US 10,254,719 B2Granted

Method and apparatus for surge prevention control of multistage compressor having one surge valve and at least one flow measuring device

AssigneeStatistics & Control, Inc.

InventorsVadim Shapiro, Andriy Nyemchyn, Alex Komm

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Abstract

A method and apparatus for surge prevention control for multistage compressors with at least two stages, at least one flow measuring device, and one overall surge recycle valve is disclosed. Furthermore, a method of accurate calculation of surge limit line for overall multistage compressor using one available flow measuring device is also disclosed. The method of surge prevention calculates multistage compressor's surge limit line as a product of individual stages surge limit lines that differs from those revealed in the prior art. This method allows accurate calculation of the distance of operating point to surge limit line that takes in account surge lines of all stages and allows reliable surge prevention control.

Claims4

Dependent claims

An apparatus for surge prevention control, said apparatus comprising:

multistage compressors with at least two stages, at least one flow measuring device, and one surge valve, said stages each being equipped with a PID surge prevention controller and said multistage compressors being capable of performing at least a six-step method comprising processor-executed steps using mathematical capabilities implementing control of controller, the method steps comprising:
first, determining a surge limit line set point of each compressor stage (ksuv) as a function of surge conditions reduced polytrophic head
(
R
c
σ
-
1
σ
)
and reduce volumetric flow rate
(
dP
v
P
)
⁢
:
k
suv
=
1
dP
ssu
*
P
v
2
*
T
ssu
*
Z
ssu
P
ssu
*
T
v
*
Z
v
*
R
csu
σ
-
1
σ
,
where Rcsu is compressor pressure ratio at surge conditions, Pssu is compressor pressure ratio at surge conditions, dPssu is surge test pressure differential across the at least one flow measuring device, Tssu is surge test temperature at the at least one flow measuring device, Zssu is surge test compressibility at the at least one flow measuring device, Pv is surge test pressure in a compressor stage suction, Tv is surge test temperature in the compressor stage suction, and Zv is surge test compressibility in the compressor stage suction;
second, calculating each stage differential pressure surge limit set point for current operating conditions as a function of the surge limit line set point of each compressor stage (ksuv) and current measured pressures and temperatures:
dP
ssui
=
1
k
suv
*
P
v
2
*
T
*
Z
P
*
T
v
*
Z
v
*
R
ci
σ
-
1
σ
,
where Rci is compressor pressure ratio at current conditions, P is pressure at the at least one flow measuring device at current conditions, T is temperature at the at least one flow measuring device at current conditions, Z is compressibility at the at least one flow measuring device at current conditions, Pv is pressure in a compressor stage suction at current conditions, Tv is temperature in the compressor stage suction at current conditions, and Zv is compressibility in the compressor stage suction at current conditions;
third, computing overall compressor surge limit set point for current operating conditions (dPsp) by selecting maximal value of all computed individual stages surge limit set points (MAX(dPspi)):
dPsp=MAX(dPspi);
fourth, calculating control line set point (SPsu) by multiplying surge line (dPssu) value by a control line multiplier (CLM):
SPsu=dPssu*CLM;
fifth, comparing current measured dP with the control line set point (SPsu);
and
sixth, modulating surge control valve based on comparison for compressor surge prevention.

86 more elements

An apparatus for accurately calculating surge limit line, comprising:

a multistage compressor equipped with a PID surge prevention controller using one available flow measuring device, one speed signal, pressure and temperature signals of suction and discharge of each stage, said multistage compressor capable of performing a method comprising processor-executed steps using mathematical capabilities implementing control of the controller, the method steps comprising:
first, determining a surge limit line set point of each compressor stage (ksuv) as a function of surge conditions reduced polytrophic head
(
R
c
σ
-
1
σ
)
and reduce volumetric flow rate
(
dP
v
P
)
⁢
:
k
suv
=
1
dP
ssu
*
P
v
2
*
T
ssu
*
Z
ssu
P
ssu
*
T
v
*
Z
v
*
R
csu
σ
-
1
σ
,
where Rcsu is compressor pressure ratio at surge conditions, Pssu is compressor pressure ratio at surge conditions, dPssu is surge test pressure differential across the at least one flow measuring device, Tssu is surge test temperature at the at least one flow measuring device, Zssu is surge test compressibilitv at the at least one flow measuring device, Pv is surge test pressure in a compressor stage suction, Tv is surge test temperature in the compressor stage suction, and Zv is surge test compressibility in the compressor stage suction;
second, calculating each stage differential pressure surge limit set point for current operating conditions as a function of the surge limit line set point of each compressor stage (ksuv) and current measured pressures and temperatures:
dP
ssui
=
1
k
suv
*
P
v
2
*
T
*
Z
P
*
T
v
*
Z
v
*
R
ci
σ
-
1
σ
,
where Rci is compressor pressure ratio at current conditions, P is pressure at the at least one flow measuring device at current conditions, T is temperature at the at least one flow measuring device at current conditions, Z is compressibility at the at least one flow measuring device at current conditions, Pv is pressure in a compressor stage suction at current conditions, Tv is temperature in the compressor stage suction at current conditions, and Zv is compressibility in the compressor stage suction at current conditions;
third, computing overall compressor surge limit set point for current operating conditions (dPsp) by selecting maximal value of all computed individual stages surge limit set points (MAX(dPspi)):
dPsp=MAX(dPspi);
and
fourth, calculating control line set point (SPsu) by multiplying surge line dPssu value by control line multiplier (CLM):
SPsu=dPssu*CLM;
fifth, comparing current measured dP with the control line set point (SPsu);
and
sixth, modulating surge control valve based on comparison for compressor surge prevention.

87 more elements

Dependencies are inferred from the claim text.

Facts

Application: 15/279,084Filed 28 Sep 2016 · continuation in part
Priority: 18 Sep 2015
Published: US 2017/0082113 A123 Mar 2017
Granted: 9 Apr 2019
Term ends: Not estimatedThe source records don’t support an estimate.

Classification14 codes

G05B 11/42
With provision for obtaining particular characteristics, e.g. proportional, integral, differential: for obtaining a characteristic which is both…
F02C 9/18
Control of working fluid flow: by bleeding, bypassing or acting on variable working fluid interconnections between turbines or compressors or…
F04D 17/12
For compressing or evacuating: multi-stage pumps
F04D 27/001
Control, e.g. regulation, of pumps, pumping installations or pumping systems specially adapted for elastic fluids: testing thereof; Determination…

Family

Application62/220,642Us provisional application · filed 18 Sep 2015
Application15/267,654Parent of this continuation-in-part · filed 16 Sep 2016
US 2017/0082113 A1Pre-grant publication · published 23 Mar 2017
US 10,177,573 B2Related patent
US 2017/0085086 A1Published application
US 10,254,719 B2This patent

From the US filing history. Foreign family members aren’t listed.