The U.S. natural gas pipeline industry is facing the twin challenges of increased flexibility and capacity expansion. To meet these challenges, the industry requires improved choices in gas compression to address new construction and enhancement of the currently installed infrastructure. The current fleet of installed reciprocating compression is primarily slow-speed integral machines. Most new reciprocating compression is and will be large, highspeed separable units.The major challenges with the fleet of slow-speed integral machines are: limited flexibility and a large range in performance. In an attempt to increase flexibility, many operators are choosing to single-act cylinders, which are causing reduced reliability and integrity. While the best performing units in the fleet exhibit thermal efficiencies between 90% and 92%, the low performers are running down to 50% with the mean at about 80%. The major cause for this large disparity is due to installation losses in the pulsation control system. In the better performers, the losses are about evenly split between installation losses and valve losses.The major challenges for high-speed machines are: cylinder nozzle pulsations, mechanical vibrations due to cylinder stretch, short valve life, and low thermal performance. To shift nozzle pulsation to higher orders, nozzles are shortened, and to dampen the amplitudes, orifices are added. The shortened nozzles result in mechanical coupling with the cylinder, thereby, causing increased vibration due to the cylinder stretch mode. Valve life is even shorter than for slow speeds and can be on the order of a few months. The thermal efficiency is 10% to 15% lower than slow-speed equipment with the best performance in the 75% to 80% range.The goal of this advanced reciprocating compression program is to develop the technology for both high speed and low speed compression that will expand unit flexibility, increase thermal efficiency, and increase reliability and integrity.Retrofit technologies that address the challenges of slow-speed integral compression are: (1) optimum turndown using a combination of speed and clearance with single-acting operation as a last resort; (2) if single-acting is required, implement infinite length nozzles to address nozzle pulsation and tunable side branch absorbers for 1x lateral pulsations; and (3) advanced valves, either the semi-active plate valve or the passive rotary valve, to extend valve life to three years with half the pressure drop. This next generation of slow-speed compression should attain 95% efficiency, a three-year valve life, and expanded turndown.New equipment technologies that address the challenges of large-horsepower, high-speed compression are: (1) optimum turndown with unit speed; (2) tapered nozzles to effectively reduce nozzle pulsation with half the pressure drop and minimization of mechanical cylinder stretch induced vibrations; (3) tunable side branch absorber or higher-order filter bottle to address lateral piping pulsations over the entire extended speed range w...

A prototype of a novel gas turbine concept is being developed to demonstrate the technical feasibility of a gas turbine design based on a straight radial flow with no axial flow turning. The prototype gas turbine consists of only two structural elements — a rotor disk and a stator shroud. The rotor consists of a centrifugal compressor and high impulse radial outward-flow turbine connected to an electric generator. The stator shroud contains the combustor and nozzles. The difference between this novel design and conventional radial gas turbine is that the compressor and turbine section are installed on the same side of the rotating wheel, while the combustor and nozzle are mounted on the stationary shroud. Thus, the entire assembly consists of two components. Technical advantages are: • Single Rotating Disk; • Compact Two-Piece Construction; • Ease of Repair and Maintenance; • High Power to Weight Ratio. This paper discusses the test set-up, instrumentation, and initial mechanical testing of the radial gas turbine. Performance predictions, rotordynamics analysis, and aerodynamic component verification are also discussed.

A prototype of a novel gas turbine concept is being developed to demonstrate the technical feasibility of a gas turbine design based on a straight radial flow with no axial flow turning. The prototype gas turbine consists of only two structural elements—a rotor disk and a stator shroud. The rotor consists of a centrifugal compressor and high impulse radial outward-flow turbine connected to an electric generator. The stator shroud contains the combustor and nozzles. The difference between this novel design and conventional radial gas turbine that the compressor and turbine section are installed on the same side of the rotating wheel, while the combustor and nozzle are mounted on the stationary shroud. Thus, the entire assembly consists of two components. Technical advantages are: • Single Rotating Disk; • Compact Two-Piece Construction; • Ease of Repair and Maintenance; • High Power to Weight Ratio. This paper discusses the combustor development and preparation for design testing of the prototype radial gas turbine.

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A novel centrifugal gas turbine design was developed and prototype tested. The research effort consisted of the design, development, and full prototype testing of a 50 HP centrifugal gas turbine. The novelty of the centrifugal gas turbine concept is that it is based on a radial flow gas turbine consisting of a centrifugal compressor and impulse turbine mounted on the same side of a rotating wheel. The radial flow-vaned combustor is mounted on the wheel’s stationary shroud; consequently, there is no 180-degree flow turning required as in conventional radial flow gas turbines. This very simple and rugged gas turbine concept has the following major advantages: • Single rotating component (i.e., mechanically simple and compact gas turbine). • Portability. • Short axial span. • High tolerance to injection of particulate matter. • Simple construction; low manufacturing costs. This project included the conceptual design, structural and aerodynamic analysis, performance prediction modeling, detailed design, prototype fabrication, test rig instrumentation, compressor/turbine characterization, rotordynamic signature, combustor design, combustor testing, controls implementation, light-off testing, no-load testing, and performance testing of the gas turbine. Design analyses that were performed included 1-D thermodynamics, finite element structural and thermal, rotordynamic, 2-D blade path optimization, and 3-D Computational Fluid Dynamics (CFD). Testing of all individual gas turbine elements (compressor, combustor, and turbine) as well as the entire assembly was completed. Tests showed that stable gas turbine combustion was achieved up to 26,000 RPM. The gas turbine reached self-sustaining power at 21,000 RPM and 405°C firing temperature. Thus, the centrifugal gas turbine concept was demonstrated to function properly and to achieve positive power output. However, the design output power was not achieved because of combustion stability range limitations at speeds above 20,000 RPM. Maximum output power achieved was 1.4 kW at 23,000 RPM. Recommendations are provided to overcome these operational limitations in the next model centrifugal gas turbine.