#Thermoacoustic

[fuckyeahfluiddynamics]

Searching for Stability in Cleaner Flames

Spiking natural gas power plants with hydrogen could help them burn cleaner as we transition away from carbon power. But burners in power plants and jet engines can be extremely finicky, thanks to thermoacoustic instabilities.  (Image and research credit: B. Ahn et al.; via APS Physics) Read the full article

[1dealist]

A closer look at a whole new different modification for Parasaurolophus, based off of the myth that it breathed fire.

This version utilizes Thermoacoustics, in which if a specific frequency resonates with it's container, it will actually change the temperature (higher on the edges, colder in the center). In this case, the center of the container is the base of the crest, while the edges are the outlets of the mouth and it's back, inspired by my recent discovery of the Ruben's Tube.

This will not only allow the Parasaurolophus to be able to breath fire (with the help of flammable gases added to it's chest cavity) but will also have a variable size of the flames on it's back for self defense (and will also look very interesting as it changes w/ frequency).

An additional note is that once the specific frequency is changed, the temperature would stabilize and the fire would go out. Interestingly enough, sound also is an excellent way of putting out fires, so they can be utilized as "fire extinguishers" as well.

[allthebrazilianpolitics]

Tourism in Brazil could benefit from climate agenda

Different tourism sectors are coming together to create itineraries aligned with the climate agenda in Belém, Pará state, combining experiences of immersion in the forest, and regional cuisine, and promoting sustainable production systems. The idea behind the initiatives is to take advantage of the opportunities brought by sustainable tourism—such as attracting investment and increasing competitiveness—and also to overcome the challenges in bringing together the major players from the two agendas.

Parys Fonseca, an entrepreneur in the lodging sector, has created a business model combining the experience of immersion in the Amazon rainforest with sustainable lodging. After consulting the Brazilian Micro and Small Business Support Service (Sebrae) in Pará, he learned about a recyclable modular structure which not only has less environmental impact at a lower cost, but also keeps room temperatures stable without artificial refrigeration.

“The installation process was really quick. In just two weeks I was renting it out as accommodation. And I thought it was better because the work was simpler, the module adapts to the environment, and it’s also thermoacoustic,” he pointed out.

Located on Murucutu Island, one of the 42 islands that make up the city of Belém, Fonseca’s resort offers visitors not only a chance to spend a night’s sleep immersed in the Amazon rainforest, but also gastronomic experiences with local products from the region’s sustainable production chain. “The next step is to create a route for tourists to learn about açaí palm production, just as there’s route on cocoa on Combu Island. Sebrae is supporting me with training and management, which has been key for the local residents and entrepreneurs alike,” he said.

Continue reading.

[maklodes]

Stirling-electric hybrid vehicles are an idea that I keep coming back to, even though this is an idea people far smarter and better at engineering than I have been trying to tackle for a very long time. (The earliest example I can think of is the GMC Stir-Lec from 1969, but it honestly wouldn’t surprise me if someone was trying to build a Stirling electric hybrid when Stanley Steamers were still battling Ford Model Ts.) All the current trends – and regulatory frameworks – are toward full electrification based on giant batteries, but Stirling-electric still captivates my imagination.

A Stirling engine has a lower power-to-weight ratio than an internal combustion engine, but how bad is it? Well, the 1986 NASA project said they had gotten it to 3.35 kg/kW. (Has there been any progress since 1986 on Stirling engines? I don’t know. There have been some new developments with thermoacoustic Stirling engines and such, but I’m not sure they’d be any better than traditional Stirling engines for this application.) With a hybrid, the most sensible approach is to make the heavy Stirling engine as weak as it can be while sustaining a desired top cruising speed – bursts of acceleration are better handled by electrical motors with better power-to-weight ratios.

It’s commonly said that a car only needs maybe 20 hp (15 kW) to cruise at a highway speed of, say, 60 mph/100 kmh. That’s not very marketable, though. If we supposed that a top sustainable speed – the top speed at which you’re burning fuel, but not draining your batteries – should be more like 90 mph, then we might want 1.5^3 = 3.375 times that much power (this is on the pessimistic assumption that air resistance is basically all resistance, since it scales worst (cubically) with speed). Other situations besides speeding, like towing or going up a long-enough upward incline that it wouldn’t just be cleared on battery alone, might also be occasions for sustained power higher than the ~15 kW highway level.  So maybe 50 kW. A stirling engine capable of producing that might weigh 170 kg.

For our electric motors, we might want, say, 150 kW, for a marketably peppy response. The motor of a Tesla Model 3 (cited in Wikipedia on a list of power densities) has got 6.26 kW/kg.  That might require 30 kg. If we’re going for a serial hybrid rather than a parallel hybrid – with no direct connection between the Stirling engine and the drivetrain, only a connection that bypasses the battery to feed electrical power to the motors directly – then the power going to the tires is just from the electric motors, not the Stirling engine. This might simplify the engineering, though..

Then there are the batteries. If we wanted four minutes of battery power at near-maximum power  – making sure to compensate for any lag in the Stirling engine heating up – then we’d want ~100 kW * ~250 seconds = 25 MJ. This is also close to the minimum for an American tax-break eligible plug-in hybrid electric vehicle, which requires a battery of at least 7 kWh, or 25.2 MJ. If we got 0.4 MJ/kg then that’s another 65 kg. One question is whether the battery has enough power, not just enough energy. I am having a hard time finding sources on this. Wikipedia pages on power density seem too pessimistic given what we see out of electric vehicles like the Model S Plaid. (100 kWh battery, 1020 hp ~=760 kW, suggesting that a battery can discharge itself in 8 minutes at most, depending on whether the Plaid is basically designed with motors that are as powerful as possible given its battery.) We might need to double the size of the batteries to power the motors enough.

So we’re adding 265-340 kg to the vehicle so far. There will probably be a bit more – regenerative braking systems, power distributing linkages, etc. On the other hand, we’ve gotta remember that we’re also taking the internal combustion engine out.

Is 280 kg too much? I suppose a comparison might be plug-in hybrids, which are rather heavy on account of an ICE-electric hybrid energy system and a rather large battery. A Subaru Crosstrek conventional has a curb weight of 3298 lbs, while the PHEV weighs in at 3,717 lbs, a difference of 190 kg. The Kia Sportage has a curb weight of 3,373 lbs, while the PHEV version weighs 4211, a difference of 380 kg.

Perhaps with some sort of modular system could add versatility to the fueling types, with different modules for gasoline, compressed natural gas or hydrogen, waste vegetable oil (perhaps a preheater would be good for something that viscous). The Stirling engine might lose a little peak power on some fuels relative to gasoline, but for ordinary, not-too-fast, not-too-hilly cruising that might just mean it runs more and it doesn’t affect the performance too much – although in times of persistent high demand for power, like climbing up a hill, towing a trailer, or just speeding, you might notice the deficiency.

One possible issue is hydrogen embrittlement. If the Stirling engine has a working fluid other than hydrogen, it would be less efficient, while if it’s using materials that are resistant to hydrogen embrittlement, then that might make it less rugged and heavier. I think they used sufficiently embrittlement-resistant stainless steel and hydrogen as a working fluid in the 1986 NASA project, but one way to cheat for a short-term test of a relatively powerful, light Stirling engine would be to just use hydrogen as a working fluid and regular steel engine parts, and if they crack like a week later, that’s after your tests are done.

I don’t really know that much about the details of obstacles to alternative ideas for cars, though. I guess I’ve been a bit car-brained since I became a car owner almost a year ago. I suspect that when you first get a job as an engineer at Ford or Honda, the first thing in your inbox is a Powerpoint attachment titled “Here’s Why We’re Not Going to Consider Your Stupid Alternative Powertrain Ideas.” Maybe if someone could leak that to me that would give me some clarity.

I guess Dean Kamen tried to get some kind of Stirling-based car going, and there's some guy, Josh MacDowell, who turned a Ford F-150 into a Stirling-Electric hybrid? Given that there's no IP protection on Stirling engines, though, I think there must be more practical obstacles that I'm not considering.

Update: One consideration I omitted was volume. Although the batteries of battery electric vehicles are infamous for being heavy, they are convenient geometrically, being dense, mostly homogeneous, and capable of being fit in almost any shape so long as the final volume is the same.

[enetarch-innovation]

Breakthrough Thermoacoustic Stirling Generator Converts to Energy With No Moving Parts | NextBigFuture.com

[enetarch-physics]

Breakthrough Thermoacoustic Stirling Generator Converts to Energy With No Moving Parts | NextBigFuture.com

[heatcharger]

New Chinese thermoacoustic Stirling engine breaks power record - Interesting Engineering

http://dlvr.it/SyppwJ

[nawapon17]

Breakthrough Thermoacoustic Stirling Generator Converts to Energy With No Moving Parts | NextBigFuture.com

[stephen-barry]

https://www.nextbigfuture.com/2023/11/breakthrough-thermoacoustic-stirling-generator-converts-to-energy-with-no-moving-parts.html

[1dealist]

Worked on one of my parasaurolophus with a 𝘴𝘭𝘪𝘨𝘩𝘵 adjustment. I think she likes it.

I will post a few more pieces later discussing how the design is mostly utilizing Thermoacoustics

[xingtia]

Several types of roofing sheets and what is the roofing sheet price?

Although roofing sheets usually require the addition of adequate insulation, they have great benefits when it comes to resisting climate change. They are usually very durable and because they are the right size and weight, they can be easily installed. Roofing sheets can be made in a variety of shapes and add inertia, so you can even find roofing sheets that are self-supporting.

Galvanized roofing sheet prices: Galvanization prevents corrosion and oxidation of the steel, while the sheets are largely maintenance-free and durable. Like other roofing sheets, they have poor acoustic and thermal insulation properties. When it rains, they produce excessive noise. Nevertheless, galvanized roofing sheets are still a good choice because they are lightweight and low in price. Galvanized steel roof panels would be advantageous over any other type of material. For example, they are far less expensive to produce than materials such as clay or stone, and they last just as long. You can expect steel roofs to last 50 years or more, especially those that are galvanized. They won't rust or be affected by external elements like standard shingles. Finally, it is a very easy material to install, as long as it is put in place by a professional. What you will be looking for is a company that produces the best-corrugated steel roofing materials.

Stainless Steel : Although they are not economical, they have a good cost/benefit ratio as they are low maintenance and last a long time. Stainless steel roofing sheets resist corrosion, impact, and weather extremes. Like other roofing sheets, their surfaces can be scratched or dented and are difficult to repair.

Copper Clad: They can be adapted to different forms, but are not economical in terms of material and installation costs. However, copper foil is outstanding for temperature changes, durability, and final decorative effect.

Thermoacoustic metal sheets price: Although they cost more than other metal sheets, they have a great advantage in controlling temperature and noise because they are covered with thermal and acoustic insulation. At the same time, they are durable and do not require greater maintenance.

[ageofkarme]

Karme proudly brought his dirty hand to his chin, rubbing it as if to ponder whether to disclose or not. "Fixing my math and trying to get a sneak peak, eh? You must have a nose for groundbreaking, magical innovations. The whole queendom will be buzzing about my handiwork eventually, so I guess I can let you in on the secret." Although, Karme's cheeky grin and shuffling knees betrayed his excitement at getting to share. For a "secret" he was incredibly loose-lipped about what he was up to, and of course he was. He was desperate for the approval of his fellow Olympians. "It's ... a perpetual motion thermoacoustic engine! A modification of the Genovian steam engine except more easily scalable to the micro size. I swear! I've already thought of a name for the first tool I put one in: Hummingbird. Cool, right?"

Weird boy with odd fixations. Karme was a few years her junior and ultimately fell into a different school, but she remembered him as a gangly and unsightly thing with a mouth that was far too large for his face. Nerd. Naturally, Althea's step onto his work was intentional. She'd had a bad morning and just wanted to feel something, but truthfully she hadn't recognized the witch until he'd spoken. A late bloomer, but that mouth was still oddly large for his face. Annoyingly, it didn't seem to bother Karme so she supposed she could indulge the weird witch's fixation, derailing his thoughts might prove to be more interesting.

Althea swept up the document from the ground and held it up to the light. "What are you building anyways?" She excelled in complex matters of spirit: inscriptions and runes to tether weaves in place. She needed to.

[eannpatterson]

If you don't succeed, try and try again...

If you don't succeed, try and try again...an update on an unexpectedly difficult project

You would not think it was difficult to build a thin flat metallic plate using a digital description of the plate and a Laser Powder Bed Fusion (L-PBF) machine which can build complex components, such as hip prostheses.  But it is.  As we have discovered since we started our research project on the thermoacoustic response of additively manufactured parts (see ‘Slow start to an exciting new…

[materialsscienceandengineering]

Putting gas under pressure

Understanding gas flames' response to acoustic perturbations at high pressure should make next-generation turbines safer and more efficient.

Soldiers marching lockstep across a bridge can cause the structure to collapse if the rhythm of their step matches the bridge's natural vibration frequency. Combustion engineers must consider a similar effect when designing the gas turbines used in electricity generation and aero-engines.

Just as soldiers' feet can cause bridge sway to reach the point of destruction, a gas turbine can be damaged, or even explode, if heat and pressure fluctuations produced by the flame couple with the acoustics of the combustion chamber. At a lesser degree, this'thermoacoustic instability hampers efficient combustion, increasing noise and pollution emissions.

Predicting and preventing thermoacoustic instabilities remains challenging for the design of a gas turbine. To improve the models used, Deanna Lacoste from KAUST's Clean Combustion Research Center and her colleagues have measured the stability of gas flames at elevated pressure.

Read more.