The internal combustion engine has a long history. In 1820 Cecil built the first working engine, but it did not get commercialized until 1860 when Lenoir sold his first engine. Since that time engines have been developed and improved by many inventors. Important developments are Nikolaus Otto's flame ignited (spark ignited) engine from 1876 and Rudolf Diesel's compression-ignited engine from 1892 [1]. Since then the internal combustion engine has been important for society in the fields of power generation and transport. In recent years, engine research has been challenged to solve air pollution issues and reduce fuel consumption.
Most climate scientists agree that the main cause of the global warming is from human development on the greenhouse gas effect. In the European Union (EU) the second biggest source of greenhouse gas after power generation is from road transport. A recent analysis showed that road transport is the source of one-fifth of the EU's total emissions of greenhouse gas and continues to increase [2]. The most important greenhouse gas from internal combustion engines is carbon dioxide (CO2). This shows the need for research towards more fuel-efficient engines leading to lower CO2 emissions.
Other pollutants from combustion engines are carbon monoxide (CO), hydrocarbons (HC), nitrogen oxide (NOx) and particulate matter (PM). They are harmful not just to the environment but also to human health. CO emissions are dangerous to humans because they bind to hemoglobin and cause blood poisoning. HC emissions increase incidence of leukemia and lung cancer. PM emissions contain microscopic solids or liquid droplets that can get deep into the lungs and cause serious health problems. NOx emissions together with HC influence the formation of ground-level ozone, which are also linked to a number of adverse effects on the respiratory system [3].
The pollutant legislations force a reduction of emissions that are emitted from road transportation. Therefore the focus is to develop clean combustion engines that minimize the environmental impact.