Enlarging the operational range of a gasoline HCCI engine by controlling the coolant temperature

The Homogeneous Charge Compression Ignition (HCCI) engine combustion uses heat energy from trapped exhaust gases enhanced by the piston compression heating to auto ignite a premixed air/gasoline mixture. As the HCCI combustion is controlled by the charge temperature, composition and pressure, it therefore, prevents the use of a direct control mechanism such as in the spark and diesel combustion. Using a large amount of trapped residual gas (TRG), is seen as one of the ways to achieve and control HCCI in a certain operating range. By varying the amount of TRG in the fresh air/fuel mixture (inside the cylinder), the charge mixture temperature, composition and pressure can be controlled and hence, the auto ignition timing and heat release rate. The controlled auto ignition (HCCI) engine concept has the potential to be highly efficient and to produce low NOx, carbon dioxide and particulate matter emissions. It has however been found that the TRG promoted HCCI combustion mainly depends on the quantity and quality of TRG, that on the other hand depend on the combustion quality of the previous cycle, valve timing, engine load and speed. In that way, the operating range in terms of engine load and speed, for a naturally aspirated HCCI engine, is restricted by a misfire at low load and by fierce (knocking) combustion at high load. One possible approach to extend the operating range of the HCCI combustion is to influence quality of the TRG by adjusting the coolant temperature. The engine coolant temperature influences the in-cylinder heat transfer process, which in turn influences the charge mixture temperature and therefore the HCCI combustion process itself. The aim of this paper is to present tests and results obtained on the single cylinder research engine, equipped with a Fully Variable Valve Train (FVVT) run over a range of coolant temperature in the HCCI combustion mode and fuelled with gasoline fuel. The results obtained suggest that with reducing the coolant temperature, the high load limit can be extended up to 14%, while with increasing the coolant temperature the low load limit can be extended up to 28%

An automotive engine charge-air intake conditioner system: analysis of fuel economy benefits in a gasoline engine application

A combination of analytical techniques has been used to quantify the potential fuel economy benefits of an automotive engine charge-air intake conditioner system applied to a spark-ignited gasoline engine. This system employs a compressor, intercooler, and expander to provide increased charge density with the possibility of reducing charge-air temperature below sink temperature. This reduction in charge-air temperature provides the potential for improved knock resistance at full load; thereby allowing the possibility of increasing compression ratio with corresponding benefits in thermodynamic cycle efficiency and part-load fuel economy. The four linked and interfaced models comprised a first-law thermodynamic model of the charge-air conditioner system, a one-dimensional engine cycle simulation, a two-zone combustion model, and a knock criterion model. An analysis was carried out under full load at 3000 r/min and showed that a charge-air conditioner system - with compressor, intercooler, and expander efficiencies of 0.8 - allowed the compression ratio to be increased by approximately half a ratio, which gave up to 1.5 per cent reduction in brake specific fuel consumption at 2000 r/min 2 bar brake mean effective pressure when compared with a conventional pressure charger intercooler system with no expander

An automotive engine charge-air intake conditioner system: thermodynamic analysis of performance characteristics

A first law thermodynamic model has been developed and used to characterize the performance of an automotive engine charge-air intake conditioner system. This system employs a compressor, intercooler, and expander to provide increased charge density with the possibility of reducing, the charge-air temperature below the sink temperature. The model was validated against experimental measurements. The variation of system effectiveness with compressor, intercooler, and expander efficiency was quantified and system operating limits were identified. While the expander was found to have a greater effect than the compressor, the performance of the system was shown to be most dependent upon intercooler effectiveness

The impact on engine performance of controlled auto ignition versus spark ignition with two methods of load control

This paper presents and discusses results taken from Lotus’ Research Active Valve Train (AVT) engine, in which advanced combustion strategies can easily be investigated because of a the functionality of its Fully Variable Valve Train. In particular, Controlled Auto Ignition can readily be initiated and controlled by a method of early exhaust valve closure and late inlet valve opening to trap exhaust gas residuals within the cylinder from one cycle to the next. The paper looks at the impact on fuel consumption and emissions (engine out BSNOx, BSTHC and BSCO) of Controlled Auto Ignition versus Spark Ignition with load control either by conventional variable density throttling or by Early Inlet Valve Closure with variable lift. The points analysed are commonly used emissions comparison points: 1300rpm 2.95bar BMEP, 1500rpm 2.62bar BMEP, 2000rpm 2bar BMEP and 2500rpm 2.62bar BMEP

Enlarging the Operational Range of a Gasoline HCCI Engine By Controlling the Coolant Temperature

The Homogeneous Charge Compression Ignition (HCCI) engine combustion uses heat energy from trapped exhaust gases enhanced by the piston compression heating to auto ignite a premixed air/gasoline mixture. As the HCCI combustion is controlled by the charge temperature, composition and pressure, it therefore, prevents the use of a direct control mechanism such as in the spark and diesel combustion. Using a large amount of trapped residual gas (TRG), is seen as one of the ways to achieve and control HCCI in a certain operating range. By varying the amount of TRG in the fresh air/fuel mixture (inside the cylinder), the charge mixture temperature, composition and pressure can be controlled and hence, the auto ignition timing and heat release rate. The controlled auto ignition (HCCI) engine concept has the potential to be highly efficient and to produce low NOx, carbon dioxide and particulate matter emissions. It has however been found that the TRG promoted HCCI combustion mainly depends on the quantity and quality of TRG, that on the other hand depend on the combustion quality of the previous cycle, valve timing, engine load and speed. In that way, the operating range in terms of engine load and speed, for a naturally aspirated HCCI engine, is restricted by a misfire at low load and by fierce (knocking) combustion at high load. One possible approach to extend the operating range of the HCCI combustion is to influence quality of the TRG by adjusting the coolant temperature. The engine coolant temperature influences the in-cylinder heat transfer process, which in turn influences the charge mixture temperature and therefore the HCCI combustion process itself. The aim of this paper is to present tests and results obtained on the single cylinder research engine, equipped with a Fully Variable Valve Train (FVVT) run over a range of coolant temperature in the HCCI combustion mode and fuelled with gasoline fuel. The results obtained suggest that with reducing the coolant temperature, the high load limit can be extended up to 14%, while with increasing the coolant temperature the low load limit can be extended up to 28%