Carlo N. Grimaldi

Injection Strategies Tuning for the Use of Bio-Derived Fuels in a Common Rail HSDI Diesel Engine

The potentialities in terms of engine performance and emissions reduction of pure biodiesel were examined on a Common Rail HSDI Diesel engine, trying to define a proper tuning of the injection strategies to bio-fuel characteristics. An experimental investigation was therefore carried out on a typical European passenger car Diesel engine, fuelled with a soybean oil derived biodiesel. A standard European diesel fuel was also used as a reference. In particular, the effects of an equal relative air/fuel ratio at full load condition were analysed; further, a sensitivity study on the outcome of the pilot injection timing and duration at part load on engine emissions was performed. Potentialities in recovering the performance gap between fossil fuel and biodiesel and in reducing NOx specific emissions, affecting only to a limited extent the biodiesel emission benefit in terms of CO, HC and FSN, were highlighted.

Thermodynamic analysis of hydraulic air compressor-gas turbine power plants

Abstract Nowadays, the most common way to improve energy conversion efficiency is the integration of different systems, thus achieving a better exploitation of the available exergy potential (e.g. combined cycles, cogeneration, etc.). As a means of producing power in hydroelectric plants hydraulic energy is commonly considered to be almost completely exploited. The aim of this paper is to analyse the possible integration of hydraulic energy sources with conventional, fossil fuel based systems; in particular, power plants based on the combination of an hydraulic air compressor (HAC) and a gas turbine are considered. In an HAC, air is entrained in the water flow in a downcomer pipe and compressed. Once separated from the water in a ‘stilling chamber’ at the bottom of the downpipe, the compressed air is supplied to a combustion chamber and then to a conventional gas turbine expander. An attractive characteristic of HACs is the capability, in principle, to perform an isothermal air compression instead of an adiabatic one, as in conventional compressors. In the present work, a thermodynamic analysis is presented of HAC-gas turbine energy conversion systems, which are compared with conventional hydroelectric and gas turbine power plants. The calculated performance levels of such systems are comparable to those of combined cycle plants, making further technical and economical investigations quite interesting.

Dependence of Flow Characteristics of a High Performance S.I. Engine Intake System on Test Pressure and Tumble Generation Conditions - Part 1: Experimental Analysis

In this paper an experimental analysis is carried out to evaluate the dependence of the flow characteristics in the intake system of a high performance 4 valve, Spark Ignition Internal Combustion Engine, on the experimental conditions at the steady flow test bench. Experimental tests are performed at different pressure levels on a Ducati Corse racing engine head, to measure the Discharge Coefficient C d and the Tumble Coefficient N T , expanding the work already presented in a previous work by the same research group: with a new test bench, the maximum test pressure level is increased up to 24 kPa, while differently-shaped tumble adaptors are used to evaluate N t . The study is aimed at determining the influence of the test pressure on C d and N T measurements, and in particular of the tumble adaptor shape. As a matter of fact, researchers usually adopt different shapes, such as the conventional T type or the L one, resulting in a non uniform base to compare results from several investigations. This work is aimed at verifying the quantitative differences that can be found by using these shapes, in particular when the separate contribution to the tumble vortex generation from one only of two intake valves has to be evaluated. The above described analysis is also useful to evaluate the C d values obtained in the different test conditions used.

Energy saving strategies in an actual confectionery plant

The achievement of a more rational use of energy can be difficult when large and complex industrial plants are considered. In the present work, an example is given of how a well-focused energy analysis, based on experimental data, can help to point out possible relevant energy savings. In particular, two different refrigeration systems have been examined for a confectionery plant in different seasons, atmospheric and production conditions, allowing us to understand the actual operation. Based on the analysis of the results, energy saving strategies have been proposed and discussed. Copyright

Experimental analysis of the actual behaviour of a natural gas fueled engine Caterpillar (CAT)-3516

Abstract In this work, first results are presented of the analysis of the behaviour, in actual, non-new operational conditions, of a lean burning, natural gas (NG) fueled, 1 MWe Caterpillar (CAT)-3516 engine, installed at the Engineering Faculty of Perugia University for the cogeneration of electrical and thermal energy. Data collected daily by the plant manager operators along 24 months of engine operation, which refer to power, electrical efficiency, NG flowrate, availability, and charge temperature, were analysed in connection with the recorded events of breakdown/defects and of maintenance/repair. An acquisition system for the continuous monitoring of several engine and plant quantities is described in detail.

Numerical Study of SI Engine Part Load Operating Conditions Using Different VVA Strategies

In SI engines, VVA (Variable Valve Actuation) technology is mainly used for the reduction of pumping losses at part load. This paper presents the results of fluid dynamic analyses on a 4V engine about the effects of different VVA strategies, by comparing and discussing the results in terms of organized charge motions, turbulence levels, flame developments, NO and CO emissions. CFD simulations cover five load control cases: comparison is among conventional throttling, EIVC (Early Intake Valve Closure) with symmetric and asymmetric intake lifts, LIVC (Late Intake Valve Closure) and symmetrical Multi-Lift strategies. 3D U-RANS simulations are performed, adopting the Extended Coherent Flamelet Model (ECFM) for the description of premixed SI combustion. The 3D model is also coupled to a 1D engine model which provides inlet/outlet boundary conditions. Simulation results highlight the potential of asymmetric Early Intake Valve Closure (EIVC) strategy which allows reducing pumping losses and, at the same time, achieving good turbulence intensity and combustion speed, if compared to other load control strategies. Multi-Lift strategy resulted excellent in terms of burn duration, but pumping losses are practically the same as in the throttled engine.Copyright

Performance Analysis of Combined Cycles: Steam Recompression vs Conventional Bottoming Cycles

A performance analysis was fulfilled to compare the steam recompression with the conventional single- and dual-pressure bottoming cycles. The optimal parameters for each cycle were found in order to maximize the exergetic efficiency. Heat transfer surface was also calculated to show the differences in the size of the heat recovery steam generator which have a direct influence on the plant’s costs.The optimal configurations for each cycle were also studied when steam injection is employed. The relative performance when steam extraction is varied between 0 and 20% of the gas turbine’s compressor inlet mass flow rate, was also examined.Copyright

Second-Law Analysis of Fluidized-Bed Steam Generators

Direct and indirect exergy balances are applied to a simplified fluidized bed combustor. The major losses are calculated, including exergy from chemical reactions (combustion, calcination, and sulfation), heat transfer, and sensible heat release to the environment (ash and solid residue flows). The analysis is applied to atmospheric and pressurized fluidized bed combustors.Copyright