Turbine Propulsion Research Articles

Advancing condition-based maintenance of naval propulsion systems with ensemble learning techniques

In the field of industrial engineering, especially in the operation of Gas Turbine (GT) propulsion systems used in frigates, ensuring reliable and efficient performance is crucial. These propulsion systems enable ships to navigate quickly, respond swiftly to threats, and successfully carry out important missions. However, the harsh conditions at sea, such as saltwater corrosion and temperature extremes, cause significant wear and tear on these systems, which can threaten both their performance and the safety of the crew. This makes accurate fault detection in GT compressors and turbines essential. This research introduces a novel approach that combines machine learning (ML) with advanced ensemble learning techniques specifically tailored for diagnosing faults in GT propulsion systems. The key innovation lies in developing a hybrid framework that leverages both the strength of traditional ML classifiers and the robustness of ensemble methods, improving the accuracy of fault diagnosis while reducing the risks of overfitting. Unlike conventional methods that focus on one type of algorithm, our method integrates diverse models to achieve better generalization and stability under varying operational conditions. Through this analysis, we assess the performance and stability of different strategies, focusing on how well this hybrid ensemble approach works compared to standard ML approaches across a variety of classifiers. The research offers valuable insights and provides a solid framework for understanding the flexibility and effectiveness of this novel technique. By connecting theory with real-world applications, this study aims to significantly improve fault detection in vital naval propulsion systems, ultimately contributing to better performance and reliability in maritime defense operations.

The impact of counterfeit components and LRUs in the navy surface warfare supply chain: A systems dynamics approach

AbstractMicroelectronics integrity is a critical issue for many industries including the Department of Defense (DoD). The military systems the DoD operates are particularly vulnerable to counterfeiting, with potentially costly or even catastrophic consequences. Counterfeits, regardless of production intent (malign or ersatz), raise significant concerns for industry and the DoD because they often demonstrate operational performance shortcomings, have lower reliability, or make components or organizations more vulnerable to attack. This article uses a systems dynamics modeling approach to explore the economics of counterfeiting for a sample system, the interactions between counterfeiters and the US Navy supply chain, and the impacts of counterfeit surveillance and detection to address the question: Is it more effective to target detection efforts at the component level or at the Line Replaceable Units level? A case study of an engine control module for the LM2500 propulsion turbine used on US Navy Arleigh Burke class guided missile destroyer (DDG‐51) platforms is provided to demonstrate the approach.

Onboard pre-combustion carbon capture with combined-cycle gas turbine power plant architectures for LNG-fuelled ship propulsion

This paper investigates the concept of pre-combustion carbon capture (Pre-CCS) with a combined cycle gas turbine (CCGT) propulsion system to achieve energy efficient carbon capture onboard a Liquid Natural Gas fuelled vessel. A basic CCGT model with energy efficiency of 51.6 % when using LNG as fuel was integrated with a Pre-CCS system composed of a steam methane reformer, water–gas shift reactors, pressure swing adsorption (SMR-PSA), and liquid CO2 storage. Various waste heat utilisation schemes integrated with the CCGT-reformer were modelled in Aspen HYSYS. The modelling of the waste heat recovery networks as energy streams integrating between various processes and unit of operations has facilitated a closed-loop simulation of various systems. It was concluded that a proper utilisation of the high-grade heat from the gas turbine (GT) exhaust and from the reformer is crucial to improve the overall energy efficiency and carbon capture rate, exemplified by a scheme where the heating needs for the SMR and the cooling needs from the water–gas-shift reactors are fully integrated. When optimised, the integrated system had an overall energy efficiency of 41.5 % and 43.2 % (i.e. an efficiency loss of 10.2–10.5 percentage points from the base CCGT system) accompanied with specific GHG emission reduction of 51.2 % and 52.3 % for operation of the GT at a turbine entry temperature of 1700 K and 1850 K, respectively. Intermediate levels of reforming, where the GT uses a mix of LNG and reformate gases, were also simulated, showing an almost linear evolution from the 100 % LNG feed to the GT to the 100 % reformate case. Such a strategy could be used for gradual evolution to meet the required CO2 reduction timeline. It was determined that the 100 % reformate case provides the highest CO2 capture rate. Estimates of other emissions from the GT assuming typical combustor residence times for the whole range of fuel blends were also carried out, showing that the overall greenhouse gas emission is dominated by CO2, given that the GT emits negligible N2O and unburnt methane. Some capital cost estimates were also made to determine the unit price of hydrogen fuel produced onboard, suggesting that the CAPEX was not prohibitive. These findings support the pre-combustion CCS − CCGT integrated system as a promising long-term decarbonisation and propulsion strategy to comply with emissions regulations, displaying good performance in terms of cost, energy consumption, and CO2 reduction. The scalability and adaptability of the proposed system for existing and new-built ships across the decarbonisation timeline is also discussed.

Abating CO2 and non-CO2 emissions with hydrogen propulsion

Abstract This contribution focuses on the abatement with hydrogen of CO2 and non-CO2 emissions. It is agenda-setting in two respects. Firstly, it challenges the globally accepted hydrocarbon sustainable aviation fuel (SAF) pathway to sustainability and recommends that our industry accelerates along the hydrogen pathway to ‘green’ aviation. Secondly, it reports a philosophical and analytical investigation of appropriate accuracy on abatement strategies for nitrogen oxides and contrails of large hydrogen airliners. For the second contribution, a comparison is made of nitrogen oxide emissions and contrail avoidance options of two hydrogen airliners and a conventional airliner of similar passenger capacity. The hydrogen aircraft are representative of the first and second innovation waves where the main difference is the weight of the hydrogen tanks. Flights of 1000, 2000, 4000 and 8000 nautical miles are explored. Cranfield’s state of the art simulators for propulsion system integration and gas turbine performance (Orion and Turbomatch) were used for this. There are two primary contributions to knowledge. The first is a new set of questions to be asked of SAF and hydrogen decarbonising features. The second is the quantification of the benefits from hydrogen on non-CO2 emissions. For the second generation of long-range hydrogen-fuelled aircraft having gas turbine propulsion, lighter tanks (needing less thrust and lower gas temperatures) are anticipated to reduce NOx emissions by over 20%; in the case of contrails, the preliminary findings indicate that regardless of the fuel, contrails could largely be avoided with fuel-burn penalties of a few per cent. Mitigating action is only needed for a small fraction of flights. For conventional aircraft this penalty results in more CO2, while for hydrogen aircraft the additional emission is water vapour. The conclusion is that our research community should continue to consider hydrogen as the key ‘greening’ option for aviation, notwithstanding the very significant costs of transition.

Power generation analysis of super-long gravity heat pipe geothermal systems

Highly-efficient and environment-benign heat extraction and utilization technologies are key to large-scale geothermal energy deployment. In recent developments, the innovative super-long gravity heat pipe (SLGHP) geothermal power plant has revolutionized deep geothermal power generation by obviating the need of flash devices or heat exchangers in vapor generation for turbine propulsion. This advancement promises substantial structural simplification, a marked reduction in exergy losses, and significant cost savings. Nevertheless, a comprehensive understanding of the performance of SLGHP power generation systems is still lacking in published research. For a single-well geothermal system, the geothermal gradient assumes critical importance as it serves as a key indicator of resource intrinsic conditions, and the depth of the well emerges as an essential controllable variable in manual drilling. The present investigation seeks to elucidate the impact of these two key parameters on the performance of SLGHP power generation systems. For this purpose, a semi-empirical formula is analytically derived to describe the heat extraction process within the SLGHP system. This formula is integrated with a thermo-economic model to evaluate the performance of the SLGHP power generation system. It is found that adjusting the two parameters can yield simultaneous increases in the heat extraction rate and the energy efficiency, thereby resulting in a significant boost in power generation of SLGHP. Specially, the SLGHP system of a 4000 m deep well and with a 0.045 K/m geothermal gradient can output 35.95 kW electricity, while that of a 5000 m deep well and with a 0.05 K/m geothermal gradient achieves 86.39 kW electricity output. In practical terms, it is found that the optimal strategy for an SLGHP power plant involves drilling multiple wells in a reservoir with a higher geothermal gradient. However, when repurposing abandoned oil/gas wells for power generation, the preference is for deep wells.

Explainable Prognostics Method through Differential Evolved RVR Ensemble of Relevance Vector Machines

Operating experience from various mechanical components indicates that their operating performance depends on non-well known physical mechanisms, while it is likely that various unexpected factors will act as catalysts for reaching the failure point. Therefore, one way to overcome the partially knowledge of physical mechanisms is the use of data-driven methods that estimate the degradation patterns and predict the failure point. Thus, there is a growing need to design and develop new and more sophisticated prognostic technologies that can estimate the remaining useful life of a mechanical component. In this work, a new method for prognostics is proposed that not only provides a prediction over the failure point but also provides an explanation over the rationale behind that prediction. The proposed method utilized tools from artificial intelligence and more specifically relevance vector machines (RVM) and differential evolution (DE). The cornerstone of the method is the assembly of an ensemble comprised of multiple RVM equipped with different kernels, and the subsequent evolution of the ensemble using the differential evolution. DE will provide a set of values for the coefficients of the ensemble. Then based on the coefficients together with their associated RVMs are used to provide an explanation over the prediction. The explanation stems from the kernels themselves as each kernel models different set of properties. The presented method is tested on a set of real-world degradation data taken from a Gas Turbine (GT) propulsion plant.

TERA of Gas Turbine Propulsion Systems for RORO Ships

Recently, regulations on emissions produced by vessels from international maritime organizations, along with the instability of fuel prices, have encouraged researchers to explore fuels and technology that are cleaner than heavy fuel oil and diesel engines. In this study, we employed the TERA method to evaluate the feasibility of using gas turbine engines with cleaner fuels as a replacement for diesel engines as a propulsion system for RORO ships. A sensitivity evaluation and risk assessment were also conducted to investigate the impact of applied emission taxes on the economic results. The findings indicated that the diesel engine emitted higher nitrogen oxide emissions than the gas turbine fuelled by natural gas and hydrogen. The gas turbine with hydrogen had zero carbon dioxide emissions, making it a sustainable energy production option. The economic aspects were evaluated based on an international route, and they revealed that economic profitability significantly depended on fuel costs and consumption. The diesel engine fuelled by marine diesel oil and the gas turbine fuelled by natural gas were economically attractive, whereas the gas turbine fuelled by hydrogen was less viable due to its high operating cost. However, in a scenario where a carbon dioxide tax was introduced, the gas turbine fuelled by hydrogen showed high potential as a low-risk investment compared to the other technologies. In summary, this study demonstrated the usefulness of the TERA method in the maritime sector for selecting and comparing various propulsion systems.

Microstructure, mechanical and thermal properties of YSZ thermal barrier coatings deposited by axial suspension plasma spraying

Yttrium-stabilized zirconia (YSZ) thermal barrier coatings (TBCs) are indispensable elements of present-day turbine propulsion systems. The ones deposited with atmospheric plasma spraying (APS) are characterized by required low thermal conductivity, but they are unable to survive frequent thermomechanical loading and therefore their application is limited to parts remaining stationary. Expanding capability of TBCs is sought in various areas, but the one realized through modification of most proliferated apparatus used for plasma spraying (PS) (from radial to axial injection) and substituting micrometric powders with the nano-structured suspension needs least changes in the industry established procedures and offers the highest property improvement. The present experiment covered the deposition of ZrO2-8Y2O3 YSZ TBC using both atmospheric and suspension PS processes. They were performed with commercial micrometric and nano-structured YSZ (8% Y2O3) powders. The coatings morphology and microstructure were characterized with 3D profilometry, scanning and transmission electron microscopy (SEM/TEM) methods. Finally, the coating’s hardness and heat conductivity were measured. This complex approach allowed to state that PS of micrometric t’-ZrO2 powder having an admixture of m-ZrO2 phase is capable of only partial improvement in its homogenization. However, the suspension PS process of nano-structured powder eliminated any traces of the monoclinic phase from the coating. The TEM microstructure observations indicated that the suspension PS coating is built by in-flight solidified droplets as well as by the melted ones flattened on arrival. A surface layer of liquefied material on solid droplets increases their adhesion to surface asperities promoting pseudo-columnar growth of the coating. The preservation of monotonic slow increase of thermal conductivity during heating of the suspension PS coating means, that its pseudo-columnar microstructure is better suited to withstand high strains during such treatment.

Next Generation Aircraft Propulsion: A Pratt & Whitney Approach

Abstract Aircraft engines that minimize fuel consumption and operate on sustainable aviation fuels are key to meeting the air transportation sector’s commitment to net zero CO2 emissions by 2050. This article reports on work to implement sustainable propulsion technologies, including advanced gas turbine propulsion technologies, engines that are compatible with approved sustainable aviation fuels, hybrid-electric propulsion, and hydrogen propulsion. The article also describes efforts to reduce the environmental footprint related to condensation trails (contrails) from aircraft engine exhaust plumes.

Performance analysis of a hybrid aircraft propulsion system using solid oxide fuel cell, lithium ion battery and gas turbine

A novel integration of a solid oxide fuel cell (SOFC), lithium ion batteries and a gas turbine propulsion system is proposed for a hybrid electric aircraft. Methane as hydrogen storage medium is fed to the propulsion system so as to avoid the limitations associated with the use of pure hydrogen storage and utilization. An internal reformer is used in the SOFC to produce hydrogen through the steam reforming and water–gas-shift reactions of the methane and steam mixture. An afterburner is used to generate the heat required for generation of electrical power in the gas turbine and preheating the SOFC reactants by burning the remaining fuel from the SOFC. Also, a pathway for liquid water input to the hybrid system is designed in a way to first circulate through the lithium ion batteries to remove generated heat from them before it is used in the remainder of system. The variations of heat generation rate and temperature of the battery with time are predicted through electrochemical and thermal models. A performance assessment of the proposed propulsion system is conducted to investigate the compatibility and applicability of the system. It is found that at 1C (charge/discharge rate of battery), the average temperature of the lithium ion battery is maintained at about 28 °C through a water-based cooling process. The optimum net electrical power output and energy efficiency of the hybrid propulsion system are achieved at compressor pressurization ratio of 7.5. Furthermore, the net electrical power produced and energy efficiency of the hybrid propulsion system reach their maximum values (i.e., 6.6 × 106 W and 46.5 %, respectively) at a SOFC temperature of 775 °C.

Archimedes Screw Turbines (ASTs) Performance Analysis using CFD Software Based on Variation of Blades Distance and Thread Number on The Pico Hydro Powerplant

Pico hydro is a power plant that uses water as turbine propulsion that can generate electricity by a generator. This research will discuss the numerical analysis of the effect of the number of threads on the turbine blades. The analysis process uses the Computational Fluid Dynamic method and the software used in ANSYS FLUENT. In variation 1 uses 9 threaded blades, variation 2 uses 6 threads, variation 3 uses 4 threads. Based on the simulation results in variation 1 with the number of blades 9 threads, the highest torque at TSR 12 is 0.00984111 Nm, power is 0.007671419 Watt. The water pressure entering the turbine blades in variation 1 is 0.097098 Pascal and the water pressure coming out of the blades is 0.047954 Pascal, there is a total pressure drop of 0.4914 Pascal. Based on the torque and power values of the Archimedes turbine in the three variations, it is known that variation 1 has the best performance followed by the other two turbine variations.

Techno-Environmental Evaluation of a Liquefied Natural Gas-Fuelled Combined Gas Turbine with Steam Cycles for Large Container Ship Propulsion Systems

Restrictions on emissions are being imposed by regional and international shipping organisations, which raise the question of which marine fuel and technology can most effectively replace heavy fuel oil and diesel engines. The aim of this study is to find appropriate advanced combined gas and steam turbine cycles for marine propulsion systems in a large container ship with respect to the evolving maritime environmental regulations. The selection criteria are the thermodynamic performance, emissions, size, and weight of advanced combined gas and steam turbine cycles in a large container ship. Two baselines are used: a diesel engine using marine diesel oil and a combined gas and steam turbine system using liquefied natural gas and marine diesel oil. Then, liquefied natural gas cycles are examined based on fuel replacement and enhanced to assess the benefits of liquefied natural gas over marine diesel oil. The results show that the enhanced liquefied natural gas combined gas and steam turbine cycles are the most efficient, at up to 1.6% higher than the other cycles. Regarding the size and weight, the combined gas and steam turbine propulsion system is approximately 24.7% lighter than the original diesel engine propulsion system.

Analysis of LNG carrier propulsion developments

The LNG market has undergone major changes and significant development in recent years. With the increase in the number of ships and the increase in the amount of gas transported, the propulsion machinery of LNG ships has also changed. For many years, the steam turbine was the only propulsion engine on this type of cargo ship. A negligible number of vessels powered by a traditional, low-speed, heavy-duty diesel engines are increasingly being replaced by new technologies. Versions of dual-fuel internal combustion engines that burn evaporated natural gas are increasingly replacing steam turbine propulsion systems. This phenomenon has been particularly pronounced in the last few years, when orders for steam turbine-powered LNG vessels have ceased. This article examines and presents the main reasons for these changes, which fall into two categories. The first is financial, as the use of new technologies can lead to significant financial savings in fuel consumption. Fuel costs can be reduced by more than 35% in some cases. The reduction in fuel consumption leads to a significant reduction in overall exhaust emissions and thus a reduction in air pollution and CO2 signature.

Parametric study on tank integration for hydrogen civil aviation propulsion

Hydrogen powered gas turbine propulsion will play a central role in the decarbonisation of civil aviation. A key challenge is the integration of large liquid hydrogen tanks into the aircraft, given the low density of liquid hydrogen. Hydrogen offers a quarter of the energy content, per unit volume and one third of the fuel weight, when compared to a conventional fuel. Optimising tank weight is seen as key to aircraft usefulness. A detailed evaluation of tanks for civil aviation is presented here, covering a very wide range of sizes and design solutions.For passenger air transport, if the choice is made not to vent, dormancy time (the time the tank can be allowed to operate without vapour or important fuel extraction) becomes a key design parameter. This paper highlights the interdependence of Maximum Allowable Operating Pressure and the amount of insulation with heating and venting, considering the influence of dormancy time.The resulting tank gravimetric efficiency is presented for cylindrical tanks with hemispheric ends (a very likely choice for tank design). Notwithstanding conservative analysis, tank gravimetric efficiencies of 65–70% can be achieved. This permits combined fuel and tank weights that are less than half of those of current aircraft. The issue that then becomes critical is the resulting large tank and aircraft volume.

Application of a Two-Stage Steam Jet Injector Unit for Latent Heat Recovery of a Marine Steam Turbine Propulsion Plant

The paper presents the results of the numerical research of the steam jet injector applications for the regenerative feed water heating systems of marine steam turbine propulsion plants. The analysis shows that the use of a single injector for a single heat exchanger results in a relative increase in the thermal efficiency of the plant by 0.6–0.9%. The analysis also indicates the legitimacy of the usage of multistage feed water heating systems, which would enable the operating parameters optimization of the injectors. The obtained steam pressure up to the value of 1.8 barA allows for the heating of the feed water up to 110 °C. For higher degrees of feed water heating in the heat exchangers, it is necessary to supply heating steam of higher pressure. Therefore, the usage of two-stage steam jet injector units was considered advisable for the analyses.

Modeling method of steam turbine generator set based on cascade feedforward PID coordinated control system

Objective In order to quickly and accurately evaluate the reliability of a steam turbine generator set under actual working conditions, it is necessary to construct a visual model of the set. Method Based on an analysis of a mathematical model of a traditional steam turbine generator set, a cascade PID method is proposed and a feedforward link added. Then, based on a Matlab Simulink environment, a visual model of the optimized control of a steam turbine generator set is built, and the steady state and fault state of the set are simulated and analyzed with the help of the simulated fault module. Results The simulation results show that the output speed of the steam turbine generator set based on cascade feedforward PID coordinated control is higher than the given speed for a short time when starting under load, but the stable value is quickly restored under the action of the control feedback. In the case of failure, the rotation speed can also fluctuate within a given range. Conclusion This modeling method of a steam turbine generator set based on a cascade feedforward PID coordinated control system can be popularized in the modeling of nuclear turbine propulsion systems, providing an analytical means of achieving the visual analysis of the unit's operation state, and saving both cost and time.

Analysis and Optimization of Atmospheric Drain Tank of Lng Carrier Steam Power Plant

The atmospheric drain condensate system of a marine steam power plant is described and evaluated from the energetic and exergetic point of view at a conventional liquefied natural gas (LNG) carrier. Energy loss and exergy destruction rate were calculated for individual stream flows joined in an atmospheric drain tank with variations of the main turbine propulsion speed rate. The energy efficiency of joining streams was noted to be above 98% at all observed points as the atmospheric drain tank was the direct heater. The exergy efficiency of the stream flows into the drain tank was in the range of 80% to 90%. The exergy stream flow to the tank was modeled and optimized by the gradient reduced gradient (GRG) method. Optimization variables comprised contaminated and clean condensate temperature of the atmospheric drain tank and distillate water inlet to the atmospheric drain tank with respect to condensate outlet temperature. The optimal temperatures improves the exergy efficiency of the tank as direct heater, to about 5% in port and 3% to 4% when the LNG carrier was at sea, which is the aim of optimizing. Proposals for improvement and recommendations are given for proper plant supervision, which may be implemented in real applications.

Automation and Electronic Control of Marine Gas Turbine Engine for Ship Revamp

Gas turbines used in propulsion ensure increased efficiency and safety, with a very good power / weight ratio and with low maintenance and operation costs. Due to becoming out-of-date and reaching the maximum operation hours and expected lifetime, which can cause malfunctioning, older turbine engines on frigates need to be replaced with newer generation propulsion engines. The paper presents the replacement of the turbine engine on a defence frigate, focusing on the automation and electronic control solution employed for a propulsion turbine, integrating state-of-the-art techniques. The electronic system ensures control, monitoring and alarm functions, including overspeed protection. A local control panel interfacing the PLC displays the operating parameters and engine controls, also providing maintenance and calibration sequences. The proposed solution enables both the local and the remote control of the ship’s gas turbine.

Three Approaches to Low-Duty Turbo Compressor Efficiency Exploitation Evaluation

This paper presents three approaches for isentropic, energy, and exergy evaluations of a low-duty liquid natural gas (LNG) vapor turbo compressor during exploitation on a conventional LNG carrier. The evaluation was conducted on the measured performance parameters under 22 various turbo compressor operating regimes. The turbo compressor performance was evaluated in the temperature span from −69 to −105 °C and during changes in the rpm of the main propulsion turbine and, consequently, the main boiler load. The results show that the highest measured turbo compressor isentropic efficiency is in agreement with the manufacturer specifications, equaling 75.23% at a main propulsion turbine rpm of 53.5. At the highest measured loads and rpm, the turbo compressor energy and exergy efficiencies reach the highest values of 57.81% and 28.51%, respectively. In each observed operating regime, the influence of the ambient temperature change on the turbo compressor exergy efficiency was investigated. At the lowest and the highest measured loads, turbo compressor energy and exergy flow streams are presented in a Sankey diagram. Techniques for cargo temperature maintenance during the ship voyage are presented, as the results show that low suction gas temperatures influence turbo compressor efficiency.

A comparative investigation of data-driven approaches based on one-class classifiers for condition monitoring of marine machinery system

The safety and reliability of ship navigation depend heavily on the performance of the marine machinery system, which can be maintained at a high level by condition based maintenance. Intelligent condition monitoring is the key to achieve condition based maintenance. However, it is not easy to realize intelligent condition monitoring in a real ship, because there are not enough labeled fault samples to train an accurate detection model. In fact, the potential value of a large number of normal samples collected by the shipboard monitoring system has not been mined out. Since one-class classifiers only need one-class samples to train the detection models, they are very suitable for such occasions. In this paper, we investigate the performance of several representative one-class classifiers, such as OCSVM (One class support vector machine), SVDD (Support vector data description), GKNN (Global k-nearest neighbors), LOF (Local outlier factor), IForest (Isolation forest) and ABOD (Angle-based outlier detection), in condition monitoring of the marine machinery system. The dataset of a marine gas turbine propulsion system is used for a case study, which is a simulation dataset verified by the real ship data. Compared with previous literatures, our new work is to investigate the performance of a variety of key one-class classifiers, not only considering the common evaluation indexes for machine learning, but also considering the sample combinations of the training dataset, distribution of misclassified samples, and the tolerance to contaminated data. The experimental results show that these algorithms have good performance in the dataset in some common evaluation indexes. However, they show some obvious performance differences in some novel evaluation indexes we proposed. This can provide decision support for the application of one-class classifiers in the condition monitoring of many other marine machinery systems.