On-board Generators Research Articles

Design of an aircraft generator with radial force control.

With the increasing electrical energy demands in aviation propulsion systems, the increase in the onboard generators' power density is inevitable. During the flight, forces coming from the gearbox or gyroscopic forces generated by flight manoeuvres like take-off and landing can act on the generators' bearings, which can lead to wear and fatigue in the bearings. Utilizing the radial force control concept in the electrical machine can relieve loads from the bearings that not only minimize the bearing losses but also increase bearing life. The objective of the MAGLEV project (Measurement and Analysis of Generator bearing Loads and Efficiency with Validation) is to study, demonstrate, and test a new class of high-speed generators with radial force control. In this paper, design steps of this type of generator and its test rig are presented and the measurement methodology used for radial force control is explained. The concept is developed in an electrical machine and is validated on a test rig by measuring required parameters like shaft displacement, vibrations and bearing temperature. Additionally, the friction moment of each generator's bearings is measured and validated in a separate test rig under comparable conditions to the bearing loads in the generator. Therefore, a novel approach to determine precisely the bearing friction in a radial load unit, rotatably supported by an additional needle bearing is used, which shows a good agreement with the calculated friction. Furthermore, new calculation methods for the operating behavior of cylindrical roller bearings with clearance are presented, which are utilized in the generator test rig.

Design of an aircraft generator with radial force control

With the increasing electrical energy demands in aviation propulsion systems, the increase in the onboard generators’ power density is inevitable. During the flight, forces coming from the gearbox or gyroscopic forces generated by flight manoeuvres like take-off and landing can act on the generators' bearings, which can lead to wear and fatigue in the bearings. Utilizing the radial force control concept in the electrical machine can relieve loads from the bearings that not only minimize the bearing losses but also increase bearing life. The objective of the MAGLEV project (Measurement and Analysis of Generator bearing Loads and Efficiency with Validation) is to study, demonstrate, and test a new class of high-speed generators with radial force control. In this paper, design steps of this type of generator and its test rig are presented and the measurement methodology used for radial force control is explained. The concept is developed in an electrical machine and is validated on a test rig by measuring required parameters like shaft displacement, vibrations and bearing temperature. Additionally, the friction moment of each generator’s bearings is measured and validated in a separate test rig under comparable conditions to the bearing loads in the generator. Therefore, a novel approach to determine precisely the bearing friction in a radial load unit, rotatably supported by an additional needle bearing is used, which shows a good agreement with the calculated friction. Furthermore, new calculation methods for the operating behavior of cylindrical roller bearings with clearance are presented, which are utilized in the generator test rig.

Design of an aircraft generator with radial force control

With the increasing electrical energy demands in aviation propulsion systems, the increase in the onboard generators’ power density is inevitable. During the flight, forces coming from the gearbox or gyroscopic forces generated by flight manoeuvres like take-off and landing can act on the generators' bearings, which can lead to wear and fatigue in the bearings. Utilizing the radial force control concept in the electrical machine can relieve loads from the bearings that not only minimize the bearing losses but also increase bearing life. The objective of the MAGLEV project (Measurement and Analysis of Generator bearing Loads and Efficiency with Validation) is to study, demonstrate, and test a new class of high-speed generators with radial force control. In this paper, design steps of this type of generator and its test rig are presented and the measurement methodology used for radial force control is explained. The concept is developed in an electrical machine and is validated on a test rig by measuring required parameters like shaft displacement, vibrations and bearing temperature. Additionally, the friction moment of each generator’s bearings is measured and validated in a separate test rig under comparable conditions to the bearing loads in the generator. Therefore, a novel approach to determine precisely the bearing friction in a radial load unit, rotatably supported by an additional needle bearing is used, which shows a good agreement with the calculated friction. Furthermore, new calculation methods for the operating behavior of cylindrical roller bearings with clearance are presented, which are utilized in the generator test rig.

A Case History of Shore Power Transformer Taps Arcing During a No-Load Condition: Understanding the Cause of Arcing

Shore Power Transformers are used to connect berthing ships at ports to use shore power from the port facilities. It has been established that using shore power instead of power from on-board generators can minimize air pollution as ships use low-grade fuel for power generation. The process of switching off the onboard generators of berthing ships and connecting to shore power is called shore-to-ship power supplies (STSPSs). To comply with mandatory air-pollution requirements, in 2014, the Port of Oakland installed STSPS projects at various berths. In 2015 at Berth 37, a 7.5-megavolt-A (MVA), cast-coil transformer within an outdoor enclosure experienced an arcing of the primary no-load tap connections at 12.47 kV. The installation and testing of Berth 37 complied with the International Electrical Testing Association. It is a normal practice to leave the transformer energized when the STSPS operation is finished. The taps arcing occurred when the transformer was energized without any load. There was no power system transient event when taps arcing occurred.

Sizing and Siting of Energy Storage Systems in a Military-Based Vehicle-to-Grid Microgrid

Due to the absence of utility power grid infrastructure in remote military bases, on-site diesel generators serve as the primary sources for power demands. Increasing efficiency and preventing frequent startup/shutdown operations of on-site diesel generators are therefore becoming a critical issue for reducing fuel cost. Application of vehicle-to-grid technology in a military-based microgrid embodies potential for significant fuel economy benefits since on-board vehicle generators and energy storage units can serve as mobile power sources that provide higher flexibility for supplying power demands. In addition, energy storage system integration is considered as an alternative solution for increasing on-site diesel generators efficiency and lessening their startup/shutdown operations. This article proposes a three-stage planning procedure for identifying the optimal locations and capacities of energy storage systems, considering multiple operating scenarios via stochastic programming. Note that on-site diesel generators and on-board vehicle generators support plug-and-play functionality, meaning their startup/shutdown operations can be decided in real time. Furthermore, network-constrained ac unit commitment model is used to optimize operation of microgrids. It is assumed that in the tested microgrid systems, several tactical military vehicles with on-board generators and energy storage units are deployed as alternative power sources. The economic merits of vehicle-to-grid implementation and energy storage system integration in a military-based microgrid are validated in the numerical studies.

A Lead-Free Spiral Bimorph Piezoelectric MEMS Energy Harvester for Enhanced Power Density

Tiny sensor nodes are the demand of smart and intelligent systems. These sensor nodes require on-board self-powered generating systems. Also, such generators should have lesser size. MEMS energy harvesters are profoundly used as the on-board self-powered generators. However, the size constrain imposes an important design trade-off on such devices. This trade-off is in-between areal dimension and the resonant frequency. In this paper, we have proposed an efficient bimorph energy harvester design which produces higher power density at very low resonance frequency. We have considered the poisonous behavior of lead-based devices as well and proposed lead-free designs in our work. The proposed design consists of a bimorph square plate of 2.25 mm2 with two Zinc Oxide (ZnO) layers of 0.5 µm each sandwiched a copper electrode layer of 1 µm. A spiral cut of 5 µm thickness is made over the plate in order to form a fixed free beam structure. Furthermore, without the inclusion of tip mass, the resonant frequency of the beam is controlled by varying the number of spiral turns. Our proposed design outperformed the previous designs by producing maximum output power of 15 nW at 110 Hz with seven spiral turns with very lower active volume. Also, it has a normalized volumetric power density of 3 × 10−2 µW/mm3 g2 Hz.

Efficiency Estimation of Synchronous Generators for Marine Applications and Verification With Shop Trial Data and Real Ship Operation Data

Three methods were explored to estimate the efficiency for the conversion of mechanical power to electrical power using synchronous generators in ships at low power factors. Generally, the generator efficiency data is provided by manufacturers as shop trial data and is measured by operating generators under power factor of 0.8 and 1.0. However, the efficiency of synchronous generators is not measured under low power factor of less than 0.8. In practice, onboard generators occasionally operate at low power factor and it is desirable to clarify their characteristics for power system designers of large vessels. By substituting the shop trial data into the proposed efficiency estimation formulas, the generator efficiency at low power factor was extrapolated. To evaluate the validity of these methods, the fuel consumption characteristics of diesel engines as prime movers was focused. The estimation of the generator efficiency was indirectly validated using a statistical analysis of long-term observational data of the generator in operation. As a result, the efficiency estimation method based on a power loss mechanism gave the most reliable result among the three estimation methods. The root mean squared error of the calculated specific fuel consumption was 3.5 g/kWh, which is approximately 1.66 % error rate.

Hybrid algorithm for optimal operation of hybrid energy systems in electric ferries

The move towards electrification of marine vessels enables the development of more efficient vessels by reducing fuel consumption and emissions. This includes incorporating electrical energy sources, storage systems and interfacing power electronic converters which increase system complexity. Therefore, an accurate and efficient power management system (PMS) is essential to achieve the optimum operation. This study aims to develop a novel hybrid meta-heuristic algorithm-based PMS for the fuel savings of hybrid electric ferries. The ferry power system used in this study comprises two diesel generator sets and a battery storage system. The proposed hybrid PMS method applies an interactive approach on the basis of a grey wolf optimizer (GWO) and fuzzy expert system to improve the computational efficiency of the algorithm. Measured load data from an existing short-haul ferry are used in the simulation under two load scenarios: normal and high load demands. The proposed fuzzy logic-grey wolf optimizer (FL-GWO) aims to minimize the operating cost of the proposed system while satisfying all operational and technical constraints of the ferry. Results show that the proposed FL-GWO provided a more accurate optimal solution set with less standard deviation than the GWO. The proposed method realized up to 3.14% and 1.81% fuel savings in normal- and high-load scenarios, respectively, compared with GWO. Moreover, the sensitivity analysis indicates that charging the battery from the onboard generators in a more uniform rate over the entire cruising period reduces the fuel consumption.

On the Issue of Building a Power Supply Complex-Electric Power Consumption of Aircraft

The article deals with the features of construction of combined airborne power supply of aircraft with the use of renewable energy sources. It has been established that the introduction of renewable energy sources into airborne electrical supply systems of aircraft takes place, however, the issue of their introduction into the structure of the primary and emergency power supply of airborne aircraft complexes remains promising and topical.Thus, due to the complex specific operating conditions, it is necessary to monitor the state of aircraft battery-operated batteries, the authors propose to implement monitoring of the status online of on-board batteries in the block, which will also perform the functions of the charger.From the onboard generators, all the electronics are powered on board aircraft, so if the generators stop working, then all the onboard equipment of the electric system of the aircraft will be blown away. In this case, in some types of aircraft, manufacturers install retractable wind power plants. In the meantime, solar cells are another of the most persistent alternative sources of electric energy in aircraft.Thus, according to the recommended variant of the system of power supply of aircraft, the unit of storage batteries has a capacity sufficient to supply in an emergency during the flight not only responsible consumers (control and navigation), but also the power supply of electromechanical complexes of the power system of electric motors.Proceeding from the fact that the modern concept of the development of aircraft put forward the requirements related to the miniaturization of onboard systems of energy and electronics, as well as requirements for the use of advanced technologies for the manufacture of aircraft design, the implementation is also relevant, if possible, (depending on the design aircraft) as an additional source of the main on-board power supply system for solar panels at level with retractable wind power plants.The article presents the version recommended by the authors of the system of airborne electrical supply of the aircraft using renewable energy sources. The authors propose the introduction of additional power sources into the structure of the main power supply system on the basis of renewable energy sources and additional, electric motors, installed in parallel with aircraft engines, with the purpose of safety-free landing of the aircraft, in the event of failure of aircraft engines and extension of its flight time.Ref. 13, fig. 3.

Comparison study between wind turbine and power kite wakes

Airborne Wind Energy (AWE) is an emerging technology in the field of renewable energy that uses kites to harvest wind energy. However, unlike for conventional wind turbines, the wind environment in AWE systems has not yet been studied in much detail. We propose a simulation framework using Large Eddy Simulation to model the wakes of such kite systems and offer a comparison with turbine-like wakes. In order to model the kite effects on the flow, a lifting line technique is used. We investigate different wake configurations related to the operation modes of wind turbines and airborne systems in drag mode. In the turbine mode, the aerodynamic torque of the blades is directly added to the flow. In the kite drag mode, the aerodynamic torque of the wings is directly balanced by an opposite torque induced by on-board generators; this results in a total torque on the flow that is zero. We present the main differences in wake characteristics, especially flow induction and vorticity fields, for the depicted operation modes both with laminar and turbulent inflows.

Plugging Ships In Yields Cleaner Air

Requiring more ships that stop in U.S. ports to receive power from the onshore electric grid rather than by burning diesel in onboard generators would be a cost-effective way to improve air quality, reports a team led by Parth Vaishnav of Carnegie Mellon University (Environ. Sci. Technol. 2015, DOI: 10.1021/acs.est.5b04860). When in port, ships commonly use diesel generators to provide necessary power, such as for lights and refrigeration. Supplying ships with power through an electric cable would reduce harmful emissions but require new equipment for ports and ships. California already requires that 50% of ship stops at ports in the state use power supplied from shore; that proportion will rise to 80% in 2020. Vaishnav and colleagues modeled the costs of the retrofits as well as the benefits of air quality improvements—reducing NOx, SO2, CO2, and particulate matter—if the requirements extended nationwide. Depending on assumptions they made about how pollutants

Shore Power for Vessels Calling at U.S. Ports: Benefits and Costs.

When in port, ships burn marine diesel in on-board generators to produce electricity and are significant contributors to poor local and regional air quality. Supplying ships with grid electricity can reduce these emissions. We use two integrated assessment models to quantify the benefits of reducing the emissions of NOX, SO2, PM2.5, and CO2 that would occur if shore power were used. Using historical vessel call data, we identify combinations of vessels and berths at U.S. ports that could be switched to shore power to yield the largest gains for society. Our results indicate that, depending on the social costs of pollution assumed, an air quality benefit of $70-150 million per year could be achieved by retrofitting a quarter to two-thirds of all vessels that call at U.S. ports. Such a benefit could be produced at no net cost to society (health and environmental benefits would be balanced by the cost of ship and port retrofit) but would require many ships to be equipped to receive shore power, even if doing so would result in a private loss for the operator. Policy makers could produce a net societal gain by implementing incentives and mandates to encourage a shift toward shore power.

Integrated thermoelectric model for on-board aircraft generators

Abstract: Electronic systems are becoming the predominant method for flight critical systems and have substituted their pneumatic or hydraulic counterparts, increasing the need for constant and uninterrupted supply of power. One of the main limitations is overheating in generators due to an increased demand of current. Overheat in the generator windings can lead to insulation degradation and hence to catastrophic failure. Therefore, understanding and monitoring heat flow through the generator is of utmost importance. Previous studies have viewed the electrical and thermal circuits as separate arrangements with little interaction between the two. This paper attempts to provide a systemic thermo-electric view of the generator and offer a method for interfacing the thermal and electrical circuits by the use of loss calculation. The long term goal of this project is to provide a means for model based health assessment and intelligent power management for on-board aircraft generator systems, while having limited information on the system itself.

Electrical characteristics of cold ironing energy supply for berthed ships

The reduction of emissions in harbours is of particular importance due to the proximity to human habitation. Vessels normally run onboard generators, typically using diesel fuel, to provide the service loads while berthed. New and upcoming regulations aim to decrease emissions from shipping, and coupled with increased environmental consciousness of ship owners and harbour operators, shore supply is becoming a more popular and feasible option. Cold ironing provides an alternative locally emission-free solution by having berthed ships plug in to the shore electrical network, such that the onboard electrical energy demand is supplied from land. Electrically, a number of different shore network topologies are possible, providing different infrastructural options of supplying power to multiple berths. This paper examines the electrical characteristics of one such installation and the impact on the shoreside electrical network for an existing port using actual visiting ship power profiles. The paper examines how the cold ironing system influences important electrical network characteristics such as bus voltages and power quality, as well as the potential impact on the rest of the utility distribution system.

Catalysts for the conversion of hydrocarbon and synthetic fuels for onboard syngas generators

The use of syngas derived on board a vehicle as a supplement to the main fuel fed to engines ensures engine operation using dilute fuel mixtures. This leads to a decrease in emission toxicity and an increase in the fuel efficiency of the engine. The preparation of new types of efficient catalysts for the conversion of hydrocarbon and synthetic fuels for onboard syngas generators requires the use of new approaches to the design of catalysts not only as catalytically active material, but also as a structural component of a chemical reactor. We prepared and tested a set of catalysts for the conversion of hydrocarbons, i.e., natural gas, diesel and biodiesel fuels, biofuels, and alcohols (ethanol, methanol) to syngas. Primary supports for the catalysts were metals grids and porous tapes; secondary supports were oxides of aluminum and magnesium deposited on or sintered to a primary support. The catalysts exhibited high thermal stability and mechanical strength, and were characterized by the conformity of the coefficients of thermal expansion of the support material and the catalytically active bed. The catalysts can be used as structural components of reactors and as a basis for the preparation of monolithic blocks and planar components of radial and planar reactors. The developed catalysts were subjected to laboratory and bench tests and examined as components of onboard generators of vehicles.

Presentations in FAM-C And FDM-A Methods and Some Problems of a Signals Theory

The FDM-A diagnostic method [2, 4] based on a frequency modulation measurement of a pulsation component as well as the FAM-C method of an alternating current frequency have been elaborated in Air Force Institute of Technology. These methods to define a level of an assembly abrasive wear as well as its localization during a normal work of a power unit. A diagnostic signal is derived from onboard generators or alternators. Each damaged part of the generator’s or alternator’s power unit is a vibration generator or modulator. The vibration is turned into oscillation in onboard generators or alternators. After many years of the FAM-C and FDM-A methods’ using it is possible to localize and define value of many faults of power units: a coupling eccentricity, a shaft skew, extender longitudinal clearances of turbine engine’s rotor assembly, a frictional resistance of bearings, a smoothness of bearing’s rolling and a bearing cage, a break of rolling bearing’s separator, a misalignment of a rotor assembly’s support, etc. In FAM-C and FDM-A methods two kinds of presentations are used: first a presentation as characteristic patterns (analogous to Fourier spectrum lines but providing to observe periodical and stochastical phenomena) as well as the presentation of the frequency versus time. From the point of view of authors in many cases they are similar to presentations known from a theory of a radio signals transmission. It is possible to find carrier wale and side spectrum lines, beats caused by summation of two signals with approximate frequencies as well as many others. If analogy is so univocal, it is possible to use many systems and dependences used in telecommunication. For example: coherence demodulation (synchronous), which authors intend to use for separation characteristic patterns of two different mechanical assemblies with approximate vibration frequencies. At the end there are presented authors’ considerations, related to superposition of signals and beats as well as reflection of these phenomena in observed power units.

Tackling ship pollution from the shore

Electrical power consumption at the shore side has rapidly grown for commercial ships. The environmental impact of the pollution created while at berth has many ports restricting the operation of onboard generators. Shutting off these on-board generators and supplying ship's power from the shore power system can reduce the air pollution emissions. With the development of medium voltage power plugs and receptacle assemblies, cold ironing projects for larger ships are more prevalent. Various organizations are working on developing standards for implementing shore power. This article will highlight the efforts of the IEEE, the International Organization for Standardization (ISO), and the International Electrotechnical Commission (IEC) to develop standards for medium-voltage on-shore power supply connections for serving commercial vessels.

The diagnosis of onboard generators (alternators)

In the paper selected problems related to diagnostics of onboard generators and alternators fitted with control systems are discussed. Problems refer to commutator generators and synchronous single- and threephase alternators. Special attention is paid to commutation effects. Results of incorrectness and possibility to detect them are discussed. There are also discussed effects associated with changes in a character of pulsation, which occur during shortings or insulation clearances in rotor or stator wiring. Possibility of diagnosis of generator’s or alternator’s parts by means of analysis of pulsation component parameters is indicated. In the case of alternators a number of diagnostic methods based on observation of changes in shape of voltage or frequency modulation, is discussed. This allows to detect many mechanical or electrical faults of generators, alternators or their control systems.

Evaluation of Generalized LFSRs as Test Pattern Generators in Two-Dimensional Scan Designs

Linear finite-state machines (LFSMs) such as linear feedback shift registers (LFSRs), cellular automata (CA), and ring generators (RGs) are used as test pattern generators in built-in self-test schemes that employ 2-D scan design. These mechanisms are usually accompanied by phase shifters (PSs) in order to avoid the degradation of the fault coverage caused by correlations/dependences in the produced test bit sequences. Given this context, we investigate in this paper the potential of generalized (or Galois) LFSRs (GLFSRs) as onboard test pattern generators. We compare GLFSRs with and without PSs against LFSMs with PSs (LFSM/PSs) for various types of LFSMs (LFSRs, CA, RGs, and dense RGs) on two accounts: channel separation and overall hardware cost. Experimental results show that GLFSRs achieve larger channel separation with lower hardware cost than LFSM/PS and attain higher fault coverage.

Design of Multiple-Input Power Converter for Hybrid Vehicles

This paper deals with designing and sizing of a multiple-input power electronic converter (MIPEC) to be used in an electric vehicle propulsion system that includes a fuel cell (FC) generator and a combined storage unit. The combined storage unit is composed by an ultracapacitors tank (UC) and a battery unit (BU). MIPEC is responsible for power-flow management on-board the vehicle for each mode of operation. Specifications for MIPEC designing come out from many considerations concerning traction drive and reference driving cycle, on-board power source and storage unit characteristics. However, to date sizing and configuration of both storage units and on-board generators are directly related to traction drive and driving profile (i.e., vehicle performances and characteristics) and no relation with power electronic interface is considered during preliminary design. Then, power electronic interface is selected in order to fit traction drive requirements with power source and storage unit characteristics; as a consequence converter mode of operation lacks of optimization, as well dynamic behavior and efficiency cannot be maximized. In this paper, MIPEC design and power source and storage unit selection are achieved at the same project stage according to traction drive requirements. Experimental results on 60-kW power electronic interface are presented.