Method of Measuring Air Specific Heat Capacity Ratio by Piston Vibration in Single-End Sealed Cylinder

Abstract

The method of measuring air specific heat capacity ratio by piston vibration in a single-end sealed cylinder. A transparent cylinder with an inner radius of r is divided into two sections, one section is sealed at the bottom and a pressure sensor is arranged. The signal line of the pressure sensor is connected to a digital oscilloscope. To measure the period T of vibration, the outer surface of the cylinder has a millimeter scale and a horizontal bubble along the length of the cylinder; inside the cylinder, there are two sealed pistons with a mass of m and a piston connecting rod. The piston connecting rod is Can be attracted by a magnetic field; put a magnet into the hollow tube end of the cylinder, touch the piston, the magnetic field attracts the stainless steel of the piston connecting rod, and then pull the piston connecting rod to the open end of the cylinder, when the magnetic field force is less than the air pressure difference The power generated, the two sealed pistons will break away from the magnet and vibrate, and the meter will measure the atmospheric pressure value P of the air; the specific heat capacity ratio of the air is given by the formula γ=4πmh / (r 2 T 2 P) calculation. The beneficial effects are: the sealed air has good elasticity; the experimental principle is more rigorous; it is a strict simple harmonic vibration; no rotation phenomenon occurs; the method for initiating vibration is simple and easy;

Description

technical field [0001] The invention relates to the measurement of physical constants, in particular, it provides a method for measuring air specific heat ratio by vibration method. Background technique [0002] Vibration method to measure specific heat capacity ratio of air is a commonly used method for measuring specific heat capacity ratio. The measurement method used in the physics laboratory, the experimental principle is detailed in "Improvement of the experimental method for measuring gas specific heat capacity ratio by vibration method", Journal of Taizhou University, December 2010 No. Volume 32, Issue 6, Page 39-42, "2 Experiments", and "Experimental Analysis of Air Specific Heat Capacity Ratio Measurement by Vibration Method, Laboratory Science, Volume 16, Issue 3, June 2013, Issue 35-37" "1.1 Principles of the original experiment". [0003] The principle adopted by the prior art, see figure 1 , the gas injection port injects gas continuously and stably, and the ...

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Problems solved by technology

[0006] (2) The non-equivalence of the force above and below the small hole does not have the mechanical conditions of simple harmonic vibration: the thrust of the steel ball A on the upper and lower ends of the small hole is different, and the thrust on the lower end of the small hole is different. The thrust of the gas is large, the thrust on the upper end (the gas leaks from the small hole) is small, and the airflow environment in which the ball moves is abrupt. Both documents are skeptical about its principle; if there is no small hole, The steel ball is subjected to the thrust produced by the pressure difference, and the small ball will always rise without vibrating. Although, in the document "Improvement of the Experimental Method for Measuring the Specific Heat Capacity Ratio of Gas by Vibration Method", it is proposed to find the equilibrium position of the steel ball below the small hole , and then produce a vibration with an amplitude of about 1cm. Due to the lack of external force, it is difficult to achieve only through the adjustment of the air flow. The reason is that the steel ball will descend when the air flow is small, the steel ball will rise when the air flow is large, and the steel ball will be stable when the air flow is appropriate. Then After the steel ball stabilizes, the airflow must be increased to promote its rise. After rising for a certain distance, it must continue to return to a suitable airflow so that the thrust generated by the pressure difference is equal to the gravity. This step is difficult to achieve;

[0007] (3) The steel ball A will rotate and collide with the tube wall during the movement: the literature "Improvement of the Experimental Method for Measuring the Specific Heat Capacity Ratio of Gases by the Vibration Method" also found the phenomenon of rotation (called spin in the literature) and collision. We found that the reflected light of ball A changed during the vibration process, and then we drew a cross on the surface of steel ball A with a red marker pen, and found that the cross of steel ball A rotated during the vibration process, and different instruments and different The direction of its rotation is also changing over time. This result shows us that the surface of the pipe wall or / and the steel ball A is not uniform, causing the steel ball A to rotate under asymmetric force. We also found that the frequency of its rotation is between Different instruments and different times also show differences. In other words, the steel ball A is not in a laminar flow environment, but has a certain turbulent flow, and its rotational kinetic energy will affect the accuracy of the measurement. Moreover, due to the uncertainty of the rotation, it cannot Quantitatively corrected

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