Refine Your Search

Search Results

Viewing 1 to 19 of 19
Technical Paper

2-Stroke Engine Options for Automotive Use: A Fundamental Comparison of Different Potential Scavenging Arrangements for Medium-Duty Truck Applications

2019-01-15
2019-01-0071
The work presented here seeks to compare different means of providing scavenging systems for an automotive 2-stroke engine. It follows on from previous work solely investigating uniflow scavenging systems, and aims to provide context for the results discovered there as well as to assess the benefits of a new scavenging system: the reverse-uniflow sleeve-valve. For the study the general performance of the engine was taken to be suitable to power a medium-duty truck, and all of the concepts discussed here were compared in terms of indicated fuel consumption for the same cylinder swept volume using a one-dimensional engine simulation package. In order to investigate the sleeve-valve designs layout drawings and analysis of the Rolls-Royce Crecy-type sleeve had to be undertaken.
Technical Paper

Review of Turbocharger Mapping and 1D Modelling Inaccuracies with Specific Focus on Two-Stag Systems

2015-09-06
2015-24-2523
The adoption of two stage serial turbochargers in combination with internal combustion engines can improve the overall efficiency of powertrain systems. In conjunction with the increase of engine volumetric efficiency, two stage boosting technologies are capable of improving torque and pedal response of small displacement engines. In two stage sequential systems, high pressure (HP) and low pressure (LP) turbochargers are packaged in a way that the exhaust gases access the LP turbine after exiting the HP turbine. On the induction side, fresh air is compressed sequentially by LP and HP compressors. The former is able to deliver elevated pressure ratios, but it is not able to highly compressor low flow rates of air. The latter turbo-machine can increase charge pressure at lower mass air flow and be by-passed at high rates of air flow.
Technical Paper

Improving Heat Transfer and Reducing Mass in a Gasoline Piston Using Additive Manufacturing

2015-04-14
2015-01-0505
Pressure and temperature levels within a modern internal combustion engine cylinder have been pushing to the limits of traditional materials and design. These operative conditions are due to the stringent emission and fuel economy standards that are forcing automotive engineers to develop engines with much higher power densities. Thus, downsized, turbocharged engines are an important technology to meet the future demands on transport efficiency. It is well known that within downsized turbocharged gasoline engines, thermal management becomes a vital issue for durability and combustion stability. In order to contribute to the understanding of engine thermal management, a conjugate heat transfer analysis of a downsized gasoline piston engine has been performed. The intent was to study the design possibilities afforded by the use of the Selective Laser Melting (SLM) additive manufacturing process.
Technical Paper

Turbocharger Dynamic Performance Prediction by Volterra Series Model

2014-10-13
2014-01-2558
Current turbocharger models are based on characteristic maps derived from experimental measurements taken under steady conditions on dedicated gas stand facility. Under these conditions heat transfer is ignored and consequently the predictive performances of the models are compromised, particularly under the part load and dynamic operating conditions that are representative of real powertrain operations. This paper proposes to apply a dynamic mathematical model that uses a polynomial structure, the Volterra Series, for the modelling of the turbocharger system. The model is calculated directly from measured performance data using an extended least squares regression. In this way, both compressor and turbine are modelled together based on data from dynamic experiments rather than steady flow data from a gas stand. The modelling approach has been applied to dynamic data taken from a physics based model, acting as a virtual test cell.
Technical Paper

Empirical Lumped-mass Approach to Modelling Heat Transfer in Automotive Turbochargers

2014-10-13
2014-01-2559
When evaluating the performance of new boosting hardware, it is a challenge to isolate the heat transfer effects inherent within measured turbine and compressor efficiencies. This work documents the construction of a lumped mass turbocharger model in the MatLab Simulink environment capable of predicting turbine and compressor metal and gas outlet temperatures based on measured or simulated inlet conditions. A production turbocharger from a representative 2.2L common rail diesel engine was instrumented to enable accurate gas and wall temperature measurements to be recorded under a variety of engine operating conditions. Initially steady-state testing was undertaken across the engine speed and load range in order that empirical Reynolds-Nusselt heat transfer relationships could be derived and incorporated into the model. Steady state model predictions were validated against further experimental data.
Journal Article

Investigating the Potential to Reduce Crankshaft Main Bearing Friction During Engine Warm-up by Raising Oil Feed Temperature

2012-04-16
2012-01-1216
Reducing friction in crankshaft bearings during cold engine operation by heating the oil supply to the main gallery has been investigated through experimental investigations and computational modelling. The experimental work was undertaken on a 2.4l DI diesel engine set up with an external heat source to supply hot oil to the gallery. The aim was to raise the film temperature in the main bearings early in the warm up, producing a reduction in oil viscosity and through this, a reduction in friction losses. The effectiveness of this approach depends on the management of heat losses from the oil. Heat transfer along the oil pathway to the bearings, and within the bearings to the journals and shells, reduces the benefit of the upstream heating.
Technical Paper

The Effects of Engine Thermal Conditions on Performance, Emissions and Fuel Consumption

2010-04-12
2010-01-0802
Engine thermal management systems (TMS) are gaining importance in engine development and calibration to achieve low fuel consumption and meet future emissions standards. To benefit from their full potential, a thorough understanding of the effects on engine behavior is necessary. Steady state tests were performed on a 2.0L direct injection diesel engine at different load points. A design of experiments (DoE) approach was used to conduct exhaust gas recirculation (EGR) and injection timing swings at different coolant temperatures. The effect of the standard engine controller and calibration was observed during these tests. The injection timing strategy included a significant dependency on coolant temperature, retarding injection by about 3° crank angle between coolant temperatures of 70°C and 86°C. In contrast, EGR strategy was essentially independent of coolant temperature, though physical interactions were present due in part to the EGR cooler.
Journal Article

Experimental Characterisation of Heat Transfer in Exhaust Pipe Sections

2008-04-14
2008-01-0391
This paper describes the characterisation of heat transfer in a series of 11 test sections designed to represent a range of configurations seen in production exhaust systems, which is part of a larger activity aimed at the accurate modeling of heat transfer and subsequent catalyst light off in production exhaust systems comprised of similar geometries. These sections include variations in wall thickness, diameter, bend angle and radius. For each section a range of transient and steady state tests were performed on a dynamic test cell using a port injected gasoline engine. In each case a correlation between observed Reynolds number (Re) and Nusselt number (Nu) was developed. A model of the system was implemented in Matlab/Simulink in which each pipe element was split into 25 sub-elements by dividing the pipe into five both axially and radially. The modeling approach was validated using the experimental data.
Journal Article

The Effect of Reducing Compression Ratio on the Work Output and Heat Release Characteristics of a DI Diesel under Cold Start Conditions

2008-04-14
2008-01-1306
An experimental investigation has been carried out to compare the indicated performance and heat release characteristics of a DI diesel engine at compression ratios of 18.4:1 and 15.4:1. The compression ratio was changed by modifying the piston bowl volume; the bore and stroke were unchanged, and the swept volume was nominally 500cc. The engine is a single cylinder variant of modern design which meets Euro 4 emissions requirements. Work output and heat release characteristics for the two compression ratios have been compared at an engine speed of 300 rev/min and test temperatures of 10, -10 and -20°C. A more limited comparison has also been made for higher speeds representative of cold idle at one test temperature (-20°C). The reduction in compression ratio generally produces an increase in peak specific indicated work output at low speeds; this is attributable to a reduction in blowby and heat transfer losses and lower peak rates of heat release increasing cumulative burn.
Technical Paper

Predictions for Nucleate Boiling - Results From a Thermal Bench Marking Exercise Under Low Flow Conditions

2002-03-04
2002-01-1028
Two predictive methods have been applied to an IC engine cooling gallery simulator to provide benchmarking heat transfer information. The object of this work was to assess the suitability and accuracy of these methods for application to future on-engine heat transfer studies. Such studies are aimed at developing predictive tools to aid in the design of precision cooling systems. The modelling techniques of Rohsenow and Chen have been used, modified and validated. Compared against experimental data, the sub-cooled form of the Chen model has been found to be most representative for the cooling gallery simulator designed specifically to meet the requirements of this work.
Technical Paper

Exhaust System Heat Transfer and Catalytic Converter Performance

1999-03-01
1999-01-0453
Three-way catalytic converters used on spark ignition engines have performance and durability characteristics which are effected by the thermal environment in which these operate. The design of the exhaust system and the location of the catalyst unit are important in controlling the range of thermal states the catalyst is exposed to. A model of system thermal behaviour has been developed to support studies of these. The exhaust system is modelled as connected pipe and junction elements with lumped thermal capacities. Heat transfer correlations for quasi-steady and transient conditions have been investigated. The catalytic converter is treated as elemental slices in series. Exothermic heat release and heat exchange between the monolith, mat, and shell are described in the model. A similar description is applied to lean NOx trap units.
Technical Paper

Correlation of Engine Heat Transfer for Heat Rejection and Warm-Up Modelling

1997-05-19
971851
A correlation for total gas-side heat transfer rate has been derived from the analysis of engine data for measured heat rejection rate, frictional dissipation, and published data on exhaust port heat transfer. The correlation is related to the form developed by Taylor and Toong, and the analysis draws on this. However, cylinder and exhaust port contributions are separated. Two empirical constants are fixed to best match predicted to measured results for heat rejection to coolant and oil cooler under steady-state conditions, and also for exhaust port heat transfer rates. The separated contributions also defined a correlation for exhaust port heat transfer rate. The description of gas-side heat transfer is suited to needs for the analysis of global thermal behaviour of engines.
Technical Paper

Intra-Cycle Resolution of Heat Transfer to Fuel in the Intake Port of an S.I. Engine

1996-10-01
961995
Previously reported studies of heat transfer between the intake port surface, gas flows in the port, and fuel deposited in surface films have been extended to examine details of the heat flux variations which occur within the engine cycle. The dynamic response characteristics of the surface-mounted heat flux sensors have been determined, and measured heat flux data corrected accordingly to account for these characteristics. Details of the model and data processing technique used are described. Corrected intra-cycle variations of heat transfer to fuel deposited have been derived for engine operating conditions at 1000 RPM covering a range of manifold pressures, fuel supply rates, port surface temperatures, and fuel injection timings. Both pump-grade gasoline and isooctane fuel have been used. The effects of operating conditions on the magnitude and features of the heat flux variations are described.
Technical Paper

Fuel Film Evaporation and Heat Transfer in the Intake Port of an S.I. Engine

1996-05-01
961120
Surface heat transfer measurements have been taken in the intake port of a single cylinder four valve SI engine running on isooctane fuel. The objective has been to establish how fuel characteristics affect trends in surface heat transfer rates for a range of engine operating conditions. The heat transfer measurements were made using heat flux gauges bonded to the intake port surface in the region where highest rates of fuel deposition occur. The influence on heat transfer rates of the deposited fuel and its subsequent behaviour has been examined by comparing fuel-wetted and dry-surface heat transfer measurements. Heat transfer changes are consistent with trends predicted by convective mass transfer over much of the range of surface temperatures from 20°C to 100°C. Towards the upper temperature limit heat transfer reaches a maximum limited by the rate and distribution of fuel deposition.
Technical Paper

Effect of Coolant Mixture Composition on Engine Heat Rejection Rate

1996-02-01
960275
The rate of heat rejection to the coolant system of an internal combustion engine depends upon coolant composition, among other factors, because this influences the coolant side heat transfer coefficient. The correlation developed by Taylor and Toong for heat transfer rate has been modified to account for this effect. The modification retains the gas-to-coolant passage thermal resistance implicit in the original correlation. The modified correlation gives predictions in agreement with experimental data. Compared to 100% water, mixtures of 50% ethylene glycol/50% water lower heat rejection rates by typically 5% and up to 25% in the extreme. This depends upon local conditions in the coolant circuit, which can give rise to different heat transfer regimes. Application of the modified correlation is outlined and illustrated.
Technical Paper

Heat Transfer Measurements in the Intake Port of a Spark Ignition Engine

1996-02-01
960273
Surface-mounted heat flux sensors have been used in the intake port of a fuel injected, spark ignition engine to investigate heat transfer between the surface, the gas flows through the port, and fuel deposited in surface films. The engine is of a four valve per cylinder design, with a bifurcated intake port. For dry-port conditions heat transfer per cycle varies between 0 and 300 J/m2 depending on location, towards the surface at low temperatures and away from the surface at fully-warm conditions. Particular attention has been given to the changes in heat transfer rate associated with fuel deposition. Typically this is of the order of 5 kW/m2 in regions of heavy fuel deposition and varies by a factor of 2 over the period of an engine cycle. During warm-up, as coolant temperature increases from 0 to 90°C, changes in heat transfer associated with fuel deposition typically increase from 300 J/m2 to 1000 J/m2.
Technical Paper

Heat Transfer to the Combustion Chamber Walls in Spark Ignition Engines

1995-02-01
950686
The cycle-by-cycle variation of heat transferred per cycle (q) to the combustion chamber surfaces of spark ignition engines has been investigated for quasi-steady and transient conditions produced by throttle movements. The heat transfer calculation is by integration of the instantaneous value over the cycle, using the Woschni correlation for the heat transfer coefficient. By examination of the results obtained, a relatively simple correlation has been identified: This holds both for quasi-steady and transient conditions and is on a per cylinder basis. The analysis has been extended to define a heat flux distribution over the surface of the chamber. This is given by: where F(x/L) is a polynomial function, q″ is the heat transfer per cycle per unit area to head and piston crown surfaces and gives the distribution along the liner
Technical Paper

The Determination of Heat Transfer from the Combustion Chambers of SI Engines

1993-04-01
931131
Two methods of determining the rate of heat transfer from the combustion chamber have been investigated. A First Law analysis is shown to be ill-conditioned because of sensitivity to heat release and gas property calculations. An alternative approach equates cycle-averaged chamber heat transfer to the difference between heat rejected to the coolant and gas heat transfer to the exhaust port. This has been examined as a basis for calibrating the Woschni correlation.
Technical Paper

A Model for the Investigation of Temperature, Heat Flow and Friction Characteristics During Engine Warm-Up

1993-04-01
931153
A computational model has been developed to support investigations of temperature, heat flow and friction characteristics, particularly in connection with warm-up behaviour. A lumped capacity model of the engine block and head, empirically derived correlations for local heat transfer and friction losses, and oil and coolant circuit descriptions form the core of the model. Validation of the model and illustrative results are reported.
X