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To ascertain energy availability and system performance, a comprehensive understanding of the systems' degradation profile and impact on overall plant reliability is imperative. The current study presents an integrated Failure Mode and Effects Analysis (FMEA)–Markovian algorithm for reliability-based instantaneous energy performance prediction for thermal energy systems. The FMEA methodology is utilized to identify and categorize the various failure modes of the gas turbines, establishing a reliability pattern that informs overall system performance. Meanwhile, the Markovian algorithm discretizes the system into states based on its operational energy performance envelope. The algorithm predicts instantaneous energy performance according to upper and lower bounds criteria. This integrated methodology has been subjected to testing in three case studies, yielding results that demonstrate improved reliability and instantaneous energy performance prediction during system degradation. It was observed that after 14 years of operation, the likelihood of major failures increases to 79.6%, 88.7%, and 82.8%, with corresponding decreases in system performance reliability of 10.1%, 4.5%, and 7.8% for the Afam, Ibom, and Sapele gas turbine plants, respectively. Furthermore, the percentage of instantaneous mean power performance relative to the rated capacity is 37.9%, 35.1%, and 46.3% for the three gas turbine plants. These results indicate that the Sapele thermal power plant performs better relative to its rated capacity. Overall, this integrated methodology serves as a valuable tool for monitoring gas turbine engine health and predicting energy performance under varying operating conditions. [ABSTRACT FROM AUTHOR]

This study develops a precise and cost-effective method for reducing the complexity of cryogenic hydrogen unintended release. For this purpose, the dominant modes of a well-characterised cryogenic hydrogen jet (Sandia National Laboratories), with stagnation pressure and temperature fixed at 5 bar and 50 K, are extracted using the proper orthogonal decomposition (POD) method. Building on validating the large eddy simulation (LES) against experimental measurements, the velocity field within the LES results is analysed near the release point. The mass fraction half-width of cryogenic hydrogen jets grows linearly with a slope of 0.1115 against the downstream distances, resembling room-temperature jets. The first 10 extracted modes from 500 LES snapshots demonstrate dominance over the remaining modes. In addition, this study evaluates the flammable gas dispersion using LES and 10-mode POD, showing POD effectively identifies high-risk areas within hydrogen's flammability range. Minor deviations (2.1–3.3%) confirm POD's reliability for hazard assessment compared with LES. Furthermore, an in-depth analysis is performed on the radial distributions of hydrogen mass fraction and centreline hydrogen mole fraction. [Display omitted] • Integrating LES and POD to extract dominant modes in Sandia's cryogenic jet release. • Processing 500 LES snapshots to extract dominant modes in hydrogen dispersion. • Evaluating fire risk with LES and 10-mode POD, highlighting POD's effectiveness. • Confirming POD's reliability with minor deviations in fire hazard assessment. • Detailed analysis of radial hydrogen mass fraction and centreline mole fraction. [ABSTRACT FROM AUTHOR]

Cryogenic liquid hydrogen offers a promising solution for achieving high-density hydrogen storage and efficient on-site distribution. However, the potential hazards associated with hydrogen leakages necessitate thorough investigations. This research aims to model cryogenic hydrogen release from circular and high aspect ratio (HAR) nozzles tested by Sandia. The test conditions cover reservoir pressures and temperatures corresponding to cryogenic hydrogen storage. The study conducts computational simulations using OpenFOAM to examine hydrogen concentration, temperature fields, mass fraction, and temperature distributions, achieving good agreement with the experimental data. To further explore, the study of velocity variations shows a consistent decay rate with room-temperature jets. The numerical data reveals comparable inverse centreline hydrogen mass fractions (0.254 for HAR and 0.26 for circular) and normalised centreline temperature decay rates (0.031 for HAR and 0.032 for circular). The present computational model holds the potential for further analysis of cryogenic hydrogen in large-scale facilities. • Comprehensive study on cryogenic hydrogen release scenarios. • Consistent hydrogen concentration decay rates for circular and HAR nozzles. • Close alignment with Sandia's experimental data for circular and HAR nozzles. • Temperature profiles closely matching experimental data for both nozzle types. • Velocity profiles indicating variations in mixing and dispersion by pressure changes. [ABSTRACT FROM AUTHOR]

In this paper, we present a real-time parameter identification approach for diagnosing faults in the exhaust gas recirculation (EGR) system of Diesel engines. The proposed diagnostics method has the ability to detect and estimate the magnitude of a leak or a restriction in the EGR valve, which are common faults in the air handling system of a Diesel engine. Real-time diagnostics is achieved using a recursive-least-squares (RLS) method, as well as, a recursive formulation of a more robust version of the RLS method referred to as recursive total-least-squares method. The method is used to identify the coefficients in a static orifice flow model of the EGR valve. The proposed approach of fault detection is successfully applied to diagnose low-flow or high-flow faults in an engine and is validated using experimental data obtained from a Diesel engine test cell and a truck. [DOI: 10.1115/1.4000655]