The Thermodynamics of Internal Combustion Engines: Examples of Insights

Abstract

A major goal of the development of internal combustion (IC) engines continues to be higher performance and efficiencies. A major aspect of achieving higher performance and efficiencies is based on fundamental thermodynamics. Both the first and second laws of thermodynamics provide strategies for and limits to the thermal efficiencies of engines. The current work provides three examples of the insights that thermodynamics provides to the performance and efficiencies of an IC engine. The first example evaluates low heat rejection engine concepts, and, based on thermodynamics, demonstrates the difficulty of this concept for increasing efficiencies. The second example compares and contrasts the thermodynamics associated with external and internal exhaust gas dilution. Finally, the third example starts with a discussion of the Otto cycle analysis and explains why this is an incorrect model for the IC engine. An important thermodynamic property that is responsible for many of the observed effects is specific heat.

Investigating the Effects of C3 and C4 Alcohol Blending on Ignition Quality of Gasoline Fuels

“…In many recent studies, , gasoline blends with ethanol have shown increased ignition delay time. For gasoline engines, a higher-ON fuel is essential to reduce engine knock. ,, A higher IDT, corresponding to a higher RON and IDT-RON/MON, was observed to demonstrate a direct relation, as shown in a recent study …”

“…For years, SI engine development to increase thermal efficiency has been impeded by engine knockthe auto-ignition of the fuel–air mixture ahead of the flame front that creates unstable pressure waves and the potential for engine damage . Blending simple alcohols with gasoline offers multiple advantages for SI engines, including reducing the severity of gasoline fuel emissions. ,, Simple alcohols, such as methanol, ethanol, n -propanol, and n -butanol, exhibit high latent heat of vaporization compared to gasoline-type fuels .…”

Chemothermally Driven Out‐of‐Equilibrium Materials for Macroscopic Motion

“…To closely mimic biology, it is desirable to use chemical fuels in synthetic out‐of‐equilibrium systems. Additionally, chemical fuels are commonly used in general applications such as combustion engines, [14] and fuel cells due to the low‐cost, convenience and high‐power density [15] . Several elegant approaches have been reported for chemically driven out‐of‐equilibrium systems using various chemical fuels such as alkylating agents, [16] carbodiimides, [17,18] thioesters, [19] ATP, [20–22] urea, [23] redox agents, [24,25] and nucleic acids [26,27] .…”

Development of a three-zone combustion model for stratified-charge spark-ignition engine

“…The work [19] uses the thermodynamic method, in particular, to calculate an ideal operating cycle of the SI engine according to the one-zone model, which does not take into account heat transfer during internal mixture formation.…”