More Electric Engine Research Articles

Analysis and Design of Embedded High-Temperature Doubly Salient Electro-Magnetic Starter/Generator for Aviation

In view of the high temperature operation characteristics of the embedded starter/generator for the more electric engine (MEE), the influence of material property change on motor performance at high temperature is studied. Furthermore, considering the influence of high temperature, the electromagnetic calculation of doubly salient electro-magnetic machine (DSEM) is carried out, and the excitation design principle of DSEM under high temperature is pointed out. The performance of DSEMs using DW310 silicon steel and 1J22 iron-cobalt alloy material was compared. Based on the silicon steel material, the structural parameters of DSEM are analyzed. According to the key parameters obtained from structural parameter analysis, Box-Behnken method and genetic algorithm were used to carry out the multi-parameter and multi-objective optimization design. The optimization objectives include excitation current, voltage ripple and cogging torque, to meet the torque and power quality requirements of MEE. Then the performance of DSEM at room temperature and high temperature is analyzed by the finite element method, which verifies the effectiveness of the design. Finally, a high-temperature and high-speed DSEM prototype was processed. At the same time, in order to cooperate with the test, a DSEM ground simulation test system platform for MEE was built to test the prototype. Its design experience lays a foundation for the embedded DSEM design of more electric aircraft.

Design rules to establish a credible More‐Electric Engine baseline power architecture concept

AbstractThe More‐Electric Engine (MEE), with its electrified engine auxiliary systems and increased multi‐shaft power offtake, is likely to become an increasingly central aspect of future More‐Electric Aircraft. Consequently, lightweight but resilient electrical power architectures are needed for these future MEE applications. However, whilst a range of MEE architectures exist in the research literature, no effective baseline architecture or standardised feature identification has been proposed to specifically address their unique design requirements. Accordingly, any underpinning technology‐focused research for critical MEE subsystems may ultimately have a reduced effectiveness without this credible baseline. Based on comprehensive design analyses, preliminary design requirements and anticipated operational modes, this article proposes key design rules for the formation of the first generic baseline MEE electrical power system architecture concept. Guidance is provided on features such as the number of power generation systems, the number and topologies of distribution channels, type of power conversion, essential load redundancy, and the location of emergency power supply. This article also provides full transparency of the design process so that key decision points can be revisited to capture application‐specific requirements and updates to certification requirements.

Research on afterburning control of more electric engine with a nonlinear fuel supply system

More electric engine (MEE) with electric pump metering fuel has the problem of unstable engine control due to the dead-zone characteristics of afterburner fuel actuator. On the basis of conventional μ modified adaptive control method, a compound modified adaptive control (CMAC) system based on neural network inverse model is proposed in this study. At first, the afterburner fuel actuator model of MEE is established through Simulink/AMESim co-simulation to study its fuel supply characteristics and reveal the reasons for dead-zone characteristics of the actuator. Subsequently, an integrated model of afterburner fuel actuator/MEE is established to investigate the effect of dead-zone characteristics on engine performance. Finally, the CMAC system for afterburner fuel flow closed-loop control based on neural network inverse model and improved μ modified adaptive control method is designed. The simulation results show that the dead-zone characteristics of afterburner fuel actuator can cause engine shaking and unstable operation. The engine thrust has a continuous fluctuation with amplitude of about 0.2%. The proposed CMAC system can effectively avoid the dead-zone interval of actuator and achieve stable transition of the engine state in the entire operating range of the afterburner fuel actuator. Thus, the stability of the control system can be significantly improved. Meanwhile, the improved μ modified adaptive control algorithm in the CMAC system has better dynamic characteristics when compared with the conventional μ modified adaptive control algorithm.

Special issue on all‐electric and hybrid‐electric flight

Special issue on all‐electric and hybrid‐electric flight

Component-Level Modeling of More Electric Auxiliary Power Units for Cooperative Control

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).

Performance Improvement of Turbofans by Electric Power Transfer

Abstract With design trends toward the more electric engine (MEE) for the more electric aircraft (MEA), novel technologies can be pinpointed for multi-spool engines. Provided that a multi-spool MEE is equipped with electrical machines connected to each of its shafts, using power electronic converters (PECs) within a common high-voltage DC bus configuration, it is possible to redistribute a desired amount of power between the engine shafts independent of their speeds. This paper presents the impact of electric power transfer (EPT) on engine performance by using a developed 0-dimensional engine model based on the inter-component volume (ICV) method and engine component maps. Generic component maps are scaled to match the design point of the CFM56-3 engine. Validating the simulation results with engine performance data from literature shows that the steady-state error of the speed and fuel consumption is within 1% and 3.5% for the high- and low-speed settings, respectively, which is acceptable for the purpose of power transfer studies. It is shown that a 400 kW EPT system is the best performing for the cases run for the CFM56-3 engine, which can halve the amount of bleed air from variable bleed valves (VBVs). Results show that EPT with the rescheduled VBVs opening improves the engine performance significantly at low-speed settings by decreasing fuel consumption and increasing surge margins. Detailed simulation results from the engine model and EPT weight penalty analysis show that fuel consumption for short- and medium-haul flights reduces by up to 0.46% and 0.79% with state-of-the-art, and 0.60% and 1.0% with future technologies, respectively. Furthermore, results show that electric power transfer can recover the surge margins of degraded engines at high-speed settings.

Robust Control for Electric Fuel Pump with Variant Nonlinear Loads Based on a New Combined Sliding Mode Surface

A class of electric fuel pump system equipped in More-electric Engines with variant loads is studied. A novel robust control method based on a combined linear and quadratic integral sliding mode surface is proposed. The linear sliding mode surface with improved exponential reaching law guarantees that nominal system has satisfying performance with reduced chattering, while the quadratic integral sliding mode surface is responsible for compensation of mismatched uncertainties, enhancing system’s robustness. Besides, mathematical model of electric fuel pump with variant load and leakages is established, which reflects both steady and dynamic characteristics of the fuel pump. In addition, it is proved that combined sliding mode surface can be reached in finite time and remains there. Stability of closed-loop system is proved as well. The effectiveness of the proposed method is verified by simulation results.

Dimensional analysis of an integrated pump and de-aerator solution in more electric aero engine oil systems

ABSTRACTAero-engine oil systems need to pump and de-aerate air-oil flows. Engine sub-components performing these tasks are undergoing important changes due to the development of more-electric engines. A new integrated pump and separation system that can be electrically entrained was developed and characterised experimentally to reduce footprint on the engine and increase reliability and performance. This prototype combines the pumping, de-aeration and de-oiling function of the scavenge part of oil systems. Previous works have failed to address in-flight performance of the prototype. To address this need, a dimensional analysis of the Pump and Separation System that allows in-flight performance prediction is proposed in this paper. This model is used to assess different prototype sizes and the influence of a more-electric engine. This analysis illustrates that by switching to an electric entrainment, the footprint of the Pump and Separation system on the engine is reduced by 34%, and de-aeration performances are improved by 55% at maximum take-off and 17% in cruise phase. This study opens the way for a more accurate design of the prototypes based on engine requirements.

Impact of Engine Certification Standards on the Design Requirements of More-Electric Engine Electrical System Architectures

The development of the More-Electric Engine (MEE) concept will see an expansion in the power levels, functionality and criticality of electrical systems within engines. However, to date, these more critical electrical systems have not been accounted for in existing engine certification standards. To begin to address this gap, this paper conducts a review of current engine certification standards in order to determine how these standards will impact on the design requirements of More-Electric Engine (MEE) electrical system architectures. The paper focuses on determining two key architectural requirements: the number of individual failures an architecture can accommodate and still remain functional and the rate at which these failures are allowed to occur. The paper concludes by proposing a comprehensive set of design requirements for MEE electrical architectures, considering various operating strategies, and demonstrates their application to example MEE electrical system architecture designs.

Conjugate Heat Transfer Analysis of Integrated Brushless Generators for More Electric Engines

In this paper, a complete conjugate heat transfer analysis of a scaled-sized prototype of an integrated air-cooled surface-mounted permanent-magnet generator for the “more-electric engine” application is presented. The selected integration position inside the aircraft's main gas turbine engine imposes the use of an unconventional cooling system, where the coolant directly flows through the machine air gap. To predict and prevent the critical working conditions of the prototype, the adopted cooling system has been investigated using a complete fluid-thermal analysis. Due to the capabilities of computational fluid dynamic software, it has been possible to analyze the temperature and flow fields inside the machine, giving an idea about the distribution of the thermal quantities both inside the solid materials and above the surfaces. The numerical model validation has been provided, comparing computed and experimental results, i.e., imposing the same working conditions, the predicted temperatures satisfactorily agree with the measured temperatures.

All-electric aircraft

While there are many technical challenges to overcome before a fully electric aircraft is operational, the benefits of such a system are significant. For the industry to move forward the More Electric Aircraft and its partner concept, the More Electric Engine (MEE) must become reality in the next 10 to 20 years. This paper discusses the development of such engines and aircraft.