Master of Science in Mechanical Engineering, Cleveland State University, 2015, Washkewicz College of Engineering

A newly developed production test stand for measuring the spray angle of a pressure swirl atomizer was constructed and used to measure a product line of these pressure swirl atomizers – the macrospray atomizer. This new test stand, utilizing constant temperature hot wire anemometers, captures the spray angle data based on the voltage drop the hot wire probes see as they traverse the spray cone of the atomizer and as fluid droplets impinge upon the wire. Datasets acquired from the experiments are compared and correlated with computational fluid dynamics (CFD) simulation data. In addition, angles obtained from another type of spray characterization technique, the spray angle device, are also compared to see how closely CFD can predict the angle as captured by this new stand and how reliable and independent of human error it is. Another nozzle with a pressure swirl atomizer, the conventional atomizer, is also simulated to compare its agreement with experimental values obtained from the spray angle device. Finally, the datasets are compared to understand if the CFD results, when compared to the two spray characterization techniques used in this thesis for both the nozzle and atomizer can be utilized to assist in future atomizer designs. For the macrospray atomizer, it was found through the experiments that the hot wire stand predicts the spray angle more accurately within 10% error. The spray angle device measured the spray angles within an error of 29% while the CFD introduced more error into the spray angle measurement obtained, within 7% to 93%. The conventional atomizer was found to have an error up to 18% with CFD results and up to 28% with the manual spray angle device.

Committee: Mounir Ibrahim Ph.D. (Committee Chair); Vikram Shyam Ph.D. (Committee Member); Ralph Volino Ph.D. (Committee Member) Subjects: Engineering; Fluid Dynamics; Mechanical Engineering

PhD, University of Cincinnati, 2024, Engineering and Applied Science: Aerospace Engineering

Aerial application of agrochemicals plays a crucial role in modern agriculture. Droplet size is a critical parameter, affecting both the efficacy of the chemicals and the risk of off-target motion, especially drift. However, the droplet size produced by the spray system in-flight is difficult to predict due to the many variables impacting the atomization process. To address various limitations with the current approach to determining droplet size, this dissertation presents the development of and justification for an in-flight droplet sizing sensor specifically designed for aerial application spray measurements. First, a study is undertaken to quantify errors in droplet size and drift estimates based on empirical modeling that does not account for the varying liquid physical properties of commonly used spray solutions. Existing wind tunnel atomization data is analyzed with commonly used drift modeling software. Key droplet size distribution statistics and near-field drift metrics for a commonly used blank solution of water with a non-ionic surfactant are compared to those from various active ingredient and adjuvant formulations. It was found that even relatively small changes in three liquid physical properties—dynamic surface tension, shear viscosity, and extensional viscosity—could result in large (over 50%) differences in both the volume contained in small droplets and near-field drift between the blank solution and the active ingredient formulations. The magnitude of these changes varied significantly depending on the sprayer configuration. Next, the development of a droplet sizing sensor based on the image-based particle shadow imagery (PSI) technique is presented to address the challenges related to predicting droplet size. Capable of real-time, in-flight measurements on commercially operating aircraft, the PSI sensor was designed to address the challenges related to predicting droplet size by simply measuring it during a spray application. A un (open full item for complete abstract)

Committee: Jongguen Lee Ph.D. (Committee Chair); Bradley K. Fritz PhD (Committee Member); Prashant Khare Ph.D. (Committee Member); Daniel Cuppoletti Ph.D. (Committee Member) Subjects: Aerospace Engineering

PhD, University of Cincinnati, 2018, Engineering and Applied Science: Aerospace Engineering

A generic novel injector was designed for multi-Lean Direct Injection (M-LDI) combustors. One of the drawbacks of the conventional pressure swirl and prefilming type airblast atomizers is the difficulty of obtaining a uniform liquid sheet under all operating conditions. Micro-channels are needed inside the injector for uniformly distributing the fuel. The problem of non-uniformity is magnified in smaller sized injectors. The non-uniform liquid sheet causes local fuel rich/lean zones leading to higher NOx emissions. To overcome these problems, a novel fuel injector was designed to improve the fuel delivery by using a porous stainless-steel material with 30 µm porosity. The porous tube also acted as a prefilming surface. Liquid and gaseous fuels can be injected through the injector. The current study investigates the aerodynamics, spray quality, fuel-air mixing and emission characteristics of the novel injectors at 4% pressure drop and atmospheric conditions. The injectors have two configurations with different counter-rotating radial-radial swirlers. And the injector 1 has a SN of 0.75 and SN of injector 2 is 0.6. The characteristics of the novel injectors are also compared with a typical airblast injector having a peanut nozzle with flow number of 1. A Central Toroidal Recirculation Zone (CTRZ) and Corner Recirculation Zone (CRZ) are observed from the aerodynamics study. Spray measurements are carried out at various equivalence ratio conditions without a confinement. D10, D32 and D0.5 are investigated on Jet-A, GTL and blended fuels. There is no significant influence of fuel types on the spray behavior due to their similar physics properties. The porous injectors generate a fine spray with weighted SMD ~45 µm at equivalence ratio of 0.6. Gaseous Fuel-air mixing studies are carried out at different equivalence ratios with and without a confinement. A fully premixed mixing profile was obtained at 0.43” downstream of the injector exit. Flame characterization (open full item for complete abstract)

Committee: San-Mou Jeng Ph.D. (Committee Chair); Jun Cai Ph.D. (Committee Member); Jongguen Lee Ph.D. (Committee Member); Bassam Mohammad Abdelnabi Ph.D. (Committee Member) Subjects: Aerospace Materials

MS, University of Cincinnati, 2005, Engineering : Mechanical Engineering

A high-resolution mechanical spray patternator has been developed for the characterization of gas turbine atomizers. Spatially resolved volumetric flux for non-reactive flows at atmospheric conditions can be accurately quantified by the patternator. The measurement technique has been shown to be effective and accurate. Diagnostic tests have been conducted to validate the overall patternator by exploring the patternation characteristics of a hollow cone, industrial spray nozzle. It has been shown that increasing the liquid injection pressure increases the equivalent spray angle and improves the patternation of the simplex nozzle. These observations are in good agreement with the literature. Throughout the process, the system has displayed good repeatability and reproducibility.

Committee: San-Mou Jeng (Advisor) Subjects:

MS, University of Cincinnati, 2004, Engineering : Aerospace Engineering

An experimental study has been conducted to study the behavior of liquid jets injected transversely into a subsonic crossflow of air. Liquid jet operating conditions are represented by the aerodynamic Weber number (We) and the liquid-air momentum ratio (q). Three injection liquids, water, Jet-A and N-Heptane, and two injection diameters (D), 0.381 and 0.762 mm, have been used to increase the range of operating conditions for the current experiments. q was restricted to 0.7-10.2 to ensure applicability to premix ducts of LPP combustors. Pulsed shadowgraphy and Phase Doppler Particle Analyzer (PDPA) techniques were used to take measurements for these experiments. Jet breakups and penetrations, and the structures of the sprays produced after breakup have been studied. Two breakup modes have been observed, column and surface breakup. The streamwise location of breakup is constant while the transverse location increases with q. Jet penetrations have been correlated with q, D and the streamwise distance (z). The volume flux of the spray exhibits a maximum in the spray core. Droplet axial velocities (Ud) exhibit a minimum below the spray core and increase with increasing transverse distance. The transverse location of the maximum in the droplet sizes occurs in the spray core for low q. Its location increases with an increase in q. Droplet sizes decrease with an increase in the crossflow velocity (U∞) while penetration increases with an increase in D or q. This property has been found to be very significant.

Committee: Dr. San-Mou Jeng (Advisor) Subjects: Engineering, Aerospace

PhD, University of Cincinnati, 2004, Engineering : Mechanical Engineering

Simplex atomizers (pressure-swirl atomizers) are widely used in air-breathing gas turbine engines as they have good atomization characteristics and are relatively simple and inexpensive to manufacture. To reduce emissions, it is critical to design fuel atomizers that can produce spray with a predetermined droplet size distribution at the desired combustor location (small mean droplet diameters and uniform local air/fuel ratios). Manufacturing methods are now available where complex atomizer geometries can be easily obtained. However to use such methods, the influence of atomizer geometry on its performance must be well understood. In this dissertation, a two-dimensional axisymmetric computational fluid dynamics (CFD) model based on the Arbitrary-Lagrangian-Eulerian (ALE) method to predict the flow in pressure-swirl atomizers was developed. The Arbitrary-Lagrangian-Eulerian method was applied so that the free interface between gas and liquid could be tracked sharply and accurately. The developed code was validated by comparison of predictions with experimental data for large scale prototype and with semi-empirical correlations at small scale. The computational predictions agreed well with experimental data for the film thickness at the exit, spray cone angle, and the pressure drop across the atomizer as well as velocity field in the swirl chamber. Using the validated code, a comprehensive parametric study on simplex atomizer performance was conducted. The geometric parameters of atomizer covered in this study include: atomizer constant, the ratio of length to diameter in swirl chamber, the ratio of length to diameter in orifice, the swirl chamber to orifice diameter ratio, inlet slot angle, trumpet angle, trumpet length, and swirl chamber convergent angle. The effects of these geometric parameters on the atomizer performance were studied for a fixed mass flow rate through the atomizer as well as for a fixed pressure drop across the atomizer. The atomizer performance (open full item for complete abstract)

Committee: Dr. Milind Jog (Advisor) Subjects: Engineering, Mechanical

MS, University of Cincinnati, 2003, Engineering : Mechanical Engineering

Five cases are examined in which a spray field generated by a commercial simplex nozzle is influenced by the counter-rotating flow structure created by a production CFM56 swirl cup. The first case involving water atomization at an equivalence ratio of 0.7 and an air temperature of 100°F acts as the baseline for this study. Subsequent cases assess the effects of different liquids, water or Jet-A fuel, of different equivalence ratios, 0.7 or 1.1, and different air temperatures, 100°F or 400°F. Digital images employing a laser sheet offer some qualitative flow visualization of the spray. In addition, measurements are conducted with a two-dimensional Phase Doppler Particle Analyzer system within close proximity to the swirl cup exit plane, which provides the three principle orthogonal velocities and a diameter distribution throughout the spray field. Combined, this information provides insight to the characteristics of liquid spray behavior and its sensitivity to varying these parameters.

Committee: Dr. San-Mou Jeng (Advisor) Subjects:

Doctor of Philosophy in Engineering, University of Toledo, 2011, College of Engineering

In this research work the flow characteristics of a type of rotary atomizer, referred to as slinger injector, were experimentally and numerically investigated at relatively low rotational speeds. Although slinger injectors provide a good level of atomization at high rotational speeds where they are intended to operate (30,000 rpm or higher), a critical aspect in small gas turbines is related to the start-up phase, which typically takes place at speeds around 10,000 rpm. The quality of atomization is very important, especially at these low speeds where smaller mean fuel droplet diameters are desirable. The current work focused on the study of atomization provided by slinger injectors at rotational speed related pertinent to the start-up phase (up to 15,000 rpm). An optical measurement system was implemented to investigate the liquid atomization provided by the slinger injector. The qualitative behavior of fuel emerging from the slinger was evaluated to determine whether a satisfactory atomization was provided within a distance compatible with the size of a small gas turbine engine combustion chamber. The size of the droplets was measured using the Global Sizing Velocimetry (GSV) system. Visualization of the primary liquid breakup process, determination of breakup lengths, and measurement of droplet size were performed by varying rotational speed, liquid flow rate, injector hole shape, size and orientation, and number of holes. Photographs of the liquid breakup, various mean and representative diameters, droplet size histograms and cumulative volume distribution are presented. The findings of this thesis show that droplet size decrease with an increase in rotational speed, as expected. Moreover, hole diameter, hole shape and flow rates affect the slinger atomization. For a given flow rate and a given rotational speed, the experimental data show that the droplet sizes decrease by increasing the hole diameter. The droplets increase in size when the flow rates is increas (open full item for complete abstract)

Committee: Abdollah A. Afjeh PhD (Advisor); K. Cyril Masiulaniec PhD (Committee Member); Terry T. Ng PhD (Committee Member); Ray D. Hixon PhD (Committee Member); Sasidhar Varanasi PhD (Committee Member) Subjects: Mechanical Engineering