A comprehensive characterization of the GPU-3 Stirling engine losses with the aid of the CFD approach is presented. Firstly, a detailed description of the losses-related phenomena along with the method of calculating each type of loss are addressed. Secondly, an energy analysis of the engine is carried out in order to specify the impact of each type of losses on the performance. Finally, the design effectivity of each component of the engine is investigated using an exergy analysis. The results reveal that the hysteresis loss occurs mainly within the working spaces due to the flow jetting during the first part of the expansion strokes. Additionally, the pressure difference between the working spaces is the main driver for the flow leakage through the appendix gap. The exposure of the displacer top wall to the jet of hot gas flowing into the expansion space during expansion stroke essentially increases the shuttle heat loss. A new definition for the regenerator effectiveness is presented to assess the quality of the heat storage and recovery processes. The energy analysis shows that regenerator thermal loss and pumping power represent the largest part of the engine losses by about 9.2% and 7.5% of the heat input, respectively. The exergy losses within regenerator and cold space are the highest values among the components, consequently, they need to be redesigned.
Detailed measurements of local heat transfer coefficients are presented for air injection through a row of holes into a crossflow. Pitch-to-diameter ratios of 2,4, and 6 are realized and the momentum flux ratio is varied in the range from 0.25 to 4.0. The injection angle of the jets is fixed at 90°. The experimental technique developed uses an Infrared Camera to measure the temperature distribution on the constant heat flux test surface. This measurement technique allows detailed spatial resolution of the heat transfer and gives information about the three-dimensional mixing process of the jets with the mainstream. The experimental results indicate a large influence of the hole spacing to diameter ratio, (s/d), on the heat transfer coefficient. With s/d = 2.0, the spanwise heat transfer coefficients in the vicinity of the injection holes are noticed to be highly uniform. For momentum flux ratios, J, greater than 1, two regions of high heat transfer coefficient exist. The first region occurs in the vicinity of the injection holes. The second region observed some distance downstream is due to the reattachment of the jets to the surface.
Design and three-dimensional simulation of a solar Dish-Stirling (SDS) engine is currently performed. The design starts with the GPU-3 Stirling engine, which is originally built to generate power from the fossil fuel exclusively. The design is conducted through three subsequent phases. Firstly, several parabolic dishes with different rim angles and number of facets are investigated to optimally design the dish concentrator. Secondly, different relative positions of the receiver aperture to the dish focal plane are tested to reach the optimal position. The optical simulation of the solar concentration process is carried out using SolTRACE software. Finally, an optimal design for a cavity receiver that involves a new structure of the heater tubes is performed. The simulation of the engine with the designed receiver is implemented using the commercial CFD code ANSYS FLUENT. Having finished the design, a comprehensive energy analysis of the designed SDS engine is carried out. The results show that a nearly uniform temperature distribution of the heater tubes throughout the cycle is achieved. The overall thermal efficiency of the designed SDS engine is about 31.8 % at a DNI of 1000 W/m2.
Low grade waste heat utilizat ion and new combustion technology are challenging tasks for researchers to achieve these objectives. This paper is concerned with the integration of coal gasification system with a comb ined gas turbine, steam turbine power plant cycles and with ammon ia-water cycle, wh ich is known as Kalina cycle. A l-maghara coal in North Sinai is used as the solid fuel in gasification process.Three cycles configurationsare compared as follows: Scheme (A) with dual pressure Heat recovery boiler with the condenser of steam cycle as the evaporator for Kalina cycle,scheme (B) with heat recovery boiler for both of steam and Kalina cycleand scheme (C), similar to scheme (A), but with a superheating in Kalina cycleto identify the most promising one for implementation. Key parameters of Kalina cycle were the main elements of comparison. Results revealed that scheme (A) has the best performance with regard to the output power, thermal efficiency and specific fuel consumption. Substantially, the integration of Kalina cycle with coal gasification comb ined cycle counterbalances the reduction of the overall efficiency due to the gasification thermal efficiency. Therefore, integration of Kalina cycle in the IC GCC is justified.Furthermo re, part load calculations were made fo r scheme (A) and identified that the integration of Kalina cycle to ICGCC imposed restrictions to Kalina cycle constrains, so that it is more economical to keep such configuration of combined plants at nearly full load conditions.
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