Category: Reciprocating Air Compressors

In order to balance the demand and supply of air, it is necessary to incorporate devices for the compressor control. The common methods of control are as follows: Example 12.1 A single-stage reciprocating air compressor is required to compress 72 m3 of air per minute from 15°C and 1.0 bar to 8 bar pressure. Find the…

If the air is cooled to the initial temperature, then there is no change in internal energy per kg mass of air, and all the work done is rejected to the cooling medium party during the compression process and the remaining after compression at constant pressure. Now, q1–2 = du + w1–2 However, du = 0 For a single-stage compressor, the heat…

The theoretical of p − V diagram for the single-stage reciprocating compressor is represented by 1–2–3–4–1 in Fig. 12.17. The actual indicator diagram is 1–2′–3–4′–1. The difference between the actual and theoretical indicator diagrams is due to the intake and discharge losses. The intake losses include the friction losses in pipe, friction loss in inlet valve, and valve inertia loss.…

The working of an air motor is similar to that of air compressor. High pressure air is admitted to the motor cylinder through a mechanically operated inlet valve and drives the piston in the forward direction. After a part of the stroke of the piston has been performed, the air supply is cut-off and the…

where A = area of the cylinder, m2 L = length of stroke, m N = rpm of compressor crank pm = mean effective pressure of air, Pa (N/m2) Theoretically, m.e.p. for a single-acting, single-stage compressor is, where ηv = volumetric efficiency of compressor Using indicator card, the m.e.p. is:

An aftercooler is used to cool the air coming out from the compressor before it enters the receiver. The air coming out from the compressor at pressure p3 is sufficiently hot at temperature T4 (Fig. 12.15). If this air is cooled in the aftercooler, then the pressure will remain p3, but the temperature will fall from T4 to T4′′. Therefore, the volume of…

Single-stage compression suffers from many disadvantages such as (i) handling of very high pressure range in one cylinder resulting in leakage past the piston, (ii) ineffective cooling of the gas, and (iii) necessitating robust construction of the cylinder to withstand the high delivery pressure. The volumetric efficiency of a single-stage compressor with fixed clearance decreases…

The volumetric efficiency of a compressor can be lowered by any of the following conditions: Figure 12.9 shows the variation in volumetric efficiency with clearance ratio (c), and the pressure ratio (p2/p1), and polytropic index of compression (n) (by changing one factor keeping the other two factors constant). The volumetric efficiency decreases with increase in both…

The volumetric efficiency of a reciprocating compressor is defined as the ratio of the actual free air delivered to the swept volume of the compressor. The free air delivered is (V1–V4), whereas the swept volume is (V1–Vc). Thus, Let  clearance ratio When referred to ambient conditions,

1 Required Work Without Clearance Consider the theoretical p−V diagram for a single-stage air compressor as shown in Fig. 12.7. The work done on air per cycle is represented by the area 1–2–3–4–1. Figure 12.7 p-V diagram without clearance W = area (a − b − 2 − 3 − a) + area (b − c − 1 − 2 − b) − area (a − c − 1 −…