330 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 41, NO. 2, FEBRUARY 2013

Ship Propulsion by Underwater PulsedHigh-Voltage Streamer Discharge

Xiao Qiong Wen

Abstract—A concept of ship propulsion by underwater pulsedhigh-voltage streamer discharge was proposed and has been ex-amined by using anode pins as the propulsion unit of a ship model.The primary experiment proves that the underwater pulsed high-voltage streamer discharge can push the ship model to travel onthe water. The maximum travelling speed of the ship model is2.3 cm/s when propelled by three anode pins at 600-Hz pulse fre-quency. The propulsion force produced by a single anode pin is ofmillinewtons order of magnitude. It was found that the maximumtravelling speed and the propulsion force could be significantlyimproved by increasing the number of the anode pins or the pulsefrequency. The propulsion efficiency is of 10−7 order of magnitudeand can be increased significantly by increasing the number of theanode pins. The most attractive feature of the ship propulsion byunderwater pulsed high-voltage streamer discharge is that there isno need for a superconductor magnet. Additionally, the connectionbetween the pulsed high-voltage streamer discharge thruster andthe power supply is only by a cable, which can provide morefreedom for the layout of the thruster on the ship.

Index Terms—High-voltage pulse, magneto-hydrodynamicpropulsion, ship propulsion, underwater electrical discharge.

I. INTRODUCTION

THE DESIRE to travel faster and quieter by ships or sub-marines is probably as old as mankind itself. Nowadays,

the ships or submarines travel mainly by propeller propulsion.However, the cavitation produced by the propeller limits itsspeed and also generates most of the noise during its travel.It has been an exciting challenge to develop a ship-propulsionmethod without the need for propellers. In 1961, Friauf [1]first proposed an innovative concept of magneto-hydrodynamicpropulsion of a ship. Since then, this idea has been investigatedextensively by many researchers [2], [3]. With the aim to reducethe fuel consumption of large ocean going ships or generatelarge travelling speeds of ships, kites have been considered as anew ship-propulsion method [4], [5].

Underwater pulsed high-voltage streamer discharges havebeen studied for decades for their various applications [6], [7],such as pulse forming line design, degradation of organic pollu-tants, and destruction of microorganisms in water environment.As shown in Fig. 1(a), when the underwater streamer discharges

Manuscript received October 3, 2012; revised November 20, 2012 andDecember 13, 2012; accepted December 13, 2012. Date of publicationJanuary 4, 2013; date of current version February 6, 2013. This work wassupported in part by the Natural Science Foundation of China under Grant11275040.

The author is with the Center for the Plasma Science and Engineering,School of Physics and Optoelectronic Technology, Dalian University of Tech-nology, Dalian 116024, China (e-mail: wenxq@dlut.edu.cn).

Color versions of one or more of the figures in this paper are available onlineat http://ieeexplore.ieee.org.

Digital Object Identifier 10.1109/TPS.2012.2235087

Fig. 1. Evolution of underwater streamer discharge. (a) Streamer propagation(reproduced from [8]). (b) Decaying process of a gas channel after discharge(reproduced from [11]).

occur, luminous plasma channels form and propagate in thewater [8]. During its propagation, the gaseous plasma channelproduces huge pressure and generates shockwave in the ambi-ent water [9], [10]. Our previous study [11] has found that atreelike gas channel remains in the water after the electricalstreamer discharge [Fig. 1(b)]. Its main branches abbreviatetoward the root of the branch, and a bubble forms at thetip of the anode. The bubble collapses and then disappears.The decaying process of the gaseous channel again producespressure and shockwave in the water [12]. According to theNewton’s law of action and reaction, it could be expectedthat the ambient water will produce pressure on the electrodeduring the streamer discharge and it could probably be used aspropulsion force for the ship.

Motivated by this idea, we have conducted a test experimentto examine the concept of ship propulsion by underwater pulsedhigh-voltage streamer discharge. Anode pins were used as apropulsion unit of a ship model in the experiment. It was foundthat the underwater pulsed high-voltage streamer dischargecould push the ship model to travel on the water. The primaryresults prove that the underwater pulsed high-voltage streamerdischarge may be a promising ship-propulsion method. In thispaper, a video record of the ship model propelled by the un-derwater pulsed high-voltage streamer discharge is presented.The propulsion force produced by the underwater pulsed high-voltage streamer discharge and the maximum traveling speedof the ship model are investigated. Finally, the propulsionefficiency of the underwater pulsed high-voltage streamer dis-charge is discussed.

0093-3813/$31.00 © 2013 IEEE

WEN: SHIP PROPULSION BY UNDERWATER PULSED HIGH-VOLTAGE STREAMER DISCHARGE 331

Fig. 2. Experimental setup.

II. EXPERIMENTAL SETUP

The scheme of the anode pin unit for ship propulsion isshown in Fig. 2(a). It contains one or three pins. Each of them isconsist of a 1-mm-diameter stainless steel rod tapering off in an∼80-μm radius hemispherical tip and was insulated except forthe very tip. The anode pin unit was mounted on the tail of theship model which is made of a nylon rod with 40-mm diameter[Fig. 2(b)]. The total length and the total mass of the ship modelwere 110 mm and 90 g, respectively.

The experimental setup is shown in Fig. 2(c). The travellingtest of the ship model was performed in an acryl bin (40× 40×40 cm3). Tap water (260 μS/cm) was used, and the depth of thewater was 30 cm. An acryl rod of 20-mm diameter was set asa supporter at the center of the acryl bin. A stainless rod of5-mm diameter was mounted on the top of the supporter forelectrical connection with the high-voltage pulse generator andthe anode pin unit of the ship model. A stainless steel plate of10-cm diameter and 2-mm thickness was set as a cathode atthe bottom of the bin. The anode pin unit of the ship modelwas connected to the stainless steel rod at the top of the acrylsupporter, which made the ship model float on the water butthe anode pins were completely immersed in the water. Byapplying a positive high-voltage pulse, the streamer discharge isgenerated from the anode pins, pushing the ship model to travelaround the acryl supporter on the water. The travelling state ofthe ship model was observed from the top of the water bin bya video camera. By analyzing the video record, the travellingspeed of the ship model can be estimated.

The streamer discharge was generated by applying a pulsedpositive high voltage with ∼35-kV maximum and ∼400-nswidth at full-width at half maximum to the anode pins througha high-voltage pulse generator. The pulse frequencies used inthis paper are 300, 600, and 1200 Hz. The discharge voltageand current were detected by a high-voltage probe (P6015A)and a current probe (Pearson 6585), respectively. Both thedischarge voltage and the current were measured by a digitaloscilloscope (Tektronix DPO4054). The typical voltage andcurrent waveform is shown in Fig. 3. The discharge energy

Fig. 3. Typical waveform of the discharge voltage and current.

Fig. 4. Method for measuring the propulsion force produced by the underwa-ter pulsed high-voltage streamer discharge.

per pulse can be calculated by integrating the product of thedischarge voltage and the current, and then, the discharge powerat different pulse frequency can be estimated.

It is difficult to measure accurately the propulsion forceproduced by the underwater pulsed high-voltage streamer. Inorder to obtain an approximate estimate of the propulsion force,a simple pendulum method shown in Fig. 4 was adopted in thispaper. During the discharge, the anode pin unit departs from theequilibrium point. By measuring the deflection of the anode pinunit, the propulsion force FP produced by the discharge wasdeduced approximately as follows:

FP = (FG − FB) sin θ (1)

where FG is gravity and FB is buoyancy. The deflection of thethruster was observed by a video camera. The gravity FG andbuoyancy FB were obtained by measuring the mass and thevolume of the thruster, respectively.

III. RESULT AND DISCUSSION

By applying the positive high-voltage pulse, the electricalstreamer discharge was generated from the anode pins, pushingthe ship model to travel around the acryl supporter on thewater. Fig. 5 shows the successive side-view images of theship model travelling on the water. All the images were takenfrom the video record shown in supplementary material 1.From the video record, it can be concluded that the underwater

332 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 41, NO. 2, FEBRUARY 2013

Fig. 5. Successive images of the ship model travelling on the water. All theimages were taken from the video record provided in supplementary material 1.The time stamp is shown at the bottom right of the image. The first image wasset as 0 s.

Fig. 6. Dependence of the maximum travelling speed of the ship model on thenumber of anode pins and the pulse frequency.

pulsed high-voltage streamer discharge is applicable for shippropulsion.

The travelling state of the ship model was also observed fromthe top of the water bin. By analyzing the video record, themaximum travelling speed of the ship model was estimated. Itis of 2.3 cm/s when propelled by three anode pins at 600-Hzpulse frequency. The dependence of the maximum travellingspeed of the ship model on the number of anode pins and thepulse frequency was investigated, and the results were plotted inFig. 6. It was found that the maximum travelling speed can besignificantly improved by increasing the number of the anodepins or the pulse frequency.

The propulsion force produced by the underwater pulsedhigh-voltage streamer discharge was measured by using themethod shown in Fig. 4. The dependence of the propulsionforce on the number of anode pins and the pulse frequency wasinvestigated. The results are shown in Fig. 7. In this paper, thepropulsion force produced by a single anode pin is of millinew-tons order of magnitude. It shows that the propulsion force canbe improved by increasing the number of the anode pins orthe pulse frequency. Previous works [13] have suggested thatby increasing the number of anode pins, more gaseous plasmachannels can be created by a single discharge pulse, whichcould be responding to the increase of the propulsion force.The increase of pulse frequency leads to the increase of thedischarge power, hence improvement of the propulsion force.

Two processes may take important role in the propulsion-force formation. The first one involves the creation and prop-agation of the gaseous plasma channels in the water, whichproduce a huge pressure to the ambient water. It has beenreported that a pressure of about 10 kbar can be generated

Fig. 7. Dependence of the propulsion force on the number of anode pins andthe pulse frequency.

by the gaseous plasma channel propagation [10]. The secondone is associated with the decay of the gaseous channels thatremained in the water after the electrical streamer discharge. Ithas been found that the gas channels that remained in the waterhave many branches; some of them grow from the tip of thepin anode, forming main branches [11]. From the main branch,some sub-branches develop. The sub-branch dilapidates rapidlyinto microbubbles, while the main branch abbreviates towardthe root of the branch. A bubble forms at the tip of the anode,and the main branch connects with it. When the main branchdisappeared, the bubble at the tip of the anode becomes aperfect sphere and approximately reaches its maximum radius.Then the bubble starts to collapse, holding its spherical shape.To understand completely the characteristic of the propulsionforce, further study is needed on these two processes of theunderwater pulsed high-voltage streamer discharge.

Based on the above results, the propulsion efficiency of theship model was estimated. The propulsion efficiency is definedin this paper as follows:

η =WP

WD(2)

where Wp is the power of the ship propulsion, and WD is thepower of the electrical streamer discharge. Wp was calculatedas the product of the propulsion force FP and the maximumtravelling speed vm:

WP = FPvm (3)

while WD at different pulse frequency f was deduced byintegrating the product of the discharge voltage V andcurrent I

WD =

T∫

0

fV Idt. (4)

The results of the dependence of propulsion efficiency on thenumber of anode pins and the pulse frequency are shown inFig. 8. It was found that the propulsion efficiency in this paperwas 10−7 order of magnitude. As can be seen in Fig. 8, thepropulsion efficiency can be increased significantly by increas-ing the number of the anode pins. This can also be attributed

WEN: SHIP PROPULSION BY UNDERWATER PULSED HIGH-VOLTAGE STREAMER DISCHARGE 333

Fig. 8. Dependence of the propulsion efficiency on the number of anode pinsand the pulse frequency.

Fig. 9. Superposition of the flow field generated by two adjoining electricaldischarge pulse.

to the fact that by increasing the number of anode pins, moregaseous plasma channels can be created by a single dischargepulse.

Fig. 8 also shows that the propulsion efficiency increases inthe range of 300–600 Hz, while it decreases with increasingpulse frequency in the range of 600–1200 Hz. We believe thatthe flow field generated in the bulk water by the underwaterpulsed high-voltage streamer discharge could play an importantrole in this behavior of the propulsion efficiency. As can be seenin Fig. 9, each electrical discharge pulse will generate a flowfield in the bulk water. Compared with the electrical streamerdischarge process, the flow field generated by a single electricaldischarge pulse in the bulk water would decay more slowly[11], [12]. It is unclear how long it would take for the flow fieldgenerated by a single electrical discharge pulse to completelydisappear from the bulk water. If the relax time of the flow fieldgenerated by a single electrical discharge pulse is longer thanthe pulse period, superposition of the flow field generated bytwo adjoining electrical discharge pulse will occur. At higherpulse frequency, the superposition of the flow field may havea serious effect on the propulsion efficiency of the ship. Thereis still no clear knowledge about the characteristic of the flowfield generated by a single electrical discharge pulse in thebulk water. It is an important issue for the ship propulsion byunderwater high-voltage streamer discharge.

IV. CONCLUSION

The concept of ship propulsion by underwater pulsed high-voltage streamer discharge has been proposed and examinedby using anode pins as the propulsion unit of a ship model.The primary results prove that the underwater pulsed high-voltage streamer discharge may be a promising ship-propulsionmethod. Although the propulsion efficiency of the underwaterpulsed high-voltage streamer discharge is very low in this paper,the results show that it can be improved by improving theelectrode structure, the working parameter of the high-voltagepulse. The most attractive feature of the concept of ship propul-sion by underwater pulsed high-voltage streamer discharge isthat there is no need for a superconductor magnet. Additionally,the connection between the high-voltage streamer dischargethruster and the power supply is only by a cable, which canprovide more freedom for the layout of the thruster on the ship.

ACKNOWLEDGMENT

The author would like to thank Prof. C.-S. Ren for his helpin the experimental setup.

REFERENCES

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Xiao Qiong Wen received the B.S. degree ingeophysics from Guilin University of Technology,Guilin, China, in 1990 and the M.S. and Ph.D.degrees in applied nuclear physics from HiroshimaUniversity, Higashihiroshima, Japan, in 1996 and1999, respectively.

He is currently an Associate Professor with theCenter for the Plasma Science and Engineering,School of Physics and Optoelectronic Technology,Dalian University of Technology, Dalian, China. Hiscurrent research interest is underwater electrical dis-

charge and its application.