Views: 0 Author: Site Editor Publish Time: 2022-08-31 Origin: Site
The A320 aircraft air conditioning system mainly consists of four major parts: regional temperature control, electronic equipment ventilation, pressurization system, cargo compartment ventilation/heating (optional). The cooling air is provided by two refrigeration components. The components are based on the principle of turbocharged refrigeration, and their performance directly affects the comfort of the cabin and cockpit.
The refrigeration components mainly include: primary and secondary heat exchangers, reheaters, condensers, water separators, ACM, flow control valve (FCV), bypass valve (BPV), and trim hot air pressure regulating valve.
In the high temperature weather in summer, due to the high temperature of the ground ram air, higher cooling efficiency is required to ensure that the outlet temperature of the air conditioning components can meet the demand in the cabin. Once the air conditioning performance of the aircraft gradually deteriorates, although there is no fault information, the cabin/cockpit temperature will be high, which will lead to the delay of the pre-flight/transit flight of the aircraft. Therefore, necessary air conditioning parameter monitoring and early warning are needed, preventive troubleshooting and replacement of poor performance components are required to improve the cooling efficiency of the air conditioning.
The cooling efficiency of A320 air conditioning components is mainly reflected in the high temperature environment on the ground. Therefore, for all collected parameters, ensure that the aircraft is on the ground, APU/engine bleed air, and the ambient temperature is above 25°C.
For Airbus series aircraft air-conditioning parameters mainly come from ECS 19 messages, you can check the meaning of relevant parameters through ISI 21.00.00031. You can also obtain real-time parameters by creating ACARS messages, and decode QAR parameters for monitoring.
Because there is no direct connection between the performance and parameters of each component in the air-conditioning assembly, it is impossible to directly judge the performance through the parameters. Then, by screening the main parameters and setting the normal range of parameters for monitoring:
Precooler outlet temperature--PIT
Ram inlet --RI
Pack compressor outlet temperature-COT
Pack water extract temperature-TW
Pack outlet temperature-TP
1. TP monitoring range: TP<15℃
Because the outlet temperature in the cooling state of the air conditioner is determined by the required temperature of the mixing chamber, and is adjusted by the opening of RI and PBV, when the conditions are RI fully open and PBV fully closed, the maximum cooling capacity is obtained. At this time, for A320 series aircraft TP<15℃ under normal flow.
2. COT monitoring range: 110°C < COT < 180°C.
The COT value depends on the opening of the RI, the secondary heat exchange performance and the compressor work. When the RI is adjusted at normal opening, the COT temperature is less than 180°C; otherwise, if the RI is fully opened and the COT cannot be guaranteed to be lower than 180°C, it is concluded that the performance of the upstream components is degraded. Then the COT monitoring interval can be set as 110°C < COT < 180°C.
3. PF monitoring interval: 45% < PF < 65%
According to the flow control principle in ISI 21.00.00031, the air-conditioning flow varies with the height of the cabin, and is basically at a constant value in the ground state. Since the parameter value is taken when the aircraft is on the ground, the interval 45% < PF < 65%
4. ΔT1 and ΔT1 monitoring interval
According to the ideal state given by Airbus, when the APU and the engine are bleed, the temperature distribution of the hot air after flowing through each component, the temperature drop between PIT, COT and TW can approximately indirectly reflect the secondary heat exchanger ( PHX) and main stage heat exchanger (MHX) performance (as shown below). Therefore, according to the actual maintenance experience, you can set:
ΔT1 =PHX= PIT – COT > 15 ℃
ΔT2 =MHX= COT – TW > 80 ℃
(1) PHX and MHX performance are indirectly reflected by ΔT1 and ΔT2.
(2) The above values are all reference values, and factors such as OAT, humidity, and bleed air state at that time need to be considered.
Judging faults based on parameter early warning
The above description is the normal monitoring interval of each parameter. Once the threshold is exceeded, a corresponding warning can be set. However, the overrun of a parameter does not directly point to a component, and a comprehensive principle analysis is required to determine the fault. The following is the actual verification case:
Case 1: Early warning of ΔT1<15℃ for the right component of an aircraft, it is verified that COT is close to 180℃ for a long time, and other parameters are normal. It was judged that the heat exchange performance of PHX was poor, resulting in a decrease in temperature. After replacing PHX, there was a turning point in ΔT1, which was accompanied by a decrease in COT.
Case 2: When the left component of an aircraft is working on the ground, the flow rate PF=36 (61 on the right side) gives an early warning. Verify that RI is fully open, TP and other parameters are normal. It is judged that the flow reduction may be caused by blockage, and the blockage of hot air is usually in the reheater and condenser (the grille is relatively dense). The condenser was removed and found to be clogged with internal lint.
Case 3: The left component of an aircraft has an early warning of TP>15℃, and it is verified that ΔT1, ΔT2, and COT are all at normal levels. The parameters are normal. It was judged that it might be a problem downstream of the heat exchanger. As a result, it was found that there was an air leak between the condenser and the water separator. After replacing the sealing ring, the TP improved below 15 °C.