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(This article is an excerpt from a white paper posted in the Automotive DesignLine Technical Paper Library and covers the bi-fuel hydrogen/gasoline internal combustion engine technology and systems, as well as basics of its hardware-in-the-loop (HIL) engine simulation system. The complete paper takes a deep dive into the HIL simulations using National Instruments' tools.)
The BMW Hydrogen 7 is the world's first premium vehicle with a bi-fueled drive concept. It is currently under development and when complete it will offer a driving experience typical of BMW. The BMW Hydrogen 7 opens the way to mobility practically free of emissions, coupled with the driving experience of a premium car. For software development tasks, set up and safeguarding of the engine control units for the BMW model platform was adapted to the hydrogen requirements and the HIL delivery was improved through the use of industrialized processes. The availability of HIL system solutions first used with the Hydrogen 7 project was also used to improve the HIL supply for other BMW power train projects.
BMW Hydrogen 7 - The First Hydrogen Serial Car
The BMW CleanEnergy hydrogen initiative aims to avoid carbon dioxide emissions by changing from carbon dioxide based fuel, such as gas and diesel, to hydrogen. The prospect of generating regenerative hydrogen is a contribution towards sustaining individual mobility for the future. The combination of a combustion engine and liquid hydrogen is superior to other concepts in terms of production costs but also customer values such as driving dynamics, reliability, and cruising range. Therefore, the BMW Hydrogen 7 is the first premium car with a hydrogen engine.
Hydrogen Engine for Sustainable Individual Mobility
With the concept of efficient dynamics for all engines, the BMW group is working to solve the fundamental conflict between higher driving performance and concurrent lower fuel consumption. A further development of this is the BMW CleanEnergy hydrogen initiative. Unlike finite fossil energy sources, hydrogen can be generated in unlimited amounts from renewable energy sources such as solar, water, wind, or biomass. BMW is focusing on the hydrogen powered combustion engine. The speed record of 300 km/h by the hydrogen powered BMW H2R demonstrated the technical potential of this engine concept. The combustion engine can convert energy with hydrogen or with gas and therefore serves as a bridge technology.
The BMW Hydrogen 7 has a bi-fueled 12 cylinder V engine that can be powered by hydrogen or by gas. This means that even with the still insufficient hydrogen infrastructure, this car provides the expected performance of a BMW for everyday use.
The limited number of serial vehicles coincides with the limited number of filling stations for hydrogen. Due to the small amounts of hydrogen needed, hydrogen is converted from conventional energy sources. However, implementing hydrogen engines in serial vehicles creates the demand for a hydrogen supply infrastructure, which in turn creates the demand for hydrogen powered cars. Here, the BMW CleanEnergy initiative is a driving force towards using new energy sources.
BMW Hydrogen 7
The BMW Hydrogen 7 corresponds with the current BMW 7. This concept is based on tested and proven technology. The variable suction valve hub and the adjustable inlet or outlet cam shafts on both engine blocks allow unthrottled valvetronic load control. When running on gas the engine uses the gasoline direct injection and when running on hydrogen the car uses an external carburetor. In the hydrogen operating mode the engine has an engine power of 191 kW and a maximum torque of 390 Nm. The advantage of the bi-fueled model is that it can bridge the gaps which currently exist in the supply chain of hydrogen filling stations.
Hydrogen, which is highly volatile at normal temperatures, is stored in liquid form in a tank at -250C in order to achieve a sufficient energy density and cruising range. The hydrogen tank is constructed as a cryo container and its super insulation corresponds to a 17 meter thick styrofoam wall. On its way to the injection valves the hydrogen becomes gaseous in a warming process. A 168 liter tank can store 8 kg of liquid hydrogen that has the energy capacity of 30 liters of gasoline. A hydrogen driven vehicle has a cruising range of 200 kilometers and an additional 500 kilometers can be covered when the car is operated with gas.
The tank system has a separate coolant branch. The operating pressure of the tank during drive operations is maintained by the evaporation of hydrogen through heat input. The CleanEnergy tank controller controls this process. This central controller of security-relevant functions also monitors the fueling procedure and the gas concentration, as well as critical tank parameters and reactions to limit values. Further functions of the controller include the management of the on-board supply system, driver information on the system status, and communication with the service center. The controller with its comprehensive redundancy features complies with the SIL3 security level (Software Integrity Level, similar to IEC Norm 61508), which is the highest requirement class in the automobile industry.
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