Numerical Analysis of a Liquid Nitrogen (LN₂) Engine for Efficient Energy Conversion

Area of Science:

• Thermodynamics
• Mechanical Engineering
• Environmental Science

Background:

• Pollution from conventional fuels necessitates alternative energy sources.
• Liquid nitrogen (LN2) offers potential as a zero-emission fuel.
• Internal combustion engines (ICEs) are a primary source of urban pollution.

Purpose of the Study:

• To simulate and analyze the performance of a four-stroke engine using direct liquid nitrogen injection.
• To assess the feasibility of a zero-emission direct injection internal evaporation (DI-IE) LN2 engine.
• To compare the performance of an LN2 engine with traditional diesel and gasoline engines.

Main Methods:

• Utilized AVL Boost simulation software, customized for LN2 modeling.
• Simulated a four-stroke engine with direct LN2 injection.
• Analyzed in-cylinder pressure, temperature, and LN2 evaporation conditions.
• Matched LN2 injection mass with air intake for optimal performance.

Main Results:

• Aspirated air enthalpy was sufficient for LN2 evaporation and expansion.
• LN2 injection generated in-cylinder pressure for the power stroke.
• Indicated mean effective pressure (IMEP) was comparable to ICEs.
• Indicated efficiency of the LN2 engine was significantly higher (56-62%) than ICEs.
• Overall efficiency, including air separation, was approximately 31%.

Conclusions:

• Direct injection internal evaporation (DI-IE) of liquid nitrogen is a viable concept for zero-emission engines.
• LN2 engines demonstrate substantially higher indicated efficiency compared to conventional ICEs.
• The technology presents a promising pathway for reducing urban pollution.