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US 2007/0185592 A1Published application
Systems and methods for detecting suction valve closure
AssigneeGeneral Electric Company
InventorRodney Stansbury
Life of this patent
Estimating the term…
Abstract
This invention relates generally to the application of an algorithm to calculate a line that intersects a dynamic pressure waveform at two points. These points represent the point immediately prior to the suction valve closure event and the point directly after the event. The distance between each sample on the dynamic pressure waveform and the corresponding sample on the calculated line is determined. The suction valve closure event is identified with the sample located at the furthest distance from the calculated line.
Claims9
A method of identifying suction valve closure in a reciprocating compressor, comprising the steps of:
- receiving pressure and volume values for a pre-determined number of samples taken during a compression cycle;
- locating a first sample with a pressure value greater than the pressure value of the sample taken closest to 180 degrees of a crankshaft rotation;
- locating a second sample with a pressure value greater than or equal to a pressure value defined as [(the pressure value of the sample taken closest to 180 degrees of the crankshaft rotation−the pressure value of the sample taken closest to 0 degrees of the crankshaft rotation) * a factor less than 1]+the pressure value of the sample taken closest to 0 degrees of the crankshaft rotation;
- storing log scaled pressure values for each sample from the second sample through the first sample;
- storing log scaled volume values for each sample from the second sample through the first sample;
- determining a best-fit linear line running through a first location where the x-value is equal to the log scaled volume value of the second sample and the y-value is equal to the log scaled pressure value of the second sample and a second location where the x-value is equal to the log scaled volume value of the first sample and the y-value is equal to the log scaled pressure value of the first sample;
- determining a second line with one-half the slope of the best-fit linear line wherein the second line intersects said best-fit linear line at the first location;
- calculating coefficients of a first best-fit 6th-order polynomial running through a third location plotted where the x-value is equal to the log scaled volume value of the sample taken closest to 0 degrees of the crankshaft rotation and the second location;
- calculating y-values for each x-value in the first best-fit 6th-order polynomial between the third location and the second location such that the y-value is equal to Axˆ6+Bxˆ5+Cxˆ4+Dxˆ3+Exˆ2+Fx+G where values A, B, C, D, E, F, and G are the coefficients calculated for the first best-fit 6th-order polynomial;
- determining the x-value for a first target point with the maximum distance from the calculated x-y point on the first best-fit 6th-order polynomial to the corresponding point on the second line between the second sample and the first sample;
- defining a first target sample as the sample associated with the x-value of the first target point;
- calculating coefficients of a second best-fit 6th-order polynomial running through a fourth location where the x-value is equal to the log scaled volume value of the sample located a pre-determined number of samples prior to the first target sample and a fifth location where the x-value is equal to the log scaled volume value of the sample located a pre-determined number of samples after the first target sample;
- calculating y-values for each x-value in the second best-fit 6th-order polynomial between the fourth location and the fifth location such that the y-value is equal to Axˆ6+Bxˆ5+Cxˆ4+Dxˆ3+Exˆ2+Fx+G where values A, B, C, D, E, F, and G are the coefficients calculated for the second best-fit 6th-order polynomial;
- determining the x-value for a second target point with the maximum distance from the calculated x-y point on the second best-fit 6th-order polynomial to the corresponding point on the second line between the fourth location and the fifth location;
- defining a second target sample as the sample associated with the x-value of the second target point;
- identifying the suction valve closure event as being located at the crankshaft rotation angle corresponding to the second target sample.
13 more elements
A system for identifying suction valve closure in a reciprocating compressor, comprising:
- means for receiving pressure and volume values for a pre-determined number of samples taken during a compression cycle;
- means for locating a first sample with a pressure value greater than the pressure value of the sample taken closest to 180 degrees of a crankshaft rotation;
- means for locating a second sample with a pressure value greater than or equal to a pressure value defined as [(the pressure value of the sample taken closest to 180 degrees of the crankshaft rotation−the pressure value of the sample taken closest to 0 degrees of the crankshaft rotation) * a factor less than 1]+the pressure value of the sample taken closest to 0 degrees of the crankshaft rotation;
- means for storing log scaled pressure values for each sample from the second sample through the first sample;
- means for storing log scaled volume values for each sample from the second sample through the first sample;
- means for determining a best-fit linear line running through a first location where the x-value is equal to the log scaled volume value of the second sample and the y-value is equal to the log scaled pressure value of the second sample and a second location where the x-value is equal to the log scaled volume value of the first sample and the y-value is equal to the log scaled pressure value of the first sample;
- means for determining a second line with one-half the slope of the best-fit linear line wherein the second line intersects said best-fit linear line at the first location;
- means for calculating coefficients of a first best-fit 6th-order polynomial running through a third location plotted where the x-value is equal to the log scaled volume value of the sample taken closest to 0 degrees of the crankshaft rotation and the second location;
- means for calculating y-values for each x-value in the first best-fit 6th-order polynomial between the third location and the second location such that the y-value is equal to Axˆ6+Bxˆ5+Cxˆ4+Dxˆ3+Exˆ2+Fx+G where values A, B, C, D, E, F, and G are the coefficients calculated for the first best-fit 6th-order polynomial;
- means for determining the x-value for a first target point with the maximum distance from the calculated x-y point on the first best-fit 6th-order polynomial to the corresponding point on the second line between the second sample and the first sample;
- means for defining a first target sample as the sample associated with the x-value of the first target point;
- means for calculating coefficients of a second best-fit 6th-order polynomial running through a fourth location where the x-value is equal to the log scaled volume value of the sample located a pre-determined number of samples prior to the first target sample and a fifth location where the x-value is equal to the log scaled volume value of the sample located a pre-determined number of samples after the first target sample;
- means for calculating y-values for each x-value in the second best-fit 6th-order polynomial between the fourth location and the fifth location such that the y-value is equal to Axˆ6+Bxˆ5+Cxˆ4+Dxˆ3+Exˆ2+Fx+G where values A, B, C, D, E, F, and G are the coefficients calculated for the second best-fit 6th-order polynomial;
- means for determining the x-value for a second target point with the maximum distance from the calculated x-y point on the second best-fit 6th-order polynomial to the corresponding point on the second line between the fourth location and the fifth location;
- means for defining a second target sample as the sample associated with the x-value of the second target point;
- means for identifying the suction valve closure event as being located at the crankshaft rotation angle corresponding to the second target sample.
13 more elements
Dependencies are inferred from the claim text.