Location Of Nozzle Research Articles

Combined simulation of micro and nanoparticles in RF inductively coupled plasma torches with the variations of metallic species and feeding nozzle location

Lagrangian scheme for microparticles and Eulerian scheme for nanoparticles are combined to analyze the synthesis of metal nanoparticles in an RF plasma torch. It was observed that the evaporation occurs actively in the hot region of the inductively coupled plasma torch and generates the monomer source. As a result, monomers are consumed for the nucleation and the condensation of microparticles and nanoparticles. By changing the location of the feeding nozzle, it is possible to control the size distributions of the synthesized nanoparticles and microparticles. Furthermore, the size distributions of silver, gold, copper, and iron particles are simulated by controlling the temperature profiles at the loading position. The nanoparticle size distribution is adjustable by the temperature fields near the injection position, affecting the melting of microparticles for given physical properties of the boiling point, the melting point, and surface tension per species.

Applying machine learning for optimization of dehumidification strategy on the modified model for the non-equilibrium condensation in steam turbines

In this study, the dehumidification strategy has been used to reduce the damages caused by the non-equilibrium condensation flow. In the first stage, the non-equilibrium condensation phenomenon modeling has been performed after a sensitivity grid size test, and validated by an Eulerian-Eulerian approach for the machine learning (ML) initial data. In the next step, the location of nozzle have been evaluated for the ML to predict the non- equilibrium phenomenon. Then, the output data of the numerical method have been used as the initial data for the ML method. Finally, after accurately ensuring the prediction of the ML from the behavior of the non-equilibrium condensing flow compared to the experimental data, the dehumidification technique has been linked to the ML. By help of the ML approach, a performance optimization has been carried out to reduce the presence of water droplets on different locations of the blade surface. In this way, the numerical simulations result by applying the ML have been linked and the final optimized model according to the defined parameters has been developed. It is noteworthy to mention that the objective functions are defined according to the energy of flow and the corrosion rate. The outcomes from such optimization could lead the designers to find the best location for suction dehumidification technique for the turbine blades. The machine learning has been linked to three optimization algorithms, including drone squadron optimization, particle swarm optimization, and genetic algorithm. According to the obtained results of the employed machine learning and optimization methodology, for the optimum case compared to the original case, 99%, 1%, 18%, and 90% reductions have been achieved for the erosion rate, entropy, loss of moisture, and droplet sizes, respectively. It means that, by performing such research one could study some optimization parameters and link them by artificial intelligence to investigate the best place for the suction dehumidification technique.

Evaluation of robotic fiber placement effect on process‐induced residual stresses using incremental hole‐drilling method

AbstractThe robotic fiber placement (RFP) process depends on continuous fusion bonding and solidifying of prepreg tows onto a substrate by subjecting them to a compression force and heat flux. However the advantages provided when using the RFP to fabricate the composite structures, it has adverse effects due to the induced residual stresses (RSs). The current work presents the effect of the RFP on the induced RSs in thermoset composites. RFP is utilized to fabricate specimens from carbon fiber reinforced polymers. Effects of placement speed, compression force, heating temperature, heating gas flowrate, and the location of the heat flux outlet nozzle are all included in the present study. A total of 69 flat panels are manufactured under different process conditions. Subsequently, the in‐depth RSs are measured using the incremental hole‐drilling method. Besides, the microstructures of the samples are also analyzed. The results show that the change in process parameters could significantly affect the induced RSs of the thermoset composites. Subjecting the samples to higher thermal and pressure loads would induce more RSs, which are attributed to the occurrence of partial curing during the manufacturing process along with the change in laminate geometry and porosity.

Numerical simulation and combustion analysis of coal and biomass co-combustion

China began entering the 14th Five-Year Plan period in 2021. With the proposed carbon-neutral long-term goal, the strategic position of clean energy is becoming increasingly prominent. using biomass power generation is one of the main application ways. In order to study the mixed combustion process of coal and biomass, this paper takes 300MW lignite boiler as the research object and uses Fluent software to explore the influence of biomass types and the location of biomass nozzle on the mixed combustion, and obtains the corresponding temperature field, flue gas component field and the distribution of pollutant NO. The results showed that when the biomass particles were sprayed into a fixed position with a certain proportion, the NO emission of wheat, corn and cotton straw was reduced, and the effect of wheat straw was the most obvious. When a certain proportion of wheat straw and coal are co-fired, the higher the biomass nozzle position, the higher the peak temperature in the main combustion zone, and the better the emission reduction effect of NO.

Multiparameter Optimization of Thrust Vector Control with Transverse Injection of a Supersonic Underexpanded Gas Jet into a Convergent Divergent Nozzle

The optimal design of the thrust vector control system of solid rocket motors (SRMs) is discussed. The injection of a supersonic underexpanded gas jet into the diverging part of the rocket engine nozzle is considered, and multiparameter optimization of the geometric shape of the injection nozzle and the parameters of jet injection into a supersonic flow is developed. The turbulent flow of viscous compressible gas in the main nozzle and injection system is simulated with the Reynolds-averaged Navier–Stokes (RANS) equations and shear stress transport (SST) turbulence model. An optimization procedure with the automatic generation of a block-structured mesh and conjugate gradient method is applied to find the optimal parameters of the problem of interest. Optimization parameters include the pressure ratio of the injected jet, the angle of inclination of the injection nozzle to the axis of the main nozzle, the distance of the injection nozzle from the throat of the main nozzle and the shape of the outlet section of the injection nozzle. The location of injection nozzle varies from 0.1 to 0.9 with respect to the length of the supersonic part of the nozzle; the angle of injection varies from 30 to 160 degrees; and the shape of the outlet section of the injection nozzle is an ellipse with an aspect ratio that varies from 0.1 to 1. The computed fluid flow in the combustion chamber is compared with experimental and computational results. The dependence of the thrust as a function of the injection parameters is obtained, and conclusions are made about the effects of the input parameters of the problem on the thrust coefficient.

Enhancing terahertz radiation from femtosecond laser filaments using local gas density modulation

We present a method to enhance the terahertz (THz) wave radiation from a femtosecond laser-induced plasma filament by controlling the local gas density within the filament. We develop a theoretical model for THz generation from a laser-induced air plasma filament and the subsequent propagation process, to account for a varying local gas density. By adjusting the local gas density along the filament, the transient current distribution along the filament and the resulting coherent superposition of terahertz waves can be controlled. The location of the gas jet nozzle and the relative phase between multicolor light fields both affect the transient current distribution and thus the strength of the generated THz field. Compared with the conventional terahertz generation by a two-color filament in a homogeneous gas, a three-color filament can realize an increase by 6.12 times in the generated THz pulse energy, with optimized local gas density modulation. Our results suggest that the THz amplification via local gas density modulation can be further improved with well-designed multicolor pulses.

Residual stress reduction in dissimilar metals weld

Conventional methods such as post-weld heat treatment is not capable to reduce residual stress (RS) in dissimilar metals weld (DMW) to the same extent as in similar weld due to mismatch between thermal expansion coefficient of base metals. The objective of this study to understand the effects of a modern in situ technique, called CO2 rapid cooling, on mechanism of RS redistributions in both similar and dissimilar metals welds. More focus of this investigation is given to the DMW. A thermo-mechanical numerical model is developed to investigate the effectiveness of various CO2 rapid cooling parameters such as power, radius, off-center, and location of the CO2 nozzle on RS distribution. The model is tested and validated with experimental data obtained from neutron diffraction measurement. Overall, this study shows that the CO2 cooling application can produce a significant RS reduction in similar weld as well as DMW. It shows that smaller CO2 nozzle can lead to lower RS magnitude considerably; however, it is not always capable to produce favorable RS distribution. In addition, since the RS distribution is asymmetric in a DMW, the implementation of CO2 cooling technique to mitigate RS need not be symmetric or uniform with respect to the weld center line. Based on the results, further recommendations to minimize RS in welded parts are provided.

Spectral Analysis of Torsional Vibrations Measured by Optical Sensors, as a Method for Diagnosing Injector Nozzle Coking in Marine Diesel Engines.

The study aimed to verify whether it is possible to diagnose the coking of a marine diesel engine injector nozzle by performing a spectral analysis of the crankshaft’s torsional vibrations. The measurements were taken using laser heads, clocked at 16 MHz. The reasons for selecting this type of optical sensors are described as well. The tests were carried out under laboratory conditions, using a test stand with a Sulzer 3AL 25/3 engine, operating under a load created by a Domel GD8 500–50/3 electric generator. A unique method is presented in the paper, which enables the measuring and calculation of torsional vibrations of engine crankshafts. The method was developed at the Chair of Marine Power Plants at the Maritime University of Gdynia. It has been proven that the distribution of differences in the values of individual harmonic components depends on the location of a defective injector nozzle in the cylinder.

Numerical study of interaction between jet with rudders on slender body at hypersonic condition

In this paper, a numerical study of the interaction between transverse cold jets on slender body in front of or between X-shape rudders with rudders in the oncoming free stream is presented. Firstly, the flow field at different jet conditions is simulated and analyzed. Then, the total force and moment amplification factors of the corresponding slender body with jet at different locations are analyzed and compared with those results of non-jet flow. Numerical results show that interactions take a great effect to the configuration of the flow field around rudders and the pressure distribution on slender surface. Moreover, the force and moment amplification changes regularly along with the location of jet nozzle.

Numerical investigation on mass and heat transfer in an ammonia oil-free twin-screw compressor with liquid injection

Ammonia is one of the most frequently employed chemical materials, while oil-free screw compressors have recently been recognised as a quite suitable compression tool for an ammonia refinement system. In this paper, a heterogeneous model with mass and heat transfer was developed to investigate the characteristics of an ammonia screw compressor. The mass diffusion equation was solved based on the proper calculation of the physical properties of ammonia water mixtures. Then the model was validated by experimental data using a two-stage compression ammonia refining system. With validated simulation results, the impact of liquid injection on the compressor power consumption and temperature glide was then predicted and analysed. It was predicted that the isentropic efficiencies of the two compressors were 75% and 64% respectively. The simulation results revealed that the mean droplet diameter of the injected liquid should be less than 100 μm in order to guarantee sufficient cooling effect and improve the compressor performance. Finally, an optimization method for the location of injection nozzle and the amount of injected liquid was proposed. A second liquid injection nozzle is recommended to be added and located after the start point of compression process where the temperature glide is maximum. And the optimal flow rate of the new liquid injection nozzle is about 70% of the liquid amount injected to the suction port.

Preparation of Silicon Nanopowder by Recycling Silicon Wafer Waste in Radio-Frequency Thermal Plasma Process

Silicon nanopowders were prepared from silicon waste by using radio-frequency thermal plasma. Silicon waste, generated from the manufacturing process of silicon wafers, was pulverized to form micrometer-sized silicon starting powder. In order to obtain as much silicon nanopowder as possible from thermal plasma processing, the enhancement of vaporization and the quenching rate of the silicon starting powder were considered as major factors. A counter-flow injection apparatus (CFIA) was introduced for improved vaporization and homogeneous nanoparticles. It was designed to inject argon as a quenching gas in the direction opposite the thermal plasma flame flow. The controlled location of the CFIA injection nozzle and the flow rate of the quenching gas affect the residence time of the injected staring powder by recirculating flow and the vapor density by gas mixing. The variation of the flow pattern inside the reactor and the characteristics of the products were investigated to determine the optimal processing environment to prepare uniform and small silicon nanopowder particles. The environment was defined by two parameters: the flow rate of the counter quenching gas and the distance between the torch and CFIA nozzles. The flow rate of the quenching gas was controlled from 30 to 70 L/min. The distance between the torch and CFIA nozzles was adjusted from 150 to 350 mm. When the quenching gas flow rate of 70 L/min and the distance of 350 mm were applied, the uniform and smallest silicon nanopowders were obtained.

Investigation on the Performance of Forward Bending Fan

Abstract The forward bending centrifugal fan features long vanes and narrow passages, and the internal flow is apt to be affected by wall boundary layer of the blade surfaces. An aerodynamic investigation on the forward bending centrifugal fan is presented in this paper. The performances of the unsteady flow field in the centrifugal fan is predicted by solving the incompressible Reynolds-averaged Navier-Stokes (RANS) equations based on the Shear Stress Transport (SST) – Scale Adaptive Simulation (SAS) turbulence model. And three-dimensional (3-D) flow phenomenon of non-uniform fluid flow is discussed through observing the flow separation and vortex distribution in the impeller region. The installation location of inlet nozzle is finally adjusted based on the calculated results, and the centrifugal fan with eccentric inlet nozzle is proposed. From the results, the eccentric inlet nozzle with L=3 mm, θ=120° could improve the internal flow of the forward bending centrifugal fan and enhance its aerodynamic performance.

Investigation of the thermal-hydraulic characteristics of supersonic steam injector

Steam injector (SI) is known as passive jet pump and heat exchanging device which operates without external power source or mechanical machineries. It utilizes direct contact condensation heat transfer between steam and water-jet as a driving mechanism of the operation and is capable of discharging subcooled water at higher pressure than the inlet fluids pressure. In addition, it has an excellent heat transfer capability, more than 1000 times that of shell and tube heat exchanger. In the present study, thermal-hydraulics characteristics of the water-jet-centered supersonic SI system were investigated from both experimental and analytical approaches. The SI body was manufactured with stainless steel equipped with overflow port. The water injection nozzle was designed with shaft-driving mechanism to freely adjust the axial location of the water nozzle and steam inlet cross sectional area. High pressure steam was supplied to the SI from once-through boiler, which is capable of supplying saturated steam at the maximum pressure of 0.63MPa for the current test facility. Water jet was injected at mass flow rate of 0.4–0.8kg/s. Pressure and temperature measurements were conducted at inlet and outlet of the steam injector system as well as at the overflow port to investigate the operation characteristics of the SI. Results showed the water-jet centered SI’s promising functionality as a passive coolant injection in view of its quick-start up, operable condition limits, discharge pressure and heat transfer capabilities at current inlet conditions. In addition, obtained experimental results were compared with analytical model to assess the predictive capability of discharge pressure value and reasonable agreement was obtained.

Effects of injection strategies and fuel injector configuration on combustion and emission characteristics of a D.I. diesel engine fueled by bio-diesel

A multi-dimensional computational fluid dynamics (CFD) modeling was conducted on a D.I. (Direct Injection) diesel engine fueled by bio-diesel based on KIVA4 code. Comprehensive chemistry prediction of bio-diesel fuel was taken into account by enhancing the combustion model of the default KIVA4 code. An advanced multi-component fuel combustion model was applied to accurately predict the oxidation of saturated and unsaturated agents of the bio-diesel fuel using a reduced chemical kinetics mechanism. In order to accurately model spray, atomization and evaporation of the bio-diesel fuel, detailed thermophysical properties of fuel components were predicted and tabulated in the fuel routine of the KIVA4 code. After the validation for cylinder pressure and heat release rate at engine mid load with experimental engine tests, further numerical studies were performed to investigate effects of injection strategies such as double and triple injection pulses and axial location of injector nozzle. It has been found that cylinder peak pressure was increased by applying double and triple injections and some enhancements on output power was also observed. Moreover, it was found that nozzle axial location has considerable effect on combustion of the bio-diesel fuel where wall impingement of the liquid bio-diesel fuel resulted in lower evaporation and higher unburnt hydro carbon (UHC) emission.

마이크로 가스터빈용 하이브리드/이중 선회제트 연소기 개발 (Part II: 비반응 유동에 관한 수치해석)

마이크로 가스터빈용 하이브리드/이중 선회제트 연소기의 비반응 유동 및 혼합특성에 관한 수치해석 연구가 수행되었다. 고정된 열부하에서 pilot 버너의 위치, 선회 각 및 방향이 주요 변수로 검토되었다. 결과로서, pilot 버너의 위치, 선회 각 및 방향의 변화는 버너 출구 근처의 난류 유동장, 특히 중앙 재순환영역 및 난류강도의 큰 변화를 초래하며, 화염안정성 및 배기성능의 큰 변화를 동반하게 된다. 실험결과와의 비교를 통해, 하이브리드/이중 선회제트 연소기의 개발을 위하여 화염안정성 및 배기의 측면에서 pilot 버너의 최적 위치, 선회각<TEX>$45^{\circ}$</TEX> 그리고 정방향 선회유동 조건들이 선택되었다. The isothermal flow structure and mixing characteristics of a hybrid/dual swirl jet combustor for micro-gas turbine (MGT) were numerically investigated. Location of pilot burner, swirl angle and direction were varied as main parameters with the identical thermal load. As a result, the variations in location of pilot nozzle, swirl angle and direction resulted in the significant change in turbulent flow field near burner exit, in particular, center toroidal recirculation zone (CTRZ) as well as turbulent intensity, and thus the flame stability and emission performance might be significantly changed. With the comparison of experimental results, the case of swirl angle <TEX>$45^{\circ}$</TEX> and co-swirl flow including optimum location of pilot burner were chosen in terms of the flame stability and emissions for the development of hybrid/dual swirl jet combustor.

마이크로 가스터빈용 하이브리드/이중 선회제트 연소기 개발 (Part I: 형상 최적화를 위한 실험연구)

마이크로 가스터빈용 하이브리드/이중 선회 제트 연소기의 형상 최적화에 대한 실험연구가 수행되었다. 고정된 열부하에서 pilot 버너의 위치 및 선회기 베인의 방향이 주요 변수로 검토되었다. 주요 결과로서, pilot 버너 및 연료 노즐의 위치변화는 버너 출구 근처의 최소 유동면적 및 재순환 유동패턴의 변화를 발생시키며, 이로 인하여 선회강도 및 화염형상이 큰 영향을 받게 된다. 선회기 베인 각도의 증가(<TEX>$30^{\circ}$</TEX>에서 <TEX>$45^{\circ}$</TEX>)는 희박가연한계 근처에서 CO 배출량을 크게 저감시킨다. 추가로 정방향 선회형상이 역방향 선회형상에 비해 보다 낮은 CO 및 NOx 배출량을 갖게 됨을 확인하였다. An optimum configuration of the hybrid/dual swirl jet combustor for a micro-gas turbine was investigated experimentally. Location of pilot nozzle, angle and direction of swirler vane were varied systematically as main parameters under the conditions of constant thermal load. The results showed that the variation in locations of inner fuel nozzle and pilot burner resulted in significant change in flame shape and swirl intensity due to the changes in recirculating flow pattern and minimum flow area near burner exit, in particular, with the significant reduction of CO emission near lean-flammability limit. In addition, it was observed that the co-swirl configuration produced less CO and NOx emissions compared to the counter-swirl configuration.

Geometrical analysis of thermo-compressors in multiple-effects distillation units based on the second law of thermodynamics

Thermo-compressors are used instead of mechanical compression devices in many industries and play a main role in the process. Through the process of designing desalination systems, amount of exergy dissipation is a very important economical factor. Most of the exergy losses in multi-effect distillation systems with thermal vapor compression (multiple-effect desalination–TVC) occur in the thermo-compressor. The aim of this article is to investigate geometrical effects in thermo-compressors by numerical methods based on the second law of thermodynamics to obtain lower exergy loss and consequently, higher entrainment ratio. A lot of geometrical parameters such as converging and diverging angles in mixing section, diffuser, nozzle location and also its throat area ratio affect thermo-compressors’ performance. The modifications in the above-mentioned parameters were applied to a thermo-compressor established in a desalination unit in Kavian petrochemical company which is working with 15 barg of motive pressure. Numerical simulation of the base model has an accurate agreement with experimental data with about 1.3% discrepancy in maximum discharge pressure and just 6.7% in entrainment ratio. Results of the analysis indicate that thermo-compressor’s performance is sensitive to the mixing area converging angle. The other parameter which mostly affects the performance is the location of nozzle in thermo-compressor’s body.

Evaluation of ultrasonic sensor for variable-rate spray applications

Automatic variable-rate sprayers require accurate measurement of canopy size. An estimate of canopy size is made by measuring the distance to the canopy at several elevations above the ground; an ultrasonic sensor was used to determine canopy distance in this study. It is sometimes necessary to conduct spray operations during harsh operating conditions. In this study ultrasonic sensors were subjected to simulated environmental and operating conditions to determine their durability and accuracy. Conditions tested included exposure to extended cold, outdoor temperatures, cross winds, temperature change, dust clouds, travel speeds and spray cloud effects. The root mean square (RMS) error in a series of measurements of the distance to a simulated plant canopy was used to test for significant difference among treatments. After exposure to outdoor cold conditions for 4 months, the RMS error in distance measured by the ultrasonic sensor increased from 3.31 to 3.55 cm, which was not statistically significant. Neither the presence of dust cloud nor the changes in cross-wind speeds over a range from 1.5–7.5 m/s had significant effects on the mean RMS errors. Varying sensor travel speed from 0.8 to 3.0 m/s had no significant influence on sensor detection distances. Increasing ambient temperature from 16.7 to 41.6 °C reduced the detection distance by 5.0 cm. The physical location of the spray nozzle with respect to the ultrasonic sensor had a significant effect on mean RMS errors. The mean RMS errors of sensor distance measurements ranged from 2.3 to 83.0 cm. The RMS errors could be reduced to acceptable values by proper controlling the sensor/spray nozzles spacing on a sprayer. In addition, multiple-synchronized sensors were tested for their measurement stability and accuracy (due to possible cross-talk errors) when mounted on a prototype sprayer. It was found that isolating the pathway of the ultrasonic wave of each sensor reduced detecting interference between sensors during multiple sensor operation. Test methods presented herein may be useful in the design of standardized testing protocols for field use distance sensors.

Pulsating jet control for manipulating the separation bubble behind the fence

An optimization study of a pulsating jet was performed to manipulate the separation bubble behind the fence. The experiments were carried out in a circulating water channel and the vertical fence was submerged in the turbulent boundary layer. The parameters used for controlling the pulsating jet included the frequency, speed and velocity profile of jet, and the geometries including angle and location of nozzle. In addition, we investigated the effect of upstream boundary layer changed by continuous suction in front of the jet nozzle. Each test case was divided into 20 phases and phase-averaged DPIV method was applied to measure the velocity field. From the results, the main mechanism of reduction of bubble length was the vortex shedding from the recirculating region. The specific jet condition and nozzle geometries which were effective to reduce the separation bubble behind the fence were found.

Mass flow and heat transfer characteristics of lift tube technology

Abstract An innovative vertical transport tube system has been developed to enhance heat transfer between fluidized beds and axial solids circulation within a fluidized bed reactor. Vertical lift tubes pick up particles from the bottom of the reactor, carry them through a fluidized bed burner before discharging them above the reactor bed surface. A full-scale experimental setup was designed to test the effects of different operating conditions on the solids flow through the lift tube. The heat transfer and mass flowrate through the lift tube are altered by varying the fluidization conditions, the motive gas flowrate and the location of a motive gas nozzle with respect to the tube. Increasing the pressure downstream of the lift tube reduces the solids flow. A preliminary study on the heat transfer benefit of the lift tubes was also performed on another laboratory apparatus: implementation of a single lift tube increased the heat transfer coefficient between the central and annular bed from 25 to 400 W/m 2 K at optimal flow conditions. This technology has been successfully implemented in a full-scale annular pyrolysis reactor.