Abstract
1. Introduction

2. Review of Previous Work in Transient Flow Simulation

3. Formulation of the Mathematical Problem

• 3.1

Governing Equations

• 3.2

Linearization of the Problem

• 3.3

Numerical Solution

4. Applications of the Simplified Model and Comparison with Experimental Data

5. Conclusions

ABSTRACT

The present paper discusses the simulation of transient flows in natural gas networks. A survey of the literature is presented and the existing methods used to solve the transient equations are reviewed. Governing partial differential equations are presented for the general problem. A linearization of the partial differential equations is then introduced. A code to solve such a system, both linearized and in its original, non - linear, form was developed. The numerical solution is accomplished by using an implicit, finite difference scheme. The program is then used to simulate transients in actual pipelines. It is shown that the linearized version can save 25% in the computational time without a major sacrifice in accuracy.

1. Introduction

The problem of simulating transient flow in natural gas networks has received significant attention in the industry for the last 20 years. There are many reasons to pursue the development of computer codes to simulate transient conditions. The most obvious application is found in the design of distribution systems. Traditionally, systems are designed to meet certain specifications based on a steady state operation. But networks rarely operate at steady state. Compressor station shut-downs due to failure or maintenance, sudden changes on a customer's demand, or any other changes introduced in the network, will induce the onset of a transient. A simulation code becomes an in dispensible tool for the design engineer needing to study how the system under consideration reacts to changes in the operating conditions. The availability of transient simulation codes can greatly reduce the cost of training dispatchers. The use of these codes as flight simulatorsis an area where not much emphasis has been placed

1. Alternatively, transient simulation codes can be used as aids in the operation of transmission lines. An application where these codes have seen only relative success is leak and rupture detection

2. Recently, in an effort to improve operating efficiency and reduce transmission costs, optimization codes have become available in the gas industry

3. Operators now have the ability to calculate the operational parameters to meet the demand with minimum fuel usage.

As a result of dynamic changes, the "optimum" point of operation may need to be shifted several times per day. Transient codes are useful to predict how the network will go from one set - point to another. Considerable effort has been put in developing software to simulate transients in natural gas pipelines. Many different approaches have been proposed to tackle the problem, and each one has been categorized as the "best" procedure. With a trade - off between accuracy and efficiency (speed of computation), one should not be surprised if such a "best" approach is, in reality, an elusive mirage.

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