IN THE SP OTLIGHT

Shared Concepts are Possible What parallels exist between the development of engines for passenger cars and commercial vehicles? What sense would joint development make? This topic dominated the panel discussion at the 3rd International Engine Congress in Baden-Baden (Germany).

The key topics were friction, emissions, supercharging and fuels. Panel members discussing the above included Professor Uwe Dieter Grebe, Managing Director, AVL List GmbH, Thomas Nickels, Senior Vice President Engineering Powertrain, MAN Truck & Bus AG, Dr. Thomas Wintrich, Head of Diesel Engine Development, Robert Bosch GmbH, Dr. Nikolai

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Ardey, Head of Powertrain Design and Integration, BMW AG, and Professor Peter Eilts, Director of the Institute of Internal Combustion Engines, TU Braunschweig, (see picture below, from left) together with MTZ Editors Dr. Alexander Heintzel and Martin Westerhoff (on sides, left and right). Read here the verdict of these experts on the core points of the discussion.

MTZ _ Minimising friction in the

THOMAS NICKELS (MAN TRUCK & BUS) _

powertrain is something that occupies car and commercial vehicle developers. What measures do you see as particularly promising for an efficient powertrain against a backdrop of overall friction minimisation?

Definitely. From a joint development perspective, it is also an area, for example, where it makes a great deal of sense for joint commercial vehicle and passenger car development, particularly for coating systems. Granted, our boundary conditions regarding durability and robustness differ slightly, but it is definitely a very fascinating area for collaboration.

DR. NIKOLAI ARDEY (BMW) _ The

biggest area for friction loss remains the combination of cylinder bore and piston. This is, of course, still at the centre of efforts to minimise friction, aside from all the other things you can achieve in the supercharger with turbochargers mounted on anti-friction bearings or in the gasket. Despite numerous individual points, the piston-cylinder bore combination is still the area attracting most attention. In future we’ll see production methods in this area like form-giving honing processes that allow even better ring calibration or less ring tension. It offers a potential threshold of around 1 to 3 % for consumption.

MTZ _ Mr. Nickels, is your approach similar?

MTZ _ Conventional drives continue to offer

significant efficiency potential. The relevant scope here includes the drivetrain and transmission in particular, as well as measures affecting the combustion engine. What role does the use of low-viscosity oils play here in reducing friction and where do the key challenges lie? PROF. DR. UWE-DIETER GREBE (AVL) _ I’m

sure we have abundant potential as far as oils are concerned. Moreover, looking at the bigger picture of current transmission technology, we can still see considerable potential in reducing friction in trans-

© Uli Regenscheit

mission, in the path taken by lubricants for example, as well as via coatings and surface quality. NICKELS _ I’d like to add that there’s also a very strong focus here with commercial vehicles. Although individual applications using 0W20 engine oils for commercial vehicle engines now exist, there are constant clashes with oil-change intervals. With commercial vehicles, customers ultimately expect us to achieve at least 100,000 to 120,000 km between oil changes, i.e. almost the useful life of a small passenger car engine. Meeting the above requirements using these types of oil is an area fraught with conflict. People do not accept the tradeoff between lower fuel consumption and servicing intervals. MTZ _ The challenge of exhaust aftertreatment has been a hot topic far longer for commercial vehicles than in the passenger vehicle field. What measures from the commercial vehicle field can be transferred to the development of car engines? ARDEY _ We have already adopted measures from the commercial vehicle industry, at least to a large extent. SCR originally comes from commercial vehicles. This is a technology that limits nitrogen oxide emissions with high flows of exhaust gas. This is a major advantage when a normal NOx storage catalytic converter becomes thermally overloaded. The only thing that couldn’t transfer were systems using compressed air, due to the lack of on-board brake compressors. Otherwise, we are already reaping the benefits of industry construction kit components originally developed for trucks. MTZ _ The conflict of objectives between nitrogen oxide and carbon dioxide emissions had to be resolved quickly for commercial vehicles because it also impacts directly on operating costs. Where were the greatest challenges?

Balance ultimately decides the issue. What do I invest in exhaust aftertreatment and what in the engine? Here we had to invest far more in exhaust aftertreatment to achieve corresponding consumption figures whilst observing the emission thresholds. It’s always a compromise. Although we would ideally avoid emissions in the engine and the subsequent need to eliminate them in exhaust aftertreatment, we are, after all, subject to physi-

NICKELS _

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IN THE SP OTLIGHT

With electric-assisted supercharging, “boundary conditions for commercial vehicle configuration are definitely different to the driving factors on the car side,” says Thomas Nickels (MAN) (© Uli Regenscheit)

cal constraints in this conflict of interests. This is why exhaust aftertreatment was the big challenge posed by the introduction of the Euro VI standard. MTZ _ Common rail is a standard in diesel

engines for commercial and passenger cars. What do you see as the maximum practical and feasible pressure level?

We see the necessity of pressure increase in passenger cars – more than a way of meeting

DR. THOMAS WINTRICH (BOSCH) _

Uwe-Dieter Grebe (AVL) is certain that dual-fuel systems, and especially the utilisation of gas, have huge potential (© Uli Regenscheit)

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On the topic of exhaust aftertreatment, “we have already adopted measures from the commercial vehicle industry, at least to a large extent,” declares Nikolai Ardey (BMW) (© Uli Regenscheit)

emission thresholds; we clearly see a “race of power”. A specific output of 110 kW/l was already announced in one presentation, and achieving such high specific performance means approaching the range of 2700 bar and more. We are developing this type of system for cars up to 3000 bar to map this high specific performance. This certainly won’t be in the mass market segment, but car manufacturers are pushing forward to this class of performance to differentiate.

With trucks it very much depends on boundary conditions. Forecasts a few years ago predicted that pressures would climb to 2500 bar. The subject has remained on hold for a while, which also reflects how emissions legislation is likely to develop. A further drastic cut in nitrogen oxide values is being discussed in California. If that goes through, I’m sure that the requirements on us in pressure terms will also intensify, and this will of course have our full attention.

“I think one important aspect from the perspective of the injection system manufacturer is,” according to Thomas Wintrich (Bosch), “the early formulation of a definition and of standards” (© Uli Regenscheit)

MTZ _ Electric-assisted supercharging is currently a hot topic for improving the transient behaviour of car diesel engines. Does that make any sense for commercial vehicles?

Boundary conditions for commercial vehicle configurations are definitely different to the driving factors on the car side, which is why I do not see the potential and sense from this angle at all. However, there might be other driving factors where use may make sense. Even so, I don’t see any application in the next years. GREBE _ You can of course speed up the air flow with an electric supercharging unit and add in a further parameter to the mixture formation where I set the air ratios that can be used to positively influence combustion conditions and therefore emissions. This means that you cannot just exploit the power of the supercharger but also the power of the air flow to achieve improvements. NICKELS _

MTZ _ Exhaust aftertreatment is accounting for an ever

larger share of the overall costs of the powertrain, for both commercial vehicles as well as cars. Dual-fuel engines are a relatively inexpensive solution that can be used to reduce raw emissions. How do you assess their potential? Are they conceivable for cars? GREBE _ Dual-fuel systems, and the utilisation of gas in particular, certainly have huge potential, particularly because we achieve CO2 reduction purely from the chemical composition of the fuel. However, we need to look at how we ultimately meet nitrogen oxide standards with this method. It remains to be seen whether we can successfully reduce overall system costs. ARDEY _ There is a further serious hurdle for diesel or stratified combustion processes due to excess air. Considerable methane is produced, which is harmful to the climate, and we first need to get the hang of how to eliminate it. 05I2016

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PROF. DR. PETER EILTS (TU BRAUNSCHWEIG) _ If I’m correct, only lambda 1 concepts can currently be certified in Europe because emissions are too high with lean concepts and methane and all hydrocarbons are lumped together here in Europe. It’s a different story in the USA, where methane is exempt and only non-methane hydrocarbons are restricted. So we need a methane-catalyst. MTZ _ The costs of a variable use of exhaust-gas-energy soon pay for themselves for commercial vehicles with high mileage. Efficient Dynamics pursued this idea at an early stage. What does the cost-benefit ratio look like for cars? ARDEY _ We have conducted numerous investigations into the use of thermoelectric exhaust energy and also into energy in the steam process. They show that the technical costs involved with the steam process in cars are simply too high. We tend to recommend this type of concept for trucks. A thermoelectric generator is an attractive concept, where sufficient space exists to install the corresponding heat exchanger in the exhaust area. It’s an interesting option but also a question of the cost-benefit ratio. However, you need relatively high exhaust temperature in gasoline as well as in diesel engines, or at least high temperature gradients, to make full use of it. There are no attractive locations in a diesel engine, either in the EGR cooler or the emissions tract. If anywhere, it would be possible in a gasoline powertrain. MTZ _ The focus in commercial vehicles is on the Rankine process

for energy recovery. Is such a system too complex for cars? GREBE _ On this point, I’d like to second what Mr. Ardey said. A closer look at the operating conditions for a car sees longer warm-up phases playing a role in the total operating time of the vehicle, with only integrally improved efficiency ultimately being of interest in real driving conditions when

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IN THE SP OTLIGHT

and the fuel quality can deteriorate considerably. In this light, what do you think of synthetic fuels containing oxygen, i.e. oxygenates, as fuels of the future? EILTS _ They are not bad for emissions. Fuels with a high proportion of oxygen generally result in fewer particulates. There are of course exceptions to this rule. The poor characteristics of FAME can be compensated for by the downstream step to HVO. I don’t think you should lump together oxygen content and the poor quality of some biogenic fuels. Oxygen content is good for particulate emissions since it reduces them. MTZ _ When will a business

case be made for it?

It is difficult to give an answer for “when” as we currently see that pricing policy for fossil fuels can have a major impact on this. However, I do think that synthetic fuels will play an important role as an energy source in future. There are many reasons why. First, we need to provide transportation services over great distances and, second, we need the ability to store energy if deciding on alternative energy sources. There is simply no alternative to a chemical compound. I believe, in physical terms, that the future lies in this direction. NICKELS _ It’s also an issue of quantities and availability. There is no doubt that HVO is a very interesting fuel but it must also be available accordingly. Emissions legislation is the next challenge. If I homologate a Euro VI engine, I can run it separately on classic diesel, P100 and HVO. If additional fuels appear, than the costs rocket significantly, and such diversification is difficult in the TCOdriven commercial vehicle sector. Hence we need to press for a reasonable legislative framework to ensure that costs remain manageable. GREBE _

For Peter Eilts (TU Braunschweig) the crucial question is “how a fuel can be affordably produced in reasonable quantities and used to run a diesel or gasoline engine” (© Uli Regenscheit)

the customer is at the wheel. In this light, the Rankine process for cars must be evaluated using a different measure of time. Here, I only see initial implementation for vehicles operated over long distances at high load, i.e. with a constant heat potential. MTZ _ What is the most appropriate way of replacing fossil diesel fuel – using synthetic fuels, under the key word power-to-liquid, or with a biogenic share? EILTS _ The

characteristics of the molecule are the crucial factor. You can extract them from power-to-liquid or using the Fischer-Tropsch process as well as constructing molecules from biomass that can be easily used in a diesel engine. A diesel engine is a relatively insusceptible piece of equipment when it comes to fuel. In my opinion it does not really matter where the fuel comes from. The crucial question will be how

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something can be produced in reasonable quantities and at a reasonable price that can be used to run a diesel or gasoline engine. WINTRICH _ I think one key aspect from the perspective of the injection system manufacturer is the early formulation of a definition and of standards so that the right injection systems can be offered accordingly. NICKELS _ Availability is an important point, which is essential when we talk about commercial vehicles. There will be diversification, but the question is whether sufficient quantities will be available, for example, for long-distance transport. With this in mind, I expect we will have to make do with the diesel engine for another year or two yet. MTZ _ Biomass-to-Liquid (BtL) fuels are seen critically in some quarters since the savings in greenhouse emissions remain marginal

MTZ _ It’s a little easier

for cars in this respect.

In principle, yes. However, if you look at the vehicle fleets, it is a very similar business, largely driven by TCO. The complexity of adaptability is already overwhelming when we need to adapt to different markets where conditions are already extremely diverse. If we then have different technologies and fuel types, it will be really challenging for the car sector.

ARDEY _

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