The use of S-CO2 as working fluid in a power cycle has been growing in recent years due to associated benefits such as highly compact power plant and high cycle thermal efficiencies for application including waste heat, solar thermal and... more
The use of S-CO2 as working fluid in a power cycle has been growing in recent years due to associated benefits such as highly compact power plant and high cycle thermal efficiencies for application including waste heat, solar thermal and nuclear power plants. Many authors have presented studies on S-CO2 cycle and its modifications and there also exists many patents which claim different embodiments of the S-CO2 cycle for different heat sources. Each author of the S-CO2 cycle embodiment uses some specific tool to analyze the cycle performance with assumed values of component efficiencies. In the S-CO2 cycle the ratio of turbine work to compressor work is relatively small and its variation may cause a significant influence on cycle performance estimation accuracy. Exact prediction of the S-CO2 cycle performance requires defining exact turbomachinery efficiency magnitudes. However, S-CO2 turbines and compressors are in development stage except for several low power scale prototypes and hence it is very difficult to make assumptions on efficiency and they need to be designed. To enable design of cycle from concept to detailed design of the turbomachinery, the authors in this work have developed a flexible design system which is starting from heat balance calculation, continues with sizing of turbomachinery flow path, through 1D/2D/3D aero and structural multidisciplinary optimization. Such a design process is iterative because a refinement of the turbomachinery efficiencies lead to change in cycle boundary conditions for turbomachinery design and the design needs to be refined by recalculation of the cycle. In the present work, four different embodiments of S-CO2 thermodynamic cycles were analyzed using assumed component efficiencies and based on the actual design of the turbomachinery components the cycle was recalculated and accurate performance of the cycle was predicted. It is observed that the turbine efficiency has significant influence on the overall cycle performance compared to the compressor efficiency.
Two-wheeler is one of the common mode of transportation in India. Being inherently unstable the two-wheelers are more prone to accidents, and account for 10,000 to 15,000 deaths every year. Head hitting the pavement is the main cause of... more
Two-wheeler is one of the common mode of transportation in India. Being inherently unstable the two-wheelers are more prone to accidents, and account for 10,000 to 15,000 deaths every year. Head hitting the pavement is the main cause of injury and fatality. Hence, use of crash helmet, which reduces the risk of severe brain injury is generally mandated in most of the major cities. To be effective, these helmets have to meet standard impact performance criteria. The resulting enclosed shell design, makes the use of these helmets in hot and humid weather conditions very uncomfortable. Heat stress causes rider discomfort, increasing chances of rider loosing concentration. Providing better ventilation around the head inside the helmet can alleviate the discomfort felt by the rider. In the present work, Computational Fluid Dynamics (CFD) simulation was used to design improved air flow path inside the helmet to enhance the ventilation around rider’s head. The routing of the grooves was des...
Aspiration in an axial compressor is normally regarded as sucking out the low momentum boundary layer from blade suction surface, thus lowering the chances of flow separation and consequently that of stall under off-design operation.... more
Aspiration in an axial compressor is normally regarded as sucking out the low momentum boundary layer from blade suction surface, thus lowering the chances of flow separation and consequently that of stall under off-design operation. However, the suction mass flow does not take part in useful work and leads to loss of engine power output. This paper deals with a new concept of natural aspiration to energize blade suction surface boundary layer by injecting some fluid from pressure to suction side through a part span slot on the blade. The energized boundary layer has lesser tendency to separate, thus enhancing stall margin. Numerical simulations were carried out to study the effect of aspiration slot location and geometry on the performance and stall margin of a transonic axial compressor rotor. The computational results without aspiration slot were in fair agreement with the published experimental data. The modified rotor, with part span aspiration, showed ~3.2% improvement in stal...
