2D MHD Simulations of the State Transitions of X-Ray Binaries Taking into Account Thermal Conduction

Thermal conduction plays an important role in bimodal accretion flows consisting of high-temperature flow and cool flow, especially when the temperature is high and/or has a steep gradient. For example, in hard-to-soft transitions of black hole accretion flows, thermal conduction between the high-temperature region and the low-temperature region is appropriately considered. We conducted two-dimensional magnetohydrodynamic (MHD) numerical simulations considering anisotropic heat conduction to study condensation of geometrically thick hot accretion flows driven by radiative cooling during state transitions. Numerical results show that the intermediate region appears between the hot corona and the cool accretion disk when we consider heat conduction. The typical temperature and number density of the intermediate region of the 10 Mo black hole at 10Rg (Rg = 3.0 x 106 cm is the Schwarzschild radius) are 4 x 1010 < T [K] < 4 x 1012 and 5 x 1015 < n [cm-3] < 5 x 1717, respectively. The thickness of intermediate region is about half of the radius. By comparing two models with or without thermal conduction, we demonstrate the effects of thermal conduction.

Numerical Simulation of Fluid-Structure Interaction in SRM under Cold-Flow Impact

The process of impacting adherent casting solid rocket motor under cool-flow impact was simulated using two-way fluid-solid coupling method by ANSYS workbench14.0. In order to truly reflect the interaction between the establishment of the flow field in the cool air impact process and the SRM grain, the impact pressure to the SRM grain was provided with reference to the structure of the shock tube. The process of the establishment and spread of the flow field pressure was simulated, according to the grain deformation under the cool air impact, the maximum deformation position of the grain was determined. The relationship between the amount of grain deformation and flow field pressure gradient was summed up by observing the law of flow field pressure distribution along the axial coupling surface.

In-Scale and Up-Scale Full Turbine Stage Measurements as a Support for Small Turbine Units Development

This paper summarizes experimental results of an aerodynamic performance study carried out on two full stage turbine test rigs. The stage under investigation was designed as a gas generator turbine for a small jet engine produced by PBS (the TJ100 engine with thrust of 1100 N and turbine tip diameter of 141 mm). The investigation was carried out alternatively on two full-stage test rigs (in-scale and scaled-up) integrated into a cool flow closed-loop wind tunnel located at VZLU. Firstly, the in-scale testing, focusing on an overall stage performance measured by means of a hydraulic dynamometer was arranged. Furthermore, some time-averaged flow field parameters in terms of total pressure, velocity and angles were acquired along the channel height upstream and downstream of the stage. The flow path authenticity and construction simplicity were strictly followed during the rig design phase and therefore original parts of the engine were mostly used. Then, the verification of results was performed with the stage scaled-up by factor 2.27. The overall stage performance was measured and compared with results of the in-scale measurement. Moreover, detail unsteady flow field measurement at the rotor exit was performed. Time-resolved data were analysed in order to study the influences of the stage load on the stage performance.

LBO Performance Comparison Between Two Combustors With Different Swirl Cups

Lean Blowout (LBO) performance is very important to the aero and ground gas turbine combustors. A typical liquid-fueled gas turbine combustor is the one with swirl cup dome which plays an important role to the LBO. The swirl cup dome comprises swirlers and nozzle usually. The swirlers serve to generate a toroidal flow reversal that entrains and recirculates a portion of the hot combustion products to mix with the incoming fresh air and fuel, so it makes the recirculation region the sustainable source of ignition. Swirlers in present study generally are two or three stages, and the nozzle takes different atomization styles, such as pressure-swirl atomization, prefilming and airblast atomization. Different swirlers matching various nozzles form all kinds of swirl cup domes, and each swirl cup dome of combustor would have different LBO performance and other combustion properties resulting from its structure characteristics. The flow flux arrangement and spray distribution are the two important factors to determine the combustor performance. Two combustor dome test rigs were investigated, of which one comprises with three air swirlers and a fuel prefilming nozzle (dome A), and the other is composed of two air swirlers and a fuel pressure nozzle (dome B). Tests were conducted to get the LBO fuel air ratio at atmospheric pressure. To explain the experimental results, numerical simulations were performed for cool flow fields of two combustors, also the cold flow field and spray of the two combustors’ dome downstream were measured by PDA with water instead of kerosine. The flame pictures near LBO were taken. The preliminary results indicated that the combustor with dome A had better spray uniformity than the one with dome B, but it had a little worse LBO performance. The air flow mass percentage of the inner swirler of dome A should decrease to some extent in order to establish a lower pressure region at the outlet of dome A, which would be helpful to decrease the LBO fuel air ratio and so as to improve the LBO performance. The two domes had their own advantages, and if the benefits of both were integrated, it was possible to design a better swirl cup dome.

Regenerator Effectiveness During Transient Operation

The transient response of regenerators is considered. The time required for regenerators to reach steady-state effectiveness is determined. Theoretical results are presented. Also, experimental results that confirm the theory are presented. It is concluded that the time required for a regenerator to reach steady-state effectiveness is τss∼NTU1+hA′1+As′CRAT4As′1-SCkN×ρcDH2RNuH1-pp This expression indicates how regenerator cores can be designed for fast effectiveness response. In dimensionless form, τXss*∼1 where τXss* is the greater of the cool-flow and warm-flow heat-capacity rates, times τss, divided by the heat capacity of the core material. This expression gives a general method for calculation of the effectiveness-response time of regenerator cores. The dimensionless response time is nearly constant with variations in regenerator system-parameter values. Also, for sufficiently high dimensionless core-rotation rates, the dimensionless response time is independent of dimensionless core-rotation rate.