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Report on Bernard Lewis Visiting Lecturer Fellowship Activities

Bernard Lewis Visiting Lecturer Fellowship, Sponsored by the Combustion Institute

Hosted by Prof. Y. C. Chao
President, Taiwan chapter of the Combustion Institute
and Prof. Shenqyang Shy, National Central University

October 2 – 9, 2005

Paul D. Ronney
Department of Aerospace and Mechanical Engineering
University of Southern California

(Click here to view photo-journal of activities in Taiwan)

Day-by-day summary (total:  8 lectures)

Location: National Central University

Lecture to the School of Engineering:  Flame Initiation by Nanosecond Plasma Discharges: Putting Some New Spark into Ignition

Abstract: The transient plasma that occurs during the formative phase (typically 50 nanoseconds) of conventional spark discharges is comprised primarily of spatially-distributed streamers prior to the formation of a single intense arc with equilibrated electron energy distribution.  The use of non-thermal transient plasma ignition (TPI) was investigated as an alternative to spark ignition (SI) for applications including internal combustion engines and pulse detonation engines (PDEs).  Bench tests in quiescent and turbulent constant-volume combustion chambers showed typically 3x shorter ignition delays and pressure rise times with TPI than with SI.  These benefits were shown to be a result of both the geometrical advantages of TPI, namely the multiple ignition sites, as well as inherent chemical effects.  Testing on a 2.5 liter 4-cylinder engine showed typically 15 – 20% increases in indicated mean effective pressure and much shorter burn durations at identical operating conditions. Moreover, the tradeoff between thermal efficiency and brake specific NOx emissions was found to improve with TPI.  It is proposed that these advantages of TPI may be exploited by either (1) the use of leaner fuel-air ratios or (2) by designing engines with lower turbulence levels, thereby reducing heat loss to cylinder walls and increasing thermal efficiency, and employing TPI to obtain sufficiently rapid burning.  Reduction in the time for deflagration to detonation transition by a factor of 4 in laboratory-scale PDEs was observed, thus TPI may prove to be an enabling technology for this application.

Presentation

Location: National Central University

Lecture to a junior-level fluid mechanics class:  Fun with Mechanical Engineering

Presentation

Location: Jhong-Li High School

Lecture to high school students:  Space Travel and Space Research

Presentation

Location: Institute for Nuclear Energy Research (INER)

Lecture to professionals at INER Micro-Solid Oxide Fuel Cells for portable power generation

Presentation

Location: National Central University

Lecture to the Department of Mechanical Engineering:  Fire in space: results from STS-107 / Columbia's final mission

Abstract: “Flame balls” are steady, convection-free, spherically symmetric flame structures that were originally predicted by Zeldovich in 1944 but not seen experimentally until 40 years later in short-duration drop tower experiments.  Flame balls represent the simplest possible interaction of chemistry and transport in flames and thus bear a similar relationship to combustion research that the fruit fly does to genetics research.  With this motivation, space flight experiments on flame balls in weakly burning flames in hydrogen-oxygen-inert and methane-oxygen-inert mixtures were conducted on the STS-107 / Columbia Space Shuttle flight.  A total of 39 tests were performed.  Most tests (by design) produced only 1 flame ball, though one test intentionally designed to produce a large number of flame balls resulted in 9 balls.  Over half of the science data was downlinked during the mission, resulting in minimal loss of science despite the loss of Columbia and its crew.  Among the accomplishments of the experiment were

  • The weakest flames ever burned, either in space or on the ground.  The weakest flame balls produced about 0.5 watts of thermal power.  By comparison a birthday candle produces about 50 watts of thermal power.
  • The leanest flames ever burned, either in space or on the ground.  The leanest hydrogen-air test points contained 3.2 mole percent H2 in air (equvalence ratio < 0.079).
  • The longest-lived flame ever burned in space (81 minutes)

Several totally new results were found, including

  • Oscillating flame balls that were predicted theoretically but heretofore never observed experimentally.
  • For some tests, particularly in methane-oxygen-sulfur hexafluoride mixtures, flame ball drift not related to gravitational disturbances nor interactions with other balls or walls.  This was a completely unexpected and as yet unexplained result.

The data obtained during the mission will keep combustion scientists busy for many years to come and will help lead to the development of cleaner, more fuel-efficient engines as well as improved methods for spacecraft fire safety assurance.

Presentation

Location: National Cheng-Kung University

Lecture to the Department of Aeronautics and Astronautics:  Microscale reacting flows and power generation: It's not the same as big devices made smaller

Abstract: Despite numerous advantages of fuels over batteries, combustion devices have not yet been employed for electrical power production and propulsion at small scales.  Most current micro-scale concepts employ scaled-down versions of existing macroscale devices, though such microdevices experience more difficulties with heat losses, friction, sealing, fabrication, assembly etc. than their macroscale counterparts.   This talk will emphasize the science of reacting flows in microscale devices including (1) performance of plastic spiral counterflow heat-recirculating "Swiss Roll" combustors, (2) catalytic combustion at microscales, (3) power generation using single-chamber solid oxide fuel cells and (4) pumping using thermal transpiration in nanoporous materials.  Practical implementation of these concepts will also be discussed.

Presentation

Location: National Cheng-Kung University

Lecture to the Department of Mechanical Engineering: Dynamics of fronts in chemical and bacterial media: If you've seen one front, you've seen them all

Abstract: Self-propagating reaction fronts occur in many chemical and physical systems possessing two key ingredients: a reactive medium (for example a fuel-air mixture in the case of flames) and an autocatalyst that is a product of the reaction that also accelerates the reaction (for example thermal energy in the case of flames).  Self-propagation occurs when the autocatalyst diffuses into the reactive medium, initiating reaction and creating more autocatalyst.  This enables reaction-diffusion fronts to propagate at steady rates far from any initiation site.  In addition to flames, propagating fronts have been observed in aqueous reactions, free-radical initiated polymerization processes and even propagating fronts of motile bacteria such as E. coli.  This talk will focus on a comparison of the dynamics of these four different types of fronts including propagation rates, extinction conditions and instability mechanisms.  Our research has shown that despite the disparate nature of the reactants and autocatalysts in these four systems, remarkably similar dynamical behavior is observed since the underlying driving mechanisms for propagation are similar.  The key role of loss mechanisms (heat, chemical species or cell death) and differential diffusion of reactant and autocatalyst ("Lewis number") is demonstrated.

Presentation

Location: National Tsing-Hua University

Lecture to the Department of Power Mechanical Engineering: Flame propagation in narrow channels: what Darrieus and Landau didn't tell you

Abstract: The flame speeds and wrinkling spectra of premixed flames propagating in quasi-2D channels (Hele-Shaw cells) were studied using CH4 and C3H8 fuels with N2 and CO2 diluents.  Upward, downward and horizontal propagation configurations were tested for varying mixture strength and thus laminar burning velocity (SL).  In this way the effects of buoyancy, thermal expansion, heat loss and Lewis number were studied.  Wrinkling and thus flame speed enhancement was observed even for downward propagating (buoyantly stable) flames have high Le (diffusive-thermally stable) due to the effects of thermal expansion (Darrieus-Landau, DL) and viscosity increase (Saffman-Taylor, ST) across the front.  The quasi-steady flame speed (UT) was always higher than (SL), typically by a factor of 3.  Values of UT/SL correlated well with a scaled growth rate parameter (K) based on the Joulin-Sivashinsky model of flame instabilities in narrow channels due to DL, ST and buoyancy effects.  The observed correlation was UT/SL = 1 + K, thus K serves a role similar to u' in turbulent combustion in the laminar flamelet regime.  Wrinkling spectra exhibited a marked change as the cell thickness decreased due to a change in the dominant instability mechanism from DL to ST.  Flame wrinkling in the plane of the cell and front curvature in the transverse dimension are found to be of similar importance in affecting UT.  These results indicate that the behavior of practical flames in confined geometries such as internal combustion engines or gas turbines is quite different from that inferred from laboratory experiments conducted in open geometries such as Bunsen, counterflow or V-flames, where thermal expansion is relaxed in the transverse directions.

Presentation

 

Narrative report

Taiwan, a small country with limited natural resources, imports 98% of energy.  As with practically all the world’s countries, the bulk of this energy is generated from combustion processes.  Taiwan generates a substantial amount of electrical power via nuclear fission, but no new nuclear power plants will be built.  Renewable energy sources such as biomass (e.g., from sugar cane) are under intense development in Taiwan, but are unlikely to replace a significant portion of the energy currently generated by fossil fuel combustion in the foreseeable future.  Consequently, raising awareness of the importance of combustion research, particularly among senior administrators and students at the universities I visited, was my primary goal.

The trip started out “off nominal” when my flight from Los Angeles was diverted to Hong Kong.  It seems that Typhoon Dragon King was unleashing its wrath on Taiwan and landing in Taipei was impossible.  From then on my Taiwanese hosts started calling me the “Dragon King” but I’m still unsure if that’s a complement or not.  Fortunately my flight was scheduled to arrive early Sunday morning, so the 10-hour delay did not affect the lecture schedule.

The lecture tour started out Monday on a hectic note as two “bonus” lectures were added to the one already scheduled.  This was fine with me; I instructed my host, Prof. Shenqyang Shy of National Central University, that I served at the pleasure of the Taiwan Section of the Combustion Institute for the whole week and that he should arrange my schedule to provide the most benefit to the Section.  Shenqyang attacked these instructions with a vengeance.  We decided that since there is a lot of public interest in space research in Taiwan, I should give a talk about the subject. Consequently, Shenqyang spent much of the day on his cell phone arranging a talk at Jhong-li High School where his son is a student.  I also gave an impromptu talk about my philosophy on “engineering scrutiny” as well as a brief history of internal combustion engines to Prof. Shy’s junior level fluid mechanics class.

By the way, I never could get the Chinese pronunciation of Prof. Shy’s name correct – something like Shuh jiao sho, where “Shuh” is Shenqyang’s family name and “jiao sho” means professor.  But I couldn’t get the tone correct on “shuh” and every time I tried to say his name in Chinese it translated as “dead professor” rather than “Professor Shy.”

In the scheduled Monday seminar I talked about transient plasma ignition of flames.  Afterwards a student asked me why he should study combustion despite the fact that internal combustion engines are dirty, noisy, lead to all kinds of environmental problems, lead to all kinds of political problems in our thirst for oil, etc., etc. – an excellent question.  Fortunately this question gave me the perfect opportunity to preach my view of the issue, and in fact I had a ready-made answer in powerpoint form (see pages 14 – 18 of this linked file).  The bottom line is (with apologies to Winston Churchill), “internal combustion engines are the worst form of vehicle propulsion, except for all the other forms.”  And by a wide margin.  But all combustion research professionals know that already.

We then had dinner at my hotel with a group of faculty and administrators from National Central University.  I was tired by the end of all this, but Shenqyang was really exhausted.  He actually had it a lot tougher than me because (1) he had to follow and understand all of my lectures, even those on topics that were familiar to me but not him and (2) he had to translate my lectures into Chinese and translate questions from students back into English.

Tuesday’s pace was notable slower, with only two lectures to deliver.  In the morning we drove to the Institute for Nuclear Energy Research (INER), about an hour away from Jhong-li.  As one would expect, this institute is primarily concerned with nuclear energy, but because of Taiwan’s new emphasis is renewable and/or clean non-nuclear energy sources, INER is very interested in the development of Solid Oxide Fuel Cells (SOFCs), among other things.  Consequently, I gave another “bonus” lecture to INER regarding our work on microscale SOFCs.  Microscale power generation is not INER’s interest, but some of our work may be applicable to larger-scale devices as well.

After lunch at INER we drove back to National Central University and I gave the second scheduled lecture, this time on the results of the Structure Of Flame Balls At Low Lewis-number (SOFBALL) space flight experiment on the ill-fated STS-107 Columbia Space Shuttle flight.  After more lab visits and chats with graduate students, Shenqyang and I caught a train to Tainan, about 3 hours to the south, in preparation for a two-day stay at National Cheng-Kung University, the home institution of Prof. Y. C. Chao, President of the Taiwan section of the Combustion Institute.

On Wednesday I gave a lecture to the Department of Aeronautics and Astronautics at NCKU on Microscale Reacting Flows and Power Generation, hosted by Prof. Chao.  After lunch at a surprisingly good Italian restaurant near campus, we drove to the Aerospace Science and Technology Research Center (ASTRC), NCKU’s “Back Forty,” a research facility outside of town housing large experiments such as a hypersonic wind tunnel, gas turbine combustors, even large-scale Swiss roll burners!  ASTRC also has a tracking station for Taiwan’s communications satellites.  I visited that facility also and I was really impressed with the knowledge that the tracking personnel had of the U. S. space program!  Back in Tainan, we had a traditional Chinese-Style banquet at a very nice restaurant with a group of faculty and students from NCKU.

Thursday I gave a lecture to the Department of Mechanical Engineering at NCKU, hosted by Prof. T. H. Lin of the ME department, on a new subject of mine, Dynamics of Fronts in Chemical and Bacterial Media.  After yet another luncheon with faculty and students, I was treated to a Tainan city tour, accompanied by 3 staff and students from NCKU.  We had short but very enjoyable visits to a museum, the oldest Confucian Temple in Taiwan and two forts.  (Tainan is an historic port city of strategic importance).  Then back to downtown Tainan, for the return train trip to Jhong-li.

Friday we drove to Hsin-Chu City, home of National Tsing-Hua University and my local hosts, Profs. J. T. Yang, C. A. Lin and T. M. Liou.  After still another luncheon I gave a my eighth and final “concert” (lecture) to the Department of Power Mechanical Engineering at Tsing Hua on Flame Propagation in Narrow Channels.  (At times I felt like a musician on tour, giving concert after concert – there’s a little Walter Mitty in all of us…)

OK, end of the technical part of the trip.  Now off to the Taipei City Airport – for the trip home?  No, I had decided to stay in Taiwan the weekend after the lecture circuit, just to do a little touring and see whatever natural attractions Taiwan had to offer.  Shenqyang had arranged for us to fly to Hua-Lien on the less-populated eastern side of Taiwan and spent Friday evening there, for the purpose of visiting nearby Taroko National Park along the Li Wu River, a place of which I had no prior knowledge or opinion, on Saturday and Sunday.  I wasn’t expecting much – after all, how much natural beauty could a small island like Taiwan have?  Looking at the maps, it was clear to me that we should rent a car and do our own driving.  I should have thought of this before the trip, but since I didn’t, I didn’t obtain an International Driver’s License, thus I could not do any driving in Taiwan.  And Shenqyang was decidedly hesitant about driving outside of areas familiar to him.  Thus it appeared that we would have to take an organized bus tour.  But after explaining the value of having our own transportation (I know, it’s the self-centered resource-hogging American viewpoint) and chanting “ROAD TRIP… ROAD TRIP… ROAD TRIP…” about 900 times, I finally convinced him.  And even Shenqyang agrees that in hindsight it was the right decision.

As it turned out, Taroko is a really spectacular marble gorge, somewhat similar to the Grand Canyon of the Verdun in southeast France.  It’s also similar to Zion National Park in the U. S., but the rock is marble, not sandstone as in Zion.  I wasn’t expecting such an impressive natural landmark!  Take a look at the pictures.  (The park pictures start at the end of page 3.)  The flood damage from the recent typhoon was incredible.  As some of the pictures such as this one show, driftwood logs washed up on trails at least 100 feet above the canyon floor.   Note the high water mark in this picture!  Most roads and trails were closed due to the flooding but we went on several short hikes, and in the evening ventured up the road to the Formosa Grand Hotel in Tiang Shan right in the heart of Taroko National Park.  This is really a great hotel in a fabulous setting, and much less expensive than I would have expected.  Due to the flooding the road past the hotel (which winds way up into the mountains to an elevation of over 3000 meters) was “closed”, but there was nothing physically blocking us from continuing, so we did.  There were many washouts in the road but they were bulldozed over so it was possible for vehicles to get through.  It was getting dark so we didn’t go up to anywhere near 3000 meters, but we did get some great views from the elevations we did reach.  Back down at the hotel, we had a great dinner.

Sunday we hiked around the hotel, across a bridge, up to a pagoda and another temple to a spot with a great view back down at the hotel.  To my surprise, breadfruit trees grew around the temple; breadfruit are very tropic and require year-round heat and humidity.  But watch out for the huge spiders!  Then on with the hiking along the Li Wu River.  We found an interesting suspension bridge across the river that went nowhere in particular.  I hiked up to a small waterfall but Shenqyang didn’t care for the bushwhacking and boulder hopping required to get there so he stayed behind.  The final hike was up to yet another but very scenic temple with some interesting underground rivers gurgling up along the trail.  Time was up so we drove back to Hua-Lien for our triumphant return flight back to Taipei City Airport, then to a department store to buy something to wear before heading to Taipei International Airport.  (Everything piece of clothing I had was dirty from a week of heat and humidity in the cities or muddy from the trails in Taroko, hence some clean clothes seemed like a friendly gesture to my fellow passengers across the Pacific.)

On the flight home the reality of the long days lecturing, visiting labs, touring canyons and the long nights preparing the next days’ lectures, coupled with the end of the adrenaline rush from the overseas travel, finally caught up with me and I had a nice 12 hour nap – just in time to get back to USC for Monday’s activities on campus without having to miss a beat.  Mission accomplished.

Summary and suggestions for future Bernard Lewis Lecturers and their host sections

First I would like to thank the Combustion Institute for sponsoring this lectureship and the Taiwanese section of the Combustion Institute for their heroic efforts in making my week in Taiwan very productive, educational and downright fun.  Special thanks and deep debts of gratitude are owed to Prof. Shenqyang Shy of National Central University for arranging almost everything and escorting me around the country, as well as Prof. Y. C. Chao, President of the Taiwan section, for his tireless support and encouragement.

If I could do this again knowing what I know now, I wouldn’t change hardly anything.  The pace was hectic but everything ran smoothly.  My only suggestion to future Bernard Lewis lecturers would be to bring a laptop loaded with Powerpoint presentations, visit lots of people and places, be flexible, and engage the combustion research community in the host country to the maximum extent possible (i.e. basically what I did.)

As I mentioned, my Taiwanese hosts prepared a very well organized visit including technical, social and sightseeing activities.  My only suggestion to future host sections would be to give the Lecturer smaller tokens of appreciation!  Or assign the Lecturer a “mule” to carry everything…  I do appreciate receiving these items, but after a while my suitcase was filled beyond capacity with plaques, books, brochures, utensil sets, etc.  I finally gave up trying to carry all of them and I imposed upon Prof. Shy to mail them home to me.