Experimental Investigations of Hydrogen-Natural Gas Engines for Maritime Applications

Abstract

A novel ship propulsion concept employs natural gas to reduce ship emissions and improve overall ship propulsion efficiency. This concept proposes a serial integration of Solid Oxide Fuel Cell (SOFC) and a natural gas engine, while anode-off gas (gas at the fuel cell exhaust) is used in the natural gas engine. This study focusses on SOFC-gas engine integration by experimentally analyzing the effects of adding hydrogen, which is the main combustible component of the fuel cell anode-off gas, in marine natural gas engines. The overall challenge is to employ the anode-off gas to improve the performance of marine natural gas engines. To study the effects of anode-off gas combustion in natural gas engines, experiments with hydrogen addition in a marine natural gas engine of 500 kW rated power were performed. Natural gas was replaced with 10 % and 20 % of hydrogen, by volume, without any penalties in terms of output power. We found that the high combustion rate of hydrogen improved combustion stability, which allowed for better air-excess ratio control. Thus allowing leaning to higher air-excess ratios and extending the, otherwise, limited operating window. Hydrogen addition also improved brake thermal efficiency by 1.2 %, while keeping NOx emissions below the maritime emission regulations. The improvement in engine efficiency with a larger operating window may help improve the load-taking capabilities of marine natural gas engines.

Experimental mild conversion of a lean burn natural gas engine with SCR to a hydrogen engine: NOx and GWP potential for marine applications

“…Previous research in the field of the use of hydrogen in marine propulsion systems included simulative investigations, 8 but also addressed experimental studies of hydrogen enriched intake air with diesel engines 9 and natural gas-hydrogen mixtures for gas engine combustion processes. 10,11 Nevertheless, the current state of knowledge of the use of pure hydrogen as a fuel is limited, especially under engine operating conditions of the displacement class of marine combustion engines. Here, we have pursued an experimental approach and used a systematic comparison with the current state of the technology of exhaust gas aftertreatment with regard to NOx reduction potential.…”

Hydrogen-natural gas combustion in a marine lean-burn SI engine: A comparitive analysis of Seiliger and double Wiebe function-based zero–dimensional modelling

“…The limited operating window also restricts the load-taking capabilities of these marine engines and retards their application to generator mode and electric ship propulsion, which results in lower overall efficiency due to conversion losses [7]- [9]. However, researchers have shown that blending hydrogen with natural gas can enhance the lean-burn capabilities of natural gas engines due to the high laminar flame speed of hydrogen, which can extend the operating window [8], [10]. Hydrogen blending also helps in reducing carbon dioxide and carbon monoxide emissions of natural gas engines [8].…”

“…However, researchers have shown that blending hydrogen with natural gas can enhance the lean-burn capabilities of natural gas engines due to the high laminar flame speed of hydrogen, which can extend the operating window [8], [10]. Hydrogen blending also helps in reducing carbon dioxide and carbon monoxide emissions of natural gas engines [8]. Various proven advantages of hydrogen-natural gas (H-NG) blends such as increased flammability limits, high flame speed, hydrogen renewability, high volumetric calorific value and reduced unburnt hydrocarbon emissions make hydrogen-natural gas a promising fuel for marine engines.…”

“…Furthermore, most of the studies employing Wiebe modelling for gaseous fuel combustion are focussed on automotive or small scale engines [33]- [35]. In NG engines, the stability of the combustion process affects the operating window between knock and misfire limits [8]. The operating window of marine NG engines reduces as the brake mean effective pressure (BMEP) scales upwards [5], [6].…”

“…The parameters a 1 and a 2 are equal and a function of combustion efficiency as given in equation 3.24.The combustion efficiency (η comb ) is determined by calculating the conversion rate of the carbon from the fuel to carbon dioxide. Thus, the combustion efficiency is estimated by dividing the carbon atoms in the exhaust carbon dioxide to the number of carbon atoms that are present in the incoming hydrogen-natural gas blend[8]. In this manner, four out of eight parameters in equation 3.23 are fixed and can be easily determined.…”