Jet Injection Research Articles

Optimization of Oxygen Injection Conditions with Different Molten Steel Levels in the EAF Refining Process by CFD Simulation

In electric arc furnace (EAF) steelmaking, oxygen jets play a crucial role in controlling stirring ability, chemical reactions, and energy consumption. During the EAF lifetime, refractory wear leads to a decrease in the molten steel level and an increase in the nozzle-to-steel distance, thereby negatively affecting the overall energy efficiency of the process. The objective of this study is to optimize the energy efficiency of the EAF refining process by adjusting the nozzle flow conditions and conducting an analysis of jet performance using computational fluid dynamics (CFD) simulation. Three types of injection jets were considered: the conventional jet, the CH4 coherent jet, and the CH4 + O2 coherent jet. The findings reveal that the shrouded flame of the coherent jet enhances jet performance by maintaining the maximum velocity, extending the potential core length, and increasing the penetration depth in the molten steel bath. To maintain the jet performance in response to an increased nozzle-to-steel distance resulting from refractory wear, transitions from the conventional jet to the CH4 coherent jet and the CH4 + O2 coherent jet are recommended once the nozzle-to-steel distance increases from its initial level of 1000 mm to 1500 mm and 2000 mm, respectively.

An Analysis Model for Predicting Windage Power Loss of Aviation Spiral Bevel Gears Under Optimal Injection Jet Layout

With the increasing rotating speed of aviation spiral bevel gears, the load-independent windage power loss caused by hydrodynamic behavior has a greater impact on transmission efficiency. An analytical model is established to predict the windage power loss of spiral bevel gears with oil injection lubrication. The improved model regards the total windage losses as the sum of oil–gas dragging effects on the tooth flank, toe/heel, circular cone surface, circumference of the teeth, and tooth root. Then the numerical method and analytical method are combined to calculate windage losses. A multi-objective NSGA-II optimization algorithm is used to optimize the jet layout parameters. The rationality and accuracy of this model are verified by comparing the calculation results of an example with data sets of existing experimental findings and computational fluid dynamics (CFD) simulation results. The calculation results show that compared with the tooth profile assumption method in the existing literature, the improved calculation formula of windage dragging effect on tooth flank can better reflect the influence of oil injection lubrication layout parameters on windage loss and make the windage loss calculation more accurate. Finally, the influence of gear body parameters, working conditions parameters, geometric parameters, and injection lubrication layout parameters on the windage loss is examined. This research provides a theoretical basis and methodological guidance for optimization design of reducing windage power loss.

Numerical Simulation of a Sonic Jet Injected into a Supersonic Crossflow With K.(l) Turbulence Model

Numerical simulation of normal injection of a sonic jet into supersonic crossflows were performed with a k-ul turbulence model. Favre-averaged Navier-Stokes equations along with k-6p equations were solved in a coupled manner by calculating inviscidfluxes with Roe's flux-dffirence splitting, central dffirencing of derivatives in the viscous terms, and by performing Runge-Kutta time integration in a finite volume formuLation. Experiments of sLot injection at several freestream Mach numbers and injection pressure ratios were simulated. It was observed that simulations agreed well at low pressure ratios but departed with increasing pressure ratio as had been observed in other simulations. A qualitative difference in the structure of the jet was observed when explicit compressibility fficts were included. In turn, the agreement with experiment improves significantly. It was also observed that imposing a lower ReynoLds number in the caLculations than the value determined from reported experimental conditions resulted in solutions expected of transitional separation and vvhich then agreed more closely with experiment.

Intradermal administration of DNA vaccine targeting Omicron SARS-CoV-2 via pyro-drive jet injector provides the prolonged neutralizing antibody production via germinal center reaction

Emerging SARS-CoV-2 Omicron variants are highly contagious with enhanced immune escape mechanisms against the initially approved COVID-19 vaccines. Therefore, we require stable alternative-platform vaccines that confer protection against newer variants of SARS-CoV-2. We designed an Omicron B.1.1.529 specific DNA vaccine using our DNA vaccine platform and evaluated the humoral and cellular immune responses. SD rats intradermally administered with Omicron-specific DNA vaccine via pyro-drive jet injector (PJI) thrice at 2-week intervals elicited high antibody titers against the Omicron subvariants as well as the ancestral strain. Indeed, the Omicron B.1.1.529-specific antibody titer and neutralizing antibody were higher than that of other strains. Longitudinal monitoring indicated that anti-spike (ancestral and Omicron) antibody titers decreased toward 30 weeks after the first vaccination dose. However, neutralization activity remained unaltered. Germinal center formation was histologically detected in lymph nodes in rats immunized with Omicron DNA vaccine. Ancestral spike-specific immune cell response was slightly weaker than Omicron spike-specific response in splenocytes with Omicron-adapted DNA vaccine, evaluated by ELISpot assay. Collectively, our findings suggest that Omicron targeting DNA vaccines via PJI can elicit robust durable antibody production mediated by germinal center reaction against this new variant as well as partially against the spike protein of other SARS-CoV-2 variants.

Numerical investigation of wide continuous particle size distribution on the supersonic powder loading oxygen jet

Supersonic oxygen-powder jet injection has spanned wide range of operations in chemical engineering. However, the ubiquitous polydispersity of solid powder known to exert different flow behavior than the monodisperse counterpart has not been revealed. In this work, numerical simulation of the supersonic oxygen-powder jet injection via the Laval nozzle is performed under the Eulerian-Lagrangian framework to explore the impact of wide continuous size distribution of solid phase on the gas-solid hydrodynamics. Specifically, the gas phase is solved using the Eulerian method, while the particle motion is tracked under the Lagrangian framework. The numerical model is well validated with the experimental measurements. The results reveal that the blending of particles restricts the gas phase expansion, leading to the obvious reduction of gas velocity and increase of gas temperature. Additionally, a narrow particle size distribution (PSD) width corresponds to a higher proportion of large particles, inducing stronger vortices and hindering gas phase expansion. With regard to solid phase, the penetration ability of particles is significantly enhanced within the supersonic gas flow by accelerating the particle velocity to about 300 m/s. Furthermore, particles with wider PSD exhibit increased sensitivity to interphase interaction, particle-particle collisions and lift forces, resulting in higher velocities, lower temperatures along the axial direction and greater dispersion along the radial direction. Lastly, the interphase heat transfer mainly occurs in the convergent section, divergent section, and one nozzle length downstream from the nozzle exit. The findings obtained in this study offer valuable insights for industrial applications.

Four-way coupled Eulerian-Lagrangian study of phase interaction mechanism in the supersonic gas-solid two-phase flow

Supersonic gas–solid jet injection has received much attention in many industrial applications such as pneumatic conveying, powdered drug delivery, steel refining process and thermal spray coating, but it is still a challenging topic due to the complex interphase interaction in compressible flows. In this work, supersonic gas–solid two-phase flow is numerically studied under the Eulerian-Lagrangian framework. After the model validation with the experimental measurement, the inherent mechanism of supersonic gas–solid flow under the conditions of different powder feeding rates and particle diameters is explored. The results demonstrate that increasing the powder feeding rate leads to the reduction of the axial velocity and penetration ability of the particles. Especially when powder feeding rate increases to 10 kg/s, serious blockage occurs in the nozzle divergence section and the conventional supersonic flow characteristic in Laval nozzle has been substantially changed. Moreover, particle diameter largely determines the dynamic and thermodynamic characteristics of the particles. Small-diameter particles exhibit better followability to the gas phase and large-diameter particles exert non-negligible impact on the gas flow, mainly reflects in weakening the expansion ability of the gas phase. The results obtained in this work provide meaningful insight for understanding the flow characteristics of supersonic gas–solid flow and benefit the operating parameters selection in industrial applications.

Conceptualisation of a novel electromechanical system for small-volume needle-free jet injection

Needle-free jet injectors are minimally invasive drug delivery systems that utilise high-velocity microjets (∼100 m/s) created by pressurising the liquid drug through a micronozzle (50–300 µm in diameter). Most of the current commercially available jet injectors use a mechanical power possessed by a compressed spring or air to pressurise the fluid inside the injection chamber to deliver the liquid drug (typically ∼100 µL in volume) into the skin matrix. However, they cannot be utilised for achieving shallow penetration depths as they lack dynamic control that can shape the real-time microjet characteristics. Recently, electrically or optically powered jet injection systems are being developed to achieve shallow penetration depth by small-volume (<5 μL) injections. However, they require complex system and have a limited injection frequency (maximum reported value is 16 Hz). Herein, we propose a novel electro-mechanical jet injection system, where a mechanically actuated source pressurises the fluid inside the injection chamber and an electrically actuated system controls the characteristics of the propelled microjet. A computational model was developed to prove the feasibility of the proposed system, and the obtained results showed that the proposed system could produce stable small-volume microjets at about 100 Hz frequency that could be utilised for drug delivery applications.

Numerical Simulation of the Interaction of High-Velocity Plasma Jets Injected in the Earth’s Ionosphere

The paper presents a numerical simulation of the dynamics of high-velocity aluminum plasma jets with multiple injection in the Earth’s ionosphere. Scenarios of single injection, counter injection, and collimation of plasma jets at a given convergence angle are considered. The gas-dynamic parameters of plasma formations and their optical characteristics are determined.

A Scientometric Analysis and Visualization of Scientific Research and Technology Innovation in Needle-free Insulin Injection From 1974 to 2022

PurposeNeedle-free jet injection has to some extent improved the quality of life of patients with diabetes, but it has not been widely used. Therefore, we analyzed articles, clinical trials, and patents of needle-free insulin injection to (1) perform a systematic and comprehensive analysis of scientific research and technology innovation in needle-free insulin injection during the past 49 years (1974 to 2022) and (2) identify the status of scientific research and technology innovation, their limitations, and future trends. MethodsWith a new perspective, we use scientometric tools, including co-word and word frequency analyses, text mining, and cluster network analysis, to provide a scientometric analysis and visualization of articles, clinical trials, and patents related to needle-free insulin injection delivery applications. FindingsPatent innovation in this field was more active than clinical research, and clinical research prevailed over basic research. Basic research and clinical trials in this field mainly involved therapy, penetration, tolerability, absorption, and pharmacokinetic properties. Drive mechanisms and needle-free injection devices were the core patent technologies in this field. ImplicationsAlthough needle-free insulin injection has been under development for decades, its full potential has not yet been reached; needle-free injection technology is still in the growth stage. The field of needleless insulin injection is dominated by patent technology innovation.

Measurement of Blood Dilution during Lancet-Free Blood Sampling.

In this paper, we report on a fluorescent and colorimetric system for measuring the dilution of capillary blood released by a needle-free jet injector. Jet injection uses a high-speed liquid jet to penetrate tissue, and in the process can release capillary blood that can be collected for performing blood tests. In this way, blood sampling can be performed without the use of a lancet. However, any injectate that mixes with the collected blood dilutes the sample and may significantly impact subsequent analyses. By adding the fluorescent marker indocyanine green to the injected liquid, the fraction of injectate mixed into the collected blood can be measured. The incorporation of colorimetry allows our system to also correct for the impact of hematocrit on fluorescence. The results from this system show that it can determine the dilution of blood that has been diluted by up to 10 %, the upper limit of dilution typically observed in lancet-free blood sampling via jet injection.Clinical Relevance- Blood samples can be collected by jet injection without significant dilution, avoiding the need for lancing.

Study of the Variation of Fuel Pressure to Improve Spraying and the Range of the Injection Jet

The current study is focused on how varying injection pressure in the fuel supply system of multi-point injection systems can improve fuel atomization and injection jet range. The aim is to achieve a more efficient mix dosage, thus improving combustion and reducing exhaust emissions. In addition, it is intended to develop a characterization of the injection actuators, specifically the injectors, through a series of tests in which the injector pressure, engine speed and injection pulse are modified. To carry out these tests, a heuristic testing technique, like the empirical approach, was implemented, and a mobile device was used to capture the spray frames of the injectors. These data were then used to generate a correlation model between injection and spray angles, considering 0.5 bar pressure variation intervals within the established ranges. This approach made it possible to visualize and record the behavior of the spray in the injector, including the spray angle, the injected fuel flow rate and the working pressure during the operation process. Following the guidelines established in the proposed methodology, a significant result was obtained by varying the pressure at 5 bar and with an injection pulse of 2 ms. In this case, a flow reduction of 66 mL of the injected fluid was achieved, which corresponds to a significant reduction in fuel consumption. Additionally, a spray angle of 10.48° was observed with optimized atomization. These results were verified on vehicles with similar injection systems by testing on the GT-600-PRO injection test bench. In summary, this study shows that by varying the injection pressure and optimizing other parameters, it is possible to achieve a significant reduction in fuel consumption and improve fuel atomization in multipoint injection systems. These findings have a significant impact on the Ecuadorian vehicle fleet and provide a scientific approach to improving fuel efficiency and performance.

Jet-Injection In Situ Production of PVDF/PCM Composite Fibers for Thermal Management.

Thermal management protects against external agents and increases the lifetime and performance of the devices in which it is implemented. Because of their ability to store and release a high amount of energy at a nearly constant temperature, phase change materials (PCMs) are promising thermoregulatory materials. Thus, the manufacture of PVDF fibers containing PCMs has advantages since PVDF is already used in elements that are susceptible to thermal management as a binder in batteries or as a base material for fabrics. This work presents a simple, versatile, in situ, cost-effective, and easy-to-scale-up method to produce PVDF-based fibers containing paraffin RT-28HC for thermal management. To achieve that goal, the microfluidic approach of coaxial flows was simplified to gravity-aided laminar jet injection into a bulk fluid, where fibers were produced by the solvent extraction mechanism. With this methodology, hollow PVDF fibers and core-shell PVDF fibers containing paraffin RT-28HC have been produced. The proposed approach resulted in fibers with up to 98 J/g of latent heat, with a hierarchical porous structure. SEM study of the fiber morphology has shown that PCM is in the form of slugs along the fibers. Such PCM distribution is maintained until the first melting cycle, when molten PCM spreads within the fiber under capillary forces, which was observed by an infrared camera. Manufactured composite fibers have shown low thermal conductivity and high elasticity, which suggest their potential application as a thermal insulation material with thermal buffer properties. Leakage tests revealed outstanding retention capacity with only 3.5% mass loss after 1000 melting/crystallization cycles. Finally, tensile tests were carried out to evaluate the mechanical properties of the fibers before and after thermal cycling.

An active mixing enhancement technique in supersonic ejectors using pulsed streamwise injections

The current study numerically investigates an active mixing enhancement technique for a supersonic ejector with a constant area mixing chamber operating under the critical regime. Streamwise control jet injections are alternatively pulsed at the top and bottom sides of the mixing chamber entrance. The induced oscillation of the primary jet enhances the bulk mixing between the primary and secondary streams. The secondary stream penetrates the primary core flow much upstream with the control strategy compared to the no-injection case, improving the onset of mixing by 65.36%. A higher spread of the primary jet along the mixing chamber height is observed with the control strategy indicating an enhanced mixing between the two streams. Dynamic mode decomposition analysis of the fluctuations of the velocity magnitude revealed that the dominant dynamic structures are determined by the pulsation frequency and a dominant flapping mode can be observed. The frequency spectrum of the primary jet oscillation revealed that the dominant frequency of oscillation is dictated by the pulsation frequency of the injection. With an increase in the control jet pulsation frequency, the amplitude of primary jet oscillation reduces near the entrance region of the mixing chamber, whereas the amplitude of oscillation far downstream reaches nearly the same value for all the cases. The power spectral analysis of the unsteady pressure fluctuations along the mixing chamber wall revealed that the wall pressure oscillations are contributed by the control jet pulsation frequency as well as the shock wave reflections produced by the supersonic jet–jet interaction within the mixing chamber.

Scalar transport and nucleation in quasi-two-dimensional starting jets and puffs

We experimentally investigate the early-stage scalar mixing and transport with solvent exchange in a quasi-two-dimensional (quasi-2D) jet. We inject an ethanol/oil mixture upward into quiescent water, forming quasi-2D turbulent buoyant jets and triggering the ouzo effect with initial Reynolds numbers, Re0=420,840, and 1680. We study two different modes of fluid supply: continuous injection to study a starting jet and finite volume injection to study a puff. While both modes start with the jet stage, the puff exhibits different characteristics in transport, entrainment, mixing, and nucleation, due to the lack of continuous fluid supply. We also inject a dyed ethanol solution as a passive scalar reference case, such that the effect of nucleation for the ethanol/oil mixture can be disentangled.For the starting jets, the total nucleated mass from the ouzo mixture seems very similar to that of the passive scalar total mass, indicating a primary nucleation site slightly above the virtual origin above the injection needle, supplying the mass flux like the passive scalar injection. With continuous mixing above the primary nucleation site, the mildly increasing nucleation rate suggests the occurrence of secondary nucleation throughout the entire ouzo jet.For the puffs, we show that the puff with the smallest Re0 propagates the fastest and its entrainment lasts the longest. We attribute the superior performance to the buoyancy effect, which transforms a turbulent puff into a turbulent thermal, and has been proven to have stronger entrainment. Although the entrainment and nucleation reduce drastically when the injection stops, the mild mixing still leads to non-zero nucleation rates and the reduced decay of the mean puff concentrations for the ouzo mixture.Adapting the theoretical framework established in Landel et al. (2012b) for quasi-2D turbulent jets and puffs, we successfully model the transport of the horizontally-integrated concentrations for the passive scalar. The fitted advection and dispersion coefficients are then used to model the transport of the ouzo mixture, from which the spatial–temporal evolution of the nucleation rate can be extracted. The spatial distribution of the nucleation rate sheds new light on the solvent exchange process in transient turbulent jet flows.

80-LB: Evaluation of the Pharmacokinetics of Glucagon-Like-Peptide-1 (GLP-1) Receptor Agonist Delivered through the BIOJET Oral Biotherapeutic Delivery Platform in Porcine Model

Glucagon-like-peptide-1 (GLP-1) receptor agonists stimulate insulin secretion and suppress glucagon release. Semaglutide is a GLP-1 agonist currently injected subcutaneously or taken orally to treat type 2 diabetes and for weight management. However, oral administration of protein/peptide therapeutics has proven difficult due to the harsh conditions of the upper gastrointestinal tract (GIT) and poor absorption rates in the small intestine. The BIOJET™ oral biotherapeutic delivery platform is an ingestible drug-device combination developed to increase drug bioavailability via needleless jet injection in the proximal small intestine following oral administration. Previous testing of an earlier, autonomously triggered version of the device in animal models was presented at ACG 2022. In this study we evaluated the pharmacokinetics (PK) of semaglutide delivered through the BIOJET device in a porcine model. Due to prolonged and variable gastric residence times in the porcine model, devices filled with semaglutide (~1mg) were administered by intraduodenal (ID) endoscopic placement and activated in the proximal small intestine of Yucatan swine. PK blood sampling was performed from 0 to 240 hours post-dose to evaluate systemic exposure of semaglutide. Seven of eight (7/8) devices were successfully placed and activated in the duodenum. All seven animals showed detectable drug levels up to ten days post-dosing and had an oral bioavailability average of 37% ± 15% (CV: 40%), ranging from 19%-60% compared to IV control. No significant clinical signs were observed in the animals. This study demonstrated that administration of the BIOJET device has the potential to achieve a magnitude greater bioavailability than the currently marketed oral semaglutide (&amp;lt; 1%). The BIOJET device could provide an alternative for the oral administration of large molecules and may improve patient compliance. Disclosure S. N. Lee: Employee; Biora Therapeutics. C. A. Stork: Employee; Biora Therapeutics. R. O. Valenzuela-rivas: Employee; Biora Therapeutics. M. Walker: Employee; Biora Therapeutics. B. J. Smith: Employee; Biora Therapeutics. J. A. Smith: None. N. Quintana: None. C. Wahl: Employee; Biora Therapeutics. S. Singh: None.

Mathematical Modelling and Fluidic Thrust Vectoring Control of a Delta Wing UAV

Pitch control of an unmanned aerial vehicle (UAV) using fluidic thrust vectoring (FTV) is a relatively novel technique requiring no moving control surfaces, such as elevators. In this paper, the authors’ previous work on the characterization of a static co-flow FTV rig is further validated using the free to pitch dynamic test bench. The deflection of a primary jet after injection of a high-velocity secondary jet was captured using the tuft flow visualization technique, along with the experimental recording of subsequent normal force impinged on the Coanda surface resulting in the pitching moment. The effect of primary and secondary flow velocities on exhaust jet deflection, as well as on the pitch angle of the aircraft, is examined. Aerodynamic gain as well as the inertia of a delta wing UAV test bench are computed through experiments and fed into the equation of motion (e.o.m). The e.o.m developed aided in the design of a model-based PID controller for pitch motion control using the multi-parameter root locus technique. The root locus tuned controller serves as a benchmark controller for performance evaluation of the genetic algorithm (GA) and particle swarm optimization (PSO) tuned controllers. Furthermore, the frequency domain metric of gain and phase margins were also employed to reach a robust control design. Experiments conducted in a simulation environment reveal that PSO-PID results in a better response of the UAV in comparison to the baseline pitch controller.

Experimental study of the injection angle impact on the column Waves: Wavelength, frequency and drop size

An experimental study was performed to investigate the influence of injection angle on further details of breakup of a circular liquid jet injected into an airstream. Wavelength and frequency of axial oscillations caused by column waves, drops size distribution, orientation and aspect ratio of these drops were measured and reported. Injection angles between 30 and 90 degrees were considered. High-speed photography and shadowgraphy techniques were utilized to visualize and record the flow. Experimental data were obtained by processing images with the help of an in-house developed code. We found that gas Weber number and the injection angle are influential on wavelength and frequency of the column waves. The wavelength decreased and the frequency increased with increasing gas Weber number or decreasing the injection angle. Also, momentum ratio, gas Weber number and injection angle were affecting drop's average diameter. By reducing the injection angle, the atomization process was prolonged and the produced drops were larger. Although the injection angle affected the average drop size and number, as long as the regime was not changed, the probability distribution of drop size was independent of the injection angle.We extended theory of Ng et al. [1] to estimate wavelength, frequency of column waves formed on the liquid jet that was injected into an airstream to account for injection angle. A relative gas Weber number was defined by using the relative velocity of the gas to that of the liquid along the flow direction. The introduced relative gas Weber number was found useful in classifying the breakup regimes of the flow. A relation was proposed to estimate these wavelengths with good agreement with our data at different injection angles and other previously published data at normal injection of liquid jets. Two separate correlations for SMD estimation were proposed for before and after bag formation in the flow.

Effect of nozzle shape and applied load on jet injection efficiency

In this paper we present new results on jet injection with the overall aim of providing an efficient drug delivery into the intradermal region of the skin. To advance upon previous work in this area, we studied the use of various geometries for the nozzle (ampule) tip, which is applied to the skin. The geometries included a regular (flat-top) nozzle, tapered nozzles (conical and parabolic), and one wide base nozzle in order to vary the local stress in the skin layers directly beneath the injector. In all of these geometries, we also varied both the applied load and the skin support (e.g., solid backing vs. porcine tissue). We found that the use of applied load combined with a wider contact area led to more consistent injections with dispersion characteristics that may be preferable for vaccinations utilizing skin-based electroporation.

Investigating the use of local nerve blocks and general anaesthesia in reducing pain during and after disbudding procedure in goat kids

ABSTRACT The aim of this study was to compare the pain responses (as measured by noise and movement) during administration of local anaesthetic and during and after disbudding in goat kids. Eighty, seven- to ten-day-old, Saanen goat kids from one farm were enrolled and randomly assigned to one of four different methods of pain relief. Twenty kids had local anaesthetic (LA) applied at two sites per horn bud (LA group), 20 kids had LA applied to the two locations using a jet injector (JI group) and 20 kids were given a general anaesthetic (GA) using a combination of 0.02 mg/kg medetomidine and 2 mg/kg ketamine followed by a horn bud block applied as per the LA group (GA group). The remaining 20 kids had no treatment other than meloxicam (control group). Although responses between goat kids and at different time periods were variable, in comparison to the control group, GA eliminated the responses associated with injection of lignocaine and the responses during the period of disbudding, and provided a reduction in head scratches and shakes across multiple time periods.

Axial water jet injection in a low head Francis turbine at part load

The part load operation of a Francis turbine generally develops a rotating vortex rope (RVR) in the draft tube, generating flow instabilities and pressure pulsations. The present work reports the axial water injection method to mitigate the RVR and its associated pulsations in the draft tube. The runner cone is modified to install a nozzle of three different designs for water jet injection. Water is injected axially at the rate of 0.5% to 2% of the main flow. Spectral analysis is performed to assess the pressure amplitude and dominating frequency affected by the water injection. Spectrogram and spatial harmonic decomposition show a reduction in synchronous and asynchronous pulsation amplitudes. The pressure recovery in the draft tube cone is also improved. The spectral analysis shows that the water injection at 1% and 1.25% is the most effective. The water injection above 1.25% to 2% causes pulsations near the draft tube bend as the water jet bounces back after striking the elbow. A sharp decrease in the Strouhal frequency is observed above 0.5% jet injection. The efficiency of the turbine is also improved by water jet injection.