Zero-emission mobility for off-highway applications
Control unit for fuel cell systems based on automotive large-scale series production
Software with integrated hydrogen, air, and coolant control
These days, mobility at many airports is already clean and quiet and produces no emissions. More and more of the vehicles seen on airfields – baggage towing tractors and other ground support equipment – are electrically powered, by fuel cell systems too. Bosch Engineering GmbH is offering control units for zero-emission off-highway applications such as these, and the wholly-owned Bosch subsidiary will be presenting its new fuel cell control unit (FCCU) for the first time at the MobiliTec specialist trade show at the 2014 Hannover trade fair.
Robust hardware, flexible software The FCCU is based on tried-and-tested Bosch automotive large-scale series production hardware. Together with newly developed software for controlling fuel cell systems, it has the flexibility to be used in various mobile and stationary applications and supports a wide variety of system configurations. The software features integrated hydrogen, air, and coolant control, so it can run a large number of operating strategies to further increase energy efficiency and keep consumption to a minimum.
Zero-emission mobility already widespread in the off-highway segment Electrification of off-highway applications – among them airport ground support vehicles, municipal vehicles, and industrial trucks – is being driven by the tightening of emissions legislation for internal-combustion engines with over 56 kilowatts of output (EU Stage IV and U.S. Tier 4 Final). This is one of the reasons why fuel cell systems are already widespread in these sectors and why hydrogen filling stations are already in place for many airports and vehicle fleets. Fuel cells generate electricity from the chemical reaction between hydrogen and oxygen, which emits nothing but pure water vapor. This makes them ideal for off-highway applications such as forklift trucks and mobile lift platforms, which must operate with zero emissions inside buildings and facilities. What’s more, vehicles with a fuel-cell powertrain are quieter and experience a much lower level of vibrations.
Bosch Engineering’s FCCU will first be applied in the “Innovative On-Board Energiewandler” (InnoROBE) project, which is funded by the German Federal Ministry of Education and Research. The company is providing the project with the central control unit for a fuel cell system that will serve as an energy source for an electrically powered baggage towing truck to increase it’s zero-emission range.
“Sports car of the century” featuring pioneering Bosch technology
Driving enjoyment and low fuel consumption thanks to direct injection
Bosch has produced over 50 million injectors and 10 million high-pressure pumps
Back in the 1950s, Bosch gasoline direct injection played an important role in one of the most famous sports cars of all time. In 1954, the technology was incorporated in the Mercedes-Benz 300 SL, a production car that would later be voted the “sports car of the century” by a panel of automotive journalists. Even at that time, gasoline direct injection was already managing to improve engine performance and fuel efficiency. In the Mercedes-Benz 300 SL, the system was primarily designed to offer agility and power. 60 years later, however, gasoline direct injection no longer stands for just performance, but also for efficiency and low emissions. This was made possible by highly precise manufacturing, sophisticated sensor technology, and advanced electronics which Bosch further refined over decades. Today, gasoline direct injection is economically viable and available for the mass market as a result.
Over 60 years ago, that could not be taken for granted. In its review of the 300 SL, the U.S. magazine Road & Track praised its “performance levels which are up there with – and even an improvement on – the best cars the automotive industry has to offer.”
Gasoline direct injection today: powerful and making strong headway Today, gasoline direct injection is even available in small cars. More and more automakers are turning to the technology, which has become a key feature of strategies to meet future emissions guidelines. Modern injectors make a major contribution to cutting CO2 emissions and fuel consumption by up to 12 percent. In combination with downsizing or turbocharging, gasoline direct injection offers improved throttle response and enhanced driving dynamics. This is due to a torque increase of up to 50 percent at low engine speeds. Thanks to improved cooling of the combustion chamber, gasoline direct injection enables higher compression by further enhancing engine knock resistance.
Bosch showed it was in for the long haul by continuing to develop its gasoline direct injection technology over a period of decades. A broader market finally emerged when stricter emissions standards were introduced in the early 2000s, and since then sales have gone from strength to strength. In 2011, Bosch celebrated two production milestones when its global manufacturing network reached a total of 25 million fuel injectors and 5 million high-pressure pumps. Just one year later, in 2012, it doubled this achievement to reach 50 million injection valves and 10 million high-pressure pumps. By the end of 2013, these figures had skyrocketed to 80 million and 20 million respectively.
Downsizing: The trend in the global automotive industry is toward small yet powerful engines. Manufacturers from Europe, the U.S., and even China are embracing downsizing concepts to build increasingly compact and economical low displacement engines which continue to offer equivalent levels of performance and driving enjoyment thanks to turbocharging. “Turbocharged three- and four-cylinder engines have taken on a dominant position, especially in the compact class,” says Dr. Rolf Bulander, the member of the board of management of Robert Bosch GmbH responsible for powertrain technology.
Combustion: Engines with gasoline direct injection prepare the air-fuel mix directly in the combustion chamber. The fuel which the injectors spray into the combustion chamber is so finely atomized that it can be ignited directly without having to mix it in the combustion chamber. This enables higher engine compression, which translates into greater efficiency. The direct injection technology also makes a major contribution to improved cylinder cooling. All that flows through the open intake valve in the intake duct is fresh air. High-pressure injection valves inject the fuel directly into the combustion chamber. This cools the combustion chamber, making basic compression higher thanks to the decreased propensity to knock.
Benefits: The economical consumption and low emissions of Bosch gasoline direct injection are due to the precise metering, preparation, and distribution of air and fuel for each individual combustion cycle. In combination with downsizing and turbocharging, gasoline direct injection offers the potential to reduce consumption and CO2 emissions by some 15 percent.
High-pressure pump and high-performance control unit Systems idea: Bosch sees gasoline direct injection as far more than just an injection process. Bosch offers a complete system comprising a high-pressure pump, high-pressure rail with injection valve, a large number of sensors, and an engine control unit. If mixture formation is homogeneous, the HDEV5 high-pressure injection valve makes a major contribution to optimum, and thus fuel efficient, combustion. Up to seven individually positioned injection holes enable the spray pattern to be adapted flexibly to different combustion chambers.
Peak performance: The high-pressure injection valve and the high-pressure pump are designed for system pressures up to 200 bar. The demand-controlled HDP5 high-pressure pump is characterized by its compact dimensions and its light weight of 780 grams. Thanks to the use of stainless steel, the current components of the gasoline direct injection system can handle ethanol blends as well as fuels of different qualities, and are thus designed for worldwide use.
Engine management: The Bosch engine control unit performs all the different functions that are required of an efficient engine management system. These include selecting the right injection pressure and the right moment to inject the fuel. To do this, the electronic control unit calculates thousands of times a minute exactly how the injection process should be performed. Bosch systems competence enables optimum networking of all the individual components to ensure they work together at maximum efficiency. The driver's requirement for more or less torque is a key input variable for controlling the mixture formation electronically. The accelerator pedal module provides this mechanical command as a sensor signal. The crankshaft sensor supplies information on the crankshaft's current speed and position. Further input is provided by the knock sensor, temperature sensor, and camshaft speed sensor. Bosch exhaust-gas treatment plays a key role in helping to meet international emissions standards. The planar wide band oxygen sensor and the thimble-type oxygen sensor measure the oxygen content of the exhaust gas and provide the electronic control unit with the basic information required to achieve optimum mixture formation.
Laser drilling: Bosch is also helping to drive forward the development of specific aspects of gasoline direct injection. The exceptionally high quality of the drilled holes in the HDEV5 injector helps ensure particularly good combustion of the fuel and helps reduce emissions at the same time. The gasoline is injected directly into the cylinder at high pressure (200 bar) through five tiny laser-drilled holes. The sharp edges and smooth inner walls of the holes ensure that the fuel is atomized into extremely small droplets. This is exactly the effect desired. The finer the spray achieved, the greater its surface area. This leads to particularly good contact with the oxygen in the air so that virtually all the gasoline is burned on ignition. For efficient, clean combustion, it is important to prevent droplets of injected fuel from being deposited on the walls of the cylinder or the surface of the piston. Such deposits result in poor-quality combustion. By drilling the five holes in the injection nozzle with different diameters, Bosch achieves the best possible control over fuel distribution in the combustion chamber. The diameters range from 0.25 millimeters down to 0.1 millimeters. The smallest openings allow less gasoline though, the larger ones slightly more. This creates a specific spray pattern in the cylinder, enabling the fuel to be used to maximum effect. Bosch, Trumpf, and the University of Jena were awarded the 2013 German Future Prize by the German Federal President for developing the innovative process for producing the holes with ultrashort pulse lasers.
Using scavenging to eliminate turbo lag: Turbochargers achieve their standard boost pressure only from a certain engine speed. Low engine power output produces a phenomenon known as “turbo lag.” Scavenging, an innovative system approach developed by Bosch, eliminates this turbo lag by briefly opening the intake and exhaust valves simultaneously, creating a dynamic head between the intake and exhaust sides of the engine and increasing the supply of fresh air in the combustion chamber. This fresh air purges the exhaust gas contained in the cylinder by forcing it through the open exhaust valve in the direction of the exhaust manifold. The increased exhaust gas mass flow generates up to 50 percent higher torque at low engine speeds, which counteracts the turbo lag.
Controlled valve operation: Future legislation aimed at reducing particulates places new challenges on internal combustion engines. With its innovative and unrivalled controlled valve operation (CVO) system solution for direct gasoline injection engines, Bosch has successfully adopted a mechatronic approach that contributes substantially to meeting future emissions limits, such as EU6 and SULEV. The key components of CVO are the Bosch electronic control unit and the Bosch high-pressure injector which – unlike conventional precontrolled injection – form a closed loop. In a CVO system, the electronic control unit records the triggering signal during the injection and determines the optimum timing for opening and closing the valve needles. This enables the electronic control unit to calculate the actual injection quantities of each individual injector and adjust this as required. This regulated control system allows even the tiniest quantities of fuel to be injected with minimal tolerances.