Exhaust Diffusion Chamber Layout for Accurate Air-Fuel Sensing
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Solution Overview
Problem
Existing exhaust gas purification systems face inefficiencies in catalyst utilization and inaccurate air/fuel ratio measurement due to uneven gas flow and sensor placement, leading to suboptimal performance and control.
Innovation Solution
An exhaust gas purification device with a diffusion chamber, orifice, and air/fuel ratio sensor arrangement that diffuses and agitates exhaust gas before measurement, ensuring uniform mixing and accurate ratio assessment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the catalyst is enlarged to ensure purifying performance, then the purifying performance is improved, but the pressure loss in the exhaust gas purifying device is increased
Solution Approach 1:
The diffusion chamber performs preliminary mixing and diffusion of exhaust gases from multiple cylinders before they enter the catalyst. This preliminary action ensures uniform distribution of exhaust gases, allowing the catalyst to operate more efficiently without requiring excessive catalyst volume, thus maintaining purifying performance while reducing pressure loss.
2Productivity
If the collection part is formed between the first exhaust passage and the second exhaust passage, then the exhaust gas flow is concentrated, but the flow rates of exhaust gas through the first and second exhaust passages are increased, shortening the time period for exhaust gas to flow through the catalyst
Solution Approach 1:
The diffusion chamber is positioned upstream of the catalyst to perform preliminary diffusion and mixing of exhaust gases from multiple cylinders. This ensures that by the time exhaust gases reach the catalyst, they are already well-mixed, which maintains effective catalytic processing time even when flow rates are concentrated.
3Ease of operation
If the air/fuel ratio sensor is arranged at the diffusion portion where exhaust gas flows converge, then the sensor can detect exhaust gas flow, but the air/fuel ratio cannot be measured accurately due to uneven mixing
Solution Approach 1:
The diffusion chamber performs preliminary mixing of exhaust gases from multiple cylinders before the gas reaches the air/fuel ratio sensor. This ensures that by the time the sensor measures the air/fuel ratio, the gases are already uniformly mixed, enabling accurate measurement even when the sensor is positioned in the convergence zone.
4Ease of operation
If the exhaust pipe structure uses individual exhaust passages connected to cylinders, then the exhaust gas can be introduced to the catalytic converter, but the swirl flow of exhaust gas tends to flow outer side in the passage, reducing efficient flow through the center portion of the catalyst
Solution Approach 1:
The diffusion chamber performs preliminary diffusion and mixing of exhaust gases from individual cylinder passages before they converge and enter the catalyst. This preliminary mixing action ensures uniform distribution of gases throughout the catalyst cross-section, preventing swirl flow from concentrating only at the outer sides and ensuring efficient utilization of the entire catalyst volume.
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
Enhances catalyst performance without size increase and achieves precise air/fuel ratio measurement by uniformly mixing exhaust gases before catalyst and sensor interaction.
Implementation Method 1
a diffusion chamber (4) arranged between the header pipe (2) and the catalytic converter (3)... in which a mainstream of the exhaust gas flowing into the diffusion chamber via the header pipe collides with a receiving surface (4a)
Implementation Method 2
an orifice (5) formed in a downstream end plate of the diffusion chamber, a cross-sectional area thereof being smaller than a cross-sectional area of an internal space of the diffusion chamber
Data Source
AI summary
An exhaust gas purification device for measuring air/fuel ratio accurately and for enhancing a purification performance without increasing a size of a catalyst. The exhaust gas purification device comprises: header pipes through which exhaust gas flows; a catalytic converter arranged downstream of the header pipes; a diffusion chamber arranged between the header pipe and the catalytic converter; and a receiving surface with which the exhaust gas flowing into the diffusion chamber collides. An orifice is formed in a downstream end plate of the diffusion chamber, and an air/fuel ratio sensor is arranged downstream of the orifice.