Fuel Injection Nozzle Bevelled Restrictive Element
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Solution Overview
Problem
Existing fuel injectors require large pressure drops across restrictions, leading to wasted energy, manufacturing complexity, and sensitivity to fuel viscosity and temperature, which affects needle behavior and injection pressure.
Innovation Solution
An injection nozzle design with a moveable restrictive element upstream of the needle guide portion, featuring a bevelled surface and large cross-sectional area, minimizes pressure drops and manufacturing complexity while reducing sensitivity to fuel viscosity and temperature, allowing for improved needle control and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a restriction is provided in the fuel injector to generate a pressure drop between the high-pressure fuel supply and the injecting end of the injection nozzle, then the needle closure speed is improved, but the injection pressure is reduced and energy is wasted
Solution Approach 1:
The invention divides the pressure drop function into two segments: a first restriction (throttle) that provides a small pressure drop to assist needle closure, and a second restriction (orifice) that provides the majority of the pressure drop. This segmentation allows the system to achieve fast needle closure without requiring the entire pressure drop to occur across the needle seat, thereby reducing the energy waste associated with large pressure drops while maintaining effective needle control
Solution Approach 2:
The invention introduces a collar with a specific geometry (including a bevelled surface) as an intermediary element between the fuel supply and the needle. This collar creates a controlled flow pattern and pressure distribution that facilitates needle closure through hydraulic forces without requiring excessive pressure differential, thus mediating between the need for fast closure and energy efficiency
2Reliability
If a restriction is provided in the fuel injector to generate a pressure drop, then the needle closure control is improved, but the manufacturing complexity increases due to accuracy requirements
Solution Approach 1:
The pressure drop function is segmented between two distinct restrictions with different functions: the first restriction (throttle) handles flow control with relaxed tolerance requirements, while the second restriction (orifice) handles the main pressure drop. This segmentation allows each component to be manufactured with appropriate precision levels, reducing overall manufacturing complexity while maintaining reliable needle closure control
Solution Approach 2:
The collar is designed to be moveable relative to the needle, allowing the restriction geometry to adapt dynamically during needle operation. This dynamic adjustment capability provides tolerance compensation, reducing the need for extremely tight manufacturing tolerances while maintaining effective needle control throughout the operating range
3Force
If a restriction is provided in the fuel injector to generate a pressure drop, then the needle closure force is increased, but the system becomes more sensitive to fuel viscosity and temperature variations
Solution Approach 1:
The hydraulic force generation is segmented between two restrictions working in series. The first restriction provides a controlled pressure drop that generates closure force, while the second restriction maintains the necessary pressure differential without being overly sensitive to fuel property variations. This segmentation reduces the overall sensitivity to viscosity and temperature changes while maintaining effective closure force
Solution Approach 2:
The invention changes the geometric parameters of the restrictions (particularly the collar dimensions and orifice size) to optimize the pressure drop characteristics. By carefully selecting these parameters, the system achieves adequate needle closure force while minimizing sensitivity to fuel viscosity and temperature variations across different operating conditions
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 achieves higher injection pressures with reduced energy consumption, simplified manufacturing, and improved needle closure and opening dynamics, minimizing the impact of fuel viscosity and temperature variations.
Implementation Method 1
a restriction within the bore for restricting the flow of fuel through the bore
Implementation Method 2
at least one downstream-facing thrust surface against which high-pressure fuel in the bore acts to provide a lifting force to the needle
Implementation Method 3
The control chamber receives fuel at high pressure from the supply passage, and is connectable to a low-pressure drain by way of a valve. The valve therefore controls the pressure of fuel in the control chamber, and hence determines the downward closing force acting on the upper end of the needle
Data Source
AI summary
An injection nozzle for injecting fuel into a combustion chamber of an internal combustion engine is disclosed. The injection nozzle comprises a nozzle body (53) having a bore (57) for receiving fuel from a supply line (12) for pressurised fuel, an outlet (56) from the bore (57) for delivering fuel to the combustion chamber, in use, and a valve needle (55) defining a needle axis and being slidable within the bore (57). The needle (55) comprises a needle guide portion (62) arranged to guide sliding movement of the needle (55) within the bore (57). The injection nozzle further comprises a restriction (61 a) within the bore (57) for restricting the flow of fuel through the bore (57), and a restrictive element (61) having an upstream side (61 b) and a downstream side (61c); the restrictive element being moveable with the needle (55) and located upstream of the needle guide portion (62). At least a part of the downstream side (61c) of the restrictive element (61) comprises a bevelled surface (61d) that extends to a peripheral edge (61 f) of the restrictive element, the bevelled surface (61d) being non-perpendicular to the needle axis.