Injection Characteristics Research Articles

Effect of inlet mass flow rate oscillation on simplex swirl injector flow based on VOF-to-DPM model

The flow characteristics of injectors with oscillations play a significant role in the mechanism of combustion instability. And combustion instability reduces engine reliability. Therefore, an efficient VOF-to-DPM model-based method is proposed to evaluate the effect of inlet mass flow rate oscillation on the injectors in liquid rocket engines. In this method, the VOF-to-DPM model, which can portray the complete spray process with less computational cost than the VOF method, is adopted to simulate the whole spray process of the injector under oscillations. The proposed method is first verified by the reported simulation work. Then, it is applied to study the flow characteristics (response and spray characteristics) of the simplex swirl injector under different inlet mass flow rate oscillations. The result of the proposed method indicates that the simplex swirl injector is sensitive to the oscillation of 200–300 Hz, which is consistent with the reported experimental work. Additionally, inlet oscillation frequency dominantly increases the phase difference while frequency and amplitude jointly determine the amplification or attenuation of the outlet mass flow. The injector with 250 Hz has a higher velocity of downstream recirculation and smaller droplets than other oscillation frequencies, which may provoke combustion instability. The numerical results are beneficial to injector design and reduce the possibility of combustion instability by active regulation. The proposed method contributes to revealing the mechanism of combustion instability and improving the reliability of liquid rocket engines.

Statistical characteristics of liquid injection by jet pump in the process of hydrocarbon production

Purpose.To determine the effective range of pressure ratios in the working fluid at the inlet to the jet pump and at its outlet and to determine the numerical characteristics of the random variable – the injection coefficient, provided that the normal distribution law is implemented and rational values of the injection coefficient are achieved, with the determination of the probability of its implementation. The methods. The calculation is carried out using the statistical numerical characteristics of the injection coefficient and the justification of the initial conditions regarding the ratio of pressures at the inlet and outlet of the jet pump. Findings. The operating pressure range is set within (60...160) bar, which corresponds to the throttling pressure when the liquid passes through the nozzle of the jet pump within the limits accepted in the oil industry. The effect on the value of the injection coefficient separately of the pressure at the inlet and outlet of the jet pump, as well as the complex effect with the determination of the probable range of pressure at the inlet within 360...460 bar and at the outlet 330...336 bar, while -the injection ratio varies from 0 to a maximum value of 0.96. The range of variation of the injection coefficient within 3 σ with the centering of the random variable and the determination of the mathematical expectation with the value of 0.48 is constructed. The originality. It was found that within half of the mean square deviation, the established value of the probability of realization of the injection coefficient is 0.383. Within the mean square deviation, the established value of the probability of realizing the injection coefficient is 0.683, which confirms the high probability of realizing the injection coefficient with a centering of 0.48 Practical implementation. The obtained results of the calculations make it possible to substantiate the design parameters and energy parameters of the system of supplying the working fluid from the surface during the design of the pump and the development of the technology of its application with the achievement of rational values of the injection coefficient. This will increase the efficiency of the jet pump for cleaning the near-stem area of the oil well and will contribute to the increase of hydrocarbon production.

High Quality Multi-Zone and 3D CFD Model of Combustion in Marine Diesel Engine Cylinder

Abstract The paper presents a 3D model of the processes taking place in the cylinder of a large 4-stroke marine engine. The model is based on CFD calculations performed on the moving mesh. The modelling range includes the full duty cycle (720° crankshaft position) and the complete geometry of the cylinder with inlet and exhaust ducts. The input data, boundary conditions and validation data were obtained by direct measurements on the real object. Fuel injection characteristics were obtained by Mie scattering measurements in a fixed-volume chamber. The modelling results have been validated in terms of the pressure characteristics of the engine’s cylinder within the entire range of its loads. The mean error did not exceed 1.42% for the maximum combustion pressure and 1.13% for the MIP (Mean Indicated Pressure). The model was also positively validated in terms of the O2 and NOx content of the exhaust gas. The mean error in this case was 1.2% for NOx fractions in the exhaust gas and 0.4% for O2 fractions. The complete model data has been made available in the research data repository on an open access basis.

Assessment of Patients Receiving Short-Interval Botulinum Toxin Chemodenervation Treatment for Laryngeal Dystonia and Essential Tremor of the Vocal Tract

The gold-standard treatment for laryngeal dystonia (LD) and essential tremor of the vocal tract (ETVT) is botulinum toxin (BoNT) chemodenervation. Although safe and effective, it is not curative, and periodic injections are required. Some medical insurance companies only cover injections at a 3-month interval, though some patients benefit from injections more frequently. To determine the proportion and characteristics of patients who receive BoNT chemodenervation treatment in intervals shorter than 90 days. This retrospective cohort study across 3 quaternary care neurolaryngology specialty practices in Washington and California recruited patients who underwent at least 4 consecutive laryngeal BoNT injections for LD and/or ETVT in the past 5 years. Data were collected from March through June 2022 and analyzed from June through December 2022. Laryngeal BoNT treatment. Biodemographic and clinical variables, injection characteristics, evolution during the 3 interinjection intervals, and lifetime laryngeal BoNT treatment data were collected from patient medical records. Logistic regression was used to assess association to the short-interval outcome, defined as an average injection interval shorter than 90 days. Of 255 patients included from the 3 institutions, 189 (74.1%) were female, and the mean (SD) age was 62.7 (14.3) years. The predominant diagnosis was adductor LD (n = 199 [78.0%]), followed by adductor dystonic voice tremor (n = 26 [10.2%]) and ETVT (n = 13 [5.1%]). Seventy patients (27.5%) received short-interval injections (<90 days). The short-interval group was younger than the long-interval group (≥90 days), with a mean (SD) age of 58.6 (15.5) years and 64.2 (13.5) years, respectively, and a mean difference of -5.7 years (95% CI, -9.6 to -1.8 years). There were no patient-related differences between the short- and long-interval groups in terms of sex, employment status, or diagnosis. This cohort study demonstrated that while insurance companies often mandate a 3-month or greater interval for BoNT chemodenervation financial coverage, there is a considerable subset of patients with LD and ETVT who receive short-interval treatment to optimize their vocal function. Short-interval chemodenervation injections demonstrate a similar adverse effect profile and do not appear to predispose to resistance through antibody formation.

Experimental Investigation on Liquid Breakup and Injection Characteristics of a Rotary Slinger Atomizer

Experimental Investigation on Liquid Breakup and Injection Characteristics of a Rotary Slinger Atomizer

Corrigendum: Experimental study on condensation and acoustic characteristics of steam underwater injection

Corrigendum: Experimental study on condensation and acoustic characteristics of steam underwater injection

Numerical simulation of trans-/near-/supercritical injection characteristics based on real fluid properties

In this paper, the trans-/near-/supercritical jet models were established using a combination of large eddy numerical simulations and real fluid equations of state (EOS) in order to systematically investigate the heat and mass transfer mixing process of the jet at supercritical pressure. The effects of EOS, injection temperature (Tinj), ambient pressure (Pamb), and the pseudo-boiling phenomena on the density field, temperature increase rate, spray penetration, spray area, spreading angle, and mixing layer thickness of the spray were investigated. The results reveal that the initial shape of the spray is connected to its thermodynamic and transport characteristics. The correctness of fuel characteristic parameters impacts the development of the jet. For trans-/near-critical sprays, the temperature rise rate, spreading angle, spray area, and mixing layer thickness are enhanced, indicating the mixing efficiency is improved by increasing the Pamb and Tinj. However, raising the Pamb has a detrimental impact if both the Tinj and the Pamb exceed the critical parameters. This is owing to the link between Tinj and pseudo-boiling temperature, which results in a trade-off between Pamb and the objects discussed above for supercritical sprays. This research is essential to comprehend the heat and mass transfer mixing process of the supercritical jet.

A rate-of-injection model for predicting single and double injection with or without fusion.

Models used to predict the instantaneous injected fuel mass are of varied interest in automotive applications, including for providing inputs to CFD calculations or for engine control. While multiple injection strategies are now commonly used in diesel engines, the overall approach may be susceptible to injection fusion, which is defined as two successive injections that are partly or totally coupled due to the short time interval between each event. In this work, a new model to predict the instantaneous mass flow rate from a diesel injector is proposed based on the analytical solution of a first-order linear dynamic system exposed to an impulsion. Experiments are also conducted to quantify the main injection characteristics of a solenoid indirect-action injector under different injection pressures, backpressures and injection durations, representing a total of 33 different conditions. From these results, a model is proposed and validated against experimental data using a single injection strategy. Then, the model is enhanced to predict split injection with and without injection fusion. Successful comparisons are realized between the model and the experiment. The model is then used to successfully simulate a piezoelectric injector experiencing different levels of fusion available in the literature so as to illustrate the universality of the proposed approach.

Research of influence of operational factors on parameters fuel delivery accumulator system CR engines RT-FLEX

The results of a computational study of the influence of operational factors on the fuel supply process by the accumulator system CR of RT-flex engines are presented. In the model used in the study of fuel supply in the accumulator system processes that occur in all its essential elements are described. As an accumulator, a constant pressure source is considered. The most detailed analysis is the operation of the injection control unit that determines the processes in the high-pressure system. Carefully presented nozzles, the elements of which are fully consistent with the real design. A change in the basic characteristics of injection with variable values of the temperature of heating the fuel, its viscosity, pressure in the accumulator and the pressure of the nozzle needle lift is considered. The most significant effect is the viscosity and pressure in the accumulator. An increase in viscosity (lowering the heating temperature) leads to a significant decrease in the cyclic supply of fuel and a decrease in the stroke of the metering piston with constant fuel supply phases. The cycle delivery increases with temperature from 500 C to 90-1100 C from 0,013 to 0,022 kg – 1,69 times. Obviously, the determining factor in this dependence is the movement metering piston injection control unit. This indicator changes in a close way, increasing in the same range from 7.4 to 10.5-10.8 mm. Additional information about the movement of the QP is the speed of its movement. In the direct (working, injection) stroke, it increases with increasing temperature in the above range from 0,135 to 0,244 m / s. As for the fuel pressure in the nozzle, then the influence of temperature is small. It decreases from 610 to 600 bar − less than 2 % (in the ratio of 1,016). This pattern indicates the decisive influence of the hydraulic resistance of the elements of the high pressure path on the pressure in the nozzle. In a similar way, the injection parameters change with decreasing pressure in the accumulator. One of the operational parameters of the fuel supply system is the liftingpressure of the nozzle, which depends on the force from the spring. To assess the influence of the pressure of the nozzle lift, the injection process was simulated at various spring tightening pressures. The range of variation of was 300-450 bar with a nominal value of 375 bar. No noticeable effect was on injection characteristics. The change in the cyclic delivery does not go beyond 3,2 %; the difference in the path of the QP for the boundaries of the range is 2,2 %, and the velocity of the QP remains within 1,8 %. The pressure in the nozzle channel remains unchanged.

Effect of ambient pressure on the performance of a gas-centered swirl coaxial injector

In this study, water and air were used as simulated media to investigate the spray characteristics of a gas-centered swirl coaxial (GCSC) injector under different ambient pressures through experimental, simulation, and theoretical approaches. The results showed that for the same liquid mass flow rate, the breakup length of the liquid film decreased with increasing ambient pressure, with the extent of the decrease diminishing as the ambient pressure increased. In addition, it was found that under the same ambient pressure, the larger the liquid mass flow rate, the shorter the liquid film breakup length. Moreover, for any gas–liquid mass flow ratio (GLR), the spray angle increased significantly with ambient pressure, and the liquid film suddenly expanded compared to the no-ambient pressure condition. At the same time, the breakup length of the liquid film increased. As ambient pressure increased, the spray angle increased while the breakup length decreased. When the GLR was small, self-pulsation occurred, which gradually disappeared with increasing ambient pressure. The frequency of self-pulsation decreased with increasing ambient pressure. The periodic self-pulsation of the spray was the result of the combined effects of the centrifugal force of the rotating liquid film, surface tension of the liquid film, aerodynamic force, and pressure difference inside and outside the liquid film. Overall, these findings provide insight into the spray characteristics of GCSC injectors under different ambient pressures, which can be of importance to the design and optimization of liquid rocket engines.

Evaluation and Application of Fractal-Based Hydraulic Constitutive Model for Unsaturated Flow in Heterogeneous Soils

The physical-based hydraulic constitutive model developed by fractal theory has received much attention, however, its performance in two-phase flows has not been fully evaluated. This study evaluates the ability of fractal-based hydraulic constitutive models to describe the two-phase flow combining mass and momentum conservation equations. After that, we investigate the injection and displacement characteristics of the amendment at NAPL (non-aqueous phase liquids)-contaminated low-permeability sites based on this fractal model. Points of interest are the effect of the location of hydraulic fracturing in layered soils on amendment injection and distribution and the corresponding key parameters. Comparison with experimental results reveals that the fractal model describes the two-phase flow behavior very well. Fractal dimension and intrinsic permeability of soils have significant effects on the two-phase flow. For layered soils, the lower part of the low-permeability layer is preferably recommended as the main fracturing and injection zone to obtain the optimal injection efficiency. Besides, due to the lower flow resistance, hydraulic fractures across layers can be treated as fractures in highly permeable layers. This work provides new insights into the application of fractal theory in describing two-phase flows.

Analysis of CRDI diesel engine characteristics operated on dual fuel mode fueled with biodiesel-hydrogen enriched producer gas under the single and multi-injection scheme

The present work aims to investigate the consequences of pilot fuel (PF) multiple injections and hydrogen manifold injection (HMI) on the combustion and tailpipe gas characteristics of a common rail direct injection (CRDI) compression ignition (CI) engine operated on dual fuel (DF) mode. The CI engine can perform on a wide variety of fuels and under high pilot fuel (PF) pressure. Pilot fuel injection (PFI) is achieved at TDC, 5, 10, and 15ºCA before the top dead center (bTDC), and divided injection consists of injecting fuel in three different magnitudes on a time basis and PF is injected into the engine cylinder at a pressure of 600 bar. In this work, the hydrogen flow rate (HFR) was fixed at 8 lpm constant and producer gas was inducted without any restriction. The investigational engine setup has the ability to deliver a PF and hydrogen (H2) precisely in all operating circumstances using a separate electronic control unit (ECU). Results showed that diesel-hydrogen enriched producer gas (HPG) operation at maximum operating conditions provided amplified thermal efficiency by 4.01% with reduced emissions, except NOx levels, compared to biodiesel-HPG operation. Further, DiSOME with the multi-injection strategy of 60 + 20+20 and 50 + 25+25, lowered thermal efficiency by 4.8% and 9.12%, respectively compared to identical fuel combinations under a single injection scheme. However, reductions in NOx levels, cylinder pressure, and HRR were observed with a multi-injection scheme. It is concluded that multi-injection results in lower BTE, changes carbon-based emissions marginally, and decreases cylinder pressure and heat release rate than the traditional fuel injection method.

Characteristics of thermo-gelation biopolymer solution injection into porous media

The objective of this study is to analyze the injection characteristics of thermo-gelation biopolymer (TG-BP) solutions for ground improvement applications. Two types of TG-BP, namely, agar and gellan gum, are utilized. Their material properties such as viscosity, interfacial tension, and contact angle are evaluated to determine their impacts on fluid flow through porous media. The results show that viscosity and contact angle are higher and interfacial tension is lower than those of water, thus leading to an increase in injectivity. Additionally, microscale experiments are conducted to evaluate the injection performance of TG-BP. The results indicate that injectivity decreases with increasing concentration of TG-BP but increases with increasing injection pressure. By considering the material properties of TG-BP, the relationship between these properties and injection performance, as well as the advantages of using TG-BP over traditional injection materials for ground improvement are discussed. The findings of this study have significant implications for the development of better injection materials and techniques for ground improvement applications.

Combustion Instabilities and its Control Techniques for Liquid Propellant Rocket Engine

It is a great challenge for us to understand and to predict the concept of liquid propellant rocket engines combustion instability due to high complex turbulent combustion process. Traditional methods have been adopted to eliminate the combustion instabilities which will increase system damping. Such methods usually suffer deficiencies with lack of study on fundamental mechanism. Difficulties have been faced during the process of various phenomena such include spray formation process, turbulent multiphase flow conditions, hydrodynamics of injection and transport characteristics of individual droplets. The ultimate aim of every engine design is to prevent occurrence of this combustion instability and to maintain reliable operation during entire span of the combustion process. This article is focused on occurrence of various type of combustion instabilities in liquid propellant rocket engine and its preventing methods in detail.

Modifying diesel fuel with nanoparticles of zinc oxide to investigate its influences on engine behaviors

In this paper, we used experimental and numerical methods to explore the effects of a diesel fuel blend containing zinc oxide (ZnO) nanoparticles at three different concentrations (0.025%, 0.05%, and 0.1%) on the combustion, injection, performance, and emission characteristics of a diesel engine running at constant speeds of 2000 rpm, 2250 rpm, 2500 rpm, 2750 rpm, and 3000 rpm, with the engine operating at full load. The results of the experiments demonstrate that DF + 0.1% ZnO increases BTE by 11.7% at 2500 rpm, while decreasing SFC by 1.67%, exhaust gas temperature by 11.4%, and NOx emissions by 10.67%. The advanced injection time and load were kept same, but a 2.3% rise in cylinder pressure was achieved when ZnO nano additions to diesel fuel were used. Moreover, CO2 emissions were reduced by 7.6% compared to 2500 rpm. In conclusion, the results prove that the nanoparticle-added test fuels improve engine efficiency, and combustion yield by reducing exhaust pollutants, and the numerical results are in good agreement with the experimental results.

Analysis of Sediment and Water Flow and Erosion Characteristics of Large Pelton Turbine Injector

Based on the solid–liquid two-phase flow model, SST k-ω model, and Lagrangian equation model of particle motion, numerical simulations of the sediment–water flow in the injector of a large Pelton turbine were conducted. The distribution rules of pressure, velocity, erosion rate, and erosion location of the injector were obtained by analyzing the sediment–water flow characteristics and sediment erosion distribution characteristics of the injector. The results revealed that the velocity distribution trend of the water inside the cylindrical jet exhibited a nonlinear distribution, and the phenomenon of “velocity deficit” occurred at the end of the needle guide and needle tip, resulting in a decrease in the jet quality of the injector. The sediment particle diameter affected the erosion rate of the needle and erosion location of the needle and nozzle port ring. This study provided guidance for sediment erosion analysis and the prediction of the utility of large Pelton turbines.

Experimental Investigation of High-Pressure Liquid Ammonia Injection under Non-Flash Boiling and Flash Boiling Conditions

Liquid ammonia is an ideal zero-carbon fuel for internal combustion engines. High-pressure injection is a key technology in organizing ammonia combustion. Characteristics of high-pressure liquid ammonia injection is lack of research. Spray behaviors are likely to change when a high-pressure diesel injector uses liquid ammonia as its fuel. This study uses high-speed imaging with a DBI method to investigate the liquid penetration, width, and spray tip velocity of high-pressure liquid ammonia injection up to 100 MPa. Non-flash and flash boiling conditions were included in the experimental conditions. Simulation was also used to evaluate the results. In non-flash boiling conditions, the Hiroyasu model provided better accuracy than the Siebers model. In flash boiling conditions, a phenomenon was found that liquid penetration and spray tip velocity were strongly suppressed in the initial stage of the injection process, this being the “spray resistance phenomenon”. The “spray resistance phenomenon” was observed when ambient pressure was below 0.7 MPa during 0–0.05 ms ASOI and was highly related to the superheated degree. The shape of near-nozzle sprays abruptly changed at 0.05 ms ASOI, indicating that strong cavitation inside the nozzle caused by needle lift effects is the key reason for the “spray resistance phenomenon”.

Numerical Simulation Study on Injection and Mixing Characteristics of Supercritical RP-3 Aviation Kerosene

A real gas calculation model is developed using the P-R equation of state to investigate the injection and mixing characteristics of supercritical RP-3 aviation kerosene in the combustion chamber. In this investigation, n-decane is used as an alternative fuel, and the physical parameters of n-decane at the supercritical state are calculated. The jet and mixing characteristics of supercritical kerosene in different combustion chamber models are investigated by this calculation model. The combustion chamber head configuration suitable for supercritical kerosene is obtained by analyzing the spatial inhomogeneity, the deviation of equivalent ratio fluctuation, and the mixing degree.

Study of Synthesis and Characterization of Pure Cus and Cufes Nanoparticles by Hydrothermal Method

Copper-based material has good electrical and optical properties but is not only physical properties and also good in antibacterial applications. Nano-structured CuS has potential value on high photocatalytic activity because of their suitable band gap and catalytic ability. CuS NP hydrogels had both adjustable physical properties and good injectable self-healing characteristics and excellent functionalities, concurrently including hemostatic ability, bacteria-killing capability, and cell migration and proliferation promotion. In vivo wound, healing, and histomorphological examinations of immunofluorescence staining in a mouse full-thickness wound model demonstrated good acceleration effects of these hydrogels for infected wound healing. A novel Chalcopyrite CuFeS nanocrystals are used as a Fenton reagent to degrade organic dyes without any additional source efficiently. Subsequently, the CuFeS2 nanocrystals/ biomass composite degradation column is made, continually degrading organic dyes. This paper demonstrates a comparative study of the synthesis and characterization of pure CuS and CuFeS nanoparticles using copper chloride, thiourea, ferric chloride and water solvent by straightforward hydrothermal methods. The synthesized material was characterized by an Xray diffraction (XRD), Scanning Electron Microscope (SEM), and Energy Dispersive X-ray spectrum (EDAX) techniques employed to study the nanostructure properties of the prepared sample. Crystallite size was determined by the Debye-Scherrer formula and found to be 15.5 nm and 20.55 nm, respectively. The EDAX spectrum showed a clear peak of present elements. An SEM image shows the morphology of the nanostructures. Optical analysis was done with UV and FTIR techniques. The pure CuS and CuFeS synthesized Tauc Relation and calculated nanomaterials bandgap came out to be 4.6eV and 4.4 eV, respectively.

A Numerical Study on the Transient Injection Characteristics of Gas Fuel Injection Devices for Direct-Injection Engines

Natural gas has emerged as one of the preferred alternative fuels for vehicles owing to its advantages of abundant reserves, cleaner combustion and lower cost. At present, the gas supply methods for natural-gas engines are mainly port fuel injection (PFI) and direct injection (DI). The transient injection characteristics of a gas fuel injection device, as the terminal executive component of the PFI or DI mode, will directly affect the key performance of a gas fuel engine. Therefore, gas fuel injection devices have been selected as the research object of this paper, with a focus on the transient injection process. To explore the impacts of valve vibration amplitude, period, frequency and velocity on transient injection characteristics, one transient computational fluid dynamics (CFD) model for gas fuel injection devices was established. The findings thereof demonstrated that there is a linear relationship between the instantaneous mass flow rate and instantaneous lift during the vibration process. However, this relationship is somewhat impacted when the valve speed is high enough. A shorter valve vibration period tends to preclude a shorter period of flow-hysteresis fluctuation. The near-field pressure fluctuation at the throat of an injection device, caused by valve vibration, initiates flow fluctuation.