Radially Configured Oil-Free Compressor Torque and Cooling

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Solution Overview

Problem

Oil-free reciprocating compressors for rail vehicles face challenges with overheating, high torque pulses, uneven dynamic balancing, and increased size due to traditional bearing designs, which affect maintainability and efficiency.

Innovation Solution

The design features a radially configured oil-free compressor with a pentagonal cross-sectional compressor housing, positioning piston cylinders in an X-shaped configuration around the circumference, and utilizing a cooling fan to create a perpendicular flow path for improved cooling and reduced torque pulses, along with single piece connecting rods for simplified assembly and maintenance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If traditional bearing designs are used in oil-free compressors, then the compressor size increases, but the maintainability and assembly simplicity deteriorate

Engineering Contradiction:

Improvecompressor sizeVSAvoidmaintainability

Core Design Contradiction:

Volume of moving objectVSEase of repair

Solution Approach 1:

The connecting rod is divided into two separate pieces: the rod body and the crankpin end. This segmentation allows the crankpin bearing to be accessed and replaced independently without removing the entire connecting rod, significantly improving maintainability while keeping the overall compressor size compact.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The crankpin bearing is extracted as a separate removable component from the connecting rod assembly. This extraction enables independent maintenance of the bearing without disassembling the entire connecting rod, resolving the contradiction between compact design and ease of repair.

Inventive Principle:

Principle #2Taking out (Extraction)

2Quantity of substance

If oil-free reciprocating compressors are used, then the need for large oil sump is reduced, but overheating problems occur

Engineering Contradiction:

Improveoil quantityVSAvoidcompressor temperature

Core Design Contradiction:

Quantity of substanceVSTemperature

Solution Approach 1:

Air is introduced as a cooling medium to replace the lubricating/cooling function of oil. The air cooling system uses pneumatic flow to remove heat from the compressor components, particularly the cylinder heads and bearings, preventing overheating in the oil-free design.

Inventive Principle:

Principle #29Pneumatics and hydraulics

Solution Approach 2:

Air acts as an intermediary cooling medium between the hot compressor components and the external environment. The air flow transfers heat away from the cylinder heads and bearings, mediating the thermal management function that would otherwise require oil.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Stability of the object's composition

If multiple piston cylinders are positioned radially, then dynamic balancing is improved, but torque pulses increase

Engineering Contradiction:

Improvedynamic balancingVSAvoidtorque pulse

Core Design Contradiction:

Stability of the object's compositionVSForce

Solution Approach 1:

The piston cylinders are positioned at asymmetric angles (30 degrees apart rather than evenly spaced) to optimize the balance between dynamic stability and torque pulse reduction. This asymmetric arrangement creates overlapping power strokes that smooth out torque variations while maintaining good dynamic balance.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The compressor utilizes periodic firing of multiple cylinders arranged to create overlapping power strokes. This periodic action smooths out torque delivery by ensuring that not all cylinders are at their peak torque point simultaneously, reducing overall torque pulses while maintaining dynamic balance.

Inventive Principle:

Principle #19Periodic action

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 reduces overall size, improves dynamic balancing, and enhances air flow for effective cooling, resulting in a more efficient and maintainable compressor with consistent torque pulses and reduced torsional forces on the driveline.

Implementation Method 1

utilizing a cooling fan to create a perpendicular flow path for improved cooling

Methodology Applied

Scientific EffectForced Convection: Forced Convection

Data Source

PatentUS10077800B2Radially configured oil-free compressor

Publication Date: 2018.09.18 WESTINGHOUSE AIR BRAKE TECH CORP

AI summary

An oil-free compressor for a rail vehicle includes a compressor housing, a first low pressure piston cylinder supported in the compressor housing, a second low pressure piston cylinder supported in the compressor housing, a first high pressure piston cylinder supported in the compressor housing, a second high pressure piston cylinder supported in the compressor housing, and a crankshaft assembly supported by the compressor housing and linked to pistons of the piston cylinders by respective connecting rods. The first and second low pressure piston cylinders and the first and second high pressure piston cylinders are positioned in an X-shaped configuration around an outer circumference of the compressor housing. The first and second high pressure piston cylinders are configured as first and second lower legs of the X-shaped configuration, and the first and second low pressure piston cylinders are configured as first and second upper legs of the X-shaped configuration.