Newly Developed Inline 4 AR Series SI Engine

Assanis

Babajimopoulos

2011

A comprehensive engine to drive-cycle modelling framework has been developed for evaluating fuel economy improvements of new engine technologies. The framework comprises three key components: (a) full engine system models and routines for the generation of engine performance and fuel consumption maps; (b) an improved experimental heat release analysis and model calibration tool, which was created by coupling an in-house heat release analysis program to an engine cycle simulation, and which can be used for model calibration and validation when experimental data are available; and (c) an integrated vehicle modelling and drive-cycle simulation platform for fuel economy assessment. The framework implementation has been demonstrated through a fuel economy study of three engine and combustion technologies: a conventional spark-ignition (SI) engine, a high compression ratio SI engine with early intake valve closing (EIVC), and a homogeneous-charge compression ignition engine (HCCI) employing a recompression valve strategy, used in dual-mode SI-HCCI operation. Simulation results for three drive cycles indicate potential fuel economy gains of the order of 7–11% for the high-compression EIVC SI engine and 7–21% for the dual-mode HCCI engine configurations. Further analysis of the latter, however, reveals frequent mode switching and short excursions in the HCCI region, which could be a challenge during practical implementation, and potentially result in reduced fuel economy gains.

Section: Engine To Drive-cycle Frameworksupporting

confidence: 52%

A comprehensive engine to drive-cycle modelling framework for the fuel economy assessment of advanced engine and combustion technologies

Assanis

Babajimopoulos

2011

“…For instance, the peak BTE for the feasible baseline engine, 34.3%, corresponds to a gasoline fuel consumption of 245 g/kW h, which is very similar to the minimum brake-specific fuel consumption (BSFC) of recent low friction NA engines (240 g/kW h). 22 The maximum BTE for the feasible high-efficiency gasoline engine is 38.2% (gasoline BSFC = 220 g/kW h) and is comparable to the minimum BSFC results from the HEDGE engine with an 11.4 compression ratio (216 g/ kW h). 35 However, the results shown in Figure 12(a)-(f) do not show a significant BTE island that is expected because the normal enrichment at high loads was not used.…”

Section: Engine Mapsmentioning

confidence: 70%

“…A 10.5:1 compression ratio is chosen for the baseline engine. 22 Since the high-efficiency gasoline engine is designed to have a higher knock resistance using cooled EGR, its compression ratio can be increased to 12:1. 23–25 Previous work has shown that when modifying a gasoline SI engine for ethanol, up to a 7.6 increase in ON allows 1 compression ratio increase.…”

Section: Fuel and Engine Configurationsmentioning

confidence: 99%

Scaling and dimensional methods to incorporate knock and flammability limits in models of high-efficiency gasoline and ethanol engines

Lewis

Lavoie

et al. 2014

Recent work has shown the utility of using simplified models with prescribed burn rates to assess the potential of advanced combustion strategies to increase engine efficiency. However, this approach can be improved by incorporating knock and flammability limits. This work incorporates such limits using a combination of simplified conceptual models that are based on theoretical understanding of knock and flame phenomenon and calibration with experimental results. Using this method, the ideal (unconstrained) and feasible (constrained by knock and flammability) potential of a high efficiency gasoline and E85 engine are compared against a baseline naturally aspirated gasoline engine. Turbocharging, dilution with EGR, and higher compression ratios are used to increase the efficiency potential of the high efficiency gasoline and E85 engines. Results demonstrate the benefit of using this simplified approach in modeling high efficiency engines: the high efficiency gasoline engine is most limited by knock while the E85 engine is limited much less; also increased EGR can be used for the E85 engine due to the higher flame speeds of ethanol. Fuel economy maps are created for each engine/fuel strategy and evaluated in a vehicle model to obtain fuel economy results. Results comparing feasible engines show that peak brake thermal efficiency (BTE) is increased by 11.4% for the high efficiency gasoline engine and 17.8% for the E85 engine, as compared to the baseline gasoline engine. Projected vehicle fuel economy (energy equivalent) improvements are 30.1% for the high efficiency gasoline, and 40.9% for the E85 engine relative to baseline.

“…Table 3 lists the operating conditions and model parameters used in the calculations. Engine speed was set at 2400 r/min, corresponding to the location of best fuel economy for a modern LD engine, 38 where mean piston speed U P = 8 m / s for the chosen engine stroke of 100 mm. Fuel air equivalence ratio, Φ, ranges from rich at 1.2 to very lean at 0.2, while Φ = 1 operation with EGR up to 80% corresponds to approximately the same range of dilution as with air.…”

Section: Model Formulationmentioning

confidence: 99%

“…The stoichiometric SI-NA engine map shows the typical upper envelope found in conventional gasoline SI engines and qualitatively agrees with engine maps available in the literature. 38 Because no high-load enrichment was used in the model, there is no ‘fuel island’. Peak load and minimum fuel consumption values are reasonable; however, the assumed combustion efficiency of 100% slightly reduces the minimum BSFC compared to published results.…”

Section: Vehicle Fuel Economymentioning

confidence: 99%

Thermodynamic sweet spot for high-efficiency, dilute, boosted gasoline engines

Lavoie

Babajimopoulos

et al. 2012

Recent developments in ignition, boosting, and control systems have opened up new opportunities for highly dilute, high-pressure combustion regimes for gasoline engines. This study analytically explores the fundamental thermodynamics of operation in these regimes under realistic burn duration, heat loss, boosting, and friction constraints. The intent is to identify the benefits of this approach and the path to achieving optimum engine and vehicle-level fuel economy. A simple engine/turbocharger model in GT-Power is used to perform a parametric study exploring the conditions for best engine efficiency. These conditions are found in the mid-dilution range, a result of the tradeoff between fluid property benefits of lean mixtures and friction benefits of higher loads. Dilution with exhaust gas is nearly as effective as air dilution when compared using a 'fuel-to-charge' equivalence ratio defined as F 0 [ F (1-RGF) where RGF is the total residual gas fraction. Optimal brake efficiencies are obtained over a range 0.45 4 F 0 4 0.65 for operation up to 3 bar manifold pressure, yielding peak temperatures under 2100 K and peak pressures under 150 bar. These conditions are intermediate between homogeneous charge compression ignition and spark-ignition regimes, and are the subject of much current research on advanced combustion modes. An engine-vehicle drive train simulation shows that accessing this thermodynamic sweet spot has the potential for vehicle fuel economy gains between 23% and 58%.