The Future Heavy-duty Engine - Basic Engine Concept for Maximum CO 2 Reduction
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The Future Heavy-duty Engine – Basic Engine Concept for Maximum CO2 Reduction
Because of stricter regulations for heavy-duty commercial vehicles, a reduction in CO2 emissions from the commercial vehicle fleet of approximately 25 % by 2027 is required in the USA; in Europe the reduction has to reach 30 % by 2030. Since the internal combustion engine will continue to be the predominant drive source for heavy long-distance transport in the foreseeable future, increasing the engine efficiency must make a significant contribution to achieving the targets. Accordingly, AVL has set itself the goal of achieving a brake thermal efficiency of 50 %. 68
THERMODYNAMIC CONCEPTS
The intended engine concept is to be ready for series production by 2024 and is to be focused on base engine technol ogy without the use of waste heat re covery or hybridization [1]. However, in order to meet the requirements of future exhaust gas legislation, which will de mand significant NOx reduction under all operating conditions, it is necessary to apply Exhaust Gas Recirculation (EGR). A Brake Thermal Efficiency (BTE) of 50 % can be achieved by using several selected thermodynamic concepts. The
AUTHORS
Andreas Horvath is Lead Engineer Design Commercial Engines in the Engineering and Technology Powertrain Systems department at AVL List GmbH in Graz (Austria).
Dipl.-Ing. Hans Felix Seitz is Lead Engineer Applied Thermodynamics in the Commercial Engines Development department at AVL List GmbH in Graz (Austria).
decisive factors for achieving this goal are the efficiency of the charging system in combination with an efficient EGR sys tem, an optimized combustion process and a reduction of wall heat losses. Three basic concepts for turbocharg ing and EGR have been defined and the main features are briefly explained in the following. A detailed description of these concepts including further thermo dynamic aspects and the requirements for future exhaust gas aftertreatment systems are published in various papers [2–6]. The main components of the indi vidual concepts and their expected mod el year 2024 availability are shown in FIGURE 1. All engine concepts presented have a displacement of 13 l. Engine concept 1 comprises a singlestage turbocharging system with a high turbocharging efficiency of 70 %. Such turbocharging technology is currently not yet available for series production on heavy commercial vehicle engines, but is considered to be feasible in the future. To ensure sufficiently high EGR rates, a Low-pressure (LP) EGR system is required in addition to the High-pressure (HP) EGR system. Due to the special challenges of applying such an LP system, extensive verifica tion is required – for example concern ing effects of condensation. Engine concept 2 is also based on a single-stage turbocharging system, but combined with a serial power turbine. By using such a turbocompound system, a conventional HP EGR system can be used to generate the required EGR rates. The turbocharger efficiency of 65 % is sufficient, and suitable tu
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