Liquid-Injected Centrifugal Compressor for Part-Load Surge Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional centrifugal compressors experience surge issues when operating at smaller part loads, leading to instability and potential damage, and existing solutions to control surge are either complex or require additional costly components.
Innovation Solution
The implementation of a centrifugal compressor system that includes a liquid injection passage and a hot gas bypass, with controlled valves to adjust refrigerant flow, allowing for the injection of liquid refrigerant into the diffuser and hot gas between the inlet guide vane and impeller, to manage gas velocity and pressure, thereby preventing surge without complex constructions or additional parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional centrifugal compressors operate at smaller part loads, then system flexibility and part load operation are improved, but surge occurs leading to instability and potential damage
Solution Approach 1:
The patent introduces a diffuser as an intermediary component between the impeller and discharge to manage the flow transition. The diffuser's gradually expanding cross-sectional area acts as a mediator that smoothly decelerates the high-velocity refrigerant gas from the impeller, preventing flow separation and surge while enabling stable part load operation.
Solution Approach 2:
The patent employs adjustable inlet guide vanes that can dynamically change the inlet flow angle and refrigerant flow rate. This dynamic adjustment capability allows the compressor to adapt to varying load conditions and maintain stable operation away from the surge line, improving both part load flexibility and surge prevention.
2Reliability
If techniques are developed to control surge, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent controls surge by changing key flow parameters through the diffuser design - specifically the cross-sectional area expansion and flow angle adjustment. By optimizing these geometric parameters, the system achieves reliable surge control without requiring complex additional components or control mechanisms.
Solution Approach 2:
The patent converts the high-velocity kinetic energy from the impeller, which could cause flow separation and surge, into useful pressure increase through the diffuser's gradual expansion. The kinetic energy that would otherwise be harmful is transformed into beneficial static pressure, preventing surge while simplifying the overall system design.
3Loss of energy
If flow rate is reduced to meet part load demand, then energy efficiency is improved, but operating point moves towards surge line causing instability
Solution Approach 1:
The adjustable inlet guide vanes dynamically adjust the inlet flow conditions to maintain stable operation at reduced flow rates. By optimizing the inlet flow angle and distribution, the system can operate efficiently at part load while keeping the operating point away from the surge line, maintaining both energy efficiency and operational stability.
Solution Approach 2:
The diffuser acts as an intermediary that stabilizes the flow transition at reduced flow rates. Its gradually expanding geometry ensures smooth deceleration and pressure recovery even when the refrigerant flow rate is reduced for part load operation, preventing the operating point from approaching the surge line while maintaining energy efficiency.
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 approach effectively prevents surge at smaller part loads, enhances compressor performance across load conditions, and reduces the risk of mechanical damage by optimizing diffuser performance and controlling gas turbulence, thus improving reliability and efficiency.
Implementation Method 1
liquid refrigerant is injected into an entrance portion of the diffuser located between the impeller and the diffuser
Implementation Method 2
hot gas bypass, with controlled valves to adjust refrigerant flow, allowing for the injection of liquid refrigerant into the diffuser and hot gas between the inlet guide vane and impeller
Implementation Method 3
injection passage extending from a discharge side of the compressor to the liquid injection valve, and a second pipe section extending from the liquid injection valve to the entrance portion of the diffuser
Implementation Method 4
Refrigerant flows in order through the inlet guide vane, the impeller and the diffuser. The impeller increases the velocity of refrigerant gas. The diffuser works to transform the velocity of refrigerant gas (dynamic pressure), given by the impeller, into (static) pressure.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A centrifugal compressor (22) for a chiller (10) includes a casing (30), an inlet guide vane (32), an impeller (34) downstream of the inlet guide vane (32), a motor (38) and a diffuser (36). The casing (30) has inlet and outlet portions with the inlet guide vane (32) disposed in the inlet portion. The impeller (34) is rotatable about a rotation axis (X) defining an axial direction. A liquid injection passage (12) is provided to inject liquid refrigerant into an area between the impeller (34) and the diffuser (36). The motor (38) rotates the impeller (34). The diffuser (36) is disposed in the outlet portion downstream from the impeller (34) with an outlet port of the liquid injection passage (12) being disposed between the impeller (34) and the diffuser (36). A controller (20) is programmed to control an amount of the liquid refrigerant injected into the area between the impeller (34) and the diffuser (36).