NASA Langley Parametric Scramjet Engine

The NASA Langley Strutless Parametric Scramjet Engine is a heat-sink, subscale scramjet engine, approximately six feet long and seven inches high, initially designed and built in the early 1980's to allow testing of a wide variety of inlet and combustor geometric parameters. In order to achieve this parametric ability, the engine has parallel top (body) and bottom (cowl) plates, between which sectional contoured sidewalls are clamped. Both of these plates are slotted to allow the sidewall sections position to be varied with respect to the model centerline. By changing sidewall sections and/or their position, a wide range of engine area distributions can be achieved, including geometric steps. Various inlet sidewalls with different sidewall sweep and compression angles, combustor sidewalls with different lengths, divergence angles and fuel injector patterns, and other various components are available. One noteworthy component of the model is a set of throttle "doors" which mount at the rear of the engine between the top and bottom plates. These doors may be used as a mass flow meter to determine the captured airflow of the inlet, to back pressure the combustor and inlet in cold flow aerodynamic tests, or used as a second geometric minimum for fueled ramjet tests. Most of the components are fabricated from oxygen-free high conductivity copper (OFHC), for its heat sink capability, and are uncooled. The only actively cooled component is the cowl leading edge. By removing the bottom or cowl plate, sections may be repositioned, moved or replaced fairly easily without the necessity of completely dismantling or removing the engine from the facility. 

The top plate is hung from a fixed system of support rails inside the test cabin of the facility from four flex beams, allowing for axial movement of the model. Rows of holes where the support rails bolt to the front and back walls of the test cabin allow the vertical position of the model to be easily changed, by supporting the model on a set of jacks and repositioning the support rails. As a consequence of the high total temperatures (~2600 R) generated by the facility, it is necessary to shield the instrumentation external to the engine and the fuel tubing from the hot flow of the test gas. Copper sheeting 1/8th inch thick was used to hand form shielding around the outside of the sidewall sections. Care was taken to minimize the external drag of the shields, while allowing sufficient flexibility and space between the sheeting and the engine to accommodate any model configuration or fuel system connection. For tests without facility boundary layer ingestion, it was necessary to not only shield the instrumentation on the top plate, but also to divert the flow which went over the top plate around the front shield and back down into the main portion of the freejet and into the catch cone. 

Excerpted from:   NASA Lanley Parametric Engine Studies, Volume I - Overall Test Program and Inlet Test Series Results  (U), by E. G. Ruf and J. A. Young, NASA CR - 201702, July, 1997.

	The original Parametric Engine tested in the 1980's.
	The Swept Strut variant of the Parametric Engine shown partially assembled in the CHSTF test cabin. The normally aft swept inlet sidewalls have been replaced with sidewalls with unswept leading edges, and a center strut with a stepped leading edge. The goal of this inlet design was to improved inlet mass capture and flow uniformity while still allowing for acceptable inlet starting characteristics.
	The Opposite Sweep variant of the Parametric Engine shown in the CHSTF test cabin. The right-hand inlet sidewall incorporates a 45 deg. forward swept leading edge in contrast to the left-hand inlet sidewall which incorporates a 30 deg. aft swept leading edge.
	The Parametric Engine with the variable exit area throttle doors installed in preparation for mechanical back pressure and fueled ramjet tests in the CHSTF. The facility nozzle extension is installed. Model shielding has been left off to show instrumentation and fuel manifold connectors.

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Last updated: Thursday, August 14, 2008 14:48