Cross flow fuel injection is a widely used approach for injecting liquid fuel in gas turbine comb... more Cross flow fuel injection is a widely used approach for injecting liquid fuel in gas turbine combustors and afterburners due to the higher penetration and rapid mixing of fuel and the cross flowing airstream. Because of the very limited residence time available in these combustors it is essential to ensure that smaller drop sizes are generated within a short axial distance from the injector in order to promote effective mixing. This requirement calls for detailed investigations into spray characteristics of different injector configurations in a cross-flow environment for identifying promising configurations. The drop size characteristics of a liquid jet issuing from a forward angled injector into a cross-flow of air were investigated experimentally at conditions relevant to gas turbine afterburners. A rig was designed and fabricated to investigate the injection of liquid jet in subsonic cross-flow with a rectangular test section of cross section measuring 50 mm by 70 mm. Experiment...
Lean operation in the primary combustion zone of a gas turbine combustor is advantageous from NOx... more Lean operation in the primary combustion zone of a gas turbine combustor is advantageous from NOx reduction point of view. The present work deals with the influence of lean primary zone operation o...
An ejector is a device that entrains a secondary flow into a high speed stream that is generated ... more An ejector is a device that entrains a secondary flow into a high speed stream that is generated by expansion of high pressure motive gas [1]. These ejectors can be broadly classified into central ejectors and annular ejectors. A large majority of applications involve central ejectors where the motive gas flow is injected along the centre of the flow passage of the secondary flow. Dutton and Carroll [2] proposed an optimization procedure for such ejectors without taking the mixed supersonic flow region into account and generated the design curves considering the constant Total temperature, Molecular weight and Specific heat ratios. However in some applications involving high temperature gases such as in ramjet/scramjet and gas turbine test facilities, an annular supersonic ejector is more appropriate where annular injection of the motive gas at the periphery of the flow passage is desired to avoid the exposure of the motive gas flow nozzle to the high temperature combustion product ...
Total temperature measurement in exhaust stream of air breathing engines like Ramjet, Scramjet an... more Total temperature measurement in exhaust stream of air breathing engines like Ramjet, Scramjet and Aircraft afterburners is a challenging task as the temperatures in such engine exhausts are above 2200K. Thermocouples for such high temperature measurement suffer from oxidation and are expensive. Optical method for this application requires high level of expertise and is expensive. Gasdynamic probe is a special type of water cooled probe and can give total temperature of the flow by measuring the flow parameters like total pressure and mass flow through the probe nozzle. The probe is very simple in construction and can be made at a low cost. This paper describes about the development of a Gasdynamic probe and calibration for probe constant for various flow parameters. NOMENCLATURE R Gas constant γ Ratio of specific heat P o1 Total pressure at inlet to the probe nozzle (first restriction) T o1 Total temperature of the gas to be measured (Total temperature inlet to the probe nozzle) A ...
In a Scramjet combustor, since the flow is supersonic, the residence time available is of the ord... more In a Scramjet combustor, since the flow is supersonic, the residence time available is of the order of 1 millisecond. So the available time for fuel-air 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. . 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. Experimental characterization is carried out by unsteady pressure measurement inside the cavity for different aspect ratios.
Wall mounted cavity has proven to be a capable candidate for fuel air mixing and flame stabilizat... more 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. . Two variants of the cavity, formed by using rectangular and ramp strut as the rear strut and plug nozzle acting as the forward strut, have been used. Drag characterization is carried out by static pressure measurement inside the cavity for different aspect ratios for these two types of cavities formed. Flow visualization has been done using time averaged Z-type schlieren technique. Open and closed cavities have been identified using distribution of coefficient of pressure in the cavity and the schlieren images taken.
When hypersonic vehicles operate at Mach numbers 4-8, the temperature of the hot parts of the com... more 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 commu...
The concept of endothermic fuels is not a strange thing to the aeronautical community. Research i... more The concept of endothermic fuels is not a strange thing to the aeronautical community. Research is going on, globally, to achieve these kinds of fuels experimentally; but restricted to laboratory scale test setup. This is because of the stringent and controlled method of cracking the fuel thermally as well as catalytically. In this research work we have followed a systematic approach, i.e, developed a laboratory scale reactor for the preliminary feasibility studies and a realistic experimental set up, for the development and analysis of the cracked fuel by simulating the conditions of combustor walls. Developing this technology indigenously involves many steps, namely identification of the suitable catalysts, developing the technology of preparation of catalytically active coatings and then the design and fabrication of the catalytic cracking core. Finally the catalytic cracking core has to be integrated to the test combustor with the experimental setup. To carry out the catalytic c...
This paper describes the design and development of Mach 3.6 water cooled facility nozzle using bo... more 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
National Aerospace Laboratories, CSIR has recently established the Aero-propulsion Mach 3.6 Tunne... more 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 th...
1 Kannan_r@nal.res.in 2 venug@nal.res.in 3 seemu-nal@nal.res.in 4 manjunathp@nal.res.in Abstract-... more 1 Kannan_r@nal.res.in 2 venug@nal.res.in 3 seemu-nal@nal.res.in 4 manjunathp@nal.res.in Abstract--The development of endothermic fuels is important for providing efficient cooling to scramjet combustors operating at high Mach numbers. Generally the fuel itself can be used as coolant for the engine elements. Since preheating the fuel is desirable before combustion, it can be circulated in heat transfer passages embedded inside the hot engine parts so that the excess heat of the engine is removed by the fuel and in the process the fuel is also regeneratively preheated to the desired temperature. Endothermic fuels pertain to a class of fuels, which make use of certain endothermic reactions to provide an additional heat sink for cooling the engine hot end parts through embedded heat exchange devices. While traditional fuels use only the sensible heat of the fuels for cooling, endothermic fuels provide cooling through two routes, namely, the absorption of the sensible heat and through th...
Cross flow fuel injection is a widely used approach for injecting liquid fuel in gas turbine comb... more Cross flow fuel injection is a widely used approach for injecting liquid fuel in gas turbine combustors and afterburners due to the higher penetration and rapid mixing of fuel and the cross flowing airstream. Because of the very limited residence time available in these combustors it is essential to ensure that smaller drop sizes are generated within a short axial distance from the injector in order to promote effective mixing. This requirement calls for detailed investigations into spray characteristics of different injector configurations in a cross-flow environment for identifying promising configurations. The drop size characteristics of a liquid jet issuing from a forward angled injector into a cross-flow of air were investigated experimentally at conditions relevant to gas turbine afterburners. A rig was designed and fabricated to investigate the injection of liquid jet in subsonic cross-flow with a rectangular test section of cross section measuring 50 mm by 70 mm. Experiment...
Lean operation in the primary combustion zone of a gas turbine combustor is advantageous from NOx... more Lean operation in the primary combustion zone of a gas turbine combustor is advantageous from NOx reduction point of view. The present work deals with the influence of lean primary zone operation o...
An ejector is a device that entrains a secondary flow into a high speed stream that is generated ... more An ejector is a device that entrains a secondary flow into a high speed stream that is generated by expansion of high pressure motive gas [1]. These ejectors can be broadly classified into central ejectors and annular ejectors. A large majority of applications involve central ejectors where the motive gas flow is injected along the centre of the flow passage of the secondary flow. Dutton and Carroll [2] proposed an optimization procedure for such ejectors without taking the mixed supersonic flow region into account and generated the design curves considering the constant Total temperature, Molecular weight and Specific heat ratios. However in some applications involving high temperature gases such as in ramjet/scramjet and gas turbine test facilities, an annular supersonic ejector is more appropriate where annular injection of the motive gas at the periphery of the flow passage is desired to avoid the exposure of the motive gas flow nozzle to the high temperature combustion product ...
Total temperature measurement in exhaust stream of air breathing engines like Ramjet, Scramjet an... more Total temperature measurement in exhaust stream of air breathing engines like Ramjet, Scramjet and Aircraft afterburners is a challenging task as the temperatures in such engine exhausts are above 2200K. Thermocouples for such high temperature measurement suffer from oxidation and are expensive. Optical method for this application requires high level of expertise and is expensive. Gasdynamic probe is a special type of water cooled probe and can give total temperature of the flow by measuring the flow parameters like total pressure and mass flow through the probe nozzle. The probe is very simple in construction and can be made at a low cost. This paper describes about the development of a Gasdynamic probe and calibration for probe constant for various flow parameters. NOMENCLATURE R Gas constant γ Ratio of specific heat P o1 Total pressure at inlet to the probe nozzle (first restriction) T o1 Total temperature of the gas to be measured (Total temperature inlet to the probe nozzle) A ...
In a Scramjet combustor, since the flow is supersonic, the residence time available is of the ord... more In a Scramjet combustor, since the flow is supersonic, the residence time available is of the order of 1 millisecond. So the available time for fuel-air 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. . 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. Experimental characterization is carried out by unsteady pressure measurement inside the cavity for different aspect ratios.
Wall mounted cavity has proven to be a capable candidate for fuel air mixing and flame stabilizat... more 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. . Two variants of the cavity, formed by using rectangular and ramp strut as the rear strut and plug nozzle acting as the forward strut, have been used. Drag characterization is carried out by static pressure measurement inside the cavity for different aspect ratios for these two types of cavities formed. Flow visualization has been done using time averaged Z-type schlieren technique. Open and closed cavities have been identified using distribution of coefficient of pressure in the cavity and the schlieren images taken.
When hypersonic vehicles operate at Mach numbers 4-8, the temperature of the hot parts of the com... more 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 commu...
The concept of endothermic fuels is not a strange thing to the aeronautical community. Research i... more The concept of endothermic fuels is not a strange thing to the aeronautical community. Research is going on, globally, to achieve these kinds of fuels experimentally; but restricted to laboratory scale test setup. This is because of the stringent and controlled method of cracking the fuel thermally as well as catalytically. In this research work we have followed a systematic approach, i.e, developed a laboratory scale reactor for the preliminary feasibility studies and a realistic experimental set up, for the development and analysis of the cracked fuel by simulating the conditions of combustor walls. Developing this technology indigenously involves many steps, namely identification of the suitable catalysts, developing the technology of preparation of catalytically active coatings and then the design and fabrication of the catalytic cracking core. Finally the catalytic cracking core has to be integrated to the test combustor with the experimental setup. To carry out the catalytic c...
This paper describes the design and development of Mach 3.6 water cooled facility nozzle using bo... more 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
National Aerospace Laboratories, CSIR has recently established the Aero-propulsion Mach 3.6 Tunne... more 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 th...
1 Kannan_r@nal.res.in 2 venug@nal.res.in 3 seemu-nal@nal.res.in 4 manjunathp@nal.res.in Abstract-... more 1 Kannan_r@nal.res.in 2 venug@nal.res.in 3 seemu-nal@nal.res.in 4 manjunathp@nal.res.in Abstract--The development of endothermic fuels is important for providing efficient cooling to scramjet combustors operating at high Mach numbers. Generally the fuel itself can be used as coolant for the engine elements. Since preheating the fuel is desirable before combustion, it can be circulated in heat transfer passages embedded inside the hot engine parts so that the excess heat of the engine is removed by the fuel and in the process the fuel is also regeneratively preheated to the desired temperature. Endothermic fuels pertain to a class of fuels, which make use of certain endothermic reactions to provide an additional heat sink for cooling the engine hot end parts through embedded heat exchange devices. While traditional fuels use only the sensible heat of the fuels for cooling, endothermic fuels provide cooling through two routes, namely, the absorption of the sensible heat and through th...
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