Related Experiment Video
Updated: Oct 6, 2025
08:34
Cryogenic Liquid Jets for High Repetition Rate Discovery Science
Published on: May 9, 2020
3.2K
Experimental Study on Entrainment Characteristics of High-Pressure Methane Free Jet
Yan Lei1, Kai Chang1, Tao Qiu1
1Department of Automotive Engineering, Beijing University of Technology, 100124 Beijing, China.
ACS Omega
|January 17, 2022
Summary
This study investigates methane jet entrainment in direct injection engines. A novel method using kinetic energy conservation accurately measures entrainment mass flow rate, crucial for engine performance.
Area of Science:
- Combustion and Engine Technology
- Fluid Dynamics
- Gas Injection Systems
Background:
- Entrainment is a critical phenomenon in high-pressure gas jet processes, particularly for natural gas direct injection engines.
- Understanding and quantifying entrainment mass flow rate is essential for optimizing engine efficiency and performance.
- Existing methods for measuring entrainment may lack accuracy or applicability in the near-nozzle field.
Purpose of the Study:
- To experimentally investigate the high-pressure methane jet and its entrainment process from a single-hole injector.
- To propose and validate a novel method for determining entrainment mass flow rate based on kinetic energy conservation.
- To analyze the influence of key variables (spring plate movement, nozzle exit mass, jet velocity) and injection pressure on entrainment.
Main Methods:
- Development of a spring-set test rig to measure spring plate moving distance (Δx).
- Utilization of the schlieren method with a constant-volume bomb (CVB) optical test rig to determine gas jet velocity (u1).
- Employing the weight method to measure methane gas jet mass at the nozzle outlet (mn), with validation in the near-nozzle field.
Main Results:
- The methane jet mass flow rate increases along the jet direction, exhibiting a two-zone entrainment process (near field and far field).
- No entrainment occurs in the nozzle exit field (Lr < 1), with mass flow rate conservation.
- Entrainment rate shows three distinct stages, influenced by injection pressure; higher pressure increases mass flow rate linearly but decreases entrainment rate.
Conclusions:
- The proposed kinetic energy conservation method is valid for measuring entrainment mass flow rate in the near-nozzle field.
- The study elucidates the two-zone entrainment behavior and three-stage entrainment rate progression of high-pressure methane jets.
- Methane injection pressure significantly impacts jet mass flow rate and entrainment dynamics, offering insights for engine design.
Related Concept Videos
01:14Free Jet
277
Free jets describe the flow of liquid exiting a reservoir through an opening into the atmosphere without resistance. The velocity (v) of the liquid jet is derived using Bernoulli's principle and expressed as:
277
01:26General External Flow Characteristics
304
The study of external flow is essential for creating structures and objects that interact efficiently and safely with moving fluids, such as air or water. When a body is immersed in a flowing fluid, it experiences two primary forces: drag, which opposes motion along the flow direction, and lift, which acts perpendicular to the flow. The shape, size, and orientation of the object influence these forces.Streamlined and Blunt Bodies in External FlowObjects in fluid flow are classified as...
304
01:17Bernoulli's Principle: Applications
4.9K
There are many devices and situations in which fluid flows at a constant height and so can be analyzed using Bernoulli's principle. These devices include, but are not limited to, entrainment devices and fluid flow measuring devices.
Entrainment devices use a high fluid speed to create low pressures and, thus, entrain one fluid into another. Some examples of these devices are given below:
Entrainment devices use a high fluid speed to create low pressures and, thus, entrain one fluid into another. Some examples of these devices are given below:
4.9K
01:11Pressure Variation in a Fluid at Rest
435
In a fluid at rest, the pressure at any point beneath the fluid surface depends solely on the depth, not on the container's shape or size. This principle, known as hydrostatic pressure, arises because, in stationary fluids, there is no acceleration, meaning the forces within the fluid balance out. Only vertical forces, caused by the weight of the fluid above, contribute to pressure changes with depth.
When measuring pressure at two different levels within the fluid, the difference in...
When measuring pressure at two different levels within the fluid, the difference in...
435