Systems and methods for determining startup pressure ratio for dynamic compressors
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Solution Overview
Problem
Dynamic compressors face challenges in accurately determining the pressure ratio at startup due to the presence of a discharge check valve that prevents high-pressure refrigerant from flowing to the compressor pressure sensor.
Innovation Solution
A system and method that utilize temperature sensors in the evaporator and condenser to estimate the pressure ratio of the dynamic compressor, allowing the controller to set a speed setpoint within the safe operating envelope of the compressor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a discharge check valve is installed downstream of the compressor to prevent high-pressure refrigerant from flowing back, then the compressor can maintain stable operation, but the pressure sensor cannot accurately measure the discharge pressure at startup
Solution Approach 1:
The patent introduces a bypass valve as an intermediary component that creates an alternative flow path during startup. This bypass allows high-pressure refrigerant to reach the pressure sensor without compromising the check valve's function of preventing reverse flow during normal operation. The bypass valve acts as a temporary mediator that resolves the conflict between maintaining operational stability and enabling accurate measurement.
Solution Approach 2:
The system performs preliminary action by opening the bypass valve before compressor startup to establish a measurement path. This preliminary configuration allows the pressure sensor to accurately detect discharge pressure during the critical startup phase. After startup completion, the bypass valve closes, and the system returns to normal operation with the check valve preventing reverse flow.
2Productivity
If the compressor operates without accurate pressure ratio information at startup, then the system can start quickly, but the compressor may operate outside the safe operating envelope
Solution Approach 1:
The patent implements feedback control by continuously monitoring discharge pressure through the bypass valve and pressure sensor during startup. The controller uses this real-time pressure information to calculate the pressure ratio and adjust the compressor speed accordingly. This feedback mechanism ensures the compressor remains within the safe operating envelope while enabling rapid startup, as the system can immediately respond to actual operating conditions rather than relying on pre-programmed conservative parameters.
Solution Approach 2:
The system dynamically adjusts the bypass valve position and compressor speed based on real-time pressure measurements. During startup, the bypass valve is opened to enable measurement, and the compressor speed is dynamically controlled based on the measured pressure ratio. As the system reaches steady state, the bypass valve dynamically closes and normal operation begins. This dynamic adaptation allows both fast startup and safe 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
This approach enables the dynamic compressor to operate within a safe envelope during startup, improving reliability by minimizing time spent outside the safe operating conditions.
Implementation Method 1
The system includes a first temperature sensor positioned within the first heat transfer fluid path of the evaporator, and a second temperature sensor positioned within the second heat transfer fluid path of the condenser
Implementation Method 2
The evaporator includes a first working fluid path and a first heat transfer fluid path thermally coupled thereto. The condenser includes a second working fluid path and a second heat transfer fluid path thermally coupled thereto
Implementation Method 3
The dynamic compressor is operable to compress a working fluid... The dynamic compressor is fluidly coupled to the first working fluid path of the evaporator and the second working fluid path of the condenser
Data Source
AI summary
A controller for a system having an evaporator, a condenser, and a dynamic compressor includes a processor and a memory, which stores instructions that program the processor to determine a first heat transfer fluid temperature at a first heat transfer fluid path of the evaporator, determine a first pressure at a first working fluid path based on first heat transfer fluid temperature, determine a second heat transfer fluid temperature at a second heat transfer fluid path of the condenser, determine a second pressure at a second working fluid path based on the second heat transfer fluid temperature, calculate an estimated pressure ratio of the compressor from the first and second pressures, determine a speed setpoint of the compressor based on the estimated pressure ratio, and operate the compressor at the speed setpoint to compress a working fluid until a condition is met.