Phenomenological Analysis of the Combustion of Gaseous Fuels to Measure the Fuel's Energy Quality and Availability to Produce Work in Si Engines, Part 2

A novel methodology is proposed to evaluate fuel´s performance in spark ignition (SI) engines based on the fuel´s energy quality and availability to produce work. Experiments used a diesel engine with a high compression ratio (CR), modified by SI operation, and using interchangeable pistons. The interchangeable pistons allowed for the generation of varying degrees of turbulence during combustion, ranging from middle to high turbulence. The generating efficiency (ηq), and the maximum electrical energy (EEmax) were measured at the knocking threshold (KT). A cooperative fuel research (CFR) engine operating at the KT was also used to measure the methane number (MN), and critical compression ratio (CCR) for gaseous fuels. Fuels with MNs ranging from 37 to 140 were used: two biogases, methane, propane, and five fuel blends of biogas with methane/propane and hydrogen. Results from both engines are linked at the KT to determine correlations between fuel´s physicochemical properties and the knocking phenomenon. Certain correlations between knocking and fuel properties were experimentally determined: energy density (ED), laminar flame speed (SL), adiabatic flame temperature (Tad), heat capacity ratio (γ), and hydrogen/carbon (H/C) ratio. Based on the results, a mathematical methodology for estimating EEmax and ηq in terms of ED, SL, Tad, γ, H/C, and MN is presented. These equations were derived from the classical maximum thermal efficiency for SI engines given by the Otto cycle efficiency (ηOtto). Fuels with MN > 97 got higher EEmax, and ηq than propane, and diesel fuels.

FLOW FIELD ON HELODECK OF A FRIGATE: A REVIEW

The various functions desired from a frontline warship such as a frigate, corvette or a destroyer, coupled with the requirement of very high speeds and economic viability restricting the size, necessitates a very dense arrangement of weapons and sensors on the top deck and superstructure. Accordingly, Navies across the world have faced several problems with respect to functions for which a good aerodynamic design for these structures is essential. Major issues include smoke nuisance created due to impinging of the ship's exhaust gases on to the top deck leading to possible suction by engine intakes and high turbulence in the ship's air-wake leading to ship aircraft interface concerns. The flow field on the helodeck is extremely complex due to its geometry and interaction with the wake of the ship’s superstructure. A knowledge of this complexity is essential for ensuring safe helo operations on the helodeck. The problem of ship helicopter interaction has hogged the lime light in recent times, due to rising demand for design of warships for increased stealth, especially in the past two decades. Consequently, several researchers in countries with advanced Navies have invested considerable resources towards evolving both experimental and numerical solutions for the problem. However, given the military nature of the operations, open literature on the subject containing details of such research, which can be used as reference material for present work, are limited. Considering the complexities involved in the problem, an attempt has been made in this paper to holistically review the widely scattered and limited literature in this field. A good amount of literature on marine helo applications emerge from the offshore industry. Keeping in mind that the fields of warship design and offshore structures are dissimilar and have their peculiar problems, informed conclusions have been made in drawing lessons from available literature.

Numerical investigation of effects of incisor angle on production of sibilant /s/

The effects of the inclination angle of the incisor on the speech production of the fricative consonant /s/ was investigated using an implicit compressible flow solver. The hierarchical structure grid was applied to reduce the grid generation time for the vocal tract geometry. The airflow and sound during the pronunciation of /s/ were simulated using the adaptively switched time stepping scheme, and the angle of the incisor in the vocal tract was changed from normal position up to 30°. The results showed that increasing the incisor angle affected the flow configuration and moved the location of the high turbulence intensity region thereby decreased the amplitudes of the sound in the frequency range from 8 to 12 kHz. Performing the Fourier transform on the velocity fluctuation, we found that the position of large magnitudes of the velocity at 10 kHz shifted toward the lip outlet when the incisor angle was increased. In addition, separate acoustic simulations showed that the shift in the potential sound source position decreased the far-field sound amplitudes above 8 kHz. These results provide the underlying insights necessary to design dental prostheses for the production of sibilant fricatives.

Effect of turbulence intensity and gradient of turbulence intensity on airfoil aerodynamic characteristics at low Reynolds number

Based on the complex flow field of vertical takeoff and landing (VTOL) aircraft with distributed propulsion, the influence of the turbulence intensity and gradient of turbulence intensity on the aerodynamic characteristics of two-dimensional airfoil under low Reynolds number was studied by solving the unsteady Reynolds averaged Navier-Stokes (URANS) Equation based on the c-type structural mesh and γ-Reθt transition model. The aerodynamic characteristics of NACA0012 airfoil at different turbulence intensities and Reynolds numbers are simulated and compared with the experimental data, which verifies the reliability of the low Reynolds number calculation method. Meanwhile, the effects of the different low Reynolds number and gradient of turbulence intensity on the aero-dynamic characteristics of airfoil are studied, and the effect mechanism of the turbulence on the flow field around airfoil is analyzed. It shows that the flow characteristics of the airfoil with high turbulence or Reynolds number are more stable, the separation bubble size is smaller, the flow separation is delayed, and the stall angle of attack is larger, but the effect of the two mechanisms on the earlier transition is different. The influence of the turbulence gradient on the airfoil is limited by the Reynolds number, and the flow separation, transition and reattachment of the airfoil with high turbulence gradient are advance. The generation and evolution of the laminar separation bubble are closely related to the turbulence intensity and Reynolds number, and its scale and location also affect the aerodynamic characteristics of the airfoil.

System Dynamics Analysis of Sugarcane Supply Chain in Indian Sugar Industry

Presently, there is high turbulence in the Indian sugar industry. The misalignment of the incentives of major stakeholders is leading the industry to a vicious downslide. Hence, it becomes important to study the current situation, its dynamics and future trends under different circumstances. In this paper, we have established the relationship between different variables and parameters using the systems dynamic approach to model the dynamics of sustainability of the sugar industry in Uttar Pradesh (UP), India. Our study revealed that to achieve sustainable development, the sugar industry must improve on resource utilization, operating cost, better supply chain coordination and transparent information flow. Based on our analysis, operational and policy level recommendations have been suggested to help the industry achieve sustainable development and improve performance.

Lopsided Blood-thinning Drug Increases the Risk of Internal Flow Choking and Shock Wave Generation Causing Asymptomatic Stroke

An overdose of blood-thinning drug reduces blood viscosity (BV) and increases Reynolds number causing high-turbulence leading to the Sanal flow choking (PMCID: PMC7267099). Asymptomatic stroke could be diminished by concurrently lessening the BV and flow turbulence by rising thermal tolerance level in terms of biofluid/blood heat capacity ratio (BHCR) or by decreasing the blood pressure ratio (BPR). In conclusion, BPR must always be lower than 1.8257 as dictated by the lowest BHCR of the evolved gas (CO2) for prohibiting asymptomatic stroke.

Discordance of Tracer Transport and Particulate Matter Fate in a Baffled Clarification System

Large eddy simulation (LES) and coupled physical laboratory-scale modeling are performed to elucidate tracer transport and particulate matter (PM) fate in a baffled clarification system. Such baffled systems are common for urban water unit operations and processes. Flow hydrodynamic indices of these systems such as short-circuiting are often examined with measurement of inert tracer transport as a surrogate for chemical or PM transport and fate. Results of this study illustrate complex interactions between turbulent flow, tracer, and various PM diameters at the system scale. PM preferential accumulation and the discordance of PM transport with respect to flow hydrodynamics are observed based on the modeling results; otherwise not practical with physical model testing. Results demonstrate that baffling can promote system tracer mixing and improve volumetric utilization by extending the mean flow path through flow separation and bifurcation. The baffle tested produced high turbulence kinetic energy near the sedimentation floor and reduced PM separation (clarification) as compared to the unbaffled system used as a control. The unbaffled system in this study yields the highest PM separation, even though significant short-circuiting occurs during the residence time distribution (RTD) of the tracer. Further analysis demonstrates the mechanistic difference between the tracer transport and the finer suspended PM as compared to larger settleable and sediment PM diameters. Results illustrate that the tracer RTD, residence time (RT) and hydraulic efficiency indices are not reliable surrogates for PM or PM-bound chemical/pathogen separation. In addition, simulations suggest a site, system or condition-specific design approach given the coupled dependence on flow and design geometry.

Mathematical Modelling and Performance Analysis of Flat Plate Solar Dryer- CFD Simulation Approach

This study focuses on the investigation of enhancing convective heat transfer between the absorber and the air inside a channel. The investigation approaches modeling different absorber through CFD simulation and validating the result with experimental data. Supplying air to both sides of the top and the bottom surfaces of the absorber increase the air mass flow rate and therefore increases the thermal efficiency of the dryer. The studies in a V-grooved absorber attain high hot air velocity; high thermal efficiency resulted from high turbulence created in the duct. For the sample taken with a flow range, 0.01kg/s to 0.06 kg/s, the high output temperature was observed in a lower temperature range and increases as the flow rate increases. At a flow rate 0.01 kg/s, the velocity of hot air passing over the V-grooved absorber attain 0.28 m/s and increased to 1.4 m/s as the mass flow rate increased to 0.06 kg/s. For the rectangular absorber, the velocity of hot air attains 0.15 m/s at a flow rate of 0.01 kg/s and increased to 1.46 m/s as the mass flow rate increases to 0.06 kg/s. The double-sided V-grooved absorber contributes 8 – 12.40% value more efficiency compared to the rectangular plate with the same flow orientation. Further investigation is recommended taking the quantitative analysis obtained in this study and generating qualitative data.