A review of oscillation mechanisms and the role of the precessing vortex core (PVC) in swirl combustion systems

An improved understanding of the mechanisms of unstable combustion in lean premixed combustors is essential to the development of stable gas turbine combustion systems. To obtain such understanding, detailed experimental studies of the phenomenology of unstable combustion are required. A number of experimental diagnostic techniques for characterizing unstable combustion and the underlying instability mechanisms are discussed. This includes techniques based on pressure, chemiluminescence emission, infrared absorption, and laser-induced fluorescence measurements. The techniques themselves are discussed briefly; however, the primary objective is to present and discuss results illustrating how these techniques can be used to characterize the mechanisms of unstable combustion, to gain an improved understanding of unstable combustion, and to develop strategies for suppressing unstable combustion in lean premixed gas turbine combustors.

Experimental Diagnostics for the Study of Combustion Instabilities in Lean Premixed Combustors

: This book has several purposes, including a broad historical summary of combustion instabilities in propulsion systems; a concise compilation of the main mechanisms for instabilities in liquid and solid fueled rockets, ramjets, thrust augmentors and gas turbines; development of a theoretical framework for investigating unsteady motions in combustion systems; and accessible surveys of the basic material required to understand the subject. Emphasis is placed throughout the book on observed behavior. For well-understood reasons, the best, and in many respects most useful quantitative data, have been obtained for solid propellant rockets. Hence that type of device occupies a special position in the subject. The book comprises nine chapters and eight annexes. Material in the annexes is not essential for reading and broadly understanding the main part of the book, but is likely interesting for those choosing to do research on the subject. The nine chapters divide into three parts.

Unsteady Motions in Combustion Chambers for Propulsion Systems

Systems, methods, and apparatus embodiments for electric power grid and network registration and management of active grid elements. Grid elements are transformed into active grid elements following initial registration of each grid element with the system, preferably through network-based communication between the grid elements and a coordinator, either in coordination with or outside of an IP-based communications network router. A multiplicity of active grid elements function in the grid for supply capacity, supply and/or load curtailment as supply or capacity. Also preferably, messaging is managed through a network by a Coordinator using IP messaging for communication with the grid elements, with the energy management system (EMS), and with the utilities, market participants, and/or grid operators.

System, method, and apparatus for electric power grid and network management of grid elements

A utility employs a method for estimating available operating reserve. Electric power consumption by at least one device serviced by the utility is determined during at least one period of time to produce power consumption data. The power consumption data is stored in a repository. A determination is made that a control event is to occur during which power is to be reduced to one or more devices. Prior to the control event and under an assumption that it is not to occur, power consumption behavior expected of the device(s) is estimated for a time period during which the control event is expected to occur based on the stored power consumption data. Additionally, prior to the control event, projected energy savings resulting from the control event are determined based on the devices' estimated power consumption behavior. An amount of available operating reserve is determined based on the projected energy savings.

System and method for estimating and providing dispatchable operating reserve energy capacity through use of active load management

Various forms of energy, such as mechanical, electrical, and/or heat energy are produced by an energy conversion mechanism (10) which includes a spool (16), the spool (16) including a shaft (22) on which a compressor (18) and turbine (20) are mounted. A generator (23) is operably connected to the energy conversion mechanism (10) for converting mechanical energy into electrical energy. Fuel and air are supplied separately to the compressor (18). A regenerator type heat exchanger (28) has a cold side for conducting compressed air traveling from an outlet of a compressor (18) to an inlet of the turbine (20), a hot side for conducting hot waste gas from the energy conversion mechanism (10), and a rotary core movable sequentially through the cold and hot sides for absorbing heat in the hot side and giving up heat in the cold side. A catalytic combustor (30) combusts the fuel at a location upstream of the turbine (20). During start-up, the catalytic combustor (30) is preheated independently of the heat exchanger (28) by an electric heater (40).

Self-contained energy center for producing mechanical, electrical, and heat energy

A gas turbine system includes a compressor side for compressing an air/fuel mixture, and a turbine side for driving the compressor side. A heat exchanger transfers heat from turbine exhaust gases to the air/fuel mixture from the compressor side. A main catalytic combustor is disposed between the heat exchanger and the turbine side for combusting the air/fuel mixture and supplying the resultant products of combustion to the turbine side. The main catalytic combustor has a volume which is sufficient for oxidizing enough fuel to achieve a predetermined turbine inlet temperature, but insufficient for oxidizing all of the fuel. A secondary catalytic combustor is disposed downstream of the turbine side for combusting at least some of the fuel that was not combusted by the main catalytic combustor. The second catalytic combustor typically operates at a lower temperature than the main catalytic combustor. The secondary catalytic combustor may constitute a separate unit, or it may be integrated with the heat exchanger.

Catalytic arrangement for gas turbine combustor

The lower temperatures associated with lean premixed combustion generally lead to lower NOx emissions; however, the benefit of lean premixed combustion may be lost if the fuel and air are poorly mixed. In this paper, we describe the development of an inexpensive fiber optic probe capable of measuring the extent of mixing. The fuel concentration is determined by laser light absorption at 3.39 μm over a short path length created by using infrared transmitting fiber optics. A hydrogen-piloted, CH4-in-air turbulent flame with a variable fuel injection location is used to vary the degree of mixedness at the burner exit. We use the optical probe to measure the level of mixedness (nonreacting) at the burner exit. The level of mixing and the mean concentration profiles are also measured by using planar laser-initiated Rayleigh scattering. NOx measurements are reported for several mixing distances. We show that at lean conditions (=0.6), incomplete mixing causes a dramatic increase in NOx production because of the exponential temperature dependence of NOx formation about =0.6. We also numerically investigate how the extent of mixing affects NOx production at various equivalence ratios and pressures. Modeling the effect of incomplete mixing on NOx formation is done with a distribution ofconvolved with numerical results from a perfectly stirred reactor in series with a plug flow reactor. The model does an excellent job of predicting the NOx increase caused by incomplete mixing at lean conditions. Model predictions at higher pressures that are typical of gas turbine conditions show good agreement with available data. In particular, for lean premixed combustion, NOx is not a function of pressure if the air and fuel are well mixed.

Use of an optical probe for time-resolved in situ measurement of local air-to-fuel ratio and extent of fuel mixing with applications to low NOx emissions in premixed gas turbines

A multi-shaft reheat turbine mechanism includes multiple turbines mounted on respective compressor shafts, and catalytic reactors feeding respective ones of the turbines. Fuel is introduced into a low pressure compressor, whereby there is no need to pressurize the fuel. The compressor side of the mechanism emits a compressed air/fuel flow, portions of which are combusted in respective ones of the catalytic reactors. The air/fuel flow traveling from the compressor side to the turbine side passes through a regenerator in heat exchanging relationship with exhaust gas from a low pressure turbine.

Multi-shaft reheat turbine mechanism for generating power

An energy producing system includes a compressor side for compressing an air/fuel mixture, and a turbine side for producing mechanical, electrical, and/or heat energy, and driving the compressor side. A catalytic combustor is disposed upstream of the turbine side for combusting a steady state air/fuel mixture during a steady state operation of the apparatus. During start-up of the system, the catalytic combustor is preheated by being supplied with a preheat air/fuel mixture capable of lighting-off therein at ambient temperature, whereby oxidization of the preheat air/fuel mixture in the catalytic combustor produces heat. The preheat air/fuel mixture is produced on-site, preferably in a reformer which burns natural gas in the presence of insufficient oxygen for complete combustion, thereby producing hydrogen and carbon monoxide.

Rajiv K. Mongia

Papers

Self-contained energy center for producing mechanical, electrical, and heat energy

Catalytic arrangement for gas turbine combustor

Use of an optical probe for time-resolved in situ measurement of local air-to-fuel ratio and extent of fuel mixing with applications to low NOx emissions in premixed gas turbines

Multi-shaft reheat turbine mechanism for generating power

Methods and apparatus for igniting a catalytic converter in a gas turbine system