Flow establishment in a generic scramjet combustor

Jacobs, Peter A.; Rogers, R. C.; Weidner, E. H.; Bittner, Robert D.

doi:10.2514/3.23566

Cited by 45 publications

(26 citation statements)

References 15 publications

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“…In previous studies the model establishment time after the passing of the starting pulse of gas has been correlated with the required number of flow lengths based on a characteristic length and velocity (see, for example, Davies and Bernstein, 1969;East et al, 1980;Jacobs et al, 1992;Lee and Lewis, 1993). For the current work an additional constraint was the requirement that 24 Height restictions imposed by the force balance prevented the model from being raised higher than shown in Figure 3.18.…”

Section: Test Time Determinationmentioning

confidence: 99%

An experimental investigation of an airframe integrated three-dimensional scramjet engine at a Mach 10 flight condition

Doherty¹

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The University of Queensland in 2014 school of mechanical and mining engineering centre for hypersonics abstract Realisation of the dream of airbreathing access-to-space requires the development of a scramjet engine that produces sufficient net thrust to enable acceleration over a wide Mach number range. With engines that are highly integrated with the airframe, the net performance of a scramjet powered vehicle is closely coupled with the vehicle attitude and is difficult to determine only from component level studies. This work investigates the influence of airframe integration on the performance of an airframe integrated scramjet through the measurement of internal pressure distribution and the direct measurement of the net lift, thrust and pitching moment using a three-component stress wave force balance. The engine chosen as the basis for this study was the Mach 12 rectangularto-elliptical shape-transition (m12rest) scramjet that was developed by Suraweera and Smart (2009) as a research engine for access-to-space applications. The inlet and combustor flowpath were integrated with a slender 6°wedge forebody, streamlined external geometry and three dimensional thrust nozzle. The scale of the engine was chosen so that the entire engine would fit within the core-flow diamond (bi-conic) produced by a Mach 10 facility nozzle. The Mach 10b facility nozzle was chosen because it is the largest nozzle current in use with the t4 Stalker Tube and because the offdesign performance of a scramjet engine is of interest for access-to-space vehicles that must accelerate over a range of Mach numbers.Freejet experiments were conducted within the t4 Stalker Tube. Two trueflight Mach 10 test conditions were used: a high pressure test condition that replicated flight at a dynamic pressure of 48 kPa and a low pressure test condition that replicated flight at a dynamic pressure of 28 kPa. Scaling of the test conditions according to the established binary scaling law was not completed due to facility operational limits.The engine featured two fuel injection stations from which gaseous hydrogen was injected. The first injection station was partway along the length of the inlet while the second injection station was at the start of the combustor behind a rearward facing circumferential step. In addition to investigating inlet-only and step-only injection, a combined scheme where 68 % of the fuel was injected from the step station and 32 % from the inlet station was also investigated.To support the analysis of the experimental results, numerical simulations of the engine with no fuel injection were conducted using the nasa code vulcan. Analysis of the simulations show that the mass capture ratio with respect to the projected inlet area is approximately 60 % at each test condition. The simulations also show that spillage of flow from the slender forebody accounts for just 12 % of the flow through the projected iii inlet area, a small but non-negligible fraction. By integrating the engine surface forces, the drag coefficient with respect ...

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Section: Test Time Determinationmentioning

confidence: 99%

An experimental investigation of an airframe integrated three-dimensional scramjet engine at a Mach 10 flight condition

Doherty¹

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“…Shock-heated , and a recompression shock (G = 140). Of these features studied, all will reach steady state well within the test time of this study with the longest, the internal flowpath boundary layer, having a conservatively estimated establishment time of 2.2 ms (Jacobs et al, 1990). The establishment of a precombustion shock train, characteristic of dual-mode combustion within a scramjet, however, has not been explicitly studied in this manner and its establishment time is not well characterized.…”

Section: Testing Scramjets In Impulse Facilitiesmentioning

confidence: 99%

“…The establishment of a precombustion shock train, characteristic of dual-mode combustion within a scramjet, however, has not been explicitly studied in this manner and its establishment time is not well characterized. It is expected that the establishment time of a precombustion shock train is greater than that of the flow structures studied by Jacobs et al (1990) because there is dynamic feedback between the separation and resulting shock structure in the isolator and the pressure rise generated by combustion downstream in the combustor.…”

Section: Testing Scramjets In Impulse Facilitiesmentioning

confidence: 99%

“…By calculating the establishment time of each flow feature expected within the scramjet, the starting time for the internal flowpath can be estimated. The flow feature which took the longest to start was the internal boundary layer which exhibits a starting time of 2.2ms (Jacobs et al, 1990). Here the velocity at the inlet throat was used as the characteristic velocity and the length of the model was used for the characteristic length for the above The end of the test time is determined either by the first of either the arrival of driver gas contamination or an unacceptable drop in pressure, taken here as 10%.…”

Section: Nozzle Starting Process and Test Time Determinationmentioning

confidence: 99%

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Test Program for a Dual-mode Scramjet

Smayda¹

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Since flow at hypersonic Mach numbers (M≥5) behaves very differently from flow at subsonic or supersonic Mach numbers, the testing of hypersonic engines involves challenges not encountered in engine testing for flight in other regimes. For hypersonic Mach numbers, thermal, chemical, radiative, and ablative effects become important.Energy and heat transfer considerations make continuous-run, full scale testing at hypersonic Mach numbers difficult or impossible. While facilities have been devised specifically to study certain aspects of hypersonic flight, no single facility has the ability to simulate all the flow conditions that a hypersonic vehicle or engine may encounter.Flight can be considered the ultimate test of a hypersonic vehicle or engine because no facility effects are present. It is often the case, however, that budgetary, thermal, structural, or other logistical limitations restrict the range of diagnostics available for flight vehicle testing. Flight programs also incur significant risk that is generally not present or is significantly reduced for ground testing programs. If an unguided rocket is used to minimize cost, the likelihood that the payload will achieve the desired test conditions decreases. If a reactive control system is utilized to increase the likelihood that the payload will achieve the desired test conditions, both complexity and cost increase significantly. As such, flight programs are nearly always augmented with significant ground testing to reduce risk and confirm engine operability limits. Often a range of wind tunnels is used in order to resolve the inherent deficiencies of any one type of ground test facility. Two common shortcomings of hypersonic test facilities are the short test time associated with shock-heated facilities and the contaminated or vitiated test gas associated with combustion-heated facilities.

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“…The instrumentation locations between the freejet and direct-connect test articles were designed to coincide as much as possible, and were for the most part in identical locations. In the UVaSCF, data acquisition of flowpath This is more than adequate for the achievement of steady state in a DMSJ [19,20]. However as described elsewhere [7], the flight design located the flowpaths on separate sides of the payload with separate forebodies.…”

Section: Ii) Experimental Techniquementioning

confidence: 99%

Comparison of a Direct-Connect and Freejet Dual-Mode Scramjet

Steva

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Flow establishment in a generic scramjet combustor

Abstract: " .'.,r.r-¢.de .c -.

Cited by 45 publications

References 15 publications

An experimental investigation of an airframe integrated three-dimensional scramjet engine at a Mach 10 flight condition

An experimental investigation of an airframe integrated three-dimensional scramjet engine at a Mach 10 flight condition

Test Program for a Dual-mode Scramjet

Comparison of a Direct-Connect and Freejet Dual-Mode Scramjet

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