Experimental Investigation And Thermodynamic Analysis Of 1kW Stirling Engine

The theoretical thermal efficiency of Stirling engine (SE) is as high as Carnot efficiency, and as an external combustion engine it has a very good exhaust characteristic, so SE has been a hot topic over the last 30 years. SE can be optimized through experiments, and the experimental results can give instructions to the theoretical design to increase the precision of the theoretical model, so the experimental investigation of SE is very important. Heat losses during the working process of SE are the main influencing factor to the performance of SE, but they are very difficult to measure and need to be estimated with the theoretical analytic tools, so the theoretical thermodynamic investigation of SE is a vital way for both scientific research and engineering application.Modification, experimental investigation, cycle analysis and exergy analysis of 1kWα-type SE were performed.Through cooperation, 1kW solar SE was modified by substituting its solar receiver with a LPG-fueled combustion chamber in SE Lab of Physical-Technical Institute of Uzbekistan Academy of Science (PTI). The metal-plate combustor with small holes was developed and the wire net was adopted in the external combustion chamber of SE.lkW SE experimental system was set up in PTI and in School of Engineering Science of University of Science and Technology of China (USTC) successively. The combustion chamber was optimized and the system of excitation was debugged by experiment.Performance experiments of 1kW SE under different charge pressures of the working gas were done in PTI. Energy balance analysis of 1kW Stirling power system was done according to the experimental results, and it was shown that the gas chamber, the heat exchangers, and the bearing of the slider-crank drive needed to be modified or replaced. After the bearing was replaced with a new one, the electrical power of the system was increased. During the performance experiment in USTC, the electrical power reached 975W, close to the rated electrical power 1kW.After comparison of different zero order analysis methods, zero order analysis was applied to 1kW SE, and the analytical value of the shaft power output was compared with the experimental value. It was shown that the analytical value of the shaft power output was lower than the lower limiting value calculated by Malmo formula method and the indicated power method, and was only 60 percent of the value calculated with Beale number method, which indicated that 1kW SE had some design problems and needed to be further optimized.The ideal adiabatic model ofα-type SE was set up and a set of equations were obtained by formula derivation. Based on the ideal adiabatic analysis, the second order adiabatic analysis was simplified and the visual program code was written. Afterwards the second order simplified analysis was applied to 1kW SE under the design operating condition and some significant results were obtained. And then the second order simplified analysis was applied to 1kW SE under three different charge pressures of the working gas. It was shown that the analytical value of the electrical power output is about 1.5 times of the experimental value, because the actual heat losses of 1kW SE such as the shuttle heat loss of the piston were high and they were not considered in the second order simplified analysis. So the second order simplified analysis still needed to be improved.The exergy loss analysis was applied to both the hot and cold ends of the fueled SE, and two methods were used to calculate the exergy losses. And then the exergy efficiency analysis was applied to the fueled SE system. The exergy efficiency expression of the system was derived and the main influencing factor was found and analyzed qualitatively. Lastly the exergy efficiency of 1kW SE was calculated separately based on Schmidt first order isothermal analysis, the second order simplified analysis and the experimental data under three different charge pressures of the working gas. It was shown that the analytical value of the exergy efficiency based on Schmidt first order isothermal analysis was two or three times of the experimental value, and the analytical value based on the second order simplified analysis was 1.5 times of the experimental value, so the method based on Schmidt first order isothermal analysis was not practical and the method based on the second order simplified analysis needs to be improved. It was also shown that the low experimental value of the exergy efficiency of the combustion chamber and SE resulted in the extremely low experimental value of the exergy efficiency of the system, which indicated that the design of both the combustion chamber and SE needed to be optimized.