Thermal efficiency improvement in high output diesel engines a comparison of a Rankine cycle with turbo-compounding

Abstract

Thermal management, in particular, heat recovery and utilisation in internal combustion engines result in improved fuel economy, reduced emissions, fast warm up and optimized cylinder head temperatures. Turbocompounding is a heat recovery technique that has been successfully used in medium and large scale engines. Heat recovery to a secondary fluid and expansion is used in large scale engines, such as in power plants in the form of heat recovery steam generators(HRSG) [1]. The present paper presents a thermodynamic analysis of turbocompounding and heat recovery and utilisation through a fluid power cycle, a technique that is also applicable to medium and small scale engines. In a fluid power cycle, the working fluid is stored in a reservoir and expanded subsequently. The reservoir acts as an energy buffer that improves the overall efficiency, significantly. This paper highlights the relative advantage of exhaust heat secondary power cycles over turbocompounding with the aid of MATLAB based QSS Toolbox [2] simulation results. Steam has been selected as the working fluid in this work for its superior heat capacity over organic fluids and gases.

A Challenging Future for the IC Engine: New Technologies and the Control Role

“…The power turbine is placed in the exhaust line and is mechanically coupled to the engine crankshaft via a gear train; -electrical turbocompounding, which consists of an electric motor/generator coupled to a turbocharger [55,56]. The generator extracts surplus power from the turbine, and the electricity produced is used to run a motor assembled/fitted to the engine crankshaft; -thermoelectric materials installed in the exhaust pipe, thus providing at least some of the powertrain electric power requirements [57,58]; -Rankine cycle, where the steam is generated from the thermal energy in the exhaust gases.…”

Thermal Management as a Force Multiplier within the Research, Development, and Engineering Command (RDECOM)

“…These efficiencies are significantly higher than those available from thermoelectrics in a similar temperature range; however, organic Rankine systems are complicated, with many moving parts, and therefore are best suited to moderate scale applications where kW's or more power is desired. Detailed models have been developed in the literature to analyze potential coupling of organic Rankine engines with thermoelectric generators for combined thermal-to-power systems with high efficiency (figure 4) (19,20). Considering the options discussed previously, the highest impact research areas in the short term definitely reside in the development of new thermoelectric materials showing a of ~1-2, the commercialization of high temperature materials and devices, as well as improved engineering and packaging of thermoelectric modules and systems to reduce parasitics and enable scale-up to the appropriate level.…”

Improved Thermoelectric Generator Performance Using High Temperature Thermoelectric Materials

“…There are multiple choices of technologies for waste thermal energy recovery in automotive applications. Among them there are Mechanical Turbo-Compounding (MTC) , electrical turbo-compounding (ETC), Thermoelectric Generator (TEG) and Organic Rankine Cycle (ORC) [1][2][3][4][5]. Each technique has its own advantages and disadvantages.…”