Hydrogen (H2) has long been recognized as a fuel having some unique and highly desirable combustion properties. Its burning in air produces mainly water, and a small amount of NOx without PM emissions. Its application as supplement fuel in dual fuel engines has been demonstrated to achieve desirable performance. Recently, there is increasing interest in adding small amount of H2 to diesel engines aiming to reduce significantly the exhaust emissions and improve to some extent the fuel economy. A number of researchers reported hydrogen’s positive effects in reducing the exhaust emissions of diesel engines. However, most of the research was conducted in small single cylinder engines under limited operating conditions. The results reported are sometimes controversial especially for the emissions of NOx. The PM emissions were usually qualitatively measured by simple smoke meters, which do not meet the requirement of current regulations. West Virginia University (WVU) proposes to conduct a detailed experimental evaluation of NOx emissions effect from H2 enhanced diesel combustion. The proposed experiments will be conducted in WVU’s certification-grade heavy-duty diesel engine test cell capable of assessing changes in NOx and fuel economy at levels under 1%. The preliminary experiments will be run on a 1999 Cummins ISM Diesel engine (without EGR), which yields very repeatable emissions and fuel consumption data. Some confirmation experiments will be run on a 2004 Cummins ISM diesel engine (with EGR). These 10.8 L series diesel engines deliver 370 HP under rated conditions and serve as representatives of typical class-8 heavy-duty diesel engines currently in use. Most of experiments will be run under steady state conditions at various engine speeds and load set points, including those described in the ECE-13 mode emission cycle. The emission data measured can be further processed to estimate the exhaust emissions under real road conditions following ECE-13 mode emissions cycle. In addition, WVU will run an FTP cycle and an ACES transient cycle with a fixed flow of H2.
In this project, WVU will explore hydrogen’s effect in enhancing the diesel engine’s combustion process, improving fuel consumption and reducing exhaust emissions including UHC, CO, NOx, PM and CO2. The amount of H2 added will be increased until a significant effect in exhaust emissions is observed. The in-cylinder pressure measured will be processed to obtain a set of combustion parameters including ignition delay, premixed combustion ratio and maximum pressure and temperature, which dominate the formation of NOx. The analysis of the combustion data will help to understand and explain the changes of exhaust emissions with H2 addition. It is also anticipated that some of the H2 added will survive the main combustion process of diesel engine. In this research, the emissions of unburned H2 will also be measured. The combustion efficiency of H2 will be employed to examine the minimum H2 addition for a positive effect on diesel engine. As reported in the literature, adding H2 to diesel engine may reduce PM emissions but increase slightly NOx emissions in some cases. If required, more experiments could be done to optimize diesel fuel injection timing, EGR rate and H2 dilution rates aiming at simultaneously reducing NOx and PM emissions. In summary, the WVU study will demonstrate the effect on emissions and fuel economy of hydrogen augmentation over a range of concentrations, using both EGR and non-EGR heavy duty engines, and will contribute to understanding the cause behind any hydrogen effects that are encountered. Specifically, the study will reveal the hydrogen concentration threshold at which emissions and efficiency effects become significant.
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