscopy-assisted removal of impacted hilo-parenchymal stones in the Wharton’s duct

The aim of this study was to evaluate the gland function of patients following endoscopy-assisted removal of impacted hilo-parenchymal stones in the Wharton’s duct. The study cohort comprised 115 patients who had undergone successful endoscopy-assisted lithotomy for hilo-parenchymal stones (mean diameter 7.7 mm). Gland function was evaluated at a mean 12 months after surgery using ultrasonography, sialography, and/or sialometry. Postoperative ultrasonography of 51 affected glands revealed a regular gland size in 58.8%, normal parenchyma density in 51.0%, and ductal ectasia in 80.4%. Postoperative sialograms of 109 affected glands were scored as type I (approximately normal) in 13 cases, type II (saccular ectasia of the hilo-parenchymal duct with/without stenosis, and no contrast retention) in 64, type III (saccular ectasia of the hilo-parenchymal duct with/without stenosis, and mild contrast retention) in 23, and type IV (poor shape of the main duct with evident contrast retention) in nine cases. The existence of ductal ectasia corresponded well to larger stone cases (P = 0.002). In the postoperative sialometry of 35 patients with unilateral stones, differences between the two sides were insignificant (P > 0.05). For patients with hilo-parenchymal submandibular gland stones, endoscopy-assisted surgery and extended postoperative follow-up help preserve the gland with good function.

Preparation and mechanical behavior of the acellular porcine common bile duct and its immunogenicity in vivo

The current clinical treatments for complications caused by hepatobiliary surgery still have some inevitable weaknesses. This study aimed to prepare the acellular porcine common bile duct (APCBD) for repairing biliary defects and damage. The porcine common bile duct was decellularized by the freeze-thaw method combined with nuclease treatment, and the efficacy of acellularization was confirmed by the DNA quantification and histological structure. The results showed that the residual DNA content was reduced from 854.67 ± 9.71 ng/mg to 5.43 ± 0.85 ng/mg, and the natural structure and shape of the bile duct were well preserved. The biomechanical properties such as the tensile strength, elastic modulus, and elongation-at-break of the APCBD in the transverse and longitudinal direction indicated that the APCBD meets the requirements of the biomechanical strength in replacement. In addition, the results of the immunotoxicity test showed there was no significant difference in the body weights, organ coefficient, hematology, and immune histology between the experimental groups (three subgroups) and the negative control group, which demonstrated the prepared APCBD had no obvious toxicity to the immune system in vivo and might be a suitable biomaterial for the bile duct repairing.