Performance Analysis of a Producer Gas-fuelled Heavy-duty SI Engine at Full-load Operation

Abstract 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 fixed-bed 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

Comparison of the Aerodynamic Performance of Four Racing Bicycle Wheels by Means of CFD Calculations

AbstractAerodynamic drag is the main source of losses in cycling so improving the bicycle aerodynamic is a fundamental key factor to increase the performance. The aim of this work is to assess the capability of CFD RANS simulations to predict the aerodynamic performance of modern racing bicycle wheels. This paper describes the design and development of a numerical model for the resolution of the airflow field surrounding four different racing wheels. Drag and side forces are resolved and compare to experimental data (and other simulation results) taken from the literature

energy efficiency ratio eer of novel air conditioning system on lpg fuelled vehicle a lab scale investigation

Alternative fuels have become an effective solution to reduce the impact of road transport on the environment. On the other hand, the growing uses of air-conditioning (AC) have contributed to worsening the fuel economy of passenger vehicles. Liquid petroleum gas (LPG), if injected in the gaseous phase to power SI engines, may allow reducing the fuel consumption due to AC devices through the recovery of cooling energy from the fuel systems. This paper presents lab-scale tests of an air conditioning system prototype for LPG-fuelled vehicles. The prototype has been assembled using standard vehicle components to quantify the cooling energy recoverable from the LPG evaporation before the fuel is injected into the engine intake manifold. Temperature and humidity of the air exiting the LPG evaporator are measured for fuel mass flow rates typical of light-duty vehicles. The energy efficiency ratio (EER) of the prototype achieves 2.72 when cooling power equals 1.2 kW. Although the system tested needs improvements, the experimental data show that the cooling energy recovered by LPG evaporation can significantly reduce the power consumption of standard AC systems in passenger cars

The Effect of Keratinized Mucosa on Peri-Implant Health and Patient-Reported Outcome Measures: A Systematic Review and Meta-Analysis

Objectives: The aim of this systematic review was to analyze the effect of keratinized mucosa (KM) on different peri-implant health-related parameters and on patient-reported outcome measures (PROMs). Material and methods: Randomized controlled trials, cohort, cross-sectional and case-control human studies with a follow-up period of at least 6 months comparing two groups of patients with presence or absence of KM, or with KM < 2 mm or & GE;2 mm were included. Primary outcomes were implant failures, PROMs and BoP (BoP/mBI). Additional outcomes were PPD, plaque accumulation (mPI/PI), gingival inflammation (GI/mGI), marginal bone loss (MBL), soft tissue recession (REC) and biological complications. Results: Fifteen studies were included (one RCT, two cohort prospective and twelve cross-sectional). Meta-analysis was performed for cross-sectional studies. Implant failure and complications were not presented as outcome measures, and five studies analyzed PROMs. Results from the meta-analysis reported no evidence of any statistical significant difference between groups in PPD, BoP and MBL, while a statistical significant difference in GI/BI, PI and REC was present in favor of the group with KW & GE; 2 mm. More biological complications were present in the group with no KM/KM < 2 mm but few cases were present to draw any conclusions. Although a meta-analysis could not be performed, a consistent trend toward the worst pain/discomfort in KM < 2 mm was observed. Conclusions: No clear evidence was found supporting the role of KM in peri-implant health and PROMs, even if more plaque and marginal inflammation were present in the KM < 2 mm group. Clinical relevance: KM could have a role in patients with erratic maintenance and patient comfort

Studio delle instabilità termoacustiche in un combustore di turbina a gas

Combustion instabilities are a major technical problem in most of industrial applications since they cause a performance deterioration of the combustion process. Under unstable operation the large amplitude oscillations of the flow induce many dangerous effects such as large mechanical vibrations, noise, augmented heat transfer rates at the combustor walls and increased pollutant emissions. In the gas turbines, an unstable heat release inside the combustion chamber can damage the hottest components of the combustor and reduce the life of the turbine blades. This study presents an investigation of the thermoacoustic behaviour of a single can gas turbine combustor. The combustor, originally conceived for operation with liquid and gaseous fossil fuels, was modified by the manufacturer to burn pure hydrogen or hydrogen/natural gas mixtures. Combustor design development was supported by experimental activities performed on a full-scale full-pressure test rig. A detailed procedure is proposed in this work to study the thermoacoustic instabilities in the combustor. Both hydrogen and natural gas operation are simulated by means of CFD RANS simulations carried out on a finite volume commercial code. The three-dimensional CFD analyses are performed on a coarse grid and take advantage of simplified numerical models to reduce the computation time. Due to this approach, the CFD analyses can simulate the time dependent thermoacoustic reactive flow field for a period of time large enough to capture unstable oscillation regimes, if present. Experimental measurements are used to impose the model boundary conditions and to validate the numerical results. The pressure signals recorded during the simulated period show a constant low-amplitude oscillation (a limit cycle) which does not affect the combustor performance. This behaviour agrees with the experimental data acquired during the combustion tests. The final part of this study compares the computed frequency spectra with the measured ones. The good agreement between the numerical results and the experimental values validate the potential of the low computational cost CFD approach to describe the thermoacoustic behaviour of the considered combustor.L'instabilità di combustione peggiora le prestazioni di un combustore a flusso continuo e pertanto deve essere considerata un fenomeno indesiderato. Fluttuazioni della pressione e del rilascio termico possono infatti causare vibrazioni meccaniche, rumore, formazione di punti caldi sulle pareti della camera di combustione e incremento delle emissioni inquinanti. La combustione instabile è particolarmente dannosa nei combustori per turbina a gas nei quali ampie oscillazioni di portata e di rilascio termico possono danneggiare irreparabilmente le parti fisse e rotanti della turbina. Nel lavoro che si presenta viene studiato il comportamento termoacustico di un combustore di turbina a gas. Il combustore esaminato è del tipo tubolare, con singolo bruciatore a fiamma diffusiva ed è stato modificato dal costruttore per essere alimentato non solo a gas naturale ma anche a idrogeno. Il processo di sviluppo è stato supportato da prove di combustione su scala reale eseguite su un banco prova in grado di riprodurre le condizioni di pieno carico. L’analisi termoacustica viene condotta seguendo una procedura di indagine basata sulla simulazione numerica del fenomeno mediante un codice numerico commerciale con modelli di turbolenza di tipo RANS. Nelle analisi numeriche i modelli numerici e le griglie di calcolo sono scelti in modo da minimizzare tempi e risorse di calcolo. In questo modo è possibile simulare un intervallo temporale sufficientemente ampio da consentire al sistema di evolvere liberamente fino alle condizioni di regime per poter così valutare l’eventuale presenza di instabilità termoacustiche. Le misure raccolte durante le prove sperimentali sono impiegate nei calcoli sia per l’imposizione delle condizioni al contorno sia per la valutazione dei risultati. I segnali di pressione registrati durante le simulazioni mostrano la permanenza di oscillazioni di pressione nel combustore caratterizzate da un’ampiezza piuttosto ridotta. Queste oscillazioni sono dunque ampiamente tollerabili dal sistema (la combustione è ovunque completa e non vi sono fenomeni di estinzione di fiamma e di surriscaldamento delle pareti del combustore), in accordo con quanto osservato durante le prove sperimentali. Gli spettri calcolati al termine delle simulazioni sono comparati con gli spettri acquisiti durante le prove di combustione. Dal confronto emerge una sostanziale corrispondenza tra i modi di vibrare calcolati e quelli misurati al banco prova

Analisi termofluidodinamica di configurazioni elementari di scambiatore acqua-fumi per caldaie domestiche

Rapporto per BSG Caldaie a Gas S.p.A. di Veron

Measure of the volumetric efficiency and evaporator device performance for a LPG SI engine

The use of LPG as fuel for spark ignition engines originally designed to be petrol fuelled is common practice in many countries. Despite some theoretical and technical advantages related to LPG fuelling of internal combustion engines, the driving force for the ever-increasing adoption of LPG as fuel for passengers cars still remains its low price. However, money saving for the end-user is falling down year after year enforcing both technical developments and scientific research. Following some previous experimental studies about the real performance of dual-fuel engines during LPG operation, 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 \u201cthird generation\u201d kit for the dual-fuel operation was tested at the dynamometer. Measures of engine performance, volumetric efficiency and change of LPG thermodynamic states in the evaporator were acquired both in steady state and transient operation of the engine. Experimental data are presented and discussed to evaluate the performance of the dual-fuel engine

Measure of the volumetric efficiency and evaporator device performance for a Liquefied Petroleum Gas SI engine

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 \u201cthird generation\u201d 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

Improvement of the Outlet Temperature Distribution of a Dual-Fuel Gas Turbine Combustor by a Simplified CFD Model

The mixing process within the dilution zone noticeably affects the temperature field in the outlet section of a gas turbine combustor. In fact, dilution jets lower the temperature of the hot flow exiting the primary zone establishing suitable temperature profile and pattern factor at the combustor outlet. Thus, the dilution zone design has a significant impact on performance and durability of the turbine. In this study, a dual fuel gas turbine combustor is investigated by a commercial finite-volume CFD code. The computational domain extends from the compressor discharge to the gas turbine inlet and it is meshed with a coarse grid since it was originally conceived for thermoacoustic analysis. The model has been already validated throughout measurements acquired during full scale isothermal and reactive tests. On the basis of the results of reactive simulations, several solutions of the dilution zone are designed to improve the uniformity of radial and circumferential temperature at the turbine inlet. The designed configurations feature number, arrangement and diameter of dilution holes which differ from the commercial configuration providing four identical dilution holes equally spaced. Advantages and drawbacks of each dilution zone layout are supported by results of numerical calculations. The results suggest that the solutions featuring two dilution holes perform better than the actual layout