A Comparison of a Spray Penetration Correlation by an Optical Obscuration Technique to Other Correlations Obtained by Different Techniques

2002 ◽  
Author(s):  
Badih A. Jawad
Keyword(s):  
Drop Size ◽  
Optical Measurement ◽  
Sampling Technique ◽  
Optical Signal ◽  
Spray Penetration ◽  
Spray Formation ◽  
Diesel Fuels ◽  
Liquid Immersion ◽  
Cylindrical Volume ◽  
Collimated Beam

Previous studies dealing with sprays have used a variety of techniques to determine spray droplets and spray penetration. In particular, the sedimentation tower method and the liquid immersion sampling technique were most popular. However, in these techniques sampling is done after spray formation is complete. The completion time of spray formation appears to vary with the conditions of injection and ambient factors, thus making measurements under transient conditions during injection difficult. A pulsed Malvern drop-size analyzer, based on Fraunhofer diffraction, was utilized to determine spray penetrations of diesel fuels under different conditions of injection, along with the effects of fuel properties. In these study, the spray is formed by injecting a calibrated amount of fuel into air. A two mm diameter collimated beam illuminated a cylindrical volume perpendicular to the axis of the fuel spray, and its attenuation was recorded and stored on the oscilloscope. With the optical measurement being synchronized to the needle lift of the injector, the output of the needle lift transducer and the optical signal was recorded simultaneously. Thus, the arrival and the duration of the spray at various positions along its axis were measured. A spray penetration correlation is obtained, and is compared to other existing correlations in the literature.

A Study on Diesel Fuel Drop Size Distribution

2000 ◽  
Author(s):  
Badih A. Jawad
Keyword(s):  
Droplet Size ◽  
Drop Size ◽  
Optical Measurement ◽  
Optical Signal ◽  
Diesel Fuels ◽  
Intermittent Behavior ◽  
Size Evolution ◽  
Cylindrical Volume ◽  
Droplet Size Distributions ◽  
Collimated Beam

Abstract A pulsed Malvern drop-size analyzer, based on Fraunhofer diffraction, was utilized to determmine droplet size size ranges of diesel fuels under different conditions of injection. the effects of fuel properties, design and operating parameters on the formation of diesal spray are discussed. In these studies, the spray is formed by injecting a calibrated amount of fuel into air with the frequency of the intermittent behavior controlled by the speed of the fuel pump. In this study, an injection cycle was tailored so that it was divided into several increments which were injected sequentially. A two mm diammeter collimated beam illuminated a cylindrical volume perpendicular to the axis of the fuel spray, and its attenuation was recorded and stored on the oscilloscope. With the optical measurement being synchronized to the needle lift of the injector, the output of the needle lift transducer and the optical signal was recorded simultaneously. Thus, the arrival and the duration of the spray at various positions along its axis were measured. The droplet size distributions were obtained directly as penetration measurements were made. However, by applying a delay time through the synchronization feature of the sizer, information about droplet size evolution within the same spray was possible. Distribution widths are plotted as a function of time for different chamber pressures, injection pressures, different positions, and different fuels. Coagulation seems to be a dominant phenomenon in these studies.

Dynamics of Intermittent Sprays

1999 ◽  
Author(s):  
Badih A. Jawad
Keyword(s):  
Droplet Size ◽  
Droplet Size Distribution ◽  
Sampling Technique ◽  
Size Distributions ◽  
Ambient Conditions ◽  
Spray Formation ◽  
Fuel Droplets ◽  
Liquid Immersion ◽  
Particle Sizer ◽  
Droplet Size Distributions

Abstract It is considered that droplet size distribution changes with time and space, since diesel fuel sprays are found to be transient and intermittent due to variations in ambient pressures. Therefore the obscuration signal (extinction of light due to particle field) obtained from a particle sizer for a single injection of fuel over the whole region of spray is necessary to determine the spray characteristics. Previous studies dealing with sprays have observed fuel droplets by use of the sedimentation tower method or liquid immersion sampling technique. However, in these technique droplets are usually sampled after spray formation is complete. The completion time of spray formation appears to vary with ambient conditions, thus making spray measurements under transient conditions during injection difficult. It is the objective of this paper to shine some light on the dynamics of spray motion, leading to a better understanding of the droplet size distributions.

Spray Penetration and Drop Size Studies of Diesel Fuels

2005 ◽  
Author(s):  
Badih A. Jawad ◽  
Chris H. Riedel ◽  
Ahmad Bazzari
Keyword(s):  
Arrival Time ◽  
Injection Pressure ◽  
Diffraction Method ◽  
Droplet Size Distribution ◽  
Chamber Pressure ◽  
Spray Penetration ◽  
Digital Oscilloscope ◽  
Diesel Fuels ◽  
Atomization Mechanism ◽  
Insight Into

Understanding the disintegration mechanism, spray penetration, and spray motion is of great importance in the design of a high quality diesel engine. The atomization process that a liquid would undergo as it is injected into a high-temperature, high-pressure air, is investigated in this work. The purpose of this study is to gain further insight into the atomization mechanism, the variation over time in droplet size distribution and spray penetration. This is done based on effect of chamber pressure, injection pressure, and type of fuel. A laser diffraction method is used to determine droplet mean diameters, single injection with synchronized time mechanism allowed the time dependent studies. Obscuration signals are obtained through a digital oscilloscope from which arrival time of spray can be measured. The spray penetration correlation obtained is compared to other correlation’s obtained from different other techniques used in the literature.

High Pressure Optical Measurements of Temperature At Turbine Rotor Inlet Conditions

2021 ◽  
Author(s):  
Scott Egbert ◽  
Darrel Zeltner ◽  
Mohsen Rezasoltani ◽  
Dale Tree
Keyword(s):  
Temperature Measurement ◽  
Optical Measurement ◽  
Spectral Band ◽  
Optical Signal ◽  
Operating Conditions ◽  
Optical Measurements ◽  
Inlet Temperature ◽  
Gas Temperature ◽  
Band Ratio ◽  
Inlet Conditions

Abstract In gas turbine engines, measurement of the rotor inlet temperature remains particularly challenging because of harsh operating conditions and limited access. The Integrated Spectral Band Ratio (ISBR) method is a non-intrusive optical emission gas temperature measurement technique suitable for this application. Optical fibers made of sapphire were used to transmit the radiative signal from the post combustion zone to a Fourier Transform Infrared (FTIR) spectrometer. The ratio of spectral bands of H2O, nominally 100 cm-1 wide between 4600 and 6200 cm-1 were used to infer temperature. ISBR and thermocouple measurements were obtained during two temperature sweeps; one at high load and one at low load (pressures of 1.2 and 0.7 MPa, respectively). The average of three thermocouples 76 mm downstream of the ISBR measurements were on the order of 200 K lower than the ISBR temperatures, consistent with a radiative correction and the heat loss between the two measurements. The change in ISBR temperature (95 K) during the sweep was similar to the change in average thermocouple temperature (89 K). Repeatability of the optical measurement at a given operating condition was on the order of ± 15 K and the absolute uncertainty of a single ISBR temperature measurement was estimated to be ± 61 K. A linear correlation with an R-squared value of 0.97 was also found between raw optical signal and thermocouple measurements suggesting that once a calibrated measurement is obtained.

Reducing Grid Dependency in Droplet Collision Modeling

2004 ◽  
Vol 126 (2) ◽  
pp. 227-233 ◽  
Author(s):  
David P. Schmidt ◽  
Christopher J. Rutland
Keyword(s):  
Drop Size ◽  
Predictive Ability ◽  
Sampling Technique ◽  
Physical Models ◽  
New Method ◽  
Droplet Collision ◽  
Numerical Errors ◽  
Mesh Dependency ◽  
Average Drop ◽  
Collision Models

Droplet collision models have been criticized for creating large mesh dependency in spray calculations. These numerical errors are very troublesome; they behave erratically and interfere with the predictive ability of physical models. The collision method used in KIVA can cause mesh dependent changes in average drop size of over 40 microns. In order to reduce mesh dependency, a new method has been developed for calculating the incidence of collision. The solution is to create a special collision mesh that is optimized for accuracy. The mesh is created automatically during the spray calculation. Additionally, a different stochastic collision sampling technique is also used. The new method, called the NTC algorithm, was incorporated into KIVA and found to be much faster than older algorithms. Calculations with 60,000 parcels required only a few CPU minutes. With the new NTC method and collision mesh, the mesh dependence of the drop size is only nine microns. This remaining mesh dependency is found to be due to the drag calculations and is not the fault of the collision algorithm.

High Pressure Optical Measurements of Temperature at Turbine Rotor Inlet Conditions

2020 ◽  
Author(s):  
Scott C. Egbert ◽  
Darrel Zeltner ◽  
Mohsen Rezasoltani ◽  
Dale R. Tree
Keyword(s):  
Temperature Measurement ◽  
Optical Measurement ◽  
Spectral Band ◽  
Optical Signal ◽  
Operating Conditions ◽  
Optical Measurements ◽  
Inlet Temperature ◽  
Gas Temperature ◽  
Band Ratio ◽  
Inlet Conditions

Abstract The measurement of combustion product gas temperature is valuable for the development and control of many combustion systems. In gas turbine engines, measurement of the rotor inlet temperature remains particularly challenging because of harsh operating conditions and limited access. The Integrated Spectral Band Ratio (ISBR) method is a non-intrusive optical emission gas temperature measurement technique suitable for this application. Optical fibers made of sapphire were used to transmit the radiative signal from the post combustion zone to a Fourier Transform Infrared (FTIR) spectrometer without the need for probe cooling. The ratio of spectral bands of H2O, nominally 100 cm−1 wide between 4600 and 6200 cm−1 were used to infer temperature. ISBR and thermocouple measurements were obtained during two temperature sweeps; one at high load and one at low load (pressures of 1.2 and 0.7MPa, respectively). The average of three thermocouples 76 mm downstream of the ISBR measurements were consistently on the order of 200 K lower, consistent with a radiative correction and the heat loss between the two measurements. The change in ISBR temperature (95 K) during the sweep was similar to the change in average thermocouple temperature (89 K). Repeatability of the optical measurement at a given operating condition was on the order of ± 15 K and the absolute uncertainty of a single ISBR temperature measurement was estimated to be ± 61 K. A linear correlation with an R-squared value of 0.97 was also found between raw optical signal and thermocouple measurements suggesting that once a calibrated measurement is obtained, changes in gas temperature can be determined using a correlation of the raw signal to produce the temperature.

Experimental Investigations of Performance Parameters of Pressure Swirl Atomizer for Kerosene Type Fuel

2009 ◽  
Author(s):  
Saurabh Dikshit ◽  
Salim Channiwala ◽  
Digvijay Kulshreshtha ◽  
Kamlesh Chaudhari
Keyword(s):  
Drop Size ◽  
Mechanical Energy ◽  
Cone Angle ◽  
Experimental Investigations ◽  
Performance Parameters ◽  
Spray Cone ◽  
Spray Penetration ◽  
Swirl Atomizer ◽  
Pressure Swirl ◽  
Pressure Swirl Atomizer

The process of atomization is one in which a liquid jet or sheet is disintegrated by the kinetic energy of the liquid itself, or by exposure to high velocity air or gas, or as a result of mechanical energy applied externally. Combustion of liquid fuels in engines and industrial furnaces is dependent on effective atomization to increase the specific surface area of the fuel and thereby achieve high rate of mixing and evaporation. The pressure swirl atomizer is most common type atomizer used for combustion in gas turbine engines and industrial furnaces. The spray penetration is of prime importance for combustion designs. Over penetration of the spray leads to impingement of the fuel on walls of furnaces and combustors. On the other hand, if spray penetration is inadequate, fuel–air mixing is unsatisfactory. Optimum engine performance is obtained when the spray penetration is matched to the size and geometry of combustors. Methods for calculating penetration are therefore essential to sound engine design. Equally important are the spray cone angles and the drop size distribution in the sprays. An attempt is being made to experimentally investigate pressure swirl atomizer performance parameters such as spray cone angle, penetration length and drop size at different injection pressures ranging from 6 bar to 18 bar.

scholarly journals An optical determination of the series resistance in Loligo.

1983 ◽  
Vol 82 (6) ◽  
pp. 807-817 ◽  
Author(s):  
B M Salzberg ◽  
F Bezanilla
Keyword(s):  
Series Resistance ◽  
Optical Measurement ◽  
Voltage Drop ◽  
Ionic Current ◽  
Giant Axon ◽  
Electrical Measurement ◽  
Optical Signal ◽  
In Series ◽  
Loligo Pealei

The resistance in series with the membrane capacitance in the giant axon of the squid Loligo pealei was measured using potentiometric probes that exhibit absorbance changes proportional to the voltage across the plasma membrane proper. The method relies upon the fact that a voltage drop across the series resistance produces a deviation in the true transmembrane voltage from that imposed by a voltage clamp. Optical measurement of the true transmembrane potential, together with electrical measurement of the ionic current, permits the immediate determination of the series resistance by Ohm's law. An alternative method monitored the amount of electronic series resistance compensation required to force the optical signal to match the shape of the reference potential. The value of the series resistance measured in artificial seawater was 3.78 +/- 0.95 omega X cm2. The estimated value of the contribution of the Schwann cell layer to the series resistance was 2.57 +/- 0.89 omega X cm2.

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