Liquid Ring Pumps for Aerospace Industry
The scope of the aerospace industry encompasses military, civil, and industrial applications. Liquid Ring Pumps and Compressors are vital for creating vacuum to achieve the various pumping and compressing objectives required in the aerospace industry.
Any of the aluminum alloys used for aerospace construction are heat treated before they are used. Heat treatment is used to reverse the effects of work hardening without changing its shape. As a metal is being rolled, pressed, and finished, a considerable amount of internal stresses builds within the crystal structure of the metal.
It is water-cooled by sprinklers and solidifies further while undergoing these processes, so these internal stresses “lock in”, causing internal tensions and compressions that make the metal harder, but more brittle. For something that needs to be subjected to extreme drag forces, such as aluminum alloy in the aerospace industry, the alloy needs to be ductile and malleable.
One form of heat treatment is annealing. This is a process where the metal is reheated before its melting point to release its internal stresses, then cooled at a controlled rate. Oxygen causes rusting and scaling, increasing the brittleness. Dissolved hydrogen tends to move towards the grain boundaries of the metal crystal structure and forms voids once the metal solidifies, creating cavitation erosion within the metal and reducing its structural integrity. Hydrogen cavitation erosion can occur with very small amounts of hydrogen. Other gasses in the air like nitrogen do not affect the metal to the degree of concern as oxygen and hydrogen, but still form voids in molten metal when it solidifies.
For bright annealing to have its degassing effect, the vacuum pressure in the annealing chamber needs to be deep. The water used to cool the metal after casting remains on the surface of the metal and evaporates during the annealing process. The vacuum pump used for bright annealing must pull a strong vacuum while taking the moisture away from the annealed metal. This will increase wear and shorten the service life if an oil-lubricated or dry-running pump is used. A wet-running pump that has minimal friction from metal-to-metal contact, strong vacuum pressure, and continuous suction to perform uniform degasification is required. For this, the liquid ring vacuum pump fits the bill. The liquid ring vacuum pump condenses vapor within its chambers, allowing more air to evacuate the annealing chamber and fill the pump. This translates to increased mass transfer rate, which boosts the efficiency of the system. The vacuum pressure of a liquid ring multi-pump or booster-pump system can reach and maintain the ultrahigh levels required for the process. The liquid ring vacuum pump is robust and has few parts, so it will be in long-lasting service with quick repair and minimal maintenance and lubrication.
Liquid ring vacuum pumps are used for wind tunnels as well. Strong continuous suction is required for proper data collection when testing a model in a vacuum wind tunnel. The liquid ring is self-priming, achieving its highest level of vacuum pressure in a short amount of time.
A wind tunnel vacuum pump needs to have precise control over pressure levels in the tunnel. The level and rate at which vacuum is pulled determines the simulated altitude conditions in the chamber, so they cannot deviate from the acceptable range.
Altitude chambers are regularly used for low-pressure endurance testing in aeronautical equipment, athletes, pilots, and military forces. It can become difficult to breathe when at such high altitudes, and the low pressure becomes disorienting. Training to adapt to such situations allows for safer flights and smoother military operations. Equipment needs to hold its structure and strength in all pressures during flight, so it needs to be tested in said altitude chambers. A vessel or room is evacuated to a certain extent by a vacuum pump. This extent is measured by elevation from sea level, as each elevation value corresponds to a different atmospheric pressure. The negative pressure is sustained throughout the training, whether it be simply sitting in it or performing flight training for pilots and military officers or actively performing endurance training for athletes like boxers and runners.
The constant and precise suction of the liquid ring vacuum pump, paired with long service life and minimal maintenance, makes it an optimal option for the construction of altitude chambers for all purposes.