Turbocharging strategy among variable geometry turbine, two-stage turbine, and asymmetric two-scroll turbine for energy and emission in diesel engines

2019 ◽  
Vol 234 (7) ◽  
pp. 900-914
Author(s):  
Dengting Zhu ◽  
Zhenzhong Sun ◽  
Xinqian Zheng
Keyword(s):  
Internal Combustion Engines ◽  
Numerical Models ◽  
Exhaust Gas Recirculation ◽  
Internal Combustion ◽  
Exhaust Gas ◽  
Combustion Engines ◽  
Variable Geometry ◽  
Two Stage ◽  
Variable Geometry Turbine ◽  
Gas Recirculation

Energy saving and emission reduction are very urgent for internal combustion engines. Turbocharging and exhaust gas recirculation technologies are very significant for emissions and fuel economy of internal combustion engines. Various after-treatment technologies in internal combustion engines have different requirements for exhaust gas recirculation rates. However, it is not clear how to choose turbocharging technologies for different exhaust gas recirculation requirements. This work has indicated the direction to the turbocharging strategy among the variable geometry, two-stage, and asymmetric twin-scroll turbocharging for different exhaust gas recirculation rates. In the paper, a test bench engine experiment was presented to validate the numerical models of the three diesel engines employed with the asymmetric twin-scroll turbine, two-stage turbine, and variable geometry turbine. On the basis of the numerical models, the turbocharging routes among the three turbocharging approaches under different requirements for EGR rates are studied, and the other significant performances of the three turbines were also discussed. The results show that there is an inflection point in the relative advantages of asymmetric, variable geometry, and two-stage turbocharged engines. At the full engine load, when the EGR rate is lower than 29%, the two-stage turbocharging technology has the best performances. However, when the exhaust gas recirculation rate is higher than 29%, the asymmetric twin-scroll turbocharging is the best choice and more appropriate for driving high exhaust gas recirculation rates. The work may offer guidelines to choose the most suitable turbocharging technology for engine engineers and manufacturers to achieve further improvements in engine energy and emissions.

Numerical Modelling of Internal Combustion Engines Fuelled by Hydrogen-Natural Gas Blends

2008 ◽  
Author(s):  
Antonio Mariani ◽  
Biagio Morrone ◽  
Andrea Unich
Keyword(s):  
Natural Gas ◽  
Internal Combustion Engines ◽  
Exhaust Gas Recirculation ◽  
Internal Combustion ◽  
Flame Speed ◽  
Operating Conditions ◽  
Nox Emissions ◽  
Exhaust Gas ◽  
Combustion Engines ◽  
Gas Recirculation

The strict rules that European Community has given for reducing vehicle emissions require new views on the choice of combustion engines and fuels. In fact, the rules will probably introduce in the near future limitations on carbon dioxide (CO2) emissions. Internal combustion engines are responsible for emission of unburned hydrocarbons (HC), nitrogen oxides (NOx) and particulate matter (PM). The aim of the present paper is the study of the effects of hydrogen-natural gas blends (HCNG) on the performance, efficiency and NOx emissions of internal combustion engines (ICE). A numerical engine model has been developed to display how the presence of hydrogen in such mixtures impacts on flame speed and burn rates. The model allows the comparison of different fuels, in terms of engine brake efficiency and pollutant emissions. An important variable for the combustion process is the ignition timing which is set employing Maximum Brake Torque (MBT) spark advance. Engine operating conditions considered in the numerical analysis have been obtained by imposing engine speed and load. Brake power, efficiency and NOx emissions are calculated for the most frequent operating conditions met by automotive engines, i.e. part load and low speed. The effect of natural gas (NG) enrichment by hydrogen on flame speed has been considered. Thus, faster combustion and the reduction of energy content in the air-fuel mixtures due to the lower density of hydrogen are taken into account. Hydrogen enrichment of natural gas improves combustion stability in critical conditions, allowing the use of extremely lean mixtures or high Exhaust Gas Recirculation rates. The results show that by employing an MBT spark advance, the HCNG blends furnish improvements of engine brake efficiency compared with compressed natural gas (CNG), which are more relevant at part loads and for the higher hydrogen content. Anyway, higher NOx emissions are observed due to the increased temperatures into the cylinders. Thus, the analysis also takes into account the Exhaust Gas Recirculation (EGR) dilution technique to reduce the NOx emissions. A large reduction of such pollutant, which has been estimated greater than 50%, can be achieved by using a 10% EGR. Furthermore higher engine efficiency is obtained using EGR due to reduced pumping work, reduced heat loss to the walls because of lower gas temperature and a reduction in the degree of dissociation in the high temperature burned gases.

A Comprehensive Physics-Based Model for Medium-Duty Diesel Engine With Exhaust Gas Recirculation

2007 ◽  
Author(s):  
Alok A. Joshi ◽  
Scott James ◽  
Peter Meckl ◽  
Galen King ◽  
Kristofer Jennings
Keyword(s):  
Heat Transfer ◽  
Exhaust Gas Recirculation ◽  
Boost Pressure ◽  
Exhaust Gas ◽  
Variable Geometry ◽  
Transfer Effects ◽  
Variable Geometry Turbine ◽  
Heat Transfer Effects ◽  
Egr Cooler ◽  
Gas Recirculation

Physics-based models of diesel engines with exhaust gas recirculation and a variable geometry turbine (EGR/VGT) have been developed extensively in the control system design community. However, these models omit the heat transfer effects of the charge-air cooler and the recirculated exhaust gas cooler in order to avoid the added complexity in model order for online implementation. Generally, there is no need to include these effects if the purpose of the model is to control the target variables, such as boost pressure and air-to-fuel ratio. In this paper, after surveying the existing state of physics-based models for the EGR/VGT subsystem, a comprehensive model of the EGR/VGT subsystem is developed. This model includes heat transfer effects in the coolers, pressure drops across air filters and pipes, and mass flow rate calculations for a variable geometry turbine and an exhaust gas recirculation control valve. The purpose and scope of this work is offline modeling-for-diagnostics. Such models, though complex, will assist in the fault sensitivity analysis of a subsystem while avoiding any destructive testing when a major design modification in the EGR/VGT subsystem is proposed. For example, the impact of charge-water or EGR cooler degradation on the boost pressure and the air-to-fuel ratio can be studied with such models to further help in designing diagnostic reasoning strategies. Simulation performed using the proposed physicsbased model demonstrates a dominant failure effect of an EGR cooler coolant leak over a charge-water cooler water leak on the properties of the intake air.

scholarly journals The benefits of a mid-route exhaust gas recirculation system for two-stage boosted engines

2017 ◽  
Vol 19 (5) ◽  
pp. 553-569 ◽  
Author(s):  
Pavlos Dimitriou ◽  
James Turner ◽  
Richard Burke ◽  
Colin Copeland
Keyword(s):  
Response Time ◽  
Internal Combustion Engines ◽  
Combustion Process ◽  
Exhaust Gas Recirculation ◽  
Exhaust Gas ◽  
Transient Performance ◽  
Short Route ◽  
Two Stage ◽  
Recirculation System ◽  
Gas Recirculation

Exhaust gas recirculation is a widely known technique applied in internal combustion engines for controlling the combustion process and harmful emissions. The recirculation of gases can be achieved either by delivering burnt gases from upstream of the turbine to downstream of the compressor (short-route) or by taking the exhaust gas from downstream of the turbine and deliver to upstream of the compressor (long-route). Although long-route system is preferred for highly boosted engines due to the higher exhaust gas recirculation availability at low engine speeds, it lacks a fast response time during transient performance compared to the short-route system. This article examines the potentials of introducing an alternative exhaust gas recirculation route which can be applied in two-stage boosted engines. The proposed mid-route exhaust gas recirculation system, applied in a gasoline engine, combines the benefits of the long routes and short routes. The system provides high exhaust gas recirculation rates at all engine speeds while the transport delay in the case of transient operation is relatively short. The potential of a hybrid exhaust gas recirculation system combining mid-route and long-route exhaust gas recirculation is examined and various components’ (i.e. compressor, turbine and coolers) sizing and transient performance studies are performed to understand the trade-offs of the system. It was demonstrated that mid-route could provide high exhaust gas recirculation particularly at high- and low engine speeds. A combination of mid-route and long-route exhaust gas recirculation can provide maximum exhaust gas recirculation rates at all speeds with a maximum fuel consumption penalty of 1.4% at engine speeds below 2500 r/min. The reduction in exhaust gas recirculation response time was of the magnitude of 50%, while the faster exhaust gas recirculation purging time combined with the smaller turbine implemented dropped the load tip-in response time by 25%. The coolers’ sizing study revealed that a long-route exhaust gas recirculation cooler is unnecessary, whereas the mid-route exhaust gas recirculation cooler can also be omitted when the flow is delivered prior an intercooler with a 25% larger cooling capacity than of the baseline engine.

scholarly journals Exhaust Gas Temperature Measurements in Diagnostics of Turbocharged Marine Internal Combustion Engines Part I Standard Measurements

2015 ◽  
Vol 22 (1) ◽  
pp. 47-54 ◽  
Author(s):  
Zbigniew Korczewski
Keyword(s):  
Internal Combustion Engines ◽  
Internal Combustion ◽  
Technical Condition ◽  
Temperature Measurements ◽  
Injection System ◽  
Exhaust Gas ◽  
Combustion Engines ◽  
Gas Temperature ◽  
Measuring Signal ◽  
Exhaust Gas Temperature

Abstract The article discusses the problem of diagnostic informativeness of exhaust gas temperature measurements in turbocharged marine internal combustion engines. Theoretical principles of the process of exhaust gas flow in turbocharger inlet channels are analysed in its dynamic and energetic aspects. Diagnostic parameters are defined which enable to formulate general evaluation of technical condition of the engine based on standard online measurements of the exhaust gas temperature. A proposal is made to extend the parametric methods of diagnosing workspaces in turbocharged marine engines by analysing time-histories of enthalpy changes of the exhaust gas flowing to the turbocompressor turbine. Such a time-history can be worked out based on dynamic measurements of the exhaust gas temperature, performed using a specially designed sheathed thermocouple. The first part of the article discusses possibilities to perform diagnostic inference about technical condition of a marine engine with pulse turbocharging system based on standard measurements of exhaust gas temperature in characteristic control cross-sections of its thermal and flow system. Selected metrological issues of online exhaust gas temperature measurements in those engines are discusses in detail, with special attention being focused on the observed disturbances and thermodynamic interpretation of the recorded measuring signal. Diagnostic informativeness of the exhaust gas temperature measurements performed in steady-state conditions of engine operation is analysed in the context of possible evaluations of technical condition of the engine workspaces, the injection system, and the fuel delivery process.

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