Method for measuring air specific heat ratio via vibration of drumhead object

Abstract

The invention discloses a method for measuring an air specific heat ratio via vibration of a drumhead object. The method comprises the following steps: covering a layer of elastic rubber at the opened end of a cylinder to form a drumhead, one end of which is opened, and fixedly adhering a sphere or a semisphere or an axially symmetric solid at the center of the drumhead, wherein the inner diameter of the cylinder is R, the inner height of the cylinder is h, the mass of the sphere or the semisphere is m and air is sealed in the cylinder; pressing the axially symmetric solid and then releasing, wherein the axially symmetric solid vibrates by suffering the elastic force of the elastic rubber of the drumhead and the elastic function of the air; obtaining the air specific heat ratio gamma which is equal to [(2pi/T)2-k/m]*3m*h/(piR2P), wherein k is the elastic coefficient of the rubber drumhead, the circumference to diameter ratio pi is equal to 3.14159, T is the period of vibration and P is the pressure of the external air. The method disclosed by the invention has the benefits that favorable elasticity is provided as the air is sealed, the experiment principle is more rigorous, a strict simple harmonic vibration is carried out, no rotation occurs, an inflation device is not required, the structure is simpler and the cost is lower.

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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