Vr Sanal Kumar

Studies on Aerodynamic Characteristics of Dump Diffusers for Modern Aircraft Engines

The geometrical optimization of dump diffusers are extremely demanding as the flow fields and stress fields are very complex and must be well understood to achieve the required design efficiencies. In this paper parametric analytical studies have been carried out for examining the aerodynamics characteristics of different dump diffusers for modern aircraft engines. Numerical studies have been carried out using SST K- ω turbulence model. This code solves SST k- ω turbulence equations using the coupled second order implicit unsteady formulation. In the numerical study, a fully implicit finite volume scheme of the compressible, Reynolds-Averaged, Navier-Stokes equations is employed. We concluded that in addition to the dump gap ratio, the aerodynamic shape of the flame tube case and the other geometric variables are also need to be optimized judiciously after considering the fluid dynamic constraints for controlling the pressure recovery and the losses.

Mechanical Characterization of a Thick-Walled Viscoelastic Hollow Cylinder under Multiaxial Stress Conditions

A brief review of the mechanical characterization of viscoelastic materials under uniaxial, biaxial and multiaxial stress condition is carried out in this paper. Parametric analytical studies have been done in a simulated tubular specimen with different internal pressure loadings at various material properties. We observed that the relaxation modulus values obtained from the thick-walled hollow cylinder analyses are higher that the traditional uniaxial and biaxial test data under the same strain level. We noticed that during the initial period, the relaxation-modulus values are almost identical and later the relaxation modulus obtained from the thick-walled hollow cylinder analysis is found significantly higher than the uniaxial and the strip biaxial test data. We conjectured that in the initial stage the stress–strain ratios are almost independent of the geometry of the test specimen and subsequently the stress conditions vary according to the shape of the specimen because the relaxation modulus is found geometry dependent when loading time advances. Note that the main objective of this characterization is not to determine the magnitude of the stress actually present in the test specimen, but to help the designer to decide the best geometry in a realistic way according to the industrial applications from the viscoelastic stress relaxation point of view.

Development of the Multifactorial Computational Models of the Solid Propellants Combustion by Means of Data Science Methods - Phase I

In this paper, we present the results of usage of data science methods, in particular artificial neural networks, for the creation of new multifactor computational models for prediction of burn rate of the solid propellants (SP). The analytical system PolyAnalyst and analytical platform Loginom were used for the model creation. The particular model developed was for burn rate prediction of double base propellants with thermite additives, both nano and micro by means of training the ANN using experimental data published in scientific literature. The basis (script) of a creation of Data Wharehouse of SP combustion was developed. The Data Wharehouse can be supplemented by new data in automated mode and serve as a basis for creating new generalized combustion models of SP and thus the beginning of work in a new direction of combustion science, which the authors propose to call �Propellant Combustion Genome� (by analogy with a very famous Materials Genome Initiative (MGI)). Propellant Combustion Genome opens possibilities for accelerating the advanced propellants development.

Conceptual design of an automatic fluid level controller for aerospace applications

In this paper an attempt has been made for the conceptual design of an automatic fluid level controller for cryogenic tank lucratively for aerospace applications. An ideal design technique of the low temperature multi-phase fluid level control system for estimating the boil-off rate and/or the flow rate to facilitating the estimation of the total quantity of effective fluid available for completing the mission based on the use of microcontroller has been presented. The proposed control system model is mainly composed of microcontroller, level sensor, temperature sensors, pump and relay. This system could estimate the actual fluid volume of the low temperature cryogenic fluid for the evaluation of the effective propulsive efficiency of the entire aerospace vehicle. The preliminary sea level test results, using water as the base fluid, show that the system model being proposed is able to monitor the liquid level very effectively and accurately for estimating the total volume of the fuel and oxidiser for estimating the operating time of the aerospace vehicle lucratively.

Studies on Gravity Influence on Solid Propellant Burn Rate

Experimental studies have been carried out using the in-house developed propellant samples at the atmospheric conditions to examine the influence of propellant surface orientation / attitude on burn rate. A series of burning tests are conducted with different grain orientations, viz., vertical, inverted and horizontal. We have observed 5 % burn rate augmentation on end-burning grains when the burning surface evolution was against the earth gravity compared to the normal vertical candle burning condition. We conjectured that the coupled effects of the instantaneous variations of the propellant burning surface attitude and the flight acceleration during the mission could alter the flame structure due to the local gravitational influence, which in turn alter the burn rate. This paper throws light for developing a suitable gravitational force dependant burn rate model for improving the performance prediction of solid rocket motors for aerospace applications.

Studies on Ignition Delay and Flame Spread in High-Performance Solid Rocket Motors

Accurate prediction of ignition delay and flame spread rate in solid propellant rocket motors is of great topical interest. In this paper using a standard k-ω turbulence model numerical studies have been carried out to examine the influence of solid rockets port geometry on ignition delay and the flame spread pattern. We observed that with the same inflow conditions and propellant properties heat flux histories and ignition time sequence are different for different port geometries. We conjectured from the numerical results that in solid rocket motors with highly loaded propellants, mass flux of the hot gases moving past the burning surface is large. Under these conditions, the convective flux to the surface of the propellant will be enhanced, which in turn enhance the local Reynolds number. This amounts a reduction in heat transfer film thickness and enhanced heat transfer to the propellant with consequent enhancement in the dynamic burn rate resulting the undesirable starting pressure transient. We concluded that, the more accurate description of gas phase to surface heat transfer process will give a better prediction and control of ignition delay and flame spread rate in solid propellant rockets.