Implementation of an exhaust system for an opposed piston two stroke HCCI engine JAVIER LAINEZ MARTÍ Master of Science Thesis Stockholm, Sweden 2010 Implementation of an exhaust system for an opposed piston two stroke HCCI engine Javier Lainez Martí Master of Science Thesis MMK 2010:15 MFM132 KTH Industrial Engineering and Management Machine Design SE-100 44 STOCKHOLM Examensarbete MMK 2010:15 MFM132 Anpassning av ett avgassystem för en motkolvs tvåtaktsmotor med HCCI-förbränning Javier Lainez Martí Godkänt Examinator Handledare 2010-06-29 Hans-Erik Ångström Hans-Erik Ångström Uppdragsgivare Kontaktperson HCCI Technologies AB Rafael Villasmil Sammanfattning Målet för detta examensarbete har varit att förbättra driften av en motkolvs tvåtaktsmotor med HCCI-förbränning. Huvudfokus för arbetet har varit på gasväxlingsprocessen, då främst avgasprocessen. Motorn har studerats med utgångspunkt från hur en tvåtakts Otto-cykel fungerar. Gasväxlingsprocessen i tvåtaktsmotorer kännetecknas av behovet av att snabbt få ut den förbrända gasen och införa ny blandning vid varje expansionstakt, samt avsaknaden av ventiler. Behovet att kunna kontrollera gasflödet genom cylindern ger upphov till två av de mest karaktäristiska systemen på tvåtaktsmotorer: spolpump samt avgaspipa. Utformningen och genomförandet av dessa två system har skapat ett flertal uppgifter som det varit nödvändigt att lösa: porttider har uppmätts, ett luftintag med trycksatt luft har byggts för att kunna ändra förhållandet på insugningsluften. Olika insprutningssystem har också testats. Slutligen har en avgaspipa installerats och trimmats in. Utifrån målsättningen, så har ett logiskt sätt att angripa problemet gjorts: • Beteende hos kompressibelt gasflöde i HCCI-motorns kanaler har studerats. • Avgasrörets dimension och dess påverkan på motor prestanda har undersökts genom att prova olika utformningar på avgasröret. • Experimentella observationer av tryckpulsationer i avgasflöden har gjorts för att kunna gör finjusteringar. Master of Science Thesis MMK 2010:15 MFM132 Implementation of an exhaust system for an opposed piston two stroke HCCI engine Javier Lainez Martí Approved Examiner Supervisor 2010-06-29 Hans-Erik Ångström Hans-Erik Ångström Commissioner Contact person HCCI Technologies AB Rafael Villasmil Abstract The aim of this thesis is the improvement of the operation of an opposed piston two stroke engine with HCCI-combustion. The main focus is the charge exchange process, concretely the exhaust process. The engine has been studied from the perspective of the two stroke Otto cycle. Charge exchange process in two stroke engines is characterized by the need of expelling the burnt gases and introducing the fresh mix each expansion stroke, and the absence of valves. Control of the gas flow through the cylinder motivates two of the most characteristic systems on two-stroke engines: scavenging compressor and exhaust pipe. The design and implementation of these two systems has needed the development of several tasks: port timing has been characterized; a compressed air intake installation has been built in order to be able to modify the inlet air conditions; different injection systems have been tested as well. Finally, an exhaust pipe has been installed and tuned. With this aim, a logical approach to the problem has been done: • The behavior of compressible gas flow through ducts has been studied. • The influence of the dimensions of the exhaust pipe has been understood by doing a design. • The experimental observation of the pressure pulse propagation through the exhaust flow has allowed the exhaust pipe tuning. Acknowledgements First of all, Hans-Erik Ångström allowed me to work in an incredible project in one of the best universities along the world. Thank you for all your advising and help. HCCI technologies AB and specially Tom Whitlock have delivered a continued interest and support for this project. Thanks to Patrick Hellgren, for all his solutions for whatever mechanical problem that took place. Without him it could have been impossible to develop this work. Thanks as well to Bengt Aronsson, Jack Ivarsson and Ulf Andorff. The people of the department have made my stay more pleasant. Thanks to Stefan, Anders, and all the others. The Shell Ecomarathon experience in Lausitzring was amazing. I am so grateful to all the members of the Agilis-V team for his passionate work and dedication. There is nothing like see the fruits of one´s labour. This experience would not have the same without all the friends that have accompanied me. Carlos, Adrián y Antonio, thank you for sharing this great year, for sure one of the best in all my life. I am really grateful to my father, for his push, and to my sister and my grandparents, for giving me happiness from Valencia. To my mother, for allowing me to live the life I want. Ester, it is impossible to explain with words what I feel towards you. Finally, to Rafael Villasmil: this is probably my first and last Master of Science, but it has been the second one for you. You should feel holder of this work as it was yours. Thank you for behaving like a brother. Contents 1. Introduction ................................................................................................................... 3 2. Definitions and considerations on angular references ............................................... 5 3. Optimization of the engine and test bench ................................................................. 7 3.1. Second block and spare parts ................................................................................... 7 3.2. Fuel .......................................................................................................................... 8 3.3. Rotary encoder ......................................................................................................... 8 3.4. Torque signal filters ................................................................................................. 9 3.5. Pressure and temperature sensors on intake manifold and exhaust circuit ............ 14 3.6. Intake compressed air supply system ..................................................................... 15 3.6.1. Objective ..................................................................................................... 15 3.6.2. Design and configuration ............................................................................ 16 3.6.2.1. Pressure regulator valve .................................................................. 16 3.6.2.2. Safety valve .................................................................................... 16 3.6.2.3. Flow meter ...................................................................................... 17 3.6.2.4. Air heater ........................................................................................ 17 3.6.3. Adjustment of an intake pressure ................................................................ 17 3.7. Oil pump ................................................................................................................ 18 3.8. Injection system modifications .............................................................................. 19 3.8.1. Bosch 0280150995 injector ........................................................................ 19 3.8.2. Injection calibration .................................................................................... 19 3.8.3. Empirical determination of the Injection Time vs Mass of fuel per injection curve .................................................................. 22 3.8.4. Comparison between different injection systems ....................................... 23 3.8.4.1. Port Injection .................................................................................. 24 3.8.4.2. Direct Injection vs Axial Deflected Direct Injection comparison .. 26 3.9. Approaches to two-stroke combustion with high compression ratio ..................... 29 4. Implementation of an exhaust system ....................................................................... 31 4.1. Exhaust gases flow in a two-stroke engine ............................................................ 31 4.2. Design of the exhaust pipe ..................................................................................... 32 4.3. Selection and modification of a commercial exhaust pipe .................................... 35 4.4. Exhaust pipe tuning ................................................................................................ 37 5. Results .......................................................................................................................... 40 5.1. Tests procedure ...................................................................................................... 40 5.2. Exhaust pipe tuning results .................................................................................... 40 5.2.1. Tuned Length .............................................................................................. 40 5.2.2. Tail pipe diameter ....................................................................................... 44 5.3. Comparison between the old exhaust pipe designed with 1-D simulation software and the new tuned commercial exhaust pipe. ........ 45 6. Conclusions .................................................................................................................. 47 1 7. Future work ................................................................................................................