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Optical emission spectroscopic (OES) measurements are acquired by collecting absolute line and continuum emission from a hydrogen/methane plasma (300 sccm H2, 3 sccm CH4, 40–70 torr, 1600–3200 W) used for diamond deposition. The experimental results are used in tandem with numerical modeling to infer plasma parameters of interest. Numerical solutions for a microwave chemical vapor deposition (CVD) reactor are generated by coupling solutions of the Boltzmann equation and the electron energy equation to a collisional-radiative model (CRM). Results indicate that the electron-neutral free-free emission, which depends strongly on neutral density, electron density, and electron temperature, is the dominant source of continuum emission. All numerical solutions are found to be inconsistent with the experimentally measured continuum emission. A meaningful interpretation, however, is possible if the electron-H2 cross-section, used for calculating electron-neutral free-free continuum emission, is increased by between 4 and 20 above the momentum cross-section value. We believe that such an increase is justified because of enhanced energy exchange in electron-molecule interactions.

A numerical study has been conducted to assess the viability of a new sealing mechanism for gas and steam turbines. This new static-to-rotating sealing mechanism is mounted on flexible legs which permit radial movement and is designed to take advantage of the hydro-dynamic pressure forces, which result from fluid leaking around the seal, to maintain an ideally small and constant clearance. Relatively simple seal geometries have been numerically tested to find an optimal shape. These results indicate that a substantial sealing improvement (between two and four times less leakage) relative to a labyrinth seal is possible. Although these results show that a brush seal is more effective than the present seal, the present seal is designed to operate in high-speed and high-temperature environments in which the brush seal would degrade.

A self-consistent pseudo-one-dimensional (zero-dimensional with diffusion) plasma model and optical emission spectroscopy are used in tandem to investigate the power coupling efficiency for a pure argon microwave plasma. The self-consistent model is developed by simultaneously solving the Boltzmann equation (for the non-Maxwellian electron energy distribution function), electron number density balance equation, energy balance equation, and the excited state rate equations in a collisional-radiative model. The absolute line emission intensity is utilized to obtain number densities of three argon excited states [4p (7147 A), 5p (4300 A), and 5d (6043 A)] in a 5 Torr, 680 W input power argon discharge. The absolute continuum emission from the plasma was utilized to determine the maximum electron number density. A comparison of the numerical and experimental data indicates that only 2%–5% (10–35 W) of the input power is deposited in the plasma. A control volume heat transfer analysis validates this claim. The...