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A joint research team led by Principal Researcher Young Choi of the Department of Mobility Power Research of the Korea Institute of Machinery and Materials (KIMM), an institute under the jurisdiction of the Ministry of Science and ICT, and Researcher Hong-gil Baek of the Zero-Carbon Engine Research Lab of Hyundai-Kia Motor Company (HMC) has developed a 2-liter class direct injection hydrogen engine that runs entirely on hydrogen.


The joint research team of KIMM and HMC injected hydrogen directly into the combustion chamber of the engine of an existing HMC hybrid vehicle, with a pressure of more than 30 bar. By using a turbo charger that improves the performance of the engine, the research team was able to maintain high thermal efficiency in all domains from the ignition of the engine to the upper limit of the engine load, allowing the engine to be stably operated throughout the entire engine operating conditions.

A port injection hydrogen engine combusts hydrogen after mixing it with air by injecting hydrogen using an upper intake port instead of injecting it into the cylinder. The amount of air that flows into the combustion chamber declines because of the space taken up by the gaseous hydrogen fuel, leading to lower fuel efficiency and poorer engine performance due to the backfire of the hydrogen fuel and air.

The direct injection hydrogen engine newly developed by the joint research team has fundamentally resolved the issue of backfire by injecting high-pressure hydrogen fuel directly into the combustion chamber. At the same time, the high compression ratio, fuel stratification, and ultra-lean combustion help to maximize thermal efficiency and improve power performance, while at the same time reducing the amount of harmful emissions.

Compared with gasoline engines, the newly developed hydrogen engine helps to reduce the emissions of carbon dioxide and fine particulates by 99% and 90%, respectively, which meets EU requirements for zero-emission vehicles.

Additionally, the hydrogen engine emits NOx of less than 15 ppm even without an aftertreatment system that purifies exhaust gases, achieving a high thermal efficiency of up to 40%.

The newly developed hydrogen engine technology is an instantaneous and economical technology that can help to replace fossil fuels, which are currently being used as the main power source for vehicles, with carbon-free hydrogen fuels.

Through collaboration with HMC, we will verify the durability of the engine and also expand the application of this technology to not only passenger vehicles but also commercial vehicles and electricity generation power units. Through continuous research and development of technologies for generating power using carbon-free fuels, we will take the lead in the realization of carbon neutrality.

—Principal Researcher Young Choi

The Korea Institute of Machinery and Materials (KIMM) is a non-profit government-funded research institute under the Ministry of Science and ICT. This research was carried out with the support of the project for the “development of liquid hydrogen engines for running drones and robots,” one of KIMM’s basic projects, as well as the project for the “evaluation of hydrogen direct injection engines” supported by HMC.


  • Cheolwoong Park, Yongrae Kim, Sechul Oh, Junho Oh, Young Choi, Hongkil Baek, Seung Woo Lee, Kyeonghyeon Lee (2022) “Effect of fuel injection timing and injection pressure on performance in a hydrogen direct injection engine,” International Journal of Hydrogen Energy, Volume 47, Issue 50, doi: 10.1016/j.ijhydene.2022.04.274


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