Review of hydrogen–gasoline SI dual fuel engines

Review of hydrogen–gasoline SI dual fuel engines.  This PDF is a review of the use of Hydrogen- gasline and Hydrogen – diesel  mixtures in internal combustion engines to improve the engine  efficiency , power , torque and performance.

Rapid depletion of conventional fossil fuels and increasing environmental concern are demanding an urgent carry out for research to find an alternate fuel which meets the fuel demand with minimum environmental impacts. Hydrogen is considered as one of the important fuel in the near future which meets the above alarming problems.

Hydrogen–gasoline dual fuel engines use hydrogen as primary fuel and gasoline as secondary fuel. In this review paper, the combustion performance, emission, and cyclic variation characteristics of a hydrogen–gasoline dual fuel engine have been critically analyzed.
According to scientific literature, hydrogen–gasoline dual fuel engines have a good thermal efficiency at low and partial loads, but the performance deteriorates at high loads. Hydrogen direct injection with gasoline port fuel injection is the optimum configuration for dual fuel engine operating on hydrogen and gasoline.

This configuration shows superior result in mitigating the abnormal combustion, but experiences high NOx emission. Employing EGR showed a maximum reduction of 77.8% of NOx emission with a EGR flowrate of 18%, further increment in flowrate leads to combustion instability.

An overview on hydrogen production and carbon footprint related with hydrogen production is also included. This review paper aims to provide comprehensive findings from past works associated with hydrogen–gasoline dual fuel approach in a spark ignition engine.

This research report (attached)was conducted S.T.P. Purayil a , Mohammad O. Hamdan b , S.A.B. Al-Omari a , M.Y.E. Selim a , E. Elnajjar a,∗
a Mechanical Engineering Department, UAE University, Al Ain, United Arab Emirates
b American University of Sharjah, University City, Sharjah, United Arab Emirates 

This is a very detailed report of using duel fuel operation of the internal combustion engine and provides evidenvce of the importance of using Hydrogen in the future for transport applications.

The dual fuel concept is an efficient potential approach for utilizing gaseous renewable fuels in SI engines. In addition, the dual fuel concept offers broad flexibility in governing the combustion process by combining the unique advantages of PFI and DI technologies and is an effective approach to achieving strict emission standards. Compared to conventional SI engines, dual fuel engines possess wide flexibility in mixture formation, enhanced cooling effect, knock mitigation, and emission reductions. Hydrogen has drawn the attention of many researchers for use as a dual fuel along with gasoline, more than any other renewable fuel. Dual fuel engines have the provision for introducing renewable fuels via either DI or PFI. However, hydrogen DI and gasoline PFI are optimal for enhancing engine performance.

Hydrogen addition showed improvements in thermal efficiency and brake power which are most pronounced at low and partial loads. Even with a small amount of hydrogen enrichment an increase of 13% in engine torque was obtained. The lean conditions are further extended with hydrogen addition which showed a drastic reduction in CO and HC emissions. The incorporation of EGR showed better result in NOx reduction. Increasing the EGR flowrate has resulted with a maximum NOx reduction of 77.8% with 18% EGR flow rate. Further increment in EGR resulted in combustion instability as well as in HC and CO emissions

The high auto-ignition temperature of hydrogen limits its use as a single fuel in the CI engines, which otherwise requires glow plug or spark plug for hydrogen combustion. So, introducing hydrogen to SI engine is the best approach to address the twin alarming global issues. Abnormal combustion like knock, preignition and backfire are more associated with hydrogen fuel. This limits the hydrogen fraction to increase beyond a certain point, which results in reduced engine performance at high engine load. This power deterioration at high load is addressed using dual fuel method along with use of conventional fossil fuels. Even though dual fuel method provides an extensible solution, approaches which can be used to further extend the hydrogen fraction over conventional fossil fuel is of prime importance, where detailed literature is still missing. The approaches for preventing the back flow of high temperature gas from the combustion chamber to intake manifold, reduction of in-cylinder hotspots like hot spark plug, residual high temperature carbon deposits and maintaining the incoming air–fuel temperature below auto-ignition temperature can be used to reduce the risk of abnormal combustion associated with the hydrogen fuel.

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