Detection of Cavitation in a Venturi Injector With a Combined Method of Strain Gauges and Numerical Simulation

2014 ◽  
Vol 136 (8) ◽  
Author(s):  
Yuncheng Xu ◽  
Yan Chen ◽  
Jianqiang He ◽  
Haijun Yan
Keyword(s):  
Flow Rate ◽  
Pressure Difference ◽  
Volume Fraction ◽  
Operating Conditions ◽  
Strain Gauges ◽  
Maximum Pressure ◽  
Operating Pressure ◽  
Average Growth ◽  
Rate Of Increase ◽  
Suction Flow

The fertilizer suction capability of a Venturi injector is dependent on the vacuum pressure in the throat portion. As the vacuum level drops below the saturation vapor pressure, the pressure decreases to a particular value corresponding to the maximum pressure difference (Δpmax) between inlet and outlet pressures, and critical cavitation is likely to occur, leading to an unstable suction flow rate and low fertilization uniformity. A new method of using strain gauges to detect cavitation in Venturi injectors was explored experimentally and verified numerically under various operating conditions. The standard deviation (SD) of the measured strain values and the simulated values of the vapor-phase volume fraction (Vf) were used to evaluate the influence of cavitation. The results showed that both the rate of increase (ηm) of the average SD and the average growth rate (AGR) of the simulated cavitation length reach relatively large values at the maximum pressure difference (Δpmax), where the measured suction flow rate simultaneously reaches a maximum. In addition, SD and Vf shared similar variation trends at pressure differences larger than the corresponding Δpmax under various conditions. This new cavitation detection method has been proved to be feasible and reliable. It helps to determine accurately the value of Δpmax at different inlet pressures and to ensure that the Venturi injector runs in a safe operating-pressure range.

Performance Enhancement by Dynamic Valve Timing of a Multistage Vacuum Micropump

2010 ◽  
Author(s):  
Karthik Kumar ◽  
Luis P. Bernal ◽  
Khalil Najafi
Keyword(s):  
Steady State ◽  
Flow Rate ◽  
Pressure Difference ◽  
Performance Enhancement ◽  
High Vacuum ◽  
Operating Pressure ◽  
Transient Operation ◽  
Valve Timing ◽  
Steady State Operation ◽  
Valve Leakage

This paper presents the results of a theoretical analysis of dynamic valve timing on the performance of a multistage peristaltic vacuum micropump. Prior work has shown that for optimum steady state performance a fixed valve timing which depends on the operating pressure can be found. However, the use of a fixed valve timing could hinder performance for transient operation when the pump is evacuating a fixed volume. At the beginning of the transient the pump operates at low pressure difference and a large flow rate would be desirable. As the pump reaches high vacuum the pressure difference is large and the flow rate is necessarily small. Astle and coworkers1–3 have shown using a reduced order model that for steady state operation short valve open time results in lower inlet pressure and flow-rate and conversely. Here we extend the model of Astle and coworkers to include transient operation, multiple coupled stages and non-ideal leaky valves, and show that dynamic valve timing (DVT) reduces the transient duration by 30% compared to high vacuum pressure valve timing. The results also show a significant reduction in resonant frequency of the pump at low pressures, and quantify the effect of valve leakage.

Effect of outlet impeller diameter on performance prediction of centrifugal pump under single-phase and cavitation flow conditions

2022 ◽  
Vol 0 (0) ◽  
Author(s):  
Ahmed Ramadhan Al-Obaidi ◽  
Ali Qubian
Keyword(s):  
Frequency Domain ◽  
Centrifugal Pump ◽  
Pressure Fluctuation ◽  
Single Phase ◽  
Static Pressure ◽  
Volume Fraction ◽  
Pressure Fluctuations ◽  
Operating Conditions ◽  
Maximum Pressure ◽  
Velocity Magnitude

Abstract In this current study, the transient numerical calculations using CFD code are carried out under different outlet impeller diameters for the flow field within a centrifugal pump under single-phase and cavitation conditions. Both qualitative and quantitative analyses are carried out on all of these results in order to better understand the flow structure within a centrifugal pump. Also, the investigations using different outlet impeller diameters configurations relating to the static pressure, velocity magnitude, vapour volume fraction variations, as well as pressure fluctuations in both time and frequency domain at the impeller and volute of the pump are analysed. Velocity and static pressure variations of the pump under different outlet impeller diameters range (200, 210 and 220 mm) are investigated. Reliable model is developed and validated, at various pump operating conditions, to analyse the characteristics of pressure fluctuations in both time and frequency domain. Cavitation occurrence, under different outlet impeller diameters and flow rates, are detected and correlated, using a CFD model (volume fraction distributions). Based on the developed model’s findings, at the set operating conditions ranges, the distribution and impact (cavitation and head-wises) of both the pressure and velocity are analysed. The average pressure fluctuation in the volute for do = 210 mm is higher than for do = 200 mm by about 6.74%, also the maximum pressure fluctuation for do = 220 mm is higher than for do = 210 mm by around 7.4%. Furthermore, the maximum pressure fluctuation in the impeller for do = 210 mm is higher than for do = 200 mm by 12.48%, also for do = 220 mm is higher than for do = 210 mm by 10.8%. The developed CFD models are proved valuable tools in identifying and optimizing the pump performance and characterization. The head for when do = 220 mm is higher than for when do = 200 mm under both single-phase and cavitation conditions by around 14.13% and 14.69%. The maximum pressure fluctuation for do = 200 mm is lower than for do = 210 mm by 41.58%. Furthermore, the maximum pressure fluctuation at the impeller for do = 220 mm is higher than the two models. There is a small clearance between the impeller and the volute for this model, leading to the pressure fluctuation amplitudes being higher than the other above models.

scholarly journals Modes of Circulation in an Inverted U-Tube Array With Condensation

1982 ◽  
Vol 104 (4) ◽  
pp. 769-773 ◽  
Author(s):  
C. Calia ◽  
P. Griffith
Keyword(s):  
Heat Transfer ◽  
Steam Generator ◽  
Flow Rate ◽  
Pressure Difference ◽  
Operating Conditions ◽  
Steam Generators ◽  
Modes Of Operation ◽  
Glass Tubes ◽  
Abnormal Operating Conditions ◽  
Plenum Pressure

An experiment and analysis was performed on an inverted U-tube steam condenser (similar to a steam generator) to determine the modes of flow that can exist as the rate of steam flow into the condenser is reduced. The condenser consisted of four glass tubes connected to a common inlet plenum and a common exit plenum. Heat-transfer and flow-rate measurements, as well as visual observations were made. Four different modes of operation were identified. Noncondensables were found to substantially alter the plenum to plenum pressure difference and aid flow stability. Satisfactory analytical descriptions of the observations have been developed as well as application of the results to the condensing behavior of nuclear steam generators under abnormal operating conditions.

Study of Uneven Distribution in Parallel Petroleum Processing Pipes

2016 ◽  
Author(s):  
Renwei Liu ◽  
Haishan Zhu ◽  
Qingping Li ◽  
Yufei Wan ◽  
Kaifeng Fan
Keyword(s):  
Flow Rate ◽  
Two Phase Flow ◽  
Operating Conditions ◽  
Uneven Distribution ◽  
Petroleum Processing ◽  
Phase Flow ◽  
Operating Pressure ◽  
Two Phase ◽  
Specific Flow ◽  
Central Platform

The aim of this article is to investigate uneven distribution of oil-gas two phase flow in parallel petroleum processing pipelines. On-site analysis on BZ35-2 central platform A and SZ36-1 central platform N/O (two typical platforms in China’s Bohai Bay) shows that uneven distribution is originated mainly by two sources: flow rate difference and dryness difference. A 3-dimensional numerical model of two-phase flow in T-junction before parallel processing units was built. Flow and dryness distribution under different operating conditions were simulated. It is demonstrated that unevenness of flow rate grows worse as the total flow rate increases or operating pressure difference between parallel units becomes larger. Moreover, unevenness of dryness is mainly caused by phase split in a tee. It can be concluded that the phase split will be more obvious when parallel units are located at different heights or gas volume fraction of feed stream and inlet flow rate is small. Besides, flow rate distribution has an effect on dryness distribution. There is a specific flow ratio that will cause the most serious phase split. Finally, according to the conclusions, modification scheme for BZ35-2 central platform A piping layout was proposed. And this work may provide some guidance for process design and practical operation of parallel units.

An Innovative Two-Phase Flow Pump and Separator Solution

2011 ◽  
Author(s):  
Franc¸ois Gruselle ◽  
Johan Steimes ◽  
Patrick Hendrick
Keyword(s):  
Flow Rate ◽  
Flow Model ◽  
Two Phase Flow ◽  
Volume Fraction ◽  
Operating Conditions ◽  
Liquid Volume ◽  
Phase Flow ◽  
Two Phase ◽  
Efficient System ◽  
Measurement Systems

The Aero-Thermo-Mechanics (ATM) department of Universite´ Libre de Bruxelles (ULB) develops a new system to simultaneously pump and separate a two-phase flow, in particular oil/air mixtures. Two-phase flows are encountered in many applications (oil extraction, flow in nuclear power plant pumps, pulp and paper processing) but the study is mainly focused on aeroengine lubrication systems. The main objective is to obtain a compact and efficient system that can both extract the gas of a two-phase flow and increase the pressure of the liquid phase. Particular care is given to the liquid flow rate lost at the gas outlet of the system. A large range of gas/liquid volume ratio has been studied, leading to different two-phase flow regimes at the inlet of the system (slug, churn or annular flow). After successful tests with water-air prototypes, which have allowed to identify the key design and working parameters, the technology has been implemented for a hot oil-air mixture. This paper presents the test results of the first oil/air prototype under real in-flight operating conditions. The tests with oil/air mixtures were performed on the aeroengine lubrication system test bench of the ATM department. The identification and implementation of appropriate two-phase flow rate measurement systems is an essential contribution to the project. Two attractive measurement systems have been considered: a Coriolis density meter for the volume fraction at the liquid outlet and radio-tracing elements for the measurement of the oil consumption at the air outlet. In parallel, the flow field in the pump and separator system has been studied with commercial CFD (Computational Fluid Dynamics) software packages. The choice of the two-phase flow model is highly dependent on the two-phase flow regime. But different regimes can simultaneously exist in the pump and separator system. So, the Eulerian two-phase flow model, the most complex and general model, seems to be the most appropriate. A coupling of this model with a dispersed phase model is under investigation to take all two-phase flow phenomena into account.

Flashback Limits for Combustion Induced Vortex Breakdown in a Swirl Burner

2002 ◽  
Author(s):  
Martin Kro¨ner ◽  
Jassin Fritz ◽  
Thomas Sattelmayer
Keyword(s):  
Flow Rate ◽  
Gas Turbines ◽  
Vortex Breakdown ◽  
Volume Fraction ◽  
Burning Velocity ◽  
Operating Conditions ◽  
High Temporal Resolution ◽  
Additional Parameter ◽  
Swirl Burner ◽  
Wide Range

Flame flashback from the combustion chamber into the mixing zone limits the reliability of swirl stabilized lean premixed combustion in gas turbines. In a former study, the combustion induced vortex breakdown (CIVB) has been identified as a prevailing flashback mechanism of swirl burners. The present study has been performed to determine the flash-back limits of a swirl burner with cylindrical premixing tube without centerbody at atmospheric conditions. The flashback limits, herein defined as the upstream flame propagation through the entire mixing tube, have been detected by a special optical flame sensor with a high temporal resolution. In order to study the effect of the relevant parameters on the flashback limits, the burning velocity of the fuel has been varied using four different natural gas-hydrogen-mixtures with a volume fraction of up to 60% hydrogen. A simple approach for the calculation of the laminar flame speeds of these mixtures is proposed which is used in the next step to correlate the experimental results. In the study, the preheat temperature of the fuel mixture was varied from 100 °C to 450 °C in order to investigate influence of the burning velocity as well as the density ratio over the flame front. Moreover, the mass flow rate has been modified in a wide range as an additional parameter of technical importance. It was found that the quenching of the chemical reaction is the governing factor for the flashback limit. A Peclet number model was successfully applied to correlate the flashback limits as a function of the mixing tube diameter, the flow rate and the laminar burning velocity. Using this model, a quench factor can be determined for the burner, which is a criterion for the flashback resistance of the swirler and which allows to calculate the flashback limit for all operating conditions on the basis of a limited number of flashback tests.

Experimental Investigation of the Performance of a Spouted Bed Dryer for Biomass: Drying Kinetics and Energy Evaluation

2020 ◽  
Vol 399 ◽  
pp. 208-217
Author(s):  
Bruno R.S. Silva ◽  
Marcelo Nascimento ◽  
L.G. Marques ◽  
Manoel Marcelo Prado
Keyword(s):  
Air Temperature ◽  
Flow Rate ◽  
Power Plants ◽  
Gas Flow ◽  
Volume Fraction ◽  
Critical Role ◽  
Operating Conditions ◽  
Optimum Operating ◽  
Spouted Bed ◽  
Drying Time

Drying is an essential pre-treatment step that plays a critical role in the energy balance of biomass power plants. This has motivated the search by cost-effective drying technologies. Within this context, the present work aims to investigate the application of a spouted bed dryer with inert solids for drying sugarcane bagasse, the most important biomass used for generating energy in Brazil. Effects of the biomass volume fraction, inlet air temperature and spouting gas flow rate on the drying time and thermal efficiency of the equipment were examined. Results show that drying time decreases by decreasing the biomass fraction and by increasing air temperature. Highest values of biomass percentage and air temperature allied to the lowest velocity of the spouting air greatly improve the efficiency of the biomass drying. Based on a balance between the energy that the product is capable of suppling and the total energy consumed by the dryer the optimum operating conditions recommended for making feasible the use of the bagasse dehydrated in spouted bed for energy purposes are: air temperature of 67°C, biomass volume fraction of 0.6 and air flow rate equal to the minimum stable spouting condition.

Flashback Limits for Combustion Induced Vortex Breakdown in a Swirl Burner

2003 ◽  
Vol 125 (3) ◽  
pp. 693-700 ◽  
Author(s):  
M. Kro¨ner ◽  
J. Fritz ◽  
T. Sattelmayer
Keyword(s):  
Flow Rate ◽  
Gas Turbines ◽  
Vortex Breakdown ◽  
Volume Fraction ◽  
Burning Velocity ◽  
Operating Conditions ◽  
High Temporal Resolution ◽  
Additional Parameter ◽  
Swirl Burner ◽  
Wide Range

Flame flashback from the combustion chamber into the mixing zone limits the reliability of swirl stabilized lean premixed combustion in gas turbines. In a former study, the combustion induced vortex breakdown (CIVB) has been identified as a prevailing flashback mechanism of swirl burners. The present study has been performed to determine the flashback limits of a swirl burner with cylindrical premixing tube without centerbody at atmospheric conditions. The flashback limits, herein defined as the upstream flame propagation through the entire mixing tube, have been detected by a special optical flame sensor with a high temporal resolution. In order to study the effect of the relevant parameters on the flashback limits, the burning velocity of the fuel has been varied using four different natural gas-hydrogen-mixtures with a volume fraction of up to 60% hydrogen. A simple approach for the calculation of the laminar flame speeds of these mixtures is proposed which is used in the next step to correlate the experimental results. In the study, the preheat temperature of the fuel mixture was varied from 100°C to 450°C in order to investigate influence of the burning velocity as well as the density ratio over the flame front. Moreover, the mass flow rate has been modified in a wide range as an additional parameter of technical importance. It was found that the quenching of the chemical reaction is the governing factor for the flashback limit. A Peclet number model was successfully applied to correlate the flashback limits as a function of the mixing tube diameter, the flow rate and the laminar burning velocity. Using this model, a quench factor can be determined for the burner, which is a criterion for the flashback resistance of the swirler and which allows to calculate the flashback limit for all operating conditions on the basis of a limited number of flashback tests.

scholarly journals Optimization the Process of Chemically Modified Carbon Nanofiber Coated Monolith via Response Surface Methodology for CO2 Capture

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1775 ◽  
Author(s):  
Mohamad Rasool Malekbala ◽  
Soroush Soltani ◽  
Suraya Abdul Rashid ◽  
Luqman Chuah Abdullah ◽  
Umer Rashid ◽  
...  
Keyword(s):  
Response Surface Methodology ◽  
Response Surface ◽  
Reaction Temperature ◽  
Flow Rate ◽  
Co2 Capture ◽  
Carbon Nanofiber ◽  
Co2 Adsorption ◽  
Operating Conditions ◽  
Co2 Uptake ◽  
Operating Pressure

In the present study, a sequence of experiments was performed to assess the influence of the key process parameters on the formation of a carbon nanofiber-coated monolith (CNFCM), using a four-level factorial design in response surface methodology (RSM). The effect of reaction temperature, hydrocarbon flow rate, catalyst and catalyst promoter were examined using RSM to enhance the formation yield of CNFs on a monolith substrate. To calculate carbon yield, a quadratic polynomial model was modified through multiple regression analysis and the best possible reaction conditions were found as follows: a reaction temperature of 800 °C, furfuryl alcohol flow of 0.08525 mL/min, ferrocene catalyst concentration of 2.21 g. According to the characterization study, the synthesized CNFs showed a high graphitization which were uniformly distributed on a monolith substrate. Besides this, the feasibility of carbon dioxide (CO2) adsorption from the gaseous mixture (N2/CO2) under a range of experimental conditions was investigated at monolithic column. To get the most out of the CO2 capture, an as-prepared sample was post-modified using ammonia. Furthermore, a deactivation model (DM) was introduced for the purpose of studying the breakthrough curves. The CO2 adsorption onto CNFCM was experimentally examined under following operating conditions: a temperature of 30–50 °C, pressure of 1–2 bar, flow rate of 50–90 mL/min, and CO2 feed amount of 10–40 vol.%. A lower adsorption capacity and shorter breakthrough time were detected by escalating the temperature. On the other hand, the capacity for CO2 adsorption increased by raising the CO2 feed amount, feed flow rate, and operating pressure. The comparative evaluation of CO2 uptake over unmodified and modified CNFCM adsorbents confirmed that the introduced modification procedure caused a substantial improvement in CO2 adsorption.

Stabilization of the Speed of the Hydraulic Motor Through Throttle Compensation for Volume Losses

2020 ◽  
Vol 26 (3) ◽  
pp. 126-130
Author(s):  
Krasimir Kalev
Keyword(s):  
Flow Rate ◽  
Hydraulic Drive ◽  
Pressure Change ◽  
Operating Conditions ◽  
Drive System ◽  
Inlet Pressure ◽  
Schematic Diagram ◽  
Hydraulic Characteristics ◽  
Hydraulic Motor ◽  
Flow Through

AbstractA schematic diagram of a hydraulic drive system is provided to stabilize the speed of the working body by compensating for volumetric losses in the hydraulic motor. The diagram shows the inclusion of an originally developed self-adjusting choke whose flow rate in the inlet pressure change range tends to reverse - with increasing pressure the flow through it decreases. Dependent on the hydraulic characteristics of the hydraulic motor and the specific operating conditions.

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