Radu Chiriac

A Study of Combustion of Hydrogen-Enriched Gasoline in a Spark Ignition Engine

An investigation has been done on the influence of small amounts of hydrogen added to hydrocarbons-air mixtures on combustion characteristics. The effect of hydrogen addition to a hydrocarbon-air mixture was firstly approached in an experimental bomb, to measure the laminar burning velocity and the shift of lean flammability limit. Experiments carried out with a single-cylinder four stroke SI engine confirmed the possibility of expanding the combustion stability limit, which correlates well with the general trend of enhancing the rate of combustion. An increase of brake thermal efficiency has been obtained with a reduction of HC emissions; the NO{sub x} emissions were higher, except for very lean mixtures.

Effects of Gasoline-Air Enrichment with HRG Gas on Efficiency and Emissions of a SI Engine

The addition of hydrogen to the gasoline-air mixture may contribute significantly towards accelerating the combustion process, with the beneficial effects on engine performance and emissions. The present contribution describes the results of an experimental research where gasoline-air mixture was enriched with a Hydrogen Rich Gas (HRG) produced by the electrical dissociation of water. The HRG analysis shows the presence of hydrogen and oxygen together with some additional species. Experiments were carried out at engine light and partial load. Detailed results of the measurements are shown, namely engine torque and efficiency, exhaust emissions, cyclic variability, heat release rates and combustion duration. The possibilities of improving engine performance and emissions in correlation with the amount of HRG, the equivalence ratio and the engine operating condition are thus outlined.

Progress in high performance, low emissions, and exergy recovery in internal combustion engines

Summary This article first gives a brief review of thermal engines designed for terrestrial transportation since the 1900s. We then outline the main developments in the state of the art and knowledge about internal combustion engines, focusing on the increasingly stringent pollution constraints imposed since the 1990s. The general concept of high-energy performance machines is analyzed from the energy, exergy, and public health point of view and illustrated with typical examples of clean energy production and zero emissions. Whereas the energy analysis revealed high potential of waste heat recovery from both exhaust and cooling system, the exergetic analysis revealed much higher recovery potential from exhaust gases. The exergy content of exhaust gases was observed to be within the range from 10.4% to 20.2% of the fuel energy. The cooling exergy is within the range from 1.2% to 3.4% of the fuel energy. The article concludes with some perspectives for the emergence of an economic model that could be applied to land-based transport systems in the framework of energy transition by 2030. Copyright

On The Possibility to Reduce Diesel Engines Emissions by Operating with Biodiesel B20 in PPC Mode

Using diesel-biodiesel blends in Diesel engine has been highlighted to offer a good opportunity in reducing the exhaust emissions for particular engine operating conditions. The blended diesel-biodiesel with up to 20 % biodiesel in petroleum diesel fuel (B20) is in production and available for use in USA being considered as viable path to be followed in the effort to reduce the effect of the greenhouse gas emissions issued by the operation of heat engines. Although previous studies investigating the effect of B20 on engines emissions led to some contradictory results, the life cycle analysis performed on the well-to-wheel base shown that 35 % reductions of CO2 emission, in respect to fossil fuels operation are possible. The association of this alternative fuel use with some new combustion concepts as homogeneous charge compression ignition (HCCI) premixed charge compression ignition (PCCI) or partially premixed combustion modes (PPC) may amplify these potential reductions. The present study continued the investigation on B20 effects by performing a set of comparative experimental tests on a conventional direct injection tractor diesel engine running alternatively with B20 and petroleum diesel fuel at 2400 rpm speed and 60 % load. The possibilities to enhance the effects of B20 fuel by PPC combustion operation mode were explored by numerical simulations using the AVL BOOST v2013.2 code. It was basically found that further improvements in decreasing emissions of Diesel engines operating with B20 can be obtained without significant changes in Diesel engines structure and adjustments.

A Conventional Approach to Estimate NOx and Soot Emissions of a Diesel Engine Fueled with Diesel and Biodiesel Fuels

The present paper describes an analysis made with two methods for the emissions estimation of an engine, when using Diesel fuel and Biodiesel, based on mathematical interpolation and approximation functions. Results are validated against experimental data obtained on an instrumented test-bed comprising a tractor Diesel engine (UTB 240555 Brasov-type) and by simulations applying the AMESIM code simulation tool. Further studying activities corresponding to the use of the models applying split-injection strategies should highlight a reliable manner to decrease NOx emissions by preserving engines performances.

Experimental and numerical assessment of ignition delay period for pure diesel and biodiesel B20

The ignition delay period for a compression ignition engine fueled alternatively with pure diesel and with biodiesel B20 has been experimentally and numerically investigated. The engine was operated under full load conditions for two speeds, 1400 rpm speed for maximum brake torque and 2400 rpm speed for maximum brake power. Different parameters suggested as important to define the start of combustion have been considered before the acceptance of a certain evaluation technique of ignition delay. Correlations between these parameters were analyzed and concluded about the best method to identify the start of combustion. The experimental results were further compared with the ignition delay predicted by some correlations. The results showed that the determined ignition delays are in good agreement with those of the Arrhenius type expressions for pure diesel fuel, while for biodiesel B20 the correlation results are significantly different than the experimental results.

Development of a Water Rankine System to Improve Diesel Engine Efficiency

One way to increase the thermal efficiency of a diesel engine is to recover the waste heat from the exhaust gases and from the cooling system. For the stationary diesel engine, used to generate electrical power, this heat may be converted in useful energy by a cogeneration system, in order to ensure hot water production. For the automotive diesel engine, however, the solution is not applicable therefore a method has to be developed in order to generate mechanical power. In this paper the authors show the design and the simulation performed with the AMESIM software tools for a heat recovery system dedicated to a diesel engine. The engine is simulated with the specific library of the software and the obtained results are used in the second part of the paper concerning the recovery system. The simulation results presented in this paper obviously need to be confronted to the experimental data before validating the prediction capability of the model so that this one could become an important tool in the efforts to emphasize how can be reduced the fuel consumption for truck diesel engines using the on board heat recovery.

Injection Technology of Enriched Hydrogen Gas to Reduce Sulfur Oxide and Fly Ash Emission

This paper presents a CFD model and the first validation set of results concerning a new technology to inject and adsorb, under safe conditions, a hydrogen enriched gas in solid fuel that has been milled, at the burner inlets of a power designated steam boiler. The present paper presents a dynamic model of enrichment technology which refers to the improvement of the classical existent technological flow of the pulverized coal burning installation in order to prepare and burn weak volatile matters pulverized fuel. The model refers to obtain an enriched hydrogen pit coal by the injection of an hydrogen enriched gas into the average ground pulverized pit coal current, the control of the gas diffusion into the porous environment of the powder particles, process that is accelerated in comparison with other gaseous component parts due to the hydrogen atom / molecule characteristics, and finally, the adsorption of this molecule into coal particles. The complex nature of this model consists in: to issue and simulate the procedure to inject and diffuse the hydrogen enriched gas in the pulverized coal current; to design and to simulate an installation to enrich by injection the pulverized pit coal in primary mixture stream — a special attention is paid to the influence of the pit coal particles porosity upon the hydrogen adsorbing process; to develop a model to simulate the burners operation in these new conditions. Burning process of this enriched pulverized pit coal is expected to produce a strong decrease in sulfur dioxide emissions and also in the flying ash concentration at the end of the furnace. A set of preliminary experimental results concerning all aspects of this technology will be also presented. These results have been obtained on a laboratory scaled installation which is located at labs of the Politehnica University of Bucharest. This installation has a storage capacity of hydrogen, a 5000 rpm ventilator mill to prepare the solid fuel. Test equipment includes Horiba gas analyzer, high speed camera and all other facilities to determine all the operational parameters. Different types of burners can be installed at this installation in order to determine an optimal procedure.Copyright