Selecting a nitrogen booster for aircraft servicing requires calculating pressure ratios, drive air requirements, and flow capacity. Here's the engineering breakdown.
Pressure Ratio Calculation
The booster output pressure is calculated from the drive air pressure and the area ratio (air piston area / gas piston area). The theoretical output equals drive air pressure multiplied by the area ratio. If the cylinder inlet pressure already exceeds this theoretical output, the booster passes through without amplifying. Otherwise, a typical mechanical efficiency factor of about 0.85 is applied to get the actual boosted output.
Neometrix example: target output of 415 kg/cm² (407 bar) at 8 bar drive air requires an area ratio of 407 / (8 x 0.85) ≈ 60:1 -- which is why the cart uses a two-stage booster design.
Cylinder Depletion Analysis
Using the ideal gas law (P1V1 = P2V2, treating nitrogen as ideal at these pressures -- real-gas compressibility corrections apply above ~200 bar), the number of complete strut charges available from a cylinder is the total nitrogen volume (cylinder volume x initial pressure) divided by the nitrogen needed per charge (strut volume x target charge pressure).
Example: a 50 L cylinder at 200 bar charging a 10 L strut to 250 bar. Without a booster, the cylinder empties before the strut reaches its target pressure. With a booster, the cylinder can be used down to full depletion, and the booster tops up the residual pressure to the target.
The Neometrix Nitrogen Cart with Booster eliminates the "cylinder too empty to charge" problem -- the booster tops up to 415 kg/cm² regardless of residual cylinder pressure, as long as compressed air is available.
→ https://neometrixgroup.com/products/Nitrogen-cart-with-Booster
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