A Turbine Wheel Design Story

1988 ◽  
Author(s):  
Wilson R. Taylor ◽  
Keith Wheless ◽  
Lee G. Gray
Keyword(s):  
Jet Fuel ◽  
Design Solution ◽  
Design Decision ◽  
Proof Of Concept ◽  
Gas Generator ◽  
Fighter Aircraft ◽  
Turbine Wheel ◽  
Power Turbine ◽  
Analytical Proof ◽  
Initial Power

A Jet Fuel Starter (JFS) is used to start the F100 main propulsion engines for the F-15 fighter aircraft. The JFS is a dual rotor machine which consists of a gas generator spool and a power turbine spool. The gas generator turbine wheel was designed to be contained within the turbine case in the event of a JFS overspeed. This is done by the inclusion of a containment ring in the turbine case. The initial power turbine wheel design was not able to be contained by its turbine case. A design decision was made to make this wheel frangible, that is, in an overspeed condition the wheel would break into small pieces which could be contained by the existing turbine case. An alternative design solution is proposed in this paper and an analytical proof-of-concept is presented.

Advanced Control System Considerations for Small Shaft-Type Aircraft Gas Turbines

1970 ◽  
Author(s):  
D. A. Prue ◽  
T. L. Soule
Keyword(s):  
Control System ◽  
Gas Turbines ◽  
Evaluation Criteria ◽  
Open Loop ◽  
Engine Control ◽  
Gas Generator ◽  
Engine Control System ◽  
Power Turbine ◽  
Advanced Control ◽  
Temperature Load

The next generation of free-turbine engines in the 2 to 5-lb/sec airflow class will undergo vast improvements in performance and efficiency. The improvements will be achieved concurrent with overall reductions in size and weight. Effort is required at optimization and miniaturization of the engine control system to keep pace with these improvements. This paper describes a conceptual design of an advanced engine control system for this class of engine. It provides gas generator and power turbine control with torque, temperature, load sharing and overspeed limiting functions. The control system was concepted to accommodate, with minimum hardware changes, such variants as regenerative cycle and/or variable power turbine geometry. In addition, considerations for closed and open loop modes of control and fluidic, electronic and hydromechanical technologies were studied to best meet a defined specification and a weighted set of evaluation criteria.

Experimental Evaluation of a Metal Mesh Bearing Damper

2000 ◽  
Vol 122 (2) ◽  
pp. 326-329 ◽  
Author(s):  
Mark Zarzour ◽  
John Vance
Keyword(s):  
Elevated Temperatures ◽  
Test Facility ◽  
Squeeze Film ◽  
Gas Generator ◽  
Metal Mesh ◽  
Previous Investigator ◽  
Spreadsheet Program ◽  
Squirrel Cage ◽  
Power Turbine ◽  
Squeeze Film Dampers

Metal mesh is a commercially available material used in many applications including seals, heat shields, filters, gaskets, aircraft engine mounts, and vibration absorbers. This material has been tested by the authors as a bearing damper in a rotordynamic test rig. The test facility was originally used to support the design of a turboprop engine, developing squirrel cages and squeeze film dampers for both the gas generator and power turbine rotors. To design the metal mesh damper, static stiffness and dynamic rap test measurements were first made on metal mesh samples in a specially designed nonrotating test fixture. These property tests were performed on samples of various densities and press fits. One sample was also tested in an Instron machine as an ancillary and redundant way to determine the stiffness. Using the stiffness test results and equations derived by a previous investigator, a spreadsheet program was written and used to size metal mesh donuts that have the radial stiffness value required to replace the squirrel cage in the power turbine. The squirrel cage and squeeze film bearing damper developed for the power turbine rotor was then replaced by a metal mesh donut sized by the computer code. Coast down tests were conducted through the first critical speed of the power turbine. The results of the metal mesh tests are compared with those obtained from previous testing with the squeeze film damper and show that the metal mesh damper has the same damping as the squeeze film at room temperature but does not lose its damping at elevated temperatures up to 103°C. Experiments were run under several different conditions, including balanced rotor, unbalanced rotor, heated metal mesh, and wet (with oil) metal mesh. The creep, or sag, of the metal mesh supporting the rotor weight was also measured over a period of several weeks and found to be very small. Based on these tests, metal mesh dampers appear to be a viable and attractive substitute for squeeze film dampers in gas turbine engines. The advantages shown by these tests include less variation of damping with temperature, ability to handle large rotor unbalance, and the ability (if required) to operate effectively in an oil free environment. Additional testing is required to determine the endurance properties, the effect of high impact or maneuver loads, and the ability to sustain blade loss loads (which squeeze films cannot handle). [S0742-4795(00)01002-4]

Experimental Evaluation of a Metal Mesh Bearing Damper

1999 ◽  
Author(s):  
Mark Zarzour ◽  
John Vance
Keyword(s):  
Elevated Temperatures ◽  
Test Facility ◽  
Squeeze Film ◽  
Gas Generator ◽  
Metal Mesh ◽  
Previous Investigator ◽  
Spreadsheet Program ◽  
Squirrel Cage ◽  
Power Turbine ◽  
Squeeze Film Dampers

Metal mesh is a commercially available material used in many applications including seals, heat shields, filters, gaskets, aircraft engine mounts, and vibration absorbers. This material has been tested by the authors as a bearing damper in a rotordynamic test rig. The test facility was originally used to support the design of a turboprop engine, developing squirrel cages and squeeze film dampers for both the gas generator and power turbine rotors. To design the metal mesh damper, static stiffness and dynamic rap test measurements were first made on metal mesh samples in a specially designed nonrotating test fixture. These property tests were performed on samples of various densities and press fits. One sample was also tested in an Instron machine as an ancillary and redundant way to determine the stiffness. Using the stiffness test results and equations derived by a previous investigator, a spreadsheet program was written and used to size metal mesh donuts that have the radial stiffness value required to replace the squirrel cage in the power turbine. The squirrel cage and squeeze film bearing damper developed for the power turbine rotor was then replaced by a metal mesh donut sized by the computer code. Coast down tests were conducted through the first critical speed of the power turbine. The results of the metal mesh tests are compared with those obtained from previous testing with the squeeze film damper and Show that the metal mesh damper has the same damping as the squeeze film at room temperature but does not lose its damping at elevated temperatures up to 103 °C. Experiments were run under several different conditions, including balanced rotor, unbalanced rotor, heated metal mesh, and wet (with oil) metal mesh. The creep, or sag, of the metal mesh supporting the rotor weight was also measured over a period of several weeks and found to be very small. Based on these tests, metal mesh dampers appear to be a viable and attractive substitute for squeeze film dampers in gas turbine engines. The advantages shown by these tests include less variation of damping with temperature, ability to handle large rotor unbalance, and the ability (if required) to operate effectively in an oil free environment. Additional testing is required to determine the endurance properties, the effect of high impact or maneuver loads, and the ability to sustain blade loss loads (which squeeze films cannot handle).

Design of Control Laws Based on Inverted Decoupling and Linear Matrix Inequality for a Turboprop Engine

2020 ◽  
Vol 142 (2) ◽  
Author(s):  
Huairong Chen ◽  
Xi Wang ◽  
Meiyin Zhu ◽  
Nannan Gu ◽  
Shubo Yang
Keyword(s):  
Linear Matrix Inequality ◽  
Linear Matrix ◽  
Matrix Inequality ◽  
Shaft Speed ◽  
Blade Angle ◽  
Gas Generator ◽  
Control Laws ◽  
Control Loops ◽  
Turboprop Engine ◽  
Power Turbine

Abstract This paper proposes a systematic approach to design control laws for a turboprop engine. The proposed approach includes interactions decoupling and control laws design based on linear matrix inequality (LMI). First, since the main objective of the turboprop engine control system is to ensure propeller-absorbed power at a constant propeller speed, the linear model of a turboprop engine can be linearized into a two-input two-output (TITO) plants, and there exist the interactions between two control loops. Because inverted decoupling can well retain the dynamic characteristics of the original system, it is used to decouple the interactions so that the TITO plant can be divided into two single-input single-output plants, that is, gas-generator shaft speed is controlled by fuel flowrate and power turbine shaft speed is controlled by blade angle. Then, the control laws are designed separately for each control loop by solving the LMI group derived from static output feedback (SOF) and regional pole placement. Finally, the proposed approach is implemented on a two-spool turboprop engine (TSTPE) integrated model. The simulation results show that there exist strong interactions between two control loops of TSTPE, applying inverted decoupling to decouple these interactions is effective, and the gas-generator shaft speed and the power turbine speed can track their commands with appropriate performance by controlling the fuel flowrate and blade angle under the action of the designed control laws and inverted decoupling.

Process Plant Application of an Aircraft-Type Gas Turbine

1969 ◽  
Author(s):  
H. B. Yancy
Keyword(s):  
Control Systems ◽  
Waste Heat ◽  
Subsequent Development ◽  
Lubricating Oil ◽  
Industrial Plant ◽  
Gas Generator ◽  
Waste Heat Boiler ◽  
Power Turbine ◽  
Petroleum Company ◽  
Helium Plant

The installation to be discussed in this paper was one of the first gas generator, power turbine, centrifugal compressor design combinations to be put in ground (as opposed to airplane) power applications. As a consequence the control systems, waste heat boiler installation and other parts of the facility proved to be other than adequate for continuous duty industrial plant use and as such, has gone through a subsequent development period to overcome the many problems that were encountered. This should be kept in mind as one reads the article. The present-day industrial gas generator units incorporate simplified and reliable control systems and other successful features as a result of this earlier experimental and prototype installation. Revisions to the Phillips Petroleum Company Dumas Helium Plant Pratt Whitney GG3C gas generator and related equipment have greatly increased onstream capabilities. Replacement of unreliable controls and electrical relays has decreased unwarranted shutdowns from 80 hr in 1963 to 8 hr in 1967. Improvements in lubricating oil have increased the time between oil changes from 300 to 3000 hr. Design changes in bearings, exhaust hood, and the lubricating oil system have increased the gas generator’s reliability. The Cooper-Bessemer RT-48 free power turbine has operated maintenance-free since startup. Cooper-Bessemer’s latest design has solved the reaction turbine hood stress cracking problem. Use of this type facility in helium plant service offers advantages, but lack of flexibility has caused a considerable amount of product loss at Dumas Helium Plant.

Regenerative Gas Turbines With Divided Expansion

2004 ◽  
Author(s):  
Brian Elmegaard ◽  
Bjo̸rn Qvale
Keyword(s):  
Mathematical Model ◽  
Gas Turbines ◽  
High Efficiency ◽  
Limited Range ◽  
Simulation Program ◽  
Operating Parameters ◽  
Gas Generator ◽  
Extensive Simulation ◽  
Power Turbine ◽  
The Mathematical Model

Recuperated gas turbines are currently drawing an increased attention due to the recent commercialization of micro gas turbines with recuperation. This system may reach a high efficiency even for the small units of less than 100kW. In order to improve the economics of the plants, ways to improve their efficiency are always of interest. Recently, two independent studies have proposed recuperated gas turbines to be configured with the turbine expansion divided, in order to obtain higher efficiency. The idea is to operate the system with a gas generator and a power turbine, and use the gas from the gas generator part for recuperation ahead of the expansion in the power turbine. The present study is more complete than the predecessors in that the ranges of the parameters have been extended and the mathematical model is more realistic using an extensive simulation program. It is confirmed that the proposed divided expansion can be advantageous under certain circumstances. But, in order for todays micro gas turbines to be competitive, the thermodynamic efficiencies will have to be rather high. This requires that all component efficiencies including the recuperator effectiveness will have to be high. The advantages of the divided expansion manifest themselves over a rather limited range of the operating parameters, that lies outside the range required to make modern micro turbines economically competitive.

Capacity Matching of Aeroderivative Gas Generator With Free Power Turbine: Challenges, Uncertainties, and Opportunities

2019 ◽  
Author(s):  
Deepak Thirumurthy ◽  
Jose Carlos Casado Coca ◽  
Kanishka Suraweera
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Systems Approach ◽  
Gas Generator ◽  
Performance Guarantees ◽  
Design Variables ◽  
Performance Trends ◽  
Power Turbine ◽  
Parameter Matching ◽  
Turbine Capacity

Abstract For gas turbines with free power turbines, the capacity or flow parameter matching is of prime importance. Accurately matched capacity enables the gas turbine to run at its optimum conditions. This ensures maximum component efficiencies, and optimum shaft speeds within mechanical limits. This paper presents the challenges, uncertainties, and opportunities associated with an accurate matching of a generic two-shaft aeroderivative HP-LP gas generator with the free power turbine. Additionally, generic performance trends, uncertainty quantification, and results from the verification program are also discussed. These results are necessary to ensure that the final free power turbine capacity is within the allowable range and hence the product meets the performance guarantees. The sensitivity of free power turbine capacity to various design variables such as the vane throat area, vane trailing edge size, and manufacturing tolerance is presented. In addition, issues that may arise due to not meeting the target capacity are also discussed. To conclude, in addition to design, analysis, and statistical studies, a system-of-systems approach is mandatory to meet the allowed variation in the free power turbine capacity and hence the desired gas turbine performance.

Optimized SGT-A35 (GT61) for Improved Emissions and Enhanced Efficiency Across the Load Range

2019 ◽  
Author(s):  
Deepak Thirumurthy ◽  
Barry Ruggiero ◽  
Gautam Chhibber ◽  
Jaskirat Singh
Keyword(s):  
Power Generation ◽  
Clean Energy ◽  
Development Project ◽  
Modular Construction ◽  
Specific Load ◽  
Gas Generator ◽  
Load Range ◽  
Fleet Size ◽  
Power Turbine ◽  
Cycle Efficiency

Abstract The RT61 is a three-stage industrial power turbine which couples with the SGT-A35 aeroderivative gas generator (formerly named Industrial RB211). It was designed for improved efficiency and modular construction for ease in maintainability. The aeroderivative SGT-A35 (GT61) product serves both oil & gas and power generation market with a fleet size of greater than 90 units. In recent years, there has been increased emphasis on clean energy, only complemented by the regulatory changes and market conditions. The power generation and oil & gas customers (upstream, midstream, and downstream) are continuously looking for opportunities to decrease their greenhouse gas emissions and reduce fuel consumption by improving the gas turbine cycle efficiency. The SGT-A35 (GT61) power turbine has > 93% isentropic efficiency and industry standard overhaul schedule of 100,000 hours. However the potential for further cycle efficiency improvements and reduction in emissions exist by optimizing the power turbine capacity to a specific load range. This served as the main motivation for this technical work. This paper discusses the engineering efforts taken in implementing the above stated improvement and further optimizing the product for reduced emissions. The improvements are discussed on the product level and on the TransCanada Pipelines fleet level. A new power turbine variant was developed on a demanding timeline driven by the customer project. A detailed development project was undertaken to establish the new operating point, aerodynamic design, and the new geometry. It was optimized to the customer project-specific load range. During the manufacturing phase, novel rapid prototyping methods were used to achieve desired lead times. Flow path change was limited to the first stage vane to minimize the introduction of new risks and uncertainties.

Optimization of LM2500 Gas Generator and Power Turbine Trim Balance Techniques

1991 ◽  
Author(s):  
Bruce D. Thompson
Keyword(s):  
Success Rate ◽  
Maximum Amplitude ◽  
Turbine Rotor ◽  
Theoretical Background ◽  
Influence Coefficient ◽  
Gas Generator ◽  
Imbalance Problem ◽  
Influence Coefficients ◽  
Power Turbine ◽  
Good Set

A procedure has been developed by the U.S. Navy to trim balance, in-place, the gas generator and power turbine rotor of the LM2500 Marine Gas Turbine Engine. This paper presents the theoretical background and the techniques necessary to optimize the procedure to balance the gas generator rotor. Additionally, a method was developed to trim balance LM2500 power turbines. To expand the implementation of both gas generator and power turbine trim balancing, a capability had to be developed to minimize the effort required (trial weight runs etc.). The objective was to able to perform consistently what are called “First Shot” trim balances. “First Shot” trim balances require only one weight placement to bring the engine vibration levels to within the specified goals (less than .002 of an inch maximum amplitude) and that being the final trim weight. It was realized that the Least Squares Influence Coefficient method, even with a good set of averaged influence coefficients, can lead to a number of trial weight experiments before the final trim weights can be placed. The method used to maximize the possibility of obtaining a “First Shot” trim balance was to use modal information to tailor the influence coefficient sets to correct the most predominant and correctable imbalance problem. Since the influence coefficients were tailored, it became necessary to be able to identify, in the initial vibration survey, the type of response a particular LM2500 has. Using modal information obtained from a LM2500 rotor dynamics model and from the early trim balance efforts it was possible to identify the modal response of a given LM2500 and optimize the trim balance of that engine. With these improved techniques a 70% success rate for “First Shot” trim balance has been achieved and the success rate of the trim balance procedure, as a whole, has been near 100%.

Development US Navy Gas Turbine Vibration Analysis Expertise: LM2500 Vibration and Trim Balance

2012 ◽  
Author(s):  
Bruce D. Thompson ◽  
Jurie Grobler
Keyword(s):  
Gas Turbine ◽  
Turbine Rotor ◽  
Gas Generator ◽  
Engine Operation ◽  
Engine Design ◽  
Power Turbine ◽  
Us Navy ◽  
Continued Use ◽  
Integrated Performance ◽  
Mean Time

Although generally reliable in-service and with an ever increasing mean time between removal, it was identified in the mid to late 1980’s that the LM2500 gas turbine in US Navy service had a problem with self generated vibration; this was principally due to imbalance in the gas generator or power turbine rotor, however, other non-synchronous sources for vibration were discovered to be important as well. The initial method for resolving this problem was to remove and repair, at a depot, the engines that exceeded the in-service alarm level. This turned out to be a very expensive approach and it was found that most engines that had excessive vibration levels in other respects (performance, etc.) were perfectly acceptable for continued use without repair. Raising the vibration alarm level was tried for a time. However, it became clear that prolonged engine operation with higher levels of vibration were detrimental to the mechanical integrity of the engine. This paper discusses the systematic approach developed to reduce LM2500 self generated vibration levels. This included monitoring system improvements, engine design & hardware improvements and the development and implementation of in-place trim balance. This paper also discusses some of the analysis and practical difficulties encountered reducing and maintaining low LM2500 vibration levels through trim balance and by other means. Also discussed is the present implementation of remotely monitoring LM2500 operating parameters, in particular vibration, through the Integrated Performance Analysis Reports (IPAR) and the Maintenance Engineering Library Server (MELS).

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