Propulsion

About: Propulsion is a research topic. Over the lifetime, 24977 publications have been published within this topic receiving 200311 citations.

A Hybrid Electric Vehicle Motor Cooling System—Design, Model, and Control

Abstract: Hybrid electric vehicle motors offer propulsion while accelerating and charge the battery pack when braking or decelerating. Though electric motors have high operating efficiency, considerable heat is generated based on required operating torque and speed. Thus, an efficient motor cooling system is needed to maintain the temperature within a prescribed range. The traditional motor liquid cooling system is effective but consumes energy to run the coolant pump and radiator fan. This paper examines the performance of a hybrid cooling system, combining heat pipes with conventional liquid cooling in a compact thermal cradle. This innovative design allows heat removal via an integrated thermal pathway by regulating various actuators (e.g., centrifugal fans, radiator pump, and fan) to minimize energy consumption. A reduced order thermal model predicts the motor's internal temperatures. Cooling performance is evaluated based on the Urban Assault driving cycle for different conditions. Numerical results show that the electric motor temperature is maintained at approximately the target value of 70 °C. Additionally, up to approximately 370 kJ of energy is saved as compared to a conventional liquid cooling system for a specific 85 kW e-motor within 1500 s run time.

Microfabricated electrospray emitter arrays with integrated extractor and accelerator electrodes for the propulsion of small spacecraft

Abstract: Microfabricated electrospray thrusters could revolutionize the spacecraft industry by providing efficient propulsion capabilities to micro and nano satellites (1–100 kg). We present the modeling, design, fabrication and characterization of a new generation of devices, for the first time integrating in the fabrication process individual accelerator electrodes capable of focusing and accelerating the emitted sprays. Integrating these electrodes is a key milestone in the development of this technology; in addition to increasing the critical performance metrics of thrust, specific impulse and propulsive efficiency, the accelerators enable a number of new system features such as power tuning and thrust vectoring and balancing. Through microfabrication, we produced high density arrays (213 emitters cm−2) of capillary emitters, assembling them at wafer-level with an extractor/accelerator electrode pair separated by micro-sandblasted glass. Through IV measurements, we could confirm that acceleration could be decoupled from the extraction of the spray—an important element towards the flexibility of this technology. We present the largest reported internally fed microfabricated arrays operation, with 127 emitters spraying in parallel, for a total beam of 10–30 µA composed by 95% of ions. Effective beam focusing was also demonstrated, with plume half-angles being reduced from approximately 30° to 15° with 2000 V acceleration. Based on these results, we predict, with 3000 V acceleration, thrust per emitter of 38.4 nN, specific impulse of 1103 s and a propulsive efficiency of 22% with <1 mW/emitter power consumption.

A novel outer-rotor permanent-magnet flux-switching machine for urban electric vehicle propulsion

Abstract: A novel twelve-stator-pole, twenty-two-rotor-pole (12/22) outer-rotor permanent-magnet flux-switching (PMFS) machine for electric propulsion in a lightweight electric vehicle is presented. Analytical equations are derived for the dimensioning of a 3-phase 5kW in-wheel motor. Optimisation techniques are employed to maximise the performance of the machine. The validity of the analytical equations is verified by finite element analysis (FEA). The results show that the PMFS machine combines the key advantages of the PM machines and the switched reluctance machine, and thus demonstrate the viability of the proposed machine as a suitable candidate for in-wheel electric propulsion.

Challenges in the silent aircraft engine design

Abstract: The Silent Aircraft Initiative goal is to design an aircraft that is imperceptible above background noise outside the airport boundary. The aircraft that fulfils this objective must also be economically competitive with conventional aircraft of the future and therefore fuel consumption and mechanical reliability are key considerations for the design. To meet these ambitious targets, a multi-fan embedded turbofan engine with boundary layer ingestion has been proposed. This configuration includes several new technologies including a variable area nozzle, a complex high-power transmission system, a Low Pressure turbine designed for low-noise, an axial-radial HP compressor, advanced acoustic liners and a low-speed fan optimized for both cruise and off-design operation. These technologies, in combination, enable a low-noise and fuel efficient propulsion system but they also introduce significant challenges into the design. These challenges include difficulties in predicting the noise and performance of the new components but there are also challenges in reducing the design risks and proving that the new concepts are realizable. This paper presents the details of the engine configuration that has been developed for the Silent Aircraft application. It describes the design approach used for the critical components and discusses the benefits of the new technologies. The new technologies are expected to offer significant benefits in noise reduction without compromising fuel burn. However, more detailed design and further research are required to fully control the additional risks generated by the system complexity.

Distributed Turboelectric Propulsion for Hybrid Wing Body Aircraft

Abstract: Meeting future goals for aircraft and air traffic system performance will require new airframes with more highly integrated propulsion. Previous studies have evaluated hybrid wing body (HWB) configurations with various numbers of engines and with increasing degrees of propulsion-airframe integration. A recently published configuration with 12 small engines partially embedded in a HWB aircraft, reviewed herein, serves as the airframe baseline for the new concept aircraft that is the subject of this paper. To achieve high cruise efficiency, a high lift-to-drag ratio HWB was adopted as the baseline airframe along with boundary layer ingestion inlets and distributed thrust nozzles to fill in the wakes generated by the vehicle. The distributed powered-lift propulsion concept for the baseline vehicle used a simple, high-lift-capable internally blown flap or jet flap system with a number of small high bypass ratio turbofan engines in the airframe. In that concept, the engine flow path from the inlet to the nozzle is direct and does not involve complicated internal ducts through the airframe to redistribute the engine flow. In addition, partially embedded engines, distributed along the upper surface of the HWB airframe, provide noise reduction through airframe shielding and promote jet flow mixing with the ambient airflow. To improve performance and to reduce noise and environmental impact even further, a drastic change in the propulsion system is proposed in this paper. The new concept adopts the previous baseline cruise-efficient short take-off and landing (CESTOL) airframe but employs a number of superconducting motors to drive the distributed fans rather than using many small conventional engines. The power to drive these electric fans is generated by two remotely located gas-turbine-driven superconducting generators. This arrangement allows many small partially embedded fans while retaining the superior efficiency of large core engines, which are physically separated but connected through electric power lines to the fans. This paper presents a brief description of the earlier CESTOL vehicle concept and the newly proposed electrically driven fan concept vehicle, using the previous CESTOL vehicle as a baseline.