This 2-liter car engine can run entirely on hydrogen

New technology allows hydrogen to be directly injected into the cylinders like an internal combustion engine.
Jijo Malayil
Fuel cell hydrogen engine
Fuel cell hydrogen engine


As the world scrambles to transition to green fuels to achieve carbon neutrality, promoting power sources that use hydrogen as a clean fuel is one strategy to further the move. Now, researchers in South Korea have developed a new technology for a passenger car hydrogen engine that promises to make it more viable for mass production. 

The powertrain developed by researchers at the Korea Institute of Machinery and Materials (KIMM) and the Zero-Carbon Engine Research Lab of Hyundai-Kia Motor Company (HMC) is a 2-liter direct injection hydrogen engine that runs entirely on hydrogen fuel.

The team claims that 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," said Young Choi, principal researcher and part of the Department of Mobility Power Research of KIMM, in a statement.

This 2-liter car engine can run entirely on hydrogen
2-liter direct-injection hydrogen engine

Higher efficiency and performance

In conventional internal-combustion powertrains that use hydrogen fuel, known as a port injection engine, it burns hydrogen as fuel after mixing it with air by injecting the power through an upper inhaling port instead of the cylinder.  

Due to this architecture, the amount of air that enters the combustion chamber decreases due to the space occupied by the hydrogen fuel, which is present in a gaseous state. This results in lower fuel efficiency and poorer engine performance because the hydrogen fuel and air backfire.

To remedy this, researchers injected high-pressure hydrogen directly into the combustion chamber. "This method utilizes a pre-mixture combustion that enables ultra-lean combustion and has the advantage of no pumping loss because the output is controlled by the amount of fuel injected without throttling the intake air," said the study. Also, because hydrogen gas does not exist in the intake pipe, backfire does not occur, which is a common trait in hydrogen-powered motors.

Due to the drop in combustion temperature, ultra-lean combustion produces low NOx emissions and good thermal efficiency during partial load situations. According to the team, the newly developed hydrogen engine helps to cut carbon dioxide and fine dust emissions by 98% and 90%, respectively, compared to gasoline engines, meeting EU (or European Union) regulations for zero-emission cars. In addition, the hydrogen engine achieves a high thermal efficiency of up to 40% while emitting nitrogen oxides of less than 15 ppm, even without an after-treatment system that cleans exhaust gases.

The team aims to test the engine extensively to verify the durability of the new technology in the long run. It will also explore the potential to develop this technology for passenger vehicles, 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," said Young.

The details regarding their research are published in the journal Science Direct.


The in-cylinder hydrogen fuel injection method (diesel engine) induces air during the intake stroke and injects hydrogen gas directly into the cylinder during the compression stroke. Fundamentally, because hydrogen gas does not exist in the intake pipe, backfire, which is the most significant challenge to increasing the torque of the hydrogen port fuel injection engine, does not occur. In this study, using the gasoline fuel injector of a gasoline direct-injection engine for passenger vehicles, hydrogen fuel was injected at high pressures of 5 MPa and 7 MPa into the cylinder, and the effects of the fuel injection timing, including the injection pressure on the output performance and efficiency of the engine, were investigated. Strategies for maximizing engine output performance were analyzed.

The fuel injection timing was retarded from before the top dead center (BTDC) 350 crank angle degrees (CAD) toward the top dead center (TDC). The minimum increase in the best torque ignition timing improved, and the efficiency and excess air ratio increased, resulting in an increase in torque and a decrease in NOx emissions. However, the retardation of the fuel injection timing is limited by an increase in the in-cylinder pressure. By increasing the fuel injection pressure, the torque performance can be improved by further retarding the fuel injection timing or increasing the fuel injection period. The maximum torque of 142.7 Nm is achieved when burning under rich conditions at the stoichiometric air-fuel ratio.

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