Transient performance of alternatively fueled internal combustion engines for naval applications

Abstract

While navies worldwide aim to reduce their exhaust gas emissions, fossil fuel dependency and signatures, engines on alternative fuels, such as natural gas and methanol, are limited by a lower dynamic load acceptance than diesel engines. This load acceptance is crucially important for naval vessels, both for high maneuverability and for handling pulsed power loads for rail-guns and directed energy weapons. Previous research into the dynamic response of natural gas engines focused on detailed in-cylinder combustion models to predict knock. These 0D/1D simulation models rely on extensive data to calibrate the combustion model, which is generally unavailable to naval engineers and scientists designing a propulsion or energy system. Additionally, these simulation models require a significant amount of computational power and rarely run in real-time. For the evaluation of the dynamic behaviour of such engines during actual manoeuvres and for their use in control oriented modelling approaches, real-time dynamic models are required for natural gas and methanol engines. This study investigates the dynamic response of a spark ignited gas engine with single point fuel injection using a Mean Value First Principle (MVFP) engine model based on the filling and emptying approach and turbocharger performance maps derived from limited data and measurements. For three relevant military scenarios we demonstrate that a gas engine with single point fuel injection driving a generator can comply with the requirements of NATO STANAG 1008 for Quality Power Supply. Furthermore, during these scenarios, transient performance of the gas engine is limited by the inertia of the air path rather than engine knocking.