The Inefficiency of Combustion

Every transformation of energy from one kind to another engenders ineffiency, through dissipation to the environment, and through divergence of forms from useful energy to unusable energy.

Critics of wind power and solar power like to point at their low conversion efficiencies, distracting our attention from fossil fuel technologies. Mario Hirz, of Graz University of Technology, answering the question “What is an efficiency of modern average car IC engines? That use petrol/gasoline/diesel”, writes that “Diesel engines up to 35% in best point, gasoline engine up to 30% in best point. In real life use, averaged about 25% for drivetrains with Diesel and about 20% for those with gasoline engines.”

Combustion, aka burning, or fuel oxidation, has two main problems in internal combustion engine (ICE) vehicles, like the average urban car; which are, that the fuel burning takes place as “free fire” in a reactor, where trillions of reactions take place randomly every microsecond, with no semblance of control or order; and in addition, the fuel used is messy, a jumble of hydrocarbons, oxygenates, and so on, with chemical modifications going on during the overall combustion process.

Would there be a way to improve on ICE designs to improve efficiency of combustion, for example, creating narrow channels with high flow for more uniform oxidation ? Or would using a purer fuel narrow the range of side reactions that lead to loss efficiency ?

In Nature, combustion is highly managed. Glucose isn’t burned with oxygen in the gut. No, respiration is done in each individual mitochondria structure inside each individual cell. In animals, oxidation is done cell by cell, in a highly controlled manner. Just the right amount of glucose and oxygen permeate the cell membrane to take part in the reactor organelles, and carbon dioxide and water waste products are efficiently routed out of the cell again (unless the cell decides it needs to hang on to some of the water : diffusion and osmosis).

In a car engine, we don’t have the luxury to compartmentalise combustion, despite things like vaporising fuel into minute droplets, and using catalytic mixers. And in point of fact, ICEs need the bulk explosion of centralised fuel burning in order to physically propel drive components. Combustion done differently is seen in fuel cell vehicles, where controlled oxidation is used to create electric current, which can be “concentrated” to the correct impulse to drive the car.

Could efficiencies of fuel use be improved at the same time as air quality and climate change are addressed in road/rail/sea/air vehicles and road/rail/sea/air vehicle fuels ?

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