On Discharge Capability and Swirl Generation Capability of Swirler
Fuel-air mixing process is one crucial key to determine the performance of a diesel engine, and it is crucially determined by swirl within cylinder. For generating strong swirl within the cylinder, a new device named swirler has been propounded. In the present paper, four swirlers have been employed to experimentally study the performance on both the discharge capability and swirl generation capability. The steady flow test bench was employed to study the both capabilities in macro-level. Then, a water-flow model was employed to observe the flow motion within the cylinder via the tested swirlers. The results indicate that adopting swirler with a suitable configuration could generate strong swirl without remarkable discharge capability loss.
An experimental investigation of two different methods for swirl induction in a multivalve engine
Abstract This paper describes an experimental investigation aimed at comparing the swirl effect induced by unbalancing the mass flow through the two intake ports of a multivalve engine head using two different methods: the first one reduced the curtain area of one of the intake valves [different lifts (DL) method]; the second one adopted a sluice-gate-shaped valve, installed upstream of the intake valves [swirl control valve (SCV) method] in order to cause a pressure drop. A steady-flow test rig (equipped with instrumentation for the discharge coefficient and swirl intensity measurement) was realized in order to compare and evaluate the results of both methods and determine their respective validity and limitations; the procedures used for both experimental methods are discussed in detail. The flow characteristics were analysed through changes of lift difference or SCV position; it was found that both DL and SCV methods are effective in swirl induction but the DL mechanism, acting on the valve curtain area, is more effective in flow unbalancing between intake ports, since the flowrate depends linearly on the curtain area. The SCV method, instead, controls the port flowrate, inducing a localized pressure drop, whose intensity depends on the flow velocity in a non-linear manner. For this reason the SCV method can achieve strong swirl intensity only with high obstruction levels, in a narrow regulation window close to full-obstruction conditions.
Turbulent mass transfer at free, gas-liquid interfaces, with applications to open-channel, bubble and jet flows
Abstract Gas absorption by a turbulent liquid in the absence of external (gas-imposed) interfacial shear is discussed. The primary tool used is dimensional analysis. Two distinct mass-transfer regimes, associated with energy-containing and energy-dissipating turbulent motions, are identified. Relationships are obtained for each regime, and a criterion, based on the turbulence Reynolds number, is determined for the applicability of each. The mass-transfer model is evaluated for four flow situations for which turbulence data are either available or can be estimated (open-channel flow with and without grid-produced turbulence, bubble flow, and jet flow).