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Increasing the efficiency of internal combustion engines while keeping the power density is a tremendous challenge. Work extraction from the exhaust flow which is wasted to environment is one possible solution to increase both power density and efficiency. In this study, the behavior of pulsating exhaust flow, as characterized by maximum pressure as well as maximum available work (exergy), are investigated to design a suitable exhaust expander to harness this exhaust exergy. However, the cyclic variation of exhaust flow is a challenge as this can seriously impact the ability to directly harness the available exhaust energy. In this poster, we attempt to estimate the exergy of the exhaust pulse. The experiments were performed on a single cylinder research engine at 1500 RPM, 5 and 2.5 bar BMEP with different boost pressures. A GT-power model is constructed to estimate instantaneous exhaust temperatures and mass flow rates and the model is validated against measured cylinder pressure and apparent heat release rate. A piezoresistive exhaust sensor is used to measure instantaneous exhaust pressures over 1000 engine cycles at various engine speeds, loads and intake charge pressures. The exergy of the exhaust pulse is estimated from one engine cycle to another and further analysis is conducted to separate out the pressure and temperature components of the exhaust exergy. We anticipate this analysis to lead to better designs of expanders that can be used for direct exhaust waste energy recovery.

A detailed second law analysis of dual fuel LTC is not yet available in the open literature even though dual fuel low temperature combustion (LTC) has been studied before. To address this gap, a previously validated, closed-cycle, multi-zone, simulation of diesel-natural gas dual fuel LTC was used to perform a second law analysis. In the current study, a 2.4-liter single-cylinder research engine operating at a nominal load of 6 bar BMEP and 1700 rpm was used. Zone-wise thermodynamic irreversibilities as well as total cumulative entropy generated and lost available work over the closed cycle were quantified. Subsequently, two convenient second-law parameters were defined: (1) the "lost available indicated mean effective pressure" (LAIMEP), which can be interpreted as an engine-size-normalized measure of available work that is lost due to thermodynamic irreversibilities (analogous to the relationship between indicated mean effective pressure and indicated work); (2) fuel conversion irreversibility (FCI), which is defined as the ratio of lost available work to total fuel chemical energy input. Finally, parametric studies were performed to quantify the effects of diesel start of injection, intake manifold temperature, and intake boost pressure on LAIMEP and FCI. The results show that significant entropy generation occurred in the flame zone (52-61 percent) and the burned zone (31-39 percent) while packets account for less than 6 percent of the overall irreversibilities. Parametric studies showed LAIMEPs in the range of 645-768 kPa and FCIs in the range of 32.8-39.2 percent at different engine operating conditions. Although the present study focused on dual fuel LTC, the conceptual definitions of LAIMEP and FCI are generally applicable for comparing the thermodynamic irreversibilities of IC engines of any size and operating on any combustion strategy