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The Recuperated Split Cycle Engine is a new type of ICE, offering a step change in efficiency and tailpipe emissions. It targets the heavy duty, long-haul sector (trucks, off-highway, rail, shipping), where electrification is most challenging, and distributed generation, where capacity is required to support rising electrification. The engine separates cold (induction, compression) and hot (combustion, expansion) parts of the cycle; waste exhaust heat is recovered between them via a recuperator, as in a recuperated gas turbine. Recent research presented at this conference [1] shows that the sonic airflows seen in the induction event give rise to extraordinary fuel mixing and clean, cool combustion, with potential for after-treated emission levels between SULEV and zero-impact (either unmeasurable or below ambient).

The recuperated split cycle engine is a fundamentally new class of internal combustion engine that offers a step change in thermal efficiency over conventional Otto and Diesel cycle engines. In a split cycle engine, the compression and combustion strokes are performed in different cylinders. Intensive cooling of the compression stroke by the injection of liquid nitrogen directly into the chamber enables the recovery of waste heat from the exhaust between the compression and combustion cylinders. Brake efficiencies of over 50% have been reported without compression cooling, rising to 60% where the compression stroke is cooled by the injection of liquid nitrogen. The technology targets the heavy duty, long-haul sector where electrification is ineffective. In this paper, results from an experimental program conducted on a single cylinder research engine, representing the combustor cylinder of a recuperated split cycle engine are reported.

A duplex 3-phase (6-phase with 2 star-points) eMachine and associated inverter, including the development of the control algorithm, for a P2 hybrid vehicle was developed. The requirements, relating to power and duty cycle, flow down from the vehicle to the eMachine: these are shown and design issues relating to the use of a 48V system presented. The focus on low cost, compact solutions runs through the work. The inverter is rated at 25 kW to drive an interior permanent magnet eMachine, supplied by a 48V dc-link. The focus of the work presented in this paper is the inverter controller development and powertrain sizing. The test results of the eMachine with the inverter are presented to show the drive system operating the 6-phase current controller and inverter.

The conventional Diesel cycles engine is now approaching the practical limits of efficiency. The recuperated split cycle engine is an alternative cycle with the potential to achieve higher efficiencies than could be achieved using a conventional engine cycle. In a split cycle engine, the compression and combustion strokes are performed in separate chambers. This enables direct cooling of the compression cylinder reducing compression work, intra cycle heat recovery and low heat rejection expansion. Previously reported analysis has shown that brake efficiencies approaching 60% are attainable, representing a 33% improvement over current advanced heavy duty diesel engine. However, the achievement of complete, stable, compression ignited combustion has remained elusive to date.

Concerns over the impact of road transport emissions on the climate have led to increased focus on how CO2 emissions could be reduced from the sector. This is of particular concern in the commercial vehicle sector, where engine downsizing and electrification have limited benefit due to the vehicle duty cycle. In this paper, we present results from an experimental program to investigate the impact of dual fueling a heavy duty engine on hydrogen and diesel. Hydrogen is potentially a zero carbon fuel, if manufactured from renewable energy but could also be manufactured on the vehicle through steam reformation of part of the liquid fuel. This opens a novel pathway for the recovery of waste heat from the exhaust system through the endothermic steam reformation process, improving the overall system efficiency. For these concepts to be viable, it is essential the dual fueled combustion system is both thermally efficient, and does not increase toxic emissions such as NOx.