Control of charge dilution in turbocharged diesel engines via exhaust valve timing

2004 ◽  
Author(s):  
H. Yilmaz ◽  
A. Stefanopoulou
Keyword(s):  
Diesel Engines ◽  
Exhaust Valve ◽  
Valve Timing

Parametric Study of the Scavenging Process in Marine Two-Stroke Diesel Engines

2015 ◽  
Author(s):  
Fredrik Herland Andersen ◽  
Stefan Mayer
Keyword(s):  
Diesel Engines ◽  
Vortex Breakdown ◽  
Initial Conditions ◽  
Combustion Process ◽  
Operating Conditions ◽  
Exhaust Valve ◽  
Delivery Ratio ◽  
Exhaust Gas ◽  
Scale Production ◽  
Cfd Model

Large commercial ships such as container vessels and bulk carriers are propelled by low-speed, uniflow scavenged two-stroke diesel engines. The integral in-cylinder process in this type of engine is the scavenging process, where the burned gas from the combustion process is evacuated through the exhaust valve and replaced with fresh air for the subsequent compression stroke. The scavenging air enters the cylinder via inlet ports which are uncovered by the piston at bottom dead center (BDC). The exhaust gas is then displaced by the fresh air. The scavenging ports are angled to introduce a swirling component to the flow. The in-cylinder swirl is beneficial for air-fuel mixture, cooling of the cylinder liner and minimizing dead zones where pockets of exhaust gas are trapped. However, a known characteristic of swirling flows is an adverse pressure gradient in the center of the flow, which might lead to a local deficit in axial velocity and the formation of central recirculation zones, known as vortex breakdown. This paper will present a CFD analysis of the scavenging process in a MAN B&W two-stroke diesel engine. The study include a parameter sweep where the operating conditions such as air amount, port timing and scavenging pressure are varied. The CFD model comprise the full geometry from scavenge receiver to exhaust receiver. Asymmetric inlet and outlet conditions is included as well as the dynamics of a moving piston and valve. Time resolved boundary conditions corresponding to measurements from an operating, full scale production, engine as well as realistic initial conditions are used in the simulations. The CFD model provides a detailed description of the in-cylinder flow from exhaust valve opening (EVO) to exhaust valve closing (EVC). The study reveals a close coupling between the volume flow (delivery ratio) and the in-cylinder bulk purity of air which appears to be independent of operating conditions, rpm, scavenge air pressure, BMEP etc. The bulk purity of air in the cylinder shows good agreement with a simple theoretical perfect displacement model.

An Investigation of the Sources of Blowby in Single-Cylinder Supercharged Diesel Engines

1978 ◽  
Vol 192 (1) ◽  
pp. 39-48 ◽  
Author(s):  
B. Bull ◽  
M. A. Voisey
Keyword(s):  
Carbon Dioxide ◽  
Diesel Engines ◽  
Piston Ring ◽  
Carbon Dioxide Concentration ◽  
Operating Conditions ◽  
Exhaust Valve ◽  
Simple Method ◽  
Single Cylinder ◽  
Carbon Dioxide Concentrations ◽  
Wide Range

Measurements of carbon dioxide concentrations in the exhaust and in the crankcase of two different types of single-cylinder, supercharged diesel engines have been used to determine the amount of exhaust gas reaching the crankcase as piston ring blowby and as leakage through the exhaust valve stem-to-guide clearance. Over a wide range of operating conditions in both engines the carbon dioxide concentration was found to be more dependent on engine fuelling rate per hour than on fuel input per stroke. It was established that blowby through the exhaust valve guide was a major contributor to crankcase contamination. A simple method has been devised, requiring only minor modifications to the engine, that permits the blowby through the piston ring pack and the exhaust valve guides to be determined separately in turbocharged production engines.

Simulation of Electric Upsetting and Forging Process for Large Marine Diesel Engine Exhaust Valves

2006 ◽  
Vol 510-511 ◽  
pp. 142-145 ◽  
Author(s):  
H.S. Jeong ◽  
J.R. Cho ◽  
Nak Kyu Lee ◽  
H.C. Park
Keyword(s):  
Diesel Engines ◽  
Manufacturing Process ◽  
Process Condition ◽  
Exhaust Valve ◽  
Experimental Result ◽  
Optimum Process ◽  
Forming Process ◽  
Marine Diesel ◽  
Electric Upsetting ◽  
Exhaust Valves

The manufacturing process of the exhaust valve in large marine diesel engines consists of an upset forging and final forming process. In the past, the exhaust valves in large marine diesel engines have been made through free forging by using the stretch forming method. This method has used the ingot and the billet as a preliminary forming process. Nimonic 80A, a superalloy, is presently used for the material of the exhaust valve. For the forming method of the valve, the electric upset method is used. Solid bar is raised up to the forming temperature by using electric energy and is continually deformed by upset pressure. The electric upsetting processing is a useful method for the high quality of exhaust valves in large marine diesel engines. It can keep the continuous grain flow, excellent mechanical property, and corrosion resistance because of the elaborate macrostructure of the valve face. The purpose of this paper is to predict the optimum process condition through simulation of the exhaust valve with a diameter of 73mm. The experimental result of an exhaust valve with a diameter of 19mm is in good agreement with the simulation result using the “QForm” that can solve electric upsetting problems. Finally, the optimal manufacturing process of the electric current and the upset load are surveyed.

Reducing combustion variation of late-phasing HCCI with cycle-to-cycle exhaust valve timing control

2010 ◽  
Vol 43 (7) ◽  
pp. 815-820 ◽  
Author(s):  
Adam. F. Jungkunz ◽  
Hsien-Hsin Liao ◽  
Nikhil Ravi ◽  
J. Christian Gerdes
Keyword(s):  
Exhaust Valve ◽  
Valve Timing ◽  
Timing Control

Intake and Exhaust Valve Timing Control on a Heavy-Duty, Direct-Injection Natural Gas Engine

2015 ◽  
Author(s):  
Bronson Patychuk ◽  
Ning Wu ◽  
Gordon McTaggart-Cowan ◽  
Philip Hill ◽  
Sandeep Munshi
Keyword(s):  
Natural Gas ◽  
Direct Injection ◽  
Exhaust Valve ◽  
Valve Timing ◽  
Heavy Duty ◽  
Timing Control ◽  
Gas Engine ◽  
Natural Gas Engine
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