Diesel engines use a different thermodynamic cycle from gasoline engines to extract energy from the fuel.
Diesel is oil. If olive oil were cheaper, it could be used perfectly in this type of engine.
Diesel is one of the many oils that oil carries. For many decades it was only used, and even today in the USA it is practically only used, for trucks, trains and ships.
But it was a valuable product that had to be thrown away and European governments began to subsidise it by promoting diesel cars with low taxes and low prices of this oil in service stations, until its use became widespread, when subsidies were eliminated and prices were brought into line with those of petrol.
The oil does not explode, but at very high temperatures and well mixed with the air, it burns and is converted into carbon monoxide (CO, which passes into CO2), water and various waste products. Since there is no explosion, not all of the oxygen in the air combines with the carbon in the oil and what remains.
Since the temperatures are very high (at points in the cylinders up to 1,200ºC) and the internal pressures are very high, it combines with the nitrogen in the air itself to form NO and NO2 (NOx), nitrogen oxides that cannot be captured by the catalysts in the exhaust pipes and are released into the atmosphere.
Diesel also carries nanoparticles (lumps of size a millionth of a millimetre) that do not burn and are released into the atmosphere through the exhaust pipes as aerosols. a standard was set that required diesel to be better filtered. Since then, cars with diesel engines do not expel the black fumes of before, but even if we do not see them, they still expel those nanoparticles.
NOx combines with certain volatile organic compounds (VOCs) and generates ozone, which on hot summer days produces the ‘ozonazo’ that causes occasional and severe breathing difficulties in sensitive people.
The main problem with NOx is that it combines with many other compounds in the atmosphere, especially in cities, such as ammonia, water vapour and other nanoparticles.
As the name suggests, these tiny particles are introduced into the lungs on a daily basis and are deposited in the bronchioles, the smallest units of the lungs, where the absorption of oxygen from the air into the blood and the removal of CO2 from the blood is (must be) carried out in the basic process of life.
Living beings have developed protection against micro-particles, which are found in nature. But the human being is producing nanoparticles and against these the nature does not have defenses, because throughout thousand million years it has not needed them.
Constant exposure to these nanoparticles eventually blinds the bronchioles and bronchioles, and gradually reduces the oxygenation capacity of the blood, in the same way as tobacco or silicosis in miners.
At some point, pulmonary emphysema occurs, when the lungs are so blinded that they can no longer exchange oxygen.
The nanoparticles are directly invisible, but at dawn and dusk, when you look at Madrid from Torrejón, for example, you see a yellow-green beret that indicates a high concentration of NOx and its harmful derivatives.
This above is science, it is chemistry and biology. But chemistry, biology, science itself, without its interaction with life and the life of human beings, has an academic interest.
The interest of science (even theoretical physics) is to be able to explain the facts of our lives, of the environment around us, of our interactions with it and with each other.
A scientist should be as aseptic towards society as possible. It is not acceptable to have a guild scheme in which some ”professionals” do their homework while others, ignorant of almost everything, assume the right to say that it is the right thing to do.
A good scientist learns, communicates and indicates courses of action, which citizens, well informed, may or may not follow. But it is not aseptic.
Similar to the chlorofluorocarbons that were designed to be able to transport meat from the great American prairies to the cities in refrigerated trains.
Replacing the harmful ammonia, and were revealed as destroying the ozone layer that protects life on Earth from the action of the ultraviolet radiation from the Sun, so trying to sell a part of the waste from oil refining has been revealed as enormously harmful to human health.
And on top of this, when we citizens strive to protect our lives, there are those who want to continue selling what they know is harmful, and to do so they have no qualms about deceiving administrations that are not a paradigm of care and attention for people either, but which do something.
Diesel engines are more efficient, from the point of view of converting oil energy into kinetic energy, than petrol engines, if only because they work at a higher temperature and pressure.
One of Volkswagen’s brands, Audi, is characterized and sold as high speed and acceleration cars for aggressive drivers, so one experiences on the roads.
To achieve high accelerations with combustion engines (instead of explosion engines) much more oxygen must be introduced into the mixture with the oil. More oxygen means more air and more nitrogen.
There is much more nitrogen to combine with an amount of unburned oxygen, than in engines that are not designed for high acceleration. This implies very high emissions, up to 40 times higher than what citizens have deemed reasonable (and still too much) for the air in their cities.
How to do this? One of the instructions from the on-board computer (car computers involve about 100,000 lines of code.
More than those in aircraft) makes the engine emit the legal requirements when its emissions are measured, and increase the air mixture when it leaves the MOT and circulates freely.
Volkswagen makes money. It is the company that sells the most cars in the world. But it wants more.
As I said here a few weeks ago, genetic and memetic instructions for competitiveness allow human societies to survive.
But the dynamics of these societies are those of complex non-linear physical systems. The extremes are exaggerated when controls are overridden.
Societies must study and understand the functioning of complex systems as physical systems and constantly apply their laws of regulation.
The alternative, what we are seeing in these first two decades of the 21st century, in which an erroneous analysis of society, that of neo-liberalism based on the idea of simple, linear systems, has led us to all sorts of excesses that we are paying for with our lives.
Science has answers to a great many questions. But it must be known, respected, supported and used.
What is happening in so many things is the same as what is happening, for example, with climate change, an issue in which many politicians, ignorant of science, reject its reality.
There is something we citizens can do, since those who govern us have other interests that are not our welfare, or at least it seems that way. We can stop buying diesel cars. We will not spend more and we will take care of ourselves in front of those who despise our lives.