Rajesh Kumar S., Nishchay Sadrani and Kannan B.T.
The purpose of this study reports the effects of aspect ratio (AR) on mean flow characteristics of the cruciform orifice jet.
Abstract
Purpose
The purpose of this study reports the effects of aspect ratio (AR) on mean flow characteristics of the cruciform orifice jet.
Design/methodology/approach
The aspect ratio is the height-to-width ratio of the lobe of the cruciform shape. The aspect ratios considered are 0.25, 0.5, 0.75, 1, 2, 3 and 4. The turbulent jet flow is issued through an orifice being fitted to the jet tunnel facility. The velocity measurements are recorded with the help of pitot-static tube connected to a digital manometer setup. The Reynolds number calculated using the equivalent diameter 50.46 × 10–3 m and exit velocity 51.23 m/s was 1.75 × 105. Based on the experimental data, the streamline velocity decay plots, the potential core length (PCL), mean velocity profiles and velocity half widths were plotted, and discussions were made based on the measured data. A smoke-based flow visualization was carried out at moderate Reynolds number 5396.
Findings
The PCL remains almost constant for the aspect ratio 0.25:1 and then starts decreasing for the aspect ratio 1:4. The decrease in PCL indicates improved mixing. The off-center peaks are found along the major axis in mean velocity profiles for almost all cruciform jets. More than one axis switching occurs and can be identified by the crossover points. The location of the first crossover point shifts forward, and the second crossover point shows an oscillating trend. The flow visualization exhibits the jet evolution, and the distance up to which the jet maintains the cruciform shape is increased with the aspect ratio.
Research limitations/implications
The experiments are limited to air in air jet under isothermal conditions.
Social implications
The cruciform orifices can be used as fuel injectors and in air-conditioning systems, thereby improving efficiency and energy usage.
Originality/value
The aspect ratio effects on PCL and axis switching are used to explain the mixing characteristics. Flow visualization was also used to support the discussion.
Details
Keywords
Shouvik Bandopadhyay, Tanooj Jagdeep, Koshika Pandey, Nishchay Sadrani and Kannan B.T.
This study aims to propose a novel configuration for turbofan engine inlets to increase the overall effectiveness of the engine.
Abstract
Purpose
This study aims to propose a novel configuration for turbofan engine inlets to increase the overall effectiveness of the engine.
Design/methodology/approach
Conventional fan has been split radially into two blisk stages, namely, core blisk and bypass blisk. The two blisks are driven by a common shaft but rotate at two different revolutions per minutes (RPMs) on the same plane of rotation simultaneously through a planetary gear mechanism. To avoid any mechanical contact between the two stages, a minimum optimum distance is kept between them.
Findings
An apt reduction ratio of planetary gears allows the bypass blisk to rotate at a lower RPM. Thus, unlike conventional geared single fan configuration, transonic speed at the blade’s tip is prevented without decreasing the core stage’s RPM. Consequently, wave drag is eradicated without compromising the engine's core performance as surplus air can always be supplied to it. Compressor stall and surge can also be significantly reduced.
Research limitations/implications
The concept is at its infancy. Extensive iterations and experimentations are required before implementing it practically.
Practical implications
The configuration fulfils to conceive a practical and industrially scalable method to extract better performance from existing engine architecture with minimal changes while reducing noise and emissions, meeting the short-term emission and noise goals unless electric or hydrogen-powered flight fully matured.
Social implications
The present concept reduces engine noise and thereby helps in reduction of airport noise pollution. This concept also helps in reducing global warming by reducing emissions.
Originality/value
The paper presents a novel configuration for a turbofan engine’s inlet fan and discusses its engineering implications and initial feasibility in detail.