Physically based volumetric efficiency model for diesel engines utilizing variable intake valve actuation

This paper describes a simple, analytical, controloriented and physically-based model for prediction of combustion timing during PCCI combustion. The model includes direct dependence on in-cylinder temperature, in-cylinder pressure, and the total in-cylinder O 2 mass fraction. It is extensively validated with experimental PCCI data from a multi-cylinder engine with almost exclusively stock hardware (stock pistons, injectors/nozzles, turbocharger, etc.) and variable valve actuation. The results show that across a wide range of input conditions the model predicts the start of combustion (SOC) within ±2 • CA of the experimental values for all but one of the 119 data points. The experimental SOC ranges from as early as −19.3 • CA to as late as +0.6 • CA by heavily exercising the control authority over SOC provided by SOI ecm , IVC/ECR modulation (ECR ranges from 12:1 to 18:1), and the engine's air-handling system. This PCCI combustion timing model can be coupled with a gas exchange model for control algorithm design.

Section: B Hydraulic Delay τ Hydmentioning

confidence: 99%

Control-oriented PCCI combustion timing model for a diesel engine utilizing flexible intake valve modulation and high EGR levels

Alstine

Kocher

Koeberlein

et al. 2012

“…As such, a more accurate approach for characterizing the effective compression process is desired for implementation in models predicting engine performance and emissions. A commonly used method for calculating the effective compression ratio, ECR, that more accurately captures the effective compression process is the pressure-based method [9], [10], [19], [20] The pressure-based method for calculating ECR uses incylinder pressure data to generate a logP-logV diagram (see Figure 1). The compression stroke is linearly extrapolated assuming polytropic compression, and the slope of this line on a log-log scale is the polytropic coefficient.…”

Section: Effective Compression Ratio Definedmentioning

confidence: 99%

“…A static volumetric efficiency equation developed in [19] is given by Equation 16. This volumetric efficiency model is physically-based and requires no tuning parameters, and was extensively experimentally validated against an advanced multi-cylinder diesel engine equipped with a variable valve actuation system, with model accuracy of 2.2% RMS (root mean square) error.…”

Section: Estimation Of Effective Compression Ratiomentioning

confidence: 99%

Effective compression ratio estimation in engines with flexible intake valve actuation

Stricker

Kocher

Koeberlein

et al. 2012

The ability to modulate the effective compression ratio (ECR) of an engine is a key enabler of advanced combustion strategies. ECR is a measure of the effective incylinder compression of gases above intake manifold conditions. An engine's ECR is usually computed from in-cylinder pressure data, requiring reliable in-cylinder pressure sensors that are not typically found on production engines. As such, a method is needed for determining the effective compression ratio using only information available from stock engine sensors, including manifold pressures and temperatures and air flows. The work outlined here presents a strategy for estimating the ECR without need for in-cylinder pressure data. The estimation scheme was transiently tested and compared to experimental engine data from a unique diesel engine test bed with flexible intake valve actuation, and was able to converge within 3 engine cycles after a transient event with less than 6% average steadystate error compared to experimental engine data.

“…The fraction of this residual mass which exits the exhaust manifold is assumed to be proportional to the pressures in the intake and exhaust manifolds. Thus, in a similar method as that used by [16], these backflow effects are captured by…”

Section: ) Burned Gas Massmentioning

confidence: 99%

“…Assuming constant specific heats and an ideal gas and plugging in Equation 16 into Equation 15, yields…”

Section: ) In-cylinder Pressurementioning

confidence: 99%

Combustion phasing model for control of a gasoline-ethanol fueled SI engine with variable valve timing

Hall

Shaver

Chauvin

et al. 2012

Abstract-Concern over the availability of fossil fuels and energy usage have produced an interest in both alternative fuels and new engine technologies such as variable valve timing to improve engine efficiency. Fuel-flexible engines permit the increased use of ethanol-gasoline blends. Ethanol is a renewable fuel which has the added advantage of improving performance in typically knock-limited operating regions due to the higher octane rating of the fuel. Furthermore, many modern engines are also being equipped with variable valve timing (VVT), a technology which allows increased control of the quantity of burned gas in-cylinder and can increase engine efficiency by reducing the need for throttling. The burned gas fraction as well as the blend ratio of ethanol impact the combustion timing and capturing these effects is essential if the combustion phasing is to be properly controlled.Combustion efficiency is typically tied to an optimal CA50 (crankangle when 50% of fuel is burned) for an engine. This paper proposes a physically-based model which captures combustion phasing and is designed to provide accurate estimates of CA50 for real-time control efforts allowing the CA50 to be adjusted to its optimal value despite changes in fuel and valve overlap. This control-oriented model was extensively validated at over 500 points across the engine operating range for four blends of gasoline and ethanol.