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Mechanical Engineering


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Everything posted by dudleybenton

  1. A utility burning landfill gas didn't realize their NOx reduction feed led to production of cyanide! Chemical reactions can be quite complex, which is why you need special software that can handle nonlinear and non-ideal problems swiftly and accurately. This figure shows the impact of air:fuel ratio on the production of cyanide, carbon monoxide, and hydrogen sulfide, three toxic gases they didn't realize they were spewing into the environment at this supposedly "green" facility. Search Amazon books for "Thermochemical Reactions" and click on "Look Inside" to read about the solution hidden for
  2. This is vague so that I'm not even sure what your question is. Are you suggesting that someone might be able to deduce the type of turbine given two temperatures? I very much doubt that. I have worked with gas turbines for years, yet your terminology is unfamiliar. I suggest you search the web for an actual turbine from one of the big manufacturers (GE, Siemens, Mitsubishi, Solar) and review the section details.
  3. Then no one should mind if you spray a little water around to keep the electronics cool. Evaporative cooling is probably the simplest, cheapest, most reliable, lightest, least complicated method to use. Compressors, refrigerants, thermo-electric, semi-conductor, and other high-tech options sound good but are usually a nightmare to implement and keep working.
  4. There are several options. What is practical depends on the application. Is this robot supposed to enter a burning building or a failed nuclear system or a wood drying kiln or what? I have had various electronic devices fail in conditions I had to put up with, like 50°C and 100% relative humidity atop a cooling tower. Have you ever been inside a coal plant or gas turbine combined cycle plant when it was running? I have been countless times. I once stepped out of a plant in Muskogee Oklahoma into 36°C bright sunlight and shivered at the temperature drop. My coworkers have had to endure 63°C amb
  5. This animated model is rendered using OpenGL. The source code is available free online along with other examples, including a T-Rex. [Google "3D Articulation"]
  6. The knight's tour is when the knight, alone on the chessboard, makes 64 moves, landing on each square once and only once. I have written millions of lines of code but have never sat through a single class on computer programming. I had to pass the course to graduate so I made a proposition. The instructor would assign me a problem. If I could solve it, I would get an A and he would never see me again. The year was 1974 and the problem was the knight's tour. Two days later I turned in the solution in FORTRAN on punch cards. I did not know he had been given the problem in graduate school but had
  7. I wrote this screen saver in 1992. It doesn't use one of the algorithms popular today. Instead, it's recursive like qsort, splitting the domain into smaller and smaller pieces. This process naturally results in triangles that are nearly equilateral. When using FEM, you want to avoid acute angles if possible.
  8. When I was in college 40+ years ago, simply running even an elaborate example using somebody else's software was not considered worthy of an advanced degree. We had to write the software ourselves. I am saddened by how many students run a model using Fluent or COMSOL or FOAM or Ansys or ABAQUS or write a bit of Python and consider the job done. You are short-changing yourself if you stop there. I can build a CFD model in 15 minutes. Don't take the easy path. The view at the end of the steep and rocky path is worth the climb.
  9. This isn't the most detailed or efficient model. It's brute force solution of the transient Navier-Stokes equation using finite differences. The nast2d source code can be found on the web.
  10. Resistance (air, road, rolling, drag, whatever) are all forces in the direction opposite of forward motion (i.e., -F). What you're integrating is Newton's 2nd Law or ΣF=d(mV)/dt where F and V are both vectors. In this case there's only one direction so the vector notation isn't necessary and dm/dt is negligible. RK4 (or Euler's method in an Excel spreadsheet) integrates A=ΣF/m=dV/dt and then V=dX/dt. The engine is providing +Power/V less the Drag so that dV/dt=P/V-D. P is a function of rpm, which is a function of V and gear ratio. D is a function of V.
  11. I suggest you get a co-op job for 3-6 months. You may soon find out what you love and hate. Give me a spot under the stairs like Harry Potter so I can work and avoid managers. You may like management. Everyone is different. We need good leaders, nerds, and hands-on workers to get the job done. In my experience, there are exceedingly few people who can actually run a company effectively. I am not one of them.
  12. I have seen this before on a variety of thread sizes, so this is not a unique problem. I run a die on the one and a tap on the other. You may need to turn the die upside down to finalize the thread, because it will be tapered on the starting side. If the two still don't fit right, it's a tolerance issue in the manufacture of the tools. The next thing to try is getting the tap and die from the same manufacturer. If it still doesn't work, you must file the threads. There are special little files in several shapes for this purpose. They're expensive, but worth the investment.
  13. see attached explanation and spreadsheet... expansion.pdf expansion.xls
  14. Isn't this exactly what a RedBox does with DVDs? Unless you want to make a lot of these dispensers and have a lot of money to spend (hopefully to recover later), you will need to find a mechanism that already exists and is already mass produced so that you can adapt it cheaply. When I needed such a thing, I went looking at what people had until I found something I could use. Vending machines would be a place to start.
  15. This is a typical example of solving an ordinary nonlinear differential equation. The details can be found in Chapter 1 of my book, Living Math, which you can read (click on "Look Inside") without buying the book. The eBook will be free on March 9th. The method to use is 4th Order Runge-Kutta, explained in Appendix B. The software is free at the link listed in the Forward. Further details can be found in my book, Differential Equations, which will be free on March 4th. The car simulation in Chapter 3 includes rpm, torque, and gear ratios. The calculations are included in the free source code p
  16. Which hydrocarbon? There are lots. I create P-T diagrams all the time. I have attached an example. You can use my Excel AddIn for refrigerants or some of the other software I provide free of charge on my website. I have written several books on the subject. Azeotropes will be free on March 6 at Amazon https://www.amazon.com/author/djamesbenton
  17. dudleybenton


    There's a friendly guy at church, who stands at the door and hands out bulletins. You'd never guess he was a Blackbird pilot. When President Reagan was frustrated with the mess in El Salvador and wanted to send a "message", my friend took the 71 up… flying the whole length of the country at low altitude, throttle wide open with afterburner. Not only did it break some windows, it ripped more than a few drawers right off the clothesline. Another friend from here refueled the 71 several times to pull this off. More than one round of drinks has been wagered on there being a non-stop, round-trip fl
  18. That's kilo-newtons per square meter. Nm is Newton-meters and is a unit of torque or work or energy, so the two are not equivalent and there is no "conversion" between the two.
  19. I have worked with the equipment you describe and have also looked inside these machines many times over the past 40 years. Your description is not accurate. There are no de-superheating nozzles anywhere near the final stage of this or any other LP steam turbine. The steam would only be superheated at the inlet. Besides, you would only desuperheat steam at the HRSG, not at the turbine, where you want it to be superheated. I have attached an actual expansion line from a similar 3-pressure system, also using an Alstom STG. I have many detailed steam cycle models for this type of system. The stea
  20. The soap bubble isn't exact, but it is approximately the optimal shape plus it's easy to visualize and it also works for shapes that aren't round. Ideally, the surface energy is minimized, which is proportional to the area and also the stresses. Consider this… >---< [abrupt necking at both ends with very narrow tube in between] would have less surface area than )===( [slight neck down on both ends with a tube in the middle having a minimum diameter close to that of the smaller end]. While the first example would have less surface area than the second, the stresses would be much larger be
  21. I won't solve your structural problem for you, but I will share a story. The hyperbolic shape of natural draft cooling towers is entirely structural. The shape is not to induce or optimize the flow of air through the tower. The shape is to achieve the least materials and expense. The thickness of the concrete in the shell is the minimum required to cover and protect the rebar. This is not true at the bottom or veil where the shell sits on columns, which is much thicker. The shape is obtained by stretching a soap bubble between two circles of wire. The soap bubble naturally achieves the surface
  22. DrD posted 1 hour ago! Are you still there? I've been so worried that COVID got you. TMR has disappeared and your phone at the rectory has been disconnected.
  23. I am an engineer and applied mathematician who just happens to write software. I've written a lot of it since 1974—about three million lines of assembler, FORTRAN, and C. I have always written software to get some particular job done. If the subject matter didn't fall into one of my areas of expertise, I worked with someone who knew the important details. Examples of this cooperation include: geohydrologists, meteorologists, and biologists. I can't imagine writing software with no particular foundation. I have never sat through a single class in computer programming. Instead, I made a wager: I
  24. Sorry to have taken so long to respond… The main difference between spark-ignition (gasoline engine) and compression-ignition (diesel engine) operation is constant volume vs. constant pressure combustion. In a gasoline engine, combustion occurs so rapidly (the fuel and air are already in the combustion chamber with the plug fires) and near the top of the stroke so that the crank has little time to rotate and the piston moves only slightly with little change in volume. In a diesel engine, the fuel is sprayed into the cylinder as the piston is falling so that combustion occurs over a longer inte
  25. Sorry to rant, but… Just to give you a little appreciation for size… It takes the total output of Norris Dam just to run the fans on the cooling towers at Browns Ferry Nuclear Plant. Think fan on the radiator of your car compared to the engine. I have published multiple papers on BFNP and the cooling towers. Chuck Bowman designed those too (steam system thermal and cooling towers) plus Cumberland Steam Plant, Paradise Steam Plant Unit 3, Watts Bar Nuclear, Sequoyah Nuclear, Bellefonte Nuclear, Phipps Bend Nuclear, Hartsville Nuclear, and Yellow Creek Nuclear. CRC Press just released Thermal En
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