Needle Stroke Research Articles

Comparative tests of diesel injectors with serial and modernized nozzles

BACKGROUND: More than 60% of agricultural tractor failures are due to diesel engine failure. Half of diesel engine failures occur in the fuel supply system, where the majority is determined by the service life of diesel injector nozzles. AIMS: The purpose of this study was to increase the durability of the nozzle by upgrading the nozzle needle. MATERIALS AND METHODS: To increase the working life of the diesel injector nozzle, a new technical solution was proposed, which consists in applying a screw channel to the bearing surface of the needle. The presence of a screw channel results in axisymmetric pressure on the needle, which gives it increased stability and prevents the possibility of skewing and freezing. A patent has been received for this invention from the Russian. To confirm the expected effect, comparative laboratory tests were carried out with a serial and upgraded atomizer design. To carry out accelerated tests, “dusty” fuel was used, obtained by adding quartz sand abrasive. During the tests, the following were assessed: atomization quality, sealing cone tightness, hydraulic density, needle stroke and effective flow area. The assessment of wear of the mating surfaces of the nozzle depends on the value of the hydraulic density. RESULTS: As a result of the experiment, it was found that for serial injectors the limiting value of hydraulic density occurs after 2500 operating hours and is characterized by a violation of tightness. For modernized injectors, the hydraulic density limit occurs after operating 4300 engine hours. CONCLUSIONS: Applying a screw channel on the bearing surface of the needle allows you to increase the life of the diesel injector by 23.

Evaluation of Forces on the Needle for Regulation of Pelton Turbine Injector

Abstract In hydropower plants, the Pelton turbine is a commonly used hydraulic turbine where flow is regulated with a dual mechanism of needle and deflector. The needle is controlled by a servomotor and governor system, where the flow rate varies by adjusting the needle strokes. The needle is operated under the hydraulic force caused by the high-water pressure inside the injector acting on the needle surface. The objective of computing the force balance in a Pelton injector is to determine the force to be supplied by the servomotor. The closing trend is crucial to design the injector for safe operation during an emergency. In this study, the function of the needle and nozzle curve generalizes the variable needle surface area, allowing the geometric properties of the nozzle and needle to be suitable for the needle force evaluation. The single-axis force transducer, which is mounted on the needle rod, has been used in the experimental method for determining the needle forces. The experimental findings are compared to analytical calculations and serve as validation for the accuracy and reliability of the computed results obtained through the analytical approach.

Integration of a needle valve mechanism with cura slicing software for improved retraction in pellet-based material extrusion

Fused granular fabrication (FGF) is a cost-effective and increasingly popular additive technology that enables the production of parts using a wide range of exotic materials that are not typically available with material extrusion additive manufacturing. This paper presents a novel needle valve approach for flow control in a FGF system that uses flexibly connected screw extruders. The addition of a needle valve to the existing system allows complex travel moves to be performed without stringing, greatly increasing the available part complexity of the printer. The needle valve is actuated by one of the 3D printer’s extruder stepper motors and can be controlled by g-code generated by off-the shelf slicer software. This paper also proposes a mathematical model for predicting the oozing volume of the valve, which is the small quantity of material that escapes through the nozzle during valve actuation. This model is important for calibration and g-code generation, which could be integrated with commercial slicers to use this needle valve design without writing custom code. The model is tested experimentally, and results show a strong correlation between predicted and measured oozing volumes. The performance of the valve is also characterized in terms of flow rate versus needle position. Experiments showed that the needle stroke (the vertical distance that the needle travels between open and closed states of the needle valve) is the most important parameter in minimizing oozing. An optimized stroke of 0.4 mm was used, with a maximum flow rate of 346 mm3/min when using a nozzle inner bore diameter of 0.8 mm. Using the optimized valve parameters, parallel cube structures were printed to demonstrate the reduction of stringing, along with various demonstration parts including a 3Dbenchy benchmark print and a soft robotic actuator. Overall, this study demonstrates that needle valves present a reliable and low-cost approach for controlling the flow of polymer in FGF systems with a remotely connected screw extruder.

Parametric Investigation of Pelton Turbine Injector under Hydro-abrasive Erosion Conditions

In high-head Pelton turbines, the injector faces severe erosion due to suspended sediment leading to a reduction in turbine efficiency and higher maintenance costs. Here, the effects of design parameters such as the bend angle of the nozzle pipe, nozzle angle, and needle angle along with an operating parameter stroke ratio on hydro-abrasive erosion of Pelton turbine injector are numerically investigated. The Volume of Fluid (VOF) model was implemented for capturing the interphase between air and water; whereas, the SST k-ω model is used for modelling the turbulence effect. For tracking the discrete phase, a Eulerian-Lagrangian based Discrete Phase Model (DPM) is considered. The bend angles led to flow circulations in the nozzle pipe causing the non-uniform distribution of sediment concentration and uneven erosion patterns. Irrespective of the bend angle, the erosion hotspot in the needle is observed toward the bend side. Further, for larger sediment particles, higher bend angles lead to more erosion rate in both the nozzle and needle and must be avoided to prevent excessive damage. As the needle angle increases from 40° to 60° for a constant nozzle angle, the nozzle erosion rate increases by 70% and the needle erosion rate decreases by 99%. Hence, an injector design can be optimized in hydro-abrasive erosion conditions by selecting a needle angle between 40° and 60°. Further, the operation of the injector at too high and low a stroke ratio results in excessive erosion of the nozzle and needle, respectively. In this study, a stroke ratio of 0.45 is found to be the most suitable for hydro-abrasive erosion conditions. Moreover, the asymmetricity in the erosion pattern of the needle increases with needle angle and stroke ratio resulting in jet quality degradation, one major reason for efficiency reduction in Pelton turbines.

Numerical investigation of highly viscous droplet generation based on level set method

Piezo-driven needle valves are widely used in electronic packaging due to their fast response, high resolution and good dispensing consistency. However, the stable generation of high-viscosity droplets is one of the key issues to its packaging quality. To investigate the formation mechanism of the high-viscosity droplet. In this paper, a 2D finite element model of the drop-on-demand injection process of the high-viscosity droplet is established based on the level set method, the droplet formation and separation processes are numerically simulated, and the reliability of the simulation results is checked by comparing the outcomes with published data. Specifically, the detailed evolution of the high-viscosity droplet formation and separation process is gained by coupling the two-phase flow-level set method and the dynamic grid technique, and the pressure distribution in the injection chamber is further discussed and the effects of operating parameters on the droplet formation volume are examined. The results of the study show that the needle motion is the main factor of pressure fluctuations in the injection chamber. Moreover, we also found that among the parameters of needle stroke, nozzle diameter, supply pressure, fluid viscosity, and surface tension, the nozzle diameter has the most significant effect on droplet volume, while surface tension has the least effect on droplet formation.

Design and experiment of a new double needle type piezoelectric jetting dispenser

To improve the performance of piezoelectric (PZT) jetting dispensers in the electronic packaging industry and address the problems of oversized, easily fatigued elastic hinges and low repetition accuracy of conventional PZT jetting dispensers with a compliant mechanism-based lever, a new double needle PZT jetting dispenser prototype was developed. The advantage of the proposed structure over compliant mechanism-based lever was demonstrated by dynamics analysis. Firstly, the design stroke of the needle and the modal state of the dispenser body were analyzed using ANSYS. Secondly, the theoretical model of adhesive injection was established, the fluid pressure change process inside the nozzle during the working cycle of the jetting dispenser was simulated using Fluent, and the effects of the supply pressure and needle stroke on the injection speed of the droplet were investigated. Finally, a test bench was built to conduct the experiment, and the results showed that the supply pressure and the driving signal duty cycle between 20% and 80% were positively correlated with the size of droplet diameter, whereas the driving signal frequency was negatively correlated with the droplet diameter, thereby validating the proposed adhesive injection model. Under the experimental conditions, the highest operating frequency of the designed PZT jetting dispenser was 400 Hz, which is close to the high-frequency level of existing studies, and the minimum droplet diameter obtained was 0.36 mm, which is 0.1–0.2 mm less than that of the existing PZT jetting dispenser with a compliant mechanism drive, meeting the industry requirements for the working performance of a PZT jetting dispenser.

Theoretical research and maintenance of electro hydraulically controlled injectors

Introduction. Nowadays the part of the diesel engines for KamAZ-740 cars are operated with fuel equipment, in which the injectors have hydro mechanical control. Their main disadvantage is the low fuel pressure in front of the injector openings (less than 60 MPa) and the lack of fuel supply control.The use of injectors with electro hydraulic control (EHC) increases the pressure in the injector cavity up to 250 MPa and control the fuel injection process. The disadvantage of the injectors with EHC is a structural complexity of a control valve, the difficulty of its regulation and coding. The object of the study is the injectors of KamAZ-740 diesel engine with electro hydraulic control of the atomizer needle stroke.The purpose of this work is to carry out theoretical research and improve the methods of maintenance of injectors with electro hydraulic control (control valve regulation and coding), which will increase their reliability, durability and ensure a reduction in diesel fuel consumption.Research methods. The study of the nozzle control valve is theoretical and calculated. The paper proposes a calculation method and performs theoretical studies for the influence of pressure (50 – 250 MPa) on the value of the effective flow section and the diameter of the nozzle holes of the sprayer.For the injectors with EHC, the control valve regulation procedure has been clarified, which consists in the fact that at the beginning of regulation, the main force acting on the ball from the side of the maximum pressure in the control chamber (for example, 200 MPa) equal to 76 N is calculated (see Figure 4). Then the required spring force of 100 N is determined (20-40% more, see Figure 5). Next, the strength of the electromagnet is estimated at 140 N (20 – 40% more of the spring force, see Figure 6).The results of theoretical research. The results of computational (theoretical) studies for the effective flow section of the sprayer and the diameter of the nozzle holes, depending on the pressure P in front of the nozzle holes, are presented.The paper defines. 1. The forces acting on the ball (57 – 105 N) depending on the pressure in the control chamber (150 – 275 MPa). 2. Spring forces (40 – 140 N) with a stiffness of 40 N /mm, depending on its compression up to 3.5 mm. 3. The forces of the electromagnet (140 – 20 N) depending on the gap between the anchor and the core (0.2 – 0.5 mm).The method of restoring the required (rated) cyclic fuel supply when it changes as a result of replacing the control valve or adjusting is considered. The calculated values of fuel supply per cycle (mm3/cycle) from the activation time are given.Conclusion. The results of the study are intended for organizations and enterprises engaged in diagnostics, restoration, adjustment and coding of injectors with electro hydraulic control for the needle stroke of sprayers. The results of computational studies can be used to refine the methodology of maintenance of fuel systems with electronic control (Common Rail).

Displacement Model of Giant Magnetostrictive Actuator for Direct-Drive Injector

Aiming at the inherent problems of non-direct-drive injectors, such as long oil circuits and a difficult precise control of the needle stroke, based on the structure of a direct-drive injector and combined with the demand for the needle drive of a truck diesel injector, this study designs and fabricates a giant magnetostrictive actuator for direct-drive injectors. A simplified model of a giant magnetostrictive actuator is established, which mainly simplifies the magnetization model to facilitate the subsequent integrated modeling of the fuel injector. An actuator output displacement test system was built, and the output waveform and frequency characteristics of the actuator were analyzed. It was found that the experimental results were in good agreement with the calculated results of the model, and the average relative error of the amplitude was 3.26%, while the average relative error of the phase difference was 3.83%, which verifies the correctness of the model. This research enriches the modeling method of giant magnetostrictive actuators and has an important reference value for the research and design of fuel injectors.

Расчет и проектирование форсунок Common Rail с учетом их продольной податливости

The experience of creating electro-hydraulic Common Rail injectors led to the conclusion that the longitudinal deformation of their parts affects the fuel supply performance. The paper presents additions to the mathematical model of fuel supply in a diesel accumulator system. These additions describe the deformation of the injector parts. The longitudinal compliance of the parts changes the course of the needle, the volume of the cavities. As shown by the analysis of the operation of three electro-hydraulic injectors, longitudinal compliance leads to an increase in the injection start delay up to 2,0...2,5° of the camshaft turn, an increase in the needle stroke up to 40 %, an increase in injection pressure, a reduction in its duration, and difficulty in organizing multiple fuel injection. The comparison with experimental data and finite element calculations showed the applicability of the supplemented mathematical model as a part of the general model of fuel injection in diesel systems. Its use allows creating more valid tools for calculating fuel supply processes and taking into account compliance when designing Common Railinjectors.

Разработка универсального приспособления для определения хода иглы распылителей тепловозных и судовых дизелей

The main malfunctions of diesel and marine diesel injectors with an increase in the needle stroke by more than 50 % of the standard value are described — an increase in the temperature of the nozzle of the sprayer, a breakthrough of cylinder gases into the cavity of the sprayer and the formation of coke, a decrease in the pressure of the injected fuel. A method is proposed for determining the maximum stroke of the needle by measuring the length of the needle shank and its conditional reduction when the needle is placed on the saddle. The device and the principle of operation of the device for determining the maximum stroke of the spray needle are shown. Drawings of the main parts of the universal device for determining the needle stroke of sprayers with a diameter from 8 to 18 mm of diesel and marine diesel engines have been developed, a prototype is made. The method of determining the motion (stroke) of the needle of the spray nozzles of diesel engines using the developed device is given.

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Utilization of High-pressure Suction for EBUS-TBNA Sampling in Suspected Lung Cancer.

Background:Sample adequacy for immediate molecular testing is paramount in lung cancer. To date, several endobronchial ultrasound with transbronchial needle aspiration (EBUS-TBNA) sampling setups have been evaluated, however, the utilization of high-pressure suction (HPS) has not yet been reported.The aim of this study was to evaluate the utilization of HPS onto the needle and its effect on sample volume and adequacy for molecular testing in patients with suspected lung cancer.Methods:We retrospectively analyzed 128 consecutive EBUS-TBNA performed for suspected lung cancer. This was confirmed in 109 patients. Other diagnoses confirmed in 12, and 7 referred for surgery. Sixty-three patients (89 targets) had HPS (May to September 2020), and compared with 46 (72 targets) who had standard vacuum syringe suction (October 2019 to March 2020). Several parameters and outcomes evaluated, such as number of needle passes, needle strokes, needle size, target size, positron emission tomography avidity, procedure time, blood content score, sample volume, adequacy for molecular testing, as well as baseline patient characteristics and complication rate.Results:There was no difference between the 2 groups in all baseline parameters and characteristics. In multivariable analysis, HPS was associated with significantly higher sample volume (11.2 vs. 9.1 mm3, P=0.036) and less additional procedures to achieve full molecular profiling (2/52 vs. 7/40, P=0.042), in necrotic targets of non−small cell lung cancer. Diagnostic yields were comparable.Conclusion:HPS appears to be simple, no-cost, and safe, promising higher sample volume compared with vacuum syringe suction, and also appears to be associated with higher success of full molecular testing with less additional procedures, in non−small cell lung cancer necrotic targets.

Dynamic characteristics of piezoelectric jetting dispenser with a double spring recovery system

Piezoelectric jetting dispenser is widely used in microelectronic packaging field. The amplification mechanism with flexible hinge is often used in the piezoelectric jetting dispenser. Because the dynamic performance of the dispenser is affected by the deformation of flexure hinge, a model using rigid body amplification mechanism and double spring recovery is proposed in this paper. The mathematical model of the recovery system is established and the dynamic analysis is carried out. The working characteristics of piezoelectric ceramics are analyzed. With the increase of load stiffness, the maximum output force increases and the maximum output displacement decreases. With the decrease of needle stroke, the pressing force between the needle and the nozzle increases. Based on the double spring recovery system, the ADAMS simulation model is established, and the influence of the pre-compression of the double springs on the pressing force between the needle and the nozzle is studied.

Design and development of fibrous filter media induced by structural characteristics of needle punched nonwoven

This article discussed the structural changes influenced by punching parameters and their impact on the functional properties of needle punched nonwoven. Three punching parameters i.e., punch density, needle penetration depth and stroke frequency were considered as process variables. Three factors three levels Box Behnken experimental design was used for sample preparation. Newly proposed structural indices were used to evaluate the fibre orientation in X and Y direction of fabric using tracer fibre technique. It was found that measured functional properties of fabrics are well correlated with considered structural indices. The fibre coverage area inferred an increase but coefficient of fibre curliness and anisotropy of inclination angle of fibre observed a decrease, with the increase of punch density, needle penetration depth and stroke frequency. Mean flow pore size followed an initial decrease and then, increase, but filtration efficiency and pressure drop followed an initial increase and then, decrease with the increase of punch density, needle penetration depth and stroke frequency. Finally, process parameters were optimized to achieve a filter media with maximum filtration efficiency and minimum pressure drop.

Optimal design of a composite fibrous filter media through vertical integration of fibres in needle punched nonwoven

Present research work investigated the vertical integration of fibres by using newly proposed structural indices in needle punched nonwoven fabric. A new methodology was also proposed to measure the orientation of fibre in the Z direction of nonwoven fabric. The colour summarization technique was used to measure the percentage of fibre transfer from different layers and area covered by holes. The influence of punch density, needle penetration depth and stroke frequency on fabric structure and properties was studied and three-factor three-level Box-Behnken experimental design was used for sample preparation. The proposed structural indices provide useful information to explain the mechanism of vertical integration of fibres during punching operation. The bursting strength, mean flow pore size, filtration efficiency and pressure drop were highly influenced by considered punching parameters. A strong correlation was observed among measured properties and structural indices. Finally, punching parameters were optimised to achieve maximum filtration efficiency at minimum pressure drop.

Acoustic Properties of Kapok Fibre

Noise pollution has become an important burning issue in today’s modern industrial era after Air and Water pollution. Noise adversely affects human health and decrease productivity in various environments. The present study tries to study the acoustic properties of natural hollow fiber-kapok to develop a cost-effective and eco-friendly sound absorbing material as an alternative of conventional sound absorbing material which is harmful to the environment. Therefore, sound absorbing material consist of a blend of Natural hollow fibres Kapok and Modal were used to produced needle-punched nonwoven fabrics. A nonwoven needle punch method to produce fabrics was selected due to its technical merits and low production cost. Different nonwoven needle punched samples were produced by varying blend ratio, web mass per unit area, needle stroke and needle depth. After conducting several pre-trial, designs of the experiment was plan using Response surface methodology - Central composite design (RSM-CCD) method. Sound absorption coefficients of the sample were measured at a different frequency of incident sound using impedance tube test method ISO 10534-2. It was observed that sample with a higher percentage of kapok fiber showed higher sound absorbency at higher Frequency of 2000 to 6000 HZ. It was also found sound absorption coefficient increased with the increased in mass per unit area, needle stocks and needle depth.

Simulation and Experiment on Droplet Volume for the Needle-Type Piezoelectric Jetting Dispenser.

The needle-type piezoelectric jetting dispenser is widely applied in the microelectronics packaging field, and it is important to control the droplet size to ensure that the droplet jetting process is successful. In this study, we analyzed the influences of system parameters, such as air pressure, nozzle size, needle strokes, and liquid properties, on droplet size and morphology by considering the droplet formation and separation process through a numerical simulation. An experimental platform was also designed to verify the reliability of the simulations and further analyze strategies for controlling the droplet size. We found that the droplet volume can be increased with an increase in air pressure, needle strokes, and nozzle size until the flow-stream or satellite droplets appear. On the other hand, very small values of these parameters will lead to adhesion or micro-dots. A large nozzle and needle displacement should be chosen for the high-viscosity liquid in order to produce normal droplets. The results also show the recommended ranges of parameter values and suitable droplet volumes for liquids with different viscosities, and these findings can be used to guide the droplet volume control process for needle-type jetting dispensers.

Numerical prediction of efficiency and cavitation for a Pelton turbine

The first part of the paper illustrates the set-up and the methodologies adopted for the numerical analysis of the flow in a 6-jet Pelton turbine with vertical axis. At first, steady state simulations of flow in a distributor for three positions of needle stroke were performed. The results were used for the calculation of flow energy losses, analysis of jet quality and setting inlet boundary conditions for runner analysis. Runner analysis was done only for the maximal opening. The purpose of runner analysis for the model size was efficiency prediction. Numerical results were validated with the results from the test rig. Simulations for the prototype were done in order to check whether water sheets evacuating from the buckets impact the previous bucket and whether there is any interaction between the evacuating water sheets and the incoming jets. Analysis was done also for one nozzle operation. In the second part of the paper cavitation prediction for the prototype of a 2-jet Pelton turbine is presented. The problem, because of computational cost, was reduced to five runner buckets and one jet. A multiphase flow consists of water, air and water vapour. For cavitation pitting the vapour has to stick to the buckets and mass transfer from vapour to water has to happen in a very short time without the presence of air. With detailed analysis of numerical results it was concluded that in this case no cavitation pitting is expected.

Influence of Punching Parameters on Fibre Orientation and Related Physical and Mechanical Properties of Needle Punched Nonwoven

In this research work, the authors have investigated the needling effect on a non-woven prepared form the webs of equal basis weight. Punch density, needle penetration depth and strokes per minute are taken as variables. Initially, it was observed that the punching parameters were influencing the fibre orientation to a great extent. Subsequently, other properties were taken into study. It was found that higher punch density and penetration depth spreading the web in its cross direction, as a result, the basis weight and thickness reducing in a great extent and other properties like basis weight, tensile strength got affected. Secondly, with the change of stroke frequency, the width of the web, as well as nonwoven, also changed due to the spreading towards the cross direction. It was found that when strokes per min increased, the basis weight thickness decreased as well as other properties got affected.

A piezoelectric jetting dispenser with a pin joint

In order to improve the performance of the piezoelectric micro jetting dispenser used in opto-electronic packaging industry, a new structure of the needle with a pin joint is suggested. Dynamic characteristics of the proposed micro jetting dispenser has been improved because the needle can swing around the joint and motion interference between the needle and the guiding part is decreased with the new structure. Compared with the original dispenser, the needle stroke of the proposed dispenser is increased 1.8 times, and the velocity of the needle increased 1.4 times. The jet performance is also improved. Adhesives with viscosity of 1.8 Pa s are jetted by the new micro dispenser smoothly. The mathematical models and dynamics simulation model are established. The tested results agree with the simulation ones, which proves that the models and the structure of the proposed dispenser are reliable.