C919 HPV Valve Detailed Overview
Introduction to HPV
The High Pressure Valve (HPV) is a critical component in the engine bleed air system. It allows the introduction of bleed air from the high-pressure stage (10th stage) of the engine and provides pressure regulation and backflow prevention.
Operating Principle of the HPV
The HPV is controlled by the Integrated Air System Controller (IASC), based on the engine's bleed air requirements and the operational status of other air users (e.g., wing anti-ice system).
Bleed Air Source Selection
Normally, bleed air is extracted from the engine's intermediate pressure (IP) stage (4th stage), which minimizes the impact on engine performance.
When IP bleed air is insufficient, the HPV introduces high-pressure (HP) air.
IASC Control Logic
The IASC uses pressure and temperature data of the IP bleed air provided by the Engine Electronic Controller (EEC) to determine the control of the HPV.
Conditions for HPV Opening
- IP bleed air pressure is insufficient
- IP bleed air temperature is insufficient and the wing anti-ice system is active (indicating increased bleed air demand)
Conditions for HPV Closing
- IP bleed air pressure is sufficient and the wing anti-ice system is not active
- IP bleed air pressure and temperature are sufficient and the wing anti-ice system is active
Note: If HP bleed air temperature reaches 500°C, the HPV will automatically close. It will reopen when the temperature drops below 490°C.
Main Functions of the HPV
- Bleed Air Source Switching: Controls the opening and closing of high-pressure engine bleed air, enabling switching between intermediate and high-pressure bleed sources to meet varying demands. (Airbus OEB62 is roughly related to this—describing HPV detachment, inability to fully close the valve, and component debris falling downstream.)
- Downstream Pressure Limiting: The HPV limits the downstream pressure to a maximum preset value (typically 80 psi ±12 psi) to prevent overpressure damage to other systems.
- Backflow Prevention: Prevents reverse flow of bleed air from the downstream side back into the engine's high-pressure stage.
HPV Installation Location
The HPV is installed inside the engine nacelle core compartment, downstream of the Intermediate Pressure Check Valve (IPCKV) and upstream of the Pressure Regulating and Shutoff Valve (PRSOV).