AIR COMPRESSORS - PERFORMANCE CHARACTERISTICS

Question 1. Using FIGURE 1 (reproduced below) select suitable compressors for each of the following delivery requirements:
(a) an output pressure of 1000 bar at a capacity of 50 m³ h^-1

(b) a capacity of 120 000 m³ h^-1 at a pressure of 50 bar

(c) a capacity of 500 m³ h^-1 at a pressure of 6 bar.

FIG. 1 (Reproduced)

Question 2. A Compressor delivers 0.5 m³ per minute of compressed air at a pressure of 5 bar absolute. Calculate the free air delivery (NTP) of the compressor. The delivery temperature is 80°C.

Question 3. A compressor compresses air from 1 bar to 9 bar absolute. If the clearance and stroke length are 5 mm and 80 mm respectively, calculate the minimum value of the polytropic index of compression required to produce a volumetric efficiency of 70%.

Question 4. What effect will increasing the delivery pressure have on the volumetric efficiency of a single-stage compressor?

Question 5. An air compressor has a total inlet volume (swept volume + clearance) of 0.04 m³, a piston diameter of 400 mm and a stroke length of 300 mm. Calculate the maximum pressure ratio if the volumetric efficiency is not to fall below 80% and the index of compression is 1.25.