Propeller Rotational Speed Research Articles

Theoretical and experimental study of a signal feature extraction algorithm for measuring propeller acceleration in a port surveillance system

Classification and identification of moving vessels by extracting particular features of the underwater radiated noise generated by the propellers for use within a port area are an attractive topic for a port underwater surveillance system. The authors first present a chirp-periodic signal model for the envelope of accelerating propeller noise, then derive the maximum-likelihood estimator (MLE) for the evaluation of acceleration and finally propose a novel algorithm for the extraction of acceleration feature on modulated noise (EAFOMN) of the propellers. In addition, a series of experiments were performed for an accelerating propeller in a large cavitation tunnel. The results of the tests show that the actual signal features of accelerating propeller noise is consistent with the presented theoretical analysis, and the proposed algorithm is efficient for passively extracting acceleration of propeller rotation speed.

Experimental study of effects of air content on cavitation and pressure fluctuations

This article studies the effects of air content on propeller cavitation and pressure fluctuations. The cavitation is observed while the pressure fluctuations on the hull are measured. When adjusting the air content, the sheet cavitation range does not change distinctly, but the pressure fluctuations see obvious differences. The amplitudes of the pressure fluctuations increase with the decrease of the air content. The results indicate that the air content has little effect on the sheet cavitation range but has an important effect on the bubble cavitation and the tip vortex cavitation. When the air content decreases, the water tensile force increases, which results in the instability of the bubble cavitation and the tip vortex cavitation and the increase of the pressure fluctuations. To minimize the scale effects, the experiments should be run at a high Reynolds number with a high nuclei content. The high Reynolds number is often realized by increasing the flow velocity and the propeller rotation speed, and the high nuclei content is often made by increasing the dissolved air content.

Self-propulsion computations using a speed controller and a discretized propeller with dynamic overset grids

A method that can be used to perform self-propulsion computations of surface ships is presented. The propeller is gridded as an overset object with a rotational velocity that is imposed by a speed controller, which finds the self-propulsion point when the ship reaches the target Froude number in a single transient computation. Dynamic overset grids are used to allow different dynamic groups to move independently, including the hull and appendages, the propeller, and the background (where the far-field boundary conditions are imposed). Predicted integral quantities include propeller rotational speed, propeller forces, and ship’s attitude, along with the complete flow field. The fluid flow is solved by employing a single-phase level set approach to model the free surface, along with a blended k−ω/k−ɛ based DES model for turbulence. Three ship hulls are evaluated: the single-propeller KVLCC1 tanker appended with a rudder, the twin propeller fully appended surface combatant model DTMB 5613, and the KCS container ship without a rudder, and the results are compared with experimental data obtained at the model scale. In the case of KCS, a more complete comparison with propulsion data is performed. It is shown that direct computation of self-propelled ships is feasible, and though very resource intensive, it provides a tool for obtaining vast flow detail.

Numerical analysis of influence of ship hull form modification on ship resistance and propulsion characteristics

After signing ship building contract shipyard’s design office orders performance of ship resistance and propulsion model tests aimed at, apart from resistance measurements, also determination of ship speed, propeller rotational speed and propulsion engine power for the designed ship, as well as improvement of its hull form, if necessary. Range of ship hull modifications is practically very limited due to cost and time reasons. Hence numerical methods, mainly CFD ones are more and more often used for such tests. In this paper consisted of three parts, are presented results of numerical calculations of hull resistance, wake and efficiency of propeller operating in non-homogenous velocity field, performed for research on 18 hull versions of B573 ship designed and built by Szczecin Nowa Shipyard.

Numerical analysis of influence of ship hull form modification on ship resistance and propulsion characteristics

Numerical analysis of influence of ship hull form modification on ship resistance and propulsion characteristics After signing ship building contract shipyard's design office orders performance of ship resistance and propulsion model tests aimed at, apart from resistance measurements, also determination of ship speed, propeller rotational speed and propulsion engine power for the designed ship, as well as improvement of its hull form, if necessary. Range of ship hull modifications is practically very limited due to cost and time reasons. Hence numerical methods, mainly CFD ones are more and more often used for such tests. In this paper consisted of three parts, are presented results of numerical calculations of hull resistance, wake and efficiency of propeller operating in non-homogenous velocity field, performed for research on 18 hull versions of B573 ship designed and built by Szczecin Nowa Shipyard.

Performance evaluation of propeller-aspirator-pump aerator

Aeration experiments were conducted in a brick masonry tank of dimension 5.25m×2.87m×1.57m to study the effects of positional angle of propeller shaft (α), submergence depth and rotational speed of shaft on standard aeration efficiency (SAE) of a propeller-aspirator-pump aerator. Non-dimensional numbers related to standard aeration efficiency (SAE) and wire power (P) termed as E and Ne, respectively, were proposed. To evaluate the optimum geometric condition, i.e., positional angle of propeller shaft (α), aeration experiments were conducted at different values of α: 30°, 45°, 60°, 75° and 90°, keeping the rotational speed N (2130rpm) and submergence depth of propeller shaft d (300mm) as constants. The results showed that SAE becomes maximum at α=75°. In a similar way, keeping the geometric condition constant (α=75°), aeration experiments were further conducted at different rotational speeds of propeller shaft, N (1420, 1775, 2130, 2485 and 2840rpm) and different values of submergence depth, d (140, 220, 300, 380 and 460mm) to evaluate the effect of dynamic conditions on aeration characteristics. It was found that E as well as Ne could be well correlated with Froude number (Fr) and Reynolds number (Re), respectively. Finally, maximum SAE of 0.42kgO2/kWh was obtained at positional angle of 75°, rotational speed of 2840rpm and submergence depth of 0.14m of propeller shaft.

Active Yaw Control of a Ducted Fan-Based MAV using Synthetic Jets

The feasibility of using active flow control to stabilize a micro ducted fan unmanned aerial vehicle in a yaw motion was investigated experimentally. Flow control was implemented using synthetic jet actuators to manipulate the flow around the vehicle's stator vanes. As a result, this mechanically simplified control approach can be used to generate a yaw moment on the vehicle instead of moving control surfaces and articulated rotor blades. The rotational control of the MAV (165.5mm in diameter and 177.8mm in height) was obtained by activating surface-mounted synthetic jets that were mounted on a set of four fixed stators downstream of the duct. The synthetic jets were located downstream of a deliberately formed local separation to enable controlled flow reattachment. The flow field around the stators and in the wake was studied using particle image velocimetry (PIV) where the geometrical angle of attack of the stators was either 0° or 6° and the propeller rotational speed was either 4,200RPM or 9,000RPM (g...

Numerical analysis of influence of ship hull form modification on ship resistance and propulsion characteristics

After signing ship building contract shipyard’s design office orders performance of ship resistance and propulsion model tests aimed at, apart from resistance measurements, also determination of ship speed, propeller rotational speed and propulsion engine power for the designed ship, as well as improvement of its hull form, if necessary. Range of ship hull modifications is practically very limited due to cost and time reasons. Hence numerical methods, mainly CFD ones are more and more often used for such tests. In this paper consisted of 3 parts, are presented results of numerical calculations of hull resistance, wake and efficiency of propeller operating in non-homogenous velocity field, performed for research on 18 hull versions of B573 ship designed and built by Szczecin Nowa Shipyard.

Mean long-term service parameters of transport ship propulsion system: Part II Propulsion engine service parameters of transport ship sailing on a given shipping route

Mean long-term service parameters of transport ship propulsion system: Part II Propulsion engine service parameters of transport ship sailing on a given shipping route During ship sailing on a given shipping route in real weather conditions all propulsion system performance parameters of the ship change along with changes of instantaneous total resistance and speed of the ship. In this paper results of calculations are presented of distribution function and mean statistical values of screw propeller thrust, rotational speed and efficiency as well as propulsion engine power output and specific fuel oil consumption occurring on selected shipping routes. On this basis new guidelines for ship propulsion system design procedure are formulated.

Mean long-term service parameters of transport ship propulsion system: Part I Screw propeller service parameters of transport ship sailing on a given shipping route

Mean long-term service parameters of transport ship propulsion system: Part I Screw propeller service parameters of transport ship sailing on a given shipping route During ship sailing on a given shipping route in real weather conditions all propulsion system performance parameters of the ship change along with changes of instantaneous total resistance and speed of the ship. In this paper results of calculations are presented of distribution function and mean statistical values of screw propeller thrust, rotational speed and efficiency as well as propulsion engine power output and specific fuel oil consumption occurring on selected shipping routes. On this basis new guidelines for ship propulsion system design procedure are formulated.

In-Flight Thrust Measurements of Propeller-Driven Airplanes

The development of a propeller model that will accurately predict airplane engine static and dynamic thrust and torque in a full range of advance ratio has provided a powerful and reliable source for propeller-driven airplane engine simulation that serves as a valuable tool for flight test analysis. A single-element propeller model that reduces the propeller characteristics to a lift and drag coefficient vs angle-of-attack formulation was found to describe accurately the propeller characteristics over a wide operating range. Measurements of airplane indicated airspeed, flight altitude, torque, propeller speed, and throttle setting are the only required parameters for in-flight thrust estimation. A check of the model showed that the predicted and measured values of static thrust, torque, and dynamic thrust were within less than 2% over a wide range of advance ratios. With an accurate model of in-flight thrust measurement, one could add a new gage on propeller-driven airplane to display the amount of available thrust for the pilot or autopilot system, which would have a great impact on both the capability of verifying airplane’s maneuvers and flight safety during recovery procedures. Nomenclature AI = propeller model parameter set C = propeller blade chord CDb = propeller blade drag coefficient CLb = propeller blade lift coefficient C P =p ower coefficient C Q = torque coefficient CT = thrust coefficient J = advance ratio, 101.34 (V/ nD ) N B = number of propeller blades n = speed, rpm Ps = shaft power Q = shaft torque R = propeller radius r = propeller blade element radius s = solidity ratio T = engine thrust x = r/R αb = blade angle of attack θ = blade angle ρ = air density ω = propeller rotational speed, rpm

자유표면과 수심깊이가 회전하는 프로펠러 주위 유동에 미치는 영향에 대한 PIV 해석

The free surface influenced the wake behind a rotating propeller and its effects were investigated experimentally in a circulating water channel with the variation of water depth. Instantaneous velocity fields were measured using two-frame PIV technique and ensemble-averaged to study the phase-averaged flow structure in the wake region. For an isolated propeller, the flow behind the propeller is affected only by the propeller rotation speed, the leading on the blades and the proximity of the propeller to the free surface. The phase-averaged mean velocity fields show that the potential wake and the viscous wake developed on the blade surfaces. The interaction between the tip vortices and the slipstream causes the oscillating trajectory of tip vortices. The presence of the free surface greatly affected the wake structure, especially for propeller immersion depth of 0.6D. At small immersion depths, the free surface modified the tip and trailing vortices and the slipstream flow structure downstream of X/D = 0.3 in the propeller wake.

Intrinsic kinetics of photocatalytic oxidation of formic and oxalic acid on immobilised TiO 2 films

Titanium dioxide (TiO 2) photocatalysis is a possible alternative/complementary technology to conventional water treatment methods. The TiO 2 catalyst may be used as slurry or it may be immobilised onto a supporting substrate. With immobilised TiO 2 films mass transfer problems occur in most photocatalytic reactors, which results in a reduction of reactor efficiency and in the accuracy of measured catalyst efficiency and kinetics. In order to determine the real intrinsic kinetics of photocatalytic reactions on immobilised TiO 2 films a stirred tank reactor (STR) was used. The reactor incorporated a propeller and a baffle, thus providing good mixing and efficient mass transfer to the TiO 2 film. Degussa P25 was immobilised onto borosilicate glass by a dip coating method and the kinetics of the photocatalytic degradation of the model pollutants, formic acid and oxalic acid were investigated as a function of catalyst loading, initial pollutant concentration and propeller rotation speed. The rate of degradation, of either acid, was not mass transfer limited at propeller speeds greater than 1000 rpm. The rate of formic acid degradation was dependent upon catalyst loading up to a maximum loading above which a decrease in the degradation rate was observed. The apparent quantum yield for the photocatalytic degradation was 5% for oxalic acid and 10% for formic acid. This compares very well with usual reported apparent quantum efficiencies for photocatalysis which are ∼1%. The photocatalytic oxidation of both acids could be described using a Langmuir–Hinshelwood kinetic model.

Control of a Miniducted-Fan Unmanned Aerial Vehicle Using Active Flow Control

An experimentalstudy of thecontrol of the e owe eld around thestatorvanes of a new miniducted-fan unmanned aerial vehicle (UAV) using synthetic jet actuators is presented. As a result, a new control approach of the UAV is proposed in which active e ow control can be used instead of moving control surfaces and articulated rotor blade. Therefore, the UAV’ s propulsion and control systems are reduced to a single moving part, a e xed pitch propeller. This mechanical simplicity makes the active e ow control application particularly attractive for development of mini- and micro-UAVs. The directional and rotational control of the UAV (0.5 m in diameter and 0.15 m in height ) can be obtained by controlling the e ow within the duct. This can be achieved by the activation of surface e uidic actuators based on synthetic jet technology that are located downstream from a miniature passive obstruction. The synthetic jets are e ush mounted on a set of four e xed stators located downstream from the propeller. In the present work the e owe eld around the stator vanes is studied using particle image velocimetry at different radial locations, where the geometrical angle of attack of the stator vanes is e xed at 10 deg and the propeller rotational speed is either 4300 or 6200 rpm. Velocity measurements in the near wake are also obtained, and the data show that as a result of the actuation the cross-stream extent of the wake and its velocity dee cit are signie cantly reduced and the e ow is quasi-steady.

Neural-fuzzy fault diagnosis in a marine propulsion shaft system

The back propagation neural network (BPNN) is applied to the fault diagnosis for the propulsive system of a ship in this paper. There exists a typical vibration signal that can be obtained as a training pattern for each type of fault. These typical vibration signals are collected as training data for the neural network to train the weights of the neural network. The input of the neural network is the characteristic parameters from the power spectrum density (PSD) of the vibration-acceleration signals measured in the shaft bearing system of a ship. By applying a combination of BPNN and fuzzy algorithm methods, an optimal propagation neural network and an optimal learning coefficient for the neural network are obtained. When faults occur, the vibration signals are collected as input of the BPNN. The BPNN will recall and judge what type of fault they belong to. Four testing types, normal condition, loose bearing, unbalanced propeller and loose base were chosen during the experiments. Forty-eight samples were taken in the range 100–500 rpm of the propeller rotational speed. The diagnosis results indicate that a correctness rate of 81.25% on average can be reached and that the best result is a correctness rate of 91.7% in the case of a loose bearing.

Random Lock-In Intervals for Tubular Structural Elements Subject to Simulated Natural Wind

This paper reports on wind tunnel experiments with an elastically suspended circular cylinder vibrating under the excitation of natural wind of high turbulence degree. The natural wind turbulence was simulated by superposing the low frequency part of the natural wind turbulence on the background high frequency turbulence of the wind tunnel flow. This was done by controlling the propeller rotation speed according to an artificially generated low frequency speed sample function drawn from a suitable random process model. The experiment provided statistical data on the intermittent random occurrence and size of strong lock-in vibrations in resonance with the vortex shedding excitation. The purpose of the experiment was to obtain data to support the formulation of a sufficiently detailed stochastic model to allow computer simulation of reasonably realistic fatigue damage accumulation at “hot spots” of tubular structural elements subject to the natural wind. The engineering relevance of the investigation is supported by comparing it with the unrealistic highly conservative rules of wind-induced fatigue commonly given in codes of practice. The stochastic lock-in model as well as the related fatigue calculation procedure is reported in the paper.

Propeller Limitations on Aircraft Engine Design

A IRCRAFT engine designers have long realized tha t propulsive efficiency is related to rotational speed, but the complete relationship between engine power, propeller speed, and airplane forward velocity has not, to the author's knowledge, been set forth. I t is necessary that the aircraft engine designer understand this relationship in order to make intelligent selection of propeller shaft speed. This paper is an a t tempt to clarify the problem and to present, qualitatively, at least, the relationship between these variables. When the values of airplane speed (m.p.h.) propeller rotational speed (r.p.m.) engine power (hp.) and atmospheric density (p) are determined, the maximum efficiency for a given propeller blade design is fixed. Stated more directly, the maximum efficiency which may be obtained by selection of a propeller with the most favorable pitch and diameter is a function of the speed-power coefficient,