Composite Piston Rod Reduces Reciprocating Compressor Mass
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Solution Overview
Problem
Large reciprocating compressors face challenges due to high inertial and gas pressure loads, leading to increased mass and weight, which necessitate larger piston rods and sliding shoes, resulting in increased dimensions, weight, and manufacturing and operating costs, as well as reduced reliability due to lubrication requirements at high pressure.
Innovation Solution
The use of a piston rod partly made of composite material, such as fiber-reinforced polymeric material, combined with metal ends, reduces weight and mass while maintaining mechanical integrity, and the incorporation of composite materials in the piston body and sliding shoes optimizes stress distribution and reduces axial length, thereby minimizing the need for extensive lubrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the piston rod cross-section is increased to withstand high reciprocating loads, then the strength and load-bearing capacity are improved, but the mass and weight of the reciprocatingly moving arrangement increase
Solution Approach 1:
The piston rod is made from a composite material consisting of a polymer matrix reinforced with high-strength fibers (such as carbon, glass, or aramid fibers). This composite structure provides exceptional strength-to-weight ratio, allowing the piston rod to withstand high reciprocating loads while maintaining significantly reduced mass compared to traditional solid metal piston rods. The fiber reinforcement directions can be optimized to match the principal stress trajectories in the piston rod.
2Stress or pressure
If the axial dimension of sliding shoes is increased to reduce specific pressure, then the specific pressure is reduced, but the axial length of the piston and overall machine dimensions increase
Solution Approach 1:
The sliding shoes are constructed from composite materials that combine low-friction surfaces with high structural strength. This allows the sliding shoes to maintain smaller axial dimensions while still supporting the required loads and maintaining acceptable specific pressure levels. The composite structure enables better stress distribution across the contact surface.
Solution Approach 2:
The sliding shoes feature localized quality variations with different material properties at different regions - the contact surface has low-friction characteristics while the structural portion provides strength. This allows optimization of the axial dimension by concentrating material properties where needed rather than uniformly increasing dimensions.
3Stress or pressure
If the sliding shoes are dimensioned to meet specific pressure requirements, then the pressure distribution is improved, but the weight of the reciprocatingly moving arrangement increases
Solution Approach 1:
Both the sliding shoes and piston rod utilize composite materials that provide high strength-to-weight ratios. This allows the sliding shoes to be dimensioned appropriately for pressure distribution without the penalty of excessive weight, as the composite materials maintain structural integrity with reduced mass compared to traditional metals.
4Reliability
If lubrication is implemented for sliding shoes at high specific pressure, then the reliability under load is improved, but manufacturing and operating costs increase and machine reliability is adversely affected
Solution Approach 1:
The sliding shoes are designed with self-lubricating composite materials that inherently reduce friction and wear without requiring external lubrication systems. The composite material structure itself provides lubrication through its composition, eliminating the need for additional lubricants and reducing maintenance requirements while operating under high pressure conditions.
Data Source
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Figure 3~5
AI summary
A double-effect reciprocating compressor is described. The compressor comprises a cylinder (3) and a reciprocatingly moving arrangement comprised of a piston (7), a crosshead (37) and a piston rod (15) connecting the crosshead to the piston. A crank-shaft (31) drives the reciprocatingly moving arrangement into reciprocating motion via a connecting rod (33). At least one part of the piston and of the piston rod is at least partly made of a composite material.