The influences of injector nozzle geometry, injection pressure and ambient air conditions on a diesel fuel spray were examined using back-lighting techniques. Both stills and high speed imaging techniques were used. Operating conditions representative of a modern turbocharged aftercooled HSDI diesel engine were achieved in an optical rapid compression machine fitted with a common rail fuel injector. Qualitative differences in spray structure were observed between tests performed with short and long injection periods. Changes in the flow structure within the nozzle could be the source of this effect. The temporal liquid penetration lengths were derived from the high-speed images. Comparisons were made between different nozzle geometries and different injection pressures. Differences were observed between VCO (Valve Covers Orifice) and mini-sac nozzles, with the mini-sac nozzles showing a higher rate of penetration under the same conditions.

Liquid air energy storage (LAES) is a class of thermo-electric energy storage that utilises cryogenic or liquid air as the storage medium. The system is charged using an air liquefier and energy is recovered through a Rankine cycle using the stored liquid air as the working fluid. The recovery, storage and recycling of cold thermal energy released during discharge more than double the overall energy efficiency of the cycle. The demand on a storage plant in a grid support application is expected to be irregular and intermittent in response to fluctuating supply from intermittent renewable generators. This will complicate the storage of thermal energy and will mean the energy flow rates in the thermal store will vary from cycle to cycle and the state of charge of the store will also vary. This paper presents an analysis of the LAES cycle. The material and configuration of the cold thermal store is discussed in particular with reference to scale and measures to mitigate losses due to the irregular and intermittent duty cycle. The paper concludes with capital and levelised cost analysis of a reference 20 MW/80 MWh LAES plant and a comparison of the levelised cost with other storage technologies.