August 22, 2011

Advanced Bosch technology for the efficient mobility of the future

“The internal-combustion engine will continue to play a major role in the future of personal mobility, and will contribute to the protection of the world’s climate and the conservation of our limited fossil-fuel reserves,” says Dr. Marcus Heyn, Executive Vice President Passenger Cars in the Bosch Diesel Systems division. The global market for new vehicles will grow from its present level of 71 million to 103 million in 2020. Of this figure, some 100 million vehicles will have an internal-combustion engine, according to external experts and market researchers at the automotive supplier. Automotive technology that helps to reduce the fuel consumption and CO2 emissions of gasoline and diesel engines will therefore gain special significance. Although highly efficient, by 2020 electric motors will play only a minor role in this reduction.

These days, many countries around the world have either agreed targets or legally binding limits for CO2 emissions, some of them ambitious. In 2009, the average new passenger car in Europe emitted 146 grams of CO2 per kilometer. The EU Commission has set its member states a target of 130 grams by 2013, and 95 grams by 2020. For 2025, experts are discussing a value of 70 grams of CO2 per kilometer for an average new vehicle. Under standard conditions, this would then mean consumption of roughly 3 liters of gasoline or 2.6 liters of diesel per 100 kilometers.

“However ambitious these targets may appear to be, they can be reached,” Heyn says. A major role here will be played by technology packages for more energy efficiency in the powertrain – packages that Bosch already has in its portfolio: hybrid concepts for the combination of internal-combustion engines and electric motors, downsizing concepts for eco­nomical gasoline and diesel engines, and energy-saving auxiliary units in the powertrain. In all, these Bosch packages allow a fuel saving of a good 30 percent to be achieved, with a corresponding reduction in CO2 – and this in both gasoline and diesel engines. Compared with the standard automotive technology in use today, consumption and CO2 emissions can be halved in total if additional measures taken by automakers are included. Even today, a number of especially economical vehicles already come close to the targets being discussed for 2020.

Downsizing, the key to saving fuel
In terms of the engine itself, the most effective measure is downsizing. Reducing displacement and the number of cylinders reduces friction losses and means less moving mass. An engine of this kind also has fewer thermal losses. Nonetheless, the aim is to achieve the same or higher engine per­formance.

An engine's performance can be maintained as long as more air is directed to it per combustion cycle than it is able to draw for itself. This is made possible by turbocharging, which provides the engine with the volume of air needed to ensure clean combustion. From the end of 2011, the joint venture Bosch Mahle Turbo Systems will produce modern turbocharger systems which are designed specifically for these new gasoline and diesel engine concepts for passenger cars and commercial vehicles. Bosch expects its joint venture to produce more than two million of these performance-optimized turbochargers in 2015.

In a gasoline engine, the condition for downsizing is direct injection. Engineers can use gasoline direct injection to cool the combustion cham­ber and at the same time achieve good scavenging without fuel losses in the gas-exchange cycle. The result is impressively high torque values even at low engine speed, something that was only possible with diesel engines before.

In diesel engines too, the potential of downsizing has still not been ex­hausted. As charge-air pressure through the turbocharger rises, Bosch engineers need to increase the injection pressure of the common-rail system as well. This makes sense in many ways. It means more diesel fuel can be injected in the same amount of time, which allows a better power yield. Alternatively, engine developers can reduce the diameter of the nozzle holes in the injectors while maintaining engine power. When com­bined with multiple pre- and post-injections, this improves mixture forma­tion in the combustion chamber, saves fuel, and leads to cleaner exhaust emissions. This is a particularly effective way of reducing nitrogen-oxide emissions.

Making auxiliary units more efficient and demand-driven
Increasingly, Bosch engineers are complementing all the technical meas­ures being applied directly to gasoline and diesel engines with more effi­cient auxiliary systems such as alternators or radiator fans. Additional CO2 improvements can be achieved by making systems demand-driven – so that they are only operated or used when they are really needed. Electric water pumps, electric power steering, and generators that recharge the battery primarily when coasting serve to improve the vehicle’s overall efficiency. One particularly effective example is the Bosch start-stop system. It stops the engine at a red light and restarts it reliably when the lights turn green. In the New European Driving Cycle, this achieves fuel savings of up to 5 percent, and as much as 8 percent in urban driving.

New technologies for more energy efficiency
Looking beyond the range of technologies that already exist for reducing fuel consumption and CO2 emissions, Bosch engineers are busy looking for ways to tap further savings potential – both in gasoline and in diesel en­gines. Here, they are studying measures such as combustion control using combustion-chamber pressure sensors. Or they are looking at variable valve control for diesel engines, not just for gasoline engines as is the case today. Work could also be done on transmissions to increase the efficiency of the automotive system, on energy recovery from exhaust heat, or on reducing the need for cooling.

Alternative fuels improve carbon footprint
Depending on regional circumstances, markets vary in the technical focus of their efforts to reduce CO2 emissions. In Brazil, for example, an impor­tant role is played by Bosch flex-fuel technology for gasoline engines. Sugar cane grown in the country is converted into ethanol, which serves as an alternative to fuels derived from crude oil. The fact that this fuel is made from renewable raw materials means it has a notable positive impact on carbon footprint. In the United States, more and more flex-fuel vehicles are being registered that can run on various gasoline-ethanol blends. Other countries and regions also take advantage of this eco-friendly effect by blending biogenic and fossil fuels – with blending levels of between five and 20 percent for both gasoline and diesel. In future, synthetic fuels based on organic waste materials will also gain in significance.

Fuel-saving technology pays off
Based on typical annual mileages for Europe and today's fuel prices there, a comparison of the fuel costs of the average car in 2010 with a car built in 2020 shows fuel cost savings over three years of operation of between 1,000 and 1,500 euros.

In other words, drivers’ operating costs are likely to be reduced by more than enough to cover the cost of all the extra technology they will have to buy in 2020 to make their cars more economical. If we consider a normal vehicle service life of some 12 years, this amounts to fuel savings of 4,000 to 6,000 euros and a reduction in CO2 emissions of between 6 and 11 metric tons.

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