A preconditioned air unit with variable frequency driving
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing preconditioned air units for aircraft on the ground face challenges related to high cost, inefficiency, and environmental impact due to reliance on auxiliary power units, and conventional systems have limitations in flexibility and serviceability.
Innovation Solution
A preconditioned air unit with a housing containing a flow duct, a blower, and multiple refrigeration systems powered by variable frequency drivers, allowing for adjustable compressor and condenser fan operation to optimize cooling capacity and efficiency, along with modular self-contained cooling modules and a central controller for flexible operation and power management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the compressor is supplied from the mains supply with fixed frequency (50 Hz or 60 Hz), then the system structure is simple, but the maximum cooling capacity is limited and cannot be adjusted to varying cooling requirements
Solution Approach 1:
The patent applies dynamics by replacing the fixed-frequency mains supply with a variable frequency driver that can dynamically adjust the compressor's operating frequency. This allows the cooling capacity to be continuously adjusted according to varying cooling requirements, transforming a static system into a dynamic one that adapts to changing conditions.
Solution Approach 2:
The patent changes the key parameter of electrical frequency from a fixed value (50 Hz or 60 Hz) to a variable parameter that can be adjusted within a wide range (e.g., 10-100 Hz). This parameter change enables flexible control of compressor speed and cooling capacity while maintaining system simplicity through integrated control.
2Reliability
If the compressor operates at maximum capacity continuously, then the cooling demand is always met, but power consumption increases and system reliability decreases due to wear
Solution Approach 1:
The variable frequency driver enables dynamic adjustment of compressor speed based on actual cooling demand. Instead of continuous maximum capacity operation, the system dynamically modulates the compressor speed, reducing wear and extending system lifetime while optimizing power consumption to match the cooling load.
Solution Approach 2:
The system incorporates feedback control where the controller monitors cooling requirements and adjusts the variable frequency driver's output accordingly. This feedback mechanism ensures the compressor operates at optimal speed to meet cooling demand without excessive power consumption or unnecessary wear, balancing reliability and energy efficiency.
3Use of energy by moving object
If conventional on/off control is used for the compressor, then the system is simple to control, but power consumption increases and system reliability decreases due to frequent starting and stopping
Solution Approach 1:
The patent replaces discrete on/off control with continuous variable frequency control. Instead of abruptly starting and stopping the compressor, the system dynamically adjusts the frequency and voltage supplied to the compressor motor, enabling smooth transitions and continuous operation that reduces power consumption and mechanical stress.
Solution Approach 2:
The control system changes from binary (on/off) to continuous parameter adjustment by varying the frequency and voltage output. This parameter change allows the compressor to operate efficiently across a wide range of cooling loads without the energy waste and reliability issues associated with frequent cycling.
4Adaptability or versatility
If a single large refrigeration system is used, then the cooling capacity is sufficient for maximum demand, but the system lacks flexibility for partial load operation and has reduced serviceability
Solution Approach 1:
The patent divides the refrigeration system into multiple independent refrigeration circuits that can operate separately or in combination. This segmentation allows flexible partial load operation where only the necessary number of circuits are activated, improving adaptability while maintaining serviceability through modular design.
Solution Approach 2:
The system dynamically configures which refrigeration circuits are active based on cooling demand. Instead of operating a single large system at partial load, the system dynamically activates or deactivates individual circuits to match the required cooling capacity, providing flexibility and improved 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 solution reduces fuel consumption, emissions, and operational costs while enhancing flexibility and serviceability by optimizing cooling capacity and efficiency, allowing continuous operation with reduced power consumption and enabling quick adaptation to varying cooling demands.
Implementation Method 1
the output voltage and frequency of the variable frequency driver are varied to control the at least one compressor in accordance with the current cooling requirement
Implementation Method 2
the at least one compressor may be controlled for provision of variable cooling capacity, e.g. in response to the temperature and flow rate of the air flow in the flow duct
Implementation Method 3
the at least one compressor in order for it to cool the airflow interacting with the respective at least one evaporator
Implementation Method 4
The blower is preferably a highly efficient centrifugal fan
Implementation Method 5
The blower is preferably mounted with vibration dampers
Implementation Method 6
To prevent cooling losses, the outer walls of the flow duct may be provided with a layer of heat insulation material
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A preconditioned air unit for supplying preconditioned air to an aircraft parked on the ground, the preconditioned air unit comprising a housing accommodating a flow duct with an air inlet for ambient air and an air outlet for connection to the parked aircraft, a blower connected with the flow duct for generation of an air flow from the air inlet toward the air outlet, at least one refrigeration system, each of which includes at least one compressor, at least one condenser, at least one expansion valve, and at least one evaporator connected in a flow circuit containing a refrigerant, and wherein the at least one evaporator interacts with the air flow in the flow duct, and at least one variable frequency driver for power supply of at least one of the at least one compressor of the at least one refrigeration system.