Thermal Management in a Scramjet-Powered Hypersonic Cruise Vehicle

Due to the large aerodynamic heating at high Mach numbers, Thermal Protection System (TPS) design considerations are critical for hypersonic vehicles, and engineers seek to incorporate heating constraints earlier in the design process. Preliminary design studies necessitate the use of low-fidelity tools for design and optimization purposes. A number of low-fidelity models exist in the open literature for full scramjet-powered hypersonic vehicles, and some of these models incorporate passive TPS models (where the material on the outer surface of the vehicle absorbs energy, preventing the energy from seeping into the structure). However, none of the models incorporate an active TPS (where the fuel is used as a coolant in the heat exchangers surrounding the engine) in addition to a passive TPS model. In the present work, active and passive TPS models were added to a full scramjet-powered vehicle model developed at the University of Michigan. For a trimmed hypersonic waverider vehicle, computations were performed to investigate the operability limits that occur due to excessive heating of the external surface, including the nose region and combustor wall region, and the heating of the hydrogen fuel, which is used as coolant. The operability limits computed include the maximum values of flight Mach number, dynamic pressure and the flight time before one of several temperature limits is exceeded. To compute operability limits, efficient aerodynamic heating and TPS models were added to the reduced order model MASIV which contains an advanced combustion analysis and a trim code. Results show the effects of varying the thickness of the three-layer thermal protection system that consists of a radiation shield, an insulation layer and the vehicle wall. Regarding the active cooling system, the heat exchanger heat flux is modeled assuming the hydrogen fuel is a supercritical fluid and lookup tables for the fuel properties at supercritical conditions are incorporated. Recirculating the heated fuel back into the fuel tank raises the fuel temperature and decreases the fuel density (increasing the volume); the analysis computes the maximum flight time before the fuel tank temperature and fuel volume exceed acceptable limits. By extending the active cooling system to a small region of the inlet (instead of just around the isolator and combustor), the operability limits are increased from a flight Mach number of 7.3 to 8.6. Optimizations for the active and passive thermal protection systems are performed. For the passive thermal protection system, the optimal insulation thickness distributions are found which minimize the insulation mass while still ensuring that the titanium skin remains below its failure temperature. At a 40 minute cruise at Mach 6 and 80 kPa free-stream dynamic pressure, the optimized insulation mass is 74 percent less than the initial condition. For the active TPS, the parameters impacting the final fuel temperature are optimized to find the minimum fuel temperature at the end of a 40 minute cruise. The coolant mass flow rate is one parameter considered in the active cooling system optimization. For cruise at Mach 8 and 60 kPa free-stream dynamic pressure, the change in coolant mass flow rate over time is first represented as a linear decrease and is later represented by a quadratic one. It is found the final fuel temperature in the quadratic case is 19 percent less than the linear case.PHDAerospace EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/144038/1/cmarley_1.pd

A numerical study of novel drag reduction techniques for blunt bodies in hypersonic flows

Numerical simulations of a full three-dimensional hemispherical body in hypersonic flow are conducted and innovative techniques involving forward injection of gas from the stagnation point of the sphere are investigated; techniques include annular (ring) and swirled injection both with and without upstream energy deposition. Objectives of the analysis are the assessment of 1) drag reductions achieved on the blunt body (including the detrimental drag effect caused by the forward-facing injection itself) and 2) stability characteristics of the jet. Studies are conducted at free-stream Mach numbers of 10 and 6.5 at standard atmospheric conditions corresponding to 30 km altitude. While centered forward injection without upstream energy deposition is confirmed to be highly unstable either with or without swirl, annular ring injection exhibits a stabilizing influence on the jet. Energy deposition upstream of the body is shown to significantly enhance stability and penetration of the forward injection jet for all techniques --Abstract, page iii

A comparison of design and model selection methods for supersaturated experiments

Various design and model selection methods are available for supersatu-rated designs having more factors than runs but little research is available ontheir comparison and evaluation. In this paper, simulated experiments areused to evaluate the use of E(s2)-optimal and Bayesian D-optimal designs,and to compare three analysis strategies representing regression, shrinkageand a novel model-averaging procedure. Suggestions are made for choosingthe values of the tuning constants for each approach. Findings include that(i) the preferred analysis is via shrinkage; (ii) designs with similar numbersof runs and factors can be effective for a considerable number of active effectsof only moderate size; and (iii) unbalanced designs can perform well. Somecomments are made on the performance of the design and analysis methodswhen effect sparsity does not hol

Cassini Ring Seismology as a Probe of Saturn's Interior I: Rigid Rotation

Seismology of the gas giants holds the potential to resolve long-standing questions about their internal structure and rotation state. We construct a family of Saturn interior models constrained by the gravity field and compute their adiabatic mode eigenfrequencies and corresponding Lindblad and vertical resonances in Saturn's C ring, where more than twenty waves with pattern speeds faster than the ring mean motion have been detected and characterized using high-resolution Cassini Visual and Infrared Mapping Spectrometer (VIMS) stellar occultation data. We present identifications of the fundamental modes of Saturn that appear to be the origin of these observed ring waves, and use their observed pattern speeds and azimuthal wavenumbers to estimate the bulk rotation period of Saturn's interior to be $10{\rm h}\, 33{\rm m}\, 38{\rm s}^{+1{\rm m}\, 52{\rm s}}_{-1{\rm m}\, 19{\rm s}}$ (median and 5%/95% quantiles), significantly faster than Voyager and Cassini measurements of periods in Saturn's kilometric radiation, the traditional proxy for Saturn's bulk rotation period. The global fit does not exhibit any clear systematics indicating strong differential rotation in Saturn's outer envelope.Comment: 19 pages, 6 figures, 3 tables, accepted to ApJ; a bug fix improves the fit, predicts faster bulk spin periods (Figure 4) and virtually eliminates evidence for strong radial differential rotation (Figure 5

Modeling an Active and Passive Thermal Protection System for a Hypersonic Vehicle

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143043/1/6.2017-0118.pd