Performance of Quiet Helicopter

2020 ◽  
Vol 2020 (1) ◽  
pp. 1-17
Author(s):  
Jarosław Stanisławski
Keyword(s):  
Equations Of Motion ◽  
Rotor Blades ◽  
Main Rotor ◽  
Rotor Speed ◽  
Flexible Rotor ◽  
Slowing Down ◽  
Helicopter Flight ◽  
Operational Envelope ◽  
The Galerkin Method ◽  
Lower Limits

AbstractNoise generated by helicopters is one of the main problems associated with the operation of rotorcrafts. Requirements for reduction of helicopter noise were reflected in the regulations introducing lower limits of acceptable rotorcraft noise. A significant source of noise generated by helicopters are the main rotor and tail rotor blades. Radical noise reduction can be obtained by slowing down the blade tips speed of main and tail rotors. Reducing the rotational speed of the blades may decrease rotor thrust and diminish helicopter performance. The problem can be solved by attaching more blades to main rotor. The paper presents results of calculation regarding improvement of the helicopter performance which can be achieved for reduced rotor speed but with increased number of rotor blades. The calculations were performed for data of hypothetical light helicopter. Results of simulation include rotor loads and blade deformations in chosen flight conditions. Equations of motion of flexible rotor blades were solved using the Galerkin method which takes into account selected eigen modes of the blades. The simulation analyzes can help to determine the performance and loads of a quiet helicopter with reduced rotor speed within the operational envelope of helicopter flight states.

scholarly journals Investigations of the vortex ring state on a helicopter main rotor based on computational methodology using URANS solver

2019 ◽  
Vol 304 ◽  
pp. 02011
Author(s):  
Wienczyslaw Stalewski ◽  
Katarzyna Surmacz
Keyword(s):  
Vortex Ring ◽  
Equations Of Motion ◽  
Rotor Blades ◽  
Main Rotor ◽  
Simplified Approach ◽  
Helicopter Flight ◽  
Computational Methodology ◽  
Helicopter Main Rotor ◽  
Sudden Decrease ◽  
Vortex Ring State

Computational investigations of the Vortex Ring State (VRS) on a helicopter main rotor have been conducted. The VRS phenomenon is a condition of powered flight that occurs most frequently during the vertical or nearly vertical descent of a rotorcraft. The characteristic feature of the VRS is a torus-shaped vortex around a rotor. The occurrence of this extensive vortex structure is a dangerous phenomenon that usually causes sudden decrease of main-rotor thrust, finally leading to an increase of the rate of descent and vibration level, disturbances of a helicopter balance, deterioration of manoeuvrability and deficit of power. The investigations presented in the paper, have been conducted based on computational methodology developed and implemented by the Authors. The methodology is based on a coupling of several methods of Computational Fluid Dynamics and Flight Dynamic. The approach consists of calculation of unsteady aerodynamic forces acting on the flying rotorcraft by simultaneous solution of the URANS equations, the equations of motion of the helicopter as well as the equations describing fluid-structure-interaction phenomena. Flow effects caused by rotating rotor blades, are modelled using a simplified approach based on the Virtual Blade Model. Using the described methodology, a series of helicopter flight simulations, in a vicinity of the VRS boundaries, have been conducted. Selected results of these simulations have been discussed in the paper.

scholarly journals A Simulation Model for Computing the Loads Generated at Landing Site During Helicopter Take-Off or Landing Operation

2019 ◽  
Vol 2019 (2) ◽  
pp. 59-75
Author(s):  
Jarosław Stanisławski
Keyword(s):  
Equations Of Motion ◽  
Landing Site ◽  
Simulation Method ◽  
Rigid Bodies ◽  
Landing Gear ◽  
Rotor Blades ◽  
Wind Gust ◽  
The Galerkin Method ◽  
Lumped Masses ◽  
And Control

Summary The paper presents simulation method and results of calculations determining behavior of helicopter and landing site loads which are generated during phase of the helicopter take-off and landing. For helicopter with whirling rotor standing on ground or touching it, the loads of landing gear depend on the parameters of helicopter movement, occurrence of wind gusts and control of pitch angle of the rotor blades. The considered model of helicopter consists of the fuselage and main transmission treated as rigid bodies connected with elastic elements. The fuselage is supported by landing gear modeled by units of spring and damping elements. The rotor blades are modeled as elastic axes with sets of lumped masses of blade segments distributed along them. The Runge-Kutta method was used to solve the equations of motion of the helicopter model. According to the Galerkin method, it was assumed that the parameters of the elastic blade motion can be treated as a combination of its bending and torsion eigen modes. For calculations, data of a hypothetical light helicopter were applied. Simulation results were presented for the cases of landing helicopter touching ground with different vertical speed and for phase of take-off including influence of rotor speed changes, wind gust and control of blade pitch. The simulation method may help to define the limits of helicopter safe operation on the landing surfaces.

scholarly journals Modelling of Helicopter Main Rotor Aerodynamic Loads in Manoeuvres

2019 ◽  
Vol 26 (4) ◽  
pp. 273-284
Author(s):  
Grzegorz Kowaleczko ◽  
Andrzej Leśniczak
Keyword(s):  
Mathematical Model ◽  
Aerodynamic Characteristics ◽  
Complex Model ◽  
Rotor Blades ◽  
Main Rotor ◽  
Aerodynamic Forces ◽  
Aerodynamic Loads ◽  
Helicopter Flight ◽  
Helicopter Main Rotor ◽  
The Mathematical Model

AbstractThe article discusses the method of modelling of the helicopter main rotor aerodynamic loads during steady state flight and manoeuvres. The ability to determine these loads was created by taking into account the motion of each blade relative to the hinges and was a result of the applied method of aerodynamic loads calculating. The first part of the work discusses the basic relationships that were used to build the mathematical model of helicopter flight. The focus was also on the method of calculating of the aerodynamic forces generated by the rotor blades. The results of simulations dedicated to the “jump to hover” manoeuvre were discussed, showing the possibilities of analysing aerodynamic loads occurring in unsteady flights. The main rotor is considered separately in an “autonomous” way and treated as a source of averaged forces and moments transferred to the hub. The motion of individual blades is neglected, and their aerodynamic characteristics are radically simplified. The motion of individual blades is neglected, and their aerodynamic characteristics are radically simplified. This can lead to significant errors when attempting to model dynamic helicopter manoeuvres. The more complex model of helicopter dynamics is discussed.

scholarly journals A Comparison of Helicopter Main Rotor Features Due to Stiffness of Rotor Blade-Hub Connection

2018 ◽  
Vol 2018 (1) ◽  
pp. 119-136
Author(s):  
Jarosław Stanisławski
Keyword(s):  
Galerkin Method ◽  
Rotor Blade ◽  
Equations Of Motion ◽  
Aerodynamic Characteristics ◽  
Kutta Method ◽  
Main Rotor ◽  
Level Flight ◽  
Runge Kutta Method ◽  
Helicopter Main Rotor ◽  
The Galerkin Method

Abstract The paper presents results of simulation calculations concerning an influence of stiffness of blade-hub connection on rotor loads and blades deflections in hover, level flight and pull up maneuver. The three versions of rotor are considered with articulated, elastic and stiff connections of blades and hub. The blades with the same distributions of stiffness, mass and the same aerodynamic characteristics are applied for all rotor cases. The rotor loads are calculated applying Runge-Kutta method to solve the equations of motion of deformable blades. According to the Galerkin method, the parameters of blades motion are treated as combination of considered blade bending and torsion eigen modes. The results of calculations indicate for possibility to generate the greater rotor control moments and to improve helicopter maneuverability in the case of applying the non-changed blade of articulated rotor combined with elastic rotor hub.

scholarly journals Effectiveness of the Compound Helicopter Configuration in Rotorcraft Performance Increase

2020 ◽  
Vol 2020 (4) ◽  
pp. 81-106
Author(s):  
Jarosław Stanisławski
Keyword(s):  
Galerkin Method ◽  
High Speed ◽  
Simulation Method ◽  
Rotor Blades ◽  
Main Rotor ◽  
Detailed Model ◽  
Compound Helicopter ◽  
Rotorcraft Performance ◽  
The Galerkin Method ◽  
Horizontal Thrust

AbstractThe article presents the results of calculations applied to compare flight envelopes of varying helicopter configurations. Performance of conventional helicopter with the main and tail rotors, in the case of compound helicopter, can be improved by applying wings and pusher propellers which generate an additional lift and horizontal thrust. The simplified model of a helicopter structure, consisting of a stiff fuselage and the main rotor treated as a stiff disk, is applied for evaluation of the rotorcraft performance and the required range of control system deflections. The more detailed model of deformable main rotor blades, applying the Galerkin method, is used to calculate rotor loads and blade deformations in defined flight states. The calculations of simulated flight states are performed considering data of a hypothetical medium class helicopter with the take-off mass of 6,000kg. In the case of both of the helicopter configurations, the articulated main rotor hub is taken under consideration. According to the Galerkin method, the elastic blade model allows to compute blade deformations as a combination of the blade bending and torsional eigen modes. Introduction of additional wing and pusher propellers allows to increase the range of operational speed over 300 km/h. Results of the simulation are presented as time-runs of rotor loads and blade deformations and in a form of disk distribution plots of rotor parameters. The simulation method can be useful in defining requirements for a high speed rotorcraft.

Vibrations of a Helicopter Rotor-Fuselage System Induced by the Main Rotor Blades in Flight

1955 ◽  
Vol 22 (3) ◽  
pp. 355-360
Author(s):  
M. Morduchow ◽  
S. W. Yuan ◽  
H. Reissner
Keyword(s):  
Theoretical Analysis ◽  
Natural Frequencies ◽  
Rotor Blades ◽  
Helicopter Rotor ◽  
Simplified Model ◽  
Main Rotor ◽  
Numerical Examples ◽  
The Masses

Abstract Based on a simplified model of the hub-fuselage structure, a theoretical analysis is made of the response of the hub and fuselage of a helicopter in flight to harmonic forces transmitted by the rotor blades to the hub both in, and normal to, the plane of rotation. The assumed structure is in the form of a plane framework with masses concentrated at the joints. Simple expressions are derived for the vibration amplitudes of the mass points as functions of the masses and natural frequencies of the hub and the fuselage. The pertinent nondimensional parameters are determined, and simple explicit conditions of resonance are derived. Numerical examples are given to illustrate the results.

Ingestion Into the Upstream Wheelspace of an Axial Turbine Stage

1994 ◽  
Vol 116 (2) ◽  
pp. 327-332 ◽  
Author(s):  
T. Green ◽  
A. B. Turner
Keyword(s):  
Pressure Distribution ◽  
Static Pressure ◽  
Three Dimensional ◽  
Computer Code ◽  
Rotor Blades ◽  
Rotor Speed ◽  
Turbine Stage ◽  
Flow Rates ◽  
Static Pressure Distribution ◽  
Axial Clearance

The upstream wheelspace of an axial air turbine stage complete with nozzle guide vanes (NGVs) and rotor blades (430 mm mean diameter) has been tested with the objective of examining the combined effect of NGVs and rotor blades on the level of mainstream ingestion for different seal flow rates. A simple axial clearance seal was used with the rotor spun up to 6650 rpm by drawing air through it from atmospheric pressure with a large centrifugal compressor. The effect of rotational speed was examined for several constant mainstream flow rates by controlling the rotor speed with an air brake. The circumferential variation in hub static pressure was measured at the trailing edge of the NGVs upstream of the seal gap and was found to affect ingestion significantly. The hub static pressure distribution on the rotor blade leading edges was rotor speed dependent and could not be measured in the experiments. The Denton three-dimensional C.F.D. computer code was used to predict the smoothed time-dependent pressure field for the rotor together with the pressure distribution downstream of the NGVs. The level and distribution of mainstream ingestion, and thus the seal effectiveness, was determined from nitrous oxide gas concentration measurements and related to static pressure measurements made throughout the wheelspace. With the axial clearance rim seal close to the rotor the presence of the blades had a complex effect. Rotor blades in connection with NGVs were found to reduce mainstream ingestion seal flow rates significantly, but a small level of ingestion existed even for very high levels of seal flow rate.

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