scholarly journals Estimates of the air-fuel ratio at the time of ignition in a pre-chamber using a narrow throat geometry

2021 ◽  
pp. 146808742110591
Author(s):  
Ponnya Hlaing ◽  
Mickael Silva ◽  
Manuel Echeverri Marquez ◽  
Emre Cenker ◽  
Moez Ben Houidi ◽  
...  
Keyword(s):  
Simulation Software ◽  
Chamber Pressure ◽  
Experimental Investigations ◽  
Cfd Model ◽  
Ignition Timing ◽  
Mixture Formation ◽  
Inlet Valve ◽  
Engine Efficiency ◽  
Excess Air ◽  
Lean Conditions

The benefits of pre-chamber combustion (PCC), such as improved engine efficiency and reduced NOx emissions, are primarily observed when operating at lean conditions with an active pre-chamber, where auxiliary fuel is supplied directly to the pre-chamber. Estimating the pre-chamber excess air ratio (λ) is important in the active pre-chamber concept to gain insights into the pre-chamber combustion phenomenon. Experimental investigations were performed using a narrow-throat pre-chamber at global-λ 1.6, 1.8, and 2.0. The fraction of fuel energy injected in the pre-chamber over the total fuel energy was fixed at 3%, 7%, and 13% for each global-λ. The mixture formation process inside the pre-chamber is first simulated using the 1-D simulation software GT-Power to analyze the pre-chamber λ at the ignition timing. However, the 1-D results were unable to reproduce the experimental observations on the pre-chamber pressure buildup accurately. Upon simulating the same conditions using the 3-D CFD software CONVERGE, the pre-chamber λ estimated from the CFD model is well-correlated to the experimental data. The CFD results indicate that the amount of fuel trapped in the pre-chamber at the inlet valve closing timing is over-predicted by the 1-D simulations. A correlation between the injected and the trapped fuel in the pre-chamber is proposed by theoretical scavenging models and applied to the 1-D simulation results to improve pre-chamber λ prediction accuracy.

Internal leakage analysis and experiment in hydraulic control system of steam turbine inlet valve

2020 ◽  
pp. 095440892097311
Author(s):  
Ying Liu ◽  
Qimin Wang ◽  
Xiaoxiao Li ◽  
Liming Wang
Keyword(s):  
Control System ◽  
Steam Turbine ◽  
Simulation Software ◽  
Hydraulic Control ◽  
Inlet Valve ◽  
Proportional Valve ◽  
Hydraulic Simulation ◽  
Turbine Inlet ◽  
Control Switch ◽  
Hydraulic Control System

In this paper, the transformation of steam turbine regulating system from mechanical hydraulic regulation to electro-hydraulic regulation is realized. And the internal leakage mechanism of the hydraulic control switch valve and the electro-hydraulic proportional valve in the system is analyzed. With the use of hydraulic simulation software AMESim, the mathematical model of the electro-hydraulic control system after transforming is established. The parameters of the hydraulic control switch valve and the electro-hydraulic proportional valve in the hydraulic control system of steam turbine inlet valve are studied under different internal leakage locations and different leakage degree, such as piston regulating time, steady position of piston, oil pressure and leakage flow flux. The fault characteristic table of internal leakage is obtained. An experimental platform for simulating internal leakage is built. The experimental curves of several physical quantities under different internal leakage conditions are obtained. The experimental results prove that the internal leakage has a great impact on the performance of the electro-hydraulic control system. The results of internal leakage experiment are consistent with those of internal leakage simulation.

scholarly journals A model-based and experimental approach for the determination of suitable variable valve timings for cold start in partial load operation of a passenger car single-cylinder diesel engine

2018 ◽  
Vol 20 (1) ◽  
pp. 141-154 ◽  
Author(s):  
P Maniatis ◽  
U Wagner ◽  
T Koch
Keyword(s):  
Diesel Engine ◽  
Experimental Investigations ◽  
Exhaust Gas ◽  
Gas Temperature ◽  
Warm Up ◽  
One Dimensional ◽  
Engine Efficiency ◽  
Residual Gas ◽  
Dimensional Simulation ◽  
Exhaust Gas Temperature

A manipulation of the charge exchange allows controlling the amount of residual gas during engine warm-up. The residual gas during the warm-up phase leads to an increase of the exhaust gas temperature and supports to reach the exhaust after-treatment system operating temperature faster. In addition, the warm residual gas increases the combustion chamber temperature, which reduces the HC and CO emissions. However, fuel consumption increases. For that reason, such heating measures should be the best compromise of both, exhaust gas temperature increase and engine efficiency, in order to provide efficient heating strategies for passenger car diesel engines. Therefore, simulative and experimental investigations are carried out at the Institute of Internal Combustion Engines of the Karlsruhe Institute of Technology to establish a reliable cam design methodology. For the experimental investigations, a modern research single-cylinder diesel engine was set up on a test bench. In addition, a one-dimensional simulation model of the experimental setup was created in order to simulate characteristics of valve lift curves and to investigate their effects on the exhaust gas temperature and the exhaust gas enthalpy flow. These simulations were based on design of experiments (DoE), so that all characteristics can be used sustainably for modeling and explaining their influences on the engine operation. This methodology allows numerically investigating promising configurations and deriving cam contours which are manufactured for testing. To assess the potential of these individual configurations, the results obtained were compared with each other as well as with the series configuration. Results show that the combination of DoE and one-dimensional simulation for the design of camshaft contours is well suited which was also validated with experimental results. Furthermore, the potential of residual gas retention by favorable configurations with a second event already revealed in various publications could be confirmed with respect to exhaust gas temperature increase and engine efficiency.

Optimization of four models flatbread bakery machines in Iran

2019 ◽  
Vol 30 (6) ◽  
pp. 3399-3434 ◽  
Author(s):  
Soroush Sadripour ◽  
Mohammad Estajloo ◽  
Seyed Abdolmehdi Hashemi ◽  
Ali J. Chamkha ◽  
Mahmoud Abbaszadeh
Keyword(s):  
Energy Consumption ◽  
Exergy Efficiency ◽  
Experimental Investigations ◽  
Content Type ◽  
Numerical Studies ◽  
Excess Air ◽  
High Preference ◽  
Energy And Exergy ◽  
Traditional Bread ◽  
Wasted Energy

Purpose The purpose of this study is to reduce energy consumption in bakeries. Due to fulfill this demand, quite a few parameters such as energy and exergy efficiency, energy waste and fuel consumption by different traditional flatbreads bakeries (Sangak, Barbari, Taftun and Lavash should be monitored and their roles should not be neglected. Design/methodology/approach In the present study, experimental measurements and mathematical modeling are used to scrutinize and investigate the effects of the aforementioned parameters on energy consumption by bakeries. Findings The results show that by doing reported methods in this paper, the wasted energy of the walls can be decreased by about 65 per cent; and also, by controlling the combustion reaction to perform with 5 per cent excess air, the wasted energy of excess air declines by about 90 per cent. And finally, the energy and exergy efficiency of bakeries is increased, and as a result, the annual energy consumption of Sangak, Barbari, Taftun and Lavash bakeries diminish about 71, 59, 57 and 40 per cent, respectively. Originality/value As evidenced by the literature review, it can be observed that neither numerical studies nor experimental investigations have been conducted about energy and exergy analyses of Iranian machinery traditional flatbread bakeries. It is clear that due to a high preference of Iranians to use the traditional bread and also the popularity of baking this kind of bread in Iran, if it is possible to enhance the traditional oven conditions to decrease the loss of natural gas instead of industrializing the bread baking, the energy consumption in the country can be optimized.

Variable Intake Valve Train to Optimize the Performance of a Large Bore Gas Engine

2016 ◽  
Author(s):  
Jan Zelenka ◽  
Claudio Hoff ◽  
Andreas Wimmer ◽  
Roland Berger ◽  
Josef Thalhauser
Keyword(s):  
Valve Train ◽  
Experimental Investigations ◽  
Intake Valve ◽  
Valve Timing ◽  
Current Standard ◽  
Gas Engine ◽  
Engine Efficiency ◽  
Variable Valve Train ◽  
Operating Strategies ◽  
Variable Valve

The present paper describes the investigations made using the electro-hydraulic intake valve timing system VCM® on a large bore gas engine. The first section explains what challenges have to be faced when developing concepts for present and future applications of large bore gas engines. Following an introduction to the VCM® system, an outline is presented of expected opportunities for using variable intake valve timing in combination with modern turbocharging concepts. The second section describes 0D/1D engine cycle simulations that were carried out to assess the influence of variable valve timing on the intake side compared to a fixed intake valve profile, which is the current standard for large bore gas engines. As a result, first predictions can be made about the gain in engine efficiency achieved with different operating strategies. In order to assess the performance potentials of the variable valve train, extensive experimental investigations were carried out on a single cylinder research engine based on GE’s Type 6 gas engine. The investigations consisted of varying engine parameters including varying the geometric compression ratio as well as the engine boundary conditions. It will be shown how intake valve timing can be used to optimize engine efficiency by improving gas exchange. Furthermore, variable intake valve timing affects the overall system behavior, e.g. distances to the engine’s operating limits. Special attention was paid to analyzing combustion itself, which is necessary due to the strong influence that intake valve timing has on the thermodynamic states of the cylinder charge.

Ethanol Lean Combustion Characteristics of a GDI Engine

2015 ◽  
Vol 798 ◽  
pp. 219-223
Author(s):  
Roberto B.R. Costa ◽  
Carlos A.J. Gomes ◽  
Fabricio J.P. Pujatti ◽  
Ramon Molina Valle ◽  
José E.M. Barros
Keyword(s):  
Engine Speed ◽  
Injection Pressure ◽  
Combustion Stability ◽  
Lean Burn ◽  
Engine Efficiency ◽  
Lean Combustion ◽  
Excess Air ◽  
Wide Range ◽  
Ethanol Combustion ◽  
Gdi Engine

In the present study, ethanol combustion analysis was carried in a wall guided type GDI engine, to achieve combustion stability under lean burn operation and to expand the flammability limit for increasing engine efficiency. Tests were performed at constant engine speed, load and injection pressure (1000 rpm, NIMEP = 3 bar, 100 bar), for a wide range of injection, ignition and mixture formation parameters. NISFC, combustion stability, PMEP and burn duration were evaluated at each excess air ratio. An improvement on fuel economy and, consequently, increased engine efficiency was achieved for excess air ratios of λ = 1.1 and λ = 1.2.

scholarly journals Numerical and Experimental Investigations of the Cavitating Behavior of an Inducer

2004 ◽  
Vol 10 (1) ◽  
pp. 15-25 ◽  
Author(s):  
F. Bakir ◽  
R. Rey ◽  
A. G. Gerber ◽  
T. Belamri ◽  
B. Hutchinson
Keyword(s):  
Bubble Dynamics ◽  
Three Dimensional ◽  
Experimental Investigations ◽  
Cfd Model ◽  
Flow Rates ◽  
Solution Approach ◽  
Robust Solutions ◽  
Density Ratios ◽  
Scalar Equations ◽  
Good Agreement

A robust CFD model is described, suitable for general three-dimensional flows with extensive cavitation at large density ratios. The model utilizes a multiphase approach, based on volume-scalar-equations, a truncated Rayleigh-Plesset equation for bubble dynamics, and specific numerical modifications (in a finite-volume solution approach) to promote robust solutions when cavitation is present. The model is implemented in the CFD software CFX TASCflow 2.12. The validation of the model was done on an inducer designed and tested at LEMFI. First, The physical model and the numerical aspects are described. Then, the experimental and numerical methodologies, at cavitating regime, are presented. Finally, for several flow rates, the comparisons between experimental and simulated results on the overall performances, head drop and cavitation figures, are discussed. For a range of flow rates, good agreement between experiment and prediction was found.

scholarly journals Errors Associated With Excess Air Multipoint Measurement Systems

2015 ◽  
Vol 36 (4) ◽  
pp. 405-423 ◽  
Author(s):  
Charlene Ramsunkar ◽  
Chris van Tonder ◽  
Walter Schmitz
Keyword(s):  
Flue Gas ◽  
Single Point ◽  
Flow Simulation ◽  
Simulation Software ◽  
Sampling Errors ◽  
Power Station ◽  
Air Content ◽  
Power Stations ◽  
Excess Air ◽  
Duct Geometry

Abstract Boiler combustion air is generally controlled by the excess air content measured at the boiler economiser outlet using oxygen (O2) analysers. Due to duct geometry and dimensions, areas of high and low O2 concentrations in the flue gas duct occur, which poses a problem in obtaining a representative measurement of O2 in the flue gas stream. Multipoint systems as opposed to single point systems are more favourable to achieve representative readings. However, ash blockages and air leakages influence the accuracy of O2 measurement. The design of multipoint system varies across ESKOMs’ Power Stations. This research was aimed at evaluating the accuracy of the multipoint oxygen measurement system installed at Power Station A and to determine the systematic errors associated with different multipoint systems designs installed at Power Stations' A and B. Using flow simulation software, FloEFDTM and Flownex®, studies were conducted on two types of multipoint system designs This study established that significantly large errors, as high as 50%, were noted between the actual and measured flue gas O2. The design of the multipoint system extraction pipes also introduces significant errors, as high as 23%, in the O2 measured. The results indicated that the sampling errors introduced with Power Station A’s system can be significantly reduced by adopting the sampling pipe design installed at Power Station B.

scholarly journals NUMERICAL INVESTIGATION ON THE EFFECTS OF GASOLINE AND HYDROGEN BLENDS ON SI ENGINE COMBUSTION

2014 ◽  
Vol 46 (1) ◽  
pp. 66-77
Author(s):  
Saugirdas Pukalskas ◽  
Alfredas Rimkus ◽  
Mindaugas Melaika ◽  
Zenonas Bogdanovičius ◽  
Jonas Matijošius
Keyword(s):  
Fuel Mixture ◽  
Simulation Software ◽  
Si Engine ◽  
Exhaust Gases ◽  
Software Analysis ◽  
Engine Efficiency ◽  
Engine Combustion ◽  
Si Engines ◽  
Analysis Of Results ◽  
Hc Emissions

Even small amount additive (10…15% by volume from whole air amount) of hydrogen (H2) into spark ignition (SI) engines obviously effects ecological parameters and engine efficiency because of H2 exclusive properties. SI engine work process simulation was made using AVL Boost simulation software. Analysis of results showed that engine power depends a lot on H2 supply technique into engine; NOx amount in exhaust gases directly proportional to the amount of H2, however, making mixture leaner up to λ = 1.6, it is possible to reach significant NOx decrease. Increased amount of H2 as an additive in fuel, changes H/C ratio in fuel mixture, also hydrogen improves properties of the mixture (particularly lean) and combustion of hydrocarbons what can be a reason of decreased HC emissions in exhaust gases. Keyword(s): Hydrogen and gasoline mixture, engine efficiency, exhaust gases, nitrous oxides, hydrocarbons, simulation.

Computational and Experimental Analysis of Direct CNG Injection and Mixture Formation in a Spark Ignition Research Engine

2010 ◽  
Author(s):  
Mirko Baratta ◽  
Andrea E. Catania ◽  
Francesco C. Pesce
Keyword(s):  
Numerical Model ◽  
Combustion Chamber ◽  
Cone Angle ◽  
Combustion Process ◽  
Laser Induced Fluorescence ◽  
Operating Conditions ◽  
Design Parameters ◽  
Experimental Investigations ◽  
Injection Timing ◽  
Mixture Formation

Direct injection (DI) of compressed natural gas (CNG) under high pressure conditions is a topic of great interest, owing to its potential for improving SI engine performance and fuel consumption. However, relevant technical difficulties have yet to be resolved in order to stabilize combustion process, especially for stratified engine operating conditions. The present paper is focused on experimental and numerical investigations of the jet formation and fuel-air mixing process in a research optical-access single-cylinder engine. The engine is based on the multi-cylinder engine under development within the European Community (EC) VII Framework Program (FP) InGAS Integrated Project, and features a centrally mounted poppet-valve injector on a pent-roof combustion chamber with a bowl in piston. Experimental investigations were made by means of the planar laser-induced fluorescence technique, and revealed a cycle-to-cycle jet shape variability. In particular, for specific cylinder pressure values at the start of injection, the jet can adhere to chamber walls for a relevant number of cycles, leading to an ‘umbrella-like’ shape. This can change the mixing capabilities of the combustion chamber and cause instabilities in the combustion process. The mentioned behaviour is strongly dependent not only on the injection and cylinder pressures, but also on important design parameters, such as needle cone angle and in-chamber injector protrusion. For this reason, in order to obtain a deep insight into the injected gas behaviour on an average cycle basis, the experimental investigation was supported by a numerical analysis. Simulations were carried out by an optimized variable-density finite-volume numerical model which was built within the Star-CD environment. A previously developed and validated ‘virtual injector’ model was implemented. The outcomes of the numerical model were compared to laser-induced fluorescence images, for both stratified- and homogeneous-charge engine operating conditions and a good agreement was obtained, substantiating the reliability of the applied computational model. Then, the effects of the injector protrusion in the combustion chamber and of injection timing were analyzed, and their impact on jet stability and mixture-formation process was analyzed.

scholarly journals 2-Stroke Scavenging in Conventional and Minimally-Modified 4-Stroke Engines for Heavy Duty Applications at Low to Medium Speeds

Inventions ◽  
2019 ◽  
Vol 4 (3) ◽  
pp. 44
Author(s):  
Dirk Rueter
Keyword(s):  
Cross Section ◽  
Direct Injection ◽  
Mechanical Efficiency ◽  
Heavy Duty ◽  
Inlet Valve ◽  
Reduced Cross Section ◽  
Flow Simulations ◽  
Engine Efficiency ◽  
Charge Pressure ◽  
Cylinder Flow

The transformation of a standard 4-stroke cylinder head into a torque-improved and gradually more efficient 2-stroke design is discussed. The concept with an effective loop scavenging via an extended inlet valve holds promise for engines at low- to medium-rotational speeds for typical designs of conventional 4-stroke cylinder heads. Calculations, flow simulations, and visualizations of experimental flows in relevant geometries and time scales indicate feasibility, followed by a small engine demonstration. Based on presumably long-forgotten and outdated patents, and the central topic of this contribution, an additional jockey rides on the inlet valve’s disk (facing away from the combustion chamber) and reshapes the in-cylinder flow into a reverted tumble. A quick gas exchange with a well-suppressed shortcut into the open exhaust is approached. For overall mechanical efficiency, the required charge pressure for scavenging is of paramount importance due to the short scavenging time and the intake’s reduced cross-section. Herein, still acceptable charging pressures are reported for scavenging periods equivalent to low or medium rotational speeds, as characteristic for heavy-duty applications. Using widely available components (charger, direct injection, variable camshaft angles) an increased engine efficiency is suggested due to the 2-stroke’s downsizing effect (relatively less internal friction as well as the promise of more torque and a decreased size).

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