Hot-jet ignition of a combustible mixture has application in internal combustion engines, detonation initiation, and wave rotor combustion. Numerical predictions are made for ignition of combustible mixtures using a traversing jet of chemically active gas at one end of a long constant-volume combustor (CVC) with an aspect ratio similar to a wave rotor channel. The CVC initially contains a stoichiometric mixture of ethylene or methane at atmospheric conditions. The traversing jet issues from a rotating prechamber that generates gaseous combustion products, assumed at chemical equilibrium for estimating major species. Turbulent combustion uses a hybrid eddy-breakup model with detailed finite-rate kinetics and a two-equation k-x model. The confined jet is observed to behave initially as a wall jet and later as a wall-impinging jet. The jet evolution, vortex structure, and mixing behavior are significantly different for traversing jets, stationary centered jets, and nearwall jets. Pressure waves in the CVC chamber affect ignition through flame vorticity generation and compression. The jet and ignition behavior are compared with high-speed video images from a prior experiment. Production of unstable intermediate species like C 2 H 4 and CH 3 appears to depend significantly on the initial jet location while relatively stable species like OH are less sensitive.

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A wave-rotor pressure-gain combustor (WRPGC) ideally provides constant-volume combustion and enables a gas turbine engine to operate on the Humphrey-Atkinson cycle. It exploits pressure (both compression and expansion) waves and confined propagating combustion to achieve pressure rise inside the combustor. This study first presents thermodynamic cycle analysis to illustrate the improvements of a gas turbine engine possible with a wave rotor combustor. Thereafter, non-steady reacting simulations are used to examine features and characteristics of a combustor rig that reproduces key features of a WRPGC. In the thermodynamic analysis, performance parameters such as thermal efficiency and specific power are estimated for different operating conditions (compressor pressure ratio and turbine inlet temperature). The performance of the WRPGC is compared with the conventional unrecuperated and recuperated engines that operates on the Brayton cycle. Fuel consumption may be reduced substantially with WRPGC introduction, while concomitantly boosting power. Simulations have been performed of the ignition of propane by a hot gas jet and subsequent turbulent flame propagation and shock-flame interaction.

The problem of wave propagation in an infinite, homogeneous, transversely isotropic polygonal cross-sectional cylinder is studied using Fourier expansion collocation method, within the framework of linearized, three dimensional theory of thermoelasticity. Three displacement potential functions are introduced, to uncouple the equations of motion and the heat conduction. The frequency equations are obtained for longitudinal and flexural (symmetric and antisymmetric) modes of vibration and are studied numerically for triangular, square, pentagonal and hexagonal cross-sectional Zinc cylinders. To study the convergence, the non-dimensional wave numbers are obtained by Fourier Expansion Collocation Method and Finite Element Method and they are compared. The computed non-dimensional wave numbers are presented in the form of dispersion curves.

In this study, the performance of regenerative cooling system for large expansion ratio rocket engines (Ae/At ∼ 100) is investigated numerically. During combustion and gas expansion, the walls of the combustion chamber and the rocket nozzle are exposed to high temperature gas (∼3500 K), which can ultimately lead to structural failure. Therefore, to protect the hardware from thermal failure, a regenerative cooling system for a cryogenic rocket engine that uses fuel (liquid hydrogen (LH)) or oxidizer (liquid oxygen (LOX)) as the cooling medium is considered. Three-dimensional simulations have been performed for both constant and variable fluid properties. The influence of the thermal properties of the material and thickness of the nozzle wall on conductive heat transfer has also been investigated. The effect of radiative heat transfer when there is no regenerative cooling system has been analyzed. In addition, heat transfer enhancement for different turbulence models and the influence of coolant used (both the fuel and oxidizer) is also investigated. It is evident from the results that a properly designed regenerative cooling system can maintain the hot side wall at a temperature well below the melting point of the wall material, which ensures the protection of nozzle hardware from thermal failure. Also, the predicted pressure drop is found to be 0.7 bar, which meets the design requirement. Numerical predictions are validated with the data available in literature.