Massimo Masi | Università degli Studi di Padova (original) (raw)

Papers by Massimo Masi

Volume 2: Combustion, Fuels and Emissions, Parts A and B, Oct 10, 2010

Proper cooling of the hot components and an optimal temperature distribution at the turbine inlet... more Proper cooling of the hot components and an optimal temperature distribution at the turbine inlet are fundamental targets for gas turbine combustors. In particular, the temperature distribution at the combustor discharge is a critical issue for the durability of the turbine blades and the high performance of the engine. At present, CFD is a widely used tool to simulate the reacting flow inside gas turbine combustors. This paper presents a numerical analysis of a single can type combustor designed to be fed both with hydrogen and natural gas. The combustor also features a steam injection system to restrain the NOx pollutants. The simulations were carried out to quantify the effect of fuel type and steam injection on the temperature field. The CFD model employs a computationally low cost approach, thus the physical domain is meshed with a coarse grid. A full-scale test campaign was performed on the combustor: temperatures at the liner wall and the combustor outlet were acquired at different operating conditions. These experimental data, which are discussed, were used to evaluate the capability of the present CFD model to predict temperature values for combustor operation with different fuels and steam-fuel ratios.

More than half a century has been spent by technicians involved in fans testing to suggest and fi... more More than half a century has been spent by technicians involved in fans testing to suggest and fix best practice procedures including also the definitions of several performance and efficiency parameters (e.g., ISO, AMCA, ASHRAE Standards...). However, the huge amount of energy used by ventilation systems and the recent introduction of the stringent European Community regulations on Energy Related Products, suggests to spend additional time on the ancient question about which and how many should be the parameters best suited to classify the performance of fans and their capability to properly use the energy input. This also because there are some attempts to fix the fan total-to-static pressure rise and the related total-to-static efficiency as the only two parameters required to assess the fan quality. Starting from basic thermodynamic principles, this paper tries to shed light on the parameters that are best suited to assess fan performance and efficiency. The general layout of a ventilation system is discussed to clearly show which and how many are the parameters required for the optimal matching between fan and system. Finally, some comments on practical advantages and drawbacks in the operation of the fan at the total-to-static best efficiency point are presented as well.

The paper deals with the aerodynamic performance of ducted axial-flow fans available in the 2020 ... more The paper deals with the aerodynamic performance of ducted axial-flow fans available in the 2020 market and aims to create a general picture of the best designs and design trends, as a tool for fan designers. To this end, the paper first presents the general formulation of the similarity approach to the fan performance analysis, including the effects of rotational speed (which affects the validity of the Reynolds similarity) and turbomachine size (which can hinder the perfect geometrical similarity of some shape details). The second part reports a statistical survey of the axial-flow fan performance based on data from catalogues of major manufacturers, and compares the resulting Cordier-lines with optimum fan designs from empirical or CFD-based models available in the literature. In addition to the global performance at maximum aeraulic and total-to-static efficiencies, this survey uses the form of dimensionless Balje-Cordier charts to identify the trends and values of other design parameters, such as hub-to-tip ratio, blade count, and blade positioning angle. As a result, a summary of the aerodynamic performance of year 2020 best designs, the improvements achieved during the last forty years, and the present design trends in contra-rotating, vane-axial, and tube-axial fan types are made available to fan designers.

Nucleation and Atmospheric Aerosols, 2019

Paddle-wheels embedded in either L-shaped or T-shaped dummy cylinders are commonly used to measur... more Paddle-wheels embedded in either L-shaped or T-shaped dummy cylinders are commonly used to measure the in-cylinder tumble motion intensity supplied by a specific engine head design at the steady-state discharge-flow bench. A few years ago, the authors designed a new in-cylinder flow meter that enables the measurement of tumble intensity without the need for L-or T-junctions. The in-cylinder flow meter demonstrated the capability: to capture different intensities of tumble motion resulting from different engine head design; to provide data well correlated with the CFD simulation of experiments. The aim of this paper is to assess the reliability of the data obtained by this new paddle-wheel device, considering that the lack of the piston crown simulacrum could strongly affect the onset and intensity of tumble flow measured at the steady-state flow-bench. To this aim, in-cylinder motion of two high-speed engine heads, as measured by the new paddle-wheel device, are compared with data from the literature, which was collected using traditional L-or Tjunction tumble meters. In addition, the results of CFD predictions for the angular momentum acting on three different Tshaped tumble meters applied on one of the two engine heads subject of the tests are studied to explain the differences in trends and values of tumble intensity data obtained by using either the new or the traditional paddle-wheel devices. Within the several limitations affecting such category of tumble meters, the results demonstrate the reliability of the new device.

Energy Conversion and Management, Aug 1, 2012

ABSTRACT The use of Liquefied Petroleum Gas (LPG) as fuel for spark ignition engines originally d... more ABSTRACT The use of Liquefied Petroleum Gas (LPG) as fuel for spark ignition engines originally designed to be gasoline fuelled is common practice in many countries. Despite this, some questions remain still open. The present paper deals with the two main problems related to LPG port-fuel SI engines: the volumetric efficiency drop and the LPG evaporator device performance. A passengers car SI engine equipped with a “third generation” kit for the dual-fuel operation was tested using a dynamometer test rig. A single-stage pressure reducer was selected as LPG evaporator, to take advantage of an additional pre-heating of the liquid LPG that allows higher power output than a two-stage device of the same size.Engine performance, volumetric efficiency and change of LPG thermodynamic states in the evaporator were measured both in steady-state and transient operation of the engine. Steady-state measurements show the advantage of LPG in terms of engine efficiency, and quantify the drop in steady-state brake torque due to the volume swept by gaseous fuel in the fresh charge admission process. On the other hand, transient measurements show that a single-stage evaporator device is capable to match overall simplicity and satisfactory performance during strong changes in engine load.

Energy Procedia, Dec 1, 2015

Biomass gasification converts a solid fuel into a gaseous mixture (syngas or producer gas) which ... more Biomass gasification converts a solid fuel into a gaseous mixture (syngas or producer gas) which can be burnt in reciprocating internal combustion engines (ICEs) to produce electrical power. A wide variety of bio-residues can be processed to obtain syngas, making biomass gasification a very interesting way to exploit the energy content of industrial by-products and agricultural wastes. This paper focuses on the operation of a spark ignition (SI) ICE burning low-heating value gas produced in a fixedbed downdraft gasifier. The biomass gasification power plant has collected more than nine months of operation till now without need of any extraordinary maintenance of the engine. Engine performance is calculated using experimental data acquired at different air-to-fuel ratios and spark timings, and then compared with results of test performed by other authors. The work is mainly aimed at analysing the effect of PG fuelling on brake power, efficiency and emissions of heavy-duty engines.

SAE technical paper series, Sep 6, 2015

Energy, May 1, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Energies, Nov 5, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

<jats:title>Abstract</jats:title> <jats:p>This work deals with the application ... more <jats:title>Abstract</jats:title> <jats:p>This work deals with the application of the open source CFD code MULTALL to the analysis of tube-axial-fans. The code has been widely validated in the literature for high-speed turbomachine flows but not applied yet to low speed tutbomachines. The aim of this work is to assess the degree of reliability of MULTALL as a tool for simulating the internal flow in industrial axial-flow fan rotors. To this end, the predictions of the steady-state air flow field in the annular sector of a 315 mm tube-axial fan obtained by MULTALL 18.3 are compared with those obtained by two state-of-the-art CFD codes and experimental data of the global aerodynamic performance of the fan and the pitch-wise averaged velocity distribution downstream of the rotor. All the steady-state RANS calculations were performed on either fully structured hexahedron or hexa-dominant grids using classical formulations of algebraic turbulence models. The pressure curve and the trend of the aeraulic efficiency in the stable operation range of the fan predicted by MULTALL show very good agreement with both the experimental data and the other CFD results. Although the estimation of the fan efficiency predicted by MULTALL can be noticeably improved by the more sophisticated state-of-the-art CFD codes, the analysis of the velocity distribution at the rotor exit supports the use of MULTALL as a reliable CFD analysis tool for designers of low-speed axial fans.</jats:p>

International Journal of Automotive and Mechanical Engineering, Oct 10, 2019

The paper addresses the problem of signal-dependent sampling of analogue signals according to loc... more The paper addresses the problem of signal-dependent sampling of analogue signals according to local bandwidth. An extended sampling theorem is given which states that signals can be sampled non-uniformly and then perfectly reconstructed if spectrum obtained by an extended Fourier transform (EFT) is bandlimited. Since, according to the theorem, the sampling instants are determined by the function used in EFT, the aim is to find such function which reflects the timevarying spectral content of the signal. This, in comparison to uniform sampling, allows reducing the number of samples required to represent the signal. The results have been demonstrated by numerical simulations on two signals.

This paper presents a simple but complete design method to obtain arbitrary vortex design tube-ax... more This paper presents a simple but complete design method to obtain arbitrary vortex design tube-axial fans starting from fixed size and rotational speed. The method couples the preliminary design method previously suggested by the authors ago with an original revised version of well-known blade design methods taken from the literature. The aim of this work is to verify the effectiveness of the method in obtaining high efficiency industrial fans. To this end, the method has been applied to a 315mm rotor-only tube-axial fan having the same size and rotational speed, and a slightly higher flow rate coefficient, as another prototype previously designed by the authors, which was demonstrated experimentally to noticeably increase the pressure coefficient of an actual 560mm industrial fan. In contrast, no constraints are imposed on the hub-to-tip ratio and pressure coefficient. The new design features a hub-to-tip ratio equal to 0.28 and radially stacked blades with aerodynamic load distribution corresponding to a roughly constant swirl at rotor exit. The ISO-5801 experimental tests showed a fan efficiency equal to 0.68, which is 6% higher than that of the previous prototype. The pressure coefficient is lower, but still 12% higher than that of the benchmark 560mm industrial fan.

Electronic Research Archive

When a malfunction occurs in a marine main engine system, the impact of the anomaly will propagat... more When a malfunction occurs in a marine main engine system, the impact of the anomaly will propagate through the system, affecting the performance of all relevant components in the system. The phenomenon of fault propagation in the system caused by induced factors can interfere with fault localization, making the latter a difficult task to solve. This paper aims at showing how the "characteristic curves method" is able to properly locate malfunctions also when more malfunctions appear simultaneously. To this end, starting from the working principle of each component of a real marine diesel engine system, comprehensive and reasonable thermal performance parameters are chosen to describe their characteristic curves and include them in a one-dimensional thermodynamic model. In particular, the model of a low-speed two stroke MAN 6S50 MC-C8.1 diesel engine is built using the AVL Boost software and obtaining errors lower than 5% between simulated values and test bench data. The be...

Applied Energy, 2022

The temporal and geographical availability of renewable energy sources is highly variable, which ... more The temporal and geographical availability of renewable energy sources is highly variable, which imposes the importance of correct choices for energy storage and energy transport systems. This paper presents a smart strategy to utilize the natural gas distribution grid to transport and store the hydrogen. The goal is twofold: evaluating the capacity limits of the grid to accommodate "green hydrogen" for preset increasing shares of renewable energy sources (RESs) and determining at the same time the optimal mix of wind, photovoltaic (PV), biomethane and power-togas systems that minimizes the investment and operation costs. To this end, the energy supply system of an entire country is modelled and optimized considering the real characteristics and pressure levels of the gas grid, which is assumed to be the only storage mechanism of green hydrogen. The operational concept is to fill up the gas grid with hydrogen during the day and with natural gas during the night while always consuming the natural gas-hydrogen blend. Green hydrogen is generated by electrolysers powered by PVs, wind turbines and biomethane power systems. Results of the optimizations showed that: i) as long as the share of RES does not exceed 20%, there is no need to use the gas grid as RES storage system, ii) from 20 to 50% of RES share the gas grid receives the surplus of electricity in the peaks that would be necessary to "complete" the dispatchability of RES electricity, iii) above 50%, the excess of electricity in the peaks has to be used to generate the thermal energy required by the consumers. The gas grid can be used as unique renewable energy carrier and storage system up to 65% of RES share.

Applied Thermal Engineering, 2017

Thermoacoustic instabilities usually result from the coupling between the oscillatory heat releas... more Thermoacoustic instabilities usually result from the coupling between the oscillatory heat release and one or more natural acoustic modes of the combustion system. When the shifting of system frequencies caused by the unsteady heat release is limited, the calculation of natural modes allows to identify which of them are excited by the flame once changes in flow temperature and composition due to combustion are considered. In this paper isothermal computational fluid dynamics simulations are performed to predict the natural modes of a heavy-duty gas turbine combustor in reactive conditions. Combustion and heat transfer are neglected in the numerical analysis to simplify the model and limit the computational effort. The natural frequencies resulting from isothermal simulations are then corrected using a rather basic post-processing approach to account for temperature and gas composition changes due to combustion process. Frequency and amplitude of the calculated modes are finally compared to experimental measurements to evaluate the capability of the acoustic analysis to capture frequency and spatial shape of the combustor natural modes excited by the flame.