Fiber-Optic Spark Plug Probe for Non-Intrusive Engine Flow Measurement
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Solution Overview
Problem
Current methods for measuring flow characteristics inside internal combustion engine cylinders are limited by the need for intrusive probes, which distort the flow and are not suitable for production engines, and lack the capability to measure three-dimensional velocity components and shear stresses in hot, high-pressure environments.
Innovation Solution
A miniature, fiber-optic probe that is traversable and capable of measuring two-component velocities, shear stresses, and normal stresses in both cold and hot flows, designed to fit into a spark plug opening and use off-the-shelf optics without moving parts, allowing for non-intrusive, multi-component flow measurements in production engines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If intrusive probes are used to measure flow characteristics inside engine cylinders, then measurement capability is improved, but flow disturbance increases and measurement accuracy deteriorates
Solution Approach 1:
The patent uses laser light as an intermediary to measure flow characteristics without physical contact with the flow field. The laser beams interact with seeding particles in the flow, and the scattered light carries velocity information that can be extracted optically, eliminating the need for intrusive probes that would otherwise disturb the flow
Solution Approach 2:
The patent replaces mechanical intrusive probes with an optical measurement system (LDA/LDV). Instead of using physical sensors that must be inserted into the flow field, the system uses laser light scattering off seeding particles to obtain velocity measurements, thereby substituting a mechanical measurement approach with an optical one that does not disturb the flow
2Measurement precision
If laser-based measurement techniques are used to avoid flow disturbance, then measurement accuracy is improved, but device complexity increases due to supporting equipment
Solution Approach 1:
The patent combines multiple laser beams (typically two or three) into a single probe head that can be inserted into the engine cylinder. The interferential pattern formed by these combined beams creates the measurement volume, merging the functions of multiple light sources and optical components into one integrated instrument that reduces overall system complexity
Solution Approach 2:
The patent designs a universal probe head that can perform multiple measurement functions (velocity components, turbulence intensity, etc.) using the same basic optical configuration. The same probe can measure different flow parameters by adjusting the detection angle and processing algorithms, eliminating the need for multiple specialized instruments
3Measurement precision
If optical probes are used for non-intrusive measurements, then flow disturbance is reduced, but access to the flow field becomes more difficult
Solution Approach 1:
The patent nests the optical measurement components (laser optics, detectors, electronics) within a compact probe head that fits into the confined space of an engine cylinder. The probe head is designed to be small enough to access difficult-to-reach flow regions while containing all necessary measurement functionality, similar to nesting smaller components within a larger system
4Ease of operation
If miniaturized probe design is used to access confined spaces, then ease of operation is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent divides the measurement system into separate functional modules: a probe head containing the optical components, fiber optic cables for light transmission, and external electronics for signal processing. This segmentation allows each module to be manufactured and tested independently, reducing the overall manufacturing precision requirements while maintaining the miniaturized design for easy access to confined flow fields
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
Enables accurate, non-intrusive measurement of flow-related parameters inside engine cylinders during normal operations, improving understanding of in-cylinder turbulence and combustion processes, and enhancing engine efficiency and emissions control.
Implementation Method 1
a transmitting lens to focus a laser light from the transmitting fiber so as to form a probe volume inside the engine beyond the transparent window
Implementation Method 2
a receiving lens to focus a scattered light from the probe volume into the receiving fiber
Implementation Method 3
receiving and transmitting fibers connected to a fiber terminator, a transmitting lens to focus a laser light from the transmitting fiber
Data Source
AI summary
A traversable, fiber-optic probe design for flow-related measurements in a production-car IC engine during normal operating conditions may be fitted into an M8 spark-plug hole and traversed as much as 50 mm in an axial direction of the spark plug, allowing measurements inside the engine cylinder including the spark plug location. Components of the laser-based system include on-table optics used to generate laser beams and a data acquisition and reduction system used to extract the information measured from the signal produced by the fiber-optic probe.