Valve Assembly Sac Volume Step Turbulent Flow Dynamics
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Solution Overview
Problem
Internal combustion engines face challenges in reducing pollutant emissions, particularly high carbon (HC) and particulate number (PN) emissions due to residual fuel in the injector nozzle after the valve needle returns to its closing position, which is not effectively cleared, violating stricter emission norms like EU6C.
Innovation Solution
A valve assembly for a fluid injector with a sac volume step and strategically positioned flow holes that induce turbulent flow dynamics, transferring kinetic energy to remaining fuel and facilitating its evacuation, thereby reducing nozzle tip wetting and emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a conventional valve needle design is used, then the valve structure is simple, but residual fuel remains in the sac volume after valve closure causing high pollutant emissions
Solution Approach 1:
The valve needle is segmented into multiple functional regions (first valve region, second valve region, third valve region, seat region) with distinct geometries. Each region serves a specific purpose: the first and second valve regions control the main flow, the third valve region with its curved profile manages the sac volume emptying, and the seat region provides sealing. This segmentation allows the single valve needle to perform multiple functions without adding separate components.
Solution Approach 2:
The invention introduces a radial dimension to the valve needle design through the third valve region's curved profile that extends outward toward the sac volume. This radial extension creates a new flow path dimension that enables effective sac volume emptying without requiring additional axial components or increasing overall valve length.
2Productivity
If the valve needle returns to closing position, then the injection cycle completes, but remaining fuel in the nozzle causes deposition and high carbon emissions
Solution Approach 1:
The third valve region of the valve needle is designed with a curved profile that protrudes into the sac volume to initiate fuel evacuation before the valve needle fully returns to its closing position. This preliminary action creates a flow path that actively removes residual fuel from the sac volume during the transition phase, preventing fuel deposition and reducing carbon emissions before the injection cycle officially ends.
3Ease of manufacture
If a simple valve needle is used, then manufacturing is easier, but it cannot effectively clear remaining fuel from the sac volume
Solution Approach 1:
The valve needle features localized geometric variations in specific regions rather than uniform complexity throughout. The first and second valve regions have standard cylindrical profiles for easy manufacturing, while the third valve region introduces a localized curved profile extension, and the seat region has a standardized sealing surface. This localized quality approach maintains ease of manufacture for the majority of the valve needle while providing the specific functional complexity needed for reliable fuel clearance in the sac volume region.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design effectively empties the sac volume of remaining fuel after the valve needle closes, reducing pollutant emissions and ensuring compliance with stringent emission regulations by enhancing flow field dynamics and preventing nozzle tip wetting.
Implementation Method 1
induce turbulent flow dynamics, transferring kinetic energy to remaining fuel and facilitating its evacuation
Data Source
Figure 1
Figure 2
Figure 3~5
AI summary
The invention relates to a valve assembly (2) for a fluid injector (1) for an internal combustion engine. The valve assembly (2) comprises a valve body with a valve recess (5), a central longitudinal axis (7), and a first axial end and a second axial end with respect to the central longitudinal axis (7). A valve needle (11) is axially moveable within the valve recess (5) with respect to the central longitudinal axis (7). In concurrence with a seal seat area (21) the valve needle (11) prevents a fluid flow through at least one flow hole (13) in its closing position and otherwise enables it. Furthermore, the injector (1) comprises a sac volume step (23) adjacent to the seal seat area (21) forming a part of a inner surface of a wall (9) of the valve body and a sac volume (25) being designed as one end of the valve recess (5) and being limited by a further part of the inner surface of the wall (9) of the valve body.