U-shaped Channel Research Articles

Contaminant dust effects on mist cooling in ribbed U-shaped channels of gas turbine blades

Mist cooling within turbine blades’ internal channels is a promising alternative to protect the blades from exceeding the temperature limit without additional coolant extraction. However, the presence of dust commonly encountered in harsh environments, such as deserts or sandstorms, can significantly affect cooling performance. This research employed numerical simulation methods and utilized the user defined function to direct the motion of mist/dust particles post-wall impact, to analyze the dust affected unsteady mist cooling effectiveness in a ribbed, U-shaped channel which is arranged within the blade to serve as a cooling passage. Additionally, this study examined the performance of mist cooling and heat transfer non-uniformity under various dust loading environments. The unsteady cooling mechanism of mist was discussed through the analysis of secondary flows induced by the inclined ribs and turning region. Enhanced cooling performance near the leading edge of the U-shaped channel was achieved by the coolant with mist under the action of a couple of vortices rotating in reverse. Moreover, this study revealed that dust particles exchanged heat with droplets and disrupted the flow fields, thereby altering the performance of mist cooling. These findings indicated that dust with smaller size, higher concentration, and greater specific heat significantly suppressed the mist cooling, but larger loading of dust led to an improvement in thermal uniformities within the channel.

Advanced design of indented-standing surface acoustic wave (i-SSAW) device for platelet-derived microparticle separation from whole blood

Isolating submicron microvesicles (MVs) from blood has become important for clinical diagnosis and researches. Advanced design of indented-standing surface acoustic wave (i-SSAW)-based device with a U-shaped microchannel is proposed for extracting platelet-derived microparticles (PDMPs) from whole blood. Unlike the previous acoustic devices, the cross-sectional shape of the microchannel was manipulated to enhance the device performance, rather than the patterned interdigitated transducers. Cross-sectional shape-dependent device performance was evaluated using rectangular channels with different heights and U-shaped channel with whole blood sample with 40 % hematocrit. Effect of the flow rates on acoustic migration of red blood cells (RBCs) was examined at 20 V fixed voltage. In addition, RBC and platelet removal was examined using different applied voltages for i-SSAW operation. Finally, high-purity (approximately 100 %) and high-recovery (approximately 55.6 %) platelet-poor plasma was separated from whole blood at 30 μL/min without platelet activation.

A novel multi-channel applicator with a U-shaped channel for vaginal intracavity brachytherapy.

Endometrial cancer is one of the most common gynecological malignancies in the world. Vaginal brachytherapy is an important postoperative adjuvant treatment for endometrial cancer. However, a common problem with existing applicators is insufficient dose at the vaginal apex. This study describes the Hangzhou (HZ) cylinder, a novel 3D printed vaginal intracavity brachytherapy applicator, detailing its characteristics, dose distribution, and clinical applications. The HZ cylinder is distinguished by its unique structure: a U-shaped channel with a 2mm diameter, a straight central axis channel of the same diameter, and 10 parallel straight channels. For comparison, standard plans were employed, designed to ensure that a minimum of 95% of the prescribed dose reached 5mm beneath the mucosal surface. We conducted comparative analyses of mucosal surface doses and doses at a 5mm depth below the mucosa between the HZ cylinder and a conventional single-channel cylinder across various treatment schemes. Additionally, the study examined dose differences in target volume and organs at risk (OARs) between actual HZ cylinder plans and hypothetical single-channel plans. In the standard plans, mucosal surface doses at the apex of the vagina were 209.32% and 200.61% of the prescribed dose with the HZ and single-channel cylinders, respectively. The doses on the left and right wall mucosal surfaces varied from 149.26% to 178.13% and 142.98% to 180.75% of the prescribed dose, and on the anterior and posterior wall mucosal surfaces varied from 128.87% to 138.50% and 142.98% to 180.75% of the prescribed dose. Analysis of 24 actual treatment plans revealed that when the vaginal tissue volume dose covering 98% (vaginal D98%) was comparable between the HZ cylinder and virtual single-channel plans (6.74±0.07Gy vs. 6.69±0.10Gy, p=0.24), rectum doses of HZ cylinder plans were significantly lower than those of single-channel plans (D1cc, 5.96±0.56Gy vs. 6.26±0.71Gy, p=0.02 and D2cc, 5.26±0.52Gy vs. 5.56±0.62Gy, p=0.02). The HZ cylinder demonstrates a reduction in dose to the rectum and bladder while maintaining adequate target volume coverage. Its mucosal surface dose is comparable to that of the traditional single-channel cylinder. These findings suggest that the HZ cylinder is a viable and potentially safer alternative for vaginal brachytherapy, warranting further investigation with larger sample sizes.

Energy and exergy performance improvement of coupled PV–TEG module by using different shaped nano-enhanced cooling channels

In this study, impacts of using different cooling channels (L, T and U-shaped) on the energy and exergy performances of combined PV/TEG (photovoltaic/thermoelectric generator) unit are numerically assessed by using FEM based three dimensional high fidelity computational simulations. Cooling performance is boosted by using ternary nanofluid in the channels. The study is conducted for a range of Reynolds numbers (Re, between 50 and 500), nanofluid cooling inlet temperatures (between 15 °C and 23 °C), and nanoparticle loading amounts (between 0 and 3%). Evaluations are done on average PV-cell temperature, PV/TEG output powers, exergy efficiency, improve potential (IP), and sustainability index (SI). U-shaped and T-shaped channels are found to offer the greatest and worst cooling performances among various cooling channels. When comparing the lowest and maximum Re cases, the average temperature drops for PV cells are 3.54 °C for T channel and 2.55 °C for U channel. Exergy efficiency is determined to be 14.2% with T-channel at Re=50 and 14.6% with U-channel at Re=500. Taking into consideration different channels, an increase in the inlet temperature from 15 °C to 23 °C leads to an average rise in cell temperature of 6 °C. The IP rises with coolant inlet temperature while using T-channel. SI values fall as input temperature increases, although values between 1.164 and 1.175 may be achieved by using different cooling channels. Using nanofluid with higher loading results in higher exergy efficiency when comparing exergetic performances, with U-channel design exhibiting the highest performance. For the range of parameters considered, the coolant inlet temperature at the channel entry has the highest effect on PV cell temperature reduction; 8.5 °C of temperature reduction is feasible. By employing U-channel cooling, the maximum value of Re, the highest loading of nanoparticles, and the lowest inlet temperature yield the best exergy efficiency. The best and worst situations’ respective exergy efficiencies are determined to be 15% and 14.1%. Utilizing T-channel cooling with water at a flow flow rate and a higher input temperature is the scenario with the biggest potential for exergy improvement; the value is 2.9. When different operational parameters are varied, the SI falls between 1.176 to 1.16.

Multi-frame temporal dense nested attention method for detecting GEO objects

The geostationary orbit is a special and important spatial orbital resource. However, space resident objects in this orbit pose potential threats to space security, characterized as dim and small targets in imaging features. To solve the problem of detecting dim and small targets in geostationary orbit, we propose a multi-frame temporal dense nested attention method, which consists of a uniform linear motion constraint module and a dense nested attention module. The dense nested attention module adopts a multi-layer U-shaped structure and channel spatial attention mechanism, which can preserve the deep features of small targets, extract and fuse features from different scales of feature maps, and finally obtain the preliminary detection results of single-frame images. The uniform linear motion constraint module uses the prior information of the target motion in the image sequence, removes false positives and supplements false negatives, and improves the detection performance. Experiments were conducted on the SpotGEO dataset publicly released by the European Space Agency. The results of our experiments indicate that our method outperforms the state-of-the-art approach, showing a 12.83% reduction in Mean Squared Error compared to the current leading method. Our method, characterized by its minimal parameter requirement and independence from extensive dataset pre-training, is ideally suited for integration into small satellite devices, enabling efficient monitoring and mitigation of resident space objects.

Buckling mechanism and modified direct strength method of CFS built-up beams with multi-box cross section

A comprehensive study on the buckling mechanism of the Cold-Formed Steel (CFS) box beam composed of C- and U-shaped channels is conducted in order to improve the accuracy of the Direct Strength Method for calculating the bending capacity of CFS beams. Experimental tests involving four-point bending are carried out on six CFS box beams with varying screw spacing and stiffener numbers. In addition, numerical analyses are performed by finite element method. Based on the investigation of experiments and parameter analysis, an elastic constraint model for web buckling is proposed and the buckling coefficient are derived by the application of a generalized variational principle. The experiments reveal an interaction between local buckling in the upper flange under compression and the web. When the upper flange in compression buckles before the web, it leads to a reduction in the lateral constraint stiffness of the flange on the web, consequently, resulting in web buckling. An elastic constraint model for web buckling is proposed, incorporating the constraint effects of the upper flange's elastic support on the web. The critical buckling stress and buckling coefficient of the model are derived using the generalized variational principle. According to the experimental and numerical analysis results, the relative restraint stiffness of the flange on the web shows effects on the buckling coefficient. As the screw spacing and the length of the pure bending area decrease, as well as the number of stiffeners increases, the relative restraint stiffness increases. Subsequently, this leads to an increase in the buckling load and ultimate displacement of the CFS beam. Considering the interaction between the buckling of flange and web, the Direct Strength Method in AISI-2016 is modified for the CFS built-up box beam composed of C- and U-shaped channels. The applicability and correctness of the proposed modified Direct Strength Method is approved through the application of multi-box CFS beams composed of 2C-2 U and 3C–2 U channels. Compared with the Effective Width Method in current Chinese code and Direct Strength Method in AISI-2016, the proposed modified DSM exhibits the highest accuracy in predicting the bending capacity of the CFS box beam. It is shown that the proposed method can be effectively employed to calculate the flexural capacity of CFS beams with multi-box under local buckling control.

Phase transition of multiple encapsulated PCMs in a U-shaped channel under MHD with ternary nanofluid

Purpose Multiple encapsulated phase change materials (PCMs) are used in a wide range of applications, including convective drying, electronic cooling, waste heat recovery and air conditioning. Therefore, it is important to understand the performance of multiple PCMs in channels with flow separation and develop methods to increase their effectiveness. The aim of the study is to analyze the phase transition dynamics of multiple encapsulated PCMs mounted in a U-shaped tube under inclined magnetic field by using ternary nanofluid. Design/methodology/approach The PCMs used in the upper horizontal channel, vertical channel and lower horizontal channel are denoted by M1, M2 and M3. Magnetic field is uniform and inclined while finite element method is used as the solution technique. Triple encapsulated-PCM system study is carried out taking into account different values of Reynolds number (Re, ranges from 300 to 1,000), Hartmann number (Ha ranges from 0 and 60), magnetic field inclination (between 0 and 90) and solid volume fraction of ternary nanofluid (between 0 and 0.03). The dynamic response of the liquid fraction is estimated for each PCM with varying Re, Ha and t using an artificial neural network. Findings It is observed that for PCMs M2 and M3, the influence of Re on the phase transition is more effective. For M2 and M3, entire transition time (t-F) lowers by approximately 47% and 47.5% when Re is increased to its maximum value, whereas it only falls by 10% for M1. The dynamic characteristics of the phase transition are impacted by imposing MGF and varying its strength and inclination. When Ha is raised from Ha = 0 to Ha = 50, the t-F for PCM-M2 (PCM-M3) falls (increases) by around 30% (29%). For PCMs M1, M2 and M3, the phase transition process accelerates by around 20%, 30% and 28% when the solid volume fraction is increased to its maximum value. Originality/value Outcomes of this research is useful for understanding the phase change behavior of multiple PCMs in separated flow and using various methods such as nano-enhanced magnetic field to improve their effectiveness. Research outputs are beneficial for initial design and optimization of using multiple PCMs in diverse energy system technologies, including solar power, waste heat recovery, air conditioning, thermal management and drying.

Experimental and simulation analysis of flow patterns and energy dissipation through sluice gates in a U-shaped channel

ABSTRACT The vertical U-shaped gate holds significant potential for widespread application in flow control within U-shaped channels, as it eliminates the necessity for constructing auxiliary hydraulic structures. The boundary conditions associated with the U-shaped gate are complex, offering distinctive hydraulic features. In this study, the hydraulic characteristics of a vertical U-shaped gate have been investigated by model test and numerical simulation on a U-shaped channel under different flow rates, and the hydraulic evolution process was analyzed. The results show that the minimum relative error of discharges is 0.4%, so the numerical simulation can accurately describe the hydraulic performance of the vertical U-shaped gate. The flow generates a contracted cross-section and presents rhomboid water waves with a ‘hump-like’ convex structure after passing the U-shaped gate, accompanied by large kinetic energy dissipation. The gate opening exerts notable influence on the free surface width. The width of the first contraction section increased by 53.88% as the gate opening ranged from 2.5 to 5.5 cm with a flow rate of 8.24 L/s. The power function relationship of upstream flow Froude number, the width of free surface and energy loss is established. The results are helpful for engineering designing and operation management of a U-shaped gate.

Remote control of fluid motion in a channel by acoustic holography

A new method for manipulating fluid movement using sound waves is presented in this paper. The method relies on acoustic streaming near the free surface of the fluid in a channel with an open top. The sound waves are modulated in phase using acoustic phase holography, which creates a periodic phase pattern from 0 to 2π along a straight path on a target plane. The paper also describes an experimental design to study the main factors influencing the method, such as frequency, number of phase patterns in the path, and sound pressure amplitude. The paper shows that phase pitch and voltage significantly affects fluid speed and that there is a good match between the theoretical and experimental results. Furthermore, the article reports additional experiments with different channel shapes to demonstrate the versatility of the method in controlling fluid motion. The highest fluid speed observed was 0.4 mm/s at a frequency of 1300 kHz and a phase pitch of 5. The paper also investigates the effect of changing the frequency on reversing the flow direction in a U-shaped channel, both experimentally and theoretically. The paper concludes that this method could be a suitable alternative to other acoustic devices for inducing fluid motion because of its simple and flexible design, fabrication, accuracy, and ability to handle complex channels.

Computational Fluid Dynamics Analysis of Flow Characteristics and Heat Transfer Variabilities in Multiple Turbine Blade Cooling Channels

Abstract In the realm of gas turbine engine technology, turbine blades are persistently subjected to extreme thermal conditions due to prolonged exposure to high-temperature gases. Given this operating environment, devising effective cooling strategies is paramount for ensuring the turbine’s safety and longevity. Despite the critical nature of this issue, existing literature scarcely addresses cooling channels that incorporate factors like variable cross-sectional attributes and rotational effects. In this study, Computational Fluid Dynamics (CFD) and numerical methodologies were employed to analyze the flow mechanism and performance of three distinct cooling channels characterized by variable cross-sectional features. The results indicate a marginal thermal performance improvement of up to 3% for U-shaped cooling channels, specifically at a Reynolds number of 20,000, in comparison to Net cooling channels. Conversely, jet impingement channels outperform U-shaped channels by an impressive margin of over 11%. Additionally, at a Reynolds number of 60,000, jet impingement cooling channels manifest a significant upsurge of nearly 25% in the ratio between average Nusselt number, and the reference Nusselt number when compared with U-shaped and Net cooling channels.

Experimental and Numerical Modeling of the Freeze–thaw Response of U-Shaped Channel Lining on Sulfate Saline Soil Foundation

Under the influence of seasonal freeze-thaw cycles, the concrete lining of channels situated on saline soil foundations is highly vulnerable to an array of deleterious phenomena, such as frost heave, salt expansion, and corrosion. To investigate the synergistic interplay among saline soil substrates, U-shaped channel lining structures, and ambient temperatures during freeze-thaw cycles, a novel Hydraulic-Thermal-Salt-Mechanical (HTSM) model is established in this study. The HTSM model elucidates the migration of moisture and salt solute, ice-water phase transitions, and sodium sulfate crystallization within unsaturated saline soils throughout the freeze-thaw cycles. It considers the variations in volume and pore solution volume before and after the phase transition of sodium sulfate. Temperature and salt frost heaving force measurements obtained from outdoor freeze-thaw cycles are compared with numerical simulation results to validate the efficacy of the HTSM model and investigate the distribution patterns of salt frost heaving force (frost swelling force) along the channel. The results showed that the frost swelling force and depth exhibit a great linear relationship and the maximum stress of the U-shaped channel appears at the bottom of the channel, highlighting the good arching force characteristics of the U-shaped structure which prove that bottom of the channel is also the most prone to fracture. Significantly, the initial water content significantly impacts the frost swelling force—it increases by 4% while the frost swelling force increases by 76%. Comparing the numerical simulation results of temperature variations, moisture changes, and salt-frost heaving forces with the outdoor experimental data, it is evident that the proposed HTSM model effectively simulates the salt-frost heaving patterns observed in U-shaped channel linings.

The dynamics of the interfacial surface of helium II–vapor in a U-shaped channel

The dynamics of the interfacial surface of helium II–vapor in a U-shaped channel

Heat transfer performance of RP-3 aviation kerosene at supercritical pressure within a rotating U-shaped channel

The combined cycle engine based on turbine is typical in the field of cycle engines. However, the problem of high temperature heat load of turbine blades is serious. In order to solve this kind of problem, the method of using hydrocarbon fuel as cooling medium to improve the cooling efficiency of turbine blades are proposed. In this paper, the flow and heat transfer characteristics of RP-3 aviation kerosene in a rotating U-shaped channel under supercritical pressure were studied by numerical simulation. The flow and heat transfer characteristics of RP-3 aviation kerosene under supercritical pressure at different rotational speeds were numerically simulated by SST k-ω model. The results show that the centrifugal section and the horizontal section show obvious fluid stratification, and the mainstream distribution in the centripetal section is relatively uniform due to the bending effect and rotational buoyancy. Compared with the heat transfer capacity in the static state of the centrifugal section, the heat transfer of the fluid in the rotating state deteriorates, recovers and strengthens with the increase in the rotational speed. Moreover, compared with the centripetal section, the rotational speed has a particularly significant effect on the heat transfer performance in the centrifugal section and the horizontal section. When the rotational speed exceeds 300 rpm, the deterioration trend of heat transfer is weakened and the overall heat transfer performance is greatly improved.

Optimization of heat transfer and friction characteristics of a rotating U-channel with a combination of variable size connecting bridges

Gas turbine blades typically feature a U-shaped or multi-flow snake channel in their mid-chord region, both incorporating a 180° turn. However, the addition of fins and dimple or protrusion turbulent flow structures can result in excessive pressure losses within the flow channel. This study aims to reduce pressure loss and improve flow uniformity by inserting one to three connecting bridges of varying sizes in the gap between the two channels. The suitability of various connecting bridges with different angles and sizes is assessed in both stationary and rotating states through simulations. Subsequently, the cooling efficiency and reduction in resistance performance of different-sized connecting bridge combinations are evaluated. A layout scheme for optimal connecting bridge placement within the U-shaped channel is proposed. Results indicate that the incorporation of a single minimum-size connecting bridge leads to an average 22.6 % decrease in overall flow resistance within the U-shaped channel, and simultaneously yields a 3.5 % increase in the overall thermal performance. When using the recommended connecting bridge angle and layout combinations, the incorporation of connecting bridges leads to an average 46 % and 49.7 % reduction in overall flow resistance within the U-shaped channel in order to counterbalance pressure losses generated by turbulent structures. This effect consequently results in a 6.5 % and 6.6 % increase of the overall thermal performance. This study offers new insights and data-backed evidence that can potentially facilitate the design of high-efficiency and low-resistance cooling methods in the mid-chord region of high-temperature turbine blades.

Numerical study of mixed convection flows in a U-shaped channel

In this work, we study numerically mixed convection flows in an open U-shaped channel. The right opening lets pass fresh air at cold temperature TC, while the walls of the channel are heated at the temperature TH > TC. Our study is based on a volume control method performed for 100 < Re < 700, Ra = 105 and Pr = 0.72. Results are presented in terms of thermal and dynamic fields, Nusselt number variation with Re, flow velocities and temperatures at the channel outlet.

Numerical investigation and optimisation of flat plate solar collectors using two swarm-based metaheuristic algorithms

In the present work, four flat-plate solar collectors of similar dimensions have been simulated using the CFD approach. Model 1 has been considered as circular with a U-shaped zigzag channel, while model 2 is a square-shaped plate. In the 3rd model, the number of turns in the channel has been increased by keeping the geometry of the pipe constant, while in the 4th model, multiple straight channels have been incorporated instead of a single U-shaped zigzag channel. Three-dimensional simulations have been primarily done to understand the effect of channel geometry area and turnings on the collector's performance. A steady-state incompressible forced convective heat transfer analysis has been performed here. Water is used as a fluid in the channel to carry heat. The results of the numerical analysis led to the conclusion that model 3 is the best flat plate solar collector where turnings are maximum. With a maximum collector performance of 41.57, model 3 performs 36.7% better than model 1. Additionally, when water flows at a rate of 8 m/s inside the collector's channel, the rate of heat transfer in model 3 is 2.5% faster than in model 1. Moreover, a global optimization study has been performed using two swarm-based metaheuristic algorithms, Gravitational Search Algorithm (GSA) and Firefly Algorithm (FA), with the aim of determining good optimum values of the design variables that will maximize collector efficiency for model 3 at different flow velocities. For model 3, the percentage variation in collector efficiency between CFD and optimised findings using metaheuristic algorithms is found to be (a) 41.08% for v = 2 m/s; (b) 28.41% for v = 4 m/s; (c) 21.71% for v = 6 m/s; and (d) 13.09% for v = 8 m/s. Therefore, it is possible to anticipate that as flow velocity increases, there will be a steady decrease in the variation between computed and optimized results.

Oscillations of the Helium II – Vapor Interface during Motion in a Channel of a Relatively Large Diameter

The article considers the motion of superfluid helium in a U-shaped cylindrical channel with a diameter significantly larger than the helium capillary constant in the approximation of an inviscid incompressible fluid. When a heat flux is applied near the end-face section of one of the channel elbows, a vapor layer emerges near the heater, and the helium II – vapor interface begins to move. The purpose of the calculation is to determine the interface position as a function of time. The heat transfer in a liquid is described using the semi-empirical Gorter-Mellink theory. The processes in the vapor are analyzed based on the methods of molecular kinetic theory. The influence of the gravity field is studied. The system of equations is reduced to an ordinary second-order differential equation, which is solved numerically. Various process development scenarios depending on the heat flux are obtained. The occurrence of oscillations is described, and the influence of parameters on the oscillation amplitude and frequency is analyzed. In this way, the previously obtained experimental data have been interpreted.

Experimental and numerical study of flow field structure in U-shaped channels with different bend sections

Time-resolved particle image velocimetry is used to study the flow characteristics of rotating U-shaped channels with different types of bend sections: one with both inner and outer walls square, one with an inner circular wall and an outer square wall, and one with both inner and outer walls circular. The rotation number varies from 0 to 0.25, at a Reynolds number of 11 500. The present work aims at providing a detailed insight of the flow field occurring within a rotating U-shaped channel, typically resembling internal cooling channel embedded into first stages of turbine blades in aeroengines. A validated numerical simulation is carried out to determine the flow mechanism. A proper orthogonal decomposition and the Ω-criterion vortex identification method are used to study the vortical distribution and flow characteristics. The results show that a bend with both inner and outer square walls produces corner vortices on the outside of the bend section, and both the separation vortex and reattachment vortex are larger than those of the other two geometrical configurations. In the channels with a circular inner wall of the bend, separation is delayed, and both the separation vortex and reattachment vortex are smaller. When both walls of the bend are square, the peak Reynolds shear stress is twice than when they are both circular. With the increase in the rotation number, the size of vortical structures changes. The Coriolis force also changes the relative size of the secondary flow in the bend section, and the vortex near the leading surface becomes larger.

Improvement in U-Shaped Channel SOI Lateral IGBT for Wider Reverse Bias Safe Operating Area

In this article, the inductive turn-off failure mechanism of U-shaped channel silicon-on-insulator lateral insulated-gate bipolar transistor (SOI-LIGBT) under high-voltage and high-current is investigated by experiments and numerical simulations. First, the measured turn-off waveforms before and after failure are compared to infer the cause of the failure. Then, the failure is reproduced by calibrated three-dimensional simulations using Sentaurus TCAD. According to the simulation and measured results, the turn-off failure is resulted from the high impact ionization in the bird’s beak region. To reveal the failure mechanism, the turn-off failure process is divided into two phases. In phase I, the electrons generated by drastic impact ionization in the bird’s beak region act as the base current to keep the operation of parasitic PNP transistor after channel pinching off. In phase II, the parasitic NPN transistor is activated due to the hole current amplified by PNP, and thus, turn-off failure occurs. Based on the revealed turn-off failure mechanism, an improved U-shaped channel SOI-LIGBT with a P-top is proposed. The P-top is arranged in the bird’s beak region to reduce the impact ionization rate. The measured results demonstrate that no failure occurs when the improved device turns off under high-voltage and high-current conditions. Compared with the conventional U-shaped channel SOI-LIGBT, the improved device obtains 275% and 23% improvements in turn-off current at a bus voltage of 450 V and reverse bias safe operation area, respectively.

Исследование характеристик U-образного плазменного канала импульсных ксеноновых ламп

The paper presents main results of investigating electrical parameters and characteristics of the pulsed xenon lamp ultraviolet radiation with a U-shaped plasma channel and caprod current leads. The gas-discharge lamp design feature suggests presence of the ballast transelectrode volumes contributing to the xenon escape from the discharge and the radiation acting from one part of the U-shaped plasma channel on the other. Literature sources devoted to the specified phenomena were analyzed. Factors influencing the xenon plasma thermophysical state were established. Due to the lack of techniques for registering the pulsed radiation in a narrow spectral range of 200--300 nm, measurement techniques and investigation hardware were considered in detail. The time interval for establishing the gas-dynamic equilibrium in a pulsed xenon lamp in the process of its entry into the nominal operating mode was determined by calculation and experiment. Studies of the Vt transelectrode volume effect on characteristics of the pulsed xenon plasma were carried out in the range of 0.16 < Vt /Vi < 0.3. It was established that the possible factors leading to a decrease in the current density and intensity of the UV radiation included the modes of electrical supply and evaporation of the quartz shell limiting the discharge. It was shown that self-radiation return in plasma contributed to an increase in the current density of the pulsed xenon lamp