Injector Performance Research Articles

A dynamic model for the drive and electro-mechanics of a solenoid based electronic fuel injector

Over recent decades, multiple iterations of emissions standards have drastically reduced the amount of polluting emissions permissible when operating commercial vehicles. Electrically controlled fuel injection systems have been crucial to achieving these standards. To be highly effective, each of the injector’s sub-systems must perform near optimally; but how can the highest standards of performance be maintained for an extended time in an aggressive, high-temperature, high-vibration, Diesel engine environment? One way might be to implicitly monitor valve condition. As a first step towards this aim, this paper discusses models of the interactions between the electrical drive and electro-hydraulic valve sub-systems of an injector developed using Matlab-Simulink®. This is a critical element in understanding how implicit sensing procedures might be developed that could provide robust, micro-second accurate injector performance across the unit’s 1 000 000 mile lifetime. Consideration is given to how the electronic controller generates drive current in the electro-magnetic sub-system and how this develops the Maxwell Pulling Force within the unit. The effect of this force on control valve pin displacement is then explored. To create a usefully representative model requires that feed-forward and feedback interactions between sub-systems are included. Various system models are described and demonstrated to be useful by comparison of their outputs to known data sets.

Effect of injection conditions on mixing performance of pintle injector for liquid rocket engines

A movable pintle injector provides an effective throttling and high combustion stability in liquid rocket engines for performing space maneuvers safely. It has a movable pintle rod that causes a variable injection area. The mass flow of simulant and pintle opening affect the mixing performance of propellants, which is concerned in this paper. Therefore, the mixing performance is studied by the effect of mass flow rate of liquid, gas and pintle opening distance. The liquid is ejected radially from a center gap to form a thin liquid sheet which is broken by gas jet from an annular gap axially. To simulate this, the Lagrangian approach was employed. A 2D-axisymmetrical model is used in which Realizable K-epsilon model as a viscous model. Then, the primary and secondary breakup are performed by employing the single injection model and wave model based on Weber number. The spray angle and SMD are compared with the experimental data for validating the breakup model. The effect of increasing the mass flow rate of liquid at the lower pintle opening results a narrow dispersion angle that causes the poor mixing quality, which is recovered by increasing the mass flow rate of gas, where the dispersion angle is became wider. And, the effect of the pintle opening distance results a wider dispersion angle thereby the case with poor mixing quality at a lower opening distance is recovered. As a result, it is observed that the case with wider dispersion angle had a wide range of the mass fraction distribution of droplets along the radial position at X/Dpt = 5.00 than the case with narrow dispersion angle. The dispersion angle, spray angle and mixing quality are compared with the correlating parameter NK. The comparison showed that the mixing quality, spray angle and dispersion angle are not changed largely after NK = 0.83.

A check valve controlled laser-induced microjet for uniform transdermal drug delivery

A narrow nozzle ejects a microjet of 150 μm in diameter with a velocity of 140 m/s a by the laser-induced bubble expansion in the designed injector. The pulsed form of the driving force at a period of 10 Hz from the connected Er:YAG laser makes it possible for multiple microjet ejections aimed at delivery of drugs into a skin target. The pulsed actuation of the microjet generation is however susceptible to the air leak which can cause the outside air to enter into the momentarily de-pressurized nozzle, leading to a significant reduction of the microjet speed during the pulsed administering of the drug. In the present study, we designed a ball-check valve injector which is less prone to an unwanted air build up inside the nozzle by controlling the nozzle pressure to remain above ambient pressure at all times. The new device is rigorously compared against the reported performance of the previous injector and has shown to maintain about 97% of the initial microjet speed regardless of the number of shots administered; likewise, the drug penetration depth into a porcine skin is improved to 1.5 to 2.25 times the previously reported penetration depths.

Determination of critical operating and geometrical parameters in diesel injectors through one dimensional modelling, design of experiments and an analysis of variance

In this paper, a design of experiments and a statistical analysis of variance (ANOVA) are performed to determine the parameters that have more influence on the mass flow rate profile in diesel injectors. The study has been carried out using a one dimensional model previously implemented by the authors. The investigation is split into two different parts. First, the analysis is focused on functional parameters such as the injection and discharge pressures, the energizing time and the fuel temperature. In the second part, the influence of 37 geometrical parameters, such as the diameters of hydraulic lines, calibrated orifices and internal volumes, among others, are analysed. The objective of the study is to quantify the impact of small variations in the nominal value of these parameters on the injection rate profile for a given injector operating condition. In the case of the functional parameters, these small variations may be attributed to possible undesired fluctuations in the conditions that the injector is submitted to. As far as the geometrical and flow parameters are concerned, the small variations studied are representative of manufacturing tolerances that could influence the injected mass flow rate. As a result, it has been noticed that the configuration of the inlet and outlet orifices of the control volume, together with the discharge coefficient of the inlet orifice, among a few others, play a remarkable role in the injector performance. The reason resides in the fact that they are in charge of controlling the behaviour of the pressure in the control volume, which importantly influences injector dynamics and therefore the injection process. Variations of only 5% in the diameter of these orifices strongly modify the shape of the rate of injection curve, influencing both the injection delay and the duration of the injection process, consequently changing the total mass delivered.

Design and Analysis of a Double-Layer Magnetic Circuit Structure for High-Force Density Hybrid Fuel Injector

This paper proposes the design and analysis of a double-layer magnetic circuit structure for a high-force density hybrid fuel injector. In general, fuel injector models have disadvantages such as a significant leakage flux and magnetic saturation; therefore, a finite-element method is used to detail the model design and reduce the leakage flux from the electromagnet pole to the lead pipe. This change can help improve the fuel injector performance. In addition, a permanent magnet (PM) is inserted to increase the force density. Moreover, the no-load performance and demagnetization characteristic of the injector are analyzed according to the injector’s working environment. The optimized hybrid fuel injector model with a PM shows substantially improved performance compared to a conventional design.

Impact of fuel on real diesel injector performance in field test

This work assessed the potential impact of diesel fuel complying with the EN 590 standard on real diesel injector performance in a long-term field test. Injector deposit formation has been attributed to diesel fuel instability during storage in relation to fuel injection equipment (FIE) operating conditions. These deposits can occur at different locations within FIE and impact on fuel spray characteristics, causing threats to the proper functioning of the fuel injectors. The long-term field tests were performed with two new vehicles fitted with an advanced common rail (CR) fuel injection system, meeting the requirements of Euro 5. A high quality diesel fuel meeting the requirements of the EN 590 standard was used for both vehicles. A scanning electron microscope with energy dispersive X-ray spectrometry (EDS) and an electron backscatter diffraction (EBSD) detector was used for observation and imaging of external, coking injector deposits around the nozzle fuel-flow holes and internal diesel injector deposits (IDID) in the area of the nozzle needle. An elemental analysis was performed by energy dispersive X-ray spectroscopy analysis (EDX). Evaluation of the macroscopic characteristics revealed that, despite the formation of external and internal injector deposits, there was no measurable loss of flow through the injectors. As a result, while injector deposits have adverse impacts on some injector macroscopic characteristics, they did not cause a significant deterioration of the injectors’ operating characteristic and their real performance.

Longitudinal phase space tomography using a booster cavity at PITZ

The knowledge of the longitudinal phase space (LPS) of electron beams is of great importance for optimizing the performance of high brightness photo injectors. To get the longitudinal phase space of an electron bunch in a linear accelerator a tomographic technique can be used. The method is based on measurements of the bunch momentum spectra while varying the bunch energy chirp. The energy chirp can be varied by one of the RF accelerating structures in the accelerator and the resulting momentum distribution can be measured with a dipole spectrometer further downstream. As a result, the longitudinal phase space can be reconstructed.Application of the tomographic technique for reconstruction of the longitudinal phase space is introduced in detail in this paper. Measurement results from the PITZ facility are shown and analyzed.

Modeling fracturing pressure parameters in predicting injector performance and permeability damage in subsea well completion multi-reservoir system

The significance of fracturing parameters which are aquifer integrity, rock properties, thermal stress, fracturing pressure and produced water quality to alter permeability damage, cake formation and injectivity performance was highlighted in a robust improved internal filtration—hydraulic model and permeability reduction model incorporating a R_{text{AT}} (c) function. The studied system is an injection well multi-reservoir formations. Field data obtained from the log and field reports and improved model were used to simulate injector, fracturing and permeability damage performance. Thus, data requirements in the R_{text{AT}} (c) function which are rock properties, water quality, aquifer integrity, fractures rates and pressures parameters were assessed for its impact on injector performance and permeability damage simulated in MATHLAB and COMSOL multi physics environment. The profile of injector performance and damage reservoir permeability to changes in rock properties and aquifer integrity were demonstrated to have a profound influence on both fracturing phenomena. Thus, sustainable re-injection scheme was shown as a direct consequence of rock mechanics parameters, well hydraulics aquifer integrity that largely depends on the initial concentration of active constituents of the produced water as well as physic-chemical properties of the host aquifer.

Design Optimization of a Vaneless “Fish-Friendly” Swirl Injector for Small Water Turbines

Large-scale power generation and delivery to remote locales is often prohibitively expensive, due in part to the excessive costs of delivering the materials required to build the necessary infrastructure. In addition, these facilities can have deleterious effects on the local ecosystem. With their reduced physical and environmental footprints, small-scale run-of-river hydroelectric facilities capable of generating power from the modest head provided by streams and rivers are attractive alternatives. Concern remains, however, for the health and safety of the local fish population in these waterways. In order to further reduce the impact of small-scale axial turbine-based hydroelectric facilities on the local fauna, AlfaStar Hydro has proposed a vaneless swirl injector to replace traditional inlet guide vanes (IGVs), as well as a “fish-friendly” rotor designed to rotate relatively slowly and with wide passages between the blades to enable the safe egress of fish drawn into the turbine. Herein, we perform a numerical study of the flow development in the vaneless swirl injector as a function of the number of revolutions and the pitch angle of the rifling in the absence of a rotor toward maximizing turbine efficiency. Swirl intensity, pressure loss in the injector, and axial and circumferential velocity distributions are incorporated as performance metrics into an objective function to optimize the casing design. Results indicate that the number of revolutions of the injector has considerably less influence on overall injector performance than does pitch angle. The casing with the best predicted performance consists of four revolutions at a pitch angle of 25 deg.

Gas Gun Model and Comparison to Experimental Performance of Pipe Guns Operating with Light Propellant Gases and Large Cryogenic Pellets

Injection of multiple large (~10 to 30 mm diameter) shattered pellets into ITER plasmas is presently part of the scheme planned to mitigate the deleterious effects of disruptions on the vessel components. To help in the design and optimize performance of the pellet injectors for this application, a model referred to as “the gas gun simulator” has been developed and benchmarked against experimental data. The computer code simulator is a Java program that models the gas-dynamics characteristics of a single-stage gas gun. Following a stepwise approach, the code utilizes a variety of input parameters to incrementally simulate and analyze the dynamics of the gun as the projectile is launched down the barrel. Using input data, the model can calculate gun performance based on physical characteristics, such as propellant-gas and fast-valve properties, barrel geometry, and pellet mass. Although the model is fundamentally generic, the present version is configured to accommodate cryogenic pellets composed of H2, D2, Ne, Ar, and mixtures of them and light propellant gases (H2, D2, and He). The pellets are solidified in situ in pipe guns that consist of stainless steel tubes and fast-acting valves that provide the propellant gas for pellet acceleration (to speeds ~200 to 700 m/s). The pellet speed is the key parameter in determining the response time of a shattered pellet system to a plasma disruption event. The calculated speeds from the code simulations of experiments were typically in excellent agreement with the measured values. With the gas gun simulator validated for many test shots and over a wide range of physical and operating parameters, it is a valuable tool for optimization of the injector design, including the fast valve design (orifice size and volume) for any operating pressure (~40 bar expected for the ITER application) and barrel length for any pellet size (mass, diameter, and length). Key design parameters and proposed values for the pellet injectors for the ITER disruption mitigation systems are discussed.

Quantitative and qualitative analysis of the mass transfer and dispersion of methane injection under continuous mode shooting

This study investigated the performance of a natural gas injector with regard to its mass transfer and fuel dispersion. A newly developed gas injector was fabricated with an injector nozzle size that was optimized based on computational fluid dynamics. High-speed injection images were analyzed with the injection parameters related to injection penetration length, injection cone angle, injection time, and injection area. Both λ (the ratio of mass per injection area) and JP(a rate of change of pixel number to change of penetration length) were employed to estimate the quantity and quality of the dispersion. As a result, a uniform distribution and well-dispersed gas properties could be explained with low λ and high JP values. The λ and JP results could be a very useful index used to quantitatively and qualitatively evaluate the performance of natural gas injection.

Geometric Effects on Liquid Oxygen/Kerosene Bi-Swirl Injector Flow Dynamics at Supercritical Conditions

A systematic study is carried out to investigate the flow dynamics and mixing of liquid oxygen/kerosene bi-swirl injectors at supercritical conditions. The theoretical framework is based on the full conservation laws and accommodates real fluid thermodynamics and transport theories over the entire range of fluid states. Turbulence closure is achieved using large-eddy simulation. A grid independence study was conducted to ensure appropriate numerical resolution and accurate flow physics. The liquid-film atomization and breakup processes at subcritical conditions are replaced by the turbulent mixing and diffusion processes typical at supercritical conditions. Various injector geometries, with differences in the recess region, post thickness, and kerosene annulus width, are examined to explore the influence of geometry on mixing efficiency and flow dynamics. A critical mixing line is defined to measure the mixedness of propellants. The presence of a recess region is found to advance the interaction of liquid oxygen and kerosene and improve mixing efficiency. A thicker post of the inner swirler or a wider annulus leads to a larger spreading angle of the inner liquid oxygen film and intercepts the outer kerosene film in a broader area, thereby enhancing mixing in the recess region. The flow structures in the recess region are complex, and the kerosene mass fraction decreases significantly near the post surface, which might increase the thermal load on the surface in the case of reacting flows. Appropriate selection of the post thickness, recess length, and annulus width must be carefully determined for optimum injector performance. The present study offers useful information in bi-swirl injector design and in studies of the underlying flow physics of swirl injection under supercritical conditions.

Influence of fuel properties on internal nozzle flow development in a multi-hole diesel injector

Fuel physical properties are known to influence in-nozzle flow behavior, in turn affecting spray formation in internal combustion engines. A series of 3D simulations was performed to model the internal nozzle flow in a five-hole mini-sac diesel injector. The goal of the study was to evaluate the behavior of two gasoline-like fuels (full-range naphtha and light naphtha) and compare them against n-Dodecane, selected from a palette used as a diesel surrogate. Simulations were carried out using a multi-phase flow representation based on the mixture model assumption with the Volume of Fluid (VOF) method, and including cavitation effects by means of the Homogeneous Relaxation Model (HRM). Validated methodologies from our previous studies were employed to account for full needle motion. Detailed simulations revealed the influence of the fuel properties on injector performance, injected fuel energy and propensity to cavitation. The three fuels were compared with respect to global parameters such as mass flow rate and area contraction coefficients, and local parameters such as pressure and velocity distribution inside the sac and orifices. Parametric investigations were also performed to understand the fuel response to changes in the fuel injection temperature, injection pressure, and geometry details. Cavitation magnitude was observed to be strongly associated with the values of saturation pressure. Owing to their higher volatility, the two gasoline-like fuels were observed to cavitate more than n-Dodecane across all the investigated conditions. While at full needle lift cavitation was reduced for all fuels, during the injection transients the gasoline-like fuels showed more propensity to cavitate inside the orifice and seat regions. This is expected to have a profound influence on nozzle erosion. Although full-range and light naphtha have lower densities compared to n-Dodecane, owing to their lower viscosity, the mass flow rate differences between the naphtha fuels and n-Dodecane were small. The analysis of fuel energy content showed that the higher lower heating value (LHV) of light naphtha helped compensate for the slightly lower total delivered mass.

Experimental characterization of high pressure gasoline direct injection sprays

An experimental investigation of multihole gasoline direct injection sprays at high injection pressures in a quiescent test chamber is carried out. A multihole injector with six injection holes and 60° spray cone angle is used for this purpose. High-speed Mie-scattering and high-speed Schlieren visualisations are used to characterise vapour penetration, liquid penetration, spray angle and velocity under typical engine high load and low load conditions. Variations of chamber conditions are also investigated in order to assess the effects of chamber temperature, density and pressure on the spray characteristics. The important chamber parameters are identified which affect the performance of multihole injectors in spark ignition engines.

Deterioration of the fuel injection parameters as a result of Common Rail injectors deposit formation

The article describes external and internal Common Rail injectors deposits formed in dynamometer engine simulation tests. It discussed not only the key reasons and factors influencing injector deposit formation but also the resulting way of fuel preparation and engine test approaches. The effects of external coking deposit as well as internal deposits two most common form types that is carboxylic soaps and organic amides on deterioration of the fuel injection parameters were assessed. The assessments covered both deposits impacts on quantitative and qualitative changes of the injectors diagnostic parameters and as a result on deterioration of the injector performance. Finally the comparisons between characteristic of dosage of one fuel injector before test and characteristics few injectors after engine tests of simulated deposit formation were made.

Positron injector of the VEPP-4M collider

The positron injector for the VEPP-4M storage ring and its successful 40-year operation are described. The injector performance has been substantially enhanced in a number of successive upgrades, enabling precision measurements of particle masses at VEPP-4M.

Hydrodynamic injection on electrophoresis microchips using an electronic micropipette

Here we report for the first time the use of an electronic micropipette as hydrodynamic (HD) injector for microchip electrophoresis (ME) devices. The micropipette was directly coupled to a PDMS device, which had been fabricated in a simple cross format with two auxiliary channels for sample volume splitting. Sample flow during the injection procedure was controlled in automatic dispenser mode using a volume of 0.6µL. Channel width and device configuration were optimized and the best results were achieved using a simple cross layout containing two auxiliary channels with 300µm width for sample splitting. The performance of the HD injector was evaluated using a model mixture of high-mobility cationic species. The results obtained were compared to the data obtained via electrokinetic (EK) injection. Overall, the HD provided better analytical performance in terms of resolution and injection-to-injection repeatability. The relative standard deviation (RSD) values for peak intensities were lower than 5% (n=10) when the micropipette was employed. In comparison with EK injection, the use of the proposed HD injector revealed an unbiased profile for a mixture containing K+ and Li+(300 µmol L−1 each) over various buffer concentrations. For EK injection, the peak areas decreased from 2.92 ± 0.20–0.72 ± 0.14Vs for K+ and from 1.30 ± 0.10–0.38 ± 0.10Vs for Li+ when the running buffer increased from 20 to 50mmolL−1. For HD injection, the peak areas for K+ and Li+ exhibited average values of 2.48±0.07 and 2.10±0.06Vs, respectively. The limits of detection (LDs) for K+, Na+ and Li+ ranged from 18 to 23µmolL−1. HD injection through an electronic micropipette allows to automatically dispense a bias-free amount of sample inside microchannels with acceptable repeatability. The proposed approach also exhibited instrumental simplicity, portability and minimal microfabrication requirements.

Disintegration process and performance of a coaxial porous injector

In order to understand the breakup performance of coaxial porous injectors, the sprays of coaxial porous injectors with two different porous material cylinder lengths were compared with those of conventional shear coaxial injectors. To allow comparison, the wall injection lengths were designed to be equivalent to the value of the recess depth. Cold flow sprays were visualized using back-lit photography methods and analyzed quantitatively with a laser diffraction apparatus, in order to study the effects of the momentum flux ratio and Weber number on the breakup for each type of injector. In case of the shear coaxial injector, the large liquid core was observed in low air mass flow rate condition. However, the destabilization of the liquid jet from the coaxial porous injector is almost complete within the inner region, near the injector face plate. Additionally, better breakup performance in low gas flow rate condition was obtained when the porous cylinder length decreased, while the shear coaxial injectors showed better breakup efficiency when the recess length increased. In conclusion, the different breakup process caused by the radial momentum in the inner region of the porous injector disintegrated the liquid core.

Effects of heated ethanol on retrofit single-hole gasoline injector performance

The main aim of this work is to explore the injector performance in terms of fuel mass flow rate and discharge coefficient when ethanol is in use with gasoline injectors at elevated temperatures. The operating fuel injection was at the pressures between 0.2 and 0.4MPa and the temperatures in a range of 40–80°C. A fuel injector test cell with electronic control for injection pulse, timing and pressure was set to 120Hz and 60min injection duration to drive three single-hole 0.34mm nozzle diameter injectors. The fuels were injected into a known volume flask at quiescence atmospheric pressure and weighed to attain the fuel mass flow rates. By this manner, the discharge coefficient can be calculated by the assumptions of quasi steady, incompressible and one dimensional flow through each injector. When operating at 40°C injection temperature, ethanol delivered greater fuel amounts than gasoline resulting in higher discharge coefficients. The temperatures of the injected fuels are shown to affect the fuel flow rates and the discharge coefficients.

Numerical Simulations of Internal Flow in an Aircraft Engine Pressure Swirl Atomizer

The internal flow and the liquid structure at the nozzle exit are investigated in a typical pressure swirl atomizer for aeroengine applications under an isothermal nonreacting environment using a two-phase flow modeling according to the volume-of-fluid numerical methodology. A parametrical analysis is performed to investigate the effect of operating conditions on the injector performances and the characteristics of the liquid jet exiting the nozzle. The liquid film thickness at the nozzle exit and the injector discharge coefficient predicted by the simulations are compared against commonly used correlations available in the literature. The influence of the turbulence model on the injector performances is also analyzed using three different models: the renormalization group model, the Reynolds stress model, and the large-eddy simulation model.