Investigation of Combustion Optimization Control Strategy for Stable Operation of Linear Internal Combustion Engine-Linear Generator Integrated System

In this paper, a thermodynamic model of a spark ignition internal combustion engine fueled with natural gas is developed in order to estimate the air-fuel-unburned gas temperature at before top dead center (BTDC). This temperature is used as controlled variable in a control loop in order to avoid the autoignition phenomena when the engine operates with a fuel with different methane number from the methane number requirement of the engine. The model formulation is based on a polytropic compression proccess whose coefficient was determined experimentally in a turbocharged internal combustion engine fueled with natural gas. To make feasible the use of differents gaseous fuels from natural gas, it was necessary to design two control strategies to avoid the knocking phenomenon and choose the best one. The ambient temperature is the disturbance considered, whose changes are significant in different places in the world. The first control strategy that was implemented is called “Robust”, which employs a conventional feedback control loop with a robust controller which is designed. The response of this control loop is compared to the response of the second control strategy called “Feedforward control”. The results obtained reveals that Feedforward control strategy has better performance than robust control strategy for this application. The control strategy and the model proposed will allow increase the range of application of gaseous fuels with low methane number (MN) leading to guarantee a safe running in internal combustion engines that currently are fueled with natural gas.

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Enhancing Engine Operations in Off-Grid Renewable Energy Applications Through the Additional Use of Hydrogen

Volume 5: Energy Systems Analysis, Thermodynamics and Sustainability; NanoEngineering for Energy; Engineering to Address Climate Change, Parts A and B ◽

10.1115/imece2010-38911 ◽

2010 ◽

Author(s):

Curtis Robbins ◽

Roger Jacobson ◽

Rick Purcell ◽

Kirk Collier ◽

Ralph Wagner ◽

...

Keyword(s):

Renewable Energy ◽

Power System ◽

Hydrogen Storage ◽

Internal Combustion Engine ◽

Hydrogen Generation ◽

Combustion Engine ◽

Current System ◽

Electrical Power ◽

Internal Combustion ◽

Integrated System

The current renewable energy transformation taking place around the world has led to drastic advances in technology that relates to the issue of climate change. Although many solutions have been found and/or created, there has yet to be one that can, on its own, solve the problem of finding an environmentally friendly energy source. This leads to the challenge of creating an integrated system which relies on several components with different types of energy. It has been the goal of this study to further enhance an off-grid renewable energy power system to supply economical, secure, and continuous electrical power, in an environmentally conscious way, for various types of loads. The previous power system consisted of a mobile unit with inverters, batteries, hydrogen generator, hydrogen storage, propane storage and an internal combustion engine generator that was connected to photovoltaics and wind turbines while being controlled and monitored by a single computer unit. The only pollutants emitted from this power system were the result of the use of propane as a backup fuel, when renewable energy was insufficient. Even though propane is a fossil fuel, its use in this study allowed the system to be simpler and more cost effective. With the assistance of Southwest Gas Corporation, a more efficient and reliable internal combustion engine was acquired. The three cylinder engine, with a 10,000 hour maintenance interval, was converted from natural gas to combust either hydrogen or propane. The engine provides mechanical power to a belt driven alternator supplying electricity to the load and other components of the system. Initial testing of the engine achieved engine dynamometer efficiency of over 40% using propane at wide open throttle and 45% using hydrogen at wide open throttle. The output under these conditions was roughly 20 HP using propane and 10 HP using hydrogen. The current system is not mobile but has the potential to be mobile by using an existing KOH electrolyzer for hydrogen generation with a larger output and hydrogen storage capacity.

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