Helicopter engineering
Software of new technological innovation to the ANGLO-ITALIAN EH101
Our self esteem in the long term and the new possibilities and challenges that we might glimpse forward to are quite a great deal dependent on the benefits that the software of new technological innovation has brought to present day solutions.
The EH one hundred and one, created by the partnership of Agusta and GKN Westland employs new technological innovation extensively. The principal new item technologies utilized are:
Sophisticated aerodynamic composite blades A composite elastomeric hub An energetic vibration command procedure (ACSR) Composite structural factors and aluminium lithium structural factors Overall health and Usage Monitoring units An all electronic AFCS automatic flight command units Digital Instrument Devices and helicopter Integrated Avionic Devices utilizing Dual Information Buses.
To highlight the benefits of just a person of these things, as an case in point, permit us contemplate the main rotor. If we had retained the aerodynamic technological innovation of the earlier era of helicopters, the plane would have required to employ two extra blades to match the general performance of the new rotor. These extra blades would have had a major consequential impact on elevated installed electricity necessities, and elevated vacant pounds and total pounds for the missions to be performed. This advancement is a immediate consequence of the 37% advancement in cruise blade loading available from the innovative aerodynamics utilized.
Helicopter vibration command
Helicopter vibration command methodology is dependent on the subsequent three problems
o rotor dynamics
o fuselage dynamics
o choice of appropriate antivibration gadget.
Helicopter rotor dynamics
Helicopter vibration from the main rotor is the primary source of complications. Minimization starts with appropriate tuning of main rotor qualities. The dynamic reaction of a rotor blade to the aerodynamic excitation is dependent on blade natural frequencies, generalized masses and modal damping which offers the amplification or reduction of blade roots, vibratory masses to the aerodynamic excitation.
The aerodynamic parameters are selected mostly to strengthen helicopter general performance in hover and in forward flight. The main parameters are
o induced velocities
o planform form : rectangular or tapered
o tip form : swept, anhedral
o twist.
Induced velocities due to the fuselage or the blade vortex interactions are a major parameter. Fuselage optimization to minimize aerodynamic drag potential customers to creating compact rotor heads. In these ailments, the blades are shut to the human body, which amplifies the interactions in conditions of fuselage induced velocities thrilling the blade and offers superior rotor head vibratory masses.
The selection of blades is thus a very major element as much as vibrations are worried. A standard argument in the helicopter community is the bigger the selection of blades the decrease the dynamic masses at the rotor head. The preference of the selection of blades is strongly influenced by other requirements like general performance, cost and autorotation ability.
The latest aerodynamic experiments are developing new blades which are no for a longer period rectangular but tapered with evolving strategies. Their twist can be modified and an anhedral additional to strengthen their performances in hover or at superior pace. The planform influences the spanwise distribution of the aerodynamic masses as properly as the dynamic qualities of the blades. Tapering potential customers, for case in point, to low generalized masses for those modal designs in which dynamic reaction and vibration stage are elevated.
High twist is favourable for hover and low pace general performance. The linear aerodynamic principle exhibits that bigger harmonics blade flatwise masses are proportional to twist. The existing blade design methodology is an optimization of aerodynamic performances as properly as a modify in internal structure to strengthen dynamic conduct. The most straightforward methodology includes retaining a margin concerning blade modal frequencies and hub excitation frequencies. It is achievable to increase the generalized mass or shift the frequency of the modes most critical for vibrations with tuning masses. Optimization techniques include local stiffness and mass changes to globally minimize aerodynamic excitations and blade reaction to obtain low N-for every-rev hub masses (second, vertical and lateral shears).
Helicopter fuselage dynamics
The fuselage reaction to rotor excitations will have to meticulously be considered to enable superior comfort plane to be acquired. The fuselage reaction may differ extensively with the excitation frequency.
The structure design will have to be supported by finite factor airframe analysis. In the design period, every main architecture preference like implementation of frames, installation of heavy sections (engines, gearbox, …) and interface concerning mechanical sections and fuselage will have to be validated by dynamics issues. As much as new structures are worried the results of composites make the prediction of natural frequencies and method designs additional hard.
The issue comes from unique new elastic coupling conditions and the structural design notion of the helicopter composite fuselages is unique from that of metals. An additional trouble is the structure identification methodology to guarantee suitable fuselage method placement : finite factor analysis as properly as correlative ground shake exams are required. The international optimization of the structural designs is impractical. This is why every corporation is seeking for simplified designs which are a great deal easier to use for parametric experiments and optimization techniques.
Antivibration equipment.
Upgrading of general performance, mission duration and versatibility seeking into elevated stage of comfort, imperfect command of compelled vibration dynamic and aerodynamic complications at design stage, involve the requirement for developing antivibration equipment. The trouble proves hard because the vibration technological innovation has to satisfy the subsequent necessities
o system with an unlimited service life
o reliability
o reduced maintenance
o minimum pounds
o minimum dimensions.
The antivibration equipment are broken down into 3 courses
o at the rotor hub
o at the rotor-to-fuselage interface – upper deck
o in the fuselage.
In these three courses, there are three types of antivibration equipment : passive, semi-energetic and energetic units.
Supply by Protechwood