This high-performance hybrid vehicle uses one electric motor per wheel for propulsion. It has a pair of tiny gas turbines that turn generators to recharge the batteries or power the motors directly. The C-X75 accelerates from 0-62 mph in 3.4 seconds and can reach a top speed of 205 mph, says Jaguar.

What caught my eye was a number in the brochure:

**35,000 liters per minute**. That's right, the twin turbines consume 35,000 liters of air per minute at top output. Hence it has huge air intakes on its lower flanks, just in front of the rear wheels.

I wonder,

*Is that more or less air than a conventional high-performance gasoline-engined car consumes?*

Let's see if elementary math can help us solve this (quite complicated) question. This is a multiple-step, higher-order, critical-thinking exercise and there are many ways to find a solution. Here's the process that makes sense to me.

I know a gasoline engine burns fuel most efficiently at a ratio of 14.7 parts of air to 1 part of fuel, by mass (weight). This is called the

*ratio. Look it up if you want to know more. I knew this from my previous career in automotive diagnostics.*

**stoichiometric***There are the gas turbines!*

Now we can start assembling our data.

**FUEL**weighs about 750 grams/liter and

**AIR**weighs 1.3 grams/liter. These are standard numbers.

750 ÷ 1.3 = 576 which means

**FUEL**is 576 times heavier than the same volume of

**AIR**or to put it another way, we will need a LOT MORE

**AIR**by volume than we do fuel (to have the same mass of both of them). Another way to say it is

*Air is less dense than gasoline*which we all know. Now for some more math.

576 x 14.7 stoichiometric air/fuel ratio = 8467.2 or to simplify things, let's round this to 8500. A conventional car will burn 8500 liters of air per liter of fuel. Any car, at any speed.

So how much fuel will we burn in a minute, or to be more precise, how many liters of fuel do we consume at 200 mph?

Stay tuned; we'll finish this tomorrow. In the meantime, would you care to take the wheel?

## No comments:

## Post a Comment

Type your comment here