A More Comprehensive Evaluation of Equation of State Influences On Compressor Performance Determination

Lectur

On the measurement of a weak classical force coupled to a quantum-mechanical oscillator. I. Issues of principle

The monitoring of a quantum-mechanical harmonic oscillator on which a classical force acts is important in a variety of high-precision experiments, such as the attempt to detect gravitational radiation. This paper reviews the standard techniques for monitoring the oscillator, and introduces a new technique which, in principle, can determine the details of the force with arbitrary accuracy, despite the quantum properties of the oscillator. The standard method for monitoring the oscillator is the "amplitude-and-phase" method (position or momentum transducer with output fed through a narrow-band amplifier). The accuracy obtainable by this method is limited by the uncertainty principle ("standard quantum limit"). To do better requires a measurement of the type which Braginsky has called "quantum nondemolition." A well known quantum nondemolition technique is "quantum counting," which can detect an arbitrarily weak classical force, but which cannot provide good accuracy in determining its precise time dependence. This paper considers extensively a new type of quantum nondemolition measurement—a "back-action-evading" measurement of the real part X_1 (or the imaginary part X_2) of the oscillator's complex amplitude. In principle X_1 can be measured "arbitrarily quickly and arbitrarily accurately," and a sequence of such measurements can lead to an arbitrarily accurate monitoring of the classical force. The authors describe explicit Gedanken experiments which demonstrate that X_1 can be measured arbitrarily quickly and arbitrarily accurately. In these experiments the measuring apparatus must be coupled to both the position (position transducer) and the momentum (momentum transducer) of the oscillator, and both couplings must be modulated sinusoidally. For a given measurement time the strength of the coupling determines the accuracy of the measurement; for arbitrarily strong coupling the measurement can be arbitrarily accurate. The "momentum transducer" is constructed by combining a "velocity transducer" with a "negative capacitor" or "negative spring." The modulated couplings are provided by an external, classical generator, which can be realized as a harmonic oscillator excited in an arbitrarily energetic, coherent state. One can avoid the use of two transducers by making "stroboscopic measurements" of X_1, in which one measures position (or momentum) at half-cycle intervals. Alternatively, one can make "continuous single-transducer" measurements of X_1 by modulating appropriately the output of a single transducer (position or momentum), and then filtering the output to pick out the information about X_1 and reject information about X_2. Continuous single-transducer measurements are useful in the case of weak coupling. In this case long measurement times are required to achieve good accuracy, and continuous single-transducer measurements are almost as good as perfectly coupled two-transducer measurements. Finally, the authors develop a theory of quantum nondemolition measurement for arbitrary systems. This paper (Paper I) concentrates on issues of principle; a sequel (Paper II) will consider issues of practice

Application of Dynamic pressure-balanced Seals in a Multi-stage Centrifugal Compressor

LecturesTest results for an ASME Power Test Code 10 (PTC) Type 1 test of a 4,500 psia (310 Bara) discharge pressure gas lift centrifugal compressor outfitted with dynamic pressure-balanced seals at the impeller eyes; shaft interstage and division wall locations are presented and compared to the same testing with conventional labyrinth seals. Both aerodynamic performance and rotor dynamic stability, obtained via operational modal analysis (OMA), are presented. A client’s motivation, along with the design and testing of dynamic pressure-balanced (DPB) seals for turbomachinery are also presented in this paper. With the DPB seals installed the test results indicate 2.8 percent lower power was required for the same head level across the entire range of inlet flows and pressure ratios, when compared to the same testing with conventional labyrinth seals. Rotordynamic stability, obtained via operational modal analysis (OMA), showed the dynamic pressure-balanced (DPB) seals exhibited log decs similar to standard labyrinth seals across the entire range of flows and pressure ratios. The foregoing demonstrates both the aerodynamic and mechanical/rotordynamic integrity of the dynamic pressure-balanced seals for oil and gas, turbomachinery applications

Centrifugal Compressor Configuration, Selection and Arrangement: A User's Perspective

TutorialThe detailed sizing and selection of centrifugal compressors may be somewhat of a mystery to the typical user. Once the suction and discharge process conditions and required flow rates are established, they are submitted to an equipment supplier for sizing and selection. The resulting combination of impeller diameters, casing sizes and operating speed determined by the equipment supplier can be puzzling to the engineer charged with evaluating the selections. This tutorial is intended to introduce the dimensional and dimensionless similarity parameters that can be utilized to perform an independent, equivalent selection for a compression application or provide a more thorough evaluation of the selections provided by an equipment supplier. These performance parameters will allow prediction of design point head and efficiency, approximate impeller diameters, and approximate compressor operating speeds. Furthermore, the inter-relationship between impeller diameter and rotational speed will be investigated to highlight the trade-offs in changing either of these design variables. The tutorial will also investigate useful mechanical parameters and guidelines that allow comparative preliminary assessment of proposed designs. When significant head and/or flow requirements exist for a specific application, it becomes necessary to divide the compression service into multiple sections and in some situations multiple casings. Although a few different ways to configure multiple compressor sections exist, there are benefits and issues associated with each of these configurations. The potential benefits and issues of different arrangement options will also be addressed in this tutorial

Centrifugal Compressor Configuration, Selection And Arrangement: A User's Perspective

TutorialThe detailed sizing and selection of centrifugal compressors may be somewhat of a mystery to the typical user. Once the suction and discharge process conditions and required flow rates are established, they are submitted to an equipment supplier for sizing and selection. The resulting combination of impeller diameters, casing sizes and operating speed determined by the equipment supplier can be puzzling to the engineer charged with evaluating the selections. This tutorial is intended to introduce the dimensional and dimensionless similarity parameters that can be utilized to perform an independent, equivalent selection for a compression application or provide a more thorough evaluation of the selections provided by an equipment supplier. These performance parameters will allow prediction of design point head and efficiency, approximate impeller diameters, and approximate compressor operating speeds. Furthermore, the inter-relationship between impeller diameter and rotational speed will be investigated to highlight the trade-offs in changing either of these design variables. The tutorial will also investigate useful mechanical parameters and guidelines that allow comparative preliminary assessment of proposed designs. When significant head and/or flow requirements exist for a specific application, it becomes necessary to divide the compression service into multiple sections and in some situations multiple casings. Although a few different ways to configure multiple compressor sections exist, there are benefits and issues associated with each of these configurations. The potential benefits and issues of different arrangement options will also be addressed in this tutorial

Compressor Controls

Discussion GroupSurge Detection Logic - Trip or not on Surge Detection? Compressor Control Redundancy Requirements Is the primary purpose of an anti-surge valve a control or protection? Check valve locations and their impact on controllability Fallback Strategies of surge control flow transmitter failure Suction throttling experience - Inside or outside of the recycle loop Cost vs Benefit of implementing load sharing Controls Obsolescenc

Advanced Topics In Centrifugal Compressor Design

Discussion Grou

Advanced Topics In Centrifugal Compressor Design

Discussion GroupSuggested Topics: Meeting current rotordynamics stability standards CO2 Compressors High flow coefficient/Mach number impellers Coupling and alignment impacts on asymmetric rotordynamics Sour gas/Chloride implications on material selection Complicated high pressure gas properties Validity of CFD modeling Modern manufacturing/forming methodologies Simulation and dynamic process modeling Helmholtz Resonators/Acoustic Attenuation Testing in extreme overload/choke conditions Tripping of compressors in surge conditions Future compressor design/development challenges Control challenges associated with sophisticated cent. compr. Design Performance and mechanical monitoring of compressor