Deposition nozzle

A cross section through the chemical vapour deposition nozzle 1, SnCl4-N2 inlet 2, H20-N2 inlet 3, glass surface 4, reaction gas evacuation 5, identical nozzle. 

A direct-write assembly is a fabrication method that employs a controlled translation stage, which moves a pattern-generating device, for example, ink deposition nozzle, to create materials with controlled architecture and composition [4], Arbitrary 3D structures can be prepared by this method. For the pol3rmeric ink solidification occurs either upon deposition into a coagulating reservoir or UV exposure. This method can be characterized to be bioinspired because they copy a nature process - direct ink writing in the form of spider webs. 

Barry et al. elegantly demonstrated the extrusion of concentrated inks of acrylamide through fine deposition nozzles in filamentary forms to fabricate defined patterns [112]. The ink also contained a photoinitiator, namely diethoxyacetophe-none, which was used to solidify the constructs via photopolymerization. Further,... 

In order to maintain high energy efficiency and ensure a long service life of the materials of construction in the combustion chamber, turbine and jet nozzle, a clean burning flame must be obtained that minimizes the heat exchange by radiation and limits the formation of carbon deposits. These qualities are determined by two procedures that determine respectively the smoke point and the luminometer index. 

To lessen the risk of pumping sludges or slurries into a unit, the practice is to leave a safety margin of 50 cm (heel) below the outlet nozzle or install a strainer on the pump suction line. The deposits accumulate with time and the tanks are periodically emptied and cleaned. 

Other examples of government and military applications of laser-based profilometry include the evaluation of rocket thruster nozzles to locate and measure flame erosion remote inspection of hypervelocity test track and the measurement of sludge deposits on tube internal surfaces. 

Finally, in yet another variant, the sample liquid stream and the gas flow are brought together at a shaped nozzle into which the liquid flows (parallel-path nebulizer). Again, the intersection of liquid film and gas flow leads to the formation of an aerosol. Obstruction of the sample flow by formation of deposits is not a problem, and the devices are easily constructed from plastics, making them robust and cheap. 

The inks formulated for jet printing must be very fluid, stable, and free of any particles that could cause clogging of the jet nozzles, and be capable of depositing and adhering to a substrate with a minimum of character fogging. They are generally formulated with soluble dye colorants in a suitable aqueous or solvent-based vehicle (9). 

Some of the earlier BWR units had feedwater heaters having copper alloy tubes. The environment of high oxygen and neutral pH water led to high copper concentrations in the feedwater and to undesirable deposits on the fuel and inlet fuel nozzles (20). In some instances, the copper deposits resulted in an increase in core pressure drop and necessitated plant power reduction. The copper alloys were eliniinated from the feedwater system in subsequent plants and most existing plants. 

Deposits sometimes block fuel nozzles and distort fuel spray patterns, lea ding to skewed temperature distribution with the possibiUty of burnout of turbiae parts by a "hot streak" exhaust. These deposits are sometimes associated with metal-containing particulates, but ia geaeral are another manifestation of fuel iastabiUty. 

An irregular trough of metal loss is apparent along the circumference of the ring (Fig. 16.4). Metal loss is severe near the nozzle holes (Fig. 16.5). The corroded zone is covered with light and dark corrosion products and deposits. Analysis of these revealed substantial quantities of copper and zinc. Microscopic examinations revealed exfoliation of the aluminum ring in corroded regions. 

To remove these undesirable but unavoidable salt deposits, a signi-fieant amount (about 1 % of mass flow) of boiler feedwater at 80-90°C is periodieally injeeted. Injeetion nozzles are typieally loeated in the inlet seetion, in the return ehannels, and in the labyrinth seals on the diseharge side of nitrous gas eompressors. This periodie flushing of the eompressor with water does have eertain disadvantages ... 

Carbon residue, pour point, and viseosity are important properties in relation to deposition and fouling. Carbon residue is found by burning a fuel sample and weighing the amount of earbon left. The earbon residue property shows the tendeney of a fuel to deposit earbon on the fuel nozzles and eombustion liner. Pour point is the lowest temperature at whieh a fuel ean be poured by gravitational aetion. Viseosity is related to the pressure loss in pipe flow. Both pour point and viseosity measure the tendeney of a fuel to foul the fuel system. Sometimes, heating of the fuel system and piping is neeessary to assure a proper flow. 

A fuel treatment system will effeetively eliminate eorrosion as a major problem, but the ash in the fuel plus the added magnesium does eause deposits in the turbine. Intermittent operation of 100 hours or less offers no problem, sinee the eharaeter of the deposit is sueh that most of it sheds upon refiring, and no speeial eleaning is required. However, the deposit does not reaeh a steady-state value with eontinuous operation and gradually plugs the first-stage nozzle area at a rate of between 5% and 12% per 100 hours. Thus, at present, residual oil use is limited to applieations where eontinuous operation of more than 1,000 hours is not required. 

Power plants in both peaking and standby modes aehieved 30,000 hours between major overhauls. It was during these operations that the deposit problem on the turbine nozzles beeame apparent. Also, deposits developed on the fuel nozzles, a situation that eould eause deviation in the fuel spray angle and related eombustion problems. Therefore, both turbine and fuel nozzles needed frequent eleaning. 

The startup speed and temperature acceleration curves as shown in Figure 19-2 are one such safety measure. If the temperature or speed are not reached in a certain time span from ignition, the turbine will be shutdown. In the early days when these acceleration and temperature curves were not used, the fuel, which was not ignited, was carried from the combustor and then deposited at the first or second turbine nozzle, where the fuel combusted which resulted in the burnout of the turbine nozzles. After an aborted start the turbine must be fully purged of any fuel before the next start is attempted. To achieve the purge of any fuel residual from the turbine, there must be about seven times the turbine volume of air that must be exhausted before combustion is once again attempted. 

Nozzles can also be installed on the flame arrester honsing for the injection of hot cleaning solntion for on-line cleaning of polymeric deposits (Dafft 1999). This is especially nseful for very large flame arresters that cannot be easily removed from service. 

Sprudel-platte, /. bubble tray, -salz, n. Karlsbad salt, -stein, m. deposit from hot springs. Spruh-apparat, m. spraying or sprinklmg apparatus. -diise,/. spray nozzle, -elektrode, /. ionizing electrode. 

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