Effect of Hydrogen Fumigation in a Dual Fueled Heavy Duty Engine

Abstract

Concerns over the impact of road transport emissions on the climate have led to increased focus on how CO2 emissions could be reduced from the sector. This is of particular concern in the commercial vehicle sector, where engine downsizing and electrification have limited benefit due to the vehicle duty cycle. In this paper, we present results from an experimental program to investigate the impact of dual fueling a heavy duty engine on hydrogen and diesel. Hydrogen is potentially a zero carbon fuel, if manufactured from renewable energy but could also be manufactured on the vehicle through steam reformation of part of the liquid fuel. This opens a novel pathway for the recovery of waste heat from the exhaust system through the endothermic steam reformation process, improving the overall system efficiency. For these concepts to be viable, it is essential the dual fueled combustion system is both thermally efficient, and does not increase toxic emissions such as NOx. The test program reported studied the impact of hydrogen injection into the engine intake system with and without Exhaust Gas Recirculation (EGR). The baseline engine was calibrated to achieve Euro VI NOx emissions with various aftertreatment strategies. The impact of displacing diesel with increased quantities of hydrogen was studied. The results are compared with a conceptual model of the hydrogen-diesel combustion process presented in the paper.

Hydrogen Fumigation on HD Diesel Engine: An Experimental and Numerical Study

“…According to the conceptual model proposed by [7] (explained at the end of Section 2), for experimental studying effect of hydrogen enrichment on diesel combustion, in each two operating points, specific hydrogen substitution ratios were selected regarding their H 2 concentration in air. Their corresponding burn rate…”

“…Adding small amounts of hydrogen led to slight reduction in indicated efficiency, potentially associated with reduced ratio of specific heats due to displacement of air. The reason for initial drop in efficiency could be due to "hydrogen slip" (incomplete combustion of hydrogen) as claimed in [7]. This issue was more pronounced at low load as the diesel fuel injected was relatively small, hence the gaseous fuel could not fully burn by entraining into the liquid fuel.…”

“…Typically, there are two main methods of supplying hydrogen: NG steam reforming (supplying $95% of industrial H 2 ) and electrolysis of water (which is a zero-carbon method but very costly). Alternatively, an innovative acquirement of hydrogen is via on-board steam reformation of part of the liquid hydrocarbon fuel, which improves the overall system efficiency by $5% via waste exhaust heat recovery [7]. Nevertheless, the vision of a "hydrogen economy" is only foreseeable when its required production energy is totally supplied from green renewable sources.…”

“…It is worthwhile to mention that lower flammability limit (LFL) plays as a turning point in dual-fuel combustion as the mechanism is affected depending on which side of LFL, the hydrogen concentration is. To clarify this point, a conceptual Hydrogen Fumigation on HD Diesel Engine: An Experimental and Numerical Study DOI: http://dx.doi.org/10.5772/intechopen.89425 model proposed within a relevant work by [7] including the following three modes was considered:…”

“…This claim is affirmed in Figure 8 particularly for H30 where all key attributes were changed for both corresponding cylinder pressure and burn rate. Indeed, the mode 1 of the proposed conceptual model [7] is well presented in H30 whereas hydrogen pre-ignition prior to diesel fuel injection has been a game changer.…”