Piston ring leakage

A reversible adiabatic process is known as isentropic. Thus, the two conditions are directly related. In actual practice compressors generate friction heat, give off heat, have valve leakage and have piston ring leakage. These deviations... 

The shaded area shown in Figure 25-9 is then the sum of the compression work wasted due to valve inefficiencies and piping pulsation problems. To this lost work must be added the detrimental effects of piston-ring leakage. 

In oxidizing, oil becomes thicker and it deposits carbon and gummy, resinous substances. These accumulate in the piston-ring grooves of reciprocating compressors and in the slots of vane-type units, and as a result, they restrict free movement of components and allow air leakage to develop. The deposits also settle in and around the valves of piston-type compressors, and prevent proper sealing. 

One effect of valve sleeve, piston ring, and cylinder wall wear is leakage of lubricating oil into the combustion chamber. When lubricating oil accumulates in the combustion chamber and bums with fuel, the exhaust smoke appears blue in color. Wear due to abrasion or corrosion has the same effect. At times, unbumed fuel can also appear as blue smoke if fuel droplets are finely dispersed in the exhaust. Blue smoke is a symptom of a mechanical problem rather than a fuel performance problem. 

Ratio of the actual flow rate (entering compressor) to the displacement rate is the volumetric efficiency T va- The volumetric efficiency is less than unity due to reexpansion of the compressed vapor in clearance volume, pressure drop (through suction and discharge valves, strainers, manifolds, etc.), internal gas leakage (through the clearance between piston rings and cylinder walls, etc.), valve inefficiencies, and due to expansion of the vapor in the suction cycle caused by the heat exchanged (hot cylinder walls, oil, motor, etc.). 

Labyrinth piston, 49 Labyrinth seal leakage, 532 Lantern ring, 74 Lapping block set, 335 Lateral critical speeds, 384 Leakage, seal, 532, 533, 534 Leland-Mueller rule, 26 Lift coefficient, 226 Liquid... 

In this work a symmetric piston seal with back-up rings is analysed. Calculations of oil film thickness, leakage flow and friction forces are carried out using the inverse hydro-dynamic theory. Measured pressure distributions, for either the whole seal including the back-up rings, for the soft seal element or for one back-up ring at a time are used as input data. 

---