Shunt Pulsation Trap for Screw Compressor NVH Reduction
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Solution Overview
Problem
Rotary screw compressors generate significant gas pulsations and induced vibrations, noise, and harshness (NVH) due to under-compression and over-compression, which are not effectively addressed by traditional serial pulsation dampeners or sliding valves, leading to low off-design efficiency and structural issues.
Innovation Solution
A shunt pulsation trap is integrated into the compressor casing in parallel with the compression chamber to attenuate gas pulsations and NVH close to the source, using a pre-opening injection port and feedback region with a pulsation dampening device to manage pressure waves and expansion waves before discharge, eliminating the need for external silencers and sliding valves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a large serial pulsation dampener is used at discharge, then gas pulsation reduction is effective (20-40 dB), but device size becomes large and pressure losses increase
Solution Approach 1:
The invention transitions from a serial dampener configuration (one-dimensional flow path) to a shunt/parallel pulsation trap configuration (two-dimensional flow path). The pulsation trap is connected in parallel to the discharge line, allowing pulsation waves to be diverted into a separate chamber where they can be dampened independently from the main gas flow, thus reducing the volume requirements while maintaining effectiveness.
Solution Approach 2:
The pulsation control function is segmented from the main discharge flow path. The shunt pulsation trap separates pulsation dampening from the primary gas flow, allowing the dampener to be smaller since it only needs to handle pulsation waves rather than the full discharge flow. This segmentation enables reduced volume while maintaining pulsation reduction capability.
2Object-affected harmful factors
If a serial pulsation dampener is used, then gas pulsation is reduced, but pressure losses increase and off-design efficiency decreases
Solution Approach 1:
By configuring the pulsation trap in parallel to the discharge line, the main gas flow passes through the discharge valve with minimal resistance, while pulsation waves are diverted into the trap chamber. This dimensional separation allows pulsation dampening without creating significant pressure drops in the main flow path, preserving off-design efficiency.
Solution Approach 2:
The shunt pulsation trap acts as an intermediary pathway for pulsation waves. Instead of forcing all gas flow through a restrictive serial dampener, the trap provides a separate route where pulsation energy can be dissipated through choked openings and volumetric expansion, leaving the main flow path relatively unrestricted.
3Productivity
If a sliding valve is used to adjust compression ratio, then off-design efficiency is improved, but device complexity and cost increase
Solution Approach 1:
The shunt pulsation trap utilizes the inherent pulsation waves generated during compression to automatically equalize pressures and improve off-design performance. The system self-regulates by allowing pulsation energy to naturally flow into the trap chamber and equalize pressures, eliminating the need for externally controlled sliding valves or complex adjustment mechanisms.
Solution Approach 2:
The invention extracts the pulsation control function from the compression ratio adjustment mechanism. Instead of using sliding valves to control both compression ratio and pulsation, the shunt trap separately handles pulsation management, allowing simpler compression ratio control while maintaining off-design efficiency through automatic pulsation equalization.
4Object-affected harmful factors
If traditional serial dampening is used, then pulsation control is achieved, but NVH (noise, vibration, harshness) is not sufficiently reduced
Solution Approach 1:
The shunt configuration creates a separate dimensional pathway for pulsation waves, allowing them to be dampened in an isolated chamber away from the main discharge path. This spatial separation prevents pulsation-induced vibrations from being transmitted to downstream equipment and piping, thereby reducing NVH while maintaining pulsation control.
Solution Approach 2:
The invention converts harmful pulsation energy into beneficial pressure equalization. By allowing pulsation waves to enter the shunt trap chamber, the system uses the pulsation energy itself to drive flow through choked openings and equalize pressures, transforming what would be harmful vibrations into a useful pressure-balancing mechanism that reduces NVH.
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 shunt pulsation trap reduces gas pulsations and NVH, improves off-design efficiency, and achieves compact size and high reliability, while minimizing flow losses and noise radiation, suitable for variable pressure ratio applications.
Implementation Method 1
a pulsation trap chamber (51) conformally surrounding said compression chamber (37) and comprising an injection port (41) branching off from said compression chamber (37) into said pulsation trap chamber (51) and a feedback region (48) communicating with said compressor outlet (38), wherein said pulsation trap chamber (51) reduces gas pulsations and the induced NVH
Implementation Method 2
using a pre-opening injection port and feedback region with a pulsation dampening device to manage pressure waves and expansion waves before discharge
Data Source
AI summary
A shunt pulsation trap for a screw compressor reduces gas pulsation and NVH, and improves off-design efficiency, without using a traditional serial pulsation dampener and a sliding valve. A screw compressor has a pair of multi-helical-lobe rotors that are housed in a compressor chamber that propel gas flow from a suction port to a discharge port of the compressor chamber. The shunt pulsation trap includes an inner casing as an integral part of the compressor chamber, and an outer casing oversized and surrounding the inner casing. The shunt pulsation trap houses at least one gas pulsation dampening device, and includes at least one injection port (trap inlet) branching off from the compressor chamber into the pulsation trap chamber and a feedback region (trap outlet) communicating with the compressor outlet.