Multi-Cylinder Engine Exhaust System with Variable Flow Passage Area
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Solution Overview
Problem
Existing exhaust systems for multi-cylinder engines face challenges in increasing engine output without a turbocharger, particularly in achieving efficient air-intake and scavenging, especially in high load and low velocity regions.
Innovation Solution
The exhaust system incorporates independent exhaust passages separated into low velocity-side and high velocity-side passages, with a flow passage area variable valve and valve drive mechanisms to optimize passage areas and timing, utilizing the ejector effect to enhance scavenging and intake efficiency across various engine speed regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the flow passage area of exhaust passages is reduced to enhance ejector effect and scavenging, then intake efficiency improves in low velocity region, but exhaust resistance increases in high velocity region
Solution Approach 1:
The exhaust passage is divided into multiple independent passages, each equipped with its own flow passage area variable valve. This segmentation allows each passage to be independently controlled, enabling the system to optimize scavenging in some passages while maintaining low exhaust resistance in others, depending on engine operating conditions.
Solution Approach 2:
The flow passage area variable valve dynamically adjusts the cross-sectional area of the exhaust passage based on engine speed and load conditions. At low engine speeds, the valve reduces passage area to enhance the ejector effect and improve scavenging. At high engine speeds, the valve opens to maximize passage area and reduce exhaust resistance, thereby resolving the contradiction between intake efficiency and exhaust resistance across different operating regions.
2Productivity
If a turbocharger is installed to increase engine output, then air-intake efficiency improves, but device complexity increases
Solution Approach 1:
The system utilizes the kinetic energy of the exhaust gas itself to create the pumping effect needed for scavenging. By controlling the flow passage area variable valve to create pressure differences, the exhaust gas automatically performs the work of drawing fresh charge into the cylinder, eliminating the need for an external turbocharger or other mechanical boosting devices.
Solution Approach 2:
The system changes the flow passage area parameter dynamically to control exhaust gas velocity and pressure distribution. By adjusting this parameter, the system generates sufficient ejector effect to achieve effective scavenging and increased air-intake without requiring additional mechanical components, thereby maintaining system simplicity while improving engine output.
3Productivity
If valve timing is optimized to enhance scavenging in high load region, then intake efficiency improves, but exhaust gas retention increases in low load region
Solution Approach 1:
The system incorporates sensors to detect engine speed, load, and exhaust gas conditions, and the ECU uses this feedback information to adjust the flow passage area variable valve timing and position. This closed-loop control enables the system to optimize scavenging during high load conditions while preventing excessive exhaust gas retention during low load conditions, adapting valve timing based on real-time operating parameters.
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 configuration effectively reduces exhaust resistance, promotes scavenging, and increases intake efficiency, thereby enhancing engine output without the need for a turbocharger.
Implementation Method 1
causes the negative pressure generated around the high velocity exhaust to work on the other independent passages in the collection part, and pumps out the exhaust in the other independent passages to the downstream side based on the so-called ejector effect
Data Source
AI summary
Provided is an exhaust system of a multi-cylinder engine capable of increasing the air-intake and thereby increasing the engine output with a simple configuration. The exhaust system is provided with low velocity-side passages 54, high velocity-side passages 53, a low velocity-side collection part 56, a high velocity-side collection part 57, and a flow passage area variable valve 58 capable of changing the flow passage area of the respective high velocity-side passages 53. The relationship of a diameter a1 of a true circle with a same area as the flow passage area of the downstream end of the low velocity-side passages 54, a diameter D1 of a true circle with a same area as the flow passage area of the downstream end of the low velocity-side collection part 56, a diameter a2 of a true circle with a same area as the flow passage area of the downstream end of the high velocity-side passages 53, and a diameter D2 of a true circle with a same area as the flow passage area of the downstream end of the high velocity-side collection part 57 is made to be a1/D1≧a2/D2. In a low velocity region R1, an exhaust valve 20 is opened during the overlap period of an intake valve 19 and the exhaust valve 20 and the flow passage area of the high velocity-side passages 53 is narrowed, and, in a high velocity region R3, the flow passage area of the high velocity-side passages 53 is set to be a maximum area.