Application Advances and Prospects of Ejector Technologies in the Field of Rail Transit Driven by Energy Conservation and Energy Transition

Yiqiao Li (), Hao Huang, Shengqiang Shen (), Yali Guo, Yong Yang and Siyuan Liu
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Yiqiao Li: Zhan Tianyou College, Dalian Jiaotong University, Dalian 116028, China
Hao Huang: Zhan Tianyou College, Dalian Jiaotong University, Dalian 116028, China
Shengqiang Shen: School of Energy and Power Engineering, Dalian University of Technology, Dalian 116024, China
Yali Guo: School of Energy and Power Engineering, Dalian University of Technology, Dalian 116024, China
Yong Yang: School of Energy and Power Engineering, Dalian University of Technology, Dalian 116024, China
Siyuan Liu: Zhan Tianyou College, Dalian Jiaotong University, Dalian 116028, China

Energies, 2025, vol. 18, issue 15, 1-37

Abstract: Rail transit as a high-energy consumption field urgently requires the adoption of clean energy innovations to reduce energy consumption and accelerate the transition to new energy applications. As an energy-saving fluid machinery, the ejector exhibits significant application potential and academic value within this field. This paper reviewed the recent advances, technical challenges, research hotspots, and future development directions of ejector applications in rail transit, aiming to address gaps in existing reviews. (1) In waste heat recovery, exhaust heat is utilized for propulsion in vehicle ejector refrigeration air conditioning systems, resulting in energy consumption being reduced by 12~17%. (2) In vehicle pneumatic pressure reduction systems, the throttle valve is replaced with an ejector, leading to an output power increase of more than 13% and providing support for zero-emission new energy vehicle applications. (3) In hydrogen supply systems, hydrogen recirculation efficiency exceeding 68.5% is achieved in fuel cells using multi-nozzle ejector technology. (4) Ejector-based active flow control enables precise ± 20 N dynamic pantograph lift adjustment at 300 km/h. However, current research still faces challenges including the tendency toward subcritical mode in fixed geometry ejectors under variable operating conditions, scarcity of application data for global warming potential refrigerants, insufficient stability of hydrogen recycling under wide power output ranges, and thermodynamic irreversibility causing turbulence loss. To address these issues, future efforts should focus on developing dynamic intelligent control technology based on machine learning, designing adjustable nozzles and other structural innovations, optimizing multi-system efficiency through hybrid architectures, and investigating global warming potential refrigerants. These strategies will facilitate the evolution of ejector technology toward greater intelligence and efficiency, thereby supporting the green transformation and energy conservation objectives of rail transit.

Keywords: ejector; engine waste heat recovery; compressed air energy storage; hydrogen supply system; pantograph lift control; energy-saving technology (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2025
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