Bosch Continues to Develop Direct Injection Technology for CNG Engines

A consortium led by Robert Bosch GmbH is leading efforts with partner companies to further accelerate the commercialization of direct injection technologies for dedicated CNG engines. Partners include Daimler AG and the Research Institute of Automotive Engineering and Vehicle Engines Stuttgart (FKFS). Umicore AG & Co. KG is also an associated partner. Following a resolution of the German Bundestag, Direct4Gas is supported with $4.3 million USD from the Federal Ministry for Economic Affairs and Energy as part of the “Increasing vehicle powertrain efficiency” initiative. The project started in January 2015 and will run until the end of 2017. The long-term objective of the consortium of automotive suppliers and automakers is to create the conditions needed for making the technology ready for production.

CNG vehicles today are generally bivalent, running on gasoline and CNG with engines designed for gasoline direct injection. For CNG operation, they are fitted with an additional manifold injection system for methane. “The problem with this configuration is that neither the combustion process nor the values for efficiency and emissions can be optimized. For this to happen, the CNG—like the gasoline—needs to be injected directly into the combustion chamber,” says Dr. Andreas Birkefeld, the project leader from Robert Bosch GmbH. Because methane behaves differently from gasoline when injected directly, it is important to optimize the combustion process for methane.

The Direct4Gas researchers and engineers will design samples of a direct injector that satisfies much higher standards than the manifold injection valves used up to now. It will have to be especially robust, gas-tight, and reliable, and meter the CNG very precisely. Modifications to the engine itself are to be kept to a minimum, so that the industry can continue using the same components as for gasoline engines. The project team will equip experimental gas engines with the newly developed injector, and test it in the laboratory and in vehicles. Researchers will also examine mixture formation, ignition, and exhaust-gas treatment and develop specific solutions. Direct injection will also be superior to manifold injection in the low-rpm range. As a result, the researchers estimate that direct injection will increase the amount of torque that can be delivered by as much as 60 percent. This would make the CNG engines of the future significantly more dynamic.