The subject of this study is the effect of in-cylinder selective non-catalytic reduction (SNCR) of NOx emissions in diesel exhaust gas by means of direct injection of aqueous urea ((NH2)2CO) into the combustion chamber. A single cylinder diesel test engine was modified to accept an electronically controlled secondary common rail injection system to deliver the aqueous urea directly into the cylinder during engine operation. Direct in-cylinder injection was chosen in order to ensure precise delivery of the reducing agent without the risk of any premature reactions taking place. Unlike direct in-cylinder injection of neat water, aqueous urea also works as a reducing agent by breaking down into ammonia (NH3) and Cyanuric Acid ((HOCN)3). These compounds serve as the primary reducing agents in the NOx reduction mechanism explored here. The main reducing agent, aqueous urea, was admixed with glycerol (C3H8O3) in an 80-20 ratio, by weight, to function as a lubricant for the secondary injector. The aqueous urea injection timing and duration is critical to the reduction of NOx emissions due to the dependence of SNCR NOx reduction on critical factors such as temperature, pressure, reducing agent to NOx ratio, Oxygen and radical content, residence time and NH3 slip. From scoping engine tests at loads of 40 percent and 80 percent at 1500 rpm, an aqueous urea injection strategy was developed. The final injection strategy chosen was four molar ratios, 4.0, 2.0, 1.0 and 0.5 with five varying injection timings of 60, 20, 10, 0, and -30 degrees after top dead center (ATDC). In addition to the base line and aqueous urea tests, water injection and an 80-20 water-glycerol solution reduction agent tests were also conducted to compare the effects of said additives as well. The comparison of baseline and SNCR operation was expected to show that the urea acted as a reducing agent, lowering NOx emissions up to 100% (based on exhaust stream studies) in the diesel exhaust gas without the aid of a catalyst. The data collected from the engine tests showed that the aqueous urea-glycerol solution secondary had no effect on the reduction of NOx and even resulted in an increase of up to 5% in some tests. This was due to the low average in-cylinder temperature as well as a short residence time, prohibiting the reduction reaction from taking place. The neat water and water-glycerol solution secondary injection was found to have a reduction effect of up to 59% on NOx production in the emissions due to the evaporative cooling effect and increased heat capacity of the water.

Growing environmental concerns are causing a large transformation within the energy industry. Within the gas turbine industry, there is a large drive to develop improved modern dry-low emission combustion systems. The aim is to enable gas turbines to run on green fuels like hydrogen, while still keeping emission as NOx down. To design these systems, a thorough understanding of the aerothermal and kinetic processes within the combustion system of a gas turbine is essential. The goal of the thesis was to develop a one-dimensional general network model of the combustion system of Siemens Energy SGT-700, which accurately could predict pressure losses, mass flows, key temperatures, and emissions. Three models were evaluated and a code that emulated some aspects of the control system was developed. The models and the code were evaluated and compared to each other and to test data from earlier test campaigns performed on SGT-700 and SGT-600. Simulations were also carried out with hydrogen as the fuel.  In the end, a model of the SGT-700 combustion chamber was developed and delivered to Siemens Energy. The model had been verified against test data and predictions made by other Siemens Energy thermodynamic calculation software, for a range of load conditions. The preforms of the model, when hydrogen was introduced into the fuel mixture, were also tested and compared to test data / En växande medvetenhet kring klimatfrågan, har medfört stora förändringar i energibranschen. I och med detta behöver även gasturbinindustrin förbättra de nuvarande dry-low emissions systemen och göra det möjligt för gasturbiner att förbränna gröna bränslen som väte. Samtidigt måste också utsläppen av NOx hållas nere. För att kunna utforma dessa system behövs en fullständig förståelse för de aerotermiska och kinetiska processerna i en gasturbins förbränningskammare. Målet med detta examensarbete var att utveckla en endimensionell generell nätverksmodell för förbränningssystemet i Siemens Energys SGT-700. Modellen skulle noggrant kunna förutsäga tryckförluster, massflöden, viktiga temperaturer samt utsläpp. Tre modeller utvärderades och en kod som emulerade vissa aspekter av styrsystemet utvecklades också. Modellerna och koden utvärderades och jämfördes mot varandra och även mot testdata från tidigare testserier som utfördes på SGT-700 och SGT-600. Simuleringar utfördes också med väte som bränsle. Slutligen levererades en modell av SGT-700 förbränningskammaren till Siemens Energy. Modellen har verifierats för en rad olika lastfall, mot testdata och data som genererats av andra termodynamisk beräkningsprogram som utvecklats av Siemens Energy. Hur modellen uppförde sig när väte var introducerat in i olika lastfall jämfördes också mot testdata