Average Mass Flow Rate Research Articles

Stochastic analysis and modeling of pharmaceutical screw feeder mass flow rates

Screw feeders, as the initial operation in continuous manufacturing of drug product processes, greatly influence the mass flow rate of pharmaceutical powders downstream. Existing flowsheet models can quickly simulate the average powder mass flow rate while custom Discrete Element Method models require prohibitively long times to simulate a minute of realistic, high-variance particle flow. We propose a hybrid deterministic-stochastic feeder flowsheet model that leverages time series analysis and an Autoregressive Moving Average (ARMA) model to quantify and simulate the observed non-random variation in feeder powder flow. To allow for improved process and controller design, our approach is quick-to-solve, high-variance, and has a low experimental overhead. By examining the deterministic model errors of three different volumetrically fed excipients, we demonstrate that the errors are leptokurtic, heavy-tailed, and display a linear dependence on their prior two seconds of state. These errors are all reasonably modeled by an ARMA(2,1) model and are parametrically distinct from each other. Furthermore, we show that refilling the feeder online significantly alters the error distribution, autocorrelation structure, and ARMA parameters. These findings lay the groundwork necessary to model and predict the realistic feeder dynamics of a much broader range of powders and operating conditions.

Thermodynamic assessment of a geothermal power and cooling cogeneration system with cryogenic energy storage

Geothermal energy is one of the main renewable energy sources for power generation and district cooling, and liquid air energy storage is an emerging technology suitable for both power and cold storages. Accordingly, a combined power and cooling cogeneration system with cryogenic energy storage is proposed in this paper, which is powered by geothermal energy and connected with the grid. The system is formed by integrating a turbine ejector cogeneration cycle with an air liquefaction cycle, a liquid air direct expansion cycle and a cryogenic organic Rankine cycle. In normal operation mode, only the turbine ejector cogeneration cycle works in the system based on the cooling load requirement. In charging operation mode, all the power produced in the system is used to liquefy air in the air liquefaction cycle owing to cheap electricity tariff. In discharging operation mode, the additional electricity is provided to meet peak time energy requirement by the direct expansion cycle and cryogenic organic Rankine cycle. A geothermal source at 180 °C with a flow rate of 100 kg/s is used as the heat source in this study, the cogeneration system has the ability to produce 15,470 kW of power and supply 4800 kW of cooling simultaneously, the system round trip efficiency is 41.07%, and the exergy efficiency of cryogenic energy storage is 60.43%. Also, the effects of geothermal energy temperature, system size, turbine mass split ratio and normalized mass flow rate on the system performance are clarified.

Simultaneous determination of particle size, velocity, and mass flow in dust-laden supersonic flows

The particle mass concentration and -mass flow rate are fundamental parameters for describing two-phase flows and are products of particle number, -size, -velocity, and -density. When investigating particle-induced heating augmentation, a detailed knowledge of these parameters is essential. In most of previous experimental studies considering particle-induced heating augmentation, only average particle mass flow rates are given, without any relation to measured particle sizes and -velocities within the flow or any indication of measurement uncertainty. In this work, particle number, individual particle sizes, and velocities were measured in a supersonic flow by means of shadowgraphy and particle tracking velocimetry (PTV). The goals are to determine measurement uncertainties, a particle velocity-size relation, and the spatial distribution of number, size, velocity, and mass flow rate across the nozzle exit. Experiments were conducted in a facility with a nozzle exit diameter of 30 mm, at Ma∞ = 2.1 and Re∞ = 8.2e7 1/m. Particles made of Al2O3 and up to 60 µm in size were used for seeding. Particle mass flow rates up to 50 kg/m2 s were achieved. It is shown that an additional correction procedure reduced common software uncertainties regarding shadowgraphy particle size determination from 14% to less than 6%. Discrepancies between calculated particle velocities and experimental data were found. In terms of spatial distribution, larger particles and a higher mass flow rate concentrate in the flow center. The determined particle mass flow rate uncertainty was up to 50% for PTV; for shadowgraphy, it was less than 17%.Graphical abstract

Four years of operational data for five hydrogen refueling stations

Worldwide about 550 hydrogen refueling stations (HRS) were in operation in 2021, of which 38%. were in Europe. With their number expected to grow even further, the collection and investigation of real-world station operative data are fundamental to tracking their activity in terms of safety issues, performances, costs, maintenance, reliability, and energy use. This paper shows and analyses the parameters that characterize the refueling of 350 bar fuel cell buses in four HRS within the 3Emotion project. The HRS are characterized by different refueling capacities, hydrogen supply schemes, storage volumes and pressures, and operational strategies. From data logs provided by the operators, a dataset of three years of operation has been created. In particular total hydrogen quantity, the fill amount dispensed to each bus, the refueling duration, the average mass flow rate, the number of refueling events and the daily number of refills, the daily profile, the utilization factor, and the availability are investigated. The results show similar hydrogen amount per fill distribution, but quite different refueling times among the stations. The average daily mass per bus is around 12.95 kg, the most frequent value 15 kg, the standard deviation 7.46. About 50% of the total amount of hydrogen is dispensed overnight and the refueling events per bus are typically every 24 hours. Finally, the station utilization is below 30% for all sites.

An Experimental Study on Cryogenic Spray Quenching of a Circular Metal Disk II—Chilldown Efficiency and Effects of Coating and Flow Pulsing

Abstract This is the second part of a two-paper series that presents the results of liquid nitrogen spray quenching of a stainless steel (SS) disk plate. The first paper focuses on the heat transfer characteristics of the liquid nitrogen spray quenching, whereas the second paper emphasizes the overall chilldown performance and efficiency. Serving as the baseline information for evaluating the effects of disk surface coating and pulse flow, the results of continuous-flow spray chilldown of a bare surface SS disk are summarized first. We found that for continuous-flow spray chilldown of a bare surface disk, the chilldown efficiency is mainly a function of the average spray mass flow rate with the trend of decreasing efficiency with increasing average mass flow rate. Additional experiments were performed to evaluate the enhancement of cryogenic spray quenching by three techniques: (1) using intermittent pulse sprays on SS bare surface, (2) coating the SS surface with a layer of low thermal conductivity Teflon film, and (3) spraying liquid nitrogen intermittently on the coated SS surface. In general, the results indicate that all three methods effectively produced higher spray efficiencies. However, it was also found that the Teflon coating was more effective than the flow pulsing. The coating produced a quick transition from film boiling to transition boiling. This quick transition shortens the poor heat transfer film boiling period and thus facilitates the switch to much higher heat transfer transition boiling and nucleate boiling periods earlier to expedite the chilldown process and enhance the heat transfer.

X-ray flares raising upon magnetar plateau as an implication of a surrounding disk of newborn magnetized neutron star

The X-ray flares have usually been ascribed to long-lasting activities of the central engine of gamma-ray bursts (GRBs), e.g., fallback accretion. The GRB X-ray plateaus, however, favor a millisecond magnetar central engine. The fallback accretion can be significantly suppressed due to the propeller effect of a magnetar. Therefore, if the propeller regime cannot resist the mass flow onto the surface of the magnetar efficiently, the X-ray flares raising upon the magnetar plateau would be expected. In this work, such peculiar cases are connected to the accretion process of the magnetars, and an implication for magnetar-disc structure is given. We investigate the repeated accretion process with multi-flare GRB 050730, and give a discussion for the accretion-induced variation of the magnetic field in GRB 111209A. Two or more flares exhibit in the GRB 050730, 060607A and 140304A; by adopting magnetar mass M = 1.4 M ⊙ and radius R = 12 km, the average mass flow rates of the corresponding surrounding disk are 3.53 × 10−4 M ⊙ s−1, 4.23 × 10−4 M ⊙ s−1, and 4.33 × 10−4 M ⊙ s−1, and the corresponding average sizes of the magnetosphere are 5.01 × 106 cm, 6.45 × 106 cm, and 1.09 × 107 cm, respectively. A statistic analysis that contains eight GRBs within 12 flares shows that the total mass loading in single flare is ∼ 2 × 10−5 M ⊙. In the lost mass of a disk, there are about 0.1% used to feed a collimated jet.

Data-based estimation and simulation of compressible pulsating flow with reverse-flow through an orifice

Highly compressible pulsating flows are often encountered in devices where knowledge of the flow rate is required but elimination of pulsations is not an option. The current work is a continuation of a previous investigation that characterized the orifice discharge coefficient Cd as a function of dimensionless groups based on pulsation characteristics. The experimental apparatus has been rebuilt in the current work to mitigate temperature and vibration problems, allowing pressure and ΔP measurements to be made very close to the test section with 159-mm of nylon tubing. Data was acquired for 77 operating conditions spanning a range of pulsation frequencies, mass flow rates and system pressures. They confirm previously reported low Cd's in 0.20 range (calculated from time-averaged pressures) at some high-pressure low-flow operating conditions. Computational Fluid Dynamics (CFD) simulations of 12 of these data points suggest that the low Cd's result from reverse flow. Flow direction changed several times during each pulsation cycle closely tracking the orifice ΔP. A ‘core-and-sheath’ phenomena was observed for reverse-flow operating conditions: a positive core flow surrounded by a sheath of negative flow transitioned to a negative core and positive sheath several times during each pulsation cycle. The simulations also suggested that velocity profiles at the orifice stay stable and similar to steady-state profiles except for periods of rapid transitions. Based on these results a data-based quasi-steady method of estimating pulsating flow has been proposed. A pair of forward and reverse flow Cd's chosen by the data are used to predict instantaneous forward and reverse flows using the steady-state orifice discharge equation for compressible flow. The instantaneous values are then summed up over the pulsation cycle to estimate average mass flow rate. Average prediction errors were within 6%. A previously proposed method where regression was used to model Cd as a function of dimensionless groupings was shown to produce similar results. Both methods are designed to extract information from experimental data in order to overcome theoretical limitations and experimental error. The data is available upon request for further understanding of the flow physics.

Constraining particle acceleration in Sgr A⋆with simultaneous GRAVITY,Spitzer,NuSTAR, andChandraobservations

We report the time-resolved spectral analysis of a bright near-infrared and moderate X-ray flare of Sgr A⋆. We obtained light curves in theM,K, andHbands in the mid- and near-infrared and in the 2 − 8 keV and 2 − 70 keV bands in the X-ray. The observed spectral slope in the near-infrared band isνLν ∝ ν0.5 ± 0.2; the spectral slope observed in the X-ray band isνLν ∝ ν−0.7 ± 0.5. Using a fast numerical implementation of a synchrotron sphere with a constant radius, magnetic field, and electron density (i.e., a one-zone model), we tested various synchrotron and synchrotron self-Compton scenarios. The observed near-infrared brightness and X-ray faintness, together with the observed spectral slopes, pose challenges for all models explored. We rule out a scenario in which the near-infrared emission is synchrotron emission and the X-ray emission is synchrotron self-Compton. Two realizations of the one-zone model can explain the observed flare and its temporal correlation: one-zone model in which the near-infrared and X-ray luminosity are produced by synchrotron self-Compton and a model in which the luminosity stems from a cooled synchrotron spectrum. Both models can describe the mean spectral energy distribution (SED) and temporal evolution similarly well. In order to describe the mean SED, both models require specific values of the maximum Lorentz factorγmax, which differ by roughly two orders of magnitude. The synchrotron self-Compton model suggests that electrons are accelerated toγmax ∼ 500, while cooled synchrotron model requires acceleration up toγmax ∼ 5 × 104. The synchrotron self-Compton scenario requires electron densities of 1010cm−3that are much larger than typical ambient densities in the accretion flow. Furthermore, it requires a variation of the particle density that is inconsistent with the average mass-flow rate inferred from polarization measurements and can therefore only be realized in an extraordinary accretion event. In contrast, assuming a source size of 1 RS, the cooled synchrotron scenario can be realized with densities and magnetic fields comparable with the ambient accretion flow. For both models, the temporal evolution is regulated through the maximum acceleration factorγmax, implying that sustained particle acceleration is required to explain at least a part of the temporal evolution of the flare.

Numerical Study on Flow and Release Characteristics of Gas Extinguishing Agent under Different Filling Pressure and Amount Conditions

The fire-extinguishing system is an indispensable fire-protection facility on the aircraft. In order to guide weight reduction of the aircraft’s fixed gas fire-extinguishing system by improving its release efficiency, so as to improve fuel economy and reduce carbon emissions, the influence of filling pressures and filling amounts on the release efficiency of gas extinguishing agent along pipelines were studied based on numerical simulations. The release process of the fire-extinguishing system was analyzed. The effects of the filling pressure and filling amount of Halon 1301 agent on the release characteristics, such as release time, mass flow rate, and gasification ratio, were studied. Results show that the release process can be divided into three major phases, which are firstly the initial rapid filling of the pipeline, secondly the concentrated release of the liquid extinguishing agent, and thirdly the gas ejection along the pipeline. The second phase can also be subdivided into two stages: the outflow of the liquid extinguishing agent from the bottle, and the release of the residual liquid extinguishing agent along the pipeline. The release characteristics of the fire-extinguishing agent were obviously affected by the filling pressures and filling amounts. When the filling pressure was relatively low (2.832 MPa), increasing the filling pressure can significantly increase the mass flow rate, shorten the release time, and reduce the gasification ratio of the extinguishing agent during the release processes. Under the same filling pressure, with the increase of the filling amount of the extinguishing agent, the release times and the gasification ratio showed a linear increase trend, while the average mass flow rates showed a linear decrease trend.

Effect of oscillation flow induced by lattices on a horizontal gas–solid two-phase flow

This study is focused on reducing the pressure drop, conveying velocity, and power consumption in a horizontal gas–solid flow. Four types of lattice models, which are fixed in the particle inlet, are proposed to easily generate the oscillation of the wake flow to easily convey the gas–solid two-phase flow. A horizontal pipeline with an inner diameter of 80 mm and length of approximately 5 m was used. Polyethylene particles with an average diameter of 2.3 mm and density of 978 kg/m3 were employed as conveying solid materials. The experimental ranges of the average gas velocity and solid mass flow rate were 10–16 m/s and 0.10–0.47 kg/s, respectively. Compared to the nonlattice gas–solid flow, reductions in the total pressure drop, conveying gas velocity, power consumption, and additional pressure loss were achieved in the range of lower gas velocity when using the lattice model. The highest reduction rates of the minimum conveying velocity and additional pressure drop were approximately 5.12% and 15.2%, respectively. In the acceleration region, the particle concentration in the flows with the lattice model was larger than that in the nonlattice flow near the upper part of the pipe and lower than those in the nonlattice flows in the lower part of the pipe. The time-mean axial particle velocity and particle fluctuating velocity in all lattice model flows were higher than those in the nonlattice flow, according to particle image velocimetry measurements, particularly in the upper part of the pipe.

Cooling performance of a passive hybrid system consisted of domed roof and solar chimney: A numerical approach

ABSTRACT Achieving efficient solutions for saving energy in buildings has become one of the significant concerns in recent years. Heating and cooling passive systems such as Trombe wall, solar chimney, and plant wall has proved to be practical, especially in hot and dry climatic conditions. In the present work, a hybrid passive system comprised of a solar chimney and a domed roof has been numerically modeled to improve the indoor air temperature distribution and comfort conditions in a test room located in Yazd, Iran. For the purpose of this study, two scenarios were investigated: various heights of the domed roof (four cases) and different locations of the inlet vents (five cases). The results included air temperature distribution, average air velocity and mass flow rate in the vents as well as comfort conditions. According to the results, the domed roof with 0.7 m height resulted in the best performance in terms of comfort conditions. Furthermore, placing the inlet vents in the lower part of the room led to more ventilation of air and better air temperature distribution and comfort conditions compared to other arrangements of the inlet vents.

Thermodynamic analysis of forced convective solar drying of cocoa with black coated sensible thermal storage material

Thermodynamic analysis of a forced convective solar dryer integrated with black coated sensible (firebrick) thermal storage material (STSM) for cocoa was investigated. The intermittent nature of solar radiation and its consequence on thermal processes such as drying necessitates the introduction of materials for heat supplement to keep the cocoa beans at a raised temperature above the ambient. As a steady flow thermodynamic system, the analysis was carried out based on the first and second laws of thermodynamics to account for the energy involved in the solar drying of cocoa beans. The maximum drying chamber utilization energy during the first and second daytime drying process was 0.739 and 0.724 kJ/kg. The energy utilization (EU) decreased with the increase in time from 12:00 to 18:00 h respectively. Also, the energy utilization ratio (EUR) ranged from 0.190 to 0.577, and 0.222 to 0.931 during the first and second daytime experiments respectively. The collector efficiency varied between 4.2 and 61.2% while the minimum and maximum solar radiation for the two daytimes were 49.6 and 759.6 W/m2 with an average mass flow rate of 0.032 kg/s. The maximum energy efficiencies for the two-day times obtained at 10:00 h were 28.0 and 58.2%. In the drying chamber, the maximum exergy (inflow and loss) for the two-day time drying process was 7.53 and 8.33 kJ/kg, and 4.83 and 8.175 kJ/kg respectively. The exergetic efficiency during the first daytime experiment varied between 1.52 and 65.81%, while it varied between 1.82 and 53.30% during the second daytime. Thus, the results obtained in this study will inform the choice of an appropriate solar dryer design by the relevant stakeholders in the cocoa industry.

Analysis of the Inner Fluid-Dynamics of Scroll Compressors and Comparison between CFD Numerical and Modelling Approaches

Scroll compressors are widely adopted machines in both refrigeration systems and heat pumps. However, their efficiency is basically poor and constitutes the main bottleneck for improving the overall system performance. In fact, due to the complex machine fluid dynamics, scroll design is mainly based on theoretical and/or semi-empirical approaches. Designs strategies that do not guarantee an in-depth analysis of the machine behavior can be supplemented with a Computation Fluid Dynamics (CFD) approach. To this purpose, in the present work, the scroll compressor inner fluid dynamics is numerically analyzed in detail using two CFD software and two different modelling strategies for the axial gap. The analysis of the fluid evolution within the scroll wraps reveals unsteady phenomena developing during the suction and discharge phases, amplified by the axial clearance with negative impact on the main fluid flow (e.g., −13% of average mass flow rate for an axial gap of 30 μ) and on the scroll performance (e.g., +26% of average absorbed power for an axial gap of 30 μ). In terms of accuracy, the k-ε offers good performance on the estimation of average quantities but proves to be inadequate for capturing the complexity of the unsteady phenomena caused by the axial gap (e.g., −19% of the absorbed power in case of perfect tip seal). The need for considering specific geometric details in design procedures is highlighted, and guidelines on the choice of the most suitable numerical model are provided depending on the analysis needs.

Analysis of Burnett Stresses and Entropy Generation for Pressure-Driven Plane Poiseuille Flow

Abstract In this paper, we undertake an analytical study of stresses (augmented and Onsager–Burnett) and entropy generation for the plane Poiseuille flow problem, and their variation with Knudsen number. The gas flow is assumed to be 2D laminar, fully developed, compressible, and isothermal; these assumptions make the problem amenable to analytical treatment. The variation of stresses and entropy generation has been analyzed over a large range of Knudsen number. The magnitude of stresses and entropy generation at a particular position in the channel has been considered. It is found that the augmented and OBurnett normal stresses are of opposite signs to the corresponding Navier–Stokes stresses, while the magnitude of the net normal stress increases with Knudsen number. The magnitude of the augmented Burnett shear stress is insignificant as compared to the augmented Burnett normal stresses. A close match between the augmented and OBurnett normal stresses has been found at low Knudsen number. However, an opposite variation has been observed between the augmented and Onsager shear stresses at high Knudsen number. A good comparison of the normalized mass flow rate with the reported value in the literature helps to validate our analysis. A minimum in the variation of normalized entropy generation against the Knudsen number (Kn) is observed at Kn close to unity, and is being reported for the first time. The magnitude of net entropy generation from the summation of Navier–Stokes and augmented Burnett stresses is found to be positive, even in the transition regime of gas flow. Further, an appearance of minimum or maximum in normalized net shear stress versus Knudsen number, depending upon the lateral position in the microchannel, has also been observed. Altogether, this analysis supports the validity of the Navier–Stokes equation with modified constitutive expression, even for higher Knudsen numbers. Moreover, the significant terms of Burnett stress are pointed out by the analysis, which can help in developing reduced-order model for these equations.

Analisis Sebelum dan Sesudah Dilakukan Proses Pembersiahan Terhadap Performa AC Tipe Split Wall Kapasitas 1 1/2 PK

Air conditioning in the room functions to regulate humidity, heating and cooling the air in the room. The purpose of this conditioning is to provide comfort for the user. The process of cleaning the condenser and evaporator pipe fins can improve compressor performance. The research was conducted on an air conditioner with a capacity of 1 1/2 PK using refrigerant R-22. With an average mass flow rate of 82.5 kg/s before cleaning and 79.6 kg/s after cleaning, it decreased by 4.4%. This has an impact on refrigeration where the average value of the impact of refrigeration before cleaning is 145.4 kJ/kg and after cleaning is 150.6 kJ/kg. This means that after the cleaning process, the evaporator can increase the refrigeration in the air conditioning system by 3.4%. The parameters used are the consumption of electrical power, the temperature of the refrigerant entering and leaving the condenser, the temperature of the refrigerant entering and leaving the evaporator. The increase in compressor performance after the cleaning process is carried out, it can be seen from the total value of electrical energy use before cleaning is 10.9 kWh, and after cleaning it becomes 8.8 kWh. This has an effect on the consumption of electrical energy to drive the compressor to be more efficient by 19.26%. COP an average of 3.6 before cleaning and after cleaning to 4.9 means an increase in compressor work by 1.3 or by 26.5%. Compressor work has decreased by 4440.4 Watts or a decrease of 26.8%.

Effect of the In-Cylinder Back Pressure on the Injection Process and Fuel Flow Characteristics in a Common-Rail Diesel Injector Using GTL Fuel

The presented paper aims to study the influence of mineral diesel fuel and synthetic Gas-To-Liquid fuel (GTL) on the injection process, fuel flow conditions, and cavitation formation in a modern common-rail injector. First, the influence on injection characteristics was studied experimentally using an injection system test bench, and numerically using the one-dimensional computational program. Afterward, the influence of fuel properties on internal fuel flow was studied numerically using a computational program. The flow inside the injector was considered as multiphase flow and was calculated through unsteady Computational Fluid Dynamics simulations using a Eulerian–Eulerian two-fluid approach. Finally, the influence of in-cylinder back pressure on the internal nozzle flow was studied at three distinctive back pressures. The obtained numerical results for injection characteristics show good agreement with the experimental ones. The results of 3D simulations indicate that differences in fuel properties influence internal fuel flow and cavitation inception. The location of cavitation formation is the same for both fuels. The cavitation formation is triggered regardless of fuel properties. The size of the cavitation area is influenced by fuel properties and also from in-cylinder back pressure. Higher values of back pressure induce smaller areas of cavitation and vice versa. Comparing the conditions at injection hole exit, diesel fuel proved slightly higher average mass flow rate and velocities, which can be attributed to differences in fluid densities and viscosities. Overall, the obtained results indicate that when considering the injection process and internal nozzle flow, GTL fuel can be used in common-rail injection systems with solenoid injectors.

Investigation on the unsteadiness of centrifugal compressor exposed to pulsating backpressure

Centrifugal compressor is exposed to pulsating backpressure due to the movement of intake valves in internal combustion engine. The performance of compressor deviates from the steady performance map, which affects the matching between turbocharger and engine. The behavior of compressor system at pulsation conditions are investigated via an in-house developed 1D unsteady code validated by experimental results. The influence of pulse frequency, magnitude and compressor characteristic curve on the compressor transient responses, including filling-emptying effect and wave dynamics, are analyzed. Results show that the strength of wave dynamics grows stronger with the increasing of pulse frequency, while the strength of filling-emptying effect increases first then decreases. The rise of pulse magnitude results in an almost linearly increasing of filling-emptying effect, while it can hardly affect the wave dynamics. Furthermore, the influence of pulsation magnitude and frequency represents the influence of local pressure gradient, and a correlation as quadratic curve can be evaluated between the pressure gradient and compressor unsteadiness. On the other hand, the influence of operating point, including the average mass flow rate and the slope of characteristic curve, is confirmed to be evidently smaller, comparing to the influence of pulsation frequency and magnitude. This study is helpful to estimate the behavior of compressor and the discrepancy of performance when operating at unsteady environment or matched with engine.

One-Dimensional Gas Flow Analysis of the Intake and Exhaust System of a Single Cylinder Diesel Engine

In order to design a diesel engine system and to predict its performance, it is necessary to analyze the gas flow of the intake and exhaust system. Gas flow analysis in a three-dimensional (3D) format needs a high-resolution workstation and an enormous amount of time for analysis. Calculation using the method of characteristics (MOC), which is a gas flow analysis in a one-dimensional (1D) format, has a fast calculation time and can be analyzed with a low-resolution workstation. However, there is a problem with poor accuracy in certain areas. It was assumed that the reason was that 1D could not implement the shape. The error that occurs in the shape of the bent pipe used in the intake and exhaust ports of the diesel engine was analyzed and to find a solution to the low accuracy, the results of the experiment and 1D analysis were compared. The discharge coefficient was calculated using the average mass flow rate, and as a result of applying it, the accuracy was improved for the maximum negative pressure by 0.56–1.93% and the maximum pressure by 3.11–7.86% among the intake pipe pressure results. The difference in phase of the exhaust pipe pressure did not improve. It is considered as a limitation of 1D analysis that does not improve even by applying the discharge coefficient. In the future, we intend to implement a bent pipe that cannot be realized in 1D using a 3D format and to prepare a method to supplement the reliability by using 1D–3D coupling.

Study on the Influence of Toilet Siphon Pipe Shape on Flushing Performance

The goal of this work was to explore the influence of toilet siphon pipe shape on flushing performance. The flushing processes of a toilet under different shape parameters were simulated by using computational fluid dynamics (CFD) with a volume of fluid (VOF) multiphase model. The effects of siphon pipe shape on flushing performance were analyzed in detail. The interpretation of the simulation results was experimentally validated. The results reveal that a toilet may obtain good flushing performance under one single shape parameter when the climbing angle, the arc width, the arc height, the pipe diameter, the climbing width, and the climbing height are about 48°, 45 mm, 210 mm, 50 mm, 90 mm and 30 mm, respectively. With the increase of the siphon pipe diameter, the toilet flushing performance peaks in the range between 50 and 53 mm rather than continuing to improve. In order to reasonably evaluate the flushing effect of the toilet, all flow parameters on a characteristic cross section of the siphon pipe, including the average velocity, the average pressure and the average mass flow rate, should be comprehensively considered instead of one single parameter. The findings of this study provide a reference for the pipe shape design of toilets.

The Influence of the Angle of Inclination of Single-Row Oval-Trench Dimples in the Stabilized Hydrodynamic Section of a Narrow Channel on the Anomalous Intensification of the Separated Turbulent Flow

The slope of an oval-trench dimple in the corridor package on the stabilized hydrodynamic section of the narrow channel has a dramatic effect on the anomalous intensification of the separated and vortex flows in the dimple, leading to a three- to fourfold decrease in the relative negative friction in the range of angles from 40° to 60°, an increase in the maximum velocity of separated and secondary flow up to 0.8 and 1.18 in relation to the average mass flow rate in the channel.