Propulsion Simulator/Stimulator Development for US Navy’s Newest Gas Turbine-Powered Ship: LHD 8 USS Makin Island

Abstract

The LHD 8 amphibious assault ship utilizes a hybrid propulsion plant, where the ship has the capability to be propelled by electric propulsion motors or gas turbine engines, all of which is controlled and monitored by a state-of-the-art Machinery Control System (MCS). Unlike the previous ships of the class which were steam powered, the hybrid drive is designed to allow economical low speed fuel efficiency on electric motors as well as a traditional gas turbine power plant for all other mission areas. This is expected to yield significant fuel savings over the life of the ship. The integrated machinery control system is likewise expected to reduce life cycle costs through reduced manning. The build specification for this ship class required that all MCS signals including the gas turbine alarms and shutdown functions be fully tested prior to initial light-off. Many of these functions are not activated, and therefore cannot be tested, until the Electronic Control Unit (ECU) senses that the gas turbine is running. Historically, previous ship classes used a manually-operated set of potentiometers to provide signals to a gas turbine ECU to simulate external inputs to allow testing of shutdown and alarm functions. For this newest class of engine however, the ECU is significantly more complex and requires the ECU to successfully progress through the start sequence, including sensed variables changing at expected rates, in order to activate the alarm and shutdown logic. In order to test this functionality, an engine simulator, physically interfaced to the ECU aboard the ship, was necessary. No system of this type is available or had ever been developed. Neither the engine or ECU manufacturer had a device for this purpose. The paper will discuss the development and implementation of a gas turbine simulator that incorporates an engine mathematical model fully compatible with the ECU controller, simulation hardware capable of supporting real-time system performance, signal conditioning necessary to provide/accept raw signals to/from the ECU, as well as a host laptop with software necessary to control simulator/stimulator and perform test functions. The paper will discuss the system requirements development, component selection, software and hardware development, and system integration and testing. Also discussed will be the results of bench testing as well as the final shipboard test results. Examples in the form of diagrams, photos, charts and schematics will be used. The paper will conclude with a discussion of the benefits of a dynamic gas turbine simulator and potential future applications.