Fuel Injector Spray Hole Step Design for Cavitation Cleaning
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Solution Overview
Problem
Existing fuel injector designs face challenges with coking deposition due to low hydraulic efficiency and fuel economy issues, particularly in diesel injectors, where conventional anti-coking methods and hole designs either fail to prevent coking effectively or compromise on spray penetration and mixing.
Innovation Solution
The design features injection holes with an inner and outer portion that intersect at a step, creating wall cavitation and turbulences to prevent coking, where the inner portion is longer and has a smaller cross-section than the outer portion, with a micro-step size between 1 µm to 10 µm, generating effective cleaning without significant hydraulic efficiency loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If low taper and low rounding injection holes are used to ensure cavitation forming, then cavitation is generated inside the injection hole, but hydraulic efficiency decreases
Solution Approach 1:
The injection hole is designed with non-uniform geometry featuring a rounded inlet portion and a tapered outlet portion with different taper angles. This local variation in geometry creates cavitation in specific zones while maintaining efficient flow in other zones, resolving the contradiction between cavitation formation and hydraulic efficiency
Solution Approach 2:
The invention changes geometric parameters of the injection hole including inlet rounding radius, outlet taper angle, and hole length-to-diameter ratio. By optimizing these parameters, the design achieves cavitation formation at controlled locations while preserving overall hydraulic efficiency for mixing and emission performance
2Length of moving object
If divergent tapered outlet portion with reduced hole length is used, then spray penetration is reduced, but hydraulic efficiency is improved
Solution Approach 1:
The invention optimizes the hole length-to-diameter ratio and outlet taper angle to achieve a balance where spray penetration is sufficiently reduced for direct injection applications while hydraulic efficiency remains high enough to maintain mixing quality and limit soot emission
3Reliability
If anti-coking film coating is applied, then coking prevention is improved, but the coating is quickly damaged in hot engine conditions
Solution Approach 1:
Instead of trying to protect the injection hole from coking through coatings, the invention converts the coking-prone environment into a beneficial cavitation zone. The controlled cavitation mechanically cleans the injection hole walls, preventing deposit accumulation without requiring protective coatings that would fail in hot engine 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
This design effectively reduces coking deposits while maintaining high hydraulic efficiency and fuel spray quality, improving fuel economy and soot emission performance.
Implementation Method 1
creating wall cavitation and turbulences to prevent coking
Implementation Method 2
creating wall cavitation and turbulences to prevent coking
Data Source
Figure 1~2
AI summary
A nozzle body (12) of a fuel injector (10) extending along a main axis (X1), the body having a peripheral wall (16) defining an inner blind bore adapted to receive a needle valve, the body extending toward a tip end wherein the peripheral wall closes forming a sac (20) volume. The nozzle body (12) is further provided with injection holes (14) arranged through the wall (16), the injection holes (14) comprising an inner portion (26) and an outer portion (28) joining together in an intersection zone wherein the inner portion is smaller than the outer portion, so that said intersection area forms a step.