Abstract: According to one embodiment of the invention, an engine system comprises a housing, an outer gerotor, an inner gerotor, a tip inlet port, a face inlet port, and a tip outlet port. The housing has a first sidewall, a second sidewall, a first endwall, and a second endwall. The outer gerotor is at least partially disposed in the housing and at least partially defines an outer gerotor chamber. The inner gerotor is at least partially disposed within the outer gerotor chamber. The tip inlet port is formed in the first sidewall and allows fluid to enter the outer gerotor chamber. The face inlet port is formed in the first endwall and allows fluid to enter the outer gerotor chamber. The tip outlet port is formed in the second sidewall and allows fluid to exit the outer gerotor chamber.