Nozzle Air Flow Research Articles

Cold-state Experimental Study on Flow Characteristics of Multi-nozzle in Natural Gas Reburning Burner

Based on the prototypes of a 130 t/h boiler, constant proportional cold-state test bench is established, flow characteristics of multi-nozzle in natural gas reburning burner and its influence on the covering effect for the upflow in the furnace are researched. Numerical simulations of this process are also made with standard turbulence model. The results show that air flow fullness in furnace is better in the case of the reburning zone with 8 nozzles compared to 4 nozzles and also coverage effect of the reburning flow for the updraft gas in the furnace is better. In the condition each nozzle airflow velocity is constant, the effect of reburning flow on coverage of up-secondary air is best when the incident angle for four corners is 14.17?, while Center of the furnace wall is 84.57. And while the best incident angle is invariable, the effect of reburning flow on coverage of up-secondary air is best when the speed of reburning gas in the corners of furnace is 51 m/s, the same to the center of the furnace wall’s.

Spray-dried rosemary extracts: Physicochemical and antioxidant properties

In this work, spray-dried rosemary extracts were obtained. A 33 Box–Behnken design was followed to evaluate the influence of drying conditions on the contents of chemical markers and “in vitro” antioxidant activity of the powder. Although the dry products lost some of their polyphenols, they still had antioxidant activities (IC50) ranging from 17.6 to 24.8μg·mL−1. Analysis of variance proved that studied factors and some of their interactions significantly affected most of the quality indicators. The best combination of conditions to use for obtaining dry rosemary extracts with adequate physicochemical and functional properties involves an extract feed rate of 6mL·min−1, a drying air inlet temperature of 140°C and a spray nozzle air flow rate of 50L·min−1.

Droplet-Particle Agglomeration of Maltodextrin and Salt in a Small-Scale Spray Dryer

The technique of in-chamber blending in practice has been investigated, by altering the configuration of a Buchi B290 small-scale spray dryer having a two-fluid nozzle, through adding an extra pipe into the chamber to agglomerate maltodextrin (DE18) particles with 20% salt solution sprayed through the atomizer. Scanning Electron Micrographs showed the importance of splash impacts between salt droplets and maltodextrin particles in this geometry, suggesting that the collision efficiency is strongly affected by whether or not the salt droplets completely surround the dry maltodextrin particles. Changing the air inlet temperature did not affect the measured amount of collisions (from Atomic Absorption Spectroscopy) significantly, but both the main air and the nozzle air flow rates had significant effects on the collision outcomes.

The effect of the salt content on the crystallization behaviour and sorption fingerprints of spray-dried lactose

Different types of salts in various proportions affect lactose crystallization. In this study, two common monovalent salts, NaCl and KCl, were used at lactose:salt ratios of 5:2 and 5:1 (w/w) to observe the change in crystallization behaviour of the mixtures compared with that of pure lactose obtained from spray drying. The same operating conditions (170 °C inlet air temperature, 38 m 3/h main air flow rate, feed pump rate 11 ml/min, nozzle air flow rate of 473 L/h) were maintained for each run in a Buchi (B-290) Mini Spray Dryer to compare the behaviour of different feed compositions. To analyse the crystallization behaviour of each spray-dried product, Moisture Sorption Characteristic diagrams and Moisture Sorption Finger-prints were used, and Scanning Electron Microscopy (SEM) micrographs of the samples have also been carried out. The results show that, at lower salt contents (lactose:salt = 5:1), both lactose/salt mixtures showed the highest change in moisture content, but there was significant difference in sorption behaviour at higher salt contents for both salts. Among all the lactose/salt powders, the lactose:NaCl mixture at a ratio of 5:2 was found to be the most crystalline product in nature.

Effects of droplet size and type of binder on the agglomerate growth mechanisms by melt agglomeration in a fluidised bed

This study was performed in order to evaluate the effects of binder droplet size and type of binder on the agglomerate growth mechanisms by melt agglomeration in a fluidised bed granulator. Lactose monohydrate was agglomerated with melted polyethylene glycol (PEG) 3000 or Gelucire 50/13 (esters of polyethylene glycol and glycerol), which was atomised at different nozzle air flow rates giving rise to median droplet sizes of 40, 60, and 80 μm. Different product temperatures were investigated, below the melting range, in the middle of the melting range, and above the melting range for each binder. The agglomerates were found to be formed by initial nucleation of lactose particles immersed in the melted binder droplets. Agglomerate growth occurred by coalescence between nuclei followed by coalescence between agglomerates. Complex effects of binder droplet size and type of binder were seen at low product temperatures. Low product temperatures resulted in smaller agglomerate sizes, because the agglomerate growth was counteracted by very high binder viscosity or solidification of the binder. At higher product temperatures, neither the binder droplet size nor the type of binder had a clear effect on the final agglomerate size.

RAPID CONDENSATIONAL GROWTH OF PARTICLES IN THE INLET OF PARTICLE SIZING INSTRUMENTS

Rapid particle growth by the condensation of water vapour resulting from expansion in the inlet of particle sizing instruments such as optical particle counters and impactors was modelled. The corrected Mason diffusion growth equation extended to the application for particles beyond the continuum region has been found suitable. The influence of particle acceleration in the nozzle air flow, modelled with the CFX-FLOW3D program, on the condensation process was considered. The study was focused on a typical inlet nozzle of an optical particle counter with an inner diameter of 0.5 mm and a length of 20 mm, connected by an additional 20 mm long conical nozzle at a flow rate of 28.5 ml s −1 . The results show that particles smaller than 1.0 μ m can grow quickly during the very short-time passage through the nozzle as the saturation in the nozzle flow can increase several times. For particles with an initial radius of 0.15 μ m, i.e. the typical minimum detectable size of many commercial optical particle sizing instruments, condensational growth will cause a size increase up to 7% in the viewing volume. The whole particle size distribution will shift to larger radii, which results in an overestimate of both particle size and number in measurements. This condensational over-numbering and sizing effect should be given concern in evaluating measurement results as well as in aerosol instrument design.

Performance of a Reduced NOx Diffusion Flame Combustor for the MS5002 Gas Turbine

This paper describes a reduced NOx diffusion flame combustor that has been developed for the MS5002 gas turbine. Laboratory tests have shown that when firing with natural gas, without water or steam injection, NOx emissions from the new combustor are about 40 percent lower than NOx emissions from the standard MS5002 combustor. CO emissions are virtually unchanged at base load, but increase at part load conditions. The laboratory results were confirmed in 1997 by a commercial demonstration test at a British Petroleum site in Prudhoe Bay, Alaska. The standard MS5002 gas turbine is equipped with a conventional, swirl stabilized diffusion flame combustion system. The twelve standard combustors in an MS5002 turbine are cylindrical cans, approximately 27 cm (10.5 in.) in diameter and 112 cm (44 in.) long. A small, annular, vortex generator surrounds the single fuel nozzle that is centered at the inlet to each can. The walls of the cans are louvered for cooling, and contain an array of mixing and dilution holes that provide the air needed to complete combustion and dilute the burned gas to the desired turbine inlet temperature. The new, reduced NOx emissions combustor (referred to as a “lean head end,” or LHE, combustor) retains all of the key features of the conventional combustor; the only significant difference is the arrangement of the mixing and dilution holes in the cylindrical combustor can. By optimizing the number, diameter, and location of these holes, NOx emissions were substantially reduced. The materials of construction, fuel nozzle, and total combustor air flow were unchanged. The differences in NOx emissions between the standard and LHE combustors, as well as the variations in NOx emissions with firing temperature, were well correlated using turbulent flame length arguments. Details of this correlation are also presented. [S0742-4795(00)01602-1]

Non-Arrhenius NO Formation Rate in One-Dimensional Nozzle Airflow

Non-Arrhenius NO Formation Rate in One-Dimensional Nozzle Airflow

Nozzle design and manufacturing influences on fuel spray circumferential uniformity

Factors that affect the circumferential uniformity of fuel sprays produced by aerating nozzles have been studied. A model nozzle delivering swirling airflows on either side of an annular fuel sheet was used to identify critical nozzle design and manufacturing influences. Detailed patternation data have been acquired for a baseline configuration and 32 modifications. The results indicated that small, fuel-annulus-gap variations can severely compromise the circumferential uniformity of the spray produced. Based on one fuel spray quality criterion, the fuel gap nonuniformity should be less than 0.002 in. (0.05 mm). Alterations in the nozzle airflow passages had a lesser, but potentially limiting, influence.

Heat Transfer of the Critical Air Flow in a Nozzle : 3rd Report, Study on Heat Transfer of the Critical Air Flow in a Convergent Nozzle

The authors have published the numerical and experimental studies of heat transfer in parallel nozzles with two-dimensional critical flows in their previous 1st and 2nd reports. In this report, the studies are extended to the case of convergent nozzles. The compressible laminar flows are considered for convergent nozzles at the critical state, and heat transfer characteristics are calculated numerically. According to the results, the critical flow rate increases with a decrease of convergent ratio, and the variation of local Nusselt numbers along the flow direction becomes small by the effects of accelerated boundary layers. Furthermore, the experimental values of mean Nusselt numbers of the critical flow "Numc" agree well with the numerical results calculated on the basis of a laminar flow in the long-size convergent nozzles. From the comparison between the experimental and the analytical results, the range of nozzle characteristics numbers where laminar flows occupy the whole length of the nozzle is determined. Beyond this range described above, a turbulence arises and a turbulent flow is predominant in the critical nozzle, therefore, an experimental expression of mean Nusselt number is presented.

Heat Transfer of the Critical Air Flow in a Nozzle : 4th Report, The Flow and Heat Transfer Characteristics of an Accelerated Transonic Air Flow in a Divergent Nozzle

This paper is concerned with the theoretical and experimental investigations of the accelerated critical air flow and heat-transfer characteristics in the divergent nozzles in which a sonic point exists midway between the inlet and the exit of nozzle fully taking into consideration the viscous effect. The compressible laminar boundary layer equations are solved numerically using a finite difference method, and a chart of the sonic line and the critical flow rate in a divergent nozzle are shown. The numerical solutions of the local and the mean Nusselt numbers of a critical nozzle are in good agreement with the experimental results. The range of critical divergent nozzles in which a laminar flow extends over the whole region of the nozzles is determined experimentally by the nozzle characteristic number and the divergent Reynolds number.

Heat Transfer of the Critical Air Flow in a Nozzle : 3rd Report, Study on Heat Transfer of the Critical Air Flow in a Convergent Nozzle

Heat Transfer of the Critical Air Flow in a Nozzle : 3rd Report, Study on Heat Transfer of the Critical Air Flow in a Convergent Nozzle

Inlet Duct-Engine Exhaust Nozzle Airflow Matching for the Supersonic Transport

Propulsion systems selected for commercial transports must provide efficient and reliable performance over a broad range of conditions. These aeroplanes are used over both short and long route segments, on non-standard days, and at a range of altitudes to meet air-line schedule requirements.This paper covers some of the design parameters that were considered in the integration of the induction system, secondary air system, jet nozzle and the basic turbojet gas generator for the SST. During recent years some of the most important gains in propulsion efficiency have resulted from the development of inlets, engines and exhaust nozzles which are matched over a broad range of operating conditions. An efficient propulsion system for a supersonic transport depends upon very close matching of these components. This, of course, requires a better understanding of the capabilities and limitations of each of these major components. For the supersonic transport, 50% or more of the gross weight will be comprised of propulsion system and fuel and less than 10% will be payload.