Helicopter flight characteristics in icing conditions

2012 ◽  
Vol 116 (1183) ◽  
pp. 963-979 ◽  
Author(s):  
Yihua Cao ◽  
Guozhi Li ◽  
R. A. Hess
Keyword(s):  
State Space Model ◽  
Liquid Water Content ◽  
Atmospheric Temperature ◽  
Ice Accretion ◽  
Handling Qualities ◽  
Helicopter Flight ◽  
Different Types ◽  
Ice Shedding ◽  
Temperature Liquid ◽  
Further Development

Abstract A method to predict the effects of rotor icing on the flight characteristics of a UH-60A helicopter is presented. By considering both natural ice shedding and different types of ice accretion due to local temperature variations on the blade surface, an improved rotor icing model was developed. Next, the effects of icing on rotor force, torque and flapping were incorporated in a nonlinear helicopter dynamic model. Based upon icing design envelopes in cumuliform clouds, trim and stability characteristics were studied. Further development of the helicopter state-space model allowed control and handling qualities characteristics to be investigated with variation of the three icing-related cloud variables (atmospheric temperature, liquid water content, and median volumetric diameter). Results indicated that this method of evaluating rotorcraft icing is both feasible and useful.

Experimental investigation on the performance degradation of helicopter rotor due to ice accretion

2021 ◽  
pp. 095441002110232
Author(s):  
Mingqi Huang ◽  
Honggang Yuan ◽  
Liangquan Wang ◽  
Xianmin Peng ◽  
Qinglin Liu
Keyword(s):  
Three Dimensional ◽  
Leading Edge ◽  
Lower Surface ◽  
Liquid Water Content ◽  
Performance Degradation ◽  
Helicopter Rotor ◽  
Ice Accretion ◽  
Noticeable Effect ◽  
Handling Qualities ◽  
Thrust And Torque

Helicopter rotor performance can be significantly altered by ice accretion which directly degrades the handling qualities and safety during flight. To obtain understanding into the effect of ice accretion on a helicopter rotor in forward flight under different icing environments, an experimental campaign was conducted in an icing wind tunnel using a rotor model with diameter at 2 m. Research was emphasized on revealing effect of liquid water content and static temperature on the rotor performance degradation. The dynamic thrust and torque of the rotor were measured by a six-component balance. Ice shape of the airfoils at specific rotor blade spanwise locations was obtained through the ice cutting process; meanwhile, the entire ice topology on the blade was scanned by means of the three-dimensional scanning technique. Results showed that ice was mainly accreted on the leading edge and lower surface of the blade. The static temperature of a icing cloud has a noticeable effect on the regime of accreted ice. The ice formation was transparent glaze at −8°C and transformed to milky rime when changed the static temperature to −20°C. Comparing to rime ice, the glaze ice on the blade is more influential to the rotor performance degradation. Particular attention is given to the fact that under extreme icing conditions, over 30% degradation of transient rotor thrust was observed.

SUBSTANTIATION OF STRATEGIES OF DIVERSIFICATION OF ACTIVITY OF MOTOR TRANSPORT ENTERPRISE AND THEIR EXPERIMENTAL VERIFICATION

2018 ◽  
Author(s):  
Oleksii Omelyanovych ◽  
◽  
Fedir Demishkan ◽  
Keyword(s):  
Economic System ◽  
Synergistic Effects ◽  
Production Capacity ◽  
Economic Conditions ◽  
Market Segments ◽  
Industrial Diversification ◽  
Diversification Strategies ◽  
Different Types ◽  
Trucking Company ◽  
Further Development

The study considered the main approaches to the concept of diversification. It was determined that there are different types of diversification depending on the sources of its origin, but the main groups of classification are: functional (by processes), commercial and resource. In general, the economic system can have four typical situations when a process of diversification (specialization) occurs: 1) specialization is more profitable than the possible option of diversification; 2) specialization is the only possible way of further development and existence for this economic system in specific economic conditions; 3) diversification is more profitable than specialization; 4) diversification is the only possible way of further existence and development. Diversification is especially important in conditions of uncertainty in the development of the external environment. In such situations, diversification is the only way to avoid collapse and achieve sustainable development. The firm makes several bets in the hope that at least one of them will win. Offensive motives include aggressive growth policies; financial opportunities; overcoming the limits of growth; achieving synergistic effects. Here it is necessary to determine the presence of defense motives for the use of diversification: the distribution of business risk; reduction of cyclical instability; replacement of the declining activity. In accordance with the objectives of the study for the trucking company, it is possible to propose the use of such diversification strategies as industrial diversification, which is realized through changes in the production capacity of the trucking company; marketing diversification, which will promote the positioning of the relocation service in different market segments, and competitive diversification, which should be carried out using the methods of portfolio analysis of the company's positioning in the market.

scholarly journals Review of Icing Effects on Wind Turbine in Cold Regions

2018 ◽  
Vol 72 ◽  
pp. 01007 ◽  
Author(s):  
Faizan Afzal ◽  
Muhammad S. Virk
Keyword(s):  
Wind Turbine ◽  
Structural Integrity ◽  
Turbine Blades ◽  
Leading Edge ◽  
Added Mass ◽  
Cold Climate ◽  
Ice Accretion ◽  
Wind Turbine Blades ◽  
Turbine Performance ◽  
Ice Shedding

This paper describes a brief overview of main issues related to atmospheric ice accretion on wind turbines installed in cold climate region. Icing has significant effects on wind turbine performance particularly from aerodynamic and structural integrity perspective, as ice accumulates mainly on the leading edge of the blades that change its aerodynamic profile shape and effects its structural dynamics due to added mass effects of ice. This research aims to provide an overview and develop further understanding of the effects of atmospheric ice accretion on wind turbine blades. One of the operational challenges of the wind turbine blade operation in icing condition is also to overcome the process of ice shedding, which may happen due to vibrations or bending of the blades. Ice shedding is dangerous phenomenon, hazardous for equipment and personnel in the immediate area.

scholarly journals Construction of the RSS V3.2 Lower-Tropospheric Temperature Dataset from the MSU and AMSU Microwave Sounders

2009 ◽  
Vol 26 (8) ◽  
pp. 1493-1509 ◽  
Author(s):  
Carl A. Mears ◽  
Frank J. Wentz
Keyword(s):  
Lower Stratosphere ◽  
Weighting Function ◽  
Lower Troposphere ◽  
Weighted Average ◽  
Atmospheric Temperature ◽  
Tropospheric Temperature ◽  
Satellite Measurements ◽  
Microwave Sounding Unit ◽  
Different Types ◽  
Microwave Sounding

Abstract Measurements made by microwave sounding instruments provide a multidecadal record of atmospheric temperature in several thick atmospheric layers. Satellite measurements began in late 1978 with the launch of the first Microwave Sounding Unit (MSU) and have continued to the present via the use of measurements from the follow-on series of instruments, the Advanced Microwave Sounding Unit (AMSU). The weighting function for MSU channel 2 is centered in the middle troposphere but contains significant weight in the lower stratosphere. To obtain an estimate of tropospheric temperature change that is free from stratospheric effects, a weighted average of MSU channel 2 measurements made at different local zenith angles is used to extrapolate the measurements toward the surface, which results in a measurement of changes in the lower troposphere. In this paper, a description is provided of methods that were used to extend the MSU method to the newer AMSU channel 5 measurements and to intercalibrate the results from the different types of satellites. Then, satellite measurements are compared to results from homogenized radiosonde datasets. The results are found to be in excellent agreement with the radiosonde results in the northern extratropics, where the majority of the radiosonde stations are located.

scholarly journals Comparison Between Two Different Types of Microcontroller in Developing Optical Tomography Controller Unit

2013 ◽  
Vol 64 (5) ◽  
Author(s):  
M. Fadzli Abdul Shaib ◽  
Ruzairi Abdul Rahim ◽  
Siti Zarina M. Muji ◽  
Naizatul Shima ◽  
Mohd Zikrillah Zawahir
Keyword(s):  
Optical Tomography ◽  
Tomography System ◽  
Different Types ◽  
Beam Projection ◽  
Further Development ◽  
Conditioning Circuit

This paper describes the comparisons on the usage of different PIC microcontroller towards the development of optical tomography controller for fan beam projection. The advantage and disadvantage for each PIC towards the development of tomography sensors is discussed. The transmission and receiving conditioning circuit integrate with PIC is presented and explained. This paper is vital for further development of optical tomography system as a whole system.

Effect of atmospheric temperature and droplet size variation on ice accretion of wind turbine blades

2010 ◽  
Vol 98 (12) ◽  
pp. 724-729 ◽  
Author(s):  
Matthew C. Homola ◽  
Muhammad S. Virk ◽  
Tomas Wallenius ◽  
Per J. Nicklasson ◽  
Per A. Sundsbø
Keyword(s):  
Wind Turbine ◽  
Droplet Size ◽  
Turbine Blades ◽  
Size Variation ◽  
Atmospheric Temperature ◽  
Ice Accretion ◽  
Wind Turbine Blades

scholarly journals Experiments on the Growth of Spongy Ice Near a Stagnant Point

1990 ◽  
Vol 36 (123) ◽  
pp. 143-150 ◽  
Author(s):  
G.S.H. Lock ◽  
I.B. Foster
Keyword(s):  
Air Temperature ◽  
Liquid Water ◽  
Cross Flow ◽  
Supercooled Water ◽  
Liquid Water Content ◽  
Air Temperatures ◽  
Stagnant Point ◽  
Air Speed ◽  
Temperature Liquid ◽  
Ice Fraction

AbstractThe paper presents experimental observations on the growth of spongy ice in the vicinity of the forward stagnation point of a disc situated in a cross flow containing supercooled water droplets. Following some preliminary observations, the discussion focuses on two quantities: the ice fraction and the rate of growth of the accretion. The data presented reveal the effects of air speed, air temperature, liquid-water content, and salinity. They also suggest two morphological regimes: at higher air temperatures, the growth appeared to be crystalline columnar; at lower temperatures, smaller crystals appeared to be randomly distributed, producing a mushy accretion.

scholarly journals Drizzle formation in stratocumulus clouds: effects of turbulent mixing

2016 ◽  
Vol 16 (3) ◽  
pp. 1849-1862 ◽  
Author(s):  
L. Magaritz-Ronen ◽  
M. Pinsky ◽  
A. Khain
Keyword(s):  
Boundary Layer ◽  
Velocity Field ◽  
Liquid Water ◽  
Turbulent Mixing ◽  
Liquid Water Content ◽  
High Humidity ◽  
Air Volume ◽  
Stratocumulus Clouds ◽  
Microphysical Processes ◽  
Further Development

Abstract. The mechanism of drizzle formation in shallow stratocumulus clouds and the effect of turbulent mixing on this process are investigated. A Lagrangian–Eularian model of the cloud-topped boundary layer is used to simulate the cloud measured during flight RF07 of the DYCOMS-II field experiment. The model contains ~ 2000 air parcels that are advected in a turbulence-like velocity field. In the model all microphysical processes are described for each Lagrangian air volume, and turbulent mixing between the parcels is also taken into account. It was found that the first large drops form in air volumes that are closest to adiabatic and characterized by high humidity, extended residence near cloud top, and maximum values of liquid water content, allowing the formation of drops as a result of efficient collisions. The first large drops form near cloud top and initiate drizzle formation in the cloud. Drizzle is developed only when turbulent mixing of parcels is included in the model. Without mixing, the cloud structure is extremely inhomogeneous and the few large drops that do form in the cloud evaporate during their sedimentation. It was found that turbulent mixing can delay the process of drizzle initiation but is essential for the further development of drizzle in the cloud.

The Development and Application of the Green Construction Technology in Small and Mid-Sized Cities - A Case Study of Jincheng, Shanxi Province

2013 ◽  
Vol 689 ◽  
pp. 125-129 ◽  
Author(s):  
Ming Min Cui ◽  
Yuan Ping Liu
Keyword(s):  
Green Buildings ◽  
Shanxi Province ◽  
Construction Technology ◽  
Green Construction ◽  
Different Types ◽  
The City ◽  
Further Development

This paper sets as the research object the development and application of the green construction technology in the city of Jincheng and makes an analysis on the representative examples selected respectively from three different types of buildings, that is, residential, office and commerrcial buildings, to summarize the technical achievements as well as raise the relevant suggestions for the further development of the green construction technology, which will play an important role to guide the improvement and advancement of the green buildings in small and mid-sized cities.

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