| 8351. |
- Tunestål, Per, et al.
(författare)
-
Closed-Loop Combustion Control of HCCI Engines
- 2003
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Ingår i: Nonlinear and Hybrid Systems in Automotive Control. ; , s. 321-334
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The HCCI engine, with its excellent potential for high efficiency and low NOx emissions, is investigated from a control perspective. Combustion timing, i.e., where in the thermodynamic cycle combustion takes place, is identified as the most challenging problem with HCCI engine control. A number of different means for controlling combustion timing are suggested, and results using a dual-fuel solution are presented. This solution uses two fuels with different ignition characteristics to control the time of autoignition. Cylinder pressure measurement is suggested for feedback of combustion timing. A simple net-heat release algorithm is applied to the measurements, and the crank angle of 50% burnt is extracted. Open-loop instability is detected in some high-load regions of the operating range. This phenomenon is explained by positive feedback between the cylinder wall heating and ignition timing processes. Closed-loop performance is hampered by time delays and model uncertainties. This problem is particularly pronounced at operating points that are open-loop unstable.
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| 8352. |
- Tunestål, Per, et al.
(författare)
-
Cylinder air/fuel ratio estimation using net heat release data
- 2003
-
Ingår i: Control Engineering Practice. - 0967-0661. ; 11:3, s. 311-318
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- An estimation model which uses the net heat release profile for estimating the cylinder air/fuel ratio of a spark ignition engine is developed. The net heat release profile is computed from the cylinder pressure trace and quantifies the conversion of chemical energy of the reactants in the charge into thermal energy. The net heat release profile does not take heat- or mass transfer into account. Cycle-averaged air/fuel ratio estimates over a range of engine speeds and loads show an RMS error of 4.1% compared to measurements in the exhaust.
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| 8353. |
- Tunestål, Per, et al.
(författare)
-
Editorial: Special Issue on emission modeling
- 2014
-
Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 15:8, s. 897-897
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 8354. |
- Tunestål, Per
(författare)
-
Estimation of the In-Cylinder Air/Fuel Ratio of an Internal Combustion Engine by the Use of Pressure Sensors
- 2001
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis investigates the use of cylinder pressure measurements for estimation of the in-cylinder air/fuel ratio in a spark ignited internal combustion engine. An estimation model which uses the net heat release profile for estimating the cylinder air/fuel ratio of a spark ignition engine is developed. The net heat release profile is computed from the cylinder pressure trace and quantifies the conversion of chemical energy of the reactants in the charge into thermal energy. The net heat release profile does not take heat- or mass transfer into account. Cycle-averaged air/fuel ratio estimates over a range of engine speeds and loads show an RMS error of 4.1% compared to measurements in the exhaust. A thermochemical model of the combustion process in an internal combustion engine is developed. It uses a simple chemical combustion reaction, polynomial fits of internal energy as function of temperature, and the first law of thermodynamics to derive a relationship between measured cylinder pressure and the progress of the combustion process. Simplifying assumptions are made to arrive at an equation which relates the net heat release to the cylinder pressure. Two methods for estimating the sensor offset of a cylinder pressure transducer are developed. Both methods fit the pressure data during the pre-combustion phase of the compression stroke to a polytropic curve. The first method assumes a known polytropic exponent, and the other estimates the polytropic exponent. The first method results in a linear least-squares problem, and the second method results in a nonlinear least-squares problem. The nonlinear least-squares problem is solved by separating out the nonlinear dependence and solving the single-variable minimization problem. For this, a finite difference Newton method is derived. Using this method, the cost of solving the nonlinear least-squares problem is only slightly higher than solving the linear least-squares problem. Both methods show good statistical behavior. Estimation error variances are inversely proportional to the number of pressure samples used for the estimation as predicted by the central limit theorem.
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| 8355. |
- Tunestål, Per, et al.
(författare)
-
HCCI Operation of a Multi-Cylinder Engine
- 2001
-
Ingår i: First Biennial Meeting of the Scandinavian-Nordic Section of the Combustion Institute. ; , s. 109-114
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A six-cylinder truck-size engine has been converted for Homogeneous Charge Compression Ignition (HCCI) operation. This work demonstrates that it is possible to run a multi-cylinder engine under HCCI operation. The ultra-low NOX characteristic of HCCI is also demonstrated. The sensitivity of combustion timing with respect to operating parameters is investigated, and a closed-loop control system is designed which utilizes the mixing ratio of two different fuels to control the timing of combustion. The performance of the control system is evaluated experimentally.
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| 8356. |
- Tunestål, Per
(författare)
-
Motortyper
- 2007
-
Ingår i: Gasdrift av fordon. - 9789185207060 ; , s. 28-47
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 8357. |
- Tunestål, Per
(författare)
-
Self tuning cylinder pressure based heat release computation
- 2007
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Ingår i: Proceedings for the 5th IFAC Symposium on Advances in Automotive Control. ; , s. 183-190
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Konferensbidrag (refereegranskat)abstract
- The paper describes a novel method for self tuning cylinder pressure based heat release computation that is suitable for online usage in e.g. combustion phasing control applications. The method estimates the polytropic exponents and cylinder pressure offsets immediately preceding and succeeding the combustion event respectively using a fast nonlinear least squares method. The polytropic exponent and the pressure offset is subsequently interpolated during the combustion event and a net heat release computation is performed based on the interpolated exponent and pressure. The result is a self tuning heat release algorithm with no need to model heat losses, crevice losses and blow-by.
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| 8358. |
- Tunestål, Per
(författare)
-
Self-tuning gross heat release computation for internal combustion engines
- 2009
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Ingår i: Control Engineering Practice. - : Elsevier BV. - 0967-0661. ; 17:4, s. 518-524
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Tidskriftsartikel (refereegranskat)abstract
- The paper describes a novel method for self-tuning gross heat release computation in internal combustion engines suitable for both online usage in combustion phasing control applications and post-processing of cylinder pressure measurements. The method estimates the polytropic exponents and cylinder pressure offsets immediately preceding and succeeding the combustion event, respectively, using a fast nonlinear least-squares method. The polytropic exponent and the pressure offset are subsequently interpolated during the combustion event and a net heat release computation is performed based on the interpolated exponent and pressure. The result is a self-tuning gross heat release algorithm with no need to model heat losses, crevice losses and blow-by explicitly. (C) 2008 Elsevier Ltd. All rights reserved.
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| 8359. |
- Tunestål, Per
(författare)
-
TDC Offset Estimation from Motored Cylinder Pressure Data based on Heat Release Shaping
- 2011
-
Ingår i: Oil & Gas Science and Technology. - : EDP Sciences. - 1294-4475. ; 66:4, s. 705-716
-
Tidskriftsartikel (refereegranskat)abstract
- Abstract in UndeterminedFinding the correct Top Dead Center (TDC) offset for an internal combustion engine is harder than it seems. This study introduces a novel method to find the TDC offset based on the simple assumption that the heat loss power through the combustion chamber walls is constant for motored cycles in a narrow Crank Angle interval around TDC. The proposed method uses nonlinear least squares optimization to find the combination of specific heat ratio and TDC offset that makes the heat loss power as constant as possible. An important subproblem is to determine the peak pressure location with high accuracy. Fitting a third order Fourier series to the motored cylinder pressure allows the pressure maximum to be estimated with a standard deviation of 0.005° Crank Angle (CA) and it can also be used instead of the measured pressure to reduce the uncertainty of the TDC estimate by approximately 50%. The standard deviation of a single-cycle TDC estimate is approximately 0.025° CA when using a crank resolution of 0.2° CA for the measurements. The bias of the TDC estimate is in the 0-0.02° CA range both when comparing to measurements with a TDC sensor and with simulated motored cycles. The method can be used both for calibration and on-board diagnostics purposes e.g. during cranking, fuel cut-off or engine switch-off. The third order Fourier series fit comes with a significant computational penalty but since it is only applied very intermittently this does not have to be a serious issue.
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| 8360. |
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