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Segmented flow is an approach that improves upon the speed in which screening, optimization, and libraries can be conducted in flow chemistry. Segmented flow uses a "Plug Flow" approach where specific volumetric experimental mixtures are created and then injected into a high-pressure flow reactor. Diffusion of the segment (reaction mixture) is ...
Chemical kinetics experiments can then be carried out in a pump–probe fashion, using a laser to initiate the reaction (for example, by preparing one of the reagents by photolysis of a precursor), followed by observation of that same species (for example, by laser-induced fluorescence) after a known time delay.
This is particularly valid in supersonic conditions, namely for flow velocities larger than the speed of sound in the fluid considered. All typical features of supersonic flows are affected by non-ideal thermodynamics, resulting in both quantitative and qualitative differences with respect to the ideal gas dynamics.
Choked flow is a limiting condition where the mass flow cannot increase with a further decrease in the downstream pressure environment for a fixed upstream pressure and temperature. For homogeneous fluids, the physical point at which the choking occurs for adiabatic conditions is when the exit plane velocity is at sonic conditions; i.e., at a ...
These experiments enable one to artificially "enter" the reaction at any point, as the initial concentrations of one experiment (the intercepting reaction) are chosen to map directly onto the anticipated concentrations at some intermediate time, t, in another (the parent reaction). One would expect the reaction progress, described by the rate ...
The gas flow rate is constant (i.e., steady) during the period of the propellant burn. The gas flow is non-turbulent and axisymmetric from gas inlet to exhaust gas exit (i.e., along the nozzle's axis of symmetry). The flow is compressible as the fluid is a gas. As the combustion gas enters the rocket nozzle, it is traveling at subsonic velocities.
A supersonic flow that is turned while there is an increase in flow area is also isentropic. Since there is an increase in area, therefore we call this an isentropic expansion. If a supersonic flow is turned abruptly and the flow area decreases, the flow is irreversible due to the generation of shock waves.
The pulsed quenched-flow method, introduced by Alan Fersht and Ross Jakes [14], eliminates the need for a long reaction tube. In this approach, the reaction is initiated as in a stopped-flow experiment, but quenching is performed using a third syringe, which delivers the quenching agent at a precise, pre-set time after initiation.