JPH0212586Y2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Field of Industrial Application The present invention relates to a device for measuring the degree of cavitation occurring in a propeller of a ship.

(b) Prior art and its problems Vessels such as ferries that navigate near seas often accelerate and decelerate repeatedly, and cavitation is therefore likely to occur. The factors that cause cavitation are the rotational speed of the propeller shaft, the pitch of the propeller, and the speed of the ship relative to the water. The occurrence of cavitation not only causes a loss of thrust and reduces the efficiency of the engine, but also may cause erosion and damage to the propeller.
Therefore, if the degree of occurrence of cavitation can be ascertained, countermeasures can be taken by changing the causes of cavitation.

To detect the degree of cavitation,
For example, it is possible to receive cavitation sound waves and analyze their frequencies, but in this case, the sensor part that receives the sound waves is susceptible to interference between propeller blades and vibrations of the ship's hull. There are drawbacks such as shells, algae, etc. adhering to the surface of the sensor, reducing its detection performance.

(C) Purpose The purpose of the present invention is to solve such conventional problems and to make it possible to effectively measure the degree of cavitation occurring in a ship's propeller.

(d) Configuration In order to achieve the above-mentioned purpose, the present invention is equipped with an ultrasonic probe placed opposite the propeller at the stern of the ship, and this ultrasonic probe is placed on the front side of the casing in which the piezoelectric vibrator is housed. is formed in a concave shape with a lens effect, and the degree of cavitation is measured by emitting ultrasonic waves to the blades of the propeller and detecting the amount of attenuation of the ultrasonic echoes reflected from the blades.

(E) Examples The present invention will be described in detail below based on the present invention shown in the drawings.

FIG. 1 is a side view showing an ultrasonic probe attached to the stern, and FIG. 2 is a sectional view of the ultrasonic probe. Cavitation measuring device 1 of this embodiment
is equipped with an ultrasonic probe 6 disposed at a position facing the propeller 4 at the stern 2. This ultrasonic probe 6
The piezoelectric vibrator 8 includes a piezoelectric vibrator 8, a buckling layer 10 provided on the back surface of the piezoelectric vibrator 8, and a casing 12 that houses the piezoelectric vibrator 8 and the buckling layer 10. The casing 12 is made of synthetic resin for corrosion resistance and acoustic impedance matching, and the front surface facing the propeller 4 is formed into a concave shape with a predetermined curvature R.

FIG. 3 is a block diagram of the cavitation measuring device. In the figure, 6 is the above-mentioned ultrasonic probe, 12 is a pulse generation circuit that generates a driving pulse to excite this ultrasonic probe 6, and 14 is a received signal output from the ultrasonic probe 6. 16 is an amplifier that amplifies the received signal sampled by the sampling circuit 14; 18 is a waveform shaping circuit that shapes the waveform of the amplified received signal; 20
is an indicator that displays the level of the received signal after waveform shaping.

In this cavitation measuring device 1, periodic drive pulses are generated from a pulse generation circuit 12, and these drive pulses are applied to the ultrasonic probe 6.
As a result, ultrasonic waves are emitted from the ultrasonic probe 6 to the propeller 4. In this case, since the front surface of the casing 12 of the ultrasonic probe 6 is formed in a concave shape, the emitted ultrasonic waves are focused on the propeller 4. If the degree of cavitation generated in the propeller 4 is large, the ultrasonic waves are attenuated to a large extent in proportion to this. The reflected waves of the ultrasonic waves attenuated by the degree of cavitation are received by the ultrasonic probe 6 again. The ultrasonic probe 6 sends a received signal corresponding to the reflected wave of the received ultrasonic wave to the sampling circuit 14 at the next stage. The sampling circuit 14 samples the received signal in synchronization with the rotation of the propeller 4. Therefore, the influence of noise due to secondary cavitation is removed. And sampling circuit 1
The received signal sampled at step 4 is amplified by an amplifier 16, and after its waveform is shaped by a waveform shaping circuit 18, the level of the received signal is displayed on a display 20. Therefore, by measuring the level displayed on the display 20 multiple times and collecting data on the degree of cavitation, it is possible to change the factors that cause cavitation, such as the rotational speed of the propeller shaft, the pitch of the propeller, and the speed of the ship relative to the water. You can take countermeasures by doing this.

(F) Effects As described above, according to the present invention, ultrasonic waves are emitted from the ultrasonic probe to the blades of the propeller, and the ultrasonic echoes reflected from the blades are received again by the ultrasonic probe. Since we now measure the degree of cavitation by detecting the amount of attenuation of the ultrasonic waves, we can limit the measurement area and effectively measure the degree of cavitation without being affected by propeller interference or hull vibration. It becomes possible to measure. Furthermore, since the ultrasonic probe vibrates, shells and algae do not adhere to it, and therefore detection performance can be prevented from deteriorating.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; Fig. 1 is a side view showing an ultrasonic probe attached to the stern, Fig. 2 is a sectional view of the ultrasonic probe, and Fig. 3 is a cavitation measuring device. FIG. 1... Cavitation measuring device, 4... Propeller, 6... Ultrasonic probe, 8... Piezoelectric vibrator,
12...Casing.

Claims (1)

[Scope of utility model registration request] The ultrasonic probe is equipped with an ultrasonic probe placed opposite the propeller at the stern, and the front surface of the casing in which the piezoelectric vibrator is housed is formed into a concave shape with a lens effect. 1. A cavitation measuring device characterized in that the degree of cavitation is measured by emitting ultrasonic waves to a blade and detecting the amount of attenuation of ultrasonic echoes reflected from the blades.