Test Plan: 9-bladed 36" Diameter Fan with Elliptical Maw in Duct with Bifurcated Exhaust and Throttles and Electrical Generator

Prepared by Richard A. Strong, PE, Proprietor, Safety Analysis Systems Co. [www.strongware.com]

As of 2005, the design is changed to use a conventional automobile road drive, rather than a hybrid electric drive.

The inventor had planned to perform testing; however, he revised his plan to have
a developer do the required testing. Some of the original test plan notions may be
worth reading about and are described below.

PROGRAM PHASED DEVELOPMENT
The Magic Dragon Aircar will have a ducted fan with exhaust throttles, to have fewer moving parts than roadable aircraft with conventional propellers that must be stowed for travelling on the road.

The program will be phased to research, develop and test the Magic Dragon Aircar in phases:
Phase 0. Literature research, budgeting, and scheduling;
Phase 1. Full-Scale ducted fan subsystem on testbed in hangarage;
Phase 2. Ducted Fan with low fuel-consumption and low-emission engine;
Phase 3. The ducted fan and engine with a generator and solar cell array and batteries;
Phase 4. All of the above with an electric motor and controller and chassis; and
Phase 5. The system will ultimately be used in a prototype Magic Dragon

A more detailed plan database example is at *WorkPlan.
Calculations are in an Excel spreadsheet "*Flade Testplan"
Tests will be conducted in the *Hangarage

TEST OBJECT
*Test Stand (Modified ERIC)

The test object is a fan driven by an engine or motor in a bifurcated duct with gills. The blade design shown in sketch above right provides for installing various blades on the hub at various root angles. Attachment of the flades to the hub will be with aircraft bolts and nuts. The material is to be determined; aircraft aluminum 2024T3 is preferred, with a nominal thickness of 1/8th inch.

The diameter is sized to fit conventional automobile design with a diameter of 36". The fan will have nine blades. The number of blades was selected to minimize noise, i.e., an odd number of blades to eliminate beating against the vertical duct splitter and the elliptical maw and an optimum of a large number to reduce acoustic loads and provide safety in case of a damaged flade and a small number for fabrication simplicity.

TEST OBJECTIVES
The objective will be to determine the net thrust available as a function of rpm from an engine or motor with known hp/rpm ratios for a range of 600-4800 rpm. The Magic Dragon system road performance goal is to provide an acceleration of 0-60 miles per hour in fifteen seconds, or 4 mph/sec, or 0.2 g. This would require a total thrust, including road drive, of 560 pounds. The electric motor drive will provide most of the acceleration. The ducted fan propulsor is intended to provide thrust for cruising only at about 35-75 mph, which is estimated to be only about 100 lbs. The required engine power would then be in the range of 25 horsepower at about 900 rpm.
Calculations for the flades are in a spreadsheet that is included in the Microsoft Excel 7 workbook *SS1.xls. The calculations are for an engine speed of 3000 rpm with 160 h.p.; the forces at half this speed are estimated to be about one-fourth of those shown for the 25 h.p. engine.
Test results will be reported in graph form showing thrust as a function of revs, velocity thumbprint-style profiles, and wall static pressures.
The expected result is an exponential curve showing a thrust-to-power ratio of approximately 4:1, less engine cooling and duct losses, where the objective is to determine these losses.
The propulsor design will be considered to be a viable system for the Dragon, if tests demonstrate a ratio of horsepower-to-thrust of over 3:1, for a net thrust of 75 lbs..

METHOD OF TEST

• The engine/motor mounting structure and inner duct walls will be fabricated and static-load-tested. The duct ring will then be added to the mounting structure. The maw, or intake, will then be fabricated and installed. The electrical generator will be installed and connected to batteries.
• Static pressures at selected points on the maw will be made.
• Thrust from the maw and from the fan will be measured separately to determine the contribution of each to total thrust. Duct drag will be measured separately from thrust. Thrust will be measured with a force scale. The methods of separating the measurements are TBD.
• Fuel flow vs. revs will be measured. Method is TBD.
• Airstream velocities will be measured immediately behind the flades to assist in determining optimum blade angles.
• Outer duct walls will be added in horizontal increments of about 12" to fit the flow (five strips). Airflow will be visualized with smoke or particles along the duct. Static pressure measurements at grid points on the duct walls are also desired.
• Fan pitch at the root will be set in increments of 10 degrees over a range of 20 to 40 degrees. Fan twist may be varied from 20 to 40 degrees. (3 points)
• Measurements of rpm and thrust will be taken in increments of about 100 rpm. over the range of 600-1800 rpm. (12 points)
• Revs will be measured with a tachometer.
• Individual pressure measurements to determine fan thrust and duct thrust and spinner thrust are desired.
• The optimum positions for the gills will be determined and the gill throttles will be installed. Gill loads and control torques will be measured to ensure proper operation. The throttles will opened and closed at the rev test points. Additional tests may be done with the throttles in an over-blocking position for reverse thrust. Transparencies may be installed in the outer duct walls to provide visualization studies of the airflow with the throttles in the blocking position.
• Airflow will be measured at the exit planes with a Pitot tube rake in a 6" X 6" grid.
• Torque measurements are desired; the means are TBD.
• Flow visualization is desired; string tufting and smoke trails may be used.
• Vibration and sound pressure measurements are desired; means are TBD.
• Meteorological data, temperature, barometric pressure, humidity and wind, will be recorded with off-the-shelf residential instruments and Weather Service observations.
• A log of test activities, drawings, photographs, and any unusual behaviors will be recorded, such as vibration, excessive noise, mechanical failure, or system malfunction will be maintained.

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TEST HARDWARE
The desired engine will be a horizontally-opposed 2- or 4-cylinder, 2- or 4-cycle, air- or liquid-cooled engine of 30-40 hp with known power vs. rpm data available.

The fan blades will be fabricated metal as shown above. Alternatively, an off-the-shelf fan with known data may be used.

For safety, the duct intake will have a screen and exits will be kept clear or barricaded.

ADDITIONAL TESTS
Various blade designs may be tested, such as varying the area by varying the tip chord.

Further testing in a wind tunnel is highly desirable, to cover in-flight speeds of up to 140 mph. Alternatively, road test may be performed on a suitable test track to acquire flight-speed data.