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The operating range in HCCI mode is limited by the excessive pressure rise rate and therefore high combustion induced noise. The HCCI range can be extended with turbocharging which enables increased dilution of the charge and thus a reduction of combustion noise. When the engine is turbocharged the intake charge will have a high temperature at increased boost pressure and can then be regulated in a cooling circuit. Limitations and benefits are examed at 2250 rpm and 400 kPa indicated mean effective pressure. It is shown that combustion stability, combustion noise and engine efficiency have to be balanced since they have optimums at different intake temperatures and combustion timings. The span for combustion timings with high combustion stability is narrower at some intake temperatures and the usage of external EGR can improve the combustion stability. It is found that the standard deviation of combustion timing is a useful tool for evaluating cycle to cycle variations.

Selective Non-Catalytic Reduction (SNCR), used to reduce the emissions of nitrogen oxides (NOx), has been a well-established technology in the power plant industry for several decades. The SNCR technique is an aftertreatment strategy based on thermal reduction of NOx at high temperatures. In the compression ignition engine application, the technology has not been applicable due to low exhaust temperatures, which makes the SCR (Selective Catalytic Reduction) system essential for efficient nitrogen oxide reduction to fulfill the environment legislation. For a general Double Compression Expansion Engine (DCEE) the complete expansion cycle is split in two separate cycles, i.e. the engine is a split cycle engine. In the first cylinder the combustion occurs and in the second stage the combustion gas is introduced and further expanded in a low-pressure expansion cylinder. The combustion cylinder is connected with the expansion cylinder through a large insulated high-pressure tank.

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.

Partially premixed combustion has the potential of high efficiency and simultaneous low soot and NOx emissions. Running the engine in PPC mode with high octane number fuels has the advantage of a longer premix period of fuel and air which reduces soot emissions, even at higher loads. The problem is the ignitability at low load and idle operating conditions. The objective is to investigate the usefulness of negative valve overlap on a light duty diesel engine running with gasoline partially premixed combustion at low load operating conditions. The idea is to use negative valve overlap to trap hot residual gases to elevate the global in-cylinder temperature to promote auto-ignition of the high octane number fuel. This is of practical interest at low engine speed and load operating conditions because it can be assumed that the available boost is limited. The problem with NVO at low load operating conditions is that the exhaust gas temperature is low.

The double compression expansion engine (DCEE) is a promising concept for high engine efficiency while fulfilling the most stringent European and US emission legislation. The complete thermodynamic cycle of the engine is split among several cylinders. Combustion of fuel occurs in the combustion cylinder and in the expansion cylinder the exhaust gases are over expanded to obtain high efficiency. A high-pressure tank is installed between these two cylinders for after-treatment purposes. One proposal is to utilize thermal reduction of nitrogen oxides (NOx) in the high-pressure tank as exhaust temperatures can be sufficiently high (above 700 °C) for the selective non-catalytic reduction (SNCR) reactions to occur. The exhaust gas residence time at these elevated exhaust temperatures is also long enough for the chemical reactions, as the volume of the high-pressure tank is substantially larger than the volume of the combustion cylinders.

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.

An estimation model which uses the gross heat release data and the fuel energy to estimate the total amount of emissions and unburned Hydro Carbon (HC) is developed. Gross heat release data is calculated from a self-tuned heat release method which uses in-cylinder pressure data for computing the energy released during combustion. The method takes all heat and mass losses into account. The method estimates the polytropic exponent and pressure offset during compression and expansion using a nonlinear least square method. Linear interpolation of polytropic exponent and pressure offset is then performed during combustion to calculate the gross heat release during combustion. Moreover the relations between the emissions specifically HC and Carbon Monoxide (CO) are investigated. The model was validated with experimental data and promising results were achieved.

Combination of right EGR rates with turbocharging has been identified as a promising way to increase the maximum load and efficiency of heavy duty spark-ignited natural gas engines. With stoichiometric conditions a three way catalyst can be used which means that regulated emissions can be kept at very low levels. However dilution limit is limited in these types of engines because of the lower burnings rate of natural gas with higher EGR rates. One way to extend the dilution limit of a natural gas engine is to run the engine with Hythane (natural gas+ some percentage hydrogen). Previously benefits of hydrogen addition to a Lean Burn natural-gas fueled engine was investigated [1] however a complete study for stoichiometric operation was not performed. This paper presents measurements made on a heavy duty 6-cylinder natural gas engine.

The present paper shows the validation of a self tuning heat release method with no need to model heat losses, crevice losses and blow by. Using the pressure and volume traces the method estimates the polytropic exponents (before, during and after the combustion event), by the use of the emission values and amount of fuel injected per cycle the algorithm calculates the total heat release. These four inputs are subsequently used for computing the heat release trace. The result is a user independent algorithm which results in more objective comparisons among operating points and different engines. In the present paper the heat release calculated with this novel method has been compared with the one computed using the Woschni correlation for modeling the heat transfer. The comparison has been made using different fuels (PRF0, PRF80, ethanol and iso-octane) making sweeps in relative air-fuel ratio, engine speed, EGR and CA 50.

Few previous publications investigate the possibility of combining multiple waste heat sources in a combustion engine waste heat recovery system. A waste heat recovery system for a HD truck diesel engine is evaluated for utilizing multiple heat sources found in a conventional HD diesel engine. In this type of engine more than 50% of heat energy goes futile. The majority of the heat energy is lost through engine exhaust and cooling devices such as EGRC (Exhaust gas recirculation cooler), CAC (Charge air cooler) and engine cooling. In this paper, the potential of usable heat recuperation from these devices using thermodynamic analysis was studied, and also an effort is made to recuperate most of the available heat energy that would otherwise be lost. A well-known way of recuperating this heat energy is by employing a Rankine cycle circuit with these devices as heat sources (single loop or dual loop), and thus this study is focused on using a Rankine cycle for the heat recovery system.