Injector Performance Research Articles

Visualizing aerosol-particle injection for diffractive-imaging experiments.

Delivering sub-micrometer particles to an intense x-ray focus is a crucial aspect of single-particle diffractive-imaging experiments at x-ray free-electron lasers. Enabling direct visualization of sub-micrometer aerosol particle streams without interfering with the operation of the particle injector can greatly improve the overall efficiency of single-particle imaging experiments by reducing the amount of time and sample consumed during measurements. We have developed in-situ non-destructive imaging diagnostics to aid real-time particle injector optimization and x-ray/particle-beam alignment, based on laser illumination schemes and fast imaging detectors. Our diagnostics are constructed to provide a non-invasive rapid feedback on injector performance during measurements, and have been demonstrated during diffraction measurements at the FLASH free-electron laser.

Response of different injector typologies to dwell time variations and a hydraulic analysis of closely-coupled and continuous rate shaping injection schedules

The multiple injection performance of Common Rail injectors has been analyzed at a hydraulic test rig as the dwell time was varied. The dependence of the injected volume on the dwell time has been investigated for direct acting piezoelectric and hydraulically-controlled (or indirect-acting) servo injectors. The injected fuel volumes in the long dwell-time range have been shown to be affected by the pressure waves that travel along the high pressure circuit for hydraulically-controlled servo injectors. On the other hand, the influence of pressure-wave-induced disturbances on multiple injection performance has been shown to be negligible for direct acting piezoelectric injectors.An analysis of closely-coupled injections has been conducted on a solenoid injector. When the dwell time is progressively reduced below a critical value, an increase in the fuel quantity that is injected in the second shot is observed. Injection fusion phenomena occur as the dwell time is diminished below a certain threshold and a maximum in the fuel volume, which is injected during the joint injections, is eventually detected for a very short electric dwell time value close to 100μs. The cycle-to-cycle dispersion around this dwell time value results to be reduced significantly.A previously developed 1D model of the fuel injection system has been applied to analyze the injector transients. Detailed knowledge of the injection dynamics in the short dwell time region is of fundamental importance to optimize the implementation of both discontinuous and continuous rate shaping strategies. At present, there is a great deal of interest in these advanced schedules, since they can allow a minimization of soot emissions, fuel consumption and combustion noise to be achieved in diesel engines equipped with indirect-acting injectors.

Fuel temperature influence on the performance of a last generation common-rail diesel ballistic injector. Part I: Experimental mass flow rate measurements and discussion

An experimental study is conducted in this paper in order to assess the influence of the fuel temperature on the performance of a last generation common-rail ballistic solenoid injector. Mass flow rate measurements are performed for a wide range of temperatures, extending from 253 to 373K, representative of all the possible operating conditions of the injector in a real diesel engine, including cold start. The high pressure line and the injector holder were refrigerated, making it possible to carefully control the fuel temperature, whereas measurements at cold conditions were carried out with the help of a climatic chamber. Relevant features such as stationary mass flow, injection delay or the behaviour at the opening and closing stages are analysed together with parameters governing the flow, such as the injector discharge coefficient.Results show an important influence of the fuel temperature, especially at low injection pressure. A low injection temperature results in a lower stationary mass flow rate, whereas injection duration is also reduced. These results will be explained mainly through the fuel properties variation induced by temperature, together with the ballistic nature of the injector used for the study.A second part of the paper introduces a one-dimensional model that makes it possible to reproduce these results and further explain them through the analysis of other relevant variables, such as the needle lift.

Fuel temperature influence on the performance of a last generation common-rail diesel ballistic injector. Part II: 1D model development, validation and analysis

A one-dimensional model of a solenoid-driven common-rail diesel injector has been developed in order to study the influence of fuel temperature on the injection process. The model has been implemented after a thorough characterization of the injector, both from the dimensional and the hydraulic point of view. In this sense, experimental tools for the determination of the geometry of the injector lines and orifices have been described in the paper, together with the hydraulic setup introduced to characterize the flow behaviour through the calibrated orifices.An extensive validation of the model has been performed by comparing the modelled mass flow rate against the experimental results introduced in the first part of the paper, which were performed for different engine-like operating conditions involving a wide range of fuel temperatures, injection pressures and energizing times. In that first part of the study, an important influence of the fuel temperature was reported, especially in terms of the dynamic behaviour of the injector, due to its ballistic nature. The results from the model have allowed to explain and further extend the findings of the experimental study by analyzing key features of the injector dynamics, such as the pressure drop established in the control volume due to the control orifices performance or the forces due to viscous friction, also assessing their influence on the needle lift laws.

Effects of Wall-Injection Length on Spray and Combustion in a Coaxial Porous Injector

The mixing performance of an injector determines the combustion performance of a bipropellant rocket engine. In the previous study, a novel coaxial porous injector concept was developed to improve the mixing performance of a shear coaxial injector. It demonstrated a higher characteristic velocity efficiency than that of a typical shear coaxial injector. To clarify the efficiency-improving mechanism of a coaxial porous injector, the combustion flowfields of both injectors were visualized using a high-speed shadowgraph technique. The effect of geometry factors on the spray core length and the combustion performance as well as the differences in the reactive spray behavior between the coaxial porous injector and the shear coaxial injector were observed. The coaxial porous injector with a different wall-injection length showed higher characteristic velocity efficiencies, shorter spray core lengths, and thicker phase-change patterns at the spray core boundary. Changes in wall-injection length had a nonmonotonic effect on both the spray core length and the characteristic velocity efficiency. As opposed to the expected results, the coaxial porous injector with the highest combustion efficiency showed the longest spray core length. The phase-change pattern width, caused by the evaporation of liquid fuel droplets, was proportional to the efficiency.

Model Based Design approach for Component Design Implementation in Automotive System Development

Modeling the systems helps in reducing the amount of time spent in performance evaluation by physical testing. Elaborated and expensive tools and tool chains assist during the development of automotive systems. The paper introduces a model based design of automotive components of vehicle and verifies the model. Simscape support an environment for modeling and simulating the physical systems spanning the magnetic, electrical, mechanical and other physical domains. Simulating the system with parameters got from field data helps in real-time capacity determination. Also, In this paper aims at developing a finite model of the solenoid injector and facilitate measurement, monitoring and prediction of the injector performance. The model is to be simulated using MATLAB/Simulink and the results obtained are to be validated with experimental data.

Macroscopic spray characteristics of wide distillation fuel (WDF)

In this study, the performance of piezoelectric and solenoid injectors were compared. With a piezoelectric injector, the spray characteristics of kerosene and G50 (gasoline/diesel blend fuel), which are kinds of WDF, were investigated and compared to diesel. The characteristics such as spray penetration, spray velocity, spray angle and air entrainment were used to understand the spray behaviour of the test fuels. The results indicate that the piezoelectric injector shows significant improvement over the conventional solenoid injector in injection response and needle opening speed, which enables precise and rapid control of injection. The trade-off effects of charge density and injection pressure on spray penetration and spray velocity are quite clear, while spray angle is almost insensitive to injection pressure. Kerosene and G50 give smaller but similar spray penetration and velocity compared to diesel. The spray angle of kerosene and G50 are larger compared to diesel. The spray volume and mass of entrained air for kerosene and G50 are higher compared to diesel, which indicates kerosene and G50 can form better fuel–air mixing, which is very important for the performance of engine when fuelled by WDF.

Optimization of magnetic circuit configuration for GDI injector based on MOSA algorithm

GDI (Gasoline Direct injection) injector is one of the most important components in GDI engine, which requires high precision and dynamic response. The magnetic circuit configuration as the key part of GDI injector which decides the magnetic force, dynamic response, energy loss and temperature rising. All these factors directly or indirectly impact on the GDI injector comprehensive performance. The aim of this investigation is to optimize the magnetic circuit configuration and improve the comprehensive performance for GDI injector. The specific factors that influence the optimum operation of the GDI injector have been analyzed based on physical theories. MOSA (Multi Objective Simulated Annealing) algorithm is used to implement the multi-objective parameters optimization for the magnetic circuit configuration. To validate the optimization results the multi-physical fields coupling simulation based on Finite Element Method (FEM) is used, and the simulation results were validated by experiments. Compared the initial configuration to the optimized one, the comprehensive performances have great improvement after optimization. The results indicate that the methods can be used to GDI injector concept design and performances prediction. The essence of the GDI injector is an ultra-high-speed and giant force solenoid valve which required high frequency response,high power density and downsizing. Simultaneously, when GDI injector work- ing, multi-physical fields coupling effect on magnetic circuit cause the coupling mechanism is compli- cate to reveal. Since 1970s, with the rapid development of mathematics and computer sciences, a lot of new algorithm and new number simulation methods were utilized in industry. With the development of the electronic technology, electronic fuel injector have chance to be used in combustion engine. But now, the environmental regulations are much more stringent conventional design methodology cannot satisfy the requirements of combustion engine for high efficiencyand clean emission. Therefore, quicker dynamic response, higher power density and smaller size GDI injectors are necessary. That means new methods should be used to improve the comprehensive performance essentially.

Boundary condition and fuel composition effects on injection processes of high-pressure sprays at the microscopic level

Detailed imaging of n-dodecane and ethanol sprays injected in a constant-flow, high-pressure, high-temperature optically accessible chamber was performed. High-speed, diffused back-illuminated long-distance microscopy was used to resolve the spray structure in the near-nozzle field. The effect of injection and ambient pressures, as well as fuel temperature and composition have been studied through measurements of the spray penetration rates, hydraulic delays and spreading angles. Additional information such as transient flow velocities have been extracted from the measurements and compared to a control-volume spray model. The analysis demonstrated the influence of outlet flow on spray development with lower penetration velocities and wider spreading angles during the transients (start and end of injection) than during the quasi-steady period of the injection. The effect of fuel composition on penetration was limited, while spreading angle measurements showed wider sprays for ethanol. In contrast, varying fuel temperature led to varying penetration velocities, while spreading angle remained constant during the quasi-steady period of the injection. Fuel temperature affected injector performance, with shorter delays as fuel temperature was increased. The comparisons between predicted and measured penetration rates showed differences suggesting that the transient behavior of the spreading angle of the sprays modified spray development significantly in the near-field. The reasonable agreement between predicted and measured flow velocity at and after the end of injection suggested that the complete mixing assumptions made by the model were valid in the near nozzle region during this period, when injected flow velocities are reduced.

Detailed design optimization of the MITICA negative ion accelerator in view of the ITER NBI

The ITER Neutral Beam Test Facility (PRIMA) is presently under construction at Consorzio RFX (Padova, Italy). PRIMA includes two experimental devices: an ITER-size ion source with low voltage extraction, called SPIDER, and the full prototype of the whole ITER Heating Neutral Beams (HNBs), called MITICA.The purpose of MITICA is to demonstrate that all operational parameters of the ITER HNB accelerator can be experimentally achieved, thus establishing a large step forward in the performances of neutral beam injectors in comparison with the present experimental devices.The design of the MITICA extractor and accelerator grids, here described in detail, was developed using an integrated approach, taking into consideration at the same time all the relevant physics and engineering aspects. Particular care was taken also to support and validate the design on the basis of the expertise and experimental data made available by the collaborating neutral beam laboratories of CEA, IPP, CCFE, NIFS and JAEA. Considering the operational requirements and the other physics constraints of the ITER HNBs, the whole design has been thoroughly optimized and improved. Furthermore, specific innovative concepts have been introduced.

Production of high current proton beams using complex H-rich molecules at GSI.

In this contribution, the concept of production of intense proton beams using molecular heavy ion beams from an ion source is described, as well as the indisputable advantages of this technique for operation of the GSI linear accelerator. The results of experimental investigations, including mass-spectra analysis and beam emittance measurements, with different ion beams (CH3(+),C2H4(+),C3H7(+)) using various gaseous and liquid substances (methane, ethane, propane, isobutane, and iodoethane) at the ion source are summarized. Further steps to improve the ion source and injector performance with molecular beams are depicted.

Injection performance and cavitation analysis of an advanced 250 MPa common rail diesel injector

The present work is to demonstrate the working process and injection performance of a new-type diesel injector, and to make a contrastive analysis of cavitation which potentially occurs near control-valves of the new and another conventional injector. The advanced injector is developed for 250MPa common rail injection systems of medium or heavy duty commercial vehicles. The originality is the development of a novel control-piston with the outward appearance of a poppet valve. The control-piston can automatically move downwards or upwards owing to pressure changes in related hydraulic chambers, and consequently appropriately activates or deactivates the function of additional inflowing control-orifices to improve system responsiveness.The injection performance demonstration was carried out by one-dimensional (1D) hydraulic mechanical simulation in combination with the experimental data input of actuators. On the other hand the cavitation evaluations, in both the conventional and new structures, were studied numerically by computational fluid dynamics (CFD) based on nonlinear cavitation model and dynamic grid method. Additionally the CFD model was validated against experimental result in terms of mass flow rate of backflow fuel in the conventional structure. The 1D simulation result shows that the new injector is capable of achieving multi-injection and ramp-shaped injection flow rate; closing-delay of injection can be reduced from 1.232 to 0.758ms, and backflow fuel quantity index can be decreased to 14.1:182.6 which means a reduction of 15.5%. As regards to the contrastive analysis of cavitation, the CFD simulation result of the new structure shows several improvements as follows: a lower velocity field (below 311.88m/s) near the control-valve, cavitation no longer occurring in the guide-hole, and a reduction of 70.22% in mass exchange rate between vapour–liquid phases near the sealing annulus of valve seat.

Numerical Investigation of the Spear Valve Configuration on the Performance of Pelton and Turgo Turbine Injectors and Runners

This paper uses two modern commercial cfd software packages to compare the performance of a standard and improved impulse turbine injector developed in a previous study. The two injector designs are compared by simulating the two-dimensional (2D) axis-symmetric cases as well as full three-dimensional (3D) cases including the bend in the branch pipe and the guide vanes. The resulting jet profiles generated by these simulations are used to initialize the inlet conditions for a full Pelton and Turgo runner simulation at different operating conditions in order to assess the impact of the injector design on the performance and efficiency of a real impulse turbine. The results showed that the optimized injector design, with steeper nozzle and spear angles, not only attains higher efficiencies in the 2D and 3D injector simulations but also produces a jet which performs better than the standard design in both the Pelton and the Turgo runner simulations. The results show that the greatest improvement in the hydraulic efficiency occurs within the injector with the improved design, showing an increase in efficiency of 0.76% for the Turgo 3D injector and 0.44% for the Pelton 3D injector. The results also show that in the case of the 3D injector, the improved injector geometry produces a jet profile which induces better overall runner performance, giving a 0.5% increase in total hydraulic efficiency for the Pelton case and 0.7% for the Turgo case.

Evaluation of friction heating in cavitating high pressure Diesel injector nozzles

Variation of fuel properties occurring during extreme fuel pressurisation in Diesel fuel injectors relative to those under atmospheric pressure and room temperature conditions may affect significantly fuel delivery, fuel injection temperature, injector durability and thus engine performance. Indicative results of flow simulations during the full injection event of a Diesel injector are presented. In addition to the Navier-Stokes equations, the enthalpy conservation equation is considered for predicting the fuel temperature. Cavitation is simulated using an Eulerian-Lagrangian cavitation model fully coupled with the flow equations. Compressible bubble dynamics based on the R-P equation also consider thermal effects. Variable fuel properties function of the local pressure and temperature are taken from literature and correspond to a reference so-called summer Diesel fuel. Fuel pressurisation up to 3000bar pressure is considered while various wall temperature boundary conditions are tested in order to compare their effect relative to those of the fuel heating caused during the depressurisation of the fuel as it passes through the injection orifices. The results indicate formation of strong temperature gradients inside the fuel injector while heating resulting from the extreme friction may result to local temperatures above the fuel's boiling point. Predictions indicate bulk fuel temperature increase of more than 100°C during the opening phase of the needle valve. Overall, it is concluded that such effects are significant for the injector performance and should be considered in relevant simulation tools.

Experimental research on the influence of the pulse injector control parameters on its flow rate

The paper presents the results of the impact of the control parameters on the fuel mass flow from the injector. The control parameters examined in the paper were: frequency and pulse width modulation of the modulated control signal (the second part of the injector control signal). The analysis covers 6 injector types of different design of the valve element and the coil. The experiments have shown that the frequency of the signal does not affect the injector performance, contrary to pulse modulation affecting the injector performance significantly.

Dynamic cavitation inside a high performance diesel injector - an experimental and CFD investigation

A combination of simulation and special experimental techniques has been used to investigate the transient flow and cavitation phenomena of a control device inside a high performance diesel injector. Dynamic cavitation behaviour was captured on a large scale transparent model, which was then used to develop and validate an advanced turbulence CFD model with Large Eddy Simulation. These techniques are used within Delphi to gain insight and optimise injector performance at real-size.

Low-Emission, Liquid Fuel Combustion System for Conventional and Alternative Fuels Developed by the Scaling Analysis

The objective of this study is to develop a theoretical basis for scalability considerations and design of a large-scale combustor utilizing flow blurring (FB) atomization. FB atomization is a recently discovered twin-fluid atomization concept, reported to produce fine spray of liquids with wide range of viscosities. Previously, we have developed and investigated a small-scale swirl-stabilized combustor of 7-kWth capacity. Spray measurements have shown that the FB injector's atomization capability is superior when compared to other techniques, such as air blast atomization. However, despite these favorable results, scalability of the FB injector and associated combustor design has never been explored for large capacity; for example, for gas turbine applications. In this study, a number of dimensionless scaling parameters that affect the processes of atomization, fuel–air mixing, and combustion are analyzed, and scaling criteria for the different components of the combustion system are selected. Constant velocity criterion is used to scale key geometric components of the system. Scaling of the nonlinear dimensions and complex geometries, such as swirler vanes and internal parts of the injector is undertaken through phenomenological analysis of the flow processes associated with the scaled component. A scaled-up 60-kWth capacity combustor with FB injector is developed and investigated for combustion performance using diesel and vegetable oil (VO) (soybean oil) as fuels. Results show that the scaled-up injector's performance is comparable to the smaller scale system in terms of flame quality, emission levels, and static flame stability. Visual flame images at different atomizing air-to-liquid ratio by mass (ALR) show mainly blue flames, especially for ALR > 2.8. Emission measurements show a general trend of lower CO and NOx levels at higher ALRs, replicating the performance of the small-scale combustion system. Flame liftoff height at different ALRs is similar for both scales. The scaled-up combustor with FB injector preformed robustly with uncompromised stability for the range of firing rates (FRs) above 50% of the design capacity. Experimental results corroborate with the scaling methodology developed in this research.

Analysis of Moving-Coil Actuator Jet Injectors for Viscous Fluids.

A jet injector is a device that can be used to deliver liquid drugs through the skin using a fluid jet, without the use of a needle. Most jet injectors are designed and used for the delivery of inviscid liquids, and are not optimized for the delivery of viscous drug compounds. To better understand the requirements for delivering viscous drugs, we have developed a mathematical model of the electromechanics of a moving-coil actuated jet injector as it delivers viscous fluids. The model builds upon previous work by incorporating the nonlinear electrical properties of the motor, compliant elements of the mechanical piston and ampoule system, and the effect of viscosity on injector characteristics. The model has been validated by monitoring the movement of the piston tip and measurements of the jet force. The results of the model indicate that the jet speed is diminished with increasing fluid viscosity, but overshoot and ringing in the jet speed is unaffected. However, a stiffer ampoule and piston will allow for a better control of the jet speed profile during an injection, and reduce ringing. We identified that the piston friction coefficient, the compliance of the injector components, and the viscous properties of the fluid are important determinants of performance when jet-injecting viscous fluids. By expanding upon previous jet injector models, this study has provided informative simulations of jet injector characteristics and performance. The model can be used to guide the design of future jet injectors for viscous fluids.

Study of Nozzle Injector Performance Using CFD

Study of Nozzle Injector Performance Using CFD

Analysis of Internal Common Rail Injector Deposits via Thermodesorption Photon Ionization Time of Flight Mass Spectrometry

Increasing reports about malfunctions in common rail injector (CRI) systems lead to a more intensive research on diesel fuel injection systems, which are working under higher pressures and temperatures. Under these conditions, deposits were formed and deteriorated the injector performance. Therefore, it is necessary to investigate the formed deposits to avoid injector sticking. Previous studies have identified different substance classes, such as alkanes, carboxylic salts, and aromatic hydrocarbons in the deposits. In particular, aromatics and polycyclic aromatic hydrocarbons (PAHs) are suspected to produce insoluble solid precipitates. In this study, thermodesorption resonance-enhanced multiphoton ionization time-of-flight mass spectrometry (REMPI–ToF–MS) as a novel analytical technique for direct measurements of aromatic-containing deposits on injector parts was performed. Experiments were carried out in a self-made test bench, where the CRI were installed. The influence of the temperature, injection pressure, injection amount of used fuel, and fuel composition on the tendency to form deposits on the metal surface of commercial CRI parts, especially its ring, was investigated. In most cases, the rings were directly analyzed by the aromatic-selective REMPI technique without any sample preparation. The temperature program of the used carbon analyzer (CA) helps to separate the desorbing material into volatile and non-volatile organic matter during the pyrolysis under a helium atmosphere within the oven of the CA. The results concentrate on the volatile organic matter desorbing step and indicate a strong influence of the temperature and fuel composition on the amount of analyzed aromatic compounds. They were not equal, with the results of thickness layer measurements in individual cases. Comprehensive analytical methods, such as single photon ionization (SPI), are needed for further information.