I was reading some interesting stuff today on the comparisons of different products and how they compared when a price:weight ratio is applied.
And generally speaking lb for lb a car comes out at the same price as a...............
Hamburger.
Nothing more than a funny little statistic to share with you on grey dull wed pm.
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Ironic, isn't it that the car should evaluate to this by weight. Of course it's a sweeping generalisation and if I recall correctly is based on something like an entry level Focus but the point stands. By contrast, weight for weight one of the jet engines we make is about equivalent to Silver in value. Pre credit market issues silver that is.
Of course the major difference is that a car engine has three strokes to cool down after each power stroke, while our motors have their poor turbine blades consistently running at 380ºC above material melting point... for another random statistic, if we could apply the same technology to an ice cube you could put it in a domestic oven and it would never melt.
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I think I have heard the comparison on the turbine blade, but the comparison to an ice cube in the oven analogy (I think that is the right word) is a good way of making Joe Public understand just how clever the engineers are at your company. That is fascinating.
Any more little gems out there ?
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Hmmm some more random thoughts on a similar line...
The force on a single Fan blade on a Boeing 777 at take off experiences a force equivalent to the weight of ten double decker busses. There are 28 of them.
Each turbine blade makes the same amount of power as an old school 3.0v10 Formula 1 car, about 900Hp each. There are about 70 turbine blades on average in each of the eight turbines... that's a lot of power.
The same aircraft uses about 5 tons less fuel to cross from London to New York than a Boeing 747 from the previous generation of Wide-body jets. It's equivalent to about 72 passenger miles per gallon.
Each engine for the new Boeing Dreamliner will generate 0.5MW of electricity - enough to power about 500 homes.
One of the latest combined cycle gas turbine power plants combined with a district heating scheme is more than 92% efficient - just a tiny fraction of the fuel's heat is wasted. So much heat is extracted from the exhaust gasses that you could put your hand less than a metre from the exhaust without getting a burn, you'd be deaf probably and windswept but not burnt. All the same I wouldn't advise it!
One of the most amazing things you can do as an engineer is to touch a jet engine running at ground idle checking it on a test bed. Another amazing one is slamming the throttle open to simulate an in air emergency and watch as the engine spools up to over 85000lbs of thrust in just over a second.
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Brilliant post, cjehuk. Full of facts, grammatically accurate and well laid out. I look forward to more posts from you.
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There are about 70 turbine blades on average in each of the eight turbines...
Does nobody bother to count them accurately?
I know what you mean, really :-)
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but.. our cars use Internal Combustion Engines , the energy is contained in steel, and is further enveloped in a car body which may be static for long periods.
The jet engine , from what I can ascertain, is open at both sides and air rushes in at 500 mph with outside temps at - 55 c and the heat gets chucked out the back, thereby creating propulsion ?
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The Jet engine is still an internal combustion engine just with a different Thermodynamic cycle being used. In simple terms there are two ways a jet engine can make thrust either make a small amount of air very hot (a small fast flow) or accelerate a lot of air by a little bit (a big slower flow). Jet airliners use the big and slow basis because it's way more efficient in fuel burn and noise levels. Military jets use a small fast flow for a smaller engine and higher top speed - plus noise isn't such an issue.
Motoring link: The engines in Thrust SSC were built on the "hot and fast" basis, as are the engines in Richard Noble's latest attempt which will use the engine from a Eurofighter.
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From HJ's report above:
"A scant 5 years ago, this 82k mile Mercedes S600 twin turbo V12 cost someone way over £90,000. Yet today, despite a postponed VED penalty, it was knocked down for £10,250."
That seems a real bargain. Still a bit surprised at how well Mini's and BMW's are keeping their value though.
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