Bunker Mulligan "Let us endeavor so to live that when we come to die even the undertaker will be sorry." ~Mark Twain

April 15, 2005

Nukes Again

Filed under: Engineering — Bunker @ 10:04 am

UML Guy also takes a poke at Kristof’s article on nukuler energy.

Damn engineers keep throwing that logic stuff at op-ed writers!

March 24, 2005

MIT Engineers

Filed under: Engineering — Bunker @ 11:06 am

You want hydrogen cars? How about this technology?

March 22, 2005

Hydrogen Cars

Filed under: Engineering — Bunker @ 6:55 pm

Dick Morris may understand politics, but he knows nothing about physics.

In what is otherwise a good article on the things Arnold is doing as Governor of California, Morris errs…

Replacing gasoline engines with hydrogen-fuel cells would eliminate two-thirds of America’s need for oil — a demand that we could meet entirely with domestically produced oil.

Well, not exactly.

A typical automobile engine is about 25-35% efficient, which means 25-35% of the energy from fuel is converted to work. That takes into account all the power the engine must generate to push the car through the air, provide power for electricity generation, and drive such things as the air conditioner compressor. The drive train itself is only about 85% efficient. Things that will always be involved in the equation, regardless of power source.

What about these hydrogen cars? Will they reduce automotive emissions? Yes. So Morris is partially correct in that his numbers refer to the amount of energy saved in automobiles. But that hydrogen must come from somewhere. And that will require burning of oil (or coal) somewhere other than in the car’s engine.

Yes, that energy conversion process will probably be far more efficient. Maybe at 65%. But the electricity must then be transported, with attendant losses–perhaps 90% efficient. That electricity is then used to separate hydrogen and oxygen. That is only about 80% efficient. Then the hydrogen must be stored at cold temperatures and/or high pressures, and that costs more energy. And losses. Let’s be generous and say it is 95% efficient.

Then, the recombination of hydrogen and oxygen in a combustion is about 75-80%.

What do all those numbers mean? Well, if we multiply all those efficiencies we get a net efficiency of 33%, and that is being generous.

Running an automobile on hydrogen is about the same as running it on gasoline, and requires just as much fuel (oil) and generates just as many fumes, although the car itself doesn’t.

One other thing people don’t realize is that the hydrogen burning with oxygen also burns with other elements in the atmosphere. After all, air is mostly nitrogen, with some oxygen and a few other gasses–not to mention particulates in the air. Hydrogen is also a prime ingredient for all acids, such as sulphuric and nitric. As in sulfur and nitrogen being combined with hydrogen in water solution.

These are all very rough numbers found in five minutes of searching the internet. I don’t write all this to say we shouldn’t be looking at alternatives. Perhaps those efficiencies can be improved. Perhaps the extraction of hydrogen can be done in other, more efficient ways. And perhaps the storage problems (remember the Hindenburg?) can be resolved. I write all this simply because too many people will take up the cause without understanding the complexities involved.

Dick Morris is but one. And as things now stand, the reduction in oil requirements would be… well, zero.


Hud is thinking along similar lines as he talks about the ozone “hole”.

December 22, 2004

Boring Engineering Stuff

Filed under: Engineering — Bunker @ 10:16 am

I have had a pretty diverse career as a mechanical engineer, and mechanical engineering is as diverse a field as there is. I’ve had to use all the tools I learned (and had to relearn) in school. Calculus, linear algebra, differential equations, thermodynamics, gas dynamics, heat transfer, materials mechanics, power transfer, structures. I am amazed at how all the things Sir Isaac Newton deduced four hundred years ago are still valid, whether it be physics or mathematics. Newtonian Physics are still quite valid and useable here on earth, and most other places and situations in the universe.

At 26 he became a lecturer at Cambridge. Twenty-six. And his brilliance hadn’t really even been exposed at that time. I’ve known some very smart, even brilliant, people. Did any of them even come close to the mind of Newton? I doubt it. He couldn’t explain his thoughts on gravity with conventional mathematics techniques, so he invented Calculus–or discovered it, your choice. Damn.

I’ve been thinking about old Issac the last two weeks as I worked on some spreadsheets to simplify the thermodynamic calculations on turboshaft engines. Every jet engine operates on the premise of converting chemical energy into thermodynamic energy in the form of heat, pressure, and velocity. The basics are the same whether the engine is a turboshaft, turboprop, turbojet, turbofan (turbo as a function of a turbine within the engine), ramjet, scramjet, or pulse jet. There is a stoichiometry common for all with a single fuel, so the air/fuel mixture changes based on the heating value of that fuel. Beyond that, the relationships between the mixture and associated heat, pressure, and velocity are all constant. Newton’s Laws.

The internal geometry of an engine is designed to get the most efficient use of those relationships. That energy is converted to rotational power through a turbine for driving the compressor in all the turbine engines. Turboshaft and turboprop engines also have another turbine which extracts energy to drive a propeller or rotor system. In other types, the energy is converted to high momentum mass flow and nozzle expansion for thrust.

Okay, you’re now bored to tears.

The last two weeks I’ve been involved in correlating two engine test cells. A correlation is more or less a dynamic calibration of the data acquisition system. We take an engine which has been run in a manufacturer’s test cell, and compare specific parameters to those obtained in the candidate cell. We can then certify that the cell is providing accurate and repeatable data. That way we know that every engine we test is performing as indicated. The following is a single sheet of the correlation data comparison:


The lines are the limits we are allowed, and the data points must fall between them (as they do here).

The task can be quite frustrating. The equations, which derive from all that work Issac did those 400 years ago, get complex and involve conversions of data from things like inches of mercury to pounds per square inch gage to inches of water to pounds per square inch absolute. That’s just pressure. Fuel flow must be converted from Hertz (in a flowmeter) to a velocity, modified for specific gravity to calculate mass flow. All the test parameters are similarly confusing when looked at in the form of a spreadsheet equation. You know, twenty sets of parentheses and every math function available. It isn’t something most people want to be responsible for. Thus, this modification of a Dilbert cartoon from one of my compatriots:


Actually, I enjoy the challenge.

October 19, 2004

Moveable Type

Filed under: Engineering — Bunker @ 1:25 pm

I’m really getting upset about the software I use on this blog. I’ve been using MT since last January. The manual isn’t friendly to someone like me who doesn’t know UNIX or servers, and I’ve run into several issues which have driven me almost over the brink.

The latest is the commenting system. I don’t moderate comments. I don’t want to. but for some reason, all on its own, my MT installation has decided I have to. I can’t understand why. I’ve checked the configuration within, and the configuration file, I’ve contacted my hosting service to see if they did some kind of upgrade which might have caused a communication error. I reloaded configuration files, and done everything else I can think of.

If any of you have run into this, or have advice on the transfer to WordPress, I would appreciate you leaving a comment.

Of course, I’ll have to approve the comment, first.

September 2, 2004


Filed under: Engineering — Bunker @ 7:37 pm

As an engineer, I’ve written just enough programs in different languages to be dangerous. I can’t say I’m arrogant about my skills in coding, but often too self-confident. I generally have little trouble with any commercial software.

Not so with MoveableType.

I know nothing of UNIX or servers, although we do have UNIX machines and it appears to be very similar to DOS. And I have absolutely no knowledge of Apache. Yet the MT User’s Manual seems to think I do. I run into problems of /www/b/u/something/something_else/ which bears little resemblance to what I think should be \www\b\u\something\something else\, and where do the b and u come from?

So, when I ran into problems, I did what every man does–sulk. Curse. Bang my head on a desk.

Then I contacted people with knowledge of such things: RAMMER. David. They, of course, responded.

Today I first backed up all my archives. That required four attempts. Then I tried to locate the portion of MT where I could change the templates to static rather than dynamic. That took some searching because I didn’t realize at first that I needed to change the templates and not the archives. Then I tried to rebuild just the individual archives, as these seemed to be the problem. Do dice. So then I rebuilt the categories. Worked. Tried individual again. Worked. Rebuild the entire site. Died in the middle.

Eventually, I got all the archives rebuilt. Then I checked the trackback link from rishon-rishon that first highlighted the problem. It still didn’t work. I found that, for some reason, that ONE individual archived post didn’t rebuild! I did an ftp of that one and rebuilt once again, and here it all is.

I spent most of the day today escorting some consultants around who will do some IT work for us. I spoke eloquently and often to them about how little I knew about hardware, and what I expected from them in the way of advice. Mercifully, I also asked them for advice on software to use, and assistance in building the necessary applications and integrating them with one another and the things we currently have running.

They think I’m smart.

Well, smart enough not to do it myself.

August 17, 2004

Fuel Cells

Filed under: Engineering — Bunker @ 1:12 pm

I know, they are the answer to our quest for renewable free energy that won’t pollute the planet. A new announcement that the technology is maturing takes the world by storm. SDB often answers these issues, but he is taking a pass because he’s tired of hearing about the new revolution. I can’t speak of the technology the researchers are studying, but the implication is that they are some form of exotic battery. I guess the term “fuel cell” is key to getting research grants.

Some of you children out there are too young to remember when nuclear energy was going to produce free electricity for everyone in the US. Checked your electric bill lately? Nuclear energy is relatively cheap, but the regulation and safety requirements drive the cost up. And the fact that we aren’t going to build any with new technology any time soon means that source is going away. And quickly.

Okay, students. Where do we get hydrogen for these fuel cells? There, in the back. No, it doesn’t grow on trees. Next? No, it doesn’t come out of a faucet. And you? Correct! It comes from water!

Ah, but a water molecule is a combination of hydrogen and oxygen atoms. When a fuel cell uses hydrogen to create energy, it does this by burning the hydrogen in an oxygen environment. The byproduct is water.

Where did that energy come from? Well, there are all kinds of energy in the world–chemical, potential, kinetic, electrical, thermal. The energy in hydrogen is chemical, converted to thermal, then to electrical. Once used, it has no more energy to offer. It has joined with another little hydrogen atom and a larger oxygen atom to become water.

Wow, you say. That’s a great cycle! We start with water, get some electricity, and end up with water again. Can’t get any cleaner or cheaper than that!

Ah, but somehow the water must first be converted to hydrogen and oxygen so that the fuel cell can recombine them back into water while generating the heat energy we need. There must be an energy balance. Energy out equals energy in minus inefficiency. So, in a perfect fuel cell, the energy inherent to the hydrogen is perfectly converted to electricity. Well, except for the energy absorbed in the recombination process. So, I guess there never can be a perfect fuel cell.

I’ve walked all around the real issue trying not to state what is obvious to engineers, and what should be obvious to others. Maybe I should point it out to those of you without any technical background. Some form of energy must be used to convert the water molecules to hydrogen and oxygen atoms Our energy balance comes into play once again. Energy out (hydrogen) equals energy in (power required to split the water molecule into hydrogen and oxygen atoms) minus inefficiency. Perhaps we’ll use electricity to do the converting. If both processes are absolutely perfect, we will create enough electricity in the whole process to equal the amount of electricity we used to create the hydrogen in the first place. No net gain. We burned oil or coal to create electricity to create hydrogen to create clean electricity.

Let me help you understand this in another way. If I want to heat water, is it more efficient to light a gas fire under a pot or set it on an electric range? The gas flame directly heats the water. Electricity must be created by first heating water into steam, using the energy in that steam to drive a turbine which rotates a generator to produce electricity. That electrical energy is then transported by wire to your house where it is converted to thermal energy to heat the water. That’s heating water to heat water. Kinda like using electricity to create electricity.

Fuel cells serve a very specific purpose. Space travel. They provide electricity with drinking water as a byproduct. Cost is not the issue in space travel. Size and weight are.

Fuel cells are not an alternate energy source.

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