A closer look at the basics of Volkswagen Group’s important new 2.0L diesel MDB engine

The EA288 2.0-liter diesel, prominently showing the closely attached exhaust aftertreatment system. Click to enlarge.

The Volkswagen Group’s new 2.0-liter TDI diesel (EA288) will eventually replace all the 2.0-liter TDI Clean Diesel engines fitted in Audi and Volkswagen TDI Clean Diesel models, and as such, is a strategically important engine. The Group was responsible for 79% of all light-duty passenger diesel sales in the US in 2013; worldwide, every fourth car sold by the Group is a diesel, said Dr. Johannes Arning, of Volkswagen’s Powertrain Product Management group.

The new 2.0L TDI is a turbocharged, common-rail, direct-injection four-cylinder engine based on the Volkswagen Group’s modular diesel toolkit (MDB, Modularen Diesel Baukasten). Volkswagen also has a modular gasoline engine toolkit, the MOB (Modularen Ottomotor Baukasten), which includes the new EA211 series. Both MDB and MOB play critical roles in the Volkswagen Group’s larger MQB modular toolkit, which is in turn one of the four main modular toolkits (modularen Baukästen) of the Group: the MQB (transverse); the MLB (longitudinal); the MSB (standard drive); and the NSF (New Small Family).

The MQB strategy of the Volkswagen Group extends from the A0 to the C-segment. There is some overlap at the low-end with the NSF and in larger vehicles with the MLB. Click to enlarge.

The MQB allows the integration of alternatives, for example, natural gas, hybrid and electric drives, in addition to the conventional gasoline and diesel power units. As one clear example, the new Golf, which is MQB-based, offers gasoline; diesel; natural gas; plug-in hybrid (the GTE); and battery-electric (the e-Golf) versions, all of which can be manufactured bumper-to-bumper on the same assembly line. Further, the hardware of the plug-in hybrid drive in the GTE is also that of the Audi A3 e-tron plug-in hybrid.

The new MDB EA288 diesel

The 2.0L EA288 diesel engine delivers 150 hp (112 kW)—an increase of 10 hp over the current engine and 236 lb-ft (320 Nm) of torque. Technical development targets for the development of the new MDB-based EA288 diesel engine were CO₂reduction; emissions reduction; performance; comfort; and costs.

Basic specs of the older 2.0L (left) vs. the new (right). Click to enlarge.

The new diesel shares only the bore spacing with the previous 2.0-liter diesel. A number of changes have been made to help reduce emissions, such as the use of a complex exhaust gas recirculation system (with high pressure EGR and a cooled low-pressure EGR); integration of the water-cooled intercooler and the EGR valve with the intake manifold (which also improves throttle response); and packaging the exhaust after-treatment components close to the engine by combining the DPF with the SCR Catalyst.

The EA288 is designed to meet the requirements of different markets. For example, depending on the emission requirements, 3 different types of exhaust gas recirculation (EGR ) can be used:

• cooled high-pressure EGR without low-pressure EGR;
• cooled low-pressure EGR without high-pressure EGR; or
• cooled low-pressure EGR and non-cooled high-pressure EGR.

Similarly, the closely-attached after-treatment devices—including an oxidation catalyst; diesel particulate filter; and NO_x storage or selective catalytic reduction system (SCR)—can be used singularly or in combination depending upon the needs of the vehicle (e.g., weight) and market regulations.

Crankcase. The crankcase—as in the previous TDI—is made of gray cast iron. The objective was to reduce crankcase weight while integrating further components. Volkswagen engineers achieved this by:

• integrating balancer shafts above the crankshaft;
• a short water jacket for the fast component heating;
• cooling of the area between the cylinders;
• integrating of thermal management measures in oil and water management;
• head bolt threads below the water jacket;
• optimization of oil guides to minimize flow losses; and
• extension of the oil return and blow-by channels to the parting plane of the oil pan.

Design criteria were:

• even cooling of the crankcase;
• cross-flow in the cylinder head from the outlet to the inlet side;
• good flow through the holes to cool the cylinder fins;
• uniform distribution of the flow to the cylinder; and
• optimization of the flow guide with additional consideration of the requirements in the warm-up.

The dual oil and vacuum pump unit. Click to enlarge.

Oil and vacuum pump. The oil/vacuum pump is designed as a dual pump, driven directly from the crankshaft by a toothed belt in oil. Both pumps are arranged in a common die-cast aluminum housing below the cylinder crankcase flanges in the oil pan. Pretensioning of the belt is specified during installation by the center distance of the components; this leads to a particularly friction-optimized drive.

The oil supply is realized by a volume-controlled vane pump. A solenoid valve can also be connected depending on the load in a low- or high-pressure stage. Thus, an optimum between lubrication and power consumption can be achieved in engine operation.

The arrangement of the vacuum pump resulted in new design requirements that required a low drive torque at cold start, among others factors. Using a double-reed valve, a sufficiently large cross section for the ejection of the oil is realized in the vacuum chamber. Thus, the drive torque can be kept low even at low temperatures . The connection to the vehicle-side vacuum line is via bores in the vacuum pump and in the cylinder crankcase.

Cylinder head. Click to enlarge.

Cylinder head. The cylinder head intake and exhaust valves are arranged one behind the other. This arrangement results in a mixed camshaft, each having an intake and exhaust control. Since the valve assembly has been changed compared to its predecessor, the channels had to be redesigned, with a focus on increasing the maximum flow with good swirl numbers.

A further innovation of the MDB concept is the thermal management system in which the cylinder head plays a central role. A micro-cooling circuit—one of three cooling circuits in the engine—is integrated into the cylinder head.

The outlet is located in the bottom plate with connection to the cylinder block, which takes the return of the water.

To increase the heat dissipation in the region close to the combustion chamber, the water jacket is divided into a lower and an upper water jacket core, each with a cooling channel. The two cooling channels are separated from each other and are guided together only at the outlet.

This enables a more uniform distribution of the cooling capacity between the individual cylinders compared to the predecessor engine.

Valve train. Click to enlarge.

Valve train. The valve train of the new MDB 2.0-liter TDI engine differs from its predecessors through the use of an integrated valve drive module ( iVM ). Thus, the camshaft bearing frame can be separated from the cylinder head to prepare it for future emission requirements. In addition, the bearing frame was optimized for friction.

Functional advantages of the iVM include:

• Valve train is designed as an independent module with appropriate manufacturing and cost advantages.
• Reducing the friction loss of the camshaft through the use of a needle bearing.
• Internal oil supply to the bearings with a separate integrated into the bearing frame oil gallery.
• Additional supply of oil to the cylinder head.

Regardless of engine capacity, the blank, valve train and cylinder head cover module are always identical. Only the size of the hole and of the valves is different.

Intercooler. Click to enlarge.

Intake manifold with integrated charge air intercooler. The MDB TDI features an intake manifold with an integrated charge air intercooler. The predecessor 2.0L TDI had already used indirect water-cooled charge air cooling were used. As a further development, the water-cooled charge air cooler for the MDB engine—as in the 1.4 liter TSI engine—is integrated into the intake manifold.

This constitutes a separate low-temperature coolant circuit with air-water heat exchanger in conjunction with a variable-speed water circulation pump.

The charge-air duct is extremely compact, and the water-cooled module enables a shorter and more compact air intake circuit. The reduced charge air volume improves the transient response of the engine significantly. Further, flow losses are reduced, and icing or condensation in the intercooler be avoided.

Comparison of the new charge air intercooling system (right) with its predecessor (left). Click to enlarge.

The integrated intercooler is supplied by Valeo and is made entirely of aluminum. The cooling body, which consists of coolant plates, fins, cover, bottom and side panels, as well as coolant connections,is fully soldered. The inlet and outlet boxes are then welded to the heat sink.

The radiator network consists of 10 pairs of brazed cold plates. The coolant flows through plates are W-shaped counter-currents to force a complete utilization of the radiator network at a reasonable pressure drop.

Through a special geometry of the coolant plates, the cooling agent flow is distributed across the width of the flat tube, and is deflected at the same time. This provides for a low pressure loss for a good heat transfer from the aluminum sheet to the coolant. At the same time the design of the cooling plates offers a high robustness with respect to the change in pressure resistance.

Air side fin thickness and fin spacing were optimized so that the cross-sectional area of the lamella can derive the maximum quantity of heat to the coolant plates and at the same time the pressure loss is minimal. Small punched openings which are arranged alternately like gills provide for a good heat transfer and also allow a flow in the transverse direction.

The exhaust side systems. Click to enlarge.

Exhaust-side. The exhaust side of the MDB engine consists of the exhaust manifold module with exhaust gas turbocharger; the exhaust after-treatment system module; and the low-pressure EGR system. As noted earlier, the components within the aftertreatment module vary depending upon the emission standard, as do the three different types of exhaust gas recirculation.

The compact design of the aftertreatment module and its close mounting to the engine enable low heat and pressure losses as well as the fast starting of the oxidizing catalytic converter and speedy heat-up of the diesel particulate filter.

EGR. At high combustion temperatures in the engine result in NO_x emissions. The higher the combustion temperature in the cylinder, and the longer its duration, the higher the proportion of NO_x in the exhaust gas. Exhaust gas recirculation (EGR ) is used to reduce engine-out NO_x, which, in conjunction in come cases with further aftertreatment, results in meeting emissions targets. The rapid oxidation of fuel molecules in the combustion cylinder is inhibited by the presence of the exhaust gas molecules; peak temperature and the resulting NO_x emissions are therefore reduced.

Both the forthcoming EU 6 emission standard as well as the even more stringent US EPA Tier 3/ California LEV III standards, call for further significant reductions NO_x compared to today. Volkswagen engineered the MDB TDI engine to be able to meet all those coming standards.

The engine features high-pressure and low-pressure EGR loops.

The recirculated exhaust gases of the high-pressure EGR have a high temperature; mixing this exhaust gas to the fresh air in the intake manifold is intended to reduce the air mass, resulting in operation with a lower air-fuel ratio. Also, the average temperature of the fresh charge increases. HP-EGR is used to address dynamic and cold start issues.

The low-pressure EGR system, integrated with the exhaust aftertreatment system, is upstream of the exhaust gas turbo; the recirculated gas is cooler, and low in particulate matter. This allows the reduction of the cylinder air mass without heating the intake air; further, the exhaust gas mass flow upstream of the turbocharger is not reduced, which enables maintaining the high exhaust gas enthalpy. Volkswagen improved the pressure losses in the LP EGR system by some 90%, bringing it down from 200 to 20–25 millibars.

Exhaust gas recirculation system. Click to enlarge.

Thermal management. The thermal management of the 2.0L TDI MDB has three cooling circuits which can operate independently.

• Micro-circuit. The micro-circuit consists of the cylinder head, the EGR cooler, the heat exchanger and an electric coolant pump.
• Main water circuit. The main water circuit includes the crankcase, engine and transmission oil cooler, front radiator and a switchable water pump.
• Low-temperature circuit. The low-temperature circuit consists of the integrated intake manifold intercooler, a front radiator and an electric coolant pump.

After cold start only the micro-circuit is operated. With increasing cooling demand, the switchable water pump is switched on. The low-temperature circuit is responsible for the indirect charge air cooling. The high- and low-temperature circuits are operated independently of each other. The aims of the thermal management system are to shorten the warm-up phase after a cold start; bring the emission-reducing components to temperature; and deliver an optimized temperature to the passenger compartment.

NSF and DOE form Partnership on Advanced Combustion Engines; goal 25-40% better LDV fuel economy and 55% BTE in heavy-duty engines; $12M in awards for FY 2012-2014

The Directorate for Engineering at the National Science Foundation (NSF) has established a partnership with the Vehicle Technologies Program (VTP) of the US Department of Energy (DOE) to address critical fundamental and applied research challenges associated with advanced combustion engine technologies. The goal of the partnership is to leverage the complementary missions of deployment and commercialization (DOE) and fundamental research and education (NSF) to address the efficiency of the internal combustion engine (ICE).
The high-level performance goals of the Partnership are a 25-40% improvement in fuel economy in a light-duty vehicle (LDV) and achieving 55% brake thermal efficiency (BTE) in heavy-duty engine systems. The Directorate for Engineering is now seeking proposals (NSF 12-559) for awards totalling up to $12 million for FY 2012, 2013, and 2014, pending availability of funds.

Liquid fuels have dominated transportation systems for over a century and will continue to do so for decades to come. Within the US alone, almost 12 million barrels of oil are consumed per day in ground transportation vehicles that are powered by the internal combustion engine (ICE). By 2035, this number is expected to grow to more than 17 million barrels per day. At the present time, sustainable energy technologies (e.g., wind, solar, electric) are not yet at the stage where they can significantly impact petroleum use. While such sustainable concepts are being developed, R&D investments that seek to improve the efficiency of the ICE stand to have a near-term impact on reducing oil consumption and the emissions they generate. The potential is significant. For example, the fuel economy of light-duty vehicles could potentially be improved by 75 percent and heavy-duty vehicles by 30 percent with concepts that are just beginning to be better understood.

Because the NSF and DOE have long invested in research and development in elements related to advanced combustion engines, these two agencies have developed a jointly funded partnership to address a problem of national importance that impacts our reliance on foreign sources of oil, while also addressing the environmental impact of performance. Specifically, proposals are solicited that are directly relevant to ICE technologies as outlined in this solicitation. The awards associated with this Solicitation will potentially enable efficiency gains in the ICE by improving the sub-processes that are addressed. Such an effort comes at a critical time in the Nation’s history as our energy security and economic well-being demands that oil consumption be reduced. This DOE and NSF partnership is directed to that end. It seeks to exploit the complementary missions of (i) research and development for NSF, and (ii) deployment and commercialization for DOE to develop the critical understanding technologies associated with ICE performance.

—Program solicitation

The partnership will be managed by the Advanced Combustion Engines R&D Sub-Program within the DOE’s VTP, and the Combustion, Fire and Plasma Systems Program; the Thermal Transport Processes Program; and the Catalysis and Biocatalysis Programs within the Chemical, Bioengineering, Environmental and Transport Systems (CBET) Division of the Directorate for Engineering at NSF. Each of these programs already includes strong components of the elements of advanced combustion engine technologies within the portfolio of projects they support.
The NSF/DOE Partnership in Advanced Combustion Engines is soliciting transformative ideas in several targeted areas with the potential to enable an increase in the efficiency of internal combustion engines while minimizing the energy penalty of meeting emissions regulations. This goal will be accomplished by directed research and development in advanced engine combustion regimes and emission control strategies, coupled with advanced fuel formulations including both non-petroleum-based and petroleum-based fuels.
Proposals are encouraged that advance transformative ideas to develop the enabling understanding for improving the efficiency of the ICE and the emissions they generate. This goal will be facilitated by fundamental research to establish the basis for new concepts, design elements and tools performed through university/industry/national laboratory partnerships. The over-arching theme is the reduction of the design cycle for testing, manufacturing and implementation of new ideas, which is currently expensive and time-consuming.
Research should focus on the fundamental thermal/fluid/chemical processes of the problem to be investigated rather than on a development and testing effort. It is also expected that a connection will be made between the understanding of the problem to be studied and the associated ICE efficiency gains, according to the NSF.

The ICE is a complex system whose operation is controlled by a wide range of processes. These include sprays that deliver the fuel to the combustion chamber and which set the initial conditions for combustion, stochastic in-cylinder dynamics for conversion of chemical energy to work that include random turbulent mixing, fuel evaporation and combustion, multi-phase fuel-air mixing, wall impingement, combustion chemistry, heat transfer and fluid interactions, and exhaust treatment (e.g., catalytic) technologies to reduce toxic gas and particulate emissions. All of these aspects require an improved understanding to realize significant efficiency gains of the ICE.

Advanced combustion regimes for the ICE have the potential to make a near-term impact on oil consumption. Development of low temperature combustion (LTC), learn-burn gasoline combustion and development of alternative (e.g., bio-derived) fuels have the potential to dramatically increase fuel economy. LTC is based on developing dilute mixtures that result in peak combustion temperatures below about 1900K in order to reduce emissions of oxides of nitrogen. With lower temperatures heat losses are reduced which enable the extraction of more energy in the expansion stroke and thereby a higher net work out and higher fuel efficiency. Additional benefits of reduced combustion temperatures include lower particulate and toxic gas emissions which are important considerations in global climate change. Optimizing evaporation, mixing, kinetics, and heat transfer to achieve high efficiencies and low emissions is the desired goal. LTC is incorporated in such processes as homogeneous charge compression ignition (HCCI), premixed charge compression ignition (PCCI) or a number of other variants that employ lean premixed and partially premixed combustion.

—Program solicitation

Key areas that must be better understood to enable LTC regimes to realize their full potential include, but are not limited to, the following:

• stochastic and deterministic in-cylinder processes that influence the stability of LTC methodologies to increase power density in LTC or lean-burn operation;
• validated, predictive models of combustion control, pollutant formation and ignition chemistry at engine-relevant pressures and temperatures;
• ignition characteristics of lean mixtures of various fuels;
• liquid fuel properties and their combustion characteristics, including bio (renewable) fuels and surrogates near wall heat transfer and unsteady reciprocating effects on boundary layer behavior;
• droplet impingement and surface heat transfer mechanisms;
• spray/droplet evaporation and combustion of bio (renewable) and surrogate fuels;
• turbulence-radiation interactions;
• atomizer design and spray type, effects of swirl, and combustion chamber geometry; and
• high temperature, low heat-loss materials for engine application.

Emission control devices must be designed to preserve any efficiency gains from in-cylinder processes; emission control may also have the potential to improve performance by reducing emissions to near-zero levels. Catalysts, in particular, have been effective for their impact on reducing NO_x, PM, non-methane organic gases (NMOG) or hydrocarbons (HC), and carbon monoxide (CO). Included are three-way catalysts, oxidation catalysts, and selective catalytic reduction (SCR) processes, lean NO_x trap or NO_x adsorber catalysts, and particulate filters. Relevant topics include, but are not limited to, the following:

• new catalysts and their performance—particularly those catalyst designs that will lower the light-off temperatures (i.e., the temperature at which 90% effectiveness is achieved) to less than 150 °C;
• new concepts for SCR, lean NO_x trap or NO_x adsorber catalysts, particulate filters and regeneration technologies;
• understanding and mitigating the negative effects of sulfur and other contaminants on catalyst durability, especially at low temperatures determination of pre-catalytic converter emissions as a function of engine combustion modes and operating parameters, and evaluation of anticipated reference catalyst performance with these input emissions;
• understanding aging mechanisms in lean NO_x traps and new models to predict catalyst performance; and
• enabling cost-effective and fuel-efficient thermal management of catalyst systems including active control.

The NSF directorate is seeking proposals involving collaborations between a lead academic PI and with industry, and/or other academic and/or national laboratory collaborators that provide complementary experimental/modeling/facility capabilities.
The Directorate for Engineering estimates 5 to 20 awards, each of up to 3-years duration. Each project team may receive support up to between $200,000 and $800,000 per year for up to three years on a continuing basis, pending availability of funds and research progress made.
Letters of intent are due by 18 June; full proposals are due by 8 August.
NSF evaluates proposals are evaluated through use of the two National Science Board (NSB)-approved merit review criteria: intellectual merit and the broader impacts of the proposed effort.



Source: Green Car Congress