Simulation of a COMPREX® Pressure Exchanger in a 1-D Code

The paper describes techniques used for optimization of timing, shaping and control of pressure wave exchangers including the prediction of pressure-flow rate characteristics of these devices. BBC Baden and ETH Zürich originally proposed them in 60's using the direct pressure exchange between exhaust gas and fresh air in a narrow channel (the COMPREX^® device).

A technique allowing COMPREX^® pressure exchanger to be simulated in detail in a commercially available 1-D cycle simulation tool has been developed. Before the design of a specific exchanger is started the layout must be carefully optimized concerning distribution gear for both fresh air and exhaust gas. Simulation facilities provided by advanced 1-D codes like GT-Power from Gamma Technologies create a valuable tool to do this task and to find alternative design solutions. The model of pressure waves inside the exchanger channels considers friction, heat exchange and throttling in distribution orifices during opening/closing phase of a specific rotor channel. It takes into account the pressure waves in the engine manifolds, which may hamper the intended function. Moreover, the model is capable of solving the interaction between the engine and an exchanger in a quite natural way. The simulation of a transient response of this boost-pressure device based on this method of the simulation is possible as well.