Auxiliary Power Unit Research Articles

Solid Oxide Fuel Cells with a Thin Film Electrolyte: A Review on Manufacturing Technologies and Electrochemical Characteristicses

Solid oxide fuel cells (SOFCs) are electrochemical systems converting the energy released during fuel oxidation into electrical energy. SOFCs are considered as a promising clean energy technology due to the high efficiency of fuel-to-power conversion and environmental friendliness. The potential applications of SOFCs extend from stationary power generation units for industrial and household facilities to auxiliary power units in vehicles and portable power sources. One of the main elements of SOFCs is a solid oxide electrolyte possessing ionic conductivity at high temperatures (above 700 °C). The main challenge in the SOFC commercialization is related to their high operating temperature, which entails materials degradation, short life-time, long start-up and shut-down times, and high cost. One of the most effective ways to reduce the SOFC operating temperature is to minimize the electrolyte thickness. In this regard, fabrication of SOFCs with a thin film electrolyte has been attracting high research activity over the past few decades. Different fabrication techniques were reported to be applicable for manufacturing thin film SOFCs, and the fuel cell performance was found to be highly dependent on the appropriate selection of materials and processing technologies. The present review is focused on state-of-the-art fabrication technologies of the thin film SOFCs. A brief survey of configurations and geometries of the thin film SOFCs and methods of deposition of solid-oxide films is given. Special attention is focused on the electrical generation performance of the thin film SOFCs.

Switched On

Microchip Technology looks at the requirements of a transportation auxiliary power unit and lays out the ideal static, dynamic characteristics of the SiC MOSFET, diode and gate drivers

Evaluation of Aircraft Auxiliary Power Unit Near-Field Acoustics for Condition Monitoring

This paper presents a comprehensive evaluation of the near-field acoustics of an aircraft auxiliary power unit (APU), based on experimental data acquired from an in-situ APU. The aim is to establish whether near-field acoustics can be implemented for online condition monitoring. The APU of Cranfield University’s demonstrator aircraft, a Boeing 737-400, has been instrumented to acquire acoustics (near-field and far-field) and vibration data in synchronization with aircraft state parameters under a wide range of operating conditions. The acquired data is first implemented to determine the efficacy of employing near-field / far-field microphones, and vibration sensors, to monitor the combustion noise and tonal frequency levels from the APU components. Subsequently, an evaluation of the broadband characteristics of the vibroacoustic data and its variations against APU states and performance parameters is conducted based on several categories of feature extraction techniques. The findings suggest that nearfield acoustics lacks the ability to capture the combustion noise process. In addition, the tonal frequencies are also lost due to the level of background noise, fluctuations in the APU speeds, and scattering effects. For the same reasons, the phase couplings occurring between the signals generated by the APU components cannot be detected using acoustic data. Nevertheless, the overall analysis substantiates that the near-field acoustic data can be used to predict the APU operating states and has the potential to be implemented for developing APU performance parameter estimation models to enable condition monitoring.

Thermodynamic Modeling of Modified Recompression Supercritical Co2 Power Cycle Using Waste Heat from Fuel Cell: Application to Aircraft Auxiliary Power Unit

Thermodynamic Modeling of Modified Recompression Supercritical Co2 Power Cycle Using Waste Heat from Fuel Cell: Application to Aircraft Auxiliary Power Unit

МИКРОПРОЦЕССОРНАЯ СИСТЕМА АВТОМАТИЧЕСКОГО УПРАВЛЕНИЯ СРЕДСТВАМИ ПРОТИВОПОЖАРНОЙ ЗАЩИТЫ САМОЛЕТА

Relevance The ever-increasing requirements for the safety of the use of aviation technology are inextricably linked with the problem of providing fire protection for aircraft, both military and civilian. The complexity of the problem of ensuring the fire safety of flights is associated with an increase in the intensity of the use of aviation equipment and the expansion of the range of functional tasks performed by it. The resulting complication of on-board equipment and an increase in the number of energy-intensive devices creates the prerequisites for the occurrence of fires on board the aircraft. At the same time, the remoteness of places where fires are possible, the variety of causes leading to fires, as well as the ambiguity of the conditions for the onset and spread, increase the likelihood of equipment failures, but also complicate the crew's activities. The purpose of the study is to implement a prospective aircraft fire protection system that will increase the effectiveness of existing fire extinguishing equipment. The relevance of this research project lies in the creation of an aircraft fire-fighting system that will provide timely detection of overheating/fire in the nacelles of the main power unit, in the compartments of the auxiliary power unit, baggage and cargo compartments and aircraft toilets; reliability of information from fire detection and elimination systems; increase the effectiveness of existing firefighting equipment. Aim of research The aim of the study is to develop a future aircraft fire protection system that will increase the effectiveness of existing fire extinguishing equipment. The objectives of the research project are: 1. Choosing a hardware complex for electronic indication and signaling of the aircraft fire-fighting system; 2. Integration of the fire protection complex into the general aircraft equipment control system. Research methods Analysis of modern high-performance aircraft fire protection systems and creation of a promising fire protection system based on the data obtained Results In the course of this research project, a hardware complex for electronic indication and signaling of the aircraft fire system was selected, and the integration of the fire protection complex into the control system of general aircraft equipment was carried out.

Optimization and realization on the coordination control strategy for auxiliary power unit of range-extended electric vehicle

The auxiliary power unit (APU) is a major power source of range-extended electric vehicle (R-EEV). Excellent coordination control strategy of APU has a great significance impact on improving the overall electrical control system performance of R-EEV. A coordination control strategy based on parameters adapt fuzzy-PID is proposed to ensure the dynamic and static response characteristics of the coordination control system. Firstly, the APU high precision simulation control model is built in GT-Power and Matlab-Simulink. Three coordination control strategies based on traditional PID control method are designed, namely, engine speed control model (ESCM), generator torque control model (GTCM), and APU speed-torque control model (AS-TCM). The three coordination control strategies are simulated on working conditions, which include start-up working condition, power raised working condition, and power reduced working condition. Combined with the PID control principle, the control performance and inherent limitations of three traditional PID control strategies (TPCS) are analyzed and compared. Then, according to the above simulation results of analysis and comparation, the parameters adapt fuzzy-PID control strategy (PAF-PCS) is designed and simulated. The results show that three control parameters ( kp, ki, kd) are changed in real time to ensure the flexibility and adaptability of the control system and improve the stability and robustness of control system. Finally, the results of bench test show that power responds quickly and no oscillation and fixed-point power generation works smoothly, which are basically consistent with the simulation results. Therefore, the PAF-PCS proposed in this paper has good feasibility and effectiveness.

Schedule Planning and Maintenance Activities Auxiliary Power Unit (APU) Boeing 737-500 Aircraft With Reliability Method

Penelitian ini bertujuan untuk merencanakan jadwal dan aktifitas maintenance yang yangefektif pada sistem auxiliary power unit sehingga tidak terjadi lagi kegagalan ataupun kerusakan yang tidak di rencanakan atau terjadi secara tiba – tiba. Kegagalan pada peralatan auxiliary power unit ada sering terjadi pada beberapa sistem kerja yaitu electrical system, Lubrication System dan Ignition System, di mana hal ini menimbulkan kerugian yang cukup besar bagi perusahaan penerbangan. Metode penelitian ini menggunakan pendekatan kualitatif dan kuantitatif, analisis kualitatif menggunakan metode Failure Mode Effect and Critically Analysis (FMECA) dengan menganalisis faktor – faktor penyebab kegagalan dan efek terjadinya kegagalan, dengan hasil penyebab kegagalan pada beberapa sitem kerja auxiliary power unit (APU) adalah sebagai berikut electrical system adalah pada komponen start Relay, Lubrication System adalah pada komponen Oil Filter, Ignition System adalah pada igniter plug. Dari hasil analisis FMECA tersebut di lakukan analisis kuantitatif dengan analisis dilakukan menggunakan metode reliability, parameter kehandalan dihitung dengan probabilitas distribusi Weibull, untuk menentukan batas kritis waktu operasional komponen ataupun part sistem yang merupakan batas kehandalan suatu sistem auxiliary power unit. Batas kritis operasional electrical system adalah sebesar 434 jam terbang, lubrication system adalah 1186 jam terbang, dan Ignition system adalah sebesar 1610 jam terbang, selanjutnya hasil tersebut di gunakan untuk menentukan jadwal maintenance yang efektif di dukung dengan perencanaan aktifitas maintenance yang tepat untuk menghilangkan penyebab – penyebab kegagalan pada peralalatan auxiliary power unit.

Analysis of the Nicolaus Copernicus Airport Activity in Terms of the Flight Operations Impact on Air Pollution

The dynamic development of aviation is associated with many benefits, but also, unfortunately, with negative effects. One of the adverse consequences is the exhaust emissions that have a negative impact on human health. It particularly affects the residents of areas neighboring airports, as airport activity deteriorates local air quality. Using the Emissions and Dispersion Modeling System, the activity of the Nicolaus Copernicus Airport was assessed in terms of the flight operations’ contribution to air contamination in the area adjacent to the airport. Emissions from three sources were compared: aircraft, ground support equipment and auxiliary power units. The concentrations of pollutants in inhabited areas located in three different directions in relation to the airport were also estimated. In addition, the effect of distance from the airport on contaminant concentrations was assessed as a function of wind direction. It was noticed that small values of pollutant concentrations, originating from airport activity, appeared within a few kilometers from the airport, even if the prevailing wind direction on a given day was opposite to the analyzed dispersion direction.

Исследование надежности судовых насосов по данным технического наблюдения

The article describes the analysis of the ship systems’ reliability at the stage of the technical design, which is based on the reliability data of individual system elements and mathematical methods of reliability theory. During the ship operation maintenance deficiencies can lead to the equipment failure, which can be prevented by the methods of instrumental diagnostics of system elements, maintenance repairs regardless of the current technical condition, and classification inspection during the ship operation. Collecting the detailed data on changes in the functional reliability of ship mechanical systems, which could confirm or deny the advantages of each of the existing methods is not enough. There has been carried out collecting, processing and analyzing the actual data on the life cycles of various pumps of ship systems at different stages of service life, as well as beyond the designated service life or operating time. There are examined the general ship systems and auxiliary power units of icebreakers and floating structures. The examined equipment has standard pumps with different capacity and efficiency. Service life, assigned resource (operating time), frequency of repair are taken as the criteria of pump reliability and durability. There have been shown the actual life cycles of pumps in dependence of the service life in years on the operating time in hours; in addition, data on the passage of maintenance repairs, maintenance, inspection of the technical condition, as well as replacement or extension of the service life are plotted on the graphs. It has been inferred that some of the pumps in the ship's systems should be replaced before the full resource was developed, while the performance of the systems as a whole was preserved or restored as a result of repairs; some pumps have exceeded their specified resource, but during the technical inspection their operation was extended, the operability of the systems was also preserved.

Design of Prototype Aircraft Noise Monitoring System Using Microcontroller

This paper was presented a design of aircraft noise monitoring system using microcontroller. This system is for monitoring noise levels to make it easier to analyze and measure noise that can be accessed remotely. The measurement results are accessed through a browser with IP address access (Internet Protocol) from the local server esp32 and also OLED 0.96 inc. Taking the noise value for 10 seconds with data samples every 1 second with aircraft noise sources consisting of APU (Auxiliary Power Unit), dual pack on and engine motoring. With each noise value of 61.5 dB, 75.6 dB and 82.5 dB.

Thermodynamic Study of a Cooled Micro Gas Turbine for a Range Extended Electric Vehicle

Carbon dioxide released by the transportation sector has a significant impact on the environment. Nowadays, the research efforts are thoroughly investing in the capability of series hybrid electric vehicles in reducing CO2 and NOX emissions. Many regulations are encouraging automakers to substitute internal combustion engines with electric vehicles. Although the latter are zero-emissions energy sources, they are expensive and have a limited autonomy range. Therefore, recent studies are interested in gas turbines (GTs) in series hybrid electric vehicles (SHEV). A gas turbine (GT) coupled to an alternator is considered as an auxiliary power unit capable of charging the battery of the electric vehicle once depleted. The microturbine is generally composed of a centrifugal compressor and a radial turbine mounted on the same shaft with a recuperator and air bearings. Based on previous researches and thermodynamic analysis, the most suitable gas turbine cycle with regard to the efficiency and the net specific work is composed of two compression stages with an intercooler, a regenerator, and two expansion stages with a reheater. It can be deduced that by increasing the turbine inlet temperature, the system efficiency increases. However, the inlet temperature is limited by turbine materials constraints and specifications. The present paper focuses on developing a more efficient GT cycle by reaching higher inlet temperatures by cooling the turbine blade. It consists of using compressed gas from the compressor and introduce them into the turbine blades. This technology takes into consideration the influence of the extracted mass of compressed air, the effectiveness of the coolant, and the turbine blade temperature on thermal efficiency. An increase of the cycle efficiency of 4.78 points is obtained for a turbine inlet temperature of 1,450 °C.

CFD Simulation Study on the Performance of a Modified Ram Air Turbine (RAT) for Power Generation in Aircrafts

The present paper aims to study the possibility of dispensing an auxiliary power unit (APU) in an aircraft powered by fossil fuels to reduce air pollution. It particularly seeks to evaluate the amount of power generated by the ram air turbine (RAT) using the novel counter-rotating technique while characterizing its optimum axial distance. The ram air turbine (RAT), which is already equipped in aircrafts, was enhanced to generate the amount of energy produced by the APU. The approach was implemented by a CRRAT system. Six airfoil profiles were tested based on 2D models and the best airfoil was chosen for implantation on the RAT and CRRAT systems. The performance of the conventional single-rotor RAT and CRRAT were analyzed using FLUENT software based on 3D models. The adopted numerical scheme was the Navier–Stokes equation with k–ω SST turbulence modeling. The dynamic mesh and user-defined function (UDF) were used to revolve the rotor turbine via wind. The results indicated that the FX63-137 airfoil profile showed a higher performance in terms of the lift-to-drag ratio compared to the other airfoils. The optimum axial distance between the two rotors was 0.087 m of the rotor diameter and the efficiency of the new CRRAT increased to almost 45% compared to the single-rotor RAT.

A Real-Time Model Predictive Controller for Power Control in Extended-Range Auxiliary Power Unit

In the power control process of the range extender, both the engine and the generator are at risk of reaching the torque output limit. The limitation not only comes from the restriction of their own torque output capacity, but also comes from the additional constraints that are established to avoid power reverse undershoot. In order to improve the system performance under time-varying torque constraints, a real-time model predictive controller (MPC) that manipulates the torque commands of the engine and the generator to track the reference power is designed. Different from the traditional penalty function method, the quadratic function is taken as the penalty function in this paper, which greatly improves the efficiency of solving the optimal solution. Meanwhile, the steady-state torque command in the feasible region is taken as the extreme point of the quadratic penalty function, which avoids the penalty coefficient tending to infinity. By adjusting the penalty coefficients of different constraints, the overall optimal solution approaches the boundary of the active inequality constraints. And according to the Karush-Kuhn-Tucker (KKT) condition, it is proved that the optimal solution of the original problem can be obtained through iteration. The effectiveness and practicability of the proposed strategy are evaluated through numerical simulations on Simulink and experiments on a range extender.

Aircraft system-level diagnosis with emphasis on maintenance decisions

This paper proposes a diagnostic technique that can predict component degradation for a number of complex systems. It improves and clarifies the capabilities of a previously proposed diagnostic approach, by identifying the degradation severity of the examined components, and uses a 3D Principal Component Analysis approach to provide an explanation for the observed diagnostic accuracy. The diagnostic results are then used, in a systematic way, to influence maintenance decisions. Having been developed for the Auxiliary Power Unit (APU), the flexibility and power of the diagnostic methodology is shown by applying it to a completely new system, the Environmental Control System (ECS). A major conclusion of this work is that the proposed diagnostic approach is able to correctly predict the health state of two aircraft systems, and potentially many more, even in cases where different fault combinations result in similar fault patterns. Based on the engineering simulation approach verified here, a diagnostic methodology suitable from aircraft conception to retirement is proposed.

Design and Evaluation of a Metal-Supported Solid Oxide Fuel Cell Vehicle Power System with Bioethanol Onboard Reforming.

A solid oxide fuel cell (SOFC) has wide stationary and mobile application prospects due to its high efficiency and fuel flexibility. The SOFC system’s performance depends on the reforming option and system design. In this paper, we designed a novel SOFC auxiliary power unit (APU) system with ethanol on-board reforming aiming at vehicle application. The thermodynamic analysis is employed to evaluate the ethanol-fueled SOFC performance of different reforming options with a metal-supported SOFC working at 600 °C and a 0.3 A/cm2 current density. The electrical efficiency of the SOFC can reach a maximum of 50% with ethanol autothermal reforming. Under the optimal reforming option and operating conditions, the conceptual SOFC-APU system design is identified with the trade-off between system efficiency and ethanol flow from the startup and stable operation phase. The results show that the system efficiency of 44.4% can be achieved with a 0.42 g/s ethanol flow at the startup phase. During the stable operation, the electrical efficiency and exergy efficiency of the SOFC-APU system can reach 55.4 and 77.1% with a 70% anode gas recirculation ratio, respectively.

COMBINED POWER PLANT OF A MOTOR VEHICLE

Currently, the most promising areas of development of motor transport are an increase of the horsepower characteristic of their power plants as well as increase of fuel efficiency, and reduction of the toxicity level of exhaust fumes. An internal combustion engine as a power unit of the car in a number of operation modes (supplemental motion, small work load, idling, etc.) works extremely inefficiently and contains the high concentration of harmful components in the exhaust fumes. Additionally, in a context of growing shortage of carbohydrate fuels and increase in their value, the problem of the fuel-burn improvement is especially acute. To improve the environmental compatibility and efficiency of power plants of the vehicles, combined cycle power plants are used. One of the most important problems that the machine construction faces is the creation of environmentally friendly and economical power plants. A hybrid power plant, which contains several power units operating on different physical principles, is proposed by the authors. The main power unit uses the energy of liquid or gaseous fuel in the mode of an internal combustion engine; the auxiliary power unit which is made as a reverse volumetrical driving machine with swinging motion of the work tools (forcers or blades), uses air power which comes from a pneumocylinder through a cooler and / or pneumatic air tank. The auxiliary power unit is equipped with a reversible invertor of the driving direction, made on the basis of a spherical slider-crank mechanism. This insures the operation of the auxiliary power unit in the mode of a pneumatic motor or compressor in accordance with the algorithm generated by the electronic control unit of the combined power plant of the vehicle. To utilize the heat energy of the exhaust fumes of the main power unit, the combined power plant is additionally equipped with a Stirling engine or steam generation module and a steam engine; in order to break energy recuperation of the vehicle it is additionally equipped with a hydraulic or electrodrive. Naturally, when choosing the specific forms of application of combined cycle power plants, any combinations of auxiliary power units are possible. They can be supplemented and / or specified based on the knowledge of specialists. Combined cycle power plants are technically complete solution. Their industrial applicability is obvious and is substantiated by experiments. Nowadays, the creation of a combined cycle power plants of a vehicle, which are a combination of several engines operating on different physical principles is the task of great economic importance. Combined power plants this allows to reduce fuel consumption per 100 km significantly, increase energy potential, horsepower characteristic and improve the environmental performance of the vehicle. The work is planned to be continued in the direction of optimization synthesis of auxiliary power units that work on different physical principles.

Adaptive hierarchical energy management design for a novel hybrid powertrain of concrete truck mixers

Due to the characteristics of a significant difference between vehicle no-load and full load, time-varying double driving conditions, two-energy-source and two-energy-consumption-unit, and high coupling electromechanical-hydraulic system, this work studies two critical technologies, including powertrain design and energy management strategy development, to solve the tricky energy optimization problem of concrete truck mixers. A novel hybrid powertrain with a single-shaft parallel for the upper-part system and extended-range for the propulsion system is proposed. On that basis, an adaptive hierarchical energy management strategy is developed including two efforts. First, a rule-based hierarchical strategy with auxiliary power unit multi-mode switching for the upper and power splitting of system power units for the lower is designed. Second, a driving condition recognizer constructed by a hybrid-optimization-based random forest algorithm and a genetic algorithm optimization-based differentiated controller is designed, which can automatically switch to the optimal strategy under current driving conditions according to recognition results. Simulation results manifest that the designed optimized driving condition recognizer performance outperforms unoptimized by 2.50%. Compared with dynamic programming and the presented rule-based hierarchical strategy, the proposed adaptive hierarchical strategy with terminal SOC converging to the lowest level has better adaptability, economy, and real application performance under a real-world composite driving condition.

A Compact, Self-Sustaining Fuel Cell Auxiliary Power Unit Operated on Diesel Fuel

A complete fuel cell-based auxiliary power unit in the 7.5 kWe power class utilizing diesel fuel was developed in accordance with the power density and start-up targets defined by the U.S. Department of Energy. The system includes a highly-integrated fuel processor with multifunctional reactors to facilitate autothermal reforming, the water-gas shift reaction, and catalytic combustion. It was designed with the help of process analyses, on the basis of which two commercial, high-temperature PEFC stacks and balance of plant components were selected. The complete system was packaged, which resulted in a volume of 187.5 l. After achieving a stable and reproducible stack performance based on a modified break-in procedure, a maximum power of 3.3 kWe was demonstrated in a single stack. Despite the strong deviation from design points resulting from a malfunctioning stack, all system functions could be validated. By scaling-up the performance of the functioning stack to the level of two stacks, a power density of 35 We l−1 could be estimated, which is close to the 40 We l−1 target. Furthermore, the start-up time could be reduced to less than 22 min, which exceeds the 30 min target. These results may bring diesel-based fuel cell auxiliary power units a step closer to use in real applications, which is supported by the demonstrated indicators.

PEM fuel cell as an auxiliary power unit for range extended hybrid electric vehicles

Significant research efforts have been invested in the automotive industry on hybrid-electrified powertrains in order to reduce the passenger cars’ dependence on oil. Powertrains electrification resulted in a wide range of hybrid vehicle architectures. Fuel consumption of these powertrains strongly relies on the energy converters performance, as well as on the energy management strategy deployed on-board. This paper investigates the potential of energy consumption savings of a serial hybrid electric vehicle (SHEV) using a hydrogen proton-exchange membrane fuel cell (PEMFC) as energy converter operating as an auxiliary power unit (APU) instead of the conventional internal combustion engine (ICE). A PEMFC model is developed and the thermodynamic system efficiency is simulated. The PEMFC APU is integrated in the modelled SHEV powertrain. The hydrogen stored on board is gaseous and pressurized under 700 bars. Energy consumption simulations are performed on WLTP cycle with 4 different battery capacities using dynamic programing as global optimal energy management strategy. The results show improved efficiency with PEMFC as an auxiliary power unit (APU) compared to ICE. The auxiliary power unit consumes less than 1 kg/100 km of hydrogen on a normalized cycle. The integration of an additional power unit based on PEMFC is studied as a solution for the extension of the range of the electric vehicles.

Ultrafine particle levels measured on board short-haul commercial passenger jet aircraft

BackgroundAirline crew members report adverse health effects during and after inhalation exposure to engine oil fumes sourced to the air supply system onboard commercial and military aircraft. Most investigations into the causal factors of their reported symptoms focus on specific chemical contaminants in the fumes. The adverse health effects reported in aircrew exposed to the aircraft air supply, bled unfiltered off the engine or Auxiliary Power Unit (APU) may be related to particulate exposures, which are widely known to effect health. While oil contaminates the aircraft air supply, some suggest that this will only occur when there is a bearing seal failure, others document that there is low level oil contamination of the air supply during normal engine operation. This brief pilot study explores whether particulate exposure may be associated with the normal engine/APU and air supply operation and to therefore increase the understanding that UFP exposures may have on crew and passengers.MethodsAn ultrafine particle counter was utilised by an experienced airline captain in the passenger cabin of four short-haul commercial passenger aircraft. All flights were under 90 min on aircraft from two different carriers ranging from 7 months to 14 years old.ResultsUFP concentrations showed maximum concentrations ranging from 31,300 to 97,800 particles/cm3 when APU was selected on as a source of air on the ground and with engine bleed air and the air conditioning packs selected on during the climb. In 2 of the 4 flights the peaks were associated with an engine oil smell. Increases in UFP particle concentrations occurred with changes in engine/APU power and air supply configuration changes.ConclusionsThis study identified increases in UFP concentrations associated with engine and APU power changes and changes in air supply configuration. These results correlated with times when engine and APU oil seals are known to be less effective, enabling oil leakage to occur. The concentrations reached in the passenger cabins exceeded those taken in other ground-based environments. UFP exposures in aircraft cabins during normal flight indicates there will be health consequences for long serving aircrew and some passengers.