Master of Science, The Ohio State University, 2020, Aero/Astro Engineering

This thesis covers the intensive research effort to elucidate the role of elevated temperature in deposition. Several experimental campaigns were conducted in this pursuit. The testing explored high temperature deposition with 0-10 micron Arizona Road Dust (ARD) with the intent of creating a yield strength model that included temperature effects and could be incorporated into the existing OSU deposition model. Experimental work was first conducted in the impulse kiln facility where small amounts of the test dust were placed on ceramic targets and rapidly exposed to temperatures between 1200K and 1500K. Trends in the packing factor confirmed the existence of two threshold values (1350K and 1425K) that could be linked to strength characteristics of the dust when exposed to high temperatures. Using the information obtained from the kiln experiments, HTDF testing was conducted between 1325K and 1525K. Exit temperatures were set at 25K intervals in this region with a constant jet velocity of 150 m/s. The capture efficiency data showed this trend with temperature and indicated a softening temperature and melting temperature of 1362K and 1512K respectively. With these critical values in hand, the Ohio State University Molten Model was created to modify yield strength with particle velocity and temperature. The model was tested using CFD and showed a good capability for capturing particle temperature effects in deposition from an impinging particle-laden jet. A subsequent test campaign was conducted to explore the effect of varying surface temperature on deposition. Hastelloy coupons with Thermal Barrier Coatings (TBCs) were subjected to a constant jet at 1600K jet and 200 m/s while being cooled via a backside impingement jet. Surface temperatures between 1455K and 1125K were impacted with 0-10 micron ARD while an IR camera monitored the surface. Coupons with higher coolant flowrates (lower surface temperature) saw significantly lower deposition rates than the higher surf (open full item for complete abstract)

Committee: Jeffrey Bons Dr. (Advisor); Randall Mathison Dr. (Committee Member) Subjects: Aerospace Engineering

Master of Science, The Ohio State University, 2010, Aeronautical and Astronautical Engineering

A new turbine research facility at The Ohio State University Aeronautical and Astronautical Research Lab has been constructed. The purpose of this facility is to re-create deposits on the surface of actual aero-engine Nozzle Guide Vane (NGV) hardware in an environment similar to what the hardware was designed for. This new facility is called the Turbine Reacting Flow Rig (TuRFR). The TuRFR provides air at temperatures up to 1200 °C and at inlet Mach numbers comparable to those found in an actual turbine (~0.1). Several validation studies have been undertaken which prove the capabilities of the TuRFR. These studies show that the temperature entering the NGV cascade is uniform, and they demonstrate the capability to provide film cooling air to the NGV cascade at flow rates and density ratios comparable to the NGV design. Deposition patterns have also been created on the surface of actual NGV hardware. Deposition was created at different flow temperatures, and it was found that deposition levels decrease with decreasing gas temperature. Also, film cooling levels were varied from 0% film cooling to 4% film cooling. It was found that with increased rates of film cooling deposition decreased. With the TuRFR capabilities demonstrated, research on the effects of deposition on the aerodynamic performance of the NGV hardware was conducted. Integrated non-dimensional total pressure loss values were calculated in an exit Rec range of 0.2x106 to 1.7x106 for a deposit roughened NGV cascade and a smooth cascade. The data suggests that deposition causes increased losses across the NGV cascade and possibly earlier transition. The data also suggests a possible region of separated flow in the NGV cascade which disappears at higher exit Reynolds numbers. These results are similar to those found in the literature.

Committee: Jeffrey Bons PhD (Advisor); James Gregory PhD (Committee Member); Ali Ameri PhD (Committee Member) Subjects: Mechanical Engineering

Master of Science, The Ohio State University, 2013, Aero/Astro Engineering

A high temperature combustion rig was used to impact bituminous and lignite coal fly ash particles on an impingement plate at conditions similar to those found in the hot section of a gas turbine engine. Individual particles were tracked using particle shadow velocimetry as they either rebounded from or deposited on the plate surface. The effects of particle size, particle impact velocity, impact angle, particle temperature, and plate temperature were explored. Particle diameter ranged from 30-800µm, impact velocity ranged from 5-160 m/s, impact angle ranged from close to 0° to 90°, and temperatures ranged from ambient conditions to 2100°F. Increasing diameter, impact velocity, and plate temperature were all shown to decrease the total coefficient of restitution. The angular coefficient of restitution was shown to decrease with increased impact angle for bituminous ash. The total coefficient of restitution versus both impact angle and particle temperature yielded unexpected trends. For bituminous ash, a peak in coefficient of restitution occurred for all temperature cases at an impingement angle of 40°. Both higher and lower impact angles resulted in a decrease in coefficient of restitution. A peak in coefficient of restitution occurs between 1250-1500°F for both the bituminous and lignite ash, decreasing at both higher and lower temperatures. Possible explanations for these unexpected results are discussed.

Committee: Jeffrey Bons Ph.D (Advisor); Jen-Ping Chen Ph.D (Committee Member) Subjects: Aerospace Engineering

Master of Science, The Ohio State University, 2012, Aero/Astro Engineering

An accelerated deposition test facility was used to study the relationship between film cooling, surface temperature, and particle temperature at impact on deposit formation. Tests were run at gas turbine representative inlet Mach numbers (0.1) and temperatures (1090°C). Deposits were created from lignite coal fly ash with median diameters of 1.3 and 8.8µm. Two CFM56-5B nozzle guide vane doublets, comprising three full passages and two half passages of flow, were utilized as the test articles. Tests were run with different levels of film cooling back flow margin and coolant temperature. Particle temperature upon impact with the vane surface was shown to be the leading factor in deposition. Since the particle must traverse the boundary layer of the cooled vane before impact, deposition is directly affected by the film and metal surface temperature as well. Film coolant jet strength showed only minor effect on deposit patterns on the leading edge. However, larger Stokes number (resulting in higher particle impact temperature) corresponded with increased deposit coverage area on the shower head region. Additionally, infrared measurements showed a strong correlation between regions of greater deposits and elevated surface temperature on the pressure surface. Thickness distribution measurements also highlighted the effect of film cooling by showing reduced deposition immediately downstream of cooling holes. A set of secondary tests were also conducted to briefly study the effect of Stokes number on leading edge deposition with no cooling, in order to support conclusions from the primary tests. It was found that larger Stokes number led to an increase in rate of deposition due to a greater number of particles being able to follow their inertial trajectories and impact the vane. Implications for engine operation in particulate-laden environments are discussed.

Committee: Jeffrey Bons PhD (Advisor); Micheal Dunn PhD (Committee Member) Subjects: Aerospace Engineering; Aerospace Materials; Engineering

Master of Science, The Ohio State University, 2024, Aerospace Engineering

The role of quartz in gas turbine hot section deposition was investigated by varying both its size and percent concentration in Air Force Research Lab test dust (AFRL-02). The size distributions of quartz tested were 0 – 3 μm, 0 – 10 μm (baseline), and 10 – 20 μm while percent concentration ranged from 0% to 100%. The experiments replicated a gas turbine effusion cooling circuit with a flow temperature of 894K and plate surface temperature of 1144K. Aerosolized AFRL-02 dust was delivered to the test article, and capture efficiency, hole capture efficiency, blockage per gram, normalized deposit height, and effective area were recorded. A quartz size distribution of 0 – 3 μm showed the greatest deposition while 10 – 20 μm consistently deposited the least. Varying percent concentration of quartz had less obvious trends. While at a size distribution of 10 – 20 μm, increasing quartz concentration decreased deposition in all four assessment parameters. For a size distribution of 0 – 3 μm, increasing quartz concentration originally decreased deposition until greatly increasing it past a concentration of 68%. Quartz has been identified as a predominantly erosive mineral to deposits, but results suggest the size distribution contributes to deposition at a rate greater than or equal to percent concentration. The following study elucidates the effects of both size and concentration of quartz in a heterogenous mineral blend.

Committee: Jeffrey Bons (Advisor); Randall Mathison (Committee Member) Subjects: Aerospace Engineering

Master of Science, The Ohio State University, 2023, Mechanical Engineering

Airborne particulate ingestion into modern, high temperature aeronautical turbine engines can cause damage to internal components, including total engine failure. Volcanic ash interactions with turbine engines has been well studied, and current research in the field focuses on other mineral based test dusts that more closely emulate desert sand and other natural materials. This work focuses on AFRL test dust, the product of an Air Force program to formulate a dust that will create engine deposits that are similar in chemical composition to those deposits found in engines post service. This test dust contains quartz, gypsum, dolomite, aplite and salt, common minerals found in Earth's crust. Utilizing high temperature facilities at The Ohio State University, a testing campaign was developed to seek further understanding of any chemical synergies between these five minerals in an impinging jet configuration. The base AFRL recipe was altered in order to remove individual minerals or increase the quantity of given mineral in proportion to the others in order to compare deposition characteristics in the context of chemical composition when compared to the base mixture. Removing any single mineral does not noticeably change capture efficiencies of AFRL when compared to the control mixture. Capture efficiencies were driven by temperature much more than any given chemical manipulations as it was found that increasing temperature will increase the capture efficiency. At a certain point, deposits cool to a shiny, glassy finish and are incredibly hard. At these temperatures, chemical synergies are better interpreted through the lens of amorphous silica glass networks and alkali network modifiers than the previously proposed ratio of calcium to silicon, although these concepts are related as a silica glass network is heavily modified by the presence of calcium. These alkali network modifiers will decrease the viscosity of a partially or fully molten deposit, and lower viscositie (open full item for complete abstract)

Committee: Lian Duan (Committee Member); Jeffrey Bons (Advisor) Subjects: Aerospace Engineering; Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2023, Mechanical Engineering

This thesis aimed to improve the numerical framework of modeling particle deposition in environments relevant to the cooling passage of the gas turbine engines. The effort comprised three main parts: (i) Investigating forces affecting particle motions. (ii) Applying smoothing techniques to improve convergence for mesh morphing. (iii) Elucidating experimental results through numerical simulations and sensitizing the OSU deposition model to temperature. Forces affecting particle trajectories were examined with a focus on turbophoretic force and Saffman lift force. Stochastic models were employed to generate the fluctuating flow velocity for modeling the turbophoretic force. Concentration and axial distributions of deposition velocity, as well as deposition velocity versus particle relaxation time, were predicted by The Discrete Random Walk model (DRW) and variations of the Continuous Random Walk model (CRW). These predictions were compared with existing experiments and direct numerical simulation (DNS) using two different geometries. Special attention was given to the inconsistent directional vector that results from solving the Langevin equation in non-rectangular geometries using location-specific coordinate systems. To achieve more physical solutions, the Langevin equation in cylindrical coordinates was derived for the pipe flows. The effect of the Saffman lift force with two random walk models was also discussed. To improve the stability of mesh morphing for modeling deposit growth, smoothing techniques were employed to reduce the irregular surface resulting from the discreteness of numerical setup and the effect of the Saffman lift force. Three schemes, the mass-based method proposed by Forsyth et al, the inverse distance weighting method and the radial basis function method, were employed to model the growth of the deposit. Because the scale of real cooling passages in gas turbine engines makes it difficult to use a fine mesh, simulations using both a fine and (open full item for complete abstract)

Committee: Jeffrey Bons Dr. (Advisor); Lian Duan Dr. (Committee Member); Randall Mathison Dr. (Committee Member) Subjects: Aerospace Engineering; Mechanical Engineering

Master of Science, The Ohio State University, 2023, Aerospace Engineering

In this thesis there are two main studies. The first is an assessment of the role of mineral composition for Air Force Research Laboratory Test Dust (AFRL) for deposition in a realistic gas turbine engine environment. The second is an attempt to recreate Arizona Road Dust (ARD) synthetically by analyzing the chemical components of the natural dust and blending synthetic minerals together to match it. In the first study, experiments were performed on an effusion cooling test article with a coolant flow temperature of 894K and surface temperature of 1144K. Aerosolized dust with a 0-10 µm particle size distribution was delivered to the test article. The mineral recipe of AFRL was altered such that the presence of each of the five components ranged from 0% to 100%. For each of these AFRL recipe experiments several results were reported including capture efficiency, hole capture efficiency, mass flow reduction per gram, and normalized deposit height. Results are compared to a previous study of the inter-mineral synergies in an impingement cooling jet at the same temperature conditions. Despite differences in experimental facility flow geometry, overall agreement was found between the trends in deposition behavior of the dust blends. The strong deposition effects that were observed were shown to be related to adhesion forces of particles, mechanical properties, and chemical properties of the dust minerals. In the second study, X-Ray Diffraction (XRD) was performed on ARD to identify minerals present in a naturally sourced dust blend. Pure minerals were mixed in quantities that matched the XRD spectrum of ARD, and oxide content of this synthetic dust blend was shown to match the ISO standard (12103-1) to which ARD conforms. Particle size distribution was also matched to ARD (0-15 µm). Experiments were then conducted in four deposition facilities, one of which was representative of turbine hot section conditions (1500-1625K) and two were representative of internal coola (open full item for complete abstract)

Committee: Datta Gaitonde (Committee Member); Jeffrey Bons (Advisor) Subjects: Aerospace Engineering

Doctor of Philosophy, The Ohio State University, 2021, Aero/Astro Engineering

The detrimental effects of deposition on gas turbine engine performance have become more pronounced as operation in climates with heavy concentrations of airborne particulate has increased over the past several decades. This has introduced relatively new and complex challenges for engine designers and maintenance teams who must account for and try to mitigate the host of negative consequences that can arise when particles accumulate on turbine hardware. The majority of deposition analysis is performed through experimental testing, whether it be in the full-scale engine environment or in a scaled-down facility. The cost involved with designing, manufacturing, and testing hardware can be exorbitant however, and thus computational models that can predict deposition behavior are an attractive and more affordable alternative. Over the past decade, a variety of models have been introduced to address this growing need. The aim of this work is two-fold and is addressed in two parts. The first goal is to improve the current state of deposition modeling by investigating the role that absolute pressure plays in the process. Experiments are first conducted in a High-Pressure Deposition Facility (HPDF) at the Aerospace Research Center (ARC) at the Ohio State University (OSU). Commercially available Arizona Road Dust (ARD) is delivered to an effusion cooling plate at a specified pressure ratio and flow temperature, and the absolute flow pressure is varied over a range of 14.77 atm to study the effect pressure has on the deposition levels and blockage of the effusion cooling holes. Two size distributions (0-3.5 and 0-10 µm) are investigated, and the results indicate that the deposition and blockage rates decrease monotonically as absolute pressure increases. This holds true for both sizes of dust, but the overall blockage rates are much higher for the 0-3.5 µm. The rate of decrease in hole blockage as pressure increases on the other hand is steeper for the 0-10 µm distributi (open full item for complete abstract)

Committee: Jeffrey Bons (Advisor); Randall Mathison (Committee Member); Sandip Mazumder (Committee Member) Subjects: Aerospace Engineering; Mechanical Engineering

Master of Science, The Ohio State University, 2016, Mechanical Engineering

The deposition of particulate in gas turbine cooling systems with a focus on single wall effusion holes was investigated. This study focused on the effect that flow turning angle into the cooling hole has on the blockage of these holes. The test hardware is based on a single walled combustor liner with angled effusion holes. By allowing the mass flow through the test system to decrease as deposition occurred the pressure drop across the test coupon was held at 3% of the discharge pressure. The mean flow turning angle was varied between favorable (10°) and adverse (130°) by mounting the plate in different orientations on a stalled plenum. The dust used was 0-10 µm Arizona Road Dust (ARD). These tests were run with a coupon temperature of 870 °C; this was achieved by use of an electric kiln. Flow reduction of the adverse test plates was around twice as much as the favorable condition; however both conditions had very similar capture efficiencies. 3D scans and sectioned test plates were used to investigate the different structures of the deposition that formed on the test plates and in the effusion holes. It is seen that turning angle does not influence the amount of captured mass but just the location of where that mass is captured and so its effect on the flow. A companion CFD study was also performed to explore the ability of computational models to predict the impact location and deposition depending on the impingement angle. This model was a simplified case and modeled a single effusion hole with the same geometry as the test plate. The inlet conditions were held constant and based on the experimental data. Particles were tracked with an Eulerian-Lagrangian method and it was seen that the predicted first impact locations closely matched the deposition seen in the experimental setup. Additionally a sticking model was used to predict deposition. It was seen that under the simulated conditions this model predicted deposition similar to the experimenta (open full item for complete abstract)

Committee: Jeffrey Bons Dr. (Advisor); Randall Mathison Dr. (Committee Member) Subjects: Aerospace Engineering; Fluid Dynamics; Mechanical Engineering

Master of Science, The Ohio State University, 2015, Aero/Astro Engineering

The development of flow blockage by particulate accumulation in the internal flow passages of a gas turbine double wall cooling scheme was studied experimentally. This parametric investigation focused on the effects of particle concentration, flow temperature, and particle size on the deposition characteristics in a cylindrical impingement/film cooling geometry. The impingement and film cooling hole layout is based on the leading edge cooling scheme of a modern nozzle guide vane (NGV). Tests were run at a constant pressure ratio of 1.02 (cavity pressure to exhaust) and the mass flow rate was permitted to decrease throughout the test as the cooling passages became obstructed. Particulate concentration was varied by holding the mass injected constant while adjusting the test injection time and rate. Particles consisted of Arizona Road Dust with distributions of 0-5, 0-10, and 0-20 µm. Flow blockage increased by 4% over a range of two orders of magnitude in particulate concentration for the smallest particle size distribution. At 452 °C the blockage levels increased to nearly four times that of the ambient conditions. Similar amounts of particulate deposited on the film cooling wall at ambient and high temperature, but the high temperature particulate caused greater blockage to the film holes. The effect of particle size was difficult to discern due to clumping of the smallest particles into large agglomerations. This clumping effect was coupled with the trend of increasing temperature. Implications for continued internal deposition research are discussed.

Committee: Jeffrey Bons Dr. (Advisor); Randall Mathison Dr. (Committee Member) Subjects: Aerospace Engineering; Fluid Dynamics; Mechanical Engineering

Master of Science, The Ohio State University, 2015, Aero/Astro Engineering

A computational study was performed to investigate deposition phenomena in a high-pressure turbine stage. Steady mixing-plane and unsteady sliding mesh calculations were utilized. Three-dimensional, steady and unsteady RANS calculations were performed in conjunction with published experiments completed on a similar turbine geometry which provided boundary conditions and pressure data to validate flow solutions. Particles were introduced into the flow domain and deposition was predicted using a Lagrangian particle tracking method with the critical viscosity model to predict deposition. For the steady method, in order to track particles from the mixing plane through the blade domain, particle positions were saved after passing through the vane domain and inserted into the blade domain using two different methods which were named averaged and preserved. Both methods yielded nearly identical results. For the unsteady simulation particles were tracked through a sliding mesh interface with particle position, velocity, and temperature preserved at exit of the vane domain and inlet of the blade domain. Deposition results for the steady mixing plane using both particle averaging techniques and unsteady sliding interface were compared for particles of different sizes. Large particles produce localized impact and deposit zones near the hub and tip for all methods. Steady methods deviated from unsteady methods at all particle diameters by neglecting unsteady vane wake motion causing different impact locations and subsequent multiple rebounds. At low Stokes numbers (2.8-11) the steady methods overpredicted impacts, by 30% and 25% respectively, because wake motion and particle drag dominated particle trajectories, pulling them away from pressure surface. At a high Stokes number (31) the steady method underpredicted impacts and deposits as wake motion caused a shift in initial impact locations. However, the larger particle inertia of these particles allowed subsequent impacts (open full item for complete abstract)

Committee: Jeffrey Bons Dr. (Advisor); Ali Ameri Dr. (Committee Member); Jen-Ping Chen Dr. (Committee Member) Subjects: Aerospace Engineering; Engineering; Fluid Dynamics; Mechanical Engineering

Master of Science, The Ohio State University, 2009, Aeronautical and Astronautical Engineering

This thesis presents the design, construction and partial operation of the Turbine Reacting Flow Rig (TuRFR), which is a high temperature turbine vane test facility at The Ohio State University's Aeronautical and Astronautical Research Laboratory. It is capable of producing combustor temperatures up to 2200°F and is rated for normal operation at pressures of 30 psig. The facility matches real engine flow parameters such as Mach number, gas temperature, density ratio, pattern factor, and turbulence level. It is designed to test industry hardware and has a modular design to allow for various turbine vane shapes and sizes. It consists of a steel base (for flow conditioning and supporting of the burner), natural gas burner (for elevating the gas temperature), spool piece (for viewing burner during operation), cone (for accelerating the flow), equilibration tube (for allowing entrained seed particles to reach thermal and kinematic equilibrium), transition piece (for sealing with the equilibration tube and transitioning from a circular to rectangular cross section), view section (for optical access to the turbine vanes), and vane holder (for securely holding the turbine vane in place during experiments). It is capable of providing film cooling air at a density ratio of 2.8, with plans to upgrade the heating system for lower density ratios. To date, the facility has been tested at mass flowrates up to 2.6 lbm/s, which is adequate mass flow to fill four 1st stage high pressure vane passages from a modern high bypass aero-engine at a representative inlet Mach number of 0.25 and gas temperature of 2200°F.

Committee: Jeffrey Bons PhD (Advisor); Mohammad Samimy PhD (Committee Member) Subjects: Aerospace Materials; Engineering