Browse Topic: Fuel consumption
Helicopters' Vertical Take-Off and Landing (VTOL) capabilities are essential for maritime operations, especially for small-deck naval vessels. Unmanned Aerial Vehicles (UAVs) offer a cheaper, expendable, and efficient alternative for certain tasks, such as reducing pilot risk and lowering fuel consumption. While the procedures to approach and land on (moving) ships are standardized and bound to established operational limits in the case of crewed helicopters, UAVs lack such guidelines. This study investigates optimal rotary-wing UAV approach trajectories to a moving ship, for varying wind conditions and relative initial positions, and for different objectives. The goal is to provide preliminary guidelines for maritime UAV recovery operations, and a preliminary estimation of performance-based operational limits. The optimal trajectories are obtained using a global path-performance optimization framework based on Optimal Control Theory. The trajectories are compared to each other and to reference cases using the Longest Common SubSequence (LCSS) similarity measure, revealing how the unmanned helicopter adjusts its path to exploit the wind direction and profile for more efficient ground speeds. The violation of performance and/or geometric constraints is used to preliminarily indicate the presence of operational boundaries. The control effort and energy consumption are used to identify optimal starting positions for the helicopter approach phase for a given wind profile and intensity.
This paper presents experimental research aimed at developing novel low lubrication methods for rotorcraft and jet engines, focusing on sustaining minimal lubrication to prevent catastrophic bearing failure during loss of lubrication (LoL) events or to increase fuel consumption performance on once-through, fuel-oil bearing lubrication engines. Utilizing two high-speed bearing test rigs simulating low and high thrust class engine conditions, the study establishes lower bounds for oil flow rates necessary to maintain thermal stability and prevent thermal runaway in hybrid ball bearings. These findings inform the design of the Zulu Pod (ZPod), a passively driven, self-contained oil delivery system that uses engine compressor bleed air to precisely meter lubricant flow. Engine test stand results demonstrate that replacing traditional fuel-oil lubrication with the ZPod system reduces thrust specific fuel consumption (TSFC) by an average of 7%, with up to 11% savings, without compromising engine thrust or bearing health. The ZPod offers a simplified, efficient alternative to fuel-lubricated systems by eliminating fuel diversion for lubrication, enhancing fuel efficiency, and maintaining bearing performance in attritable or single-use engines. Additionally, the study highlights the potential of minimal lubrication supplied by the ZPod to extend operational life during LoL scenarios, enabling safer aircraft recovery. Future work will focus on extending testing to higher thrust classes and optimizing ZPod designs for broader applications.
In this paper, a comprehensive dynamic simulation of a parallel hybrid gas-electric single main rotor helicopter involving a motor/generator (MG) pair and a differential planetary gear transmission (PGT) arrangement forming an electronic continuously variable transmission (E-CVT) was performed. This notional hybrid electric helicopter was sized based on a retrofit of a dual engine, 10000 lb, 2500 Hp class helicopter. The total weight added by the electric components was 182 lbs which increased the propulsion system weight from 1184 to 1366 lbs. The simulation results found that at 110 kts cruise, the hybrid electric system enabled a 27% reduction in main rotor rpm which resulted in an 18% reduction in the fuel burn rate. It is concluded that use of an E-CVT parallel hybrid propulsion system offers potential for increased flight range and reduced fuel consumption in medium to large-scale helicopter applications.
There are a large number of curves and slopes in the mountainous areas. Unreasonable acceleration and deceleration in these areas will increase the burden of the brake system and the fuel consumption of the vehicle. The main purpose of this paper is to introduce a speed planning and promotion system for commercial vehicles in mountainous areas. The wind, slope, curve, engine brake, and rolling resistances are analyzed to establish the thermal model of the brake system. Based on the thermal model, the safe speed of the brake system is acquired. The maximum safe speed on the turning section is generated by the vehicle dynamic model. And the economic speed is calculated according to the fuel consumption model. The planning speed is provided based on these models. This system can guide the driver to handle the vehicle speed more reasonably. According to the simulation, compared to cruise control, speed planning can save fuel consumption at a mean value of 9.13% in typical mountainous areas. The field test of a typical commercial vehicle shows that this system can increase fuel efficiency by 4.26% compared to an experienced driver during a journey in a mountainous area.
The tiltrotor aircraft has the capability to extend its performance characteristics compared to the conventional helicopter. However, the performance features, namely the maximum flight duration and flight range, are determined by a series of factors, such as the nacelle angle, the aerodynamic interference, and the effect of the fuel consumption. In this article, a novel performance investigation method is put forward combining the flight dynamics model, the automatic differentiation arithmetic embedded inverse simulation method, and the fuel consumption model. Then, the maximum flight duration and range are calculated and analyzed. The results indicate that the maximum flight range of the example XV-15 tiltrotor is 837 km, and its maximum flight duration is 3.86 h, and both of the results occurs when the tiltrotor aircraft is in the airplane mode. Also, the fuel consumption is an influential aspect, and the control strategy should be altered across the flight to maintain the best performance. Lastly, the calculation efficiency of the method is validated, and the results show that the time-cost is lower than the real-time period, suggesting the real-time requirement is still satisfied.
The global aviation industry adopted a set of targets to mitigate CO2 emissions resulting from air transportation in 2009. The engine fuel burn is the main driver of CO2 emission; hence it will be the focus of this study. Rotorcraft are designed for supporting different types of missions or operations that are different from fixed wing aircraft. For this reason, the rotorcraft strategy for addressing the carbon impact should mainly target the new emerging technologies that will assist in reducing the fuel consumption and the deployment of Sustainable Aviation Fuels (SAF). This paper presents a forecast of the contribution level that could be achieved by rotorcraft industry in CO2 emission reduction in the period up to 2050. A projection of growth in civil rotorcraft fleet worldwide is provided as the starting point. Several new emerging technologies for both rotorcraft and engine together with the implementation scheme and their projected positive net impact on CO2 emission level are considered. Further, the contribution from SAF deployment in rotorcraft operation is analyzed. It is generally recognized that as much as 80% reduction in overall CO2 life cycle emission can be achieved from SAF relative to the fossil-based fuels or Conventional Aviation Fuels (CAF). However, some critical parameters used in predicting the SAF benefits remain uncertain. These pertain to fuel resources, economy, investment and policies. Therefore, consistent with previous studies, several fuel substitution scenarios are considered ranging from the most conservative to an optimistic projection.
The investigation presented in this paper is part of the international research project VARI-SPEED, which aims to invent a mass optimized speed variable drivetrain comprising a main gearbox with variable transmission ratio and a rotor suitable for rotor speed variation. A mass estimation model for the Sikorsky UH-60A drivetrain including a compound split was set up. Hydraulic, electric and mechanic variator technologies were investigated regarding their mass, torque and RPM properties. An optimization model was set up to find: 1.) The best variator technology for the mass optimized drivetrain. 2.) The best drivetrain for the mass optimized variator technology and 3.) The mass minimum if variator and drivetrain are considered both in the optimization loop. The research is performed to find out the influence of the variator technology on the mass and the design of the speed variable drivetrain. Furthermore, it is investigated, whether there is a preferable variator technology for rotor speed variation in rotorcraft. The investigation showed that the variator module has a significant influence on the optimal solution and that an individual optimization strategy is necessary for different drivetrain architectures as well as for different variator technologies. The electric variator technology seems to have the highest potential to enable an efficient variable rotor speed technology. At the moment the design is too heavy to gain benefits in efficiency. The mass estimation and optimization of the whole drivetrain including the variator is the basis to enable an assessment of usability of the variable rotor speed technology. Variation of the rotor speed within the drivetrain enables the turboshaft engine, the rotor and the auxiliary units each to operate at their optimal speeds. Rotor speed variation can overcome the divergent requirements between hover and fast forward flight, which is important for future rotorcraft like inventions in Future Vertical Lift (FVL) in the USA and CleanSky in Europe. Furthermore, it increases the efficiency, decreases fuel consumption andCO2- emission and reduces noise and environmental impact of rotorcraft.
A phenomenological simulation for a variable-voltage hybrid-electric powertrain was developed and compared with test data acquired on a 4 hp powertrain to understand the fundamental characteristics of such a system. The powertrain was modeled component by component, and compared with over 500 experimental data points, from the engine alone to the engine generator, to the engine-generator with four distributed propulsors. The principal conclusion of the predictive simulation and the experimental data was that generator voltage is a key parameter that needs careful control relative to rotor speed. For any operating state -- defined by rotor torque and RPM -- the generator voltage should be minimized to minimize engine specific fuel consumption. In general the system is influenced more by the engine generator than electric motors. Hence greater rotor torque and lower rotor RPM is desired. It was found that steady state performance can be confidently predicted with the engine model, if the thermal efficiency is calibrated with engine data. The overall understanding gained from this work is that the optimal operation of hybrid-electric powertrains in VTOL is closely coupled with controls and rotor aeromechanics as well as engine gas dynamics and thermodynamics, but can be captured with relatively simple phenomenological models.
Items per page:
50
1 – 50 of 2585