Engine Exhaust Port Research Articles

The Effect of Crankshaft Phasing and Port Timing Asymmetry on Opposed-Piston Engine Thermal Efficiency

Opposed-piston, two-stroke engines reveal degrees of freedom that make them excellent candidates for next generation, highly efficient internal combustion engines for hybrid electric vehicles and power systems. This article reports simulation results that explore the influence of key control and geometrical parameters, specifically crankshaft phasing and intake and exhaust port height-to-stroke ratios, in obtaining best thermal efficiency. A model of a 0.75 L, single-cylinder opposed-piston two-stroke engine is exercised to predict fuel consumption as engine speed, load, crankshaft phasing, intake and exhaust port height-to-stroke ratios, and stoichiometry are varied for medium-duty truck and range extender applications. Under stoichiometric operation, optimal crankshaft phasing is seen at 0–5°, lower than reported in the literature. If stoichiometric operation is not mandated, best fuel consumption is achieved at an air-to-fuel equivalence ratio λ = 1.25 and 5–10° crankshaft phase angle, enabling a ~10 g/kWh (~4%) improvement in average brake-specific fuel consumption across medium-duty truck operating points. In range extender form, the engine provides 30 kW output power in accordance with a survey of range extender engines. In this role, there is a clear distinction between low-speed, high-load operation and vice versa. The decision as to which is more appropriate would be based on minimizing total owning and operating cost, itself a trade-off between better thermal efficiency (and thus lower fuel cost) and greater durability.

Flow Analysis and Theoretical Design of Diesel Engine Exhaust Port

Exhaust port is an important part of a diesel engine which affects the combustion and emission. It is important to have a good design for exhaust port. In this paper, the calculation formula of the optimal area ratio (Kopt) of outlet and inlet of exhaust port was derived. The formula shows that Kopt is only determined by relative pressure difference (RPD). Then influence of the area ratio (K) of outlet and inlet on flow capacity of exhaust port and the trend of Kopt with relative pressure difference were studied numerically to verify the validity and applicability of the formula. The numerical results shows that the mass flow rate increases first and then keeps constant with the increase of K at the same RPD. Kopt exists and decreases first and then keeps constant with the increase of RPD. The numerical trend is consistent with theoretical trend and the errors between maximum mass flow rates of numerical results and actual mass flow rates at theoretical optimal area ratios are all less than 5% meeting engineering accuracy. It is indicated that the derived formula is correct and applicable. When an exhaust port is designed, the outlet area can be estimated by this formula.

Novel Electrically Stimulated Catalytic Converter Prototype for Replacement of Conventional Auto Exhaust Emission Converters

High voltage electrostatics and corona discharge are utilized for various applications in pollution and environmental control. The traditional applications have many flaws due to improper construction of electrode design and assembly that cause system failure, in particular when electrically stimulated devices are exposed to high humidity. A new innovative-patented design by Hamade, electrically stimulated catalytic converter (ESCC), eliminates such flaws and shows the wide practical applications of the new design. The new design utilized previous patented designs and work of the same inventor but retrofitted for catalytic auto exhaust emission control. The current and previous patents include: employing electrically stimulated filtration (ESF) to replace high efficiency particulate air (HEPA) filters, treatment of biological and infectious diseases, electret fabrication, and, most notably, the invention of a new electrically stimulated catalytic converter (ESCC). The electrically stimulated catalytic converter invention includes an exhaust conduit fed from the engine exhaust port with a housed corona charger apparatus. The opposite end is opened to the atmosphere outside of the vehicle or connected to a reduced-size catalytic converter. The corona charger is intrusively or non-intrusively associated with a main flow path defined by the exhaust conduit. The corona charger includes at least one electrode, which may be recessed away from, the main flow path. A plurality of corona chargers may be used in various combinations, optimally a two dimensional grid. The electrically stimulated catalytic converter is adapted to treat and eliminate auto exhaust pollution emission to air.

Least Square Adaptation of a Fast Diesel Engine NOx Emissions Model

The paper focuses on the development of an adaptive NOx emissions model, whose intended deployment is to provide accurate estimation, throughout engine lifetime, in correspondence of the engine exhaust port of a Diesel propulsion system. Particularly, black-box modelling approach is proposed, which specifically in this paper takes advantage of an intake manifold oxygen estimator previously developed. The resulting multi-linear regression model was preliminary validated in steady-state conditions. Upon successful verification of model accuracy, the above NOx predictor was integrated within a least-square adaptation algorithm, which relies on the experimental NOx measurement performed downstream the selective catalytic reduction catalyst. Therefore, it was possible to perform further validation analyses, both to assess prediction reliability in transient conditions, as well as to verify the adaptation capability of the proposed least-square-based algorithm.

An Adaptive Neuro-Fuzzy Inference System (ANFIS) model for prediction of thermal contact conductance between exhaust valve and its seat

Exhaust valve and its seat in an internal combustion engine reach high temperatures due to the hot gases exit through the engine exhaust port. This high temperature must decrease in order to avoid damaging of the combustion chamber and the engine itself. This high amount of heat can be taken away from the exhaust valve to its seat when they are in contact, then it will be transferred to the coolant. Therefore, study of heat transfer between the exhaust valve and its seat is necessary. In this paper, the capabilities of a neuro-fuzzy approach, namely ANFIS (Adaptive Network based Fuzzy Inference System) have been studied for estimating the rate of the heat transfer between the exhaust valve and its seat. The ANFIS model is formed by means of input–output data set taken from the experimental study and the inverse solution using the Conjugate Gradient Method (CGM) with adjoint problem. It is shown that the ANFIS architecture can estimate the heat transfer rate between the exhaust valve and its seat very accurately by means of input–output pairs obtained either from the actual system or the inverse method. It is also shown that based on the error analysis between the different algorithms, gaussmf membership function provided the best model for estimating the thermal contact conductance between exhaust valve and its seat. The calculated Root Mean Square Error (RMSE) of the ANFIS architecture with the gaussmf membership function when compared against the experiment is 0.00017439.

Flow effects due to valve and piston motion in an internal combustion engine exhaust port

Performance optimization regarding e.g. exhaust valve strategies in an internal combustion engine is often performed based on one-dimensional simulation investigation. Commonly, a discharge coefficient is used to describe the flow behavior in complex geometries, such as the exhaust port. This discharge coefficient for an exhaust port is obtained by laboratory experiments at fixed valve lifts, room temperatures, and low total pressure drops. The present study investigates the consequences of the valve and piston motion onto the energy losses and the discharge coefficient. Therefore, Large Eddy Simulations are performed in a realistic internal combustion geometry using three different modeling strategies, i.e. fixed valve lift and fixed piston, moving piston and fixed valve lift, and moving piston and moving valve, to estimate the energy losses. The differences in the flow field development with the different modeling approaches is delineated and the dynamic effects onto the primary quantities, e.g. discharge coefficient, are quantified. Considering the motion of piston and valves leads to negative total pressure losses during the exhaust cycle, which cannot be observed at fixed valve lifts. Additionally, the induced flow structures develop differently when valve motion is taken into consideration, which leads to a significant disparity of mass flow rates evolving through the two individual valve ports. However, accounting for piston motion and limited valve motion, leads to a minor discharge coefficient alteration of about one to two percent.

Cold and Thermal Flow Field Analysis of Gasoline Engine Exhaust Port Based on CFD and RE

Exhaust passage is a significant part of the gasoline engine, its structure will affects the gas flow characteristics of the engine directly [1]. So, research and analysis of the exhaust tract is essential. In this paper, a detailed analysis of the flow field under cold state and hot state was made. For a start, the method of laser scanning and UG software were used to reverse modeling engine exhaust port and get the three-dimensional model. The next, the unstructured grid with local mesh refinement scheme was used to mesh this three-dimensional model with ICEM. After this, numerical simulations of the exhaust passage with five different valve lifts were carried out under thermal and cold conditions. Finally, comparing the velocity field and pressure field of the exhaust passage under cold state and thermal state, it can be find that the flow field under hot and cold state have similar characteristics. The results of this paper can provide a theoretical basis for following researches of the engine exhaust port.

The Simulation and Optimization on Flow Field in Intake Port of Engine Based on RE and CFD

Intake port is an important part of the gasoline engine, its structure will influence the gas flow characteristics which directly affects the performance of the engine [1]. In this paper, three-dimensional CFD calculation and structural optimization were used to research the performance of gasoline engine. Firstly, the method of laser scanning and UG software were used to reverse modeling engine exhaust port and get the three-dimensional model. Secondly, after setting boundary conditions and turbulence models, the air flowing through the intake ports were simulated by FLUENT software respectively. Finally, based on numerical methods, the pressure field, velocity field were shown. The results of the simulation of flow field characteristics analysis show that the simulation and experimental results are in good agreement.

Flow effects due to pulsation in an internal combustion engine exhaust port

In an internal combustion engine, the residual energy remaining after combustion in the exhaust gasses can be partially recovered by a downstream arranged device. The exhaust port represents the passage guiding the exhaust gasses from the combustion chamber to the energy recovering device, e.g. a turbocharger. Thus, energy losses in the course of transmission shall be reduced as much as possible. However, in one-dimensional engine models used for engine design, the exhaust port is reduced to its discharge coefficient, which is commonly measured under constant inflow conditions neglecting engine-like flow pulsation. In this present study, the influence of different boundary conditions on the energy losses and flow development during the exhaust stroke are analyzed numerically regarding two cases, i.e. using simple constant and pulsating boundary conditions. The compressible flow in an exhaust port geometry of a truck engine is investigated using three-dimensional Large Eddy Simulations (LES). The results contrast the importance of applying engine-like boundary conditions in order to estimate accurately the flow induced losses and the discharge coefficient of the exhaust port. The instantaneous flow field alters significantly when pulsating boundary conditions are applied. Thus, the induced losses by the unsteady flow motion and the secondary flow motion are increased with inflow pulsations. The discharge coefficient decreased about 2% with flow pulsation. A modal flow decomposition method, i.e. Proper Orthogonal Decomposition (POD), is used to analyze the coherent structures induced with the particular inflow and outflow conditions. The differences in the flow field for different boundary conditions suggest to incorporate a modeling parameter accounting for the quality of the flow at the turbocharger turbine inlet in one-dimensional simulations.

3-Dimensional Modeling of Hydrocarbon Oxidation in the Exhaust Port of a Spark Ignition Engine

A three-dimensional model for oxidation of unburned hydrocarbons at the SI engine exhaust port has been developed. The computational mesh with a moving grid for the valve motion is constructed for the port geometry of a single-cylinder research engine. A 4-step oxidation model is used to predict the HC oxidation and the coefficients of the model are modified for the port oxidation environment with the results of a full chemical kinetic mechanism. The measured THC concentrations at the cylinder exit (3 positions) are used as the inlet concentration for the simulation and the temperatures of the core gases and boundary zone gases in the cylinder are obtained from a three-zone cycle simulation. The simulation result shows that the degree of the THC oxidation in the exhausl port at 1,000 rpm, IMEP 550 kPa, stoichiometic condition is 31.5%. The effects of inlet gas temperature, oxygen concentration, heat transfer, and engine operating conditions on the THC oxidation have been investigated. THC oxidation in the exhaust port is predicted to be between 14% and 46% depending on the engine operating conditions. The simulation results are in good agreement with other research results.

Estimation of Hydrocarbon Oxidation by Measuring He Concentrations in an SI Engine Exhaust Port

In order to investigate the exhaust structure and secondary oxidation of unburned hydrocarbon (HC) in the exhaust port, concentrations of individual HC species were measured in exhaust process, the degree of oxidation were obtained. Using a solenoid-driven fast sampling system on single-cylinder research engine fueled with 94% propane, the profiles of unburned hydrocarbons (HCs) and non-fuel HCs with a propane fueled engine were obtained from several locations in the exhaust port during the exhaust process. The sampled gases were analyzed using a gas chromatography of HC species with 4 or lesser carbon atoms. The change of total HC concentration and HC fractions of major components through the exhaust port were discussed. The results showed that non-uniform distribution of HC concentration existed around the exhaust valve and changed with time, and that the exhaust gas exhibited nearly uniform concentration profile at port exit, which was due to mixing and oxidation. Also it could be known that bulk gas with relatively high HC concentration came out through the bottom of the exhaust valve. To estimate the mass-based degree of HC oxidation in the exhaust port from measured HC concentrations, a 3-zone diagnostic cycle simulation and plug flow modeling were used. The degree of oxidation ranged between 26 % and 36 % corresponding to the engine operation conditions

Estimation of Hydrocarbon Oxidation by Measuring HC Concentrations in an SI Engine Exhaust Port

Using a solenoid-driven fast sampling system and gas chromatography (GC), the profiles of unburned hydrocarbons (HCs) and non-fuel HCs in a propane-fueled-engine were obtained at several positions in the exhaust port during the exhaust process. Changes in the total HC concentration and HC fractions of major components along the exhaust port are discussed and compared with other research results. The results show that the stratification of HC concentration exists around the exhaust valve. The increase of 10% in the fraction of non-fuel components along the exhaust port reflects significant HC oxidation. The results also show that a bulk gas with relatively high HC concentration comes out through the bottom of the exhaust valve. A cycle simulation and plug flow modeling were used to estimate the mass-averaged percentage of the HC oxidation in the exhaust port. Model predictions of HC oxidation are consistent with current and previous experimental results. The percentage of the HC oxidation in the exhaust port ranges between 26% and 36%, depending on the engine operation conditions. Retarded spark timing and lea n operating conditions increases HC oxidation at the exhaust port.

Muffler for an internal combustion engine

A muffler for a two-stroke internal combustion engine having a housing and a partition wall which cooperate to define a first chamber adjacent an engine exhaust port and a second chamber remote from the engine. A catalyzer element is housed within the second chamber. A discharge pipe extends from an outlet of the catalyzer element and through the first chamber to atmosphere. An outer pipe surrounds a portion of the discharge pipe within the first chamber and cooperates therewith to define a passage whereby exhaust gas within the first chamber is directed through the partition wall and into the second chamber. Heat from the treated exhaust gas flowing through the discharge pipe is transferred to the exhaust gas flowing through the passage to preheat the exhaust gas prior to reaching the catalyzer element, thereby reducing the time required to bring the catalyzer element to an operating temperature following engine start-up.

A Numerical Study of Tunnel Fires

Abstract An analytical model of the hydrocarbon oxidation processes in an engine exhaust port was developed. A thermodynamic analysis was used to obtain the exhaust gas conditions as a function of lime and axial distance in the port. The major features of the exhaust port processes were described by submodels for the pan heat transfer, reaction rates. and instantaneous and overall levels of hydrocarbon concentrations as functions of engine conditions. Experimental determinations of the fraction of hydrocarbons oxidized in the exhaust port were obtained in engine experiments by the injection of a quench gas at selected locations within the port. By differencing the hydrocarbon concentrations observed during quenching and non-quenching operation, the degree of hydrocarbon oxidation was determined for each location. Analytical and experimental results were in good agreement for a range of engine operating conditions. The fraction of hydrocarbons reacted in the exhaust port ranged between about 2 and 70 percent for the various engine conditions examined for both the model and the experiment. These results were dominated by changes of gas temperatures, port residence times and oxygen concentration which occurred due to variations in the engine operating conditions and due to the injection of secondary air. The model was also used to examine hydrocarbon oxidation in the port as a function of cylinder gas temperature, port wall temperature, port length and port cross-sectional area.

Unburned Methanol and Formaldehyde in Exhaust Gases from a Methanol Fueled S. I. Engine

With the aid of a derivative spectrophotometer, emission characteristics of formaldehyde from a methanol fueled S. I. engine were obtained. Formaldehyde and unburned methanol were measured at several distances along the exhaust tube for various air-fuel equivalence ratios and ignition timings. Experiments show that dominant oxidation of unburned methanol in exhaust system is obtained at temperatures above 400°C. However, formaldehyde levels were maintained during the exhaust movement for a fuel rich mixture. In fuel lean operation, formaldehyde increased in exhaust tube. This fact suggests that formaldehyde is formed by the oxidation of unburned methanol during the exhaust process, and the formation already begins in the cylinder. Careful experiments using a heated tube reactor set at engine exhaust port, and kept at a constant temperature range of 300-650°C probe that formaldehyde accumulation occurs in exhaust system at a temperature range of approximately 400-600°C.

An experimental and analytical study of heat transfer in an engine exhaust port

Because of the increasing need for precise information on engine processes, this study developed and experimentally verified models for the instantaneous heat transfer in an engine exhaust port. Experimental measurements were made of the instantaneous cylinder pressure and instantaneous exhaust gas temperature for a range of engine operating conditions. The pressure measurements were used to obtain the instantaneous cylinder gas state and the temperature measurements were used to validate the heat transfer models. The exhaust port heat transfer was dominated by jet induced large-scale fluid motion as opposed to wallshear generated fluid motion. An analysis based on the jet velocity through the valve opening correctly estimated the heat transfer due to this large-scale motion. Models for the instantaneous exhaust port heat transfer provided excellent agreement with measurements as a function of engine operating conditions.