ISSN: 2277-3754 ISO 9001:2008 Certified International Journal of Engineering and Innovative Technology (IJEIT) Volume 3, Issue 6, December 2013 249 Abstract — The design of the powertrains for transportation on the road is even more oriented to the emission reduction. Recently, green-house gases commitments added new technological challenges. Energy recovery from exhaust gases has a great potential considering the amount of mechanical or electrical work which could be generated on board. The paper considers the recovery which could be obtained from the exhaust gases expanding them in an additional turbine (turbo compounding). An engine model has been developed and validated thanks to an extensive experimental activity which concerned the F1C Iveco engine equipped with a Variable Geometry Turbine (VGT). Two potential technologies are presented and the recovery has been calculated by the model which behaves as a virtual engine platform. Energy recoverable has been estimated referring to engine operating points which reproduce the NEDC and the ESC13 approval cycle. Index Terms—Energy, engine, ice, recovery I. INTRODUCTION Since many years the road transportation sector is facing a period of strong technological transformations aimed at reducing harmful emissions and, more recently, CO 2 emissions i.e. fuel consumption. The real technological surprise was that emission reduction has been reached without losing the expected mechanical engine performances (torque, speed, fun to drive, etc…). The results obtained were excellent: in the last two decades specific power (per unit of swept volume) increased of a factor of 1.5 while emission level of a factor of 10. The EURO limits cut emission levels progressively (and significantly) and technology followed step by step, producing cleaner and powerful engines. Recently, a new driver appeared; this is related to the CO 2 emission which is directly associated to the fuel consumption reduction. Car manufacturers introduced immediately many new technologies to limit CO 2 emissions “to the root”: downsizing, turbocharging, start and stop systems, tire pressure monitoring are just few of the measures which could achieve significant fuel savings. They are eroding the distance between actual CO 2 emissions per km (for passenger cars) and emission targets. Figure 1 shows the international commitments on CO 2 emissions for light duty vehicles and all the geographical contexts seems to converge to a common limit by 2025 close to 90 gCO 2 /km. One of the biggest challenge today to reduce co 2 emissions is energy recovery, a key sector because of the quantitative importance: exhaust gases of an internal combustion engine have an energy content equal to about one-third of the chemical energy of the fuel. Even a limited recovery of this energy into mechanical or electrical form would represent a significant contribution.[2-3] Fig 1 CO 2 emissions in different regions [1]. Energy recovery from exhaust gas has an additional advantage particularly important in the engine sector: Figure 2 reports the cost increase related to different technologies (which reduces CO2 emissions) per unit of CO2 not emitted: intervention on friction losses (oil improvement), tire rolling resistance, engine cooling and energy recovery from the exhaust gas are among the cheapest technologies, so expected to enter quickly into the market [4]. Hybridization technologies have the greatest CO2 potential reduction but at very high costs and they require a strong revision of the power train. Exhaust gas leaving cylinders has two mains energy contributions: the first is related to its pressure, the second to its temperature. Therefore, work could be recovered:  by means of a direct expansion, considering that gas pressure leaving the cylinders is greater than ambient pressure;  By means of a heat recovery, being the gas temperature higher than ambient temperature. Heat recovered produces the vaporization of a high pressure organic fluid which expands and produces work inside a proper expander. The fluid is, then, condensed and pressurized, realizing a thermodynamic cycle (ORC, Organic Rankine Cycle) [5-6]. Turbo compound systems to recover energy in ICE R. Cipollone, D. Di Battista, A. Gualtieri