Variable Displacement Compressor Noise Control via Dynamic Displacement Adjustment
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Solution Overview
Problem
Vehicle air cooling systems with variable displacement compressors generate refrigerant flow noise at low compressor speeds and mild temperatures due to a two-phase mixture of liquid and gas refrigerant, leading to discomfort and decreased driver satisfaction.
Innovation Solution
A controller is configured to generate a current signal defining compressor displacement based on compressor speed and ambient temperature to reduce refrigerant flow noise by adjusting the compressor current and suction pressure, thereby eliminating the noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the compressor operates at low speeds to meet low cooling demands, then energy efficiency is improved, but refrigerant flow noise increases due to two-phase mixture operation
Solution Approach 1:
The controller dynamically adjusts compressor displacement as a controllable parameter to exit the gurgling zone. By modifying the displacement parameter in response to detected noise conditions, the system changes the operating characteristics of the compressor to eliminate two-phase mixture flow noise while maintaining energy efficiency at appropriate operating points.
Solution Approach 2:
The system employs feedback control by monitoring compressor operating conditions (speed, displacement, ambient temperature) and using this information to adjust displacement in real-time. The controller continuously evaluates whether the compressor is operating within the gurgling zone and modifies displacement accordingly, creating a closed-loop control system that prevents noise generation.
2Productivity
If the compressor displacement is reduced to match low cooling demands, then cooling capacity is optimized, but refrigerant flow noise is generated due to two-phase mixture
Solution Approach 1:
The compressor displacement is made dynamically adjustable rather than fixed, allowing the system to adapt to varying cooling demands while avoiding noise-generating operating conditions. The controller modulates displacement in real-time based on ambient temperature, compressor speed, and cooling requirements, enabling the system to maintain optimal cooling capacity without entering the gurgling zone.
Solution Approach 2:
The system changes the displacement parameter to exit the problematic operating region where two-phase mixture causes noise. By adjusting displacement as a controllable variable, the system can maintain appropriate cooling capacity while shifting operating points away from the gurgling zone, thereby eliminating noise without sacrificing cooling performance.
3Temperature
If the compressor operates in the gurgling zone to maintain evaporator temperature, then temperature control is improved, but noise and vibrations increase
Solution Approach 1:
The controller uses feedback from temperature sensors and operating condition monitors to determine when the compressor is operating within the gurgling zone. Based on this feedback, the system adjusts displacement to exit the noisy operating region while maintaining evaporator temperature within acceptable ranges, thus eliminating noise and vibrations without compromising temperature control.
Solution Approach 2:
The displacement parameter is modified to change the compressor's operating characteristics and exit the gurgling zone. By adjusting displacement, the system alters the refrigerant flow dynamics to eliminate two-phase mixture noise and vibrations while maintaining the evaporator temperature control necessary for proper system operation.
Data Source
AI summary
A vehicle cooling system may include a variable displacement compressor, and a controller configured to, in response to a determination that the compressor is operating within a gurgling zone that is defined by a predefined range of compressor speeds and currents, generate a current signal defining a displacement for the compressor based on a speed of the compressor and an ambient temperature to control the displacement to reduce refrigerant flow noise.