External Exhaust Gas Recirculation Research Articles

Scalar dissipation rate based multi-zone model for early-injected and conventional diesel engine combustion

Low-temperature combustion (LTC) concepts, such as Homogeneous Charge Compression Ignition (HCCI) or Premixed-Charge Compression Ignition (PCCI), have the potential of simultaneous reducing nitrogen oxides (NOx), soot, and unburned hydrocarbons (uHC). However, the successful implementation for internal combustion engines is difficult. Control strategies need to be employed to ensure appropriate combustion phasing over wide ranges of operating conditions. Model-based engine control is particularly successful when physics-based models are employed. Multi-zone combustion models represent potential candidates for efficiently computing combustion in PCCI diesel engines. Multi-zone models were originally developed for HCCI gasoline engine combustion and did not account for mixing between zones due to the relatively homogeneous mixture while later developments considered small inhomogeneities. However, for diesel or PCCI combustion, this is not justified due to noticeable fuel stratification. Therefore, a novel mixing model for multi-zone modeling accounting for mass and energy exchange between zones is presented in this work. The model is derived from the representative interactive flamelet (RIF) model and thus depends on the scalar dissipation rate as well as the mixture fraction in each zone. The multi-zone model can be used as a stand-alone model after performing a number of non-reactive computational fluid dynamics (CFD) simulations to train an empirical, engine-specific model for the scalar dissipation rate. With the stand-alone model, cost-efficient parameter studies can be performed, with further model reduction, the use in model-based control algorithms is also possible. For validation of the stand-alone multi-zone model, experiments were conducted with a four-cylinder diesel engine. 105 operation conditions including variations in start of injection (SOI), injected fuel mass (FMI), and external exhaust gas recirculation (EGR) were selected to assess the model performance. CFD simulations applying the RIF model were carried out for representative cases to further assist in validating and analyzing the new multi-zone model. Predictions of the multi-zone model regarding indicated mean effective pressure (IMEP), combustion phasing (CA50), and emissions of nitrogen monoxide as well as unburned hydrocarbons are compared against experimental data and results from numerical simulations. Overall good agreement over various operating conditions was found demonstrating the capability of the multi-zone model to adequately capture PCCI diesel engine combustion.

Development of a Miller cycle engine with single-stage boosting and cooled external exhaust gas recirculation

In this paper, the development of a Miller cycle gasoline engine which has a high compression ratio from 11.5:1 to 12.5:1, single-stage turbocharging and external cooled exhaust gas recirculation is described. The improvement in the fuel economy by adding external cooled exhaust gas recirculation to the Miller cycle engine at different geometric compression ratios were experimentally evaluated in part-load operating conditions. The potential of adding external cooled exhaust gas recirculation in full-load conditions to mitigate pre-ignition in order to allow higher geometric compression ratios to be utilized was also assessed. An average of 3.2% additional improvement in the fuel economy was achieved by adding external cooled exhaust gas recirculation to the Miller cycle engine at a geometric compression ratio of 11.5:1. It was also demonstrated that the fuel consumption of the engine with external cooled exhaust gas recirculation was reduced by 3–7% in a wide range of part-load operating conditions and that the engine output of the Miller cycle engine at a geometric compression ratio of 12.5:1 increased at 2000 r/min in the full-load condition. The Miller cycle engine with external cooled exhaust gas recirculation at a geometric compression ratio of 12.5:1 achieved a broad brake specific fuel consumption range of 220 g/kW h or lower, with the lowest brake specific fuel consumption of 215 g/kW h. While there are still challenges in implementing external cooled exhaust gas recirculation, the Miller cycle engine with single-stage turbocharging and external cooled exhaust gas recirculation showed its potential for substantial improvement in the fuel economy as one of the technical pathways to meet future requirements in reducing carbon dioxide emissions.

Experimental Study on HCCI Combustion in a Small Engine with Various Fuels and EGR

ABSTRACTBecause Asian countries have a large number of motorcycles, motorcycle engine exhaust emission poses a major problem in the region. Homogeneous charge compression ignition (HCCI) is a promising combustion technology with high efficiency and low nitrogen oxide emission. This study investigated the combustion characteristics of HCCI in a 150 cc motorcycle engine with three types of dual fuel. The main fuels consisted of dimethyl ether (DME), kerosene, and n-heptane, and gasoline was the additive fuel. External exhaust gas recirculation (EGR) was used to expand the operating range of the engine. All test points were executed under stable HCCI operation with a coefficient of variation 0.9. The findings suggest that adjusting the CA50 to a value greater than 5° after top dead center, or limiting the maximum cylinder pressure to < 50 bar is crucial to preventing excessive pressure rising. Overall, kerosene was deemed unsuitable for engines because of its high sulfur content, whereas DME is considered an excellent option.

Controlled SSCI With Moderate End-Gas Auto-Ignition for Fuel Economy Improvement and Knock Suppression

Hybrid combustion mode including flame propagation induced by spark ignition (SI) and auto-ignition could be an effective method to improve fuel economy and suppress engine knock simultaneously. An experimental research on controlled spark-assisted stratified compression ignition (SSCI) for this purpose was conducted in a gasoline direct injection (GDI) engine with high compression ratio. At wide open throttle (WOT) and minimum spark advance for best torque (MBT) condition without turbocharging, direct injection was used to form desired stoichiometric stratified mixture while 20% cooled external exhaust gas recirculation (e-EGR) was sucked into the cylinder. The combustion characteristics of controlled SSCI show two-stage heat release, where the first stage is caused by SI and the second stage is due to moderate auto-ignition. Compared with engine knock, the second stage heat release of controlled SSCI shows smooth pressure curve without pressure oscillation. This is due to the low energy density mixture around the cylinder wall caused by cooled e-EGR. The stratified mixture could suppress knock. Fuel economy and combustion characteristics of the baseline and the controlled SSCI combustion were compared. The baseline GDI engine reaches a maximum of 8.9 bar brake mean effective pressure (BMEP) with brake specific fuel consumption (BSFC) of 291 g/(kWh), and the controlled SSCI combustion achieves a maximum of 8.3 bar BMEP with BSFC of 256 g/(kWh), improving the fuel economy over 12% while maintaining approximately the same power. The results show that controlled SSCI with two-stage heat releases is a potential combustion strategy to suppress engine knock while achieving high efficiency of the high compression ratio gasoline engine.

A study on combustion control and operating range expansion of gasoline HCCI

Because of the combustion principle of a gasoline HCCI (homogeneous charge compression ignition) engine, the operating range is limited within a narrow area. The objectives of this study were to extend the operating range of gasoline HCCI combustion and to develop control logic. To extend the high load operating range, several strategies including external EGR (exhaust gas recirculation), EGR stratification, fuel stratification and valve timing swing were adopted. Among these strategies, EGR stratification, asymmetric injection and open valve injection are novel techniques. The high load boundary of the low speed region was improved more than that of the high speed region. The improvement in the low load boundary was due to the direct injection during negative valve overlap. In terms of stabilizing the HCCI combustion phase, the peak pressure value and pressure rising rate of a cycle were important factors when considering the ringing intensity equation. Coefficient of variation of combustion was also used to judge the stabilization of the combustion. In this study, using these variables, the engine was controlled within the maps which were determined from the experiment. The indicated mean effective pressure calculated from real-time data followed the target load successfully without severe problems.

Experimental study on partially premixed compression ignition combustion fueled with a low octane number primary reference fuel using two-stage fuel supplying

An experimental study of partially premixed compression ignition combustion with low octane fuel was conducted on a single-cylinder engine. The effects of the external exhaust gas recirculation and intake boost on this partially premixed compression ignition combustion and emissions were investigated. During the experiments, a trade-off relationship between the NOx and smoke emissions was observed in this partially premixed compression ignition combustion. However, heavy exhaust gas recirculation usage has the potential to decrease NOx and soot emissions simultaneously at the expense of the fuel economy. It is determined that at an increased intake port pressure, the maximum in-cylinder pressure increases, and the ignition timing of the high-temperature combustion is retarded. Also, the peak value of the low-temperature combustion is slightly depressed, the peak value of the high-temperature heat release decreases significantly, and the maximum value of the diffusing burn increases to some extent. Compared to natural aspirated condition, the partially premixed compression ignition combustion with intake boost has the capability of simultaneously reducing NOx and soot emissions to ultra-low levels, that is, the intake boost could be an important strategy for the combustion and emission improvement in this advanced engine combustion mode.

Water injection for gasoline engines: Potentials, challenges, and solutions

Further significant CO2 emission reduction beyond 2020 is mandatory in the United States and might also become mandatory in Europe, depending on the passenger car CO2 legislation, which is to be enacted. Hybrid and plug-in hybrid vehicles might account for a big portion of these CO2 reductions as a consequence of the favourable current legislative treatment which does not associate CO2 emissions from electric power generation with vehicle CO2 emissions. Nevertheless, these powertrains benefit from a highly efficient combustion engine. Exhaust heat recovery poses new synergetic possibilities for technologies to mitigate knock like cooled external exhaust gas recirculation and condensed water injection. The condensed water injection concept, which is proposed in this article, demonstrates a potential for efficiency increase of 3.3% – 3.8% in the region of the minimum specific fuel consumption on a stoichiometric combustion concept with Miller cycle and cooled external exhaust gas recirculation. Further improvement of the efficiency of up to 16% is possible at full-load operation. If water injection is used in addition to homogeneous lean combustion, an efficiency gain of 4.5% in the region of the minimum specific fuel consumption is achieved.

INFLUENCE OF HOT BURNED GAS UTILIZATION ON THE EXHAUST EMISSION CHARACTERISTICS OF A CONTROLLED AUTO-IGNITION TWO-STROKE CYCLE ENGINE

A controlled auto-ignition (CAI) two-stroke cycle engine suggests an exceptional aspect and promising future for internal combustion engines (ICEs), such as a higher power-toweight ratio, higher combustion efficiency and lower exhaust gas emissions. Conventional two-stroke cycle engines emit higher exhaust gas emissions and offer lower fuel saving economy. Most of these drawbacks can be addressed if CAI combustion is associated with a two-stroke cycle engine. An experimental investigation is carried out based on a single-cylinder CAI two-stroke cycle engine using Internal and External Exhaust Gas Recirculation (In-EGR and Ex-EGR) and fuels with different octane numbers to investigate the exhaust emissions characteristics. The experimental results indicate a remarkable improvement in the engine's exhaust gas emissions. The concentration of uHC and CO emissions decreased with application of In/Ex-EGR. However, NOx emission increased with the use of In-EGR

Characterizing dilute combustion instabilities in a multi-cylinder spark-ignited engine using symbolic analysis.

Spark-ignited internal combustion engines have evolved considerably in recent years in response to increasingly stringent regulations for emissions and fuel economy. One new advanced engine strategy ustilizes high levels of exhaust gas recirculation (EGR) to reduce combustion temperatures, thereby increasing thermodynamic efficiency and reducing nitrogen oxide emissions. While this strategy can be highly effective, it also poses major control and design challenges due to the large combustion oscillations that develop at sufficiently high EGR levels. Previous research has documented that combustion instabilities can propagate between successive engine cycles in individual cylinders via self-generated feedback of reactive species and thermal energy in the retained residual exhaust gases. In this work, we use symbolic analysis to characterize multi-cylinder combustion oscillations in an experimental engine operating with external EGR. At low levels of EGR, intra-cylinder oscillations are clearly visible and appear to be associated with brief, intermittent coupling among cylinders. As EGR is increased further, a point is reached where all four cylinders lock almost completely in phase and alternate simultaneously between two distinct bi-stable combustion states. From a practical perspective, it is important to understand the causes of this phenomenon and develop diagnostics that might be applied to ameliorate its effects. We demonstrate here that two approaches for symbolizing the engine combustion measurements can provide useful probes for characterizing these instabilities.

Investigations into the influence of internal and external exhaust gas recirculation on the combustion stability in an optical gasoline spark ignition engine

Combustion stability is the major concern for engines operated in highly diluted conditions, particularly during the mode transition between controlled autoignition and spark ignition. In this research, studies were performed to investigate the influence of the dilution of internal exhaust gas recirculation and the dilution of external exhaust gas recirculation on early flame development and combustion stability in a single-cylinder optical engine. It is found that a higher external exhaust gas recirculation rate slows do‘wn the early flame development, which is responsible for the higher cyclic fluctuation of combustion. The cyclic variation in the normalized flame area matches well the coefficient of variation of the early flame development period, which decreases with development of the flame. The dilution of the internal exhaust gas recirculation shows a more complicated influence on the combustion than the dilution of the external exhaust gas recirculation does. Although more hot residual gas is trapped in the cylinder, the increase in the internal exhaust gas recirculation rate does not contribute to the promotion of the in-cylinder thermal state in the studied cases. However, with a moderate increase in the internal exhaust gas recirculation rate from 9.8% to 13%, faster initial flame kernel formation is observed, which benefits the combustion by accelerating the early flame development, advancing the combustion timing and stabilizing the combustion. With the internal exhaust gas recirculation rate further increased to 19.6%, a sharp decrease in the mean expansion speed of the flame front results in a retarded early flame development and a slower heat release, which leads to severe deterioration in the combustion stability. In addition, by substituting part of the external exhaust gas recirculation with internal exhaust gas recirculation, an advanced combustion timing, a shorter combustion duration and an improved combustion stability can be achieved; this implies that a higher total exhaust gas recirculation tolerance can be achieved with the same limitation of the coefficient of variation in the indicated mean effective pressure. This result can be instructive in optimizing the control strategy of the valve timing and the external exhaust gas recirculation rate during the mode transition between controlled autoignition and spark ignition.

A thermodynamic comparison of external and internal exhaust gas dilution for high-efficiency internal combustion engines

The use of exhaust gases for creating dilute mixtures for internal combustion engines has been shown to play an important role for the development of high-efficiency engines. These exhaust gases may be recirculated with external piping, or they may be retained in the cylinder by altering the valve timings. A thermodynamic cycle simulation was used to determine the thermodynamic advantages and disadvantages of external and internal methods of providing the exhaust gases for an automotive engine at constant load and speed. For the external exhaust gas recirculation, four (4) levels of cooling were examined, and for the internal exhaust gas recirculation, the use of negative valve overlap and delayed exhaust valve closing were assessed. A measure of the total amount of recirculated and retained exhaust gases is the burned gas percentage. In general, the thermal efficiencies decreased for most of these methods as the burned gas percentage increased. These decreases were due to increased cylinder heat transfer (in spite of the decreases in the gas temperatures) which was due to increases in the convective heat transfer coefficient. For the highly cooled external exhaust gas recirculation configuration, a slight increase in the thermal efficiencies was obtained, but this level of cooling might not be practical.

Effect of Exhaust Gas Recirculation in NOx Control for Compression Ignition and Homogeneous Charge Compression Ignition Engines

Abstract Exhaust Gas Recirculation (EGR) is a potential option for controlling in-cylinder NOx in automobiles. This paper aims to study the effect of EGR on NOx emissions and in Compression Ignition (CI) engines at various conditions. To this end, low dimensional models are developed using a first principles approach without recourse to empirics. Fuel oxidation represented by a three-step global kinetic model coupled with the Zeldovich mechanism for NOx formation is used to predict the composition of the entire spectrum of engine-out gases. Solution of the conservation equations using MATLAB provides the in-cylinder variation of parameters like volume, pressure, torque, speed and work done and species (Fuel, CO, CO 2 , NO X , etc.) with respect to Crank Angle Displacement (CAD). The inlet conditions are the fuel-air equivalence ratio, engine specifications and the inlet air temperature. The simulations are validated against experimental pressure profiles from the literature. External EGR is then implemented to study its effect on engine-out emissions under cold start conditions. The effect of EGR at various combinations of engine operating conditions is examined in detail.

EXHAUST GAS DOSE UNIFORMITY IN MODERN DIESEL ENGINES

Currently, the environment protection challenges the designers and manufacturers of combustion engines due to the fact that the engine emits toxic compounds, which are hazardous to the life organisms. Increasingly strict regulations concerning emission of the exhaust gases forces application of the innovative technologies or improvement of the presently used. One of systems, which reduce the toxicity of the exhaust gases, is the Exhaust Gas Recirculation (EGR) system. This solution reverse part of the exhaust gases back into the manifold and mixes it with fresh inlet air. In consequence, the combustion temperature decreases. Less oxygen reacts with nitrogen and more connects with carbon and hydrogen. Presently there are two types of EGR system i.e. internal and external. In case of the first one part of the exhaust gases remains in the combustion chamber after the combustion but its construction is not complicated. The external EGR system uses one valve of the exhaust gas recirculation system located on the manifold. This location can result of the uneven portion of exhaust gases directed to the combustion chamber. In consequence, the decrease on the temperature is also uneven and therefore different portion of nitrogen oxide in the exhaust gases.

Closed-loop control of HCCI combustion for DME using external EGR and rebreathed EGR to reduce pressure-rise rate with combustion-phasing retard

This study experimentally investigates the effects of the combustion phasing on the homogeneous charge compression ignition (HCCI) combustion, and implements a closed-loop control of HCCI combustion to reduce pressure-rise rate (PRR) with combustion-phasing retard. The experiments were conducted using dimethyl ether (DME) in a single-cylinder HCCI research engine equipped with an exhaust gas recirculation (EGR) loop for external EGR and a two-stage exhaust cam for rebreathed EGR. The results show that a maximum PRR (PRRmax) and a maximum in-cylinder charge temperature decreases with combustion-phasing retard. However, excessive combustion-phasing retard leads to unacceptable coefficient of variation (COV) of CA50 and IMEP with partial-burn and/or misfire cycles. To dampen increasing cycle-to-cycle variations around the limit of combustion-phasing retard, the closed-loop control of HCCI combustion was implemented using three feedback variables. Finally, stable stoichiometric HCCI operation could be achieved with extensive combustion-phasing retard while maintaining acceptable PRRmax with the higher level of IMEP.

Combined Effects of Late IVC and EGR on Low-load Diesel Combustion

The increasing demand for improved efficiency of diesel engines requires more advanced combustion solutions. These solutions include the use of variable valve timings in combination with more traditional methods such as EGR, turbocharging and advanced injection systems. By modifying the characteristics of the charge air, further hardware optimization becomes possible. In the current investigation, the effect of late intake valve closing (LIVC) was investigated together with the effect of (external) exhaust gas recirculation (EGR) in a single cylinder heavy duty diesel engine. Different injection timings and injection pressures were investigated. The mass flow of oxygen was kept constant in order to show how the density and temperature of the reactant mixture affect the combustion and emission characteristics. The combustion results showed that if the oxygen mass flow is kept constant, an EGR approach is more efficient than LIVC in lowering fuel consumption due to the effects of increased cylinder gas flow which improves fuel conversion efficiency. It was shown that the ignition delay for a fixed combustion phasing was independent of EGR but could be increased by LIVC. The peak pressure was more strongly affected by EGR due to the larger gas flow but this response can be reduced by means of LIVC. After compensating for combustion timing effects, the reduced peak pressure was mainly attributed to reduced effective compression ratio resulting from the LIVC. The results show how variable valve timing can be used as one important tool to obtain better combustion characteristics and thus enable more efficient powertrains.

A Converted Two-Stroke Cycle Engine for Compression Ignition Combustion

A new kind of alternative combustion concept that has attracted attention intensively in recent years is called controlled auto-ignition (CAI) combustion. CAI combustion has been proposed and partially implemented with the aim of both improving the thermal efficiency of internal combustion engines, achieving cleaner exhaust emissions and lower cyclic variation. An experimental study is conducted through a CAI two-stroke cycle engine in order to investigate the influence of internal exhaust gas recirculation (In-EGR) and external exhaust gas recirculation (Ex-EGR) variation in relation to combustion cyclic variability and exhaust emissions characteristics. Results implied that cyclic variation of both combustion-related and pressure-related parameter is substantially improved. Furthermore remarkable decreased exhaust emissions, unburned hydrocarbon (uHC), carbon monoxide (CO) and nitric dioxide (NOX), was observed.

Experimental investigation of the influence of internal and external EGR on the combustion characteristics of a controlled auto-ignition two-stroke cycle engine

A two-stroke cycle engine incorporated with a controlled auto-ignition combustion approach presents a high thermodynamic efficiency, ultra-low exhaust emissions and high power-to-weight ratio features for future demand of prime movers. The start of auto-ignition, control of the auto-ignition and its cyclic variability, are major concerns that should be addressed in the combustion timing control of controlled auto-ignition engines. Several studies have been performed to examine the effect of internal exhaust gas recirculation utilization on auto-ignited two-stroke cycle engines. However, far too little attention has been devoted to study on the influence of external exhaust gas recirculation on the cyclic variation and the combustion characteristics of controlled auto-ignition two-stroke cycle engines. The purpose of this study is to examine the influence of external exhaust gas recirculation in combination with internal exhaust gas recirculation on the combustion characteristics and the cyclic variability of a controlled auto-ignition two-stroke engine using fuel with different octane numbers. In a detailed experimental investigation, the combustion-related and pressure-related parameters of the engine are examined and statistically associated with the coefficient of variation and the standard deviation. The outcomes of the investigation indicates that the most influential controlled auto-ignition combustion phasing parameters can be managed appropriately via regulating the internal and external exhaust gas recirculation and fuel octane number. In general, start of auto-ignition and its cyclic variability are predominantly affected by external exhaust gas recirculation variation rather than internal exhaust gas recirculation. Furthermore, although the magnitude of low temperature heat release is substantially influenced by external exhaust gas recirculation variation, timing of low temperature heat release is more influenced by internal exhaust gas recirculation approach.

The effect of diluent composition on homogeneous charge compression ignition auto-ignition and combustion duration

In this work, the effect of diluent composition is studied on the ignition timing and combustion duration of homogeneous charge compression ignition (HCCI) combustion. Full-cycle 3-D computational fluid dynamics (CFD) simulations were performed using two different dilution schemes, one which employs air dilution and the other which employs external exhaust gas recirculation (eEGR) dilution. Both cases used a fixed breathing strategy, and had the same fueling rate and engine speed typical of automotive applications. A premixed fuel–air mixture was used in the intake charge to avoid the fuel stratification effects associated with direct injection, while the valve events were selected to minimize the internal residual and its associated thermal and compositional stratification. With ignition timing held constant near top dead center (TDC) for both methods, there is a 10% increase in the combustion duration going from air to eEGR dilution. While the thermal stratification prior to ignition is similar for both methods, the eEGR-dilute case has an overall higher temperature throughout the charge. A reactivity stratification analysis, based on the distribution of ignition delays within the charge prior to ignition, showed nearly identical initial reactivity for the two methods, with the higher temperatures of the eEGR case compensating for this method’s lower oxygen content. A quasi-dimensional multi-zone model was subsequently used to decouple the chemical kinetic and thermodynamic effects of eEGR on the combustion process. This analysis showed that the primary factor contributing to the longer combustion duration for the eEGR-dilute case is the lower ratio of specific heats (γ) in the unburned charge post-ignition which is thought to lower the rate of compression-induced heating of the unburned charge by the ignited and burning regions, leading to slower sequential auto-ignition.

Combustion and emission characteristics of a DME (dimethyl ether)-diesel dual fuel premixed charge compression ignition engine with EGR (exhaust gas recirculation)

In this study, effects of DME (dimethyl ether) pre-mixing ratio and cooled external EGR (exhaust gas recirculation) rate on combustion, performance and emission characteristics of a DME-diesel dual fuel PCCI (premixed charge compression ignition) engine were investigated in a 2105 engine. PCCI combustion at a high pre-mixing ratio exhibited a three-stage-combustion behavior. The peak values of heat release rate and pressure rise rate increased in HCCI (homogeneous charge compression ignition) combustion stage and decreased in diesel diffusion combustion stage. A higher DME pre-mixing ratio caused lower smoke and NOx (nitrogen oxides) emissions but higher HC (hydrocarbons) and CO (carbon monoxide) emissions. Adopting EGR, the peak values of in-cylinder pressure and calculated mean charge temperature decreased. Meanwhile, the crank-angle positions corresponding to the maximum heat release rate and maximum pressure rise rate lagged respectively. Equivalent brake specific fuel consumption increased. With an increase in EGR rate, NOx emission decreased sharply, however, smoke, HC and CO emissions increased. Nevertheless, decreasing levels in maximum values of in-cylinder pressure and temperature, heat release rate and pressure rise rate, as well as lagging degrees in crank-angle positions corresponding to the above-mentioned maximum values, gradually weakened with an increase in DME pre-mixing ratio.

Intermediate Alcohol-Gasoline Blends, Fuels for Enabling Increased Engine Efficiency and Powertrain Possibilities

The present study experimentally investigates spark-ignited combustion with 87 AKI E0 gasoline in its neat form and in mid-level alcohol-gasoline blends with 24% vol./vol. iso-butanol-gasoline (IB24) and 30% vol./vol. ethanol-gasoline (E30). A single-cylinder research engine is used with a low and high compression ratio of 9.2:1 and 11.85:1 respectively. The engine is equipped with hydraulically actuated valves, laboratory intake air, and is capable of external exhaust gas recirculation (EGR). All fuels are operated to full-load conditions with =1, using both 0% and 15% external cooled EGR. The results demonstrate that higher octane number bio-fuels better utilize higher compression ratios with high stoichiometric torque capability. Specifically, the unique properties of ethanol enabled a doubling of the stoichiometric torque capability with the 11.85:1 compression ratio using E30 as compared to 87 AKI, up to 20 bar IMEPg at =1 (with 15% EGR, 18.5 bar with 0% EGR). EGR was shown to provide thermodynamic advantages with all fuels. The results demonstrate that E30 may further the downsizing and downspeeding of engines by achieving increased low speed torque, even with high compression ratios. The results suggest that at mid-level alcohol-gasoline blends, engine and vehicle optimization can offset the reduced fuel energy content of alcohol-gasoline more » blends, and likely reduce vehicle fuel consumption and tailpipe CO2 emissions. « less