The diesel engine has been under attack for decades. Known as the dirty little brother of the fuel family, diesel has been labelled an environmental disaster that pollutes both local and global environments.
This is a great shame for Rudolf Diesel’s legacy, for the design is in many ways superior to the petrol engine. Popular Mechanics magazine rightly states that, “The diesel engine has always been the most efficient internal combustion engine available.”
But while it is rarely recognised for its efficiency, it has always been known as a high polluting engine.
It is a reputation that is rightfully owned with plenty of evidence pointing towards the impact from diesel emissions and its lack of sustainability.
For example, the UK government’s Department for Environment, Food and Rural Affairs (Defra) found that, “NO2is responsible for about 23,500 deaths in the UK each year.” And while the British Government advises that, “There is currently no unequivocal evidence to link diesel with the incidence of cancer in humans,” they also state that, “there is limited evidence for carcinogenicity in animals following prolonged exposure.”
While last year, the UN's World Health Organisation declared that, “diesel exhaust caused cancer and was comparable in its effects to secondary cigarette smoking.”
These findings (and the inevitable media headlines) have led to ever stricter emission controls, forcing a number of car manufacturers to reconsider the future of diesel engines in their vehicles.
As the BBC reported in 2016, “Senior Renault executive Thierry Bollore has said that tougher emissions standards and testing methods would make diesel engines uneconomic to make.” Adding that, “By 2020, when more stringent EU emissions standards come into force, Renault cars such as the Clio and the Megane are unlikely to have diesel engine variants.”
This is a bold move for many car makers. For example, of the 1.6 million cars Renault sold in Europe last year 60% run on diesel.
However, there is good news for Renault and truck drivers everywhere, as a team of scientists from TU Wien have invented a diesel engine that can run on as much as 70% biofuel. As the scientific journal Phys.org reports, “In the tests carried out, the replacement of diesel with the alcohol fuel was gradually increased. These tests showed that up to 70 percent of the diesel fuel can be replaced with bioethanol – and this even had a positive effect on the efficiency of the engine.”
This is a significant breakthrough, as previously diesel engines could not run on fuels with high ethanol or bio-fuel mixes, as they often failed to ignite. To solve this challenge, the researchers developed a dual-firing engine.
As Prof. Bernhard Geringer from the Institute for Powertrains and Automotive Technology explains, "Ignition is initiated by means of a direct injection diesel fuel jet, like in conventional diesel engines. In our model, however, the alcoholic fuel is added to the intake air upstream of the engine. It is then ignited after the diesel ignition in the combustion chamber. In a manner of speaking, the diesel functions as a spark plug for the bioethanol."
"We measured an increase in efficiency of up to 6.1 percent, and that alone improves the environmental balance of the engine," adds Aleksandar Damyanov, part of the TU Wien team.
Furthermore, it does this with increased performance, and lower emissions, with tests showing a reduction in CO2 emissions by up to 39%.
The results have now been published, with the TU Wien website stating that, " Various operating points were tested at an engine test bench at TU Wien – from a low engine load to high-load operation, over a speed range of 1500 rpm to 3000 rpm. In all cases, a significant reduction was recorded in the soot mass and number of hazardous fine dust particles produced.”
"Our results clearly show that bioethanol can be successfully used as a substitute fuel in a dual-fuel diesel engine, and that this concept has significant benefits for the environment," adds Geringer. "In many areas, we will not be able to do without diesel engines in the medium to long term – trucks and tractors, for example. E-mobility has its limits here. With our dual-fuel technology, it is possible to significantly improve sustainability and emissions performance in these particular areas."
With governments everywhere striving for more sustainability that runs on 70% biofuel could make a huge impact. With lower emissions and a more efficient output, the new design will provide a viable alternative to petrol engines and a new lease of life to Rudolf Diesel’s legacy.
Who said diesel was dead?
If you would like to read more about advances in biofuel and biofuel additives, then please take a look at the AG CHEMI GROUP blog page.