Nozzle characteristics

Manufacturers of thermal anemometers provide small rigs for their calibration. They typically consist of a nozzle, an air supply unit, and a regulating valve. The probe is placed into the nozzle jet. The reference velocity is calculated from the nozzle upstream pressure and nozzle characteristics. Due to its small size, this type of rig can be used only for hot-wire or other thermal anemometers. ... 

McCafferty, R. J., Effect of Fuels and Fuel-Nozzle Characteristics on Performance of... 

A double concentric swirl burner is used with a commercially available air-assist nozzle to atomize the fuel. Nozzle characteristics, atomization airflow rate, and fuel flow rate were maintained constant throughout the experiments. 

One of the main difficulties with water cannon systems is that the behaviour of free water jets is very complex. Bulk properties of a water jet could potentially be calculated by examining mass flow rate and average jet velocity. However, it is extremely imlikely that the effective load on a particular individual could be calculated from first principles due to minor fluctuations in pump or nozzle characteristics. This makes water cannons unpredictable as a weapon and also has consequences due to the significant safety and training implications implied. 

Droplet size, particularly at high velocities, is controlled primarily by the relative velocity between liquid and air and in part by fuel viscosity and density (7). Surface tension has a minor effect. Minimum droplet size is achieved when the nozzle is designed to provide maximum physical contact between air and fuel. Hence primary air is introduced within the nozzle to provide both swid and shearing forces. Vaporization time is characteristically related to the square of droplet diameter and is inversely proportional to pressure drop across the atomizer (7). 

The resulting motion of the beam is detected by the pneumatic nozzle amphfier, which, by proper sizing of the nozzle and fixed orifice diameters, causes the pressure internal to the nozzle to rise and fall with vertical beam motion. The internal nozzle pressure is routed to the pneumatic relay. The relay, which is constructed like the booster relay described in the Valve Control Devices subsection, has a direct hnear input-to-output pressure characteristic. The output of the relay is the controller s output and is piped away to the final control element. 

Tne performance characteristics of pipe-waU-tap nozzles (Fig. 10-17) and throat-tap nozzles are reviewed by Wyler and Benedict [J. Eng. Power, 97, 569-575 (1975)]. 

Spray characteristics of pressure nozzles depend on the pressure and nozzle-orifice size. Pressure affects not only the spray characteristics but also the capacity. If it is desired to reduce the amount of liquid sprayed by lowering the pressure, then the spray may become coarser. To correct this, a smaller orifice would be inserted, which might then require a higher pressure to produce the desired capacity, and a spray that would be finer than desired might result. Multiple nozzles tend to overcome this inflexible charac teristic of pressure atomization, although several nozzles on a diyer complicate the chamber design and air-flow pattern and risk collision of particles, resulting in nonuniformity of spray and particle size. 

Minimize moisture hiiildiip losses. Avoid formulations which exhibit adhesive characteristics with respect to process walls. Maintain spray nozzles to avoid caking and nozzle drip. Avoid spray entrainment in process air streams, and spraying process walls. 

Volume of vessel (free volume V) Shape of vessel (area and aspect ratio) Type of dust cloud distribution (ISO method/pneumatic-loading method) Dust explosihility characteristics Maximum explosion overpressure P ax Maximum explosion constant K ax Minimum ignition temperature MIT Type of explosion suppressant and its suppression efficiency Type of HRD suppressors number and free volume of HRD suppressors and the outlet diameter and valve opening time Suppressant charge and propelling agent pressure Fittings elbow and/or stub pipe and type of nozzle Type of explosion detector(s) dynamic or threshold pressure, UV or IR radiation, effective system activation overpressure Hardware deployment location of HRD suppressor(s) on vessel... 

It is the energy in the liquid rec]uired to overcome the friction los.ses from the suction nozzle to the eye of the impeller without causing vaporization. It is a characteristic of the pump and is indicated on the pump s curve. It varies by design, size, and the operating conditions. It is determined by a lift test, producing a negative pressure in inches of mercury and converted into feet of required NPSH. 

If the calculated blending time is longer than desired, nozzle discharge flow rate can be increased or, nozzle diameter increased. Consideration of nozzle recirculation line pressure drops and pump characteristics is required to select the parameter to change. 

The effect of exhaust performance on room air movement is limited compared to the effect produced by air jets. The distance from the opening to the point where air velocity drops to 10% of the initial velocity value (Fig. 7.14) is approximately equal to one characteristic si2e of the exhaust opening (D for the round duct) and 60 characteristic sizes for the supply outlet (60D for the round nozzle). 

As in the case of the characteristic, theoretical values of characteristic K2 depend upon supply conditions. According to Shepelev," in the case of air supply through a nozzle with a uniform outlet velocity profile, K X-K = (1 +Pr)/ (2ir0.082 ). Thus, when = 6.88 and Pr = 0.7, A, = 5.85. Grimitlyn suggests the following relation between K2 and coefficients ... 

Considering that most of the data were obtained using round nozzles with jet characteristics close to ideal discharge conditions (K = 6.88, A, = 5.85), Eq. (7.92) can be ptesented as ... 

The characteristic feature of the main stream and horizontal directing jet interaction is that the directing jets are supplied through nozzles located at some distance from each other and from the outlet supplying the main stream (Fig. 7.55). 

This discussion will address needs, applications, performance characteristics, and design considerations for LVHV exhaust ventilation. The applications are primarily for dust control. LVHV systems can be effective for protecting workers from dust exposures and for recovering valuable process materials. The equipment, excepting the nozzles, involves technology that is the same as for large central vacuum cleaning systems. 

Nozzle Performance Characteristics Relatively little has been done to prescribe design guidelines for these applications. Published guidelines consist largely of drawings and limited data originating from LVHV equipment suppliers. 

Nozzle Static Pressure Loss Overall nozzle static pressure loss (SPN) was tested for all of the experimental LVHV nozzles.Experimental testing has confirmed what would be expected, that nozzle shape and size variation can cause great differences in overall static pressure loss, especially at high airflow velocities. Figure 10.25l/ compares SPN versus Vq (cm Hg versus m s" inch Hg versus fpm) characteristics for five circular nozzles. The plain wedge had the steepest rising curve, followed by the plain circular nozzle. Both of... 

FIGURE 10.25 Nozzle static pressure loss (SPN) characteristics for circular experimental LVHV exhaust nozzles. ... 

Install Disk with Pressure Membrone up. When inverted, the Disk Bursts ot obout 65% Increase in Pressure. Disk Must be Positioned True Center of Vent Line ond Nozzle. If Eccentric, Burst Characteristics Might Not Hold True. 

Figure 4-163 shows a steel body PDC bit with standard-size cutters lightly set on a deep inner cone profile. This bit has changeable nozzles and is best described as having a ribbed flow pattern although there are open face characteristics near the center and bladed characteristics near the gage. The lADC classification code in this case is S 7 4 4. 

Optimal hydraulics is the proper balance of hydraulic parameters (flowrate and equivalent nozzle size) that satisfy chosen criteria of optimization. Hydraulic quantities used to characterize jet bit performance include hydraulic horsepower, jet impact force, jet velocity, Reynolds number at the nozzle, generalized drilling rate or cost per foot drilled. While designing the hydraulic program the limitations due to cuttings transport in the annulus and pump performance characteristics must be included. 

There may be variations from box to box, depending on differences in fog characteristics as influenced by the design of the spray nozzles, the pressure at which the brine enters the nozzle, and the constancy of this pressure... 

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