Hans-Erik Ångström

Partially pre-mixed auto-ignition of gasoline to attain low smoke and low NOx at high load in a compression ignition engine and comparison with a diesel fuel

A Swedish MK1 diesel fuel and a European gasoline of ∼95 RON have been compared in a single cylinder CI engine operating at 1200 RPM with an intake pressure of 2 bar abs., intake temperature of 40° ...

Advantages of Fuels with High Resistance to Auto-ignition in Late-injection, Low-temperature, Compression Ignition Combustion

Oxides of nitrogen (NOx) and smoke can be simultaneously reduced in compression ignition engines by getting combustion to occur at low temperatures and by delaying the heat release till after the ...

Integrated Simulation and Engine Test of Closed Loop HCCI Control by aid of Variable Valve Timings

Integrated Simulation and Engine Test of Closed Loop HCCI Control by aid of Variable Valve Timings

Auto-ignition quality of Diesel-like fuels in HCCI engines

In Homogeneous Charge Compression Ignition (HCCI) engines heat release occurs by auto-ignition and hence the fuel auto-ignition quality is very important. The auto-ignition quality of Diesel fuel ...

A Method of Defining Ignition Quality of Fuels in HCCI Engines

A homogeneous charge compression ignition (HCCI) engine has been run at different operating conditions with fuels of different RON and MON and different chemistries. The ignition quality of the f ...

Transient Control of HCCI Through Combined Intake and Exhaust Valve Actuation

This doctoral thesis is about controlling the combustion timing of the combustion concept Homogeneous Charge Compression Ignition, HCCI, by means of variable valve timings. The HCCI research usually is regarded to have started in Japan during the later part of the 1970´s. The world of HCCI has since grown and HCCI is of today researched worldwide. Of particular interest from a Swedish point of view is that Lund Institute of Technology has emerged as one of the world leading HCCI laboratories. The idea with HCCI is to combine the Otto and Diesel engine. As in an Otto engine the charge is premixed but as in a Diesel engine the operation is unthrottled and the compression heat causes the ignition. The combustion that follows the ignition takes place homogeneously and overall lean. The result is ultra low NOx and particulate emissions combined with high total efficiency. A difficulty with the HCCI-concept is that it only works in a narrow area and that there is no direct way to control the Start Of Combustion, SOC. Out of this follows that timing/phasing of the combustion is one of the main difficulties with HCCI combustion concepts. This is particularly emphasized during transient operation and calls for feedback control of the combustion timing. This work investigates one method, the variable valve timing, to achieve feedback control of the combustion phasing. From the work it can be concluded that the variable valve timing can control the combustion phasing during engine transients. In order to improve the performance a non-linear compensation from ignition delay to valve timings has been suggested, incorporated in a control structure and tested in engine test. The engine test has been performed in a single cylinder engine based on a Scania truck engine. The speed range from 500 to 1750 rpm and the load range 1.26 and 10.5 bar of netIMEP has been covered with fair transient performance.

Auto-ignition Quality of Gasoline-Like Fuels in HCCI Engines

Auto-ignition of fuel mixtures was investigated both theoretically and experimentally to gain further understanding of the fuel chemistry. A homogeneous charge compression ignition (HCCI) engine was run under different operating conditions with fuels of different RON and MON and different chemistries. Fuels considered were primary reference fuels and toluene/n-heptane blends. The experiments were modeled with a single-zone adiabatic model together with detailed chemical kinetic models. In the model validation, co-oxidation reactions between the individual fuel components were found to be important in order to predict HCCI experiments, shock-tube ignition delay time data, and ignition delay times in rapid compression machines. The kinetic models with added co-oxidation reactions further predicted that an n-heptane/toluene fuel with the same RON as the corresponding primary reference fuel had higher resistance to auto-ignition in HCCI combustion for lower intake temperatures and higher intake pressures. However, for higher intake temperatures and lower intake pressures the n-heptane/toluene fuel and the PRF fuel had similar combustion phasing.

Optimizing Engine Concepts by Using a Simple Model for Knock Prediction

This licentiate thesis concerns the modeling of spark ignition engine combustion for use in one dimensional simulation tools. Modeling of knock is of particular interest when modeling turbocharged engines since knock usually limits the possible engine output at high load. The knocking sound is an acoustic phenomenon with pressure oscillations triggered by autoignition of the unburned charge ahead of the propagating flame front and it is potentially damaging to the engine. To be able to predict knock it is essential to predict the temperature and pressure in the unburned charge ahead of the flame front. Hence, an adequate combustion model is needed. The combustion model presented here is based on established correlations of laminar burning velocity which are used to predict changes in combustion duration relative to a base operating condition. Turbulence influence is captured in empirical correlations to the engine operating parameters spark advance and engine speed. This approach makes the combustion model predictive in terms of changes in gas properties such as mixture strength, residual gas content, pressure and temperature. However, a base operating condition and calibration of the turbulence correlations is still needed when using this combustion model. The empirical models presented in this thesis are based on extensive measurements on a turbocharged four cylinder passenger car engine. The knock model is simply a calibration of the Arrhenius type equation for ignition delay in the widely used Livengood-Wu knock integral to the particular fuel and engine used in this work.

An empirical SI combustion model using laminar burning velocity correlations

Predictive simulation models are needed in order to exploit the full benefits of 1-D engine simulation. Simulation model alterations such as cam phasing affect the gas composition and gas state in ...

The Influence of NO on the Combustion Phasing in an HCCI Engine

In this work the influence of NO on combustion phasing has been studied experimentally in a single cylinder HCCI engine. A isooctane/n-heptane blend (PRF), a toluene/n-heptane mixture (TRF) and a ...