Reference data generation of spray characteristics in relation to large 2-stroke marine diesel engines using a novel spray combustion chamber concept

Abstract

The availability of appropriate reference data for combustion in large 2-stroke marine diesel engines is a prerequisite for the further development of Computation Fluid Dynamics tools. In order to enable the acquisition of such data at relevant physical dimensions (bore) and operational parameters (pressure, temperature), including flow characteristics (swirl) and the low fuel qualities involved, a novel experimental test facility has been realized. The core element is a disk-shaped constant volume spray combustion chamber of diameter 500 mm with peripheral injection into a swirl flow. Thermo- and fluid dynamic conditions at start of injection similar to those in real engines are achieved by feeding the chamber via inclined intake channels with pressurized and heated process gas provided by a pressure vessel/heat regenerating system. The chamber design includes comprehensive possibilities for optical access as well as various injector arrangement options and the injection system is prepared for running on typical marine fuels. Reference data for the fuel spray propagation has been acquired by means of shadow-imaging measurements: This involved the variation of key parameters such as gas pressure and temperature (up to 9 MPa, 930 K), number of injector orifices (1/2/5) and the spray orientation (10 deg counter to 40 deg co-swirl) relative to the gas flow. The spray propagation data collected at conditions representative of the operation of large 2-stroke marine diesel engines contributes to a better understanding of the underlying phenomena and enable the validation of simulation tools at such conditions. The new spray combustion chamber thus fills a clear gap and must be considered a reference setup for those applications.