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An inertial particle separator (IPS) is a particulate removal device typically installed at the inlet of a gas turbine to mitigate effects of sand ingestion on the engine. This system can minimize particulate ingestion during helicopter landings in austere brownout conditions so as to increase engine life. Typically, IPS systems have lower engine power losses than alternative engine inlet filtration technologies. The present study investigates the effect of IPS particle removal and power losses as a function of scavenge leg geometry. Performance was evaluated based on particle separation efficiency, particle image velocimetry, and surface flow visualization, as well as power loss and mass flow rate variations. Of the various scavenge geometries considered, it was found that flow constriction with a hub-side ramp most improved separation efficiency, while also stabilizing mass flow rates and generally reducing power loss. This is attributed to a reduction in the level of flow separation by the addition of a favorable pressure gradient and geometry changes downstream of the attached flow region.

Previously reported experiments of inertial particle separator (IPS) geometries have focused on standardized sand mixtures that are a particle mixture of various materials, shapes and sizes. These factors make it difficult to understand the effect of particle size and material properties on overall separator efficiency, effects known to be critical to system performance. To address this problem, spherical glass particles with three different nominal diameters were introduced into a two-dimensional wind tunnel configuration representing the critical flow features of an IPS. The facility was used to investigate three different Outer Surface Geometries (OSGs) as well as three different flow splits, i.e. ratios of scavenge mass flow rate to total mass flow rate. The results indicated that large particles with nominal diameters of 120μm yielded near 100% efficiency indicating that these particle trajectories are dominated by inertia and wall reflections. As particles became smaller, their separation efficiency decreased, especially at low flow splits. This is attributed to an increased influence of aerodynamic effects associated with particle drag and the OSG. These results were then used to validate a model for determining separation efficiency as a function of particle diameter and flow split. Using this model, experimental and computational data found in the literature are compared, identifying critical particle and flow characteristics for IPS design.

Design and testing of a wave-rotor constant-volume combustor achieved stable combustion at near-atmospheric inlet conditions and demonstrated the potential of pressure-gain combustion using a wave ...

An inertial particle separator is one method of reducing the amount of sand and dust ingested by gas turbine engines. This is important because sand and dust often limit the useful life of engines operating in austere environments. To further improve the efficiency of inertial particle separator systems, an in-depth study of the multiphase flow dynamics has been undertaken. An experimental method was chosen to fill the void of available data and provide useful information for model validation. Using a facility at the University of Virginia, experiments have been conducted using three different inertial particle separator geometries. Surface flow visualization of each geometry is conducted using an oil-streak method to identify key flow structures. Separation efficiencies were calculated for an A4 coarse Arizona test dust (International Organization for Standardization 12103-1) over a range of operating conditions for each geometry.

The effects of sand and dust ingestion often limit the useful life of turbine engines operating in austere environments and efforts are needed to reduce the quantity of particulate entering the engine. Several Engine Air Particle Separation (EAPS) systems exist to accomplish this task. Inertial Particle Separators (IPS) are of particular interest because they offer significant weight savings and are more compact. This study focuses on the how small particles are affected by the dynamic fluid forces present in the IPS. Using Multi-Phase Particle Image Velocimetry (MP-PIV), 10um and 35um glass spheres were tracked through the IPS. Further, the data was also used to analyze the particles Coefficient of Restitution, (CORn), where they impact the Outer Surface Geometry (OSG) of the IPS.Copyright © 2014 by Rolls-Royce North America Inc.

Understanding the underlying flow mechanisms of inertial particle separators is important to creating more efficient separators. Previous experiments have utilized test dusts that vary dramatically in size and shape. These factors make it difficult to validate computational models due to the complexity that they introduce into the system; on top of an already complex flow field. Efficiency measurements were completed using spherical particles to isolate these effects on IPS efficiency. Three different particle sizes were tested at three different flow splits on each geometry. Large particles were shown to bounce through the IPS with near 100% efficiency at any flow split. As particles become smaller, their separation efficiency decreases due to the increase of fluid influences. The smallest spheres tested showed significant loss in efficiency that is more than expected. These effects are important to understand for modeling and prediction of IPS operation and efficiency.

The effects of sand and dust ingestion often limit the useful life of turbine engines operating in austere environments and efforts are needed to reduce the quantity of particulate entering the engine. Engine integral particle separators are one technology that can be used to remove sand and dust from the incoming air. Integral particle separators offer significant weight savings, are more compact, and have a lower total pressure loss, but may be less efficient compared with airframe installed separator technologies. In order to further improve the efficiency of integral particle separators, an in depth study of the multidimensional multiphase flow dynamics has been undertaken. A facility has been designed and built at the University of Virginia capable of reproducing various flow conditions that are seen in separator systems to understand the related particle and flow physics. The facility is capable of measuring overall sand separation efficiency and can accommodate several different measurement techniques in the tunnel test section, such as surface flow visualization and optical diagnostic techniques. This work is focused on the detailed description of the facility development. In addition, preliminary measurements of efficiency and surface flow visualizations are also presented as an indication of further work.

Renewed interest in pressure gain combustion applied as a replacement of conventional combustors within gas turbine engines creates the potential for greatly increased capability engines in the marine power market segment. A limited analysis has been conducted to estimate the degree of improvements possible in engine thermal efficiency and specific work for a type of wave rotor device utilizing these principles. The analysis considers a realistic level of component losses. The features of this innovative technology are compared with those of more common incremental improvement types of technology for the purpose of assessing potentials for initial market entry within the marine gas turbine market. Both recuperation and non-recuperation cycles are analyzed. Specific fuel consumption improvements in excess of 35% over those of a Brayton cycle are indicated. The technology exhibits the greatest percentage potential in improving efficiency for engines utilizing relatively low or moderate mechanical compression pressure ratios. Specific work increases are indicated to be of an equally dramatic magnitude. The advantages of the pressure gain combustion approach are reviewed as well as its technology development status.

A review of recent testing has been performed to assess the viability of a wave-rotorbased pressure-gain combustor. Tests accomplished in 2009 at the Purdue Zucrow lab on the Wave Rotor Combustor Rig (WRCR) provide basic information on the combustion processes achievable in a wave rotor passage. During a 30 day test period, 34 successful tests were completed, the longest of which was a 3-second firing was completed which totaled nearly 2,000 individual combustion events. Analysis of the results indicated stable combustor operation. The operability of the device is assessed regarding stability and combustion speeds. Agreement with predicted operation is examined. Potential for successful integration into a gas turbine as a replacement of a conventional combustor is addressed.

Recent trends in small advanced gas turbine engines call for higher turbine inlet temperatures. Advances in radial turbine technology have opened the way for a cooled metallic radial turbine capable of withstanding turbine inlet temperatures of 2500 F while meeting the challenge of high efficiency in this small flow size range. In response to this need, a small air-cooled radial turbine has been designed utilizing internal blade coolant passages. The coolant flow passage design is uniquely tailored to simultaneously meet rotor cooling needs and rotor fabrication constraints. The rotor flow-path design seeks to realize improved aerodynamic blade loading characteristics and high efficiency while satisfying rotor life requirements. An up-scaled version of the final engine rotor is currently under fabrication and, after instrumentation, will be tested in the warm turbine test facility at the NASA Lewis Research Center.

Pressure gain combustion in a wave rotor approaching the thermodynamic ideal of constant volume combustion has been proposed to significantly enhance the performance of gas turbine engines. A computational and experimental program is currently being conducted to investigate the combustion process and performance of a wave rotor with detonative and near-detonative internal combustion. An innovative and flexible preliminary design of the test rig is presented to demonstrate the operation and performance of the system. A preliminary design method based on a sequence of computational models is used to design wave processes for testing in the rig and to define rig geometry and operating conditions. The operating cycle allows for propagation of the combustion front from the exit end of the combustion channel to the inlet end. This is similar to and motivated by the Constant Volume Combustor (CVC) concept that seeks to produce a relatively uniform set of outflow conditions in both spatial and time coordinates.Copyright © 2004 by ASME

A novel version of a type of Pulse Detonation Engine (PDE) cycle has been developed using detonation combustion within the passages of a wave rotor. The innovation uses an internal stationary duct to supply a premixed fuel -air to the tubes whil e also eliminating the feedback of unsteady gas -dynamic interactions through the inlet and nozzle. Although believed to be broad in its potential application, initial steps in applying analytical modeling are aimed at developing the concept into a high pre ssure gain device suitable for use in a gas turbine engine. Termed the Constant Volume Combustor (CVC), the device is currently studied as a replacement for conventional constant pressure combustion systems and able to achieve a step improvement in engine performance. Gas dynamic predictions have been made using the NASA one dimensional non -steady code for simulation and analysis of wave rotors including combustion. Initial modeling results for the CVC confirm the cycle’s ability to deliver a downstream gas flow of high pressure gain. Results also predicted an inlet and outlet flowstream vastly more uniform in time and space than conventional PDE approaches. Furthermore, a range of design parameters is examined for the CVC’s ability to deliver exit temperatu re levels relevant to a turbine engine. Pressure gain performance increases realized with systematic design parameter examination are presented. A very limited examination of the inclusion of further loss mechanisms has been briefly addressed. A comparison of overall operating performance is made to pressure gain estimates obtained using a simple thermodynamic combustor model.

A wave rotor topped gas turbine engine has been identified which incorporates five basic requirements of a successful demonstrator engine. Predicted performance maps of the wave rotor cycle have been used along with maps of existing gas turbine hardware in a design point study. The effects of wave rotor topping on the engine cycle and the subsequent need to rematch compressor and turbine sections in the topped engine are addressed. Comparison of performance of the resulting engine is made on the basis of wave rotor topped engine versus an appropriate baseline engine using common shaft compressor hardware. The topped engine design clearly demonstrates an improvement in shaft horsepower and SFC. Predicted off design part power engine performance for the wave rotor topped engine is presented including that at engine idle conditions. Operation of the engine at off design is closely examined with wave rotor operation at less than design burner outlet temperatures and rotor speeds. Challenges remaining in the development of a demonstrator engine are addressed.Copyright © 1996 by ASME