A Virtual Gas Turbine Laboratory

A Virtual Gas Turbine Laboratory

Benson, M.; Boettner, D.; Arnas, Ö.; Van Poppel, B. United States Military Academy at West Point

Key words: Virtual Laboratory, Gas Turbine Education, Remote Laboratory Abstract: As many thermodynamics courses do not have the luxury of operating a gas turbine laboratory, these experiences with the virtual laboratory are offered as an effective option. Three experiences are described: an actual hands-on gas turbine laboratory, the first generation virtual laboratory, and an improved virtual laboratory. By digitally reproducing the laboratory setup, introduction, instrumentation, and data collection, the virtual experience captures the essence of the laboratory. After viewing web-based laboratory media files, and obtaining data through remote laboratory interaction, students use individually obtained data sets to complete an engineering laboratory report. The newly revised version includes the best of both worlds in mechanical engineering labs: a hands-on approach supplemented with the virtual laboratory.

1 Introduction 1.1

The United States Military Academy

The United States Military Academy (USMA) at West Point, NY, is located 50 miles north of New York City. It was founded in 1802 as an academy that educated officers for the United States Army. In 1812, upon recognizing the need for engineers, USMA changed its curriculum to educate engineers for the Army and a young nation, starting the nation’s first department of engineering. Today USMA offers a broad variety of majors for students to select, but it is still known primarily for its engineering programs [1]. USMA also remains one of the primary ways to become a commissioned officer in the United States Army. 1.2

Mechanical Engineering Laboratories

At USMA, the Gas Turbine Laboratory is one of several ‘hands-on’ laboratory exercises cadets have within the Department of Civil and Mechanical Engineering. From the mechanical engineering perspective, many of these labs have potential to grow from simple exercises of students manipulating equipment basics to obtain laboratory data, to interactive experiences matching the desirability to see, touch, and feel equipment with a wider range of safe and maintainable operating variables achievable through virtual laboratory development. While there are dozens of labs used within the department, the truly hands-on labs include the Comparative Fuels Research laboratory, the Pipe Friction laboratory, Iron Carbide materials research, and Charpy Impact testing. Because of the broad range of disciplines covered,

students taking courses in any engineering discipline at USMA are likely to participate in hands-on laboratories. 1.3

Thermodynamics

Thermodynamics at USMA offers students a one-semester investigation of principles of thermodynamics. Approximately 200 students each year are enrolled, making it one of the broadest reaching engineering classes at USMA. Many of the applications find their basis in Army vehicles and equipment. Gas turbines represent an important concept in this course, covering almost 10% of the semester. Cadets encounter several applications of gas turbines after graduating and entering the Army, including engines found on helicopters, tanks, and other platforms. A virtual laboratory was created to overcome some devastating results of weather at West Point during the summer of 2003. The test cell facility was rendered unusable for classroom instruction due to deteriorated building conditions, and the time required to move the engines to a new facility exceeded the time available for the faculty. Rather than cancel the event, a natural solution was the creation of a virtual lab. 1.4

Virtual Laboratory

The USMA virtual laboratory presented “a challenge for learning technology [to] harness the new multimedia possibilities to construct powerful environments for structured, competence based learning” [2]. Moreover, as today’s laboratories require upkeep and modern equipment, a general lack of resources may increase the challenge of continued operation of expensive laboratory equipment. Thus, creating cost-effective virtual laboratories before that occurs is a reasonable precaution [3]. While a number of institutions have created virtual laboratory events, many of these are web-based applets and Java-based programs, and most have limited interactivity (variation of only a single parameter, etc.) [4]. One of the leading current developers of virtual labs is Michael Kartweil who says ‘virtual labs may be particularly valuable in part-time engineering programs and those at community colleges, where space and funding for labs may be scarce’ [4]. A key difference in the USMA laboratory is that the student responds to a stimulating virtual environment in which actual performance characteristics of the engine are involved, and the actual engine is integrated throughout lab development through data, as well as both audio and visual media. Engineering educators apply thirteen primary objectives for learning in engineering laboratory events [5]. Inherent in these learning objectives that include such topics as instrumentation, experiment, data analysis, psychomoter, and sensory awareness, is imbedded a requirement for physical system understanding – not a small challenge for the virtual lab developer! The lab development for this work represents one solution to adequately meeting as many of these important objectives as physically possible in the virtual environment.

2 The Actual Gas Turbine Laboratory 2.1

Laboratory Preparation

All cadets conduct a ‘hands-on’ gas turbine laboratory as part of the Thermodynamics course. They conduct a two hour laboratory taking measurements on a T-62T-40-1 gas turbine engine, the auxiliary power unit (APU) on the Army’s UH-60 Blackhawk helicopter. Prior to coming to the laboratory, cadets complete a pre-laboratory assignment to familiarize them

with the APU. They understand where this engine is used, why it is needed, and how it is modelled thermodynamically. The pre-laboratory requires the cadets to compare the ideal Brayton cycle with an actual gas turbine cycle. Additionally, the pre-laboratory asks the cadets to determine the nature, type, and location of sensors required to gather sufficient data to analyze the engine’s performance. After completing the pre-laboratory exercise, the cadets are better prepared to make efficient use of the two hours available during the laboratory. 2.2

Laboratory Environment

When they come to the laboratory, the cadets are introduced to general gas turbine design. Instructors use an easily assembled/disassembled Mars gas turbine to review the basics behind how these engines work. In 1950 the Solar Aircraft Company built the Mars engine shown in Figure 1 so that the Navy could run its fire fighting pumps.

Figure 1: Mars Gas Turbine Engine Prior to the laboratory, students have seen some gas turbine components and have studied the Brayton cycle in class. By disassembling a gas turbine they have never seen, the cadets are able to apply what they know about the engines to “reverse-engineer” the device. Instructors help them through the process of determining which component performs which critical portion of the cycle. While disassembling the Mars gas turbine engine, cadets realize for the first time that one of the advantages of gas turbines is the simplicity of the engine. They understand that the engine in their car could never be disassembled nearly as fast as the five minutes it takes to disassemble the Mars engine. The laboratory then turns to the actual gas turbine engine used, shown in Figure 2, to take data. Large poster boards show an exploded view of the engine (see Figure 3), which helps bridge the intellectual gap for many cadets between cycle analysis and the actual engine before them.

Figure 2: T62-40-1 Gas Turbine Engine (APU from UH-60 Blackhawk Helicopter)

Figure 3: Exploded View of APU Around the test stand, cadets identify where and why sensors are located. They learn how a water-jacket dynamometer works and how to use it to determine the power the gas turbine produces. After discussing additional topics such as how the pilots start the engine, what light-off is, and secondary functions of the auxiliary power unit, data collection can begin. When these engines are turned on and they observe this relatively small auxiliary power unit roaring inside the test cell, the cadets sense perhaps for the first time how much power the engine produces. Cadets record compressor inlet and exit temperatures, compressor exit pressure, engine torque and RPM data for four experimental runs. They then use the remainder of their two hours to complete a report. Cadets answer questions requiring the use of the 1st Law of Thermodynamics, isentropic relations, isentropic efficiencies, thermal efficiencies, and the ideal gas equation of state. Students determine what assumptions were used for each calculation and their impact on theoretical performance calculations. By the conclusion of the laboratory, cadets have a good appreciation for gas turbines. They now understand basic principles, advantages and disadvantages of this engine type, and have enough rudimentary knowledge to set up a similar experiment to obtain data necessary to analyze a gas turbine engine [6].

3 The Virtual Laboratory 3.1

Original Virtual Laboratory Components

The original USMA Gas turbine virtual laboratory experience consists of four primary modules: Pre-Laboratory; Laboratory Data Collection and Analysis; Laboratory Report; and Feedback Survey. The development and execution procedures for the first three modules are presented in detail in the remainder of this section. This version is presented in some detail because it was developed rapidly out of necessity – something any organization with an expensive engine laboratory should consider even as an emergency backup. 3.1.1 Pre-Laboratory The Pre-Laboratory experience in the virtual laboratory is much different than the actual laboratory. Cadets view the first of two digital media files consisting of a 15 minute video and a graded exercise. Course faculty developed the pre-laboratory video around three components: Voice-over narration with PowerPoint slides reviewing the basics of gas turbines and the Brayton cycle; An assembly, disassembly, and component study of a simple gas turbine engine (Mars) similar to the one used in the lab; And engine specifications and uses.

The video is placed on an internal server and can be viewed either directly as a DVD in the classroom or through web-streaming using a media player or similar program. After watching the video, students complete a graded pre-laboratory exercise electronically. Success with the pre-laboratory requirements requires a level of preparation such that students come to the classroom ready to smoothly conduct the remainder of the virtual laboratory. 3.1.2 Laboratory Data Collection Upon arriving in a wireless classroom, students view the virtual laboratory on individual laptops. Two versions of this 11 minute video were created so that differing data could be obtained for separate classes. Within this video, voice over narration again accompanies PowerPoint slides reviewing the most essential components of the laboratory analysis portion: the Cold Air Standard equations for actual Brayton cycle analysis; Methods to calculate combustion efficiencies; And a review of data and instrumentation. After the review, the laboratory video shows the engine start. With appropriate audio and video projection quality, a realistic environment of sight and sound can be achieved giving an accurate depiction of the actual experimental conditions. The video shows a full view of the engine and highlights key engine components and instrumentation. Moving to the data panel, the video identifies each of the data display devices. The dynamometer output display is shown as an example in Figure 4.

Figure 4. Example Data Display After a brief pause to allow students to prepare for data collection, four experimental runs are conducted as in the actual laboratory. Each run differs as the dynamometer is adjusted to reach a distinct engine load. World-wide web links to the pre-laboratory and the data recording modules are currently available at the following web addresses: http://www.usma.edu/asx/CME_ME301.asx http://www.usma.edu/asx/CME_ME301b.asx http://www.usma.edu/asx/CME_ME301c.asx 3.1.3 Laboratory Report After recording the data, students spend the next 80 minutes of the laboratory performing the same required calculations and answering a variety of discussion-oriented questions as those students taking the actual lab. Students are encouraged to leverage the technological resources available to them during this portion of the exercise (spreadsheets, internet, and mathematical software). Upon completion of their work, students digitally submit their laboratory reports.

3.2

Revised Virtual Laboratory

The revised virtual laboratory is in its final stages of development. This laboratory takes the experiences of the rapidly built and implemented original virtual laboratory and applies the pedagogy to provide a better environment for the student to achieve the overall laboratory objective of conducting tests on a gas turbine engine to determine engine performance characteristics. The best of the original laboratory is maintained. Video clips of engine operation, audio of engine light-off, and an operational Blackhawk helicopter video are all embedded to create an environment that in some ways exceeds the realism of the actual laboratory! More importantly, however, is that the easily accessible revised virtual laboratory is basically maintenance free, available worldwide, and able to be operated through a range of conditions. 3.2.1 Pre-Laboratory Component The pre-laboratory video and work remains much the same as in the original virtual laboratory discussed previously. As we conduct the pre-laboratory in conjunction with actual equipment, cadets view the pre-laboratory files, and also see, touch, and feel the actual equipment when they conduct the laboratory locally. Finally, an assessment is still conducted and submitted manually rather than digitally allowing more comprehensive engineering calculations and analysis to occur. 3.2.2 Virtual Laboratory Data Collection and Laboratory Report The newest version of the USMA virtual laboratory data collection component is a marked departure from the original virtual laboratory described above. Developed using a completely different procedure than the original, National Instruments LabView software is utilized in conjunction with a manufacturer supplied engine performance program to produce an event that is now decidedly interactive. Students manipulate input conditions including ambient pressure and temperature, forward flight speed (as this is a helicopter application), and altitude. In addition, the student inputs the desired engine power, spanning the entire operational range of the engine. The information is sent to a calculation program that outputs operating parameters representative of minimum engine performance. A sample screen shot is provided in Figure 5. Students will use data for the current pressure and temperature of their laboratory environment, and conduct engine testing through the full range of available power. They answer general questions regarding the impact of flight speed and altitude. They also conduct detailed analysis of engine operating performance through the applied power ranges. The resulting plot of engine efficiency as a function of output horsepower will show the optimal operating point for a general test-environment condition. The students complete a laboratory report within the two-hour class period. If they are completing this event from a location outside the classroom, they complete the report at the discretion of the instructor.

Figure 5. Interactive Virtual Laboratory Display Panel

4 Conclusions and Recommendations While finishing touches are still under construction as of this writing, all major components are in place and operational. The entire suite of files utilized in the virtual laboratory needs packaging such that these files can be presented as part of a larger integrated experience. Actual laboratory data will eventually replace the manufacturer cycle deck currently used for predictive performance. The remote panel application lets a limited number of personnel (based on site licenses for the LabView program) access and have interactive capability with the web-based remote panel of the actual LabView screen used for the virtual lab. Thus, the

students are able to ‘operate’ the engine realistically as the manufacturer sub-routine enforces practical limits on engine use. The laboratory has wide accessibility because of its ready access through the internet. Students can rapidly see the impacts of their changes in a variety of operating parameters. This new version integrates actual engine performance that can be seen, touched, and felt, with a virtual experience in which students can test a gas turbine engine’s performance in a completely new way. The authors would like to thank Hamilton-Sundstrand Corporation for its gracious provision of the T-62T-40-1 Engine Cycle Deck. This proprietary software can only be obtained with direct permission of Hamilton-Sundstrand Corporation. The views expressed herein are those of the authors and do not purport to reflect the position of the United States Military Academy, the United States Army, or the Department of Defense.

References: [1] Office of the Dean, 1998, “Educating Army Leaders for the 21st Century,” United States Military Academy, West Point, New York, p. 5. [2] Boyle, T., Stevens-Wood, B., Feng, Zhu, Tikka, A., 1996. “Structured Learning in a Virtual Environment.” Computers and Education, 26(1-3), 41-49. [3] Swain, N., and Anderson, J., “Application of Graphical Programming, Object Oriented Programming, and Virtual Instruments in Education.” http://www.cs.utep.edu/chitta/hmcs/cit99.swain.doc. [4] http://www.scienceblog.com/community/older/1997/A/199700623.html. Science Blog from Johns Hopkins University. “’Virtual’ lab Lets Students Tackle Engineering Tasks On the Web.’ downloaded, 9/2/2004. [5] Feisel, L., and Peterson, G., “A Colloquy on Learning Objectives for Engineering Education Laboratories.” 2002 ASEE Annual Conference and Exhibition, Montreal, Canada. [6] Benson, M., Van Poppel, B., Boettner, D., Arnas, A., “A Virtual Gas Turbine Laboratory for an Undergraduate Thermodynamics Course.” ASME – IGTI, Proceedings of Turbo Expo June 2004, Vienna, Austria.

Author(s): Michael Benson, MAJ, P.E. Daisie Boettner, COL, PhD. Ozer Arnas, PhD, P.E. Bret Van Poppel, MAJ United States Military Academy at West Point (Dept of Civil and Mechanical Engineering) Mahan Hall West Point, NY 10996 [email protected]