Numerical Investigation on the Effects of Natural Gas and Hydrogen Blends on Engine Combustion

Abstract The use of hydrogen blended with natural gas is a viable alternative to pure fossil fuels because of the expected reduction of the total pollutant emissions and increase of effi- ciency. These blends offer a valid opportunity for tackling sustainable transportation, in view of the future stringent emission limits for road vehicles. The aim of the present paper is the investigation of the performance of internal combustion engines fuelled by such blends. A numerical investigation on the characteristics of natural gas–hydrogen blends as well as their effect on engine performance is carried out. The activity is focused on the influence of such blends on flame propagation speed. Combustion pattern modelling allows the comparison of engine brake efficiency and power output using different fuels. Results showed that there is an increase in engine efficiency only if Maximum Brake Torque (MBT) spark advance is used for each fuel. Moreover, an economic analysis has been carried out to determine the over cost of hydrogen in such blends, showing percent increments by using these fuels about between 10 and 34%

Experimental investigation of a multiple disk centrifugal pump

The work presents an experimental investigation of the characteristics of a centrifugal pump equipped with a multiple disks rotor specifically designed to operate in the optimal flow regimes. Global measurements are carried out with controlled accuracy while the machine is processing an highly viscous Newtonian lubricating oil in a closed loop system. Results, presented in non dimensional form, indicate that the work transfer is truly efficient, and leads to stable flow conditions all across the performance map. Rotor efficiencies in excess to 80% are measured in a wide range of flow coefficients, thus demonstrating that the theoretical achievements of the late 70s pertaining to the single pair of co-rotating disks can be attained in a true machine environment, provided the optimal wheel flow conditions are preserved. Overall pump efficiency is penalized by inadequate diffusion systems, and not by rotor work transferring mechanisms

The Impact of Natural Gas-Hydrogen Blends on Internal Combustion Engines Performance and Emissions

ABSTRACT The fossil fuel consumption and the related environmental impact are important issues for the world research community: hydrogen seems to be a good alternative to fossil fuels provided that it is produced from renewable energy sources. The aim of the present work is the comparison between natural gas and a hydrogen-natural gas blend (HCNG in the following) in terms of exhaust emissions and fuel consumption. A passenger car has been tested on a chassis dynamometer according to the European emission regulations, without any change on engine calibration (i.e. spark advance). The HCNG blend used during the test has a 12% vol. of hydrogen content. CO emissions showed a reduction of about 19% when HCNG blend is used, while HC emissions remained constant. A 70% increase was observed for NOx emissions with HCNG. A 3% reduction for CO2 emission was observed using HCNG because of the lower carbon content in the blend and the reduced fuel consumption on a mass basis. There is not significant variation of fuel consumption on energy basis, probably due to the effect of a non optimal ignition timing

NUMERICAL EVALUATION OF INTERNAL COMBUSTION SPARK IGNITION ENGINES PERFORMANCE FUELLED WITH HYDROGEN – NATURAL GAS BLENDS

"a b s t r a c t. The dependence of road transportation from fossil fuels and the related economic and environmentalconsequencesimposes. thediversificationof energysources.Hydrogencanstrongly. contribute to this goal because it can be produced from different renewable energy sources.. In order to boost the development of hydrogen technology and reduce the dependence. from conventional fossil fuels, hydrogen can be used in internal combustion engines added. to natural gas. Hydrogen-natural gas blends, commonly named HCNG, can be distributed. using the natural gas infrastructures without significant modifications if hydrogen content. is lower than 30% in volume.. In this paper a numerical model has been developed to predict the performance and. emissions of an internal combustion engine fuelled by natural gas and hydrogen e natural. gas blends. The analysis displayed the impact of hydrogen addition on engine brake effi-. ciency and NOx emission. Stoichiometric air-to-fuel ratio was considered for each fuel in. order to assure an efficient exhaust after-treatment adopting a three-way catalyst. Exhaust. gas recirculation (EGR) was investigated with the aim at improving engine efficiency and. reducing NOx emissions respect to undiluted charge. In fact, HCNG blends combustion. properties are particularly suitable for EGR, assuring a stable combustion also when the. charge is diluted. Maximum brake torque (MBT) ignition timing has been adopted for all. fuels and operating conditions investigated.. Simulations were performed at conditions reproducing engine operation on a passenger. car over the New European Driving Cycle (NEDC). Results were displayed in terms of fuel. consumption in MJ\/km and NOx emissions in g\/km.. The results showed that HCNG blends improved engine brake efficiency, particularly at. low loads and for the highest hydrogen content, with fuel consumptions on energy basis. over NEDC 2.5%, 4.7% and 5.7% lower than CNG, for HCNG 10, 20 and 30 respectively. NOx. emissions increased of about 4% for HCNG 10, 11% for HCNG 20 and 20% for HCNG 30, due. to the higher in-cylinder gas temperatures. Further investigations, performed adopting 10%. EGR for HCNG blends, showed a large reduction of NOx emission, over 80% compared with. natural gas (without EGR), with a positive effect also on engine efficiency. The decrease in. fuel consumption using HCNG blends together with EGR, compared with natural gas, was. 5.4%, 6.6% and 7.7% for HCNG 10, 20 and 30, respectively.