Curved Valve Needle Profile for Fuel Flow Stability
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Solution Overview
Problem
In common rail fuel injection systems, low lift conditions lead to fuel flow instability as it transitions from following the valve needle to the sac volume, causing chaotic flow regimes, spray variations, and reduced engine performance and efficiency.
Innovation Solution
The injection nozzle design features a valve needle with a third region having a curved profile that guides fuel from the sac volume to the nozzle outlets, eliminating flow instability by providing a smooth and continuous path, especially at low lift conditions, and ensuring a precise seal with a steeply sloped wall portion and optimized clearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the valve needle is lifted to enable fuel delivery, then fuel flow is improved, but flow instability occurs during transition causing spray variations
Solution Approach 1:
The valve needle incorporates a curved profile section (third region) that provides a smooth, continuous surface for fuel flow transition. This curved geometry eliminates sharp edges and abrupt transitions that cause flow separation and instability, ensuring stable fuel delivery across the full range of valve lifts.
Solution Approach 2:
The invention modifies the geometric parameters of the valve needle by adding a specifically shaped third region with defined curvature and length. This parameter change transforms the flow characteristics from unstable (flapping between needle and sac wall) to stable, maintaining consistent spray patterns throughout the injection cycle.
2Productivity
If the valve needle follows the sac volume wall, then fuel flow to outlets is improved, but chaotic flow regime develops causing spray fluctuations
Solution Approach 1:
The curved profile of the third region on the valve needle creates a smooth transition surface that guides fuel flow continuously toward the outlet entry openings. This curved geometry prevents the flow from detaching and becoming chaotic, maintaining stable attachment to the needle surface throughout the injection process.
Solution Approach 2:
The third region acts as an intermediary flow guidance element between the sac volume and the outlet passages. It mediates the transition of fuel flow from the sac volume environment to the outlet entry openings, ensuring smooth, controlled flow without chaotic fluctuations.
3Manufacturing precision
If the valve needle has a precise seal with the seating, then fuel delivery control is improved, but flow transition instability occurs at low lift conditions
Solution Approach 1:
The curved profile section provides a smooth transition surface that eliminates sharp edges near the seal region. This curvature ensures that even at low lift conditions where flow transitions are most critical, the fuel flows smoothly without separation or instability, while the seal precision is maintained through the first and second regions.
Solution Approach 2:
The valve needle is designed with different regional characteristics: the first and second regions provide precise sealing functionality, while the third region specifically addresses flow transition stability. This local differentiation allows each region to optimize its specific function without compromising the others.
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
This design enhances flow efficiency, reduces spray variations, and improves fuel delivery accuracy, leading to lower emissions and increased engine performance by stabilizing fuel flow from low to high lift conditions.
Implementation Method 1
a valve needle of the injection nozzle is controlled by means of a piezoelectric actuator
Data Source
Figure 1
Figure 2a
Figure 2b
AI summary
An injection nozzle (30) for an internal combustion engine, the injection nozzle (30) comprising a nozzle body (32) provided with a bore (36) within which a valve needle (34) is moveable, the valve needle (34) being engageable with a substantially conical valve seating (38) to control fuel delivery through a set of nozzle outlets (40), said nozzle outlets including respective entry openings (40a) defined in a wall of a sac volume of the nozzle body, wherein the valve needle includes a first valve region (52), a second valve region (54) and a seat region (60) defined by a transition between the first and second valve regions (52, 54) which seats against the valve seating (38) when the nozzle is in a non-injecting state. The valve needle (34) comprises a third valve region (62), adjacent the second valve region, the third valve region having an outer surface (65) defining a curved profile, the end of the outer surface (65) terminating substantially in alignment with the entry openings (40a).