Ejection Cycle Research Articles

Numerical investigations on the effect of frequency on synthetic jet impingement cooling using multiple orifice

A synthetic jet generally consists of a cavity with a driver attached on one side and an orifice on the opposite side. When the driver moves back and forth, the jet will generate an unsteady flow through the orifice and the flow will move downstream to a surface forming an impinging flow. When the jet is in the ejection cycle, the diaphragm will expel flow out from the orifice and form a vortex near the orifice. If the propulsion is large enough, the vortex will move downstream before the jet orifice flow reverses and starts to suck in flow. The computational process is carried out using the commercial software ANSYS Fluent. In this study, the heat transfer characteristics of synthetic jet impingement cooling with multiple orifice (1 and 2 orifices) are analyze with different operating frequencies (f=100 Hz to f=500 Hz and f=1 Hz to f=5 Hz) with different Reynolds numbers (Re=10000 and 20000) The results demonstrate that high frequency synthetic jets show better heat removal capacity than lower frequency at the same Reynolds number.

In-vivo validation of a nomogram with isostiffness-lines for the assessment of aortic stenosis severity

Abstract Background In patients with low-flow, low-gradient aortic stenosis, the aortic valve opening area (AVA) projected at a higher standardized transvalvular flow (Q) is used to assess the severity of aortic stenosis. It assumes a linear relation between Q and AVA. We investigated whether a sigmoid function better captured this relation and whether a nomogram could be constructed. Methods We measured instantaneous AVA and Q in 142 patients with the whole spectrum of AS including very low-flow situation on one ejection cycle. We defined a linear and a sigmoid function containing hyperparameters as well as the relative stiffness. Using a k-fold cross validation algorithm, we first trained the hyperparameters of each function on the subgroup of patients with normal aortic valve. Using the obtained hyperparameters, we then fitted the relative stiffness for each of the patients with AS on the lowest 70%, 50%, 30% and 10% Q of the {Q:AVA} data points of the ejection cycle. We then assessed the accuracy of the two models by computing the mean squared error (MSE) of the predicted AVA vs the measured AVA on the remaining 30%, 50%, 70% and 90% data points and the Akaike Information Criterion (AIC). A receiver operating characteristic (ROC) analysis with computation of its area under the curve (AUC) was performed on the entire range of possible threshold of the relative stiffness to discriminate between severe from non severe aortic stenosis. Results The sigmoid consistently better predicted the remaining 70%, 50%, 30% and 10% AVA than the linear model (MSE: 6.62e-6 vs 14.11e-6, 4.90e-6 vs 12.39e-6, 4.90e-6 vs 14.84e-6, 4.90e-6 vs 22.99e-6; AIC: -7933 vs -7428, -13341 vs -12328, -13341 vs -16990, -13341 vs -21031, respectively). The first figure depicts the assessment of the AVA predicted with the linear (left panel) and sigmoid (right panel) model with Q of the 30% highest Q values with linear regression. The black line on the linear regression graphs represent the identity function (f (x) = x). The closer to this line are the points, the more accurate is the prediction. In the ROC analysis, the calculated AUC was 0.88, performed on all patients with relative stiffness obtained on the first 70% Q of the {Q;AVA} data points. The most discriminative relative stiffness threshold was 1.51 with a corresponding accuracy of 0.85. The second figure depicts a nomogram with mean and confidence interval of iso-stiffness lines for each severity with the following color code: group of normal aortic valve in green, group of mild aortic stenosis in blue, group of moderate aortic stenosis in orange and group of severe aortic stenosis in red. The iso-stiffness line with most discriminant relative stiffness computed on the group of patients with moderate and severe aortic stenosis is depicted in black. Conclusion This study allows to construct a nomogram to compare the stiffness of the aortic valve of any patient at any Q, simplifying the severity grading system of AS.Accuracy of AVA predictionNomogram with iso-stiffness lines

Prediction of Both E-Jet Printing Ejection Cycle Time and Droplet Diameter Based on Random Forest Regression.

Electrohydrodynamic jet (E-jet) printing has broad application prospects in the preparation of flexible electronics and optical devices. Ejection cycle time and droplet size are two key factors affecting E-jet-printing quality, but due to the complex process of E-jet printing, it remains a challenge to establish accurate relationships among ejection cycle time and droplet diameter and printing parameters. This paper develops a model based on random forest regression (RFR) for E-jet-printing prediction. Trained with 72 groups of experimental data obtained under four printing parameters (voltage, nozzle-to-substrate distance, liquid viscosity, and liquid conductivity), the RFR model achieved a MAPE (mean absolute percent error) of 4.35% and an RMSE (root mean square error) of 0.04 ms for eject cycle prediction, as well as a MAPE of 2.89% and an RMSE of 0.96 μm for droplet diameter prediction. With limited training data, the RFR model achieved the best prediction accuracy among several machine-learning models (RFR, CART, SVR, and ANN). The proposed prediction model provides an efficient and effective way to simultaneously predict the ejection cycle time and droplet diameter, advancing E-jet printing toward the goal of accurate, drop-on-demand printing.

Research on wet gas separation method based on swirl and ejection cycle technology

Gas-liquid co-production often occurs in the middle and late stages of natural gas production. Efficient wet gas separation is very important in natural gas transportation and measurement. The traditional separation device has a relatively low separation efficiency due to the flow patterns, a new type of pipe separator was designed based on the swirl and ejection cycle technology. A new systematical separation procedure with three main steps was proposed simultaneously. The wet gas was forced to form an annular flow by a swirler. Then, the liquid film flows into the annular gap. The wave layer was introduced into the swirl separation again with the self-circulating ejection system for fine separation finally. Laboratory experiments and Computational Fluid Dynamics (CFD) simulations show that the additional swirl process can decrease the flow pattern influence effectively, and the separation efficiency can increase to more than 90%. The separation efficiency is mainly determined by the gas superficial velocity, and while the velocity of the inlet gas is less than 21 m/s, the separation efficiency is up to 93%. The separation efficiency prediction model was established based on liquid film porosity, and the prediction relative error is less than 10%. The new device, the separation procedure, and the test results can provide constructive technical reference for the real-world pipe separator application.

Pre-expansion ejector absorption power cycle for ocean thermal energy conversion

Ocean thermal energy conversion technology has limited applications due to low energy utilization efficiency. This study proposes a pre-expansion ejector absorption power cycle for ocean thermal energy conversion. To enhance the turbine output, a pre-expansion separator heated by discharged warm seawater, along with an ejector, was introduced between the generator and absorber. A thermodynamic analysis strategy for the proposed cycle was conducted using MATLAB and Aspen Plus. A performance comparison between the pre-expansion ejector absorption cycle, traditional ejection cycle, and non-ejection two-stage absorption cycle under the ocean thermal energy working conditions was conducted. Parametric analysis was performed to investigate the cycle performance. In addition, the working range of the pre-expansion ejector was analyzed. The results show that the ejection-driven turbine output work effectively increased by 79.38% with the pre-expansion process, although the thermal efficiency slightly decreased. When the temperatures of warm and cold seawater were 26–32 °C and 4–7 °C, the lower and upper boundaries of the pre-expansion pressure are 560 kPa and 680 kPa, respectively. When the pre-expansion pressure varied from 600 to 660 kPa, the entrainment ratio and turbine outlet pressure drop were 0.541–1.018 and 344.9–348.9 kPa, respectively. The pre-expansion pressure and temperature of the cold source influence the cycle performance in a more complex manner because there exists a working range for the ejector, which is dominated by the pre-expansion pressure and influenced by the temperature of the heat and cold source.

Physical Properties of Modified Polyphenylene Oxide as a Composite Material for Hydrogen Fuel Cell Stack Enclosure Suitable for Injection Molding

There is an increasing need for securing development technology for suitable materials to obtain more productive and lightweight automobile parts, including hydrogen fuel cell stack enclosures. Due to the poor moldability of Poly-Phenylene Oxide (PPO), which excels in terms of mechanical, thermal, and electrical properties, studies are being actively conducted to commercialize modified-PPO (mPPO). However, there is a lack of studies regarding injection molding analysis for pre-verification of the suitability of injection molding in the process of developing engineering plastic resins. Thus, this study utilized the following procedure: (1) it measured the physical properties of mPPO, (2) it selected sample candidates, (3) it applied the Design Of Experiments (DOE) to conduct an injection molding analysis, and finally, (4) it proposed an enclosure-dedicated mPPO due to its suitability for injection molding. The results of this study demonstrated the excellent moldability of mPPO with a mixing ratio of PPO 50%/Poly-Amide66(PA66) 50% among 16 samples by investigating the fill time, deflection, time to reach ejection temperature, void phenomenon and cycle time. Therefore, mPPO with a mixing ratio of PPO 50%/PA66 50% will exhibit the best moldability and increased productivity in manufacturing enclosures.

Advanced exergy analysis of a jet ejector refrigeration cycle used to cool down the intake air in an internal combustion engine

This paper describes a jet ejection cycle coupled to a 1.5 L diesel engine to reduce the intake air temperature using the waste heat of the exhaust gases. This cycle is evaluated by means of conventional and advanced exergy analysis. The conventional analysis allows to determine the origin and magnitude of the irreversibilities, whereas the advanced analysis sheds light on the mutual interdependencies between components and the real improvement potential considering technological limitations. From the conventional exergy analysis it is inferred that more than a half of exergy destruction is due to generator followed by ejector (one third part) and condenser. However, the advanced exergy analysis suggests that the ejector plays a prominent role because the avoidable endogenous part corresponds to 42% of total exergy destruction in that component whereas the avoidable part of exergy destruction in the generator is mostly exogenous (83%). Hence, exergy destruction could be significantly reduced if improvement efforts are focused on the ejector instead of other components like the generator.

Advanced exergy analysis of a jet ejector refrigeration cycle used to cool down the intake air in an internal combustion engine

This paper describes a jet ejection cycle coupled to a 1.5 L diesel engine to reduce the intake air temperature using the waste heat of the exhaust gases. This cycle is evaluated by means of conventional and advanced exergy analysis. The conventional analysis allows to determine the origin and magnitude of the irreversibilities, whereas the advanced analysis sheds light on the mutual interdependencies between components and the real improvement potential considering technological limitations. From the conventional exergy analysis it is inferred that more than a half of exergy destruction is due to generator followed by ejector (one third part) and condenser. However, the advanced exergy analysis suggests that the ejector plays a prominent role because the avoidable endogenous part corresponds to 42% of total exergy destruction in that component whereas the avoidable part of exergy destruction in the generator is mostly exogenous (83%). Hence, exergy destruction could be significantly reduced if improvement efforts are focused on the ejector instead of other components like the generator.

Thermodynamic analysis and optimization of a jet ejector refrigeration cycle used to cool down the intake air in an IC engine

The present paper evaluates a jet ejector refrigeration system intended to cool down diesel engine intake below ambient conditions. Performance is assessed by means of 1D thermodynamic model of the cycle fed with ejector maps obtained with CFD code using R134a as working fluid. In the first study, no particular ejector geometry is fixed thus allowing the genetic algorithm to adapt the cycle to different engine conditions. Following this approach engine intake temperatures close to 0 ∘C can be attained in those engine operating points in which exhaust thermal power is sufficient to drive the jet-ejector refrigeration system. In the second evaluation, ejection cycle configuration which provided best results for the most frequent operating point in a standard driving, designated as 2000 rpm and 50% load, is selected. With this particular configuration the rest of engine operating points are reassessed. In this study performance degradation is found away from the design point showing that ejector size is a limiting factor.

Left Ventricular Isovolumetric Relaxation Time Is Prolonged in Fetal Long-QT Syndrome.

Long-QT syndrome (LQTS), an inherited cardiac repolarization disorder, is an important cause of fetal and neonatal mortality. Detecting LQTS prenatally is challenging. A fetal heart rate (FHR) less than third percentile for gestational age is specific for LQTS, but the sensitivity is only ≈50%. Left ventricular isovolumetric relaxation time (LVIRT) was evaluated as a potential diagnostic marker for fetal LQTS. LV isovolumetric contraction time, LV ejection time, LVIRT, cycle length, and FHR were measured using pulsed Doppler waveforms in fetuses. Time intervals were expressed as percentages of cycle length, and the LV myocardial performance index was calculated. Single measurements were stratified by gestational age and compared between LQTS fetuses and controls. Receiver-operator curves were performed for FHR and normalized LVIRT (N-LVIRT). A linear mixed-effect model including multiple measurements was used to analyze trends in FHR, N-LVIRT, and LV myocardial performance index. There were 33 LQTS fetuses and 469 controls included. In LQTS fetuses, the LVIRT was prolonged in all gestational age groups (P<0.001), as was the N-LVIRT. The best cutoff to diagnose LQTS was N-LVIRT ≥11.3 at ≤20 weeks (92% sensitivity, 70% specificity). Simultaneous analysis of N-LVIRT and FHR improved the sensitivity and specificity for LQTS (area under the curve=0.96; 95% confidence interval, 0.82-1.00 at 21-30 weeks). N-LVIRT, LV myocardial performance index, and FHR trends differed significantly between LQTS fetuses and controls through gestation. The LVIRT is prolonged in LQTS fetuses. Findings of a prolonged N-LVIRT and sinus bradycardia can improve the prenatal detection of fetal LQTS.

Connecting the Failure of K Theory inside and above Vegetation Canopies and Ejection–Sweep Cycles by a Large-Eddy Simulation

AbstractParameterizations of biosphere–atmosphere interaction processes in climate models and other hydrological applications require characterization of turbulent transport of momentum and scalars between vegetation canopies and the atmosphere, which is often modeled using a turbulent analogy to molecular diffusion processes. Simple flux–gradient approaches (K theory) fail for canopy turbulence, however. One cause is turbulent transport by large coherent eddies at the canopy scale, which can be linked to sweep–ejection events and bear signatures of nonlocal organized eddy motions. The K theory, which parameterizes the turbulent flux or stress proportional to the local concentration or velocity gradient, fails to account for these nonlocal organized motions. The connection to sweep–ejection cycles and the local turbulent flux can be traced back to the turbulence triple moment . In this work, large-eddy simulation is used to investigate the diagnostic connection between the failure of K theory and sweep–ejection motions. Analyzed schemes are quadrant analysis and complete and incomplete cumulant expansion methods. The latter approaches introduce a turbulence time scale in the modeling. Furthermore, it is found that the momentum flux and sensible heat flux need different formulations for the turbulence time scale. Accounting for buoyancy in stratified conditions is also deemed important in addition to accounting for nonlocal events to predict the correct momentum or scalar fluxes.

Performances and compactness of a cooling system powered with PEMFC thermal effluent

The thermodynamic study of a small scale cooling system combining an ORC cycle and a refrigeration cycle is carried out. The system includes the same components as those used for ejection cycles except that a combination of a vane compressor and a vane expander replaces the usual ejector. Real fluids properties, efficiencies of the pump, the compressor and the expender and pressure drops are considered. The isentropic efficiency of the expander was measured experimentally and the data were used in the thermodynamic model to simulate the complete system in steady state. The system is designed for operating with a 2kW heating source at 65°C corresponding to the heat rejected by a domestic PEMFC-type cell and a parametric study assess its performance, compactness and sensitivity when operating at off design. The evaporating temperature varies from −9.5°C to +10.5°C and the condensing temperature varies from 20.1 to 40.1°C. Over the 12 fluids tested here, R1270 appears to be the most promising fluid, providing high performance, good compactness, low environmental nuisance and low off design sensitivity.

Effects of lubricant and part geometry on the ejection characteristics during die compaction

ABSTRACTThe ejection of a part following die compaction is a critical step in manufacturing powder metal and ceramic parts as well as pharmaceutical tablets. In this paper, the ejection of die-compacted hollow cylinders of heights 0.5 and 1.2 cm from Fe–2%Cu–0.5%C powders mixed with various amounts of (0.2–0.8 wt-%) of ethylene-bis-stearamide (EBS) was studied to understand the effect of lubricant amount and part geometry on the ejection process. Additionally, the ejection data of gears of 0.5 and 1.2 cm die compacted from Fe–2%Cu–0.5%C powders with 0.8 wt-% EBS was analysed to understand the effect of geometry on the ejection process. Several ejection parameters were found to be sensitive to the amount of EBS as well as the size and shape of the parts. The results from the present study indicated that the major portion of the ejection cycle involved the movement of the part within the die.

Meropenem, levofloxacin and linezolid in human plasma of critical care patients: A fast semi-automated micro-extraction by packed sorbent UHPLC-PDA method for their simultaneous determination

An ultra high-performance liquid chromatographic (UHPLC) method with PDA detection was developed and validated for the simultaneous quantification of meropenem, linezolid, and levofloxacin in human plasma and applied in human plasma of critical care patients. A semi-automated microextraction by packed sorbent (MEPS) for sample preparation was used. All parameters in the extraction step (pH, sample volume, sample dilution and number of aspiration – ejection cycles) and in the desorption step (percentage of acetonitrile in the solvent of elution and number of aspirations of elution solvent through the device) were statistically significant when the recovery was used as response. The method showed good linearity with correlation coefficients, r2>0.9991 for the three drugs, as well as high precision (RSD%<10.83% in each case). Accuracy ranged from −7.8% to +6.7%. The limit of quantification of the three drugs was established at 0.01μg/mL for linezolid and levofloxacin and 0.02μg/mL for meropenem. Linezolid, meropenem, levofloxacin and the internal standard were extracted from human plasma with a mean recovery ranged from 92.4% to 97.4%. During validation, the concentration of meropenem, linezolid and levofloxacin was found to be stable after 3 freeze-thaw cycles and for at least 24h after extraction. This method will be subsequently used to quantify the drugs in patients to establish if the dosage regimen given is sufficient to eradicate the infection at the target site.

Development and validation of a fast micro-extraction by packed sorbent UHPLC-PDA method for the simultaneous determination of linezolid and ciprofloxacin in human plasma from patients with hospital-acquired pneumonia

An ultra high-performance liquid chromatographic (UHPLC) method with PDA detection was developed and validated for the simultaneous quantification of linezolid and ciprofloxacin in human plasma and applied in hospital acquired pneumonia patients (HAP). The method uses a semi-automated microextraction by packed sorbent for sample preparation. All parameters in the extraction step (pH, sample volume, sample dilution and number of aspiration - ejection cycles) and in the desorption step (percentage of acetonitrile in the solvent of elution and number of aspirations of elution solvent through the device) were statistically significant when the recovery was used as response. The method showed good linearity with correlation coefficients, r2>0.9995 for the two drugs, as well as high precision (RSD%<9.77% in each case), accuracy ranged from −6.2% to +8.2. The limit of quantification of the two drugs was established at 0.01 and 0.02μg/mL for ciprofloxacin and linezolid, respectively. Linezolid, ciprofloxacin and internal standard were extracted from human plasma with a mean recovery ranging from 92.4% to 97.4%. During validation, the concentrations of linezolid and ciprofloxacin were found to be stable after 3 freeze-thaw cycles and for at least 24h after extraction. This method will subsequently be used to quantify the drugs dosage in patients with HAP to establish if the dosage regimen given is sufficient to eradicate the infection at the target site.

A cycle-based evolutionary algorithm for the fixed-charge capacitated multi-commodity network design problem

This paper presents an evolutionary algorithm for the fixed-charge multicommodity network design problem (MCNDP), which concerns routing multiple commodities from origins to destinations by designing a network through selecting arcs, with an objective of minimizing the fixed costs of the selected arcs plus the variable costs of the flows on each arc. The proposed algorithm evolves a pool of solutions using principles of scatter search, interlinked with an iterated local search as an improvement method. New cycle-based neighborhood operators are presented which enable complete or partial re-routing of multiple commodities. An efficient perturbation strategy, inspired by ejection chains, is introduced to perform local compound cycle-based moves to explore different parts of the solution space. The algorithm also allows infeasible solutions violating arc capacities while performing the “ejection cycles”, and subsequently restores feasibility by systematically applying correction moves. Computational experiments on benchmark MCNDP instances show that the proposed solution method consistently produces high-quality solutions in reasonable computational times.

A high-resolution wide-field radio survey of M51

We present the highest resolution, wide-field radio survey of a nearby face-on starforming galaxy to date. The multi-phase centre technique is used to survey the entire disk of M51 (77 square arc minutes) at a maximum resolution of 5 milli-arcseconds on a single 8 hr pointing with the European VLBI Network at 18 cm. In total, 7 billion pixels were imaged using 192 phase centres that resulted in the detection of six sources: the Seyfert nucleus, the supernova SN 2011dh, and four background AGNs. Using the wealth of archival data available in the radio (MERLIN and the VLA), optical (Hubble Space Telescope) and X-rays (Chandra) the properties of the individual sources were investigated in detail. The combined multi-wavelength observations reveal a very complex and puzzling core region that includes a low-luminosity parsec scale core-jet structure typical of AGNs, with evidence for a lateral shift corresponding to 0.27c. Furthermore, there is evidence for a fossil radio hotspot located 1.44 kpc from the Seyfert nucleus that may have resulted from a previous ejection cycle. Our study provides measures of the supernova and star-formation rates that are comparable to independent studies at other wavelengths, and places further limits on the radio and X-ray luminosity evolution of the supernovae SN 1994I, SN 2005cs and SN 2011dh. The radio images of background AGN reveal complex morphologies that are indicative of powerful radio galaxies, and confirmed via the X-ray and optical properties.

Single-Pass Baling of Corn Stover

A single-pass corn grain and stover harvester was produced by coupling a combine harvester and a towed large-round baler. An accumulation hopper and metering system were added to the baler to allow for continuous collection of stover through the bale wrapping and ejection cycles. Both the accumulation metering system and the baler were powered hydraulically by the combine. When harvesting with an ear-snapper header at an average rate of 5.6 ha h-1 and stover collection rate of 1.4 Mg ha-1, combine fuel use was increased by an average of 11% over baseline operation without the baler. Bale dry densities of 164 to 206 kg m-3 were achieved with this configuration. The accumulator and feed system capacity were more than sufficient to handle the mass flow collected with the ear-snapper header, so while harvesting grain the baler was only operated for 38% of the total harvest time. When using a whole-plant header to achieve average stover collection rates of 4.5 Mg ha-1, combine area capacity was reduced by more than 50% and the accumulator feed system was less effective at unloading the long stalks collected. Increasing the aggressiveness of the combine residue chopper reduced the hopper unloading time by 69%, but the additional size reduction also increased combine fuel use by 7%.

Comparison of ejection events in the jet and accretion disc outflows in 3C 111

We present a comparison of the parameters of accretion disc outflows and the jet of the broad-line radio galaxy 3C 111 on sub-pc scales. We make use of published X-ray observations of ultra-fast outflows (UFOs) and new 43GHz VLBA images to track the jet knots ejection. We find that the superluminal jet coexists with the mildly relativistic outflows on sub-pc scales, possibly indicating a transverse stratification of a global flow. The two are roughly in pressure equilibrium, with the UFOs potentially providing additional support for the initial jet collimation. The UFOs are much more massive than the jet, but their kinetic power is probably about an order of magnitude lower, at least for the observations considered here. However, their momentum flux is equivalent and both of them are powerful enough to exert a concurrent feedback impact on the surrounding environment. A link between these components is naturally predicted in the context of MHD models for jet/outflow formation. However, given the high radiation throughput of AGNs, radiation pressure should also be taken into account. From the comparison with the long-term 2-10keV RXTE light curve we find that the UFOs are preferentially detected during periods of increasing flux. We also find the possibility to place the UFOs within the known X-ray dips-jet ejection cycles, which has been shown to be a strong proof of the disc-jet connection, in analogue with stellar-mass black holes. However, given the limited number of observations presently available, these relations are only tentative and additional spectral monitoring is needed to test them conclusively.

Suitability of coupling a solar powered ejection cycle with a vapour compression refrigerating machine

The most commonly employed technology for cold production is vapour compression, mainly due to the high efficiency of such devices. However, a major operating issue is the strong dependency of system efficiency and capacity on ambient temperature, which in turn leads to low yearly performance and to a low capacity factor.On the other hand, solar cooling is gaining an increasing appeal as a way to locally exploit renewable energy sources and reducing carbon footprint. Many thermally driven systems are being currently studied, among these the ejection reverse cycle is being proposed as an interesting alternative due to its simplicity, low cost and reliability.The present paper aims to analyse a complex system in which the solar powered ejection machine is used to increase the efficiency of a traditional vapour compression machine by subtracting heat from the condenser. By means of a transient analysis, performed with a reference building and with climate data corresponding to four different system locations worldwide, the year-round performance of such a system in a space cooling application is estimated in terms of energy balance and savings on power costs with respect to the traditional solutions, in order to evaluate its potential benefits and to highlight some issues related to system design and operation. A sensitivity analysis is also performed with respect to solar collector area and equipment sizing, showing how the latter is an important optimisation parameter when designing the system.