Numerical Methods for Simulating Multiphase Electrohydrodynamic Flows with Application to Liquid Fuel Injection

One approach to small-scale fuel injection is to capitalize upon the benefits of electrohydrodynamics (EHD) and enhance fuel atomization. There are many potential advantages to EHD aided atomization for combustion, such as smaller droplets, wider spray cone, and the ability to control and tune the spray for improved performance. Electrohydrodynamic flows and sprays have drawn increasing interest in recent years, yet key questions regarding the complex interactions among electrostatic charge, electric fields, and the dynamics of atomizing liquids remain unanswered. The complex, multi-physics and multi-scale nature of EHD atomization processes limits both experimental and computational explorations. In this work, novel, numerically sharp methods are developed and subsequently employed in high-fidelity direct numerical simulations of electrically charged liquid hydrocarbon jets. The level set approach is combined with the ghost fluid method (GFM) to accurately simulate primary atomization phenomena for this class of flows. Surface effects at the phase interface as well as bulk dynamics are modeled in an accurate and robust manner. The new methods are implemented within a conservative finite difference scheme of high-order accuracy that employs state-of-the-art interface transport techniques. This approach, validated using several cases with exact analytic solutions, demonstrates significant improvements in accuracy and efficiency compared to previous methods used for EHD simulations. As a final validation, the computational scheme is applied in direct numerical simulation of a charged and uncharged liquid kerosene jet. Then, a detailed numerical study of EHD atomization is conducted for a range of relevant dimensionless parameters to predict the onset of liquid break-up, identify characteristic modes of liquid disintegration, and report elucidating statistics such as drop size and spray dispersion. Because the methodologies developed and validated in this work open new, simulations-based avenues of exploration within a broader category of electrohydrodynamics, some perspectives on extensions or continuations of this work are offered in conclusion

Tip casing heat transfer measurements of a film-cooled turbine stage in a short duration facility

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2001.Includes bibliographical references (p. 139-140).by Bret P. Van Poppel.S.M

Undergraduate Internal Flow Pipe Friction Laboratory

Hydrodynamics laboratory experiences have supported the United States Military Academy’s civil and mechanical engineering programs for nearly 50 years. A recent effort revitalized and significantly improved the pipe friction hydrodynamics laboratory, a system originally built by the U.S. Army Corps of Engineers Waterways Experiment Station in the 1950s. The experimental apparatus includes a 3 hp electric pump capable of delivering a steady flow of liquid up to 5:1 lbm=s fed from a 100 gallon (US) reservoir. The test section is a horizontal copper pipe of 0:75 in diameter which issues fluid into a transparent, plastic visualization chamber. Mineral oil is the working fluid, chosen for its favorable physical properties that enable a broad range of flow regimes for data analysis and flow visualization. The test section is instrumented with digital pressure gauges and an ultrasonic flow meter, installed as part of the revitalization project. A collection tank on a mass scale provides a manual method for estimating flow rate during experimental trials. The improved laboratory significantly expands the range of data that may be collected, with students now able to accurately measure pressure, temperature, flow rate, and pipe geometric data. Students compute Reynolds number to characterize flow regime, estimate pressure gradient, and predict the friction factor given an estimate for the pipe’s roughness coefficient for several flow rates. A pre-laboratory exercise requires students to derive a functional form of the steady-flow mechanical pipe flow equation and employ dimensional analysis to identify the non-dimensional parameters required to achieve dynamic similitude. The upgraded laboratory offers a relevant, comprehensive application to deepen students’ conceptual understanding of internal fluid flow, hydrodynamics, and modeling and similarity principles

Undergraduate Heat Exchanger Laboratory

Heat exchangers are a fundamental part of many industrial and household devices, and a focus in the United States Military Academy at West Point’s undergraduate heat transfer course within the school’s Department of Civil and Mechanical Engineering. Recently, the department expanded laboratory capabilities to enhance student learning through hands-on experimentation. Prior to this project, a heat exchanger laboratory did not exist for student use, so a new apparatus was designed, developed, built, tested, and will be implemented as a laboratory experience in West Point’s heat transfer course. The experimental apparatus includes a fan-cooled heat sink, a high-efficiency water heater, two pumps for water circulation, and numerous valves to change both the direction and route of the flows. This design allows students to test three types of heat exchangers: shell-in-tube, concentric, and flat plate. These devices allow students to evaluate parallel-flow, counter-flow, and cross-flow heat exchangers. The test section is instrumented with flow meters for the hot and cold flows as well as thermocouples at the entrance and exit of each heat exchanger. As part of this laboratory experience, students measure, collect, and analyze data, compare experimental results to theory, and assess error and uncertainty. This heat exchanger laboratory provide realistic, hands-on experience with experimental apparatus, laboratory procedure, instrumentation, and engineering technicians, all of which help students gain physical understanding of the thermal-fluids concepts

The West Point BattleBot Competition

Three cadet teams at the United States Military Academy each design, budget, build, and test a middleweight, non-stomping BattleBot according to the rules of the national competition.[1] In 2003 we emphasized two aspects of this multidisciplinary, hands-on project--the importance of the final competition and project planning as a military operation. We observed three significant results of this change: 1) increased competitiveness and learning; 2) successful introduction of the Military Decision Making Process (MDMP); and 3) learning valuable leadership and teamwork lessons

An Enhanced Gas Turbine Engine Laboratory: A Learning Platform Supporting an Undergraduate Engineering Curriculum

A gas turbine engine has supported the U.S. Military Academy’s mechanical engineering program for nearly three decades. Recent, substantial enhancements to the engine, controls, and data acquisition systems greatly increased the student experience by leveraging its broad capabilities beyond the original laboratory learning objectives. In this way, the laboratory served as a learning platform for more than just instruction on gas turbine fundamentals and the Brayton cycle. The engine is a refurbished auxiliary power unit from Pratt & Whitney Aeropower, installed in the Embrauer 120 and similar to a unit installed on a U.S. Army helicopter. Whereas the original laboratory experience permitted students to test the engine at three different loads applied by a water brake dynamometer, the revised experience allowed for a broader range of test conditions. The original laboratory included single point measurements of three temperatures and two pressures, along with the fuel flow rate, dynamometer torque, and engine speed. The revised laboratory allowed the user to vary bleed air and engine loads across an operational envelope at a user-specified acquisition rate. The improved data acquisition system used LabVIEW (TM) and included multiple state sensors for pressure, temperature, fuel flow, bleed air, and dynamometer performance, thereby enabling a more complete analysis by accounting for the energy transported by bleed airflow and absorbed by the water brake. Students then quantified the uncertainty in their measurements and analysis. The new emphasis on uncertainty quantification, part of a program-level initiative, challenged students’ notion of “substitute and solve” while also familiarizing them with large, experimental data sets. The re-envisioned laboratory raised the students’ level in the cognitive domain and served as their premier engine experience. Rather than merely observing engine adjustments across a small range of conditions, students designed their own laboratory experience. With the updated approach, students viewed a graphic of the turbine’s laboratory operating range and chose the key variables of interest – selecting data points within the laboratory operating range – and then justified their selections. The enhanced experience added analysis of flow exergy and exergetic efficiency. The exercise also challenged students to hypothesize why actual turbine performance was less than predicted and determine sources of error and uncertainty. Moreover, the new laboratory offers opportunities to expand the turbine engine’s utility from supporting a single thermal-fluids course to a multidisciplinary learning platform. Concluding remarks address concepts for augmenting course instruction in other courses within the curriculum, including heat transfer, mechanical vibrations, and dynamic modeling and controls

Three Dimensional Velocity And Temperature Field Measurements Of Internal And External Turbine Blade Features Using Magnetic Resonance Thermometry

Magnetic resonance thermometry (MRT) is a maturing diagnostic tool used to measure three-dimensional temperature fields. It has a great potential for investigating fluid flows within complex geometries leveraging medical grade magnetic resonance imaging (MRI) equipment and software along with novel measurement techniques. The efficacy of the method in engineering applications increases when coupled with other well-established MRI-based techniques such as magnetic resonance velocimetry (MRV). In this study, a challenging geometry is presented with the direct application to a complex gas turbine blade cooling scheme. Turbulent external flow with a Reynolds number of 136,000 passes a hollowed NACA-0012 airfoil with internal cooling features. Inserts within the airfoil, fed by a second flow line with an average temperature difference of 30 K from the main flow and a temperature-dependent Reynolds number in excess of 1,800, produces a conjugate heat transfer scenario including impingement cooling on the inside surface of the airfoil. The airfoil cooling scheme also includes zonal recirculation, surface film cooling, and trailing edge ejection features. The entire airfoil surface is constructed of a stereolithography resin—Accura 60—with low thermal conductivity. The three-dimensional internal and external velocity field is measured using an MRV. The fluid temperature field is measured within and outside of the airfoil with an MRT, and the results are compared with a computational fluid dynamics (CFD) solution to assess the current state of the art for combined MRV/MRT techniques for investigating these complex internal and external flows. The accompanying CFD analysis provides a prediction of the velocity and temperature fields, allowing for errors in the MRT technique to be estimated