1513

Item 1513

DESIGN: UniCopter ~ Pusher Prop - Variable Speed Rotors and Prop - Propeller

Notes:

Optimize prop twist etc for cruise, since the prop is not relevant to climb ??

From Rotary Wing Forum:

"I'm still confused on tip speed. Judka says no more than .75 mach. One prop manufacturer says .92 mach for best efficency and less noise. I find .82 mach in several places. My EAA chapter pres says .85 mach."

"I am trying to understand the compromises of prop size and rpm. When I read some of the available information it would apear that 3800 rpm (91% of Mach) on a sixty inch prop is efficent and quiet. Others seem to feel that 3400 rpm(81% of Mach) is as much as you would want to run with a 60 inch prop."

For Mach 0.85 the propeller's speed will be 3531 rpm, and for Mach 0.80 the propeller's speed will be 3321 rpm.

The speed of the propeller during cruise is 3,300 rpm.

Mach 1 = 1087 ft/sec.

The tip circumference of a 5 ft diameter propeller is 15.71ft

Suppliers of In-flight Variable Pitch Propellers:

GSC Systems
Ivo

Calculations done by Prop Optimizer:

PROP OPTIMIZER INPUT DEFINITIONS are on file Input.def Have hard copy.

The program PROP OPTIMIZER is in the computer. It appears to be quite sophisticated, however it is a demo program and is limited to 2 blades, Clark-Y airfoil and optimizes only for cruise.

There is an earlier attempt called 'DaveTest' in the 'Prop 20' folder that can be upgraded to suit.

File Name - Full_Uni

Full UniCopter

CONTROL

IOPT= 1 2 3 4 5

PDES= 0

END

DESLIM

ABMIN=

AFLIM= 60.00000000000000 150.0000000000000

CLDES= 0.0000000000000000

DMAX= 60.00000000000000

END

DESVAR

ADRAG= 3.000000000000000

AFDES= 91.56589217959902

ALTCRS= 1000.000000000000

KS= 1.850000000000000

DIAM= 56.93585789454863

OSWALD= 0.8510000000000000

PITCH= 104.3197616468756

RPMCRS= 2523.630235329021

SPAN= 23.00000000000000

VCRS= 187.5000000000000

WTGRSS= 1320.000000000000

END

TABLES

STA= 0.2000000000000000 0.3000000000000000

0.4000000000000000 0.5000000000000000

0.6000000000000000 0.7000000000000000

0.8000000000000000 0.9000000000000000

1.000000000000000

CHORD= 4.485340308311932 4.417419686430269

4.376151460476852 4.318547895083541

4.171529840124497 3.892109560231573

3.507799206040385 2.943800118010361

2.279209729218887

TCTAB= 0.4064000000000000 0.2937000000000000

0.2436000000000000 0.2007000000000000

0.1684000000000000 0.1440000000000000

0.1355000000000000 0.1151000000000000

0.9020000000000000E-01

END

NRUN Number of trial designs run

PAYOFF Objective or merit function. A quantitative measure of

the design goal such as maximum velocity or climb rate.

ADRAG=

END

Full UniCopter

@ 08/20/07 17:57:49.22

>>>> OPTIMIZED DESIGN:

VARIABLE INITIALLY OPTIMIZED LOWER LIMIT UPPER LIMIT

AFDES 91.5659 150.000 60.0000 150.000

DIAM 56.9359 60.0000 12.0000 60.0000

PITCH 104.320 66.8980 52.1599 208.640

RPM 2523.63 2700.00 1800.00 2700.00

VCRS 187.500 185.889 140.625 234.375

PROPELLER DESIGN CRUISE PERFORMANCE

NUMBER OF BLADES = 2 VELOCITY, MPH = 185.889

BLADE ACTIVITY FACTOR= 150.000 ALTITUDE, FEET = 1000.00

DIAMETER, INCHES = 60.0000 DENSITY, SLUGS = 0.230921E-02

GEOMETRIC PITCH, IN = 66.8980 THRUST, POUNDS = 305.765

EFFECTIVE PITCH, IN = 72.7033 DRAG, POUNDS = 305.765

ABSOLUTE PITCH, IN = 83.4743 THRUST HP = 151.569

SHAFT HP = 173.823

ALPHA @ 0LL DEG @75%R= 3.34472 HP AVAILABLE = 173.823

DESIGN LIFT COEF, CL = 0.4293 PROPELLER RPM = 2700.00

THRUST COEF, CT = 0.1046 ENGINE RPM = 2700.00

POWER COEF, CP = 0.1454 REDUCT FACTOR = 1.00000

ADVANCE RATIO, J = 1.21172 SFC, LB/HP/HR = 0.520000

MILES/GALLON = 12.3394

EFFICIENCY, ETA = 0.871971 FUEL FLOW, PPH = 90.3881

ETA COMPRESS CORRECT.= 0.00% FUEL FLOW, GPH = 15.0647

ETA PROFILE DRAG CORR= -0.53% SOUND SPEED,FPS= 1112.56

ETA DIAMETER CORRECT.= 0.60% TIP SPEED, FPS = 757.615

ADRAG, SQ FT = 3.00000 TIP MACH NUMBER= 0.680962

CONSTRAINT VALUES MEASURE THE SUCCESS OF THE OPTIMIZATION.

EQUALITY CONSTRAINTS ARE SATISFIED WHEN = 0

INEQUALITY CONSTRAINTS ARE SATISFIED WHEN >= 0

TYPE: EQUALITY = 0, UPPER BOUND = 1, LOWER BOUND = -1

SYSTEM CONSTRAINT VALUES:

NAME TYPE ACTIVE INACTIVE REQUIREMENT

CRUISE SHP=HPA 0 -0.1050E-10 SATISFIED

THRUST=DRAG 0 0.7436E-12 SATISFIED

ALPHA>=ABMIN -1 3345. SATISFIED

PAYOFF= 39.2083 (-VCRS) TRIAL RUNS = 321

GENERAL NOMENCLATURE

AFDES Activity factor per blade. The higher the activity factor,

the more power a blade can absorb (or is required). For a

given diameter, activity factor increases with blade width.

ALPHA Blade angle-of-attack at the 75% radius, degrees. The angle

the incoming air flow makes with the airfoil zero-lift-line.

ANGLE Blade pitch angle at 75% tip radius station measured

with respect to the plane of rotation, degrees.

CL Blade lift coefficient. Design lift coefficient for cruise.

CP Power coefficient: A non dimensional ratio relating power

required to air density, propeller speed squared and

propeller diameter raised to the fifth power. Power

required is proportional to the fifth power of diameter

for other factors being equal.

GENERAL NOMENCLATURE

CT Thrust coefficient: A non dimensional ratio relating thrust

produced to air density, propeller speed squared and

propeller diameter raised to the fourth power. Thrust

produced is proportional to the fourth power of diameter

for other factors being equal.

CS SPEED_POWER coefficient, J/CP^(1/5). A design parameter used

in determining maximum efficiency for cruise propellers.

DIAM Propeller diameter, inches

DRAG Aircraft drag, pounds

ETA Propeller efficiency: ETA=CT*J/CP

A measure of how much power is delivered to the air stream

by the propeller relative to power delivered by the engine.

This value includes compressibility, profile drag and

relative diameter corrections.

GENERAL NOMENCLATURE

ETA COMPRESS CORRECT: A factor indicating the percentage propeller

efficiency is reduced due to sonic compressibility effects

at the blade tip. Zero indicates no compressibility losses.

The optimizer tries to design on balance to minimum loss.

ETA PROFILE DRAG CORR: An efficiency correction due to blade width

or total activity factor and represents the induced losses.

ETA DIAMETER CORRECT: Corrects for the relative influence of body

and engine nacelle size to propeller diameter. Assuming that

the reference point is accounted for in the effective pitch

and ADRAG calibration, this correction is the increase or

decrease in efficiency from the calibrated reference point.

FFGPH Fuel flow in gallons per hour

FFPPH Fuel flow in pounds per hour

HPA Maximum Horsepower Available from the engine at any

given engine rpm.

GENERAL NOMENCLATURE

J Advance ratio J=(V*88)/(RPM*DIAMETER) Where: V=mph,

DIAMETER=ft. In flight the propeller advances a distance

of J times the DIAMETER per revolution.

MPG Aircraft miles per gallon of fuel

NB Number of blades

PITCH Pitch of chord line at the 75% radius station, inches.

The geometric or theoretical advance of the propeller

per revolution.

RHO Atmospheric density, slugs

SFC Specific fuel consumption, lb/hp/hr

SHP Shaft horsepower required at the propeller shaft before

efficiency losses.

THRUST Propeller thrust, pounds

GENERAL NOMENCLATURE

THP Net Thrust Horsepower delivered to the atmosphere by the

propeller after efficiency losses and required for flight,

(THP=SHP*ETA).

TPMACH Tip Mach number

V Aircraft velocity, miles/hour

VS Speed of sound, feet/second

VT Tip speed, feet/second

NRUN Number of trial designs run

PAYOFF Objective or merit function. A quantitative measure of

the design goal such as maximum velocity or climb rate.

PROP OPTIMIZER (tm)

BATES ENGINEERING, 2742 Swansboro Road, Placerville, CA 95667

Phone/FAX 916-622-1886

Copy Date 12/11/94

Calculations Done by Props17:

This is very simple. See the file

JavaProp by Martin Hepperle:

JavaProp

More Sources for Prop Calculations;

Use the programs PROP20 and [props18.exe], in the computer.

Booklet 'Single Blade Torqueless Helicopter Design', pages 87 to 98, on the bookshelf

The full set of pages of the classic book 'Aircraft Propeller Design' by Weick [1930] is available from the India digital library site. By entering the following into Google [Aircraft Propeller Design. Author1. Fred E Weick. Author2. Subject. Aerodynamics . Language. english. Barcode. 1010010031915.]

http://www.dli.ernet.in/scripts/FullindexDefault.htm?path1=/data/upload/0031/920&first=1&last=305&barcode=1010010031915

For More Information See:

DESIGN: UniCopter ~ Pusher Prop - General - Pusher Prop Assist

DESIGN: UniCopter ~ Pusher Prop - Configuration - Propeller - Single

DESIGN: UniCopter - Pusher Propeller

Last Revised: November 25, 2008