Rodica Niculescu

Analytical synthesis and computer-aided kinematic analysis of a continuously variable valve lift mechanism

This paper presents an original continuously variable intake valve lift mechanism designed for the automotive spark ignition engines. The paper first presents the analytical kinematic synthesis of the variable intake valve lift mechanism, which consists in finding out the required intake cam profile starting from an imposed intake valve lift law. Then, by using the obtained cam profile, a computer-aided kinematic analysis of the variable intake valve lift mechanism is performed using commercial CAD software. The accuracy of the motion conversion performed with CAD software is validated by checking the degree of correlation between the resulted intake valve lift law and the imposed law used when performing the analytical synthesis. The goals of the kinematic analysis are first to find the partial laws of the intake valve lift, corresponding to the engine part loads and second, to find the transfer functions of the elements used to command the mechanism, i.e. the dependency between these elements and the intake valve lift law. The designed variable intake valve lift mechanism is successfully operated on an engine prototype and proved its energetic improvement potential.

INTER-CYLINDER DISTRIBUTION OF DI-ETHYL-ETHER INJECTED INTO THE INTAKE MANIFOLD OF A DIESEL ENGINE USING CFD SIMULATION

This paper is a consequence of a study on assessing the cold-starting performance of a compression ignition engine fuelled with different blends of fossil diesel fuel and biodiesel. Through experimental investigations, it was found that the engine starting at −20 °C was no longer possible in the case of using B50 (50 % diesel + 50 % biofuel made from sunflower oil). In order to determine the engine starting in this particular situation, Di-Ethyl-Ether (DEE) was injected into the intake manifold. DEE being a highly flammable substance, the result was a sudden and explosive engine starting, the peak pressure in the monitored cylinder in the first successful engine cycle being almost twice the one which is usually considered as normal. As a consequence of this observation, we wondered what happened in the other 3 engine’s cylinders which were not monitored with pressure sensors. Since the cause of the sudden and explosive engine starting was the DEE, our question is in which way the DEE injected into the intake manifold was distributed to each of the 4 cylinders of the engine. Does the extremely high peak of pressure occur in the other 3 cylinders, as well? Since only one cylinder was monitored with a pressure sensor, the method which was used to find the answer to the question mentioned before was to use a CFD approach. Thus, this paper’s objective is to present the method used in order to find the inter-cylinder distribution of the injected DEE.

Issues Concerning the Determination of the Correspondence Between Low Pressure Distillation and Gas Chromatography Analysis of Biodiesel. Preliminary Results

Increased environmental awareness and depletion of fossil petroleum resources are driving the automotive industry to seek out and use alternative fuels. The most eminent alternative fuels for replacing fossil fuels in internal combustion engines are biofuels (biodiesel and bioethanol).

On the effect of Di-Ethyl-Ether (DEE) injection upon the cold starting of a biodiesel fuelled compression ignition engine

The use of biodiesel fuel in compression ignition engines has the potential to reduce CO2, which can lead to a reduction in global warming and environmental hazards. Biodiesel is an attractive fuel, as it is made from renewable resources. A major drawback associated with the use of biodiesel, however, is its poor cold flow properties, which have a direct influence on the cold starting performance of the engine. This paper is a consequence of a study on assessing the cold-starting performance of a compression ignition engine fueled with different blends of fossil diesel fuel and biodiesel. Through experimental investigations, it was found that the engine starting at -20°C was no longer possible in the case of using B50 (50% diesel + 50% biofuel made from sunflower oil). In order to “force” the engine starting in this particular situation, Di-Ethyl-Ether (DEE) was injected into the intake manifold. DEE being a highly flammable substance, the result was a sudden and explosive engine starting, the peak pressu...

Assessment of real driving emissions via portable emission measurement system

The European Commission approved a so-called Real Driving Emission (RDE) test in response to the criticisms to the current driving cycle used at chassis dyno for homologation purpose (NEDC): it is considered outdated and misleading since air pollutants in real driving conditions are higher than the certification thresholds. So, what’s at stake is the air quality which degraded continuously despite the ever-increasing severity of the regulations. Thus, from September 2017, the RDE test will become part of the type approval process for all cars sold in Europe. As its name points out, it will include “real world driving” using a portable emissions measurement system (PEMS). The paper presents the RDE features as well as the challenges which comes with its implementation: PEMS mounting, testing environment, boundary conditions, repeatability, engine map requirements. The results presented in the paper issued from the existing cooperation on this topic between University of Pitesti and Renault Technologie Roumanie.

Development of a test method for distillation of diesel-biodiesel-alcohols mixtures at reduced pressure

Increased environmental awareness and depletion of fossil petroleum resources are driving the automotive industry to seek out and use alternative fuels. For instance, the biofuel is a major renewable energy source to supplement declining fossil fuel resources. The addition of alcohols like methanol and ethanol is practical in biodiesel blends due to its miscibility with the pure biodiesel. Alcohols also improve physico-chemical properties of biodiesel blends, which lead to improved combustion efficiency. Proper volatility of fuels is critical to the operation of internal combustion engines with respect to both performance and emissions. Volatility may be characterised by various measurements, the most common of which are vapour pressure, distillation and the vapour/liquid ratio. The presence of ethanol or other oxygenates may affect these properties and, as a result, performance and emissions, as well. However, in the case of diesel-biodiesel-alcohols mixtures, the variance of component volatility makes difficult the analysis of the overall volatility. Thus, the paper presents an experimental method of distilling diesel-biodiesel-alcohols mixtures by adjusting the boiler pressure of an i-Fischer Dist equipment.

Diagnosing the Operation of a Locomotive Diesel Engine Based on the Analysis of Used Oil in the Period Between Two Technical Revisions

Technical inspection of a motor vehicle is an activity that should not be neglected and that is deemed to be binding both within the warranty period, but especially post - warranty. An engine malfunction may be due to unsuitable use of fuels and lubricants, resulting in a decrease in lubricating performances and protection of the oil. On the other hand, the wear degree and wear nature of engine lubricant can provide clues related to possible engine faults, for example: leaks for the combustion chamber, incomplete burn of fuel, improper thickness of the oil film, etc. The paper aims to determine viscosity, density, water content, fuel dilution and solid compounds of used oil. Based on these data will perform diagnostic analysis of locomotive diesel engine operation.

Study on the engine oil's wear based on the flash point

Increasing energy performance of internal combustion engines is largely influenced by frictional forces that arise between moving parts. Thus, in this respect, the nature and quality of the engine oil used is an important factor. Equally important is the effect of various engine injection strategies upon the oil quality. In other words, its of utmost importance to maintain the quality of engine oil during engines operation. Oil dilution is one of the most common causes that lead to its wear, creating lubrication problems. Moreover, at low temperatures operating conditions, the oil dilution with diesel fuel produces wax. When starting the engine, this may lead to lubrication deficiencies and even oil starvation with negative consequences on the engine mechanism parts wear (piston, rings and cylinders) but also crankcase bearings wear.Engine oil dilution with diesel fuel have several causes: wear of rings and/or injectors, late post-injection strategy for the sake of particulate filter regeneration, etc.This paper presents a study on the degree of deterioration of engine oils as a result of dilution with diesel fuel. The analysed oils used for this study were taken from various models of engines equipped with diesel particulate filter. The assessment is based on the determination of oil flash point and dilution degree using the apparatus Eraflash produced by Eralytics, Austria. Eraflash measurement is directly under the latest and safest standards ASTM D6450 & D7094), which are in excellent correlation with ASTM D93 Pensky - Martens ASTM D56 TAG methods; it uses the Continuous Closed Cup method for finding the Flash Point (CCCFP).