Exhaust Runner Research Articles

PFI SI engine fueled with ethanol with exhaust gas rebreathing: Thermal efficiency optimization with thermodynamic modeling and ANN-PSO application

An ethanol-fueled Atkinson cycle PFI SI engine using exhaust rebreathing (ER) was evaluated under 110 different operating conditions. While ethanol is an important biofuel to reduce greenhouse gas emissions, Atkinson cycle engines have been studied as low-consumption alternatives for hybrid architecture vehicles. The operating conditions were validated with GT-Power® and the resulting combustion and performance parameters were trained by a series of artificial neural network (ANN) structures in order to learn and reproduce the non-linear correlations. The ANN structures were analyzed by number of nodes, hidden layers, and optimization methods. TPA results showed that ER tests had higher indicated thermal efficiency and lower combustion temperatures than both the standard Atkinson cycle and Otto cycle conventional throttled valve strategy with a similar engine setup. The best ANN to accurately predict all six outputs with easy-to-measure operating conditions was a combined ANN-PSO model, with two hidden layers with [30 10] nodes to predict net IMEP, airflow, total mass trapped and burned mass percentage, and a complementary 10-nodes PSO hidden layer, to predict PMEP, and the average exhaust runner temperature. The final model can predict and calibrate an Atkinson cycle PFI SI engine operating with ER with significant accuracy and no need for further TPA simulations.

Automatic Design of Overflow System for Preventing Gas Defects by Considering the Direction of Molten Metal Flow

In die casting, gas defects occur if the molten metal entrains the gas inside the shot sleeve and mold and remains inside the product after filling. Therefore, an exhaust system such as an exhaust runner or overflow is generally designed at the die casting mold to discharge the gas-entrained molten metal outside the mold completely. In addition, an overflow has a broader designable area than an exhaust runner has and can discharge the gas-entrained molten metal, which an exhaust runner cannot. Therefore, designing the overflows at appropriate positions and volumes in die casting is essential. In recent years, research regarding the design of the overflow positions has been conducted by combining optimization theory and computational fluid dynamics (CFD). However, optimizing the overflow positions only can cause gas defects in the product and the unnecessary discharge of molten metal due to the overflow volume excess. Moreover, applying those methods is difficult because the analysis to verify the exhaust system includes the entire mold as the analysis domain, which increases calculation time. In this research, we propose the automatic overflow design system to discharge the gas-entrained molten metal inside the product completely by estimating the direction of molten metal flow and evaluating the efficiency of overflow design positions. Finally, we verified the effectiveness of the proposed system by actual die casting experiments using the proposed overflow shape.

Formation of CH2O and UHC emissions during catalyst-heating operation in compression ignition engines: High-speed FID and mid-IR extinction diagnostics

To comply with increasingly stringent pollutant emissions regulations, catalyst-heating operation in diesel engines is critical to achieving rapid light-off of exhaust aftertreatment catalysts during the first minutes of cold start. Current approaches to catalyst-heating operation typically involve one or more late post injections to retard combustion phasing and increase exhaust gas temperatures. The ability to retard post injection timings while maintaining acceptable pollutant emissions levels is pivotal for improved catalyst-heating operations. This experimental study aims to provide further insight into unburned hydrocarbons (UHC) and formaldehyde (CH2O) formation under catalyst-heating operation.In this study, high-speed laser extinction based measurements of CH2O are demonstrated in an optically accessible exhaust runner, and high-speed UHC measurements are also performed using a fast flame ionization detector analyzer during catalyst-heating operation. Time-resolved CH2O and UHC emission measurements are used to analyze the effect of each injection event in a five-injection strategy (two pilots, one main and two posts) on the pollutant emissions. The first pilot injection generates a significant amount of UHC unevenly distributed in the chamber, with UHC trapped primarily in the upper-cylinder and inside-the-bowl regions. The fuel delivered with the second pilot injection partially burns the unburned fuel from the first pilot injection particularly in inner-bowl region, creating short-chain hydrocarbons corresponding to formation of CH2O. UHC is dramatically reduced in the presence of the main injection, reinforcing the hypothesis by showing large CH2O emission during intermediate and later exhaust process. The first post injection produces UHC and CH2O in the upper-cylinder area due to over-mixing, which is further promoted by the second post injection, while these post-injections do not substantially affect near-bowl emissions.

CFD Analysis of Exhaust System of a Formula Racing Vehicle

This study investigates about the designing and Computational Fluid Dynamics (CFD) analysis of the exhaust system of a formula student vehicle. Based on FSAE rules KTM Duke 390 engine is used and the noise level is to keep below 110 dB. The main aim of the design is to have a smooth flow exhaust gases without restriction to increase engine efficiency and to keep minimal backpressure. An absorptive type of muffler is finalized to attenuate the sound levels. Based on three different equations, exhaust runner dimensions are calculated and CFD analysis is performed to choose the optimum runner dimensions. Using ASHRAE guidelines muffler dimensions range is calculated. Using Ricardo software based on effective volumetric efficiency analysis, volume of muffler that fits in ASHRAE dimension range was finalized. Both runner and muffler are analyzed and CFD analysis was carried out which resulted in streamline velocity profile of the exhaust gas and acceptable values of pressure, velocity and velocity streamline was found. CFD analysis of the full exhaust system was carried out to understand the flow characteristics of exhaust gases.

Design and Fabrication of Exhaust System of Formula Student Car

Abstract— The overall aim of this paper is to refine the design and manufacturing techniques of the exhaust system of FSAE cars. The main objective of this paper is selection of ideal geometry of the 4-cylinder engine (GSX R600) exhaust manifold in terms of optimization of back pressure and reduction in gross weight of the exhaust system. For achieving this, we have considered runner length and diameter, muffler diameter, flow of gases in the exhaust manifold, volumetric efficiency, etc. Softwares used in design and validation are Solid works, Ansys and GT Suite. Keywords— FSAE, Exhaust Runners, Collector, muffler, CFD, 1-D engine simulation, NRC

Physics-based modeling of homogeneous charge compression ignition engines with exhaust throttling

Homogeneous charge compression ignition (HCCI) engines create a more efficient power source for either stationary power generators or automotive applications. Due to the absence of direct actuation of ignition, HCCI based combustion control is quite challenging. For the purpose of control synthesis and design, a crank-angle based dynamic model of an HCCI engine with internal exhaust gas recirculation (EGR) is proposed in this paper. The HCCI autoignition timing is controlled by the amount of internal EGR induced by the cost effective exhaust throttling strategy. The zero dimensional single zone model is developed based on conservation of mass and energy and ideal gas law. The model is comprised of five subsystems: cylinder volume, intake, and exhaust runners along with combustion and heat-transfer models. Inputs to the model include engine speed, intake temperature, fueling rate, intake, and exhaust throttle positions. Outputs of the model contain the pressure, temperature, mass and burned gas fraction in the intake, exhaust and cylinder, air-to-fuel ratio (AFR), heat release rate, combustion phasing, and the indicated mean effective pressure (IMEP). The model is developed based on MATLAB/Simulink and validated against experimental data under steady-state and transient conditions at various intake temperatures, fueling levels, and exhaust throttle positions. Results demonstrate that by changing the exhaust throttle position, the pressure in the exhaust runner is regulated. As a result, the residual gas fraction is altered, leading to changes in mixture temperature and thus control of the HCCI combustion phasing. In the end, closed loop simulation is conducted with a linear quadratic Gaussian (LQG) controller applied to the crank-angle based model for regulation of combustion timing CA50 using exhaust throttle during load (fueling level) changes. In the future, this model can be utilized for control development and hardware in the loop (HIL) simulation.

Exhaust Tuning of an Internal Combustion Engine by the Combined Effects of Variable Exhaust Pipe Diameter and an Exhaust Valve Timing System

Changes to engine geometry and specifications can produce better torque, power, volumetric efficiency and more. The technique known as wave tuning can lead to better engine torque and power. This paper focuses on increasing the engine torque by improving the exhaust fluid flow through the exhaust manifold. Phasing and intensity of the pressure waves in the exhaust manifold have significant effects on scavenging, valve overlapping and pumping losses. In this research, individual and combined effects of variable exhaust runner diameter and exhaust valve timing on the fluid flow from exhaust of the engine are studied using computer simulation. An engine simulation software, Ricardo Wave, is utilized in this research. The analysis is conducted on a 1-D model of a KTM 510 cc single cylinder, four-stroke Sl engine. The data gathered shows that varying only the exhaust pipe diameter continuously with speed yields an average of 4.23% improvement in torque from the original engine model. However, due to practical constraints, the diameter is limited to vary in three steps (36 mm, 45 mm and 60 mm). This has reduced the average improvement of torque to 3.78%. Varying the valve timing alone gains an average of 1.94% improvement in torque. Varying both the exhaust pipe diameter in three steps and the exhaust valve timing yields an average of 4.69% improvement in torque. This average is conducted over the engine speed ranges from 2000 to 11,000 rpm.

Flow measurements in the exhaust system of a motorized engine

Stereo Particle Image Velocimetry (SPIV) is used to measure the highly turbulent flow in the upstream region of the catalytic converter for a four stroke IC engine. These experiments are conducted for a motorized engine to investigate the feasibility of using SPIV for exhaust flow measurements in a firing IC engine in our future research. The results obtained here can also be used for validation of the CFD models. The measured flow is highly three dimensional, non-uniform with large magnitudes of turbulence indicating recirculating flow structures. These structures show signatures of jet flows coming out of the exhaust valves at all exhaust crank angles. The triangular shape and location for the end face of each exhaust runner pipe, the length and geometry of the runners also affect the flow mixing process upstream of the catalytic converter contributing to the complexity of this flow. Although majority of the exhaust flow passes through the catalytic converter, some will recirculate due to impingement of the exhaust jets on the surface of the catalyst.

In-cylinder pressure based model for exhaust temperature estimation in internal combustion engines

Exhaust temperature is a valuable parameter for engine control. However, measurement conditions at the engine exhaust and the slow dynamic response of temperature sensors difficult the determination of the instantaneous exhaust temperature. The present paper proposes a methodology for estimating the exhaust temperature exclusively relying in-cylinder pressure signal, engine speed and exhaust lambda.The presented methodology can replace or actualize widespread look-up table models for correcting calibration offsets, due to ageing, sensor bias or disturbances associated with the engine operation. The method uses the existence of resonant modes in the in-cylinder pressure for inferring the trapped mass and the in-cylinder temperature. An isentropic expansion of the gasses through the valves is assumed for estimating the cylinder outlet temperature of the gases, and the gas temperature drop along the exhaust runner and manifold is modelled through a nodal thermal model. The method was compared with current models under steady and transient conditions in a four stroke CI engine. Variations of injection, EGR, intake pressure and rail pressure were performed under steady operation and the transient response of the method was validated under specific transient test and at the WLTP cycle. A time invariant first order model was used for comparing the estimated temperature with that provided by the experimental sensors.

Multi-level computational exploration of advanced combustion engine operating strategies

Advanced combustion engine (ACE) research is typically carried out on single-cylinder research engines. These engines are designed to tightly control fueling and conditions at intake valve closure (IVC) and to precisely measure in-cylinder conditions and emissions. However, to be able to measure and control engine operation so precisely, these research engines typically do not feature intake and exhaust tracts that resemble those in production engines, specifically in regards to turbomachinery, heat exchangers, and exhaust gas recirculation (EGR) systems. For this reason, these research engines are effective for understanding in-cylinder combustion parameters such as heat release rate, burn duration, combustion efficiency, pollutant formation, and exhaust valve opening (EVO) conditions.This paper applies high fidelity simulations to determine the feasibility of achieving a chosen single cylinder engine operating point on a production type homogeneous charge compression ignition (HCCI) engine, using a partial fuel stratification (PFS) strategy. To accomplish this, a Converge 3 dimensional (3D) – computational fluid dynamics (CFD) model of the experimental combustion chamber and intake and exhaust runners was created to simulate the experimental engine. This model was used to simulate an operating point achieved experimentally, as well as to determine the sensitivity of the operating point to variations in intake pressure, intake temperature, injection timing, injected mass, and EGR fraction. The results from these simulations were fed into a 1-dimensional engine simulation created in AVL Boost, featuring production-type intake and exhaust systems, including turbomachinery and heat exchangers necessary to create the required IVC conditions. This full engine simulation was used to assess the cycle efficiency of the engine at the experimental operating condition, and to assess whether changes to this operating point in intake temperature, intake pressure, direct injection timing, or fueling are beneficial to the cycle efficiency and engine-out emissions. In addition, the sensitivity of promising engine operating points to injection timing and injection mass are determined to evaluate the potential stability of these operating points.

Adaptive control of homogeneous charge compression ignition engines

SUMMARYThis paper presents an adaptive controller, which maintains consistent ignition timing control of a gasoline homogeneous charge compression ignition engine with high dilution in the presence of uncertainty or unknown variation in plant parameters such as exhaust runner wall temperature and cylinder charge properties. The control of the combustion timing is based on manipulating the charge temperature through internal dilution, which is achieved by controlling the lift of a secondary opening of the exhaust valves, also known as the rebreathing lift. The adaptive controller is designed on the basis of a simplified bilinear parametric model, which contains only the cycle‐to‐cycle combustion timing dynamics. Implementation of the designed adaptive controller involves feedforward of the injected fuel and feedback of the combustion timings CA50 and CA90 when 50% and 90% of energy are released, respectively, which alleviates the impact of inevitable errors in estimation of in‐cylinder charge properties such as temperature, pressure, and compositions. It is shown through convergence analysis and closed‐loop simulation of a full‐order engine model that the adaptive controller is able to drive the combustion timing CA50 to desired set points by stabilizing the bilinear dynamics when plant parameters are changing. Copyright © 2013 John Wiley & Sons, Ltd.

The CFD Analysis of Exhaust Runner for GW15 Gasoline Engine

In order to improve GW15 gasoline engine’s power and economy, AVL BOOST/FIRE software has been applied to the simulation of the engine’s one-dimensional and coupled 1D-3D simulation. First, optimal length of exhaust runner was obtained by simulation with BOOST, and proposed two types of structures schemes. Then, the better one was selected for BOOST and FIRE coupling in order to further optimize the exhaust runner according to the numerical simulation results. Finally, the engine performances were verified through experiment. The results indicate that both the engine’s maximal torque and maximal power increase, specific fuel consumption decreases.

Input Observer-Based Individual Cylinder Air-Fuel Ratio Control: Modelling, Design and Validation

A general approach is proposed to address the cylinder-to-cylinder air-fuel ratio (AFR) balancing control problem using a single universal exhaust gas oxygen (UEGO) sensor. Using the multirate sampling technique, a control-oriented engine model, well combining the fuel delivery dynamics and exhaust gas dynamics, is established. Gas mixing phenomena is characterized by a gas mixing matrix, which is valid both for equal-length and unequal-length exhaust runners. Based on the developed model, the observability of the individual cylinder AFR estimation problem is analyzed using the input observability concept. An input observer using the one-step forward feedback is proposed to design the estimator. Using the estimated AFR, a decoupled PI compensator is designed for each cylinder to compensate the cylinder-by-cylinder variations. Finally, the proposed approach is verified by simulation and experimental results.

Closed-loop Individual Cylinder Air-Fuel Ratio Control via UEGO Signal Spectral Analysis

The paper presents the development and real time application of an original closed-loop individual cylinder AFR control system, based on a spectral analysis of the lambda sensor signal measured at the confluence of the various exhaust runners. The observation that any type of AFR disparity between the various cylinders is reflected in a specific harmonic content of the AFR signal spectrum, represents the starting point of the project. The proposed approach has been designed in order to be compatible with onboard application. The AFR individual cylinder closed-loop controller has been tested in real time, by implementing it in a virtual Electronic Control Unit, using rapid control prototyping techniques. The results observed on a 4 cylinder Spark Ignition 1.2 liter engine are encouraging, since in the investigated engine operating conditions the controller is able to guarantee AFR inequality below 0.01 lambda. The paper shows how the proposed controller can be applied to other engine configurations (6, 8, or 12 cylinder engines), if a lambda sensor is available per each engine bank.

Experimental Validation of the Addition Principle for Pulsating Flow in Close-Coupled Catalyst Manifolds

Designing an exhaust manifold with close-coupled catalyst (CCC) relies heavily on time-consuming transient computional fluid dynamics. The current paper provides experimental validation of the addition principle for pulsating flow in CCC manifolds. The addition principle states that the time-averaged catalyst velocity distribution in pulsating flow equals a linear combination of velocity distributions obtained for steady flow through each of the exhaust runners. A charged motored engine flow rig provides cold pulsating flow in the exhaust manifold featuring blow down and displacement phases, typical of fired engine conditions. Oscillating hot-wire anemometry is used to measure the bidirectional velocity, with a maximum measurable negative velocity of −1m∕s. In part load and zero load conditions, instantaneous reverse flow occurs following the blow-down phase. The two-stage nature of the exhaust stroke combined with strong Helmholtz resonances results in strong fluctuations of the time-resolved mean catalyst velocity. The validity of the addition principle is quantified based on the shape and magnitude similarity between steady and pulsating flow distributions. Appropriate nondimensional groups are used to characterize the flow and quantify the similarity. Statistical significances are provided for the addition principle’s validity. The addition principle is valid when the nondimensional scavenging number S exceeds a critical value Scrit, corresponding to cases of low engine speed and/or high flow rate. This study suggests that the CCC manifold efficiency with respect to catalyst flow uniformity could be quantified using a single scalar parameter, i.e., Scrit. The results from the current study are discussed with respect to previously reported results. The combined results are in good agreement and provide a thorough statistically founded experimental validation of the addition principle, based on a broad applicability range.

95/02023 Hydrocarbon oxidation in the exhaust port and runner of a spark ignition enigine

95/02023 Hydrocarbon oxidation in the exhaust port and runner of a spark ignition enigine