Future Diesel Engines

Abstract

This chapter provides a survey of technology trends expected in future diesel engines. Although diesel engines have dramatically changed over the years, the basic qualities that initially made these engines desirable remain the same: fuel economy, performance, reliability, and durability. Performance, reliability, and durability have seen big advances, but perhaps one of the largest changes in the modern diesel engines is the addition of sociability as a key driver and the introduction of diesel exhaust aftertreatment as a result. Requirements on fuel efficiency and emissions are motivated by global economic and environmental implications of the use of fossil fuels. These technology-forcing-factors are expected to play crucial roles in developing future engines as well. Irrespective of the geographic region, engine manufacturers will have to seek an integrated perspective and significant advancements in the fuel quality and subsystems dealing with air handling, fuel systems, combustion, controls and exhaust aftertreatment are expected. There is an increasing trend to move towards cleaner combustion strategies that can significantly reduce the levels of emissions within the cylinder itself by operating in non-traditional diesel engine operating regimes or by controlling fuel composition. The quest for alternative energy sources for diesel engines is expected to continue for reasons of energy independence, emissions reduction, fuel efficiency and GHG reduction. Use of natural gas and biofuels produced from indigenous options are being actively pursued. Hybridization of diesel is in early stages and is continued to be a key enabler for GHG and emissions reduction, as well as fuel efficiency. High pressure common rail injection with precise control of number of pulses and duration, and flexible control of injection rate shaping are being developed, and it is expected that optimization of nozzle design and ECU control strategies will complement these developments. Challenges lie in ensuring fuel quality and in sensors and control systems development. High efficiency aftertreatment systems that integrate oxidation catalysts, wall-flow DPFs, de-NOx catalysts, HC and DEF injectors as well as sensors and closed loop controls are being pursued. Devices with combined functionalities (such as SCR-F) are particularly interesting. For today’s engines, aftertreatment integration and optimization is as critical and complex as turbocharger mapping and fuel injector tuning. The development of intake charge filtration systems will be motivated by need to improve filtration capacity, efficiency and pressure drop reduction. Use of Organic Rankine cycle and electric turbo-compounding are promising for waste energy recovery. Though turbocharger and EGR technologies have reached relative maturity, their optimum integration will be crucial in view of incorporation of advanced combustion, after-treatment and waste heat recovery technologies.