Exhaust Device Independent Passages Cavity Chamber
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Solution Overview
Problem
Multicylinder engines experience a fall in volumetric efficiency in the intermediate rotation range, which affects torque over a wide rotation range, as existing exhaust devices fail to effectively manage exhaust interference and pressure waves.
Innovation Solution
An exhaust device with independent exhaust passages and a mixing pipe, coupled with a cavity expansion chamber, generates a negative pressure wave that overlaps with the intake valve opening period, promoting scavenging and maintaining high volumetric efficiency across various speed ranges by optimizing the distance and timing of valve operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If exhaust passages of non-sequential cylinders are bundled and converged as a tapered exhaust pipe to provide an ejector effect, then exhaust interference between cylinders is prevented, but volumetric efficiency falls in the intermediate rotation range
Solution Approach 1:
The exhaust system is divided into multiple independent exhaust passages (one for each cylinder) that remain separate throughout their length, rather than being bundled together. This segmentation prevents exhaust gases from different cylinders from interfering with each other while maintaining individual flow paths that preserve volumetric efficiency across all rotation ranges.
Solution Approach 2:
The harmful mixing of exhaust flows from different cylinders is eliminated by extracting each cylinder's exhaust flow into its own dedicated passage. The independent passages prevent the harmful interaction that occurs when exhausts are bundled, thereby maintaining volumetric efficiency without requiring an ejector effect.
2Productivity
If the open period of exhaust valve and intake valve overlap for a predetermined period, then scavenging is promoted and volumetric efficiency is improved, but exhaust pressure wave timing must be precisely controlled
Solution Approach 1:
The valve timing parameters are optimized to create a predetermined overlap period between exhaust valve closing and intake valve opening. This parameter change allows the exhaust pressure wave generated during the overlap period to travel through the independent exhaust passage and reflect as a negative pressure wave that enhances scavenging, thereby improving volumetric efficiency through controlled parameter adjustment.
3Productivity
If independent exhaust passages are used instead of bundled exhaust passages, then volumetric efficiency is maintained in intermediate speed range, but device complexity increases
Solution Approach 1:
The exhaust system uses segmented independent passages for each cylinder rather than a single bundled passage. While this increases structural complexity, it maintains volumetric efficiency by preventing exhaust interference. The segmentation is implemented in a straightforward manner with each passage directly connecting its cylinder to the exhaust manifold.
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 solution prevents a fall in volumetric efficiency in the intermediate speed range, enhances torque over a wide rotation range, and ensures efficient scavenging by leveraging the ejector effect and inertia charging in low, intermediate, and high speed ranges.
Implementation Method 1
a negative pressure wave is generated due to an exhaust pressure wave generated by opening the exhaust valve reaching and being reflected by the cavity expansion chamber
Implementation Method 2
an ejector effect is provided in this narrowed portion to prevent exhaust interference between the cylinders
Implementation Method 3
an ejector effect is provided in this narrowed portion to prevent exhaust interference between the cylinders
Implementation Method 4
an open period of the exhaust valve and an open period of the intake valve of the cylinder of which the exhaust valve has been opened overlap for a predetermined period
Data Source
AI summary
An exhaust device includes a plurality of independent exhaust passages connected to an exhaust port of one cylinder or a plurality of cylinders that are non-sequential in exhaust order, and a mixing pipe into which exhaust that has passed through the respective independent exhaust passages flows. The downstream ends of the respective independent exhaust passages are connected in a bundled form to the upstream end of the mixing pipe. A cavity expansion chamber is disposed in an exhaust passage downstream from the mixing pipe. The cavity expansion chamber is disposed in a position (at a distance L2) such that, in the intermediate speed range, a negative pressure wave generated due to an exhaust pressure wave generated by opening an exhaust valve being reflected by the cavity expansion chamber reaches the exhaust port during an overlap period of the exhaust valve and an intake valve of the cylinder.