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‘Dual Engine’ Combining Gasoline and Diesel is the ‘Heart’ of Future Vehicles
 

World’s First Attempt from SNU Research Team

(December 12) Prof. Kyoungdoug Min (Dept. of Mechanical and Aerospace Engineering), Director of the SNU Institute of Advanced Machines and Design, shows the dual combustion engine currently in development. The dual combustion engine simultaneously uses two types of fuels, diesel and gasoline, utilizing the advantages of each type. By Shin-young Yoon, Dong-a Science ashilla@donga.com

It resembled a human heart. The engine, about as big as a chair, was hanging at the height of an adult’s chest. The pipes, where fuel goes in and gas comes out of, were intricately winded together, as bulky as a muscle. The complex electric wires were like blood vessels. This was the room where the new heart of future vehicles was being created.

In the afternoon of December 12^th, Professor Kyoungdoug Min (Dept. of Mechanical and Aerospace Engineering), Director of the SNU Institute of Advanced Machines and Design, led us to the Testing Laboratory building right next to the Institute. This building was donated by the Hyundai Motor Company to be used for research in future automotive vehicles. “We were running tests just recently so the wires are all over the place,” said Sanghyun Chu, a student researcher (Dept. of Mechanical and Aerospace Engineering) who had been working in the lab.

The engine being tested uses two types of fuel simultaneously. Passenger cars run on either diesel or gasoline engine, but this one uses both at the same time. It is called a ‘dual fuel engine’ as it uses two types of fuels, or a ‘dual combustion engine’ as it combines fuels for combustion. There is a single engine with two injectors which allows gasoline and diesel to be directly injected to the engine for combustion. The technology has been in development for the past 4 years; no one in the world has been successful so far.

The reason for developing such a technology is that it combines just the advantages of gasoline and diesel. In the case of diesel engines, the fuel spontaneously ignites and combusts without any external sources of ignition when the fuel is injected at a high-temperature, high-pressure setting.

‘Direct injection’ system, which utilizes this property, is widely used in diesel cars. On the other hand, gasoline doesn’t undergo spontaneous combustion like diesel. So there needs to be a high-temperature, high-pressure setting where it is mixed with air. This mixture is then injected into the engine and ignited with a spark plug.

One possible disadvantage of the diesel direct injection system is that if the fuel and air doesn’t mix well, the combustion turns out to be incomplete and causes fine dust pollution. Upping the combustion temperature can prevent fine dust, but it instead generates nitrogen oxides, another cause of air pollution. Currently, after-treatment technologies do the job of getting rid of fine dust.

But diesel engines can improve efficiency and increase engine power. Their thermal efficiency is about 20% higher than that of gasoline engines, and they have a relatively lower amount of greenhouse gas emissions. So countries that emphasize cutting greenhouse gas emissions—Germany, for example—are researching diesel engines.

Gasoline direct injection engine, in which gasoline is directly injected and ignited just like diesel engines, is the fruition of such research projects. There’s also PCCI, which introduced a process where fuel and air is mixed in diesel engines, similar to how gasoline engines work. Japan is also active in researching how to combine diesel and gasoline engines. In Japan’s homogeneous charge compression ignition (HCCI) engine, the fuel is combined and compressed before undergoing combustion. “People often ask if there’s even anything left to research in terms of car engines. But there are numerous possibilities of what future engines might look like,” Director Min said.

Director Min and Mr. Chu are attempting to combine the advantages of diesel and gasoline by developing an engine where two types of fuel are injected at the same time—which is the dual combustion engine in development. Currently, the development is its early stages, where basic procedures are being tested with a single cylinder. But positive results are coming out already. Compared to the current diesel engine, the new engine’s fuel efficiency is about 5.6% higher, while the amount of nitrogen dioxides and fine dust emission are 72% and 98.7% lowered, respectively. Especially, fine dust emission has been greatly reduced to the point that the diesel particulate filter (DPF) is no longer necessary.  

Link to article:  http://news.donga.com/3/all/20181214/93284546/1