Milinda Suraweera | The University of Queensland, Australia (original) (raw)

Papers by Milinda Suraweera

Journal of Propulsion and Power, 2011

To investigate the supersonic combustion patterns in scramjet engines, a model scramjet engine wa... more To investigate the supersonic combustion patterns in scramjet engines, a model scramjet engine was tested in the T4 free-piston shock tunnel. The test model had a rectangular intake, which compressed the freestream flow through a series of four shock waves upstream of the combustor entrance. A cavity flame holder was installed in the supersonic combustor to improve ignition. The freestream test condition was fixed at Mach 7.6, at an altitude of 31 km. This experimental study investigated the effects of varying fuel equivalence ratios, the influence of the cavity flame holder, and the effects of cowl shape. As a result, supersonic combustion was observed at equivalence ratios between 0.11 and 0.18. Measurements indicated that the engine thermally choked at a fuel equivalence ratio of 0.40. Furthermore, the cavity flame holder and the W-shaped cowl showed improved pressure distribution due to greater reaction intensity. With the aid of numerical analysis, the cavity and the W-shaped cowl are shown to be effective in fuel–air mixing.

AIAA Journal, 2006

Te results of a shock-tunnel study in which skin friction, heat transfer rates, and static pressu... more Te results of a shock-tunnel study in which skin friction, heat transfer rates, and static pressure are measured in hypervelocity turbulent boundary layers. Shock-tunnel measurements of skin friction and heat transfer rates show a trend of decreasing Reynolds analogy factor with increasing skin friction coefficient. Thetrend is apparently independent of stagnation enthalpy, unit Reynolds number, and Mach number for the range of conditions examined. The effect of oxygen dissociation within the boundary layer because as the source of the observed trend is discounted as similar Reynolds analogy factors are obtained when either air or nitrogen is used as the test gas.

Journal of Propulsion and Power, 2018

16th AIAA/DLR/DGLR International Space Planes and Hypersonic Systems and Technologies Conference, 2009

The HyShot 2 flight in 2002 pioneered a low cost method of hypersonic testing using sounding rock... more The HyShot 2 flight in 2002 pioneered a low cost method of hypersonic testing using sounding rockets. In a further development of this technology, Flight 7 of the HIFiRE Program will deploy a free-flying scramjet powered payload that is planned to enter the atmosphere at a high flight path angle at approximately Mach 8. The HIFiRE 7 payload consists of two back-to-back three-dimensional scramjet engines set within a trailing flare for aerodynamic stability. The scientific goals of the flight are to perform a direct measurement of the thrust generated by the scramjet flowpaths, and to compare the measured thrust with estimates based on ground testing. This paper describes the motivation, launch procedure, flowpath development and ground testing for the flight which is scheduled for March 2011. Copyright

The high levels of viscous drag that are produced at hypersonic velocities pose a considerable ba... more The high levels of viscous drag that are produced at hypersonic velocities pose a considerable barrier to the successful development and operation of scramjet flight vehicles. The higher density flow that passes through a scramjet combustor produces a large component of the overall viscous drag of the vehicle. The present study investigates a skin friction reduction method, in which hydrogen is injected and combusted within a turbulent boundary layer, over a range of conditions in the hypersonic regime. Results from an experimental and numerical study of skin friction levels obtained when hydrogen is injected into turbulent boundary layers are presented. Measurements are reported from experiments in the T4 free-piston reflected shock tunnel. Hydrogen was injected from a 3 mm high slot into the boundary layer on the flat surface of one of the walls of a duct 100 mm wide, 60 mm high, and 1745 mm long. The experiments were conducted at Mach numbers ranging from 4.2 to 5.9, flow nozzle-...

Model Scramjet engine is tested with T4 free-piston shock tunnel at University of Queensland, Aus... more Model Scramjet engine is tested with T4 free-piston shock tunnel at University of Queensland, Australia. Basically, test condition is fixed as Mach 7.6 at 31 km altitude. With this condition, variation effects of fuel equivalence ratio, cavity, cowl setting and angle of attack were investigated. In the results, supersonic combustion was observed with low and middle fuel equivalence ratio. At high equivalence ratio, thermal choking was occurred due to the intensive reaction. Cavity and W-shape cowl showed early ignition and enhanced mixing respectively.

Conventional wind-tunnel force-measurement techniques are not suitable for use in the short test ... more Conventional wind-tunnel force-measurement techniques are not suitable for use in the short test times available in shock tunnels. Conventional force balances rely on the establishment of a state of static force equilibrium between the test model and its support structure. Then strains in the supports are used to infer the forces on the model based on the calibration of the balance. In a shock tunnel there is usually insufficient time for a state of static force equilibrium to be established (Bernstein, 1975). The solution to this problem for all but the smallest and lightest models, is to infer the forces on the model from the dynamic response to the aerodynamic forces exerted on the model during the test time. Various techniques have been implemented to solve this problem including free-flying models with the motion tracked either photographically (Bernstein, 1975) or using accelerometers (Sahoo et al., 2005) and combinations of strains measured in the model support structure and acceleration of the model (e.g. Storkmann et al., 1998). Another technique, that has been developed at The University of Queensland, is the stress wave force measurement technique (Sanderson and Simmons, 1991). In this technique the aerodynamic forces on the model are inferred from the transient response of the system using deconvolution techniques. A stress wave force balance is calibrated dynamically by applying a transient force and measuring the response of the balance in the form of strains induced by stress waves propagating through the model and its support structure. The result of the calibration tests is the system's impulse response function. In an experiment, the response of the system to the aerodynamic loads on the model is measured and deconvolution is used to infer the time-history of aerodynamic loads that would cause the measured response. This system has been validated for single-component force measurement for models of increasing complexity (e.g. Tuttle et al., 1995, Sabean et al., 1999) and has been applied to multiple-component force measurement (e.g. Mee et al., 1996; Smith et al., 2001). It is mainly used these days to make detailed measurements on scramjet engines (e.g. Robinson et al, 2004, 2006; Tanimizu et al., 2007) and to measure the drag due to skin friction in scramjet combustors (e.g. Kirchhartz, 2008). Stalker (2005) developed an analysis showing that the local skin friction coefficient in turbulent boundary layers can be reduced when heat is released in the boundary layer. This has been applied to scramjet combustors where the local skin friction coefficient has been shown to be reduced (Suraweera 2006; Kirchhartz et al., 2008). Work is ongoing to investigate how well boundary layer combustion for skin friction might be implemented into practical scramjet combustors.

Journal of Propulsion and Power, 2009

Journal of Propulsion & Power, 2018

Results are presented on the freejet testing of a 75%-scale replica of the HIFiRE 7 scramjet. The... more Results are presented on the freejet testing of a 75%-scale replica of the HIFiRE 7 scramjet. The HIFiRE 7 scramjet flowpath includes a two-dimensional forebody, a rectangular-to-elliptical shape transition inlet, an elliptical combustor, and a thrust nozzle. Only porthole injectors are used, giving the internal flowpath a clean configuration suitable for high-Mach-number operation with no physical obstructions to the flow. Furthermore, the structure of the shock waves in the scramjet is tailored to introduce a shock-wave/boundary-layer interaction in the combustor to promote fuel ignition. The objective of the experiments is to investigate the performance of this scramjet flowpath at a simulated flight Mach number of 7.5 and an altitude of 29.5 km with gaseous hydrogen as the fuel. Static pressure measurements show that robust combustion can be sustained in the flowpath at a range of equivalence ratios between 0.48 and 0.84. Based on these experiments, a fuel equivalence ratio of 0.8 is recommended for the flight. Corresponding surface heat transfer measurements reveal that, when the fuel–air mixtures ignite and burn, the surface heat transfer levels in the combustor and nozzle increase to as much as three times the fuel-off levels. A quasi-one-dimensional cycle analysis of the tests shows that the overall fuel-based combustion efficiency of this engine is 89% at the fuelling conditions planned for the flight. Nomenclature C p = specific heats at constant pressure H = enthalpy h = altitude M = Mach number p = pressure q = dynamic pressure _ q w = wall heat transfer r = recovery factor of 0.88 St = Stanton number T = temperature T aw = adiabatic wall temperature u = axial velocity x = distance from leading edge of forebody α = angle of attack γ = ratio of specific heats ϕ = equivalence ratio Subscripts e = nozzle-exit condition f = flight condition s = nozzle-supply condition w = conditions at the wall

International Journal of Forensic Engineering, 2014

HIFiRE 7 Flight Test Update 29 April, 2015. Recently, the HIFiRE 7 flight was launched fro... more HIFiRE 7 Flight Test Update 29 April, 2015.

Recently, the HIFiRE 7 flight was launched from the western coast of Norway. The HIFiRE 7 payload consisted of two back-to-back three-dimensional scramjet engines set within a trailing flare for aerodynamic stability during deployment as a free-flyer. The scientific goals of the flight were to perform a direct measurement of the thrust generated by the scramjet flowpaths, and to compare the measured thrust with estimates based on ground testing.

To date, it was one of the most advanced scramjet flowpaths ever flight tested. The launch and most of the return leg of the flight performed as planned. However, no telemetry and hence no engine data was returned to ground stations during the experimental window of the flight envelope. Presently, the full characterisation of the failure is undetermined. The payload and the remaining stack impacted the surface within operational guidelines.

The flight represented years of design and testing by a relatively small group of extremely, hardworking people. I thank you all for your efforts. Shit happens…

M.Suraweera

Journal of Propulsion and Power, Dec 2011

Results from an experimental and numerical study of skin friction levels obtained when hydrogen i... more Results from an experimental and numerical study of skin friction levels obtained when hydrogen is injected into turbulent boundary layers are presented. Measurements are reported from experiments in the T4 free-piston reflected shock tunnel. Hydrogen was injected from a 3 mm high slot into the boundary layer on the flat surface of one of the walls of a duct 100 mm wide, 60 mm high, and 1745 mm long. The experiments were conducted at Mach numbers ranging from 4.2 to 4.7, flow stagnation enthalpies of 4.8 MJ/kg to 9.5 MJ/kg, static pressures of 59 kPa to 86 kPa, and Reynolds numbers of 8.9  106 m-1 to 17.2  106 m-1. Hydrogen fuel was injected 245 mm downstream of the inlet through a 3 mm slot. Mass flow rates of 0 kg/s/m and 0.36 kg/s/m, at a nozzle area ratio of 1.7, were used for test flows of air. Combustion occurred at all flow conditions with results indicating a maximum reduction in skin friction coefficient, of approximately 80% of the level measured with no injection. Skin friction reductions of approximately 60% were obtained at two other test flows. Measured heat transfer levels were found to be comparable with levels obtained without injection, for most of the experimental conditions. Hydrogen injection into a test flow of nitrogen was also trialed at all flow conditions to compare with the results obtained when fuel was injected into an air flow, in order to identify the effects of combustion. In general, the results showed that reductions in local skin friction coefficient were greater when combustion occurred than when fuel was injected and did not burn. This paper is unpublished.

School of Mining and Mechanical Engineering Departmental Report, Dec 2009

A report of the M12REST scramjet ground test program at ‘on - design’ test conditions, conduc... more A report of the M12REST scramjet ground test program
at ‘on
-
design’ test
conditions, conducted from January 1
st
to June 24
th
, 2009 in the T4 Shock Tunnel Facility at the Centre for Hypersonics, The University of Queensland, is presented. The study was performed to investigate discrepancies between numerical and experimental results of a previous 2007 test program involving the M12REST scramjet engine. Off-design results of the engine in the 2007 study demonstrated good agreement between numerical and experimental results (Suraweera and Smart, 2009). However, on-design experimental results showed a large pressure region on the forward section of the inlet that could not be replicated using a computational fluid dynamics (CFD) code (White and Morrison, 1999). The present study trialled combinations of ten distinct boundary layer trip configurations, in order to investigate whether this large pressure region was the result of local flow separation. A blunt 3 mm radius leading edge and a longer 500 mm forebody were also separately tested.
Three new ‘on
-
design’ flow conditions
(four in total) were also tested. Pressure and heat transfer measurements were taken along the engine flowpath. A description of the T4 Shock Tunnel and its operating characteristics has been given. Drawings of the proposed test model and extraneous test articles have also been provided. All 45 test runs executed during the experimental campaign have been listed, along with the corresponding flow properties for four test conditions. Mean pressure and Stanton number distributions for significant tunnel runs, illustrating the effects of various boundary layer trip and engine fuelling configurations, have been presented. The fuel used was gaseous hydrogen. Supersonic and subsonic combustion was measured at a range of fuel equivalence ratios for two of the test conditions (3 and 4). Inlet injection was found to produce separated flow regions within the inlet, and hence the fuelling scheme was discontinued. Step injection was tested successfully at a range of equivalence

3
ratios. In terms of combustion induced increases in pressure, higher levels were seen when engine was run with the M11 enthalpy test condition 4. However, the engine was able to operate in true scramjet mode with the inflow of the M12 enthalpy test condition 3. Furthermore, the engine was found to be more stable at this condition as the combustion induced pressure rise was contained by the isolator.

16th AIAA/DLR/DGLR International Space Planes and Hypersonic Systems and Technologies Conference Proceedings, Oct 22, 2009

Journal of Propulsion and Power, Jun 2009

A shock tunnel investigation of a scramjet with a rectangular-to-elliptical shape transition (RES... more A shock tunnel investigation of a scramjet with a rectangular-to-elliptical shape transition (REST) inlet and an elliptical combustor has been conducted at conditions simulating flight at Mach 8.7. The inlet was designed using a quasi-streamline-tracing method to have a design point of Mach 12.0 and operation down to Mach 6.0. The elliptical combustor began with a rearward facing step around its perimeter, and was followed by a constant area and diverging section. The flowpath was completed by a short thrust nozzle. Gaseous hydrogen fuel was injected either through multiple portholes on the intake, or a series of 48 portholes on the rearward facing step at the combustor entrance, or a combination of the two. All fuelling configurations resulted in a positive thrust coefficient at equivalence ratios above 0.3 without the use of ignition aids. Fuel injection in the intake produced robust combustion and good internal thrust levels, but led to inlet unstart at fuel equivalence ratios above 0.61. Stable, mixing limited combustion was observed for fuel injection at the step at all fuel equivalence ratios up to 1.23. Combined intake and step injection was observed to have the best performance. These experimental results demonstrate that REST scramjets, designed for access-to-space applications, can operate efficiently at conditions below the design Mach number.

46th AIAA Aerospace Sciences Meeting and Exhibit Proceedings, Jan 1, 2011

A shock tunnel investigation of a scramjet with a rectangular-to-elliptical shape transition (RES... more A shock tunnel investigation of a scramjet with a rectangular-to-elliptical shape transition (REST) inlet and an elliptical combustor has been conducted at conditions simulating flight at Mach 8.7. The inlet was designed using a quasi-streamline-tracing method to have a design point of Mach 12 and operation down to Mach 6.0. The inlet had a geometric contraction ratio of 6.61, an internal contraction ratio of 2.26, and was preceded by a 150 mm long forebody. The elliptical combustor had both a constant area and diverging section, and was followed by a short thrust nozzle to a total area ratio of 8.0. Gaseous hydrogen fuel was injected via three 4 mm diameter portholes on the intake, and through a series of 1.5 mm diameter portholes on a rearward facing step at the combustor entrance, to promote skin friction reduction as a result of boundary layer combustion. Stable combustion was observed at all fuel equivalence ratios up to 1.23, with positive values of thrust coefficient for the internal flowpath at equivalence ratios above 0.3. These experimental results demonstrate that REST scramjets, designed for access-to-space applications, can operate efficiently at conditions below the design Mach number.

Journal of Propulsion and Power, 2011

AIAA Journal, 2006

Journal of Propulsion and Power, 2018

16th AIAA/DLR/DGLR International Space Planes and Hypersonic Systems and Technologies Conference, 2009

Journal of Propulsion and Power, 2009

Journal of Propulsion & Power, 2018

International Journal of Forensic Engineering, 2014

HIFiRE 7 Flight Test Update 29 April, 2015. Recently, the HIFiRE 7 flight was launched fro... more HIFiRE 7 Flight Test Update 29 April, 2015.

The flight represented years of design and testing by a relatively small group of extremely, hardworking people. I thank you all for your efforts. Shit happens…

M.Suraweera

Journal of Propulsion and Power, Dec 2011

School of Mining and Mechanical Engineering Departmental Report, Dec 2009

16th AIAA/DLR/DGLR International Space Planes and Hypersonic Systems and Technologies Conference Proceedings, Oct 22, 2009

Journal of Propulsion and Power, Jun 2009

46th AIAA Aerospace Sciences Meeting and Exhibit Proceedings, Jan 1, 2011

A shock tunnel investigation of a scramjet with a rectangular-to-elliptical shape transition (RES... more A shock tunnel investigation of a scramjet with a rectangular-to-elliptical shape transition (REST) inlet and an elliptical combustor has been conducted at conditions simulating flight at Mach 8.7. The inlet was designed using a quasi-streamline-tracing method to have a design point of Mach 12 and operation down to Mach 6.0. The inlet had a geometric contraction ratio of 6.61, an internal contraction ratio of 2.26, and was preceded by a 150 mm long forebody. The elliptical combustor had both a constant area and diverging section, and was followed by a short thrust nozzle to a total area ratio of 8.0. Gaseous hydrogen fuel was injected via three 4 mm diameter portholes on the intake, and through a series of 1.5 mm diameter portholes on a rearward facing step at the combustor entrance, to promote skin friction reduction as a result of boundary layer combustion. Stable combustion was observed at all fuel equivalence ratios up to 1.23, with positive values of thrust coefficient for the internal flowpath at equivalence ratios above 0.3. These experimental results demonstrate that REST scramjets, designed for access-to-space applications, can operate efficiently at conditions below the design Mach number.