Antonio Giuffrida

Modelling and Simulation of a Hydraulic Breaker

Abstract This paper deals with the simulation of the working behaviour of a hydraulic breaker. A detailed parameterised model was realized in order to simulate physical phenomena occurring during the functioning of the machine. An appreciable agreement between experimental and theoretical pressure and frequency encouraged about the quality of the model. The dynamic behaviour of the moving masses was presented and thoroughly discussed. As a special remark, it is to be highlighted that the theoretical results suggested by the model came out not to vary if the real waveform concerning input flow rate is replaced with its average.

On the Effects of Syngas Clean-Up Temperature in IGCCs

This paper deals with the thermodynamic analysis of an IGCC power plant with hot syngas clean-up, where sulfur, particulate matter and trace contaminants are removed without cooling the syngas down to near-ambient temperature. With particular attention to the simulation of the desulfurization unit, adopting a regenerative process using a ZnO-based sorbent, a range of clean-up temperatures was investigated in order to evaluate its effects on overall plant performance. The study reveals the attractive chance of achieving overall electric efficiencies around 50%. However, a limited sensitivity of IGCC efficiency on desulfurization temperature was also obtained, since no significant improvements were accomplished for temperatures over 400°C. In order to support and better understand the results, a second law analysis was also carried out for the assessed cases. In addition, the effects of syngas clean-up temperature on the design and operation of the main IGCC processes and components, which can be relevant, were discussed.Copyright

CO2 Capture From Air-Blown Gasification-Based Combined Cycles

This paper focuses on an air-blown gasification-based combined cycle where CO2 is removed from the coal-derived gas before fuelling the combustion turbine. On the basis of public information from Mitsubishi Heavy Industries (MHI), the air-blown gasifier was modeled and its performance was investigated by the authors in a previous study. Here, with reference to a possible IGCC power plant with such a gasification technology, the possibility of removing CO2 from the coal-derived fuel gas is considered. The main differences between the two IGCCs, without and with CO2 capture, are gas used for coal loading (N2 or CO2), the layout of the syngas cooling and treatment sections (owing to the presence of watergas shift reactions and CO2 absorption process) and the composition of the fuel used in the combustion turbine. The results highlight that IGCC efficiency reduces by about 10.8% points when realizing CO2 capture, mainly due to the steam consumption in shift reactors and CO2 solvent regeneration and to power consumption for CO2 compression. However, the calculated efficiency penalty is in line with the values typical of IGCCs with oxygen-blown gasifier and CO2 capture.The power balances of the assessed cases are reported in detail and the main technical issues are discussed in the paper. The results of a sensitivity analysis are also reported to assess the effects of different steam to carbon ratios in the shift reactors.© 2012 ASME

Revamping, Energy Efficiency, and Exergy Analysis of an Existing Upstream Gas Treatment Facility

Surface oil and gas treatment facilities in service for decades are likely to be oversized due to the natural depletion of their reservoirs. Despite these plants might have been designed modularly, meaning they comprise multiple identical units serving the same task, such units operate often in conditions far from the design. This work analyzes the revamping options of an existing upstream gas facility, chosen because representative of a wide set of plants. It presents a flexible process simulation model, implemented in the HYSYS environment and dynamically linked to an Excel spreadsheet, which includes the performance maps of all turbomachineries and the main characteristics of the investigated modifications. The model may be used to run simulations for various gas input conditions and to predict the performance over 1 year of operation and for different possible future scenarios. The first objective is to assess economically the considered options, which shall be applied only if yielding short return times of the investment since the reservoir is mature. Moreover, all options are appreciated adopting a figure of merit, here defined, that compares the overall energy consumption to the one calculated with state-of-the-art technologies. In addition, exergy and environmental analyses are executed.

Numerical Investigations on the Working Cycle of a Hydraulic Breaker: Off-Design Performance and Influence of Design Parameters

Abstract This paper deals with theoretical considerations and numerical simulations concerning the working behaviour of a hydraulic breaker. At first, some formulations coming from sufficiently reasonable considerations on the working principle of the breaker, based on the hypothesis of the motion of the striking mass as uniformly accelerated, are proposed. Later, a previously realized parameterised model is used in order to investigate the influence of the inlet flow rate and of the most important design parameters on the behaviour of the machine. This analysis allows the characterization of these parameters affecting breaker performance, suggesting possible design improvements which may lead to better performance in terms of both impact energy and efficiency.

Study of the delivery behaviour of a pump for common rail fuel injection equipment

Abstract This work deals with the delivery flowrate of a radial piston pump for common rail fuel injection equipment. At first, attention is paid to the volumetric efficiency of the pump, presenting basic formulas and reviewing common theory. A new efficiency model is proposed and considerations regarding the pump running under large pressure differences between suction and delivery and variable driving speeds are formulated in order to realize difficulties in pump filling. Later, a numerical model simulating the working behaviour of the pump is used to investigate the effects of variable inlet pressures under high delivery pressure and different driving speeds. Comparisons between numerical results and experimental data referring to the delivery behaviour of the pump are reported, as well as in-cylinder pressure diagrams, necessary to realize filling deficiencies quickly. The flowrate delivered by the investigated pump depends on both the inlet and outlet pressures. Increasing the driving speed beyond certain values does not result in proportional flowrate at pump delivery.

Adding the Teaching of Claw Rotor Compressors to Fluid Machinery Courses

This paper deals with a rotary positive-displacement machine with built-in compression, the study of which is usually neglected in courses on fluid machinery for mechanical engineering students. First, the working principles of the claw rotor compressor are presented; then basic thermodynamic considerations, leading to the formulation of volumetric efficiency, are reported. The volumetric efficiency of the compressor is reviewed as a function dependent on filling and leakages, leading to the definition of the delivery efficiency. Considering the filling efficiency alone, formulated according to a thermodynamic analysis of the closed system, it is possible to determine the limit pressure ratio that causes no flow from the compressor. The ideal work is also formulated and a comparison with the sliding vane compressor is made. Some considerations that deprive the compressor of its ideality are advanced in order to avoid misleading conclusions.

Investigation on Realizing Fuel Rate Shaping Using a Common Rail Injector

The present work deals with the first researches into the real capabilities of an electronically controlled injector for common rail systems in realizing a proper shaping of the fuel rate with particular reference to its rising profile. Injectors equipped with standard and geometrically modified control valves have been investigated in detail by means of computer modeling and simulation. Experiments have been carried out in order to validate the feasibility of such a shaping and the injection rate meter based on the method proposed by Bosch was used. The main result of this work is a noteworthy dependence of the fuel rate on geometrical modifications in the piloting stage of the injector, since a certain difference in the slope of the first part of the fuel rate has been attained. The injector model has been finally used to investigate further geometrical modifications to be realized in order to achieve the desired fuel rate shaping.Copyright

Proposal of a Profile Geometry Suitable for Claw Rotor Compressors

Claw rotor compressors are rotary positive displacement machines with built-in compression. They are characterized by greater performance if compared to Roots blowers and are more efficient in discharging gas at pressures substantially higher than at suction. This paper aims at proposing a rotor profile suitable for the claw-type mechanism, with thorough indication of the profile geometry. After presenting some graphical cases of rotor profiles, drawn according to the proposed geometry, comparisons with a reference profile suggest that the proposed one seems to be preferable from a filling point of view.Copyright

On the Pressure Relief Valve for the Lubrication System of an Internal Combustion Engine

The lubrication system for automotive internal combustion engines consists of several components. Oil flow rate for lubrication is generated by a positive displacement pump equipped with a pressure relief valve, usually present in the casing of the pump to prevent high oil pressures building up in the system and to deliver to the sump the exceeding generated flow rate. This study focuses on the static and dynamic characteristics of the pressure relief valve with considerations about the stability of the overall system, according to design parameters of both the valve and the system itself.Copyright