Gas Dynamic Design Analyses of Charging Zone for Reverse-Flow Pressure Wave Superchargers

Abstract

The paper is focused on a comprehensive and systematic gas dynamic analysis of the high-pressure phase (charging zone) of pressure wave superchargers. The procedure is documented for a four-port reverse flow (RF) wave rotor, the typical configuration for engine wave superchargers, also named Comprex. A one-dimensional analytical gas dynamic model is employed to calculate flow characteristics inside the channels. Existing normal shock wave equations along with isentropic relations for expansion waves are used for calculations. Useful design parameters such as cycle timing and port widths are determined by formulating traveling times of the waves inside the channels. The gas dynamic study of the internal wave process demonstrates its fundamental dependence on the externally imposed compression ratio of the pressure wave supercharger.

Validation of a Numerical Quasi-One-Dimensional Model for Wave Rotor Turbines With Curved Channels

“…Furthermore, the number of cycles per rotation and the port solution needs to be provided. An initial guess and rough layout can be devised through the analytical tools given by [43,[56][57][58]. Subsequently, all matrices used throughout the computation are, along with the spatial domain, initialised.…”

Nonsteady Shock Wave Attenuation Due to Leakage

“…The primary cause of leakage in a wave rotor lies in that the rotor channel pressure is generally not equal to the cavity pressure, as a result of which gases are driven by the pressure difference to flow between the channel and the cavity through the rotor-stator gap, especially when the incident shock wave reaches the channel end and reflects since the pressure difference reaches its maximum. Figure 1 shows the above waves in the high pressure part of the wave diagram, which was analyzed in detail in Akbari's analytical design work [27].…”

“…The primary cause of leakage in a wave rotor lies in that the rotor channel pressure is generally not equal to the cavity pressure, as a result of which gases are driven by the pressure difference to flow between the channel and the cavity through the rotor-stator gap, especially when the incident shock wave reaches the channel end and reflects since the pressure difference reaches its maximum. Figure 1 shows the above waves in the high pressure part of the wave diagram, which was analyzed in detail in Akbari's analytical design work [27]. As illustrated in Figure 1, the majority of the gases in the rotor channel are driven to the stationary exhaust port, whereas a minority of them are driven to the cavity in the form of radial leakage, as shown in Figure 2; in addition, at the moment the exhaust port opens, the rotor channels are located on the two sides of the port leading edge and consequently the gases in them are in the states in front of the incident shock and behind the reflected shock respectively, as a result of which the gases are driven to flow between the adjacent rotor channels in the form of circumferential leakage due to inter-channel pressure difference.…”

Wave Rotor Research Program at Michigan State University

“…Akbari and Müller at MSU have introduced 25,26 a relatively simple one-dimensional gasdynamic model of the high-pressure phase (charging process) to calculate flow characteristics inside four-port wave rotors channels. In the high-pressure process, compression waves transfer the energy directly from a fluid at a higher pressure (driver fluid) to another fluid at a lower pressure (driven fluid).…”