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Effect of the Injector Pressure-Building Process on Dynamic Gas Flow Characteristics of a Highly Turbulent
Hailang Sang1,2, Yu Ye2, Yan Lei3
1Institute of Energy Storage Science and Engineering, Tianjin University, Tianjin 300072, China.
ACS Omega
|May 4, 2026
Summary
High-pressure hydrogen direct injection (DI) shows promise for efficient, low-emission engines. This study reveals transient shock cell evolution and Mach disk dynamics during injection, crucial for optimizing engine performance.
Area of Science:
- Combustion Science and Engineering
- Fluid Dynamics
- Internal Combustion Engines
Background:
- High-pressure hydrogen direct injection (DI) offers high thermal efficiency and ultralow emissions.
- Hydrogen jets at high nozzle pressure ratios (NPR) exhibit turbulent underexpanded behavior with shock waves.
- Understanding transient shock cell evolution is key to optimizing hydrogen DI.
Purpose of the Study:
- To investigate transient shock cell evolution and Mach disk parameters during high-pressure hydrogen injection.
- To analyze the inner pressure building-up process and its effect on jet stabilization.
- To provide empirical corrections for Mach disk dimension estimation in underexpanded jets.
Main Methods:
- Experimental testing of the injector inner pressure building-up process.
- Three-dimensional large-eddy simulation (LES) to model the underexpanded hydrogen jet.
- Analysis of Mach disk dimension parameters (Lc, Wdisk, Hdisk) and their evolution.
Main Results:
- Inner pressure stabilization is delayed by the transient pressure-building process.
- Mach disk dimensions (Lc, Wdisk, Hdisk) show phased evolution: initial growth followed by stabilization.
- Shock waves in underexpanded jets lead to minimal entrainment in the near-nozzle region (Z/D < 8).
Conclusions:
- Transient shock cell behavior necessitates empirical correction for Mach disk estimation (CH = 0.85-0.9 for NPR ≥ 90).
- Dynamic delay in hydrogen jet characteristics is significant, especially for shorter injection cycles.
- Accounting for dynamic hydrogen jet behavior is essential for optimizing engine design and performance.
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