Compressor Lubrication Using Refrigerant with Throttle Valve Control
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Solution Overview
Problem
Refrigeration apparatuses face challenges in maintaining adequate lubrication during low load operations, as refrigerant in a gaseous state is insufficient for lubrication, risking compressor damage, and excessive liquid refrigerant can flood the rotor cavity, leading to potential damage.
Innovation Solution
A refrigeration apparatus with a lubrication refrigerant line connected between the condenser and expansion valve, featuring a throttle valve, downstream pressure and temperature detectors, and a control unit to monitor and control the refrigerant flow, ensuring it remains in a liquid state and at sufficient flow for any load, using pressure drop and temperature measurements to manage the refrigerant state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If refrigerant flow is increased to ensure sufficient lubrication during low load operation, then lubrication reliability is improved, but the risk of rotor cavity flooding increases
Solution Approach 1:
The system employs pressure detectors and temperature detectors that continuously monitor refrigerant conditions in the lubrication line. The control unit receives this feedback and dynamically adjusts the throttle valve to maintain optimal refrigerant flow, ensuring sufficient lubrication while preventing rotor cavity flooding across varying load conditions
Solution Approach 2:
The throttle valve is dynamically controlled based on real-time refrigerant state measurements. The system transitions from static flow control to dynamic adjustment, adapting the refrigerant flow rate to match actual compressor needs under different operating loads, thereby resolving the contradiction between sufficient lubrication and flooding prevention
2Object-affected harmful factors
If refrigerant flow is decreased to prevent rotor cavity flooding, then flooding risk is reduced, but lubrication insufficiency occurs during low load operation
Solution Approach 1:
Pressure and temperature detectors provide continuous feedback on refrigerant state. The control unit uses this information to adjust the throttle valve, ensuring the refrigerant remains in liquid state with appropriate flow rate to prevent both flooding and lubrication insufficiency
Solution Approach 2:
The system monitors and controls refrigerant parameters (pressure, temperature, flow rate) to maintain the refrigerant in the desired liquid state. By dynamically adjusting these parameters through the throttle valve, the system ensures adequate lubrication without causing flooding
3Productivity
If refrigerant is used as lubricant without oil, then environmental friendliness is improved, but lubrication control complexity increases
Solution Approach 1:
The refrigerant serves dual functions as both cooling medium and lubricant, eliminating the need for separate oil systems. The control system manages both refrigeration and lubrication functions through a unified approach, reducing overall system complexity despite the multi-functionality requirement
Solution Approach 2:
The refrigerant automatically provides lubrication to the compressor without requiring separate lubrication oil. The system leverages the refrigerant's own properties and flow to accomplish lubrication, simplifying the overall material system while adding control mechanisms to manage the dual function
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
Ensures consistent and sufficient lubrication of the compressor across all operational loads, preventing damage from inadequate lubrication during low load conditions and avoiding overflooding, thus ensuring reliable operation.
Implementation Method 1
a throttle valve (20) adapted to vary the lubrication refrigerant flow entering the compressor
Implementation Method 2
a downstream pressure detector (30) configured to measure refrigerant pressure downstream the throttle valve (20) and upstream the compressor (4)
Implementation Method 3
a downstream temperature detector (32) configured to measure refrigerant temperature downstream the throttle valve (20) and upstream the compressor (4)
Implementation Method 4
a control unit (CU) adapted to determine the state of the refrigerant in the lubrication refrigerant line (18) using the measurements of the downstream pressure detector (30) and the downstream temperature detector (32)
Data Source
AI summary
A refrigeration apparatus (1) includes a main refrigerant circuit (2) including a positive displacement compressor (4), a condenser (6), an expansion valve (8), and an evaporator (10), through which a refrigerant circulates successively in a closed loop circulation, a lubrication refrigerant line (18) connected to the main refrigerant circuit (2) between the condenser (6) and the expansion valve (8) or to the condenser (6), in which circulates a portion of the refrigerant of the main refrigerant circuit (2) and connected to the compressor (4) for lubrication of the compressor (4) with the refrigerant. The lubrication refrigerant line (18) includes, upstream from the compressor (4): a throttle valve (20) adapted to vary the lubrication refrigerant flow entering the compressor (4), a downstream pressure detector (30) configured to measure refrigerant pressure (P3) downstream the throttle valve (20) and upstream the compressor (4).