[Q&A Question 294] 11.8.2017

Changes in compression ratio, changes in inlet temperature, temperature, pressure, and flow rate of cooling water, low heat transfer efficiency due to scaling in the working chamber jacket, and the influence of ambient temperature, etc.

Factors that affect the outlet temperature include: inlet air temperature, pressure ratio, and compression index.

Compression ratio: the higher it is, the higher the outlet temperature； Cooling water, return water temperature, and exhaust temperature are proportional to each other ； Air valve leakage, exhaust valve leakage, low outlet pressure, high intake temperature, relatively low exhaust temperature ； For compression media, the higher the molecular weight, the higher the exhaust temperature

Abnormal exhaust valve operation is caused by excessive temperature of the compressed gas； The influence of inhalation temperature levels ； Damage to the next stage’s suction valve or improper sealing has an impact ； The level of suction pressure affects the compression ratio ； The previous cooler did not have good cooling performance, which was affected by the inlet temperature.

The higher the compression ratio, the higher the outlet temperature; another factor is whether cooling water is in use

Intake air temperature, pressure ratio, and compression index. Possible faults: 1. Low intercooling efficiency, or excessive scale buildup in the intercooler that hinders heat exchange; as a result, the intake temperature in the subsequent stages will be high, and so will the exhaust temperature. 2. Air leakage from the valve and piston rings not only leads to an increase in exhaust temperature but also causes changes in the pressure between stages; whenever the pressure ratio is higher than normal, it results in an increase in exhaust temperature. 3. For water-cooled machines, a lack of water or insufficient water volume can cause the exhaust temperature to rise.

1. A decrease in the speed of the prime mover that drives the compressor (usually a motor), either due to too low voltage or a reduced power grid frequency, or a loose belt that results in lower compressor speed, will all lead to a reduction in the volume of exhaust gas； 2. If the clearance volume is too high compared to the design value, the exhaust volume will decrease significantly ； 3. An increase in inhalation resistance (including the resistance of the air filter, the inhalation pipes, and the air valves) reduces the pressure of the gas inside the intake cylinder, leading to a decrease in the amount of air drawn in, and consequently a reduction in the exhaust volume as well ； 4. Insufficient cooling of the cylinder leads to an increase in the cylinder wall temperature, which heats the air drawn in. This causes the air to expand, resulting in a decrease in the amount of air drawn in; this in turn also leads to a reduction in the amount of exhaust gas expelled ； 5. An increase in external leakage from the compressor will directly reduce the exhaust volume. External leaks are divided into two categories: one is when gas escapes directly into the atmosphere or the first-stage intake pipeline; such leaks occur outside the compressor and clearly constitute external leaks ； Secondly, during the expansion or intake process in the first-stage cylinder, the gas that leaks from the high-pressure stage into the first-stage cylinder through the first exhaust valve, due to the poor sealing of this exhaust valve, also constitutes an external leakage. External leaks often occur at locations such as the packing box, piston rings, and intake and exhaust valves. Therefore, if these areas are not properly sealed, it will lead to external leakage of compressed gas, affecting the compressor’s displacement.

The influencing factors include: ① Inlet temperature: A higher inlet temperature results in a higher outlet temperature. ②Compression ratio: A higher compression ratio results in an increased outlet temperature. ③Gas adiabatic index: A higher adiabatic index results in a higher outlet temperature. ④Cylinder lubrication condition: Poor lubrication, high outlet temperature. ⑤Cooling effect: If the water temperature is high or the water flow is poor, the outlet temperature will be high.

1. The inhaled gas is too hot; adjust the expansion valve. 2. Compressor failure: (1) The exhaust valve disc is broken; the cylinder head needs to be opened ； (2) The safety bypass valve is leaking; check and inspect or adjust the exhaust valve disc.