Numerical Investigation of the Scavenging Flow in a Two-stroke Engine with Passive Intake Valves PDF Download
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Author: Philip Jozef Oliver
Publisher:
ISBN:
Category :
Languages : en
Pages : 250
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Book Description
The development of a numerical model of a two-stroke engine is undertaken to study the scavenging characteristics of the engine. The engine design is unique in its use of 16 passive intake valves in the cylinder head which, along with the exhaust ports located at bottom centre (BC), give the engine a top-down uniflow-scavenged configuration. Each valve constitutes a small stainless steel platelet within a cavity in the cylinder head which reacts to the pressure difference across the cylinder head. The principle focus of this study is the transient simulation of the scavenging flow using dynamic meshing to model the piston motion and the response of the passive intake valves to the scavenging flow for varied engine speed and peak pressure. A flowbench study of the steady flow through the cylinder head into a duct is incorporated as a step in the development of the transient numerical model. Validation of the numerical predictions is undertaken by comparing results from an experimental flowbench for the steady case and using a cold-flow scavenging rig for the transient simulations. Both the steady flow through the cylinder head and the unsteady flow within the cylinder indicate the presence of a recirculation region on the cylinder axis. As a result, short-circuiting of scavenging gas becomes considerable and leads to scavenging characteristics comparable to Hopkinson's perfect mixing one-dimensional scavenging model.
Author: Philip Jozef Oliver
Publisher:
ISBN:
Category :
Languages : en
Pages : 250
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Book Description
The development of a numerical model of a two-stroke engine is undertaken to study the scavenging characteristics of the engine. The engine design is unique in its use of 16 passive intake valves in the cylinder head which, along with the exhaust ports located at bottom centre (BC), give the engine a top-down uniflow-scavenged configuration. Each valve constitutes a small stainless steel platelet within a cavity in the cylinder head which reacts to the pressure difference across the cylinder head. The principle focus of this study is the transient simulation of the scavenging flow using dynamic meshing to model the piston motion and the response of the passive intake valves to the scavenging flow for varied engine speed and peak pressure. A flowbench study of the steady flow through the cylinder head into a duct is incorporated as a step in the development of the transient numerical model. Validation of the numerical predictions is undertaken by comparing results from an experimental flowbench for the steady case and using a cold-flow scavenging rig for the transient simulations. Both the steady flow through the cylinder head and the unsteady flow within the cylinder indicate the presence of a recirculation region on the cylinder axis. As a result, short-circuiting of scavenging gas becomes considerable and leads to scavenging characteristics comparable to Hopkinson's perfect mixing one-dimensional scavenging model.
Author: Iain Kyle Fraser
Publisher:
ISBN:
Category :
Languages : en
Pages : 170
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Book Description
An innovative two-stroke engine has been under development at Queen's University. Traditional crankcase-scavenged two-stroke engines have laboured to meet emissions standards and achieve fuel economy comparable to four-stroke engines. The engine in question makes use of a modified Eaton-type supercharger to enable air-only scavenging, with this it utilizes direct fuel injection which occurs after the exhaust ports have closed, these two elements combine to eliminate the combustion of lubricating oil in the cylinder and short-circuiting of the fuel-air mixture into the exhaust. By having passive check valves in the cylinder head to regulate the inflow of scavenging air, and exhaust ports located near bottom centre this results in a top-down uniflow-scavenged configuration, as well as retaining a simplistic engine design. In the two-stroke cycle, using the intake charge to replace the combustion products with fresh air during scavenging is critical to engine performance. In this engine the scavenging charge is produced by a set of passive intake check valves, and because of this the scavenging timing is important. These valves are important because they govern the volume of combustion products that are forced out of the cylinder during scavenging, and hence the efficiency of combustion in the engine. To evaluate the engine design criteria, a validated computational fluid dynamic (CFD) model was used to offer insight into how the in-cylinder flow developed during scavenging. The CFD model of this engine was used to test different check-valve geometries to see how they affect the scavenging flow in the cylinder. The goal of this is to assist in entraining more of the combustion products which would result in more being exhausted from the cylinder. A more favourable design was found, and a design produced to be taken onto the next step of testing.
Author: Paul J. Schweiger
Publisher:
ISBN:
Category :
Languages : en
Pages : 346
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Book Description
Author: Society of Automotive Engineers
Publisher:
ISBN:
Category : Technical literature
Languages : en
Pages : 664
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Book Description
Author: David Michael Bevan
Publisher:
ISBN:
Category :
Languages : en
Pages : 234
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Book Description
Author: Douglas J. Lofgren
Publisher:
ISBN:
Category :
Languages : en
Pages : 382
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Book Description
Author: John B. Allen
Publisher:
ISBN:
Category :
Languages : en
Pages : 177
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Book Description
Author: Yip. Lay Huat
Publisher:
ISBN:
Category : Two-stroke cycle engines
Languages : en
Pages :
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Book Description
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 702
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Book Description
Author: JohnB. Heywood
Publisher: Routledge
ISBN: 1351406450
Category : Technology & Engineering
Languages : en
Pages : 425
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Book Description
This book addresses the two-stroke cycle internal combustion engine, used in compact, lightweight form in everything from motorcycles to chainsaws to outboard motors, and in large sizes for marine propulsion and power generation. It first provides an overview of the principles, characteristics, applications, and history of the two-stroke cycle engine, followed by descriptions and evaluations of various types of models that have been developed to predict aspects of two-stroke engine operation.
