Study On A High Accuracy Gas Calorific Value Measurement System And Gas Mass Weighing Techniques

Gas calorific value measurement system can be defined as a calorimetric technique which determine the heat energy released by completely burning a given quantity gas. Heat released during combustion is transmitted to a stirred water bath. Gas calorific value is obtained by determining the medium temperature rising. Due to the high precision of mass and temperature measurement, a high measurement accuracy can be obtained. It is usually used for national gas calorific value standard devices and laboratory gas calorific value determination. In this thesis, the principle of the high accuracy gas calorimeter was studied, the designing theories and methods were discussed in detail, the gases supplying and the gas mass measurement sub-systems were developed. The main works are as following:1. Study on the principle of the high accuracy gas calorimeter. Through studying the relevant theories and key techniques of the Rossini-type gas calorimeter, the main parameters for a calorimeter and the methods to determine values of them were obtained. A calorimeter is composed of some subsystems, including gas distribution system, gas mass measurement system, combustion and gas heat measurement system, and the flue gas composition detection system. A given quantity of gas(about 1 g) burns in a combustion chamber, the heat released is transmitted to water bath. Calorific value is calculated by measuring the temperature rise of the medium.2. Development of the gas supply system and the gas weighing setup. The specific research works include the proportional control scheme for oxygen, argon and fuel gas, the design of gas supply pipe system, the pipe size, the method to determine parameters for control valves. In the study, the program of gases transmission has been completed. The test results indicate that the tightness and the gas supply performance of the gas supply system are great, fulfilling the design requirement. In order to eliminate the influence of temperature, humidity and pressure, the mass of the gas is determined by the double-balls weighing method. In addition, the design of gas weighing setup and the planning method of automatic measuring device are introduced, the mathematic model of control parts is established.3. Study on the computational model of adiabatic temperature rise. In order to ensure the heat medium without heat transfer with the environment, usually, the temperature of jacket(ambient temperature) should be same with heat medium temperature. But the method can’t be achieved. The study used the isoperibolic calorimeter to steady the heat transfer boundary temperature constant. The temperature-time curve is divided into three periods: a pre-heating or stabilization period, a heat release period and a post-heating or stabilization period. Five different existing methods for the determination of the adiabatic temperature rise are elaborated in this paper.