Performance Of Thermal Engine Research Articles

Theoretical analyses on a piston-based thermal engine for thermal underwater glider

• Heat transfer models on thermal engines for TUG are built and verified. • Performance of thermal engine are optimized based on the models. • A piston-type configuration is proposed for thermal engine. Thermal underwater glider (TUG) harvests the ocean thermal energy and glides for a few thousands of kilometers range in a self-propelled manner. Theoretical models on the ocean thermal energy conversion process have been well established for evaluating the conversion efficiency. However, the heat transfer process is rarely modeled for TUG, leading to an inadequate quantification on the output power. In this work, comprehensive theoretical models with both energy conversion and heat transfer processes are conducted on a piston type TUG. The models well predict the performance of the thermal engine as compared with the reported experimental data. The effects of the surface seawater temperature, nitrogen gas volume, nitrogen gas pressure, phase change material (PCM) volume, seawater velocity as well as the gliding angle on the performance of the thermal engine are discussed. The results show that the the effective output power of the nitrogen tank varies from 0.4 to 1.0 W when 4 L PCM is employed in the thermal engine. A lower initial nitrogen volume (1.0 to 0.6 L), larger initial nitrogen pressure (1.0 to 5.0 MPa), larger PCM volume (2.0 to 5.0 L), greater seawater velocity (0–3 m/s) and larger gliding angle (20° to 90°) is beneficial for the improvement of the energy conversion efficiency and output power of the thermal engine. This proposed theoretical models are essential for optimizing the design and operating parameters of thermal engine of a TUG.

Biodiesel production from waste cooking oil using heterogeneous catalysts and its operational characteristics on variable compression ratio CI engine

In the present work, the optimum biodiesel conversion from waste cooking oil to biodiesel through transesterification method was investigated. The base catalyzed transesterification under different reactant proportions such as the molar ratio of alcohol to oil and mass ratio of catalyst to oil was studied for optimum production of biodiesel. The optimum condition for base catalyzed transesterification of waste cooking oil was determined to be 12:1 and 5 wt% of zinc doped calcium oxide. The fuel properties of the produced biodiesel such as the calorific value, flash point and density were examined and compared to conventional diesel. The properties of produced biodiesel and their blend for different ratios (B20, B40, B60, B80 and B100) were comparable with properties of diesel oil and ASTM biodiesel standards. Tests have been conducted on CI engine which runs at a constant speed of 1500 rpm, injection pressure of 200 bar, compression ratio 15:1 and 17.5, and varying engine load. The performance parameters include brake thermal efficiency, brake specific energy consumption and emissions parameters such as Carbon monoxide (CO), Hydrocarbon (HC), Oxides of Nitrogen (NOx) and smoke opacity varying with engine load (BP). Diesel engine's thermal performance and emission parameters such as CO, HC, and NOx on different biodiesel blends demonstrate that biodiesel produced from waste cooking oil using heterogeneous catalyst was suitable to be used as diesel oil blends and had lesser emissions as compared to conventional diesel.

Theoretical and experimental investigation of Alfa type bio mass Stirling engine with effect of regenerator effectiveness, heat transfer, and properties of working fluid

A bio mass Stirling cycle engine system with all necessary components is designed for 1 kW power output. The designed engine is simulated for air standard cycle analysis for thermodynamic performance evaluation. The relationship of cycle efficiency and power output with temperature ratio, initial pressure, and regenerator effectiveness is established. The effect of engine heat transfer, regenerator effectiveness, and properties of the working fluid on cycle performance is studied with the help of cycle simulation, and the optimum values of the temperature ratio and regeneration effectiveness are obtained. The designed and simulated engine is constructed with all necessary components and tested for validation of simulation results. The engine cycle efficiencies attained in this simulation is from 54% to 38% for corresponding regeneration effectiveness from 1 to 0.6. The temperature ratio 0.25 has shown best engine thermal performance. The results of experimentation show close association with simulation results. The results obtained by the simulation will be useful in selection of temperature range and proper working fluid for Stirling engine and will provide helpful guideline to design Stirling engine components.