Thesis: M.S., Massachusetts Institute of Technology, Department of Chemical Engineering, 1982 / Bibliography: leaves 59-60. / by Willie K. Chan. / M.S. / M.S. Massachusetts Institute of Technology, Department of Chemical Engineering

Liquid droplet impingement on aircraft can be problematic as it leads to ice accretion. There have been many incidents of aircraft disasters involving ice accretion, such as American Eagle Flight 4184. Understanding liquid droplet impingement is critical in designing aircraft that can mitigate the damages caused by icing. However, the FAA's regulations are only specified for "Appendix C" droplets; thus, aircraft designs may not be safe when accounting for droplets such as Supercooled Large Droplets. The assumptions of many models, such as the Taylor-Analogy Breakup (TAB) model, are no longer accurate for Supercooled Large Droplets, and the physics of those models break down. Computational modeling is used to simulate droplets in the SLD regime. A Lagrangian reference frame is used in this formulation. In this reference frame, a Volume of Fluid variation of the Navier-Stokes equations is used to resolve and isolate a single droplet. Experimental data shows conflicting results for Weber Number ranges in different primary breakup mechanisms. The goal of this research is to develop a computational model of a water droplet and test it against experimental data. This work shows that the scientific consensus on Weber Number ranges for different breakup modes may not necessarily be accurate, as the computational model agrees with some sets of experimental data, but contradicts others.

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ABSTRACT The performance of aircraft engines can be significantly affected by the variety of foreign particles that are mixed into the air while operating under miscellaneous conditions. In particular, aircraft engines that operate in sandy or dusty conditions may fail within minutes of exposure to particle-laden flow due to foreign particle deposition on hot section components or erosion occurring on the compressor and turbine blades. For these reasons, the effect of sand ingestion on erosion, which may occur in the turbine and compressor blades, was studied in this master's thesis. In this master's thesis, the effect of sand ingestion on erosion on the M250 turboshaft engine's compressor blades will be investigated with the aid of numerical methods. In this study, we used the OpenFOAM software to solve the multiphase flow problem from the standpoint of finite control methods and the Eulerian-Lagrangian framework. The initial sand distribution conditions were taken from the Ph.D. thesis written by Olshefski, K. T. (2023) [1]. The compressor blade was modeled as 2D, which has a NACA 6510 profile shape, with a chord length of 63 mm. The results show that the leading edge and the suction side of the compressor, i.e. the upper half of the compressor, eroded more compared to the trailing edge, and the pressure side. Results also show that as the sand particle distribution becomes non-uniform the most eroded region shifts toward the trailing edge. In addition, for varying angles of attack, the region where the erosion occurs alters periodically. We observed that as the angle of attack increases, the eroded region shifts toward the trailing edge, but when the angle of attack is kept increasing the eroded region shifts back to the leading edge again. In conclusion, the non-uniformity of sand particle loading has a strong effect on the determination of the eroded regions. Furthermore, the variation of the angle of attack has a huge role in both the determination of eroded regions and the amount of eroded material. / Master of Science / GENERAL AUDIENCE ABSTRACT In this master's thesis, the effect of sand ingestion on compressor blade erosion was investigated with the help of numerical methods. The compressor is one of the vital parts of air-breathing engines such as turboshaft, turbofan, turbojet, and turboprop engines. Therefore, the erosion on the compressor blades may cause pressure surges, which could cause severe problems in the operation of aircraft or airplanes operating under dusty conditions. Historically, it is reported that a TransAmerican aircraft propelled by Alison T-56 engines lost two of its four engines after 3 to 4 minutes of exposure to volcanic ash while flying over Mt. St. Helens in 1980. Another example of the effects of sand ingestion is an MV-22 Osprey crash that happened during a training exercise in Hawaii, claiming the lives of two US Marines and injuring twenty other personnel in 2015. It was attributed that the cause of the fatal accident was the ingestion of dust that caused engine failure. Therefore, our intention in studying this field is to have an understanding of the regions of compressor blades that are vulnerable to erosion. In this master's thesis, numerical methods based on the finite volume method were used to obtain numerical solutions to estimate erosion on the compressor blade by utilizing OpenFOAM. We would like to recommend a nice OpenFOAM tutorial for those who are interested in applying numerical methods using OpenFOAM, taught by Jozsef Nagy accessible on YouTube, https://www.youtube.com/@OpenFOAMJozsefNagy. Also, for creating geometry and mesh generation of an airfoil for the use of OpenFOAM, we would like to recommend the tutorial presented by Ali Ikhsanul, accessible on YouTube via this link https://www.youtube.com/@aliikhsanul7982. These tutorial videos could help those who are interested in Openfoam but do not have much experience with Openfoam. The work in this master's thesis indicates that the leading edge of the compressor blade is more prone to be eroded than the trailing edge. In addition, it is shown that the eroded region distribution is highly dependent on the angle of attack of sand particles.

The gasification of carbonaceous fuel materials offers significant potential for the production of both energy and chemical products. Advancement of gasification technologies may be expedited through the use of computational fluid dynamics, as virtual reactor design offers a low cost method for system prototyping. To that end, a series of numerical studies were conducted to identify a computational modeling strategy for the simulation of coal gasification in fluidized bed reactors. The efforts set forth by this work first involved the development of a validatable hydrodynamic modeling strategy for the simulation of sand and coal fluidization. Those fluidization models were then applied to systems at elevated temperatures and polydisperse systems that featured a complex material injection geometry, for which no experimental data exists. A method for establishing similitude between 2-D and 3-D multiphase systems that feature non-symmetric material injection were then delineated and numerically tested. Following the development of the hydrodynamic modeling strategy, simulations of coal gasification were conducted using three different chemistry models. Simulated results were compared to experimental outcomes in an effort to assess the validity of each gasification chemistry model. The chemistry model that exhibited the highest degree of agreement with the experimental findings was then further analyzed identify areas of potential improvement. / Ph. D.

Creating effective models predicting particle entrainment behavior within axisymmetric turbulent jets is of significant interest to many areas of study. Research into multiphase flows within turbulent structures has primarily focused on specific geometries for a target application, with little interest in generalized cases. In this research, the entrainment characteristics of various particle sizes and densities were simulated by determining the distribution of particles across a surface after the particles had fallen out of entrainment within the jet core. The model was based on an experimental set-up created by Lieutenant Zachary Robertson, which consists of a particle injection system designed to load particles into a fully developed pipe [1]. This pipe flow then exits into an otherwise quiescent environment (created within a wind tunnel), creating an axisymmetric turbulent round jet. The particles injected were designed to test the effect of both particle size and density on the entrainment characteristics. The data generated by the model indicated that, for all particle types tested, the distribution across the bottom surface of the wind tunnel followed a standard Gaussian distribution. Experimentation yielded similar results, with the exception that some of the experimental trials showed distributions with significantly non-zero skewness. The model produced results with the highest correlation to experimentation for cases with the smallest Stokes number (small size/density), indicating that the trajectory of particles with the highest level of interaction with the flow were the easiest to predict. This was contrasted by the high Stokes number particles which appear to follow standard rectilinear motion. / Master of Science