Casual Discussion Engineering stuff

Nilgiri

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Its kind of a hobby too I feel in many ways, so I will place stuff here from time to time and see what happens, what the interest is and also convos etc.

I will be happy to answer questions that I can or just discuss things etc from stuff that I post.

Others can also contribute videos they find that are interesting or in their scope/field....but objective is what you find of highest quality/interest to share with others (and you have some background knowledge/details to expand upon with interested parties)...and hopefully presented in as layman's terms as possible (without too much technical stuff etc which is maybe where further discussion can progress).

Starting off with 7 deadly sins of aircraft design (its a long hour+ lecture, so feel free to watch/listen in parts):


Can reply in thread or simply hit watch thread to get alerts to it.
 

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How torpedoes work; contrast to common belief, they are not intended to have a direct contact on the target.
The phenomena is best seen here:

Stability of the ships, again according to the common belief, the center of gravity shall be stationed below the center of the buoyancy for the balance, but no:
 

Nilgiri

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Everyone owes it to themselves (if they haven't already) knowing the basics of semiconductor solar technology, given it is going to be a huge increasing part of electricity generation profile in the years to come.

This video does a very good job in laying out the basics:


It reminds me quite a bit of how my dad (who worked in a semiconductor MNC for his career) would fill my head with all this kind of information when I was still kind of young to really grasp it. I have long since overall understood and used the technology myself haha.

For those that would like a bit more expansion on where the improvement in efficiency is broadly headed....it is by use of a larger profile of semiconductor materials (that have different band gaps to silicon and thus able to use more of the incident sunlight emission spectrum when you multi-layer and multi-junction by stacking them up etc...given lot of these materials are not constrained by silicon's "indirect bandgap" which wastes energy by lattice vibration)

A good summary of this can be found here for those interested:


There are of course engineering, design and cost challenges of this approach (you will notice the page is from 2002) and this forms the ongoing research and development of this technology currently.

Some of the recent news on it (multijunction):

 

Combat-Master

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This article gives an overview related to stealth submarine propulsion system, in particular recently being developed by IdeaLab, closed loop Supercritical Carbon Dioxide (sCO2) Brayton power cycle based Air Independent Propulsion (AIP).

AIP allows a submarine to run its electric motor and other electrical systems without using the batteries. It reduces the frequency with which the submarine has to put its mast above the surface to suck in air for the diesel engines to recharge the batteries. The submarine still has to snort for brief periods on most days in order to ventilate, but is much less exposed than conventional diesel-electric submarines. During operations, if the tactical situation prohibits ventilation then the submarine can delay snorting for much longer than normal. And it can revert to lighting oxygen candles (or equivalent) in dire situations. Therefore the submarine can remain submerged for much longer, giving the submarine commander much greater flexibility. There are currently over 50 AIP submarines in service around the world, with the number likely to double in the coming decade.

Let’s discuss and compare IdeaLab’s new sCO2 Brayton power cycle AIP with existing technologies. We will describe sCO2 Brayton power cycle based AIP system in detail and provide brief discussion on existing technologies.

What is Supercritical CO2?
Supercritical CO2 is a fluid state of carbon dioxide where it is held above its critical point (i.e., critical pressure and temperature). The density at that point is similar to that of a liquid and allows for the pumping power needed in a compressor to be significantly reduced, thus significantly increasing the thermal-to-electric energy conversion efficiency.

The IdeaLab Solution
Basically, IdeaLab is developing a thermal-to-electric power conversion technology in a configuration called the recompression closed Brayton cycle (RCBC) that uses supercritical carbon dioxide as the working fluid, rather than steam, thereby dramatically increasing conversion efficiency compared to the steam Rankine cycle.

The primary reason for improved power conversion efficiency is simply that the use of sCO2 as the working fluid in a Brayton cycle requires less work to convert a given thermal input to electricity. In general, increased efficiency represents increased output for the same thermal input, regardless of the thermal source (natural gas, nuclear, solar or coal). Where fuel costs are a significant portion of overall costs (coal and natural gas fired plants), the benefit is reduced fuel costs. Where capital investments are high (nuclear and concentrating solar power), the benefit is increased output for the initial investment.

img_4128.png



IdeaLab sCO2 Power Cycle Benefits as AIP
IdeaLab sCO2 AIP power conversion technology offers a number of benefits over competing AIP Technologies. Most important of all is having 25% higher volume power density (Figure 1) makes IdeaLab AIP power system a strong candidate while the weight stays half of the competing AIP technologies such Fuel Cell and Stirling (Figure 2).

Other benefit is increased efficiency (resulting in increased electricity/power production for same thermal input) due to using sCO2 that provides extra 7 points compared to close challenger fuel cells (Figure 3).

IdeaLab sCO2 AIP system consists of high pressure piping loop that allows depths of 1200 m without any other CO2 disposal pump system on board. Excess CO2 can be stored in vessel if desired.

IdeaLab sCO2 AIP power module is capable of providing up to 4MW electric power. Traction system could be configured so that 4MW burst of energy can be directed to drive system. This is serious advantage over other existing AIP technologies that has limited low speeds due to maximum power drainage problems.

Due to innovative hybrid catalytic combustion chamber; diesel, JP-8 or liquefied natural gas can be used as fuel. Based on conceptual mission analysis, with 100 tons of diesel fuel, sCO2 AIP system could potentially stay submerged 90 days and provide 20,000 km mission range between refuels. This unsurpassed capability compared to existing AIP technologies gives a conventional submarine nuclear-submarine like potency and stealth. Also having high speed turbomachinery as an inherent design future mutes all the noise concerns that a diesel or stirling engine has.

Challenges
All these benefits brings up new challenges as well. Before the benefits of sCO2 AIP power cycle can be realized, it must be shown to be ready and reliable. In concert with the Undersecretaries for Defence Industries (SSM), IdeaLab has been conducting research and development to deliver a technology that is ready for field implementation. In fact, IdeaLab has adopted the following mission statement “By the end of FY 2018, IdeaLab shall develop a fully operational up to 1 MWe R&D Demonstration sCO2 Brayton Power Conversion System that will allow the systematic identification and retirement of technical risks and testing of components for the marine application of this technology.” Ongoing activities in support of that mission include:

  • Confirm viability of existing components (bearings and gas seals) and suitability of materials,
  • Accommodate a wide range of operating parameters and applications,
  • Integrate and scale up existing technologies into a new application, and
  • Develop robust operating procedures for operating at critical point.
Future Applications
sCO2 power cycles are potentially applicable to a wide variety of power-generation applications. Nuclear power, concentrated solar thermal, fossil fuel boilers, geothermal, and floating shipboard propulsion systems have all been identified as favourable applications for sCO2 cycles and would replace traditional steam Rankine cycles.

We will end this article by discussing briefly competing existing technologies.

Stirling Engines
The original Stirling Engine was patented in 1816 by British engineer Robert Stirling as a rival to the steam engine. Although successful, it was largely replaced by the electric motor in the early 1900s and almost forgotten, until the Swedes looked for clever ways to propel a submarine. The engine’s heat is produced in a combustion chamber but it is separated from the actual engine. The heat is transferred to the engine’s working gas (e.g. oxygen), operating in a completely closed system. The working gas forces the pistons in the engine to move, thus producing mechanical energy. Although Stirling engines are well tested and simple, they are relatively bulky, comparatively noisy due to moving parts. Limits the submarine’s operating depth to about 200 m when in use.

Fuel Cells
Fuel cells mix oxygen with a hydrogen-rich chemical to produce an electric current. Fuel cells use an electrochemical reaction in which oxygen and a hydrogen-rich fuel combine to form water, and electricity. Unlike internal combustion engines, the fuel is not combusted. Instead the energy is released electrocatalytically. Fuel Cell AIP was developed in the 1980s for the German Navy. The main system in use today is the German designed Seimens PEM (Polymer Electrolyte Module), but Indian and American firms also supply them for AIP submarines. Fuel cells have a high power density and generally provide the longest endurance of current AIP systems. They are very quiet and the technology is seen as offering further potential. Major downside is Fuel cells are being expensive and complex.

MESMA
MESMA is a French system which runs a steam turbine off the chemical reaction between ethanol and oxygen. In many respects the system is based on the nuclear propulsion but with an alternative heat source. Only Pakistan fields this type of AIP currently. MESMA has a high power output potentially allowing greatest underwater speed but it is relatively thirsty, noisy and has complex plumbing.

Power to Volume;
Most important of all is having 25% higher volume power density (Figure 1)
Q7PWaA.jpg



Power to weight;
Weight half of the competing AIP technologies such Fuel Cell and Stirling (Figure 2).
XXbJ0o.jpg


Power production efficiency;
Other benefit is increased efficiency (resulting in increased electricity/power production for same thermal input) due to using sCO2 that provides extra 7 points compared to close challenger fuel cells (Figure 3).
bGvYrY.jpg



Size comparison
AAOZLFOTO_11816716_040520171144250000_D_GEN_20170504000000_aa-picture-20170504-11816716.jpg



Model
aL6yP4.jpg
 

Nilgiri

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The interesting approach with Yamato was the incorporation lived lessons/experience from such classes as Fuso and Nagato .

This shows in the boilerwork and funnel plumbing for it...given the severe issues that arose from the earlier classes not designing this as a priority but rather side by side with the bridge/mast (pagoda) and weapon requirements etc. This caused a number of awkward retrofits in these classes to improve navigation, comms and overall officer viability from the bridge especially in unfriendly combat situations.

With Yamato (given it was going to be especially bigger than anything else), the propulsion had to be well prioritised (hence you see the super boiler size and super funnel approach and having it slanted away from the bridge etc).

However this eventually made Yamato class quite something of a resource hog too and it was not a marathon runner by any stretch, and thus saw limited actual combat of relevance in WW2...given the stretched logistical nature of the theatres where persistence and endurance was crucial.

The sobering lessons of real war can be quite crushing...even when you design something seemingly to handle it better. All improvements can have tradeoffs, some hidden for a long time too.
 

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The interesting approach with Yamato was the incorporation lived lessons/experience from such classes as Fuso and Nagato .

This shows in the boilerwork and funnel plumbing for it...given the severe issues that arose from the earlier classes not designing this as a priority but rather side by side with the bridge/mast (pagoda) and weapon requirements etc. This caused a number of awkward retrofits in these classes to improve navigation, comms and overall officer viability from the bridge especially in unfriendly combat situations.

With Yamato (given it was going to be especially bigger than anything else), the propulsion had to be well prioritised (hence you see the super boiler size and super funnel approach and having it slanted away from the bridge etc).

However this eventually made Yamato class quite something of a resource hog too and it was not a marathon runner by any stretch, and thus saw limited actual combat of relevance in WW2...given the stretched logistical nature of the theatres where persistence and endurance was crucial.

The sobering lessons of real war can be quite crushing...even when you design something seemingly to handle it better. All improvements can have tradeoffs, some hidden for a long time too.
There's more to come. I'll post it soon.
 

Nilgiri

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^^^ Published in 1985, this summary captures the basic snapshot of the US space program up to that year...an interesting style of presentation not found in the modern documentaries we have today.

The program (mostly NASA) was/is the gold reference for comparing/contrasting with other countries at the same time (notably USSR) and also after (China, India, Japan, EU etc) by looking at the development and deployment and re-development and maturity stages of involved systems and technologies. The apex in my opinion was the apollo 11 mission.

It must be said that one must also account for the raw monetary+intellectual availability and assignment involved from the get go when comparing across countries though.
 

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Damage handling in WWII era ships, the report is covering the cases in depth, and damage handling was crucial back in time, as much as firepower and armor of the ship which is highly related with training and morale of the personnel. Unlike modern era, the computations took place by hand and heavily relied on experience of commanders of particular (chief captain for stability) .
Basics of hierarchical system in ships ,the wikipedia article covers basics of the management system which similarly exists in warships with slightly different roles optimized for warships.
The link below is the report of the damage and repairs of the multiple WWII era ships suffered aerial bombardment, torpedo or explosion damage.
https://www.history.navy.mil/resear.../s/structural-repairs-forward-areas-wwii.html
 

Nilgiri

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I know bunch of members dont like this vlogger, but I had to post this given the sheer level of old school engineering concentrated in one area.

I mean steam powered + belt-driven system (you can see all the mechanical analogues to electrical stuff we take for granted today to source and distribute power)....and what I'm going to call a cam-controlled saw lathe and dremel lathe lol....for the actual production side of the item.


I've always been super fascinated with this kind of stuff.
 

Nilgiri

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Many years back I took apart my parent's cuckoo clock to fix it given time it spent in storage (long story) that took its toll (at their request because they couldn't easily find someone to do that and figured I was an "Engineer").....

All somewhat unsuccessfully but boy did I learn a lot in the exploratory careful surgery. (Happy ending it did get fixed in the end by a refurbisher we found later).

All those interested in such intricate mechanics (and/or classic westerns) might find this interesting.

Probably greatest ending to a western (IMO) has the pocketwatch chimes scene (spoiler alert if you haven't watched this movie and plan to etc):


Obviously the chimes in the movie are representative...given actual watch chimes (mechanical) of this compact size... won't sound anything like that or be that long (or have orchestral accompaniment heh)...

So I got around to looking up what such might actually sound like and what their mechanism is etc and I found this guy:



Absolutely fascinating stuff I must say. Here is a really intricate one:


I am going to look into getting one for my dad for his next birthday.
 

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