Selection of Suitable Type of Nozzles for Development of Electrostatic Induction Nozzle

The electrostatic induction mechanism, which superimposes charges on pesticide spray droplets, creates an impact on deposition and wraparound effect on leaf surfaces Smaller droplets have a higher capability to charge accumulation over the surface of the droplet as compared with larger droplets. This paper studied the effect of nozzle type (flat fan, hollow cone, and full cone nozzle), orifice area (1 and 1.5 mm2), and operating pressure (3-5kg cm-2) on spray droplet characteristics on soil bin. Water-sensitive papers were analysed by image analysis software to get the droplet characteristics. The smallest droplets of a hollow cone, flat fan, and full cone were 130, 142, and 279.76 µm respectively produced at 5kg cm-2 and orifice opening 1 mm2. With an increase of pressure droplet size and relative span was decreased for all selective nozzle. From the selected nozzles, the lowest relative span of 0.89 was found with a hollow cone nozzle at 5 kg cm-2 pressure and orifice size of 1 mm2. Among all the selected nozzles hollow cone nozzle produced the smallest droplet sizes and lowest relative span for all selected parameters.

Influence of Cavitation in Common-Rail Diesel Nozzles on the Soot Formation Process through Measuring Soot Emissions

The influence of cavitation in common-rail diesel nozzles on the soot formation process has been analysed experimentally. The soot formation process was characterized by measuring soot emissions in a single-cylinder engine, which was mounted on a test bench equipped with an opacimeter. In order to do this, operating conditions where the soot oxidation process was equivalent were chosen, whereby differences in the soot formation process were possible to be analysed. The results achieved confirm that cavitation provokes a soot formation process reduction. This reduction can be attributed by combining results of three effects: a reduction of the effective diameter, an increase in effective injection velocity, and an increase in turbulence level inside the nozzle orifice leading to a longer lift-off length. The three effects lead to a decrease in relative fuel/air ratio at the lift-off, therefore explaining the soot formation reduction.

Revised Model of Abrasive Water Jet Cutting for Industrial Use

Research performed by the author in the last decade led him to a revision of his older analytical models used for a description and evaluation of abrasive water jet (AWJ) cutting. The review has shown that the power of 1.5 selected for the traverse speed thirty years ago was influenced by the precision of measuring devices. Therefore, the correlation of results calculated from a theoretical model with the results of experiments performed then led to an increasing of the traverse speed exponent above the value derived from the theoretical base. Contemporary measurements, with more precise devices, show that the power suitable for the traverse speed is essentially the same as the value derived in the theoretical description, i.e., it is equal to “one”. Simultaneously, the replacement of the diameter of the water nozzle (orifice) by the focusing (abrasive) tube diameter in the respective equations has been discussed, because this factor is very important for the AWJ machining. Some applications of the revised model are presented and discussed, particularly the reduced forms for a quick recalculation of the changed conditions. The correlation seems to be very good for the results calculated from the present model and those determined from experiments. The improved model shows potential to be a significant tool for preparation of the control software with higher precision in determination of results and higher calculation speed.

Alternative Geometric Arrangements of the Nozzle Outlet Orifice for Liquid Micro-Jet Focusing in Gas Dynamic Virtual Nozzles

Liquid micro-jets are crucial for sample delivery of protein crystals and other macromolecular samples in serial femtosecond crystallography. When combined with MHz repetition rate sources, such as the European X-ray free-electron laser (EuXFEL) facility, it is important that the diffraction patterns are collected before the samples are damaged. This requires extremely thin and very fast jets. In this paper we first explore numerically the influence of different nozzle orifice designs on jet parameters and finally compare our simulations with the experimental data obtained for one particular design. A gas dynamic virtual nozzle (GDVN) model, based on a mixture formulation of Newtonian, compressible, two-phase flow, is numerically solved with the finite volume method and volume of fluid approach to deal with the moving boundary between the gas and liquid phases. The goal is to maximize the jet velocity and its length while minimizing the jet thickness. The design studies incorporate differently shaped nozzle orifices, including an elongated orifice with a constant diameter and an orifice with a diverging angle. These are extensions of the nozzle geometry we investigated in our previous studies. Based on these simulations it is concluded that the extension of the constant diameter channel makes a negligible contribution to the jet’s length and its velocity. A change in the angle of the nozzle outlet orifice, however, has a significant effect on jet parameters. We find these kinds of simulation extremely useful for testing and optimizing novel nozzle designs.

Impact of alternative and fossil diesel fuels on internal flow of injection nozzle

This work presents a computational study about the effect of different fossil fuels (Diesel and GTL) and renewable (Farnesane and Biodiesel) on the characteristics of the nozzle fuel internal flow (speed flow, cavitation, mass flow rate and discharge coefficient). This investigation was focused on the pass of fuel from the volume around the tip of the injector needle to the nozzle holes. Several engine-operating conditions, characteristic of urban driving conditions, were tested. These conditions, characterized by their injection pressure and injection timing as well as the experimental rates of fuel injected, were simulated with all mentioned fuels. Solenoid operated seven holes injector, 0.15 mm orifice diameter was used. Results show the effect of fuel origin on the internal flow along the nozzle orifice of the injector. Among the results obtained are the following: at medium load the effect of the needle lift on the cavitation generation is more significant than the fluid circulation velocity and fuel origin impacts as follows: Biodiesel > GTL > Farnesane > Diesel; while, at medium or high engine speed, an increase of engine load causes a decrease of cavitation generation and fuel origin impacts as follows: Diesel >> Farnesane > GTL > Biodiesel.

Les Investigations of Periodic Cavitation Shedding with Special Emphasis On Three-Dimensional Asymmetry in a Scaled-Up Nozzle Orifice

The periodic shedding of cloud cavitation in a nozzle orifice has a significant influence on the flow field and may have destructive effects. Most of the existing research on the shedding of cloud cavitation in an orifice is based on experimental visualization with focus on the 2D motion of the re-entrant jet and the shedding mechanism. However, the actual cloud cavitation shedding in an orifice is a complex 3D process. Some limited signs of three-dimensionality and asymmetry in cylindrical orifices have been detected recently, but the 3D shedding characteristics remain unclear. In this paper, the cavitation regimes and periodic shedding process in the scaled-up nozzle orifice used by Stanley experiment were simulated with Large Eddy Simulation (LES). The re-entrant jet and periodic shedding mechanism, as well as the shedding frequency, were analyzed from 2D and 3D perspectives. The main results show that the simulated cavitation regimes and the 2D periodic shedding mechanism agree fairly well with the experimental observations, but more 3D features are revealed. By analyzing the 3D shedding process and the three-dimensionality caused by the inclination of the closure line, the three-dimensional asymmetric shedding mode with phase difference p is revealed. Based upon this finding, the shedding frequency and Strouhal number are calculated. The corresponding relationships between shedding frequencies and the frequency peaks of the power spectrum density (PSD) for pressure fluctuations are also confirmed. These results extend the understanding of the unsteady cavitating flow within nozzle orifices from 2D to 3D patterns.

Acoustic and Flow Aspects of Synthetic Jet Actuators with Chevron Orifices

The use of a chevron nozzle/orifice is one of the methods of heat transfer enhancement and noise reduction. In the case of synthetic jets, the number of papers on this topic is small. Therefore, a synthetic jet actuator with three different chevron orifices and one circular orifice is investigated. The aim of this study is to find the impact of orifice shape on centerline velocity (measured with a hot-wire anemometer) and determine if the chevron orifice reduces the generated noise. The sound pressure level was strongly dependent on the input actuator’s power, and only one chevron orifice ensured noise reduction for low power (p = 6; 8 W). At real power p = 12 W, the sound pressure level was lower for each chevron orifice actuator than in the case of the circular orifice actuator. It is shown that the application of a chevron nozzle does not have to provide noise reduction. It is important in the case of the design of new actuators that are to operate in places where noise levels should be limited (e.g., offices).