Exhaust Gas Recirculation System Research Articles

A characteristic study and optimization of in-cylinder configuration for particulate matters reduction in an off-highway diesel engine with mechanical fuel injection system

This paper shows development challenges for 11-liter heavy-duty off-highway diesel engines to meet Tier 3 emission regulations with a base diesel engine compliant with Tier 2 emission regulations. In the case of the installation of an exhaust gas recirculation (EGR) system for reduction of NOx emissions, there exists a risk of increased particulate matters (PM) emissions. An in-cylinder PM reduction is still necessary since a diesel particulate filter (DPF) after-treatment system is not under the consideration. The objective of this research is to see whether the base engine has a potential to meet Tier 3 emission regulations by changing in-cylinder configuration parameters including the bowl shape, injector position, the number of intake and exhaust valves, injector tip protrusion, and injector tip specifications such as nozzle spray angle and nozzle flow rate. These parameters are very important parts which enhance the air and fuel mixing process that helps the combustion process. Thus, the optimization of these design variables is essential to improve combustion efficiency and emissions reduction. In this study, the multi-dimensional computational fluid dynamics (CFD) code KIVA-3V is used to perform combustion simulations. The Kelvin–Helmholtz/Rayleigh–Taylor (KH-RT) model is employed for spray breakup and a reduced chemical mechanism for n-heptane is employed to simulate ignition delay and combustion of diesel fuel. To verify the simulation results, engine bench tests were performed with installations of the final version of in-cylinder geometry in C1-8 mode which is one of main test cycles to meet Tier 3 emission regulations. Finally, Tier 3 emission regulations have been met with the currently optimized in-cylinder configuration parameters.

Application of an EGR system in a direct injection diesel engine to reduce NOx emissions

This work presents the application of an exhaust gas recirculation (EGR) system in a direct injection diesel engine operating with diesel oil containing 7% biodiesel (B7). EGR rates of up to 10% were applied with the primary aim to reduce oxides of nitrogen (NOx) emissions. The experiments were conducted in a 44 kW diesel power generator to evaluate engine performance and emissions for different load settings. The use of EGR caused a peak pressure reduction during the combustion process and a decrease in thermal efficiency, mainly at high engine loads. A reduction of NOx emissions of up to 26% was achieved, though penalizing carbon monoxide (CO) and total hydrocarbons (THC) emissions.

Design of combustion bowl geometry to meet final Tier 4 of 11 L non-road heavy-duty diesel engine with multi-dimensional combustion simulation

To comply with the new non-road emission standards, final Tier 4, two big strategies have been applied to the 11 L heavy-duty diesel engine. The first strategy is to apply Exhaust gas recirculation and selectivity catalytic reduction system to meet the NOx limitation. The other one is to apply low swirl ratio (for higher volumetric efficiency) and multi-hole nozzle, a high pressure direct injection, and an optimized combustion system in order to reduce PM emission. Both strategies put a focus on the optimization of combustion system. In this study, a ULPC bowl concept applied in the previous works has been successfully verified in 11 L heavy-duty diesel engine with wellvalidated 3D combustion simulation, and the ULPC bowl shape has been geometrically optimized. A rough 0D calculation is used to calculate the fuel split ratio of the various ULPC bowl shapes. In the rated-power operating condition of the final Tier 4 engine which is deduced by 1D cyclic simulation, the optimal fuel split ratio of the injected fuel has been verified. Also, additional geometric optimization has been achieved without changing the optimal fuel split ratio. From these results, soot has been reduced by about 30% with ULPC optimum bowl shape against the Tier 3 re-entrant bowl shape.

On Decoupling Control of the VGT-EGR System in Diesel Engines: A New Framework

In this brief, a novel decoupling solution is proposed for the variable-geometry turbine (VGT) and exhaust gas recirculation (EGR) system of diesel engines based on the principle of active disturbance rejection control. This complex, double-input, double-output, VGT-EGR system is treated as two ideal, decoupled integrators for the purpose of control design, while all other dynamics that deviate from the ideal model, including cross coupling and dynamic variations due to operating point changes, and all other uncertainties are treated as the total disturbance to be estimated and canceled. Since the estimation of the total disturbance is bandwidth limited in the VGT-EGR system, feedforward controllers, one static and one dynamic, are used to speed up the response. The proposed controller is simple to implement, easy to tune, and able to handle a wide range of uncertainties without retuning or gain-scheduling. Its effectiveness has been validated in simulation, experimental tests, as well as in mathematical analysis, proving the inverse relationship between the tracking error and the controller bandwidth.

Experimental investigation to study the effects of using hot and partially cold EGR in direct injection diesel engine

Major exhaust emissions from diesel engines are CO, CO2, PM, UHC and NOx, of which NOx is one of the most harmful. A number of techniques have been utilized to control NOx emissions and exhaust gas recirculation (EGR) is one of the widely used techniques that show outstanding results in NOx reduction in both light and heavy duty diesel engines. In the present study, the experiment has been conducted on a four-stroke, single-cylinder water cooled diesel engine. Here, a long-route EGR system was used in both hot (insulated) and partially cooled (without insulation) conditions. EGR rate was varied from 0 to 24% in steps of 6% and the engine ran at various load conditions. The research objective was to investigate the effects of varying EGR ratios and temperatures on engine performance parameters and determine the effective EGR rate where the engine gives high performance, low fuel consumption and produces low emissions.

Particulate Fouling and Challenges of Metal Foam Heat Exchangers

ABSTRACTIn recent years, open-cell metal foam has gained attention for utilization for exhaust gas recirculation coolers due to its large surface area and porous structure. Theoretically, the porous foam structure would have better transfer heat through conduction and convection processes. However, the exhaust gases that enter the cooler would carry particulate matter, which may deposit within the foam structure. The existing fouling studies cannot explain the underlying mechanisms of particulate deposition thoroughly within the foam structure. This study reviews the particulate fouling of heat exchangers, particularly in the exhaust gas recirculation system. Some past approaches to investigate fouling, particle transport, and deposition in the metal foam heat exchangers for many different applications are also included. In addition, this study also includes the challenges that lie ahead in implementing the metal foam heat exchangers in the industries.

Performance Analysis of a Reciprocating Piston Expander and a Plate Type Exhaust Gas Recirculation Boiler in a Water-Based Rankine Cycle for Heat Recovery from a Heavy Duty Diesel Engine

The exhaust gas in an internal combustion engine provides favorable conditions for a waste-heat recovery (WHR) system. The highest potential is achieved by the Rankine cycle as a heat recovery technology. There are only few experimental studies that investigate full-scale systems using water-based working fluids and their effects on the performance and operation of a Rankine cycle heat recovery system. This paper discusses experimental results and practical challenges with a WHR system when utilizing heat from the exhaust gas recirculation system of a truck engine. The results showed that the boiler’s pinch point necessitated trade-offs between maintaining adequate boiling pressure while achieving acceptable cooling of the EGR and superheating of the water. The expander used in the system had a geometric compression ratio of 21 together with a steam outlet timing that caused high re-compression. Inlet pressures of up to 30 bar were therefore required for a stable expander power output. Such high pressures increased the pump power, and reduced the EGR cooling in the boiler because of pinch-point effects. Simulations indicated that reducing the expander’s compression ratio from 21 to 13 would allow 30% lower steam supply pressures without adversely affecting the expander’s power output.

Analysis of a gas system with a recirculation of the flue gases and carbon dioxide capture

EU regulations in the field of climate policy imposes strict limits on the emission of pollutants. In addition, there are ongoing work on systems to CO2 capture, which is considered a major cause of global warming on Earth. During gas combustion emits significantly less pollution and carbon dioxide which ifs their advantage. However, because of the limited CO2 emission it is possible to introduce the uptake of said compound by chemical absorption, predisposed to be used for the coal-fired plants. Low concentrations of carbon dioxide in the exhaust gas can be increased by using exhaust gas recirculation system of a gas turbine, while reducing energy consumption during capture. In addition, the second topic discussed in the article relates to the use of hydrogen fuel for gas system. It has been shown that hydrogen admixture injection for natural gas affect considerable reduction emission carbon dioxide. This article presents the change in the operating parameters of the combined cycle with installation of CO2 capture and exhaust gas recirculation. Built a mathematical model of the system using the code of Ebsilon Professional and performed parametric calculations. In the report, there was conducted an analysis of the dependence of the change of LHV of gaseous fuel which is a mixture of natural gas and hydrogen for proper work of the gas turbine installation. The built model and obtained results are useful in the analysis of combined cycle systems integrated with separation of carbon dioxide from the flue gas.

An Approach to the Prototyping of an Optimized Limited Stroke Actuator to Drive a Low Pressure Exhaust Gas Recirculation Valve.

The purpose of this article is to describe the design of a limited stroke actuator and the corresponding prototype to drive a Low Pressure (LP) Exhaust Gas Recirculation (EGR) valve for use in Internal Combustion Engines (ICEs). The direct drive actuator topology is an axial flux machine with two air gaps in order to minimize the rotor inertia and a bipolar surface-mounted permanent magnet in order to respect an 80° angular stroke. Firstly, the actuator will be described and optimized under constraints of a 150 ms time response, a 0.363 N·m minimal torque on an angular range from 0° to 80° and prototyping constraints. Secondly, the finite element method (FEM) using the FLUX-3D® software (CEDRAT, Meylan, France) will be used to check the actuator performances with consideration of the nonlinear effect of the iron material. Thirdly, a prototype will be made and characterized to compare its measurement results with the analytical model and the FEM model results. With these electromechanical behavior measurements, a numerical model is created with Simulink® in order to simulate an EGR system with this direct drive actuator under all operating conditions. Last but not least, the energy consumption of this machine will be estimated to evaluate the efficiency of the proposed EGR electromechanical system.

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.

Dual Fuel Turbocharged Engine Operated with Exhaust Gas Recirculation

AbstractWith good combustion characteristics, hydrogen has been developing as a clean alternative fuel of engines. This study is to develop a diesel/hydrogen dual fuel engine. The hydrogen was added at inlet port in a 4-cylinder direct injection turbocharged diesel engine with an EGR (Exhaust Gas Recirculation) system to investigate engine performance and exhaust pollutant. The measured items are composed of the gas pressure of cylinder, crank angle, consumption rate of diesel, consumption rate of hydrogen, air flow rate, emissions (HC, CO2, NOX, and Smoke), and so on. The authors analyze how the addition of hydrogen with EGR system influences the engine performance and emissions. The diesel/hydrogen dual fuel turbocharged engine can increase the brake thermal efficiency with a greater decrease in emissions compared with the turbocharged diesel engine. Furthermore, the authors little altered the engine structure to get the positive effect of energy saving and pollutant decreasing.

High-Speed Multiplexed Spatiotemporally Resolved Measurements of Exhaust Gas Recirculation Dynamics in a Multi-Cylinder Engine Using Laser Absorption Spectroscopy.

The need for more environmentally friendly and efficient energy conversion is of paramount importance in developing and designing next-generation internal combustion (IC) engines for transportation applications. One effective solution to reducing emissions of mono-nitrogen oxides (NOx) is exhaust gas recirculation (EGR), which has been widely implemented in modern vehicles. However, cylinder-to-cylinder and cycle-to-cycle variations in the charge-gas uniformity can be a major barrier to optimum EGR implementation on multi-cylinder engines, and can limit performance, stability, and efficiency. Precise knowledge and fine control over the EGR system is therefore crucial, particularly for optimizing advanced engine concepts such as reactivity controlled compression ignition (RCCI). An absorption-based laser diagnostic was developed to study spatiotemporal charge-gas distributions in an IC engine intake manifold in real-time. The laser was tuned to an absorption band of carbon dioxide (CO2), a standard exhaust-gas marker, near 2.7 µm. The sensor was capable of probing four separate measurement locations simultaneously, and independently analyzing EGR fraction at speeds of 5 kHz (1.2 crank-angle degree (CAD) at 1 k RPM) or faster with high accuracy. The probes were used to study spatiotemporal EGR non-uniformities in the intake manifold and ultimately promote the development of more efficient and higher performance engines.

Pressure model based coordinated control of VGT and dual-loop EGR in a diesel engine air-path system

This paper describes a pressure-model-based coordinated control method of a variable geometry turbine (VGT) and dual-loop exhaust gas recirculation (EGR) in a diesel engine air-path system. Conventionally, air fraction or burnt gas fraction states are controlled for the control of dual-loop EGR systems, but fraction control is not practical since sensors for fractions are not available on production engines. In fact, there is still great controversy over how best to select control outputs for dual-loop EGR systems. In this paper, pressure and mass flow states are chosen as control outputs without fraction states considering the availability and reliability of sensors. A coordinated controller based on the simple control-oriented model is designed with practical aspects, which is applicable for simultaneous operations of high pressure (HP) EGR, low pressure (LP) EGR, and VGT. In addition, the controller adopts the method of input-output linearization using back-stepping to solve the chronic problems of conventional pressure-based controllers such as coupling effects between operations of HP EGR, and VGT. The control performance is verified by simulation based on the proven GT-POWER model of a heavy-duty 6000cc diesel engine air-path.

Metal foams as gas coolers for exhaust gas recirculation systems subjected to particulate fouling

This paper presents experimental results indicating the benefits and challenges associated with the use of metal foams as Exhaust Gas Recirculation (EGR) coolers. Fouling of such heat exchangers is a critical issue and, as such, special attention has been paid to address this very issue in the present study where a soot generator has been employed to simulate the engine running condition. Effects of aluminium foam PPI and height as well as gas velocity are investigated. It has been noted that proper design of the foam can lead to significantly higher heat transfer rate and reasonable pressure drop compared to no-foam cases. More interestingly, it is demonstrated that the foams can be cleaned easily without relying on expensive cleaning techniques. Using simple brush-cleaning, the foams can be reused as EGR gas coolers with a performance penalty of only 17% (compared to a new or clean foam).

Experimental analysis of diesel engine exhaust gas coupled with water desalination for improved potable water production

Exhaust gas temperature of diesel engine is higher compared with a petrol engine and also creates higher pollution in the environment. Exhaust gas recirculation system and many other systems have used for reuse of exhaust gas to improve the performance of diesel engine, but the use of diesel engine for production of potable water production is still unattended by the researchers. The main aim of this research work is to use the waste heat of exhaust gas for potable water production from the low-capacity desalination system integrated with a evaporator and condenser unit. In this work, single pass evaporator and water-cooled condenser used for evaporation and condensation of saline water were designed and fabricated by locally available materials. The experiments were performed on a 10 HP diesel engine with varying the load to get potable water. It has found that 4.2 L/hr of potable water is obtained from the exhaust gas without varying the performance of the engine. Also, it has found that, temperature of saline water is heated more than 70°C in the condenser unit.

Feedforward Controller Design for EGR and VGT Systems based on Cylinder Pressure Information and Air Path Model

This study proposes a feedforward control method for exhaust gas recirculation (EGR) and variable geometry turbocharger (VGT) systems based on cylinder pressure information and air path model. The proposed method calculates EGR rate and exhaust manifold pressure using cylinder pressure information which provides accurate combustion state information. The accuracy of the air system model was improved according to the precise information of the EGR rate and exhaust pressure; subsequently, the performance of the proposed model based feedforward controller was enhanced. The proposed feedforward controller was implemented in an in-house developed engine management system and validated through the engine experiments under steady and transient conditions.

Decoupled, Disturbance Rejection Control for A Turbocharged Diesel Engine with Dual-loop EGR System

Dual-loop exhaust gas recirculation (EGR) with variable geometry turbocharger (VGT) provides a flexible architecture for achieving desired intake manifold conditions, including temperature, pressure and oxygen concentration, which are critical for advanced combustion mode control in modern engines. However, the highly nonlinear system dynamics and strong coupling effects between loops make the widely used, control oriented model failed to trace the system states well, especially in transient situations. This paper presents a control method for this nonlinear, multi-input multi-output (MIMO) system with the compensation for modeling error and disturbance. By taking both the advantages of the knowledge of system dynamics and the idea of disturbance rejection, the modified active disturbance rejection control (ADRC) with extended states observer (ESO) was utilized to achieve such a control objective. Here, the term "disturbance" lumps all the internal and external errors, including the modeling errors and coupling effects. By actively estimating the disturbance and compensating its effects, the intake manifold conditions can be controlled in a decoupled fashion. The proposed method was validated through high-fidelity GT-Power model simulations.

EGR 쿨러 Type에 따른 열교환성능에 관한 실험적 연구

Nitrogen oxide(NOx) emission reductions are required to meet the strict emission regulations for environmental protection. Most of the Exhaust Gas Recirculation(EGR) system applied to a diesel engine can relatively decrease the NOx at a low cost, but it has a disadvantage in that the PM generation is promoted due to the hot intake air temperature. Thus, high heat exchange efficiency of the EGR cooler is required for an effective removal of NOx. In this study, heat exchange efficiency for various types of heat exchangers used in EGR cooler was measured under same conditions, and determined best heat exchange performance shape depending on type of heat exchanger.

Switching strategy between HP (high pressure)- and LPEGR (low pressure exhaust gas recirculation) systems for reduced fuel consumption and emissions

EGR (Exhaust gas recirculation) plays a major role in current Diesel internal combustion engines as a cost-effective solution to reduce NOx emissions. EGR systems will suffer a significant evolution with the introduction of NOx after-treatment and the proliferation of more complex EGR architectures such as low pressure EGR or dual EGR. In this paper the combination of HPEGR (high pressure EGR) LPEGR (low pressure EGR) is presented as a method to minimise fuel consumption with reduced NOx emissions. Particularly, the paper proposes to switch between HPEGR and LPEGR architectures depending on the engine operating conditions in order to exploit the potential of both systems. In this sense, given a driving cycle, in the case at hand the NEDC, the proposed strategy seeks the EGR layout to use at each instant of the cycle to minimise the fuel consumption such that NOx emissions are kept below a certain limit. The experimental results obtained show that combining both EGR systems sequentially along the NEDC allows to keep NOx emission below a much lower limit with minimum fuel consumption.

Experimental characterization of cooled EGR in a gasoline direct injection engine for reducing fuel consumption and nitrogen oxide emission

The emphasis on increasing fuel economy and reducing emissions is increasing. Attention has turned to how the performance of a gasoline direct injection (GDI) engine can be improved to achieve lower fuel consumption and NOx emission. Therefore, positive effects can reduce fuel consumption and NOx emission as well as knock suppression. The cooled exhaust gas recirculation (EGR) ranges within the characteristic map are characterized from the experimental results at various speeds and brake mean effective pressures in a GDI engine. The results show that the application of cooled EGR system brought in 3.63 % reduction as for the fuel consumption and 4.34 % as for NOx emission.