Effect of Rotor Tip Casing Treatment on the Performance and Stability of a Transonic Axial Compressor

In a transonic compressor rotor, tip leakage flow interacts with passage shock, casing boundary layer and secondary flow. This leads to increase in total pressure loss and reduction of compressor stability margin. Casing treatment is one of the passive endwall geometry modification technique to control tip leakage flow interaction. In the present investigation effect of rotor tip casing treatment is investigated on performance and stability of a NASA 37 transonic compressor stage. Existing literature reveals, that endwall casing treatment slots i.e., porous casing treatment, axial slots axially skewed slots, circumferential grooves, recirculating casing treatment etc. are able to improve compressor stability margin with penalty on stage efficiency. Turbomachinery engineers and scientists are still focusing their research work to identify an endwall casing treatment configuration with improves both compressor stall margin as well as stage efficiency. Hence in the current work, as an innovative idea, effect of casing treatment slot along rotor tip mean camber line is investigated on NASA 37 compressor stage. Casing treatment slot with rectangular cross-section was created along the rotor tip mean camber line. Four different casing treatment configurations were created by changing number of slots on rotor casing surface. In all four configurations casing treatment slot width and height remains same. Flow simulation of NASA 37 compressor stage was performed with all these four casing treatment configurations. A maximum stall margin improvement of 3% was achieved with a particular slot configuration, but without any increase in compressor stage efficiency.

Anaerobic Digestion of Lignocellulosic Waste Materials

Nowadays, the climate mitigation policies of EU promote the energy production based on renewable resources. Anaerobic digestion (AD) constitutes a biochemical process that can convert lignocellulosic materials into biogas, used for chemical products isolation or energy production, in the form of electricity, heat or fuels. Such practices are accompanied by several economic, environmental and climatic benefits. The method of AD is an effective method of utilization of several different low-value and negative-cost highly available materials of residual character, such as the lignocellulosic wastes coming from forest, agricultural or marine biomass utilization processes, in order to convert them into directly usable energy. Lignin depolymerization remains a great challenge for the establishment of a full scale process for AD of lignin waste. This review analyzes the method of anaerobic digestion (biomethanation), summarizes the technology and standards involved, the progress achieved so far on the depolymerization/pre-treatment methods of lignocellulosic bio-wastes and the respective residual byproducts coming from industrial processes, aiming to their conversion into energy and the current attempts concerning the utilization of the produced biogas. Substrates’ mechanical, physical, thermal, chemical, and biological pretreatments or a combination of those before biogas production enhance the hydrolysis stage efficiency and, therefore, biogas generation. AD systems are immensely expanding globally, especially in Europe, meeting the high demands of humans for clean energy.

Multiple Criteria Decision-Making for Developing an International Game Participation Strategy: A Novel Application of the Data Envelopment Analysis (DEA) Two-Stage Efficiency Process

Background: This study aims to develop an efficient future game participation strategy for teenaged athletes based on an analysis of the 2019 International Table Tennis Federation (ITTF) World Tour game expenditure efficiency and prize-winning efficiency. Methods: In this research, Chinese Taipei (TPE) players served as the main research subjects. The input and output categories were determined through a literature analysis. A two-stage efficiency process of data envelopment analysis (DEA) and Boston consulting group (BCG) matrix were applied in this study to facilitate the calculation. Results: Based on a slack variable analysis, local travel expenses are the key elements impacting efficiency. The game recommendation order was based on a BCG matrix. The top seven recommended games were the Japan Open, Czech Open, Australian Open, Bulgarian Open, Austrian Open, China Open, and German Open. Conclusion: The results of this current study provide efficient game participation recommendations for teenaged athletes. Long-term follow-up records of game participation information should be developed to provide teenaged athletes with a precise efficiency analysis.

NON-DIMENSIONAL PARAMETERS FOR COMPARING CONVENTIONAL AND COUNTER-ROTATING TURBOMACHIN

Counter-rotating turbomachines have the potential to be high efficiency, high power density devices. Comparisons between conventional and counter-rotating turbomachines in the literature make multiple and often contradicting conclusions about their relative performance. By adopting appropriate non-dimensional parameters, based on relative blade speed, the design space of conventional machines can be extended to include those with counter-rotation. This allows engineers familiar with conventional turbomachinery to transfer their experience to counter-rotating machines. By matching appropriate non-dimensional parameters the loss mechanisms directly affected by counter-rotation can be determined. A series of computational studies are performed to investigate the relative performance of conventional and counter-rotating turbines with the same non-dimensional design parameters. Each study targets a specific loss source, highlighting which phenomena are directly due to counter-rotation and which are solely due to blade design. The studies range from two-dimensional blade sections to threedimensional finite radius stages. It is shown that, at hub-to-tip ratios approaching unity, with matched non-dimensional design parameters, the stage efficiency and work output are identical for both types of machine. However, a counter-rotating turbine in the study is shown to have an efficiency advantage over a conventional machine of up to 0:35 percentage points for a hub-to-tip ratio of 0:65. This is due to differences in absolute velocity producing different spanwise blade designs.

Research on Efficiency of Animation Enterprises Based on Two-Stage DEA Network System Model of Sharing Input Resources

This research constructs a two-stage DEA network system model of shared input resources to evaluate the efficiency of animation companies: the first-stage efficiency to reflect the production quantity and the second-stage efficiency to reflect the production quality of animation products, where the quality of animation products is judged based on the market recognition of the animation products. The overall efficiency in the research model is used to describe the development of animation enterprises. According to the result, it is concluded that the overall efficiency of the surveyed animation companies and the efficiency of each sub-stage have shown an upward trend, which is in line with the growth of the company's development.

Impact of Rotor-Casing Effusion Cooling on Turbine Performance and Operating Point: An Experimental, Computational, and Theoretical Study

It is known that a secondary effect of rotor-casing effusion cooling is to modify and potentially spoil the rotor over-tip leakage flow. Studies have shown both positive and negative impacts on high-pressure (HP) stage aerodynamic performance and heat transfer, although there remains no consensus on whether the net effect is beneficial when both aerodynamic and thermal effects are accounted for simultaneously. An effect that has not been extensively discussed in the literature is the change in stage operating point that arises due to mass introduction midway through the machine. This effect complicates the analysis of the true performance impact on a turbine and must be accounted for in an assessment of the overall benefit of such a system. In this paper, we develop a low-order (“mean-line”) analysis in an attempt to bring clarity to this issue. We then present results from experiments conducted in the Oxford Turbine Research Facility, a 1.5-stage transonic rotating facility capable of matching non-dimensional engine conditions. In the experiments, effusion cooling was implemented over a sector of the rotor casing spanning 24 degrees or four rotor-blade pitches. Rotor-exit radial traverse and HP vane loading measurements were conducted locally to the cooled sector. Results are compared to baseline tests conducted without cooling. To assess the degree to which experimental results with only a sector of the annulus cooled would provide an accurate indication of stage operating point changes (when measured local to the annulus) in an annular (engine-like) environment, unsteady Reynolds-averaged Navier–Stokes (URANS) simulations were performed. In particular, simulations of a full annulus with an effusion-cooled sector were compared to a periodic simulation with fully annular effusion cooling. The results—perhaps surprisingly—suggest that a cooled sector is sufficient to infer the changes in an annular system, provided measurements are performed locally to the sector. Experiments conducted with fixed 1.5-stage boundary conditions showed increases in both mid-stage static pressure and stage-exit total pressure with cooling. The mean-line model and URANS predictions were in good agreement with the experimental data and also showed an increase in stage reaction and a reduction in turbine-inlet (mainstream) mass flowrate with cooling. Finally, the URANS predictions were used to show that with cooling, there are changes both locally to the cooled casing (changes to the tip-leakage and secondary flow structures) and globally (changes to the bulk-flow velocity triangles). An absolute stage efficiency benefit of 0.7% was predicted for a coolant-to-mainstream mass flowrate ratio of 2.2%. By running with a number of different boundary conditions, steady RANS simulations were used to estimate the relative contributions to the efficiency improvement due to the changes in operating point and aerodynamics in the blade-tip region. For the present configuration, both changes contribute positively to the improvement in stage efficiency.

The Effect of Reaction on Compressor Performance

Reaction is the fundamental parameter by which the asymmetry of the velocity triangle of a stage is set. Little is understood about the effect that reaction has on either the efficiency or the operating range of a compressor. A particular difficulty in understanding the effect of reaction is that the rotor and stator have a natural asymmetry caused by the centrifugal effects in the rotor boundary layer being much larger than that in the stator boundary layer. In this paper a novel approach has been taken: McKenzie's ‘linear repeating stage’ concept is used to remove the centrifugal effects. The centrifugal effects are then reintroduced as a body force. This allows the velocity triangle effect and centrifugal force effect to be decoupled. The paper shows the surprising result that, depending on how the solidity is set, a 50% reaction stage can either result in the maximum, or the minimum, profile loss. When the centrifugal effects are removed, 50% reaction is shown to minimise endwall loss, maximise stage efficiency and maximise operating range. When the centrifugal effects are reintroduced, the compressor with the maximum design efficiency is found to rise in reaction by 5% (from 50% reaction to 55% reaction) and the compressor with the maximum operating range is found to rise in reaction by 15% (from 50% reaction to 65% reaction).