ENHANCED SEQUENTIAL METHOD FOR SOLVING PRESSURE/FLOW NETWORK PARAMETERS IN A REAL-TIME DISTRIBUTED INDUSTRIAL PROCESS SIMULATION SYSTEM

• US 20130204587A1
• Filed: 02/02/2012
• Published: 08/08/2013
• Est. Priority Date: 02/02/2012
• Status: Active Grant

• Current Assignee: Emerson Process Management Power & Water Solutions Incorporated (Emerson Electric Company)
• Original Assignee: Emerson Process Management Power & Water Solutions Incorporated (Emerson Electric Company)
• Inventors: Cheng, Xu, Wen, Chengtao
• Granted Patent: US 9,052,703 B2
• Time in Patent Office: Days
• US Class Current: 703/2
• CPC Class Codes: G05B 17/02 electric
• CPC Class Codes: G05B 2219/2203 Grid, array of controllers
• CPC Class Codes: G05B 2219/2213 Local processor uses data from own local store and data from other stations
• CPC Class Codes: G05B 2219/2214 Multicontrollers, multimicrocomputers, multiprocessing
• CPC Class Codes: G05D 16/20 characterised by the use of electric means
• CPC Class Codes: G05D 16/2006 with direct action of electric energy on controlling means combination of electric and non-electric auxiliary G05D16/2093
• CPC Class Codes: G05D 16/2066 using controlling means acting on the pressure source
• CPC Class Codes: G05D 16/2073 with a plurality of pressure sources
• CPC Class Codes: G05D 7/0688 by combined action on throttling means and flow sources G05D7/0694 takes precedence
• CPC Class Codes: G06F 30/23 using finite element methods [FEM] or finite difference methods [FDM]
• CPC Class Codes: G06F 30/367 Design verification, e.g. using simulation, simulation program with integrated circuit emphasis [SPICE], direct methods or relaxation methods

Abstract

A pressure and flow calculation technique can be used in a distributed process network simulation system that uses the sequential solving method to perform better or faster simulations of a process flow, especially with respect to process junction nodes at which flow either converges or diverges. The pressure and flow variable determination technique uses a grouped node identification technique that identifies a local set of nodes for each junction node of the process network to use when solving for the pressure at the junction node, a grouped node iteration technique that uses the grouped set of nodes at each junction node to perform iterative pressure calculations at the junction node, and a flow-based pressure calibration technique at each junction node to enable the system to perform highly accurate pressure and flow variable determination at each junction node in real-time.

Claims

1. A distributed simulation system for simulating the operation of a process network having a set of physical plant elements through which mass flows, comprising:

a computer network including a plurality of drops and a communication network that communicatively couples the plurality of drops, wherein each of the plurality of drops includes a processor; and

a multiplicity of processor implemented simulation modules, each of the multiplicity of simulation modules including a process model that models the operation of a different one of the physical plant elements, wherein a first one of the simulation modules and a second one of the simulation modules are located in different ones of the plurality of drops;

wherein a plurality of the simulation modules are junction node simulation modules that model the operation of different junction nodes within the process network at which flow within the process network converges or diverges, each of the junction node simulation modules including;

a memory that stores a definition of a grouped set of nodes associated with a base junction node, the base junction node being one of the junction nodes within the process network, the grouped set of nodes for the base junction node being less than all of the nodes of the process network and including the base junction node and one or more further junction nodes and one or more boundary nodes, the boundary nodes being nodes within the process network that are adjacent to the base junction node or one of the one or more further junction nodes; and

a routine that executes on a processor to iteratively solve for the pressure at the base junction node during each of a number of simulation cycles using a set of pressure and flow equations based on the grouped set of nodes for the base junction node, to calculate the pressure at the base junction node.

2. The simulation system of claim 1, wherein the first one of the simulation modules models the operation of a first one of the set of physical plant elements and the second one of the simulation modules models the operation of a second one of the set of physical plant elements disposed downstream of the first one of the set of physical plant elements, wherein the process model of the first simulation module uses a value of a pressure variable calculated by the second simulation module to produce an output associated with the operation of the physical plant element modeled by the first simulation module, and wherein the first and second simulation modules communicate calculated pressure variable information between one another to perform simulation of mass flow between the first physical plant element and the second physical plant element.

3. The simulation system of claim 1, wherein the routine iteratively solves for the pressure at the base junction node during each of a number of simulation cycles by performing a multiplicity of iterations during each of the number of simulation cycles, wherein each iteration includes sequentially solving for the pressure at each of the base junction node and the one or more further junction nodes of the grouped set of nodes for the base junction node using a previously calculated value for the pressures at the others of the base junction node and the one or more further junction nodes in the grouped set of nodes for the base junction node, and determining a mass flow balance in one or more of the base junction node and the one or more further junction nodes using the calculated pressures to determine if flow balance is achieved at the one of the base junction node or the one or more further junction nodes.

4. The simulation system of claim 3, wherein the routine performs the multiplicity of iterations for the base junction node by continuing to perform a new iteration during a particular simulation cycle if flow balance is not achieved at the one of the base junction node or the one or more further junction nodes during a current iteration of the particular simulation cycle.

5. The simulation system of claim 3, wherein the routine performs a multiplicity of iterations for the base junction node during a particular simulation cycle by halting the performance of a new iteration if flow balance is achieved at the one of the base junction node or the one or more further junction nodes or if a predetermined number of iterations has been performed during the particular simulation cycle.

6. The simulation system of claim 1, wherein the routine iteratively solves for the pressure at each of the base junction node and the one or more further junction nodes of the grouped set of nodes for the base junction node during a simulation cycle by setting the pressures at one or more of the boundary nodes of the grouped set of nodes for the base junction node to fixed values.

7. The simulation system of claim 6, wherein the routine sets the pressures at each of the boundary nodes of the grouped set of nodes for the base junction node to fixed values by determining the fixed values as values calculated by a simulation module associated with the one or more boundary nodes in a previous simulation cycle.

8. The simulation system of claim 1, wherein each of the memories for the simulation modules stores a grouped set of nodes for a simulation module that includes a fixed number of junction nodes that is the same for each of the grouped set of nodes.

9. The simulation system of claim 1, wherein each of the memories for the simulation modules stores a grouped set of nodes for a simulation module that includes a number of junction nodes placed in the grouped set of nodes based on the distance of a junction node within the process network from the base junction node.

10. The simulation system of claim 1, wherein each of the memories for the simulation modules stores a grouped set of nodes for a simulation module that includes all nodes immediately upstream or downstream of each of the base junction node and the one or more further junction nodes of the grouped set of nodes as the boundary nodes for the grouped set of nodes.

11. The simulation system of claim 1, wherein the routine for one of the plurality of simulation modules performs a pressure calibration technique for a base junction node during a first simulation cycle to develop a calibrated variable value for use by the one of the plurality of simulation modules in the next simulation cycle for the base junction node to calculate the pressure at the base junction node.

12. The simulation system of claim 11, wherein the routine performs the pressure calibration technique for the base junction node by determining a calibrated flow conductance within an input flow path for the base junction node.

13. The simulation system of claim 11, wherein the routine performs the pressure calibration technique when a maximum number of iterations has been performed at the simulation module during a simulation cycle without reaching a flow balance for the base junction node.

14. The simulation system of claim 1, further including a composite network routine that determines the grouped set of nodes for each base junction node by determining a condensed process network having multiple process elements in a single flow path of the process network combined into a composite process element and using the condensed process network to determine the grouped set of nodes for each base junction node.

15. The simulation system of claim 1, wherein the routine solves for the pressure at each of the base junction node and the one or more further junction nodes in two or more iterations to determine a new pressure at each of the base junction node and the one or more further junction nodes using previously determined values for the pressure at each of the other of the base junction node and the one or more further junction nodes during each of the iterations and using fixed pressure values at each of the boundary nodes of the grouped set of nodes during each of the iterations.

16. The simulation system of claim 1, wherein the plurality of junction node simulation modules are disposed in the same drop.

17. A method of simulating the operation of a process network having a set of physical plant elements through which mass flows including a plurality of junction nodes at which mass flow within the process network converges or diverges, comprising:

using a computer device to determine a grouped set of nodes for each of a plurality of base junction nodes within the process network, wherein a particular grouped set of nodes for a particular base junction node includes a set of selected junction nodes including the particular base junction node and one or more further junction nodes other than the particular base junction node, and a set of boundary nodes including nodes that are adjacent to one or more of the set of selected junction nodes, and wherein the set of selected junction nodes for the grouped set of nodes for the particular base junction node includes less than all of the junction nodes within the process network;

using one or more computer devices to iteratively solve for the pressure at each of the base junction nodes during each of a number of simulation cycles using a set of equations based on the grouped set of nodes determined for each base junction node to calculate the pressures at each of the base junction nodes; and

using one or more computer devices to determine flows in the process network based on the pressure values determined for the base junction nodes during each simulation cycle.

18. The method of claim 17, wherein iteratively solving for the pressure at each of the base junction nodes during a simulation cycle includes, for a particular base junction node, performing a multiplicity of iterations, wherein each iteration includes sequentially solving for the pressure at each of the set of selected junction nodes of the grouped set of nodes for the particular base junction node using a previously calculated value for the pressures at the others of the set of selected junction nodes in the grouped set of nodes for the particular base junction node, and determining a mass flow balance in one or more of the set of selected junction nodes using the calculated pressures to determine if flow balance is achieved at the one or more of the set of selected junction nodes.

19. The method of claim 18, wherein performing a multiplicity of iterations for the particular base junction node includes continuing to perform a new iteration if flow balance is not achieved at the one or more of the set of selected junction nodes.

20. The method of claim 18, wherein performing a multiplicity of iterations for the particular base junction node includes halting the performance of a new iteration if flow balance is achieved at the one or more of the set of selected junction nodes or if a predetermined number of iterations has been performed during the simulation cycle.

21. The method of claim 18, wherein iteratively solving for the pressure for each of the base junction nodes during a simulation cycle includes, for a particular base junction node, setting the pressures at each of the boundary nodes of the grouped set of nodes for the particular base junction node to fixed values that remain the same during each iteration of the simulation cycle.

22. The method of claim 21, wherein setting the pressures at each of the boundary nodes of the grouped set of nodes for the particular base junction node to fixed values includes determining the fixed values as values calculated for the boundary nodes in a previous simulation cycle.

23. The method of claim 17, wherein determining a grouped set of nodes for each of a plurality of base junction nodes within the process network includes selecting a fixed number of junction nodes to be placed in the grouped set of nodes for each of the plurality of base junction nodes.

24. The method of claim 17, wherein determining a grouped set of nodes for each of a plurality of base junction nodes within the process network includes selecting the further junction nodes to be placed in each of the grouped set of nodes for each of the plurality of base junction nodes based on the distance of a further junction node from a base junction node.

25. The method of claim 17, wherein determining a grouped set of nodes for each of a plurality of base junction nodes within the process network includes selecting all nodes immediately upstream or downstream of each of the set of selected junction nodes of a particular grouped set of nodes as the boundary nodes for the particular grouped set of nodes.

26. The method of claim 17, further including performing a pressure calibration technique for a particular base junction node during a first simulation cycle to develop a calibrated variable value for use in the next simulation cycle for the particular base junction nodes to calculate the pressure at the particular base junction node.

27. The method of claim 26, further including performing the pressure calibration technique for the particular base junction node by determining a calibrated flow conductance within an input flow path of the particular base junction node.

28. The method of claim 26, including performing the pressure calibration technique when a maximum number of iterations has been reached during a simulation cycle without reaching a flow balance at the particular base junction node.

29. The method of claim 26, including performing the pressure calibration technique when a flow balance summation at the particular base junction node is greater than a threshold value after iteratively solving for the pressure at the particular base junction node.

30. The method of claim 17, further including determining a condensed process network having multiple process elements in a single flow path of the process network combined into a composite process element and wherein using a computer device to determine a grouped set of nodes for each of a plurality of base junction nodes within the process network uses nodes defined by the condensed process network to determine a grouped set of nodes for each of the plurality of base junction nodes.

31. The method of claim 30, further including determining a composite flow conductance for the composite process element based on a set of flow conductance values for each of the multiple process elements within the flow path.

32. The method of claim 17, further including using a set of separately executable simulation modules to perform a simulation for different ones of the plurality of base junction nodes, wherein each of the set of simulation modules executes using a different one of the grouped sets of nodes.

33. The method of claim 17, wherein two or more of the grouped sets of nodes includes a different group of nodes of the process network.

34. A simulation system for simulating the operation of a process network having a set of physical plant elements through which mass flows, wherein the process network includes a plurality of junction nodes at which flow converges or diverges, comprising:

a multiplicity of processor implemented simulation modules stored on a computer memory, each of the multiplicity of simulation modules including a process model that models the operation of a different one of the physical plant elements to determine pressures at the different physical plant elements, and including a communication routine that communicates with other simulation modules to communicate the determined pressures, wherein each of the simulation modules includes;

a memory that stores a definition of a grouped set of nodes associated with a base junction node, the base junction node being one of the junction nodes within the process network, the grouped set of nodes for the base junction node being less than all of the nodes of the process network and including

     1) a selected set of junction nodes including the base junction node and one or more further junction nodes, and

     2) one or more boundary nodes, the boundary nodes being nodes within the process network that are adjacent to at least one of the selected set of junction nodes; and

a routine that executes on a processor to iteratively solve for the pressure for the base junction node during each of a number of simulation cycles using a set of pressure and flow equations based on the grouped set of nodes for the base junction node to calculate the pressure at the base junction node, wherein, the routine iteratively solves for the pressure for the base junction node during a simulation cycle by performing a multiplicity of iterations, wherein during each iteration the routine sequentially solves for the pressure at each of the selected set of junction nodes of the grouped set of nodes for the base junction node using a previously calculated value for the pressures at the others of the selected set of junction nodes in the grouped set of nodes for the base junction node and using fixed values for the pressures at each of the boundary nodes of the grouped set of nodes for the base junction node, and determines a mass flow balance at one or more of the selected set of junction nodes using the calculated pressures to determine if flow balance is achieved at the one or more of the selected set of junction nodes.

35. The simulation system of claim 34, wherein the routine performs a multiplicity of iterations for the base junction node by continuing to perform a new iteration if flow balance is not achieved at the one or more of the selected set of junction nodes in a current iteration.

36. The simulation system of claim 34, wherein the routine performs a multiplicity of iterations for the base junction node by halting the performance of a new iteration when either a flow balance is achieved at the one or more of the selected set of junction nodes or a predetermined number of iterations has been performed during the simulation cycle.

37. The simulation system of claim 34, wherein the routine iteratively solves for the pressure for the base junction node during a simulation cycle by setting the pressures at each of the boundary nodes of the grouped set of nodes for the base junction node to fixed values that remain the same during each iteration of the simulation cycle.

38. The simulation system of claim 37, wherein the routine sets the pressures at each of the boundary nodes of the grouped set of nodes for the base junction node to fixed values by determining the fixed values as values previously calculated for the boundary nodes in a previous simulation cycle.

39. The simulation system of claim 34, further including a node determination routine stored on a memory that executes on a processor to determine the definition of a grouped set of nodes associated with a base junction node, wherein the node determination routine selects a fixed number of junction nodes to be placed in the grouped set of nodes associated with a base junction node as the selected set of junction nodes for the base junction node.

40. The simulation system of claim 34, further including a node determination routine stored on a memory that executes on a processor to determine the definition of a grouped set of nodes associated with a base junction node, wherein the node determination routine selects the further junction nodes to be placed in the selected set of junction nodes for the grouped set of nodes based on the distance of a junction node from the base junction node within the process network.

41. The simulation system of claim 34, further including a node determination routine stored on a memory that executes on a processor to determine the definition of a grouped set of nodes associated with a base junction node, wherein the node determining routine selects all nodes immediately upstream or downstream of each of the selected set of junction nodes as the boundary nodes for the grouped set of nodes for the base junction node.

42. The simulation system of claim 34, further including a node determination routine stored on a memory that executes on a processor to determine a condensed process network having multiple process elements in a single flow path of the process network combined into a composite process element and wherein the node determination routine uses the condensed process network to determine the definition of a grouped set of nodes for a base junction nodes within the process network.

43. The simulation system of claim 42, wherein the node determination routine determines a composite flow conductance for the composite process element based on a set of flow conductance values for each of the multiple process elements within the single flow path.

44. The simulation system of claim 34, wherein the simulation module includes a calibration routine that performs a pressure calibration technique for the base junction node during a first simulation cycle to develop a calibrated variable value for use in the next simulation cycle for the base junction nodes to calculate the pressure at the base junction node.

45. The simulation system of claim 44, wherein the calibration routine performs the pressure calibration technique for a base junction node by determining a calibrated flow conductance within an input flow path of the base junction node.

46. The simulation system of claim 45, wherein the calibration routine performs the pressure calibration technique when a flow balance summation at the base junction node is greater than a threshold value after iteratively solving for the pressure at the base junction node.