High Pressure Exhaust Gas Recirculation Research Articles

The influence of injection pressure and exhaust gas recirculation on a VCR engine fueled by microalgae biodiesel

AbstractBiodiesel has been chosen as a decent alternative to diesel in the context of establishing environmentally pleasant conditions and saving petroleum‐based resources for future generations. It is well‐established that biodiesel‐powered diesel engines may achieve outcomes equivalent to those of diesel engines. The current investigation was conducted to study the effect of injection pressure (190, 210, and 230 bar) and exhaust gas recirculation (EGR) (5%, 10%, and 15%) on a single‐cylinder variable compression ratio (VCR) diesel engine running using a B20 (20% MB + 80% PD) blend of microalgae biodiesel (MABD). This experiment was conducted in two stages. During the first stage of experimentation, the efficiency and emission characteristics of a diesel engine with a B20 blend of MABD at various fuel injection pressures and fresh air were investigated. During the second phase, fresh air was mixed with 5%, 10%, and 15% exhaust gases, and the experiment was conducted. It was discovered that increasing injection pressure to 230 bar provided considerable improvements. Brake thermal efficiency increased by 2.35%, brake‐specific fuel consumption decreased by 3.57% and pollutants such as carbon monoxide (CO), hydrocarbon, and smoke were reduced by more than 50% compared to conventional diesel. These reductions were similarly significant (over 22%) as compared to the B20 blend at lower injection pressure (210 bar). However, there was a slight trade‐off: nitrogen oxide (NOx) emissions increased partially (3.14%), while exhaust gas temperature (EGT) increased by 1.72% at a higher pressure. The study then investigated the influence of EGR (5%, 10%, and 15%) at various injection pressures. The optimal value seems to be 10% EGR at 230 bar injection pressure. This combination substantially reduced NOx emissions (by over 41% compared to the normal B20 blend) and EGT (by more than 8%), while having no notable effect on other performance or emission variables. Overall, the results show that employing a B20 MABD blend with high injection pressure (230 bar) and moderate EGR (10%) improves engine performance while reducing hazardous emissions.

Multi-mode operation of a novel dual-pressure steam rankine cycle system recovering multi-grade waste heat from a marine two-stroke engine equipped with the high-pressure exhaust gas recirculation system

As a promising technology for marine two-stroke engines satisfying the IMO Tier Ⅲ NOx regulation, the high-pressure exhaust gas recirculation (HP-EGR) systems in multi-mode operation significantly redistribute the waste heat, thereby complicating the design and control of the waste heat recovery (WHR) systems. In this paper, a novel dual-pressure steam Rankine cycle (SRC) is proposed to recover multi-grade waste heat from marine engines in multi-mode operation. The HP-EGR system is designed on the 6EX340 engine, followed by the evaluation of waste heat distribution in multi-modes. Detailed thermodynamic and economic analyses of the designed SRC and the combined cycle power plant are then conducted. The results show that the thermal efficiency of the designed SRC is 8.1 %–13.3 % in Tier II mode, increasing to 10.1 %–15.7 % in Tier III mode, attributable to a 16 %–42 % increase in waste heat exergy. Considering typical propulsion profiles, the reduction in weighted average fuel consumption for the combined cycle power plant reaches up to 3.4 % in Tier II operation and 6.1 % in Tier III operation. When 12.5 % of sailing time is spent within ECAs, the combined cycle power plant is expected to yield up to 4 % in annual fuel cost savings.

Numerical studies on the flow characteristic of the marine two-stroke engine integrated with the high-pressure exhaust gas recirculation system

The high-pressure exhaust gas recirculation (HP-EGR) has been well-proven for marine engines complying with the IMO Tier Ⅲ NOx regulation. Considering different turbocharged scavenging schemes and emission control modes, intake and exhaust gas management is critical to the HP-EGR design. However, few theoretical studies on it were reported. This paper aims at providing a case study on the flow characteristic of the turbocharged HP-EGR system. With the proposed topology structure of the typical HP-EGR layout, numerical studies on the turbocharged scavenging and EGR design were conducted based on the 6EX340 two-stroke engine. The result showed that the flow characteristic of the turbocharged two-stroke engine can be graphically depicted by simplifying the cylinder and turbine as multi-nozzle in series. According to the nozzle flow equation of uniflow scavenging, there exists an optimum turbine flow area to maximize the scavenging mass flow. Effects of EGR, cylinder bypass, and exhaust gas bypass on the flow characteristic of the two-stroke engine depend on the turbocharger matching. The out-cylinder scavenging and in-cylinder combustion should be optimized interactively to fully explore the fuel economy and NOx trade-off. Finally, the proposed design procedure can provide good guidance for the design and control of the HP-EGR system.

Influence of cooling loss on the energy and exergy distribution of heavy-duty diesel engines based on two-stage variable supercharging, VVT, and EGR

The application of mechanisms such as exhaust gas recirculation (EGR) coupled with variable valve timing (VVT) and a variable geometry turbocharger (VGT) can improve engine efficiency; however, the energy laws and loss distribution after EGR, VVT, and VGT changes are unclear, restricting the optimization of engine structures and corresponding strategies. Herein, a six-cylinder engine is studied, revealing that the cooling loss of the high-pressure (HP) EGR loop is an important factor affecting the engine energy distribution. The cooling loss accounts for 10.00%–20.00% of the total energy, with an average increase of 1.73%, surpassing other energy losses growth rates. The low-pressure (LP) EGR loop considerably reduces cooling losses. The cooling loss of the LP EGR loop is only 64.05% of the HP EGR loop at a 20% EGR rate. When the EGR rate is >10%, the resulting lower cooling losses effectively improve the engine efficiency and the indicated thermal efficiency (ITE) of the LP EGR loop is 0.20%–0.33% higher than that of the HP EGR loop; when the EGR rate is 21%, the ITE of the LP EGR loop reaches 49.52%. By studying the variation in exergy with operating parameters, it is found that while increasing the EGR rate from 15% to 20%, the proportion of available exergy increases by adjusting the VVT to −85° crank angle after top dead center (CA ATDC) or adjusting the VGT to 47.5% under the original operating scheme of the LP EGR loop (−146° CA ATDC; VGT = 42.5%). The available exergy increases from 71.22%–71.42% (−146° CA ATDC; VGT = 42.5%; original device) to 71.88%–71.58% (−146° CA ATDC; VGT = 47.5%) and 72.02%–72.21% (−85° CA ATDC; VGT = 42.5%). This study explores the energy distribution under different operating schemes, providing theoretical guidance for further improving the thermal efficiency of the entire device.

Efficiency of limiting nitrogen oxides emissions by exhaust gas recirculation systems of marine internal combustion engines

The subject of this study is systems for ensuring environmental safety of marine internal combustion engines, in particular, technologies for limiting emissions of nitrogen oxides (NOx). The regulatory requirements for reducing emissions are presented in the paper. The main theoretical aspects of the problem of nitrogen oxides formation during combustion in a diesel engine are considered. On the basis of these theoretical aspects the effectiveness of using various methods to achieve the requirements for the permissible level of NOx concentration in the exhaust gases is assessed. Exhaust gas recirculation (EGR) systems and selective catalytic reduction (SCR) systems are considered as the main technologies; they allow achieving the highest indicators of nitrogen oxide emissions control in accordance with the requirements of the Tier 3 standard. Taking into account the peculiarities of the requirements for the design and layout of systems as part of a ship power plant, as well as operational and investment costs, the main attention in the work is paid to systems of indirect influence on the engine in-cylinder processes, which include exhaust gas recirculation systems. Based on the comparison of high and low pressure EGR, the advantages and disadvantages of the designs are determined. It is noted that high-pressure exhaust gas recirculation systems have a number of advantages, which primarily include the compactness and high speed of the system response to changes in operational conditions. On the example of the leading manufacturers developments, the potential capabilities of the high-pressure EGR system and the engine characteristics confirming the effectiveness of its use are demonstrated. Based on the results of the work, a conclusion about the high efficiency and expediency of using exhaust gas recirculation systems to meet the requirements of the current environmental safety standards of ship power plants is made.

Parametric Analysis and Optimization for Thermal Efficiency Improvement in a Turbocharged Diesel Engine with Peak Cylinder Pressure Constraints

While the original equipment manufacturers are developing engines that can withstand higher PCP, the methodology to maximize the thermal efficiency gain with different PCP limits is still not well-known or documented in the literature. This study aims to provide guidance on how to co-optimize air system parameters, compression ratio, and intake valve closing (IVC) timing of heavy-duty turbocharged diesel engines to enhance thermal efficiency with peak cylinder pressure (PCP) constraints. In this study, a one-dimensional turbocharged engine model is established and validated by experimental data. The effects of turbocharger efficiency, boost pressure, high-pressure exhaust gas recirculation (HP EGR) ratio, compression ratio (CR), and IVC timing on diesel engine efficiency are assessed under PCP constraints through parametric analysis. The results indicate that for enhancing engine thermal efficiency under limited PCP, an increment in boost pressure and CR, and late IVC timing compared to baseline is required. By multiple parameter optimization, the best parameter combination under different PCP constraints is proposed. At a PCP limit of 20 MPa, the combination of a compression ratio of 18.57, boost pressure of 298 kPa, and IVC timing of −95.2 °CA ATDC yields a 1.56% (absolute value) improvement in ITEn over the baseline condition. Raising the PCP limits from 20 MPa to 25 MPa requires increasing the compression ratio to 21.92, boost pressure to 308 kPa, and delaying the intake valve closing timing to −88.7 °CA ATDC, which results in an absolute improvement of 0.86% in ITEn. Baseline engine configuration is updated accordingly to validate the thermal efficiency improvement strategy at a 25 MPa PCP limitation. Experimental results demonstrate a 2.2% (absolute value) improvement in brake thermal efficiency and 1.98% (absolute value) improvement in overall energy efficiency.

Study on the Effect of Exhaust Gas Recirculation Coupled Variable Geometry Turbocharger and Fuel Quantity Control on Transient Performance of Turbocharged Diesel Engine

With increasingly stringent emissions regulations, there are growing demands for the transient performance of diesel engines. This study conducted a transient bench test on a two-stage turbocharged heavy-duty diesel engine to optimize its performance during a load increase (20% to 100% in 1 s) at a constant speed (1200 RPM) transient process. The results showed that the transient control scheme using the low-pressure EGR system resulted in a 42.1% reduction in the peak value of soot emission, a 24.8% decrease in the peak value of NOx emission, a 9.14% decrease in ISFC and a 30.6% increase in maximum IMEP achieved in 1 s, compared to the steady-state optimization control scheme without EGR. Transient control scheme using the high-pressure EGR system resulted in a 24.4% reduction in the peak value of soot emission, a 31.8% reduction in the peak value of NOx emission, a 9.52% reduction in ISFC, and a 31.7% increase in maximum IMEP achieved in 1 s. The comparison of high and low-pressure EGR systems revealed that the low-pressure EGR system produced lower compromising emissions, while alterations in control parameters for the diesel engine with a high-pressure EGR system had a more significant impact on the transient process performance.

Study on the Effects of Exhaust Gas Recirculation and Fuel Injection Strategy on Transient Process Performance of Diesel Engines

To meet increasingly stringent emission regulations, this study investigates the transient process of a heavy-duty diesel engine equipped with a two-stage turbocharger. The study focuses on analyzing the impact of the EGR system and fuel injection strategy during a transient process of a load increase (20% to 100% in 1 s) at a constant speed (1300 rpm). The research results showed that delaying the opening time of the high-pressure EGR valve from 0.1 s to 0.5 s reduces peak carbon soot emissions by 51.3%, with only a 3.13% increase in NOx emissions. By extending the high-pressure exhaust gas recirculation mixing length, the issue of an excessively high fuel–oxygen equivalence ratio caused by uneven exhaust gas mixing in individual cylinders can be avoided, resulting in a maximum reduction of 47.0% in peak soot emissions. Building on exhaust gas recirculation optimization, further modifications to the main and post-injection strategies led to a 28.1% reduction in soot emissions, a 4.73% decrease in peak NOx emissions, and a minor increase of 1.87% in the indicated fuel specific consumption compared to the single-injection strategy. The significant reduction in soot emissions will provide benefits for public health and environmental sustainability.

A Modular Approach for Diesel Engine Air Path Control Based on Nonlinear MPC

This article presents a systematic approach to realize highly dynamic control strategies for the air path of diesel engines. It is based on grey-box models of individual air path components, designed to be applied in nonlinear model predictive control (NMPC). Specifically, they are suited for algorithmic differentiation and gradient-based optimization. This modular approach allows to derive models for a variety of complex air path systems and can be identified with a low amount of measurement data. An NMPC structure, which is based on these models, enables the tracking of arbitrary air path reference signals and allows the introduction of further control objectives for overactuated systems. We demonstrate our approach’s general applicability and effectiveness on two different laboratory engines using rapid control prototyping hardware. For a turbocharged light-duty diesel engine with dual-loop exhaust gas recirculation (EGR), we apply the proposed control structure to track intake manifold gas conditions while simultaneously minimizing engine pumping losses. Experimental results show an excellent tracking performance and reduced pumping losses compared to other control strategies. For a turbocharged heavy-duty engine with high-pressure EGR, we experimentally demonstrate a superior tracking performance to that obtained with a reference controller. Due to the modular and systematic approach, the algorithm design is straightforward, and the experimental calibration effort is low.

Numerical investigations on the effects of EGR routes on the combustion characteristics and efficiency of a heavy-duty SI methanol engine

Exhaust gas recirculation (EGR) is one effective strategy to improve the thermal efficiency of the heavy-duty spark-ignition (SI) methanol engine. The high EGR tolerance of methanol engine raises new requirements for the EGR system. In this study, the influences of three different EGR routes, high-pressure EGR (HP-EGR), low-pressure EGR (LP-EGR), and high-low-pressure EGR (HLP-EGR) on the engine performance were studied by the one-dimensional simulation with the predictive combustion sub-model. The investigation was conducted at 1000 rpm and 1400 rpm, and 50% and 100% full load. Results show that EGR routes influence both the combustion characteristics and pumping mean effective pressure (PMEP), thus affecting the brake specific fuel consumption (BSFC). The EGR route with the lower internal EGR rate has a lower in-cylinder temperature at the compression stroke, a weaker knock tendency and a more advanced combustion phase. The effects of EGR routes on BSFC are more significant at the higher engine speed. The optimal BSFC of HP-EGR is lower than that of HLP-EGR and LP-EGR by up to 16.4 g/k·Wh and 21.2 g/k·Wh. Considering the engine performance at all engine operating conditions, HP-EGR is the optimal EGR route while LP-EGR is the worst one for the heavy-duty SI methanol engine.

Effect of High and Low Pressure EGR on Diesel Engine Matched with Mechanical Turbo-compound

The mode of exhaust gas recirculation (EGR) and the flow of recirculated exhaust greatly impact the exhaust heat recovery of the mechanical turbo-compound. A matching mechanical turbo-compound of the diesel engine is established with GT-power software to study the effect of EGR mode and EGR rate on it, and the effect of EGR rate on the working performance of diesel engine and the mechanical turbo-compound under high-pressure EGR mode and low-pressure EGR mode is also studied. The results show that compared with the original engine, the effective thermal efficiency of the diesel engine matched with mechanical turbo-compound has been improved. Under the two EGR modes, as the EGR rate increase, the effective thermal efficiencies of diesel engine matched with mechanical turbo-compound and the original engine are decreasing. Under the maximum torque condition, the fuel economy of mechanical compound turbine diesel engine matched with low-pressure EGR system is better than with high-pressure EGR system; while underrated power condition, the fuel economy difference of mechanical compound turbine diesel engine matched with high-pressure EGR system and low-pressure EGR system is small.

Effects of high pressure and high-low pressure EGR strategies on the knock tendency, combustion, and performance of a stoichiometric operation natural gas engine

EGR strategies play an important role in improving the combustion and performance of a stoichiometric operation natural gas engine. Based on the numerical simulation and experimental validation, the effects of two EGR strategies, namely high pressure (HP) EGR and high-low pressure (HLP) EGR on the combustion behavior and knock tendency of a natural gas engine were investigated. The optimal EGR rates and spark timings under different full load conditions were obtained, and the reason of the HLP EGR strategy in improving fuel economy was quantitatively evaluated. The simulation results showed that compared with the HP EGR strategy, the optimal EGR rates are reduced and the optimal spark timings are delayed for the HLP EGR strategy. This is due to that the lower boost pressure makes it unnecessary for the HLP EGR strategy to adopt higher EGR rates to suppress knock. Meanwhile, the HLP EGR strategy shortens the flame development period and rapid combustion duration, makes the center of heat release rate curve closer to TDC, increases the peak values of in-cylinder pressure and heat release rate, and significantly reduces the pumping losses. As a result, the HLP EGR strategy increases the indicated thermal efficiency by 3.4% − 7.3%. The dyno experiment of the natural gas engine with the optimized EGR rates and spark timings showed that compared with the HP EGR strategy, the HLP EGR strategy reduces the specific gas consumption by 5.82% − 8.83%. The engine energy balance analysis showed that the in-cylinder heat-transfer losses and exhaust energy for the HLP EGR strategy are reduced, contributing to the fuel saving rates by 2.18% − 2.47% and 4.02% − 6.91%, respectively. While the friction losses are increased, resulting in the reduction in the fuel saving rates by −0.38% to −0.55%. Therefore, the reduction of exhaust energy is the most important fuel saving factor for the HLP EGR strategy.

Utilization of Hydrotreated Vegetable Oil (HVO) in a Euro 6 Dual-Loop EGR Diesel Engine: Behavior as a Drop-In Fuel and Potentialities along Calibration Parameter Sweeps

This study examines the effects on combustion, engine performance and exhaust pollutant emissions of a modern Euro 6, dual-loop EGR, compression ignition engine running on regular EN590-compliant diesel and hydrotreated vegetable oil (HVO). First, the potential of HVO as a “drop-in” fuel, i.e., without changes to the original, baseline diesel-oriented calibration, was highlighted and compared to regular diesel results. This showed how the use of HVO can reduce engine-out emissions of soot (by up to 67%), HC and CO (by up to 40%), while NOx levels remain relatively unchanged. Fuel consumption was also reduced, by about 3%, and slightly lower combustion noise levels were detected, too. HVO has a lower viscosity and a higher cetane number than diesel. Since these parameters have a significant impact on mixture formation and the subsequent combustion process, an engine pre-calibrated for regular diesel fuel could not fully exploit the potential of another sustainable fuel. Therefore, the effects of the most influential calibration parameters available on the tested engine platform, i.e., high-pressure and low-pressure EGR, fuel injection pressure, main injection timing, pilot quantity and dwell-time, were analyzed along single-parameter sweeps. The substantial reduction in engine-out soot, HC and CO levels brought about by HVO could give the possibility to implement additional measures to limit NOx emissions, combustion noise and/or fuel consumption compared to diesel. For example, higher proportion of LP EGR and/or smaller pilot quantity could be exploited with HVO, at low load, to reduce NOx emissions to a greater extent than diesel, without incurring penalties in terms of incomplete combustion species. Conversely, at higher load, delayed main injection timings and reduced rail pressure could reduce combustion noise without exceeding soot levels of the baseline diesel case.

Impacts of using EGR and different DI-fuels on RCCI engine emissions, performance, and combustion characteristics

• EGR contributed to further reductions in NOx emissions in RCCI combustion. • Improvements in BTE and BSFC were achieved by using EGR in RCCI combustion. • Better RCCI operation with EGR requires an alternating premixed fraction. • Increased biodiesel dose in DI-Fuel lead to an increment in NOx emissions. Exhaust gas recirculation (EGR) seems to be a critical parameter in developed RCCI operations for controlling emissions, in-cylinder charge reactivity as well as combustion phasing. The most advantages of utilizing the RCCI burning technique are the simultaneous decrease of PM as well as NOx emissions. Nevertheless, significant challenges remain, such as extreme HC and CO emissions. The purpose of this work is to investigate the effects of external, hot, and high-pressure EGR as well as different DI-Fuels on RCCI combustion under various load conditions. The tests were performed on direct injection, single-cylinder, and four-stroke modified diesel engine (peak power 5 KW under 1500 rpm) operating in RCCI mode with an EGR system. To initiate ignition, high reactivity fuel (biodiesel/diesel blends) was injected directly inside the engine's cylinder whereas low reactivity fuel (LPG) was induced into to intake mixing chamber. EGR at various ratios (30%, 20%, and 10%) was introduced into the engine via the intake mixing chamber, and experiments were done under various loads. The results show that increasing EGR results in a slight increment in BTE under medium and high engine loads. NOx emissions from diesel engines operating in traditional RCCI mode declined dramatically, and they decreased even further with the addition of EGR. The CO and HC emission levels, on the other hand, are slightly greater when EGR is used. Increasing the proportion of biodiesel in DI-Fuel is resulting in a decrement in BTE and NOx emissions in addition to an increment in BSFC, CO, and HC emissions.

Experimental energy and exergy analysis of turbocharged marine low-speed engine with high pressure exhaust gas recirculation

Exhaust gas recirculation (EGR) has been widely applied on marine low-speed engine for the Tier III standard. However, few studies focus on energy and exergy analysis to improve the deterioration of fuel economy caused by EGR. This study fills in this gap based on the related experiment. Results show that about 35% EGR rate could achieve the Tier III standard, while cylinder bypass (CB) may raise NOx due to the coupling of CB and exhaust receiver. Subsequent energy analysis shows that improving fuel consumption should start with reducing the energy of heat transfer and exhaust gas. But, the exergy analysis indicates that reducing the irreversibility will be more efficient. The irreversibility mainly comes from in-cylinder, turbocharger and intercoolers. According to the instantaneous in-cylinder exergy analysis, the corresponding irreversibility is due to charge mixing and combustion. Reducing temperature gradient and proportion of premixed combustion are effective methods to inhibit it. EGR has opposite impacts on in-cylinder irreversibility caused by combustion: it enhances this irreversibility by rising maximum temperature and prolonging combustion duration (25% load); but it also raises the proportion of premixed combustion, which will inhibit this irreversibility (100% and 75% load). As for the irreversibility from turbocharger, it is negatively correlated with EGR rate, because of CB reducing exhaust temperature. Whereas, due to the existence of EGR intercooler, the irreversibility caused by intercoolers are positively related with EGR rate.

Design and thermodynamics analysis of marine dual fuel low speed engine with methane reforming integrated high pressure exhaust gas recirculation system

The carbon–neutral target leads to the development of low-carbon\\zero-carbon marine fuels. Natural gas is currently one of the most competitive low-carbon fuels, however, the low compression ratio used to control knock combustion limits the improvement of thermal efficiency of natural gas engines. Meanwhile, low-pressure injection natural gas engines also suffer from methane slip. In this paper, a system including a fuel reformer and a natural gas engine with a high-pressure EGR of 20% was proposed. EGR could reduce NOx emission and control methane slip but it will decrease the thermal efficiency. Fuel reforming could improve engine thermal efficiency and increase flame propagation speed but it will increase NOx emission. Moreover, EGR could also provide higher temperature energy for fuel reforming. Therefore, the proposed system was designed to achieve the complementary advantages between EGR and fuel reforming. The results showed that the thermal efficiency of the proposed system was 49.3% at the reforming ratio of 5%, which is 2% higher than the original engine and 4.7% higher than the EGR engine. In addition, the methane slip was reduced by 20% and the NOx emission was 2.93 g/kWh, which can meet the IMO Tier III. Finally, the thermo-economic analysis of the system and the EEDI calculation were carried out. The results showed that the annual fuel cost saved by installing the system on the ship was approximately US $151,726 and the EEDI was reduced by 3.75%

An Experimental and Computational Investigation of Tailor-Developed Combustion and Air-Handling System Concepts in a Heavy-Duty Gasoline Compression Ignition Engine

This study investigates using tailor-developed combustion and air-handling system concepts to achieve high-efficiency, clean gasoline compression ignition (GCI) combustion, aimed at addressing a future heavy-duty ultralow NOx standard of 0.027 g/kWh at the vehicle tailpipe and the tightening CO2 limits around the world by combining GCI with a cost-effective engine aftertreatment system. The development activities were conducted based on a 15 L heavy-duty diesel engine. By taking an analysis-led design approach, a first-generation (Gen1) GCI engine concept was developed and tested, encompassing tailor-designed piston bowl geometry, fuel spray pattern, and swirl motion paired with a customized, fixed-geometry, two-stage turbocharging system and a high-pressure EGR loop with two-stage cooling. Across four key steady-state operating points, the Gen1 GCI concept demonstrated 85–95% lower smoke and 2–3% better diesel-equivalent gross indicated fuel consumption compared to the diesel baseline at 1 g/kWh engine-out NOx. By upgrading to a Gen2 air-handling concept that was composed of a prototype, single-stage, variable-geometry turbocharger and a less restrictive EGR loop, 1D system-level analysis predicted that the pumping mean effective pressure was reduced by 43–54% and the diesel-equivalent brake-specific fuel consumption was improved by 2–4%, thereby demonstrating the performance enhancement potential of refining the air-handling system.

NOx–Smoke Trade-off Characteristics in a Palm Oil-Fueled CRDI Diesel Engine under Various Injection Pressures and EGR Rates

Palm oil is one of the most common and productive vegetable oils, so it is often used as an excellent feedstock for biodiesel production. However, due to the high viscosity and other issues of palm oil, it cannot be directly used as an alternative fuel for diesel engines unless some treatment is carried out. In this study, the effects of palm oil-diesel blend fuel on the nitrogen oxides (NOx)–smoke trade-off characteristics were investigated in a common rail direct injection (CRDI) diesel engine under various injection pressures and exhaust gas recirculation (EGR) rates. It was found that NOx and smoke from the combustion of fuel containing 50% palm oil (P50D50) were simultaneously suppressed by 3% and 3.1% compared with diesel fuel at an injection pressure of 400 bar, respectively. The performance of P50D50 was comparable to that of diesel, but at high injection pressure and high EGR rate, it showed shorter ignition delay (ID) and lower smoke emission.

Design and Thermodynamics Analysis of Marine Dual Fuel Low Speed Engine with Methane Reforming Integrated High Pressure Exhaust Gas Recirculation System

Design and Thermodynamics Analysis of Marine Dual Fuel Low Speed Engine with Methane Reforming Integrated High Pressure Exhaust Gas Recirculation System

Experimental study on ultra-low raw emissions in diesel/methanol dual fuel engine based on dual-loop EGR

In this paper, an experimental investigation on achieving ultra-low raw emissions in a diesel/methanol dual fuel engine based on dual-loop EGR was carried out. The effect of dual-loop EGR (High pressure EGR and low pressure EGR) on the combustion, performance and emissions of methanol engine has been studied comprehensively. The results show that ultra-low NOx (<0.4g/kWh) and PM (<10 mg/kWh) emissions can be achieved simultaneously in diesel methanol dual fuel engine with the help of EGR. The combustion phase is delayed with the increase of EGR rate in both EGR modes. However, the methanol equivalence ratio and in cylinder combustion temperature in high pressure EGR mode are significantly higher than those in low pressure EGR mode. Therefore, the CO and THC emissions are obviously lower in high pressure EGR mode than that in low pressure EGR mode. The combustion efficiency and brake thermal efficiency of the engine are 1.9% and 9.6% higher in high pressure EGR mode than those in low pressure EGR mode, respectively.