Numerical investigation of turbolag reduction in HD CNG engines by means of exhaust valve variable actuation and spark timing control

In the American continent, the most frequently used alternative fuel is ethanol. Especially in Brazil, various blends of gasoline–ethanol fuels are widely spread. The vehicle using blended fuel is called flexible fuel vehicle. Because of several selections for the blending ratios in gas stations, the fuel properties may vary after refueling depending on a driver’s selection. Also, the combustion characteristics of the flexible fuel vehicle engine may change. In order to respond to the flexible fuel vehicle market in Brazil, a study on blended fuels is performed. The main purpose of this study is to enhance performance of the flexible fuel vehicle engine to target Brazilian market. Therefore, we investigated combustion characteristics and optimal spark timings of the blended fuels with various blending ratios to improve the performance of the flexible fuel vehicle engine. As a tool for prediction of the optimal spark timing for the 1.6L flexible fuel vehicle engine, the empirical equation was suggested. The validity of the equation was investigated by comparing the predicted optimal spark timings with the stock spark timings through engine tests. When the stock spark timings of E0 and E100 were optimal, the empirical equation predicted the actual optimal spark timings for blended fuels with a good accuracy. In all conditions, by optimizing spark timing control, performance was improved. Especially, torque improvements of E30 and E50 fuels were 5.4% and 1.8%, respectively, without affecting combustion stability. From these results, it was concluded that the linear interpolation method is not suitable for flexible fuel vehicle engine control. Instead of linear interpolation method, optimal spark timing which reflects specific octane numbers of gasoline–ethanol blended fuels should be applied to maximize performance of the flexible fuel vehicle engine. The results of this study are expected to save the effort required for engine calibration when developing new flexible fuel vehicle engines and to be used as a basic strategy to improve the performance of other flexible fuel vehicle engines.

Download Full-text

Turbocharged CNG Engines for Urban Transportation: Evaluation of Turbolag Reduction Strategies by Means of Computational Analyses

ASME 2009 Internal Combustion Engine Division Spring Technical Conference ◽

10.1115/ices2009-76067 ◽

2009 ◽

Cited By ~ 1

Author(s):

Mirko Baratta ◽

Ezio Spessa

Keyword(s):

Public Transportation ◽

High Performance ◽

Exhaust Valve ◽

Liquid Fuels ◽

Transient Condition ◽

Specific Reference ◽

Engine Model ◽

Spark Timing ◽

Pollutant Reduction ◽

1D Numerical Simulation

Nowadays, many urban buses for public transportation are fuelled by compressed natural gas (CNG), due to its potential for energy saving and pollutant reduction, with specific reference to particulate matter emissions. However, turbocharging is required to recover the gaseous-fuel related power gap with respect to more traditional engines running on liquid fuels. Therefore, turbolag reduction is fundamental to achieve high performance during engine transients. Significant support for the study of turbocharged CNG engines and guidelines for the turbomatching process can be provided by 1D numerical simulation tools. In this paper, the topic of turbolag reduction is analyzed, and different strategies, namely, Early-Exhaust Valve Opening-Variable Valve Actuation (E-EVO-VVA) and spark timing control for combustion retard (ComR), are analyzed by means of a specifically developed and calibrated GT-POWER® engine model. Tip-in maneuvers in which the engine was coupled to a torque hydraulic converter under stall conditions were investigated, so as to reproduce a typical load transient condition for an urban bus accelerating from engine idle. The best improvement of turbolag was obtained by combining E-EVO-VVA and ComR, with a reduction of turbolag ranging from 60% to 70%. When a limit on the incylinder pressure is introduced, in order to prevent excessive exhaust valve mechanical stresses, the higher achievable reduction in turbolag was found to be between 35% and 45%.

Download Full-text

Reducing combustion variation of late-phasing HCCI with cycle-to-cycle exhaust valve timing control

IFAC Proceedings Volumes ◽

10.3182/20100712-3-de-2013.00161 ◽

2010 ◽

Vol 43 (7) ◽

pp. 815-820 ◽

Cited By ~ 4

Author(s):

Adam. F. Jungkunz ◽

Hsien-Hsin Liao ◽

Nikhil Ravi ◽

J. Christian Gerdes

Keyword(s):

Exhaust Valve ◽

Valve Timing ◽

Timing Control

Download Full-text

Intake and Exhaust Valve Timing Control on a Heavy-Duty, Direct-Injection Natural Gas Engine

10.4271/2015-01-0864 ◽

2015 ◽

Cited By ~ 6

Author(s):

Bronson Patychuk ◽

Ning Wu ◽

Gordon McTaggart-Cowan ◽

Philip Hill ◽

Sandeep Munshi

Keyword(s):

Natural Gas ◽

Direct Injection ◽

Exhaust Valve ◽

Valve Timing ◽

Heavy Duty ◽

Timing Control ◽

Gas Engine ◽

Natural Gas Engine

Download Full-text

A Comparison Between Combustion Phase Indicators for Optimal Spark Timing

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.2939012 ◽

2008 ◽

Vol 130 (5) ◽

Cited By ~ 36

Author(s):

Emiliano Pipitone

Keyword(s):

Combustion Engine ◽

Reference Value ◽

Timing Control ◽

Maximum Heat ◽

Loop Control ◽

Spark Timing ◽

Combustion Phase ◽

Pressure Peak ◽

Fixed Reference ◽

Main Engine

The closed-loop control of internal combustion engine spark timing may be accomplished by means of a combustion phase indicator, i.e., a parameter, derived from in-cylinder pressure analysis, whose variation is mainly referable to combustion phase shift and assumes a fixed reference value under optimal spark timing operation. The aim of the present work is a comparison between different combustion phase indicators, focusing on the performance attainable by a feedback spark timing control, which uses the indicator as pilot variable. An extensive experimental investigation has been carried out, verifying the relationship between indicators’ optimal values and the main engine running parameters: engine speed, load, and mixture strength. Moreover, assessment on the effect of the most common pressure measurement problems (which are mainly related to pressure referencing, sampling resolution, top dead center determination, and cycle-by-cycle variations) on the indicators’ values and on the performance attainable by the spark timing control is included. The results of the comparison point out two indicators as the most suitable: the location of pressure peak and the location of maximum heat release rate. The latter, not available in literature, has been introduced by the author as an alternative to the 50% of mass fraction burned.

Download Full-text