Length Of Deflector Research Articles

CFD analysis and RSM-based design optimization of axial air-assisted sprayer deflectors for orchards

To reduce pesticide waste caused by uneven airflow distribution, the geometry parameters of axial air-assisted sprayer deflectors were investigated for potential influence on air outlet velocities. Computational fluid dynamics (CFD) was employed to simulate the complex interactions between the airflow discharged from the air-assisted sprayer and the neighboring environment, investigating the effects of the length and mounting angles of the upper and lower deflectors on the airflow distribution. The validated CFD model was combined with the response surface methodology (RSM) with root mean square error of 1.461 m s−1 and mean relative error of 22.01%, respectively. RSM with four factors and five levels was employed to optimize the geometric parameters of the sprayer deflectors, including upper deflector length, upper deflector mounting angle, lower deflector length and lower deflector mounting angle. Based on the least squares analysis of RSM, the influence of each factor and their interactions on the airflow distribution from the sprayer outlet were estimated. The optimal values of upper deflector length, upper deflector mounting angle, lower deflector length and lower deflector mounting angle were 495 mm, 65°, 205 mm and 15°, respectively. The coefficient of variation (CV) of the air velocities from the optimized sprayer outlet was reduced by 29.95%, indicating an improvement in the uniformity of the airflow distribution and an enhancement in pesticide utilization.

Experimental investigation and structural optimization prediction of a novel carbon stripper for solid-fuel chemical looping combustion

The addition of carbon stripper (CS) can effectively improve the carbon conversion efficiency in the fuel reactor of solid-fuel chemical looping combustion system. An independent CS system is constructed, and the feasibility of the system is verified through feasibility tests and reference work condition tests. The effects of important conditions on the separation performance of CS are also explored based on the experimental platform. It is found that increasing the main gas velocity and cross-flow velocity in the air reactor can effectively improve the directional separation efficiency of binary particles. On the other hand, based on the Computational Fluid Dynamics platform, the important structural factors, including baffle angle, deflector angle and deflector length of the CS, are studied for the directional separation mechanism of binary particles. The results show that a CS structure with the baffle length of 140 mm, the baffle angle of 110°, the deflector length of 40 mm, and the deflector angle of 60° exhibits good directional separation performance. In this case, the separation efficiency of quartz sand is close to 100%, and that of polyvinyl chloride (PVC) particles can reach a high value of 93.7%, demonstrating the high separation efficiency and promising application prospects of this novel CS.

Influence of deflector on the impact dynamics of debris flow against rigid barrier

A deflector is a structure installed at the crest of a rigid barrier to prevent the over-spilling of debris flow from damaging the downstream infrastructures and human lives. Despite its clear practical value, the fundamental interaction mechanism of debris flow and deflector has not yet been elucidated scientifically. In this study, flume tests were conducted to calibrate a smoothed particle hydrodynamic (SPH) model to investigate the influence of deflector geometry (length and angle) on the flow-deflector interaction mechanism as well as reducing design barrier height. Water flows and viscous debris flows with a Froude number of around 5 were modelled to represent geophysical flows. Flume test and numerical simulation results reveal that the optimal deflector configuration has a normalised projected length (projected deflector length to frontal flow depth) of LP/h0 = 1.0 with angles (θ) of 0° and 45°. A modified analytical impact equation is proposed, which conservatively predicts the peak impact force exerted on a deflector with an upper bound to measured and computed values. The normalised barrier height (ratio between barrier height and frontal flow depth) also plays a key role in over-spilling dynamics. For a barrier without a deflector, over-spilling would occur when HB/h0≤ 9.0. However, for barriers with deflectors, over-spilling occurs only if HB/h0≤ 4.7. Installing a deflector allows reduction of barrier height by up to 50% while preventing over-spilling.

The effect and mechanism of the flow deflector on ignition performance of the centrally staged combustor

Lean premixed prevaporized combustors with a centrally staged scheme are capable to reduce NOx emissions. Ignition is one of the key performances of the centrally staged combustor. The present study proposes a novel method to improve ignition performance by using a flow deflector. The effects of various flow deflector lengths and pressure drops on ignition performance and flame kernel propagation are investigated in this work. It is found that ignition performance is significantly improved by the flow deflector. The ignition process is obtained using a high-speed camera under different operating conditions. The timescale of the successful ignition process is analyzed using a statistical method, revealing the effects of the flow deflector length and pressure drop on the timescale of each phase of ignition. The flame kernel propagation trajectory is extracted and analyzed by combining the flow and spray fields. The mechanism of the flow deflector is analyzed by numerical simulation. It is found that with the flow deflector, the local fuel/air ratio and droplet diameter are both improved, which benefits ignition performance. This work proves that the flow deflector is a potential method to improve ignition.

Design and Numerical Optimization of Gas Guidance System in Casting Silicon Furnace by the Orthogonal Experiment

3D global simulations were performed to investigate the gas flow and impurities transport in casting silicon furnace under the influence of a unique designed spray-type gas guidance system (GGS). The simulation results show that, the intensity of backflow at crucible outlet had no obvious change with the application of this GGS, but the flow area of backflow was effectively inhibited above the melt free surface and the kinetic rate of reaction was weakened at the cover. Finally, the area-average concentration of CO at the melt free surface was decreased by 31 %. The GGS was optimized by the orthogonal experiment, including the argon flow rate (Q), length of deflector (L) and distance between GGS and melt free surface (H). When Q = 40 L/min, H = 50 mm and L = 50 mm, the GGS had the most obvious effect on removing impurities.

Experimental and numerical studies on deflector configuration in straight flood channel for heterogeneous flow enhancement and fish habitat improvements

For ecological restoration of concrete flood channels, installing current deflectors is a straightforward, cost-effective, and efficient approach with minimal maintenance. It is important to find the appropriate arrangement, orientation, number, protrusion length, width, and spacing of deflectors to achieve an effective flow pattern. In this research, indoor flume experiments were carried out to identify the flow conditions and fish trajectories in the absence and presence of deflectors. Deflectors were found to enhance the flow heterogeneity and benefit the upstream movement of fish in the floodway. To further optimize the design, a 2D numerical simulation was conducted to predict the effectiveness of different deflector configurations. The results showed that compared with aligned deflectors or solid triangles, staggered deflectors and central islands were more suitable for the creation of non-uniform flows and pool areas. The optimum orientation of deflectors was perpendicular to the flow. A set of four deflectors with appropriate intervals along the channel was highly recommended. It was found that the ideal contraction ratio (α= deflector length / channel width) was between 25% and 50% to protect the river bank and bed from erosion. As the width of the deflector had less effect on the flow pattern, the narrowest deflector with a ratio (β) between deflector width and channel width of approximately 17%, was found to be preferable considering the construction cost. The ratio (γ) between deflector spacing and channel width was proposed to be set from 1.67 to 2.5 for flow concentration and sinuosity generation.

Experimental investigation of energy dissipation on flip buckets with triangular deflectors

ABSTRACT Flip buckets are commonly used to discharge flow from a hydraulic structure to the downstream as ski jump when flow velocity is large. Deflectors can be used to increase the efficiency of energy dissipation by flip buckets. This wedge-shaped structure deflects a portion of the flow by splitting it on the bucket. In this study, the effect of triangular deflectors which are used continuously across the channel, on energy dissipation by a flip bucket was experimentally investigated. For this purpose, a triangular deflector with three side lengths (3, 6 and 9 cm) and seven angles equal to 12°,17°, 22°, 27°, 32°, 37° and 42° was tested under different hydraulic conditions and the results were compared with a flip bucket without a deflector. The experiments were carried out in a laboratory flume with a length of 15 m, a width of 0.3 m and a height of 0.5 m. The results indicate that the model with a deflector increased energy dissipation by 8.2 to 22.7 percent as compared to that without a deflector. Increasing the deflector angle and side length initially increased energy dissipation, but then decreased it at large angles and lengths. An optimum angle of 27° to 32° was obtained with an optimal deflector length (L) to the Reynolds number (R) ratio of 0.46. A correlation was proposed to predict energy dissipation by the flip bucket with a triangular deflector using multivariate nonlinear regression.

Experimental and numerical validation of the influence on Savonius turbine caused by rear deflector

Savonius turbine is a popular vertical shaft power generation turbine for its small starting torque and outstanding cost effectiveness. Installing the deflector on the Savonius turbine is a cost-effective way to increase its power performance. In this study, a passive positioning system is proposed, so as to settle the matter that the deflector is unable to be kept in the suitable position autonomically. The system acclimatizes itself to the inflow automatically with the help of the rear deflector that is impinged by the incoming flow. In order to demonstrate power performance of the presented system, the influence of the rear deflector on Savonius turbine is experimentally and numerically investigated through towing tank tests and 2D CFD simulations. The results indicate that: the lower deflector length and farther distance from the center of rotation, the weaker effect on the power coefficient. Considering the engineering requirements of power generation device, the optimal placement of the deflector is achieved. When the distance from the center of rotation is 0.82 times than the turbine’s diameter, the suppressing effect on the power coefficient is less than 3% in this operating condition.

Evaluation of a chicory root cold store humidification system using computational fluid dynamics

Humidification of chicory root cold stores helps in maintaining the quality and extending the postharvest storage time of chicory roots. Low evaporation rate of the sprayed droplets at such sub-zero temperatures (−2 °C to −1 °C) favours surface deposition that could have an adverse effect on the efficiency of the storage room. A three-dimensional computational fluid dynamics (CFD) model was developed and used to predict the storage room air velocity, temperature and humidity distributions, and fate of the water droplets that were sprayed for humidifying the storage room. The humidification system in a chicory root cold store was then optimized. The efficiency of the humidification system was affected by length of cold air deflector, stack height, number of nozzles and duration of humidification. Elongating the air deflector, reducing the stack height, reducing the number of nozzles and shortening the humidification time increased the amount of droplet evaporated and decreased the amount of droplet deposited on the stack. The following combinations of room design and operating parameters could clearly give the best performance of the humidification system: deflector length of 0.8 m, two nozzles with an interval humidification of 1.5 min on and 2 min off cycle and stack height of 3.4 m.

Abrupt deflected supercritical water flow in sloped channels

The effect of the bottom slope on abrupt deflected supercritical water flow was experimentally and theoretically studied. Model tests were conducted in a flume of 1.2 m wide and 2.6 m long with sloped bottom at an angle 35.54°, its length of deflector was 0.2 m and the deflection angles were 15° and 30°. An approximate method for calculatjng the shock wave angle and depth ratio of the abrupt deflected supercritical water flow was suggested, and a correction coefficient for the hydrodynamic pressure was introduced to generalize the momentum equation in the direction perpendicular to the shock front. It must be noticed that in the sloped channel the shock wave angle and the depth ratio are no longer constant as those in the horizontal channels, but slowly change along the shock front. The calculated results are in good agreement with measured data.

Deflector designs for fish habitat restoration.

Paired current deflectors are structures that are installed on each bank of a river to locally reduce the width of the channel, thereby creating flow acceleration and promoting scouring. These instream habitat structures have been used extensively in restoration projects to create pool habitat for fish, but there are many discrepancies in deflector design recommendations in terms of orientation, height, and length. Our objectives were to (1) examine how the angle, height, and length of paired deflectors affect scour hole dimensions and potential for bank erosion; and (2) test the applicability to paired deflectors of existing equations for scour hole depth and volume. Three deflector angles (45 degrees, 90 degrees, and 135 degrees), two deflector heights (with flow under and over the deflector height), and two lengths (reducing the width by 25% and 50%) were investigated using uniform sand in a laboratory flume. Results showed a 26-30% smaller scour depth resulting from 45 degrees deflectors than from 90 degrees deflectors and a 5-10% smaller scour depth for 135 degrees deflectors compared to 90 degrees deflectors. The volume of scour and the potential for bank erosion were greater when flow was under the height of the deflectors rather than overtopping and when the length of deflector was increased. When flow was under the deflector height, 135 degrees deflectors had the highest amount of bank erosion; whereas during overtopping flow conditions, 90 degrees deflectors had the greatest bank erosion potential. Values predicted by the model of Kuhnle and others were closest to observed scour depth and volume measurements. The assumption that upstream-oriented deflectors always generate the largest scour should be revised.

Design of the Deflector for the rf Beam Separator at the Brookhaven AGS

The design of the iris-loaded deflector for the Panofsky type rf beam separator now under construction at the Brookhaven AGS is presented. General expressions for the transverse momentum acquired by an ultrarelativistic particle traversing the deflector are derived from the field equations. Useful figures of merit (shunt impedance R, series impedance Z, quality factor Q, R/Q, etc.) are defined. Computational results for the aperture radius a, the guide radius b, Q, R/Q, and R as functions of group velocity vg, the number of irises per wavelength N, and iris thickness d/w are presented for structures with the phase velocity vp=c. They are compared with experimental results reported from deflection tests. The design procedure of a deflector is developed for the realistic case that the shunt impedance varies with group velocity. Optimization of operating frequency fπ/2, deflector length l, vg, d/w, and N is carried out. Higher order modes in iris-loaded waveguides are investigated and methods for the suppression of mode degeneracies are outlined. The effect of the mechanical tolerances on the phase shift per cell Φ is considered. The chosen deflector structure has λ0=10.495 cm, N=4, Φ=½π, d/w=0.8, 2a=48.13 mm, 2b=116.71 mm, l=3.07 m, rounded iris edges, and lateral rods as mode stabilizers. ``Cold'' measurements on cavities and waveguides are described, and a precise R/Q perturbation method is detailed. Pertinent results are fπ/2=2856.35 Mc, Q=8700, phase error per cell ΔΦ=2.7° rms, R/Q=1.41 kΩ/m, vg/c=−0.0204, αl≈0.5. It is concluded that a klystron pulse of ≥14 MW is sufficient to give a 1 mrad peak deflection of 18 GeV/c particles.