Temperature is a fundamental parameter in describing the operational state of engine bearings. Monitoring the temperature of engine bearings in use has become a standard feature for many engines.
As a critical monitoring parameter for the operation of motors and their bearings, analysis of this parameter is a vital method for evaluating the operational status and failure analysis of motors and bearings.
From the perspective of engine bearing temperature analysis, firstly, in terms of time, engine bearing temperature is a value that emerges over time. Therefore, temperature analysis can be approached from a time domain perspective.
Furthermore, considering the engine as a whole and the bearing as a component, there will always be a temperature distribution at any given time. Consequently, the temperature analysis of engine bearings can also be started from the perspective of temperature distribution.
Time domain analysis of engine bearing temperature
Time domain engine bearing temperature analysis is, in essence, the study of how engine bearing temperature changes over time. The impact of time on temperature is a more direct reflection of changes in bearing condition, load status and environmental conditions over time.
For a motor bearing in normal use, when the motor is not running, the temperature of the bearing is the same as that of the motor housing and shaft. At this point, the engine is not running and does not generate heat, and the bearing is not working so it does not heat up either. Thus, the engine bearing temperature aligns with the ambient temperature. This provides a reference point for motor bearing temperature, considering factors such as air temperature and heat conducted by adjacent equipment.
In the case of a running motor, all parts (including windings, seals, bearings, etc.) will generate heat during operation. As part of the overall mechanism, there is heat conduction between them.
At this time, if the engine load increases or a component malfunction occurs, it will cause a change in the engine bearing temperature. This change in bearing temperature is a means of time domain analysis for engine bearing temperature.
Firstly, engineers, through temperature monitoring, notice that the engine bearing temperature is higher than its historical average, indicating the need to solve abnormal temperature problems.
As mentioned previously, component failure is one of the reasons, but not the only one, for this temperature change. Therefore, diagnosing these causes forms the basis for fault diagnosis and analysis.
Years ago, I came across a complaint about an engine bearing where the normal bearing temperature was 50 degrees, but the temperature of an engine end bearing reached 60 degrees. Engineers suggested possible failures based on changing engine bearing temperatures.
However, at the scene, they discovered that the drive end of the engine bearing was located in the engine's cooling air outlet, where the temperature was already 56 degrees. In other words, the motor bearing operating in an environment above 50 degrees could not maintain its temperature at 50 degrees. This assessment was made by observing the temperature change and considering the ambient temperature.
Furthermore, big data technology offers more possibilities for analyzing the temperature of engine bearings in the time domain. For example, whether the motor bearing temperature change trend under load is in line with the general trend, and whether the motor temperature change trend matches the expected load change trend.
Analysis of the temperature distribution of engine bearings
Our previous discussion focused on analyzing how the temperature of isolated points on engine bearings changes over time, a concept known as time-domain temperature analysis. In reality, for any equipment as a whole, when it operates and generates heat, a specific distribution is presented at different locations of the same equipment due to heat transfer.
For an engine, such heat distribution manifests a certain pattern under normal conditions, while under abnormal conditions, the heat distribution may deviate from this “normal distribution”.
Before proceeding with the analysis of the temperature distribution of engine bearings, it is essential to understand whether different parts of the engine function as a “heat source” or “thermal resistance” during operation.
The transition of a part from “thermal resistor” to “heat source” during engine operation may indicate a problem with that part.
Engineers can use thermal imaging to analyze the temperature distribution of an engine. However, often, even without thermal imaging equipment, the relationship between temperatures at different measurement points can reflect certain heat distribution patterns.
A common question is whether the temperature of the bearing inside the engine is higher than that of the engine body itself.
To be more precise, is the bearing a heat source for the engine?
Understanding the “normal distribution” of engine bearings is essential to answer this question.
Initially, as the bearings rotate, friction occurs internally, generating heat. Therefore, in fact, bearings serve as one of the heat sources during engine operation.
However, this answer may not be comprehensive. Although bearings are a source of heat, their temperature is not necessarily higher than that of the engine. In fact, bearings are a secondary source of heat within the engine, with their temperatures largely influenced by the engine.
In other words, bearing temperature should not be the main contributor to increased engine temperature. This statement represents the concept under “normal conditions”. Any discrepancy between the actual engine temperature distribution and this statement should be a cause for concern.
