System and method of determining centrifugal turbomachinery remaining life
View Patent ↗A centrifugal turbomachine includes an impeller and a speed sensor arranged to detect a speed associated with an impeller speed. A temperature sensor is arranged to detect a temperature associated with an impeller exit temperature. A controls system has impeller parameters, which includes the impeller speed and exit temperature. A calculation methodology is used to mathematically manipulate the impeller parameters to determine a remaining life of the impeller. A program response, such as a warning indication, is triggered by the control system in response to the remaining life reaching a threshold. The controls system monitors the speed and temperature of the impeller. The controls system internally calculates the remaining life based upon the speed and the temperature. In one example, a change in remaining life is calculated in response to a change in speed that results in an impeller stress that exceeds an endurance strength for the impeller.
1. A turbomachine comprising:
an impeller;
a speed sensor arranged to detect a speed associated with an impeller speed;
a temperature sensor arranged to detect a temperature associated with an impeller exit temperature;
a controls system having impeller parameters including impeller speed and exit temperature, a calculation methodology mathematically manipulating the impeller parameters to determine a remaining life of the impeller, and a programmed response triggered by the controls system in response to the remaining life reaching a threshold; and
wherein the impeller parameters include stress characteristics of the impeller having fatigue strength modification factors including at least one of impeller surface finish, load on an impeller area, and size of an impeller feature.
2. The centrifugal turbomachine according to claim 1 , wherein said speed sensor detects a speed of a shaft supporting the impeller.
3. The centrifugal turbomachine according to claim 1 , wherein the temperature sensor is arranged near an impeller exit.
4. The centrifugal turbomachine according to claim 1 , wherein the calculation methodology is based upon Palmgren-Miner cycle-ratio summation.
5. The centrifugal turbomachine according to claim 1 , wherein the calculation methodology is based upon Manson's approach.
6. The centrifugal turbomachine according to claim 1 , wherein the impeller parameters include material properties of the impeller.
7. The centrifugal turbomachine according to claim 1 , wherein the stress characteristics include at least one of maximum impeller stress as a function of speed, fatigue strength as a function of temperature, stress ratio, and cycles to failure relative to maximum stress.
8. The centrifugal turbomachine according to claim 1 , wherein the programmed response is a warning indication.
9. A method of calculating impeller remaining life comprising the steps of:
a) monitoring a speed of an impeller;
b) monitoring a temperature associated with the impeller;
c) iteratively calculating a remaining life of the impeller based upon a change in the speed and the temperature;
d) producing a warning indication when the remaining life reaches a threshold; and
e) avoiding an undesired change in speed when the remaining life reaches the threshold.
10. The method according to claim 9 , wherein step c) includes iteratively calculating remaining life at a rate corresponding a stress cycle produced by the change in speed.
11. The method according to claim 10 , wherein step c) includes calculating a change in life attributable to the change in speed.
12. The method according to claim 9 , wherein step c) is based upon calculating the remaining life as a function of a stress ratio.
13. The method according to claim 9 , wherein step c) uses a maximum design stress of the impeller.
14. A turbomachine comprising:
an impeller;
a speed sensor arranged to detect a speed associated with an impeller speed;
a temperature sensor arranged to detect a temperature associated with an impeller exit temperature; and
a controls system having impeller parameters including impeller speed and exit temperature, a calculation methodology mathematically manipulating the impeller parameters to determine a remaining life of the impeller based upon changes in the impeller speed, and a programmed response triggered by the controls system in response to the remaining life reaching a threshold, the programmed response including avoidance of undesired changes in the impeller speed.
15. The turbomachine according to claim 14 , wherein the avoidance of undesired changes in the impeller speed includes operating the impeller at a fixed speed.
16. The turbomachine according to claim 15 , wherein the fixed speed includes a full speed condition.