# US 8,751,170 B2 · Method for determining the fatigue of a pump rotor of a gas turbopump

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- Number: US 8,751,170 B2
- Document ID: US8751170B2
- Status: Granted
- Kind: B2
- Application number: 12/528,210
- Filed: 2008-01-16
- Published: 2011-02-24
- Granted: 2014-06-10
- Earliest claimed: 2007-02-24
- Assignees: Oerlikon Leybold Vacuum GmbH
- Applicants: Roland Blumenthal; Michael Froitzheim; Thomas Palten; Dieter Bohry; Manfred Kiefer
- Inventors: Roland Blumenthal; Michael Froitzheim; Thomas Palten; Dieter Bohry; Manfred Kiefer
- Web page: https://patentgrep.com/patent/US8751170B2

## CPC

- G01M 5/00: Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings (G01M9/00 takes precedence)
- F04B 23/00: Pumping installations or systems (pumps characterised by combination with, or adaptation to, specific driving engines or motors F04B17/00)
- F04D 19/042: {Turbomolecular vacuum pumps}
- F04D 27/001: {Testing thereof; Determination or simulation of flow characteristics; Stall or surge detection, e.g. condition monitoring}
- F04D 29/059: Roller bearings
- G06F 17/40: Data acquisition and logging (for input to computer G06F3/00)
- G16Z 99/00: Subject matter not provided for in other main groups of this subclass
- G01M: TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- F04B: POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS (machines for liquids, or pumps, of rotary-piston or oscillating-piston type F04C; non-positive-displacement pumps F04D; pumping of fluid by direct contact of another fluid or by using inertia of fluid to be pumped F04F)
- F04D: NON-POSITIVE-DISPLACEMENT PUMPS (engine fuel-injection pumps F02M; ion pumps H01J41/12; electrodynamic pumps H02K44/02)
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)
- G16Z: INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR SPECIFIC APPLICATION FIELDS, NOT OTHERWISE PROVIDED FOR

## Abstract

A method for determining the fatigue of the pump rotor of a gas turbopump comprises the following method steps: continuous determination of the rotational speed (n) of the pump rotor, determination of the local rotational speed maxima and minima of a temporal rotational speed profile under consideration, association of the rotational speed maxima and minima with each other to form pairs, determination of a pair fatigue value (L) for each of the rotational speed pairs, and accumulation of all pair fatigue values (L) to form a total fatigue value (Ltot). In this manner it is possible to determine the cyclic stress for the pump rotor of a vacuum pump and to include it in the calculation of a total fatigue value.

## Claims

### Claim 1

A method for determining the fatigue of the pump rotor of a gas turbopump, comprising the following method steps:
continuously determining a rotational speed of the pump rotor,
determining local rotational speed maxima and minima of a temporal rotational speed profile under consideration,
associating the rotational speed maxima and minima with each other to form pairs,
determining a pair fatigue value for each of the rotational speed pairs,
accumulating the pair fatigue values to form a total fatigue value, and
outputting a fatigue signal in response to the total fatigue value exceeding a total fatigue limit value in order to determine a fatigue state.

### Claim 2 (depends on 1)

The method for determining the fatigue of the pump rotor of a gas turbopump of claim 1, wherein the local rotational speed maxima and minima are zero crossings of the temporal profile of the rotor acceleration.

### Claim 3 (depends on 1)

The method for determining the fatigue of the pump rotor of a gas turbopump of claim 1, wherein the step of determining the rotational speed of the rotor is performed at constant time intervals.

### Claim 4 (depends on 1)

The method for determining the fatigue of the pump rotor of a gas turbopump of claim 1, wherein the pair fatigue value is determined by a polynomial that is at least square.

### Claim 5 (depends on 1)

The method for determining the fatigue of the pump rotor of a gas turbopump of claim 1, wherein the step of determining the creep fatigue values includes:
continuously determining the creep fatigue values from the rotational speed of the rotor and a rotor temperature and the step of accumulating the pair fatigue values includes continuously accumulating the pair fatigue values to form the total fatigue value.

### Claim 6 (depends on 1)

The method for determining the fatigue of the pump rotor of a gas turbopump of claim 1, wherein the step of determining the pair fatigue value includes evaluating at least a cubic polynomial.

### Claim 7 (depends on 1)

The method for determining the fatigue of the pump rotor of a gas turbopump of claim 1, further including:
providing an alarm in response to the fatigue signal exceeding the total fatigue limit value.

### Claim 8 (depends on 1)

The method for determining the fatigue of the pump rotor of a gas turbopump of claim 1, further including:
storing the local rotational speed maxima and minima in one or more memories.

### Claim 9 (depends on 1)

The method for determining the fatigue of the pump rotor of a gas turbopump of claim 1, wherein the steps of determining local rotational speed maxima and minima of a temporal rotational speed profile under consideration, associating the rotational speed maxima and minima with each other to form pairs, determining a pair fatigue value for each of the rotational speed pairs, accumulating the pair fatigue values to form a total fatigue value, and outputting a fatigue signal in response to the total fatigue value exceeding a total fatigue limit value are performed with a computer.

### Claim 10 (depends on 1)

The method for determining the fatigue of the pump rotor of a gas turbopump of claim 1, wherein the steps of determining local rotational speed maxima and minima of the temporal rotational speed profile, associating the rotational speed maxima and minima with each other to form pairs, determining a pair fatigue value for each of the rotational speed pairs, accumulating the pair fatigue values to form a total fatigue value, and, outputting a fatigue signal in response to the total fatigue value exceeding a total fatigue limit value are performed with a computer.

### Claim 11 (depends on 1)

The method for determining the fatigue of the pump rotor of a gas turbopump of claim 1, wherein determining the pair fatigue value includes determining at least one characteristic stress of the rotational speed pairs.

### Claim 12 (depends on 11)

The method for determining the fatigue of the pump rotor of a gas turbopump of claim 11, wherein the characteristic stress is a mean stress of the respective rotational speed pair.

### Claim 13

An apparatus for determining fatigue of a pump rotor of a turbopump comprising one or more processors programmed to:
continuously receive a rotational speed of the pump rotor,
determine local rotational speed maxima and minima of a temporal rotational speed profile under consideration,
associate the rotational speed maxima and minima with each other to form pairs,
determine a pair fatigue value for each of the rotational speed pairs, and
accumulate the pair fatigue values to determine a fatigue state.

### Claim 14 (depends on 13)

The apparatus for determining a fatigue of a pump rotor of a turbopump of claim 13, wherein the one or more processors are further programmed to:
output a fatigue signal in response to the total fatigue value exceeding a total fatigue limit value.

### Claim 15

A method for determining the fatigue of the pump rotor of a gas turbopump comprising the following method steps:
with a speed sensor device, continuously determining a rotational speed of the gas turbopump rotor and outputting a temporal rotation speed profile;
determining local rotational speed maxima and minima of the temporal rotational speed profile;
associating the rotational speed maxima and minima with each other to form pairs;
determining a pair fatigue value for each of the rotational speed pairs;
accumulating the pair fatigue values to form a total fatigue value; and
at an output, outputting a fatigue signal in response to the total fatigue value exceeding a total fatigue limit value in order to determine a fatigue state.