US4156578A — Control of centrifugal compressors

Claim 1

Independent Claim 138 words

Apparatus comprising a centrifugal compressor; means for producing in operation a first signal which is functionally related to the ratio ##EQU27## where g is the acceleration due to gravity, h p is the polytropic head produced by the compressor, and Vc is the velocity of sound in inlet gas entering the compressor; means for producing in operation a second signal which is functionally related to Mn 2 , where Mn (the Mach Number) is the ratio of the flow velocity V of the gas at the inlet to the compressor to the velocity of sound Vc therein; and control means for preventing surging of the compressor, said control means being controlled by said first and second signals, and ensuring that in operation ##EQU28## where K and k are parameters whose values depend on the characteristics of the compressor.

Claim 2

Dependent Claim 138 words

Apparatus comprising a centrifugal compressor; means for producing in operation a first signal which is functionally related to the ratio ##EQU27## where g is the acceleration due to gravity, h p is the polytropic head produced by the compressor, and Vc is the velocity of sound in inlet gas entering the compressor; means for producing in operation a second signal which is functionally related to Mn 2 , where Mn (the Mach Number) is the ratio of the flow velocity V of the gas at the inlet to the compressor to the velocity of sound Vc therein; and control means for preventing surging of the compressor, said control means being controlled by said first and second signals, and ensuring that in operation ##EQU28## where K and k are parameters whose values depend on the characteristics of the compressor.

Claim 3

Dependent Claim 41 words

Apparatus as claimed in claim 1 in which the means for producing the first signal is responsive to the ratio P 2 /P 1 , where P 1 is the compressor inlet pressure and P 2 is the compressor outlet pressure.

Claim 4

Dependent Claim 58 words

Apparatus as claimed in claim 1 in which the means for producing the second signal is responsive to the ratio Δp/n P 1 where Δp is the differential pressure across a throttling member disposed in an inlet duct of the compressor, n is the polytropic exponent of the said gas, and P 1 is the compressor inlet pressure.

Claim 5

Dependent Claim 12 words

Apparatus as claimed in claim 3 in which n is a constant.

Claim 6

Dependent Claim 166 words

Apparatus comprising a centrifugal compressor; means for producing in operation a first signal which is functionally related to the ratio ##EQU29## where g is the acceleration due to gravity, h p is the polytropic head produced by the compressor, and Vc is the velocity of sound in inlet gas entering the compressor; means for producing in operation a second signal which is functionally related to Mn 2 , where Mn (the Mach Number) is the ratio of the flow velocity V of the gas at the inlet of the compressor to the velocity of sound Vc therein; control means which are controlled by said first and second signals and which ensure that in operation ##EQU30## where K and k are parameters whose values depend on the characteristics of the compressor, and a duct, having a control valve therein, which communicates with the outlet end of the compressor, the said control means controlling opening and closing of the control valve, whereby surging of the compressor is avoided.

Claim 7

Dependent Claim 166 words

Apparatus comprising a centrifugal compressor; means for producing in operation a first signal which is functionally related to the ratio ##EQU29## where g is the acceleration due to gravity, h p is the polytropic head produced by the compressor, and Vc is the velocity of sound in inlet gas entering the compressor; means for producing in operation a second signal which is functionally related to Mn 2 , where Mn (the Mach Number) is the ratio of the flow velocity V of the gas at the inlet of the compressor to the velocity of sound Vc therein; control means which are controlled by said first and second signals and which ensure that in operation ##EQU30## where K and k are parameters whose values depend on the characteristics of the compressor, and a duct, having a control valve therein, which communicates with the outlet end of the compressor, the said control means controlling opening and closing of the control valve, whereby surging of the compressor is avoided.

Claim 8

Dependent Claim 28 words

Apparatus as claimed in claim 5 in which the said duct is a by-pass duct which is connected across the compressor between the inlet and outlet ends thereof.

Claim 9

Dependent Claim 32 words

Apparatus as claimed in claim 6 in which the by-pass duct passes through a heat exchanger so that gas flowing from the said outlet end to the said inlet end is cooled.

Claim 10

Dependent Claim 22 words

Apparatus as claimed in claim 5 in which the said duct is a venting duct whose outlet end is open to atmosphere.

Claim 11

Independent Claim 123 words

A method of controlling a centrifugal compression producing a first signal which is functionally related to the ratio ##EQU31## where g is the acceleration due to gravity, h p is the polytropic head produced by the compressor, and Vc is the speed of sound in inlet gas entering the compressor; producing a second signal which is functionally related to Mn 2 , where Mn (the Mach Number) is the ratio of the flow velocity V of the gas at the inlet to the compressor to the velocity of sound Vc therein; and employing said first and second signals to prevent surging of the compressor by ensuring that ##EQU32## where K and k are parameters whose values depend on the characteristics of the compressor.

Claim 12

Independent Claim 123 words

A method of controlling a centrifugal compression producing a first signal which is functionally related to the ratio ##EQU31## where g is the acceleration due to gravity, h p is the polytropic head produced by the compressor, and Vc is the speed of sound in inlet gas entering the compressor; producing a second signal which is functionally related to Mn 2 , where Mn (the Mach Number) is the ratio of the flow velocity V of the gas at the inlet to the compressor to the velocity of sound Vc therein; and employing said first and second signals to prevent surging of the compressor by ensuring that ##EQU32## where K and k are parameters whose values depend on the characteristics of the compressor.

Claim 13

Dependent Claim 14 words

A method as claimed in claim 9 in which it is arranged that ##EQU33##

Claim 14

Dependent Claim 48 words

A method as claimed in claim 9 in which it is arranged that ##EQU34## where Δ p is the differential pressure across a throttling member disposed in an inlet duct of the compressor, P 1 is the compressor inlet pressure, and P 2 is the compressor outlet pressure.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1982-05-28	1982-11-27	1983-05-29	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1986-05-28	1986-11-27	1987-05-29	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1990-05-28	1990-11-27	1991-05-29	$7700.00	Window Closed / Lapsed

Control of centrifugal compressors

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