Lean combustion methods can reduce both consumption and also CO2 emissions. "But ignition is more difficult here", explains Michael Günther, head of the Advance Engineering for Gasoline Engine Thermodynamics department at IAV. "We therefore have to shift the ignition limit from lambda values between 0.7 and 1.5 to lambda values between 2 and 2.5."
Ignition systems therefore need to make a leap in technology, following around 130 years in which little has happened in this field. Initial attempts are already being made, such as a new actuation method with constant current sources to give the spark a longer life. One important topic at the conference was corona ignition, which IAV has been looking at for years now and which could reach manufacturing readiness at BMW in the near future. Here a high-frequency field heats electrons that ignite the mixture as "cold plasma". The advantage of the method is that it shortens the combustion delay to allow for later ignition. This enhances the ignition performance of lean mixtures.
Microwave-enhanced laser ignition is still at the research stage. Here, microwaves enlarge the hot focus point of a laser in the mixture, making it easier to inflame mixtures that are difficult to ignite. Some development engineers in Asia are pursuing an unusual approach: they are looking at eight-fold ignition in the cylinder head gasket in combination with the conventional spark plug to generate many ignition points, resulting in faster combustion.
Another method featured at the conference consists of measuring the ion current across the spark plug, making it possible to monitor the intensity of combustion and to detect misfiring. "Ignition has once again become an exciting field", summarizes Günther. "There is meanwhile a global community looking into this subject which comes together at our conference every two years." In 2018 the experts will be meeting again to share their latest thoughts in the search for "igniting" ideas.