Single Orifice Plate Research Articles

Study on degradation of Basic Violet 1 and heat generation by parallel orifice plate hydrodynamic cavitation

Hydrodynamic cavitation (HC) technology with double parallel orifice plates can further enhance the degradation effect and heat generation efficiency and play an important role in practical large-scale organic wastewater treatment and energy saving. In this study, based on the optimal hole numbers in single orifice plate, the influences of the hole number and distribution in double parallel orifice plate on Basic Violet 1 (BV-1) degradation and heat generation are studied in detail. Furthermore, the effects of some experimental parameters (inlet pressure, initial concentration, solution temperature and solution volume) on BV-1 degradation and heat generation in 4 + 4 parallel orifice plate HC system are deeply studied. Then, the effect of added H2O2 on the BV-1 degradation and heat generation is also investigated. In addition, the capturing experiments of free radicals (•OH and •O2-) are carried out. Finally, the BV-1 degradation pathway and possible degradation mechanism are proposed by analyzing the data of UV–vis spectrum, LC-MS and total organic carbon (TOC). The final results show that the solution temperature can be raised from 20.05 °C to 57.71 °C under the experimental conditions of 4 + 4 parallel orifice plates, 3.0 bar inlet pressure, 5.0 L total solution volume and 10 mg/L initial concentration for 90 min continuous circulation and the BV-1 degradation ratio can be achieved by 75.98 %. The system can generate 785.40 kJ heat at 48.50 USD/m3 cost and achieve 29.09 % thermal efficiency. For 1:30 molar ratio of BV-1 and H2O2, the solution temperature can be further raised to 63.32 °C in 90 min continuous cycling. 95.38 % BV-1 degradation ratio can be obtained and the 909.72 kJ heat can be generated, reaching the 33.69 % thermal efficiency. It is hoped that this work can provide a new strategy for enhancing the degradation of organic dyes and resource utilization of heat by using double parallel orifice plate HC technology.

Comparative study on the onset of detonation in methane–oxygen mixtures: initiation in a smooth tube and re-initiation downstreamof a single orifice plate

Comparative study on the onset of detonation in methane–oxygen mixtures: initiation in a smooth tube and re-initiation downstreamof a single orifice plate

Experimental study on prediction model of wet gas pressure drop across single-orifice plate in horizontal pipes in the low gas phase Froude number region

The pressure drop prediction of wet gas across single-orifice plate in horizontal pipes had been solved satisfactorily under an annular-mist flow in the upstream of orifice plates. However, this pressure drop prediction is still not clearly determined when the upstream is in an intermittent flow or stratified flow, which is corresponding to a region of low Fr G (gas phase Froude number) in the flow pattern map of wet gases. In this study, the wet gas pressure drop across a single-orifice plate was experimentally investigated in the low Fr G region. By the experiment, the flow pattern transition in the downstream of single-orifice plates, as well as the effects of Fr G and Fr L (liquid phase Froude number) on Φ G (gas phase multiplier), were determined and compared when the upstream is in the flow pattern transition and the stratified flow region, respectively. Prediction performances were examined on the available pressure drop models. It was found that no model could be capable of jointly predicting the wet gas pressure drop in the low Fr G region with an acceptable accuracy. With a new method of correlating Fr G and Fr L simultaneously, new correlations were proposed for the low Fr G region. Among which the modified Chisholm model shows the best prediction accuracies, with the prediction deviations of Φ G being within 7% and 3% when the upstream is in flow pattern transition and stratified flow region, respectively.

Microbubbles generation by an orifice spraying method in a water-gas dispersion flooding system for enhanced oil recovery

In China, many oilfields with low permeability and heterogeneity have entered the secondary oil recovery stage, in which more oil displacement agents for expanding sweep volume has become a key technology. A water-gas dispersion flooding system is reasonably proposed to change the seepage resistance and adjust the mobility ratio. In this EOR technique, the generation of micron-sized bubbles in the low-permeability reservoir is of considerable interest. In this study, a visual device by using an orifice spraying method was designed to simulate reservoir conditions with high temperature and high pressure, and efficiently to produce more microbubbles. Based on the orifice spraying method, the morphological characteristics of microbubbles generated by different orifice plate materials were compared, which provided the choice of the microbubbles generation by the orifice spraying method for laboratory experiments. Besides, the influence of different factors on the quantity and size of microbubbles produced by a single orifice plate was presented in detail. The experimental results showed that the diameter of the microbubbles generated by the orifice spraying method under a hypothetic reservoir condition was about 10–100 μm. These visual experimental devices were practically designed to meet the demand of the micron-level pores and throats to enhance oil recovery in low-permeability reservoirs. This investigation of microbubbles generation provided the basic research means for further preparation of a water-gas dispersion flooding system.

Experimental study on the detonation propagation behaviors through a small-bore orifice plate in hydrogen-air mixtures

In this study, the regimes of detonation transmission through a single orifice plate were investigated systematically in a 6-m length and 90-mm inner diameter round tube. A series of experiments on the detonation propagation mechanisms in hydrogen-air mixtures were performed. A single obstacle with different orifice size (d) from 10 to 60 mm was adopted to study the effects of the induced perturbations on the detonation propagation. Here, the thickness of orifice plate (δ) was fixed at 10.33 mm. Detonation velocity was determined from the time-of-arrival (TOA) of the detonation wave recorded by eight high-speed piezoelectric pressure transducers (PCB102B06). Detonation cellular size was obtained by the smoked foil technique. The characteristic of detonation velocity evolution were quantitatively analyzed after it passes through a single obstacle, and particular attention was paid to the cases for which the blockage ratio (BR) is greater than 0.9, i.e., the cases of small hole diameter of d < 25 mm. The experimental results showed that, in a smooth tube, only super-critical condition and sub-critical condition can be observed. After the orifice plate is introduced into the tube, critical condition occurs. The detonation re-initiation with distinct cellular structures was experimentally observed. Of note is that when the blockage ratio (BR) values in the range of 0.802–0.96, it was easier to detonate at the fuel-lean side. Finally, the critical condition for detonation propagation through an orifice plate was quantified as d/λ > 1 where λ is the detonation cell size.

Valorization of Rendering Fats to Produce Biodiesel by Single and Multi Orifice Plate Cavitation Reactor

The aim of this work is focused on the valorization of category two rendering pig fats, to evaluate their use as source of biodiesel by hydrodynamic cavitation reactors. The optimum reaction conditions have been previously determined in laboratory, obtaining as optimum values 60 °C, 1 wt% of sodium hydroxide, fat to methanol molar ratio of 1:6. The design of the cavitation reactor orifice plates has been carried out taking into account these optimum conditions. The design is based on the cavitation number as a function of the degree of advancement of reaction, which ensures that cavitation occurs through the entire reaction time. Then, the cavitation reactor was used in a pilot plant to study different configurations of orifice plates. The results obtained indicate that it is more efficient to use cavitation reactors with consecutive orifice plates (9.05 g/kJ) instead of traditional stirring reactor (3.75 g/kJ) or single orifice plate reactors (6.7 g/kJ). This reactor also allows reaching higher FAME content (90%) compared to a stirring reactor (85%). It also allows reducing the residence time up to 5 min from 22 min of a stirring reactor or from 10 min of a single orifice plate reactor.

On the explosion characteristics of hydrogen-air mixtures in a constant volume vessel with an orifice plate

In this study, we performed experiments in a cylinder vessel with a single orifice plate to study the explosion characteristics of hydrogen-air mixtures at room temperature (298K) and ambient pressure (1atm). The blockage ratio (BR) and position of the orifice plate were various. Explosion characteristics, i.e., maximum explosion pressure (Pmax), combustion duration (θ) and maximum pressure rise rate ((dp/dt)max) were derived based on the pressure evolution. The results show that both the maximum explosion pressure and combustion duration are independent of the orifice plate. However, the effects of the orifice plate on the maximum rate of pressure rate are significant. Depending on the position and blockage ratio, the effects are different. The orifice plate acts as a heat sink when the distance between the orifice plate (S) is very close, making (dp/dt)max decrease (compared with that obtained without the orifice plate). The orifice plate acts as “turbulence-generator” as S increases; thus, (dp/dt)max increases. Further, the influences of the blockage ratio as well as laminar burning velocity on the maximum pressure rise rate are also analyzed.

Effect of a single orifice plate on methane-air explosion in a constant volume vessel: Position and blockage ratio dependence

In this study, the explosion behaviors of methane-air mixtures were investigated experimentally in a cylinder vessel (210 mm inner diameter and 210 mm height) filled with a single orifice plate at atmospheric pressure (1 atm) and room temperature (298 K). The equivalence ratios of the test mixtures ranged from 0.7 to 1.3. The blockage ratios of the orifice plates were from 0.49 to 0.94, and the distance between the orifice plates and the ignition point (S) were 25 mm, 50 mm and 75 mm. The results show that the maximum explosion pressure in the presence of an orifice plate. However, the effects of the orifice plate on the maximum rate of pressure rise are various. At the fuel-lean side, the maximum pressure rise rate is increased significantly (larger than that of the stoichiometric condition). As the distance between the orifice plate and ignitor increases, the maximum pressure rise rate increases. In the case of the fuel-rich conditions, the maximum pressure rise rate is the smallest forS = 25 mm, followed by the no plate condition, S = 50 mm andS = 75 mm. The mechanisms are left for further study.

Mass transfer enhancement as a function of oscillatory baffled reactor design

Air-water two-phase flow regimes were identified quantitatively and qualitatively for four designs of oscillatory baffled reactor (OBR) over a range of oscillation conditions in semi-batch mode operation (continuous gas phase; batch liquid phase). The baffle designs assessed were helical baffles, smooth periodic constrictions, single orifice plate baffles and multi-orifice plate baffles. Oscillation in a smooth-walled tube was also characterised for comparison purposes. The designs were characterised over a range of oscillatory Reynolds number (Reo = 0–8000) and aeration rates, vvm = 0–1. All the reactors had the same geometrical parameters such as diameter, ratio of length to diameter etc. Three distinct flow regimes (bubbly flow, slug flow, and churn flow) were identified, which were similar to those found in conventional bubble columns (BCs), but the bubbly flow regime, which exhibits the highest rates of mass transfer, was observed over a wider range of oscillatory liquid velocities in OBRs. This was due to the flow patterns (usually vortices) and shear engendered by the interactions of the oscillatory flows and the baffle designs, which resulted in coalescence and breakage of the bubbles. The volumetric mass transfer coefficients, kLa, were significantly increased in the multi-orifice design, up to 7-fold, compared with that for a steady flow (no oscillatory flow) in a smooth tube (unbaffled column).

Residence time distribution in multiorifice baffled tubes: A numerical study

The fluid flow and the transport of species in an intensified topology of oscillatory baffled reactors is analyzed here by means of CFD. The classic configuration with equidistant single orifice plate baffles has been replaced by multiple-orifice disks, of the same open cross-sectional area. The flow through these disks generates an array of parallel jets downstream and upstream, exhibiting various swirl structures that increase the radial mixing.Time-dependent flow patterns are presented here for configurations of disks with 1, 3, 7, 19 and 43 orifices. The evaluation of their mixing performance has been accomplished by injecting a pulse of a tracer, for a constant oscillatory Reynolds number of Reo=800. The concentration-time profile of the tracer throughout the reactor was analyzed and an axial dispersion coefficient was derived on the basis of a 1D plug flow with dispersion model. It was clear that the quality of plug flow increased with increasing number of holes. Pressure-drop was reported by means of Fanning friction factor and power density dissipation.

Influence Experiment for the Spacing Distance of Orifice Plates to Local Resistance Coefficient in the Pressure Delivery Pipeline

In order to research the influence rule of the spacing distance between orifice plates to the local resistance coefficient and total local water head losses , carried out the experiment research through set the two different relative distance of orifice plates in the pressure delivery pipeline. The experimental results showed that: When the relative distance, the results of total local water head losses calculated by the traditional hydraulics formula with the real measured data, the maximal relative error was less than 3%. This shown that when the relative distance was big, it was no necessary to consider the influence of the relative distance between orifice plates. However, when the relative distance, the real measured data of the total local water losses was much smaller than the calculated data by the traditional calculation formula, the maximal relative error was reached 239.5%. It was explained that when the relative distance was relative small, existed the adjoining influence between orifice plates, so the total local water losses by the multi-orifice plates was not equal to the sum of each water head loss by the single orifice plate, and the total local head loss was not necessarily increased with the number of orifice plates increasing. Whether or not the increasing total local water head losses was closely related with the relative distance of the orifice plates. The traditional local water head loss calculation formula in the hydraulics should be corrected and modified.

Investigation into higher-order mode propagation through orifice plates in circular ducts

Most established techniques for analyzing sound transmission in ducts containing orifices plates are only applicable for plane wave propagation. Once the wavelength of the sound approaches the cross section of the duct, higher order mode propagation in the system must be considered in the analysis. This is a numerically intensive activity if fully coupled calculations of the higher order modes are undertaken. This investigation estimates the acoustic fields in a duct with a simple orifice plate installed using an uncoupled model to estimate the higher order mode contribution. The uncoupled model is then used as the basis for a hybrid decomposition approach to estimate the sound field in the regions before and after the orifice plate installed in a circular duct. This approach is applied to a duct, excited by a point source over a wide frequency range, containing a single orifice plate installed a distance inside the duct. Different orifice plates with one, two and multiple openings are investigated. Of particular interest is the location of the point source relative to the duct axis. If the source is located concentric to the duct axis then, without any orifice plate present, only axially symmetric higher order modes may be excited in the duct. Thus, the investigation considers the point source located in the concentric position and in eccentric positions to vary the contribution from the different types of higher order mode. Estimates of the acoustic fields in the duct obtained using the hybrid decomposition approach are compared with measured data and the applicability of using an uncoupled estimate for the acoustic fields is commented on.

Experimental Studies of Liquid Weeping and Bubbling Phenomena at Submerged Orifices

Experimental studies on the liquid weeping phenomenon at a submerged circular orifice have been conducted under a range of superficial orifice gas velocities (0.25 cm/s to 100 m/s), column and plate specifications, orifice sizes, fluid properties, and pressures up to 3.5 MPa. As the primary focus of this study, weeping rates and bubble formation at a single-orifice plate are investigated while operating within the bubbling regime at velocities of 0.25−100 cm/s. Upon monitoring of the pressure fluctuations within the plenum region, the bubbling frequency and nominal bubble size are determined to provide insight into the weeping phenomenon. Under similar scrutiny, weeping in the jetting regime, which is generally ignored or disregarded as trivial, is briefly considered for long-term consequences for industrial plants that typically operate over month or year periods.

Detonation wave propagation through a single orifice plate in a circular tube

Detonation behavior associated with the propagation of a detonation wave through an orifice plate located within a circular tube is investigated. The tube and orifice diameter used in the study are 27.3 cm and 10 cm, respectively. The test gas used is hydrogen-air at 1 atmosphere and at various initial temperatures up to 650 K. Immediately after the orifice, the detonation wave decouples and either fails or reinitiates. The reinitiation process is characterized by either spontaneous initiation, initiation due to shock reflection, or deflagration-to-detonation transition (DDT). In the case of DDT, transition is preceded by the degeneration of the decoupled detonation wave to a velocity consistent with a CJ deflagration. Delineation between these various propagation regimes could not be correlated with the detonation cell size, λ, and orifice diameter, d . The data, although limited, demonstrate for the first time that the d c /λ =13 critical tube criterion obtained at room temperature may not apply at elevated temperature conditions. The evidence for this is data obtained at 500 K that shows no detonation transmission for 30% hydrogen in air that corresponds to d/λ =16.7. The tests also indicate that a simple d/λ correlation cannot be used to determine when reinitiation due to shock reflection is possible. For example, at 650 K detonation wave failure was observed for d/λ d/λ

Intermittent transition from bubbling to jetting regime in gas-liquid two phase flows

The transition from bubbling to jetting regime in nitrogen-water system was studied experimentally. The gas was introduced into a pool of stagnant liquid through a single orifice plate above a gas chamber. Two quantities were measured: pressure fluctuations in the gas chamber and velocity of liquid circulations near the orifice. Individual bubbles were formed at low gas flow rates (bubbling regime) while a continuous jet of gas was formed at high rates (jetting regime). The transition from bubbling to jetting regime (transition regime) displayed intermittent character. Jetting bursts of various length appeared at random in originally periodic pressure signal. The distribution of bubbling portion in the pressure signal was hyperbolical with exponent −1.33 indicating type III intermittency. Similar characteristic time scales were found in power spectra of both signals. 1/ f noise was revealed in the velocity spectrum. This kind of noise usually accompanies intermittent transitions. These results implied that liquid circulations with 1/ f noise induced by bubbles affected the bubble dynamics itself as a feed-back and caused the intermittent regime transition. The point of the regime transition was indicated by a sudden drop of Kolmogorov entropy, correlation dimension of the attractor, and Mann-Whitney statistic calculated from pressure signal. An explanation for this drop is suggested on the base of combination of properties of two attractors coexisting/competing within the intermittency range.

Preliminary Studies of the Sound Radiated by Orifices in Pipelines

The sound radiated by orifices in pipelines is studied analytically and experimentally. At Mach numbers less than about 0.1, the sound is generated as from a simple source by mass flow fluctuations that are caused by the shedding of vortices from the orifice edge. The spectrum of sound energy has peaks in it, indicating a tonal quality of the noise. At higher Mach numbers, the sound is of a dipole nature, has a wide frequency base, and can be evaluated by considering the fluctuating force exerted by the orifice plate on the jet. Sound generation by multiple orifices in a single-orifice plate is also studied. Two cases are dealt with. First, the number of orifices of a constant diameter is increased and, second, the number of orifices is increased, maintaining a constant total area. Preliminary experiments verify the theoretical relationships for single and multiple orifices. The results are presented in the form of dimensionless spectral-density distributions versus the Strouhal number. [Work sponsored by the U. S. Department of the Navy, Bureau of Ships, contract No. NObs-88200.]