Intake Duct Research Articles

Fluid Properties at Gas Turbine Inlet Due to Fogging Considering Evaporation and Condensation Phenomena as Well as Icing Risk

This study reports on numerically calculated thermophysical properties of air entering a gas turbine compressor after passing through an intake duct affected by different cooling techniques. Case of reference is unaffected ambient air (referenced to as unaffected) passing the intake duct. Furthermore, ambient air cooled down to wet bulb temperature by (overspray) fogging (referenced to as wet) was considered. The third case shows air cooled down to the same temperature as it was reached in the wet case but by using chillers (referenced to as chilled). Equilibrium and nonequilibrium properties according to the occurring evaporation and condensation phenomena were compared. Equilibrium conditions seem to have a reduced inlet icing risk for the wet case compared to the chilled case. However, comparing the wet case to the unaffected case showed a higher icing risk for the wet case at low ambient relative humidity. In contrast to equilibrium conditions, a consideration of nonequilibrium conditions resulted in an increased icing risk due to almost negligible condensation rates.

Influence of Intake on Fan Blade Flutter

The main aim of this paper is to study the influence of upstream reflections on flutter of a fan blade. To achieve this goal, flutter analysis of a complete fan assembly with an intake duct and the downstream outlet guide vanes (OGVs) (whole low pressure (LP) domain) is undertaken using a validated computational fluid dynamics (CFD) model. The computed results show good correlation with measured data. Due to space constraints, only upstream (intake) reflections are analyzed in this paper. It will be shown that the correct prediction of flutter boundary for a fan blade requires modeling of the intake and different intakes would produce different flutter boundaries for the same fan blade. However, the “blade only” and intake damping are independent and the total damping can be obtained from the sum of the two contributions. In order to gain further insight into the physics of the problem, the pressure waves created by blade vibration are split into an upstream and a downstream traveling wave in the intake. The splitting of the pressure wave allows one to establish a relationship between the phase and amplitude of the reflected waves and flutter stability of the blade. By using this approach, a simple reflection model can be used to model the intake effects.

A comprehensive modeling study of in-cylinder fluid flows in a high-swirl, light-duty optical diesel engine

The effectiveness of computational fluid dynamics modeling as a tool for researching fuel-lean, low temperature engine combustion strategies relies on its capability to capture the local fluid flow properties that affect spray dynamics, mixture preparation and ignition kinetics. In this study, a comprehensive model of an optically accessible, single-cylinder light-duty diesel engine was developed for engine combustion research. The computational model includes the realistic combustion chamber and ducts geometries. Variable orientation throttles in the intake ducts were modeled to reproduce variable swirl generation. Full induction stroke calculations were run over a portfolio of intake swirl conditions, and validated against extensive measurements featuring global intake swirl ratios, in-cylinder particle image velocimetry (PIV)-measured velocity fields and swirl centers. The results showed good agreement with the experiments, and the model was used to understand the effects of different swirl generation strategies on the in-cylinder flow field. The implications of using simplified sector mesh geometries on the predictiveness of in-cylinder flow and turbulence quantities are described.

3D CFD Analysis of the Influence of Some Geometrical Engine Parameters on Small PFI Engine Performances – the Effects on the Tumble Motion and the Mean Turbulent Intensity Distribution

In scooter/motorbike engines coherent and stable tumble motion generation is still considered an effective mean in order to both reduce engine emissions and promote higher levels of combustion efficiency. The promotion of a stable and coherent tumble structure is largely believed in literature to enhance in-cylinder turbulence accelerating combustion process. In small PFI engine layout and weight constraints limit the adoption of more advanced concepts. In previous technical papers the authors demonstrated the influence of head shape and squish area on tumble vortex formation, development, breakdown and on final value of turbulence close to spark plug for small PFI engines. The main result of the this research was that the combustion chamber having the less squish area resulted to have the highest level of turbulence close to spark plug at ignition time. The geometry under analysis in the current paper is a 3-valves pent-roof motorcycle engine. 3D CFD simulations were ran at 6500rpm with AVL FIRE code. The chosen engine geometry was the geometry found to be the best set-up in terms of turbulence and combustion performances in the previous paper. In the present paper the head shape and the squish area were kept constant and the following engine parameters were varied: the intake duct angle (the angle of the intake duct entering the head was reduced of 6%, i.e. it was more directed toward the exhaust side of the chamber), the piston shape, and finally the compression ratio (it was reduced of 9%). The main goal of the current analysis is to understand which of these parameters is predominant in accelerating combustion for directing engine design toward the best set-up.

Pre-lift Valve Actuation Strategy for the Performance Improvement of a DISI VVA Turbocharged Engine

Modern internal combustion engines (ICEs) are becoming more and more complex in order to achieve not only better power and torque performance, but also to respect the pollutant emissions and the fuel consumption (CO2) limits.The turbocharger, advanced valve actuation systems (VVA) and the EGR circuit allow the ICE's load control together with the traditional throttle valve and spark advance. Thus, an higher number of operating parameters are available for the calibration engineer to achieve the required performance target (minimum fuel consumption at part load, maximum power and torque at full load, etc.). On the other hand, the increased degrees of freedom may frustrate the potentialities of so complex systems because of the effort needed to identify the optimal engine control strategies. The development of proper numerical models may assist and direct the experimental activity in order to reduce the related times and costs.Although VVA solutions could bring a reduction in the specific fuel consumption thanks to an important de-throttling of the intake system, unfortunately they can simultaneously lead to higher noise levels radiated by the intake mouth. In fact, in this case, the pressure waves travelling through the intake ducts are not properly damped by the throttle valve.In this paper a numerical methodology is developed to define the engine calibration and the intake valve lift profile that simultaneously minimize the BSFC and the noise at part load. The engine object of the study is a turbocharged Spark-Ignition Direct Injection (SIDI) ICE equipped by a lost motion valve actuation system for the intake valves. In this study, the commercial 1D thermo fluid-dynamic code GT-PowerTM is provided with user routines for the description of the combustion process and the handing of variable valve lift profiles. The engine model is thus integrated with a commercial optimization code (modeFRONTIERTM) to identify the optimized load control strategies to achieve the set objectives. The proposed methodology is also used for the definition of unconventional valve lift profiles. Particularly, the advantages related to the use of a small pre-lift before the main valve lift profile are estimated compared to a conventional EIVC strategy.

Development of a Emission Compliant, High Efficiency, Two-valve DI Diesel Engine for Off-road Application

Nowadays, environmental concerns are posing a great challenge to DI Diesel engines. Increasingly tightening emission limits require a higher attention on combustion efficiency. A high efficiency Diesel engine can be developed only mastering all the parameters that can affect the combustion and, therefore, NOx and soot emissions. In this scenario, computational fluid-dynamics can prove its power guaranteeing a deeper understanding of mixture formation process and combustion.In this work, the development of an engine in order to fulfill Tier 4i emission standard will be presented, the Tier 4i compliance must be reached without an excessive increase of the final cost of the engine. Originally, the engine was a two-valve engine supplied with a DPF, since no SCR aftertreatment is supplied, NOx emission target are achieved through external exhaust gas recirculation and retarding the start of injection.Through combustion process simulations, performed with the CFD code KIVA3D, varying different geometric parameters and the intensity of the swirl ratio, the interaction between the swirl flow field, generated by the intake duct, the reverse squish motion, and motions aerodynamically generated by spray has been investigated leading to a better interaction between the flow field, the fuel spray and the piston bowl geometry and to the definition of a new engine lay-out. The study shows how, given the need of retarded injection for limiting NOx emission, the decrease of swirl ratio, when combined with a proper piston bowl design, allows a significant decrease of soot emissions and the achievement of Tier 4i emission standard.The study has been validated comparing the intake phase simulations, performed with the CFD code Fire v2009 v3, followed by the combustion process performed with the KIVA3D code, with the experimental result obtained from the engine assembled following the developed design.

Tumble Motion Generation in Small Gasoline Engines: A New Methodological Approach for the Analysis of the Influence of the Intake Duct Geometrical Parameters

For motorbike and motor scooter applications, the optimization of the tumble generation is considered an effective way to improve the combustion system efficiency and to lower the emissions, considering also that the two-wheels layout represents an obstacle in adopting the advanced post-treatment concepts designed for the automotive applications.During the last years the deep re-examination of the engine design for lowering the engine emissions involved the two-wheel vehicles too. The IC-engine overall efficiency plays a fundamental role in determining the final raw emissions. From this point of view, the optimization of the in-cylinder flow organization is mandatory. In detail, in SI-engines the generation of a coherent tumble vortex having dimensions comparable to the engine stroke could be of primary importance to extend the engines’ ignition limits toward the field of the dilute/lean mixtures.The aim of the paper is to introduce a new analysis approach for a deep insight of the 3D-CFD results performed to assess the intake duct geometry influence on the tumble motion generation during both the intake and the compression strokes. All the CFD simulations presented in the paper were performed by the AVL-FIRE v.2010 CFD code on a SI 4 valve engine characterized by an unit displacement of 250cm3. The tumble structure was changed during the analysis by changing the angle set defining the intake port shape. The stroke-to-bore engine ratio was kept constant to 0.7. The effects of the tumble variations were evaluated in terms of the tumble ratio, the turbulent kinetic energy and the vortex characterization at IVC.

Evaluation of the Mixture Formation Process of High Performance Engine with a Combined Experimental and Numerical Methodology

The combustion process of a Port Fuel Injection (PFI) engine is deeply influenced by the mixture formation process. The needs of reducing engine emission and fuel consumption push the engine manufactures to implement new advanced experimental and numerical techniques to better control the mixture quality. The local mixture air-index at the spark plug is closely related to combustion instabilities and the Indicated Mean Effective Pressure (IMEP) Coefficient of Variation (CoV) well correlates with the variability of the flame kernel development. The control of air to fuel ratio is especially critical for high performance engines: due to the low stroke-to-bore ratio the maximum power is reached at very high regimes, letting little time to the fuel to evaporate and mixing with air. The injector located upstream the throttle causes a lot of fuel to impinge the throttle and intake duct walls, slowing down the dynamics of mixture formation under part load conditions.The aim of the paper is to present a multi-cycle methodology for the simulation of the injection and the mixture formation processes of high performance PFI engine, in order to evaluate both the quality of combustion and the fuel dynamics in the intake duct.The phenomena involved in the process are highly heterogeneous, and particular care must be taken to the choice of CFD models and their validation. In the present work all the main models involved in the simulations are validated against experimental tests available in the literature, selected based on the similarity of physical conditions of those of the engine configuration under analysis. The lagrangian spray is initialized with a semi-empirical methodology, based on available experimental data, and its interaction with the wall is simulated by means of the Kuhnke model, so to take into account the high wall temperature of the intake valves during impingement. The dynamics of the wall film are accurately represented by the activation of momentum equation of wall film and a validation of its dynamics is accomplished against proper test cases.The methodology is applied in two different engine configurations with separate objectives: a part load condition, where the dynamics of fuel in the intake duct is crucial to ensure drivability, a full load configuration, for the evaluation of mixture quality and combustion stability.

Comparisons of Hydraulic Performance in Permanent Maglev Pump for Water-Jet Propulsion

The operation of water-jet propulsion can generate nonuniform inflow that may be detrimental to the performance of the water-jets. To reduce disadvantages of the nonuniform inflow, a rim-driven water-jet propulsion was designed depending on the technology of passive magnetic levitation. Insufficient understanding of large performance deviations between the normal water-jets (shaft) and permanent maglev water-jets (shaftless) is a major problem in this paper. CFD was directly adopted in the feasibility and superiority of permanent maglev water-jets. Comparison and discussion of the hydraulic performance were carried out. The shaftless duct firstly has a drop in hydraulic losses ( K1), since it effectively avoids the formation and evolution of the instability secondary vortex by the normalized helicity analysis. Then, the shaftless intake duct improves the inflow field of the water-jet pump, with consequencing the drop in the backflow and blocking on the blade shroud. So that the shaftless water-jet pump delivers higher flow rate and head to the propulsion than the shaft. Eventually, not only can the shaftless model increase the thrust and efficiency, but it has the ability to extend the working range and broaden the high efficiency region as well.

The Analysis of Diesel Engine Intake System Simulation Based on Multivariate Joint Optimization

The paper was based on multivariable joint optimization. It established an optimization process of diesel engine intake system. The simulation model was built in AVL-BOOST and tested by experiments. As the design variables of intake system parameters (diameter and length of intake duct and intake manifold) were used to orthogonal test. Through the calculation of the engine performance optimization, the sum of paper was the impact of key parameters of the intake system on the performance of engine, and the influence of variable parameters on the volumetric efficiency of engine. These works provided a theoretical reference of intake system optimization design.

Mass flow estimation with model bias correction for a turbocharged Diesel engine

A systematic design method for mass flow estimation with correction for model bias is proposed. Based on an augmented observable Mean Value Engine Model (MVEM) of a turbocharged Diesel engine, the online estimation of states with additional biases is performed to compute the mass flows for different places. A correction method is applied, that utilizes estimated biases which are in a least-square sense redistributed between the correction terms to the uncertain mass flow maps and then added to the estimated mass flows. An Extended Kalman Filter (EKF) is tested off-line on production car engine data where the combination of an intake manifold pressure sensor, exhaust manifold pressure sensor and turbocharger speed sensor is compared and discussed in different sensor fusions. It is shown that the correction method improves the uncorrected estimated air mass flow which is validated against the airflow data measured in the intake duct.

Potentialities of a Common Rail Injection System for the Control of Dual Fuel Biodiesel-Producer Gas Combustion and Emissions

This paper conducts an extensive experimental campaign for dual fuel biodiesel-producer gas combustion development and the related pollutant emissions and reports the results with the aim of highlighting the effect of biodiesel pilot injection parameters. For this purpose, a common rail diesel research engine was converted to operate in dual fuel mode; the gaseous fuel was introduced into the engine through an indirect injector housed well upstream of the engine intake duct; and the composition of the gaseous fuel simulating the producer gas was obtained using a mixing system able to generate a gaseous mixture of carbon monoxide (CO), hydrogen (H2), and nitrogen (N2) with the desired amount for each of them. The biodiesel pilot injection required to ignite the gaseous fuel was instead sprayed into the cylinder using a common rail high-pressure injection system. During tests, the biodiesel injection amount, pressure, and advance were varied on several levels, together with the composition and amount of gaseous fuel. The cylinder pressure was sampled and, from it, heat release rate and indicated mean effective pressure were estimated. Moreover, gaseous pollutant emissions at the exhaust were measured. The results demonstrate that biodiesel pilot injection parameters are crucial to control the development of combustion and emission levels when the engine is operated in dual fuel biodiesel-producer gas mode. Therefore, the potentialities of the common-rail high-pressure injection system may be developed to optimize as much as possible the operation of such engines in terms of power output, increase in combustion efficiency, and reduction of environmental impact.

INFLUENCE OF THE MARINE 4-STROKE DIESEL ENGINE MALFUNCTIONS ON THE NITRIC OXIDES EMISSION

The article presents the results of the laboratory study on nitric oxides (NOx) emission level from marine fourstroke diesel engine. The object of the study was laboratory piston engine, operating at constant speed. Measured engine parameters were necessary to determine the NOx emission in accordance of the requirements of the Annex VI to MARPOL 73/78 Convention. The study consisted of tests during the engine operation without malfunctions and engine operation with simulated malfunctions. Malfunctions of the charge gas exchange in the form of throttling of the air intake duct and the throttling of the exhaust gas duct were taken into account in the simulations. Measurements during the engine operation with simulated malfunctions of the fuel pump on one of the cylinders were also carried out. Mentioned malfunctions were delay of the fuel injection by 5° of the crankshaft angle position and the leakage of the fuel pump of the second engine cylinder. The simulated malfunctions decrease the total weighted NOx emission in all considered the engine loads. All simulated malfunctions resulted in an increase of the NOx emissions during engine operation at low the engine loads and a decrease of the mentioned emission at maximum the engine loads operation. The calculations of the weighted specific fuel consumption present a little change in engine efficiency which are within the range of measuring error of the used method.

에어 덕트용 PET 니들펀칭 부직포의 제조 및 물성에 관한 연구

An air intake duct is an automotive part for transferring outside air to the internal combustion engine where the air and fuel are mixed and consumed. While this part has been primarily made of engineering plastics, many manufacturers are attempting to apply textile nonwovens due to their superior sound absorbing performance and lightweight characteristics. In this paper, we studied the manufacturing process of needle punched nonwoven fabric and analyzed various properties in order to investigate the applicability of textile nonwoven as a material for automobile air intake ducts. The nonwoven web was prepared by opening, mixing and carding PET staple fibers and binder fibers. The web was physically bonded by the needle punching process. In addition, we applied heated air through the nonwoven web to improve the mechanical properties of the needle punched nonwoven fabrics by the thermal bonding of interlocking constituent fibers. The results of the tensile test of the nonwoven demonstrated that the hot air treatment to the needle punched nonwoven decreased the elongation of nonwoven, which significantly affects the processability of the air duct production process. Also, the porous structure of the nonwoven improved the sound absorbtion property compared to normal PP plastic. Therefore, the air intake duct made of PET needle punched nonwoven could contribute to decreasing the noise level inside automobiles.

Radon concentration of outdoor air: measured by an ionization chamber for radioisotope monitoring system at radioisotope institute

Gas-flow ionization chambers for radioisotope (RI) monitoring systems at RI institutes throughout Japan are commonly used to measure RIs which leak from the RI institutes. Before the Japan’s 2011 Tohoku earthquake [11 March 2011, moment magnitude (M w) 9.0], ionization current data measured with a gas-flow ionization chamber at the RI institute of Fukushima Medical University were found to change. The question we must raise is whether the variation ionization current can be considered to the variation of outdoor radon concentration. The conversion factors (from ionization current to radon concentration in air) of the gas-flow ionization chamber can be obtained by measuring four levels of radon concentration (outdoor air, indoor air, high level and radon-free gas) with an AlphaGUARD monitor and the chamber itself. The two gas-flow ionization chambers consist of the air intake and terminal exhaust duct of the RI institute. It was found that the radon concentration in the exhaust air was the same as that in the air intake. This study provided evidence that variations of outdoor radon concentration could be determined using gas-flow ionization chambers for RI monitoring systems.

Computer Simulation of the Filling Process of Air Intake Hood Based on ProCAST

The intake hood is the part which riveted in the external skin of the aircraft. During the flight of the aircraft, the engine casing is cooled down by the high-speed airflow which flows through the air intake duct. As the components suffer the impact of the high-speed airflow, the appearance of the intake hood must meet the requirements of the aerodynamic property. At the same time, its manufacturing quality has a certain impact on the aerodynamic performance of the aircraft, so its synthetic mechanical property is required high. The traditional air intake hoods are block-combination welded by the aluminum alloy sheet. Its complicated working procedure, long production cycle, high costs and the difficult weld methods make it difficult to guarantee the welding quality. In order to improve the useful life of the air intake hood, to lower the production difficulty and to solve the quality risks in the production due to the method of weld, in this article, the high-strength aluminum alloy ZL101A and plaster mould investment casting were used to mold the intake hood based on the three-dimensional geometric modeling of the air intake hood by software Pro/E, and then, the filling and solidification process of the air intake hood was simulated by the casting simulation software ProCAST to predict the defects such as misrun, cold shut, wrapped in air, the thermal centre and the residual stress and deformation which were displayed in the filling and the solidification processes of the metal. Then, the casting process of the air intake hood can be optimized to achieve a decrease or avoid casting defects in the actual production.

A novel adaptive algorithm with an IIR filter and a variable step size for active noise control in a short duct

The intake system in an automotive engine has a short duct compared with that of the exhaust system. The filtered-x LMS (FX-LMS) algorithm has been applied to the active noise control (ANC) system in a short acoustic duct. This algorithm design is based on the FIR (finite impulse response) filter; however, it has a slow convergence issue due to a large number of zero coefficients. To improve the convergence performance, the step size of the LMS algorithm was modified from fixed to variable. However, this algorithm is still not suitable for the ANC system of a short acoustic duct because the reference signal is affected by the backward acoustic wave propagated from a secondary source. Therefore, the recursive filtered-u LMS algorithm (FU-LMS) based on the infinite impulse response (IIR) is developed to consider backward acoustic propagation. Generally, this algorithm has a stability problem. The stability issue was improved using an error-smoothing filter. In this paper, the recursive LMS algorithm with a variable step size and smoothing error filter is designed. This recursive LMS algorithm, the FU-VSSLMS algorithm, uses an IIR filter. With fast convergence and good stability, this algorithm is suitable for the ANC system in a short acoustic duct, such as the intake system of an automotive engine. This algorithm is applied to the ANC system of a short acoustic duct. The disturbance signals used as primary noise source are a sinusoidal signal embedded in white noise and the chirp signal, which has a variable instantaneous frequency. The test results demonstrate that the FU-VSSLMS algorithm has a superior convergence performance when compared with the FX-LMS and FX-LMS algorithms. The algorithm can be successfully applied to the ANC system in a short duct, such as the intake duct.

Large-Eddy Simulation and experimental study of cycle-to-cycle variations of stable and unstable operating points in a spark ignition engine

This article presents a comparison between experiments and Large-Eddy Simulation (LES) of a spark ignition engine on two operating points: a stable one characterized by low cycle-to-cycle variations (CCV) and an unstable one with high CCV. In order to match the experimental cycle sample, 75 full cycles (with combustion) are computed by LES. LES results are compared with experiments by means of pressure signals in the intake and exhaust ducts, in-cylinder pressure, chemiluminescence and OH Planar Laser Induced Fluorescence (PLIF). Results show that LES is able to: (1) reproduce the flame behavior in both cases (low and high CCV) in terms of position, shape and timing; (2) distinguish a stable point from an unstable one; (3) predict quantitatively the CCV levels of the two fired operating points. For the unstable case, part of the observed CCV is due to incomplete combustion. The results are then used to analyze the incomplete combustion phenomenon which occurs for some cycles of the unstable point and propose modification of the spark location to control CCV.

Verification and validation of a CFD model for simulations of large-scale compartment fires

Abstract A fire field model is being developed at IRSN to simulate a fire in mechanically ventilated compartments. This numerical tool has the specificity of being one of the rare fire field model that allows us determination of over or underpressure peaks and reverse flow in intake ducts of the ventilation network. Although dedicated to fire simulations in confined environments, the ISIS computer code is a field model, also called CFD model, and thus enables to simulate many academic and industrial flows. The assessment process of such a numerical tool is a complex task and requires a suitable methodology. The purpose of this paper is therefore to outline an adaptation of the wellknown V&V method applied to the verification and validation processes of a fire field model. Numerical methods and physical models used in the code are briefly presented first. Afterwards, the verification and validation phases of the fire field model dealt with and exhibit comparisons to analytical, manufactured or benchmark solutions for the verification phase and the development of a building-block approach for the validation phase. For these two V&V phases, an example is clearly described in detail: the first illustrates a test case from the verification matrix while the second refers to a complete system from the validation process and describes a fire simulation in a large-scale compartment mechanically ventilated. The results, in good agreement with the experimental measurements show that the code is validated for these types of fire scenarios.

Verification and validation study of URANS simulations for an axial waterjet propelled large high-speed ship

The accurate prediction of waterjet propulsion using computational fluid dynamics (CFD) is of interest for performance analyses of existing waterjet designs as well as for improvement and design optimization of new waterjet propulsion systems for high-speed marine vehicles. The present work is performed for three main purposes: (1) to investigate the capability of a URANS flow solver, CFDSHIP-IOWA, for the accurate simulation of waterjet propelled ships, including waterjet–hull interactions; (2) to carry out detailed verification and validation (VV and (3) to identify optimization opportunities for intake duct shape design. A concentrated effort is applied to VV hence, one objective for subsequent optimization studies could be maximizing the inlet efficiency. Overall, the V&V work indicates that the present approach is an efficient tool for predicting the performance of waterjet propelled JHSS ships and paves the way for future optimization work. The main objective of the optimization will be reduction of powering requirements by increasing the inlet efficiency through modification of intake duct shape.