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2020-07 20 Important News

[Academics][Researcher of the Month] Reducing Fine Dust From GDI Engines

The increasing amount of fine dust is threatening modern people’s daily lives. In response to the problem, Professor Park Sung-wook (Division of Mechanical Engineering) has been studying ways to decrease the amount of fine dust in the air while maintaining the efficiency of automobile engines. In his recent research paper titled “Effects of spray behavior and wall impingement on particulate matter emissions in a direct injection spark ignition engine equipped with a high pressure injection system,” Park presented a solution to lowering the amount of fine dust emitted by Gasoline Direct Injection (GDI) engines of gasoline-powered cars. The research focuses on spray visualization, particle number (PN) measurement experiments, injection timing, and an engine load being varied to examine their effects on the way fuel sprays move when being injected inside a combustion chamber, hereinafter referred to as the spray behavior. The analysis was based on time-averaged spray images, spray variations between cycles, combustion, and PN emission characteristics. "The motivation behind this research was the prevalent misconception that diesel cars are the main source of fine dust, when in fact gasoline cars’ GDI engines emit just as substantial an amount of fine dust," said Park. Professor Park Sung-wook (Division of Mechanical Engineering) experimented in order to help automobiles emit less fine dust. (Photo courtesy of Park) What Park considered most important in the research was the PN emission characteristics. He endeavored to find new ways to decrease PN emission in the air instead of reducing the dust's total weight. “What matters the most in reducing fine dust is the size of each dust particle," explained Park. "The combined weight of the dispersed fine dust is secondary - for the size of the particle determines its harmfulness to the human body.” After 5 years’ cooperation with Hyundai Motor Company, Hyundai KEFICO, the Ministry of Environment, and the Ministry of Industry, Park and his team have been able to conclude that when fuel is injected at a high pressure, the flow in the combustion chamber is strengthened, and the atomization of the fuel spray is propelled in action in order to decrease fine dust in the air. “This has been a significant research project during which we have found ways to decrease the amount of fine dust emitted by existing hybrid automobiles and internal combustion automobiles, without having to accelerate the commercialization of electric cars, which would be difficult to do for several more years.” Park said five great students have earned their doctorate degrees through this experiment and thanked his pupils for constantly helping him in times of distress and uncertainty. Park with his student. He thanked his students for helping him through times of uncertainty and distress. (Photo courtesy of Park) Lee Yoon-seo cipcd0909@hanyang.ac.kr

2020-06 01

[Academics][Researcher of the Month] Effective Use of Photocatalysts to Combat Environmental Problems

Numerous attempts have been made by engineers to apply technology to our everyday problems. Professor Park Jae-woo (Department of Civil and Environmental Engineering) tackles one of the most critical problems of our time, environmental pollution, using the special characteristics of nano photocatalysts. His research focuses on resolving the problems caused during the reduction-oxidation process of photocatalysts. Through his research, he has discovered that the use of the Charge Transfer Layer (CTL) is significantly effective, and expects the findings to help organic pollutants decompose through photocatalysts, which will lead to a cleaner society. For the past 15 years, Park has been conducting research on the development of magnetic-cored dendrimers and nano-photocatalysts for the purpose of environmental purification. According to Park, nano-photocatalysts have the power to commence oxidation in hazardous substances by separating electrons from holes. This process of oxidation converts substances into water and carbon dioxide gas, which are harmless to the environment. However, despite their striking capabilities, photocatalysts have their shortcomings. In his research, Park focused on compromising with the photocatalysts' technical problem. For the past 15 years, Professor Park Jae-woo (Department of Civil and Environmental Engineering) has been conducting research on the development of nano-photocatalysts for the purpose of environmental purification. The problem with the use of photocatalysts One of the biggest disadvantages of using the reduction-oxidation of photocatalysts is that electrons have the tendency to return to their respective electron holes. Their tendency to recombine after separation lowered the rate at which photocatalysts oxidized harmful substances, and many researchers have sought out ways to prevent the recombination of electrons with the electron holes. The existing methods such as doping, facet, and core-shell merely slow down the rate at which electrons recombine with electron holes and fail to completely separate them. However, Park has succeeded in permanently separating the electrons using the CTL. How was CTL used? A photocatalyst which utilizes the CTL is comprised of three components: the photocatalyst which forms a pair of electrons and electron holes, the CTL which moves the electrons selectively, and the collector which accumulates and stores the moved electrons. Here, the CTL, being the main component, carries the electrons while inhibiting their passage through electron holes. As a result, the electron is moved from the photocatalyst to the electron collector, and suppresses them from recombining. What makes Park and his team’s accomplishment so unique is the fact that their work did not stop at only delaying the recombination, as previous methods had done, but also entirely prevented recombination by separating the electrons and shutting down the reverse-travelling by maintaining a high level of catalyst reaction. The result of the research “We have conducted two experiments to prove there is an increased activation of catalysts by using the CTL in the mentioned study,” said Park. He continued, “The first, is hydrolysis. A catalyst under the influence of the CTL displayed 78% higher hydrogenative yield than the existing one in the visible ray photography. Then, in the experiment with the subject bisphenol A, which is an organic pollutant, the catalyst showed a very high 93% removal rate after three hours of reaction." Park also believes that catalysts utilizing the CTL can be applied to energy and environment-related fields in an extensive range. Park said, “I want to thank my graduate school students, whose effort and sweat have made all this possible.” Park expressed gratitude to his graduate school students, whose effort and hard work have made the project possible. “It motivates me to reflect on my mindset when I see students working so hard on the research topic.” He especially thanked Hassan Anwer (Civil and Environmental Engineering, Doctoral program) for his devotion to the research. Lee Yoon-seo cipcd0909@hanyang.ac.kr