Dynamic Scheduling of Internal Exhaust Gas Recirculation Systems

Experimental investigation of the influence of internal and external EGR on the combustion characteristics of a controlled auto-ignition two-stroke cycle engine

<div class="section abstract">We describe a CHEMKIN-based multi-zone model that simulates the expected combustion variations in a single-cylinder engine fueled with iso-octane as the engine transitions from spark-ignited (SI) combustion to homogenous charge compression ignition (HCCI) combustion. The model includes a 63-species reaction mechanism and mass and energy balances for the cylinder and the exhaust flow. For this study we assumed that the SI-to-HCCI transition is implemented by means of increasing the internal exhaust gas recirculation (EGR) at constant engine speed. This transition scenario is consistent with that implemented in previously reported experimental measurements on an experimental engine equipped with variable valve actuation. We find that the model captures many of the important experimental trends, including stable SI combustion at low EGR (~0.10), a transition to highly unstable combustion at intermediate EGR, and finally stable HCCI combustion at very high EGR (~0.75). Remaining differences between the predicted and experimental instability patterns indicate that there is further room for model improvement.</div>

Abstract: The principal objectives of this study were to examine in-cylinder combustion pressure oscillation characteristics of soybean biodiesel in time domain and time-frequency domain, and their influences on the control and operational parameters, such as injection timing, exhaust gas recirculation (EGR) ratio, engine load and engine speed. In this study, the combustion pressure oscillation characteristics of biodiesel engine for various injection timing, EGR ratio and engine speed were investigated. The corresponding relation of pressure characteristics in the time domain and frequency domain were obtained. The results showed that the pressure oscillation and peak pressure rise acceleration occurred mainly in the diffusion combustion, and the peak pressure rise rate located in the premixed combustion. The in-cylinder pressure level curve can be divided into three stages. The pressure levels of stage 1, stage 2 and stage 3 represent the peak in-cylinder pressure, the maximum amplitude of pressure rise rate and pressure rise acceleration, respectively. As the injection timing retards, the pressure levels of stage 1 and stage 3 decrease gradually. The pressure level curve of stage 3 with 25o before top dead center (BTDC) is the highest and the oscillation is the most significant. It is worth noting that the location of each stage with various operate conditions is not fixed. At 0.41 MPa indicated mean effective pressure (IMEP), with the increase of EGR rate, the pressure levels of stage 1 and stage 2 decrease gradually. The pressure level curve of stage 3 and the maximum amplitude of pressure rise acceleration with 0% EGR rate are the highest. The oscillation with 0% EGR rate is the most significant at 0.41 MPa IMEP. Compared to 0.41 MPa IMEP, the frequency bands of stage 1 and stage 2 at 1.1 MPa IMEP are relatively low due to the soft combustion in the cylinder. As EGR rate increases, the pressure level of stage 1 decreases, and those of stage 2 and stage 3 increase gradually. The oscillation with 30% EGR rate is the most significant. With the increase of engine speed, the pressure levels of stage 1 and stage 2 decrease, and move to the low frequency. The pressure level in the high frequency domain at 1600 r/min is less than that at 1100 r/min, and the combustion process is smooth. Keywords: combustion pressure oscillation, soybean biodiesel, injection timing, exhaust gas recirculation, engine speed DOI: 10.3965/j.ijabe.20160906.1680 Citation: Ma P, Liu H L, Liu S Y. Experimental study on combustion pressure oscillation of soybean bio diesel oil. Int J Agric & Biol Eng, 2016; 9(6): 156－166.

In this paper, an experimental study evaluating the effect of exhaust gas recirculation (EGR) and liquefied petroleum gas (LPG) onboard systems attached to a single cylinder DI diesel engine running with diesel is presented. Tests were performed at the minimum (1400 rpm) and maximum engine speeds (4100 rpm). The engine were tested under four different operating modes mainly; (a) standard test condition, (b) engine with EGR system, (c) engine with LPG system and (d) the engine with EGR and LPG onboard systems. Parameters that been measured during the tests are percentage of oxygen (O2) content, carbon monoxide (CO) emissions, carbon dioxide (CO2) and unburned hydrocarbon (UHC) emissions. Results show for the exhaust emissions, the engine with LPG onboard system emits higher CO and UHC emissions for both engine speeds. According to the experimental results it can be concluded that the use of EGR system increased the exhaust gas temperature and CO2emissions. While the engine with EGR and LPG onboard systems have influenced much on the increase in CO and UHC emissions for both engine speeds.

Automobile emissions are the main source of greenhouse gases (GHG) accumulation in environment. As old engines (Euro III or earlier) produce more emissions and it will be difficult to entirely stop their usage especially in developing and underdeveloped nations, it is desired that appropriate emission reduction technologies are tested on such engines to analyze their feasibility and economical acceptability. While most such studies have been conducted on constant speed stationary engines and modern engines, this study tried to analyze the effectiveness of exhaust gas recirculation (EGR) system on a Euro‐1, water‐cooled, direct injection, variable speed, compression ignition (C.I.) engine in a laboratory setup in India. This was done by testing an electronic control unit (ECU)‐controlled EGR valve running the engine on different speeds; with different torques, as also with varying EGR percentages. Then optimum value of EGR valve opening for each set of engine speed and torque was determined, that is, corresponding to minimum oxides of nitrogen (NOx). Optimum EGR valve position was programmatically fed, for each set of torque and engine speed (in RPM), into EGR ECU and then the engine was run at varying speeds and torques and the emissions were verified in the automated mode. It was found that using EGR, NOx emissions were substantially reduced (average 45% reduction), without significantly impacting the engine performance. However, smoke emission increased with EGR. In order to counter the adverse effects, additional emission reduction technologies should be used in tandem with EGR. © 2017 American Institute of Chemical Engineers Environ Prog, 36: 1685–1693, 2017

A new exhaust gas recirculation (EGR) system has been devised. The system utilizes the throttle plate as a secondary controller of EGR flow. Over a series of sudden-deceleration tests, from various engine speeds and loads to idle, the new system showed a complete absence of the misfires which characterized the standard system. Furthermore, EGR flow characteristics differed markedly between the new and standard systems. The new system improved the responsiveness of the EGR system, potentially reducing both HC and NO{sub x} emissions. Further advantages of the new system include simplicity and low component cost.

Skip-firing (or cylinder de-activation) was assessed as a method of sampling CO2 from directly in the cylinder at higher speeds than previously possible. CO2 was directly sampled from one cylinder of a 1-litre 3-cylinder gasoline engine to determine the residual gas fraction using a fast response CO/CO2 analyser. Acquisition of data for similar measurements is typically limited to engine speeds of below 1300 rpm to allow full resolution of the sample, through the analyser that has an 8 millisecond finite response time. In order to sample in-cylinder CO2 at higher engine speeds a skip-firing method is developed. By shutting off ignition intermittently during engine operation, the residual CO2 from the last firing cycle can be measured at significantly higher engine speeds. Comparison of residual gas fraction CO2 at low speeds for normal and skip-fire operation shows good correlation. This suggests that skip-firing is a suitable method for directly measuring internal exhaust gas recirculation up to at least 3000 rpm. The measurements obtained may provide a useful tool for validating internal exhaust gas recirculation models and could be used to calculate combustion air-fuel ratio from the CO and CO2 content of the burned gas. These are typically complicated parameters to predict due to the slow response time and sensitivity to hydrocarbons of wide-band oxygen sensors. A differing pattern of residual gas fraction change with increasing speed was seen between normal and skipfire operation.

Gaseous fuels have a high CO2-reduction potential and knock resistance due to their chemical and thermal properties, which make them an interesting fuel alternative for the use in modern spark-ignited engines. Within this research project the stoichiometric and homogeneous combustion process with compressed natural gas (CNG) direct injection is investigated in combination with high-load exhaust gas recirculation (EGR).To study the flow characteristics and mixture formation of CNG injection in a combustion chamber, experimental investigations were performed in a low-pressure injection chamber and on an optically accessible single-cylinder engine. The CNG spray investigations in the low-pressure injection chamber were performed with the aim to macroscopically characterize the natural gas jet using the Schlieren technique and planar laser-induced fluorescence (pLIF). A 3D-CFD model was created and validated with the optical single cylinder investigations and a qualitative PIV method at low-end torque and catalyst heating conditions. Both central and lateral injection positions were investigated using PIV and these results proved a good compatibility with the 3D-CFD simulations. Both the optical investigations in the low-pressure chamber and with the motored, optically accessible single-cylinder engine show that the direct natural gas injection with the side injector position has advantages compared to the central position, since the primary and secondary tumble are increased by an early and late injection timing.Experimental studies with the thermodynamic single-cylinder research engine show that the potential to control combustion using EGR is limited, however, an optimum combustion phasing could be maintained despite a lower combustion speed.The dilution capability of CNG was investigated using both EGR and excess air using two compression ratios of CR = 13 and 14.7. The investigations with excess air dilution showed the highest in-crease in indicated efficiency. The CR = 13 configuration allowed an increase of ~2.5%-points and a maximum air/fuel-ratio of λ = 1.5.A 0D/1D engine model was created using a predictive combustion model (SITurb) for the direct injection of natural gas and validated using measurement results. The investigations showed that low-pressure EGR cannot be used for high-load EGR with single supercharging due to reaching the com-pressor map limits. Therefore, a high-pressure EGR system was implemented.A Ford Eco Boost Engine was used for the engine tests and modified for CNG operation. The full-load tests at IMEP = 23 bar showed that no reduction in the cylinder peak pressure could be achieved with cooled EGR at constant center of combustion. The indicated efficiency could be slightly in-creased up to n = 4500 1/min due to the reduced wall heat losses. NOX emissions were significantly reduced over the entire speed range from 25–62% at 5% EGR. However, HC, CH4, and CO emissions increased simultaneously by 6–26%. No knocking occurred throughout the entire full-load test at IMEP = 23 bar. A trend line comparison indicates that the results are transferable to engines with higher peak pressure limits.A longitudinal dynamics simulation of an RDE cycle indicated a reduction of CO2 emissions by 22%.KeywordsCompressed natural gasExhaust gas recirculationSingle-cylinder engine

EGR modeling and fuzzy evaluation of Low-Speed Two-Stroke marine diesel engines

The simultaneous application of new low-NOx emissions standards and greenhouse gas (GHG) rules has placed great pressure on the commercial vehicle industry and has driven demand for innovative solutions. One potential solution, gasoline compression ignition (GCI), utilizes gasoline’s lower reactivity to promote partially premixed combustion and extract efficiency while reducing the PM-NOx trade-off curve. Gasoline’s volatility allows for the use of higher levels of exhaust gas recirculation (EGR), a key enabler of GCI combustion. In order to deliver higher levels of EGR while maintaining sufficient boost pressure, a tailored and efficient air-handling system is critical. This work presents the analysis-led development of a low-NOx GCI air-handling system including both turbocharger matching and EGR configuration for a prototype heavy-duty GCI engine based on a model year 2013 Cummins ISX diesel engine using low octane gasoline (RON80). In the analysis-driven development process, a 1D engine system-level analysis was closely coupled with closed-cycle 3D CFD GCI combustion development. Three different boost systems were investigated using a validated 1D engine model: 1) the production turbocharger; 2) an off-the-shelf single-stage waste-gate turbocharger; 3) a prototype single-stage variable geometry turbocharger. For each boost system, three EGR configurations were evaluated: 1) a high-pressure EGR route; 2) a low-pressure EGR route; 3) a dual-loop EGR route. The air-handling system performance was first investigated over five steady-state engine operating conditions extracted from the ramped modal cycle supplemental emissions test. Then, through cosimulation using a Simulink-based engine controls model, the best performing candidates under transient operation through the Heavy-Duty Federal Test Procedure certification cycle were identified. The production turbocharger, designed for 4–6 g/kWh engine-out NOx, suffered from low combined turbocharger efficiency under the low-NOx GCI thermal boundary conditions. The prototype 1-Stage variable geometry turbocharger, when used with a high-pressure EGR configuration, demonstrated higher combined efficiencies, while the waste-gate turbocharger showed the best results when used with a dual-loop EGR system. All low-pressure only EGR configurations were found to incur additional pumping penalties due to the need for a back pressure valve to drive sufficient EGR levels. In the transient test cycle analysis, the single-stage high-pressure EGR system was capable of delivering the target boost and EGR, while the off-the-shelf waste-gate turbocharger, with its higher mass inertia, showed slower turbine response and a resulting lag in boost response. Unsurprisingly, the dual-loop EGR system also suffered from delays in EGR delivery during engine acceleration. In summary, the prototype single-stage variable geometry turbocharger with a high-pressure EGR system produced the best performance over both the steady-state and transient engine cycles and was identified as the best candidate for the prototype low-NOx heavy-duty GCI engine.

This paper presents a model-based control strategy for the engine speed trajectory tracking and the control of the Exhaust Gas Recirculation (EGR) flow and Variable Geometry Turbocharger (VGT) flow. The engine speed is modeled as a non-linear model containing explicitly the expression of the fuel conversion efficiency. Generally speaking, in literature, its modeling obtained from experiments has two main expressions defined as polynomial or exponential forms. This paper focuses on the engine speed stabilization when the fuel conversion efficiency is modeled with the exponential form which is more realistic in the case of passenger cars. This work proposes a new smooth stabilization law around a desired engine speed value. On the other hand, a second loop is added to control the EGR and VGT flows. Simulation results are proposed to highlight the closed-loop control accuracy.

<div class="htmlview paragraph">Two methods have been achieved of facilitating controlled auto-ignition (CAI) combustion in a 4-stroke engine. This has been accomplished without the need to pre-heat intake air and was made possible through the use of the Active Valve Train (AVT) system. AVT was used to vary the amount of trapped exhaust gasses (otherwise known as exhaust residuals) inside the cylinder prior to the compression stroke. Both methods represent examples of internal exhaust gas recirculation (EGR). It was observed that the amount of internal EGR determined the combustion initiation point as a function of crank angle, thus demonstrating that both methods are controllable reproducible processes. Initial results (taken at 2000rpm and 3.5bar IMEP) show that this combustion significantly reduces NOx emissions to ultra-low levels compared to conventional spark ignition combustion. Data presented here represents the first published results of our internal EGR methodologies. At present, this combustion is being investigated across a wide range of engine speed and load points. This data will be published in the near future.</div>

This paper presents the results of the diesel engine research on the indicator and heat realized diagrams for VW 1.9 TDI working in 2 modes: with standard, non-cooled EGR system, and without this system. All of measurement was carried out on the some engine speed – 2000 rpm (speed of maximum engine torque) and various engine load. Some of the analyzed parameters were read directly from the measurement systems (e.g. indicator diagrams) or engine controller (e.g. start of injection) and the rest of them had to be calculated. The calculation of rate of heat release (dQ/dα) was based on the well-known mathematical model. When the exhaust gas recirculation valve is open, the maximum of combustion pressure and rate of maximum kinetic heat release (dQk/dα)max are smaller than when the valve is closed. These facts are connected with the shorter self-combustion delay for engine working with EGR. But this is also associated with reduction of the rate of maximum diffusion heat release (dQd/dα)max, which means that more particulates (PM) are excreted into the atmosphere. This fact explains e.g. significantly higher smog of exhaust gases for diesel engine which works with EGR system. The analysis results show that exhaust gas recirculation system slightly deteriorates the energetic parameters of VW 1.9 TDI engine, but, at the same time, significantly reduces the level of toxic nitrogen oxides in exhaust gases

Owing to the energy crisis and pollution problems of today investigations have concentrated on decreasing fuel consumption and on lowering the concentration of toxic components in combustion products by using exhaust gas after treatments methods like PM filters and EGR for NOx reduction. In this study, the combustion characteristics of diesel fuel were compared with that pr oduced from adding EGR at several percentages to air manifold. The tests were performed in a four-cylinder direct injection (DI) diesel engine at constant engine speed (1500 rpm) and variable loads (from no load to 86 kN/m2), the tests were repeated with constant load (77 kN/m2) and variable engine speeds (from 1250 to 3000 rpm).The experimental results showed that adding EGR to diesel engine provided significant reductions in brake power (bp), brake thermal efficiency and exhaust gas temperatures, while high increments in brake specific fuel consumption (bsfc). High EGR percentage (as 30% in this article) caused an 11.7% reduction in brake thermal efficiency, 26.38% reduction in exhaust gas temperatures and 12.28% in volumetric efficiency at full load conditions.

The increasing demand of motorcycle for humans is directly proportional to the gas emissions by motorcycle. It will cause air condition bad and can cause health problems for humans. One of the solutions for the problem gas emissions produced by motorcycle is doing a modification on exhaust pipe with using Exhaust Gas Recirculation (EGR). This study aims to know the effect of EGR on exhaust gas emission of Honda Supra X 100. The research uses the experimental methods. Emission testing be held to determine the effect after using EGR on the resulting exhaust gas elements by varying the conditions of the mixture (rich and lean), engine speed (1500, 2500, 3500, 4500, 5500 rpm) and fuel (premium, pertalite). The result after using EGR, increased emissions of HC, decreased emissions of CO, increased and decreased CO2 and increased AFR values.