Galleryless Steel Piston Thermal Management
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Solution Overview
Problem
Diesel engine pistons with high compression height are dynamically unstable, leading to piston slap and noise issues, which are exacerbated by the need to dampen diesel knock and manage thermal loads, resulting in bulkier designs that increase friction and noise.
Innovation Solution
A galleryless steel piston with a reduced compression height, low heat transfer coating on the upper crown, and ribs on the undercrown surface for rigidity, combined with an improved connecting rod design, to minimize weight and noise while maintaining structural integrity and cooling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the compression height of the piston is increased to accommodate combustion pressures and thermal loads, then the structural strength and thermal management are improved, but the dynamic stability deteriorates leading to piston slap and noise
Solution Approach 1:
The patent changes the physical parameters of the piston by applying a low heat transfer coating on the crown surface and adding ribs on the undercrown surface. This modifies the thermal and structural parameters without increasing the compression height, thereby maintaining dynamic stability while accommodating combustion pressures and thermal loads.
Solution Approach 2:
The patent uses a composite structure combining a low heat transfer coating material with the steel piston body. The coating material has different thermal properties than the bulk steel, creating a composite structure that manages heat transfer differently than solid steel alone, allowing reduced compression height while maintaining thermal load capacity.
2Object-affected harmful factors
If the compression height of the piston is increased to dampen diesel knock, then the noise dampening is improved, but the device bulkiness and friction increase
Solution Approach 1:
The patent modifies the thermal parameters of the piston crown through the low heat transfer coating, which changes how heat is managed during combustion. This parameter change allows the piston to dampen diesel knock effectively without requiring increased compression height, thus avoiding additional bulkiness.
3Stability of the object's composition
If the compression height of the piston is increased, then the mass above the pin bore axis increases improving stability, but the overall piston mass increases leading to more piston slap
Solution Approach 1:
The patent changes the structural parameters by adding ribs on the undercrown surface, which modifies the mass distribution and rigidity without significantly increasing overall piston mass. The low heat transfer coating also changes thermal parameters, allowing reduced compression height while maintaining stability.
Solution Approach 2:
The patent segments the piston structure by adding ribs on the undercrown surface. These ribs create a segmented reinforcement pattern that provides structural stability and rigidity without requiring a solid increase in compression height or overall mass, thereby reducing piston slap.
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 results in a smoother, quieter engine operation with reduced piston slap, increased waste heat recovery, and improved thermal efficiency, achieving a 7% to 15% increase in thermal brake efficiency and a 28% reduction in apparent weight compared to traditional pistons.
Implementation Method 1
a low heat transfer coating along an upper crown of the piston to provide a lower temperature along a ring belt and undercrown surface
Data Source
AI summary
A steel piston for coupling to a connecting rod and wrist pin is provided. The piston includes a body with an upper crown presenting a combustion surface for exposure to a combustion chamber. The upper crown presents an undercrown surface which is openly exposed as viewed from an underside of the piston and not bounded by a cooling gallery. The body includes a ring belt and pin bosses depending from the ring belt and presenting a pin bore for receiving the wrist pin. The body also includes ribs disposed along the undercrown surface. The body includes a ratio of compression height to outer diameter (CH/D) ranging from 34.8% to 42.0%. The piston also includes a low heat transfer coating on the combustion surface, and the low heat transfer coating has a thermal conductivity of about 0.20 to 0.80 W/m·K.