Current predictive emission monitoring (PEM) techniques are briefly reviewed and the concept for a general predictive model was favorably evaluated. Utilizing the commercial process simulation software ASPEN PLUS®, a one dimensional model based on fundamental principles of gas turbine thermodynamics and combustion processes was constructed. Employing a set of 22 reactions including the Zeldovich mechanism, the model predicted for thermal NOx formation. It accounted for combustor geometry, dilution air injection along the combustor annulus, convective heat transfer across the liner, flame length, and full-load inlet flows. The combustor was subdivided into slices, each of which was modeled by a plug flow reactor, giving insight into profiles of NOx formation, species concentration and temperature along the combustor’s length, as well as quantifying the residence time in the combustor. The simulation predicted the levels of NOx for a particular gas turbine combustor and determined the effects of various parameters, such as flame length, hydrocarbon conversion ratio and recycle zones.

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A study of pressure oscillations occurring in small centrifugal compressor systems without a plenum is presented. Active and passive surge control were investigated theoretically and experimentally for systems with various inlet and discharge piping configurations. The determination of static and dynamic stability criteria was based on Greitzer’s (1981) lumped parameter model modified to accommodate capacitance of the piping. Experimentally, passive control using globe valves closely coupled to the compressor prevented the occurrence of surge even with the flow reduced to zero. Active control with a sleeve valve located at the compressor was effective but involved a significant component of passive throttling which reduced the compressor efficiency. With an oscillator connected to a short side branch at the compressor, effective active control was achieved without throttling. Both methods of active control reduced the flow rate at surge onset by about 30 percent. In general, the experiments qualitatively confirmed the derived stability criteria.

This paper presents a method to determine the effective friction factor and overall heat transfer coefficient for a high-pressure, natural gas pipeline during fully transient flow conditions. Time-varying SCADA (supervisory control and data acquisition) measurements at the pipeline boundaries (i.e., inlet and outlet) provide boundary conditions for a transient flow model, as well as additional information which is utilized to determine these parameters. The resulting friction factor and overall heat transfer coefficient minimize the least-squared difference between the additional SCADA measurements at the pipeline outlet and the corresponding values predicted from the transient flow model. This concept is referred to as parameter estimation. The transient flow model is based on a numerical solution of the one-dimensional conservation equations (i.e., continuity, momentum, and energy) which are discretized using a highly accurate compact finite-difference scheme. The transient flow model and parameter estimation is incorporated into a computer program that is initially tested on a simple pipeline with steady flow conditions. The predicted outlet pressure and temperature using the estimated friction factor and overall heat transfer coefficient exactly matches the corresponding prescribed values. Subsequently, a portion of the Foothills Pipe Line Ltd. transmission system in Alberta is considered using time-varying SCADA flow measurements. The resulting outlet pressure and temperature from the transient flow model are in good agreement with SCADA measurements for this pipeline section.

This paper presents a method to determine the effective friction factor and overall heat transfer coefficient for a high pressure, natural gas pipeline during fully transient flow conditions. Time varying SCADA (Supervisory Control And Data Acquisition) measurements at the pipeline boundaries (i.e., inlet and outlet) provide boundary conditions for a transient flow model as well as additional information that is utilized to determine these parameters. The resulting friction factor and overall heat transfer coefficient minimize the least-squared difference between the additional SCADA measurements at the pipeline outlet and the corresponding values predicted from the transient flow model. This concept is referred to as parameter estimation. The transient flow model is based on a numerical solution of the one-dimensional, unsteady flow equations (i.e., continuity, momentum and energy) which are discretized using a highly accurate compact finite-difference scheme. The transient flow model and parameter estimation are incorporated into a computer program that is initially tested on a simple pipeline with steady flow conditions. Here, the predicted outlet pressure and temperature, using the estimated friction factor and overall heat transfer coefficient, exactly matches the corresponding prescribed values. Subsequently, a portion of the Foothills Pipe Line Ltd. transmission system in Alberta is considered using time varying SCADA flow measurements. The resulting outlet pressure and temperature from the transient flow model are in good agreement with SCADA measurements at this location.