Turbine Lube Oil Research Articles

Coking of gas turbine lubrication oils at elevated temperatures

Over the last several decades, turbine efficiency has improved significantly, resulting in higher turbine operating temperatures that negatively affect the lubricating oil circulating through the system. Exposure to high temperatures results in oil degradation and the eventual formation of solid deposits in the oil which greatly limit the oil’s ability to reduce wear and cool the turbine components. An experimental apparatus was designed and built to allow for the studying and better understanding of this phenomenon. The apparatus consists of a flow loop with a heated test section through which the oil is pumped. The oil that comes into contact with the hot surfaces degrades and forms solid deposits. As time passes, the deposit buildup decreases the heat transfer that occurs at the test section. The bulk oil temperatures into and out of the test section are used as indicators of the deposit induction time and buildup rate, and the deposits may be analyzed at the end of the experiment. Air or an inert gas may be used to pressurize the system up to 69 bar, while test section surface temperatures may be as high as 650°C. Data from one of the initial tests performed with the apparatus using a gas turbine lube oil are included in this paper. The test resulted in the clear formation of solid deposits on the heated surfaces and in the data that show the decrease in the bulk oil temperature over time due to their formation. Assembly and testing of the apparatus have been completed, and it is now fully operational and ready for future studies on lubricating oil thermal degradation and oxidation.

Numerical Study of Reducer Modification with Adjuster Opening Variations on Turbine Lube Oil Pipe

The success criteria of the power plant are represented by EAF (Equivalent Availability Factor) value. In 2021, one of the causes of the Forced Outage (FO) at Adipala Steam Power Plant was the failure of the main lube oil turbine pipe. The sudden contraction of the reducer resulted in the previous failure. Modifications were made to the reducer using a conical shape to reduce the number of welding processes and minimize the probability of failure. Therefore, a study on reducer modification needs to be carried out to study the impact of changing the shape of the reducer and changing the opening check valve on process parameters and flow in the main lube oil turbine pipe. The modification of the reducer was the main focus in this study. This research aims to analyze the pressure of turbine lube oil in the existing adjuster and the modified adjuster, using the Computational Fluid Dynamics technique with check valve adjuster variations (distance between the tip of the check valve and the inner wall of the reducer). The inlet boundary condition was defined by a pressure inlet of 285803.4 Pa. Outlet boundary condition was set by a mass flow of 65.72 kg/s. The curve surface was set as wall boundary conditions with a stationary wall, no-slip, and standard roughness model. The oil pressure in the modified adjuster increased compared to the oil pressure in the existing adjuster. The pressure on the oil flow was required to distribute oil to the turbine bearings. With the small increase in pressure after the modification, the turbine lube oil transfer improved. The pressure drop (Δ P ) value that occurred in the conical-shaped modified adjuster was smaller than the pressure drop (Δ P ) in the existing adjuster. This is because the resistance on the modified adjuster was less than the existing adjuster. The flow streamlines that formed backflow and vortex on the conical modified adjuster were less compared to the existing adjuster due to fewer obstacles in the conical modified adjuster.

Correction to: Improvement of 3-Way Valve for Temperature Control of Gas Turbine Lube Oil in CCPP

The affiliation of Hyoseo Kwak has been changed to: School of Mechanlcal and Automotive Engineering, Youngsan University, Yangsan, 288, Junam-ro, Yangsan-si, Gveonasananam-do 50510 South Korea

Improvement of 3-Way Valve for Temperature Control of Gas Turbine Lube Oil in CCPP

Lubrication oil, which is supplied to rotating elements in gas turbines of combined-cycle power generation, is used to maintain the efficiency of electricity production. The gas turbines are exposed to high-temperature environment due to the thermal energy obtained from fossil fuel, which degrades the performance of the lubricating oil. A system for controlling the temperature of the oil is essential, but there are a few problems in the case of the temperature control valve in the system, such as the hunting phenomenon, with which the target mass flow rate cannot be achieved, fatigue fracture and leakage. In this study, finite element analysis was performed to overcome these issues. The hunting phenomenon was prevented by redesigning the orifice shape of the valve cage. The fatigue fracture and self-loosening of the clamp bolt were overcome by changing the bolt size and tightening torque. In addition, a proper O-ring was selected to prevent leakage. The performance of a prototype was also tested to verify the reliability of the finite element analysis.

A Never-Ending Learning Method for Fault Diagnostics in Energy Systems Operating in Evolving Environments

Condition monitoring (CM) in the energy industry is limited by the lack of pre-classified data about the normal and/or abnormal plant states and the continuous evolution of its operational conditions. The objective is to develop a CM model able to: (1) Detect abnormal conditions and classify the type of anomaly; (2) recognize novel plant behaviors; (3) select representative examples of the novel classes for labeling by an expert; (4) automatically update the CM model. A CM model based on the never-ending learning paradigm is developed. It develops a dictionary containing labeled prototypical subsequences of signal values representing normal conditions and anomalies, which is continuously updated by using a dendrogram to identify groups of similar subsequences of novel classes and to select those subsequences to be labelled by an expert. A 1-nearest neighbor classifier is trained to online detect abnormal conditions and classify their types. The proposed CM model is applied to a synthetic case study and a real case study concerning the monitoring of the tank pressure of an aero derivative gas turbine lube oil system. The CM model provides satisfactory performances in terms of classification accuracy, while remarkably reducing the expert efforts for data labeling and model (periodic) updating.

Experiences with ASTM D02 Practices D4378 and D6224 for Turbine Oils and Auxiliary Power Plant Equipment Condition Monitoring Programs

Abstract Condition monitoring practices ASTM D4378 [2011, “Section Five, Petroleum Products, Lubricants, and Fossil Fuels,” Annual Book of ASTM Standards, Vol. 05.02, ASTM International, West Conshohocken, PA] and ASTM D6224 [2009, “Standard Practice for In-Service Monitoring of Lubricating Oil for Auxiliary Power Plant Equipment,” Annual Book of ASTM Standards, Vol. 05.02, ASTM International, West Conshohocken, PA] are important activities at the SC C00 as they are the benchmark today in the power generation industry for condition monitoring and maintenance practices. With the need for increased equipment and plant efficiency in the modern economy, these methods contribute to an improved reliability and better utilization of modern turbine lubricants. In conjunction with the latest ASTM D4303 [Annual Book of ASTM Standards, ASTM International, West Conshohocken, PA] (the new turbine oil specification) these methods help the end-users to better understand the condition of their in-service lubricants and by turning them into immediate maintenance actions. This paper will include a few case studies, presenting the different experiences with the integration of these in-service practices, and how they are evolving with the original equipment manufacturers’ equipment developments and turbine lube oil developments.