Overview of Important Considerations in Wet Gas Compression Testing and Analysis
During upstream production of natural gas fields, it is common that a gas-liquid mixture of product is brought to the surface. The mixture, termed wet gas, is generally made up of mostly gas with a small amount of liquid, typically up to 5% by volume of the mixture. Because of the difficulties of compressing wet gas, the practical approach has been to separate the liquid and gas phases before compression. However, large separation equipment is unfavorable for subsea installations because of the cost to place machinery on the sea floor. Instead, a compressor designed for wet gas operation is preferred because it eliminates the need for large separation equipment leading to plant simplification and cost reduction. To address this design need, researchers have been active in addressing the challenges with wet gas compression. As result, experimental work has been conducted to study the effects of wet gas on compressor aerodynamic and mechanical performance. This experimental research has presented many challenges in recreating wet gas conditions and quantifying the effect of the liquid on the compressor performance. The results from this testing have helped to characterize the performance effects. But so far each work has focused on a range of test variables without identifying those that have the largest effect on compressor performance. This paper aims to provide the reader with an overview of the completed wet gas research, the challenges associated with doing the experimental work, and a discussion of the resulting trends observed in most of the wet gas research. This will include an in-depth review of relevant literature on wet gas compression testing and performance, a discussion of the important
UNDERSTANDING WET GAS IN A SUPERCRITICAL CARBON DIOXIDE CYCLE
Biographies Melissa Poerner, P.E. is a Senior Research Engineer at Southwest Research Institute. Her background includes work related to analysis and testing of compressors and other large machinery in adverse conditions such as wet gas or corrosive gas. She is directly involved with design, operation, and project management of machinery test programs. Ms. Poerner graduated from Texas A&M University in 2007 and Georgia Institute of Technology in 2012 with a B.S. and M.S degrees in Mechanical Engineering. She is a registered professional engineer in the State of Texas.
Rotordynamic Stability Measurement During Full-Load, Full-Pressure Testing Of A 6000 Psi Reinjection Centrifugal Compressor.
Full-load, full-pressure rotordynamic stability measurements were conducted on a seven-stage, back-to-back centrifugal compressor. To validate rotordynamic predictions, the rotor was excited while operating at full load and full pressure during factory testing. This was accomplished through means of a magnetic bearing, which was attached to the free end of the rotor. This device injected an asynchronous force into the rotor system to excite the first forward whirling mode. This technique measures the rotor’s logarithmic decrement (log dec), which indicates the level of stability, or damping, in the rotor. The device is designed to be nonintrusive to the original dynamics of the rotor and may be easily installed/removed on the test stand. This paper discusses the techniques used to measure the rotordynamic stability from a fullload, full-pressure test of a 6000 psi reinjection compressor. The results demonstrate the effectiveness of swirl brakes and damper seals in producing a compressor that becomes more stable as discharge pressure increases. This approach to compressor design is in stark contrast to traditional designs in which the stability degrades with increasing pressure, ultimately leading to rotordynamic instability. This technology ensures trouble-free startup and operation of these compressors in the field, minimizing risk for the end-user.