A Method of Measuring Air Specific Heat Capacity Ratio by Vibration Method

Abstract

The invention provides a method for measuring air specific heat ratio through the adoption of the vibration method, relates to measurement of physical constant and overcomes problems existing in the conventional technology. The technical scheme adopted by the method is as follows: a cylinder with a sealed upper end and an opened lower end is provided, wherein a spirit bubble is arranged in the plane surface on the outer side of the upper end surface; one or more air holes are formed in the upper part on the side surface of the cylinder and can be sealed through sealing nuts; the cylinder is vertically fixed on a support; a spring is connected between the plane surface at the upper end on the inner side of the cylinder and a piston; the upper end of a suspension line is fixed to the center of the lower end face of the piston; a heavy object is tied to the lower end of the suspension line; when the air holes are open, the vibration period T1 of the heavy object equals to 2Pi(m / k)<0.5>; when all the air holes are sealed, the vibration period of the heavy object is T and the air specific heat ratio gamma equals to 4Pimh(T1<2> minus T<2>) / (r<2>PT<2>T1<2>), wherein Pi is the ratio of the circumference of a circle to its diameter, m is the quality sum of the piston and the heavy object, k is the elastic coefficient of the spring, P is the pressure of the sealed air and r is the inner diameter of the cylinder. The method has the benefits that the sealed air is elastic, the experiment principle is stricter, strict simple harmonic vibration is realized, rotation is avoided and the device is simpler in structure and lower in cost.

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 on the top and bottom of the small hole does not have the mechanical conditions of simple harmonic vibration: the thrust of 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, and the thrust on the upper end (the gas leaks from the small hole) is small. The airflow environment in which the steel ball A moves is abrupt. Both documents are skeptical about its principle; if there is no small hole , the steel ball A is subjected to the thrust produced by the pressure difference, and the steel ball A will always rise without vibrating. Although, in the document "Improvement of the experimental method for measuring the gas specific heat capacity ratio by vibration method", it is proposed to find the steel ball under the small hole The balance position of A will 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 A will fall when the air flow is small, and the steel ball A will rise when the air flow is large. Then the steel ball A is stable, then after the steel ball A is stable, the airflow must be increased to promote its rise, and after a certain distance, it must immediately return to the appropriate airflow mentioned above, so that the thrust generated by the pressure difference is equal to the gravity. This step hard to accomplish;

The literature "Improvement of the Experimental Method for Measuring Gas Specific Heat Capacity Ratio by Vibration Method" also found rotation (called spin in the literature) and collision phenomena. During the vibration process of steel ball A, we found that its reflected light changed, and then we marked it with red The pen draws a cross on the surface of the steel ball A, and it is found that the cross of the steel ball A rotates during the vibration process, and the direction of rotation changes with different instruments and at different times. This result is presented to us by the tube wall or / And the surface of the steel ball A is not uniform, and the asymmetric flow of the airflow at the small hole causes the steel ball A to rotate under asymmetric force. We also found that the frequency of its rotation also shows differences in different instruments and at different times. In other words, the steel ball A is not in a laminar flow environment, but has a certain turbulent flow, its rotational kinetic energy will affect the accuracy of the measurement, and, due to the uncertainty of the rotation, it cannot be corrected quantitatively

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