Engineering topics

Paull, A.

Publications and source records attributed to Paull, A..

At least 19 records

NASA NTRS2000

HyShot-T4 Supersonic Combustion Experiments

A series of experiments were initiated to investigate the operation of a two-dimensional, hypersonic, airbreathing engine (scramjet) inclined at angles of attack to the freestream. The experiments were undertaken to obtain data for use in the Hyshot flight test program. Experiments on the Hyshot scramjet were under taken in the T4 shock tunnel. Experiments were made at a nominal total enthalpy of 3.0MJkg (exp -1) using a nozzle that produced flows with a Mach number of approximately 6.5. The conditions produced correspond to flight at Mach 7.6 at an altitude range of 35.7-21.4km. A summary of the flow conditions is included. The scramjet was tested at 0, plus 2, plus 4, minus 2 and minus 4 degrees angle of attack. Experiments were also undertaken at 2 and 4 degrees angle of skew.

Paull, A.↗

NASA NTRS1998

Experiments on Cruise Propulsion with a Hydrogen Scramjet

Measurement of drag have been made in a shock tunnel on a simple integrated vehicle engine combination for hypersonic cruise with hydrogen scramjet propulsion. The test flow Mach number was 6.4, and the velocity was 2.45 kms(exp -1). Zero Drag, which is the necessary condition for cruise, was achieved as the equivalence ratio approached one. It was found that an analysis using established aerodynamic concept was adequate for predicting drag in the case of no combustion. When combustion occurred results of direct connect experiments provided was qualitative guide to the measured levels of drag, and indicated that thrust nozzle combustion was taking place. An heuristic analysis is used to point to the important effect this may have on propulsive lift.

Stalker, R. J.↗

NASA NTRS1997

Shock Tunnel Studies of Scramjet Phenomena 1995

Reports by the research staff and graduate students of the Mechanical Engineering Department at the University of Queensland are collected and presented. These reports cover various studies related to the advancement of scramjet technology and the operation of advanced hypervelocity shock-expansion tubes. The report topics include the experimental studies of mixing and combustion in a scramjet flow path, the measurement of integrated thrust and skin friction, and the development of a free-piston-driven expansion tunnel capable delivering a test gas at super orbital velocities.

Morgan, R. G.↗

NASA NTRS1997

Shock Tunnel Studies of Scramjet Phenomena 1994

Morgan, R. G.↗

NASA NTRS1995

Scramjet thrust measurement in a shock tunnel

This note reports tests in a shock tunnel in which a fully integrated scamjet configuration produced net thrust. The experiments not only showed that impluse facilities can be used for assessing thrust performance, but also were a demonstration of the application of a new technique to the measurement of thrust on scramjet configurations in shock tunnels. These two developments are of significance because scramjets are expected to operate at speeds well in excess of 2 km/s, and shock tunnels offer a means of generating high Mach number flows at such speeds.

Paull, A.↗

NASA NTRS1995

Shock Tunnel Studies of Scramjet Phenomena 1993

Reports by the staff of the University of Queensland on various research studies related to the advancement of scramjet technology and hypervelocity pulse test facilities are presented. These reports document the tests conducted in the reflected shock tunnel T4 and supporting research facilities that have been used to study the injection, mixing, and combustion of hydrogen fuel in generic scramjets at flow conditions typical of hypersonic flight. In addition, topics include the development of instrumentation and measurement technology, such as combustor wall shear and stream composition in pulse facilities, and numerical studies and analyses of the scramjet combustor process and the test facility operation. This research activity is Supplement 10 under NASA Grant NAGw-674.

Stalker, R. J.↗

NASA NTRS1995

Thrust measurements of a complete axisymmetric scramjet in an impulse facility

This paper describes tests which were conducted in the hypersonic impulse facility T4 on a fully integrated axisymmetric scramjet configuration. In these tests the net force on the scramjet vehicle was measured using a deconvolution force balance. This measurement technique and its application to a complex model such as the scramjet are discussed. Results are presented for the scramjet's aerodynamic drag and the net force on the scramjet when fuel is injected into the combustion chambers. It is shown that a scramjet using a hydrogen-silane fuel produces greater thrust than its aerodynamic drag at flight speeds equivalent to 260 m/s.

Paull, A.↗

NASA NTRS1995

Scramjet thrust measurement in a shock tunnel

This note reports tests in a shock tunnel in which a fully integrated scramjet configuration produced net thrust. The experiments not only showed that impulse facilities can be used for assessing thrust performance, but also were a demonstration of the application of a new technique to the measurement of thrust on scramjet configurations in shock tunnels. These two developments are of significance because scramjets are expected to operate at speeds well in excess of 2 km/sec, and shock tunnels offer a means of generating high Mach number flows at such speeds.

Paull, A.↗

NASA NTRS1995

Measurements of scramjet thrust in shock tunnels

By using results obtained in tests on supersonic combustion of hydrogen in air, the conditions governing model size and operating pressure levels for shock tunnel experiments on models of flight vehicles with scramjet propulsion are established. It is seen that large models are required. The development of the stress wave force balance is then described, and its use as a method of measuring thrust/drag on such models is discussed. Test results on a simple, fully integrated scramjet model, with intakes, combustion chambers, thrust surfaces and exterior surfaces, using a 13 percent silane 87 percent hydrogen fuel mixture, showed that a steady state with thrust generation could be achieved within the shock tunnel test time, and the thrust could be measured. Results are presented for a range of stagnation enthalpies, and show that the scramjet model produces net positive thrust at velocities up to 2.4 km/sec.

Stalker, R. J.↗

NASA NTRS1995

Supersonic combustion ramjet propulsion experiments in a shock tunnel

Measurements have been made of the propulsive effect of supersonic combustion ramjets incorporated into a simple axisymmetric model in a free piston shock tunnel. The nominal Mach number was 6, and the stagnation enthalpy varied from 2.8 MJ kg(exp -1) to 8.5 MJ kg(exp -1). A mixture of 13 percent silane and 87 percent hydrogen was used as fuel, and experiments were conducted at equivalence ratios up to approximately 0.8. The measurements involved the axial force on the model, and were made using a stress wave force balance, which is a recently developed technique for measuring forces in shock tunnels. A net thrust was experienced up to a stagnation enthalpy of 3.7 MJ kg(exp -1), but as the stagnation enthalpy increased, an increasing net drag was recorded. pitot and static pressure measurements showed that the combustion was supersonic. The results were found to compare satisfactorily with predictions based on established theoretical models, used with some simplifying approximations. The rapid reduction of net thrust with increasing stagnation enthalpy was seen to arise from increasing precombustion temperature, showing the need to control this variable if thrust performance was to be maintained over a range of stagnation enthalpies. Both the inviscid and viscous drag were seen to be relatively insensitive to stagnation enthalpy, with the combustion chambers making a particularly significant contribution to drag. The maximum fuel specific impulse achieved in the experiments was only 175 sec., but the theory indicates that there is considerable scope for improvement on this through aerodynamic design.

Paull, A.↗

NASA NTRS1995

A skin friction gauge for impulsive flows

A new skin friction gauge has been designed for use in impulsive facilities. The gauge was tested in the T4 free piston shock tunnel, at the University of Queensland, using a 1.5 m long plate that formed one of the inner walls of a rectangular duct. The test gas was fair and the test section free stream flow had a stagnation enthalpy of 4.7 MJ/kg. Measurements were conducted in a laminar and turbulent boundary layer. The measurements compared well with laminar and turbulent analytical theory.

Goyne, C. P.↗

NASA NTRS1993

Shock tunnel studies of scramjet phenomena, supplement 7

Reports by the staff of the University of Queensland on various research studies related to the advancement of scramjet technology are presented. These reports document the tests conducted in the reflected shock tunnel T4 and supporting research facilities that have been used to study the injection, mixing, and combustion of hydrogen fuel in generic scramjets at flow conditions typical of hypersonic flight. In addition, topics include the development of instrumentation and measurement technology, such as combustor wall shear and stream composition in pulse facilities, and numerical studies and analyses of the scramjet combustor process and the test facility operation. This research activity is Supplement 7 under NASA Grant NAGW-674.

Bakos, R. J.↗

NASA NTRS1993

Hypersonic ignition and thrust production in a scramjet

Experimental results are given for the specific impulse produced by a two-dimensional scramjet at flight speeds ranging between 2.5 and 5.5 km/s with a combustion chamber Mach number of 4.5. Both hydrogen and ethane fuels were used. Results show that provided sufficiently high pressures and sufficiently long combustion chambers are used specific impulses in excess of 1500 s can be obtained with hydrogen. Ethane produced specific impulses less than 600 s with the same conditions and model configuration.

Paull, A.↗

NASA NTRS1993

Shock tunnel studies of scramjet phenomena, supplement 6

Wendt, M.↗

NASA NTRS1992

Test flow disturbances in an expansion tube

The operation of an expansion tube is investigated theoretically with emphasis on the factors that have limited the utility of the expansion tube in the past. It is shown why the window of steady test conditions is narrow and how this window can be expanded so that these facilities can be used in a variety of hypersonic research. The theoretical predictions are supported by centerline Pitot pressure measurements using air as the test gas.

Paull, A.↗

NASA NTRS1992

Skin-friction gauge for use in hypervelocity impulse facilities

A transducer is presented which can measure as rise-time of about 20 microsec, and is thereby applicable to measurements in the high-enthalpy flows associated with hypervelocity impulse facilities. Results are presented which demonstrate the effectiveness of the concept in the case of skin-friction measurements conducted on a flat plate at Mach 3.2. The calibration used was against theoretical skin-friction values in a simple flow.

Kelly, G. M.↗

NASA NTRS1992

Acoustic waves in shock tunnels and expansion tubes

It is shown that disturbances in shock and expansion tubes can be modelled as lateral acoustic waves. The ratio of sound speed across the driver-test gas interface is shown to govern the quantity of noise in the test gas. Frequency 'focusing' which is fundamental to centered unsteady expansions is discussed and displayed in centerline pitot pressure measurements.

Paull, A.↗

NASA NTRS1992

Development of a skin friction gauge for use in an impulse facility

Tests of a prototype skin friction gauge at Mach 3.2 in a small free piston shock tunnel demonstrate the effectiveness of the design concept and the calibration against theoretical skin friction values in a simple flow. The gauge has a rise time of about 20 microsec, sufficiently short for most shock tunnel applications and approaching the rise times needed for expansion tube applications.

Kelly, G. M.↗