Search Results

Styrene, or ethylbenzene, is mainly used as a monomer for the production of polymers, most notably Styrofoam. In the synthetis of styrene, the feedstock of benzene and ethylene is converted into aromatic oxygenates such as benzaldehyde, 2-phenyl ethanol and acetophenone. Benzaldehyde and phenyl ethanol are low value side streams, while acetophenone is a high value intermediate product. The side streams are now principally rejected from the process and burnt for process heat. Previous in-house research has shown that such aromatic oxygenates are suitable as diesel fuel additives and can in some cases improve the soot-NOx trade-off. In this study acetophenone, benzaldehyde and 2-phenyl ethanol are each added to commercial EN590 diesel at a ratio of 1:9, with the goal to ascertain whether or not the lower value benzaldehyde and 2-phenyl ethanol can perform on par with the higher value acetophenone. These compounds are now used in pure form.

In an attempt to extend the upper load limit for Homogeneous Charge Compression Ignition (HCCI), supercharging in combination with Exhaust Gas Recirculation (EGR) have been applied. Two different boost pressures were used, 1.1 bar and 1.5 bar. High EGR rates were used in order to reduce the combustion rate. The highest obtained IMEP was 16 bar. This was achieved with the higher boost pressure, at close to stoichiometric conditions and with approximately 50 % EGR. Natural gas was used as the main fuel. In the case with the higher boost pressure, iso-octane was used as pilot fuel, to improve the ignition properties of the mixture. This made it possible to use a lower compression ratio and thereby reducing the maximum cylinder pressure. The tests were performed on a single cylinder engine operated at low speed (1000 rpm). The test engine was equipped with a modified cylinder head, having a Variable Compression Ratio (VCR) mechanism.

This paper discusses the effects of cooled EGR on a turbo charged multi cylinder HCCI engine. A six cylinder, 12 liter, Scania D12 truck engine is modified for HCCI operation. It is fitted with port fuel injection of ethanol and n-heptane and cylinder pressure sensors for closed loop combustion control. The effects of EGR are studied in different operating regimes of the engine. During idle, low speed and no load, the focus is on the effects on combustion efficiency, emissions of unburned hydrocarbons and CO. At intermediate load, run without turbocharging to achieve a well defined experiment, combustion efficiency and emissions from incomplete combustion are still of interest. However the effect on NOx and the thermodynamic effect on thermal efficiency, from a different gas composition, are studied as well. At high load and boost pressure the main focus is NOx emissions and the ability to run high mean effective pressure without exceeding the physical constraints of the engine.

A naturally aspirated in-line six-cylinder 2.9-litre Volvo engine is operated in Homogeneous Charge Compression Ignition (HCCI) mode, using camshafts with low lift and short duration generating negative valve overlap. This implementation requires only minor modifications of the standard SI engine and allows SI operation outside the operating range of HCCI. Standard port fuel injection is used and pistons and cylinder head are unchanged from the automotive application. A heat exchanger is utilized to heat or cool the intake air, not as a means of combustion control but in order to simulate realistic variations in ambient temperature. The combustion is monitored in real time using cylinder pressure sensors. HCCI through negative valve overlap is recognized as one of the possible implementation strategies of HCCI closest to production. However, for a practical application the intake temperature will vary both geographically and from time to time.

2-D LDV measurements were performed on two different cylinder designs in a fired two-stroke engine running with wide-open throttle at 9000 rpm. The cylinders examined were one with open transfer channels and one with cup handle transfer channels. Optical access to the cylinder was achieved by removing the silencer and thereby gain optical access through the exhaust port. No addition of seeding was made, since the fuel droplets were not entirely vaporized as they entered the cylinder and thus served as seeding. Results show that the loop-scavenging effect was poor with open transfer channels, but clearly detectable with cup handle channels. The RMS-value, “turbulence”, was low close to the transfer ports in both cylinders, but increased rapidly in the middle of the cylinder. The seeding density was used to obtain information about the fuel concentration in the cylinder during scavenging.

This study is focused on the effect of different valve strategies on the in-cylinder flow and combustion A conventional four-valve pentroof engine was modified to enable optical access to the combustion chamber To get information on the flow, a two-component LDV system was applied The combustion was monitored by the use of cylinder pressure in a one-zone heat release model The results show that the flow in the cylinder with the valves operating in the standard configuration has an expected tumble characteristic In this case the high frequency turbulence is homogeneous and has a peak approximately 20 CAD BTDC With one valve deactivated, the flow shows a swirling pattern The turbulence is then less homogeneous but the level of turbulence is increased When the single inlet valve was phased late against the crankshaft dramatic effects on the flow resulted The late inlet valve opening introduced a low cylinder pressure before the valve opened The high pressure difference across the valve introduced a high-velocity jet into the cylinder Turbulence was increased by a factor of two by this operational mode When two inlet valves were used, a reduction of turbulence resulted from a very late inlet cam phase

The different roles played by small and large eddies in engine combustion were studied. Experiments compared natural gas combustion in a converted, single cylinder Volvo TD 102 engine and in a 125 mm cubical cell. Turbulence is used to enhance flame growth, ideally giving better efficiency and reduced cyclic variation. Both engine and test cell results showed that flame growth rate correlated best with the level of high frequency, small eddy turbulence. The more effective, small eddy turbulence also tended to lower cyclic variations. Large scales and bulk flows convected the flame relative to cool surfaces and were most important to the initial flame kernel.

Ion current measurements can give information useful for controlling the combustion stability in a multi-cylinder engine. Operation near the dilution limit (air or EGR) can be achieved and it can be optimized individually for the cylinders, resulting in a system with better engine stability for highly diluted mixtures. This method will also compensate for engine wear, e.g. changes in volumetric efficiency and fuel injector characteristics. Especially in a port injected engine, changes in fuel injector characteristics can lead to increased emissions and deteriorated engine performance when operating with a closed-loop lambda control system. One problem using the ion-current signal to control engine stability near the lean limit is the weak signal resulting in low signal to noise ratio. Measurements presented in this paper were made on a turbocharged 9.6 liter six cylinder natural gas engine with port injection.

This study applies a state feedback based Closed-Loop Combustion Control (CLCC) using Fast Thermal Management (FTM) on a multi cylinder Variable Compression Ratio (VCR) engine. At speeds above 1500 rpm is the FTM's bandwidth broadened by using the VCR feature of this engine, according to a predefined map, which is a function of load and engine speed. Below 1500 rpm is the PID based CLCC using VCR applied instead of the FTM while slow cylinder balancing is effectuated by the FTM. Performance of the two CLCC controllers are evaluated during an European EC2000 drive cycle, while HC, CO and CO2 emissions are measured online by a Fast Response Infrared (FRI) emission equipment. A load and speed map calculated for an 1.6L Opel Astra is used to get reference values for the dynamometer speed and the load control. The drive cycle test is initiated from a hot engine and hence no cold start is included. Commercial RON/MON 92/82 gasoline, which corresponds to US regular, is utilized.

Variable compression ratio (VCR) technology has long been recognized as a method for improving the automobile engine performance, efficiency, fuel economy with reduced emission. This paper presents a design of hydraulically actuated piston based on the VCR piston proposed by the British Internal Combustion Engine Research Institute (BICERI). In this design, the compression height of the piston automatically changes in response to engine cylinder pressure by controlling the lubrication oil flow via valves in the piston. In addition, numerical models including piston kinetic model, oil hydraulic model, compression ratio model and etc., have been established to evaluate the piston properties. The oil flow characteristics between two chambers in VCR piston have been investigated and the response behaviors of VCR engine and normal engine, such as compression pressure and peak cylinder pressure, are compared at different engine loads.

Autoignition of a homogeneous mixture is very sensitive to operating conditions. Therefore fast combustion phasing control is necessary for reliable operation. There are several means to control the combustion phasing of a Homogeneous Charge Compression Ignition (HCCI) engine. This paper presents cycle-to-cycle cylinder individual control results from a six-cylinder HCCI engine using a Variable Valve 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 Gaussian control (LQG) and PID control. In the control design of the MPC and LQG controller, dynamic models obtained by system identification were used. Successful experiments were performed on a port-injected six-cylinder heavy-duty Diesel engine operating in HCCI mode.