Mach 4 Performance of a Fixed-Geometry Hypersonic Inlet with Rectangular-to-Elliptical Shape Transition
Wind-tunnel testing of a hypersonic inlet with rectangular-to-elliptical shape transition has been conducted at Mach 4.0. These tests were performed to investigate the starting and back-pressure limits of this fixed-geometry inlet at conditions well below the Mach 5.7 design point. Results showed that the inlet required side spillage holes in order to self-start at Mach 4.0. Once started, the inlet generated a compression ratio of 12.6, captured almost 80% of available air and withstood a back-pressure ratio of 30.3 relative to tunnel static pressure. The spillage penalty for self-starting was estimated to be 4% of available air. These experimental results, along with previous experimental results at Mach 6.2 (Smart, M.K, “Experimental Testing of a Hypersonic Inlet with Rectangular-to-Elliptical Shape Transition”, Journal of Propulsion and Power, Vol. 17, No. 2, pp 276-283, 2001)indicate that fixed-geometry inlets with rectangular-toelliptical shape transition are a viable configuration for airframe-integrated scramjets that operate over a significant Mach number range.
Supersonic combustion ramjet missile
During the period of 1962-1978, the Applied Physics Laboratory of Johns Hopkins University developed the technology for a family of missiles named SCRAM for use as fleet defense weapons. SCRAM is the acronym for supersonic combustion ramjet missile. The development work began with the conceptual design of two missile configurations and calculations of the expected performance for a variety of missions to provide defense for the surface fleet. A novel class of multimodule fixed-geometry hypersonic inlets was designed and wind-tunnel models were built and tested at Mach numbers of 4-10 at angles of attack up to 15 deg. Injector and combustor development was carried out in direct connect test apparatus. Considerable effort was directed to the development and testing of a wide variety of storable, reactive liquid fuels including boranes and aluminum alkyls. Many new testing techniques and diagnostic instruments were developed that are still key elements of scramjet test operations. The program culminated with the testing of the entire engine in free jets at Mach numbers of 57.3 and the design of a family of revised vehicle configurations that could exploit the full capability of the performance observed in the ground test program. This article presents the highlights of the technology program and references recently released documents.
Effects of reservoir volume on performance of pulse tube cooler.
A pulse tube cooler has the advantages of long-life and low-vibration over conventional cryocoolers such as G-M and Stirling coolers because of the absence of moving parts at low temperature. On the other hand, the combination of a reservoir and orifice is indispensable to optimize the performance of pulse tube coolers. In order to make the pulse tube cooler compact for practical applications, the volume of reservoir should be minimized. This paper analyzes the effects of the reservoir volume on the thermodynamic performance of various components in a simple orifice and a double-inlet pulse tube cooler by combining a linearized model with a thermodynamic analysis. Expressions of entropy production for those components are presented. The results show that the reservoir volume has a significant influence on the entropy production in the various components when the reservoir to pulse tube volume ratio is smaller than about 5. The ratio is important to determine the minimum reservoir volume for a pulse tube cooler. Optimum settings for a double-inlet pulse tube cooler are also discussed.