Low-pressure Exhaust Gas Recirculation System Research Articles

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.

Energy recovery potential by replacing the exhaust gases recirculation valve with an additional turbocharger in a heavy-duty engine

A simulation-based assessment of different twin-turbocharging configurations allowing energy recovery from the exhaust gas recirculation flow is performed in a heavy-duty engine from the basis of a single-stage turbocharging architecture. This baseline configuration consists of a single stage turbocharged engine with a low-pressure exhaust gas recirculation system. Experimental data from the baseline engine tests are used to calibrate the model. The novelty of this study is to evaluate the energy recovery potential from the low-pressure exhaust gas recirculation flow by replacing its control valve with a turbine so that the flow energy is not lost due to the expansion across the valve. This additional turbine is coupled to a compressor placed in the intake line so that the turbocharging system is converted into a twin-turbocharging architecture. Different twin-turbocharging configurations are tested to attain maximum exhaust gas recirculation rates at 1100, 1500, and 2200 rpm engine speeds with boost pressures ranging from 1.8 to 2.6 bar. Fuel consumption calculations have been performed at constant exhaust gas recirculation rates for all three speeds as well as 1500 rpm partial load operation to attain 11.5 bar of brake mean effective pressure. The results in 8 engine running conditions show that twin-turbocharging with the compressors in series configuration with the exhaust gas recirculation turbine discharging after the first stage benefits, in average, from increasing about 5% maximum exhaust gas recirculation rates and saves up to 7% in fuel economy compared to the single-stage turbocharging layout.

On combustion instability induced by water condensation in a low-pressure exhaust gas recirculation system for spark-ignition engines

Water condensation in low-pressure exhaust gas recirculation systems is a concern because of a potential impact on components durability, but its implication into the operation of modern spark-ignition engines has not been investigated in detail. In this work, such aspects are evaluated by tests in a turbocharged multi-cylinder engine installed in a climatic test bench. First, a previously developed and validated zero-dimensional model is used to identify conditions where condensation is produced inside the water charge-air cooler, so that the compressor durability and operation is not affected. Then, different engine points are tested with a constant 25% of recirculated rate. Results show that combustion instability can increase up to 6% (absolute) due to droplets accumulation and release inside the water charge-air cooler, confirmed by an endoscope at the WCAC outlet . The evaporation of these droplets during the intake stroke causes charge overleaning in specific cycles, affecting combustion and inducing occasional misfires. Consequently, the fuel consumption and unburned hydrocarbons can be increased up to 4% and 30%, respectively, compared to the results achieved without condensation. The low speed and load condition was clearly the most affected by the sudden dilution given the lower in-cylinder temperatures. The combustion model shows that condensation formation and eventual overleaning phenomenon is increased if low or zero-carbon fuels such as natural gas, methanol, hydrogen or ammonia are used. Results showed an increased temperature for condensation compared to a traditional gasoline, around 10 ∘C for methane and methanol and 20 ∘C for hydrogen and ammonia.

Development of an experimental test bench and a psychrometric model for assessing condensation on a low-pressure exhaust gas recirculation cooler

A test bench has been designed to assess condensation formation produced on the interior of a low-pressure exhaust gas recirculation cooler working with hot stream of humid air representing an engine warm-up stage, when its coolant starts from very cold conditions. An experimental campaign has been conducted with three different exhaust gas recirculation mass flow rates, four exhaust gas recirculation inlet temperatures and three different coolant initial temperatures, covering common conditions found in the low-pressure exhaust gas recirculation system of internal combustion engines under cold starts. The transient experimental results are analyzed and compared with a simple psychrometric condensation model, obtaining a good correlation and reproducing the trends of the condensation, even though an overprediction of the condensates of around 20%–40% exists due to the strong hypotheses assumed. The warm-up tests are most sensitive to the initial coolant temperature. For example, an engine starting at –10 °C ambient temperature could require 10 min to stop producing water in the low-pressure exhaust gas recirculation cooler, with an accumulated quantity during the warm-up of about 100 mL of condensates.

Experimental study on the effect of high-pressure and low-pressure exhaust gas recirculation on gasoline engine and turbocharger

The effects of high-pressure and low-pressure exhaust gas recirculation on engine and turbocharger performance were investigated in a turbocharged gasoline direct injection engine. Some performances, such as engine combustion, fuel consumption, intake and exhaust, and turbocharger operating conditions, were compared at wide open throttle and partial load with the high-pressure and low-pressure exhaust gas recirculation systems. The reasons for these changes are analyzed. The results showed EGR system of gasoline engine could optimize the cylinder combustion, reduce pumping mean effective pressure and lower fuel consumption. Low-pressure exhaust gas recirculation system has higher thermal efficiency than high-pressure exhaust gas recirculation, especially on partial load condition. The main reasons are as follows: more exhaust energy is used by the turbocharger with low-pressure exhaust gas recirculation system, and the lower exhaust gas temperature of engine would optimize the combustion in cylinder.

三菱UE機関における低圧EGRシステムの開発

At the MEPC66, it was decided that as of 2016, IMO Tier III regulations would require nitrogen oxides (NOx) reductions of approx. 76% from Tier II levels. To comply with IMO Tier III regulations, we have developed a low pressure Exhaust Gas Recirculation (LP-EGR) system that has strong NOx reduction potential. It has been confirmed through studies using our 4UE-X3 test engine that the NOx emissions of our LP-EGR system comply with IMO Tier III regulations and that the increase in fuel consumption was less than 1.5%. Recently, an engine integrating almost every component of the LP-EGR system was applied to the 4UE-X3. Through tests and evaluations of this system, we carefully worked out the consumption volumes and life-cycle costs of our LP-EGR system. As a result, the system is IMO Tier III regulation-compliant and offers advanced environmental protection and user-benefits.

Exergy and energy analysis of high-pressure and low-pressure exhaust gas recirculation system of a diesel engine

Exergy and energy analysis of high-pressure and low-pressure exhaust gas recirculation system of a diesel engine

Considerations on the low-pressure exhaust gas recirculation system control in turbocharged diesel engines

Although high-pressure exhaust gas recirculation has been commonly used in turbocharged diesel engines for controlling the NOx formation, recent advances in after-treatment and material technology ...

LP-EGR이 적용된 디젤 엔진 인터쿨러용 알루미늄 튜브의 내식성 향상

Recently, various after-treatment systems, such as LP-EGR(Low Pressure-Exhaust Gas Recirculation), SCR(Selective Catalytic Reduction) and LNT(Lean NOx Trap), were developed to obey the stringent emission regulations of diesel engine. There are many researches on LP-EGR system because it has advantages of NOx reduction and low fuel consumption. But, condensation water is generated in internal of intercooler tube and it contains various types of anion that cause the corrosion of aluminium tube. In this study, it is examined that the condensation water effects on corrosion of aluminium tube. And method for improvement of corrosion characteristics is investigated using the dipping and electrochemical test.

Soot particle size and pollutant emissions characterization from a LD diesel engine equipped with high pressure and low pressure EGR system and operated with conventional and PCCI combustion

The paper analyses the soot Particle Size Distribution Function (PSDF) measurements carried out at the exhaust of a modern automotive diesel engine equipped with a low-pressure Exhaust Gas Recirculation (EGR) system and operating with conventional and Premixed Charge Compression Ignition (PCCI). The results have indicated significant benefits in terms of exhaust raw particle number emission with the adoption of low-pressure EGR system and PCCI calibration and, thanks to the peculiarity of the operating mode of Low Pressure EGR (LPEGR) system, have highlighted the complex link between in-cylinder charge composition and the PSDF characteristics.

Effects of low pressure exhaust gas recirculation on regulated and unregulated gaseous emissions during NEDC in a light-duty diesel engine

Regulated and unregulated gaseous emissions with high pressure and low pressure EGR (exhaust gas recirculation) system were tested in a 4-cylinder, light-duty diesel EURO IV engine typically used in European vehicles. Four different engine calibrations with the low pressure EGR system were studied. Regulated emissions of NO X , CO, HC and CO 2 were measured for each configuration. Unburned Hydrocarbon Speciation, HCHO (formaldehyde), HCOOH (formic acid) and N 2O (nitrous oxide) were also measured in order to determine the MIR (maximum incremental reactivity) of the gaseous emissions. Pollutants were measured without the DOC (diesel oxidation catalyst) to gather data about raw emissions. When the low pressure EGR system was used, decreases in NO X , N 2O and fuel consumption were observed and significant increases HC, CO and unregulated emissions; this is the result of a lower intake manifold temperature, which provides a higher gas density which modifies the combustion process. The potential of tropospheric ozone production was higher in all cases when the low pressure EGR was used.

Volkswagen’s new 2.0 l TDI engine for the most stringent emission standards — Part 1

Having already being launched in Europe in the VW Tiguan and Audi A4, Common Rail engines have been redeveloped to comply with the strictest exhaust fume limits in the world, namely the Tier 2 Bin5 emission legislation in the USA, and will consequently be launched in the VW Jetta there mid-2008. As well as internal engine features like an optimised injection system, a low-pressure exhaust gas recirculation system and a new method of cylinder pressure control, a technical highlight is the implementation of an NOx exhaust gas aftertreatment system. These new engine components require the development of new control algorithms and intensive coordination of parameters for this entirely new combustion process.