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In this paper, environmental impact analysis is applied to the various auxiliary power units (APUs) used for commercial aircraft in air transportation sector. The exhaust emissions of different auxiliary power units used in commercial aircraft are investigated. The emission index ( EI ), global warming potential ( GWP ) rate, global warming potential index ( GWPI ), environmental impact ( EnI ) rate, environmental impact index ( EnII ), environmental damage cost ( EDC ) rate, and environmental damage cost index ( EDCI ) of the exhaust emissions of APUs are computed. The GTCP36-300 model APU has the lowest total emission rate (TER) with 1.333 kg/h, the GTC85-129 model APU has the maximum total environmental index (TEI) by 24.719 g/kg-fuel, the GTCP36-300 model APU has the best total global warming potential value with 2709.176 kg/h CO 2_eqv , the TSCP700 model APU has the worst global warming potential index rate as 52.481 kg/kWh CO 2_eqv , the best total environmental damage cost rate is calculated to be 3.717 €/h for GTC85-72 model APU, the TSCP700 model APU has the highest environmental damage cost index with 0.130 €/kWh, the maximum total environmental impact is computed to be 5656.378 mPts/h for GTCP660 model APU, and the best total environmental impact index is determined for the GTC85-72 model APU.

This study proposes a novel paradigm for enhancing the fault detection and isolation (FDI) of gas generators in all-electric auxiliary power unit (APU) by utilizing shaft power information from the starter/generator. First, we conduct an investigation into the challenges and opportunities for FDI that are brought about by APU electrification. Our analysis reveals that the electrification of APUs opens new possibilities for utilizing shaft power estimates from starters/generators to improve gas generator FDI. We then provide comprehensive theoretical and analytical evidence demonstrating why, how, and to what extent the shaft power information from the starter/generator can fundamentally enhance the estimation accuracy of system states and health parameters of the gas generator, while also identifying key factors influencing these improvements in FDI performance. The effectiveness of the proposed paradigm and its theoretical foundations are validated through extensive Monte Carlo simulation runs. The research findings provide a unique perspective in addressing three fundamental questions—why joint fault diagnosis of the starter/generator and gas generator in all-electric APUs is essential, how it can be implemented, and what factors determine its effectiveness—thereby opening up promising new avenues for FDI technologies in all-electric APU systems.

The acceleration control law based on the rotor acceleration N-Dot has been widely applied in the design of aero-engine control systems, especially in the design of transient control law. Its advantage lies in the fact that it can guarantee the consistency of the acceleration performance of engine, not affected by engine manufacturing error, component performance degradation, and so on so forth. During the development of full authority electronic control system (FADEC) for an auxiliary power unit (APU), an acceleration control law is designed based on N-Dot and corrected with turbine inlet gas temperature for APU. The modified N-Dot acceleration control law is verified through rig test and the results show that the designed control system by integrating the modified N-Dot acceleration control law with the limit protection control can effectively prevent the engine from surge and over-speed during the acceleration process, and fully take advantage of the acceleration performance of the engine.

Today, the more electric aircraft (MEA) concept is gaining tremendous popularity. As a key component of the MEA, a more electric auxiliary power unit (MEAPU) integrated model with high accuracy and real-time performance is essential when conducting cooperative control and hardware-in-the-loop (HIL) test research. This paper proposes a novel MEAPU integrated model consisting of a MEAPU component-level-model (CLM) and a starter-generator (SG) model. Firstly, a MEAPU CLM was built and a continuous scaling method for the component characteristic map in the CLM is proposed to improve the model’s accuracy. Then, a double winding induction starter-generator (DWISG) model based on the electromagnetic theory, which is quite time consuming, was simplified using the pulse width modulation (PWM) rectifier linearization method. Finally, considering the coupling relationship between the MEAPU CLM and DWISG, an accurate real-time MEAPU integrated model was built and its simulation results were analyzed. Compared with the test results, the error of the proposed model was less than 0.5%; meanwhile its single-step simulation time was less than 20 ms, which can meet the demands of cooperative control and HIL test research. Furthermore, the continuous scaling method and PWM rectifier linearization method were found to be effective for modeling other MEAPUs and more electric engines (MEE).

The in-situ prognostics and health management of aircraft auxiliary power unit faces difficulty using the sparse on-wing sensing data. As the key technology of prognostics and health management, remaining useful life prediction of in-situ aircraft auxiliary power unit is hard to achieve accurate results. To solve this problem, we propose one kind of quantitative analysis of its on-wing sensing data to implement remaining useful life prediction of auxiliary power unit. Except the most important performance parameter exhaust gas temperature, the other potential parameters are utilized based on mutual information, which can be used as the quantitative metric. In this way, the quantitative threshold of mutual information for enhancing remaining useful life prediction result can be determined. The implemented cross-validation experiments verify the effectiveness of the proposed method. The real on-wing sensing data of auxiliary power unit for experiment are from China Southern Airlines Company Limited Shenyang Maintenance Base, which spends over $6.5 million on auxiliary power unit maintenance and repair each year for the fleet of over 500 aircrafts. Although the relative improvement is not too large, it is helpful to reduce the maintenance and repair cost.

In this study, three different configurations of a solid oxide fuel cell and gas microturbine hybrid system are evaluated for application in auxiliary power units. The first configuration is a common hybrid system in auxiliary power units, utilizing a fuel cell stack in the structure of the gas turbine cycle. The other configurations use two series and parallel fuel cell stacks in the structure of the gas turbine cycle. The main purpose of this research is thermodynamic analysis, evaluation of the performance of the proposed hybrid systems in similar conditions, and selection of an appropriate system in terms of efficiency, power generation, and entropy generation rate. In this study, the utilized fuel cells were subjected to electrochemical, thermodynamic, and thermal analyses and their working temperatures were calculated under various working conditions. Results indicate that the hybrid system with two series stacks had maximum power generation and efficiency compared with the other two cases. Moreover, the simple hybrid system and the system with two parallel stacks had relatively equal pure power generation and efficiency. According to the investigations, hybrid system with two series fuel cell stacks, which had 3424 and 1712 cells, respectively, can achieve the electrical efficiency of over 48%. A hybrid system with two parallel fuel cell stacks, in which each stack had 2568 cells, had the electrical efficiency of 46.3%. Findings suggested that maximum electrical efficiency occurred between the pressure ratios of 5–6 in the proposed hybrid systems.

In the context of the ongoing development of renewable energy sources, coal-fired units are undergoing a gradual transformation into auxiliary power sources. Consequently, there is an urgent need to enhance the deep-peaking capability of these units. The present paper investigates the combustion behavior of a pulverized coal boiler across four different operational scenarios of 360 MW, 300 MW, 240 MW, and 180 MW using CFD numerical simulation. The boiler in question is a 600 MW supercritical cyclone hedge boiler. The results demonstrate a decline in the aggregate temperature within the furnace chamber with a reduction in load, coal feed, and air supply. At 60%, 50%, 40%, and 30% of the rated load, the NOx concentrations at the furnace outlet are 481.56 ppm, 477.01 ppm, 472.32 ppm, and 469.63 ppm, respectively. With a decrease in the boiler load, a downward trend in the NOx concentrations at the furnace outlet is evident.

The ejection theory is widely used in industrial fields such as drainage, cooling, vacuum. Many ejection devices are applied in civil aircraft due to their simple design and easy layout. This article introduces several types of ejection applications in multiple systems of civil aircrafts. Then a CFD simulation of the APU (Auxiliary Power Unit) compartment drainage ejector is conducted to analyse the influence on the drainage function by different arrangements.

This paper describes the algorithm developed by the authors for matching the workflow of the auxiliary power unit to the air turbine used when starting the engine. This technique is applied to determine the possibility of starting a gas turbine engine, calculate its time and basic parameters under all operating conditions (including in flight), as well as to select a new auxiliary power unit (APU) or an air turbine for an existing system. The developed technique considers structural, strength, operational and other limitations. The results were implemented as a computer program.

In the early phase of a power system’s black start, the battery energy storage system (BESS) emerges as an effective auxiliary power source. However, a significant and challenging issue during this phase is the initiation of large-capacity induction motor (IM) auxiliary devices. This paper introduces an analytical and evaluative approach for the starting capacity of IM loads with BESSs in parallel, along with an optimized BESS capacity configuration plan. Initially, the mathematical models for both BESS and IM are dissected, establishing a dynamic equivalent circuit for the paralleled BESSs initiating IM loads under a master-slave control strategy. Subsequently, the voltage/current constraints on the energy storage side are taken into account to define the stable operation range of the black-start isolated power grid. Following this, an evaluation method and metric for the starting capability of paralleled BESSs with IM loads are introduced. An optimization plan for the capacity configuration and distribution of grid-forming (GFM) and grid-following (GFL) controlled BESSs is devised based on these metrics. The validity of the proposed metrics and configuration scheme is ultimately confirmed through MATLAB/SIMULINK simulation.