Development of Combustion Driven Heating System for Semi-Free Jet Test Rig

National Aerospace Laboratories, CSIR has recently established the Aero-propulsion Mach 3.6 Tunnel for the experimental research on 'High Speed Combustors. It is a blow down type test facility and simulates the scramjet inlet conditions of Mach number and temperature corresponding to the flight Mach number of 6 and altitude of 25 km. The flow conditions obtained at the test section are – Mach number 3.6, total temperature 1700 K, pressure 18 bar, mass flow rates of 25 kg/s with 10 seconds of test duration. The combustion driven heating method with upstream injection of replenishment oxygen has been adapted. The heating system consists of two combustors namely Pre-Heater -01 and Pre-Heater -02. Pre-heater -01 is an aero engine ‘can type’ combustor which heats air from 300 K to 800 K. The liners and fuel injectors from time expired R-11 aero engine were modified to suit to the requirements. Pre-Heater-02 is an ‘afterburner type’ combustion chamber developed for the facility, which heats the air from 800 K to 1700 K. This paper discusses about the development of the pre-heaters and its performances

Development of a Mixed Bed Catalytic System for Providing Endothermic Cooling with in-situ Generation of Hydrogen Gas for Scramjet Combustors

When hypersonic vehicles operate at Mach numbers 4-8, the temperature of the hot parts of the combustor would increase from approximately 1000K to 4000K, and the thermal management of such large quantities of waste heat becomes an important design consideration. Endothermic cooling provides an efficient method of cooling scramjet combustors by making use of certain endothermic reactions, like for example, the catalytic cracking reaction. Apart from providing endothermic cooling, this technology can also be used for the in-situ generation of hydrogen gas in the cracked fuel. The presence of hydrogen decreases the ignition time and ignition delay of kerosene and it also helps in anchoring flames at high speeds of airflow in a scramjet combustor. We have developed a mixed bed catalytic system consisting of molecular sieves and reformax-100 catalysts for proving endothermic cooling as well as the in-situ generation of hydrogen gas. The results of our findings are described in this communication

Experimental Investigation of Spray Characteristics in Subsonic Crossflows

The breakup of a liquid jet, in a crossflow leading to the evolution of the spray plume downstream is an important aspect that needs to be well understood for improving combustion efficiency and reduction of emissions for airbreathing propulsion engines. The drop size characteristics of a liquid jet in a non swirling crossflow of air were investigated experimentally at conditions relevant to ramjets and gas turbine afterburners. Experiments were done with a 1.0 mm diameter plain orifice nozzle which was flush mounted on the bottom plate of test section to provide normal injection. Laser diffraction using Malvern Spraytec particle analyzer was used to measure drops size and distributions in the near field of the jet. The momentum flux ratio was varied to address a reasonable range of liquid flow rates as in practical devices. The sprays were characterized using the non dimensional parameters such as the Weber number and the momentum flux ratio and drop sizes were measured at an axial distance of 50 mm from the injector. Results indicate that as one goes from the bottom to the top of the spray plume, the drop size distribution becomes narrower. Further with increase in the momentum flux ratio the volume concentration across the plume becomes highly non uniform and depends on the measurement point in the expanding spray lume

Development of Mach 3.6 water cooled facility nozzle

This paper describes the design and development of Mach 3.6 water cooled facility nozzle using both analytical and computational approaches and highlights the subsequent experimental tests which showed that the results were in agreement with the design intent. The nozzle has been designed based on method of characteristics to get uniform Mach number at the exit plane. Nozzle operating conditions are 25 bar total pressure, 1700 K total temperature and 30 kg/s total mass flow rate with an exit area of 350 mm x 350 mm. In addition to the above effort, computational studies were made to predict and validate the flow in the Mach 3.6 nozzle that was designed to produce a uniform supersonic flow. ANSYS-Fluent commercial code was used to compute the flow through a 2-Dimensional convergent divergent nozzle. The geometry and grid were generated using the pre-processor (GAMBIT). In order to capture the boundary layer efficiently, fine grid was generated near the wall. The conservation equations were discretized with 2nd order upwind scheme. Three different mesh sizes were taken for the grid independence study and five different turbulence models were used for assessing the appropriate model. 2-D steady state RANS (Reynolds Averaged Navier-Stokes) equations were used for computation. Among the models investigated, SST k- and RNGk- turbulence models were found to give better agreement

Characterization of Strut-mounted 'Through Cavity' for scramjet applications

Scramjet is a variant of ramjet where combustion happens at supersonic speeds. At these supersonic speeds residence time available is of the order of 1 millisecond. So the available time for fuelair mixing, atomization, vaporization and combustion is very low. Wall mounted cavity has proven to be a capable candidate for fuel air mixing and flame stabilization for scramjet. Because of inherent advantages like symmetric flow, avoidance of base wall cooling, symmetric fuelling feasibility etc exploration of strut-mounted ‘through cavity’ has been done. It is a novel configuration formed in the space between two struts immersed in a supersonic flow in tandem. Pressure oscillations inside the cavity are result of unsteadiness in the flow, caused by the interaction of shear layer with the compression wave generated inside the cavity. Experimental characterization is carried out by unsteady pressure measurement inside the cavity for aspect ratios of 2 to 14. Two variants of the cavity, formed by using rectangular and ramp strut as the rear strut and plug nozzle acts as the forward strut, have been used. Width of the cavity has been kept constant. Cavity sees the flow Mach number of 2, total pressure of 7 bar and total temperature of 300 K. Dominant modes of pressure fluctuations are captured at each configuration and effect of aspect ratios and cavity variants are observed. Stable and unstable cavities have been observed. Variation of amplitude of pressure oscillation inside the cavity, along the length of the cavity has also been notice

Development of automated test sequence for mach 3.5 propulsion test facility

Data acquisition and control software plays a pivotal role in operating advanced test facilities. Development of automated test sequence (ATS) for the operation and control of Semi-Free Jet Test Facility (SFJTF) is presented. This paper explains the hardware used to realize the ATS, discrete (on / off) and continuous (PID) control logics developed to operate the facility in a fully automated mode, safety interlocks used and value added features like on-line monitoring of critical facility parameters, manual override etc,. Typical test results of Mach number, total temperature and total pressure are presented for the test runs conducted with the developed ATS

Establishment of aeropropulsion mach 3.6 test facility for high speed combustor research (AIAA 2013-2624)

National Aerospace Laboratories has recently established the Aeropropulsion Mach 3.6 test facility for experimental research on 'High Speed Combustors'. This is a blow down type test facility and simulates the combustor inlet conditions of Mach number and Temperature corresponding to the flight Mach number of 6 and an altitude of 25 km. The details of the facility, it's operation and flow characteristics have been described in this paper. The salient features of the control system of the facility has also been discussed. The facility was commissioned and operationalized in March 2012 and the flow conditions obtained at the test section are Mach number 3.6, total temperature 1700 K, pressure 18 bar with 12 s of effective test duration. This facility can be used as a semi-freejet test facility for the experimental research on the high speed combustors

Pilot ignition development and full scale AB testing

An experimental investigation on the development of a pilot ignition system, using a novel flame ball method, has been successfully carried out for GTRE's Kaveri engine afterburner. The flame ball concept was proved in the specially set-up elemental test facility, which had high altitude simulation capability. Detailed ignition tests incorporating the newly developed pilot ignition system was carried out, under simulated conditions, in the elemental test facility and in the specially set-up full-scale Kaveri engine afterburner facility. Recommendations were made on teh dimensions, location and the type of fuel injector to be used in the pilot ignition system. The pilot ignition system has been successfully developed and tested under full-scale conditions at Bangalore

Experimental studies on a liquid fuelled medium scaled valved pulsejet

A pulsejet is a simple propulsive device where the combustion occurs in pulses and the propulsive effort is achieved from the reaction to the rearward flow of hot gases. Pulsejets offer a compelling alternative for small scale propulsion requirements. In this work a valved pulsejet configuration popularly known as dynajet was investigated using different fuels and thermal barrier coatings for the valves to assess its performance and improve its durability. Successful sustained pulsations were obtained with three liquid fuels namely petrol, methanol and a mixture of methanol and nitro methane. The effort included measurement of thrust, fuel consumption and temperature. The effect of using a zirconia based thermal barrier coatings on the valves to improve the valve life was also investigated. It was observed that among the fuels investigated petrol gave the best specific impulse and further the thermal barrier coatings had a negligible impact on extending the valve life

Economic performance and marine policy implications of mud spiny lobster mariculture in Tropical Sea Cages, North-Eastern Arabian Sea, India: An empirical study in marine economics

Lobsters are one of the premium ocean resources and a highly sought-after seafood commodity globally. The increasing demand for spiny lobsters in both domestic and international markets has led to a growing interest in mariculture as a means of meeting demand. Capture-based mariculture (CBM) by the coastal communities is the only way to cater the existing demand. However, there is scant published information and continued ambiguity on the viability of spiny lobster aquaculture in the Indian subcontinent and a similar gap exists in countries engaged in lobster fattening. Thus, to bridge the gap between the viability information and CBM stakeholders, we examined the profitability and economic performance of mud spiny lobster, Panulirus polyphagus, production in open sea farming systems, specifically sea cages. Our analysis focused on economic indicators such as input costs and return value. We found that the estimated annual revenue for a single operation was USD $3605.04, with an internal rate of return (IRR) of 33$1226.17, demonstrating profitability. Despite this, certain bottlenecks such as limited seedstock and feed availability and cost concerns, disease management issues, regulatory complexities, market demand fluctuations limit the expansion of the industry beyond a certain threshold. This study provides useful information for enterprise building and developing better strategies for building food security and supporting traditional communities-oriented commercial lobster farming in India, and potentially in other lobster farming nations as well