Two-Valve Engine Combustion Noise Suppression
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Solution Overview
Problem
Two-valve engines face a trade-off between improving fuel efficiency through rapid combustion, which increases combustion noise due to pressure rise rates, and reducing noise, especially when using bearings with lower support stiffness.
Innovation Solution
The engine design incorporates a combination of swirling and tumble flows in the combustion chamber by arranging the intake passage and ignition device to minimize initial pressure rise and promote efficient flame propagation, using a concave portion on the piston surface to maintain the swirling flow and a convex portion to retard flame propagation, thereby reducing combustion noise and enhancing fuel efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If rapid combustion is achieved through enhanced tumble flow, then fuel efficiency is improved, but combustion noise increases due to higher pressure rise rate
Solution Approach 1:
The combustion chamber is divided into multiple zones with different flow characteristics. The tumble flow is segmented into regions with varying swirl intensities, allowing rapid combustion in some areas while controlling pressure rise in others. This spatial segmentation enables simultaneous achievement of fast combustion and noise reduction.
Solution Approach 2:
Different regions of the combustion chamber are given different flow qualities. The intake passage design creates a tumble flow with enhanced swirl in specific zones, while other regions maintain more moderate flow characteristics. This local differentiation allows optimization of combustion speed in certain areas without excessively increasing pressure rise rate throughout the entire chamber.
2Object-generated harmful factors
If roller bearing is adopted to suppress combustion noise propagation, then support stiffness of crankshaft is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent replaces expensive, complex roller bearings with simpler, more economical ball bearings. While ball bearings have shorter service life compared to roller bearings, they provide sufficient noise suppression functionality at lower cost and with reduced manufacturing complexity. This substitution aligns with the principle of using simpler components when they adequately fulfill the required function.
Solution Approach 2:
The patent changes the bearing type parameter from roller bearing to ball bearing, accepting a trade-off in support stiffness in exchange for reduced complexity and cost. This parameter change is compensated by optimizing other engine parameters, such as combustion chamber geometry and flow characteristics, to achieve overall noise control without requiring the higher stiffness of roller bearings.
3Productivity
If intake passage is arranged to enhance tumble flow for rapid combustion, then fuel efficiency improves, but combustion noise increases due to higher pressure rise rate
Solution Approach 1:
The intake passage is designed with asymmetric geometry that generates a tumble flow with non-uniform swirl distribution. The passage cross-section and routing are asymmetrically configured to create stronger swirl in specific regions while maintaining overall tumble flow for rapid combustion. This asymmetric design allows differential control of combustion intensity across the combustion chamber.
Solution Approach 2:
The intake passage incorporates curved and rounded geometries that promote rotational flow patterns. The curved passage design generates centrifugal forces that enhance swirl component of the tumble flow, creating a more rotational flow structure. This curvature-induced swirl helps control pressure rise rate while maintaining combustion speed through optimized flow circulation.
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 suppresses combustion noise while maintaining improved fuel efficiency, even with ball bearings of lower support stiffness, by controlling the flame propagation and maintaining the swirling flow, thus optimizing combustion duration.
Implementation Method 1
the enhancement of a tumble flow, which is a vortex of a mixed gas in a combustion chamber
Implementation Method 2
the mixed gas is rapidly combusted because the mixed gas has a strong flow due to the enhancement of the tumble flow
Data Source
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AI summary
The present teaching provides a two-valve engine configured to suppress a combustion noise occurrence while improving fuel efficiency. A two-valve engine includes: a crankshaft; a rolling bearing; a piston part; a cylinder part that cooperates with the piston part to define a combustion chamber, the cylinder part including a cylinder head part and a cylinder body part, the cylinder head part having one intake port and one exhaust port, the cylinder body part having a cylinder bore; a fuel injector part; and an ignition device arranged in one of two regions that are defined by dividing the combustion chamber by a straight line passing through a center of the intake port and a center of the exhaust port, wherein the piston part has a concave portion in a top surface thereof, the area over which the region where the ignition device is not arranged overlaps the concave portion is smaller than the area over which the region where the ignition device is arranged overlaps the concave portion, and the intake passage is arranged such that the region where the ignition device is not arranged, which overlaps the concave portion over a smaller area, is located on a straight line that is an extension of a center line of the intake passage from the center of the intake port.