Gas turbine engines for propulsion operate under harsh conditions including gas temperatures that exceed the melting point of the metal, high mechanical stresses, and particulate ingestion such as sand. To maintain a low and uniform metal temperature to extend the life of a turbine component, a complex scheme of internal convective cooling and external film-cooling is required. Gas turbine engines operated in sandy or dusty environments can ingest a large quantity of sand into the mainstream and, more importantly, into the cooling system. Sand ingested into the coolant system has the potential to reduce or block off the flow intended to cool the turbine blades or vanes. If the source of coolant air to a critical region of a turbine blade were partially blocked, it would result in a substantial reduction in component life. This study includes establishing a methodology for testing sand ingestion characteristics on a simulated turbine component with film-cooling holes at room temperature and engine temperatures. The study evaluates a simple array of laser drilled film-cooling holes, similar to a showerhead on the leading edge of an airfoil. The blocking characteristics of this design indicate that increasing the airflow or decreasing the sand amount results in a decreased blockage. It was also determined that as the metal temperature increases, the blockage from a given amount of sand increases. The methodology used in the primary portion of this thesis was modified to test sand ingestion characteristics on actual turbine blades with film-cooling holes at room temperature and engine temperatures. The study evaluated the blockage performance of several different turbine blades including the F-100-229-full, F-100-229-TE, and the F-119 with a new trailing edge cooling methodology know as a microcircuit. It was shown that increasing the airflow or pressure ratio, or decreasing the sand amount would result in decreased blockage. It was also shown that over a certain metal and coolant temperature, the blockage is significantly worsened. However, it was also shown on the F-119 turbine blade that below a given metal temperature, there is no impact of metal or coolant temperature on sand blockage. / Master of Science

Modern gas turbine engines operate in environments where particle ingestion, especially sand ingestion, can affect the cooling of various turbine parts. The most critical areas are in the combustor and the first stage components of the turbine. Gas temperatures in these areas are the highest compared to other areas and exceed the melting points of the constituent metals. To extend the life of hot section components, internal convective cooling and external film-cooling are required. This study examined the effects of sand ingestion on various cooling geometries. The first part investigated impingement and film-cooling implemented in a double-walled cooling geometry for the purpose of reducing sand size and thereby reducing blockage due to sand ingestion. The second part analyzed the cooling performance of actual turbine blade outer air seals injected with sand. Results from these studies showed areas of impingement that promote particle fragmentation are advantageous in reducing particle size and reducing blockage due to particle ingestion. Blockage was significantly increased based on the percentage of large particles present in the sand samples. Increasing the pressure ratio and decreasing the sand amount were also shown to reduce blockage. / Master of Science

When a gas turbine operates in a particle laden environment, such as a desert, small solid particles are ingested into the engine. The ingested sand particles can cause damage to engine components and reduce the service life of the engine. Particle ingestion causes the erosion of metal blades and vanes, and, if the firing temperature is hot enough, deposition of molten particles in the hot sections of the engine. Both deposition and erosion phenomena can severely reduce overall engine performance. The Coefficient of Restitution (COR) is a measure of the particle-wall interaction, and has been widely used to quantify particle rebound characteristics in past particle impact studies. This work investigates the effects of temperature on sand particle impact characteristics by measuring the COR and other deposition related impact parameters. The first study presented as part of the dissertation contains a description of a novel method used to measure COR using a Particle Tracking Velocimetry (PTV) method. This is combined with Computational Fluid Dynamics (CFD) flow field to allow for an accurate determination of the particle impact velocity. The methodology described in this paper allows for measurement of the COR in a wide range of test conditions in a relatively simple manner. The COR data for two different sizes of Arizona Road Dust (ARD) and one size of glass beads are presented in this paper. Target material was stainless steel 304 and the impact angle was varied from 25 to 85 degrees. The second study details the first quantification of the COR of san particles at elevated temperatures. Temperatures used in this study were 533 K, 866 K, and 1073 K. In this study the mass flow rate through the experimental setup was fixed. This meant that velocity and temperature were coupled. Target material for this study was stainless steel 304 and the impact angle was varied from 30° to 80°. The COR was found to decrease substantially at the temperatures and velocity increased. It was determined that the decrease in COR was almost certainly caused by the increase in velocity, and not the decrease in temperature. The third study contains COR results at elevated temperatures. Significant improvements from the method used to calculate COR in the first paper are described. The particle used for these tests was an ARD sand of 20-40 μm size. Target materials used were stainless steel 304 and Hastelloy X. The particles impinged on the target coupon at a velocity of 28m/s. Tests were performed at three different temperatures, 300 K (ambient), 873 K, and 1073 K to simulate temperatures seen in gas turbine cooling flows. The angle of impingement of the bulk flow sand on the coupon was varied between 30° and 80°. A substantial decrease in COR was discovered at the elevated temperatures of this experiment. Hastelloy X exhibited a much larger decrease in COR than does stainless steel 304. The results were compared to previously published literature. The final study also used the ARD size of 20-40 μm. The target material was a nickel alloy Hastelloy X. Experiments for this study were performed at a constant velocity of 70m/s. Various temperatures ranging from 1073 K up to and including 1323 K were studied. Particle angle of impact was varied between 30° and 80°. Significant deposition was observed and quantified at the highest two temperatures. The COR of the ARD sand at the highest temperatures was found not to change despite the occurrence of deposition. At elevated temperatures, many of the particles are not molten due to sand's non-homogenous and crystalline nature. These particles rebound from the target with little if any change in COR. / Ph. D.

Many gas turbine engines operate in harsh environments where the engine can ingest solid particles. Particles can accelerate the deterioration of an engine and reduce the engine’s service life. Understanding particle interactions with the materials used in gas turbines, at representative engine conditions, can improve the design and development of turbomachinery operating in particle laden environments. Coefficient of Restitution (COR) is a measure of the particle/wall interactions and is used to study erosion and deposition. This study presents data taken using the Virginia Tech Aerothermal Rig. Arizona Road Dust (ARD) of 20-40 μm is injected into a flow field to measure the effects of temperature and velocity on particle rebound from a polished high temperature material coupon. The high temperature coupon was tested at different temperatures of ambient (300K), 873K, 1073K, 1173 K, 1223 K, 1273 K, and 1323 K while the velocity of the flow field was held constant at 28 m/s or 70 m/s. The impingement angle of the coupon was varied from 30° to 80° for each temperature tested. The results show an increase in deposition as the temperature approaches the melting temperature of sand. The results have also been compared to previously published literature. / Master of Science

Particle ingestion and deposition is an issue of concern for gas turbine engines operating in harsh environments. The ingested particles accelerate the deterioration of engine components and thus reduce its service life. This effect is observed to a greater extent in aircrafts/helicopters operating in particle laden environment. Understanding the effects of particle ingestion at engine representative condition leads to improved designs for turbomachinery. Experiments have been in an Aerothermal Rig facility at Virginia Tech to study particle deposition at engine representative temperatures. The Aerothermal Rig was upgraded to achieve air temperatures of up to 1100°C at the test section. The experiments are performed using Arizona Road Dust (ARD) of 20-40 μm size range. The temperature of air and particles are around 1100°C at a constant velocity of 70 m/s. The target coupon is made of Hastelloy X, a nickel-based alloy and the angle at which the particles impact the coupon varies from 30° to 80°. The experiments were performed with different amounts of total particle injected, concentration, and coupon angle to understand their effects on deposition. Similar research was carried out in the past at the same facility to study particle deposition at temperatures up to 1050°C and 70 m/s flow velocity. However, this previous research only studied how the coupon angle affects particle deposition; other parameters such as total particle input and particle concentration were not studied. It was found that particle deposition increases significantly at higher temperatures beyond 1050°C for higher coupon angle and amount of sand injected. Results from current study also show that deposition increases with increase in total sand injected, concentration, and coupon angle for a given temperature and velocity. / Master of Science

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 / 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.

Particle ingestion is a prevalent issue for jet engines. During operation, sand and ash particles enter the engine and can cause serious problems, including erosion and buildup of Calcia-Magnesia-Alumina-Silicate (CMAS) deposits. Analyzing the particle mass concentration of the airflow can help better understand this issue. This can best be accomplished by sampling particles with a sampling probe at various locations within an engine. The present study is a continuation of a previous study that developed and evaluated a novel sampling probe. The present study seeks to modify the probe to optimize its sampling capability, to evaluate the aerodynamics of the modified probe through Particle Imaging Velocimetry (PIV), to gain insight on its ability to sample smaller particles, to characterize the movement of larger particles as they are sampled using Particle Tracking Velocimetry (PTV), and to develop a method to physically measure particle mass concentration. To accomplish this, a free jet rig was used to create a particle-laden flow, and the probe was placed at the jet exit to sample particles. A laser and camera system were used to capture images of the probe for PIV and PTV. A particle collection apparatus was designed to collect and weigh particles captured by the probe to measure mass concentration. The PIV results indicate that the probe exhibits sub-isokinetic sampling behavior. However, the PTV results show that large particles are not affected by non-isokinetic conditions. The mass concentration measured by the probe decreases when the flow Mach number increases due to the higher flow velocity causing particles to be spaced further apart. The mass concentration measured by the probe decreases when the probe yaw angle increases due to lower projected probe inlet area. / Master of Science / Sand and ash particles are harmful to jet engines. Particle ingestion can greatly affect the useful life of the engine. Particles erode the machinery within the engine, and they also melt to form mineral deposits, all of which degrades performance. One method that is being developed to better understand this problem is to sample particles at various locations in the engine using a sampling probe. The concept of a sampling probe is simple: particles are captured by the probe inside the engine, and the particles are collected outside the engine for analysis. This would give insight on particle behavior in the engine. The present study is a continuation of a previous study that developed and evaluated a novel sampling probe. The present study seeks to modify the probe to optimize its sampling capability, to use advanced imaging techniques to characterize the movement of air and particles entering the probe, and to safely collect and weigh particles captured by the probe. A compressed air jet was used to accelerate particles and create a particle-laden environment akin to the inside of an engine. The probe was placed at the exit of the jet to sample particles. A laser and camera system were used to capture images of the probe during the particle-sampling process. A particle collection apparatus was designed to safely collect and store particles captured by the probe for weighing. The image and weight data were then used to make conclusions about the probe's sampling capability.

Particle ingestion remains an important concern for turbine engines, specifically those in aircraft. Sand and related particles tend to become suspended in air, posing an omnipresent health threat to engine components. This issue is most prevalent during operation in sandy environments at low altitudes. Takeoffs and landings can blow a significant quantity of particulates into the air; these particulates may then be ingested by the engine. Helicopters and other Vertical Takeoff and Landing (VTOL) aircraft are at high risk of engine damage in these conditions. Compressor blades are especially vulnerable, as they may encounter the largest of particles. Robust and thorough experimental and computational studies have been conducted to understand the relationships between particle type, shape, and size and their effects on compressor and turbine blade wear. However, there is a lack of literature that focuses on sampling particles directly from the flow inside an engine. Instead, experimental studies that estimate the trajectories and behavior of particles are based upon the resulting erosion of blades and the expected aerodynamics and physics of the region. It is important to close this gap to fully understand the role of particulates in eroding engine components. This study investigated the performance of a particle-sampling probe designed to collect particles after the first compressor stage of a Rolls-Royce Allison Model 250 turboshaft engine. The engine was not used in this investigation; rather, a rig that creates a particle-laden jet was developed in order to determine probe sampling sensitivity with respect to varying angles of attack and flow Mach number. Particle image velocimetry (PIV) was utilized to understand the aerodynamic effects of the probe on smaller particles. / Master of Science / Aircraft jet engines are constantly exposed to particles suspended in the atmosphere. Most jet engines contain several stages of spinning blades. The first series of stages near the front of the engine comprise the compressor, while the series towards the end of the engine comprise the turbine. Engines depend on compressor blades to add energy to the flow via compression and turbine blades to extract energy from the flow after combustion. Thus, they are critical for the successful operation of the engine. The constant impact of airborne particulates against these blades causes erosion, which alters blade geometry and thereby engine performance. Depending on the turbine inlet temperature, particles may melt and clog the cooling passages in turbine blades, causing serious damage as the blades reach temperatures above their intended operating regime. These damages inhibit the ability of the engine to operate properly and pose a serious safety risk if left unchecked. In literature, experimental engine erosion correlations and numerical models of particle trajectories through the engine have been developed; however, none of these studies collected particles directly from the compressor region of the engine. In this study, a probe was developed and evaluated for the purpose of sampling particulates between the first and second compressor stages of a Rolls-Royce Allison Model 250 turboshaft engine. The probe's efficacy and aerodynamic properties were analyzed such that the probe will provide processable data when inserted into the engine. The methods to obtain this data include particle-sampling and particle image velocimetry (PIV).