Events that take place very rapidly must be observed with a camera with a very high frame rate. For this a high speed camera system from Photron in conjunction with Xenon headlights (cold light) with rates from 1 up to 2 kW is used. With this camera a maximum resolution of 1024 x 1024 pixels at an image capture rate of up to 2000 frames per second can be achieved. Depending on the problem, by lowering the resolution, it is possible to achieve an image capture rate of up to 120,000 fps. This is made possible by using a CMOS sensor.

An observation of cavitation on rotating propellers is consequently possible. The advantage compared to the conventional stroboscopic technique lies in the possibility of an evaluation of the cavitation dynamics on the basis of video recordings and thus also their influence on the erosion. The main place of use for the high speed camera system is the cavitation tunnel.

The specification for a propeller design generally includes limits for the pressure fluctuations induced by the propeller. Moreover, acoustic limits are specified in special ships (naval and research vessels and yachts). Cavitation phenomena at propellers or appendages mainly lead to a significant increase in the amplitudes of the vibrations. Therefore pressure fluctuation, vibration and sound measurements are performed in conjunction with cavitation. In the cavitation tunnel, pressure sensors and hydrophones are placed in the stern area above the propeller or at positions of interest on the hull.

The pressure pulses induced by the propeller are measured with absolute pressure sensors. Typically, an array of sensors, 11 to 16, above the propeller is arranged.

If evidence of higher frequency levels at the hull is of interest, hydrophones are arranged in close range of the model propeller in the outer skin of the model. To determine the noise spectra induced by the propeller, hydrophones are placed on the windows or directly inside the test section of the cavitation tunnel.

For the analysis and comparison of acoustically optimised propellers, direct measurement of vibrations is carried out on the propeller. A high frequency acoustic emission sensor is installed with pre-amplifier and transmitter in a special hub cap. The sampling rate is 44100 Hz.

Ducted Propellers

Kempf & Remmers dynamometers are used for propeller drives. The forces at the nozzle are measured with Kempf & Remmers single and multi-component balances that are coupled to the dynamometers.

Main Paramters Dynamometer/Balances for Ducted Propellers
		FK1/R35I	H29/R35X	H39/R35X	H39/R37	H36/R35X	J25/R37
Thrust Tmax	[N]	*	400	1000	1000	2000	3000
Torque Qmax	[Nm]	*	15	50	50	100	150
Nozzle Thrust TDmax	[N]	200	500	500	800	500	800
* Using Interior Drive Dynamometer

 

Contra-rotating Propeller

The SVA has the Kempf & Remmers contra-rotation dynamometer R40 for open water and propulsion testing. Open water tests with contra-rotating propellers can also be performed via the coupling of the H29 and H39 dynamometers in the towing tank. For the investigation of contra-rotating propellers, the K15A cavitation tunnel was equipped with J25 and H36 dynamometers from Kempf & Remmers. The dynamometers can be arranged in the measurement section so that measurements with contra-rotating propellers are possible at different distances.

Main Paramaters Dynamometer/Balances for Contra-rotating Propellers
		FK4/R40/R35I	H29/H39/R35X	J25/H36/R35X
Thrust Tmax1	[N]	150	400	3000
Thrust Tmax2	[N]	150	1000	2000
Torque Qmax1	[Nm]	6	15	150
Torque Qmax2	[Nm]	6	50	100
Housing Resistance TPodmax	[N]	200	500	500

 

Thrusters and Podded Drives

Model tests with azimuthing thrusters and podded drives are a focus of the work of the SVA. For the realisation of measurement tasks in open water, cavitation, propulsion and manoeuvring, different propulsion and measuring systems have been developed by the SVA. The system forces of the thruster and podded drive are measured with 3- or 6-component balances.

Main Parameters Balances for SVA Thruster Dynamometer
			R37SR1/SR2	R37SR3/SR4	R37	R200
Forces	Fx1 = Fy1 = Fy2	[N]	200	500	800	1000
	Fz1 = Fz1 = Fz2	[N]	–	1000	500	2000
Turntable	Fx	[N]	100	100	manual	5000
	Fy	[N]	100	100		3400
	Fz	[N]	600	600		5000
	Mx1 = My	[Nm]	–	–		500
	Mz	[Nm]	15	15		60

 
The drive of the propeller and the measurement of the forces and moments on the propeller are carried out with SVA thruster dynamometers. Thruster dynamometers are available at the SVA for tests with thrusters or podded drives with pull, push, twin and contra-rotating propellers.

Main Parameters SVA Thruster Dynamometer for Single Propeller Systems
		Z65/1 – /4	Z200	Z600/4, Z600/6
Thrust Tmax	[N]	50	200	600
Torque Qmax	[Nm]	1	7	20
Transmission		*	1.615:1	2:1
Housing Resistance TPodmax	[N]	200	500	500
Total Torque QGmax	[Nm]	1	2.4	17
* Drive with an electric motor in the housing

 

Main Parameters SVA Thruster Dynamometer for Double Propeller Systems
		TP200/1…/2	TP400/1…/2	CRP400	CRP600
Thrust Tmax	[N]	200	400	400	600
Torque Qmax	[Nm]	7	20	20	20
Transmission		1.1	2.1	2:1	2:1
Total Torque QGmax	[Nm]	6	17	17	17

 

Context Related References/Research Themes

[1] Gutsche, F.: Düsenpropeller in Theorie und Experiment, Jahrbuch der STG, Bd.53, 1959
[2] Schroeder, G.: Wirkungsgrad von Düsenpropellern mit unterschiedlicher Düsen- und Propellerform, Schiffbautechnik, 1967
[3] Heinke, H.-J.; Philipp, O.: Development of a skew blade shape for ducted controllable pitch propeller systems, Proceedings, PROPCAV’95, Newcastle, 1995
[4] Schulze, R.; Manke, H.: Propellersysteme mit Ostdüsen“, HANSA, 137, 2, 2000
[5] Schmidt, D.: Propulsionsuntersuchungen mit Einzelpropeller und Gegenlaufpropeller am Modell eines Containerschiffes, Schiffbauforschung 14 1/2/1975
[6] Heinke, H.-J.: Azimuthing propulsion – Experiences of SVA, 6. SVA – Forum „Azimuthing Propulsion – new challenges and chances“, Potsdam, 1998, Schiffbauforschung, 38. Jahrgang (1999) Heft Nr. 1
[7] Kaul, S.; Heinke, H.-J.; Abdel-Maksoud, M.: Hydrodynamische Optimierung von Podded Drives und aktuelle Anwendungen in der Großausführung, 54. Sitzung des FA „Schiffshydrodynamik“ der STG, Hamburg, September 2000
[8] Heinke, H.-J.: Investigations about the forces and moments at podded drives, First International Conference on Technological Advances in Podded Propulsion, Newcastle, UK, April 2004
[9] Heinke, H.-J.: Hydrodynamische Untersuchungen für einen Podded Drive mit HTS-Synchronmaschine, Statustagung Schifffahrt und Meerestechnik, Bundesministerium für Wirtschaft und Technologie, 03. Dezember 2009, Rostock-Warnemünde