Improvement of Wet Gas Compressor Performance using Gas Ejection, 18-R8327
Principal Investigator
Grant Musgrove
Inclusive Dates: 07/02/12 – Current
Background — During upstream production of natural gas, the gas brought to the surface is compressed so that it can be injected into a pipeline and transported elsewhere. Sometimes the gas brought to the surface is a mixture including a small amount of liquid hydrocarbons, up to 5% volume fraction. Because a compressor is designed for dry gas only, the mixture of gas and liquid degrade the performance of the compressor to require much more power. By requiring more power, large drivers are needed that increase the cost and size of the compressor system. However, the required size of the driver is not known because a proven method does not exist to accurately predict compressor performance under wet gas conditions. The current solution is to avoid the problem of wet compression altogether by separating the gas and liquid at the well-head. Again, the cost and footprint of the system is increased because of the separation equipment. Therefore, the one attractive option to solve the wet gas problem is to modify the compressor such that wet gas has little effect on performance. Fundamental aerodynamic testing of airfoils in air-water flows have indicated that aerodynamic losses are likely responsible for the increase in power required of wet gas compression. Observations are reported that the liquid in contact with the airfoil surface in the form of droplets and film is to blame for the airfoil performance loss; however, the results lack detailed measurements and flow observations that can be applied to compressor operating conditions. Detailed information about the aerodynamic effects of wet gas flows and a solution to recover lost performance is needed to improve compressor designs to handle wet gas flows.
Approach — In this IR&D project, a NACA 0012 airfoil is studied in a large-scale wind tunnel using air and water to simulate wet gas conditions. The objective is to both study the effects of wet gas on aerodynamic performance as well as develop a concept to use air ejected from the airfoil surface to create a film barrier to keep the liquid from coming in contact with the airfoil surface. Aerodynamic performance is evaluated from measured lift, drag, and surface pressures along an airfoil in wet-gas flow, including highly resolved particle image velocimetry (PIV) methods. This project is conducted in two phases using computational predictions and experimental measurements. In the first phase, the effects of airfoil performance with wet gas over a range of operating conditions are studied with experimental measurements and computational predictions using a lattice-Boltzmann fluid solver; whereby the computational predictions can be directly compared to measurements. During the second phase, gas ejection concepts are studied using computational simulations before measuring the performance of the best gas ejection concept.
Accomplishments — Accomplishments include the wind tunnel and airfoil test article design and construction. The airfoil is constructed using Fused Deposition Modeling (FDM), a rapid prototyping technique, to reduce hardware cost and allow complex internal geometries planned in phase 2 of the project. In parallel, a lattice-Boltzmann solver is being developed to simulate the airfoil performance in air-water flow at the planned test conditions.
