Centrifugal Compressor Hot Gas Injection for Surge Range Expansion
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Solution Overview
Problem
Conventional centrifugal compressors face challenges with reduced operation range due to surge phenomena and gas turbulence, which can cause mechanical damage and instability, especially when using magnetic bearings, and require large-sized pipes for hot gas bypass systems, increasing costs.
Innovation Solution
A centrifugal compressor design that incorporates a hot gas injection passage between the inlet guide vane and the impeller, controlled by a controller to manage the amount of hot gas refrigerant, along with a liquid injection passage to adjust the flow, allowing for expanded operation range without increased costs and reducing turbulence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a hot gas bypass is provided to connect the discharge side and suction side of the compressor, then the operation range of the compressor is expanded, but a large-sized pipe is required which increases costs
Solution Approach 1:
The patent changes the spatial arrangement by injecting hot gas at an angle (e.g., 45 degrees) relative to the suction port rather than using a direct bypass connection. This dimensional change allows the hot gas to mix with the suction gas more effectively while using a smaller pipe diameter, thus expanding the operation range without requiring large-sized pipes that会增加成本
Solution Approach 2:
The patent applies local quality by creating a specific injection region near the suction port where hot gas is introduced at a controlled angle and position. This localized injection approach optimizes the mixing efficiency in a specific area, allowing effective surge control with smaller pipe dimensions compared to a full bypass system
2Productivity
If the inlet guide vane opening position is small, then gas turbulence occurs between the inlet guide vane and impeller, but this causes shaft vibration in magnetic bearings
Solution Approach 1:
The patent applies preliminary anti-action by introducing hot gas into the suction port region before the compressed gas enters the impeller. This pre-mixing of hot gas creates a more uniform flow pattern that counteracts the turbulence generated by small inlet guide vane openings, thereby preventing shaft vibration in magnetic bearings while maintaining capacity control
3Productivity
If flow rate is reduced during part load operation, then the operating point moves towards the surge line, but this causes flow recirculation and surge
Solution Approach 1:
The patent changes the temperature parameter by injecting hot gas into the suction flow. This parameter change (increasing gas temperature) modifies the density and flow characteristics, allowing the system to operate at reduced flow rates without reaching the surge line. The hot gas injection effectively shifts the surge curve, enabling stable part-load operation
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 solution effectively expands the operation range of the compressor, reduces shaft vibrations in magnetic bearings, and minimizes turbulence, enhancing stability and efficiency while potentially reducing costs by using smaller pipe diameters for hot gas bypass.
Implementation Method 1
a hot gas injection passage arranged and configured to inject hot gas refrigerant between the inlet guide vane and the impeller
Implementation Method 2
The diffuser works to transform the velocity of refrigerant gas (dynamic pressure), given by the impeller, into (static) pressure
Implementation Method 3
The impeller increases the velocity of refrigerant gas
Implementation Method 4
a liquid injection passage arranged and configured to inject liquid refrigerant into an entrance portion of the diffuser
Data Source
AI summary
A centrifugal compressor for a chiller includes a casing, an inlet guide vane, an impeller downstream of the inlet guide vane, a motor and a diffuser. The casing has inlet and outlet portions with the inlet guide vane disposed in the inlet portion. The impeller is rotatable about a rotation axis defining an axial direction. The motor rotates the impeller. The diffuser is disposed in the outlet portion downstream from the impeller with an outlet port of the outlet portion being disposed between the impeller and the diffuser. A hot gas injection passage is provided to inject hot gas refrigerant between the inlet guide vane and the impeller. A controller is programmed to control an amount of the hot gas refrigerant.