Propulsion Characteristics Research Articles

Ionic Propulsion Based on Heated Taylor Cones of Ionic Liquids

Electrical propulsion characteristics of emissions from heated Taylor cones in vacuo are investigated for the ionic liquid 1-ethyl-3-methylimidazoliumbis(perfluoroethylsulfonyl)imide. Low specific impulses are encounteredat room temperature. However, the drop size decreases and the ion currents become very large at increasing temperatures, leading above 119°C to the appearance of a purely ionic regime with currents in excess of 4 μA. This mode of operation leads to thrusts approaching 1 μN per Taylor cone, at a specific impulse above 2000 s. The ion beam is dominated by the dimer ion (∼80%), with a mass-over-charge ratio larger than 600 amu, substantially larger than possible with traditional ion sources. The purely ionic regime had been previously observed in roomtemperature 1-ethyl-3-methylimidazolium + -BF 4 , but this is the first report where this regime exists over a wide range of currents. The levels of both thrust and specific impulse reported are considerably higher than those previously attained from single Taylor cones of organic electrolytes.

Numerical simulation of thrust generating flow past a pitching airfoil

Earlier analytical and experimental studies predict that pitching motions at high frequency can generate thrust on the airfoil. The present work is an effort towards a systematic understanding of the influence of various parameters on thrust generation from a harmonically pitching airfoil. Quantitative instantaneous force computations have been discussed together with qualitative vortex patterns using a 2-D discrete vortex simulation of incompressible viscous flow. In general, thrust force increases with the oscillation frequency. The trend is very similar to the inviscid theory prediction. Further, the thrust force is seen to decrease with the increase in mean angle of attack. However, in a clear deviation from inviscid theory trends, pitching at high amplitudes about high mean angle of attack, only drag is observed for high values of reduced frequency considered. The effect of location of the pitching axis is also found to be significant on the propulsive characteristics of the airfoil.

Effect of the Ratio of Differently Charged Ions on the Integral Parameters of Stationary Plasma Thrusters of the ATON Type

The main integral parameters of stationary plasma thrusters (SPTs) of the ATON type with the outer channel diameters 60 mm (model A-3) and 100 mm (model A-5) are presented. The SPT characteristics have been studied for the propellant (Xe) consumption rates $$\dot m$$ = 2 and 1 mg/s for A-3 and $$\dot m$$ = 4 and 1.5 mg/s for A-5. Special attention has been devoted to the operation of SPT models at high voltages and low propellant consumption rates. An increase in the voltage has to be accompanied by a corresponding change in the magnetic field topograph and by an increase in the magnetic field intensity at the channel edge, which leads to a decrease in the discharge current and its oscillations. Model A-3 operating at $$\dot m$$ = 1 mg/s and a voltage somewhat below 1000 V exhibited a specific momentum of ∼3400 s. The integral characteristics of SPTs depend on the ratio of differently charged ions in the plasma. The most efficient operation of the plasma source is observed in the case of equal concentrations of singly and doubly charged xenon ions. A new method is proposed for evaluation of the limiting SPT efficiency using only the current-voltage and propulsion characteristics of discharge.

진동하는 평판들에서의 플래핑 추진

이산와류법(discrete vortex method)을 이용하여 진통하는 평판들로부터 추력발생을 연구하였다. 평판들과 후류들은 이산와류로 나타내었다. 진동하는 평판들 사이의 복잡한 공력상호작용을 정확히 계산하기 위하여 와핵모델(vortex core model)과 와핵첨가법(vortex core addition scheme)을 사용하였다. 단일 평판이 히빙진동을 할 경우 나타나는 후류를 계산하여 기존의 유동가시화 결과와 비교하였다. 피칭진동 시 평판에서 발생하는 후류형상이 평판들의 추진 특성에 미치는 영향을 조사하였다. 3가지 방식(1. 하나의 평판은 고정 다른 평판은 진동, 2. 두개의 평판이 같은 위상으로 진동, 3. 두개의 평판이 반대의 위상으로 진동)으로 진동하는 평판들의 추진특성을 계산하였다. 반대의 위상으로 진통하는 평판이 가장 큰 추진력을 보였다. The propulsive characteristics of oscillating flat plates are investigated using a discrete vortex method. The plates and their wakes are represented by discrete point vortices. To analyze the closely coupled aerodynamic interference between the plates, a vortex core model and a vortex core addition scheme are combined. A calculated wake shape for a flat plate in heaving oscillation is compared with flow visualization. The effect of wake shapes on the propulsive characteristics of the plates in pitching oscillation is investigated. The propulsive characteristics of oscillating plates with three cases (1. one is stationary and another is oscillating, 2. both oscillating in phase, 3. both oscillating out of phase) are calculated. The plates oscillating out of phase showed the largest thrust force among the three cases.

Hull Form Optimization for Hydrodynamic Performance

A method for optimizing hull forms with respect to their hydrodynamic performance in calm and rough water is presented. The method is based on an initial optimization of a parent hull form for seakeeping and the improvement of the resulting optimum hull form for calm water resistance. In the first part of the method, variant hull forms differing from a parent in the main dimensions and/or in one or more hull form parameters, such as CWP, LCF, CB, LCB, KB, CP, are automatically generated and their seakeeping qualities evaluated. When appropriate ranges for the principal characteristics and parameters of the hull form under investigation are prescribed, a formal optimization procedure is used to obtain the variant with the best seakeeping behavior. The weighted sum of the resonant values of selected ship responses for a number of ship speeds and headings in regular waves forms the objective function. The Hooke and Jeeves algorithm is used to accomplish the optimization. The procedure results in a set of trends regarding the proposed variations of the selected hull form parameters, within the specified constraints. These trends are then applied on the parent hull to derive an optimized hull form with fair lines. Subsequently, this hull form can be locally modified to improve its calm water resistance or, as it should be done, its propulsion characteristics. The applicability of the method is demonstrated in two cases: a conventional reefer ship and a naval destroyer. Scaled models of the parent and the optimized hull forms have been tested for calm water resistance and seakeeping. In both cases the validity of the methodology is demonstrated.

Resistance and Self-Propulsion Simulations for a Series-60, CB = 0.6 Hull at Model and Full Scale

A finite-volume method solves the Reynolds-averaged Navier-Stokes equations in conjunction with the ĸ-ε turbulence model to simulate resistance and propulsion tests. The free surface is calculated through an iterative steady-state, marching algorithm. An actuator disk is employed to model the propeller operation. Calculations for Series-60, CB = 0.6 hull at both model and full scale investigate the trends of the resistance and propulsive characteristics

高速走行可能な管内移動マイクロアクチュエータ

I have earlier proposed a new microactuator that operates on the resonance energy of a system excited by electromagnetic force, which can move at high speed in the vertical direction. It was possible for that actuator to move only one direction, however. In this paper, a new actuator that can perform reversible motion is proposed. Shape memory alloy and a coil spring are used for change in the direction of motion. The sizes of the prototype actuators were 8 mm and 4 mm in diameter. In the experiment, the new actuator showed the same high propulsion characteristics as shown in the previous work. This actuator has many possible applications for small pipe inspections, repair, and long-distance movement.

Discussion of Paper 1: Resistance and Propulsion Characteristics of the VWS Hard Chine Catamaran Hull Series '89

The authors wish to thank the discussers for their comments and questions. Some questions were raised because we could not include all specific details and explanations concerning the layout of the Series '89 due to space limitations. We are grateful to Dr. Savitsky for his friendly introduction to our subject.

Causes and effects of underwater noise on fish abundance estimation

The power of modern research vessels using diesel engines means significant levels of noise may be radiated underwater. At low frequencies a surveying vessel must not cause fish avoidance behaviour when it is using trawl or acoustic assessment methods. All the main mechanisms that form the essential propulsion system are described and discussed in terms of underwater radiated noise. Diesel engines, generators and propulsion motors contribute significantly to the low frequency spectrum and an illustration is given of underwater noise when an unsuitable propulsion system is used. Avoidance behaviour by a herring school is shown due to a noisy vessel, by contrast there is an example of no reaction of herring to a noise-reduced vessel. Propellers are major sources of both low and high frequency noise. The latter should not reduce echo sounder detection range, nor contaminate echo integrator recordings. Underwater noise levels from four vessels with different machinery and propulsion characteristics are seen in relation to ambient noise levels at 18 kHz. Fish detection is examined in relation to sea background noise and vessel self-noise. Calculated detection ranges for fish target strength classes from –30 to –60 dB at 38 kHz are shown for six vessels travelling at 11 knots, based on self-noise measurements. Echo sounder noise levels from several vessels at 120 and 200 kHz are tabulated. Beyond 100 kHz the effect of vessel-radiated noise is usually insignificant; levels up to that frequency are proposed in the International Council for the Exploration of the Sea (ICES) Cooperative Research Report No. 209 of 1995.

Dynamics of Two-Joint Dolphinlike Propulsion Mechanism (6th Report, Examination by Three-Dimensonal Panel Method into Effects Which is unable to be Treated by Linear Theory)

In the preceding papers, we developed a linear theory for a two-joint dolphinlike propulsion mechanism, which was a simplified model of high speed swimming animals. However, the effect of the simplification implied in that theory has not been quantitatively discussed so far. To this end, in this paper, by using the three-dimensional panel method, the effects which authors' linear theory can not treat on propulsive characteristics are examined. First, we investigate the fluid force acting on the body part. It is found that the calculated values of the amplitude of the fluid force by the linear theory becomes 10 to 20% larger than those by the panel method, while the values of the phase of the fluid force by those two methods agree well. Next, we examined the effects of the presence of the body and the surging motion of the caudal fin on propulsive characteristics. It is found that the presence of the body makes the propulsive efficiency slightly lower and that the surging of the caudal fin produces higher thrust but lower propulsive efficiency.

水ロケットの推力特性制御の一方法

The propulsive characteristics of water rockets are analyzed theoretically and experimentally. The unsteady thrust force acting on a PET bottle and the air pressure inside the bottle are measured simultaneously by the thrust test stand we have developed. The semi-empirical thrust history is obtained utilizing the air pressure history and it is compared with the measured thrust history. The results show qualitative agreement. The observation of the flow inside bottle by a high-speed video camera shows that the air precedes water when it is about to be discharged entirely. We have developed a flow regulator attached to the nozzle cap to reduce the precursor air discharge that is considered as a result of the swirling flow inside the bottle. The experimental results show that the air discharge and the body vibration are suppressed effectively.

Effects of seirogan (wood creosote) on propulsive colonic motility and stool characteristics in ambulatory mini-pigs.

Our goal was to determine whether Seirogan, an herbal medicine used as an antidiarrheal agent, modifies colonic function, including motility. Experiments were performed on four female Yucatan mini-pigs with established permanent cecal fistulas providing direct access to the colon. Long-term recordings of proximal colonic motility were accomplished by a solid-state probe (six pressure ports 10 cm apart), and a motility index was calculated. Stool viscosity was also measured. The laxative bisacodyl (15 mg/kg) was used to induce colonic motility (increase in motility index) and stool softening, prior to investigating the effect of Seirogan (2-15 mg/kg per os twice a day) or a vehicle control. Seirogan (15 mg/kg), but not the placebo, reversed the bisacodyl-induced stool softening and restored the motility index to normal values by reducing the number of propagating contractions. Taken together the results suggest that inhibition of proximal colonic motility by Seirogan may contribute to its antidiarrheal action.

Theoretical study of the field distributions in a linear electrohydrodynamic charged particle source for space applications

Electrohydrodynamic sources have been proposed as thrusters in electric space propulsion. Compared with chemical propulsion, electric propulsion is characterized by a relatively low thrust and high exhaust velocity of the propellant. These inherent characteristics of electric propulsion offer direct applications in space missions. A study of a field emission electric propulsion system has centered around an emitter modular unit. This module has evolved from a simple single-pin or point source emitter, through linear arrays of stacked needles to the solid slit type emitter module used by Bartoli et al. [J. Phys. D: Appl. Phys. L7 (1984) 2473; J. IEEE Trans. Plasma Sci. P515 (1987) 593]. To model the device, Mitterauer assumed the liquid metal emitter to be an infinitely long cylinder. In order to preserve the symmetry and make the problem tractable, he assumed the accelerator electrode to be a concentric cylinder, which was then used to study the condition for the onset of instability within a surface capillary wave model. Although this model can be used to estimate the field, it does not exhibit the actual geometry associated with the finite size in the device. In this paper, we use a more accurate model to simulate the experimental configuration. The electric field distributions for a finite slit-type liquid metal charged particle source emitter with a parallel planar anode are calculated using an analytic truncated series solution of Laplace's equation. This approach obviates the difficulties of the finite element method which becomes computationally less efficient when there are large gradients in the electric field. The form of the charge density on the emitter is approximated by a truncated series whose coefficients are determined by the boundary conditions on the emitter and the anode. The electric potential and field distribution are determined in both the plane perpendicular to the slit and in the plane of the slit. The calculated field distribution, as a function of scale of the device, suggests the significance of geometry for controlling the spatial characteristics of the emitted current density.

Propulsive Performance of Hypersonic Oblique Detonation Wave and Shock-Induced Combustion Ramjets

A comparative study is presented of the propulsive characteristics of hypersonic detonation wave and shockinduced combustion ramjets. The same ramjet design methodology is used to assess the propulsive performance of both types of ramjets. The lower ‐upper symmetric Gauss ‐Seidel scheme combined with a symmetric shockcapturing total variation diminishing scheme are used to solve the Euler equations describing thetwo-dimensional hydrogen/air combustible e owe eld with nonequilibrium chemical reactions including 13 species (H2, O2, H, O, OH, H2O, HO2, H2O2, N, NO, HNO, N 2, and NO2). Results obtained for e ight Mach numbers 12< ‐ M1 < ‐ 16 and for a e ight dynamic pressure of 67,032 Pa (1400 psf) show that combustor entrance temperatures Tce (or inlet compression ratios ) substantially lower than the near ignition values of hydrogen/air mixture, adopted for the generation of a near Chapman ‐Jouguet oblique detonation wave in the combustor, entail signie cant performance augmentation. For the considered range of e ight Mach numbers and value of e ight dynamic pressure, the thrust of a shock-induced combustion ramjet is maximum for 650 <‐ Tce < ‐ 700 K, and at this point the combustion is entirely shock induced. The thrust generation can be enhanced by more than 10% and the fuel specie c impulses improved by more than one-third over their magnitudes corresponding to maximum thrust detonation wave ramjets.

Architecture of the caudal vena cava wall of the dog at the level of the liver caudate lobe

The vascular segment of the caudal vena cava of the dog at the level of the caudate lobe was shown to be intimately related to hepatic tissue through the hepatic capsule and parenchyma. The tunica adventitia of the caudal vena cava was formed mainly by smooth muscle cells with collagen and elastic fibers arranged in bundles. The thin tunica media of the vein was also formed by smooth muscle cells, collagen and elastic fibers arranged in bundles. The tunica intima presented an elastic subendothelial network. The hepatic segment of the caudal vena cava showed a myoconnective architecture and propulsive characteristics in terms of its hemodynamic pattern.

Managing Maneuverability and Rear Stability of Adjustable Manual Wheelchairs: An Update

In the late 1970s, the introduction of new materials and, more importantly, new ideas has changed wheelchair users' potential for wheelchair mobility. The new generation of wheelchairs can be adjusted (Fig. 1) to provide a better fit to the user (legrest length, backrest height, armrest height, and width between the rear wheels), better posture (seat angle), and modifiable propulsion characteristics (axle position relative to user and rear wheel camber). The health care professional's challenge is to “optimize” wheelchair technology for each user. Decisions must be made about adjustments and configurations, and these decisions will determine how much effort will be required of the user and how stable the wheelchair will be. Simple decision criteria for wheelchair configuration are not found in the literature. The decisions are complex because the interaction of user, wheelchair, and environmental characteristics must be considered. The purposes of this article are to describe wheelchair characteristics and to discuss how adjustments can be made to manage these characteristics. Figure 1. Illustration of an adjustable manual wheelchair showing commonly available adjustments. Brubaker1,2 identified biomechanical factors that affect wheelchair performance in order to illustrate the advantages of adjustable manual wheelchairs compared with “standard” wheelchairs. In the opinion of most experts, adjustable manual chairs have less rearward stability than standard chairs and, therefore, are more easily tipped backward. This increased potential to tip backward can be a disadvantage, although Brubaker argued that “standard” wheelchairs are more stable than they need to be for most users and, consequently, require more effort to propel. The adjustable wheelchair requires less effort to propel and turn than a standard wheelchair, which is its performance advantage. To propel a manual wheelchair, rolling resistance and the side slope effect need to be overcome.1 Rolling resistance is the force that must be overcome by the …

Maneuverability and smoke emission constraints in marine diesel propulsion

A multivariable control scheme is designed that reduces smoke generation on an experimental marine diesel engine equipped with a variable geometry turbocharger. The variable geometry turbocharger allows the improvement of the steady-state ship hydrodynamic and propulsion characteristics and requires coordination with the injected mass fuel to achieve a good transient performance.

A fusion propulsion system for rapid interplanetary travel

A propulsion system with capabilities that far exceed conventional and nuclear thermal systems is proposed for human exploration of the solar system and beyond. It makes use of fusion nuclear reactions, and is based on the magnetic mirror configuration which was studied extensively as a potential terrestrial power reactor. Unlike the conventional mirror machine, however, the proposed device will confine a plasma of such density and temperature as to make the ion-ion collision mean free path much shorter than the plasma length. Under these conditions the plasma behaves like a fluid and its escape from the machine is analogous to the flow of a gas into vacuum from a vessel with a hole, hence the name gasdynamic mirror (GDM) (See Fig. 1). Recent studies of this system reveal that the conditions for its performance as a propulsion system are much less stringent than those imposed by an economically viable power reactor. This is reflected by the small energy magnification factor Q (ratio of fusion power to injected power) required by the propulsion system when compared to that of the power reactor. The plasma confinement in this device is provided by a magnetic field that is stronger at the ends than it is at the center thereby providing the necessary reflecting force for containment while allowing a certain fraction of the energetic particles to escape to generate the thrust. The plasma dynamics and the corresponding propulsion characteristics of GDM can be obtained from a set of coupled conservation equations which yield, among other things, the specific impulse and thrust of such an engine. Typical values of the specific impulse is 1.26 × 10 5 seconds and a thrust of tens of kilonewtons for a system with a dry mass of about 230mT. Such a propulsion system is shown to be about 44 m long and to make a round trip to Mars in less than five months. In this paper we examine the various physics and engineering considerations that lead to the modest vehicle mass noted above.

Incomplete Mixing and Off-Design Effects on Shock-Induced Combustion Ramjet Performance

A shock-induced combustion ramjet (“ shcramjet”) model is described to investigate the effects of incomplete fuel/air mixing and off-design e ight conditions on its performance characteristics. A fully implicit, fully coupled, Newton-iteration, lower ‐uppersymmetric Gauss ‐Seidel scheme is employed to solvethe Euler equationsat steady state. This scheme is coupled with a nonequilibrium chemistry model consisting of 33 reactions and 13 species. Axisymmetric and planar shcramjet e owe elds with variable equivalence ratio proe les representing extreme deviations from homogeneous fuel/air mixing are numerically solved for a range of e ight Mach numbers at a constant dynamic pressure of 1400 psf. Results show that incomplete fuel/air mixing gives rise to a combination of detonative combustion and simple shock-induced combustion. Comparison of overall performance characteristics to shcramjets with homogeneous, stoichiometric fuel/air mixtures demonstrates the degree of performance degradation. The propulsive characteristics of mixed-compression ramjets are calculated in off-design operating regimes corresponding to inlet Mach numbers above and below design Mach numbers of 12, 16, and 20; for externalcompression ramjets, the propulsive characteristics are calculated for inlet Mach numbers below design Mach numbers of 12, 16, and 20. It is found that the propulsive properties of the engines deteriorate when they are operated at off-design conditions. For mixed-compression ramjets operating at lower-than-design Mach numbers, the degradation in thrust production is due primarily to reduced heat release in the engine nozzle. At higher-thandesign Mach numbers, thrust production is reduced only slightly due to a modie ed nozzle geometry, required to ensure convergence of the numerical method. Generation of thrust for external-compression ramjets deteriorates at lower-than-design Mach numbers due to a high-pressure zone created in the combustor by the impingement of the detonation wave on the engine surface upstream of the design point. Mixed-compression ramjets are found to provide superior performance to external-compression ramjets at off-design operation. External-compression ramjetsarefound to bemoresensitiveto off-designoperation than mixed-compression ramjets.Itisconcludedthat the engine geometry must be varied as e ight conditions change if degradation in engine performance at off-design conditions is to be avoided.

2906 水ロケット推力特性とノズル改良設計

The propulsive characteristics of water rockets have been analyzed experimentally by the thrust test stand. It can measure the unsteady thrust force acting on a PET bottle and the air pressure inside the bottle simultaneously. The result of the observation by a video camera shows that air precedes water when it is about to be discharged entirely, and the measured thrust history indicates that it decreases suddenly then. We have developed a flow regulator to reduce the precursor air discharge which is considered as a result of the swirling flow inside the bottle. The experimental results show that the air discharge is suppressed and the thrust history is improved to have a potential for higher altitude.