Variable Choking Section in Diesel Fuel Injector
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Solution Overview
Problem
The existing fuel injector designs for large two-stroke diesel engines face challenges in efficiently controlling the needle movement due to the large size of the outlet flow restrictor, which increases control valve design complexity, energy loss, and reduces efficiency, especially when the seat diameter to control chamber diameter ratio is high, necessitating larger components and slower actuators.
Innovation Solution
The design incorporates a variable choking section in the inlet flow restrictor that moves between a choked and un-choked position, allowing a smaller outlet flow restrictor to initiate injector opening, reducing the control flow rate and enabling the use of smaller, faster actuators while maintaining injector efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a larger outlet flow restrictor is used to achieve required depressurisation of the control chamber, then the injector opening control is improved, but the control valve design becomes more complex and the actuator size increases
Solution Approach 1:
The inlet flow restrictor is segmented into a fixed portion and a movable portion that can shift between choked and un-choked positions. This segmentation allows the system to achieve effective control chamber depressurisation when needed (choked position) while avoiding continuous large flow requirements (un-choked position), thereby reducing control valve complexity and actuator size.
Solution Approach 2:
The inlet flow restrictor transitions from a static component to a dynamic one that can change its flow restriction characteristics. The movable portion responds to pressure differential forces, automatically adjusting the flow rate through the inlet restrictor based on operating conditions, which enables smaller outlet restrictors and simpler control valves.
2Reliability
If a larger outlet flow restrictor is used to ensure sufficient control chamber depressurisation, then the injector opening is reliable, but the energy loss increases due to higher control flow rate
Solution Approach 1:
The dynamic movable portion of the inlet flow restrictor adjusts the flow restriction based on real-time pressure conditions. When the needle is closed, the restrictor is choked to minimize control flow and energy loss. When the needle opens, the restrictor becomes un-choked to allow sufficient depressurisation. This dynamic adjustment maintains reliable injector opening while minimizing continuous energy loss.
Solution Approach 2:
The system changes the flow restriction parameter of the inlet restrictor based on operating conditions. By transitioning between choked and un-choked states, the system optimizes the balance between control chamber depressurisation efficiency and energy loss, enabling smaller outlet flow restrictors that reduce parasitic control flow rates.
3Stress or pressure
If a larger outlet flow restrictor is used to achieve required depressurisation, then the control chamber pressure can be reduced effectively, but the actuator size and switching time increase
Solution Approach 1:
By segmenting the inlet flow restrictor into fixed and movable portions, the system achieves effective control chamber depressurisation through coordinated action of both restrictors rather than relying on a single large outlet restrictor. This allows the use of smaller outlet restrictors that enable faster-responding, more compact actuators with reduced switching times.
Solution Approach 2:
The system changes the flow restriction parameters dynamically - the movable portion transitions between choked and un-choked states to optimize depressurisation efficiency. This enables the use of smaller outlet restrictors that reduce the force requirements on actuators, allowing for faster switching times and more compact actuator designs.
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 solution minimizes control flow rates, allowing for faster and more compact actuators, increasing overall engine efficiency and reducing auxiliary power demand, with a negligible cost of implementation and improved switching times.
Implementation Method 1
a variable choking section, movable between a choked position corresponding to a fully closed position of the injection needle and an un-choked position corresponding to a position of initial opening of the needle
Implementation Method 2
An electrically-operated control valve modulates the hydraulic pressure in a control chamber, which generates a force acting in the direction of closing the injector
Implementation Method 3
The pressurized fuel in a delivery chamber upstream of the valve seat acts in the direction of raising the needle from its seat and hence in the opening direction
Implementation Method 4
the control chamber is connected to the high-pressure line by means of an inlet flow restrictor and to a discharge line by means of an outlet flow restrictor
Data Source
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AI summary
An electrically controlled fuel injector for large diesel engines, comprising: - a body (22) having a delivery chamber (24) connected to a fuel supply line (26) and provided with a conical valve seat (28); - a needle (30) extending through said delivery chamber (24) and having a conical sealing surface (32) cooperating with said valve seat (28), the needle (30) being movable along a longitudinal axis (A) between a closed position wherein said conical sealing surface (32) abuts against said conical valve seat (28) and an open position wherein said conical sealing surface (32) is spaced apart from said conical valve seat (28), wherein the hydraulic pressure into said delivery chamber (24) generates a first hydraulic force pushing the needle (30) towards its open position; - a control chamber (44) connected to said fuel supply line (26) through an inlet flow restrictor (48) and connected to a discharge line (50) through an outlet flow restrictor (52), wherein the hydraulic pressure into said control chamber (44) generates a second hydraulic force pushing the needle (30) towards its closed position; - an electrically-operated control valve (54) for selectively opening and closing hydraulic communication between said control chamber (44) and a low pressure volume (14); wherein said inlet flow restrictor (48) includes a variable choking section (60), movable between a choked position corresponding to a fully closed position of the needle (30) an un-choked position corresponding to an initial opening of the needle (30).