Hydrogen Fueled Spark-Ignition Engines Predictive and Experimental Performance

Abstract

Hydrogen is well recognized as a suitable fuel for spark-ignition engine applications that has many unique attractive features and limitations. It is a fuel that can continue potentially to meet the ever-increasingly stringent regulations for exhaust and greenhouse gas emissions. The application of hydrogen as an engine fuel has been tried over many decades by numerous investigators with varying degrees of success. However, the performance data reported often tend not to display consistent agreement between the various investigators, mainly because of the wide differences in engine type, size, operating conditions used, and the differing criteria employed to judge whether knock is taking place or not. With the ever-increasing interest in hydrogen as an engine fuel, there is a need to be able to model extensively various features of the performance of spark ignition (S.I.) hydrogen engines so as to investigate and compare reliably the performance of widely different engines under a wide variety of operating conditions. In the paper we employ a quasidimensional two-zone model for the operation of S.I. engines when fueled with hydrogen. In this approach, the engine combustion chamber at any instant of time during combustion is considered to be divided into two temporally varying zones: a burned zone and an unburned zone. The model incorporates a detailed chemical kinetic model scheme of 30 reaction steps and 12 species, to simulate the oxidation reactions of hydrogen in air. A knock prediction model, developed previously for S.I. methane-hydrogen fueled engine applications was extended to consider operation on hydrogen. The effects of changes in operating conditions, including a very wide range of variations in the equivalence ratio on the onset of knock and its intensity, combustion duration, power, efficiency, and operational limits were investigated. The results of this predictive approach were shown to validate well against the corresponding experimental results, obtained mostly in a variable compression ratio CFR engine. On this basis, the effects of changes in some of the key operational engine variables, such as compression ratio, intake temperature, and spark timing are presented and discussed. Some guidelines for superior knock-free operation of engines on hydrogen are also made.

Hydrogen-fueled internal combustion engines

“…A comparison to experimental results showed good agreement for variation of compression ratio, air-fuel equivalence ratio and intake air temperature [162]. These results suggest that the operating regime of a hydrogen engine is strongly limited by the occurrence of knocking combustion.…”

“…Li and Karim use a two-zone quasi-dimensional model with a triangular combustion rate law fitted to experimental data coupled to a chemical kinetic scheme [162]. They propose a knock criterion, comparing the energy released by end-gas reactions to the energy released by the normal flame propagation.…”

Comparisons of hydrogen and gasoline combustion knock in a spark ignition engine

“…Tang et al [1] used lean mixtures at CR of 12.5:1 and 14.5:1 as did Smith et al [15] without occurrence of knock. However Karim et al [16] in experimental and theoretical work indicate wide knocking regions even at CRs as low as 6. It can be concluded that the operational regions of combustion knock depends on a number of engine operation parameters including intake air temperature and intake pressure and will vary for different engine design and configuration.…”

Performance Evaluation of External Mixture Formation Strategy in Hydrogen Fueled Engine

“…The drive for the adoption of this technique is supported by a considerable set of advantages. It can be installed easily with only simple modification required (Lee, Yi & Kim, 1995) and the cost is low (Li & Karim, 2006). The flow rate of supplied hydrogen can also be controlled conveniently (Sierens & Verhelst, 2001).…”