Difficulté
Difficile
Durée
1 jour(s)
Coût
50 EUR (€)
Description
Things about stirling engines
Introduction
We now live in a post-covid world, and wether you're part of
those who think billionaires take very seriously climate change and want
to address the question with population "regulation" and with survivalists bunkers,
or wether you're part of those who think billionaires don't care and just want
to keep on getting richer and richer until the last drop of petrol,
it becomes urgent to find alternatives to facism and to the models we are offered,
and it includes technical alternatives.
Stirling engine was invented in the XIX century, before combustion engine
and there are a few "mainstream" industrial uses, in particular in the 60s-70s
(Ford Torino,American ship Caloric).
Also called "hot air engine", its principle is to move hot air alternatively from 1
cold zone to 1 hot zone and gather the mecanic force produced by air dilatation
and by air contraction.
High performance Stirling engines have necessited a lot of research and development and have achieved yields
with higher performances than combustion engines (around 40%).
They are reliable, silent, and have high yields.
They are however better adapted to regular regimes.
Étape 1 - web literature review
We hereby list a few videos of diy stirling engine
more or less diy and in french language
We can find engines made with a coca cola can (DDM Brico Voyageur https://www.youtube.com/watch?v=nBxKOkYx2rI), wooden engine made with glass syringes for the pistons (Incroyables Experiences https://www.youtube.com/watch?v=s79odgWz6BM) , a 125 cm3 manufactured engine with an estimated power of 0,8kW to 8kW (0,6 horsepower to 6 horsepower) considered the measurement of 800 rpm and a tray mass estimated between 100g and 1kg (French Stirling Fablab https://www.youtube.com/watch?v=Z24dZ3St_JE from series https://www.youtube.com/playlist?list=PLE1TyIvCXNyjlvWRi10LUsEMXKyRS6Ltx on channel https://www.youtube.com/@FrenchStirlingFablab) You can find notably resources to try to build your own stirling engine that you won't find in this tutorial As a bonus, for teachers, 1 example of a tractor and crane toys build in meccano here: http://cm1cm2.ceyreste.free.fr/stirling.html</translate> |Step_Picture_00=Moteur_Stirling_Stirling_moteur_air_chaud.mp4 |Step_Picture_01=Moteur_Stirling_Moteur_thermique_fait_maison.mp4 |Step_Picture_02=Moteur_Stirling_TUTO_INCROYABLE_MOTEUR_STIRLING_AMAZING_STIRLING_ENGINE_THE_LAST_EPISODE_S1_Ep7_.mp4 }} {{Tuto Step |Step_Title=<translate>Toy power</translate> |Step_Content=<translate>We will now try to measure the power of stirling engines called "scientific toys" that we can find on aliexpress or on resselers like science labs You will find attached two videos showing 1 stirling engine "scientific toy" that run with a flame as a heat source coming from 1 candle or 1 alcool container combustion. The engine comes with 1 small container and a wick that has to be filled with alcool that produces power adapted to the engine (video 1). In the video with the candle (video 2), the candle flame doesnt produce a power adapted and the engine only runs for a few seconds and then stops and becomes very capricious to restart (a bit aleatory after a few tries even after cooldown). Therefore we measure the power of the two flames (video 3 and 4): time to boil 10mL of water from 20°C to 100°C energy=10*80 cal=800*4,184J=3347,2J time for alcool lamp flame: 40s to 1min (wether simmering or boiling) time for candle: 90 to 120s "alcool lamp:" max_power=3347/40=84W min_power=3347/60=56W "candle" max_power=3347/90=37W min_power=3347/120=28W To try to measure yields, we fix a mass to the motor (her a broken nut of 5g in video 5) and we measure tork traction as well as angular speed. Broken nut mass is 5g and is fixed at a distance of d=3cm of the rotation axis. Rotation speed measurement with a 25€ tachymeter this tuesday 25 june 2024: the tachymeter works by friction (rubber traction that turns an axis of which rotation speed is measured): the traction happens after half a second to 1 second and displays values between 100 and 500 rpm and makes the engine stops. Rotation speed measurement with 1 laser tachymeter (video 5): 1400 rpm with 5g broken nut attached at 3cm of axis Rotation speed measurement with laser tachymeter for engine 2 (video 6): 1000 to 5000 rpm with 5g broken nut attached at 1,6 cm of the axis <br />The yields is low, but we must recall this is a toy and not a engine made for performance. We could however make the measurement exercise with high performance scientific toy (multi cylinders, vertical mover, smaller wheel, etc.). Industrial stirling engines can have yields up to 40%.</translate> |Step_Picture_00=Moteur_Stirling_fonctionnement_lampe.mp4 |Step_Picture_01=Moteur_Stirling_bougie.mp4 |Step_Picture_02=Moteur_Stirling_source_chaleur.mp4 |Step_Picture_03=Moteur_Stirling_bouillir_bougie.mp4 |Step_Picture_04=Moteur_Stirling_tachy2.mp4 |Step_Picture_05=Moteur_Stirling_00023.mp4 }} {{Tuto Step |Step_Title=<translate>Rotation speed verification with video analysis</translate> |Step_Content=<translate>To measure angular speed, we will use two software: 1 python code sample based on opencv, and ffmpeg python commands: <pre> sudo apt install virtualenv virtualenv --python=/usr/bin/python3 . source bin/activate pip3 install opencv-python import cv2 import os def charger_images_video(video_filename, output_folder): """ Loads video frames from a file and saves each frame as a JPG image. Args: video_filename: The path to the video file. output_folder: The folder where to save JPG images. Returns: A NumPy array containing the video images (3D array: frames, rows, cols). """ # Open video with OpenCV cap = cv2.VideoCapture(video_filename) #Check successful opening if not cap.isOpened(): print("Erreur d'ouverture du fichier vidéo:", video_filename) return None # Check that the output folder exists, if not create it if not os.path.exists(output_folder): os.makedirs(output_folder) # Empty list to store video frames images_list = [] frame_number = 0 # Play video frames frame by frame while True: ret, frame = cap.read() # Check image playback if not ret: break # Save each frame as a JPG image frame_filename = os.path.join(output_folder, f'frame_{frame_number:04d}.jpg') cv2.imwrite(frame_filename, frame) # Add image to list images_list.append(frame) frame_number += 1 # Close video capture cap.release() return images_list # Example of use video_filename = '00009.MTS' output_folder = 'frames' images_list = charger_images_video(video_filename, output_folder) </pre> commands ffmpeg: <pre> sudo apt install ffmpeg ffmpeg -i 00009.MTS -vf fps=25 output_frame_%04d.png </pre> You can reproduce the measurement with the source video file (link at the bottom of this step) and the previous sample code Unfortunately at this stage of the experiment, the 25fps video doesnt allow a correct measurement the angular speed of the engine is too fast and produces blurred images on the video broken down in 25 frames per second Unfortunately the captation at 60fps or more is expensive (sony camera or zcam at more than 1000€ on amazon. the advantage is you have 14 days to test the camera and get reimbursed if it doesnt fit) we can find 60fps webcam but after a test (Svpro Full HD 1080P Webcam USB Objectif de Mise au Point Manuelle 4 mm, 30fps/60fps/100fps Caméras de Bureau USB CMOS OV2710 pour Linux Windows Android Mac OS, Plug and Play at 33€ on amazon) this wednesday 26 of june, it captures at 30fps. And you cant really configure video captation software adequately, see this page for exemple where there are no parameters to define fps: https://wiki.archlinux.org/title/Webcam_setup test with zcam e2: video of 60s at 60fps (in theory 3600 frames) with a bit of therebentin (no more alcool 90° confiscated by the cops): the engine runs but visibly slower than when the container is full of 90° alcool. We verify rotation speed. Strangely, i have a message "process stopped" at frame 273 with python script and ffmpeg does the job and we obtain half a rotation between two consecutive frames, which means 30 rotations per second, which is indeed 1800 rpm File available here if you want to verify: https://vpn.matangi.dev/stirling.mp4 (1,8Go)</translate> }} {{Tuto Step |Step_Title=<translate>Power the engine with a solar source</translate> |Step_Content=<translate>Making a high performance stirling engine requires a lot of research and development (go! for hackers who want to leak phillips brazil archive of the ford torino - yes 60s and 70s is not only great for music-) In theory, with a 40% yield, it requires a solar receptor of 2,5m2 (aproximatively a receptor of 90cm radius) for a motor of 1kW we will here scale based on the flame power that runs the engine correctly: 60W to 90W We will first use 1 small concentrator on which we will fix bits of broken mirrors (after a fixation test it is dramatically worse than with the initial surface of the reflector) and measure the time it takes to have a small quantity of water boil and we will make a linear scaling for an adapted diameter (the sun power received is linear of the surface being lit with sun rays) test this sunny tuesday june 2024 6cm radius concentrators on the photo : the reflecting surface is made of "bumps" not necessarily as good as dedicated reflectors surfaces that can be bought for example at solar brother (https://www.solarbrother.com/acheter/reflecteur-solaire-adhesif-s-reflect-500/)
When putting a finger at the center of the concentrator at noon and pointing at the sun, sensation almost being burnt with a lighter after 5s.
The test for boiling 3mL of water failed, maybe because the surface is not smooth enough, maybe because the container makes too much shadow on the concentrator, maybe because the concentrator is not well enough oriented to the sun or because the container is not well placed at the focal converging point of the sun rays
The sunlight is approximately 1000W/m2, and the surface of the concentrator around: 3,14*0,06*0,06=0,0113m2
The power of the concentrator is therfore theorically around: 0,0113*1000=11,3W
To get a power of 90W at noon (we can modulate to lower at another time or when the sunlight is lower), it would require a reflector of radius r:
r=√(90/3,14*1000)=√(90/3140)=√(0,02866242)=0,17m
We would therefore need a piece of sphere of around 34cm of diameter
The parabolic antenna retrieved in a recycling shop is around 60cm diameter, which is way too large, the surface being linear to the squar of the radius (in first approximation)
We will therefore buy a parabolic antenna of 40cm diameter (not found smaller and stick solar reflector tape
Test 12/07 : negative with 40cm parabolic antenna and reflector tape: the cylinder of the piston is transparent and the heat of the concentrated sun rays doesnt heaten up well the cylinder. We cant take to pieces the egine to put steel whool inside, like in stage 1 video. Test tomorrow with tinfoil glued to the cylinder. Otherwise, we need to find an engine with metal cylinder
Video is bugged and not uploadable, test again when digital weather is better
negative test of 13/07 noon with tinfoil on cylinder: finetuning the parabolic antenna on the cylinder is difficult, need to be very accurate and with the gear i have (a mic leg) it requires to suspend the engine in the air, etc.
negative test of the 16 of july 18h: parabolic antenna of 40cm, concentrated sunlight rays ok, insufficient solar power
negative test of 23 july 18h: parabolic antenna of 60cm, concentrated sunlight rays too scattered, insufficient solar power
the concentrated sunlight square is too scattered. It seems it would be appropriate to do a concentrator with a higher degree of concentration (a real sphere piece)
8.25 test: moulding made with a 85cm yoga balloon. 45 diameter concentrator, a bit too small
I ordered a 150cm baloon on the 26th of August
11.28: managed to build a 80cm diameter solar concentrator with a 150cm yoga baloon. Negative test for powering a stirling engine, the solar rays are too scattered (see video).
Next experimentation with a fresnel lens
Dedicated tutorial building solar concentrators : https://wiki.lowtechlab.org/wiki/Concentrateurs_solaires
Étape 2 - Make and optimize a mobile solar receptor
Here i pass you the ball
First, we need to think about a concentrator that follows the sun dynamically during the day based on its position (the variables are date and time and possibly latitude and longitude)
and more importantly: that is able to gather and send sunlight rays concentrated to a fixed point at any time during the day
Then, we can imagine 1 thing based on several concentrators of distinct diameters adapted to a varying sunlight
We then have an infinite source of renewable energy, transportable that will work with a range of sunlight with a tresholds
We can even imagine 1 society where machines dont run when there's not enough sunlight, but this is science fiction
To give some landmarks, the biggest one piece mirrors we are currently able to make are telescope mirrors of 30m diameter
Telescope mirrors of 5m to 10m are more common for big telescopes
Im not a specialist, just a democratiser/populariser concerned with climate change
and the rise of facism
Therefore and at this time of my experiment, I'm wondering about two practical aspects for an everyday us
to stop the engine (you dont only need to stop injection)
for longer use: keep the cold source cold enough and long enough without oversizing the power on the hot source input (for a high performance deltaT or ratio)
And because at a time of looming facism rising in many countries, we must stop auto censorship to talk politics when speaking in one own's name
1 government that would take seriously climate change would have long ago put
stirling engine at exams, encouraged consortiums to work on that,
and created mixed groups of engineers, technicians, diy workers without diplomas from different territories to work on this type of questions!
Scientific knowledge is contextual of epochs and this is not only in spatial engineering (going on the moon)
we have lost knowledge. If lobbies prevent from putting forgotten reliable and robust techniques at the agenda ,
it's politics role to create necessary incentives!
Étape 3 - Your turn
here you are, you have now web resources to make your own stirling engine, clues to do research on high performance engine manufacturers, a methodology to test and verify rotation speed lower than 3600 rpm in context of digital surveillance and shackle, and ideas for concentrator engines based on dynamic concentrators
For an sun tracking algorithm, you can have a look at the code her:
Dimensionner et faire un tracker solaire photovolatïque low tech
However, a device based on 4 photoelectric cells and a small maximum seeking electronic circuit to drive motors could replace a hard coded algorithm honorably and adapt to all latitudes and longitude without tweaking
I also hav a problem with sabotaged concentrators (scratches, reflector tape taken off) quite quickly, but im sur you will find ways of avoiding that too!
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