Gas Injection System Research Articles

Up-scaling of a Low Temperature PACVD Process for the Deposition of α/γ-Nanocrystalline Alumina Coated Tools for Thixocasting of 1.2208 steel

An industrial-scale pulsed plasma-assisted chemical vapor deposition (PACVD) process for crystalline alumina growth was developed. To obtain a homogeneous coating thickness distribution over complex geometries and large dimensions, a suitable gas injection system was designed. A phase formation diagram for alumina coatings as a function of pulse length and cathode voltage has been compiled, allowing for the deposition of dense α/γ-Al2O3 coatings at a substrate temperature of 590 °C. Moulds coated with an α/γ-Al2O3 coating were utilized in steel thixocasting at temperatures of ∼1400 °C. The coatings were intact after thixocasting and showed significantly improved chemical wear resistance compared to plain steel moulds.

Recent developments in Wärtsilä gas engines

A power generation industry is evolving very fast nowadays. A lot of modern technologies have become available recently for a product development process. Also new types of fuels have appeared on the market. All these factors have caused significant changes in a power generation approach. New products enabling more environment-friendly technologies have been introduced by many key-players on the market. This paper describes briefly needs and directions of gas engines development in modern power generation industry. It also presents shortly history of Wärtsilä gas engines together with present gas engine portfolio covering products like: spark ignited gas engine, conventional dual-fuel one and a dual-fuel engine equipped with high-pressure direct gas injection system. The paper focuses on the most important aspects of the recent Wärtsilä gas engines development process explaining also achieved benefits. It covers main features and new fuels introduced during development of specific engine which are key factors for customers willing to use the most modern technology in this field.

W1101-(3) マイクロショットピーニングのテクスチャリングへの適用可能性(【W1101】テクスチャ表面のトライボロジー,ワークショップ)

The present study described applicability of micro shot peening treatments as a tool for surface modification. The developed peening apparatus having a direct gas injection system was consisted from the double walled nozzle and the particle storage tank enclosing rubber balls and was possible to fabricate the surface texture consisted from isolated micro dimples resulted from individual particle impacts. The friction coefficient of the micro dimpled texture surface was approximately 0.003 mated with parallel grooved surface in lubricated condition. In addition, it was possible to apply oil repellence and functional gradients to the surface using mixed particles as the impact media. It was confirmed that the application of the oil repellence was effective for the decrease in the friction coefficient on higher sliding speed region and that the anti wear property of the functional gradient surface was excellent on the abrasive wear condition.

Fabrication of Ultra High Nitrogen Austenitic Stainless Steel by NH3 Solution Nitriding

Nitrogen addition to stainless steels is very effective for improving mechanical properties and corrosion resistance. N2 solution nitriding is one of the possible methods to produce high nitrogen stainless steel. However, the nitriding rate by N2 gas is significantly small and also the attainable nitrogen contents in Fe–Cr alloys is less than 1 mass% in general. NH3 nitriding is an attractive alternative since NH3–H2 gas mixtures have high corresponding nitrogen potential than that of pure N2 gas.In the present study, aiming for the enhancement of the nitriding rate and the increase of nitrogen contents more than 1 mass%, NH3 and N2 solution nitriding of Fe–Cr alloys under various conditions has been carried out and their behaviors of nitrogen absorption in Fe–Cr alloys are investigated. It is found that the suppression of the pre-decomposition of NH3 before it reaches the sample is critical for the effective NH3 nitriding. Compared with the N contents after 1 h nitriding, NH3 nitriding is found to be about 5 times faster than that of N2 (0.1 MPa) nitriding under the present experimental conditions. In addition the N contents more than 1 mass% were easily achieved by NH3 nitriding. By using devised NH3 gas injection system to minimize the pre-decomposition of NH3 gas, austenitic Fe–23.5Cr alloys with more than 3 mass% of nitrogen (ultra high nitrogen stainless steel) that had never been achieved by solution nitriding was successfully produced.

Modular ultrahigh vacuum-compatible gas-injection system with an adjustable gas flow for focused particle beam-induced deposition

A gas-injection system (GIS) heats up a powdery substance and transports the resulting gas through a capillary into a vacuum chamber. Such a system can be used to guide a (metal)organic precursor gas very close to the focal area of an electron or ion beam, where a permanent deposit is created and adheres to the substrate. This process is known as focused particle beam-induced deposition. The authors present design principles and give construction details of a GIS suitable for ultrahigh vacuum usage. The GIS is composed of several self-contained components which can be customized rather independently. It allows for a continuously adjustable gas-flow rate. The GIS was attached to a standard scanning electron microscope (JEOL 6100) and tested with the tungsten precursor W(CO)6. The analysis of the deposits by means of atomic force microscopy and energy dispersive x-ray spectroscopy provides clear evidence that excellent gas-flow-rate stability and ensuing growth rate and metal-content reproducibility are experienced.

ITER Divertor System Integration

The main function of the ITER divertor system is to exhaust the major part of the alpha particle power as well as helium and impurities from the plasma. In order to fulfil these functions a divertor, a cooling system, a high vacuum pumping system, diagnostics and a gas injection system need to be integrated into the lower part of the vacuum vessel and into the divertor level ports. All components need to be assembled/disassembled using RH tools. The integration of all these systems has been undertaken to ensure that the overall functionality of the divertor is preserved, while fulfilling the requirements of each specific system.

Optimized molecule supply from nozzle-based gas injection systems for focused electron- and ion-beam induced deposition and etching: simulation and experiment

We simulated and measured near-field distributions of molecules impinging on a flat substrate from tube-based nozzles with varying exit aperture geometries (straight, bevelled and doubly perforated). Simulations were performed with the test-particle Monte Carlo approach taking into account the Knudsen number (molecular/transient flow) at the nozzle exit. Distributions were measured via thermal decomposition of Co2(CO)8 molecules on a homogeneously heated substrate. For all geometries and Knudsen numbers a good match between the simulation and experiment was found. For the first time the maximum accessible molecule flux with respect to the total flux exiting the nozzle could be quantified: it is around 7% for a straight cylindrical tube, around 27% for a bevelled tube and around 32% for a doubly perforated tube, all nozzles being 300 µm distant from the substrate and having a 400 µm aperture. Optimum substrate–nozzle angles were determined and shadow effects quantified.

Porous plug gas injection systems for studies of hydrocarbon dissociation and transport in the DIII-D tokamak

A probe has been designed, constructed, and successfully used to inject methane into the DIII-D lower divertor in a manner imitating natural release by chemical erosion. This porous plug injector (PPI) probe consists of a self-contained gas reservoir with an integrated pressure gauge and a 3 cm diameter porous surface through which gas is injected into the lower divertor of the tokamak. The probe is positioned flush with the divertor target surface by means of the divertor materials evaluation system. Two gas delivery systems were developed: in the first, gas flow is regulated by a remotely controlled microvalve and in the second by a fixed micro-orifice flow restrictor. Because of the large area of the porous surface through which gas is admitted, the injected hydrocarbon molecules see a local carbon surface (>90% carbon) similar to that seen by hydrocarbons being emitted by chemical sputtering from surrounding carbon tiles. The distributed gas source also reduces the disturbance to the local plasma while providing sufficient signal for spectroscopic detection. In situ spectroscopic measurements with the PPI in DIII-D allow the direct calibration of response for measured plasma conditions from a known influx of gas.

Studies on Polypropylene/Carbon Fiber Composite Foams by Nozzle-Based Microcellular Injection Molding System

A continuous production of microcellular polypropylene (PP)/30% carbon fiber composite was achieved in a newly developed nozzle-based microcellular injection molding system. In this work, a conventional injection molding machine was retrofitted with a nitrogen (N2) gas injection system. A specially designed “injection cum mixing nozzle” was added between the machine barrel and a shut-off nozzle to form a polymer/gas mixture as against barrel injection where the screw and barrel are usually modified for gas insertion. The foamed plastic was formed due to the thermodynamic instability caused by sudden pressure drop in the mold. The effectiveness of foam molding system developed in this study was verified by change of process parameters resulting into variety of cell morphology and cell size. Further, PP/30% carbon fiber composite was injection molded into ASTM tensile test sample with both conventional and foam molding system. These samples were then subjected to scanning electron microscope (SEM) as well as tensile testing to study the effect of injection speed on the cell morphology and tensile properties of foam molded composites. It was observed that cell size decreased and cell density increased with increase in injection speed. The mechanical properties of the foamed composites depend largely on the processing conditions.

A velocity map imaging detector with an integrated gas injection system

We present the design of a velocity map imaging spectrometer where the target gas is injected from a capillary that is integrated in the repeller plate of the ion optics assembly that drives electrons/ions formed by ionization or dissociation to a two-dimensional detector. The geometry of this design allows the use of gas densities in the interaction region that are two to three orders of magnitude higher than the densities that are used in standard velocity map imaging spectrometers, making the detector suitable for working with weak light sources such as newly developed attosecond pulse sources, or (quasi-)cw sources such as synchrotrons. In a test where monoenergetic photoelectrons were generated by six-photon ionization of Xe (utilizing the second harmonic of a neodymium doped Nd:YAG), the kinetic energy resolution of the spectrometer was found to be DeltaE/E=1.8%. This number was found to be in good agreement with Monte Carlo simulations.

Activation and measurement of nonevaporable getter films

An experimental setup for studying the pumping and capacity properties of nonevaporable getter (NEG)-coated films has been designed and built in the ASTeC Vacuum Science Laboratory at Daresbury Laboratory. The measurement system is based on the dynamic expansion method with a gas injection system that is capable of injecting the residual gases present in a typical UHV system, such as H2, CO, CO2, and CH4. The test particle Monte Carlo model was used for accurate evaluation of NEG film sticking probability from the pressure reading during gas injection. The experimental measurements with NEG-coated samples have shown that the NEG film can be poisoned during the NEG film activation (and/or regeneration) by molecules of CO and CO2 desorbed from uncoated parts of the vacuum chamber. The effect of NEG film poisoning was reduced by lowering the temperature of the uncoated parts of the vacuum chamber during the NEG film activation and, as a result, a new activation procedure was developed for vacuum systems containing NEG-coated parts.

3D-DIVIMP-HC modeling analysis of methane injection into DIII-D using the DiMES porous plug injector

A self-contained gas injection system for the Divertor Material Evaluation System (DiMES) on DIII-D, the porous plug injector (PPI), has been employed for in situ study of chemical erosion in the tokamak divertor environment by injection of CH 4 [A.G. McLean et al., these Proceedings]. A new interpretive code, 3D-DIVIMP-HC, has been developed and applied to the interpretation of the CH, CI, and CII emissions. Particular emphasis is placed on the interpretation of 2D filtered-camera (TV) pictures in CH, CI and CII light taken from a view essentially straight down on the PPI. The code replicates sufficient measurements to conclude that most of the basic elements of the controlling physics and chemistry have been identified and incorporated in the code-model.

Characterization of chemical sputtering using the Mark II DiMES porous plug injector in attached and semi-detached divertor plasmas of DIII-D

An improved, self-contained gas injection system for the divertor material evaluation system (DiMES) on DIII-D has been employed for in situ study of chemical erosion in the tokamak divertor environment. To minimize perturbation to local plasma, the Mark II porous plug injector (PPI) releases methane through a porous graphite surface at the outer strike point at a rate precisely controlled by a micro-orifice flow restrictor to be approximately equal as that predicted for intrinsic chemical sputtering. Effective photon efficiencies resulting from CH 4 are found to be 58 ± 12 in an attached divertor ( n e ∼ 1.5 × 10 13/cm 3, T e ∼ 25 eV, T surf ∼ 450 K), and 94 ± 20 in a semi-detached cold divertor ( n e ∼ 6.0 × 10 13/cm 3, T e ∼ 2–3 eV, T surf ∼ 350 K). These values are significantly more than previous measurements in similar plasma conditions, indicating the importance of the injection rate and local re-erosion for the integrity of this analysis. The contribution of chemical versus physical sputtering to the source of C + at the target is assessed through simultaneous measurement of CII line, and CD plus CH-band emissions during release of CH 4 from the PPI, then compared with that seen in intrinsic sputtering.

Projection maskless patterning for nanotechnology applications

Projection maskless patterning (PMLP) is based on a programmable aperture plate system and on charged particle projection optics with 200× reduction, providing thousands of electron or ion (H+, He+, Ar+, Xe+, C60−) beams working in parallel on the substrate. As part of the European CHARPAN project a PMLP proof-of-concept tool has been realized. Using resolution templates, with 10keV H+ multibeams a resolution of 16nm lines and spaces was achieved in HSQ resist across the proof-of-concept tool 25×25μm2 exposure field at an exposure dose of 25μC∕cm2. Enhancing the dose by 10% there was <1nm increase in linewidth. With 10keV Ar+ multibeams resistless nanopatterning of various materials was accomplished. Inserting a wired programmable aperture plate system providing ∼4000 beams, first HSQ resist exposure and patterning results have been accomplished, implementing gray scale exposure techniques. The system is being upgraded to a PMLP engineering tool integrating an aperture plate system with complementary metal oxide semiconductor electronics providing ∼40000 programmable beams, a precursor gas injection system for in situ ion multibeam induced etching and deposition, and a laser-interferometer controlled high-precision vacuum stage. Industrial PMLP nanotechnology applications are discussed.

Numerical modelling studies of flow and mixing phenomena in gas stirred steel ladles

A three-dimensional computational fluid dynamics (CFD) model was developed to simulate the fluid flow and mixing phenomena in a gas stirred ladle. Particular attention was paid to incorporate the effect of slippage between rising gas bubbles and surrounding fluid in the numerical model, to capture the relevant flow physics in a more effective manner. Various parametric studies were undertaken to examine the effects of gas flow rate, bottom nozzle configurations and tracer addition locations on mixing time. It was observed that the arrangement of bottom nozzles has a great effect on the mixing behaviour in a gas stirred ladle, with off centric gas injection producing shorter mixing time. Mixing time was found to be sensitive to the tracer addition position, particularly for the axisymmetric bottom gas injection system. The predicted results were compared with reported experimental observations and a very good agreement was observed in this regard, thereby establishing the authenticity of the proposed formulation.

OmniGIS Gas Injection System for Ion Beam Induced Deposition and Etching

Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008

Modelling and predictive control of a new injection system for compressed natural gas engines

In internal combustion engines equipped with the common rail injection system the accurate metering of the air/fuel mixture strictly depends on the pressure regulation. Accuracy in metering is difficult to be achieved especially for compressed natural gas (CNG) injection systems, as the gas compressibility makes the fuel delivery process more complex. Since the controller design requires a model of the injection system, this paper presents a physics-based state-space model of an innovative CNG injection system. The model parameters only depend on well defined geometrical data and fuel properties. Comparing simulation and experimental results in different operating conditions validates the model. Further, the proposed model is used for designing a generalized predictive controller for the injection pressure regulation, which is implemented in few steps. Experimental results show the effectiveness of the proposed approach.

Design and construction of vacuum control system on EAST

The construction of experimental advanced superconducting tokamak (EAST) was finished at the end of 2006 in Hefei, China. Its vacuum system, an important subsystem, has been commissioned in February 2006. The design and construction of this vacuum control system are described in this paper. The requirements for remote automation, distributed control and centralized management, high reliability and expansibility have been taken into account in the design. There are three levels of control in vacuum control system. The bottom level control is performed on the local instruments manually; the medium level control is based on Siemens S7-400 PLC; the top level control is conducted on IPCs with communication through profi_bus network. In addition remote handling and centralized monitoring could be realized by a remote control server. The control system could achieve pumping and fueling of the whole vacuum system. Besides that, it also includes the data acquisition of the pressure and temperature. The details are discussed on the monitoring of vacuum system states including cooling water, power and compressed air, etc., safeguards of plasma chamber and cryostat chamber and vacuum equipments, choosing of control modes corresponding to the plasma discharge and wall conditioning. At the end, the parts of EAST device protection system related to vacuum and gas injection system will also be introduced.

Numerical characterisation and experimental validation of AusIron top submerged multi-injection system

The present paper presents a numerical study of the fluid flow structure inside an elliptical liquid bath, agitated by a top submerged gas injection system. Using the Eulerian–Eulerian approach, a three-dimension gas–liquid transient numerical model coupled with the standard k-ϵ model is developed. Various combinations of operating parameters are investigated and the numerical predictions are validated against the laser doppler anemometer (LDA) experimental data. The results indicate that at a higher gas flowrate a better mixing at the bottom of the bath is achieved. On the effect of the lance submergence a deeper submergence level gives highly improved agitation and mixing within the bath. The comparisons of the numerical predictions with experimental data under various operating conditions show a reasonable agreement for both mean velocity and turbulent fluid flow characteristics. Furthermore, the development of a new empirical correlation based on Froude number is presented.

Focus on materials

Focus on materials