3,880 research outputs found
Real-time control of lean blowout and nox emissions in a turbine
Issued as final reportNational Aeronautics and Space Administratio
Higher spin polynomial solutions of quantum Knizhnik--Zamolodchikov equation
We provide explicit formulae for highest-weight to highest-weight correlation
functions of perfect vertex operators of at
arbitrary integer level . They are given in terms of certain Macdonald
polynomials. We apply this construction to the computation of the ground state
of higher spin vertex models, spin chains (spin XXZ) or loop models in
the root of unity case
Computer program to determine the irrotational nozzle admittance
Irrotational nozzle admittance is the boundary condition that must be satisfied by combustor flow oscillations at nozzle entrance. Defined as the ratio of axial velocity perturbation to the pressure perturbation at nozzle entrance, nozzle admittance can also be used to determine whether wave motion in nozzle under consideration adds or removes energy from combustor oscillations
Instanton -- Antiinstanton interaction and asymptotics of perturbation theory expansion in double well oscillator
Instanton -- antiinstanton pair is considered as a source of singularity at
the Borel plane for the ground state energy of anharmonic oscillator. The
problem of defining the short range instanton -- antiinstanton interaction
reduces to calculation of a smooth part of the Borel function, which cannot be
found without explicit calculation of several terms of ordinary perturbation
theory. On the other hand, the large order terms of perturbative expansion are
dominated by large fluctuations in the functional integral like well separated
instanton and antiinstanton.
The preasymptotics () of large order perturbation theory
contribution to the ground state energy of anharmonic oscillator was found
analytically. To this end the subleading long range asymptotics of the
classical instanton -- antiinstanton interaction, the one -- loop quantum
contribution to instanton -- antiinstanton interaction and the second quantum
correction to a single instanton density were considered.Comment: 12 pages, Latex, BUDKERINP 94-2
Spectral analysis of the free orthogonal matrix
We compute the spectral measure of the standard generators of the
Wang algebra . We show in particular that this measure has support
, and that it has no atoms. The computation is
done by using various techniques, involving the general Wang algebra ,
a representation of due to Woronowicz, and several calculations with
orthogonal polynomials.Comment: 22 pages, 4 figure
The prediction of the nonlinear behavior of unstable liquid rockets
Analytical technique for solving nonlinear combustion problems associated with liquid propellant rocket engine
Development of an analytical technique for the optimization of jet engine and duct acoustic liners
A special integral representation of the external solutions of the Helmholtz equation is described. The analytical technique developed for the generation of the optimum acoustic admittance for an arbitrary axisymmetric body is also presented along with some numerical procedures and some preliminary results for a straight duct
The prediction of nonlinear three dimensional combustion instability in liquid rockets with conventional nozzles
An analytical technique is developed to solve nonlinear three-dimensional, transverse and axial combustion instability problems associated with liquid-propellant rocket motors. The Method of Weighted Residuals is used to determine the nonlinear stability characteristics of a cylindrical combustor with uniform injection of propellants at one end and a conventional DeLaval nozzle at the other end. Crocco's pressure sensitive time-lag model is used to describe the unsteady combustion process. The developed model predicts the transient behavior and nonlinear wave shapes as well as limit-cycle amplitudes and frequencies typical of unstable motor operation. The limit-cycle amplitude increases with increasing sensitivity of the combustion process to pressure oscillations. For transverse instabilities, calculated pressure waveforms exhibit sharp peaks and shallow minima, and the frequency of oscillation is within a few percent of the pure acoustic mode frequency. For axial instabilities, the theory predicts a steep-fronted wave moving back and forth along the combustor
Development of an analytical technique for the optimization of jet engine and duct acoustic liners
A new method was developed for the calculation of optimum constant admittance solutions for the minimization of the sound radiated from an arbitrary axisymmetric body. This method utilizes both the integral equation technique used in the calculation of the optimum non-constant admittance liners and the independent solution generated as a by product of these calculations. The results generated by both these methods are presented for three duct geometries: (1) a straight duct; (2) the QCSEE inlet; and (3) the QCSEE inlet less its centerbody
The prediction of nonlinear longitudinal combustion instability in liquid propellant rockets
An analytical technique was developed to solve nonlinear longitudinal combustion instability problems. The analysis yields the transient and limit cycle behavior of unstable motors and the threshold amplitude required to trigger a linearly stable motor into unstable operation. The limit cycle waveforms were found to exhibit shock wave characteristics for most unstable engine operating conditions. A method of correlating the analytical solutions with experimental data was developed. Calculated results indicate that a second-order solution adequately describes the behavior of combustion instability oscillations over a broad range of engine operating conditions, but that higher order effects must be accounted for in order to investigate engine triggering
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