Fuel Injector Laminar Inflow Channel Cold Start Dynamics
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Solution Overview
Problem
Existing fuel injectors struggle to maintain a target injection quantity during the warm-up phase of internal combustion engines, especially at low temperatures where fuel viscosity is high, leading to insufficient fuel injection without increasing design and control effort.
Innovation Solution
Designing the inflow channel to create a laminar flow, which reduces flow rate with higher viscosity, resulting in a sharper pressure drop in the control chamber and delayed pressure buildup, enhancing the dynamics of the nozzle needle movement to achieve the desired injection quantity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional inlet bore is used to supply fuel to the control chamber, then the flow rate is independent of viscosity due to turbulent flow through an orifice, but the injection quantity is insufficient during cold start when fuel viscosity is high
Solution Approach 1:
The patent changes the flow regime parameter from turbulent to laminar by designing the inflow channel with specific dimensions (diameter and length) that satisfy the Reynolds number criterion for laminar flow. This parameter change makes the flow rate viscosity-dependent, allowing the system to automatically compensate for high fuel viscosity during cold start without additional control mechanisms.
Solution Approach 2:
The patent uses hydraulic principles by designing the inflow channel dimensions to establish laminar flow conditions. The channel geometry is specifically calculated to maintain Reynolds number below the critical value, creating a hydraulic system where flow rate is directly influenced by fuel viscosity, thereby enabling temperature-compensated injection quantity.
2Adaptability or versatility
If the inflow channel is designed to create laminar flow, then the flow rate becomes dependent on viscosity enabling temperature compensation, but the flow rate through the channel is reduced
Solution Approach 1:
The patent changes the flow regime parameter from turbulent to laminar by designing the inflow channel with specific dimensions (diameter and length) that satisfy the Reynolds number criterion for laminar flow. This parameter change makes the flow rate viscosity-dependent, allowing the system to automatically compensate for high fuel viscosity during cold start without additional control mechanisms.
3Productivity
If an orifice is used in the inlet bore to control flow, then the flow becomes turbulent and independent of viscosity, but the flow dynamics cannot respond to viscosity changes for temperature compensation
Solution Approach 1:
The patent changes the flow regime parameter from turbulent to laminar by designing the inflow channel with specific dimensions (diameter and length) that satisfy the Reynolds number criterion for laminar flow. This parameter change makes the flow rate viscosity-dependent, allowing the system to automatically compensate for high fuel viscosity during cold start without additional control mechanisms.
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 ensures a temperature- and viscosity-dependent injection quantity is achieved with minimal effort, improving fuel delivery into the combustion chamber by adjusting the flow rate based on fuel viscosity.
Implementation Method 1
the at least one inflow channel, via which fuel flows from the high-pressure chamber into the control chamber of the fuel injector, is designed to form a laminar flow
Data Source
Figure 1
Figure 2~3
AI summary
The invention relates to a fuel injector (10) comprising an injector housing (11) in which at least one injection port (17) is designed for injecting fuel into the combustion chamber of an internal combustion engine, wherein the through flow through the at least one injection port (17) can be controlled by means of an injection member (15), in particular a nozzle needle, reciprocatingly moveable in a longitudinal axis (12), wherein the injection member (15) is arranged in a high pressure chamber (18) and has an end region, sunk into an element (25; 25a) delimiting a control chamber (45) facing away from the at least one injection port (17), and wherein the high pressure chamber (18) is hydraulically connected to the control chamber (45) via at least one inflow channel (48, 49; 51; 55) and can be depressurized into a low pressure region (50) via an outflow channel (46). According to the invention the at least one inflow channel (48, 49; 51; 55) is designed to form a laminar through flow of the fuel.