Angled Piston Crown Reducing Clearance Volume in Reciprocating Compressors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Reciprocating compressors, especially oil-free designs for rail vehicles, face inefficiencies due to increased clearance volumes caused by piston tilt at top dead center, leading to reduced air delivery and potential compressor failure from excessive heat or vibration.
Innovation Solution
A piston assembly with an angled portion at the second end, configured to compensate for piston tilt during the reciprocating cycle, reducing clearance volume between the piston and cylinder head/valve, thereby maintaining efficient air delivery without increasing overall clearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the piston is designed with a traditional flat top shape, then the manufacturing is simple and the structure is straightforward, but the clearance volume increases due to piston tilt at top dead center, reducing volumetric efficiency
Solution Approach 1:
The piston crown is designed with an angled portion instead of a traditional flat top, creating an asymmetric shape that compensates for piston tilt during the reciprocating cycle. This angled configuration reduces the clearance volume between the piston and cylinder head/valve assembly, thereby improving volumetric efficiency while maintaining manufacturing feasibility
Solution Approach 2:
The piston geometry is modified by changing the crown shape parameter from flat to angled, with the angle specifically designed to counteract the piston tilt angle. This parameter change optimizes the clearance volume throughout the compression cycle, enhancing the compressor's volumetric efficiency without complicating the overall piston structure
2Productivity
If the clearance volume is reduced to improve volumetric efficiency, then air delivery increases, but the piston may contact the cylinder head/valve due to piston tilt, causing compressor failure
Solution Approach 1:
The angled portion on the piston crown is designed in advance to counteract the piston tilt that occurs during operation. By pre-configuring the angle to match the expected tilt angle, the piston maintains adequate clearance from the cylinder head/valve throughout the compression cycle, preventing contact and ensuring reliable operation while maximizing air delivery
Solution Approach 2:
The asymmetric angled crown design creates a compensation mechanism where the angled surface offsets the tilt-induced clearance reduction on one side by maintaining clearance on the opposite side, thereby preventing piston-to-valve contact while minimizing overall clearance volume
3Productivity
If an angled portion is added to the piston to compensate for tilt, then volumetric efficiency improves, but the piston shape becomes more complex
Solution Approach 1:
Instead of making the entire piston complex, only the crown portion is modified with an angled surface while the rest of the piston structure remains conventional. This localized modification achieves the desired volumetric efficiency improvement without significantly increasing overall piston complexity or manufacturing difficulty
Data Source
AI summary
A piston assembly for reducing clearance volume in a reciprocating compressor for compensating for piston tilt and improving the volumetric efficiency of the compressor includes a piston located within a piston cylinder, the piston having a first end and a second end, a wrist pin associated with the first end of the piston, and a cylinder head/valve assembly associated with the second end of the piston, wherein at least a portion of the second end of the piston includes an angled portion. The piston having the angled portion can be used with oil free cylinders and trunk type pistons. The piston can also be used in a multiple stage, multiple cylinder compressor including a series of piston assemblies. A method of increasing the volumetric efficiency of a reciprocating compressor can also be achieved using the piston having an angled portion.