Propulsion Plant Research Articles

Approximate calculation of initial conditions of a spacecraft with solar electric-rocket propulsion plant starting while transferring from highly elliptic orbit to geostationary one

Approximate calculation of initial conditions of a spacecraft with solar electric-rocket propulsion plant starting while transferring from highly elliptic orbit to geostationary one

Considerations regarding the anti-icing system for the ship propulsion plant with gas turbine

Vessels that have navigation routes in areas with ambient temperatures that can drop below + 5 [°C], with a relative humidity of over 65%, will have implemented technical solutions for monitoring and combating ice accumulations in the intake routes of gas turbine power plants. Because gas turbines are not designed and built to allow the admission of foreign objects (in this case - ice), it is necessary to avoid the accumulation of ice through anti-icing systems and not to melt ice through defrost systems. Naval anti-icing systems may have as a source of energy flow compressed air, supersaturated steam, exhaust gases, electricity or a combination of those listed. The monitoring and optimization of the operation of the anti-icing system gives the gas turbine power plant an operation as close as possible to the normal regimes stipulated in the ship's construction or retrofit specification.

Identification of Gate Turn-off Thyristor Switching Patterns Using Acoustic Emission Sensors.

Modern seagoing ships are often equipped with converters which utilize semiconductor power electronics devices like thyristors or power transistors. Most of them are used in driving applications such as powerful main propulsion plants, auxiliary podded drives and thrusters. When it comes to main propulsion drives the power gets seriously high, thus the need for use of medium voltage power electronics devices arises. As it turns out, power electronic parts are the most susceptible to faults or failures in the whole electric drive system. These devices require efficient cooling, so manufacturers design housings in a way that best dissipates heat from the inside of the chips to the metal housing. This results in susceptibility to damage due to the heterogeneity of combined materials and the difference in temperature expansion of elements inside the power device. Currently used methods of prediction of damage and wear of semiconductor elements are limited to measurements of electrical quantities generated by devices during operation and not quite effective in case of early-stage damage to semiconductor layers. The article presents an introduction and preliminary tests of a method utilizing an acoustic emission sensor which can be used in detecting early stage damages of the gate turn-off thyristor. Theoretical considerations and chosen experimental results of initial measurements of acoustic emission signals of the medium voltage gate turn-off thyristor are presented.

An empirical analysis on the operational profile of liquefied natural gas carriers with steam propulsion plants

AbstractLiquefied natural gas (LNG) offers negligible NOx and SOx emissions as well as reductions in CO2 compared with other liquid hydrocarbons. LNG is a significant player in the global energy mix, with a projection of 40% increase in demand for the next two decades. It is anticipated that the expected rise in demand will cause the fleet of LNG carriers (LNGC) to expand. This work concentrates on steam-powered LNGC, which accounted for 47% of the LNGC fleet in 2018. It performs an empirical analysis of continuous monitoring data that provide high levels of accuracy and transparency. The analysis is done on data collected from 40 LNGCs for over a year to estimate the fleet's operational profile, fuel mix and energy performance. The findings of this work are relevant for bottom-up analysis and simulation models that depend on technical assumptions, but also for emission studies such as the upcoming Fourth International Maritime Organization Greenhouse Gases study.

Wavelet Transforms of Diagnosable Signals from Ship Power Complexes in a MATLAB Environment

The use of digital technologies in the systems of diagnostics and monitoring of units of a ship’s propulsion plant can significantly increase the efficiency and quality of assessing the technical condition of operated objects in the online mode as well as expand the class of practical problems to be solved. Digital processing of signals of complex configuration at a qualitatively new level is an indispensable condition for a critical improvement in the course of processing the current values of diagnosable parameters, increasing the reliability and trouble-free performance of a ship’s technical equipment during operation. A method of approximation has been discussed in the paper. Moreover, the paper provides an algorithm for analyzing the signal of the indicator diagram of a marine diesel engine, the spectrum of which contains high-frequency components and short-term pulses indicating deviations from the normal operating mode, the assessment of which is practically impossible with the traditionally applied methods of spectral analysis of signals. The approximation method is based on the use of wavelet analysis, which makes it possible to deeply explore such modes. Examples of using wavelet analysis to approximate one-dimensional signals of elements and systems of a ship’s power complexes are given.

Simulation study for injection of two-phase fuel mixture into a cylindrical afterburner with asymmetric air inlet

A method is developed for secondary data processing of the results of simulation of two-phase flow in an afterburner with a complex geometry. This method offers a prediction for mixing process efficiency (quality estimate) and combustion efficiency in an afterburner of a power plant. The opportunities of this method were demonstrated at the example of simulation of mixing the two-phase fuel with air in the afterburner of a model power plant with gas generation outlay. The paper presents a mathematical model for studied processes and the simulation results. The fuel was the gasification products (GP) of a high-energy composition (a mixture of gaseous and condensed phases). An algorithm was applied for processing the mathematical simulation results: the output is the evaluation of mixing between GP condensed phase and air flow. The parametric study offers the dependencies for size distributions of GP particles in the afterburner cross sections. The limiting values for GP combustion efficiency in the afterburner were evaluated from analysis of GP flow (gas and condensed phases) mixing with air flow. Simulation gives the data on the influence of injection configuration and GP condensed phase dispersion profile on the mixing efficiency in the afterburner. The results of study can be useful in recommendations for gaining on the cycle efficiency in novel propulsion plants.

Integrated Load-Split Scheme for Hybrid Ship Propulsion Considering Transient Propeller Load and Environmental Disturbance

Abstract This work addresses the design and experimental implementation in real-time of an integrated predictive load-split management system for the transient and fluctuating propeller load sharing. Control-oriented modeling of the power system was performed based on experimental data gathered from the hybrid plant and on first principles for the diesel engine behavior and battery charging. Propulsion plant and environmental disturbance models are developed to simulate realistic marine load application. A nonlinear model predictive control (NMPC) scheme is proposed for the optimal transient power-split problem of a hybrid diesel-electric marine propulsion plant. The NMPC scheme directly controls the torque output of the diesel engine and the electric motor/generator ensuring that certain constraints concerning the system overloading are met, avoiding fast accelerations and load fluctuations of the diesel engine that affect engine performance. To achieve offset-free model predictive control (MPC) control, an observer is developed to provide the propeller law parameter to the NMPC for load estimation. The control system was experimentally tested in real-time operation. Results showed that controller rejected load disturbances and maintained the desired rotational speed of the powertrain as well as the desirable state of charge (SOC) in battery within the power plant limits, achieving smooth power transitions and mitigation of power fluctuations of the diesel engine.

Automatic Calculation of Torsional Vibrations on Marine Propulsion Plant Using Marine Two-Stroke Diesel Engine: Algorithms and Software

For a sea-going ship to be built new or reconstructed, the main propulsion plant (MPP) consisting of a marine diesel engine (MDE), driving the ship propeller, is mandatory to be calculated with the torsional vibrations (TVs) in accordance with the Rules for the Classification and Construction of Sea-Going Ships, such as Russian Maritime Register of Shipping (RMR), DNV, ABS, and VR. The TV calculations (TVC) are conducted at normal working regimes and at misfire regimes (called by Normal or Misfire regimes relatively) with only one of cylinders of MDE while engine speed range covers from the minimum to maximum values of the operation speeds. The TVC on the MPP are incredibly sophisticated calculations and are conducted with special software for TVC. The paper presents the algorithms and software for automatic calculating the TVs (SATVC) basing on the made mathematical models, algorithms and coded in LabView by authors. The SATVC was automatic calculated the freedom TVs (FTVs), excited torsional moments (ETM), excited TVs (ETVs), permitted torsional pressures (PTP), and common management (CTVC). In the article were shown the probated results of TVC using the SATVC for the MPP on MV.HR.34000 DWT which built in Pha Rung Shipyard, Viet Nam.

Increasing the Energy Efficiency of an Internal Combustion Engine for Ship Propulsion with Bottom ORCs

The study examines the option of adding a bottom Organic Rankine Cycle (ORC) for energy recovery from an internal combustion engine (ICE) for ship propulsion. In fact, energy recovery from the exhaust gas normally rejected to the atmosphere and eventually from the cooling water circuit (usually rejected to the sea) can significantly reduce the fuel consumption of a naval ICE during its operation. In the paper, different possible bottom ORC configurations are considered and simulated using the Aspen® code. Different working fluids are taken into account, jointly with regenerative and two-temperature levels designs. The energy recovery allowed by each solution is evaluated for different engine load, allowing the identification of the most suitable ORC configuration. For the selected case, the preliminary design of the main heat exchangers is carried out and the off-design performance of the whole combined propulsion plant (ICE + ORC) is evaluated, leading to a preliminary analysis of cost saving during normal ship operation. The results of this analysis show an increase in power output of about 10% and an expected Payback Time of less than 6 years.

Automatic Predicting Torsional Vibrations on Main Propulsion Plants, Installed Two-Stroke Diesel Engines: Algorithms and Software

The main propulsion plant (MPP) on marine sea-going ships consisting of a diesel engine as the main engine and driving the ship propeller is with the torsional vibrations to be calculated in accordance with the Rules for the Classification and Construction of Sea-Going Ships. The Rules are given by one of maritime registers in the world that are the members of IACS, such as Russian Maritime Register of Shipping (RMR), DNV, ABS, at el. The TV calculation (TVC) on the MPP usually is certainly a monumental calculation task and is conducted with special software for TVC. Nowadays, in accordance with the Rules, almost modern software products for TVC have the abilities to calculate the TVs at normal working regimes and at misfire regimes (called by Normal or Misfire regimes relatively) with only one of cylinders of marine diesel engine (MDE) while engine speed range covers from the minimum to maximum values of the operation speeds. The paper presents improved algorithms and software for automatic calculating the TVs (SATVC) at the Normal and the Misfire regimes, in which the misfiring processes appear not only in one cylinder, but also in two of the MDE cylinders together. The SATVC was based on the made mathematical models, algorithms and coded in LabView by authors. The SATVC consists of modules for automatic calculation of freedom TVs (FTVs), excited torsional moments (ETM), excited TVs (ETVs), permitted torsional pressures (PTP), and common management (CTVC). TVC at every working regime of MDE was automatically conducted in the following procedure: Configuration of the MPP for TVC; Calculation of FTVs; Calculation of ETM; Calculation of ETVs); Calculation of ETVs, and solution of the TVC in considered working regime. The working regime of MDE was modeled by a vector of firing coefficients (VFC) of every MDE cylinder.

Influence of propulsion installation performance on travel efficiency

This paper presents an analysis of exploitation parameters for naval propulsion plant at different operating regimes. For naval propulsion plant with internal combustion engines, is considered as independent variables which give its operating regimes. Functional parameters of analysis of navigational regimes considered representative of the operation of the ship. Propulsion of the ship is provided by a fixed pitch propeller that allows modification propulsion performance by adjusting a single parameter function: speed propeller.

Optimization of the propulsion plant of a Liquefied Natural Gas transport ship

Stricter emission regulations and variability of fuel prices pose the focus on the optimization of steam turbine based propulsion plants of Liquefied Natural Gas (LNG) ships. The efficiency of such a propulsion plant has been improved in this work by studying the introduction of reheating and preheating stages in the onboard regenerative Rankine cycle. A thermodynamic model of the propulsion plant has been developed from the facility diagrams, being validated afterwards with available experimental data from actual ship operation. The predictions of different scenarios obtained by the model when introducing modifications in the power propulsion cycle showed promising results. It was found that a combination of preheating and reheating stages was found to increase the cycle efficiency up to 33.71%, reducing fuel consumption in around 20 t/day and CO2 emissions in more than 20,000 t per year. An exergy analysis of the impact of cycle modifications and an economic assessment of the proposed investment plan were performed. It was found that the boiler was the main contributor to exergy destruction, fact that justifies the cycle modifications performed. The economic analysis of the investment plan of implementing the selected alternative provided benefits even in a conservative scenario, with an Internal Rate of Return higher than 12% and a Pay-Back Period less than 9 years for all the studied scenarios. In summary, a practical industrial application of thermodynamic and exergy analysis to the propulsion plant of a LNG ship has been shown, allowing an efficiency, economic and environmental improvement.

Application of the Kalman filtering technique for nonlinear state estimation in propulsion system

The estimation of the propulsion system states and especially of the main engine is essential for control, diagnosis and performance evaluation. If all the required sensors were available, providing required measurements, the state and performance monitoring is of no particular difficulty. However, not all the required parameters can be measured directly, or the addition of multiple measurement channels is out of appropriateness. Furthermore, the propulsion plant state dynamics is justified by propeller load torque fluctuation that in turn is caused by fluctuating effective inflow velocity into the propeller, and which cannot be measured directly. Thus, the problem of estimating unmeasured state and disturbance variables of the propulsion system is considered and formulated as the design of an unknown input observer under model uncertainty and nonlinearity. To solve the design problem, this paper introduces a nonlinear engine dynamic model to catch the internal engine states and an unscented Kalman filter for concurrently performing disturbance and state estimation. The effectiveness is verified through the experiments.

Experimental study in vibration monitoring of main diesel engine installed on motor vessel KN168

Monitoring vibrations (VMs) of the sea-going ships are necessary to measure and control under the Rules for Classification and Construction of Sea-going Ships of some national registers, such as Russian Maritime Register (RMR) of shipping, Edit 2014. The VM is important and necessary for safety marine diesel engine (MDE) in its technical operation at dangerous levels of torsional, axial or lateral vibrations (TVs, AVs, LVs), which appear in practice at some abnormal regimes, especially on the two-stroke MDE and its main propulsion plant (MPP). This paper presents the results of experimental study for monitoring vibration of the four-stroke MDE, and it’s MPP in the sea — trail test of the MV.KN168, designed and manufactured by Hong Ha Shipyard (Haiphong, Vietnam, 2017). The vibration signals were measured and analyzed using Multi-channel Measurement and Monitoring Vibration System (MMMVS) made by Vietnam Maritime University (VMU).The vibration research results on the four-stroke MDE of the MV.KN168 indicated that the vibration levels of the every measured position lie in the allowable limitations.

The importance of the engine-propeller model accuracy on the performance prediction of a marine propulsion system in the presence of waves

The shipping industry is the heart of international trading activities and the global economy. Maritime transport contributes to environmental pollution through the emission of greenhouse gases. New mandatory regulations aim at improving the environmental performance of ships by encouraging power reduction and alternative fuels. These requirements drew attention to the estimation of the ship performance in the presence of waves considering unconventional combustibles. Investigating the effects of waves on untraditional propulsion plants could help to design more environmentally friendly ships. The purpose of this paper is to determine the importance of the time-varying wake field, ship motions, propeller emergence, and engine response on the performance in waves of a marine propulsion system powered by a medium-speed LNG engine. This is performed by comparing the engine-propeller performance estimated by modelling the propulsion plant at three different levels of complexity. The results illustrated the poor prediction accuracy of the propulsion system performance in waves when the time-varying wake field, ship motions, and propeller emergence are neglected. The influence of the engine response on the performance prediction of the engine-propeller system was negligible. The outcomes of this paper demonstrate the importance of considering the effects of the waves on the propulsion system of a ship during the optimization phase.

Development of a Multiphysics Real-Time Simulator for Model-Based Design of a DC Shipboard Microgrid

Recent and strict regulations in the maritime sector regarding exhaust gas emissions has led to an evolution of shipboard systems with a progressive increase of complexity, from the early utilization of electric propulsion to the realization of an integrated shipboard power system organized as a microgrid. Therefore, novel approaches, such as the model-based design, start to be experimented by industries to obtain multiphysics models able to study the impact of different designing solutions. In this context, this paper illustrates in detail the development of a multiphysics simulation framework, able to mimic the behaviour of a DC electric ship equipped with electric propulsion, rotating generators and battery energy storage systems. The simulation platform has been realized within the retrofitting project of a Ro-Ro Pax vessel, to size components and to validate control strategies before the system commissioning. It has been implemented on the Opal-RT simulator, as the core component of the future research infrastructure of the University of Genoa, which will include power converters, storage systems, and a ship bridge simulator. The proposed model includes the propulsion plant, characterized by propellers and ship dynamics, and the entire shipboard power system. Each component has been detailed together with its own regulators, such as the automatic voltage regulator of synchronous generators, the torque control of permanent magnet synchronous motors and the current control loop of power converters. The paper illustrates also details concerning the practical deployment of the proposed models within the real-time simulator, in order to share the computational effort among the available processor cores.

Development and Validation of 4 Stroke Marine Diesel Engine Numerical Model

Increasing demands on energy efficiency and environmental acceptance are being imposed on marine propulsion plants. The fulfilment of the conditions set by the MARPOL Convention, Annex VI, regarding the emissions from exhaust gases of marine diesel engines is of particular interest. This paper presents the development and validation of a zero-dimensional, single-zone diesel engine numerical model. Presented numerical model is based on the law of conservation of energy and mass and solving the resulting differential equations. The single-zone model will serve as the basis for a model where the cylinder space is divided into two or three zones during combustion. In this way, the multi-zone model will allow the modelling of nitrogen oxide emissions with satisfactory accuracy. Validation of the diesel engine model was carried out for the Wärtsilä 12V50DF 11700 kW motor designed to drive a synchronous alternator. Obtained results and deviations of certain parameters in the operation of the engine with respect to the data obtained from the measurements on the test bed, are more than satisfactory regarding complexity of the numerical model. This confirmed the usability of the model for research purposes to optimize the marine diesel engine.

ОСОБЛИВОСТІ КОНСТРУКТИВНИХ СХЕМ ДВИГУНІВ З ІМПУЛЬСНИМИ ДЕТОНАЦІЙНИМИ КАМЕРАМИ

The pressure of the products of chemical reactions in the chamber of a rocket engine increases significantly if the rocket fuel components burn in the detonation mode. In this case, it can get to a simpler and more reliable expulsion propellant feed system instead of a turbopump feed system. The value of heat release power (MW / liter) of detonation engines is several orders of magnitude larger than that of aircraft and rocket engines operating in the Brighton cycle. The high rate of energy released in the detonation mode can significantly reduce the mass, the inertia, and overall dimensions of the propulsion system. Due to these features, detonation chambers are advisable to be used as part of ejector pulsed detonation engines, together with a turbine – in electric power generators of spacecraft, in a hybrid design – together with turbofan or turboprop engines, etc. In the article are considered various design schemes of pulse detonation engines (PDE): single-chamber and multi-chamber pulsed detonation engines; an ejector PDE system; a hybrid PDE and an integrated detonation-turbine unit with a detonation chamber in the form of a spiral and with a multi-chamber detonation device. The possibility of pulsation frequency increase is realized in the multi-chamber pulsed detonation engine, and the possibility of thrust size increase is realized in PDE with ejector. Replacing traditional chambers with detonation chambers in the construction of gas turbine jet engine will allow providing a decrease in propellant flow rate value from 8 % to 10 % on some estimations. In the hybrid detonation propulsion plant advantages inherent to the detonation cycle combine with positive features of a turbo-compressor jet engine. A combination of PDE and turbine allows creating the cogeneration propulsion system in that a turbine is used for the production of electric power, and detonation chamber – for the creation of thrust impulse. Practical realization of hybrid pulse detonation turbo-engine and the integrated detonation-turbine device is possible if two key complex problems will be solved. These problems are the detonation waves weakening on input in a turbine and the bearing and shaft necessary work resource increasing into a detonation pulsating stream

Decay detection of a marine gas turbine with contaminated data based on isolation forest approach

ABSTRACT Machine learning is an effective way to realise the condition monitoring of marine machinery. However, it is challenging to realise this purpose based on supervised learning in practice due to the lack of labelled data. To overcome this problem, we propose to use isolation forest to realise the decay detection of a marine gas turbine with normal data. Besides, we consider the impact of data contamination for the first time compared with previous literatures. We also experiment with the same datasets with support vector data description (SVDD) as a comparison. The results show that the isolation forest is very suitable for the decay detection of the marine gas turbine, and it shows a significant advantage over support vector data description in the tolerance to contaminated data. The dataset we experiment with is from a real-data validated numerical simulator developed for a Frigate’s propulsion plant.

Energy Loss Analysis at the Gland Seals of a Marine Turbo-Generator Steam Turbine

The paper presents an analysis of marine Turbo-Generator Steam Turbine (TGST) energy losses at turbine gland seals. The analyzed TGST is one of two identical Turbo-Generator Steam Turbines mounted in the steam propulsion plant of a commercial LNG carrier. Research is based on the TGST measurement data obtained during exploitation at three different loads. The turbine front gland seal is the most important element which defines TGST operating parameters, energy losses and energy efficiencies. The front gland seal should have as many chambers as possible in order to minimize the leaked steam mass flow rate, which will result in a turbine energy losses’ decrease and in an increase in energy efficiency. The steam mass flow rate leakage through the TGST rear gland seal has a low or negligible influence on turbine operating parameters, energy losses and energy efficiencies. The highest turbine energy efficiencies are noted at a high load – on which TGST operation is preferable.