Duct Configuration Research Articles

Numerical Investigation of Hydrodynamic Characteristics of a Rim-Driven Thruster Coupled with an Underwater Vehicle

In this paper, the hydrodynamic characteristics of a rim-driven thruster (RDT) behind the hull of an underwater vehicle are investigated. The studied underwater vehicle is the benchmark DARPA (Defense Advanced Research Projects Agency) suboff model, with and without full appendages. In order to verify and validate the numerical model, a grid sensitivity analysis is made for the AFF-1, AFF-8 and the ducted propeller cases, respectively. Then, the resistance and pressure distribution over the surface of the suboff with and without appendages are compared with available experimental measurements and good correlations were observed. As for the propeller, a well-studied ducted propeller, the 19A duct in combination with Ka-47 blades, is employed, and the numerical results exhibit a close relationship with the available experimental data under a wide range of advance coefficients. Afterwards, the self-propulsion characteristics of the suboff models propelled by RDTs using different duct configurations are studied, more specifically, the unsteady effects of the flow field induced by the interactions between propeller and hull under various working conditions. The results indicate that due to the influence of the hull, the RDTs operate in different working conditions compared to open water and exhibit distinct hydrodynamic characteristics. Moreover, the duct profile can have a significant effect on the unsteady pressure fluctuations in the flow field, especially in the vicinity of the propeller.

Electromagnetic wave scattering in plasma beam-driven waveguides under strong magnetic fields

This study analyzes the scattering of electromagnetic waves in a cold and uniform plasma-filled waveguide driven by an intense relativistic plasma beam under a strong magnetic field. The strong interaction of plasma with electromagnetic waves enables its potential use in different types of waveguides. The Helmholtz equation governs the boundary value problem, which is solved by incorporating the mode matching technique. Invoking the boundary and matching conditions and the derived orthogonality and dispersion relations in this scheme gives an exact solution to the scattering problem. The numerical results shed light on the occurrence of reflection and transmission and flow of power. The power flux is plotted against angular frequency and various duct configurations. The solution is completely validated through the benefit of analytical and numerical results. The investigation of this structure reveals not only its mathematical, but also its physical features.

A comparative study of hydrodynamic performance between ducted and non-ducted Archimedes spiral hydrokinetic turbines

The Archimedes spiral hydrokinetic turbine (ASHT), as a novel type of horizontal-axis hydrokinetic turbine, is well suited for deployment in the low-speed ocean current environment. Besides, integrating hydrokinetic turbines within a duct stands out as a prospective approach to enhance the efficiency of energy harvesting. In this study, a duct is implemented with the aim of enhancing the performance of ASHT. Using the commercial code program ANSYS-FLUENT, the Reynolds-averaged Navier-Stokes (RANS) equations are solved along with the SST k-ω turbulence model to elucidate the distinctive hydrodynamic characteristics of ASHT and its ducted configuration (DASHT). The findings revealed a consistent outperformance of the DASHT over the ASHT, achieving a notable maximum improvement of 122% in the power coefficient (CP). The ASHT exhibits turbulence near the blade tips, generating large spiral tip vortex, while the DASHT, with its duct, induces significant turbulence, resulting in a wider range of vortex structures. Furthermore, the DASHT shows better energy harvesting due to enhanced diffusion under yawed flow. The wake asymmetry and increased turbulence are observed as the yaw angle increases, affecting vortex structures differently in ASHT and DASHT. At higher yaw angle, the DASHT vortex splits into two parts, contributing to a more complex wake structure.

Numerical investigation and performance comparison of UAV propeller with varying duct configuration

PurposeThe purpose of this study is to investigate the effects of propeller thrust with two different duct configurations. Propellers in a quadcopter play an indispensable role in generating the necessary thrust and torque to keep the drone flying and manoeuvring. Based on the specific purpose of the unmanned aerial vehicle, both the altitude and attitude can be varied by the amount of thrust produced.Design/methodology/approachThis paper deals with the generation of three numerical models such as plain rotor, rotor with fixed duct and rotor with rotating duct and the comparison of their amount of generated thrust. The plain rotor numerical analysis was compared with the experimental results. The rotor taken for the analysis was 15 mm*5.5 mm TAROT 650. Thrust was measured for all models at four different angular speeds, such as 2,500 rpm, 4,000 rpm, 5,500 rpm and 7,000 rpm.FindingsDue to the suction pressure gradient on the duct inlet surface, the additional amount of lift is produced, and it is the best way of increasing propulsion efficiency and its aerodynamic performance as it reduces the tip loss at the tip of the propeller. The turbulence model taken for the numerical analysis was k−ε.Originality/valueThe rotating duct is expected to provide additional thrust by the increased upward force due to the rotation of duct. The rotating duct produced the optimal results between the plain model and ducted model. At the highest speed of 7,000 rpm, the ducted propeller produced 24.97 N, and the rotating duct propeller produced 23.89 N, whereas the plain propeller produced 23 N thrust. Nearly 8.6% of the thrust improvement is observed in duct and 3.87% in rotating duct.

Transient cold-front-water through y-shaped aluminium ducts: nature of turbulence, non-equilibrium thermodynamics, and velocity at the converged and diverged outlets

Abstract The interaction between water motion efficiency, outlet control mechanisms, and energy dynamics management hinges significantly on turbulence characteristics. However, understanding the influence of input velocities and duct features on outlets remains elusive. This study employs the realizable k − ɛ viscous model and Reynolds-averaged Navier–Stokes equations (RANS equations) to explore transient water dynamics encountering a cold front through ducts leading to convergence or divergence. Using Ansys Fluent 2023R2 and the waterlight workflow, meticulous meshing of the ducts is executed to capture flow intricacies accurately. Grid independence, suitable boundary conditions, and solver settings are carefully considered to ensure reliable results for investigating four key research questions. Duct bending introduces non-uniformities in velocity distribution, impacting exit velocity and altering flow characteristics and turbulence. In Case III, centrifugal forces from a 90° bend result in higher outlet velocities at the convergent exit and secondary flow patterns like swirls and vortexes. Additionally, entrance velocities influence Reynolds numbers, affecting mixing, heat transfer coefficients, and flow regimes, thereby optimizing thermal conductivity. This comprehensive investigation sheds light on optimizing water dynamics and energy management across various duct configurations, offering valuable insights into efficient flow control and thermal performance enhancement.

Exploring the Impact of Diverse Cooling Duct Configurations on Photovoltaic Panel Performance

Photovoltaic (PV) panels are an emerging technology that captures solar energy and produces electricity. One key concern with PV panels is the detrimental effect of high temperatures on their performance and efficiency, which is leading to a shorter service life. Cooling the panels can help to maintain appropriate working temperatures, reduce the adverse effects of heat, and increase overall energy production. This research aims to investigate experimentally and numerically the effectiveness of a cooling channel with different configurations in lowering PV panels' temperature. The findings of the experiments show that cooling methods improved panel efficiency by 0.35% and reduced the intake temperature by 7%. In numerical analysis, different 3D cooling channel geometries were investigated, and the tapered duct was found to be the best in reducing Tav at 1.73%.

Evaluation of the cooling performance of a crushed-rock interlayer embankment with longitudinal ventilation ducts in a pan-Arctic permafrost region

In pan-Arctic permafrost regions, longitudinal ventilation ducts are often installed in embankments to cool the underlying permafrost and thereby ensure road stability. However, the current design methods for embankments with longitudinal ventilation ducts (ED) normally simplify the conjugate heat transfer process between the duct wall and air in the duct. In this study, based on the chimney effect and the theory of fluid flow and heat transfer, we propose an improved numerical method for evaluating the cooling performance of the ED. Using this method, we conduct an assessment of the influences of duct configuration on the efficiency of ventilation duct cooling in winter. The results indicate that increasing the diameter of the duct and the height of the duct outlet can effectively improve the radial cooling range of the ventilation duct. However, the cooling performance of the ventilation duct becomes worse when the length of the duct is increased. To address the limited cooling performance of the ED, we design a crushed-rock interlayer embankment installed with longitudinal ventilation ducts (CED). It is found that the CED is more effective at maintaining the long-term thermal stability of the road in a typical pan-Arctic permafrost region when compared to the ED and the crushed-rock interlayer embankment. Furthermore, a cost analysis of the four different embankment designs reveals that the CED is a financially viable option for embankment construction in permafrost regions.

The chronic pancreatitis (CP) Type Cambridge 2 as a cause of unclear upper abdominal pain: a radiologically underestimated diagnosis

AbstractThe time interval from symptom onset to the diagnosis of chronic pancreatitis (CP) remains disproportionately long today due to nonspecific symptoms and the absence of a definitive laboratory marker. Nevertheless, mortality is increased by 3.6 times compared to the general population. Additionally, the risk of developing pancreatic carcinoma is 16 times higher in the presence of CP. According to the current S3 guideline, the morphological staging of CP should be based on the Cambridge Classification for CT/MRCP. Most radiologists morphologically associate CP with Cambridge Stage 4, which is characterized by classic calcifications. The subtle morphologies of earlier Cambridge Stages are often unrecognized, leading to delayed diagnosis. The aim of this study was to diagnose CP at Cambridge Stage 2 as the cause of unexplained upper abdominal discomfort.A retrospective analysis was conducted on 266 patients with unexplained upper abdominal pain who underwent outpatient MRI with MRCP between January 1, 2021, and October 1, 2023. The criteria for Cambridge Stage 2 were evaluated: pancreatic duct in the corpus measuring between 2 and 4 mm, pancreatic hypertrophy, cystic changes < 10 mm, irregularities in the duct, or > 3 pathological side branches. Patients with known tumors or other leading diagnoses, which explained the discomfort, were excluded.25 patients (15 female, 10 male) met the criteria for CP Stage 2 (9%). Ductal dilation between 2 and 4 mm was visible in 21 cases. Pancreatic hypertrophy was observed in six cases. Cystic changes < 10 mm were identified in three cases. Irregularities in the duct (“wavy duct”) were diagnosed in 19 patients. Dilation of > 3 side branches was recognized in 17 cases. Lipase levels were additionally determined, with 13 patients showing pathologically elevated levels (> 60 U/l).CP at Cambridge Stage 2 is an important and underestimated diagnosis in patients with unexplained upper abdominal pain in the outpatient setting. Radiologists should pay attention not only to common signs like calcifications, large cysts, or duct strictures but also to subtle changes such as duct irregularities (“wavy duct configuration”) and pathologically dilated side branches, which could lead to a significantly earlier diagnosis of CP. Lipase determination may be an additional indication of chronic pancreatitis in this context.

Analysis of Increased Induced Voltages on the Sheath of Double-Circuit Underground Transmission Lines Guaranteeing Ampacity

This paper quantifies and discusses the increase in induced voltage on a sheath due to changes in duct banks in terms of type and dimensions along an underground transmission line, guaranteeing the ampacity required for a project. The four most common duct banks in double-circuit underground transmission lines with phase transposition were considered in this study, along with two special cross-bonding techniques: continuous cross-bonding (CCB) and sectionalized cross-bonding (SCB). These techniques aim to reduce sheath currents and enhance the distribution of the induced voltage on the sheath. The analysis considers two distinct scenarios in which the profile of the induced voltage is calculated: the first one accounts for underground obstructions, intersections with important traffic avenues, and ground with high excavation costs that force changes in the duct bank dimensions and configuration, which is the most exact and realistic case. The second one solely considers one typical configuration of a duct bank along the route. This last scenario is normally applied to calculate the induced voltage when an underground transmission design is required. The results show that when installing cables at a greater depth, it is imperative to increase the distance between them to guarantee the ampacity. The induced voltage on the sheath will rise as the distance increases. Furthermore, the results reveal that instead of calculating the induced voltage by considering the scenario that is exact and most like a real case, it is enough to calculate following the second scenario and then add a scaling factor according to each duct bank configuration.

The comparative transient prediction on hydrodynamic characteristics and flow field properties of pump-jets with accelerating and decelerating ducts

Pump-jet holds a pivotal position in various marine applications, underscoring the need for comprehending their transient behavior for the purpose of design enhancement and performance refinement. This paper employs Reynolds-averaged Navier–Stokes equations method in conjunction with Detached Eddy Simulation model. The study delves into the ramifications of accelerating and decelerating ducts, distinguished by camber f and attack angles α, on transient hydrodynamic characteristics. The hydrodynamic characteristics are investigated numerically, after the validation of the numerical methodology by comparing simulation outcomes against experimental results. Subsequently, the study delves into propulsion characteristics, followed by an exploration of time-domain and frequency-domain data transformed through fast Fourier transform to analyze thrust fluctuations and pulsating pressures. Additionally, a detailed examination of pressure distribution and velocity field is provided, aiming to dissect the mechanisms through the variations in f and α influence the flow field. Findings suggest that the outlet velocity of accelerating ducts significantly surpasses the inlet velocity, a behavior contrasted by decelerating ducts. Notably, the patterns of accelerating and decelerating ducts resulting from alterations in f exhibit consistent characteristics with those brought about by changes in α. However, several opposite characteristics surface in transient flow field due to the distinct modifications in the duct profile. Furthermore, by considering vorticity magnitude distribution and vortices, a comparative analysis elucidates the effects of varying f and α on rotor and stator trailing vortices. This contributes to understanding the flow instability mechanism under differing duct configurations. It is evident that changes in f and α exert significant influence on both performance and flow field.

Numerical analysis of accelerating and decelerating ducts modified by camber on the unsteady flow field of pump-jet

Utilizing the Reynolds-averaged Navier-Stokes equations method in conjunction with Detached Eddy Simulation model, this paper investigates effects of duct camber (f) on transient hydrodynamic characteristics, particularly propulsion performance and flow field behavior. The research begins by validating the numerical methodology through experimental and numerical assessments of propeller VP1304 and a pump-jet operating under mooring conditions. The exploration commences with examining propulsion characteristics, followed by analyzing time-domain and frequency-domain data, wherein thrust fluctuations and pulsating pressures are scrutinized via fast Fourier transform (FFT). The pressure distribution and velocity field are subsequently presented to unveil the mechanisms triggered by variations in f. Comparative findings highlight that in cases of pump-jets with lower camber, the outlet velocity exceeds the inlet velocity, a trend contrary to scenarios involving higher f values. Additionally, by analyzing vorticity magnitude distribution and vortices, this study attains comparative insights into the effects of accelerating and decelerating ducts on rotor and stator trailing vortices, offering a window into the flow instability mechanism amidst diverse duct configurations. The results showcased to demonstrate the substantial impact of f variation on hydrodynamic properties. This comprehensive investigation yields practical guidance for the optimal design of pump-jets, potentially informing future design endeavours.

Unsteady Investigation of Intermediate Turbine Ducts Under the Influence of Purge Flows

Abstract The aerodynamic flow field at the outlet of a high-pressure turbine (HPT) stage in a modern turbofan engine is highly unsteady and strongly influenced by periodic fluctuations from the HPT rotor, also interacting with the HPT stationary vanes. Downstream of the last HPT stage, the flow enters the intermediate turbine duct (ITD), where new unsteady components are generated, due to the interaction between the incoming flow and the struts supporting the ITD. This paper illustrates the differences between the unsteady flow behavior in two state-of-the-art ITD configurations for turbofan engines: the turbine center frame and the turbine vane frame. The experimental results discussed in this work are obtained in the Transonic Test Turbine Facility, situated at Graz University of Technology, Austria. To achieve engine-representative operating conditions at the ITD inlet and outlet sections, the tested setups include not only the duct, but also the last HPT stage and the first low-pressure turbine stage row. Additionally, the test rig features a secondary air supply system, capable of feeding purge air to every stator–rotor cavity in the test vehicle. Unsteady measurement data at the inlet and outlet of the two duct configurations are acquired with fast-response aerodynamic pressure probes, for two purge flow conditions. Azimuthal mode decomposition is applied to phase-averaged data at selected radial positions, to isolate and quantify the contribution of different interaction modes to the overall unsteady flow field.

Assessing the impact of ventilation systems on indoor air quality: a mock-up experiment in Dubai

Indoor Air Quality (IAQ) has become an important concern in Dubai, driven by public health awareness, environmental regulations, and government initiatives. The Dubai Municipality has introduced guidelines and standards for IAQ in residential and non-residential buildings, emphasizing ventilation, material selection, and testing protocols. IAQ monitoring and testing are encouraged, and public awareness campaigns educate individuals about IAQ and its impact on health. Green building regulations in Dubai also address IAQ considerations. The Dubai Municipality has comprehensively assessed IAQ in public buildings, leading to stringent regulations. However, research on IAQ improvement and challenges associated with apartment ventilation systems is limited. This study aims to evaluate the IAQ improvement and potential issues of a ventilation system in an apartment through a mock-up experiment. Factors such as air volume, ventilation system type, and supply/exhaust duct configuration are analyzed. The results show that installing a ventilation device with a ventilation rate of 0.3–0.8 times/h reduces Formaldehyde (HCHO) and Volatile Organic Compounds (VOCs) concentrations by 30%–50%. The IAQ improvement is not significantly influenced by air volume. Each room supply/exhaust method shows a 10% higher reduction in VOC concentrations than the supply/kitchen exhaust unit method. Preventing backflow and addressing cold drafts are recommended during ventilation system installation. Noise measurements comply with standards in most cases. These findings contribute to developing guidelines for ventilation system design and installation in apartments, promoting healthier indoor environments. Further research with a broader range of ventilation devices and real-world conditions is recommended to validate these findings.

Heat transfer enhancement in finned annulus of elliptic-circular heat exchanger

In this numerical study, a trapezoidal finned elliptic-circular heat exchanger is investigated for thermal performance based on the various geometrical parameters. The inner core of this exchanger is circular and augmented with trapezoidal fins longitudinally, whereas the outer core is elliptic. For the first time, the trapezoidal fins are used in this specific duct configuration. The configuration of the proposed heat exchanger depends on the number of fins, fin height and ratio of the radius of the inner circle to the semi-minor axis of the ellipse The material of the inner circular core and trapezoidal fins is assumed to have infinite thermal conductivity. The constant heat flux condition is imposed on the inner pipe and trapezoidal fins, whereas the adiabatic condition is considered for the outer elliptical core of the heat exchanger. The simulation is performed using the finite volume method based on the software ANSYS Fluent. The friction factor (fRe) and Nusselt number (Nu) have been computed and plotted for various fin configurations. The results suggest that the performance of the heat exchanger can be effectively influenced by the number of fins, fin height and radius of the inner circular pipe. For practical interest, a larger number of trapezoidal fins with a higher height and are recommended.

Endoscopic Ultrasound in Pancreatic Duct Anomalies.

Embryological development of the pancreas is a complex phenomenon and, therefore, it can have multiple developmental aberrations. Fortunately, the majority of these pancreatic ductal anomalies are asymptomatic with no clinical relevance and are incidentally detected during diagnostic cross-sectional imaging or endoscopic retrograde cholangiopancreatography (ERCP) or autopsy. Occasionally, pancreatic duct anomalies can result in symptoms like abdominal pain or recurrent pancreatitis. Also, an accurate pre-operative diagnosis of ductal anomalies can prevent inadvertent duct injury during surgery. Conventionally, ERCP had been used for an accurate diagnosis of pancreatic duct anomalies. However, because it is invasive and associated with a risk of pancreatitis, it has been replaced with magnetic resonance cholangiopancreatography (MRCP). MRCP has demonstrated high sensitivity and specificity for the diagnosis of ductal anomalies, which can be further improved with the use of secretin-enhanced MRCP. Endoscopic ultrasound (EUS) is a new diagnostic and interventional tool in the armamentarium of endoscopists and has demonstrated promising results in the detection of pancreatic duct variations and anomalies. Along with the visualization of the course and configuration of the pancreatic duct, EUS can also visualize changes in the pancreatic parenchyma, thereby helping with an early diagnosis of any co-existent pancreatic disease. Absence of the stack sign and crossed duct sign are important EUS features to diagnose pancreas divisum. EUS can also help with the diagnosis of other congenital ductal anomalies like annular pancreas, ansa pancreatica, and anomalous pancreaticobiliary union, although the published experience is limited.

Experimental Investigation on Hover Performance of a Ducted Coaxial-Rotor UAV.

This paper presents experimental investigations on aerodynamic performance of a ducted coaxial-rotor system to evaluate its potential application as a small unmanned aerial vehicle (SUAV). Aimed at determining the influence of design parameters (rotor spacing, tip clearance and rotor position within the duct) on hover performance, a variety of systematic measurements for several correlative configurations (single/coaxial rotor with or without a duct) in terms of thrust and torque, as well as power, were conducted in an attempt to identify a better aerodynamic configuration. The experimental results for the coaxial-rotor system indicated that varying rotor spacing affected the thrust-sharing proportion between the two rotors, but this had no significant effect on the propulsive efficiency. The optimal H/R ratio was identified as being 0.40, due to a larger thrust and stronger stability in the case of identical rotation speeds. As for the ducted single-rotor configuration, the tip clearance played a dominant role in improving its thrust performance, especially for smaller gaps (δ≤0.015R), while the rotor position made subordinate contributions. The maximum performance was obtained with the rotor located at the P5 position (0.31Cd from the duct lip), which resulted in an enhancement of approximately 20% in power loading over the isolated single rotor. When the coaxial rotors were surrounded within the duct, the system thrust for a given power degraded with the increasing rotor spacing, which was mainly attributed to the upper rotor suffering from heavier leakage losses. And hence, the ducted coaxial-rotor system with S1 spacing had the best propulsion efficiency and hover performance with a figure of merit of 0.61.

Compound Heat Transfer Enhancement in Dimpled and Sinusoidal Metal Solar Wall Ducts Fitted with Wired Inserts

An improved Metal Solar Wall (MSW) with integrated thermal energy storage is presented in this research. The proposed MSW makes use of two, combined, enhanced heat transfer methods. One of the methods is characterized by filling the tested ducts with a commercially available copper Wired Inserts (WI), while the other one uses dimpled or sinusoidal shaped duct walls instead of plane walls. Ducts having square or semi-circular cross sectional areas are tested in this work.A developed numerical model for simulating the transported thermal energy in MSW is solved by finite difference method. The model is described by system of three governing energy equations. An experimental test rig has been built and six new duct configurations have been fabricated and tested. Air is passed through the six ducts with Reynolds numbers from 1825 to 7300.Six, new, correlations for Nusselt number and friction factor are developed to assess the benefits that are gained from using the WI and the dimpled and sine-wave duct walls. It is found that higher heat transfer rates are achieved using the Dimpled, semi–circular duct with Wired Inserts (DCWI). Also, it is found that Nusselt number and the pressure drop in the DCWI are respectively(44.2% -100%) and (101.27% - 172.8%) greater than those of the flat duct with WI. The improvement in Nusselt number for flat duct with WI is found to be (1.4 – 2) times the values for flat duct with no WI. The results demonstrated that DCWI provides enhancements efficiency value that is higher than those obtained from other types of ducts. The developed MSW ducts have added to local knowledge a better understanding of the compound heat transfer enhancement.

Hydro-thermal performance of fabric air duct (FAD): Experimental and CFD simulation assessments

Nowadays, fabric air duct (FAD) systems are the most cost-effective, and aesthetically appealing way to evenly distribute heated or cooled air to large open interior spaces. There is a need to develop a proper procedure to calculate the friction factor and Nusselt number of the air flow inside these types of fabric air ducts because of their great impact on the design of central air conditioning systems. Therefore, the main objective of this research is to carry out laboratory and numerical experiments to establish a certain technique of calculation of the friction factor and Nusselt number inside fabric air ducts and to develop validated CFD air distribution model capable of predicting the air flow pattern and heat transfer parameters inside different configurations of fabric air ducts. By controlling these parameters, FAD systems can be balanced and designed. For this purpose, three fabric air ducts made of porous and non-porous polyester with different outlet ports distribution and have a diameter of 60 cm and a length of 3 m have been experimentally assessed under variation of inlet Reynold numbers ranging from 9.9x103 to 1.47x105. The results showed that the maximum error between laboratory and numerical values for the mean friction factor and mean Nusselt number was 4.9% and 4.8% respectively, which was within an acceptable range according to previous studies. Based on the results analysis empirical correlations were obtained for their importance in achieving a well-balanced FAD system. One of the most significant equations that were obtained in this research was the relationship between the Nusselt number and Reynold number. For porous duct was Nu=127.69Re0.148, non-porous duct 4,8 o'clock air slots was Nu=4.51Re0.49 and non-porous duct 3,9 o'clock air slots was Nu=40.82Re0.139. The relationship between friction factor with Reynold number for porous duct was f=0.251e−0.0000067Re, non-porous duct 4,8 o'clock air slots was f=0.397e−0.000017Re and non-porous duct 3,9 o'clock air slots was f=0.529e−0.000025Re. All correlations are valid only within the range of conditions considered in current experimental study.

Influence of Duct Configurations on the Performance of Solar-Assisted Heat Pump Dryer for Drying Tobacco Leaves

In the present study, a solar-assisted heat pump dryer (SAHPD) has been designed, fabricated, and tested its performance on drying tobacco leaves. The hot air generated from the solar collector and condenser unit of the heat pump was used as a source of heat in the drying chamber. In this study, we investigated the influence of three duct configurations (open, partially closed, and completely closed) on the thermal performance of SAHPD to establish the best configuration for drying tobacco leaves. The average drying temperature was found to be 66, 64, and 60°C; the coefficient of performance of the heat pump was 3.4, 3.2, and 3.0; the heat energy contribution from the solar collector was 6.6%, 5.0%, and 5.1% while for the condenser was 93.4%, 95.0%, and 94.9%, and electrical energy consumption was 2.3, 2.8, and 2.6 kWh, for the open, partially closed, and completely closed duct system, respectively. Based on these results, the open system demonstrated the best performance. According to the study’s findings, SAHPD has been shown to be an energy-efficient method of drying tobacco leaves and is environmentally friendly as opposed to the conventional use of wood fuel, which results in environmental pollution, desertification, and deforestation.

Parametric evaluation of ducted fuel injection in an optically accessible mixing-controlled compression-ignition engine with two- and four-duct assemblies

Ducted fuel injection (DFI) is a strategy to improve fuel/charge-gas mixing in direct-injection compression-ignition engines. DFI involves injecting fuel along the axis of a small tube in the combustion chamber, which promotes the formation of locally leaner mixtures in the autoignition zone relative to conventional diesel combustion. Previous work has demonstrated that DFI is effective at curtailing engine-out soot emissions across a wide range of operating conditions. This study extends previous investigations, presenting engine-out emissions and efficiency trends between ducted two-orifice and ducted four-orifice injector tip configurations. For each configuration, parameters investigated include injection pressure, injection duration, intake manifold pressure, intake manifold temperature, start of combustion timing, and intake-oxygen mole fraction. For both configurations and across all parameters, DFI reduced engine-out soot emissions compared to conventional diesel combustion, with little effect on other emissions and engine efficiency. Emissions trends for both configurations were qualitatively the same across the parameters investigated. The four-duct configuration had higher thermal efficiency and indicated-specific engine-out nitrogen oxide emissions but lower indicated-specific engine-out hydrocarbon and carbon monoxide emissions than the two-duct assembly. Both configurations achieved indicated-specific engine-out emissions for both soot and nitrogen oxides that comply with current on- and off-road heavy-duty regulations in the United States without exhaust-gas aftertreatment at an intake-oxygen mole fraction of 12%. High-speed in-cylinder imaging of natural soot luminosity shows that some conditions include a second soot-production phase late in the cycle. The probability of these late-cycle events is sensitive to both the number of ducted sprays and the operating conditions.