| 1. |
- Bengtsson, Johan, et al.
(författare)
-
Closed-loop Combustion Control of Homogeneous Charge Compression Ignition (HCCI) Engine Dynamics
- 2004
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Ingår i: International Journal of Adaptive Control and Signal Processing. - : Wiley. - 0890-6327 .- 1099-1115. ; 18:2, s. 167-179
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Tidskriftsartikel (refereegranskat)abstract
- Homogeneous charge compression ignition (HCCI) is a hybrid of the sparkignition and compression ignition engine concepts. As in a sparkignition engine, a homogeneous fuel-air mixture is created in theinlet system. During the compression stroke the temperature of themixture increases and reaches the point of auto ignition, just as in acompression ignition engine (or Diesel). One challenge with HCCI engines isthe need for good timing control of the combustion. Auto ignition of ahomogeneous mixture is very sensitive to operating condition. Evensmall variations of the load can change the timing from too early totoo late combustion. Thus a fast combustion timing control isnecessary since it sets the performance limitation of the loadcontrol. As measurement for combustion timing feedback, the crank angleof 50% burnt has been used. This paper performs a comparative studyof different cylinder-pressure based methods for estimating the crankangle of 50% burnt. The estimates are compared in terms of accuracy,robustness and feasibility for cycle-to-cycle real-time control.Dynamic models of CA50 are estimated using system identification asa means to find models relevant to engine control.
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| 2. |
- Bengtsson, Johan, et al.
(författare)
-
Control of Homogeneous Charge Compression Ignition (HCCI) Engine Dynamics
- 2004
-
Ingår i: Proceedings of the 2004 American Control Conference, ACC : June 30 - July 2, 2004, Boston Sheraton Hotel, Boston, Massachusetts. - 0743-1619. - 0780383354 ; 5, s. 4048-4053
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Konferensbidrag (refereegranskat)abstract
- The Homogeneous Charge Compression Ignition (HCCI) combustionconcept lacks direct ignition timing control, instead the autoignition depends on the operating condition. Since auto ignition of ahomogeneous mixture is very sensitive to operating conditions, a fastcombustion timing control is necessary for reliable operation. Hence,feedback is needed and the crank angle of 50% burnt (CA50) has provedto be a reliable feedback indicator of on-going combustion inpractice. CA50 or other methods for detecting on-going cylinderpressure used in the feedback control of a HCCI engine all rely onpressure sensors. This paper presents a newcandidate for control of HCCI engine by using the electronicconductive properties in the reaction zone. This phenomenon is calledion current. This paper perform combustion timing control based on ioncurrent and compare it with control based on pressure sensor. Thecombustion timing control is performed on cycle-to-cycle basis and the engine is a one-cylinder version of a heavy duty engine equipped with a port injection system using dual fuels.
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| 3. |
- Bengtsson, Johan, et al.
(författare)
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Hybrid Control of Homogeneous Charge Compression Ignition (HCCI) Engine Dynamics
- 2006
-
Ingår i: International Journal of Control. - : Informa UK Limited. - 0020-7179 .- 1366-5820. ; 79:5, s. 422-448
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Tidskriftsartikel (refereegranskat)abstract
- The homogeneous charge compression ignition ( HCCI) combustion engine principle lacks direct ignition timing control, instead the auto-ignition depends on the operating condition. Since auto-ignition of a homogeneous mixture is very sensitive to operating conditions, fast combustion phasing control is necessary for reliable operation. For this paper, a six-cylinder heavy-duty HCCI engine was controlled on a cycle-to-cycle basis in real time. Sensors, actuators and control structures for control of the HCCI combustion were compared. Among several actuators for HCCI engine control suggested, two actuators were compared-i.e., dual-fuel actuation and variable valve actuation (VVA). As for control principles, model predictive control (MPC) has several desirable features and today MPC can be applied to relatively fast systems, such as VVA and dual-fuel actuation. For sensor feedback control of the HCCI engine, cylinder pressure and ion current - i.e., the electronic conductive properties in the reaction zone - were compared. Combustion phasing control based on ion current was compared to control based on cylinder pressure. For the purpose of control synthesis requiring dynamic models, system identification provided models of the HCCI combustion, the models being validated by stochastic model validation. With such models providing a basis for model-based control, MPC control results were compared to PID and LQG control results. While satisfying the constraints on cylinder pressure, both control of the combustion phasing and control of load torque was achieved with simultaneous minimization of the fuel consumption and emissions.
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| 4. |
- Bengtsson, Johan, et al.
(författare)
-
Model Predictive Control of Homogeneous Charge Compression Ignition (HCCI) Engine Dynamics
- 2006
-
Ingår i: 2006 IEEE Conference on Computer Aided Control System Design, 2006 IEEE International Conference on Control Applications, 2006 IEEE International Symposium on Intelligent Control. ; , s. 1675-1680
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Konferensbidrag (refereegranskat)abstract
- The Homogeneous Charge Compression Ignition ({HCCI}) combustion principle lacks direct ignition timing control, instead the auto-ignition depends on the operating condition and fast combustion phasing control is necessary for reliable operation. A six-cylinder heavy-duty HCCI engine was controlled on a cycle-to-cycle basis in real time using a variety of sensors, actuators and control structures for control of the {HCCI} combustion in comparison. Combustion phasing control based on ion current was compared to feedback control based on cylinder pressure. Two actuators were compared, dual fuel and Variable Valve Actuation (VVA). Model-based control synthesis requiring dynamic models of low complexity and HCCI combustion models were estimated by system identification and by physical modeling. The models identified by system identification were used to design model-predictive control (MPC) with several desirable features and today applicable to relatively fast systems. Both control of the combustion phasing and control of load-torque with simultaneous minimization of the fuel consumption and emissions were included.
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| 5. |
- Bengtsson, Johan, et al.
(författare)
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Modeling of HCCI Engine Combustion for Control Analysis
- 2004
-
Ingår i: Proceedings 43rd IEEE Conference on Decision and Control. - 0191-2216. - 0780386825 ; 2, s. 1682-1687
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Konferensbidrag (refereegranskat)abstract
- Operation of homogeneous charge compression ignition (HCCI) enginesare very sensitive to timing variations in the combustion of theair-fuel charge mixture and require precise control of the ignitioninstant to run properly. It is therefore essential to understand thecharacteristics of timing variations under various operatingconditions in order to find suitable control strategies. This paperpresents a first step towards the construction of an HCCI enginemodel aimed at studies on timing control strategies. The goal is to(qualitatively) reproduce the timing effects that may be observed ona real engine. The proposed model includes a lumped chemical kineticmodel for hydrocarbon fuels to predict autoignition. Single-cyclesimulations are compared with experimental results from a realengine to validate the model.
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| 6. |
- Bengtsson, Johan, et al.
(författare)
-
Multi-Output Control of a Heavy Duty HCCI Engine Using Variable Valve Actuation and Model Predictive Control
- 2006
-
Ingår i: 2006 SAE World Congress. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International.
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Konferensbidrag (refereegranskat)abstract
- Autoignition of a homogeneous mixture is very sensitive to operating conditions, therefore fast control is necessary for reliable operation. There exists several means to control the combustion phasing of an Homogeneous Charge Compression Ignition (HCCI) engine, but most of the presented controlled HCCI result has been performed with single-input single-output controllers. In order to fully operate an HCCI engine several output variables need to be controlled simultaneously, for example, load, combustion phasing, cylinder pressure and emissions. As these output variables have an effect on each other, the controller should be of a structure which includes the cross-couplings between the output variables. A Model Predictive Control (MPC) controller is proposed as a solution to the problem of load-torque control with simultaneous minimization of the fuel consumption and emissions, while satisfying the constraints on cylinder pressure. One of the major motivations for using MPC is that it explicitly takes the constraints into account. When operating an HCCI engine there are several contraints present, for example on the cylinder pressure and on the emissions. A drawback of MPC is the potentially large on-line computational effort, which has historically limited its application to relative slow and/or small applications. Today, MPC can be applied in relative fast systems, and we will demonstrate that it can be used for control of HCCI engine dynamics on a cycle-to-cycle basis. As feedback signal of the combustion phasing, the crank angle for 50% burned, based on cylinder pressure, is used. In the control design of the MPC controllers (one for each cylinder), dynamic models obtained by system identification were used. This paper presents cycle-to-cycle cylinder individual control results from a six-cylinder HCCI engine using a Variable Valve Actuation (VVA) system and MPC controllers.
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| 7. |
- Bengtsson, Johan, et al.
(författare)
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System Identification of Homogenous Charge Compression Ignition (HCCI) Engine Dynamics
- 2004
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Ingår i: Advances in Automotive Control. - 0080442501 ; 37:22, s. 37-37
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Konferensbidrag (refereegranskat)abstract
- Homogeneous Charge Compression Ignition (HCCI) combustion lacksdirect ignition timing control, instead the auto ignition depends on the operatingcondition. Since auto ignition of a homogeneous mixture is very sensitive tooperating condition a fast combustion timing control is necessary for reliableoperation, the ignition timing control design requiring appropriate modelsand system output variables for its feedback design. This paper demonstratesthe use of system modeling and identification as a means to find modelsrelevant to the engine control. The identification methods used were varioussubspace-based methods. An LQG controller was designed based on the estimatedmodels and tested on a six-cylinder heavy duty engine running in HCCI operation.
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| 8. |
- Ekholm, Kent, et al.
(författare)
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Ethanol-Diesel Fumigation in a Multi-Cylinder Engine
- 2008
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Ingår i: SAE technical paper 2008-01-0033.
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Konferensbidrag (refereegranskat)abstract
- Fumigation was studied in a 12 L six-cylinder heavy-duty engine. Port-injected ethanol was ignited with a small amount of diesel injected into the cylinder. The setup left much freedom for influencing the combustion process, and the aim of this study was to find operation modes that result in a combustion resembling that of a homogeneous charge compression ignition (HCCI) engine with high efficiency and low NOx emissions. Igniting the ethanol-air mixture using direct-injected diesel has attractive properties compared to traditional HCCI operation where the ethanol is ignited by pressure alone. No preheating of the mixture is required, and the amount of diesel injected can be used to control the heat release rate. The two fuel injection systems provide a larger flexibility in extending the HCCI operating range to low and high loads. It was shown that cylinder-to-cylinder variations present a considerable challenge for this type of combustion. By using closed-loop cylinder-individual control based on incylinder pressure sensors, combustion was successfully harmonized between the cylinders. Successful fumigation operation was verified up to 18.4 bar BMEP at a fixed engine speed of 1450 rpm. Two load points (4.6 bar BMEP and 9.2 bar BMEP) were studied in detail. Different diesel injection timings, diesel ratios, and EGR rates were investigated, and comparisons were drawn to pure diesel operation of the same engine. At medium load (9.2 bar BMEP), it was possible to obtain a stable HCCI-like combustion with low NOx emissions (0.1 g/kWh), reasonably high brake efficiency (37 %), and low pressure derivatives (5 bar/CAD). High load operation (18.4 bar BMEP) resulted in low pressure derivatives (5.5 bar/CAD), acceptable brake efficency (36 %), and relatively low NOx emissions (0.34 g/kWh).
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| 9. |
- Ekholm, Kent, et al.
(författare)
-
Ethanol-Diesel Fumigation in a Multi-Cylinder Engine
- 2009
-
Ingår i: SAE International Journal of Fuels and Lubricants. - 1946-3952. ; 1:1, s. 26-36
-
Tidskriftsartikel (refereegranskat)abstract
- Fumigation was studied in a 12 L six-cylinder heavy-duty engine. Port-injected ethanol was ignited with a small amount of diesel injected into the cylinder. The setup left much freedom for influencing the combustion process, and the aim of this study was to find operation modes that result in a combustion resembling that of a homogeneous charge compression ignition (HCCI) engine with high efficiency and low NOx emissions. Igniting the ethanol-air mixture using direct-injected diesel has attractive properties compared to traditional HCCI operation where the ethanol is ignited by pressure alone. No preheating of the mixture is required, and the amount of diesel injected can be used to control the heat release rate. The two fuel injection systems provide a larger flexibility in extending the HCCI operating range to low and high loads. It was shown that cylinder-to-cylinder variations present a challenge for this type of combustion. By using closed-loop cylinder-individual control of pressure derivatives and IMEP with the amounts of fuels injected, combustion was successfully harmonized between the cylinders. Successful fumigation operation was verified up to 18.4 bar BMEP at a fixed engine speed of 1450 rpm. Two load points (4.6 bar BMEP and 9.2 bar BMEP) were studied in detail. Different diesel injection timings, diesel ratios, and EGR rates were investigated, and comparisons were drawn to pure diesel operation of the same engine. At medium load (9.2 bar BMEP), it was possible to obtain a stable HCCI-like combustion with low NOx emissions (0.1 g/kWh), reasonably high brake efficiency (38 %), and low pressure derivatives (5 bar/CAD). High load operation (18.4 bar BMEP) resulted in low pressure derivatives (5.5 bar/CAD), acceptable brake efficency (38 %), and relatively low NOx emissions (0.34 g/kWh).
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| 10. |
- Henningsson, Maria, et al.
(författare)
-
Closed-Loop Control of Combustion Phasing in an HCCI Engine Using VVA and Variable EGR
- 2007. - 10
-
Ingår i: 5th IFAC Symposium on Advances in Automotive Control. ; 40, s. 501-506
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Konferensbidrag (refereegranskat)abstract
- A homogeneous charge compression ignition (HCCI) engine requires closed-loop control of combustion phasing for reliable operation. Variable valve actuation (VVA) has previously been shown to enable cycle-to-cycle, cylinder-individual control with high precision, but suffers from a narrow operating range. Adding variable exhaust gas recirculation (EGR) to the closed-loop control structure can extend the operating range. A mid-ranging control structure is presented here for combined VVA and EGR actuations in a multi-cylinder engine. The control structure is simple to implement and preserves the fast, cylinder-individual, and precise actuation of the VVA system while extending the operating range. Experimental results verify the performance of the control structure.
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| 11. |
- Henningsson, Maria, et al.
(författare)
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Dynamic Mapping of Diesel Engine through System identification
- 2012
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Ingår i: Identification for Automotive Systems. - London : Springer London. - 0170-8643. ; LNCIS 418, s. 223-239
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Konferensbidrag (refereegranskat)abstract
- From a control design point of view, modern diesel engines are dynamic, nonlinear, MIMO systems. This paper presents a method to find low-complexity black-box dynamic models suitable for model predictive control (MPC) of NOx and soot emissions based on on-line emissions measurements. A four-input-five-output representation of the engine is considered, with fuel injection timing, fuel injection duration, exhaust gas recirculation (EGR) and variable geometry turbo (VGT) valve positions as inputs, and indicated mean effective pressure, combustion phasing, peak pressure derivative, NOx emissions, and soot emissions as outputs. Experimental data were collected on a six-cylinder heavy-duty engine at 30 operating points. The identification procedure starts by identifying local linear models at each operating point. To reduce the number of dynamic models necessary to describe the engine dynamics, Wiener models are introduced and a clustering algorithm is proposed. A resulting set of two to five dynamic models is shown to be able to predict all outputs at all operating points with good accuracy.
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| 12. |
- Henningsson, Maria, et al.
(författare)
-
Dynamic Mapping of Diesel Engine through System Identification
- 2010
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Ingår i: Proceedings of the 2010 American Control Conference. - 2378-5861 .- 0743-1619. - 9781424474264 - 9781424474271 ; , s. 3015-3020
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Konferensbidrag (refereegranskat)abstract
- From a control design point of view, modern diesel engines are dynamic, nonlinear, MIMO systems. This paper presents a method to find low-complexity black-box dynamic models suitable for model predictive control (MPC) of NOx and soot emissions based on on-line emissions measurements. A four-input-five-output representation of the engine is considered, with fuel injection timing, fuel injection duration, exhaust gas recirculation (EGR) and variable geometry turbo (VGT) valve positions as inputs, and indicated mean effective pressure, combustion phasing, peak pressure derivative, NOx emissions, and soot emissions as outputs. Experimental data were collected on a six-cylinder heavy-duty engine at 30 operating points. The identification procedure starts by identifying local linear models at each operating point. To reduce the number of dynamic models necessary to describe the engine dynamics, Wiener models are introduced and a clustering algorithm is proposed. A resulting set of two to five dynamic models is shown to be able to predict all outputs at all operating points with good accuracy.
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| 13. |
- Henningsson, Maria, et al.
(författare)
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LQG Control for Minimization of Emissions in a Diesel Engine
- 2008
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Ingår i: 2008 IEEE International Conference on Control Applications, Vol1 and 2. - 1085-1992. - 9781424422227 ; , s. 303-308
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Konferensbidrag (refereegranskat)abstract
- The problem of minimizing emissions of NO. and soot in a diesel engine using fuel injection timings and exhaust gas recirculation (EGR) valve position in a low-pressure EGR system as control variables is addressed. Two feedback variables are computed from in-cylinder pressure sensor data, the crank angle degree of 50 % fuel burnt, and the ignition delay. Empirical maps of NO, and soot according to the feedback variables form the basis of a quadratic cost function in the feedback variables which is minimized by LQG control. For a multi-cylinder engine, the number of control variables will be less than the number of output variables to be controlled, and the consequences of this setup for the LQG controller is addressed. Experimental results verify the performance of the controller at a fixed operating point of a six-cylinder heavy-duty engine.
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| 14. |
- Henningsson, Maria, et al.
(författare)
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Multiple-Input Multiple-Output Model Predictive Control of a Diesel Engine
- 2010
-
Ingår i: IFAC Proceedings Volumes (IFAC-PapersOnline). - 2405-8963. ; 43:7, s. 131-136
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Tidskriftsartikel (refereegranskat)abstract
- Traditionally, diesel engine control has had to rely on indirect feedback variables and empirical open-loop maps because direct measurements of the variables representing high-level objectives, such as emissions, have not been available in production engines. With new sensors being developed, the opportunity opens to design the controller directly based on high-level objectives. In this paper, we propose to use model predictive control as a systematic way to go directly from high-level specifications to a control algorithm. The controller uses four actuator variables and five measured variables and is based on a model obtained through system identification. Experimental results on a six-cylinder heavy-duty engine around a fixed operating point demonstrate the potential of the control scheme.
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| 15. |
- Strandh, Petter
(författare)
-
Combustion Engine Models for Hybrid Vehicle System Development
- 2002
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This report is part of a project that is called Generic hybrid systems. Its objective is to simulate and investigate electric hybrid drive trains. The goal of this work has been to develop combustion engine models that are computer efficient, but still has the potential of giving both qualitative and quantitative results. For instance, if the model is run in a less ideal manner the model will show an increase in both fuel consumption and exhaust emissions. Both a spark ignition DSI or OttoE engine as well as a compression ignition DCI or DieselE engine model have been developed. The SIengine model has been partially validated through the use of transient testing. The thesis also contains a proof of concept study that is called TES Transient Emission Sampling, which is a method for measuring exhaust emissions during transients.
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| 16. |
- Strandh, Petter, et al.
(författare)
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Cycle-to-Cycle Control of a Dual-Fuel HCCI Engine
- 2004
-
Ingår i: SAE Paper 2004-01-0941. - 0148-7191. - 0768013550 ; SP-1819
-
Konferensbidrag (refereegranskat)abstract
- A known problem of the HCCI engine is its lack of direct control andits requirements of feedback control. Today there exists severaldifferent means to control an HCCI engine, such as dual fuels,variable valve actuation, inlet temperature and compression ratio.Independent of actuation method a sensor is needed. In this paper weperform closed-loop control based on two different sensors, pressureand ion current sensor. Results showing that they give similar controlperformance within their operating range are presented.Also a comparison of two methods of designing HCCI timing controller,manual tuning and model based design is presented. A PIDcontroller is used as an example of a manually tuned controller. ALinear Quadratic Gaussian controller exemplifies model basedcontroller design. The models used in the design were estimated usingsystem identification methods.The system used in this paper performs control on cycle-to-cyclebasis. This leads to fast and robust control. Dual fuels withdifferent octane numbers were used to control the combustion timing.The engine was a 12 liter 6 cylinder heavy-duty diesel engine modifiedwith a port fuel injection system which has dual fuels connected.
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| 17. |
- Strandh, Petter
(författare)
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HCCI Operation - Closed loop combustion control using VVA or dual fuel
- 2006
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The current technology within combustion engines have the possibility of handling the more stringent legislative demands on combustion engines. However the required solutions are getting more expensive and technically challenging. One possible way towards a more simple exhaust aftertreatment system is the use of the Homogeneous Charge Compression Ignition (HCCI) engine cycle. The main advantage of the HCCI engine is its low output of NOx exhaust emissions. Because of its indirect combustion initiation the main disadvantage is that it requires closed loop control of its combustion process. Two methods for engine timing control were used, dual fuels or variable valve actuation(VVA). With dual fuels the timing change was achieved by changing the autoignition properties of the homogeneous charge and with VVA, timing control was achieved by changing the effective compression ratio. This thesis focuses on the control of the HCCI engine. For the purpose of studying control of the HCCI engine, special engine control software was developed. This software aimed towards engine cycle-to-cycle control and actuation. Another aid in the development was the use of Matlab/Simulink for the design of powerful control algorithms. Successful system identification control design has been shown. Different control strategies were tested, amongst the most successful was the use of Model Predictive Control (MPC), which is a control strategy that can take care of the nonlinear behavior of the dynamic engine system and its actuators. It was concluded that low order models were sufficient for capturing the important HCCI engine dynamics. The use of ion current for detection and control of the HCCI combustion was also shown. A method for obtaining combustion timing from the ion current was defined and investigated. Closed-loop control using ion currents on an HCCI engine was demonstrated.
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| 18. |
- Strandh, Petter, et al.
(författare)
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Ion Current Sensing for HCCI Combustion Feedback
- 2003
-
Ingår i: SAE Technical Papers. - 0148-7191. ; :2003-01-3216
-
Konferensbidrag (refereegranskat)abstract
- Measurement of ion current signal from HCCI combustionwas performed. The aim of the work was to investigateif a measurable ion current signal exists and if it is possible to obtain useful information about the combustion process. Furthermore, influence of mixture quality in termsof air/fuel ratio and EGR on the ion current signal wasstudied. A conventional spark plug was used as ionizationsensor. A DC voltage (85 Volt) was applied acrossthe electrode gap. By measuring the current through thegap the state of the gas can be probed. A comparisonbetween measured pressure and ion current signal wasperformed, and dynamic models were estimated by usingsystem identification methods.The study shows that an ion current signal can be obtainedfrom HCCI combustion and that the signal levelis very sensitive to the fuel/air equivalence ratio. Themost important result from this study is that the ion current signal proved to be an excellent indicator of the actual combustion timing which is crucial piece of information for HCCI control.
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| 19. |
- Strandh, Petter, et al.
(författare)
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Variable Valve Actuation for Timing Control of a Homogeneous Charge Compression Ignition Engine
- 2005
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Ingår i: SAE Technical Papers 2005-01-0147. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191.
-
Konferensbidrag (refereegranskat)abstract
- Autoignition of a homogeneous mixture is very sensitiveto operating conditions. Therefore fast combustion phasingcontrol is necessary for reliable operation. There areseveral means to control the combustion phasing of a Homogeneous Charge Compression Ignition (HCCI) engine.This paper presents cycle-to-cycle cylinder individual controlresults from a six-cylinder HCCI engine using a VariableValve Actuation (VVA) system. As feedback signal,the crank angle for 50% burned, based on cylinder pressure,is used. Three control structures are evaluated,Model Predictive Control (MPC), Linear Quadratic Gaussiancontrol (LQG) and PID control. In the control designof the MPC and LQG controller, dynamic models obtainedby system identication were used. Successful experimentswere performed on a port-injected six-cylinderheavy-duty Diesel engine operating in HCCI mode.
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| 20. |
- Vressner, Andreas, et al.
(författare)
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Multiple Point Ion Current Diagnostics in an HCCI Engine
- 2004
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Ingår i: SAE Transactions, Journal of Engines. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0096-736X. ; 113:3, s. 544-550
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Tidskriftsartikel (refereegranskat)abstract
- Interest in ion current sensing for HCCI combustion arises when a feedback signal from some sort of combustion sensor is needed in order to determine the state of the combustion process. A previous study has revealed that ion current sensors in the form of spark plugs can be used instead of expensive piezoelectric transducers for HCCI combustion sensing. Sufficiently high ion current levels were achieved when using relatively rich mixtures diluted with EGR. The study also shows that it is not the actual dilution per se but the actual air/fuel equivalence ratio which is important for the signal level. Conclusions were made that it is possible to obtain information on combustion timing and oscillating wave phenomena from the measurements. However, the study showed that the ion current is local compared to the pressure which is global in the combustion chamber. This observation triggered the present study where the aim is to investigate the ion current at different locations in the combustion chamber. The ion current was measured simultaneously at seven locations in the combustion chamber. In order to achieve this, 6 spark plugs were fitted circumferentially in a spacer placed between the cylinder block and the head. The seventh spark plug was placed in the cylinder head. Individual DC sources of 85 volts were applied across the spark plug gaps. The present study indicates that the combustion timing seems to be dependent on the wall temperature at the different spark plug locations. The largest difference in timing between different locations in the combustion chamber was 2 CAD. The ion current amplitude varies with different spark plug locations up to 1.5 μA. The signal strength increases with decreasing air/fuel ratio and is also affected by dilution.
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