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Viewing 1 to 30 of 42
2011-04-12
Journal Article
2011-01-0709
Alexander Darlington, Nick Collings, Keith Glover
Common-rail fuel injection systems on modern light-duty diesel engines are effectively able to respond instantaneously to changes in the demanded injection quantity. In contrast, the air-system is subject to significantly slower dynamics, primarily due to filling/emptying effects in the manifolds and turbocharger inertia. The behavior of the air-path in a diesel engine is therefore the main limiting factor in terms of engine-out emissions during transient operation. This paper presents a simple mean-value model for the air-path during throttled operation, which is used to design a feed-forward controller that delivers very rapid changes in the in-cylinder charge properties. The feed-forward control action is validated using a state-of-the-art sampling system that allows true cycle-by-cycle measurement of the in-cylinder CO₂ concentration.
2014-04-01
Journal Article
2014-01-1219
Orian Welling, James Moss, John Williams, Nick Collings
One of the limits on the maximum fuel efficiency benefit to be gained from turbocharged, downsized gasoline engines is the occurrence of low speed pre-ignition (LSPI). LSPI may lead to high pressures and extreme knock (megaknock or superknock) which can cause severe engine damage. Though the mechanism leading to megaknock is not completely resolved, LSPI is thought to arise from local auto-ignition of areas in the cylinder which are rich in low ignition delay “contaminants” such as engine oil and/or heavy ends of gasoline. These contaminants are introduced to the combustion chamber at various points in the engine cycle (e.g. entering from the top land crevice during blow-down or washed from the cylinder walls during DI wall impingement). This paper describes a method for testing the propensity of different contaminants to cause a local pre-ignition in a gasoline engine. During one cycle, a small amount of contaminant is injected into one cylinder of a 4 cylinder engine.
2014-04-01
Technical Paper
2014-01-1213
Orian Welling, Nick Collings, John Williams, James Moss
Abstract One of the limits on the maximum fuel efficiency benefit to be gained from turbocharged, downsized gasoline engines is the occurrence of pre-ignitions at low engine speed. These pre-ignitions may lead to high pressures and extreme knock (megaknock or superknock) which can cause severe engine damage. Though the mechanism leading to megaknock is not completely resolved, pre-ignitions are thought to arise from local autoignition of areas in the cylinder which are rich in low ignition delay “contaminants” such as engine oil and/or heavy ends of gasoline. These contaminants are introduced to the combustion chamber at various points in the engine cycle (e.g. entering from the top land crevice during blow-down or washed from the cylinder walls during DI wall impingement).
2010-04-12
Journal Article
2010-01-1245
Hao Wu, Nick Collings, Simon Regitz, Jonathan Etheridge, Markus Kraft
In HCCI engines, the Air/Fuel Ratio (AFR) and Residual Gas Fraction (RGF) are difficult to control during the SI-HCCI-SI transition, and this may result in incomplete combustion and/or high pressure raise rates. As a result, there may be undesirably high engine load fluctuations. The objectives of this work are to further understand this process and develop control methods to minimize these load fluctuations. This paper presents data on instantaneous AFR and RGF measurements, both taken by novel experimental techniques. The data provides an insight into the cyclic AFR and RGF fluctuations during the switch. These results suggest that the relatively slow change in the intake Manifold Air Pressure (MAP) and actuation time of the Variable Valve Timing (VVT) are the main causes of undesired AFR and RGF fluctuations, and hence an unacceptable Net IMEP (NIMEP) fluctuation. We also found large cylinder-to-cylinder AFR variations during the transition.
2010-04-12
Journal Article
2010-01-0574
Jonathan Etheridge, Sebastian Mosbach, Markus Kraft, Hao Wu, Nick Collings
A Stochastic Reactor Model (SRM) has been used to simulate the transition from Spark Ignition (SI) mode to Homogeneous Charge Compression Ignition (HCCI) mode in a four cylinder in-line four-stroke naturally aspirated direct injection SI engine with cam profile switching. The SRM is coupled with GT-Power, a one-dimensional engine simulation tool used for modelling engine breathing during the open valve portion of the engine cycle, enabling multi-cycle simulations. The model is initially calibrated in both modes using steady state data from SI and HCCI operation. The mode change is achieved by switching the cam profiles and phasing, resulting in a Negative Valve Overlap (NVO), opening the throttle, advancing the spark timing and reducing the fuel mass as well as utilising a pilot injection. Experimental data is presented along with the simulation results.
2009-11-02
Journal Article
2009-01-2698
Johannes Arning, Tashiv Ramsander, Nick Collings
Gasoline Homogeneous Charge Compression Ignition (HCCI) combustion has been studied widely in the past decade. However, in HCCI engines using negative valve overlap (NVO), there is still uncertainty as to whether the effect of pilot injection during NVO on the start of combustion is primarily due to heat release of the pilot fuel during NVO or whether it is due to pilot fuel reformation. This paper presents data taken on a 4-cylinder gasoline direct injection, spark ignition/HCCI engine with a dual cam system, capable of recompressing residual gas. Engine in-cylinder samples are extracted at various points during the engine cycle through a high-speed sampling system and directly analysed with a gas chromatograph and flame ionisation detector. Engine parameter sweeps are performed for different pilot injection timings and quantities at a medium load point.
2013-04-08
Technical Paper
2013-01-1051
Kieran Hegarty, Paul Dickinson, Dariusz Cieslar, Nick Collings
Recent work has investigated the use of O₂ concentration in the intake manifold as a control variable for diesel engines. It has been recognized as a very good indicator of NOX emissions especially during transient operation, however, much of the work is concentrated on estimating the O₂ concentration as opposed to measuring it. This work investigates Universal Exhaust Gas Oxygen (UEGO) sensors and their potential to be used for such measurements. In previous work it was shown that these sensors can be operated in a controlled pressure environment such that their response time is of the order 10 ms. In this paper, it is shown how the key causes of variation (and therefore potential sources of error) in sensor output, namely, pressure and temperature are largely mitigated by operating the sensors in such an environment. Experiments were undertaken on a representative light-duty diesel engine using modified UEGO sensors in the intake and exhaust system.
2013-04-08
Technical Paper
2013-01-1310
Dariusz Cieslar, Nick Collings, Paul Dickinson, Keith Glover, Alexander Darlington
A key challenge in achieving good transient performance of highly boosted engines is the difficulty of accelerating the turbocharger from low air flow conditions (“turbo lag”). Multi-stage turbocharging, electric turbocharger assistance, electric compressors and hybrid powertrains are helpful in the mitigation of this deficit, but these technologies add significant cost and integration effort. Air-assist systems have the potential to be more cost-effective. Injecting compressed air into the intake manifold has received considerable attention, but the performance improvement offered by this concept is severely constrained by the compressor surge limit. The literature describes many schemes for generating the compressed gas, often involving significant mechanical complexity and/or cost. In this paper we demonstrate a novel exhaust assist system in which a reservoir is charged during braking.
2010-05-05
Technical Paper
2010-01-1507
Johannes Arning, Hao Wu, Nick Collings
A novel method of measuring cylinder gas temperature in an internal combustion engine cylinder is introduced. The physical basis for the technique is that the flow rate through an orifice is a function of the temperature of the gas flowing through the orifice. Using a pressure transducer in the cylinder, and another in a chamber connected to the cylinder via an orifice, it is shown how the cylinder temperature can be determined with useful sensitivity. In this paper the governing equations are derived, which show that the heat transfer characteristics of the chamber are critical to the performance of the system, and that isothermal or adiabatic conditions give the optimum performance. For a typical internal combustion engine, it is found that the pre-compression cylinder temperature is related to the chamber pressure late in the compression process with sensitivity of the order of 0.005 bar/K.
2012-09-10
Technical Paper
2012-01-1735
Alexander Darlington, Dariusz Cieslar, Nick Collings, Keith Glover
Delivering acceptable low end torque and good transient response is a significant challenge for all turbocharged engines. As downsized gasoline engines and Diesel engines make up a larger and larger proportion of the light-duty engines entering the market, the issue takes on greater significance. Several schemes have been proposed to improve torque response in highly boosted engines, including the use of electrical assist turbochargers and compressed air assist. In this paper we examine these methods with respect to their effectiveness in improving transient response and their relative performance along with some of the practical considerations for real world application. Results shown in this paper are from 1-D simulations using the Ricardo WAVE software package.
2012-04-16
Technical Paper
2012-01-0896
Feilong Liu, Gehan A. J. Amaratunga, Nick Collings, Ahmed Soliman
The information provided by the in-cylinder pressure signal is of great importance for modern engine management systems. The obtained information is implemented to improve the control and diagnostics of the combustion process in order to meet the stringent emission regulations and to improve vehicle reliability and drivability. The work presented in this paper covers the experimental study and proposes a comprehensive and practical solution for the estimation of the in-cylinder pressure from the crankshaft speed fluctuation. Also, the paper emphasizes the feasibility and practicality aspects of the estimation techniques, for the real-time online application. In this study an engine dynamics model based estimation method is proposed. A discrete-time transformed form of a rigid-body crankshaft dynamics model is constructed based on the kinetic energy theorem, as the basis expression for total torque estimation.
1998-02-01
Technical Paper
980788
Sergei Schurov, Nick Collings, Tim Hands, Mark Peckham, James Burrell
A novel Fast Response Chemiluminescence Detector and a Fast Flame Ionization detector have been used to examine the instantaneous NO and unburnt hydrocarbon concentration in the cylinder and exhaust port of a DI Diesel engine. The in-cylinder results indicate very high levels of NO in the premixed phase of combustion, followed by generally lower levels during the diffusion burning phase. Hydrocarbon signals also indicate significant detail. The in-cylinder uHC signal is consistent with the probe location being between two of the fuel sprays. Both in-cylinder and exhaust results indicate rather high cyclic variability in the NO levels at steady conditions. Variations in the timing and structure of the exhaust uHC signal during the valve open period with load may give insight into the fuel spray/air motion.
1995-10-01
Technical Paper
952485
Sergei M. Schurov, Nick Collings
Abstract The transport of fuel during cold start in the intake of a port-injected engine has been investigated using a standard engine with very little modification. A fast response FID sampling from the intake manifold is used to measure the instantaneous vapor concentration during the start. At short times after the start, the engine is stopped, and the port under investigation isolated. The engine is then warmed up by passing hot water through it and at the same time is flushed with hot air, in the port and the cylinder. This evaporates the liquid fuel, and by integrating the vapor concentration multiplied by mass flow of the displaced gas, the fuel mass in the isolated port and cylinder is measured. It is shown how the mass of liquid in the port at the time at which the engine is stopped can reliably be related to the concentration measurement.
1996-10-01
Technical Paper
961926
Sergei Schurov, Tim Summers, Nick Collings
Abstract Understanding mixture formation phenomena during the first few cycles of an engine cold start is extremely important for achieving the minimum engine-out emission levels at the time when the catalytic converter is not yet operational. Of special importance is the structure of the charge (film, droplets and vapour) which enters the cylinder during this time interval as well as its concentration profile. However, direct experimental studies of the fuel behaviour in the inlet port have so far been less than fully successful due to the brevity of the process and lack of a suitable experimental technique. We present measurements of the hydrocarbon (HC) concentration in the manifold and port of a production SI engine using the Fast Response Flame Ionisation Detector (FRFID).
1994-10-01
Technical Paper
941874
Sergei M. Schurov, Nick Collings
Abstract The paper presents a computer simulation of flow and heat transfer phenomena in the intake port of a spark ignition engine with port fuel injection. Engine cold starting conditions are studied including the effects of in-cylinder mixture back flow into the port. One dimensional air flow and wall fuel film flow models and a two dimensional fuel droplet flow model have been developed using a combination of finite difference approaches. As a result, predictions are obtained that provide detailed picture of the air-fuel mixture properties along the intake port. The model may be of special importance for exhaust gas ignition system simulation as it will provide data concerning mixture formation under conditions of excessive fuel injection during engine start-up. The calculations performed are shown to be phenomenologically correct.
1998-05-04
Technical Paper
981439
Jian Li, Nick Collings, Tom Ma
A novel mechanical method of achieving a rapid switch between stoichiometric and lean conditions for SI engines is explored. Two and three throttle configurations, a switch strategy which employs a standard intake manifold and an assembly of pipes and throttle(s), are investigated numerically by using a one-dimensional engine simulation program based on the method of characteristics. The results indicate that it is possible to achieve rapid AFR switch without a torque jump, i.e. unperceptible to the driver.
1998-02-23
Technical Paper
980400
Mark Peckham, Tim Hands, James Burrell, Nick Collings, Sergei Schurov
A new fast response NO detector, based on the chemiluminescence (CLD) method has been used to measure continuous, real time levels of NO in the cylinder, and simultaneously in the exhaust port of a virtually unmodified production SI engine. The real time NO concentration data show a great deal of information. Simultaneous NO measurements taken in-cylinder at sample points a few millimetres apart show substantial differences. Exhaust and in-cylinder levels from the same cycle show even greater differences, though the levels on average are well correlated.
2006-10-16
Technical Paper
2006-01-3276
Stelios Karagiorgis, Nick Collings, Keith Glover, Neil Coghlan, Anthemios Petridis
This paper is concerned with the Residual Gas Fraction measurement and estimation on a Homogeneous Charge Compression Ignition (HCCI) engine. A novel in-cylinder gas sampling technique was employed to obtain cyclic dynamic measurements of CO2 concentration in the compression stroke and in combination with CO2 concentration measurements in the exhaust stroke, cyclic Residual Gas Fraction was measured. The measurements were compared to estimations from a physical, 4-cylinder, single-zone model of the HCCI cycle and good agreement was found in steady engine running conditions. Some form of oscillating behaviour that HCCI exhibits because of exhaust gas coupling was studied and the model was modified to simulate this behaviour.
2006-10-16
Technical Paper
2006-01-3425
Feilong Liu, Gehan A. J. Amaratunga, Nick Collings
The cylinder pressure signal, as an instantaneous and direct measure of the engine operation, contains valuable information for closed loop engine control and offers very useful engine monitoring and control capabilities. The estimation technique for cylinder pressure has been investigated for many years. Based on the Frequency Analysis Method, a synthetic estimation method is proposed in this paper to estimate pressure. Methods that are successful in obtaining a more accurate estimated cylinder pressure over a wider range of crankshaft angle are reported. Quantitative results obtained from application of the method are also given.
2006-10-16
Technical Paper
2006-01-3373
Alex Darlington, Keith Glover, Nick Collings
Simple air-path models for modern (VGT/EGR equipped) diesel engines are in common use, and have been reported in the literature. This paper addresses some of the shortcomings of control-oriented models to allow better prediction of the cylinder charge properties. A fast response CO2 analyzer is used to validate the model by comparing the recorded and predicted CO2 concentrations in both the intake port and exhaust manifold of one of the cylinders. Data showing the recorded NOx emissions and exhaust gas opacity during a step change in engine load illustrate the spikes in both NOx and smoke seen during transient conditions. The predicted cylinder charge properties from the model are examined and compared with the measured NOx and opacity. Together, the emissions data and charge properties paint a consistent picture of the phenomena occurring during the transient. Alternative strategies for the fueling and cylinder charge during these load transients are investigated and discussed.
2007-10-29
Technical Paper
2007-01-4058
Adam Weall, Nick Collings
Partially premixed compression ignition (PPCI) engines operating with a low temperature highly homogeneous charge have been demonstrated previously using conventional diesel fuel. The short ignition delay of conventional diesel fuel requires high fuel injection pressures to achieve adequate premixing along with high levels of EGR (exhaust gas recirculation) to achieve low NOx emissions. Low load operating regions are typified by substantial emissions of CO and HC and there exists an upper operating load limitation due to very high rates of in-cylinder gas pressure rise. In this study mixtures of gasoline and diesel fuel were investigated using a multi-cylinder light duty diesel engine. It was found that an increased proportion of gasoline fuel reduced smoke emissions at higher operating loads through an increase in charge premixing resulting from an increase in ignition delay and higher fuel volatility.
2007-07-23
Technical Paper
2007-01-2020
Adam Weall, Nick Collings
Highly homogeneous compression ignition is difficult to achieve in a direct injection diesel engine. The difficulty of achieving adequate fuel vaporization and the problems of fuel spray wall impingement are the main factors. Limitation of the maximum operating load results from high rates of pressure rise that occur in this combustion regime. The levels of HC and CO emissions are raised substantially when compared with conventional combustion and remain a significant emission factor. In this study, two methods of achieving highly homogeneous combustion in a direct injection diesel engine were investigated, Nissan MK type and early injection. The effects of fuel injection pressure, injection timing, EGR level, EGR cooler efficiency and compression ratio were examined using a conventional 4 cylinder 2.0L common rail diesel engine with 18.4:1 and 14.4:1 compression ratios.
2009-04-20
Journal Article
2009-01-0130
Jonathan Etheridge, Sebastian Mosbach, Markus Kraft, Hao Wu, Nick Collings
A previously developed Stochastic Reactor Model (SRM) is used to simulate combustion in a four cylinder in-line four-stroke naturally aspirated direct injection Spark Ignition (SI) engine modified to run in Homogeneous Charge Compression Ignition (HCCI) mode with a Negative Valve Overlap (NVO). A portion of the fuel is injected during NVO to increase the cylinder temperature and enable HCCI combustion at a compression ratio of 12:1. The model is coupled with GT-Power, a one-dimensional engine simulation tool used for the open valve portion of the engine cycle. The SRM is used to model in-cylinder mixing, heat transfer and chemistry during the NVO and main combustion. Direct injection is simulated during NVO in order to predict heat release and internal Exhaust Gas Recycle (EGR) composition and mass. The NOx emissions and simulated pressure profiles match experimental data well, including the cyclic fluctuations.
2009-06-15
Journal Article
2009-01-1791
Adam Weall, Nick Collings
The objective of this study was to examine the operating characteristics of a light duty multi cylinder compression ignition engine with regular gasoline fuel at low engine speed and load. The effects of fuel stratification by means of multiple injections as well as the sensitivity of auto-ignition and burn rate to intake pressure and temperature are presented. The measurements used in this study included gaseous emissions, filter smoke opacity and in-cylinder indicated information. It was found that stable, low emission operation was possible with raised intake manifold pressure and temperature, and that fuel stratification can lead to an increase in stability and a reduced reliance on increased temperature and pressure. It was also found that the auto-ignition delay sensitivity of gasoline to intake temperature and pressure was low within the operating window considered in this study.
2015-09-01
Technical Paper
2015-01-1980
Paul B. Dickinson, Keith Glover, Nick Collings, Y. Yamashita, Y. Yashiro, T. Hoshi
There is a trend towards increasing the degree of engine downsizing due to its potential for reducing fuel consumption and hence lowering CO2 emissions. However, downsizing introduces significant challenges for the engine airpath hardware and control, if driveability is to be maintained at an acceptable level. The transient response of the engine is affected by both the hardware selection and the associated controller. In order to understand the potential performance and limitations of the possible airpath hardware, a mean value model of the engine under consideration can be utilized. One benefit of these models is that they can be used as the basis of a model predictive controller which gives close to optimal performance with minimal tuning effort. In this paper we examine different two-stage series sequential turbocharger arrangements.
1999-03-01
Technical Paper
1999-01-1314
Jian Li, Nick Collings
A semi-empirical model of fuel transport in the intake manifold of spark ignition engines, which assumes a fraction of injected fuel deposits onto the port walls and describes the detailed fuel film phenomena, is proposed. The model is applied in the throttle ramp transients during which both the air and the fuel flow change significantly. The predicted air fuel ratio excursions, engine torque etc, are in good agreement with the experimental data. Also simulated is another kind of transience, which has only an air flow jump, i.e. with fuelling rate constant, when the engine jumps between stoichiometric and lean running. The results are again in satisfactory agreement with experiment.
1999-03-01
Technical Paper
1999-01-0208
Richard Ford, Nick Collings
Two new techniques are introduced for measuring the residual gas fraction in internal combustion engines. Both techniques use a fast chemiluminescent detection (CLD) type NO sensor. The measurement is made in real-time and requires a single misfire of the engine. Development of the techniques revealed several unexpected, but interesting effects; the results obtained show good agreement with existing knowledge.
2000-10-16
Technical Paper
2000-01-2870
George Kontarakis, Nick Collings, Tom Ma
A standard port fuel injected, unthrottled single cylinder four-stroke SI engine, with a compression ratio of 10.3:1, and using standard gasoline fuel, has been adapted to operate in the homogeneous charge compression ignition (HCCI) mode, by modifying the valve timing. It has been found that over a speed range of between 1300 and 2000 rpm, and lambda values of between 0.95 and 1.1, stable operation is achieved without spark ignition. The internal EGR rate was estimated to be about 60%, and emissions of NOX were typically 0.25 g/kWh. Practical implementation of this HCCI concept will require variable valve timing, which will also enable reversion to standard SI operation for maximum power.
1999-10-25
Technical Paper
1999-01-3477
Cory Sutela, Nick Collings, Tim Hands
A fast response sensor for measuring carbon dioxide concentration has been developed for laboratory research and tested on a spark ignition engine. The sensor uses the well known infra-red absorption technique with a miniaturized detection system and short capillary sampling tubes, giving a time constant of approximately 5 milliseconds; this is sufficiently fast to observe changes in CO2 levels on a cycle-by-cycle basis under normal operating conditions. The sensor is easily located in the exhaust system and operates continuously. The sensor was tested on a standard production four cylinder spark-ignition engine to observe changes in CO2 concentration in exhaust gas under steady state and transient operating conditions. The processed sensor signal was compared to a standard air-to-fuel ratio (AFR) sensor in the exhaust stream and the results are presented here. The high frequency response CO2 measurements give new insights into both engine and catalyst transient operation.
2000-10-16
Technical Paper
2000-01-2837
Daniel E. Davison, Stephen J. Cornelius, Nick Collings, Keith Glover
This paper presents experimental data showing unexpected transient behaviour in several production universal exhaust gas oxygen (UEGO) sensors. The spike-like transients occur when passing through the stoichiometric point, and are particularly significant when passing from rich to lean. The paper illustrates how the spikes are affected by exhaust gas flow rate, deviation of air-to-fuel ratio (AFR) from stoichiometry, and rate of change of AFR while passing through stoichiometry. The spikes are most sensitive to the rate at which AFR passes through stoichiometry. Brief discussions on possible causes for the spikes, and on undesirable consequences for feedback control applications, are included.
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