Targeted Steps on the Way to the Optimum Powertrain

April 26, 2016 // Powertrain synthesis and thermal energy recovery: Engineering partner IAV is focusing on these two topics at the 37th International Vienna Engine Symposium on April 28 and 29.

Berlin. At the Vienna Engine Symposium, the company is presenting its unique methodology for identifying the optimum powertrain from millions of available options. The booth is also showcasing the prototype of a reciprocating steam expander for commercial vehicles that uses the Organic Rankine Cycle (ORC) and is capable of cutting fuel consumption by no less than five percent.

IAV Powertrain Synthesis – New Approaches to Complex Challenges

Low CO2 emissions, high mileage and brand-typical ride comfort – these are just some of the demands OEMs need to consider in developing new vehicles. A key part of all this is played by the powertrain which must be decided upon at an early stage in the development process. Yet today it is no longer sufficient to optimize the engine, transmission or e-motor in isolation of each other: The high level of complexity of modern powertrains demands an integrated development process. 

“IAV Powertrain Synthesis is a methodology that is capable of identifying the global optimum for any vehicle and fleet application from a large number of options. All scenarios and propulsion configurations of combustion engines, transmissions, e-motors, power electronics, batteries, operating strategies, vehicles and topologies are channeled into the synthesis and variation process,” says Wolfgang Wukisiewitsch, Senior Vice President for Engine and Transmission Development at IAV. Depending on the case in hand, detailed cycle, mileage and cost computations can be conducted and automatically evaluated for several million options. This culminates in a clear recommendation for the optimum solution under given boundary conditions. 

The new methodology is primarily aimed at system architects and decision-makers with overarching responsibility for fleet targets and demands as well as at heads in charge of powertrain development – in other words, at all experts making fundamental strategy decisions beyond the level of individual components.

Recovering Heat to Save Fuel

Ever tighter CO2 fleet ceilings and demands for the lowest possible total cost of ownership in the commercial-vehicle segment are making technologies for recovering waste heat more and more attractive. “Particularly promising is the Organic Rankine Cycle (ORC) in which a steam-operated engine runs on a working medium other than water. It promises the best cost-benefit ratio because ORC attains a relatively high level of efficiency at comparatively low exhaust gas temperatures”, says Oliver Dingel, Senior Consultant for Energy Management at IAV. “Commercial-vehicle manufacturers in particular are taking a very close look at ORC and other technologies for recovering exhaust heat”.

In Vienna, IAV is showing the prototype of a reciprocating steam expander for commercial vehicles. It uses climate-friendly ethanol and has demonstrated its performance and reliability over a period of several hundreds of hours on the test bench. The steam expander reaches maximum efficiency of 13 percent and delivers up to twelve kilowatts of power. It weighs in at a mere 16.3 kilograms and can be manufactured at low cost in volume production on account of its simple configuration. Measurements have shown it is capable of reducing a commercial vehicle’s fuel consumption by as much as five percent. This means the additional cost of the system pays for itself in as little as two years or so.

Besides the reciprocal steam expander and other components, such as a constant-pressure turbine and exhaust gas heat exchangers, IAV has also developed operating and control strategies that ensure reliable operation from the complex steam cycle. Connected to an ORC cycle, they have been tested and optimized on a dynamic test bench in the commercial-vehicle engine. In the meantime, the technology is so advanced that it could be developed straight away for application in volume production, with the market seeing initial commercial vehicles using a fuel-saving ORC expander in around three years at the latest.