Jeffrey S. Patterson

Impact of Non-Uniform Leading Edge Coatings on the Aerodynamic Performance of Compressor Airfoils

Abstract : A computational fluid dynamic (CFD) investigation is presented that provides predictions of the aerodynamic impact of uniform and non-uniform coatings applied to the leading edge of a compressor airfoil in a cascade. Using a NACA 65(12)10 airfoil, coating profiles of varying leading edge non-uniformity were added. This non-uniformity is typical of that expected due to fluid being drawn away from the leading edge during the coating process. The CFD code, RVCQ3D, is a steady, quasi-three-dimensional Reynolds Averaged Navier-Stokes (RANS) solver. A k-omega turbulence model was used for the Reynolds Stress closure. The code predicted that these changes in leading edge shape can lead to alternating pressure gradients in the first few percent of chord that create small separation bubbles and possibly early transition to turbulence. The change in total pressure loss and trailing edge deviation are presented as a function of the coating non-uniformity parameter. Results are presented for six leading edge profiles over a range of incidences and inlet Mach numbers from 0.6 to 0.8. Reynolds number was 600,000 and free-stream turbulence was 6%. A two-dimensional map is provided that shows the allowable degree of coating non-uniformity as a function of incidence and inlet Mach number.

United States Navy 501-K34 Gas Turbine Engine RADCON Effort

On the afternoon of March 11, 2011 at 2:46pm, a 9.0 magnitude earthquake took place 231 miles northeast of Tokyo, Japan, at a depth of 15.2 miles. The earthquake caused a tsunami with 30 foot waves that damaged several nuclear reactors in the area. It was the fourth largest earthquake on record (since 1900) and the largest to hit Japan. On March 12, 2011, the United States Government launched Operation Tomodachi to provide humanitarian relief aid to Japan. In all, a total of 24,000 troops, 189 aircraft, 24 naval ships, supported this relief effort, at a cost of

Removals for Cause: A 35-Year Assessment of LM2500 Engine Removals by the United States Navy

90.0 million. The U.S. Navy provided material support, personnel movement, search and rescue missions and damage surveys. During the operation, 11 gas turbine U.S. warships operated within the radioactive plume. As a result, numerous gas turbine engines ingested radiological contaminants and are now operating under Radiological Controls (RADCON). This paper will describe the events that lead to Operation Tomodachi, as well as the resultant efforts on the U.S. Navy’s Japanese based gas turbine fleet. In addition, this paper will outline the U.S. Navy’s effort to decontaminate, overhaul and return these RADCON assets back into the fleet.Copyright

Analysis of Stall Precursors and Determination of Optimum Signal Processing Methods for an LM-2500 Gas Turbine

The United States (US) Navy has operated the General Electric LM2500 gas turbine on all its surface combatants for the past 35 years. The LM2500 is utilized as the propulsion engine aboard the US Navy’s newest surface combatants including the FFG 7, CG 47 and DDG 51 Class ships. The US Navy owns and operates 400 LM2500 engines. An on-condition maintenance philosophy is employed whereby engines are run-to-failure rather than removed from service upon achieving some operating milestone. This paper assesses the reasons for the removal of the US Navy’s LM2500s over their entire service life with a focus on how fleet maintenance capabilities have impacted and affected the cause for engine replacements over time.Copyright

Improvements to Compressor Prognostics Algorithm for US Navy Ship Service Gas Turbine Generator Sets

This paper presents an analysis of data taken from several stall initiation events on a GE LM-2500 gas turbine engine. Specifically, the time series of three separate pressure signals located at compressor stages 3, 6, and 15 were analyzed utilizing various signal processing methods to determine the most reliable indicator of incipient stall for this engine. The spectral analyses performed showed that rotating precursor waves traveling around the annulus at approximately half of the rotor speed were the best indicators. Non-linear chaotic time series analyses were also used to predict stall, but it was not as reliable an indicator. Several algorithms were used and it was determined that stall wave perturbations can be reliably identified about 900 revolutions prior to the stall. This work indicates that a single pressure signal located at stage 3 on an LM-2500 gas turbine is sufficient to provide advance warning of more than 2 seconds prior to the fully developed stall event.

USNS LCPL Roy M. Wheat: Zorya DT-59 Gas Turbine Installation and Integration

The Naval Surface Warfare Center Gas Turbine Emerging Technologies section conducted land-based testing on a gas turbine generator set in December 2003. The purpose of this testing, which was conducted on a Rolls Royce/Allison 501-K17 gas turbine, was to collect data that could be used to improve a previously developed computer program for predicting optimal compressor wash time intervals. For the purpose of Phase I of this testing, fouling was accomplished by injecting salt into the gas turbine inlet air stream. Phase II of this testing will consist of fouling the middle and back regions of the compressor. Influence coefficients can then be developed for each of these regions indicating how a given region affects overall performance. Typically, in a marine environment, fouling of the front stages occurs due to ingested salt while fouling in middle and rear regions occurs from a combination of ingested salt and oil seal leakage. A number of sensors, including compressor inlet and discharge condition probes, bleed air flow and fuel flow meters, were added in order to monitor engine performance during the testing. In addition, hardware was added to both ingest and monitor the concentration of salt in gas turbine inlet air. For Phase II testing, middle and rear stages of the 14-stage compressor shall be accessed through existing 5th and 10th stage bleed ports. A salt solution will be physically applied to the blades while the compressor is rotated by hand. Results from Phase I indicate that front stage compressor fouling causes a clear increase in inlet static pressure. This is due to the mass flow restriction through the compressor. Additional results are currently being summarized, and data is being utilized to improve the 501-K17 compressor wash prognostics algorithm previously noted.© 2005 ASME

Rolls Royce/Allison 501-K Gas Turbine: Anti-Fouling Compressor Coatings Shipboard — Phase I

In June 1997, the U.S. Navy purchased the Soviet military cargo ship “Vladimir Vaslyaev” for conversion to the USNS LCPL Roy M. Wheat for use in the Maritime Prepositioning Force. This paper documents the efforts of NSWCCD and dB Associates in supporting the installation, startup, and integration of the ship’s controls with the two Zorya DT-59 main propulsion gas turbine engines (GTE’s). The installation documentation developed included a video record of the port and starboard gas turbine installations, as well as information that aided in the development of the Engineering Operational Procedures (EOP). The integration for the DT-59s focused on providing engine speed sensors, an engine vibration monitoring system and engine reversing protection circuits.© 2004 ASME

Compressor Fouling Testing on Rolls Royce/Allison 501-K17 and General Electric LM2500 Gas Turbine Engines

Naval Surface Warfare Center Carderock Division (NSWCCD) Gas Turbine Emerging Technologies Code 9334 conducted a land-based evaluation of fouling-resistant compressor coatings for the 501-K17 Ship Service Gas Turbine Generator (SSGTG) [1]. The purpose of this evaluation was to determine whether such coatings could be used to decrease the rate of compressor fouling and associated fuel consumption. Based upon favorable results from the land-based evaluation, a similar coated compressor gas turbine engine was installed onboard a United States Navy vessel. Two data acquisition computer (DAC) systems and additional sensors necessary to monitor and compare both the coated test engine and an uncoated control engine were added. The goal of this shipboard evaluation was to verify land-based results in a shipboard environment. Upon completion of the DAC installation, the two gas turbine engines were operated and initial data was stored. Shipboard data was compared to land-based data to verify validity and initial compressor performance. The shipboard evaluation is scheduled for completion in June 2003, at which time data will be analyzed and results published.Copyright

Allison 501-K17 SSGTGS Technical Directive Experience

As part of the Gas Turbine Condition Based Maintenance (CBM) Program, Naval Surface Warfare Center, Carderock Division Code 9334 conducted compressor fouling testing on the General Electric LM2500 and Rolls Royce/Allison 501-K Series gas turbines. The objective of these tests was to determine the feasibility of quantifying compressor performance degradation using existing and/or added engine sensors. The end goal of these tests will be to implement an algorithm in the Navy Fleet that will determine the optimum time to detergent crank wash each gas turbine based upon compressor health, fuel economy and other factors which must be determined. Fouling tests were conducted at the Land Based Engineering Site (LBES). For each gas turbine, the test plan that was utilized consisted of injecting a salt solution into the gas turbine inlet, gathering compressor performance and fuel economy data, analyzing the data to verify sensor trends, and assessing the usefulness of each parameter in determining compressor and overall gas turbine health. Based upon data collected during these fouling tests, it seems feasible to accomplish the end goal. Impact Technologies, who analyzed the data sets for both of these fouling tests, has developed a prognostic modeling approach for each of these gas turbines using a combination of the data and probabilistic analysis.Copyright

Using an Auxiliary Power Unit (APU) Gas Turbine Engine to Start the LSD-41 Class Diesel Engines

The Allison 501-K17 Ship Service Gas Turbine Generator Set (SSGTGS) is used is provide ship board electrical power on several U.S. Navy Class ships, including the DD-963 Spruance Destroyer, the DDG-993 Kidd Guided Missile Destroyer and CG-47 Ticonderoga Guided Missile Cruiser Classes. The first of these units were placed in service during the mid 1970s. The Naval Sea Systems Command (NAVSEA) in conjunction with the Naval Surface Warfare Center, Carderock Division, Ship Systems Engineering Station (NSWCCD-SSES) have undertaken a major upgrade effort to improve the reliability, operation, serviceability and maintainability of the unit. This paper examines the process of this program and details the specific improvements made to the unit as a result of this effort. In addition, this paper outlines the experience gained as a result of installing these upgrades in the Fleet.Copyright